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  • 1.
    Ajaxon, Ingrid
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Can Bone Void Fillers Carry Load?: Behaviour of Calcium Phosphate Cements Under Different Loading Scenarios2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Calcium phosphate cements (CPCs) are used as bone void fillers and as complements to hardware in fracture fixation. The aim of this thesis was to investigate the possibilities and limitations of the CPCs’ mechanical properties, and find out if these ceramic bone cements can carry application-specific loads, alone or as part of a construct. Recently developed experimental brushite and apatite cements were found to have a significantly higher strength in compression, tension and flexion compared to the commercially available CPCs chronOS™ Inject and Norian® SRS®. By using a high-resolution measurement technique the elastic moduli of the CPCs were determined and found to be at least twice as high compared to earlier measurements, and closer to cortical bone than trabecular bone. Using the same method, Poisson's ratio for pure CPCs was determined for the first time. A non-destructive porosity measurement method for wet brushite cements was developed, and subsequently used to study the porosity increase during in vitro degradation. The compressive strength of the experimental brushite cement was still higher than that of trabecular bone after 25 weeks of degradation, showing that the cement can carry high loads over a time span sufficiently long for a fracture to heal. This thesis also presents the first ever fatigue results for acidic CPCs, and confirms the importance of testing the materials under cyclic loading as the cements may fail at stress levels much lower than the material’s quasi-static compressive strength. A decrease in fatigue life was found for brushite cements containing higher amounts of monetite. Increasing porosity and testing in a physiological buffer solution (PBS), rather than air, also decreased the fatigue life. However, the experimental brushite cement had a high probability of surviving loads found in the spine when tested in PBS, which has previously never been accomplished for acidic CPCs. In conclusion, available brushite cements may be able to carry the load alone in scenarios where the cortical shell is intact, the loading is mainly compressive, and the expected maximum stress is below 10 MPa. Under such circumstances this CPC may be the preferred choice over less biocompatible and non-degradable materials.

    List of papers
    1. Mechanical Properties of Brushite Calcium Phosphate Cements
    Open this publication in new window or tab >>Mechanical Properties of Brushite Calcium Phosphate Cements
    2017 (English)In: The World Scientific Encyclopedia of Nanomedicine and Bioengineering II: Bioimplants, Regenerative Medicine, and Nano-Cancer Diagnosis and Phototherapy: Volume 3: Design of Bioactive Materials for Bone Repair and Regeneration / [ed] Shi, D., Singapore: World Scientific Pte Ltd. , 2017Chapter in book (Refereed)
    Place, publisher, year, edition, pages
    Singapore: World Scientific Pte Ltd., 2017
    National Category
    Biomaterials Science Ceramics Medical Materials
    Identifiers
    urn:nbn:se:uu:diva-316712 (URN)978-981-4667-58-6 (ISBN)
    Funder
    Swedish Research Council, GA 621-2011-6258
    Available from: 2017-03-22 Created: 2017-03-22 Last updated: 2017-03-22
    2. Compressive, diametral tensile and biaxial flexural strength of cutting-edge calcium phosphate cements
    Open this publication in new window or tab >>Compressive, diametral tensile and biaxial flexural strength of cutting-edge calcium phosphate cements
    Show others...
    2016 (English)In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 60, p. 617-627Article in journal (Refereed) Published
    Abstract [en]

    Calcium phosphate cements (CPCs) are widely used in bone repair. Currently there are two main types of CPCs, brushite and apatite. The aim of this project was to evaluate the mechanical properties of particularly promising experimental brushite and apatite formulations in comparison to commercially available brushite- and apatite-based cements (chronOS Inject and Norian® SRS®, respectively), and in particular evaluate the diametral tensile strength and biaxial flexural strength of these cements in both wet and dry conditions for the first time. The cements׳ porosity and their compressive, diametral tensile and biaxial flexural strength were tested in wet (or moist) and dry conditions. The surface morphology was characterized by scanning electron microscopy. Phase composition was assessed with X-ray diffraction. It was found that the novel experimental cements showed better mechanical properties than the commercially available cements, in all loading scenarios. The highest compressive strength (57.2±6.5 MPa before drying and 69.5±6.0 MPa after drying) was found for the experimental brushite cement. This cement also showed the highest wet diametral tensile strength (10.0±0.8 MPa) and wet biaxial flexural strength (30.7±1.8 MPa). It was also the cement that presented the lowest porosity (approx. 12%). The influence of water content was found to depend on cement type, with some cements showing higher mechanical properties after drying and some no difference after drying.

    Keywords
    Calcium phosphate cement; Brushite; Apatite; Compressive strength; Tensile strength; Flexural strength
    National Category
    Ceramics
    Identifiers
    urn:nbn:se:uu:diva-284218 (URN)10.1016/j.jmbbm.2016.03.028 (DOI)000378969100055 ()27082025 (PubMedID)
    Funder
    The Swedish Foundation for International Cooperation in Research and Higher Education (STINT), IG2011-2047Swedish Research Council, 621-2011-6258
    Available from: 2016-04-15 Created: 2016-04-15 Last updated: 2018-08-10Bibliographically approved
    3. Elastic properties and strain-to-crack-initation of calcium phosphate bone cements: Revelations of a high-resolution measurement technique
    Open this publication in new window or tab >>Elastic properties and strain-to-crack-initation of calcium phosphate bone cements: Revelations of a high-resolution measurement technique
    Show others...
    2017 (English)In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 74, p. 428-437Article in journal (Refereed) Published
    Abstract [en]

    Calcium phosphate cements (CPCs) should ideally have mechanical properties similar to those of the bone tissue the material is used to replace or repair. Usually, the compressive strength of the CPCs is reported and, more rarely, the elastic modulus. Conversely, scarce or no data are available on Poisson's ratio and strain-to-crack-initiation. This is unfortunate, as data on the elastic response is key to, e.g., numerical model accuracy. In this study, the compressive behaviour of brushite, monetite and apatite cements was fully characterised. Measurement of the surface strains was done using a digital image correlation (DIC) technique, and compared to results obtained with the commonly used built-in displacement measurement of the materials testers. The collected data showed that the use of fixed compression platens, as opposed to spherically seated ones, may in some cases underestimate the compressive strength by up to 40%. Also, the built-in measurements may underestimate the elastic modulus by up to 62% as compared to DIC measurements. Using DIC, the brushite cement was found to be much stiffer (24.3 ± 2.3 GPa) than the apatite (13.5 ± 1.6 GPa) and monetite (7.1 ± 1.0 GPa) cements, and elastic moduli were inversely related to the porosity of the materials. Poisson's ratio was determined to be 0.26 ± 0.02 for brushite, 0.21 ± 0.02 for apatite and 0.20 ± 0.03 for monetite. All investigated CPCs showed low strain-to-crack-initiation (0.17–0.19%). In summary, the elastic modulus of CPCs is substantially higher than previously reported and it is concluded that an accurate procedure is a prerequisite in order to properly compare the mechanical properties of different CPC formulations. It is recommended to use spherically seated platens and measuring the strain at a relevant resolution and on the specimen surface.

    National Category
    Ceramics Medical Materials Biomaterials Science
    Identifiers
    urn:nbn:se:uu:diva-316718 (URN)10.1016/j.jmbbm.2017.06.023 (DOI)000410253500046 ()28735216 (PubMedID)
    Funder
    The Swedish Foundation for International Cooperation in Research and Higher Education (STINT), IG2011-2047Swedish Research Council, 621-2011-6258
    Available from: 2017-03-22 Created: 2017-03-22 Last updated: 2017-12-04Bibliographically approved
    4. Evaluation of a porosity measurement method for wet calcium phosphate cements
    Open this publication in new window or tab >>Evaluation of a porosity measurement method for wet calcium phosphate cements
    Show others...
    2015 (English)In: Journal of biomaterials applications, ISSN 0885-3282, E-ISSN 1530-8022, Vol. 30, no 5, p. 526-536Article in journal (Refereed) Published
    Abstract [en]

    The porosity of a calcium phosphate cement is a key parameter as it affects several important properties of the cement. However, a successful, non-destructive porosity measurement method that does not include drying has not yet been reported for calcium phosphate cements. The aim of this study was to evaluate isopropanol solvent exchange as such a method. Two different types of calcium phosphate cements were used, one basic (hydroxyapatite) and one acidic (brushite). The cements were allowed to set in an aqueous environment and then immersed in isopropanol and stored under three different conditions: at room temperature, at room temperature under vacuum (300 mbar) or at 37􏰀C. The specimen mass was monitored regularly. Solvent exchange took much longer time to reach steady state in hydroxyapatite cements compared to brushite cements, 350 and 18 h, respectively. Furthermore, the immersion affected the quasi-static compressive strength of the hydroxyapatite cements. However, the strength and phase composition of the brushite cements were not affected by isopropanol immersion, suggesting that isopropanol solvent exchange can be used for brushite calcium phosphate cements. The main advantages with this method are that it is non-destructive, fast, easy and the porosity can be evaluated while the cements remain wet, allowing for further analysis on the same specimen. 

    Place, publisher, year, edition, pages
    Sage Publications, 2015
    Keywords
    Calcium phosphate, bone cement, porosity, solvent exchange, brushite, hydroxyapatite
    National Category
    Ceramics Biomaterials Science Medical Materials
    Research subject
    Engineering Science with specialization in Materials Science
    Identifiers
    urn:nbn:se:uu:diva-258636 (URN)10.1177/0885328215594293 (DOI)000367743900003 ()26163278 (PubMedID)
    Funder
    The Swedish Foundation for International Cooperation in Research and Higher Education (STINT), IG2011-2047Swedish Research Council, 621-2011-6258
    Available from: 2015-07-17 Created: 2015-07-17 Last updated: 2017-12-04Bibliographically approved
    5. Long-term in vitro degradation of a high-strength brushite cement in water, PBS, and serum solution
    Open this publication in new window or tab >>Long-term in vitro degradation of a high-strength brushite cement in water, PBS, and serum solution
    2015 (English)In: BioMed Research International, ISSN 2314-6133, E-ISSN 2314-6141, article id 575079Article in journal (Refereed) Published
    Abstract [en]

    Bone loss and fractures may call for the use of bone substituting materials, such as calcium phosphate cements (CPCs). CPCs can be degradable, and, to determine their limitations in terms of applications, their mechanical as well as chemical properties need to be evaluated over longer periods of time, under physiological conditions. However, there is lack of data on how the in vitro degradation affects high-strength brushite CPCs over longer periods of time, that is, longer than it takes for a bone fracture to heal. This study aimed at evaluating the long-term in vitro degradation properties of a high-strength brushite CPC in three different solutions: water, phosphate buffered saline, and a serum solution. Microcomputed tomography was used to evaluate the degradation nondestructively, complemented with gravimetric analysis. The compressive strength, chemical composition, and microstructure were also evaluated. Major changes from 10 weeks onwards were seen, in terms of formation of a porous outer layer of octacalcium phosphate on the specimens with a concomitant change in phase composition, increased porosity, decrease in object volume, and mechanical properties. This study illustrates the importance of long-term evaluation of similar cement compositions to be able to predict the material’s physical changes over a relevant time frame. 

    Place, publisher, year, edition, pages
    Hindawi Publishing Corporation, 2015
    Keywords
    Calcium phosphate, brushite, bone cement, degradation, in vitro, solvent exchange, compressive strength, micro-CT, porosity
    National Category
    Ceramics Bio Materials Biomaterials Science Medical Materials
    Research subject
    Engineering Science with specialization in Materials Science
    Identifiers
    urn:nbn:se:uu:diva-265319 (URN)10.1155/2015/575079 (DOI)000364660000001 ()
    Funder
    The Swedish Foundation for International Cooperation in Research and Higher Education (STINT), IG2011-207Swedish Research Council, 621-2011-6258
    Available from: 2015-10-27 Created: 2015-10-27 Last updated: 2017-12-01Bibliographically approved
    6. Compressive fatigue properties of an acidic calcium phosphate cement—effect of phase composition
    Open this publication in new window or tab >>Compressive fatigue properties of an acidic calcium phosphate cement—effect of phase composition
    2017 (English)In: Journal of materials science. Materials in medicine, ISSN 0957-4530, E-ISSN 1573-4838, Vol. 28, no 3, article id 41Article in journal (Refereed) Published
    Abstract [en]

    Calcium phosphate cements (CPCs) are synthetic bone grafting materials that can be used in fracture stabilization and to fill bone voids after, e.g., bone tumour excision. Currently there are several calcium phosphate-based formulations available, but their use is partly limited by a lack of knowledge of their mechanical properties, in particular their resistance to mechanical loading over longer periods of time. Furthermore, depending on, e.g., setting conditions, the end product of acidic CPCs may be mainly brushite or monetite, which have been found to behave differently under quasi-static loading. The objectives of this study were to evaluate the compressive fatigue properties of acidic CPCs, as well as the effect of phase composition on these properties. Hence, brushite cements stored for different lengths of time and with different amounts of monetite were investigated under quasi-static and dynamic compression. Both storage and brushite-to-monetite phase transformation was found to have a pronounced effect both on quasi-static compressive strength and fatigue performance of the cements, whereby a substantial phase transformation gave rise to a lower mechanical resistance. The brushite cements investigated in this study had the potential to survive 5 million cycles at a maximum compressive stress of 13 MPa. Given the limited amount of published data on fatigue properties of CPCs, this study provides an important insight into the compressive fatigue behaviour of such materials. 

    Keywords
    Bone cement, brushite, monetite, fatigue, mechanical properties
    National Category
    Ceramics Medical Materials Biomaterials Science
    Research subject
    Engineering Science with specialization in Materials Science
    Identifiers
    urn:nbn:se:uu:diva-314237 (URN)10.1007/s10856-017-5851-5 (DOI)000394242700006 ()28144853 (PubMedID)
    Funder
    Swedish Research Council, 621-2011-6258
    Available from: 2017-02-03 Created: 2017-01-31 Last updated: 2017-11-29Bibliographically approved
    7. Compressive fatigue properties of a high-strength, degradable calcium phosphate bone cement – influence of porosity and environment
    Open this publication in new window or tab >>Compressive fatigue properties of a high-strength, degradable calcium phosphate bone cement – influence of porosity and environment
    (English)Manuscript (preprint) (Other academic)
    National Category
    Ceramics Medical Materials Biomaterials Science
    Identifiers
    urn:nbn:se:uu:diva-316717 (URN)
    Funder
    Swedish Research Council, 621-2011-6258
    Available from: 2017-03-22 Created: 2017-03-22 Last updated: 2017-03-22
  • 2.
    Ajaxon, Ingrid
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Acciaioli, Alice
    Istituto Ortopedico Rizzoli, Laboratorio di Tecnologia Medica.
    Lionello, Giacomo
    Istituto Ortopedico Rizzoli, Laboratorio di Tecnologia Medica.
    Ginebra, Maria-Pau
    Biomaterials, Biomechanics and Tissue Engineering Group, Dept. of Materials Science and Metallurgy, Technical University of Catalonia (UPC).
    Öhman, Caroline
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Baleani, Massimilliano
    Istituto Ortopedico Rizzoli, Laboratorio di Tecnologia Medica.
    Persson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Elastic properties and strain-to-crack-initation of calcium phosphate bone cements: Revelations of a high-resolution measurement technique2017In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 74, p. 428-437Article in journal (Refereed)
    Abstract [en]

    Calcium phosphate cements (CPCs) should ideally have mechanical properties similar to those of the bone tissue the material is used to replace or repair. Usually, the compressive strength of the CPCs is reported and, more rarely, the elastic modulus. Conversely, scarce or no data are available on Poisson's ratio and strain-to-crack-initiation. This is unfortunate, as data on the elastic response is key to, e.g., numerical model accuracy. In this study, the compressive behaviour of brushite, monetite and apatite cements was fully characterised. Measurement of the surface strains was done using a digital image correlation (DIC) technique, and compared to results obtained with the commonly used built-in displacement measurement of the materials testers. The collected data showed that the use of fixed compression platens, as opposed to spherically seated ones, may in some cases underestimate the compressive strength by up to 40%. Also, the built-in measurements may underestimate the elastic modulus by up to 62% as compared to DIC measurements. Using DIC, the brushite cement was found to be much stiffer (24.3 ± 2.3 GPa) than the apatite (13.5 ± 1.6 GPa) and monetite (7.1 ± 1.0 GPa) cements, and elastic moduli were inversely related to the porosity of the materials. Poisson's ratio was determined to be 0.26 ± 0.02 for brushite, 0.21 ± 0.02 for apatite and 0.20 ± 0.03 for monetite. All investigated CPCs showed low strain-to-crack-initiation (0.17–0.19%). In summary, the elastic modulus of CPCs is substantially higher than previously reported and it is concluded that an accurate procedure is a prerequisite in order to properly compare the mechanical properties of different CPC formulations. It is recommended to use spherically seated platens and measuring the strain at a relevant resolution and on the specimen surface.

  • 3.
    Ajaxon, Ingrid
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Acciaioli, Alice
    Lionello, Giacomo
    Ginebra, Maria-Pau
    Öhman, Caroline
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Persson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Baleani, Massimiliano
    Compressive strength increase of calcium phosphate bone cements is accompanied by a stiffness increase2016Conference paper (Other academic)
  • 4.
    Ajaxon, Ingrid
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Holmberg, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Öhman Mägi, Caroline
    Persson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Fatigue life of a brushite cement under cyclic compressive loading2017Conference paper (Refereed)
  • 5.
    Ajaxon, Ingrid
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Holmberg, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Öhman Mägi, Caroline
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Persson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Long-term degradation of brushite cements in three different liquids2016Conference paper (Other academic)
  • 6.
    Ajaxon, Ingrid
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Holmberg, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Öhman Mägi, Caroline
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Persson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    The influence of porosity on the fatigue properties of brushite cement2016In: Biomaterials for tissue engineering models, 2016Conference paper (Other academic)
  • 7.
    Ajaxon, Ingrid
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Holmberg, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Öhman-Mägi, Caroline
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Persson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Compressive fatigue properties of a high-strength, degradable calcium phosphate bone cement – influence of porosity and environmentManuscript (preprint) (Other academic)
  • 8.
    Ajaxon, Ingrid
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Lionello, Giacomo
    bLaboratorio di Tecnologia Medica, Istituto Ortopedico Rizzoli, Italy.
    Ginebra, Maria-Pau
    cBiomaterials, Biomechanics and Tissue Engineering Group, Department of Materials Science and Metallurgy, Technical University of Catalonia .
    Öhman, Caroline
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Baleani, Massimiliano
    bLaboratorio di Tecnologia Medica, Istituto Ortopedico Rizzoli, Italy.
    Persson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Local stiffness measurements in apatite and brushite cements2015Conference paper (Other academic)
  • 9.
    Ajaxon, Ingrid
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Maazouz, Yassine
    Biomaterials, Biomechanics and Tissue Engineering Group, Dept. of Materials Science and Metallurgy, Technical University of Catalonia .
    Ginebra, Maria-Pau
    Biomaterials, Biomechanics and Tissue Engineering Group, Dept. of Materials Science and Metallurgy, Technical University of Catalonia .
    Öhman, Caroline
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Persson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    A non-drying porosity evaluation method for calcium phosphate cements2014In: 26th Symposium and Annual Meeting of the International Society for Ceramics in Medicine, 2014, p. 68-68Conference paper (Refereed)
  • 10.
    Ajaxon, Ingrid
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Maazouz, Yassine
    Ginebra, Maria-Pau
    Öhman, Caroline
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Persson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Evaluation of a porosity measurement method for wet calcium phosphate cements2015In: Journal of biomaterials applications, ISSN 0885-3282, E-ISSN 1530-8022, Vol. 30, no 5, p. 526-536Article in journal (Refereed)
    Abstract [en]

    The porosity of a calcium phosphate cement is a key parameter as it affects several important properties of the cement. However, a successful, non-destructive porosity measurement method that does not include drying has not yet been reported for calcium phosphate cements. The aim of this study was to evaluate isopropanol solvent exchange as such a method. Two different types of calcium phosphate cements were used, one basic (hydroxyapatite) and one acidic (brushite). The cements were allowed to set in an aqueous environment and then immersed in isopropanol and stored under three different conditions: at room temperature, at room temperature under vacuum (300 mbar) or at 37􏰀C. The specimen mass was monitored regularly. Solvent exchange took much longer time to reach steady state in hydroxyapatite cements compared to brushite cements, 350 and 18 h, respectively. Furthermore, the immersion affected the quasi-static compressive strength of the hydroxyapatite cements. However, the strength and phase composition of the brushite cements were not affected by isopropanol immersion, suggesting that isopropanol solvent exchange can be used for brushite calcium phosphate cements. The main advantages with this method are that it is non-destructive, fast, easy and the porosity can be evaluated while the cements remain wet, allowing for further analysis on the same specimen. 

  • 11.
    Ajaxon, Ingrid
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Persson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Mechanical Properties of Brushite Calcium Phosphate Cements2017In: The World Scientific Encyclopedia of Nanomedicine and Bioengineering II: Bioimplants, Regenerative Medicine, and Nano-Cancer Diagnosis and Phototherapy: Volume 3: Design of Bioactive Materials for Bone Repair and Regeneration / [ed] Shi, D., Singapore: World Scientific Pte Ltd. , 2017Chapter in book (Refereed)
  • 12.
    Ajaxon, Ingrid
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Öhman, Caroline
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Persson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Compressive Fatigue Properties of Acidic Calcium Phosphate Cement2014In: Proceedings of 7th World Congress of Biomechanics, 2014Conference paper (Refereed)
  • 13.
    Ajaxon, Ingrid
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Öhman, Caroline
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Persson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Long-term in vitro degradation of a high-strength brushite cement in water, PBS, and serum solution2015In: BioMed Research International, ISSN 2314-6133, E-ISSN 2314-6141, article id 575079Article in journal (Refereed)
    Abstract [en]

    Bone loss and fractures may call for the use of bone substituting materials, such as calcium phosphate cements (CPCs). CPCs can be degradable, and, to determine their limitations in terms of applications, their mechanical as well as chemical properties need to be evaluated over longer periods of time, under physiological conditions. However, there is lack of data on how the in vitro degradation affects high-strength brushite CPCs over longer periods of time, that is, longer than it takes for a bone fracture to heal. This study aimed at evaluating the long-term in vitro degradation properties of a high-strength brushite CPC in three different solutions: water, phosphate buffered saline, and a serum solution. Microcomputed tomography was used to evaluate the degradation nondestructively, complemented with gravimetric analysis. The compressive strength, chemical composition, and microstructure were also evaluated. Major changes from 10 weeks onwards were seen, in terms of formation of a porous outer layer of octacalcium phosphate on the specimens with a concomitant change in phase composition, increased porosity, decrease in object volume, and mechanical properties. This study illustrates the importance of long-term evaluation of similar cement compositions to be able to predict the material’s physical changes over a relevant time frame. 

  • 14.
    Ajaxon, Ingrid
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Öhman Mägi, Caroline
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Persson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Compressive fatigue properties of an acidic calcium phosphate cement—effect of phase composition2017In: Journal of materials science. Materials in medicine, ISSN 0957-4530, E-ISSN 1573-4838, Vol. 28, no 3, article id 41Article in journal (Refereed)
    Abstract [en]

    Calcium phosphate cements (CPCs) are synthetic bone grafting materials that can be used in fracture stabilization and to fill bone voids after, e.g., bone tumour excision. Currently there are several calcium phosphate-based formulations available, but their use is partly limited by a lack of knowledge of their mechanical properties, in particular their resistance to mechanical loading over longer periods of time. Furthermore, depending on, e.g., setting conditions, the end product of acidic CPCs may be mainly brushite or monetite, which have been found to behave differently under quasi-static loading. The objectives of this study were to evaluate the compressive fatigue properties of acidic CPCs, as well as the effect of phase composition on these properties. Hence, brushite cements stored for different lengths of time and with different amounts of monetite were investigated under quasi-static and dynamic compression. Both storage and brushite-to-monetite phase transformation was found to have a pronounced effect both on quasi-static compressive strength and fatigue performance of the cements, whereby a substantial phase transformation gave rise to a lower mechanical resistance. The brushite cements investigated in this study had the potential to survive 5 million cycles at a maximum compressive stress of 13 MPa. Given the limited amount of published data on fatigue properties of CPCs, this study provides an important insight into the compressive fatigue behaviour of such materials. 

  • 15.
    Altskog, Frida
    Gotland University, School of the Humanities and Social Science.
    Keramisk List: produktutveckling för Askersunds Kakelmakeri2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In this report presents a thesis by Frida Altskog performed in collaboration with Askersunds Kakelmakeri. The project’s goal has been to produce a ceramic ledge after the company’s specifications. The company’s desire and production facilities have been in focus.  This report includes a collection of facts and gives an overview of the ceramic material, production of ceramic products and how production of hand-made tiles and clinker is made. A analysis of target group and market have been a guide line through the projects ideas and realizations.  The final product is a ceramic ledge that can combine with three different patterns. Classic, modern and oriental. It can be combined and adjustable on different surfaces. The form of the ledge is effective to produce and it can be made in Askersund kakelmakeris pottery.

  • 16.
    Barba, Albert
    et al.
    Biomaterials, Biomechanics and Tissue Engineering Group, Department of Materials Science and Metallurgical Engineering, Universitat Politècnica de Catalunya.
    Maazouz, Yassine
    Biomaterials, Biomechanics and Tissue Engineering Group, Department of Materials Science and Metallurgical Engineering, Universitat Politècnica de Catalunya.
    Diez-Escudero, Anna
    Biomaterials, Biomechanics and Tissue Engineering Group, Department of Materials Science and Metallurgical Engineering, Universitat Politècnica de Catalunya.
    Rappe, Katrin
    Bone Healing Group, Small Animal Surgery Department, Veterinary School, Universitat Autònoma de Barcelona.
    Espanol, Montserrat
    Biomaterials, Biomechanics and Tissue Engineering Group, Department of Materials Science and Metallurgical Engineering, Universitat Politècnica de Catalunya.
    Montufar, Edgar
    Biomaterials, Biomechanics and Tissue Engineering Group, Department of Materials Science and Metallurgical Engineering, Universitat Politècnica de Catalunya.
    Öhman, Caroline
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Persson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Fontecha, Pedro
    Bone Healing Group, Small Animal Surgery Department, Veterinary School, Universitat Autònoma de Barcelona.
    Manzanares, Maria-Cristina
    Human Anatomy and Embryology Unit, Department of Pathology and Experimental Therapeutics, Universitat de Barcelona.
    Franch, Jordi
    Bone Healing Group, Small Animal Surgery Department, Veterinary School, Universitat Autònoma de Barcelona.
    Ginebra, Maria-Pau
    Biomaterials, Biomechanics and Tissue Engineering Group, Department of Materials Science and Metallurgical Engineering, Universitat Politècnica de Catalunya.
    Osteogenesis by foamed and 3D-printed nanostructured calcium phosphate scaffolds: Effect of pore architecture2018In: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 79, p. 135-147Article in journal (Refereed)
    Abstract [en]

    There is an urgent need of synthetic bone grafts with enhanced osteogenic capacity. This can be achieved by combining biomaterials with exogenous growth factors, which however can have numerous undesired side effects, but also by tuning the intrinsic biomaterial properties. In a previous study, we showed the synergistic effect of nanostructure and pore architecture of biomimetic calcium deficient hydroxyapatite (CDHA) scaffolds in enhancing osteoinduction, i.e. fostering the differentiation of mesenchymal stem cells to bone forming cells. This was demonstrated by assessing bone formation after implanting the scaffolds intramuscularly. The present study goes one step forward, since it analyzes the effect of the geometrical features of the same CDHA scaffolds, obtained either by 3D-printing or by foaming, on the osteogenic potential and resorption behaviour in a bony environment. After 6 and 12 weeks of intraosseous implantation, both bone formation and material degradation had been drastically affected by the macropore architecture of the scaffolds. Whereas nanostructured CDHA was shown to be highly osteoconductive both in the robocast and foamed scaffolds, a superior osteogenic capacity was observed in the foamed scaffolds, which was associated with their higher intrinsic osteoinductive potential. Moreover, they showed a significantly higher cell-mediated degradation than the robocast constructs, with a simultaneous and progressive replacement of the scaffold by new bone. In conclusion, these results demonstrate that the control of macropore architecture is a crucial parameter in the design of synthetic bone grafts, which allows fostering both material degradation and new bone formation. Statement of Significance 3D-printing technologies open new perspectives for the design of patient-specific bone grafts, since they allow customizing the external shape together with the internal architecture of implants. In this respect, it is important to design the appropriate pore geometry to maximize the bone healing capacity of these implants. The present study analyses the effect of pore architecture of nanostructured hydroxyapatite scaffolds, obtained either by 3D-printing or foaming, on the osteogenic potential and scaffold resorption in an in vivo model. While nanostructured hydroxyapatite showed excellent osteoconductive properties irrespective of pore geometry, we demonstrated that the spherical, concave macropores of foamed scaffolds significantly promoted both material resorption and bone regeneration compared to the 3D-printed scaffolds with orthogonal-patterned struts and therefore prismatic, convex macropores.

  • 17.
    Berg, Camilla
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Influence of Magnesium in theFormation of Phosphate Spheres: A simple method for the fabrication of sphericalparticles of calcium and magnesium phosphate2017Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Calcium phosphates and recently also magnesium phosphates, are used for medical applications, due to their biocompatibility and bioactivity. These properites makes spherical particles of calcium and magnesium phosphate suitable for carrier materials for drug delivery applications. By creating porous and/or hollow particles itis possible to load the particles with a drug and control therelease of the active substance.

    In this work, an ion-induced method for the synthesis of spherical calcium and magnesium phosphates was developed. A simple precipitation reaction was used, where substituting magnesium ions could replace the function of templates, such as surfactants or micelles, to induce the formation of spheres of a certain size and morphology.

    Experimental results showed that magnesium had an inhibitory effect on the nucleation and crystal growth of calcium phosphates. By using substituting ions as a structural regulator, it was possible to alter the size, morphology and phase composition of the spheres. At low magnesium concentrations, the spheres had a smooth surface andwere between 200 nanometer to 1 micrometer in diameter and composed of hydroxyapatite and/or magnesium-substituted beta-TCP. At higher magnesium concentrations, the spheres were about 10-50 micrometer with a rough, flaky surface. Results also proved that calcium ionshave the same effect on the crystallisation and self-assembly of magnesium phosphates. Apart from the magnesium concentration, reaction temperature proved to have a high influence on the sphereformation, whereas Ca/P ratio and reaction times above three hours did not affect the sphere formation to the same extent.

  • 18.
    Berg, Camilla
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Xia, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Ion substitution induced formation of spherical ceramic particles2019In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 45, no 8, p. 10385-10393Article in journal (Refereed)
    Abstract [en]

    How to precipitate ceramic nano- and microspheres in water based solutions only using inorganic ions is a challenge. In this study, spherical particles of alkaline earth phosphates and fluorides were synthesized using a precipitation reaction. Substituting ions, through inhibition of crystal growth, was used to induce sphere formation and to alter the morphology, size and composition of the spheres. The difference in ionic radius between the substituting ion (Mg, Ca and Sr) and the main cation (Sr and Ba) influenced the critical concentration to allow for sphere formation as well as the crystallinity. The larger difference, the lower was the concentration needed to form spheres. Low concentrations of Mg was enough to generate amorphous spheres of Sr- and Ba- phosphates whereas higher concentrations were needed if the radius difference were smaller. An increasing degree of substitution leads to a decrease in crystallinity of precipitated particles. The degree of substitution was determined to 16-55% where a low degree of ion substitution in the phosphates resulted in the formation of spheres (500-800 nm) with rough surfaces composed of apatite like phases. A higher degree of substitution resulted in amorphous spheres (500 nm- (1) mu m) with smooth surfaces.

  • 19.
    Berglund, Martin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Persson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    A High-Performance Microplasma Source for Highly Sensitive and Robust Gas Analysis2014In: Proc. of Micronano System Workshop 2014, Uppsala, Sweden, May 15-16, 2014, 2014Conference paper (Other academic)
  • 20.
    Berglund, Martin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Persson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Evaluation of dielectric properties of HTCC alumina for realization of plasma sources2015In: Journal of Electronic Materials, ISSN 0361-5235, E-ISSN 1543-186X, Vol. 44, no 10, p. 3654-3660Article in journal (Refereed)
    Abstract [en]

    As the sensitivity of optogalvanic spectroscopy based on prototype microplasma sources increases, contamination from composite materials in the printed circuit board used starts to become a concern. In this paper, a transfer to high-temperature cofired alumina and platinum is made and evaluated. The high-purity alumina provides an inert plasma environment, and allows for temperatures above 1000A degrees C, which is beneficial for future integration of a combustor. To facilitate the design of high-end plasma sources, characterization of the radio frequency (RF) parameters of the materials around 2.6 GHz is carried out. A RF resonator structure was fabricated in both microstrip and stripline configurations. These resonators were geometrically and electrically characterized, and epsilon (r) and tan were calculated using the RF waveguide design tool Wcalc. The resulting epsilon (r) for the microstrip and stripline was found to be 10.68 (+/- 0.12) and 9.65 (+/- 0.14), respectively. The average tan of all devices was found to be 0.0011 (+/- 0.0007). With these parameters, a series of proof-of-concept plasma sources were fabricated and evaluated. Some problems in the fabrication stemmed from the lamination and difficulties with the screen-printing, but a functioning plasma source was demonstrated.

  • 21.
    Cai, Bing
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Ceramic Materials for Administration of Potent Drugs2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis aimed to investigate and document the potential of applying ceramics in two specific drug delivery applications: tamper-resistant opioid formulations and transdermal enhancement protrusions.

    Geopolymers were developed into the matrix for a tamper-resistant formulation, aiming to protect drug substances from non-medical abuse. The synthesis conditions and excipients composition of the geopolymer-based formulation were modified in this work to facilitate a stable and extended drug delivery. Results showed that 37ºC 100% humidity for 48 hours were applicable conditions to obtain geopolymer with suitable mechanical strength and porosity. Moreover, it was found that the integration of poly(methyl acrylate) into the geopolymer-based formulation could reduce the drug release at low pH and, meanwhile, maintain the mechanical strength. Therefore, the geopolymer-based drug formulations concluded from these studies were applied in oral and transdermal delivery systems. Evidence of the tamper-resistance of geopolymer-based oral and transdermal formulations was documented and compared to the corresponding commercial opioid formulations. The results provided experimental support for the positive effects of geopolymers as drug carriers for the tamper-resistance of oral and transdermal delivery systems.

    Self-setting bioceramics, calcium phosphate and calcium sulfate were fabricated into transdermal enhancement protrusions in this work for the first time. Results showed that, under mild conditions, both bioceramics could form pyramid-shaped needles in the micron size. The drug release from these needles could be controlled by the bulk surface area, porosity and degradation of the bioceramics. An in vitro insertion test showed that the bioceramic microneedles had enough mechanical strength to insert into skin. Further optimization on the geometry of needles and the substrate material was also performed. The higher aspect-ratio needles with a flexible and self-swellable substrate could release most of the drug content within 4 hours and could penetrate through the stratum corneum by manual insertion. This study explored the potential application of bioceramics in transdermal enhancement protrusions and showed promising indication of their future developments.

    List of papers
    1. The effect of curing conditions on compression strength and porosity of metakaolin-based geopolymers
    Open this publication in new window or tab >>The effect of curing conditions on compression strength and porosity of metakaolin-based geopolymers
    2013 (English)In: Developments in Strategic Materials and Computational Design IV, John Wiley & Sons, 2013Conference paper, Published paper (Refereed)
    Abstract [en]

    Geopolymers have been suggested to use as construction, waste treatment and fire proof materials and even drug delivery material due to its excellent mechanical strength, chemical stability and flame resistance. The aim of this study was to investigate the influence of temperature, time and humidity during curing on mechanical strength and porosity of geopolymers.

    The geopolymer precursor paste was obtained by mixing metakaolin, waterglass and de-ionized water. The paste was molded into cylindrical rubber moulds (6  12 mm) and cured under different conditions: i.e. temperatures (ambient temperature, 37°C and 90°C), humidity and time (24, 48 and 96 hours). The compressive strength was determined using a universal testing machine. Helium pycnometer was used to measure the porosity. Via x-ray diffraction the phase composition of the cured samples was determined.

    Elongated curing slightly decreased the total porosity of the tested geopolymers. Higher curing temperature increased the compressive strength after 24 hour but did not affect strength for longer curing times. In general, the samples cured in moisture had higher mechanical strength than those cured in air. But low compression strength of samples cured under high temperature and long time showed that some water content in geopolymer was essential to retaining its microstructure.

    Place, publisher, year, edition, pages
    John Wiley & Sons, 2013
    Series
    Ceramic Engineering and Science Proceedings
    National Category
    Medical Materials
    Identifiers
    urn:nbn:se:uu:diva-219258 (URN)10.1002/9781118807743.ch5 (DOI)
    Conference
    37th International Conference and Expo on Advanced Ceramics and Composites; 27 Jan - 1 Feb 2013; Daytona Beach, Fia., USA
    Funder
    Swedish Research Council
    Available from: 2014-02-25 Created: 2014-02-25 Last updated: 2018-02-08Bibliographically approved
    2. Polymer excipients enable sustained drug release in low pH from mechanically strong inorganic geopolymers
    Open this publication in new window or tab >>Polymer excipients enable sustained drug release in low pH from mechanically strong inorganic geopolymers
    Show others...
    2012 (English)In: Results in Pharma Sciences, ISSN 2211-2863, Vol. 2, p. 23-28Article in journal (Refereed) Published
    Place, publisher, year, edition, pages
    Elsevier, 2012
    National Category
    Pharmaceutical Sciences Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-161811 (URN)10.1016/j.rinphs.2012.02.001 (DOI)
    Available from: 2011-11-17 Created: 2011-11-17 Last updated: 2018-11-05
    3. Evaluation of the resistance of a geopolymer-based drug delivery system to tampering
    Open this publication in new window or tab >>Evaluation of the resistance of a geopolymer-based drug delivery system to tampering
    2014 (English)In: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 465, no 1-2, p. 169-174Article in journal (Refereed) Published
    Abstract [en]

    Tamper-resistance is an important property of controlled-release formulations of opioid drugs. Tamper-resistant formulations aim to increase the degree of effort required to override the controlled release of the drug molecules from extended-release formulations for the purpose of non-medical use. In this study, the resistance of a geopolymer-based formulation to tampering was evaluated by comparing it with a commercial controlled-release tablet using several methods commonly used by drug abusers. Because of its high compressive strength and resistance to heat, much more effort and time was required to extract the drug from the geopolymer-based formulation. Moreover, in the drug-release test, the geopolymer-based formulation maintained its controlled-release characteristics after milling, while the drug was released immediately from the milled commercial tablets, potentially resulting in dose dumping. Although the tampering methods used in this study does not cover all methods that abuser could access, the results obtained by the described methods showed that the geopolymer matrix increased the degree of effort required to override the controlled release of the drug, suggesting that the formulation has improved resistance to some common drug-abuse tampering methods. The geopolymer matrix has the potential to make the opioid product less accessible and attractive to non-medical users.

    National Category
    Medical Materials
    Research subject
    Engineering Science with specialization in Materials Science
    Identifiers
    urn:nbn:se:uu:diva-219255 (URN)10.1016/j.ijpharm.2014.02.029 (DOI)000333675100022 ()
    Funder
    Swedish Research Council
    Available from: 2014-02-25 Created: 2014-02-25 Last updated: 2018-02-08Bibliographically approved
    4. Development and evaluation of a tampering resistant transdermal fentanyl patch
    Open this publication in new window or tab >>Development and evaluation of a tampering resistant transdermal fentanyl patch
    2015 (English)In: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 488, no 1-2, p. 102-107Article in journal (Refereed) Published
    Keywords
    Transdermal patch, Tamper-resistance, Geopolymer, Fentanyl, Abuse, Drug delivery
    National Category
    Ceramics Substance Abuse
    Identifiers
    urn:nbn:se:uu:diva-245029 (URN)10.1016/j.ijpharm.2015.04.061 (DOI)000355887100013 ()25913120 (PubMedID)
    Available from: 2015-02-24 Created: 2015-02-24 Last updated: 2018-02-08Bibliographically approved
    5. Self-setting bioceramic microscopic protrusions for transdermal drug delivery
    Open this publication in new window or tab >>Self-setting bioceramic microscopic protrusions for transdermal drug delivery
    2014 (English)In: Journal of materials chemistry. B, ISSN 2050-750X, E-ISSN 2050-7518, Vol. 2, no 36, p. 5992-5998Article in journal (Refereed) Published
    Abstract [en]

    Microneedle (MN) technology offers both an efficient and a minimally invasive transdermal drug delivery strategy. The current MNs, made of silicon and metal, have poor biocompatibility and low drug loading, while the polymer MNs have some constraints related to mechanical strength and storage conditions. In this study, self-setting bioceramics were explored as substitutes for the current MN materials for the first time. Self-setting bioceramic microneedles were fabricated using a master mold by a procedure under mild conditions, which could minimize the drug degradation during fabrication and also facilitates a higher drug loading capability than the other current ceramic microneedles. The drug release and mechanical strength were correlated with the microstructure and porosity of the needles. As observed by SEM and microCT, the ceramic paste could fully fill the geometry of the mould and was cured into an array of micro-sized needles. The drug release study showed that the release rate from this type of MN array could be controlled by the bulk surface area, porosity and resorption rate of the ceramic needles. Applying the MNs to porcine skin indicated that the needles were able to pierce the stratum corneum of the skin. We successfully prepared the bioceramic needles that have high mechanical strength and are resorbable, which can promote safe, efficient and successful transdermal drug delivery.

    National Category
    Bio Materials Engineering and Technology
    Research subject
    Engineering Science with specialization in Materials Science
    Identifiers
    urn:nbn:se:uu:diva-233125 (URN)10.1039/c4tb00764f (DOI)000341300300007 ()
    Conference
    microneedles 2014, Baltimore, May 19-21, 2014
    Available from: 2014-09-29 Created: 2014-09-29 Last updated: 2018-02-08
    6. Bioceramic microneedles with flexible and self-swelling substrate
    Open this publication in new window or tab >>Bioceramic microneedles with flexible and self-swelling substrate
    (English)Article in journal (Other academic) Submitted
    Keywords
    Microneedles; Bioceramics; Controlled-release; Skin penetration; Clonidine
    National Category
    Biomaterials Science Ceramics
    Identifiers
    urn:nbn:se:uu:diva-246404 (URN)
    Available from: 2015-03-06 Created: 2015-03-06 Last updated: 2018-02-08
  • 22.
    Cai, Bing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Bredenberg, Susanne
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Development and evaluation of a tampering resistant transdermal fentanyl patch2015In: International Journal of Pharmaceutics, ISSN 0378-5173, E-ISSN 1873-3476, Vol. 488, no 1-2, p. 102-107Article in journal (Refereed)
  • 23.
    Cai, Bing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Bredenberg, Susanne
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Aluminum release from geopolymer-based opioid formulation2014Conference paper (Refereed)
  • 24.
    Cai, Bing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Bredenberg, Susanne
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Evaluation of the effect of polymer content on drug release and mechanical strength of a geopolymer ER formulation for opioid drugs2014Conference paper (Refereed)
  • 25.
    Cai, Bing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Xia, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Bredenberg, Susanne
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Development and evaluation of self-setting bioceramic microneedles2014Conference paper (Refereed)
  • 26.
    Cai, Bing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Xia, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Bredenberg, Susanne
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Bioceramic microneedles with flexible and self-swelling substrateArticle in journal (Other academic)
  • 27.
    Chen, Song
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Cai, Yixiao
    Engqvist, Håkan
    Xia, Wei
    Controlling bioactivity of glass ionomer cement by incorporating calcium silicatesIn: Biomatter, ISSN 2159-2527, E-ISSN 2159-2535Article in journal (Refereed)
    Abstract
  • 28.
    Chen, Song
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Xia, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Glass Ionomer Cement Modified by White Portland Cement2014Conference paper (Refereed)
  • 29.
    Chen, Song
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Xia, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Handling and setting properties of a bioactive glass ionomer cement2015Conference paper (Refereed)
  • 30.
    Chen, Song
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Xia, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Synthesis and characterization of monetite with thin nacre-like structure2016Conference paper (Refereed)
  • 31.
    Chen, Song
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Xia, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Two Paste-type Glass Ionomer Cement2014Conference paper (Refereed)
  • 32.
    Chen, Song
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Gururaj, Satwik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Xia, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Synthesis of Ag doped calcium phosphate particles and their antibacterial effect as additives in dental glass ionomer cements2016In: Journal of materials science. Materials in medicine, ISSN 0957-4530, E-ISSN 1573-4838, Vol. 27, no 11, article id 172Article in journal (Refereed)
    Abstract [en]

    Developing dental restorations with enhanced antibacterial properties has been a constant quest for materials scientists. The aim of this study was to synthesize silver doped calcium phosphate particles and use them to improve antibacterial properties of conventional glass ionomer cement. The Ag doped monetite (Ag-DCPA) and hydroxyapatite (Ag-HA) were synthesized by precipitation method and characterized using X-ray diffraction, scanning electron microscope and X-ray fluorescence spectroscopy. The antibacterial properties of the cements aged for 1 day and 7 days were evaluated by direct contact measurement using staphylococcus epidermis Xen 43. Ion concentrations (F- and Ag+) and pH were measured to correlate to the results of the antibacterial study. The compressive strength of the cements was evaluated with a crosshead speed of 1 mm/min. The glass ionomer cements containing silver doped hydroxyapatite or monetite showed improved antibacterial properties. Addition of silver doped hydroxyapatite or monetite did not change the pH and ion release of F-. Concentration of Ag+ was under the detection limit (0.001 mg/L) for all samples. Silver doped hydroxyapatite or monetite had no effect on the compressive strength of glass ionomer cement.

  • 33.
    Engstrand, Johanna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Åberg, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Influence of water content on hardening and handling of a premixed calcium phosphate cement2013In: Materials science & engineering. C, biomimetic materials, sensors and systems, ISSN 0928-4931, E-ISSN 1873-0191, Vol. 33, no 1, p. 527-531Article in journal (Refereed)
    Abstract [en]

    Handling of calcium phosphate cements is difficult, where problems often arise during mixing, transferring tosyringes, and subsequent injection. Via the use of premixed cements the risk of handling complications is reduced. However, for premixed cements to work in a clinical situation the setting time needs to be improved. The objective of this study is to investigate the influence of the addition of water on the properties of premixed cement. Monetite-forming premixed cements with small amounts of added water (less than 6.8 wt.%) were prepared and the influence on injectability, working time, setting time and mechanical strength was evaluated. The results showed that the addition of small amounts of water had significant influence on the properties of the premixed cement. With the addition of just 1.7 wt.% water, the force needed to extrude the cement from a syringe was reduced from 107 (±15)N to 39 (±9)N, the compression strength was almost doubled, and the setting time decreased from 29 (±4)min to 19 (±2)min, while the working time remained 5 to 6 h. This study demonstrates the importance of controlling the water content in premixed cement pastes and how water can be used to improve the properties of premixed cements.

  • 34.
    Engstrand Unosson, Johanna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Persson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    An evaluation of methods to determine the porosity of calcium phosphate cements2015In: Journal of Biomedical Materials Research. Part B - Applied biomaterials, ISSN 1552-4973, E-ISSN 1552-4981, Vol. 103, no 1, p. 62-71Article in journal (Refereed)
    Abstract [en]

    The porosity of a material can be determined using a diversity of methods; however, the results from these methods have so far not been compared and analyzed for calcium phosphate cements (CPCs). The aim of this study was to compare a fast and easy method for porosity measurements with some commonly used porosity methods for CPCs. The investigated method is based on the assumption that when a wet cement sample is dried, the volume of the evaporated water is equal to the volume of pores within the cement. Moreover, different methods of drying the cements were evaluated for acidic CPCs. The results showed that drying at room temperature (22°C ±1°C) is preferable, since a phase transformation was observed at higher temperatures. The results also showed that drying for 24 hours in vacuum was sufficient to achieve water free cements. The porosity measured was found to vary between the porosity methods evaluated herein, and to get a complete picture of a cement’s porosity more than one method is recommended. Water evaporation, is, however, a fast and easy method to estimate the porosity of CPCs and could simplify porosity measurements in the future.

  • 35.
    Fu, Le
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Spark plasma sintered ZrO2-SiO2 glass ceramics and Si3N4 bioceramics2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis focuses on elaboration and characterization of two types of bioceramics: one is ZrO2-SiO2 nanocrystalline glass ceramic (NCGC) for dental application. The goal is to develop new ZrO2-SiO2 NCGCs with a combination of high strength and high translucency; the other is biodegradable Si3N4 ceramics for spinal fusion. This project aims to improve the osteointergration property of Si3N4 ceramics. Translucent glass ceramics typically suffer from impaired mechanical properties, compared to full-ceramics. We presented a method of obtaining ZrO2-SiO2 NCGCs, with a microstructure of monocrystalline ZrO2 nanoparticles (NPs), embedded in an amorphous SiO2 matrix. Raw powders containing different ZrO2 contents were prepared by the sol-gel method, followed by the spark plasma sintering (SPS). The NCGC with a composition of 35%ZrO2-65%SiO2 (molar ratio, 35Zr) was transparent. Tetragonal ZrO2 NPs were spherical with a diameter of 20–40 nm. The average flexural strength of 35Zr NCGC was 234 MPa. To improve the flexural strength, NCGCs with compositions of 45%ZrO2-55%SiO2 (45Zr), 55%ZrO2-45%SiO2 (55Zr), 65%ZrO2-35%SiO2 (65Zr) were also elaborated. All NCGCs showed high translucency. The flexural strength of the NCGCs significantly increased with the increase of ZrO2 content, achieving as high as 1014 MPa for 65Zr NCGC.  ZrO2 NPs in 65Zr NCGC were ellipsoidal and had a core-shell structure with a thin Zr/Si interfacial layer as the shell. Some of the ZrO2 NPs were connected and formed ZrOnanofibers. Moreover, the ZrOnanofibers were orderly stacked in short-range to form the 3D nano-architecture. The high flexural strength of the 65Zr NCGC mainly originates from synergistic strengthening effects of the thin Zr/Si interfacial layer and 3D stacked nano-architecture. Regarding biodegradable Si3N4 bioceramics, we used a ternary sintering additive of SrO, MgO and SiO2.   The mechanical properties of the developed Si3N4 bioceramics were comparable to those of traditional Si3N4 ceramics. Sr2+, Mg2+, and Si4+ ions released from the intergranular glass phase after immersion in solution, indicating that the developed Si3N4 bioceramics showed certain biodegradable ability. These ions enhanced the proliferation and differentiation of preosteoblasts. Meanwhile, the ionic dissolution products did not show any toxic effects to the development or physiology of zebrafish embryos.

    List of papers
    1. Transparent single crystalline ZrO2-SiO2 glass nanoceramic sintered by SPS
    Open this publication in new window or tab >>Transparent single crystalline ZrO2-SiO2 glass nanoceramic sintered by SPS
    Show others...
    2016 (English)In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 36, no 14, p. 3487-3494Article in journal (Refereed) Published
    Abstract [en]

    Transparent ZrO2-SiO2 glass ceramics show potential for application in the dental industry. The application of this material prepared by a sol-gel method was hindered by the difficulties in obtaining large dimension samples. Spark plasma sintering (SPS) offers the possibility of achieving transparent ZrO2-SiO2 glass ceramics. In this study, a ZrO2-SiO2 powder was prepared by the sol-gel method and subsequently sintered by SPS. Varied sintering temperatures and pressures were explored to achieve better mechanical strength and transparency. TEM results showed single crystalline ZrO2 spherical nanocrystals (approximately 20 nm) homogenously embedded in the SiO2 matrix. Tetragonal ZrO2 was the only crystalline phase in all specimens. With sintering conditions of 1200 degrees C and 30 MPa, a glass ceramic with fracture toughness of 4.13 MPa was obtained. This value is similar to the commercial dental glass ceramic of IPS e.max (R) Press. The studied transparent glass ceramic with high transparency and moderate mechanical strength shows promise for dental application.

    Keywords
    ZrO2-SiO2, Single crystalline spheres, Transparent glass ceramic, SPS, Sol-gel
    National Category
    Materials Engineering
    Identifiers
    urn:nbn:se:uu:diva-301007 (URN)10.1016/j.jeurceramsoc.2016.05.016 (DOI)000379888400029 ()
    External cooperation:
    Funder
    Carl Tryggers foundation
    Available from: 2016-08-17 Created: 2016-08-17 Last updated: 2018-08-12Bibliographically approved
    2. Highly translucent and strong ZrO2-SiO2 nanocrystalline glass ceramicprepared by sol-gel method and spark plasma sintering with fine 3Dmicrostructure for dental restoration
    Open this publication in new window or tab >>Highly translucent and strong ZrO2-SiO2 nanocrystalline glass ceramicprepared by sol-gel method and spark plasma sintering with fine 3Dmicrostructure for dental restoration
    2017 (English)In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 37, p. 4067-4081Article in journal (Refereed) Published
    Abstract [en]

    Balance of better mechanical strength and good translucency for dental restorative materials is alwaysa challenge. A translucent glass ceramic/ceramic with improved mechanical properties or a strongglass ceramic/ceramic with good translucency would therefore be interesting for dental application.Nanocrystalline glass ceramics (NCGC) attract a lot attention because of their superior optical andmechanical properties. This study aims to obtain ZrO2-SiO2 nanocrystalline glass-ceramic that possesseshigh mechanical strength as well as excellent translucency by controlling the content, size, and connectionof nanocrystalline ZrO2 in a ZrO2-SiO2 glass-ceramic material. Toward this end, well-homogenized nano-powders with three different compositions, 45%ZrO2-55%SiO2 (molar ratio, 45Zr), 55%ZrO2-45%SiO2(55Zr), and 65%ZrO2-35%SiO2 (65Zr), were synthesized, followed by a fast sintering process. Highly-translucent nanocrystalline glass ceramics composed of tetragonal ZrO2 were obtained. Samples withhigh zirconia content showed that the structure of the skeleton was predominately built by nano-sizedellipsoidal ZrO2 particles bonded by grain boundaries, with amorphous SiO2 filling the voids betweenthe ZrO2 particles. The achieved flexural strength measured by piston-on-three-ball test was as high as1014 MPa. To our knowledge, this is one of the highest flexural strength values of glass ceramics everreported, which is higher than transparent zirconia and alumina ceramics. The 3D structure of nanocrys-talline zirconia in silica matrix did enhance the flexural strength of the NCGC. The results of this studysuggest that the new ZrO2-SiO2 NCGC has great potential of using as dental restoration.

    Keywords
    Nanocrystalline glass ceramics, ZrO2-SiO2, Translucency, High strength, 3D microstructure
    National Category
    Physical Sciences Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-330141 (URN)10.1016/j.jeurceramsoc.2017.05.039 (DOI)
    Funder
    Carl Tryggers foundation
    Available from: 2017-09-26 Created: 2017-09-26 Last updated: 2018-08-12
    3. Ultrastrong translucent glass ceramic with nanocrystalline, biomimetic structure
    Open this publication in new window or tab >>Ultrastrong translucent glass ceramic with nanocrystalline, biomimetic structure
    Show others...
    2018 (English)In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 18, no 11, p. 7146-7154Article in journal (Refereed) Published
    Abstract [en]

    Transparent/translucent glass ceramics (GCs) have broad applications in biomedicine, armor, energy, and constructions. However, GCs with improved optical properties typically suffer from impaired mechanical properties, compared to traditional sintered full-ceramics. We present a method of obtaining high-strength, translucent GCs by preparing ZrO2-SiO2 nanocrystalline glass ceramics (NCGCs), with a microstructure of monocrystalline ZrO2 nanoparticles (NPs), embedded in an amorphous SiO2 matrix. The ZrO2-SiO2 NCGC with a composition of 65%ZrO2-35%SiO2 (molar ratio, 65Zr) achieved an average flexural strength of 1 GPa. This is one of the highest flexural strength values ever reported for GCs. ZrO2 NPs have a core-shell structure, and the shell is a thin (2–3 nm) amorphous Zr/Si interfacial layer that provides strong bonding between the ZrO2 NPs and SiO2 matrix. The diffusion of Si atoms into the ZrO2 NPs forms a Zr-O-Si superlattice. Electron tomography results show that some of the ZrO2 NPs are connected in one direction, forming in situ ZrO2 nanofibers (with length of ~500 nm), and that the ZrO2 nanofibers are stacked in an ordered way in all three dimensions. The nano-architecture of the ZrO2 nanofibers mimics the architecture of mineralized collagen fibril in cortical bone. Strong interface bonding enables efficient load transfer from the SiO2 matrix to the 3D nano-architecture built by ZrO2 nanofibers and NPs, and the 3D nano-architecture carries the majority of the external load. These two factors synergistically contribute to the high strength of the 65Zr NCGC. This study deepens our fundamental understanding of the microstructure-mechanical strength relationship, which could guide the design and manufacture of other high-strength, translucent GCs.

    Keywords
    glass ceramic, translucency, high strength, biomimetic structure, 3D nano-architecture
    National Category
    Nano Technology
    Identifiers
    urn:nbn:se:uu:diva-356884 (URN)10.1021/acs.nanolett.8b03220 (DOI)000451102100065 ()30335389 (PubMedID)
    Funder
    Carl Tryggers foundation
    Note

    Le Fu and Ling Xie contributed to this work equally and are co-first authors

    Available from: 2018-08-08 Created: 2018-08-08 Last updated: 2018-12-21Bibliographically approved
    4. Spark plasma sintering of biodegradable Si3N4 bioceramic with Sr, Mg and Si as sintering additives for spinal fusion
    Open this publication in new window or tab >>Spark plasma sintering of biodegradable Si3N4 bioceramic with Sr, Mg and Si as sintering additives for spinal fusion
    2018 (English)In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 38, no 4, p. 2110-2119Article in journal (Refereed) Published
    Abstract [en]

    Silicon nitride (Si3N4) bioceramics with standard sintering additives (Al2O3 and Y2O3) are used in spinal fusion. Alternative Si3N4 bioceramics with biologically beneficial sintering additives could lead to improved osseoin- tegrative properties. The aim of this study is to obtain dense and strong Si3N4 bioceramics by using SrO, MgO and SiO2 as sintering additives, and evaluate the effect of these sintering additives on microstructures and properties of Si3N4 bioceramics. Raw powders with 10 wt% and 18 wt% sintering additives were sintered by spark plasma sintering. Samples sintered at 1750 °C, with an applied pressure of 60 MPa and a holding time of 3 min, showed the highest content of β-Si3N4 (94.9%). The mechanical properties of the developed Si3N4 bio- ceramics are comparable to the mechanical properties of currently used structural Si3N4 ceramics sintered with standard sintering additives (Al2O3 and Y2O3). The highest flexural strength of the developed Si3N4 bioceramics reached 1079 MPa. Ion release results showed that Sr2+,Mg2+ and Si4+ ions kept leaching out within 10 days’ immersion. The degradable Si3N4 bioceramics with adequate strength and biologically beneficial sintering ad- ditives show the promise for load bearing biomedical applications, such as spinal fusion.

    National Category
    Natural Sciences Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-331879 (URN)10.1016/j.jeurceramsoc.2017.10.003 (DOI)000424716700136 ()
    Funder
    Carl Tryggers foundation
    Available from: 2017-10-19 Created: 2017-10-19 Last updated: 2018-08-12Bibliographically approved
    5. Biodegradable Si3N4 bioceramic sintered with Sr, Mg and Si for spinal fusion: Surface characterization and biological evaluation
    Open this publication in new window or tab >>Biodegradable Si3N4 bioceramic sintered with Sr, Mg and Si for spinal fusion: Surface characterization and biological evaluation
    Show others...
    2018 (English)In: Applied Materials Today, ISSN 2352-9407, Vol. 12, p. 260-275Article in journal (Refereed) Published
    Abstract [en]

    Silicon nitride (Si3N4) is an industrial ceramic used in spinal fusion and maxillofacial reconstructionbecause of its excellent mechanical properties and good biocompatibility. This study compares the sur-face properties, apatite formation ability, bacterial infection, cell-biomaterial interactions, and in vivotoxicity (zebrafish) of newly developed Si3N4 bioceramics (sintered with bioactive sintering additivesSrO, MgO and SiO2) with two standard biomaterials; titanium (Ti) and traditional Si3N4 bioceramics (sin-tered with standard sintering additives Al2O3 and Y2O3). In general, Si3N4 bioceramics (both the newlydeveloped and the traditional) displayed less in vitro bacterial affinity than Ti, which may arise fromdifferences in the surface properties between these two types of material. The newly developed Si3N4bioceramics developed lower biofilm coverage and thinner biofilm, compared to traditional Si3N4 bioce-ramics. The effects of ionic dissolution products (leach) on proliferation and differentiation of MC3T3-E1cell were also investigated. Ionic dissolution products containing moderate amount of Sr, Mg and Siions (approximately 4.72 mg/L, 3.26 mg/L and 3.67 mg/L, respectively) stimulated osteoblast prolifera-tion during the first 2 days in culture. Interestingly, ionic dissolution products from the traditional Si3N4bioceramics that contained small amount of Si and Y ions achieved the greatest stimulatory effect foralkaline phosphatase activity after 7 days culture. The toxicity of ionic dissolution products was investi-gated in a putative developmental biology model: zebrafish (Danio rerio). No toxicity, or developmentalabnormalities, was observed in zebrafish embryos exposed to ionic dissolution products, for up to 144 hpost fertilization. These newly developed Si3N4 bioceramics with bioactive sintering additives show greatpotential as orthopedic implants, for applications such as spinal fusion cages. Future work will focus onevaluation of the newly developed Si3N4 bioceramics using a large animal model.

    Keywords
    Si3N4 bioceramic, Spinal fusion, Biocompatibility, Bioactive ions, Zebrafish
    National Category
    Medical Materials
    Identifiers
    urn:nbn:se:uu:diva-356522 (URN)10.1016/j.apmt.2018.06.002 (DOI)000443213700023 ()
    Funder
    Carl Tryggers foundation
    Available from: 2018-07-30 Created: 2018-07-30 Last updated: 2019-06-26Bibliographically approved
  • 36.
    Fu, Le
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Andersson, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Unosson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Xia, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Influence of alkali metal additives on phase transition of translucent ZrO2/SiO2 glass ceramics prepared by a sol-gel method2015In: European Cells and Materials, ISSN 1473-2262, E-ISSN 1473-2262, Vol. 29Article in journal (Refereed)
  • 37.
    Fu, Le
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Xia, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Highly translucent and strong ZrO2-SiO2 nanocrystalline glass ceramic prepared by sol-gel method and spark plasma sintering with fine 3D microstructure for dental restoration2017In: Journal of the European Ceramic Society, ISSN 0955-2219, E-ISSN 1873-619X, Vol. 37, no 13, p. 4067-4081Article in journal (Refereed)
    Abstract [en]

    Balance of better mechanical strength and good translucency for dental restorative materials is always a challenge. A translucent glass ceramic/ceramic with improved mechanical properties or a strong glass ceramic/ceramic with good translucency would therefore be interesting for dental application. Nanocrystalline glass ceramics (NCGC) attract a lot attention because of their superior optical and mechanical properties. This study aims to obtain ZrO2-SiO2 nanocrystalline glass-ceramic that possesses high mechanical strength as well as excellent translucency by controlling the content, size, and connection of nanocrystalline ZrO2 in a ZrO2-SiO2 glass-ceramic material. Toward this end, well-homogenized nano powders with three different compositions, 45%ZrO2-55%SiO2 (molar ratio, 45Zr), 55%ZrO2-45%SiO2 (55Zr), and 65%ZrO2-35%SiO2 (65Zr), were synthesized, followed by a fast sintering process. Highly translucent nanocrystalline glass ceramics composed of tetragonal ZrO2 were obtained. Samples with high zirconia content showed that the structure of the skeleton was predominately built by nano-sized ellipsoidal ZrO2 particles bonded by grain boundaries, with amorphous SiO2 filling the voids between the ZrO2 particles. The achieved flexural strength measured by piston-on-three-ball test was as high as 1014 MPa. To our knowledge, this is one of the highest flexural strength values of glass ceramics ever reported, which is higher than transparent zirconia and alumina ceramics. The 3D structure of nanocrystalline zirconia in silica matrix did enhance the flexural strength of the NCGC. The results of this study suggest that the new ZrO2-SiO2 NCGC has great potential of using as dental restoration.

  • 38.
    Gallinetti, Sara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Öhman Mägi, Caroline
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Characterization of multiphasic calcium phosphate cements with improved degradation rate2016Conference paper (Refereed)
  • 39.
    Gallinetti, Sara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Öhman Mägi, Caroline
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Long-term degradation of novel multiphasic calcium phosphate cements2017Conference paper (Refereed)
  • 40.
    Gallinetti, Sara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Öhman-Mägi, Caroline
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Micro-CT as a tool to study crack initiation and propagation in ceramic bone cements2018Conference paper (Refereed)
  • 41.
    Hans, Marcus
    et al.
    Rhein Westfal TH Aachen, Mat Chem, Aachen, Germany.
    Patterer, Lena
    Rhein Westfal TH Aachen, Mat Chem, Aachen, Germany.
    Music, Denis
    Rhein Westfal TH Aachen, Mat Chem, Aachen, Germany.
    Holzapfel, Damian M.
    Rhein Westfal TH Aachen, Mat Chem, Aachen, Germany.
    Evertz, Simon
    Rhein Westfal TH Aachen, Mat Chem, Aachen, Germany.
    Schnabel, Volker
    Rhein Westfal TH Aachen, Mat Chem, Aachen, Germany.
    Stelzer, Bastian
    Rhein Westfal TH Aachen, Mat Chem, Aachen, Germany.
    Primetzhofer, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Voelker, Bernhard
    Rhein Westfal TH Aachen, Mat Chem, Aachen, Germany; Max Planck Inst Eisenforsch GmbH, Dusseldorf, Germany.
    Widrig, Beno
    Oerlikon Surface Solut AG, Oerlikon Balzers, Balzers, Liechtenstein.
    Eriksson, Anders O.
    Oerlikon Surface Solut AG, Oerlikon Balzers, Balzers, Liechtenstein.
    Ramm, Juergen
    Oerlikon Surface Solut AG, Oerlikon Balzers, Balzers, Liechtenstein.
    Arndt, Mirjam
    Oerlikon Surface Solut AG, Oerlikon Balzers, Balzers, Liechtenstein.
    Rudigier, Helmut
    Oerlikon Surface Solut AG, Oerlikon Balzers, Pfaffikon, Switzerland.
    Schneider, Jochen M.
    Rhein Westfal TH Aachen, Mat Chem, Aachen, Germany.
    Stress-Dependent Elasticity of TiAlN Coatings2019In: Coatings, ISSN 2079-6412, Vol. 9, no 1, article id 24Article in journal (Refereed)
    Abstract [en]

    We investigate the effect of continuous vs. periodically interrupted plasma exposure during cathodic arc evaporation on the elastic modulus as well as the residual stress state of metastable cubic TiAlN coatings. Nanoindentation reveals that the elastic modulus of TiAlN grown at floating potential with continuous plasma exposure is 7%-11% larger than for coatings grown with periodically interrupted plasma exposure due to substrate rotation. In combination with X-ray stress analysis, it is evident that the elastic modulus is governed by the residual stress state. The experimental dependence of the elastic modulus on the stress state is in excellent agreement with ab initio predictions. The macroparticle surface coverage exhibits a strong angular dependence as both density and size of incorporated macroparticles are significantly lower during continuous plasma exposure. Scanning transmission electron microscopy in combination with energy dispersive X-ray spectroscopy reveals the formation of underdense boundary regions between the matrix and TiN-rich macroparticles. The estimated porosity is on the order of 1% and a porosity-induced elastic modulus reduction of 5%-9% may be expected based on effective medium theory. It appears reasonable to assume that these underdense boundary regions enable stress relaxation causing the experimentally determined reduction in elastic modulus as the population of macroparticles is increased.

  • 42.
    Khaji, Zhara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Sturesson, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Klintberg, Lena
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Extending Microsensor Technology to Very High Temperatures2014Conference paper (Other academic)
  • 43.
    Koh, Ilsoo
    et al.
    ETH, Inst Biomech, HPP-O14,Honggerbergring 64, CH-8093 Zurich, Switzerland;ETH, Lab Surface Sci & Technol, Zurich, Switzerland.
    Gombert, Yvonne
    ETH, Inst Biomech, HPP-O14,Honggerbergring 64, CH-8093 Zurich, Switzerland.
    Persson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Helgason, Benedikt
    ETH, Inst Biomech, HPP-O14,Honggerbergring 64, CH-8093 Zurich, Switzerland.
    Ferguson, Stephen J.
    ETH, Inst Biomech, HPP-O14,Honggerbergring 64, CH-8093 Zurich, Switzerland.
    Ceramic cement as a potential stand-alone treatment for bone fractures: an in vitro study of ceramic-bone composites2016In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 61, p. 519-529Article in journal (Refereed)
    Abstract [en]

    Background: A vertebral burst fracture (VBF) treated with vertebroplasty using a ceramic cement consists of four regions; native bone fragments, native ceramic cement, ceramic cement-trabecular bone (ceramic-bone) composite and ceramic-bone interface. Although the mechanical properties of native bone and native ceramic cements have been well investigated, the mechanical properties of ceramic-bone composite and ceramic-bone interface remain unknown. Therefore, the aim of this study was to determine the mechanical properties of ceramic-bone composites and ceramic-bone interfaces. Two types of ceramic cement, calcium aluminate (CAC) with (w/F) and without (wo/F) fiber reinforcement, were investigated. Methods: Ceramic-bone composite (Full, wo/F and w/F) and ceramic-bone interface (Fract, wo/F and w/F) groups were tested to determine their compressive and tensile properties. While a continuous bone cylinder was used for samples in the Full groups, each bone cylinder for the samples in the Fract groups contained a 3 mm geometrical discontinuity to mimic the fracture gaps in VBFs. Two Cement groups (wo/F and w/F) and a Bone group were included in the study as controls. Micro-CT images were used to determine the bone morphological parameters, as potential predictors of the mechanical properties of Full and Fract groups. Results: The compressive strengths of Full and Fract groups were substantially lower than native CAC, but higher than bone. The tensile strength of the Full group was equal to bone, while the tensile strength of the Fract group was equivalent to CAC. Variable relationships between the bone morphological parameters and mechanical properties of Full and Fract groups were observed. Fiber reinforcement at an injectable level had a minimal influence on the mechanical properties. Conclusions: CAC augmentation does not provide adequate stabilization of bone fragments. The interface between bone and cement represents a weak point. The effect of cement augmentation cannot be predicted by bone morphological properties.

  • 44.
    Larsson, Niklas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Gradient formation in cemented carbides with 85Ni:15Fe-binder phase2015Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In today’s inserts used for metal cutting the binder phase consists of cobalt (Co).However, EU’s REACH programme and the U.S’s National Toxicity Programme(NTP) classified Co as toxic/carcinogenic. Therefore, there is a strong need toinvestigate alternative binder phases. This thesis covers sintering and characterisationof cemented carbide with a binder phase consisting of nickel (Ni) and iron (Fe) withthe composition of 85Ni:15Fe. The aim was to study the gradient formation of turninginsert and find sintering processes to achieve a gradient structure with the targetedthickness of 26 microns.

    Simulations in ThermoCalc provided a suitable composition and a starting point forsintering parameters. The influences of sintering process parameters, such as holdingtime, temperature and counter pressure on the formation of the gradient zone wereinvestigated. Hot isostatic pressing (HIP) sintering was done in order to study thegradient formation as well as to reduce the porosity when needed. Sintered insertswere analysed by light optical microscopy.

    It was found that there are at least three possible ways to control the formation ofthe gradient: sintering in vacuum with a holding time of 20 min at 1450°C, sintering at1450°C with a counter pressure of 5 mbar nitrogen, and sintering with a counterpressure of 11.5 mbar followed by a double sinter-hip with 55 bar argon atmosphere.However, only the last process fulfilled the microstructure criteria in terms ofporosity and binder phase distribution. It is clear that the formation of gradient zonesin 85Ni:15Fe can be predicted, however calculations and simulations need to beoptimized in order to get more accurate results.

  • 45.
    Lekholm, Ville
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Palmer, Kristoffer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Ericson, Fredric
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Ceramic cold gas microthruster with integrated flow sensor2011In: PowerMEMS 2011 Technical digest: The 11th International Workshop on Micro and Nanotechnology for Power Generation and Energy Conversion Applications / [ed] Young-Ho Cho, Daejeon, Republic of Korea: Cell Bench Research Center, KAIST , 2011, p. 167-170Conference paper (Refereed)
    Abstract [en]

    For aggressive environments, the material properties of silicon become a limitation. Macroscopically, ceramics are as common for high-temperature applications as is silicon in miniaturized systems, but this group of materials has been little exploited for MEMS components. This paper describes the  design, manufacturing and characterization of a ceramic, heated cold-gas microthruster with integrated flow sensor, using HTCC processing and silicon tools. The calorimetric flow sensor is integrated in the structure, and heaters are embedded in the stagnation chamber of the nozzle. The heater was shown to improve the efficiency of the thruster, as confirmed by measurements of the flow rate. Flow rate changes were seen as changes in resistance of the fabricated flow sensor. The choice of yttria stabilized zirconia as material for the components make them robust and capable of withstanding  very high temperatures. Samples have been shown  capable of achieving temperatures locally exceeding 1000ºC.

  • 46.
    Liu, Yang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. Harbin Institute of Technology.
    Zhang, mingfu
    Harbin Institute of Technology.
    Wu, Dan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wang, Tao
    Harbin Institute of Technology.
    Ying, Nie
    Harbin Institute of Technology.
    Han, Jiecai
    Harbin Institute of Technology.
    Xia, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Microstructures and mechanical properties of Al2O3/YAG:Ce3+ eutectics with different Ce3+concentrations grown by HDS method2019In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669Article in journal (Refereed)
  • 47.
    Luo, Jun
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Calcium Phosphate Based Biomaterials for Bone Augmentation2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Basic (apatite-based) calcium phosphate cements (CPCs), and acidic (brushite and monetite-based) CPCs are used as bone replacement materials because of their bioactivity, mouldability and ability to harden in place. However, their application is limited by their inherent brittleness and difficulties related to their handling. The current thesis aimed to provide solutions to these limitations.

    To assess the baseline, the mechanical properties of two promising experimental and two commercially available apatite and brushite cements were investigated. The two experimental CPCs exhibited significantly higher mechanical strengths than the two commercially available ones, warranting further advancement of the former towards clinical use.

    The setting reaction of brushite cements was, for the first time, quantitatively studied in the first seconds and minutes, using synchrotron X-ray diffraction. The reaction was found to include a fast nucleation induction period (<9 s), nucleation (<18 s), brushite content increase and setting completion. The effect of the commonly used retardant citric acid – which usually also gives stronger brushite cements - was also evaluated, providing important information for further cement development.  

    To overcome complicated usage and short shelf life of acidic CPCs, a ready-to-use acidic CPC was developed by mixing a monocalcium phosphate monohydrate (MCPM) paste and a β-tricalcium phosphate (β-TCP) paste with suitable amounts of citric acid. The CPC showed adequate shelf life, good cohesion and mechanical performance.

    To mitigate against the brittle behavior of CPCs, i) poly(vinyl alcohol) fibres were used to reinforce apatite cements, significantly improving the apatite matrix’s toughness and resistance to cracking; ii) injectable, ready-to-use organic-inorganic composites with partly elastomeric compression behavior were designed based on silk fibroin hydrogels and acidic calcium phosphates, and their ability for antibiotic drug delivery was assessed. 

    In summary, insights into the functional properties of currently available CPCs as well as the setting process of brushite cements were gained and several new calcium phosphate-based formulations were developed to overcome some of the drawbacks of traditional CPCs. Further studies, in particular of the biological response, are needed to verify the potential of the developed materials for future use in the clinical setting. 

     

    List of papers
    1. Compressive, diametral tensile and biaxial flexural strength of cutting-edge calcium phosphate cements
    Open this publication in new window or tab >>Compressive, diametral tensile and biaxial flexural strength of cutting-edge calcium phosphate cements
    Show others...
    2016 (English)In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 60, p. 617-627Article in journal (Refereed) Published
    Abstract [en]

    Calcium phosphate cements (CPCs) are widely used in bone repair. Currently there are two main types of CPCs, brushite and apatite. The aim of this project was to evaluate the mechanical properties of particularly promising experimental brushite and apatite formulations in comparison to commercially available brushite- and apatite-based cements (chronOS Inject and Norian® SRS®, respectively), and in particular evaluate the diametral tensile strength and biaxial flexural strength of these cements in both wet and dry conditions for the first time. The cements׳ porosity and their compressive, diametral tensile and biaxial flexural strength were tested in wet (or moist) and dry conditions. The surface morphology was characterized by scanning electron microscopy. Phase composition was assessed with X-ray diffraction. It was found that the novel experimental cements showed better mechanical properties than the commercially available cements, in all loading scenarios. The highest compressive strength (57.2±6.5 MPa before drying and 69.5±6.0 MPa after drying) was found for the experimental brushite cement. This cement also showed the highest wet diametral tensile strength (10.0±0.8 MPa) and wet biaxial flexural strength (30.7±1.8 MPa). It was also the cement that presented the lowest porosity (approx. 12%). The influence of water content was found to depend on cement type, with some cements showing higher mechanical properties after drying and some no difference after drying.

    Keywords
    Calcium phosphate cement; Brushite; Apatite; Compressive strength; Tensile strength; Flexural strength
    National Category
    Ceramics
    Identifiers
    urn:nbn:se:uu:diva-284218 (URN)10.1016/j.jmbbm.2016.03.028 (DOI)000378969100055 ()27082025 (PubMedID)
    Funder
    The Swedish Foundation for International Cooperation in Research and Higher Education (STINT), IG2011-2047Swedish Research Council, 621-2011-6258
    Available from: 2016-04-15 Created: 2016-04-15 Last updated: 2018-08-10Bibliographically approved
    2. In-situ Synchrotron X-ray Diffraction Analysis of the Setting Process of Brushite Cement: Reaction and Crystal Growth
    Open this publication in new window or tab >>In-situ Synchrotron X-ray Diffraction Analysis of the Setting Process of Brushite Cement: Reaction and Crystal Growth
    Show others...
    2017 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 41, p. 36392-36399Article in journal (Refereed) Published
    Abstract [en]

    Brushite cements are fast self-setting materials that can be used as bone substitute materials. Although tracing their fast setting process is a challenge, it is important for the understanding of the same, which in turn is important for the material’s further development and use in the clinics. In this study, the setting rate, phase formation, and crystal growth of brushite cements were quantitatively studied by in situ synchrotron powder X-ray diffraction (SXRD) on a time scale of seconds. The influence of reactant ratios and a retardant (citric acid) on the setting reaction were analyzed. To complement the in situ investigations, scanning electron microscopy was carried out for ex situ morphological evolution of crystals. The initial reaction followed a four-step process, including a fast nucleation induction period, nucleation, crystal growth, and completion of the setting. The brushite crystal size grew up to the micro scale within 1 min, and the brushite content increased linearly after the nucleation until all monocalcium phosphate monohydrate (MCPM; Ca(H2PO4)2·H2O) had dissolved within minutes, followed by a slow increase until the end of the monitoring. By adjusting the MCPM to the β-tricalcium phosphate (β-TCP, β-Ca3(PO4)2) ratio in the starting powders, the brushite/monetite ratio in the cements could be modified. In the presence of citric acid, the formation of brushite nuclei was not significantly retarded, whereas the increase in brushite content and the growth of crystal size were effectively hindered. The amount of monetite also increased by adding citric acid. This is the first time that the brushite setting process has been characterized in the first seconds and minutes of the reaction by SXRD.

    Keywords
    synchrotron X-ray diffraction, setting reaction process, brushite cement, crystal size, citric acid, MCPM/β-TCP ratio
    National Category
    Engineering and Technology Medical Materials Biomaterials Science
    Research subject
    Engineering Science with specialization in Materials Science
    Identifiers
    urn:nbn:se:uu:diva-330146 (URN)10.1021/acsami.7b10159 (DOI)000413503700092 ()
    Available from: 2017-09-26 Created: 2017-09-26 Last updated: 2018-08-10Bibliographically approved
    3. A ready-to-use acidic calcium phosphate cement
    Open this publication in new window or tab >>A ready-to-use acidic calcium phosphate cement
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Premixed calcium phosphate cements have been developed to simplify the usage of traditional calcium phosphate cements and reduce the influence of the setting reaction on the delivery process. However, difficulties in achieving a good cohesion, adequate shelf life and sufficient mechanical properties have so far impeded their use in clinical applications, especially for the more degradable acidic calcium phosphate cements.

    In this study, a brushite cement was developed from a series of ready-to-use calcium phosphate pastes. The brushite cement paste was formed via mixing of a monocalcium phosphate monohydrate (MCPM) paste and a β-tricalcium phosphate (β-TCP) paste with good injectability and adequate shelf life. The MCPM paste was based on a water-immiscible liquid with two surfactants and the β-TCP paste on a sodium hylauronate aqueous solution. The effect of citric acid as a retardant was assessed. Formulations with suitable amounts of citric acid showed good cohesion and mechanical performance with potential for future clinical applications.

    Keywords
    Ready-to-use, acidic calcium phosphate cement, brushite, cohesion, injectability, shelf life
    National Category
    Ceramics
    Identifiers
    urn:nbn:se:uu:diva-356978 (URN)
    Available from: 2018-08-09 Created: 2018-08-09 Last updated: 2018-08-10
    4. The addition of poly(vinyl alcohol) fibres to apatitic calcium phosphate cement can improve its toughness
    Open this publication in new window or tab >>The addition of poly(vinyl alcohol) fibres to apatitic calcium phosphate cement can improve its toughness
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Calcium phosphate cements, and in particular hydroxyapatite cements, have been widely investigated for use as bone void fillers due to their chemical similarity to bone and related osteoconductivity. However, they are brittle, which limits their use to non-load-bearing applications.

    The aim of the current study was to improve the toughness of hydroxyapatite cements through fibre reinforcement. The effect of the addition of hydrophilic, poly(vinyl-alcohol) (PVA) fibres to hydroxyapatite cement was evaluated in terms of mechanical properties, including compressive strength, diametral tensile strength and toughness (work of fracture), as well as setting time, phase composition and cement morphology. The fibre reinforcement enhanced the fracture resistance of the hydroxyapatite cement, but also simultaneously reduced the compressive strength and setting time of the cements. However, cement with 5 wt% of fibres (of powder component) could be considered a good compromise, with a compressive strength of 46.5 ± 4.6 MPa (compared to 62.3 ± 12.8 MPa of that without fibres), i.e. still much greater than that of human trabecular bone (0.1-14 MPa). A significantly higher diametral tensile strength (9.2 ± 0.4 MPa) was found for this cement compared to that without fibres (7.4 ± 1.5 MPa). The work of fracture increased four times to 9.1 ± 1.5 kJ/m2 in comparison to the pristine apatite. In summary, the hydroxyapatite cements could be reinforced by suitable amounts of PVA fibres, which resulted in enhancing the material’s structural integrity and ductility, and increased the material’s resistance to cracking.

    Keywords
    fibre reinforcement, apatite cement, poly(vinyl alcohol), composite, compressive strength, work of fracture, diametral tensile strength, toughness
    National Category
    Ceramics
    Identifiers
    urn:nbn:se:uu:diva-356979 (URN)
    Available from: 2018-08-09 Created: 2018-08-09 Last updated: 2018-08-10
    5. Silk fibroin hydrogels induced and reinforced by acidic calcium phosphate – A simple way of producing injectable, bioactive and drug-loadable composites for biomedical applications
    Open this publication in new window or tab >>Silk fibroin hydrogels induced and reinforced by acidic calcium phosphate – A simple way of producing injectable, bioactive and drug-loadable composites for biomedical applications
    (English)Manuscript (preprint) (Other academic)
    Keywords
    silk fibroin, acidic calcium phosphates, composites, hydrogels, mechanical strength, drug-loadable
    National Category
    Ceramics Composite Science and Engineering
    Identifiers
    urn:nbn:se:uu:diva-356991 (URN)
    Available from: 2018-08-10 Created: 2018-08-10 Last updated: 2018-08-10
  • 48.
    Luo, Jun
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Ajaxon, Ingrid
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Ginebra, Maria Pau
    Research Centre in Biomedical Engineering, Biomaterials Division, Department of Materials Science and Metallurgy, Technical University of Catalonia (UPC).
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Persson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Compressive, diametral tensile and biaxial flexural strength of cutting-edge calcium phosphate cements2016In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 60, p. 617-627Article in journal (Refereed)
    Abstract [en]

    Calcium phosphate cements (CPCs) are widely used in bone repair. Currently there are two main types of CPCs, brushite and apatite. The aim of this project was to evaluate the mechanical properties of particularly promising experimental brushite and apatite formulations in comparison to commercially available brushite- and apatite-based cements (chronOS Inject and Norian® SRS®, respectively), and in particular evaluate the diametral tensile strength and biaxial flexural strength of these cements in both wet and dry conditions for the first time. The cements׳ porosity and their compressive, diametral tensile and biaxial flexural strength were tested in wet (or moist) and dry conditions. The surface morphology was characterized by scanning electron microscopy. Phase composition was assessed with X-ray diffraction. It was found that the novel experimental cements showed better mechanical properties than the commercially available cements, in all loading scenarios. The highest compressive strength (57.2±6.5 MPa before drying and 69.5±6.0 MPa after drying) was found for the experimental brushite cement. This cement also showed the highest wet diametral tensile strength (10.0±0.8 MPa) and wet biaxial flexural strength (30.7±1.8 MPa). It was also the cement that presented the lowest porosity (approx. 12%). The influence of water content was found to depend on cement type, with some cements showing higher mechanical properties after drying and some no difference after drying.

  • 49.
    Luo, Jun
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Persson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    A ready-to-use acidic, brushite-forming calcium phosphate cement2018In: Acta Biomaterialia, ISSN 1742-7061, E-ISSN 1878-7568, Vol. 81, p. 304-314Article in journal (Refereed)
    Abstract [en]

    Premixed calcium phosphate cements have been developed to simplify the usage of traditional calcium phosphate cements and reduce the influence of the setting reaction on the delivery process. However, difficulties in achieving a good cohesion, adequate shelf life and sufficient mechanical properties have so far impeded their use in clinical applications, especially for the more degradable acidic calcium phosphate cements. In this study, a brushite cement was developed from a series of ready-to-use calcium phosphate pastes. The brushite cement paste was formed via mixing of a monocalcium phosphate monohydrate (MCPM) paste and a beta-tricalcium phosphate (beta-TCP) paste with good injectability and adequate shelf life. The MCPM paste was based on a water-immiscible liquid with two surfactants and the beta-Tcp paste on a sodium hyaluronate aqueous solution. The effect of citric acid as a retardant was assessed. Formulations with suitable amounts of citric acid showed good cohesion and mechanical performance with potential for future clinical applications. Statement of Significance Acidic calcium phosphate cements have attracted extensive attention as bone substitute materials due to their ability to resorb faster than basic calcium phosphate cements in vivo. However, traditionally, short working times and low mechanical strength have limited their clinical application. Premixed cements could simplify the clinical use as well as improve property reproducibility, but short shelf lives, low cohesion and low mechanical properties have restricted the development. In this study, an injectable ready-to-use two-phase system consisting of an MCPM paste and a beta-TCP paste was developed based on acidic cement. It shows good cohesion, compressive strength and adequate shelf life, which has the potential to be used in a dual chamber system for simplified and fast filling of bone defects in a minimally invasive manner. This will reduce surgery time, decrease the risk of contamination and ensure repeatable results.

  • 50.
    Luo, Jun
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Engqvist, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Persson, Cecilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    A ready-to-use acidic calcium phosphate cementManuscript (preprint) (Other academic)
    Abstract [en]

    Premixed calcium phosphate cements have been developed to simplify the usage of traditional calcium phosphate cements and reduce the influence of the setting reaction on the delivery process. However, difficulties in achieving a good cohesion, adequate shelf life and sufficient mechanical properties have so far impeded their use in clinical applications, especially for the more degradable acidic calcium phosphate cements.

    In this study, a brushite cement was developed from a series of ready-to-use calcium phosphate pastes. The brushite cement paste was formed via mixing of a monocalcium phosphate monohydrate (MCPM) paste and a β-tricalcium phosphate (β-TCP) paste with good injectability and adequate shelf life. The MCPM paste was based on a water-immiscible liquid with two surfactants and the β-TCP paste on a sodium hylauronate aqueous solution. The effect of citric acid as a retardant was assessed. Formulations with suitable amounts of citric acid showed good cohesion and mechanical performance with potential for future clinical applications.

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