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Publications (10 of 332) Show all publications
Qin, T., Qin, W., Ma, M., Zhang, D., Hu, S., Zhang, P., . . . Engqvist, H. (2018). A novel rapid synthesis, characterization and applications of calcium phosphate nanspheres from Baltic seawater. Ceramics International
Open this publication in new window or tab >>A novel rapid synthesis, characterization and applications of calcium phosphate nanspheres from Baltic seawater
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2018 (English)In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956Article in journal (Refereed) In press
Abstract [en]

Due to the considerable high bio-compatibility, calcium phosphate nanoparticles are widely used in biomedicalapplications. This study proposes a novel strategy for low-cost manufacturing calcium phosphate nanoporousspheres. The controlled reaction only took less than five minutes, when using Baltic seawater with the dissolvedcalcium concentration of 2.2 mM as the calcium resources. Porous nanospheres were obtained, with spheresranging from 50 to 130 nm. The obtained nanospheres possess high drug-loading capacity and exhibit sustainedrelease and pH-dependent properties. In addition, this method provides a general efficient strategy to synthesizeother low-cost inorganic nanospheres from seawater.

National Category
Ceramics
Identifiers
urn:nbn:se:uu:diva-350780 (URN)
Available from: 2018-05-16 Created: 2018-05-16 Last updated: 2018-06-04Bibliographically approved
Sladkova, M., Pujari-Palmer, M., Öhman, C., Cheng, J., Al-Ansari, S., Saad, M., . . . de Peppo, G. M. (2018). Engineering human bone grafts with new macroporous calcium phosphate cement scaffolds. Journal of Tissue Engineering and Regenerative Medicine, 12(3), 715-726
Open this publication in new window or tab >>Engineering human bone grafts with new macroporous calcium phosphate cement scaffolds
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2018 (English)In: Journal of Tissue Engineering and Regenerative Medicine, ISSN 1932-6254, E-ISSN 1932-7005, Vol. 12, no 3, p. 715-726Article in journal (Refereed) Published
Abstract [en]

Bone engineering opens the possibility to grow large amounts of tissue products by combining patient-specific cells with compliant biomaterials. Decellularized tissue matrices represent suitable biomaterials, but availability, long processing time, excessive cost, and concerns on pathogen transmission have led to the development of biomimetic synthetic alternatives. We recently fabricated calcium phosphate cement (CPC) scaffolds with variable macroporosity using a facile synthesis method with minimal manufacturing steps and demonstrated long-term biocompatibility in vitro. However, there is no knowledge on the potential use of these scaffolds for bone engineering and whether the porosity of the scaffolds affects osteogenic differentiation and tissue formation in vitro. In this study, we explored the bone engineering potential of CPC scaffolds with two different macroporosities using human mesenchymal progenitors derived from induced pluripotent stem cells (iPSC-MP) or isolated from bone marrow (BMSC). Biomimetic decellularized bone scaffolds were used as reference material in all experiments. The results demonstrate that, irrespective of their macroporosity, the CPC scaffolds tested in this study support attachment, viability, and growth of iPSC-MP and BMSC cells similarly to decellularized bone. Importantly, the tested materials sustained differentiation of the cells as evidenced by increased expression of osteogenic markers and formation of a mineralized tissue. In conclusion, the results of this study suggest that the CPC scaffolds fabricated using our method are suitable to engineer bone grafts from different cell sources and could lead to the development of safe and more affordable tissue grafts for reconstructive dentistry and orthopaedics and in vitro models for basic and applied research.

National Category
Other Medical Engineering
Research subject
Engineering Science with specialization in Materials Science
Identifiers
urn:nbn:se:uu:diva-335996 (URN)10.1002/term.2491 (DOI)000427137100061 ()28635177 (PubMedID)
Funder
EU, FP7, Seventh Framework Programme
Available from: 2017-12-11 Created: 2017-12-11 Last updated: 2018-06-04Bibliographically approved
Pujari-Palmer, M., Robo, C., Persson, C., Procter, P. & Engqvist, H. (2018). Influence of cement compressive strength and porosity on augmentation performance in a model of orthopedic screw pull-out. Journal of The Mechanical Behavior of Biomedical Materials, 77, 624-633
Open this publication in new window or tab >>Influence of cement compressive strength and porosity on augmentation performance in a model of orthopedic screw pull-out
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2018 (English)In: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 77, p. 624-633Article in journal (Refereed) Published
Abstract [en]

Disease and injuries that affect the skeletal system may require surgical intervention and internal fixation, i.e. orthopedic plate and screw insertion, to stabilize the injury and facilitate tissue repair. If the surrounding bone quality is poor the screws may migrate, or the bone may fail, resulting in screw pull-out. Though numerous studies have shown that cement augmentation of the interface between bone and implant can increase screw holding strength in bone, the physical properties of cement that influence pull-out force have not been investigated. The present study sought to determine how the physical properties of calcium phosphate cements (CPCs), and the strength of the biological or synthetic material surrounding the augmented screw, affected the corresponding orthopedic screw pull-out force in urethane foam models of healthy and osteoporotic bone (Sawbones). In the simplest model, where only the bond strength between screw thread and cement (without Sawbone) was tested, the correlation between pull-out force and cement compressive strength (R2 = 0.79) was weaker than correlation with total cement porosity (R2 = 0.89). In open pore Sawbone that mimics “healthy” cancellous bone density the stronger cements produced higher pull-out force (50-60% increase). Higher strength, lower porosity, cements also produced higher pull-out forces (50-190% increase) in Sawbones with cortical fixation if the failure strength of the cortical material was similar to (bovine tibial bone), or greater than (metal shell), actual cortical bone. This result is of particular clinical relevance where fixation with a metal plate implant is indicated, as the nearby metal can simulate a thicker cortical shell and, thereby, increase the pull-out force of screws augmented with stronger cements. The improvement in pull-out force was apparent even at low augmentation volumes of 0.5 ml (50% increase), which suggest that in clinical situations where augmentation volume is limited the stronger, lower porosity CPCs may still produce a significant improvement in screw holding strength. When correlations of all the tested models were compared both cement porosity and compressive strength accurately predicted pull-out force (R2=1.00, R2=0.808), though prediction accuracy depended upon the strength of the material surrounding the Sawbone. The correlations strength was low for bone with no, or weak, cortical fixation. Higher strength and lower porosity CPCs also produced greater pull-out force (1-1.5 kN) than commercial CPC (0.2-0.5kN), but lower pull-out force than PMMA (2-3 kN). The results of this study suggest that the likelihood of screw fixation failure may be reduced by selecting calcium phosphate cements with lower porosity and higher bulk strength, in patients with healthy bone mineral density and/or sufficient cortical thickness. This is of particular clinical relevance when fixation with metal plates is indicated, or where the augmentation volume is limited.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Screw pull-out, Orthopedic screw augmentation, Calcium phosphate cement, Bioceramic, Bone biomechanics, Sawbones, Cortical fixation
National Category
Medical Materials Ceramics Applied Mechanics Biomaterials Science
Research subject
Engineering Science with specialization in Materials Science
Identifiers
urn:nbn:se:uu:diva-320157 (URN)10.1016/j.jmbbm.2017.10.016 (DOI)000418309500073 ()29100205 (PubMedID)
Funder
Swedish Research Council, 621–2011-3399EU, FP7, Seventh Framework Programme, 262948
Available from: 2017-04-16 Created: 2017-04-16 Last updated: 2018-02-16Bibliographically approved
Qin, T., Ma, M., Qin, W., Xiao, X., Nikolajeff, F. & Engqvist, H. (2018). Rapid precipitation of Mg-doped fluoride-based submicron spheres and evolution study. Journal of Solid State Chemistry (260), 142-146
Open this publication in new window or tab >>Rapid precipitation of Mg-doped fluoride-based submicron spheres and evolution study
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2018 (English)In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, no 260, p. 142-146Article in journal (Refereed) Published
National Category
Signal Processing
Identifiers
urn:nbn:se:uu:diva-350781 (URN)000428005000021 ()
Available from: 2018-05-16 Created: 2018-05-16 Last updated: 2018-06-04Bibliographically approved
Fu, L., Engqvist, H. & Xia, W. (2018). Spark plasma sintering of biodegradable Si3N4 bioceramic with Sr, Mg and Si as sintering additives for spinal fusion. Journal of the European Ceramic Society, 38(4), 2110-2119
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: 2018-04-06Bibliographically approved
Persson, J., Helgason, B., Engqvist, H., Ferguson, S. & Persson, C. (2018). Stiffness and strength of cranioplastic implant systems in comparison to cranial bone. Journal of Cranio-Maxillofacial Surgery, 46(3), 418-423
Open this publication in new window or tab >>Stiffness and strength of cranioplastic implant systems in comparison to cranial bone
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2018 (English)In: Journal of Cranio-Maxillofacial Surgery, ISSN 1010-5182, E-ISSN 1878-4119, Vol. 46, no 3, p. 418-423Article in journal (Refereed) Published
Abstract [en]

Purpose: The aim of this study was to evaluate skull replacement options after decompressive craniectomy by systematically investigating which combination of geometrical properties and material selection would result in a mechanical response comparable in stiffness to that of native skull bone and a strength as high or higher than the same. Materials and methods: The study was conducted using a Finite Element Model of the top part of a human skull. Native skull bone, autografts and commercial implants made of PEEK, solid titanium, two titanium meshes and a titanium-ceramic composite were modeled under a set load to evaluate deformation and maximum stress. Results: The computational result showed a large variation of the strength and effective stiffness of the autografts and implants. The stiffness of native bone varied by a factor of 20 and the strength by a factor of eight. The implants span the entire span of the native skull, both in stiffness and strength. Conclusion: All the investigated implant materials had a potential for having the same effective stiffness as the native skull bone. All the materials also had the potential to be as strong as the native bone. To match inherent properties, the best choice of material and thickness is thus patient specific, depending on the quality of the patient's native bone.

Keywords
Craniectomy, Cranioplasty, OSSDSIGN cranial, Craniocurve, KLS martin mesh system, Mechanical properties
National Category
Medical Materials Biomaterials Science
Research subject
Engineering Science with specialization in Materials Science
Identifiers
urn:nbn:se:uu:diva-347586 (URN)10.1016/j.jcms.2017.11.025 (DOI)000425712500007 ()
Funder
EU, Horizon 2020, E!9741
Available from: 2018-04-04 Created: 2018-04-04 Last updated: 2018-04-26Bibliographically approved
Qin, T., Zhang, P., Wani, I. H., Han, Y., LEIFER, K., Nikolajeff, F. & Engqvist, H. (2017). A general strategy for template-free and low-cost synthesis of inorganic hollow spheres. Powder Technology, 319, 163-171
Open this publication in new window or tab >>A general strategy for template-free and low-cost synthesis of inorganic hollow spheres
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2017 (English)In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 319, p. 163-171Article in journal (Refereed) Published
Abstract [en]

Inorganic hollow spheres have a great potential in many fields, such as calcium phosphate (Ca3(PO4)2) as carriers of active ingredients and local delivery. They are typically synthesized by the methods that reply on template-based strategies. However, the template residue and energy consumption during template removal are drawbacks. Currently developed template-free methods remain challenges such as time, cost and complicated procedures. In this paper, we introduce a general low-cost and template-free precipitation method with simple procedure. A series of inorganic hollow spheres, including calcium phosphate, calcium fluoride, strontium phosphate, strontium fluoride, barium phosphate and barium fluoride via magnesium were successfully synthesized, respectively. Based on these experimental results, a new model is proposed to explain the mechanism of the hollow inorganic spheres formation. This paper provides a general method to synthesize inorganic hollow spheres, which may have an important indication to other systems.

Keywords
Inorganic, Spheres, Hollow, Mechanism
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-333956 (URN)10.1016/j.powtec.2017.06.051 (DOI)000407982600016 ()
Available from: 2017-12-13 Created: 2017-12-13 Last updated: 2018-06-04Bibliographically approved
Garbani, M., Xia, W., Rhyner, C., Prati, M., Scheynius, A., Malissen, B., . . . Terhorst-Molawi, D. (2017). Allergen-loaded strontium-doped hydroxyapatite spheres improve allergen-specific immunotherapy in mice. Allergy. European Journal of Allergy and Clinical Immunology, 72(4), 570-578
Open this publication in new window or tab >>Allergen-loaded strontium-doped hydroxyapatite spheres improve allergen-specific immunotherapy in mice
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2017 (English)In: Allergy. European Journal of Allergy and Clinical Immunology, ISSN 0105-4538, E-ISSN 1398-9995, Vol. 72, no 4, p. 570-578Article in journal (Refereed) Published
Abstract [en]

Background

Immunomodulatory interventions play a key role in the treatment of infections and cancer as well as allergic diseases. Adjuvants such as micro- and nanoparticles are often added to immunomodulatory therapies to enhance the triggered immune response. Here, we report the immunological assessment of novel and economically manufactured microparticle adjuvants, namely strontium-doped hydroxyapatite porous spheres (SHAS), which we suggest for the use as adjuvant and carrier in allergen-specific immunotherapy (ASIT).

Methods and Results

Scanning electron microscopy revealed that the synthesis procedure developed for the production of SHAS results in a highly homogeneous population of spheres. SHAS bound and released proteins such as ovalbumin (OVA) or the major cat allergen Fel d 1. SHAS-OVA were taken up by human monocyte-derived dendritic cells (mdDCs) and murine DCs and did not have any necrotic or apoptotic effects even at high densities. In a murine model of ASIT for allergic asthmatic inflammation we found that OVA released from subcutaneously injected SHAS-OVA led to a sustained stimulation of both CD4+ and CD8+ T-cells. ASIT with SHAS-OVA as compared to soluble OVA resulted in similar humoral responses but in a higher efficacy as assessed by symptom scoring.

Conclusion

We conclude that SHAS may constitute a suitable carrier and adjuvant for ASIT with great potential due to its unique protein-binding properties.

National Category
Medical Materials
Identifiers
urn:nbn:se:uu:diva-310479 (URN)10.1111/all.13041 (DOI)000397489400007 ()27590538 (PubMedID)
Funder
Swedish Research Council, 2013-5419
Available from: 2016-12-16 Created: 2016-12-16 Last updated: 2017-05-15Bibliographically approved
Ting, M., Jefferies, S. R., Xia, W., Engqvist, H. & Suzuki, J. B. (2017). Classification and Effects of Implant Surface Modification on the Bone: Human Cell-Based In Vitro Studies. Journal of Oral Implantology, 43(1), 58-83
Open this publication in new window or tab >>Classification and Effects of Implant Surface Modification on the Bone: Human Cell-Based In Vitro Studies
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2017 (English)In: Journal of Oral Implantology, ISSN 0160-6972, E-ISSN 1548-1336, Vol. 43, no 1, p. 58-83Article, review/survey (Refereed) Published
Abstract [en]

Implant surfaces are continuously being improved to achieve faster osseointegration and a stronger bone to implant interface. This review will present the various implant surfaces, the parameters for implant surface characterization, and the corresponding in vitro human cell-based studies determining the strength and quality of the bone-implant contact. These in vitro cell-based studies are the basis for animal and clinical studies and are the prelude to further reviews on how these surfaces would perform when subjected to the oral environment and functional loading.

Place, publisher, year, edition, pages
ALLEN PRESS INC, 2017
Keywords
titanium, dental implant, implant surface morphology, osseointegration, surface topography
National Category
Medical and Health Sciences Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-320997 (URN)10.1563/aaid-joi-D-16-00079 (DOI)000395366200011 ()27897464 (PubMedID)
Available from: 2017-04-28 Created: 2017-04-28 Last updated: 2017-04-28Bibliographically approved
Xia, W., Fu, L. & Engqvist, H. (2017). Critical cracking thickness of calcium phosphates biomimetic coating: Verification via a Singh-Tirumkudulu model. Ceramics International, 43, 15729-15734
Open this publication in new window or tab >>Critical cracking thickness of calcium phosphates biomimetic coating: Verification via a Singh-Tirumkudulu model
2017 (English)In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 43, p. 15729-15734Article in journal (Refereed) Published
Abstract [en]

Despite the many advantages of biomimetic calcium phosphates (CaPs) coatings, there is a troublesome problem of low cohesion in the coatings. The low cohesion originates from the absence of bonding between CaP crystals, leading to cracks during drying of the coatings. In this study, based on a simplified Singh-Tirumkudulu model, the critical cracking thickness (CCT) of biomimetic CaPs coatings has been calculated. CaPs crystal size is the key factor influencing the CCT, except for the particle's shear modulus. Biomimetic CaPs coatings with different thickness have been prepared by soaking Ti substrates with a transition layer of TiO2 (rutile) in Dulbecco's phosphate buffer saline solution (DPBS) for 1, 2, 4 and 6 weeks. The morphology, thickness, and whether cracks formed or not were evaluated by SEM. The simplified Singh and Tirumkudulu model has been verified in terms of our experimental results and data obtained from previous literatures. Via dedicated experiments and calculations it is concluded that a thickness of about approximately 2 gm is the critical value for a crack-free CaPs coating given that the CaPs crystal size is smaller than 100 nm. The model could be used in the future design of crack-free biomimetic coatings.

National Category
Medical Materials
Identifiers
urn:nbn:se:uu:diva-330143 (URN)10.1016/j.ceramint.2017.08.134 (DOI)000413175300158 ()
Available from: 2017-09-26 Created: 2017-09-26 Last updated: 2018-02-05Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-9529-650X

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