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Fowler, L., Janson, O., Engqvist, H., Norgren, S. & Öhman, C. (2019). Antibacterial investigation of titanium-copper alloys using luminescent Staphylococcus epidermidis in a direct contact test. Materials science & engineering. C, biomimetic materials, sensors and systems, 97, 707-714
Open this publication in new window or tab >>Antibacterial investigation of titanium-copper alloys using luminescent Staphylococcus epidermidis in a direct contact test
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2019 (English)In: Materials science & engineering. C, biomimetic materials, sensors and systems, ISSN 0928-4931, E-ISSN 1873-0191, Vol. 97, p. 707-714Article in journal (Refereed) Published
Abstract [en]

Commercially pure titanium (CP-Ti), used as oral implants, is often populated by various bacterial colonies in the oral cavity. These bacteria can cause Peri-implantitis, leading to loss of bone tissue and failure of implants. With the increased awareness of antibiotic resistance, research has been directed towards alternative solutions and recent findings have indicated titanium-copper (Ti-Cu) alloys as a promising antibacterial material. The aim of this study was to produce homogeneous Ti-Cu alloys, with various concentrations of copper, and to characterise their antibacterial properties through direct contact tests, using luminescent bacteria, in addition to traditional materials characterisation techniques. Samples of CP-Ti and four different Ti-Cu alloys (1, 2.5, 3 and 10 wt%Cu) were produced in an arc-furnace, heated treated and rapidly quenched. X-ray diffraction revealed that Ti2Cu, was present only in the 10 wt%Cu alloy, however, scanning electron microscopy (SEM) indicated precipitates at the grain boundaries of the 3 wt%Cu alloy, which were confirmed to be of a copper rich phase by energy dispersive x-ray spectroscopy (EDS) analysis. EDS line scans confirmed that the alloys were homogenous. After 6 h, a trend between copper content and antibacterial rate could be observed, with the 10 wt%Cu alloy having the highest rate. SEM confirmed fewer bacteria on the 3 wt%Cu and especially the 10 wt%Cu samples. Although the 10 wt%Cu alloy gave the best antibacterial results, it is desired that the Cu concentration is below similar to 3 wt%Cu to maintain similar mechanical and corrosive performance as CP-Ti. Therefore, it is proposed that future work focuses on the 3 wt%Cu alloy.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2019
Keywords
Copper, Titanium, Antibacterial, S. epidermidis, Ti2Cu
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:uu:diva-378615 (URN)10.1016/j.msec.2018.12.050 (DOI)000457952800069 ()30678959 (PubMedID)
Available from: 2019-03-11 Created: 2019-03-11 Last updated: 2019-03-11Bibliographically approved
Zhu, W., Ma, Q., Borg, S., Öhman Mägi, C., Weng, X., Engqvist, H. & Xia, W. (2019). Cemented injectable multi-phased porous bone grafts for the treatment of femoral head necrosis. Journal of materials chemistry. B, 7(18), 2997-3006
Open this publication in new window or tab >>Cemented injectable multi-phased porous bone grafts for the treatment of femoral head necrosis
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2019 (English)In: Journal of materials chemistry. B, ISSN 2050-750X, E-ISSN 2050-7518, Vol. 7, no 18, p. 2997-3006Article in journal (Refereed) Published
Abstract [en]

Femoral head necrosis (FHN) can induce musculoskeletal disability. It presents a challenge from diagnostic and therapeutic points of view. Open surgery for the treatment of FHN is not an optimal route. To minimize the surgery window, an injectable material with a porous structure and bioactive nature is preferred. The fabrication of an injectable porous bone graft via a simple route was the aim of our study. Therefore, cemented multi-phased calcium phosphate porous granules have been studied with varied phase compositions, pore sizes and porosities, and degradation rates. Granules templated by PEG 100-600 mu m were chosen for cell toxicity and in vitro osteogenic potential testing. Rabbits, making up a femoral head necrosis model, were implanted with granule A. Mature cancellous bone tissue was observed in the femoral head defect after 2 months implantation. The results indicate that the newly formed injectable bioactive porous grafts could be a good candidate for the treatment of femoral head necrosis.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2019
National Category
Orthopaedics
Identifiers
urn:nbn:se:uu:diva-390518 (URN)10.1039/c9tb00238c (DOI)000472921600011 ()
Available from: 2019-08-14 Created: 2019-08-14 Last updated: 2019-08-14Bibliographically approved
Sladkova, M., Cheng, J., Palmer, M., Chen, S., Lin, C., Xia, W., . . . de Peppo, G. M. (2019). Comparison of Decellularized Cow and Human Bone for Engineering Bone Grafts with Human Induced Pluripotent Stem Cells. Tissue Engineering. Part A, 25(3-4), 288-301
Open this publication in new window or tab >>Comparison of Decellularized Cow and Human Bone for Engineering Bone Grafts with Human Induced Pluripotent Stem Cells
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2019 (English)In: Tissue Engineering. Part A, ISSN 1937-3341, E-ISSN 1937-335X, Vol. 25, no 3-4, p. 288-301Article in journal (Refereed) Published
Abstract [en]

Bone engineering makes it possible to grow unlimited amounts of viable tissue products for basic and applied research, and for clinical applications. A common trend in tissue engineering is the use of decellularized tissue matrices as scaffolding materials, which display structural, mechanical, and biological attributes typical of the native tissue. Due to the limited availability and high cost of human samples, decellularized tissue matrices are typically derived from animal sources. It is unclear, however, whether interspecies differences in tissue parameters will influence the quality of tissue grafts that are engineered using human stem cells. In this study, decellularized cow and human bone scaffolds were compared for engineering bone grafts using human induced pluripotent stem cell-derived mesodermal progenitor cells. After seeding, the cell-scaffold constructs were cultured for 5 weeks in osteogenic medium under dynamic conditions in perfusion bioreactors. The architectural and chemical properties of the scaffolds were studied using microscopic, spectroscopic, and thermogravimetric techniques, while cell behavior and formation of mineralized tissue were assessed using a combination of molecular assays, histological methods, and imaging technologies. The results show that while scaffolds derived from cow and human bone differ somewhat in architecture and composition, both equally support cell viability, tissue growth, and formation of a mineralized bone matrix. Taken together, the results suggest that scaffolds derived from cow bone represent a suitable and convenient alternative to engineer human bone grafts for various biomedical applications.

Place, publisher, year, edition, pages
MARY ANN LIEBERT, INC, 2019
Keywords
biomaterial scaffold, bone engineering, induced pluripotent stem cells, mesenchymal stem cells, osteogenic differentiation, tissue decellularization
National Category
Biomaterials Science Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-369891 (URN)10.1089/ten.tea.2018.0149 (DOI)000448565100001 ()
Funder
EU, FP7, Seventh Framework Programme
Note

De 2 första författarna delar förstaförfattarskapet.

Available from: 2018-12-19 Created: 2018-12-19 Last updated: 2019-04-17Bibliographically approved
Janson, O., Sörensen, J. H., Strömme, M., Engqvist, H., Procter, P. & Welch, K. (2019). Evaluation of an alkali-treated and hydroxyapatite-coated orthopedic implant loaded with tobramycin. Journal of biomaterials applications
Open this publication in new window or tab >>Evaluation of an alkali-treated and hydroxyapatite-coated orthopedic implant loaded with tobramycin
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2019 (English)In: Journal of biomaterials applications, ISSN 0885-3282, E-ISSN 1530-8022Article in journal (Refereed) Published
Abstract [en]

An approximately 1-µm thick hydroxyapatite coating was biomimetically deposited on an alkali-treated, commercially available orthopedic screw surface (type II anodized titanium). Tobramycin loaded into the coating via a simple soaking method was shown to provide a sustained release above the minimal inhibitory concentration 0.2 µg/µl for up to two days. Agar diffusion tests showed that the tobramycin-loaded coating was able to produce a zone of inhibition against Staphylococcus aureus for up to five days. Biocompatibility testing using outgrowth endothelial cells and primary osteoblasts suggested that good cell compatibility of the coating can be expected in vivo. A rabbit distal femur condyle model was used for in vivo evaluation of the antibacterial efficacy of the tobramycin-loaded coating, and this pilot study showed that the release of tobramycin was sufficient to locally eliminate very large amounts of bacteria in vivo (inoculation dose 104–105 CFU S. aureus/test site).

Place, publisher, year, edition, pages
SAGE Publications Ltd STM, 2019
National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials; Engineering Science with specialization in Materials Science
Identifiers
urn:nbn:se:uu:diva-390827 (URN)10.1177/0885328219867968 (DOI)
Available from: 2019-08-14 Created: 2019-08-14 Last updated: 2019-08-14
Sundblom, J., Gallinetti, S., Birgersson, U., Engqvist, H. & Kihlström, L. (2019). Gentamicin loading of calcium phosphate implants: implications for cranioplasty. Acta Neurochirurgica, 161(6), 1255-1259
Open this publication in new window or tab >>Gentamicin loading of calcium phosphate implants: implications for cranioplasty
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2019 (English)In: Acta Neurochirurgica, ISSN 0001-6268, E-ISSN 0942-0940, Vol. 161, no 6, p. 1255-1259Article in journal (Refereed) Published
Abstract [en]

BackgroundSurgical site infections (SSI) are a significant risk in cranioplasty, with reported rates of around 8-9%. The most common bacteria associated with these nosocomial infections are of the Staphylococcus species, which have the ability to form biofilm. The possibility to deliver antibiotics, such as gentamicin, locally rather than systemically could potentially lower the early postoperative SSI. Various antibiotic dosages are being applied clinically, without any true consensus on the effectiveness.MethodsDrug release from calcium phosphate (CaP), polyetheretherketone (PEEK), and titanium (Ti) samples was evaluated. Microbiological studies with Staphylococcus aureus (SA) and Staphylococcus epidermidis (SE) including strains from clinical infection were used to establish clinically relevant concentrations.ResultsThe CaP samples were able to retain and release gentamicin overtime, whereas the Ti and PEEK samples did not show any drug uptake or release. A gentamicin loading concentration of 400g/ml was shown to be effective in in vitro microbiological studies with both SA and SE.ConclusionsOut of the three materials studied, only CaP could be loaded with gentamicin. An initial loading concentration of 400g/ml appears to establish an effective gentamicin concentration, possibly translating into a clinical benefit in cranioplasty.

Place, publisher, year, edition, pages
SPRINGER WIEN, 2019
Keywords
Gentamicin, Calcium phosphate, Titanium, PEEK, Staphylococcus, Uptake-release
National Category
Neurology
Identifiers
urn:nbn:se:uu:diva-385970 (URN)10.1007/s00701-019-03895-4 (DOI)000468224800029 ()31041594 (PubMedID)
Available from: 2019-06-18 Created: 2019-06-18 Last updated: 2019-06-18Bibliographically approved
Berg, C., Engqvist, H. & Xia, W. (2019). Ion substitution induced formation of spherical ceramic particles. Ceramics International, 45(8), 10385-10393
Open this publication in new window or tab >>Ion substitution induced formation of spherical ceramic particles
2019 (English)In: Ceramics International, ISSN 0272-8842, E-ISSN 1873-3956, Vol. 45, no 8, p. 10385-10393Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
ELSEVIER SCI LTD, 2019
Keywords
Powders, Chemical preparation, Chemical properties
National Category
Ceramics
Identifiers
urn:nbn:se:uu:diva-383145 (URN)10.1016/j.ceramint.2019.02.097 (DOI)000465058500089 ()
Funder
Swedish Research Council, 2013-5419
Available from: 2019-05-10 Created: 2019-05-10 Last updated: 2019-05-10Bibliographically approved
Luo, J., Faivre, J., Engqvist, H. & Persson, C. (2019). The Addition of Poly(Vinyl Alcohol) Fibers to Apatitic Calcium Phosphate Cement Can Improve Its Toughness. Materials, 12(9), Article ID 1531.
Open this publication in new window or tab >>The Addition of Poly(Vinyl Alcohol) Fibers to Apatitic Calcium Phosphate Cement Can Improve Its Toughness
2019 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 9, article id 1531Article in journal (Refereed) Published
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 fiber reinforcement. The effect of the addition of hydrophilic, poly(vinyl-alcohol) (PVA) fibers 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 fiber 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 fibers (of the 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 fibers), 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 fibers (7.4 +/- 1.5 MPa). The work of fracture increased four times to 9.1 +/- 1.5 kJ/m(2) in comparison to the pristine apatite. In summary, the hydroxyapatite cements could be reinforced by suitable amounts of PVA fibers, which resulted in enhancing the material's structural integrity and ductility, and increased the material's resistance to cracking.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
fiber 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-387969 (URN)10.3390/ma12091531 (DOI)000469757500172 ()31083315 (PubMedID)
Available from: 2019-06-27 Created: 2019-06-27 Last updated: 2019-06-27Bibliographically approved
Tkachenko, S., Datskevich, O., Kulak, L., Persson, C. & Engqvist, H. (2019). The Effect of Al Addition on the Tribological Behavior of Ti-Si-Zr Alloys. Journal of tribology, 141(4), Article ID 041604.
Open this publication in new window or tab >>The Effect of Al Addition on the Tribological Behavior of Ti-Si-Zr Alloys
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2019 (English)In: Journal of tribology, ISSN 0742-4787, E-ISSN 1528-8897, Vol. 141, no 4, article id 041604Article in journal (Refereed) Published
Abstract [en]

While commercial biomedical titanium alloys present excellent biocompatibility and corrosion resistance, their poor wear resistance remains a major limitation. In this study, alloying with aluminum was used to improve the tribological performance of an experimental Ti-Si-Zr alloy. The effect of Al content on the alloy's microstructure and mechanical properties was evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Vickers hardness measurements. Sliding wear testing was performed in a ball-on-disk setup, using stainless steel and silicon nitride counterparts and serum solution lubrication. Microstructural examinations showed that an increase in Al content induced a change from eutectic cell microstructure to regular near-equiaxed particles and produced a solid solution strengthening, increasing alloy's hardness. The adhesive tendencies of the alpha-Ti matrix to the counterpart dominated the frictional response, and a lower friction coefficient was found against silicon nitride compared to stainless steel. In wear tests against stainless steel counterparts, the alloys showed significantly higher wear rates than the CoCr and Ti-6Al-4V references due to severe abrasive wear, induced by the adhesion of titanium matrix to the counterpart. The Al addition had a positive effect on the wear resistance against silicon nitride due to the solid solution strengthening and the change in microstructure, which reduced the risk of brittle delamination. However, while this gave a trend for a lower wear rate against silicon nitride than the Ti-6Al-4V alloy, the wear rate was still approximately three times higher than that of CoCr.

Keywords
nonferrous metals, sliding wear, electron microscopy, hardness, two-body abrasion
National Category
Tribology (Interacting Surfaces including Friction, Lubrication and Wear) Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:uu:diva-379021 (URN)10.1115/1.4042098 (DOI)000459212000009 ()
Available from: 2019-03-12 Created: 2019-03-12 Last updated: 2019-03-12Bibliographically approved
Hulsart Billström, G., Janson, O., Engqvist, H., Welch, K. & Hong, J. (2019). Thromboinflammation as bioactivity assessment of H2O2-alkali modified titanium surfaces. Journal of materials science. Materials in medicine, 30(6), Article ID 66.
Open this publication in new window or tab >>Thromboinflammation as bioactivity assessment of H2O2-alkali modified titanium surfaces
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2019 (English)In: Journal of materials science. Materials in medicine, ISSN 0957-4530, E-ISSN 1573-4838, Vol. 30, no 6, article id 66Article in journal (Refereed) Published
Abstract [en]

The release of growth factors from platelets, mediated by the coagulation and the complement system, plays an important role in the bone formation around implants. This study aimed at exploring the thromboinflammatory response of H2O2-alkali soaked commercially pure titanium grade 2 discs exposed to whole human blood, as a way to assess the bioactivity of the discs. Commercially pure titanium grade 2 discs were modified by soaking in H2O2, NaOH and Ca(OH)2. The platelet aggregation, coagulation activation and complement activation was assessed by exposing the discs to fresh whole blood from human donors. The platelet aggregation was examined by a cell counter and the coagulation and complement activation were assessed by ELISA-measurements of the concentration of thrombin-antithrombin complex, C3a and terminal complement complex. The modified surface showed a statistically significant increased platelet aggregation, coagulation activation and complement activation compared to unexposed blood. The surface also showed a statistically significant increase of coagulation activation compared to PVC. The results of this study showed that the H2O2-alkali soaked surfaces induced a thromboinflammatory response that indicates that the surfaces are bioactive.

National Category
Other Materials Engineering Biomaterials Science
Identifiers
urn:nbn:se:uu:diva-358034 (URN)10.1007/s10856-019-6248-4 (DOI)000468976700001 ()31127371 (PubMedID)
Funder
Swedish Research Council, 2016-2075-5.1; 2016-04519Vinnova
Available from: 2018-08-23 Created: 2018-08-23 Last updated: 2019-06-25Bibliographically approved
Janson, O., Gururaj, S., Pujari-Palmer, S., Karlsson Ott, M., Strømme, M., Engqvist, H. & Welch, K. (2019). Titanium surface modification to enhance antibacterial and bioactive properties while retaining biocompatibility. Materials science & engineering. C, biomimetic materials, sensors and systems, 96, 272-279
Open this publication in new window or tab >>Titanium surface modification to enhance antibacterial and bioactive properties while retaining biocompatibility
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2019 (English)In: Materials science & engineering. C, biomimetic materials, sensors and systems, ISSN 0928-4931, E-ISSN 1873-0191, Vol. 96, p. 272-279Article in journal (Refereed) Published
Abstract [en]

Bacterial infections associated with metal implants are severe problems affecting a considerable amount of people with dental or orthopedic implants. This study aims to examine the antibacterial effect of a Titanium-peroxy gel layer on the modified surface of commercially pure titanium grade 2. Variations in a multi-step surface modification procedure were tested to determine the best combination that provided an antibacterial effect while enhancing bioactivity without compromising biocompatibility. Soaking the surfaces in 30 wt% hydrogen peroxide held at 80 °C provided antibacterial activity while subsequent surface treatments in concentrated sodium and calcium hydroxide solutions were preformed to enhance bioactivity. Staphylococcus epidermidis was used to determine the antibacterial effect through both direct contact and biofilm inhibition tests while human dermal fibroblast cells and MC3T3 pre osteoblast cells were utilized to test biocompatibility. The greatest antibacterial effect was observed with only hydrogen peroxide treatment, but the resulting surface was neither bioactive nor biocompatible. It was found that subsequent surface treatments with sodium hydroxide followed by calcium hydroxide provided a bioactive surface that was also biocompatible. Additionally, a final treatment with autoclaving showed positive effects with regards to enhanced bioactivity. This multi-step surface modification procedure offers a promising, non-antibiotic, solution for combatting infections associated with biomedical implants.

Keywords
Titanium, Antibacterial, Bioactivity, Cell viability, Sodium titanate, Calcium titanate
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-358023 (URN)10.1016/j.msec.2018.11.021 (DOI)000456760700027 ()30606532 (PubMedID)
Funder
Vinnova
Available from: 2018-08-23 Created: 2018-08-23 Last updated: 2019-03-15Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-9529-650X

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