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Magnesium-based composites with improved in vitro surface biocompatibility.

Huan Z, Leeflang S, Zhou J, Duszczyk J - J Mater Sci Mater Med (2010)

Bottom Line: In this study, bioactive glass (BG, 45S5) particles were added to a biodegradable magnesium alloy (ZK30) through a semi-solid high-pressure casting process in order to improve the surface biocompatibility of the biomaterial and potentially its bioactivity.SEM, EDX and EPMA showed the retention of the morphological characteristics and composition of BG particles in the as-cast composite materials.In vitro tests in a cell culture medium confirmed that the composites indeed possessed an enhanced ability to induce the deposition of a bone-like apatite layer on the surface, indicating an improved surface biocompatibility as compared with the matrix alloy.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering, Delft University of Technology, Mekelweg 2, 2628 CD, Delft, The Netherlands.

ABSTRACT
In this study, bioactive glass (BG, 45S5) particles were added to a biodegradable magnesium alloy (ZK30) through a semi-solid high-pressure casting process in order to improve the surface biocompatibility of the biomaterial and potentially its bioactivity. The observation of the as-cast microstructures of ZK30-BG composites indicated homogeneous dispersion of BG particles in the matrix. SEM, EDX and EPMA showed the retention of the morphological characteristics and composition of BG particles in the as-cast composite materials. In vitro tests in a cell culture medium confirmed that the composites indeed possessed an enhanced ability to induce the deposition of a bone-like apatite layer on the surface, indicating an improved surface biocompatibility as compared with the matrix alloy.

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SEM micrographs of the ZK30 alloy (a) and the composites with 3.4% (b), 6.9% (c) and 14.3% (d) BG particles by volume after immersion in E-MEM for 24 h
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Fig5: SEM micrographs of the ZK30 alloy (a) and the composites with 3.4% (b), 6.9% (c) and 14.3% (d) BG particles by volume after immersion in E-MEM for 24 h

Mentions: The surface morphologies of the composites after immersion in E-MEM for 24 h are shown in Fig. 5. During immersion, pitting corrosion indeed occurred on the surface of the ZK30 alloy sample without BG reinforcement (Fig. 5a). In contrast, a deposition layer was formed on the surface of the composite samples, and the area of this layer increased with increasing volume fraction of BG particles in the composite (Fig. 5b, d). EDX analysis of the surface layer showed increases in the Ca atomic percent and Ca/P molar ratio, as the volume fraction of BG particles increased from 0 to 14.3% (Fig. 6). The Ca/P ratios of the composites in the range of 1.2–1.35, being lower than the theoretical value (1.67), show that the newly formed apatite layer is a Ca-deficient apatite layer, consistent with the properties of bone-like apatite formed on an HA-bioglass composite [19] and on bioglass [20]. The results indicated that the BG particles present in the composite were indeed able to induce faster and more homogeneous deposition of a Ca- and P-rich layer on the magnesium alloy matrix. The operating mechanism of spontaneous apatite formation on metallic magnesium may be as follows [21]: an ionic exchange between Mg2+ from the substrate and H+ from the soaking medium takes place, leading to an increase in pH; higher pH values increase the supersaturation degree of the cell culture medium with respect to apatite. The result is the nucleation and growth of a Ca-, P- and Mg-rich ceramic layer on the magnesium substrate. With the addition of BG particles, apart from the supersaturation caused by the elevated pH environment, the apatite layer formation is accelerated due to the release of Ca2+ from the partial dissolution of BG particles. The silicon dissolved from the BG particles surface may act as a nucleating agent [18], thereby accelerating the formation of the apatite layer which can significantly improve the surface biocompatibility of the material [8, 9]. In combination with the consideration on the compressive strengths of the composites (Fig. 2), the ZK30-BG composite with 6.9% BG by volume showed the best balanced properties. Further research on the biocompatibility and bioactivity of the composites and other aspects relevant to the biomedical application will be carried out to optimize both material design and processing further. Fig. 5


Magnesium-based composites with improved in vitro surface biocompatibility.

Huan Z, Leeflang S, Zhou J, Duszczyk J - J Mater Sci Mater Med (2010)

SEM micrographs of the ZK30 alloy (a) and the composites with 3.4% (b), 6.9% (c) and 14.3% (d) BG particles by volume after immersion in E-MEM for 24 h
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2991183&req=5

Fig5: SEM micrographs of the ZK30 alloy (a) and the composites with 3.4% (b), 6.9% (c) and 14.3% (d) BG particles by volume after immersion in E-MEM for 24 h
Mentions: The surface morphologies of the composites after immersion in E-MEM for 24 h are shown in Fig. 5. During immersion, pitting corrosion indeed occurred on the surface of the ZK30 alloy sample without BG reinforcement (Fig. 5a). In contrast, a deposition layer was formed on the surface of the composite samples, and the area of this layer increased with increasing volume fraction of BG particles in the composite (Fig. 5b, d). EDX analysis of the surface layer showed increases in the Ca atomic percent and Ca/P molar ratio, as the volume fraction of BG particles increased from 0 to 14.3% (Fig. 6). The Ca/P ratios of the composites in the range of 1.2–1.35, being lower than the theoretical value (1.67), show that the newly formed apatite layer is a Ca-deficient apatite layer, consistent with the properties of bone-like apatite formed on an HA-bioglass composite [19] and on bioglass [20]. The results indicated that the BG particles present in the composite were indeed able to induce faster and more homogeneous deposition of a Ca- and P-rich layer on the magnesium alloy matrix. The operating mechanism of spontaneous apatite formation on metallic magnesium may be as follows [21]: an ionic exchange between Mg2+ from the substrate and H+ from the soaking medium takes place, leading to an increase in pH; higher pH values increase the supersaturation degree of the cell culture medium with respect to apatite. The result is the nucleation and growth of a Ca-, P- and Mg-rich ceramic layer on the magnesium substrate. With the addition of BG particles, apart from the supersaturation caused by the elevated pH environment, the apatite layer formation is accelerated due to the release of Ca2+ from the partial dissolution of BG particles. The silicon dissolved from the BG particles surface may act as a nucleating agent [18], thereby accelerating the formation of the apatite layer which can significantly improve the surface biocompatibility of the material [8, 9]. In combination with the consideration on the compressive strengths of the composites (Fig. 2), the ZK30-BG composite with 6.9% BG by volume showed the best balanced properties. Further research on the biocompatibility and bioactivity of the composites and other aspects relevant to the biomedical application will be carried out to optimize both material design and processing further. Fig. 5

Bottom Line: In this study, bioactive glass (BG, 45S5) particles were added to a biodegradable magnesium alloy (ZK30) through a semi-solid high-pressure casting process in order to improve the surface biocompatibility of the biomaterial and potentially its bioactivity.SEM, EDX and EPMA showed the retention of the morphological characteristics and composition of BG particles in the as-cast composite materials.In vitro tests in a cell culture medium confirmed that the composites indeed possessed an enhanced ability to induce the deposition of a bone-like apatite layer on the surface, indicating an improved surface biocompatibility as compared with the matrix alloy.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering, Delft University of Technology, Mekelweg 2, 2628 CD, Delft, The Netherlands.

ABSTRACT
In this study, bioactive glass (BG, 45S5) particles were added to a biodegradable magnesium alloy (ZK30) through a semi-solid high-pressure casting process in order to improve the surface biocompatibility of the biomaterial and potentially its bioactivity. The observation of the as-cast microstructures of ZK30-BG composites indicated homogeneous dispersion of BG particles in the matrix. SEM, EDX and EPMA showed the retention of the morphological characteristics and composition of BG particles in the as-cast composite materials. In vitro tests in a cell culture medium confirmed that the composites indeed possessed an enhanced ability to induce the deposition of a bone-like apatite layer on the surface, indicating an improved surface biocompatibility as compared with the matrix alloy.

Show MeSH
Related in: MedlinePlus