Abstract
A new generation of organic/inorganic composites is offering a promising approach for creating biocompatible and biodegradable materials with mechanical properties that match that of human bone better than traditional metallic implants. Here, we report a novel technique whereby hydroxyapatite powder is encapsulated in polylactide-based microspheres, processed by an emulsion-solvent evaporation method, and then used as the building blocks to produce dense, microstructurally-uniform composites through a hot pressing route. The mechanical properties of these composites––both ab initio and after in vitro degradation in a simulated environment- were subsequently characterized. Although despite in vitro degradation remains an issue, the Young’s modulus, bending strength and fracture resistance were higher than the corresponding minimum values for human cortical bone. These results suggest that the hot-pressing of hydroxyapatite/polylactide microspheres can be a viable route for the synthesis of load-bearing bone-replacement materials.
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Notes
The conventional route mentioned here has been detailed elsewhere [22] and involved dissolving PLA in methylene chloride and adding HA powders/whiskers to the solution. The slurry was dried to remove the residual solvent and the dried pellets hot pressed under various conditions (time, temperature and pressure).
A stirring time of 2 h was employed to obtain uniform spheres as it was noticed that with longer times, the microspheres began to disintegrate.
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Acknowledgements
This work was supported by the National Institutes of Health (NIH) under Grant No. 5R01 DE015633. We acknowledge the support of the dedicated tomography beamline (BL 8.3.2) at the Advanced Light Source (ALS), supported by the Department of Energy under Contract No. DE-AC03-76SF00098. The authors also wish to thank Drs. Alastair MacDowell, John H. Kinney and Robert O. Ritchie for many helpful discussions.
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Russias, J., Saiz, E., Nalla, R.K. et al. Microspheres as building blocks for hydroxyapatite/polylactide biodegradable composites. J Mater Sci 41, 5127–5133 (2006). https://doi.org/10.1007/s10853-006-0449-1
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DOI: https://doi.org/10.1007/s10853-006-0449-1