Chitosan/Calcium Phosphate Scaffolds for Bone Tissue Engineering
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Chitosan/calcium phosphate scaffolds for bone tissue engineering Yong Zhang Miqin Zhang Department of Materials Science & Engineering, University of Washington Seattle, WA 98195-2120, U.S.A. ABSTRACT This research involves synthesis and characterization of biodegradable 3dimensional polymer/calcium phosphate hybrid matrices as scaffolds for bone tissue regeneration. The scaffolds are comprised of chitosan and calcium phosphates [βtricalcium phosphate (β-TCP), invert glass] and have combined optimum mechanical and biological properties of the two materials. Chitosan is a biocompatible and biodegradable polymer, and has rich hydroxyl groups for surface modification. Calcium phosphate crystals and invert glass are used as powder fillers to reinforce the scaffolds and increase bioactivity of the scaffolds. The scaffolds are fabricated using a thermally induced phase separation technique. The principal advantages of this technique are its low cost, low shrinkage levels, low sintering temperatures, and its ability to produce a variety of microstructures of various shapes and sizes. The osteoblast-like MG63 cells are seeded on the scaffolds to study the attachment and proliferation of the cells. The hydroxyl groups on the scaffolds are used to graft arginine-glycine-aspartate (RGD) peptides for promoting bone cell attachment and new tissue formation. INTRODUCTION Tissue engineering concepts have been applied to develop a cell-based repairing material for bone repair [1, 2], founded upon the use of polymeric scaffolds to support, reinforce and in some cases organize the tissue regeneration. Chitosan, made of glucosamine and N-acetylglucosamine units linked by 1-4 glycosidic bonds, has been proven to be biologically renewable, biodegradable, biocompatible, non-antigenic, non-toxic, and biofunctional [3]. Chitosan and some of its complexes have been studied for use in a number of biomedical applications, including wound dressings [4], drug delivery systems [5−7] and space filling implants [8]. The use of chitosan for tissue engineering as a scaffolding material has also been reported [9]. However, chitosan is mechanically weak and lacks of bioactivity, which hinders their biomedical applications. Calcium phosphates are excellent candidates for bone repair and regeneration biomaterials since their chemical compositions are similar to the inorganic component of bone [10]. It is desirable to develop a composite material with favorable material properties of chitosan and calcium phosphates. In this study, β-tricalcium phosphate (β-TCP) and calcium phosphate invert glasses (CaO/P2O5≈2.0), are used as powder fillers to reinforce the chitosan scaffold. The morphological microstructures of the composite scaffolds are examined by environmental scanning electron microscope (ESEM). Compression testing was conducted to evaluate the elastic modulus and yield strength of the scaffolds with different ratios of calcium phosphates to chitosan. Human osteosarcoma cell lines, MG63, were grown on the composite scaffolds and the adhesion peptide-
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