Chitosan/carbonated hydroxyapatite composite coatings: Fabrication, structure and biocompatibility

Chitosan/carbonated hydroxyapatite composite coatings (CCHCs) were fabricated according to the following steps: (i) preparation of calcium carbonate coatings (CCCs) on Ti6Al4V substrates by electrophoretic deposition; (ii) transformation of CCCs into carbonated hydroxyapatite coatings (CHACs) in a phosphate buffer solution (PBS); and (iii) formation of CCHCs by modification of CHACs with chitosan. Inorganic constituents in CCHCs are plate-like carbonated hydroxyapatite particles with a low crystallinity. Interestingly, macropores with a pore size of 0.5–2 μm still remain among the carbonated hydroxyapatite plates even after the chitosan deposits homogeneously on the coatings. Moreover, CCHCs have moderately hydrophilic surfaces with a contact angle of 29.4° due to the presence of the chitosan. Biocompatibility tests have been carried out by using human bone mesenchymal stem cells (hBMSCs) as cell models. The hBMSCs show better cell morphology, adhesion, spreading and proliferation on CCHCs than on CHACs. The excellent biocompatibility of CCHCs is mainly attributed to the organic/inorganic compositions, macroporous structure and moderately hydrophilic surfaces. Hence, CCHCs have great potentials for bone implants.