Electrophoretic deposition of composite hydroxyapatite–chitosan–heparin coatings

Electrophoretic deposition method has been developed for the fabrication of organic–inorganic composite coatings for biomedical applications. The coatings were obtained as multilayer and functionally graded materials (FGM). Needle-shaped hydroxyapatite (HA) particles were prepared by a wet chemical method and used for the fabrication of chitosan–HA layers. The HA particles in the chitosan matrix showed preferred orientation of c-axis parallel to the substrate surface. Multilayer coatings were obtained, which contained pure chitosan layers and composite HA–chitosan layers. The thickness of the multilayer coatings was in the range of 2–100 μm. The thickness of the individual layers can be varied by the variation of deposition conditions. The feasibility of co-deposition of chitosan and heparin has been demonstrated. The proposed mechanism of heparin deposition is based on the use of non-stoichiometric chitosan–heparin complexes. The deposition yield and coating composition have been studied at various deposition conditions. The addition of heparin to chitosan solutions resulted in increasing deposition rate. Composite chitosan–heparin layers were used for the surface modification of HA–chitosan coatings. Obtained results pave the way for the electrophoretic fabrication of novel FGM coatings for biomedical implants with improved blood compatibility. The coatings were studied by X-ray diffraction analysis, thermogravimetric and differential thermal analysis, electron microscopy, and Fourier transform infrared spectroscopy.