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 mu m. 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. (C) 2008 Elsevier B.V. All rights reserved.