Electrophoretic Deposition of Gelatin/Hydroxyapatite Composite Coatings onto a Stainless Steel Substrate

Biodegradable polymers and bioactive ceramics are being combined in a variety of novel materials for tissue engineering scaffolds. These composite systems, which combine the useful mechanical properties of polymers with the bioactivity of ceramics, seem to be a promising choice for bone tissue engineering. In recent years, the use of biopolymers that gelate on cooling has received a lot of attention with regards to the production of laminates and coatings. In this work, we report the incorporation of hydroxyapatite (HA) into a gelatin coating on stainless steel substrate using colloidal processing technology. A titania (Ti) buffer layer prepared by dip coating was inserted to improve the bonding strength between the HA/gelatin layer and stainless steel substrate. The suspensions, composed of 1 vol% of HA and three different additions of gelatin, were formulated with a focus on rheological properties for codeposition of both phases by electrophoretic deposition (EPD). The composite coatings performed by EPD were investigated in terms of deposition efficiency and kinetics over different deposition times. The EPD process was performed at both ambient temperature and the gelling temperature of the suspension. While at room temperature no electrophoretic growth of the layers was observed, the thermal gelation of gelatin promotes the growth of a homogeneous, well-adherent coating.