Incorporation of bovine serum albumin in calcium phosphate coating on titanium.

Calcium phosphate (Ca-P) and bovine serum albumin (BSA) were coprecipitated as a coating on commercially pure titanium (cpTi) with a high protein loading (15 wt %) by employing a recently developed wet-chemistry technique. It was observed that the incorporation of BSA significantly modified the morphology, composition, and crystallinity of the Ca-P coating. The Ca-P coating without BSA is a mixture of hydroxyapatite (HA) and octacalcium phosphate (OCP) with sharp-edged thin OCP crystal plates on the top layer, whereas only an HA phase was detected in the Ca-P/BSA coating. The crystal plates in the latter had a more rounded appearance. The Ca-P/BSA coatings were immersed respectively in neutral (pH 7.4) and acidic (starting pH 4.0) phosphate-buffered saline (PBS) at 37 degrees C over a 14-day period. No protein release was detected in the neutral PBS during the immersion; however, a continuous release of BSA was measured in the acidic PBS, subsequently leading to the formation of a very dense and well-adherent composite coating of BSA and Ca-P on cpTi. The present study provides the possibility to achieve a long-term effective release of biologically active proteins from a Ca-P-coated metallic implant.