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Understanding and controlling the process of electrochemical deposition (ECD) of a mineralized collagen coating on metallic orthopedic implants is important for engineering highly bioactive coatings. In this work, the influence of different ECD parameters was investigated. The results showed that the mineralization degree of the coatings increased with deposition time, voltage potential and H2O2 addition, while chitosan addition led to weakening of mineralization, heavy mineralization resulted in a porous coating morphology. Furthermore, two typical coatings, dense and porous, were analyzed to investigate their microstructure and evaluated for their cytocompatibility; the dense coating showed better osteoblast adhesion and proliferation. Based on our understanding of how the different coating parameters influenced the coating, we proposed an ECD process in which the pH gradient near the cathode and the collagen isoelectric point were suggested to play crucial roles in controlling the mineralization and morphology of the coatings. The proposed ECD process may offer a guide for controlled deposition of a desired bioactive coating.

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Biphasic alpha-tricalcium phosphate/beta-tricalcium phosphate (alpha/beta-TCP) with a designed phase ratio is thought to have controllable dissolution-reprecipitation behavior that is significant in the repair and regeneration of bone. Amorphous calcium phosphate (ACP) was selected as a precursor to prepare biphasic alpha/beta-TCP. The influence of polyethylene glycol (PEG) content in ACP on its crystallization, or on the phase ratio of the resulting biphasic TCP, was investigated. ACP was synthesized by the reaction of Ca(NO(3))(2) with (NH(4))(2)HPO(4) using PEG as an additive. Depending on the amount of PEG addition, resulting ACP could be crystallized to alpha-TCP, beta-TCP or biphasic alpha/beta-TCP after heat-treatment at 800 degrees C, showing that PEG addition is a critical factor to tailor the phase ratio of biphasic alpha/beta-TCP. One reason for the influence of PEG is that ACP with different PEG content could have two types of unit structures that tend to form alpha-TCP and beta-TCP after crystallization.