Pulse Electrochemical Driven Synthesis of Hydroxyapatite and Silver Composite Coatings by Chitosan Mediation

Attention has been always paid to long-term antibacterial property of biomaterial surface. In this study, the antibacterial hydroxyapatite (HA) and silver (Ag) composite coatings are prepared in situ using pulse electrochemical driven by regulation of chitosan. The influence of both Ag+ and the salt on the composition and the morphology of the composite coatings was investigated. The underlying mechanism regulated to HA and Ag nanoparticles formation by chitosan (CS) was studied. The study showed that the optimized experimental conditions were the following: potential of -1.3 V, Ag+ concentration of 0.06 g.L-1, Ca2+ concentration of 5 mmol.L-1. Under these conditions, the biological activity of the composite coatings, their antibacterial properties and physiological stability were examined. The results showed that the composite coatings were composed of nano-spherical with three-phases of HA, Ag and CS, where Ag and HA nanoparticles were uniformly distributed in the composite coatings, and covered by a layer of CS. The composite coatings were immersed in supersaturated calcium phosphate solution (SCPS) for mineralization for 10 days at 37 degrees C. The biomimetic mineralization process of the surface of the composite coatings produced fine aticular neat rows of HA with preferential growth of the (002) crystal plane at 25.8 degrees. This indicated that the composite coatings could form apatite in the fast mineralized solution. Also, it was found that bioactivities of the composite coatings were pretty good. In order to examine the physiological stability of the composite coating, the composite coating was immersed in phosphate buffer solution (PBS) at 37 degrees C. In composite coatings, the presence of CS reduced the double ion release rates of Ca2+ and Ag+ , leading to good physical stability. The antibacterial testing of the composite coatings on bacterial strains, including Escherichia coli and Staphylococcus aureus, illustrated antibacterial properties with rates over 99%.