Preparation And Characterization Of HA/Ag Composite Coatings By Electrochemical Deposition On Titanium Surfaces

Titanium and its alloy have been widely used in orthopedics due to their excellent mechanical property, biocompatibility and anti-corrosion capability. However, it is bioinert and cannot form direct bonding with bone tissue. Hydroxyapatite (HA) is the main inorganic composition of bone tissue and has been used for hard tissue repair because it has good biocompatibility and bioactivity, and is able to chemically bond to bone tissue. Titanium with HA coatings have attracted much attention due to the combination of good mechanical properties and superior bicompatibility.Bacterial infection is one of the main causes of failure of implants in clinics. Silver (Ag) has strong bectericidal ability and can kill a broad spectrum of microbial. It also exhbits low toxicity toward to mammalian cell. Incorporating silver into the HA coatings is an attractive method to impart HA coatings with antibacterial properties. However, Ag particles in the coatings are easy to agglomerate. The uniform distribution of Ag is still a challenge and which in turn affects the application of the coatings.In this study, we employed pulsed electrochemical deposition (PED) to co-deposit HA and Ag simultaneously, which realized the uniform distribition of Ag particles in the coatings. This method is based on the use of a well-designed electrolyte containing Ca2+, PO43-, A(?)+ and L-Cysteine, in which cystein works as the coordination agent to stabilize free Ag ions. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Energy Dispersive Spectroscopy (EDS), and tensile strength strength test were used to characterize the morphology, composition and tensile adheison strength of the composite coatings. It was found that the coatings had a network structure composed of needle-like HA with Ag nano-dots uniformly distributing in it. [Ca2+]= 5.0 mmol/l, [PO43-]= 3.0 mmol/l, pH:4.0, pusled potential=-2V, and the deposition time= 2 h were the optium experimental conditions.The antibacterial test and osteoblast (Sprague-Dawley rat) culture were used to evaluate the antibacterial effect and biocompatibility of HA/Ag composite coatings, respectively. The results indicated the coatings fabricated in 0.5 mmol/l Ag+ electrolyte had good biocompatibility and good antibacterial effects on two types of bacteria, E. coli and S.albus.The coatings went through heat treatments at different temperature. The results showed the tensile adheison strength of coatings was improved after heat treatments. HA in the composite coatings started to transform intoβ-TCP at nearly 700℃. The antibacterial test and osteoblast (Sprague-Dawley rat) culture demonstrated heat treatments enhanced the biocompatibility without sacrificing the antibacterial properties of the coatings. In summary, this study provided an alternative method to prepare bioactive surfaces with bactericidal ability for biomedical devices.