Development of single-phase silver-doped antibacterial CDHA coatings on Ti6Al4V with sustained release

The main theme of this study is to report the development and characterization of single-phase silver-doped calcium deficient hydroxyapatite (Ag-CDHA) coatings on titanium alloy (Ti6Al4V) substrates. Physical evaluations on such coatings like X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), water contact angle and also determining the release profile of Ag+ ions by inductive coupled plasma (ICP) technique are analyzed in this paper. In-vitro test assays such as zone of inhibition test, counting of colony forming units and adherent bacteria assay are used to confirm the antibacterial effectiveness of the coatings against gram negative Escherichia coli and gram positive Staphylococcus aureus bacteria. MC3T3 pre-osteoblasts are used to appraise the cytocompatibility of the as-fabricated coatings. XRD analysis states that in spite of Ag doping, single-phase compositions of CDHA can be retained by combining the modified low-temperature biomimetic coating technology with microwave irradiation. Whole pattern fitting (WPF) and Rietveld refinement of XRD patterns confirm that microwaves helps in successful incorporation and homogeneous distribution of dopant (Ag+ ions) within the CDHA lattice. This results in a controlled and sustained release of Ag+ ions over a period of 14 days. In comparison, Ag-CDHA composite coatings have been reported till date and they do not have a controlled release of Ag+. Antibacterial results confirm good bactericidal effect of Ag-CDHA coatings against both bacteria strains thus suggesting that the need for systemic delivery of antibiotics to treat bacterial infections at implantation sites could be eliminated. Cytocompatibility test indicates that the released amount of Ag+ ions do not hinder pre-osteoblast cell proliferation and SEM images confirm the successful attachment and spreading of MC3T3 cells all over the coatings.