Silver-doped hydroxyapatite coatings formed on Ti-6Al-4V substrates and their characterization

Coatings with antibacterial components for medical implants are recommended to reduce the risk of bacterial infections. Therefore hydroxyapatite (HA) coatings with addition of chitosan (CS) and silver (Ag) are proposed in this work in an attempt to resolve this problem. Ti-6Al-4V substrates were modified by a chitosan film to study the influence of surface modification on the formation of the HA-Ag and HA-CS-Ag coatings. Using a thermal substrate method, HA and HA-CS coatings doped with Ag(+) were prepared at low substrate temperatures (90°C). Coated surfaces were examined using X-ray diffraction and scanning electron microscopy. The amount of silver in the deposited coatings was analyzed by atomic absorption spectroscopy. From this study it is concluded that the substrate surface modified by a chitosan film promotes the coating formation and increases the antibacterial activity of produced coatings against a strain of Escherichia coli. The adhesion of E. coli (ATCC 25922) to sheep erythrocytes was decreased by 14% as compared with the reference samples without Ag. It could be explained by the inhibition of bacterial adhesins by Ag(+) ions released. The combined action of silver ions and chitosan resulted in a 21% decrease in adhesive index.