Preparation of an antibacterial amorphous thin film by radiofrequency magnetron sputtering using a 65ZnO–30P2O5–5Nb2O5 glass

Abstract A zinc phosphate invert glass consisting of orthophosphate and pyrophosphate groups, with a composition of 65ZnO–30P2O5–5Nb2O5 in mol%, showed antibacterial activity that provides biological safety owing to its well-controlled Zn2+ ion-releasing behavior. In the present work, in order to fundamentally understand the possibility of using bio-functional coating on dental implant surfaces, a glassy thin film was deposited on silica glass or a metallic titanium substrate by radiofrequency magnetron sputtering using the 65ZnO–30P2O5–5Nb2O5 glass as the target material. The resultant coating was an amorphous thin film consisting of orthophosphate and pyrophosphate groups with a trace amount of a metaphosphate group. Although the amounts of orthophosphate and pyrophosphate groups in the film were smaller and larger, respectively, than those in the target glass, the condensation of these phosphate groups could be controlled to a trace amount even during the deposition. The thin film showed effective antibacterial activities against Gram-negative and -positive bacteria without cytotoxicity to osteoblast-like cells. The thickness of the film after being soaked in a Tris buffer solution reduced gradually with a ratio of ~10 nm/d; thus, it showed a relatively-high durability.