New solutions for combatting implant bacterial infection based on silver nano-dispersed and gallium incorporated phosphate bioactive glass sputtered films:A preliminary study

Ag/Ga were incorporated into resorbable orthopaedic phosphate bioactive glasses(PBG,containing P,Ca,Mg,Na,and Fe)thin films to demonstrate their potential to limit growth of Staphylococcus aureus and Escherichia coli in post-operative prosthetic implantation.Dual target consecutive co-sputtering was uniquely employed to produce a 46 nm Ag:PBG composite observed by high resolution TEM to consist of uniformly dispersed~5 nm metallic Ag nano-particles in a glass matrix.Ga^(3+)was integrated into a phosphate glass preform target which was magnetron sputtered to film thicknesses of~400 or 1400 nm.All coatings exhibited high surface energy of 75.4-77.3 mN/m,attributed to the presence of hydrolytic P-O-P structural surface bonds.Degradation profiles obtained in deionized water,nutrient broth and cell culture medium showed varying ion release profiles,whereby Ga release was measured in 1400 nm coating by ICP-MS to be~6,27,and 4 ppm respectively,fully dissolving by 24 h.Solubility of Ag nanoparticles was only observed in nutrient broth(~9 ppm by 24 h).Quantification of colony forming units after 24 h showed encouraging antibacterial efficacy towards both S.aureus(4-log reduction for Ag:PBG and 6-log reduction for Ga-PBG≈1400 nm)and E.coli(5-log reduction for all physical vapour deposited layers)strains.Human Hs27 fibroblast and mesenchymal stem cell line in vitro tests indicated good cytocompatibility for all sputtered layers,with a marginal cell proliferation inertia in the case of the Ag:PBG composite thin film.The study therefore highlights the(i)significant manufacturing development via the controlled inclusion of metallic nanoparticles into a PBG glass matrix by dual consecutive target co-sputtering and(ii)potential of PBG resorbable thin-film structures to incorporate and release cytocompatible/antibacterial oxides.Both architectures showed prospective bio-functional performance for a future generation of endo-osseous implant-type coatings.