Atomic layer deposition of biocompatible multifunctional ZnO-TiO2 nanocoatings on the surface of additively manufactured nitinol

In order to enhance the corrosion resistance and bioactivity of the additively manufactured nitinol alloy, ZnO-TiO2 (ZTO) nanocoatings have been synthesised by atomic layer deposition. The supercycle approach was employed to deposit 40 nm coatings with varying ZnO/TiO2 ratios: 5/1, 1/1, 1/5 and 1/20. The results demonstrated that this approach permitted the coating composition to be varied over a wide range. The study of anticorrosion properties in physiological Ringer's solution revealed that the coatings, depending on their composition, are capable of reducing the corrosion rate of nitinol by a value ranging from 4 to 58 times. In vitro studies have demonstrated high viability, good adhesion and spreading of human osteoblast-like MG-63 and mesenchymal stem FetMSC cells on the surface of all samples except those with high zinc content (ZnO and ZTO-5/1). All coatings induced differentiation of both cell lines in the osteogenic direction and demonstrated antibacterial activity against multi-drug resistant A. baumannii (>96 %) and P. aeruginosa (>90 %) strains. The results indicate the considerable potential of the developed methodology for the ALD of ZTO that combine the biocompatibility of titanium oxide, the antibacterial properties of zinc oxide and their overall stability and effectiveness for the protection of nitinol against biocorrosion.