Annealed thin-film zirconia coating adhered on 316L stainless steel as a bio-inert indwelling needle

A 316L stainless steel plate was covered with a ZrO₂ coating using the sol-gel dip coating technique, and preliminary in vitro and in vivo studies were conducted. The morphology and crystal structure of the coatings were examined using scanning electron microscope and X-ray diffraction, and their surface chemical structures were characterised using X-ray photoelectron spectroscopy. The quality and adhesion of the coatings on the substrate were measured using a nano-indenter with lateral force and scratch modes. ZrO₂ was formed on a 316L plate at various temperatures, resulting in different crystalline structures, surface morphologies, and integration with the 316L surface. The optimal conditions to produce ZrO₂-316L are an annealing temperature of 500°C and duration of 1h (ZrO₂/316L_500), yielding an adhesive force of 595μN. 3T3 cell morphology, adhesion, and viability using the live/dead cell staining protocol were assessed. Cell affinity was significantly enhanced on the surface of ZrO₂/316L_500, compared to the as prepared sample. Furthermore, after mice were injected with 316L and ZrO₂/316L_500 needles for durations of up to 72h, wound contraction, inflammation, and proliferation were compared. The results indicate that the ZrO₂/316L_500 needle exhibits high potential as a bio-inert coating and that it can be applied to scalpels and indwelling needles.