Sol–gel-based zirconia biocoatings on metal structurally enhanced by polyethylene glycol

For medical components, 316L stainless steel (SS) is widely used. After a period of time, its surface naturally generates a passive oxide layer. Although this layer prevents oxidation or corrosion in an air environment, corrosion still occurs with environmental variation. Thin-film ZrO₂ coatings on 316L SS deposited using a sol–gel process are a promising solution. In this work, a modified sol–gel process that uses polyethylene glycol as the binding agent was applied to improve the adhesion and reduce the thickness of ZrO₂ coatings on 316L SS. The physical, chemical, and topographical properties of ZrO₂ coatings were evaluated. Human umbilical vein endothelial cells were cultured on ZrO₂/316L SS and stained with fluorescent dyes to observe their morphology. Then, the 3-(4, 5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS assay) was used to evaluate their proliferation activity on ZrO₂/316L SS. The pro-inflammatory responses from the cells on ZrO₂/316L SS were further assessed using the enzyme-linked immunosorbent assay. The results show that an appropriate annealing process is required to remove solvents and additives and to improve the mechanical properties of ZrO₂ coatings. The addition of polyethylene glycol reduces the annealing temperature, enhances the mechanical properties of ZrO₂ coatings, and maintains surface biocompatibility. This paper contributes to the understanding of the cells viability, ZrO₂ sol–gel film cytotoxicity, and 316L SS stainless steel biocompatibility.

Figure shows that the up-regulation of MCP-1 in HUVECs was time- and dose-dependent. With increasing treatment time, the released concentration of MCP-1 increased. A significant difference among doses became obvious after 4 h of treatment. Hence, the examination of pro-inflammatory responses was performed at 4 h after HUVEC incubation on the samples. The concentration of MCP-1 released by HUVECs cultured on the surface of 316L SS (the control) was higher than those on ZrO₂/316L SS.