2020 Volume 33 Issue 2 Pages 167-175
Recently, zirconia (ZrO2) has gained increasing importance and popularity as an implant material in addition to titanium (Ti). Fibronectin (FN) consists of cell-adhesive molecules that enhance the adhesion and migration of cells. The specific binding of FN on the surface of Ti or ZrO2 may serve to enhance the osseointegration and biological sealing at the epithelium-implant interface. Accordingly, it is important to analyze the response and application of FN to Ti and ZrO2 surfaces. Superhydrophilic surface modification with plasma treatment is reported to enhance the adsorption of the proteins to implant materials. This study aimed to evaluate the binding behavior of FN on the plasma-treated ZrO2 surface in comparison with the Ti surface. In addition, the mechanism of enhancement of the adsorption of FN is considered by surface analysis.
Atmospheric-pressure plasma treatments were performed to a Ti or ZrO2 sensor (Ti-Plasma, ZrO2-Plasma) that was designed for quartz crystal microbalance (QCM-D) apparatus. An untreated titanium sensor (Ti-Air, ZrO2-Air) and gold sensor (Au-Air) were used as controls. Laser scanning microscopic observation, X-ray photoelectron spectroscopic analysis (XPS), contact-angle measurement and evaluation of surface energy were performed. Subsequently, adsorption behavior of FN was assessed using the QCM-D method. Surface energy, and in particular, cp components in the Plasma group, were increased compared to those in the Air group. The amount of FN adsorption was increased in the Ti-Air and ZrO2-Air groups compared to Au-Air. In addition, the specific binding of FN was increased in the plasma-treated groups (Ti-Plasma and ZrO2-Plasma) compared with the untreated groups (Ti-Air, ZrO2-Air). No apparent differences in FN adsorption were recognized between the Ti and ZrO2 groups. The reason was considered to be that similar kinds of oxides and hydroxyl groups were detected on both Ti and ZrO2. The amount of FN adsorption was increased in the plasma-treated groups, because the carbon contents were decreased and basic-hydroxyl groups with positive charge were increased by the plasma treatment, leading to an increase in the amount of FN adsorption that has negative charge.
These results suggested that FN adsorption behavior is almost the same between Ti and ZrO2 and that plasma treatment may promote the adsorption of FN to titanium and ZrO2.