Biomimetic surface functionalization of Ti metal incorporated with Ca-Zn and evaluation of in-vitro biological properties

Abstract

This study aims at incorporating Ca2+ and Zn2+ions into the nano-structured titania layer over Ti metal by a simple chemical and thermal treatment approach. The incorporation of these ions was controlled by varying the volumetric ratios of calcium nitrate and zinc nitrate solution on the alkali pre-treated Ti metal followed by heat treatment at 600 °C. The elemental incorporation of Ca predominantly forms calcium titanate and rutile TiO2, while the simultaneous incorporation of Ca-Zn developed anatase TiO2. Subsequently, the optimized Ca-Zn ratio with predominant anatase TiO2 over the surface (Ti-Na-2.5Ca:7.5Zn) of Ti metal was subjected to further detailed evaluation of surface properties and in-vitro characteristics. This dual-element incorporated nanonetwork structure has shown significant improvement in surface roughness and wettability which influence the rate of protein adsorption. Further detailed evaluation displayed the existence of incorporated Zn2+ as ZnO, which supported the Zn/ZnO mediated antibacterial activity against Staphylococcus aureus and Escherichia coli. In-vitro studies also showed the biocompatible efficiency of Ca and Zn ions through their cell adhesion ability, mitochondrial potential, cell viability, and nuclear integrity with minimum effect on single-cell DNA damage towards MG-63 cells. The mRNA expression levels of osteogenic genes such as OSX, RUNX2, OPN, and OCN were analysed using RT-PCR in the MG-63 cells that are cultured over surface-modified Ti metal which further explained the effect of incorporated Ca and Zn ions in regulating their expression. A similar supporting analysis was found during the mineralization process as well, thus this particular surface modification is expected to fasten osteointegration in in-vivo. These promising results suggest our Ca-Zn-incorporated Ti metal as a potential candidate for bone implant applications.