The osteoinduction of RGD and Mg ion functionalized bioactive zirconia coating.

The objective of this study was to investigate the adhesion, proliferation and mineralization of osteoblasts on arginine-glycine-aspartic acid (RGD)- and magnesium ion (Mg+)-decorated zirconia coatings. The zirconia coatings were prepared via a plasma spray; RGD and Mg+ were immobilized via a silane-coupling agent and ion implantation, respectively. This study employed scanning electron microscopy (SEM) to observe the surface morphology of RGD- and Mg+-decorated zirconia coatings; surface roughness and wettability were also measured. The initial adhesion of osteoblasts was measured, and cell morphology and focal adhesion were observed. In addition, the expressions of the integrins a1, a2, a5, av, and ß1 were measured using RT-PCR. A cell count was conducted to measure proliferation. The expressions of ALP and OCN were detected based on a western blot analysis, and mineralized nodules were observed to visualize the mineralization of osteoblasts. A nanoscale surface structure could be found on the Mg+-decorated zirconia coating, and the RGD-decorated zirconia coating showed better wettability (p < 0.05). Cells on the RGD- and Mg+-decorated zirconia coating possessed better spreading properties than did cells on nondecorated surfaces, and more focal adhesion was observed. The higher expressions of the integrins a5, av and ß1 were found on the RGD-decorated zirconia coating (p < 0.05). The western blot results demonstrated that the introduction of Mg+ heightened the expressions of ALP and OCN. More and bigger mineralized nodules were observed on the Mg+- and RGD-decorated zirconia coating, which consisted of small mineralized nodules. RGD- and Mg+-functionalized zirconia coating facilitates the osteogenic reaction of osteoblasts. RGD improves the adhesion of osteoblasts, and Mg+ benefits the mineralization of osteoblasts. In addition, a synergistic effect was found between RGD and Mg+, allowing better performances with regard to adhesion, proliferation and mineralization when the two were used together rather than as separate decorations.