Osteoblastic behavior to zirconium coating on Ti-6Al-4V alloy

Abstract

Purpose: The purpose of this study was to assess the surface characteristics and the biocompatibility of zirconium (Zr) coating on Ti-6Al-4V alloy surface by radio frequency (RF) magnetron sputtering method.

Materials and methods: The zirconium films were developed on Ti-6Al-4V discs using RF magnetron sputtering method. Surface profile, surface composition, surface roughness and surface energy were evaluated. Electrochemical test was performed to evaluate the corrosion behavior. Cell proliferation, alkaline phosphatase (ALP) activity and gene expression of mineralized matrix markers were measured.

Results: SEM and EDS analysis showed that zirconium deposition was performed successfully on Ti-6Al-4V alloy substrate. Ti-6Al-4V group and Zr-coating group showed no significant difference in surface roughness (P>.05). Surface energy was significantly higher in Zr-coating group than in Ti-6Al-4V group (P<.05). No difference in cell morphology was observed between Ti-6Al-4V group and Zr-coating group. Cell proliferation was higher in Zr-coating group than Ti-6Al-4V group at 1, 3 and 5 days (P<.05). Zr-coating group showed higher ALP activity level than Ti-6Al-4V group (P<.05). The mRNA expressions of bone sialoprotein (BSP) and osteocalcin (OCN) on Zr-coating group increased approximately 1.2-fold and 2.1-fold respectively, compared to that of Ti-6Al-4V group.

Conclusion: These results suggest that zirconium coating on Ti-6Al-4V alloy could enhance the early osteoblast responses. This property could make non-toxic metal coatings on Ti-6Al-4V alloy suitable for orthopedic and dental implants.

Keywords: Biocompatible materials; Cell proliferation; Surface properties; Surface-coated materials; Titanium; Zirconium.

Fig. 1

AFM and SEM images of (A and A') Ti-6Al-4V and (B and B') Zr-coating group. The inserted shows Zr peaks of Zr-coating group.

Fig. 2

Cross-sectional view of Zr-coating group by SEM.

Fig. 3

(A) Water contact angle and (B) surface energy. The star (^*) indicates significant difference compared with Ti-6Al-4V group.

Fig. 4

Potentiodynamic polarization curve of (A) Ti-6Al-4V group and (B) Zr-coating group.

Fig. 5

Morphology of osteoblasts at 24 hour incubation on (A) Ti-6Al-4V group and (B) Zr-coating group.

Fig. 6

Proportion of spreading cells of stage 3 and stage 4. The same letters (a, b) indicate significant differences.

Fig. 7

Cell proliferation assay after 1, 3 and 5 days. The same letters (a, b, c) indicate significant differences.

Fig. 8

Alkaline phosphatase activity after 7 days. The star (^*) indicates significant difference compared with Ti-6Al-4V group.

Fig. 9

Reverse transcription-polymerase chain reaction (RT-PCR) analysis of bone sialoprotein (BSP), collagen Type-I (COL-I) and osteocalcin (OCN). Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was used as a reference.