In Vitro Biological Activity of Osteoblasts on Nickel-Titanium Shape Memory Alloy

Kim, Yong Sik; Rhee, Seung Koo; Sohn, Jong Min; Chung, Jin Wha; Choi, Dong Won; Kwon, Soon Yong

Abstract

The unique properties of the nickel-titanium shape memory alloy (NiTi) have provided the enabling technology and potential for many applications in the orthopaedic and dental fields. In this study, the cytocompatibility of NiTi was analyzed by investigating the biological activity of osteoblasts on NiTi in vitro, followed by comparative analysis of their activity on commercially pure titanium (CP-Ti). Using an in vitro osteoblast culture model for durations from 4 hours to 1 week, cellular characteristics including number, cell spreading, alignment, and elongation of osteoblasts cultured on grit blasted NiTi, grit blasted CP-Ti, and tissue culture polystyrene (TCP) as a control were characterized. Measurement of total DNA of osteoblasts on CP-Ti, NiTi, and TCP was performed using relatively new fluorescent methods for DNA quantification, and the proliferation of living cells was determined using colorimetric methods. Furthermore, cellular function of osteoblasts was assessed by quantifying alkaline phosphatase enzyme content as a function of exposure to the materials. In terms of morphology, osteoblasts were observed to spread to the greatest extent on TCP followed by NiTi, then CP-Ti. Proliferation based on DNA quantification and biochemical activity was highest for TCP surfaces in general, however, NiTi supported proliferation to a level comparable to CP-Ti. The levels of alkaline phosphatase activity between the three groups were not significantly different. Overall, when compared with CP-Ti, NiTi shows remarkable cytocompatibility with osteoblasts in vitro.