Preliminary investigation of the effects of surface treatments on biological response to shape memory NiTi stents

Nickel-titanium (NiTi) offers many advantages for the fabrication of corona ry stents: shape memory, superelasticity, and radiopacity. However, many au thors highlighted the selective dissolution of Ni from the alloy during the corrosion process that could lead to potential toxicity. The improvement o f the NiTi stent's corrosion resistance by different surface treatments (el ectropolishing, heat treatment, and nitric acid passivation) was reported i n a previous article. In the present study a comparative biocompatibility e valuation of such stents was performed through in vitro and in vivo assays. A cell proliferation test was completed to evaluate the cytotoxicity of su rface treated NiTi using human fibroblasts. Then a stent implantation was p erformed in rabbit paramuscular muscle to study the inflammatory response g enerated by the same implants. Cell proliferation tests generally indicated an in vitro biocompatibility of our samples similar to the control group. An in vivo implantation study demonstrated the gradual overall reduction wi th time of the fibrocellular capsule thickness surrounding the implants. Af ter a 12-week implantation period, the fibrous capsules surrounding the dif ferent implants tended toward the same value of 0.07 mm, which suggested th at all surface treatments produced a similar biological response. This low value of the fibrocellular capsule indicated that our NiTi surface treated implants were relatively inert. (C) 1999 John Wiley & Sons,Inc.