The cytotoxicity of corrosion products of nitinol stent wire on cultured smooth muscle cells.

Although nitinol is one of most popular materi- als of intravascular stents, there are still few confirmative biocompatibility data available, especially in vascular smooth muscle cells. In this report, the nitinol wires were corroded in Dulbecco's modified Eagle's medium with con- stant electrochemical breakdown voltage and the superna- tant and precipitates of corrosion products were prepared as culture media. The dose and time effects of different con- centrations of corrosion products on the growth and mor- phology of smooth muscle cells were evaluated with ( 3 H)- thymidine uptake ratio and cell cycle sorter. Both the super- natant and precipitate of the corrosive products of nitinol wire were toxic to the primary cultured rat aortic smooth muscle cells. The growth inhibition was correlated well with the increased concentrations of the corrosion products. Al- though small stimulation was found with released nickel concentration of 0.95 ± 0.23 ppm, the growth inhibition be- came significant when the nickel concentration was above 9 ppm. The corrosion products also altered cell morphology, induced cell necrosis, and decreased cell numbers. The cell replication was inhibited at the G0-G1 to S transition phase. This was the first study to demonstrate the cytotoxicity of corrosion products of current nitinol stent wire on smooth muscle cells, which might affect the postimplantation neo- intimal hyperplasia and the patency rate of cardiovascular stents. © 2000 John Wiley & Sons, Inc. J Biomed Mater Res, 52, 395-403, 2000.