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

Abstract

Although nitinol is one of most popular materials 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 constant electrochemical breakdown voltage and the supernatant and precipitates of corrosion products were prepared as culture media. The dose and time effects of different concentrations of corrosion products on the growth and morphology of smooth muscle cells were evaluated with [(3)H]-thymidine uptake ratio and cell cycle sorter. Both the supernatant 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. Although small stimulation was found with released nickel concentration of 0.95 +/- 0.23 ppm, the growth inhibition became 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 neointimal hyperplasia and the patency rate of cardiovascular stents.

Development of Ti-Nb-Zr shape memory alloys

“…In addition, their mechanical behavior is closer to the one of cortical bones, compared to usual biocompatible materials such as stainless steels and Ti-based alloys currently used. Ni-Ti family of alloys (also known through its Nitinol representative) has been the unique mark of the SMAs, and in spite of concerns related to the presence of Ni [1], the use in biological applications has been tolerated for some years due to the above mentioned complex of properties. In fact, the TiO 2 layer that is present at the surface of commercially finished material is thought to contribute to the good biocompatibility of Ni-Ti by acting as a barrier to Ni ion migration and dissolution out from the surface [2].…”

Atualização sobre endopróteses vasculares (stents): dos estudos experimentais à prática clínica

“…Além disso, possui grande elasticidade e resistência à fratura. Nitinol é a sigla de Nickel Titanium Naval Ordinance Laboratories, cuja liga metálica foi inicialmente desenvolvida para fins militares 18 A fratura de stents de nitinol pode estar relacionada ao polimento e ao revestimento da superfície do stent com óxidos amorfos 19,20 .…”

“…A liberação lenta de íons metais nos tecidos que circundam o local de implante do stent pode ser a razão da resposta inflamatória e hiperplásica local. Os produtos corrosivos das ligas de metal, comumente utilizados na fabricação de stents, (aço inoxidável 316 L e o nitinol) demonstram biotoxicidade 19,31 . O nitinol demonstrou ter efeito inflamatório por causar um aumento da secreção de interleucina-1 ß pelos monóci-tos 32 .…”

“…Os resultados não demonstraram diferença estatística entre os grupos, sendo que nesse tipo de artéria, a principal causa de falência dos stents estaria relacionada a fatores mecâ-nicos com conseqüente fratura dos stents em longo prazo 58,59 . Por exemplo, stents de nitinol podem apresentar fratura relacionada à cobertura e ao polimento com óxi-dos amorfos 19,20 .…”

Growth inhibition of cultured smooth muscle cells by corrosion products of 316 L stainless steel wire

“…6,7 In a recent study, we demonstrated the cytotoxicity of corrosion products of nitinol stent wire on cultured smooth muscle cells. 8 In the present investigation, we aimed to study the effects of corrosion products of 316 L stainless steel wire on the growth and morphology of cultured rat aortic smooth muscle cells. In addition, the affected phases of cell replication were analyzed by cell cycle sorter.…”