Surface modification of stainless steel using nitrous oxide/oxygen glow discharge plasma for biomedical application

Summary form only given, as follows. Plasma treatment is a unique technique used to alter biomaterial surface property and its consequent biological response. In this study nitrous oxide and oxygen plasma was used to modify the surface of 316 stainless steel chips. The goal is to impart unique biological characteristics to the material surface. Stainless steel wafers (0.71 cm /spl times/ 0.71 cm) were cleaned, rinsed exhaustively with water, and dried. The wafers were treated with the gas plasma of mixed N/sub 2/O and O/sub 2/ at molar ratios of 0:1, 1:4, 1:2, 2:3, 1:1, 3:2, 4:1, and 1:0. The plasma was generated at 110 W and 50 mTorr with a total mass flow rate of 50 sccm, and the treatment time was 45 seconds. It is found the molar ratio of N/sub 2/O to O/sub 2/ in the mixture at 1:1 causes high apoptotic percentage. Contact angle data shows that the surface of stainless. steel samples becomes very hydrophilic after the plasma modification. The high resolution data of ESCA indicates that there is a certain amount of nitrate (NO) formed on the plasma treated surfaces, which is considered to play important role to apoptosis. The ESCA depth profile of up to 25 nm from the top surface shows that the elemental composition is changed by the plasma treatment mainly within 6 nm of the surface. The results indicate that mixed gas N/sub 2/O/O/sub 2/ plasmas impart a unique character to stainless steel by forming bioactive layer on the surface. The decreased platelet and leukocyte attachment, combined with increased apoptosis in fibroblasts is a distinct combination of biological responses arising from the mixed gas plasma treatment. These initial results suggest it may be of particular use relative to stainless steel stents where decreased platelet and leukocyte attachment are advantageous and induction of apoptosis could limit in-stent restenosis.