Evaluation of ion implantation for anti-thrombogenic coronary stent in vitro and in vivo

The aim of this study was to evaluate the effect of ion implantation on the surface of anti-thrombogenic coronary stent. Nitrogen (N) was implanted into the cobalt-chromium surface by using an ion source under a plasma environment to enhance its hardness and surface modification. The N ion dosage was 1 × 1015 ions/cm2. All analysis results of the ion implanted stent were compared with those of bare metal stent. The N component and distribution were confirmed by auger electron spectroscopy. Microhardness was significantly increased after 40 min of implantation (415.3 ± 12.38 HV, 18.9 ± 2.62%). The surface was altered to hydrophobic status through ion implantation (30.6 ± 1.12% in contact angle increment). Platelet adhesion, and smooth muscle cell migration and proliferation were prevented in the ion implanted group (43.9%, 11.2%, and 45.1%, respectively). To verify the in vitro result, stents were implanted to rabbit iliac artery and isolated at 4 weeks post implantation. Then, the stents were subjected to histological analysis. No significant differences in injury score, internal elastic lamina, lumen area, and restenosis rate were found. However, the fibrin score was more significantly decreased in the ion beam-implanted group (2.5 ± 0.15) than in the bare metal stent group (1.8 ± 0.31, n = 10, p < 0.05). Taken together, ion beam implantation may be an efficient accessorial tool for preventing in-stent restenosis and in-stent thrombosis.