High nitrogen stainless steel drug-eluting stent - Assessment of pharmacokinetics and preclinical safety in vivo

Pharmacokinetic analyses were performed using 20 pigs for 120-days implantation, while one sirolimus-eluting stent was implanted into one of their coronary artery. At different time points, the residual sirolimus on the stent, delivered locally (to artery wall), regionally (to adjacent and downstream muscle) and systemically (to plasma and visceral organs), was detected throughout 120 days. Preclinical safety evaluation was performed using 32 pigs for 180-days implantation to study the safety of metal platform material and the effectiveness of sirolimus eluting coating on the HNS stent. The neointima area, restenosis rate and inflammatory grade for HNS and control group stents were detected and analyzed. Approximately 80% sirolimus was eluted from the sirolimus-eluting stents after 30-days implantation in vivo. Additionally, there was sustained sirolimus in the artery wall, cardiac muscle and heart throughout 120-days implantation, and sirolimus accumulated to the peak at 90-days implantation. It was inferred that the sirolimus eluting stent in this study was covered by neointima before 90-days implantation, indicating that the sirolimus eluting coating on the HNS stent was safe and effective. Very little sirolimus was distributed in visceral organs after 14-days implantation. HNS sirolimus-eluting stent exhibited lower restenosis rate and lower inflammatory grade than control group, which verified that the sirolimus-eluting coating design in this study was reasonable and practical. In addition, there were no significant difference in restenosis rate and inflammatory score between HNS bare-metal stent and drug-eluting stents, illustrating that HNS has good bio-compatibility and is suitable to use as coronary artery stent material.