Carrier free rapamycin loaded drug eluting stent: In vitro and in vivo evaluation

In the search for improving the performance of drug eluting stent (DES) various developments are in progress worldwide including use of carrier free DES, use of biodegradable polymers, biodegradable stents etc. In this work, carrier free-rapamycin (RM) coated DES has been prepared, and evaluated by in vitro and in vivo procedures necessary for clinical development. In vitro drug release from the developed stents was carried in different release media, normal saline-isopropanol (NS-IP), phosphate buffer (PB), phosphate buffer saline (PBS) and in human plasma. Simultaneously, drug released at site of implantation and biocompatibility of developed stents was determined after subcutaneous implantation in the SD rats. Developed stent coating method enables fabrication of controllable and homogeneous crystalline RM coatings on stent scaffolds. Continuous release of RM was observed in different release conditions with different release rate, maximum in NS-IP and least in PB. Similarly, after subcutaneous implantation of these stents, RM was found in surrounding tissues and in implanted stent up to 28 days. Biocompatibility studies showed no evidence for presence of necrosis, foreign body giant cell reaction or any type of increased severity of inflammatory reaction, proving potential of developed stents for further clinical development.