Drug Loaded Polymeric Blends For Developing Vascular Stents

Abstract

In-stent restenosis and neo-intimal hyperplasia are long-term limitations of metallic stents. Local delivery of medications to transluminal angioplasty sites to prevent restenosis is receiving worldwide attention. Development of localized application of antiproliferative agents, and gene therapy via bio-degradable coatings on metallic substrates proved to be successful in reducing restenosis but was limited by the problems of limited drug load, etc. The presence of a foreign object for a long period of time may lead to the further narrowing of the treated lesion. The rationale for usage of bioresorbable drug eluting stents is the ability to store large quantities of drug and deliver measured quantities of the drug during the entire time the stent is present. This way one could hope for efficient repression of the proliferation of smooth muscle cells, effectively leading to control over restenosis. One might also enhance the endothelialization of the treated stent by absorbed promoters in the stent fiber matrix. v The aim of the study was to modify the mechanical characteristics, improve degradation performance and develop a curcumin loaded stent with favorable elution characteristics on the biodegradable PLLA based stent designed by Su [1]. We have achieved the desired control of the polymeric substrate by modifying and redesigning the bioresorbable fibers, employing different polymer blends of various compositions. The degradation rate of the optimal blend was 12% loss of weight over 4 weeks incubation in saline at 37 Deg C. The thermal analysis showed a melt temperature of 169 Deg C, thereby allowing loading of curcumin in the stent matrix during melt extrusion. We mechanically tested stents made from various polymer blends. The stent inflation pressure ranged from 3-5 atmospheres. Recoil following incubation in 37 Deg C saline varied from 2-10 % over a period of 1-4 weeks, depending on polymer blend. We found that most of the results in regards to stent performance testing were comparable to the mono-polymer stents designed and developed by Su [1] and Satasiya [2]. We conclude that a stent made of selected polymer blends could perform better in many aspects, including drug elution, inflammatory response and mechanical performance than previous drug-eluting bioresorbable stent models.