Nanosecond Laser Induced Periodic Surface Structures on Drug Elution Profiles in Stents

Abstract

Drug-eluting stents (DESs) have profoundly affected the field of interventional cardiology as a transformative technology by dramatically reducing the problem of in-stent restenosis. However, the development of adverse, late stent thrombosis (LST) raises the question of the safety profile of the DES. The aim of the study is to develop better DESs that can increase the amount of drug (sirolimus) loading while slowing down the drug release rate and potentially eliminating the polymer, all of which are expected to aid in the prevention of LST. Nanosecond pulsed laser texturing of Nitinol stent surfaces was first performed and the surface topography was analyzed using an optical profilometer. The results showed that the surface texture parameters such as surface area ratio, its roughness, volume of fluid retained per unit area, and mean valley slope suitable for drug adhesion, retention, and elution were significantly increased due to laser texturing. Subsequently, the drug elution profiles were studied for four different types of stents: laser-textured and untreated stents coated with the drug only and the drug-polymer. Laser texturing reduced the cumulative sirolimus release from 73% to 25% in drug only coated stents and from 93% to 45% in drug-polymer coated stents and showed promise for applying polymer-free drug coatings on the DES.