Advances in coronary stent technology--active drug-loaded stent surfaces for prevention of restenosis and improvement of biocompatibility.

Beyond their originally sole mechanical function, current drug-eluting stents (DES) implement the concept of local drug delivery for the re-opening of stenotic arterial vessels, and for prevention of in-stent restenosis as one of the major limitations of conventional bare metal stents (BMS). Current DES consist of a permanent metallic stent platform and an active agent being released from a drug-incorporated polymer coating or a porous stent surface. Although DES have impressively demonstrated their capability of reducing in-stent restenosis, their safety remains under debate due to potential risks, such as delayed healing, late thrombosis and hypersensitivity demanding further development. Current advancements in the stent design address the stent platform, the pharmacologically active substance and/or the drug carrier. For instance, novel biocompatible absorbable stent platforms and drug carriers are developed and novel drugs with a differential effect on vascular endothelial and smooth muscle cells, providing efficient inhibition of muscle cells without altering the endothelial cell function, are identified. Moreover, biofunctionalization of the stent's surface with capture molecules for endothelial progenitor cells are under investigation in order to achieve an in situ endothelialization of the implant. In this context, this review paper discusses the current advances in coronary stent technology with a special focus on novel stent platforms, drugs and stent coatings for the prevention of restenosis and improvement of biocompatibility.