In-vitro blood and vascular compatibility of sirolimus-eluting organic/inorganic hybrid stent coatings.

The surface characteristics of coronary stents play a pivotal role in inhibiting in-stent restenosis and late-stent thrombosis. In this study, a sol-gel-derived silica xerogel-chitosan hybrid coating was applied to Co-Cr stent and was reported, for the first time, as a biocompatible drug delivery tool in vascular stent application. A dense and uniform chitosan-silica xerogel hybrid coating (<1-μm thick) was applied on bare Co-Cr material. Sirolimus was well incorporated into the hybrid coatings without re-crystallization. The chitosan-silica hybrid coating with 30 wt% silica xerogel showed better mechanical stability and good adhesive strength without any cracking or delamination. The chitosan-silica hybrid coated Co-Cr surface exhibited significantly improved wettability and corrosion resistance compared to the chitosan coated Co-Cr surface. In addition, the hybrid coating layer enabled efficient loading of sirolimus, owing to the unique mesoporous structure of silica xerogel, which further allowed the sustained release of sirolimus over 3 weeks. In-vitro tests with human umbilical cord vein endothelial cells and blood platelets confirmed that the chitosan-silica hybrid coating had excellent cytocompatibility and hemocompatibilty. Thus, this study demonstrated that the chitosan-silica hybrid material is a promising material for coating coronary stents, with minimal risk of in-stent restenosis and thrombogenicity.