Abstract
Background: Many clinical trails have shown that drug-eluting stents are effective in reducing restenosis. These stents are commonly coated with nondegradable polymers as a drug reservoir. However, as the drug is completely eluted, the permanent presence of the nondegradable polymer may induce unfavorable effects. The study was to develop a novel drug eluting stent with a biodegradable collagen coating. Preparation of this stent and its in vitro characteristics and drug release profiles are reported. Methods: A spray coating process was developed to prepare the stent coated with collagen. The force required to remove the collagen coating from the metal stent was investigated by AFM (atomic force microscopy) and a balloon-expansion device. Collagen and sirolimus were sprayed layer-by-layer alternatively onto the external surface of the stent and subsequently crosslinked by genipin, a naturally occurring crosslinking agent. The in vitro hemocompatibility and degradability of the collagen coatings with distinct degrees of crosslinking were evaluated (n = 5). Four forms of the sirolimus-loaded stents were examined in an in vitro elution experiment: a low dose of ~30 mg per stent (0.78 mg/mm2) with or without topcoat; and a high dose of ~65 mg per stent (1.70 mg/mm2) with or without topcoat (n = 3). Results: The results obtained in the AFM examination and the balloon expansion test demonstrated that the collagen coating adhered tightly to the stent surface. The hemocompatibility and the resistance against enzymatic degradation of the genipin-crosslinked collagen increased significantly as its degree of crosslinking increased. The results of the in vitro drug elution study showed that release of sirolimus from the stent without topcoat was able to maintain more than 14 days. The drug release study for the stent with topcoat is currently underway. Conclusions: The aforementioned results indicated that the drug eluting stent developed in the study has a tightly adhered multi-layer collagen coating and can be used as a drug reservoir to sustain release of sirolimus.