Research On Preparation And Properties Of The Drug-loading Aliphatic Polycarbonate Coating Stents

Percutaneous coronary intervention (PCI) has experienced angioplasty balloon, bare metal stents (BMS) and drug-eluting stent (DES) for more than30years. DES can delivery drugs directly to the targeted lesion site and decreases coronary restenosis rate to less than10%. DES is prepared with a layer or two layers of durable polymer coating on the metal stent surface in order to complete the purpose of medicine and drug delivery. The polymer and BMS will permanently retain in the blood vessel. The durable polymer may lead to vascular delay healing and (very) late stent thrombosis. Therefore, the motivation behind the development of newer devices has been the attainment of optimal antirestenotic efficacy at a minimum of arterial wall toxicity. Biodegradable polymer DES is one of the research trends.Biodegradable polymer DES offer controlled elution of active drug from the stent backbone by means of a biocompatible polymer coating, which after completion of its useful function, slowly degrades to inert organic monomers, thereby dissipating the risk associated with the long-term presence of durable polymer in the coronary vessel wall. Aliphatic polycarbonate (APC) has been shown to have good biodegradability and biocompatibility in vivo. In this paper, APC is reported as stent coating material and is directly coated on the surface of316L stainless steel stent. The paper includes the following contents:1. The surface treatment of316L stainless steel stent and spray-coating procedure of DES are investigated, and the appropriate process parameters are gained. And then effects of preparation methods on property and drug release kinetics of sirolimus-loading DES are discussed, finally the reasons for different effects are theoretically analyzed in detail.2. Mass loss and water intake rate of APC are studied in phosphate buffered saline (PBS). Poly(ethylene carbonate)(PEC) and poly(propylene ethylene carbonate)(PPEC) are preferably chosen as stent coating materials according to the experimental results. Then the excellent biocompatibilities of PEC and PPEC are preliminarily demonstrated by in vitro cytotoxicity test (MTT assay), hemolysis test and partial thromboplastin time test (PTT). 3. PPEC is synthesized by ethylene oxide (EO), propylene oxide (PO) and carbon dioxide (CO2) and catalyzed by glutaric zinc (ZnGA). Then in vitro feasibility studies of the utility of PEC and PPEC as coating materials for drug-eluting stent are reported. All the experimental results demonstrate that drug-loading APC coating stents have broad application prospects.4. Factors to affect drug release of DES are researched in vitro. The factors include drug free polymer, drug gradient layer, the mass ratio of carrier and drug, different drug carriers and drug release medium. The results can optimize the design of biodegradable drug carrier and DES.