摘要Background Drug-eluting stents represent a major advance in interventional cardiology.However,the current drugeluting stents have significant limitations.One of the major problems is very late stent thrombosis,which is likely caused by inflammation and a hypersensitivity reaction related to a polymer on the stent.A polymer-free sirolimus-eluting stent with a unique nano-porous surface has been developed.This study aimed to evaluate this novel polymer-free sirolimuseluting stent for its efficacy and safety in a pig model.Methods Stents were directly coated with sirolimus (a drug concentration of 2.2 μg/mm2 on the stent surface).The polymer-free sirolimus-eluting stents (PFSES) were compared to standard polymer-coated sirolimus-eluting stents (PCSES) and bare-metal stents (BMS) in 18 pigs.Results At one month the degree of neointimal hyperplasia was similar between the two sirolimus-eluting stent groups and was significantly less compared to BMS ((1.93±0.51) mm2,(1.57±0.69) mm2 vs.(4.45±1.05) mm2,P ＜0.05) At three months,PFSES maintained the low level of neointima ((2.41±0.99) mm2 vs.(4.32±1.16) mm2,P ＜0.05),whereas PCSES had developed significant neointimal proliferation similar to BMS.The inflammation level was significantly higher in PCSES when compared with BMS three months post-implantation (2.50±0.55 vs.0.83±0.75,P ＜0.05) whereas PFSES showed a low level of inflammation comparable to PCSES (1.33±0.52 vs.2.50±0.55,P ＜0.05).Conclusion The PFSES is effective and safe,and appears to be superior to standard PCSEs.