The Study Of Biodegradable Intravascular Stents

Purpose1 To prepare biodegradable intravascular stents (BIS) with biodegradable materials poly-L-acid (PLLA) and Polyl (1-lactide-co-glycolide) (PLLGA), the capability of BIS is similar to metallic stents.2 To investigate BIS's biocompatibility, and evaluate the histopathological findings at a fixed timetable after the BIS implanted so as to determine the possibility of BIS implanted into arteries.3 To prepare drug eluting BIS with antiproliferation agent-paclitaxel, and both the drug release BIS and bare BIS (without any drug) be implanted into iliac arteries of canine models of restenosis, to assess the effect of paclitaxel releasing drug BIS at preventing neointimal hyperplasia.Materials and Methods1 Spiral BIS were prepared with PLLA (153 kDa, type A), PLLGA (141 kDa, type B), and PLLGA(141 kDa, contains paclitaxel, type C). The stringent physical and mechanical properties of the BIS were tested.2 Spiral BISs (type A and B) were implanted into iliac arteries of 8 canines, the animals were euthanized according to a fixed timetable for histopathological assessment.3 Both paclitaxel containing BIS and bare BIS were implanted into iliac arteries of the canine models of restenosis (n=8), the animals were euthanized 6 weeks after implantation for histopathological and immunohistochemical assessment.Results1 The strut of three types BIS is from 0.5mm, the diameter of BIS from 12mm., and the length from 3cm.2 Fibrosis was evidence surrounded the Struts of BIS Iwk days after implantation, and scarce blood platelets were deposited on it. At 2wk, endothelization of the BIS was not completed. At 4wk, the struts were covered completely by neointima. At 8wk, the neointima seemed not to be thickening, the arteries' wall were smooth and intact.3 Some significant differences were noted between the paclitaxel BIS group and bare BIS group. The mean lumen area(LA)of bare BIS was smaller than that of the paclitaxel BIS group (77586 n m2 vsl13 435μ m2, p<0. 001 = . And the mean intimal area (IA) of bare BIS was larger than that of paclitaxel BIS group (24 803 μ m2 vs 12 931 μm2, p<0.001). The PCNA positive ratio of bare BIS group was higherthan that of paclitaxel group (38%±15%vs 11%±0. 31%, P<0.01).Conclusson1 The mechanical characteristics of spiral BIS could fulfill the stringent physical, mechanical and chemical properties for the stents implanting to arteries. Characteristics of type A are superior to that of type B and C.2 Spiral BIS is convenient to be deployed with stringent mechanical properties and good biocompatibility. After implanted into arteries, the BIS do not induce sever inflammatory or foreign body reaction. At 8wk, BISs were covered completely by neointima, after 8wk, the neointima thickening seem reduced.3 BIS as a vehicle of loadingand releasing drugs could be inhibit significantly the VSMC and neointimal hyperplasia with antiproliferration agent-paclitaxel. BIS is promising and a now strategy in preventing restenosis.