Abstract： Objective To explore the embolization effect of new platinum coils coated with [4COOH-P (DLLA-co-TMC)] biodegradable polymer and released vascular endothelial growth factor (VEGF) into intracranial aneurysms on rat intracranial aneurysms. Methods A total of 54 adult healthy female SD rats were randomly divided into Group Ⅰ with general platinum coils, Group Ⅱ with polymer-coated platinum coils and Group Ⅲ with platinum coils modified with VEGF (n=18).The right common carotid arteries (CCA) of rats in each group were exposed; and the 8 mm lengths of platinum coil segments were inserted into the ligated right CCA of rats. The distal right CCA was performed ligation and restored the blood flow; 6 rats each time at 15,30 and 90 d after the surgery were chosen;and the distal right CCA was used as aneurysm models,and the left CCA without the coil placement or surgical disruption in Group I with general platinum coil was chosen as normal control.The proliferation and fibrosis of endothelial cells were observed by HE staining; von Willebrand Factor (vWF) expression was detected by immunohistochemical staining; and VEGF expression was examined by Western blotting. Results Cellular proliferation and fibrosis in Group Ⅲ with platinum coils modified with VEGF enjoyed significantly higher grade than those in Group Ⅰ with general platinum coils 10,60 and 90d after the surgery (P＜0.05); Cellular proliferation and fibrosis in Group Ⅲ with platinum coils modified with VEGF enjoyed significantly higher grades than those in Group Ⅱ with polymer-coated platinum coils 30 d after the surgery (P＜0.05).Pathological observations showed that the massive intimal hyperplasia and substantial clot completely occluded the aneurysm lumen in Group Ⅲ with platinum coils modified with VEGF; New small blood vessels having vwf-positive expression were noted in the fiberized tissues;the thrombosis in Group Ⅰ with general platinum coils and Group Ⅱ with polymer-coat platinum coils were not fully organized and showed loose hyperplasia structure with a large number of internal spaces.Western blotting indicated that the VEGF level in Group Ⅲ with platinum coils modified with VEGF were significantly higher than that in other groups 15 and 30 d after the operation,however,the VEGF level in Group Ⅲ with platinum coils modified with VEGF 90 d after the surgery was decreased because the lumen completed fibration and degradation of 4COOH-P (DLLA-co-TMC). Conclusion The VEGF-eontaining biodegradable polymer,by slowly releasing VEGF to modify the surface of platinum coils, could enhance the cellular proliferation, thrombosis and formation of dense fibrous tissue in aneurysm lumen; as compared with general platinum coils,these new platinum coils could occlude the rat aneurysm faster and more completely.