小干扰RNA分子（siRNA）临床应用的关键是递释系统。课题前期制备的具有自主知识产权的偶联结构cRGD-siVEGFR2（血管内皮细胞生长因子受体2），能靶向ανβ3受体表达的肿瘤组织，抑制血管生成及肿瘤生长。本课题根据优化cRGD以增强细胞摄取及内体逃逸等理论，设计及筛选得到与ανβ3受体结合活性更强及内体逃逸量最大的XRGD结构；化学修饰及筛选得到沉默效率高及稳定性好的的siVEGFR2-X及siPI3K-X(胞内磷脂酰肌醇激3-酶)分子；化学键偶联XRGD与siRNA，得到XRGD-siRNA分子。体外评价该siRNA递释系统对ανβ3受体表达细胞的靶向性、摄取强度、 细胞内转运、内体释放、及基因沉默等生物学功能及机制；建立小鼠原位脑胶质瘤模型，考察其体内分布、单独及联合两种siRNA给药后的药效学。综合评价XRGD-siRNA偶联物作为siRNA分子肿瘤靶向高效递释系统的可能性。

The key to make siRNA therapy into reality is to develop a high efficiency delivery system. The current nanoparticle-mediated delivery system for the clinical application of siRNA remains facing challenges, including formulation stability, safety, low transfection efficiency, etc. In the previous study, a proprietary cRGD-siVEGFR2 (specifically silence vascular endothelial growth factor receptor-2, VEGFR2) was engineered, which can specifically target ανβ3 receptor-expressed tumor tissue in vitro and in vivo, and inhibited angiogenesis and tumor growth. In the present study, we will optimize the XRGD structure based on the mechanism of cellular uptake, endocytosis and endosomal escape, which make XRGD bind with ανβ3 receptor much stronger. With the theory of chemical modifications for oligonucleotide, we will synthesize and screen chemically modified siHVR2-X and siPI3K-X which show much stronger biological activity and much higher gene silence efficacy. Subsequently, XRGD-siRNA molecules were synthesized by combining XRGD with siRNA (siVEGFR2-X or siPI3K-X). In vitro, we will evaluate characteristics of XRGD-siRNA, including cellular uptake, transport, endosomal release and biological function. In vivo, we will establish subcutaneous and in situ glioma mice models to study the bio-distribution, pharmacodynamics and toxicity of XRGD-siRNA. Combining with results in vitro and in vivo, we will value the XRGD-siRNA conjugate as a platform for siRNA to therapy disease in clinic.