骨质疏松症用骨靶向降钙素可注射控释体系的构建及机理研究

In the treatment of osteoporosis, due to the short half-life and the broad distribution of receptors in vivo, salmon calcitonin (sCT) usually exhibits low bioavailability and high clearance rate after subcutaneous injection, leading to limited therapeutic effects. In order to resolve these problems, this project attemps to design and study a series of bone-targeted sCT and their injectable controlled release systems. By modifing the amino acid in non-functional section of sCT and introducing bisphosphonates (BP) as bone-targeted molecules, we will obtain a series of bone-targeted BP-sCT. Then, we will prepare temperature-sensitive systems based on degradable star-polymers with negative charge. These systems can form gels in vivo after subcutaneous injection and are used to load BP-sCT. The specific adsorption of BP-sCT with different molecular structures on hard tissue will be studied. And these BP-sCT loaded systems will also be investigated in terms of physicochemical properties and in vitro release profiles. The in vivo release behaviors, degradation profiles, targeting capability on bone and restoration capability of the bone trabecular will be studied using osteoporosis disease model rats. With the help of computer simulation, we will also investigate the mechanisms. This project can provide valuable mechanism basis for the development of new anti-osteoporosis drugs and delivery systems.

骨质疏松症治疗中，由于半衰期短和体内药物受体分布广泛，鲑鱼降钙素（sCT）在皮下注射后存在着生物利用度低、体内清除率高等关键问题，因而难以达到理想的治疗效果。本申请拟从多肽/蛋白质药物的结构-功能角度出发，设计并制备一系列骨靶向降钙素可注射控释给药体系。通过对sCT非功能活性区进行改性，引入不同的二膦酸盐类（BP）骨靶向分子，制备出具有骨靶向性的BP-sCT。进一步设计基于可降解星型聚合物的、带负电荷的温敏高分子材料用以负载BP-sCT，注射后可在体内原位形成凝胶以控释药物，用于治疗骨质疏松症。研究具有不同分子结构的BP-sCT在生物体硬组织上的特异性吸附能力，以及载药体系的理化性能和体外控释行为；通过骨质疏松症模型动物系统研究该载药温敏凝胶在大鼠体内的控释行为、降解行为、骨靶向能力及修复骨小梁的能力。配合计算模拟，阐明其作用机制，为制备新型抗骨质疏松症药物和给药系统提供理论依据。

在骨质疏松症的治疗中，由于半衰期短和体内药物受体分布广泛，降钙素在皮下注射后存在着生物利用度低、体内清除率高等关键问题，本项目通过采用骨桥蛋白启迪的天冬氨酸六肽作为靶向分子，通过化学偶联，将降钙素1-7号位的二硫键打开与之结合，合成了位点明确、合成高效且不破坏降钙素活性的改性多肽药物；改性后的降钙素药物在注射后可以富集于骨组织，其靶向股骨组织的药物浓度与原鲑鱼降钙素相比提升了近3倍，并在注射相同药物剂量的条件下，对骨小梁的数目和骨密度的增加比原降钙素效果明显；通过免疫原性和生物相容性等分析评价，说明骨靶向降钙素药物新剂型具有潜在的医用价值。另一方面，本项目设计了PLGA-PEG-PLGA、羟丙基甲壳素等温度敏感的可注射水凝胶体系，对降钙素实现了可注射和长效缓释的应用。其在接近人体温度时发生相转变；可降解，自身和降解产物均无细胞毒性，生物相容性好。例如，采用鲑鱼降钙素与氧化海藻酸钠制备的复合物负载于水凝胶中，鲑鱼降钙素从原位胶凝载药系统中的持续释放，单次皮下注射药物释放可达30天左右。负载药物的水凝胶系统可以维持鲑鱼降钙素的药物活性，对于治疗糖皮质激素诱导的骨质减少的大鼠股骨显示出持续的降低血清钙浓度并对骨小梁具有重建作用。而负载降钙素的羟丙基甲壳素控释体系可以实现体内外药物缓释长达28天，并且降血钙效果是sCT注射试剂的2.38倍，说明这种生物信号识别增强的温敏水凝胶缓释体系具有潜在的关节腔注射应用价值。.本项目总计发表标注基金号论文19篇，包括Journal of Controlled Release等，授权发明专利3项。本工作有望为治疗骨质疏松症等世界性难题提供有益的新思路。