基于生物催化/VEGFR/PDGFR双靶标介导的中药脂质体给药系统的构建及评价

The conventional chemical approach is characterized by poor regioselectivity, the requirement of protection/deprotection and being environmently unfriendly. A promising alternative, green biocatalysis, has advantages such as mild reaction conditions, high efficiency and high selectivity. This research employs the enzymatic synthesis of ligands using lipases dissolved in low toxic organic solvent. Besides, the optimization of some crucial variables of the reaction, the screening of enzymes of high regioselectivity and efficiency, and liver active targeting liposomes will also be investigated.. Inhibition of tumor angiogenesis leads to a lack of oxygen and nutrients in the tumor and therefore has become a standard of care for many solid tumor therapies. Dual inhibition of vascular endothelial growth factor receptor (VEGFR) and platelet-derived growth factor receptor (PDGFR) protein kinase activities is a popular strategy for targeting tumor angiogenesis. Tumor cells targetable Venenum Bufonis loaded long circulation liposomes mediated by pazopanib or linifanib will be enzymatic synthesized by using highly efficient and regioselective preparation. The effects of some variables on the enzymatic reaction in different media and lipases were characterized. This research investigates the preparation, pharmacokinetics, tissue distribution, along with its mechanism of growth inhibition of cancer cell and induction of cancer cell apoptosis. Targeting mechanism of drug promoted by carriers is explained by A549 and A498 cell. In a word, this delivery system is a promising novel strategy to improve the bioavailability of natural drugs. These correlational studies have not yet been reported.

化学合成法存在区域选择性差、需要保护/脱保护步骤和环境不友好等诸多问题。反应条件温和、高效、高区域选择性和绿色的生物催化法是一条极具前景的替代途径。本项目拟在低毒性非水有机溶剂中生物催化VEGFR/PDGFR双靶点抑制剂pazopanib或linifanib与胆固醇等反应生成靶头，并优化生物催化合成条件，筛选出高效、高区域选择性的酶。拟进一步研究靶头-PEG修饰蟾酥脂质体，通过PEG柔性手臂的长循环行为提高与靶标VEGFR/PDGFR结合率，强化主动寻靶功能，对pazopanib或linifanib介导的蟾酥长循环脂质体给药系统进行系统研究，结合A549及A498细胞模型对pazopanib或linifanib修饰的主动肿瘤靶向性进行评价。为中药肿瘤靶向制剂的制备提供实验基础和绿色环保的实验方法，为改善天然药物生物有效性提供新的研究策略，相关研究未见报道。

脂质体配体的生物催化合成具有高初速率、高底物转化率、高选择性、环境保护和减少能源消耗等优点，已成为立体选择性合成中绿色的替代方案。脂肪酶具有稳定性好、易于与反应混合物分离、可重复使用等优点。本研究使用来自南极假丝酵母属（Novozym 435）的脂肪酶B作为催化剂，通过生物催化反应一步合成叶酸-聚乙二醇-胆固醇聚合物、叶酸-聚乙二醇单硬脂酸酯聚合物，并制备叶酸功能化的蟾酥脂质体、叶酸功能化的白桦脂酸脂质体。对其形貌、粒径、电位、包封率、稳定性、细胞毒性、细胞摄取、细胞凋亡、细胞定位、细胞周期等进行了研究。该脂质体能被HepG2细胞（叶酸受体阳性细胞）选择性摄取，显示出更强的细胞毒性，而A549细胞（叶酸受体阴性细胞）细胞摄取程度没有显着差异。叶酸功能化的荧光脂质体的细胞摄取效果显著高于非叶酸功能化的荧光脂质体。进一步研究发现，脂质体可诱导A549细胞发生凋亡，导致细胞生长抑制，作用于线粒体而引起增殖抑制作用，能使A549细胞阻滞在G0/G1期，随着浓度增加阻滞作用越明显。这些为一步反应生物催化修饰脂质体的靶向给药系统提供新的研究方法和思路。