聚乙二醇化树状高分子载体构建纳米给药系统促进普罗布考口服相关疗效及机理研究

Probucol is a cholesterol-lowing and anti-atherosclerosis drug. However, the therapeutic effects and clinic application of this drug have been limited by its poor water solubility in gastrointestinal fluid, low transportation and irregular absorption through intestine barriers. PAMAM dendrimers are branched nano-sized polymers with hydrophilic surface and hydrophobic internal structure, which benefit to conjugate or encapsulate drugs to increase dissolution, trans-membrane transportation and absorption of the water insoluble drugs. In this project, G5-PEG and G7-PEG are used as drug carriers, four different pharmaceutical techniques (complex, conjugate, nano-liposome, nano-structured lipid carrier) will be applied to prepare dendrimer-probucol nano-scale drug delivery system (NDDS). The physical-chemical characteristics, dissolution and drug release efficiencies of the NDDS will be studied. The trans-membrane uptakes, transportation and mechanisms of the dendrimer-probucol NDDS will be studied on Caco-2 cell monolayers, which are broadly used as the in vitro intestinal absorption model. With western diet fed LDL receptor deficient (LDLR-/-) mice as the hyperlipidemia and atherosclerosis disease models, and commercialized probucol tablets as positive drug control, the oral absorption bioavailability, therapeutic effects (cholesterol-lowing, anti-arteriosclerosis, etc), bio-security （toxicities, side effects, etc）of the dendrimer-probucol NDDS will be studied. This study will illuminate the improvement effects and mechanisms of dendrimer-based NDDS on the oral absorption and therapeutic effects of water-insoluble drugs.

普罗布考是临床广泛应用的口服降血脂和抗动脉粥样硬化药物。但该药水溶性极差，口服后胃肠道的溶出少、跨膜吸收差且不规则，严重影响了该药的药效和临床应用。树状高分子纳米载体具有独特的多分支的结构、表层亲水、内核疏水的特性，为嫁接和装载药物以改善药物的溶解性和透生物膜吸收提供了优越条件。本研究以G5-PEG 和G7-PEG树状高分子为载体，采用复合法、化学键合法、纳米脂质体、纳米脂质载体等方法构建载体-普罗布考纳米给药系统，研究载体、不同构建方法和条件对药物的理化性质、溶解与释放的影响；以Caco-2细胞单层为小肠吸收模型，研究载体及纳米给药系统对药物跨膜转运的促进作用及其机制；以LDLR-/-小鼠喂饲高脂饲料造成高脂血症和动脉粥样硬化模型，研究纳米给药系统的口服生物利用度、降脂及抗动脉粥样硬化的药效和生物安全性。阐明以树状高分子为载体构建纳米给药系统对提高难溶性药物的口服吸收及相关功效的作用。

本研究以脂溶性药物普罗布考（PB）为模型药物，以树状高分子为载体，分别采用物理复合、脂质体及脂质载体等制剂技术制备PB纳米剂型，研究载体表面结构和代数及剂型因素对PB水溶性、跨膜吸收及降脂药效的影响；以Caco-2细胞为模型，研究不同纳米剂型对PB跨膜转运与内吞途径的影响。我们的研究结果表明不同表面结构和荷电性的树状高分子（G5-NH2、G5-COOH、G5-OH、G5-PEG）对药物的增溶能力不同， PEG化的G5（G5-PEG）和G7（G7-PEG）对普罗布考增溶效果最佳。三种纳米剂型对PB的溶解与吸收均有促进作用，但包封率与载药量纳米脂质载体（PB-NLC）>纳米脂质体（PB-Nanolipo）>纳米复合物（PB-Complex）；G5-PEG及G7-PEG修饰不影响纳米剂型的粒径、包封率及载药量，且G5-PEG或G7-PEG修饰，可显著减少纳米剂型的突释，并显著增加药物的释放总量，并可显著增加纳米剂型对温度和储存时间的稳定性。在Caco-2细胞上，G5-PEG纳米复合物能显著增加PB的跨细胞膜转运；G5-PEG修饰纳米剂型能显著提高PB的跨膜转运和胞内摄取，且纳米脂质载体对PB的促进作用>纳米脂质体>纳米复合物。树状高分子载体及纳米剂型促进PB跨膜转运机制受P-gp外排泵影响，与Clathrin途径有关，但与Caveolae途径无关，不受Tight Junction 调控。以LDLR-/-小鼠喂饲高脂饲料造成高胆固醇血症模型的体内研究结果表明纳米剂型能显著增加PB的口服生物利用度,G5-PEG修饰的纳米剂型对PB生物利用度和降血脂效果的提高显著优于无修饰的纳米剂型。本研究对采用纳米剂型提高难溶性药物口服吸收与药效提供依据，对改善此类药物临床治疗药效不稳定等问题具有重要现实意义。