基于纳米氧化石墨烯构建可程序释药的双敏感联合给药系统

The use of single chemotherapeutic drug has shown some limitations in anti-tumor treatment, such as high toxicity and development of drug resistance. Generally, a co-delivery system with synergistic combination of two or more drugs engineered with stimulus responsive mechanism is a promising strategy to overcome these limitations. With high drug loading effiency, extraordinary chemical structural properties as well as identified biocompatibility, graphene oxide (GO) have greatly attracted the attention of researchers, providing a promising approach. In this proposal, we attempt to design a combination drug delivery system based on PEGylated nano-graphene oxide (mPEG-GO), which can program release different drugs in a controllable way triggered by different stimuli signals. Methotrexate (MTX) and Doxorubicin hydrochloride (DXR) are chosen as the two model drugs due to their excellent anti-tumor efficiency against various solid tumors. They, however, are drugs with different anticancer mechanisms, showing synergistic therapeutic effect in clinical use. MTX is conjugated on GO via a disulfide linkage which can be destroyed quickly in a reducing environment, while DXR is physically loaded on GO driven by noncovalent π-π stacking interaction. After intravenous injection, an increased circulation half-life of GO nanosheets drug carrier augments accumulation at the tumor site through the enhanced permeability and retention (EPR) effect.Then DXR release in the tumor acidic microenvironment triggered by tumor pH. Followed by that, the GO nanosheet drug carrier is internalized via endocytosis thereby initiating rapid disulfide cleavage of a stabilizing MTX, triggering rapid release of MTX. The specially engineered GO nanosheet drug carrier is designed to meet the desired therapeutic requirements of synergistic combination two drugs and payload program release in a tumor selective way. we are going to investigate the relationship between the two drug release behavior and the GO assembly mechanism. In cellular level, we are going to observe the drug distribution in the tumor cells released from GO nanosheets and the anti-tumor effect of the designed combination drug system.

针对肿瘤单一药物治疗易产生细胞耐药性的问题，临床上需要药物载体能同时负载多种药物并可智能调控释放。氧化石墨烯(GO)以其高药物负载率、独特的化学性质及已证实的良好生物相容性为构建此类药物载体提供了新方法。本项目以聚乙二醇功能化的GO纳米层(mPEG-GO)为基本单元，拟构建一种双敏感机制调控下，两种药物程序释放的联合给药系统。药物模型采用不呈交叉耐药性、有协同治疗作用的甲氨蝶呤(MTX)和盐酸阿霉素(DXR)。该载药纳米层静脉注射后，借助EPR效应靶向至肿瘤组织，在肿瘤酸性微环境下首先酸触释放π-π共轭负载的DXR；随后在细胞内高谷胱甘肽还原环境下，快速释放MTX。实现两种药物先后程序释放，联合作用。其中MTX以还原环境下可快速裂解的二硫键为连接化学键合在GO上。项目拟通过体外实验阐明两种药物与GO的组装机制及程序释放行为；同时在细胞水平上考察载药纳米层在肿瘤细胞内的分布及联合给药疗效。

针对传统抗肿瘤药物在临床应用中存在选择性差、耐药性强、毒副作用明显等问题，以及药物传递中的关键科学问题，本项目设计合成了基于氧化石墨烯的药物载体，对氧化石墨烯进行多种修饰（聚乙二醇、超分子β-环糊精、透明质酸），并赋予其多种智能响应性（pH、谷胱甘肽），同时负载多种药物（阿霉素，甲氨蝶呤），及多层次靶向性（组织、肿瘤细胞）。利用这些功能构建了多重响应、多药物不同释放方式的联合给药系统，实现了多种药物的可控释放及被动靶向传递。.为了解决肿瘤抗药耐药性问题，构建了双药物双重释放系统。一种药物通过物理吸附到氧化石墨烯表面，另一种药物通过化学键合到氧化石墨烯片层上，实验表明在高谷胱甘肽还原环境下，药物MTX在56 h内累积释药量达71.97%；同时在酸性(pH 5.0左右) 溶液中，药物阿霉素在56 h 的累积释药量达 61.31%。此药物载体既能满足体内长循环的作用，又能携带肿瘤药物被动靶向到肿瘤组织，在高谷胱甘肽作用下，二硫键断裂，释放出化学键合的肿瘤药物MTX，达到药物快速释放的作用；同时在肿瘤组织低的pH作用下，物理负载的阿霉素缓慢释放。此药物载体构建了一种将两种药物快速释放和缓释相结合的联合给药系统，在肿瘤治疗方面具有重要的意义。除此之外，为了进一步深入研究谷胱甘肽响应下的药物递释行为，本项目针对肿瘤谷胱甘肽还原敏感环境，设计了一系列二硫键连接的核壳结构的药物载体，比如以二硫键连接的透明质酸修饰的氧化石墨烯药物载体，以二硫键连接的聚乙二醇-聚多肽胶束药物载体，药物载体通过主动或EPR效应聚集于肿瘤组织处，进入肿瘤细胞后，在细胞内高谷胱甘肽环境下，壳层和核层脱落，药物快速释放，从而提高细胞凋亡率。本项目为研究多响应、多药物不同释放方式的联合给药系统奠定了基础。