多功能磁性纳米药物载体的构建及其肿瘤治疗与磁共振成像一体化研究

The drug delivery and MRI imaging of superparamagnetic iron oxide nanoparticles (SPIONs) are still poorly developed due to lack of specific targeting, stability of drug loading, and controllability in drug release and so on. Because of the remarkable differences between cancer cell and normal cell, a SPIONs drug carrier system which has folate-specific targeting and reduction-sensitivity was proposed in order to solve this problem. Firstly, Doxorubicin (Dox), dopamine (DA), and folate-modified PEG (FA-PEG) were covalently bonded into disulfide linkage contained polyester by Michael addition reaction. Secondly, the drug carrier nano-particle (Dox-NP) was prepared by reaction between DA and SPIONs. In this system, covalently bonded Dox was used to improve the stability of drug loading, and the quick degradation of Dox-NP by GSH reduction and folate-specific targeting facilitated a highly efficient targeted drug release and decreasing of side effect. In addition, a high SPIONs concentration in tumor was acquired to improve the MRI contrast. In this study, the model of anti-tumor experiment will be established in vitro and in vivo, and the reduction-sensitivity, drug release ability, toxicity experiment, and MRI imaging study will be carried out, to provide theory evidence for improving the integration of cancer diagnosis and therapy.

超顺磁性氧化铁纳米粒子SPIONs在实现药物传递以及磁共振成像MRI诊疗一体化研究中仍存在靶向性差、载药稳定性低、药物释放可控性不足等缺陷。由于肿瘤细胞与正常细胞存在显著差异，本课题提出一种兼具靶向及还原响应性的SPIONs药物载体，有望解决以上难题。将阿霉素Dox、多巴胺DA、叶酸修饰聚乙二醇等通过Michael加成反应键连于含二硫键聚酯主链上，利用DA与SPIONs粒子键连而制备药物载体粒子Dox-NP。Dox的化学连接有助于提高载药稳定性；叶酸受体靶向及细胞内谷胱甘肽还原作用使Dox-NP快速崩解，可高效靶向释药，减少毒副作用；在肿瘤部位获得高SPIONs浓度，可提高MRI检测效果。本课题拟建立该药物载体的体内外抗肿瘤作用模型实验，并对其还原响应性、释放效率以及毒性等进行研究，利用MRI技术进行体内外成像实验，为发展磁性纳米粒子的肿瘤诊疗一体化应用提供理论依据。

对肿瘤的磁共振成像（MRI）诊断以及药物治疗一体化研究是目前癌症治疗的新策略。高效的MRI成像材料需具备良好的生物稳定性、高弛豫效能以及较长的体内半衰期；同时药物递送过程中应克服靶向性差、载药稳定性低、药物释放可控性不足等缺陷。申请者通过Michael加成反应将多巴胺（DA）、阿霉素（DOX）、叶酸聚乙二醇（FA-PEG）等功能结构接枝于含二硫键聚酯主链上，利用多巴胺配体交换反应将聚合物外壳牢固包裹于SPIONs之上，制备了一种兼具靶向功能、载药稳定的超顺磁性纳米粒子药物载体系统（MNPs-DOX）。本项目对所制备的MNPs-DOX系统的化学结构与纳米形态进行了全面的表征，实验结果表明含二硫键并接枝DA、DOX、FA-PEG、PEG的多功能线性聚合物成功包裹于SPIONs之上，且在水溶液中以纳米微球形态长期稳定分散，所制备的MNPs-DOX系统与预期一致。同时，本项目对该MNPs-DOX系统的体外MRI成像以及靶向药物释放（包括还原响应性、体外药物释放、细胞摄取、细胞毒性等）进行了研究。研究表明所制备的MNPs-DOX系统具有良好的还原响应性，在GSH刺激条件下可高效释药；在细胞实验中，空白纳米粒子MNPs对HUVEC细胞表现出良好生物相容性，而MNPs-DOX对HeLa细胞有明显毒性，可有效抑制肿瘤细胞的存活率。同时通过CLSM实验发现MNPs-DOX可被HeLa细胞有效摄入，表现出良好的靶向性能。如将该MNPs-DOX系统用于抗肿瘤药物，由于其具有用量少、毒副作用小、肿瘤抑制率高以及MRI灵敏度好，有望为磁性纳米载体材料在肿瘤诊疗一体化中的研究提供一种新的思路，实现产业化。