具有靶向缓释作用的磁性温敏凝胶载体装载丝裂霉素灌注治疗膀胱肿瘤的机制研究

The patients who underwent transurethral resection of bladder tumor need intravesical chemotherapy to prevent tumor recurrence. Mitomycin C is widely used with the characteristics of low price and high efficacy, but there is still a high recurrence rate. The treatment effect will fall off because of short duration of the drug in bladder due to periodic urination. The epithelial barrier of urinary tract severely hinders the drug absorption and greatly limits its antitumor effect. In our previous study, a carrier system that contained Fe3O4 magnetic nanoparticles dispersed within the thermosensitive hydrogel based on chitosan was developed and exhibits good superparamagnetic behavior. The carrier system forms a free-flowing solution at room temperature and becomes a viscous hydrogel at body temperature. A magnetic field around the bladder was applied to make the carrier resistant to excretion and the residence time in bladder was extended. On this basis, the project intends to use the characteristics of gel carrier to extend the time of mitomycin C in bladder, increases the permeability of the urinary tract epithelium and improves the curative effect. Emphasis is laid on the influence of physical and chemical indicators of the carrier on slow-release performance, at the same time, the effect of gel carrier on transcellular and paracellular mechanisms in the urinary epithelial barrier is studied and the security of application and validation of antitumor effect are confirmed. This topic put forwards a new method to enhance the curative effect of mitomycin C through improvements to the mode of delivery, improve the prognosis and reduce the economic burden of individuals and society and finally provide a theoretical and practical basis for improvement on intravesical instillation and drugs.

膀胱癌患者术后需化疗药物灌注以预防复发。丝裂霉素价格低廉，应用广泛，疗效确切，但仍有较高复发率。由于周期性排尿，灌注后药物膀胱内作用时间短，使疗效减弱；且尿路上皮存在穿透屏障，严重阻碍药物吸收，极大限制了其抗肿瘤作用。我们前期研究构建了基于壳聚糖的具有靶向缓释作用的温敏凝胶载体，搭载磁性纳米粒后具有良好的磁响应性。室温下为液态，灌注后转为凝胶。在膀胱周围施加磁场可大幅延长载体在膀胱内的滞留时间。本项目拟利用凝胶载体的特性，延长丝裂霉素的膀胱内作用时间，增加尿路上皮的通透性，提高疗效。重点研究载体的理化指标对缓释性能的影响，同时对凝胶载体通过跨细胞及细胞旁途径增强上皮通透性的作用机制进行研究，最终完成体内应用的安全性及抗肿瘤作用验证。本课题提出了增强丝裂霉素疗效的新方法，通过对投送方式的改进，改善患者预后，同时减轻个人及社会的经济负担，为后续膀胱癌灌注方法及药物的改良提供基础与实践依据。

膀胱癌患者术后需化疗药物灌注以预防复发。由于周期性排尿，灌注后药物膀胱内作用时间短，使疗效减弱；且尿路上皮存在穿透屏障，严重阻碍药物吸收，极大限制了其抗肿瘤作用。本项目针对这一情况，成功构建了具有磁性的壳聚糖温敏凝胶载体，并成功装载丝裂霉素（MMC），制成Fe3O4-MMC-CS/GP载体系统。经过验证，Fe3O4-MMC-CS/GP具有温敏特性及磁响应性，可以用于膀胱灌注；在体内外均可以迅速转化为固体凝胶，进一步研究发现，CS分子量、脱乙酰度、温度均可影响该凝胶载体系统转化速率，可通过调整配方参数来改变凝胶转化时间，最终制备了适于灌注应用的最优方案。Fe3O4-MMC-CS/GP凝胶呈疏松多孔的网格结构，具有良好的吸水溶胀性及降解能力，应用安全，实验动物未出现明显的并发症。体外实验显示Fe3O4-MMC-CS/GP具有缓释 MMC 的作用，降低药物突释，延长半衰期，而且在膀胱内滞留时间增加，提高了MMC的生物利用度，显著增加了尿路上皮对MMC的吸收。进一步的动物实验显示，与传统MMC灌注相比，Fe3O4-MMC-CS/GP在体内外实验中均具有更强的抗肿瘤活性，而且诱导凋亡能力更强，大鼠生存率更高。本项目通过以上研究，通过对MMC投送方式的改进，改善膀胱癌患者的预后，同时减轻个人及社会的经济负担，为后续膀胱癌灌注方法及药物的改良提供基础与实践依据。项目中所构建的载体经过进一步研究有望使其发展为一种临床应用潜力巨大的通用型膀胱载体缓释系统，可应用于腺性膀胱炎、膀胱过度活动症等疾病的灌注治疗，为临床提供了一种新的治疗选择。.

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