基于温度和葡萄糖双重响应性生物微囊的胰岛素控制释放研究

The treatment of diabetes lies in developing novel functional carriers, which are expected to have the unique capability of monitoring blood glucose levels continuously and dispensing insulin correctly. Hence, this project is proposing to create a smart self-regulated insulin delivery system according to the changes in glucose concentration. A random copolymer bearing PNIPAAm and AAPBA is synthesized by free radical polymerization. The effects of species and mixing ratio of monomers, reactive condition and synthetic route on the end-product properties have been revealed. Then, the copolymer microcapsules are fabricated by bottom-spray fluidized bed and template method. The influence of solution concentration, atomized time, droplet size, microsphere dimension and annealing way on the wall thickness and particle size of the microcapsules have also been discussed. The microcapsules with glucose and temperature sensitivity are available for effective loading and controlled release of exogenous insulin. It describes the interaction between the factors including environment temperature, glucose concentration, material composition, microcapsule dimension and the outcomes of response speed, load capacity, encapsulation efficiency and controlled release ability of copolymer microcapsules. Finally, the insulinoma cells employed to secrete insulin in response to glucose are embedded in the copolymer microcapsules to explore the relationship between insulin production and environmental glucose concentration. The intelligent drug delivery system is supposed to mimic insulin secretion in physiological manner, and further providing new perspective and technical support for the development of artificial pancreas.

目前，糖尿病的治疗进展期于开发能够实时监测机体血糖浓度以及精确释放特定剂量胰岛素的功能载体。本项目拟创建一种可根据环境葡萄糖浓度变化情况而进行自我调节的智能胰岛素递送系统。采用自由基聚合法合成以PNIPAAm和AAPBA为主体的无规共聚物，揭示单体种类和配比、反应条件、合成途径对终产物性能的影响规律；运用流化床底喷技术和模板腐蚀法制备共聚物微囊，探讨溶液浓度、雾化时间、喷雾粒径、微球尺寸、退火程度对微囊壁厚和粒径的调控准则；利用微囊的温度和葡萄糖双重响应特性实现外源性胰岛素的有效负载和可控释放，阐述环境温度、葡萄糖浓度、材料组成及微囊尺度对微囊响应速度、载药容量、包封性能和控释能力的作用模式；完成胰岛素瘤细胞的包埋与葡萄糖响应性胰岛素分泌与释放，探究细胞胰岛素分泌量与环境葡萄糖浓度之间的反馈机制。以期创建的智能给药系统能够模拟机体胰岛素的分泌模式，为人工胰腺的研发提供崭新思路及技术支持。

目前，糖尿病的治疗进展在于开发能够实时监测机体血糖浓度以及精确释放特定剂量胰岛素的功能载体。本项目创建了一种可根据环境葡萄糖浓度变化情况而进行自我调节的智能胰岛素递送系统。首先采用自由基聚合法合成以N-异丙基丙烯酰胺和3-丙烯酰胺基苯硼酸为主要成分的无规共聚物，并借助自制的气液固三相流化床反应器运用底喷包衣技术在经由羟基活化处理的玻璃微球表面涂覆未键合的共聚物涂层，然后通过加热退火方式使共聚物颗粒固定接枝于微球表面，并采用HF溶解玻璃模板，形成共聚物微囊。随即进行外源性胰岛素的负载和控释研究，并对释放的胰岛素进行生物活性检测。最后相继完成胰岛素瘤βTC6细胞在共聚物微囊中的包埋操控、生长增殖观察和葡萄糖响应性分泌胰岛素功能监测等工作。实验结果表明利用底喷包衣技术和模板腐蚀法制备的共聚物微囊依然维持原有共聚物的温度和葡萄糖双重响应特性，并且具有优良的可逆性和稳定性；经过不同浓度、逐步上升浓度以及脉冲变化浓度的三种类型葡萄糖刺激方式实验，证实共聚物微囊孔径随葡萄糖浓度的提升而不断增大，胰岛素释放量也随之增加，同时释放的胰岛素依然保持生物活性；包埋于共聚物微囊中的βTC6细胞生长状态良好、扩增能力强、可在葡萄糖刺激下产生胰岛素；由于微囊结构限制，与游离βTC6细胞的胰岛素分泌量（即释放量0.5mg∙mL-1）相比，固定化βTC6细胞的胰岛素释放峰值所对应的葡萄糖浓度升至2mg∙mL-1，此种释放模式非常有利，即在不断消耗葡萄糖的同时，胰岛素释放量始终处于峰值状态，这对于糖尿病的临床治疗十分奏效。本项目创建的智能给药系统能够模拟机体胰岛素的分泌模式，为人工胰腺的研发提供崭新思路及技术支持。