现有直接重编程技术因采用病毒载体而制约其临床转化，本项目以阳离子多糖-碳量子点为载体，自组装构建高效、安全、可细胞标记示踪的多功能非病毒纳米基因传递系统。主要内容包括：制备表面修饰有阳离子多糖的碳量子点，评价其荧光量子效率、细胞毒性、标记示踪性能和基因转染效率，运用FRET研究其传递机理；以单因子（Sox2）、两因子（Ascl1、Brn2）和三因子（Ascl1、Brn2、Mytl1）为模型基因将成纤维细胞直接转化为神经细胞，评价转分化速度与效率；制备三维组织工程支架，碳量子点标记示踪三维支架中细胞的生长特性，并与二维体系比较转分化速度与效率、特异因子表达等方面差异；建立大鼠脊髓损伤模型，碳量子点示踪细胞在脊髓损伤区的迁移与增殖，以大鼠后肢运动功能、碳量子点逆行标记大脑皮质运动区神经元、有关蛋白表达等指标, 评价移植修复效果。本项研究可为细胞直接重编程提供新载体、新技术、新方法。

The existing methods for direct reprogramming involve viral vectors, thus limiting their clinical translation. This project constructs an efficient, safe and cell labeling multifunctional non-viral self-assembly nano gene delivery system. The main contents include the following items: Preparation of carbon quantum dots (CDs) with surface modification by cationized polysaccharides; examination of the fluorescence quantum efficiency, cytotoxicity, tracking performance, gene transfection efficiency and investigation of the delivery mechanisms using the fluorescence resonance energy transfer (FRET); Direct reprogramming of the fibroblasts into neurons by employing the single-factor (Sox2), two-factor (Ascl1 and Brn2) and a three-factor combination (Ascl1, Brn2 and Mytl1) as model genes, and evaluating the transdifferentiation speed and efficiency; Fabrication of three-dimensional (3D) tissue engineering scaffolds, observing the cell growth characteristics in the CDs-labeling 3D scaffolds, and comparing with the two-dimensional system in the aspects of neuron formation speed, transdifferentiation efficiency as well as the expression of specific factors; Establishing a rat spinal cord injury model, observing the ODs-labeled cells' migration and proliferation in the region of spinal cord injury, and assessing transplantation repairing effect resulting from the induced neurons using indicators such as the motor functions of rats' hind limbs, retrograde labeling of neurons in the cerebral cortex motor area with CDs, and the expression of related proteins. This project can provide a brand-new carrier with novel techniques and methodologies for the somatic direct reprogramming.