As a non-viral gene vector, long PEI chains are more effective but also more cytotoxic. To solve this problem, people have tried to use disulfide (âSâSâ) to link short PEI chains into a long one to generate highly efficient and less cytotoxic gene vectors because âSâSâ is degradable inside the cell. In order to investigate when and where âSâSâ is cleaved during intracellular trafficking, we designed and synthesized rhodamine B labeled linear PEI chains (Mn â 3 kg molâ1) with one end modified with a mercapto-group so that they can be coupled together via one disulfide bond in the middle and one rhodamine B molecule on each side of the disulfide bond, where fluorescence is self-quenched because two rhodamine B molecules are closely linked together. The cleavage of the âSâSâ bond separates the two rhodamine B molecules and enhances their fluorescent intensity. In addition, plasmid DNA was also modified with bodipy, a FRET donor of rhodamine B. Using this specially prepared PEI, we studied the intracellular trafficking of the PEI/DNA polyplexes by using flow cytometry and confocal laser scanning microscopy. Our results reveal that (1) DNA is gradually dissociated from the polyplex before the disulfide bond's cleavage; (2) some of polyplexes escaped from endosomes before reaching lysosomes; and (3) the disulfide bonds are mainly cleaved inside lysosomes at â¼5 h post-transfection.
作为非病毒
基因载体,长PEI链更有效,但细胞毒性也更大。为了解决这个问题,人们尝试用二
硫化物(âSâSâ)将短聚
乙烯醇链连接成长聚
乙烯醇链,以产生高效且细胞毒性较低的
基因载体,因为âSâSâ在细胞内可以降解。为了研究âSâSâ在细胞内迁移过程中何时何地被裂解,我们设计并合成了
罗丹明B标记的线性PEI链(Mnâ 3 kg molâ1),其一端用巯基修饰,这样它们就可以通过中间的一个二
硫键和二
硫键两侧的一个
罗丹明B分子耦合在一起,由于两个
罗丹明B分子紧密连接在一起,荧光就会自淬。二
硫键的裂解将两个
罗丹明 B 分子分开,并增强了它们的荧光强度。此外,我们还用
罗丹明 B 的 FRET 供体 bodipy 修饰了质粒 DNA。利用这种特殊制备的 PEI,我们使用流式细胞仪和激光共聚焦扫描显微镜研究了 PEI/DNA 多聚体在细胞内的迁移。结果表明:(1)DNA在二
硫键裂解前逐渐从多聚体中解离;(2)部分多聚体在到达溶酶体前从内体逸出;(3)二
硫键主要在转染后§¼5 h在溶酶体内裂解。