CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, PR China.
Biomaterials. 2010 Aug;31(23):6075-86. doi: 10.1016/j.biomaterials.2010.04.042. Epub 2010 May 20.
Targeted gene delivery systems have attracted great attention due to their potential in directing the therapeutic genes to the target cells. However, due to their low efficiency, most of the successful applications of polymeric vectors have been focused on genes which can achieve robust expression. Minicircle DNA (mcDNA) is a powerful candidate in terms of improving gene expression and prolonging the lifespan of gene expression. In this study, we have combined folate/poly(ethylene glycol) modified polyethylenimine and mcDNA as a new tumor gene delivery system. We found that folate-labeled polyplexes were homogenous, with a size ranging from 60 to 85 nm. mcDNA increased folate-labeled vector based gene expression 2-8 fold in folate receptor-positive cells. Results of folic acid competition assay indicated that mcDNA mediated by folate-labeled vector were internalized into cells through receptor-mediated endocytosis. The investigation of the endocytosis pathway of the polyplexes showed that a large portion of them escaped from endo/lysosome and the polyplexes were associated before being separated in the nucleus. Furthermore, in vivo optical imaging and luciferase assays demonstrated that systemic delivery of the folate-labeled polyplexes resulted in preferential accumulation of transgenes in folate receptor-positive tumors, and mcDNA mediated approach achieved 2.3 fold higher gene expressions in tumors than conventional plasmid. Cytotoxicity assays showed that PEG-shielding of the polyplexes reduced the toxicity of PEI.
靶向基因传递系统因其将治疗基因靶向靶细胞的潜力而受到极大关注。然而，由于其效率低下，大多数成功应用的聚合物载体都集中在能够实现强大表达的基因上。微环 DNA（mcDNA）在提高基因表达和延长基因表达寿命方面是一个强有力的候选者。在这项研究中，我们将叶酸/聚乙二醇修饰的聚乙烯亚胺和 mcDNA 结合作为一种新型肿瘤基因传递系统。我们发现叶酸标记的超分子聚合物是均匀的，大小在 60 到 85nm 之间。mcDNA 使叶酸受体阳性细胞中基于叶酸标记载体的基因表达增加了 2-8 倍。叶酸竞争测定结果表明，mcDNA 通过叶酸标记载体介导的内吞作用进入细胞。对超分子聚合物内吞途径的研究表明，其中很大一部分从内体/溶酶体中逃逸出来，并且在核内分离之前与超分子聚合物结合。此外，体内光学成像和荧光素酶检测表明，叶酸标记的超分子聚合物的全身给药导致转基因在叶酸受体阳性肿瘤中的优先积累，而 mcDNA 介导的方法在肿瘤中的基因表达比常规质粒高 2.3 倍。细胞毒性试验表明，聚乙二醇化可降低 PEI 的毒性。
