Yue Yanan, Wu Chi
Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong.
Biomater Sci. 2013 Feb 3;1(2):152-170. doi: 10.1039/c2bm00030j. Epub 2012 Oct 1.
The development of safe, efficient and controllable gene-delivery vectors has become a bottleneck to human gene therapy. Synthetic polymeric vectors, although safer than viral carriers, generally do not possess the required efficacy, apparently due to a lack of functionality to overcome at least one of many intracellular gene-delivery obstacles. Currently, the exact mechanisms of how these polymeric vectors navigate each intracellular obstacle ("slit"), as well as their particular physical/chemical properties that contribute to efficient intracellular trafficking remain largely unknown, making it rather difficult to further improve the efficacy of non-viral polymeric vectors in vitro and in vivo. In this review, we first give a brief overview of synthetic polymeric vectors that have been designed and developed for gene delivery and highlight some promising candidates for clinical applications. Our main focus is on discussing the intracellular trafficking mechanisms of the DNA-polymer complexes ("polyplexes"), with less effort on the DNA-polymer complexation in the extracellular space as well as the in vivo systemic administration of genes in animal models and human clinical trials. In particular, we identified and discussed four critical, but often over-looked issues for successful DNA-polymer intracellular trafficking, especially our recent confirmation that it is free cationic polymer chains in the solution mixture of DNA and polymer that actually promote gene transfection and the polycationic chains within the polyplexes mainly play a protective role. Instead of the previously proposed and widely used escape model from late endolysosomes, the current hypothesis is that free polycationic chains with a sufficient length (∼20 nm) can block the initial endocytic-vesicle-to-endolysosome pathway.
安全、高效且可控的基因递送载体的开发已成为人类基因治疗的瓶颈。合成聚合物载体虽然比病毒载体更安全，但通常不具备所需的功效，这显然是由于缺乏克服众多细胞内基因递送障碍中至少一种的功能。目前，这些聚合物载体如何跨越每个细胞内障碍（“缝隙”）的确切机制，以及它们有助于高效细胞内转运的特定物理/化学性质，在很大程度上仍然未知，这使得进一步提高非病毒聚合物载体在体外和体内的功效相当困难。在本综述中，我们首先简要概述为基因递送而设计和开发的合成聚合物载体，并强调一些有临床应用前景的候选载体。我们主要关注讨论DNA-聚合物复合物（“多聚体”）的细胞内转运机制，而较少关注细胞外空间中的DNA-聚合物复合以及动物模型和人类临床试验中基因的体内全身给药。特别是，我们确定并讨论了DNA-聚合物成功进行细胞内转运的四个关键但常被忽视的问题，尤其是我们最近证实，在DNA与聚合物的溶液混合物中，是游离的阳离子聚合物链实际上促进了基因转染，而多聚体内的聚阳离子链主要起保护作用。当前的假设是，具有足够长度（约20纳米）的游离聚阳离子链可以阻断初始的内吞小泡到内溶酶体的途径，而不是先前提出并广泛使用的从晚期内溶酶体逃逸的模型。
