Biomacromolecules. 2018 May 14;19(5):1508-1516. doi: 10.1021/acs.biomac.8b00170. Epub 2018 Mar 30.
Despite its promises for biomedical applications, the lack of solubility in a physiological solution, the limited molecular interactions with nucleic acids due to the rigid backbone, and the inefficient intracellular release limit the use of chitosan, a natural cationic polysaccharide, for gene delivery. In this study, a flexible, aqueous-soluble aminoethoxy branch was conjugated to the primary hydroxyl group of chitosan via an acid-cleavable ketal linkage, resulting in acid-transforming chitosan (ATC) with greatly increased aqueous solubility, improved siRNA complexation, and degradability in response to an acidic pH. Acid-hydrolysis of ketal linkages, which triggers the loss of the flexible, cationic aminoethoxy branch, transforms ATC to the native form of chitosan with low water solubility, reduces molecular interaction with siRNA, and cooperatively facilitates the cytosolic release of siRNA. The siRNA complexation by ATC resulted in stable polyplexes under a neutral physiological condition, rapid cytosolic siRNA release from the mildly acidic endosome/lysosome, and substantial silencing of GFP expression in cells, notably with minimal cytotoxicity. This study demonstrates a molecularly engineered natural polymer for a biomedical application.
尽管壳聚糖作为一种天然阳离子多糖在生物医学应用中具有广阔的前景，但由于其在生理溶液中溶解度低、刚性骨架导致与核酸的分子相互作用有限以及细胞内释放效率低下，限制了其在基因传递方面的应用。在本研究中，通过酸不稳定的缩醛键将柔性的、水溶性的乙氧基分支连接到壳聚糖的伯羟基上，得到了酸响应性的壳聚糖（ATC），其水溶性显著提高，与 siRNA 的复合能力增强，并且在酸性 pH 下可降解。缩醛键的酸水解会导致失去柔性的阳离子乙氧基分支，从而使 ATC 转化为低水溶性的天然壳聚糖形式，降低与 siRNA 的分子相互作用，并协同促进 siRNA 的细胞质释放。ATC 与 siRNA 的复合在中性生理条件下形成稳定的聚阳离子复合物，可快速从轻度酸性的内体/溶酶体中释放细胞质中的 siRNA，并显著抑制 GFP 表达，同时具有最小的细胞毒性。本研究展示了一种经过分子设计的天然聚合物在生物医学中的应用。
