Chan Peggy, Kurisawa Motoichi, Chung Joo Eun, Yang Yi-Yan
Institute of Bioengineering and Nanotechnology, 31 Biopolis Way, The Nanos #04-01, Singapore 138669, Singapore.
Biomaterials. 2007 Jan;28(3):540-9. doi: 10.1016/j.biomaterials.2006.08.046. Epub 2006 Sep 25.
Poor water solubility and low transfection efficiency of chitosan are major drawbacks for its use as a gene delivery carrier. PEGylation can increase its solubility, and folate conjugation may improve gene transfection efficiency due to promoted uptake of folate receptor-bearing tumor cells. The aim of this study was to synthesize and characterize folate-poly(ethylene glycol)-grafted chitosan (FA-PEG-Chi) for targeted plasmid DNA delivery to tumor cells. Gel electrophoresis study showed strong DNA binding ability of modified chitosan. The pH(50) values, defined as the pH when the transmittance of a polymer solution at 600 nm has reached 50% of the original value, suggested that the water solubility of PEGylated chitosan had improved significantly. Regression analysis of pH(50) value as a function of substitution degree of PEG yielded an almost linear correlation for PEG-Chi and FA-PEG-Chi. The solubility of PEGylated chitosan decreased slightly by further conjugation of folic acid due to the relatively more hydrophobic nature of folic acid when compared to PEG. In addition, the chitosan-based DNA complexes did not induce remarkable cytotoxicity against HEK 293 cells. FA-PEG-Chi can be a promising gene carrier due to its solubility in physiological pH, efficiency in condensing DNA, low cytotoxicity and targeting ability.
壳聚糖的水溶性差和转染效率低是其作为基因递送载体应用的主要缺点。聚乙二醇化可以增加其溶解度，而叶酸偶联可能由于促进含叶酸受体的肿瘤细胞摄取而提高基因转染效率。本研究的目的是合成并表征叶酸-聚（乙二醇）接枝壳聚糖（FA-PEG-Chi），用于将质粒DNA靶向递送至肿瘤细胞。凝胶电泳研究表明修饰后的壳聚糖具有很强的DNA结合能力。pH(50)值定义为聚合物溶液在600nm处的透光率达到原始值的50%时的pH值，这表明聚乙二醇化壳聚糖的水溶性有了显著提高。以pH(50)值作为聚乙二醇取代度的函数进行回归分析，结果显示PEG-Chi和FA-PEG-Chi呈现出几乎线性的相关性。与聚乙二醇相比，叶酸相对更具疏水性，因此进一步偶联叶酸会使聚乙二醇化壳聚糖的溶解度略有下降。此外，基于壳聚糖的DNA复合物对HEK 293细胞没有显著的细胞毒性。由于FA-PEG-Chi在生理pH下具有溶解性、能够有效凝聚DNA、细胞毒性低且具有靶向能力，因此它可能是一种很有前景的基因载体。
