Effects of molecular weight and pyridinium moiety on water-soluble chitosan derivatives for mediated gene delivery

The aim of this study is to investigate the effects of molecular weight, the pyridinium/trimethyl ammonium (Py/Tr) ratio, the nitrogen atoms (N) in the methylated N-(3-pyridylmethyl) chitosan chloride (M3-PyMeChC)/the phosphorus atoms (P) in DNA (N/P) ratio, and the physicochemical properties of nanopolyplexes on transfection efficiency. The water-soluble chitosan derivative, M3-PyMeChC, was used as a non-viral vector to deliver pEGFP-C2 into human hepatoma (Huh7) cell lines. The results revealed that higher molecular weight M3-PyMeChC was able to form complexes completely with DNA at lower N/P ratios than that with lower molecular weights, which led to higher transfection efficiency. Moreover, the M3-PyMeChC with higher Py/Tr ratios showed superior transfection efficiency at lower Py/Tr ratios at all N/P ratios studied. The highest transfection efficiency for the nanopolyplexes occurred for a molecular weight of 82 kDa at a N/P ratio of 5. The results indicated that the hydrophobic effect of pyridinium moiety could enhance gene transfection efficiency, which can be attributed to the dissociation of DNA from nanopolyplexes. High Py/Tr ratios in nanopolyplexes tended to decrease cytotoxicity due to delocalization of positive charge into a pyridine ring while high N/P ratios and molecular weight increased cytotoxicity. Our results showed that the vector was able to spread the positive charge by delocalizing it into a heterocyclic ring, suggesting to a promising approach to mediate higher levels of gene transfection.