Selective Modification of Chitosan to Enable the Formation of Chitosan-DNA Condensates by Electron Donator Stabilization

Chitosan, a polyaminosaccharide, has been investigated for its use in the field of drug-delivery and biomaterial applications because of its natural biocompatibility and polycationic properties. Chemical modifications of chitosan have been attempted in an effort to increase the transfection efficiency with respect to gene delivery applications; however, it is unknown how these modifications affect the formation of the condensates. This study attempts to determine the effects of modification of the cationic center of chitosan on the ability to condense DNA. Specifically, electron-donating or -withdrawing groups were used as modifiers of the cationic charge on the chitosan backbone to stabilize the protonated form of chitosan, which is necessary to form condensates and increase the efficiency of the polymer to condense DNA by yielding condensates at a lower nitrogen to phosphorous (N : P) ratio. While an N : P ratio of 7 is needed to condense DNA with unmodified chitosan, phthalate-modified chitosan yielded condensates were obtained at an N : P ratio of 1.0.