Synthesis of biodegradable polycationic methoxy poly(ethylene glycol)–polyethylenimine–chitosan and its potential as gene carrier

Methoxy poly(ethylene glycol)–polyethylenimine–chitosan (mPEG–PEI–CS) was synthesized via chitosan conjugated with polyethylenimine and methoxy poly(ethylene glycol). The intermediates and final copolymer were characterized and confirmed by 1H NMR and FT-IR spectra. mPEG–PEI–CS was water soluble and its intrinsic viscosity was 0.446 dL/g. The contents of mPEG and PEI conjugated in the copolymer were 51.3% (w/w) and 28.9% (w/w), and the degree of substitution of PEI by mPEG was 176%. Gel electrophoresis confirmed that DNA was retained completely by the copolymer nanoparticles. The average diameter and zeta potential of mPEG–PEI–CS/DNA were 155 nm and 17.5 mV. The transfection of human embryonic kidney 293 (HEK293) cells proved that mPEG–PEI–CS/VRfat-1 plasmid had little toxicity on the growth and gene expression of cells, and the ratio of ω-3/ω-6 fatty acids was obviously increased after 72 h transfection compared to CS/VRfat-1 (P < 0.05). These indicated that mPEG–PEI–CS was a promising effective gene delivery and package molecule.