Degradable copolymer based on amphiphilic N-octyl-N-quatenary chitosan and low-molecular weight polyethylenimine for gene delivery

Chitosan shows particularly high biocompatibility and fairly low cytotoxicity. However, chitosan is insoluble at physiological pH. Moreover, it lacks charge, so shows poor transfection. In order to develop a new type of gene vector with high transfection efficiency and low cytotoxicity, amphiphilic chitosan was synthesized and linked with low-molecular weight polyethylenimine (PEI). We first synthesized amphiphilic chitosan - N-octyl-N-quatenary chitosan (OTMCS), then prepared degradable PEI derivates by cross-linking low-molecular weight PEI with amphiphilic chitosan to produce a new polymeric gene vector (OTMCS-PEI). The new gene vector was characterized by various physicochemical methods. We also determined its cytotoxicity and gene transfecton efficiency in vitro and in vivo. The vector showed controlled degradation. It was very stable and showed excellent buffering capacity. The particle sizes of the OTMCS-PEI/DNA complexes were around 150-200 nm with proper zeta potentials from 10 mV to 30 mV. The polymer could protect plasmid DNA from being digested by DNase I at a concentration of 2.25 U DNase I/μg DNA. Furthermore, they were resistant to dissociation induced by 50% fetal bovine serum and 1100 μg/mL sodium heparin. OTMCS-PEI revealed lower cytotoxicity, even at higher doses. Compared with PEI 25 KDa, the OTMCS-PEI/DNA complexes also showed higher transfection efficiency in vitro and in vivo. OTMCS-PEI was a potential candidate as a safe and efficient gene vector for gene therapy.