Chitosan-PEI graft copolymers for pDNA delivery: fabrication and in vitro properties

Chitosan is generally biocompatible, biodegradable, mucoadhesive, non-toxic and non-immunogenic. Even though it has been shown to be able to condense nucleic acids (NA) (both DNA and RNA) and to protect them from nuclease degradation, its poor water solubility and low transfection efficacy have impeded its use as a gene carrier. On the other hand, high molecular weight polyethylenimine (PEI) (Mw = 25 kDa) is generally deemed efficient in transfection, but its high cytotoxicity makes it not a suitable vector in vitro. In order to fabricate a polymer with the merit of low toxicity of chitosan and high transfectability of PEI, we have conjugated chitosan with low molecular weight non-toxic PEI (MW= 0.8 kDa and 1.3 kDa) with a coupling reagent-mediated approach. We found that the resultant products (CP0.8 K and CP1.3 K) not only exhibited low cytotoxicity in vitro, but also showed high transfectability in a panel of cell lines (B16-F1, U87, C666-1 and HeLa). Our results indicate that CP0.8K and CP1.3 K have great potential as gene carriers in vitro, in vivo or even clinically.