Core-shell structured chitosan-polyethylenimine nanoparticles for gene delivery: Improved stability, cellular uptake, and transfection efficiency

Gene therapy has emerged as a promising treatment option for various acquired and inherited diseases. The delivery of nucleic acids relies on so-called vectors that condense and encapsulate their cargo, generating stable nano-sized particles. Especially non-viral gene delivery systems are of increasing interest. However, accomplishing therapeutic levels of transgene expression and limited tolerability of these systems remain a challenge. Therefore, we investigate in the present study the improvement of nucleic acid delivery using depolymerized chitosan – polyethylenimine DNA core complexes (dCS-PEI/DNA). These core complexes are further entrapped into a variety of dCS-based shells, functionalized with poly(ethylene glycol) (PEG) spacers conjugated to ionic moieties (amino or carboxylate groups) and cell penetrating peptides. This modular approach allowed to evaluate the effect of the shell functional components on the physico-chemical particle characteristics and biological effects in vitro. The optimized ternary complex combines a core-dCS-LPEI/DNA complex with a shell consisting of dCS-PEG-COOH, which resulted in improved encapsulation of nucleic acid, accelerated cellular uptake, enhanced transfection efficiency, and superior transfection potency in human hepatoma HuH-7 cells and mouse primary hepatocytes. Effects on transgene expression are confirmed in vivo in wild-type mice following retrograde intrabiliary infusion. After administration to mice of only 100 ng complexed nanovector DNA, ternary complexes induce a high reporter gene signal for three days. We conclude that ternary core-shell structured particles comprising functionalized chitosan are a promising gene delivery technology for both in vitro as well as in vivo applications. The modular design will facilitate the development of chemically modified derivatives.