Thiolated trimethyl chitosan nanocomplexes as gene carriers with high in vitro and in vivo transfection efficiency

Trimethyl chitosan–cysteine conjugate (TMC–Cys) was evaluated as non-viral gene carriers to combine the advantages of TMC and thiolated chitosan. TMC–Cys with various molecular weights (30, 100, and 200 kDa) and quaternization degrees (15 and 30%) was allowed to form polyelectrolyte nanocomplexes with plasmid encoding enhanced green fluorescence protein (pEGFP), which demonstrated preferable diameters of below 200 nm and zeta potentials of + 15 to + 20 mV. Cell binding and uptake of TMC–Cys/pEGFP nanocomplexes (TMC–Cys NC) were enhanced 2.4–3.0 and 1.4–3.0 folds, respectively, compared to TMC/pEGFP nanocomplexes (TMC NC). pEGFP could be easily released from TMC–Cys NC at the intracellular glutathione concentration, which promoted its nuclear transport and accumulation. Consequently, TMC–Cys NC showed a 1.4 to 3.2-fold increase in the transfection efficiency in HEK293 cells as compared to TMC NC and the optimal TMC–Cys(100,30) NC showed a 1.5-fold enhancement than Lipofectamine2000. Such results were further confirmed by in vivo transfection with a 2.3-fold and 4.1-fold higher transfection efficiency of TMC–Cys(100,30) NC than TMC(100,30) NC and Lipofectamine2000, respectively. Therefore, TMC–Cys/DNA nanocomplexes could be a promising gene delivery system with in vitro and in vivo superiority to Lipofectamine2000.

Graphical abstractThiolated trimethyl chitosan (TMC–Cys)/pEGFP nanocomplexes improve both in vitro and in vivo transfection efficiency.Figure optionsDownload full-size imageDownload as PowerPoint slide