Triphenylamine coupled chitosan with high buffering capacity and low viscosity for enhanced transfection in mammalian cells, in vitro and in vivo

Chitosan and its derivatives show excellent biological properties, including biocompatibility, biodegradability and non-allergenicity. The primary amines of chitosan are responsible for its cationic nature, which confer its electrostatic binding with anionic DNA and protects from DNA degradation during intracellular delivery. However, its poor physical properties, such as low water solubility and high viscosity, severely hamper the transfection efficiency and in vivo applicability of chitosan based gene transporters. In this study, highly soluble triphenylamine coupled chitosan (TPAC) was synthesized by coupling triphenylamine (TPA) with primary amines of low molecular weight (LMW) chitosan, offering lower viscosity at biological pH and at the concentrations required for in vivo gene delivery. TPAC inherits a higher buffering capacity due to the tertiary amines of TPA leading to enhanced endosomal escape compared to native LMW chitosan. Intracellular fate and co-localization studies of TPAC showed decreased co-localization of polyplexes with lysosomes, demonstrating an increased availability of delivered plasmid DNA to the nucleus. Low viscosity and smaller pGL3/TPAC polyplex size enabled in vivo studies in Balb/c mice through intravenous injection. The in vitro transfection and in vivo biodistribution of the pGL3/TPAC nanoplexes showed higher luciferase expression compared to chitosan, polyethyleneimine (PEI 25K) and lipofectamine®. Physicochemical characterization, cell viability assays, and degradation studies demonstrated that TPAC meets the standards of a good transfection agent.