Functionalized O-carboxymethyl-chitosan/polyethylenimine based novel dual pH-responsive nanocarriers for controlled co-delivery of DOX and genes

A novel dual pH-sensitive co-delivery system, programmed to respond to tumor extracellular pH (6.0–7.0) and intracellular pH (4.5–6.5) environments, was designed for the controlled co-delivery of DOX and genes. Tumor intracellular pH-sensitive cationic doxorubicin (DOX)–poly(ethyleneimine) (PEI) conjugates (DOX–PEI, DP) were synthesized via pH-sensitive hydrazone bonds. As O-carboxymethyl-chitosan (CMCS) possesses cationic charges under pH 6.5 and is anionically charged above pH 7.0, tumor extracellular pH (6.0–7.0) triggered charge reversal CMCS–poly(ethylene glycol) (PEG)–aspargine–glycine–arginine (NGR) copolymers (CMCS–PEG–NGR, CPN) were synthesized. The two materials with different properties help to construct the dual pH-sensitive co-delivery system. First, the cationic DP interacts with anionic pDNA to form a DOX and gene co-loaded DP/pDNA (DPD) core. Then, anionic CPN is adsorbed on the surfaces of the positive charged DPD to form dual pH-sensitive CPN/DPD (CDPD). CDPD and DPD exhibited spherical shapes, uniform particle size distributions (137.4 ± 2.7 nm and 80.0 ± 4.2 nm, respectively), and positive zeta potentials (8.25 mV and 23.59 mV, respectively). Targeted cellular uptakes of CDPD were confirmed (cellular uptakes of CDPD were 92.49 ± 2.28% and 67.82 ± 0.07% in CD13-positive A549 cells and CD13-negative HepG2 cells, respectively). The dissociation of CPN from CDPD at acidic tumor tissue was evaluated (transfection efficiencies of CDPD at pH 7.4 and pH 6.0 were 11.43 ± 0.59% and 20.20 ± 1.21%, respectively). The internalized DPD programmable release of DOX and pDNA was investigated under simulated endosomal conditions. The results suggest that dual pH-sensitive CDPD was conducive to targeted delivery and the novel functional materials ensured the successful construction of novel dual pH-sensitive CDPD using a simple method.