Bioreducible crosslinked cationic nanopolyplexes from clickable polyethylenimines enabling robust cancer gene therapy

Bioreducible crosslinked polyplexes from branched polyethylenimine (BPEI, 10 kDa) were successfully constructed through DNA neutralization by disulfide-linked azidated BPEI (PAZ) and subsequent DNA condensation by azadibenzocyclooctyne-modified BPEI (PDB), following their self-crosslinking via azide-azadibenzocyclooctyne click chemistry. Click-crosslinked cationic polyplexes (c-polyplexes) revealed high extracellular colloidal stability against negative heparin and ions while intracellular bioreducible degradability for efficient gene unpacking. In vitro gene transfection in cancer cells indicated that the c-polyplexes produced markedly higher transfection efficiency than non-crosslinked counterparts in the serum. The c-polyplexes also had prolonged circulation kinetics, elevated gene accumulation level in SKOV-3 tumor xenografted in a mouse model and in turn superior transgene expression in the tumor. By small hairpin RNA for VEGF silencing, the c-polyplexes exerted significant tumor growth inhibition following with low systemic toxicity in the mouse. This study highlights the design of clickable polycations to construct crosslinked cationic nanopolyplexes for intravenous gene delivery against cancer.