Tunable membrane-penetrating bioreductive nanogels based on guanidinylated dendrimers for programmable gene delivery

For safe and effective delivery of nucleic acid, a series of tunable membrane-penetrating nanogels were developed, which were constructed from reversibly cross-linked guanidinylated poly(_L-lysine) dendrimers with various guanidination degrees and cross-linking degrees. The designed nanogels electrostatically interacted with DNA, resulting in condensed nanogelplexes with size of about 100 nm and positive zeta potential of 35 mV. Increased DNA complexing ability of nanogels can be achieved via increasing the guanidination degree. The presence of reductive agents gave rise to cleavage of disulfide bonds in PK₃G₃₀D₂, in accompany with the collapse and swelling of nanogelplexes. Compared with PEI and PK₃D₂ lacking of guanidine groups, PK₃G₃₀D₂ bearing 30 guanidine groups exhibited the highest transfection performance with good biocompatibility in serum-containing medium. Meanwhile, guanidination in collaboration with reversible cross-linking also promoted cellular internalization, lysosomal escape and release of DNA from condensed nanogelplexes, resulting in substantially improved transfection synergistically. The enhanced transfection efficiency by the guanidine-rich PK₃G₃₀D₂ was also achieved in tibialis anterior muscles and tumor xenografts in mice. These results reveal these bioreductive and guanidinylated nanogels with synergistic effects might hold great potential for developing gene delivery system.