Redox-triggered intracellular dePEGylation based on diselenide-linked polycations for DNA delivery

Extracellular stability to protect DNA against nucleases and stimulus-triggered intracellular DNA release are key factors in designing non-viral gene vectors. In this study, the diselenide-linked polycation mPEG-SeSe-PEI was developed as a new type of PEG-detachable gene vector for redox-responsive gene delivery. The corresponding stable analog mPEG-PEI and the disulfide-linked polycation mPEG-SS-PEI were synthesized as controls. The results showed that all the PEGylated polycations could condense DNA into tightly packed spherical nanoparticles about 80 nm in size, which showed excellent stability under physiological conditions. The results of zeta-potential measurements, stability tests and DNA release ability assay indicated that at a GSH concentration of 0.3 mM, the diselenide bonds were more easily cleaved than disulfide bonds, which facilitated dePEGylation and DNA release. Meanwhile, it was interestingly found that mPEG-SeSe-PEI/DNA polyplexes showed higher gene expression than mPEG-SS-PEI/DNA polyplexes in both HEK293T and HepG2 cells. Confocal laser scanning microscope (CLSM) images revealed that mPEG-SeSe-PEI/DNA polyplexes showed more efficient endosomal escape ability than mPEG-SS-PEI/DNA polyplexes. Based on these results, the diselenide bonds as a novel strategy are more suitable to address the challenging problem of extracellular stability and intracellular DNA release.