Tumor-targeting and redox-responsive photo-cross-linked nanogel derived from multifunctional hyaluronic acid-lipoic acid conjugates for enhanced in vivo protein delivery.

The fabrication of a secure and efficacious nanosystem for intracellular protein delivery is greatly desired, which relies on coordination of the interactions among loading ability, systemic stability, precise tumor targeting, successful endo-lysosomal evasion, and on-demand release characteristics. Herein, we constructed tumor-targeting and redox-responsive photo-crosslinkable nanogels (TRNGs) via UV light-induced ring-opening polymerization (ROP) of lipoic acid moieties incorporated in the side chain of methoxy poly (ethylene glycol) and diethylenetriamine-modified hyaluronic acid (HA-g-mPEG/Deta-c-LA) to create disulfide cross-linked core for the in vivo delivery of cytochrome c (CC). The TRNGs had satisfactory stability for 48 h in physiological environments and high CC encapsulation efficiency via multi-physical interactions. In vivo and in vitro fluorescence imaging proved the preferential accumulation of CC-loaded TRNGs in tumor tissues of human lung tumor-bearing mice and these nanoparticles were efficiently taken up into the CD44-positive A549 cells through CD44-mediated endocytosis compared to CD44-negative HepG2 cells. In addition, the nanoparticles underwent swift exocytosis from the endo-lysosomal compartment, thus promoting the liberation of CC within a reducing intracellular environment. The in vitro therapeutic outcomes proved that empty TRNGs presented excellent biocompatibility and minimal cytotoxicity, whereas CC-loaded TRNGs demonstrated a superior capacity to kill A549 cells compared to free CC and exhibited low effect on CD44-negative HepG2 cells. Moreover, CC-loaded TRNGs also had enhanced antitumor activity without eliciting any adverse effects. Our study highlighted the potential of TRNGs as a novel nanoplatform for the treatment of protein-based cancers.