Stimuli-responsive biohybrid nanogels with self-immolative linkers for protein protection and traceless release

Nanogels have been applied in protein delivery due to the nanoscale sizes and the crosslinked structures. However, the release of protein molecules from the nanogels without damages to the structures and functionalities is quite a challenging research subject. In this research, responsive self-immolative linker dithioethyl carbamate bond is introduced to connect protein and polymer in the nanogel so that traceless release of protein occurs upon addition of glutathione (GSH) or dithiothreitol (DTT). Thermoresponsive polymer poly(di(ethylene glycol) methyl ether methacrylate-co-2-(2-(2-hydroxyethyl) disulfanyl) ethyl methacrylate) was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization, and was modified with 4-nitrophenyl chloroformate yielding polymer chains with pendant dithioethyl carbonate groups. The dithioethyl carbonate groups were reacted with amine groups of lipases resulting in the formation of dithioethyl carbamate bonds. Meanwhile, biohybrid nanogels were prepared by crosslinking the polymer chains with lipases. The immobilized lipase in the nanogels exhibited enhanced heat and acid resistance. Once the nanogels were treated with GSH or DTT, lipase could be released with no residual groups and most of its bioactivity was recovered.