Hypoxia-responsive hyaluronic acid nanogels with improved endo/lysosomal escape ability for tumor-targeted cytochrome c delivery

An ideal protein therapeutic effect depends on the protein drug-carrying nanocarrier to achieve high loading efficiency, excellent systemic stability, specific tumor targeting, rapid endo/lysosomal escape, and controlled protein release behavior. Herein, novel and interesting hypoxia-responsive nanogels with improved endo/lysosomal escape ability are reported in this work for tumor-targeted protein delivery. These nanogels can encapsulate a cationic protein, cytochrome C (CC), inside their cores with good stability in various media and thus protect the protein from degradation during blood circulation. In this nanogel system, monomethoxy poly(ethylene glycol) (mPEG) is conjugated to hyaluronic acid (HA) and serves as an outer shell for improving stability of the nanostructure, and the anionic HA is employed for encapsulation of cationic CC through multiphysical interactions with a high loading efficiency. The nanogel system is crosslinked using a hypoxia-responsive crosslinker for subsequent triggered release of CC. Due to presence of the hypoxia-responsive crosslinker, more than 80% of the loaded CC can be released within 24 h under hypoxic conditions. The in vitro experimental results demonstrate that these nanogels can effectively deliver CC into cancer cells via CD44-mediated tumor targeting, subsequently enable rapid endo/lysosomal escape, and trigger CC release under hypoxic conditions. In addition, cytotoxicity test confirms that the CC-loaded nanogels exhibit much higher cytotoxicity to cancer cells at hypoxic condition than that at normoxic condition, which indicates that this nano-platform is a promising candidate for tumor-targeting protein delivery and efficient cancer therapy.