Chitosan oligosaccharide-functionalized nano-prodrug for cascade chemotherapy through oxidative stress amplification

Redox nanoparticles have been extensively developed for chemotherapy. However, the intracellular oxidative stress induced by constant aberrant glutathione (GSH), reactive oxygen species (ROS) and gamma-glutamyl transpeptidase (GGT) homeostasis remains the primary cause of evading tumor apoptosis. Herein, an oxidative stress-amplification strategy was designed using a pH-GSH-H2O2-GGT sensitive nano-prodrug for precise synergistic chemotherapy. The disulfide bond- conjugated doxorubicin prodrug (DOX-ss) was constructed as a GSH-scavenger. Then, phenylboronic acid (PBA), DOX-ss and poly (γ-glutamic acid) (γ-PGA) were successively conjugated using chitosan oligosaccharide (COS) to obtain the nano-prodrug PBA-COS-ss-DOX/γ-PGA. The PBA-COS-ss-DOX/γ-PGA prodrug could tightly attach to the polymer chain segment by atom transfer radical polymerization. Simultaneously, the drug interacted relatively weakly with the polymer by encapsulating ionic crosslinkers in DOX@PBA-COS/γ-PGA. The disulfide bond of the DOX-ss prodrug as a GSH-scavenger could be activated using overexpressed GSH to release DOX. Particularly, PBA-COS-ss-DOX/γ-PGA could prevent premature drug leakage and facilitate DOX delivery by GGT-targeting and intracellular H2O2-cleavable linker in human hepatocellular carcinoma (HepG2) cells. Concurrently, the nano-prodrug induced strong oxidative stress and tumor cell apoptosis. Collectively, the pH-GSH-H2O2-GGT responsive nano-prodrug shows potential for synergistic tumor therapy.