Amplification of Oxygen-Independent Free Radicals Based on a Glutathione Depletion and Biosynthesis Inhibition Strategy for Photothermal and Thermodynamic Therapy of Hypoxic Tumors.

Thermodynamic therapy (TDT) based on oxygen-independent free radicals exhibits promising potential for the treatment of hypoxic tumors. However, its therapeutic efficacy is seriously limited by the premature release of the drug and the free radical scavenging effect of glutathione (GSH) in tumors. Herein, we report a GSH depletion and biosynthesis inhibition strategy using EGCG/Fe-camouflaged gold nanorod core/ZIF-8 shell nanoparticles embedded with azo initiator 2,2'-azobis[2-(2-imidazolin-2-yl) propane] dihydrochloride (AIPH) and L-buthionine-sulfoximine (BSO) for tumor-targeting photothermal (PTT) and thermodynamic therapy (TDT). This nanoplatform (GNR@ZIF-8-AIPH/BSO@EGCG/Fe, GZABEF) endows a pH-responsive release performance. With the 67 kDa lamin receptor (67LR)-targeting ability of EGCG, GZABEF could selectively release oxygen-independent free radicals in tumor cells under 1064 nm laser irradiation. More importantly, Fe-mediated GSH depletion and BSO-mediated GSH biosynthesis inhibition significantly boosted the accumulation of alkyl radicals. In 4T1 cells, GZABEF induced cancer cell death via intracellular GSH depletion and GSH peroxidase 4 (GPX4) inactivation. In a subcutaneous xenograft model of 4T1, GZABEF demonstrated remarkable tumor growth inhibition (78.2%). In addition, excellent biosafety and biocompatibility of GZABEF were observed both in vitro and in vivo. This study provides inspiration for amplified TDT/PTT-mediated antitumor efficacy.