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, Fe3+-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.

Free-Radical Cascade Generated by AIPH/Fe3O4-Coloaded Nanoparticles Enhances MRI-Guided Chemo/Thermodynamic Hypoxic Tumor Therapy

Free radicals, including reactive oxygen species (ROS), play a critical role in determining cell's fate. When the level of free radicals is increased to a fatal value, it causes cancer cells to undergo senescence or cell death. Strategies that target this mechanism offer promising therapies against cancer. However, efficient and sustainable systems that generate free radicals, especially oxygen-independent systems, remain deficient. Herein, functionalized PLGA-based nanocomposites that efficiently co-deliver magnetic nanoparticles and 2,2'-azobis[2-(2-imidazolin-2-yl) propane]-dihydrochloride (AIPH) were fabricated to achieve photothermal-induced thermodynamic therapy combined with macrophage polarization strategies; this therapy targets hypoxic tumors through the generation of an oxygen-independent free-radical cascade. These hybrid NPs can accumulate in the tumor microenvironment, and the encapsulated MNPs not only serve as contrast agents for enhanced magnetic resonance imaging but also exhibit the expected photothermal conversion and trigger the decomposition of AIPH to generate free radicals, thus causing cancer cell death. More importantly, the cell debris from apoptotic or necrotic cancer cells carries nondegraded MNPs, which can be endocytosed by recruited TAMs. MNPs can further induce TAMs to polarize to the M1 subtype to subsequently generate ROS. This study provides an alternative method for the generation of an oxygen-independent free-radical cascade for tumor co-therapy guided by magnetic resonance imaging PTT/TDT.