GSH-depleting metal–polyphenol-network nanoparticles with dual enzyme activities induce enhanced ferroptosis

Ferroptosis is a non-apoptotic form of regulated cell death. The efficiency of ferroptosis is restrained in the tumor microenvironment (TME) by overexpression of glutathione (GSH) and insufficient production of hydrogen peroxide (H₂O₂). In this work, theranostic nanoparticles Ce-aMOFs@Fe³⁺-EGCG, termed MEFs, are developed by coating uniform Ce-based amorphous metal-organic frameworks (Ce-aMOFs) with epigallocatechin gallate (EGCG) and Fe³⁺. Fe³⁺ is chelated by the adjacent phenol hydroxyl groups in EGCG. In the tumor cell interior, overexpressed GSH and weak acidic medium degrade the coating to release Fe³⁺ and EGCG accompanied by exposure of Ce-aMOFs. Fe³⁺ and EGCG consume GSH along with turning Fe³⁺ into Fe²⁺. Ce-aMOFs act as a nanozyme possessing dual-enzymatic activities, i.e. superoxide dismutase (SOD)- and phosphatase-like activities. In the TME, Ce-aMOFs catalyze the conversion of endogenous superoxide (O₂˙^-) into H₂O₂, and Fe²⁺ catalyzes H₂O₂ to generate toxic hydroxyl radicals (˙OH), which may further induce tumor cell death through ferroptosis. In addition, the phosphatase-like activity of Ce-aMOFs may sustainably dephosphorylate NADPH and effectively inhibit intracellular biosynthesis of GSH. Therefore, MEFs ensure down-regulation of intracellular GSH levels and up-regulation of oxidative pressure, which enhance the ferroptosis effect.