A tumor microenvironment responsive nanoplatform with oxidative stress amplification for effective MRI-based visual tumor ferroptosis

As a promising new form of non-apoptotic regulated cell death, ferroptosis has potential as an effective supplement to apoptosis-based cancer treatments. However, high intracellular glutathione (GSH) levels and insufficient hydrogen peroxide (H2O2) in the tumor limit the efficacy of ferroptosis. Here, we designed a theranostic nanoplatform, named FCS/GCS, by incorporating amphiphilic polymer skeletal (P-SS-D), cinnamaldehyde prodrug (CA-OH) and iron ions (Fe3+)/gadolinium ions (Gd3+) via chelation reactions between Fe3+/Gd3+ and polyphenols. When delivered in the tumor microenvironment with high GSH level, the nanoparticles are depolymerized by the poly(disulfide) backbone of P-SS-D. The activated CA consumes the GSH and elevates intracellular H2O2, followed by a high level of Fenton reaction to generate abundant •OH levels. The generation of reactive oxygen species (ROS) further accelerates CA activation. The GSH consumption by disulfide, CA and Fe3+, downregulates GPX4 and generates •OH, which accelerate lipid peroxides (LPO) accumulation and consequently enhances ferroptosis. Additionally, the released Gd3+ may serve as a contrast agent for tumor-specific T1-weighted magnetic resonance imaging (MRI). Thus, the rationally designed FCS/GCS system is a promising strategy for effective MRI-based visual ferroptosis therapy.