Novel ultrathin ferrous sulfide nanosheets: Towards replacing black phosphorus in anticancer nanotheranostics

Biodegradable two-dimensional nanomaterials could be a significant breakthrough in the field of oncology nanotheranostic agents, which are rapidly emerging as promising candidates for tumor theranostic applications. Herein, a novel biodegradable ferrous sulfide nanosheet (FeS NS) is developed. Compared to the traditional photothermal material, black phosphorus nanosheet (BP NS), FeS demonstrates superior degradability and enhanced photothermal performance, and making it ideal for efficient photothermal therapy (PTT) of tumors. In the acidic tumor microenvironment, FeS degrades and releases H₂S, which inhibits mitochondrial respiration and ATP production. This process leads to a reduction in heat shock protein expression, lowering the resistance of tumor cells to photothermal stimulation, and improving the efficacy of PTT. The released Fe²⁺ exhibits efficient peroxidase activity, triggering ferroptosis in tumor cells. Furthermore, due to its superparamagnetic nature, FeS NSs could accumulate at the tumor site and provide a strong magnetic resonance imaging (MRI) signal for imaging-guided tumor therapy. Overall, as a promising alternative to BP, the FeS NSs are a potentially innovative nanotheranostic agent of tumors, offering a synergistic approach to ferroptosis−PTT with MRI guidance.