Iron oxide nanozymes enhanced by ascorbic acid for macrophage-based cancer therapy

In recent years, using pharmacological ascorbic acid has emerged as a promising therapeutic approach in cancer treatment, owing to its capacity to induce extracellular hydrogen peroxide (H₂O₂) production in solid tumors. The H₂O₂ is then converted into cytotoxic hydroxyl free radicals (HO˙) by redox-active Fe²⁺ inside cells. However, the high dosage of ascorbic acid required for efficacy is hampered by adverse effects such as kidney stone formation. In a recent study, we demonstrated the efficient catalytic conversion of H₂O₂ to HO˙ by wüstite (Fe_1-O) nanoparticles (WNPs) through a heterogenous Fenton reaction. Here, we explore whether WNPs can enhance the therapeutic potential of ascorbic acid, thus mitigating its dose-related limitations. Our findings reveal distinct pH dependencies for WNPs and ascorbic acid in the Fenton reaction and H₂O₂ generation, respectively. Importantly, WNPs exhibit the capability to either impede or enhance the cytotoxic effect of ascorbic acid, depending on the spatial segregation of the two reagents by cellular compartments. Furthermore, our study demonstrates that treatment with ascorbic acid promotes the polarization of WNP-loaded macrophages toward a pro-inflammatory M1 phenotype, significantly suppressing the growth of 4T1 breast cancer cells. This study highlights the importance of orchestrating the interplay between ascorbic acid and nanozymes in cancer therapy and presents a novel macrophage-based cell therapy approach.