Biomimetic Synthesis of Multinuclear Metal‐Oxo Bridges Under Mild Aqueous Conditions for Catalytic Cancer Therapy

In biological systems, enzymes achieve efficient catalysis by precisely assembling multinuclear metal-oxo bridges, such as Fe─O─Fe motifs, under physiological conditions. However, constructing such structures in synthetic systems, particularly under mild aqueous conditions, remains challenging. Here, we report a self-assembled helical polymer that creates a protein-like microenvironment and enables the biomimetic construction of Fe─O─Fe structures in a synthetic polymer system under mild, neutral aqueous conditions. This strategy increases the stability constant of iron coordination by two orders of magnitude and endows the resulting complex with pH-gated catalytic behavior: the complex remains catalytically inert under neutral conditions but exhibits more than 20-fold enhanced peroxidase-like activity in the weakly acidic tumor microenvironment. Moreover, oxo-bridge formation significantly enhances near-infrared absorption, enabling a robust photothermal effect. Without any exogenous drug payload, the complex selectively induces ferroptosis and immunogenic cell death in tumor cells, leading to complete tumor eradication in a mouse model. This work establishes a biomimetic strategy for constructing metal-oxo-bridged clusters and provides mechanistic insights into the structure-function relationships of metalloprotein-inspired materials.