Stabilized and Controlled Release of Radicals within Copper Formate-Based Nanozymes for Biosensing

[Image: see text] Fenton-like radical processes are widely utilized to explain catalytic mechanisms of peroxidase-like nanozymes, which exhibit remarkable catalytic activity, cost-effectiveness, and stability. However, there is still a need for a comprehensive understanding of the formation, stabilization, and transformation of such radicals. Herein, a copper formate-based nanozyme (Cuf-TMB) was fabricated via a pre-catalytic strategy under ambient conditions. The as-prepared nanozyme shows comparable catalytic activity (K(m), 1.02 × 10(–5) mM(–1); K(cat), 3.09 × 10(–2) s(–1)) and kinetics to those of natural peroxidase toward H(2)O(2) decomposition. This is attributed to the feasible oxidation by *OH species via the *O intermediate, as indicated by density functional theory calculations. The key ·OH radicals were detected to be stable for over 52 days and can be released in a controlled manner during the catalytic process via in situ electron spin-resonance spectroscopy measurements. Based on the understanding, an ultrasensitive biosensing platform was constructed for the sensitive monitoring of biochemical indicators in clinic settings.