Bioinspired CuZn-N/C Single-Atom Nanozyme with High Substrate Specificity for Selective Online Monitoring of Epinephrine in Living Brain

Though many elegant laccase mimics have emerged, these mimics generally have no substrate selectivity as well as low activity, making it difficult to fulfill the demand for monitoring in physiological conditions. Herein, inspired by the Cu-N ligand structure in the active site of natural laccase, we revealed that a carbon nanomaterial with atomically dispersed Cu and Zn atoms (CuZn-N/C) and a well-defined ligand structure could function as an effective laccase mimic for selectively catalyzing epinephrine (EP) oxidation. Catalytic activity of the CuZn-N/C nanozyme was superior to those of Cu-N/C and Zn-N/C and featured a K_m value nearly 3-fold lower than that of natural laccase, which indicated that CuZn-N/C has a better affinity for EP. Density functional theory (DFT) revealed the mechanism of the superior catalytic ability of dual-metal CuZn-N/C as follows: (1) the exact distance of the two metal atoms in the CuZn-N/C catalyst makes it suitable for adsorption of the EP molecule, and the CuZn-N/C catalyst can offer the second hydrogen bond that stabilizes the adsorption; (2) molecular orbitals and density of states indicate that the strong interaction between the EP molecule and CuZn-N/C is important for EP catalytic oxidization. Furthermore, a sensitive and selective online optical detection platform (OODP) is constructed for determining EP with a low limit of detection (LOD) of 0.235 μM and a linear range of 0.2-20 μM. The system allows real-time measurement of EP release in the rat brain in vivo following ischemia with dexmedetomidine administration. This work not only provides an idea of designing efficient laccase mimics but also builds a promising chemical platform for better understanding EP-related drug action for ischemic cerebrovascular illnesses and opens up possibilities to explore brain function.