One Probe, Two Readouts: A Fluorescent Nanozyme Facilitates Cascade Catalysis and On-Demand Bimodal Detection of Hepatic ALT and AST.

Probing the activities of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) is of significance for clinical diagnosis of hepatic diseases and monitoring of therapeutic effects. Traditional detection methods often rely on a single signal driven by cascade catalysis of multiple natural enzymes, exposing weaknesses, including poor robustness and limited reliability. To overcome the deficiencies, here we design a novel nanoprobe (Na2V6O16/Cu-MOF) with both peroxidase-like catalytic and luminescent properties and establish a colorimetric/fluorescence bimodal method for the on-demand sensing of hepatic ALT and AST. In the bifunctional nanozyme, Na2V6O16 exhibits reposeful enzyme-like activity to trigger the oxidation chromogenic process of 3,3',5,5'-tetramethylbenzidine (TMB) via H2O2-dependent free radical formation, and the 2-aminoterephthalic acid-coordinated Cu-MOF presents stable luminescence, which can be quenched by blue oxTMB from nanozyme catalysis via the inner filter effect. The presence of ALT or AST mediates the generation of H2O2, which consequently modulates the colorimetric turn-on and fluorescence readouts. With the enzyme-nanozyme cascade catalysis facilitated by Na2V6O16/Cu-MOF as well as its fluorescent feature, high-sensitivity bimodal detection of ALT and AST was obtained. Importantly, the established system offers robust catalytic performance, and the on-demand readouts enable mutual verification of different responses, both of which jointly improve the dependability of target analysis. Our work provides a reliable strategy for transaminase biomarker detection, contributing new insights into the design of multifunctional nanozymes and their applications in constructing advanced catalytic sensing platforms.