Microneedle‐Integrated FePc–MOF–MXene Nanozyme Patch for In Vivo L‐Cysteine Monitoring

Abstract Advancing clinical diagnostics requires platforms that combine catalytic efficiency, biocompatibility, and real‐time, in vivo accessibility. Herein, this study reports a structurally integrated FePc–ZIF‐8–MX nanozyme that combines the redox activity of FePc, the porous confinement of ZIF‐8, and the electrical conductivity of MX. Synthesized via a low‐energy, ambient‐condition process, this hybrid enables efficient electron transfer, enhanced analyte enrichment, and sustained catalytic activity in physiological environments. To translate this functionality into a wearable diagnostic format, the hybrid is seamlessly incorporated into a microneedle array, offering minimally invasive access to interstitial fluid for continuous L‐cysteine (L‐Cys) monitoring. The resulting platform exhibits high selectivity and sensitivity across complex biological matrices, including serum, urine, cultured cells, and a murine model of myocardial infarction. This study presents a multifunctional electrochemical platform that enables on‐body metabolite monitoring through a microneedle‐integrated nanozyme interface. To the best of our knowledge, it constitutes the first realization of real‐time, in vivo L‐Cys sensing in this format, setting a new benchmark for precision biosensing in translational healthcare.