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

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.