Iron Single‐Atom Catalysts on MXenes for Ultrasensitive Monitoring of Adrenal Tumor Markers and Cellular Dopamine

Abstract Neuroblastoma and pheochromocytoma are the most prevalent malignancies of the adrenal medulla. They are currently diagnosed by measuring urinary catecholamines using high‐performance liquid chromatography‐mass spectrometry, which is expensive, bulky, and tedious. Electrochemical detectors stand out as low‐cost alternatives; however, further development of functional materials with adequate sensitivity is still required to attain clinically useful diagnostic devices. Here, Ti₃C₂T_x MXene nanosheets stabilized with iron single‐atom catalysts (Fe‐SACs), anchored on the surface, are synthesized and utilized as efficient electrocatalysts for the determination of catecholamine (dopamine (DA)) and its end‐products (vanillylmandelic acid (VMA) and homovanillic acid (HVA)). The Fe‐SACs/Ti₃C₂T_x exhibits low oxidation overpotentials with high signal amplifications up to 610%, 290%, and 420%, and sensitive detection limits of 1.0, 5.0, and 10 nM for DA, VMA, and HVA, respectively. The presence of the atomic Fe elements on the Ti₃C₂T_x nanosheets is confirmed using high‐resolution scanning transmission electron microscopy and X‐ray photoelectron spectroscopy. The Fe‐SACs/Ti₃C₂T_x sensor tracks the in situ production of DA in PC12 cells and found practically useful in analyzing human urine samples. The Fe‐SACs/Ti₃C₂T_x stands out as a sensitive diagnostic platform for evaluating the progression of tumors and the quality of cellular DA communications