Co/Mn-Doped Oxide Nanosheets with Dual Enzyme-Like Activity for Early Visual Diagnosis of Pheochromocytoma

Pheochromocytoma may be overlooked or misdiagnosed in its early stages, resulting in serious clinical consequences. To comprehensively and accurately diagnose pheochromocytoma, we established a smartphone-assisted colorimetric sensing platform for the determination of two biomarkers of pheochromocytoma: epinephrine (Epi) and glutathione (GSH). In this article, Co/Mn-doped oxide nanosheets (CoMnNSs) with oxidase-like and laccase-like activities have been synthesized via a one-step process. Compared to MnO2 nanosheets (MnO2 NSs), CoMnNSs have stronger catalytic activity due to the doping of the transition metal Co. Under optimal conditions, the oxidase-like and laccase-like activities of CoMnNSs were utilized for the determination of GSH and Epi, respectively, and the assay could be completed within 3 min, with the limits of detection (LOD) of 0.15 and 0.52 μM, respectively. Besides, the practicability of the established approach was confirmed in human serum samples with satisfactory recoveries. The experimental results indicated that the designed sensor demonstrated excellent sensitivity and selectivity. Thus, this work not only widens the idea for early visual diagnosis of pheochromocytoma but also confirms the effectiveness of the transition-metal doping strategy, which offers a simple, economical, and gentle means of modulating nanozyme activity.