Work

Manganese oxide (MnOx) as peroxidase-mimicking nanozymes with valence-dependent activity for single-use colorimetric bioassays

Year: 2025

Type: article

Abstract: Manganese oxide (MnO x )-based nanozymes have attracted growing interest due to their low cost, high catalytic robustness, and adjustable oxidation states that influence enzyme-mimicking performance. In this study, we report a systematic approach to synthesize MnO x nanocomposites with tunable Mn valence states via a two-step pyrolysis of Mn-BTC precursors, enabling us to explore their valence-dependent peroxidase-like activities. Among the synthesized forms, Mn 3 O 4 exhibited the highest catalytic efficiency by facilitating the decomposition of H₂O₂ to generate hydroxyl radicals (•OH), which oxidize tetramethylbenzidine (TMB) to produce a blue-colored product. The catalytic mechanism was supported by UV–vis spectroscopy and fluorescence assays. Kinetic studies revealed low Km values, indicating high substrate affinity. Leveraging these properties, we further developed a disposable paper-based colorimetric bioassay using Mn 3 O 4 , which demonstrated excellent selectivity, sensitivity, and a low detection limit (0.25 μM in solution and 6.77 μM on paper). This work not only elucidates the correlation between Mn valence state and catalytic behavior but also provides a promising strategy for designing efficient nanozymes for low-cost, portable biosensing platforms.

Source: Scientific Reports

DOI: 10.1038/s41598-025-26164-0