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<p>Manganese oxide (MnO<sub>x</sub>)-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<sub>x</sub> 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<sub>3</sub>O<sub>4</sub> 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<sub>3</sub>O<sub>4</sub>, which demonstrated excellent selectivity, sensitivity, and a low detection limit (0.25&#xa0;μM in solution and 6.77&#xa0;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.</p>

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

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年11月26日

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  • Zhao Zhang,
  • Tian Zhang,
  • Henghan Dai,
  • Zengyu Hui,
  • Lumin Wang,
  • Jianing An,
  • Xin Liu,
  • Hong Shan,
  • Haoran Zheng,
  • Gengzhi Sun

摘要

Manganese oxide (MnOx)-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 MnOx 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, Mn3O4 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 Mn3O4, 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.