Regulation of the Oxidase-like Activity of an α-Mn2O3 Nanozyme by Tween 80 for Sensitively Sensing Glutathione

Abstract Effective regulation of nanozyme activity is crucial for the accurate and sensitive analysis of targets in complex biological matrices. In this work, an α-Mn2O3 nanozyme (Tw-Mn2O3) was prepared through the hydrothermal-roasting method using manganese acetate (MnAc2·4H2O) as a manganese source and Tween-80 as an activity modulator. The oxidase-like (OXD) activity of Tw-Mn2O3 was regulated by adjusting the amount of Tween-80 and evaluated using 3,3′,5,5′-tetramethylbenzidine (TMB) and o-phenylenediamine (OPD) as chromogenic substrates. The optimal activity was obtained when 0.23 mmol Tween-80 was added, featuring rich surface oxygen vacancies and Mn3+/Mn4+ pairs that activate dissolved oxygen to generate •O2− for catalysis. Tw-Mn2O3 exhibited typical Michaelis−Menten kinetics with the Km of 0.12 and Vm of 17.17 × 10−8 M/s. Owing to the inhibitory effect of GSH, a colorimetric method based on Tw-Mn2O3 for glutathione (GSH) detection was constructed with the linear range of 1.25−50 μM and a low detection limit (LOD) of 0.15 μM. The constructed method exhibited excellent anti-interference and selectivity for GSH detection. Furthermore, a smartphone-assisted colorimetric method was developed to achieve quantitative detection of GSH with a good linearity in the range of 5−37.5 μM and an LOD down to 1.7 μM. This work not only demonstrated a simple strategy to modulate OXD-like activity of α-Mn2O3 but also established a reliable analytical method for GSH detection.