Manganese-based metal–organic frameworks with oxidase properties break the temperature limitation of nano enzymes for glutathione detection

Abstract

Solving the enzyme activity loss caused by temperature changes is significant in fields such as catalytic biology. Herein, an Mn-based metal–organic framework (Mn/BTC-MOF) enzyme with efficient oxidase-like activity was prepared using a one-step hydrothermal method. The nanozyme demonstrated superior catalytic oxidation performance in the temperature range of 0–50 °C. The minimal loss of its enzyme-like activity across varying temperatures challenges the conventional wisdom that enzymes achieve peak activity solely under ideal temperature settings. The Mn/BTC-MOF, exhibiting oxidase-like characteristics, efficiently catalyzed the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to form the blue-colored oxidized TMB, even in the absence of hydrogen peroxide (H₂O₂). This capability is primarily due to the presence of Mn in mixed oxidation states (Mn³⁺/Mn²⁺) coupled with a high affinity for the substrate, indicated by a low Michaelis constant (K_m = 0.02 mM). Leveraging this oxidase-like behavior of Mn/BTC-MOF, a colorimetric assay was created to quantify glutathione in human serum, featuring a linear response within the range of 0–65 μM. This study opens a new way for the development and utilization of wide-temperature-adaptive enzymes.