Tuning the oxidase mimics activity of manganese oxides via control of their growth conditions for highly sensitive detection of glutathione.

Different manganese oxides materials with various crystalline structures were prepared from KMnO 4 by using a cationic polymer branched polyethyleneimine (BPEI) as the reducing agent and structure directing agent through a hydrothermal process. By varying BPEI concentration, wire-like MnO 2 , rod-like MnOOH/Mn 3 O 4 and octahedral-like Mn 3 O 4 nanoparticles were controllably synthesized, respectively. The as-prepared manganese oxides were characterized by XRD, FT-IR, TEM, SEM and nitrogen adsorption-desorption measurements. The intrinsic enzyme-like activity of the synthesized manganese oxides was evaluated by using 3,3′,5,5′-tetramethylbenzidine (TMB) as the substrate in the absence of H 2 O 2 . It was shown that the mesoporous wire-like MnO 2 was best-performing with a highly oxidase-like catalytic activity in the model reaction. The effect of synthetic conditions of mesoporous wire-like MnO 2 on its oxidase-like activity was further investigated. Based on the selective inhibition of glutathione (GSH) on the high oxidase-like activity of as-prepared MnO 2 , a selective and sensitive colorimetric assay for GSH has been established. The limit of detection (LOD) for GSH was as low as 0.11 μM and the developed method was successfully applied to the detection of GSH in human serum samples. [ABSTRACT FROM AUTHOR]