Peroxidase-like activity of MoS nanoflakes with different modifications and their application for HO and glucose detection.

MoS nanoflakes (MoS NFs) with a diameter of ∼390 nm were obtained by a facile one-pot hydrothermal method and the NFs exhibited intrinsic peroxidase-like activity. After being modified by commonly used biocompatible surfactants including polyethyleneimine (PEI), polyacrylic acid (PAA), polyvinylpyrrolidone (PVP), and cysteine (Cys), the peroxidase-like catalytic activities of MoS NFs were investigated by using 3,3',5,5'-tetramethylbenzidine (TMB) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)diammonium salt (ABTS) as chromogenic substrates. Compared to the polymer modified MoS NFs, Cys functionalized MoS NFs exhibited a high catalytic activity toward HO in the presence of TMB or ABTS. Zeta potential and Michaelis-Menten analyses implied that the electrostatic force induced affinity or repulsion between the MoS NFs and substrates, as well as surface modifications of the MoS NFs played a key role in the catalytic reactions. Notably, a new peroxidase-like catalytic reaction mechanism was proposed based on the formation of a transient state of Cys-MoS NFs containing HO and ABTS, and the catalytic reaction could occur because the Cys on the surface of the MoS NFs served as an electron transfer bridge between HO and ABTS. Based on this finding, we also established a platform for colorimetric detection of HO and glucose using Cys-MoS NFs as a peroxidase substitution. The limit of detection (LOD) was determined to be 4.103 μmol L for HO, and the linear range (LR) was from 0 to 0.3 mmol L. The LOD for glucose was 33.51 μmol L and the LR was from 0.05 to 1 mmol L, which is suitable for biomedical diagnosis. This work provides a new insight into the catalytic mechanism of peroxidase-like MoS NFs, and paves the way for enzyme-like nanomaterials to be used for medical diagnosis.