Peroxidase-like activity of vanadium tetrasulfide submicrospheres and its application to the colorimetric detection of hydrogen peroxide and L-cysteine.

It is demonstrated that vanadium tetrasulfide (VS4) exhibits peroxidase (POx)-like activity which follows Michaelis-Menten kinetics when using H2O2 as a co-substrate. Electron spin resonance spectroscopy was use to analyze the catalytic mechanism. It suggests that the enzyme mimicking activity is caused by decomposing H2O2 into hydroxyl radicals. The method was used to quantify H2O2 by using 3,3',5,5'-tetramethylbenzidine as the substrate which results in the formation of a blue coloration (with an absorption peak at 652 nm). H2O2 can be detected in the 50 to 300 μM concentration range, and the detection limit is 5.0 μM. The assay for L-cysteine (L-cys) is based on the capability of oxTMB to oxidize L-cys to form L-cystine. The colorimetric L-cys assay has a linear response in the 5 to 100 μM concentration range and a 2.5 μM detection limit. Graphical abstractSchematic representation of the enzyme mimicking activity of vanadium tetrasulfide (VS4) submicrospheres originated from the decomposition of hydrogen peroxide (H2O2) to generate reactive hydroxyl radical (·OH) and the colorimetric detection of L-cysteine.