Facile synthesis of Co3O4/g-C3N4 with enhanced peroxidase-like activity for colorimetric detection of glutathione and L-cysteine

Abstract

Biothiols, such as glutathione (GSH) and L-cysteine (L-Cys), were essential for maintaining human physiological homeostasis, and their abnormal levels are closely associated with various diseases. Herein, a composite nanoenzyme Co3O4/g-C3N4 with significantly enhanced peroxidase-like activity was successfully synthesized by combining ZIF-67-derived Co3O4 with graphitic carbon nitride (g-C3N4). The 3,3′,5,5′-tetramethylbenzidine (TMB) could be efficiently oxidized to blue TMB (oxTMB) by Co3O4/g-C3N4 in the presence of H2O2, while biothiols (GSH and L-Cys) inhibited this catalytic reaction due to their antioxidant properties, leading to a visible color fading. Based on the mechanism, a colorimetric detection method was established for quantitative analysis of GSH and L-Cys with linear ranges of 0~30 μM for GSH and 1~30 μM for L-Cys, respectively. Moverover, a convenient smartphone-assisted sensing platform was established for detection of GSH and L-Cys benefiting from the Co3O4/g-C3N4 based colorimetric strategy. These established methods had been applied to detect GSH and L-Cys in human urine, which showed great potential for self-health monitoring.