Ultrasensitive chemiluminescent biosensor for the detection of cholesterol based on synergetic peroxidase-like activity of MoS2 and graphene quantum dots

Developing a novel non-enzyme mimetic in biosensors is of great significance. Here, a synergetic peroxidase-like activity was disclosed for mixed MoS2 quantum dots (MoS2 QDs) and graphene quantum dots (GQDs). The high catalytic effect of this mixture was studied on the chemiluminescence system. It was observed that the simultaneous presence of MoS2 QDs and GQDs had a powerful enhancing effect on the chemiluminescence (CL) emission of rhodamine B (RB)-H2O2 reaction. MoS2 QDs and GQDs mixture (prepared with a ratio of 3:2) showed a superior catalytic activity when compared to each of the constituents. A linear relationship was acquired between the CL emission intensity and H2O2 concentration in the range of 1.5-460 nmol L-1. On the other hand, since the enzymatic oxidation of cholesterol leads to the production of H2O2; the offered CL system was examined to detect cholesterol after its oxidation by cholesterol oxidase (ChOx) enzyme. Herein, a further improvement was achieved by MoS2 nanosheets. The MoS2 nanosheets increased the performance of ChOx in cholesterol oxidation process. The obtained results confirmed a highly selective and sensitive determination of cholesterol concentration in a linear dynamic range of 0.08-300 mu mol L-1, with a detection limit (3S) of 35 nmol L-1. The developed method was successfully applied for the detection of cholesterol level in human serum samples.