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 µmol 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.