Ultrasensitive enzyme-free electrochemical immunosensor for microcystin-LR using molybdenum disulfide/gold nanoclusters nanocomposites as platform and Au@Pt core-shell nanoparticles as signal enhancer

Abstract An ultrasensitive enzyme-free electrochemical immunosensor was developed for microcystin- LR (MC-LR) detection based on a unique competitive detection scheme using molybdenum disulfide (MoS2) nanosheets/BSA-stabilized gold nanoclusters (AuNCs) composite and Au core/Pt shell nanoparticles (Au@PtNPs). MoS2/AuNCs nanocomposite was used for a platform for immobilizing more antibody due to its large surface area and excellent biocompatibility. This enzyme-free immunosensor is coupled with a robust immunosandwich format employing Au@PtNPs-labeled antibody as a non-enzymatic reporter. Due to high catalytic efficiency and good stability of Au@PtNPs, Au@PtNPs-immobilized antibody competed for target antigen to form an antibody-antigen immunocomplex and further amplified the electrochemical signal. Thus, the concentration of the MC-LR is directly proportional to the electrochemical signal of immunosensor. Under optimized conditions, the proposed enzyme-free immunosensor was employed to detect MC-LR and exhibited a wide linear range of 1.0 ng L−1–1.0 mg L−1 with low detection limit of 0.3 ng L−1 (S/N = 3). This ultrasensitive and high specific nonenzymatic electrochemical immunoassay shows promising application in environmental and food monitoring.