An electrochemical non-enzymatic immunosensor for ultrasensitive detection of microcystin-LR using carbon nanofibers as the matrix

Abstract

This work designed an ultrasensitive non-enzymatic immunosensor for microcystin-LR (MC-LR) detection using carbon nanofibers (CNFs) as immobilization matrix and gold nanoparticles (AuNPs) as an electrochemical label. The carboxylic group functionalized CNFs could well disperse in water for at least three months, and CNFs modified electrode showed high conductivity and enhanced electron transfer. The immunosensor was constructed by immobilizing MC-LR antigen on CNFs modified electrode. With a competitive immunoassay format, the coated MC-LR antigen competed for MC-LR antibody with added target MC-LR to form antibody-antigen immunocomplex. Subsequently, the immunocomplex reacted with AuNPs labeled secondary antibodies, and the bound AuNPs were finally electro-oxidized in 0.1M HCl to produce AuCl4− for differential pulse voltammetric detection of MC-LR. Under optimal conditions, the immunosensor exhibited a wide linear response to MC-LR ranging from 0.0025 to 5μgL−1 with a detection limit of 1.68ngL−1 at a signal to noise of 3. This method showed good accuracy, acceptable precision and reproducibility. The assay results of MC-LR in polluted water were in a good agreement with the reference values. The proposed ultrasensitive immunoassay showed the promising application in environmental monitoring and public health.