An ultrasensitive competitive immunosensor for impedimetric detection of microcystin-LR via antibody-conjugated enzymatic biocatalytic precipitation

摘要

Herein we design a sensitive impedimetric immunosensor for quantitative detection of microcystin-LR (MC-LR) by combining antibody-conjugated enzymatic biocatalytic precipitation reaction and a competitive format. MC-LR-bovine serum albumin (MC-LR-BSA), which conjugated onto the nanogold-modified glassy carbon electrode through cysteamine and glutaraldehyde, was introduced as an analyte competitor. Competitive assays were performed by incubating the target MC-LR and the analyte competitor with horseradish peroxidase-labeled monoclonal anti-MC-LR antibodies (HRP-mAb). After the competitive reaction, HRP were introduced as the signal labels onto the immunosensor, accelerating the biocatalytic precipitation reaction of substrate 4-chloro-1-naphthol with the aid of H_2O_2. The enzymatically generated insoluble precipitate formed an insulting layer on the electrode surface and efficiently restricted the electron transfer of redox probe Fe(CN)_6~(4-/3-), resulting in an enhanced amplification of impedimetric signal. The impedimetric signal decreased with the increase of concentration of MC-LR, and exhibited a dynamic linear range from 0.01 to 100μg L~(-1) with a detection limit of 0.004 μg L~(-1). The proposed immunosensing method can be applied for rapid detection of MC-LR in real water samples with accuracy comparable to the high-performance liquid chromatography. The platform shows good precision, high sensitivity and specificity, which opening a promising horizon for monitoring of cyanobacterial pollution in environmental matrices.