Bioelectrochemical magnetic immunosensing of trichloropyridinol: A potential insecticide biomarker

A fast, simple and sensitive bioelectrochemical magnetic immunosensing method is developed to monitor a potential insecticide biomarker, trichloropyridinol (TCP), in environmental sample. A magnet/glassy carbon (MGC) working electrode was used to accumulate immunocomplex associated magnetic beads and separate free and unbound reagents after liquid phase competitive immunoreaction among TCP antibody coated magnetic beads, TCP analyte and horseradish peroxidase (HRP) labeled TCP The activity of HRP tracers was monitored by square-wave voltammetry (SWV) by scanning electrocactive enzymatic product in the presence of 3,3',5,5'-tetramethylbenzidine dihydrochloride and hydrogen peroxide (TMB-H2O2) substrate solution. The electrochemical signal of enzymatic product was greatly enhanced by dual accumulation events: magnetic accumulation of enzyme tracers bound magnetic beads and constant potential accumulation of enzymatic product. The voltammetric characteristics of substrate and enzymatic product were investigated, and the parameters of SWV analysis and immunoassay were optimized. Under the optimal conditions the immunosensor was used to measure as low as 5 ng L-1 (ppt) TCP, which is 50-fold lower than the value indicated by the manufacture of the TCP RaPID Assay kit (0.25 mu g/L, colorimetric detection). The performance of the developed immunosensing system was successfully evaluated with river water samples spiked with TCP, indicating this convenient and sensitive technique offers great promise for decentralized environmental application. This technique could be readily used for detection of other environmental contaminants by developing specific antibodies against the contaminants and are expected to open new opportunities for environmental monitoring and public health.