Electrochemical Immunosensor For Detection Of Microcystin-LR In Water

Two different electrochemical immunosensors based on screen-printedcarbon electrode (SPCE) have been successfully developed. The first one is anamperometric immunosensor system based on the integrated principle ofelectrocatalytic reduction and indirect competitive immunoassay, which hasbeen developed by using a self-made osmium redox polymer (OsPVP) modifiedon SPCE. The second one is a new impedimetric immunosensor based on themodification of multi-wall carbon nanotube (MWCNT). Both biosensors canachieve the rapid and accurate detection of trace pollutants in water samples.Based on the detailed evaluation of the factors affecting sensor performance,taken microcystin-(leucine-arginine)(MC-LR) for example, the modifyingscheme of amperometric and impedimetric immunosensor and the measurementmethod of the pollutants in water were established.The results obtained from this study listed as follows:(1) OsPVP wascovalently co-immobilized on the surface of SPCE with bovine serum albumin(BSA) and hapten-carrier conjugates MC-LR-ovalbumin (MC-LR-OVA), whichwere synthesized by mixing MC-LR and OVA activated by glutaraldehyde.(2)MWCNT was modified on the surface of SPCE by preparing a stablepolyethyleneimine-MWCNT (MWCNT-PEI) suspension, in which the PEI wasapplied as the dispersant agent. After the mixture was immobilized, and then theMC-LR-OVA activated was covalently bound to electrode surface via thecondensation reaction between the aldehyde groups of conjugate and the aminegroups of MWCNT-PEI.(3) The morphology and electrochemical properties ofthe sensor modified was evaluated by scanning electron microscopy, cyclicvoltammetry, and electrochemical impedance spectroscopy. The results showthat good binding of monoclonal antibody against MC-LR (Anti-MC-LR) andlow non-specific adsorption was monitored.(4) The experimental results ofmatrix effect in real water sample indicated that the concentration of methanolunder the scope of the experimental conditions didn't affect the monitoring ofsamples, the proposed pH was6~8, and the high concentration of Cu2+and humus on the immunoassay which could affect the performance ofimmunosensor could be effectively compromised when1%EDTA and10mg/mL BSA were added to the pre-incubated mixture.(5) The detection limit ofamperometric immunosensor for MC-LR was found to be0.17μg/L with thequantitative detection range of0.43~10.72μg/L, and the total analysis time wasapproximately80min. The detection limit of impedimetric immunosensor forMC-LR was found to be0.58μg/L with the quantitative detection range of0.76~7.40μg/L, and the total analysis time was approximately55min. Severalwater samples of different origins were measured with less than15%deviationof the detection and the recovery ratio of MC-LR was determined to be83%~121%. The determination results of the samples including MC-LR were ingood correlation by those obtained from high performance liquidchromatography. This indicates that the prepared immunosensor can beapplicable to meet requirements of environmental monitoring for the tracepollutants with good accuracy and stability.