Conductometric biosensors based on cholinesterases for sensitive detection of pesticides

Abstract

ABSTUCTDisposable conductometric microbiosensors based on immobilization of acetyl and butyrylcholinesterases (BuChEs) on interdigitated electrodes were fabricated. Enzymes were immobilized by crosslinking with bovine serum albumin and the differential output between the pair of electrodes covered with the enzyme membrane and the pair covered with albumin only was recorded. On the basis of these biosensors, a biochemical assay for pesticides in liquids was developed. Respective detection limits were 5 X lo-" M for diisopropyl fluorophosphate (DFP), lo-' M for trichlorfon, and M for paraoxon-methyl and paraoxon-ethyl for the assavs based on the enzymes tested. The presence of pesticides in the sample in concentration exceeding the detection limits can be detected after only 10 minutes of incubation, whereas, in order to extend the range of the determined pesticide concentration and to improve the accuracy of the assay, it is better to use incubation times longer than 30 minutes. Use of pyridin-2-aldoximide methiodide as reactivating agent allowed one to achieve the complete recovery of the sensor response when it was incubated in lowconcentrated pesticide solutions, e.g., less than M for paraoxon-methyl and during a short time, e.g., 10 to 20 minutes, for M paraoxon-methyl solution.

Biosensors based on cholinesterase inhibition for insecticides, nerve agents and aflatoxin B1 detection (review)

“…Recently current driven ion fluxes of a polymeric membrane ion-selective electrode for BChE potentiometric biosensing was published on Journal of American Chemical Society [68]. ii) conductimetric: the reaction can be monitored by measurement of conductivity variation [69,70] iii) amperometric: for the monoenzymatic amperometric biosensors, a synthetic substrate must be used; in fact, acetylthiocholine was adopted instead of acetylcholine. The enzymatic reaction hydrolyses the acetylthiocholine to acetic acid and thiocholine (Eq.…”

Cholinesterase-based biosensors

“…This results in the changes in solution conductivity inside the layer with immobilized enzyme. The conductivity measurements are usually performed by applying a small-amplitude voltage to the electrodes 81 . The main drawback of conductometric biosensors compared to amperometric and potentiometric ones is their relatively lower sensitivity.…”

Investigation and Optimization of Reactivation Butyrylcholinesterase-Based Biosensor for Inhibitory Analysis of Pesticides

“…Частина з них функціонують на основі холінестеразної ре-акції з використанням різноманітних типів перетворювачів: амперометричних, оптич-них, кондуктометричних, потенціометричних, спектроскопічних та інших [9][10][11]. Але всі ці біосенсори мають спільну проблему -фосфо-рорганічні пестициди інактивують фермент незворотно.…”