Disposable cholinesterase biosensor for the detection of pesticides in water-miscible organic solvents

A disposable cholinesterase biosensor based on screen-printed electrodes was assembled and used to assess the effect of miscible organic solvents on the acetylcholinesterase activity and on the inhibitory effect of organophosphorus pesticides on acetylcholinesterase activity. Acetonitrile, ethanol and DMSO were tested in a range 0-30% mixed with phosphate buffer (0.1M, pH 7). With 5% acetonitrile and 10% ethanol, an increase of the recorded current was observed. The addition of 0.2% polyethylenimine to the enzyme preparation, before immobilisation, allowed the utilisation of 15% acetonitrile without negative effect on the enzyme activity. An inhibition calibration curve was obtained using chlorpyrifos-ethyl-oxon, a compound widely used for agricultural purposes. The lowest detectable amount was 1ppb following an incubation time of 10min. The use of 5% acetonitrile and 0.2% polyethylenimine did not interfere with the enzyme-inhibitor interactions.