Immobilization of enzyme on screen-printed electrode by exposure to glutaraldehyde vapour for the construction of amperometric acetylcholinesterase electrodes

A new technique based on exposure to the vapour of glutaraldehyde was used to immobilize acetylcholinesterase on the surface of screen-printed electrodes. The printed planar electrodes drop-covered with a layer of enzymes were supported horizontally over glutaradehyde solutions in a closed vessel for minutes at 37 degrees C. The immobilization of enzymes was accomplished in batches. To test the device a small volume of acetylthiocholine substrate solution was directly dropped on the surface of the exposed biosensor, which is a suitable way to operate in the field. The coefficients of variation of 3.8% (n=8) and 7.3% (n=6) were calculated for the response for 30 mu l 17.5 mM acetylthiocholine solution with these electrodes exposed in the same batch or different batches, respectively, indicating an acceptable reproducibility. The sensors were also used to detect the pesticide paraoxon. Incubation of the sensor for 10 min in paraoxon solution resulted in a calibration plot of the percentage inhibition versus the logarithm of paraoxon concentration that was linear over the range 1.8 x 10(-7)-5.4 x 10(-5) M, which corresponds to 10.31-88.75% enzyme inhibition. (C) 1999 Elsevier Science B.V. All rights reserved.