IMMOBILIZATION OF ENZYMES ON SCREEN-PRINTED SENSORS VIA AN HISTIDINE TAIL. APPLICATION TO THE DETECTION OF PESTICIDES USING MODIFIED CHOLINESTERASE

Abstract A new screen-printed electrode for the detection of pesticides is described based on the immobilisation of acetylcholinesterase (AChE) by a metal chelate (Ni-NTA silica). This sensor was used to detect the inhibitory effects of organophosphorus and carbamate pesticides on acetylcholinesterase activity. The immobilisation method takes advantages of the ability of Ni2+ to bind to peptides or proteins containing histidine residues. The only requirement for this immobilisation to occur using a metal chelate is the presence of a histidine tail on the enzyme molecule. The AChE was modified by genetic engineering to incorporate six histidine tails. With the optimised procedure described, a good sensor stability and a high sensitivity were obtained. The sensor was tested for the detection of the pesticides paraoxon, dichlorvos and chlorpyrifos ethyl oxon, the detection level being respectively 4.1, 0.5 and 0.1 ppb. Keywords: AcetylcholinesteraseHistidine tailDisposable biosensorPesticide Acknowledgments