Abstract
In this paper the results for the construction of a gold/mercaptobenzothiazole/polyaniline/ acetylcholinesterase/polyvinylacetate (Au/ MBT/PANI/AChE/PVAc) thick-film biosensor for the determination of certain carbamate pesticide solutions in selected aqueous organic sol- vent solutions are reported. AChE biosensors are designed to complement the classical analytical methods of pesticide detection. The Au/ MBT/PANI/AChE/PVAc electrocatalytic biosensor device was constructed by encapsulating acetylcholinesterase (AChE) enzyme in the PANI polymer composite, followed by the coating of poly(vinyl acetate) (PVAc) on top to secure the biosensor film from disintegration in the organic solvents evaluated. The electroactive substrate called acetylthiocholine (ATCh) was employed to provide the movement of electrons in the amperometric biosensor. The voltammetric results have shown that the current shifts more anodically as the Au/MBT/PANI/AChE/PVAc bio- sensor responded to successive acetylthiocholine (ATCh) substrate addition under anaerobic conditions in 0.1 M phosphate buffer, KCl (pH 7.2) solution and aqueous organic solvent solutions. For the Au/MBT/PANI/AChE/PVAc biosensor, various performance and stability parame- ters were evaluated. These factors include the optimal enzyme loading, effect of pH, long-term stability of the biosensor, temperature stability of the biosensor, the effect of polar organic solvents, and the effect of non-polar organic solvents on the amperometric behavior of the biosen- sor. The biosensor constructed in this study offered a reasonable linear range between 0.25 to 3.45 nM for the detection of carbofuran, al- dicarb and dioxacarb pesticide solutions. The detection limits for the individual carbamate pesticides were 0.249 nM for carbofuran, followed by 1.209 nM for aldicarb and 1.572 nM for dioxacarb.
Highlights
The use of pesticides in the agricultural industry is still widespread as it is seen to increase the yield of crops, despite the negative impacts it may have on the environment and human health
It was observed that the Au/MBT/PANI/ AChE/poly(vinyl acetate) (PVAc) biosensor constructed in this study offered a reasonable linear range for the carbamate pesticides determined and the detection limit was lower than some of those reported in literature [Table-5]
An AChE biosensor based on the immobilisation of the enzyme in a PANI/PVAc polymer matrix on an Au/MBT modified electrode was developed for the determination of nanoMolar concentrations of carbofuran, aldicarb and dioxacarb carbamate pesticide solutions
Summary
The use of pesticides in the agricultural industry is still widespread as it is seen to increase the yield of crops, despite the negative impacts it may have on the environment and human health. The last two decades have seen an increasing growth in the routine application of organophosphorous (OP) and carbamate (CM) pesticides in the agricultural community. This has lead to increasing concerns with respect to the disastrous effects on the environment and on human, animal and insect health [1,2,3]. Organophosphate (OP) and carbamates (CM) pesticides inhibit the activity of the enzyme called acetylcholinesterase (AChE) in vertebrates and insects. Any inhibition of the activity of AChE leads to an increase in acetylcholine in the synapses, which in turn disrupts neurotransmission. Symptoms of acute toxicity include increased salivation, headaches, convulsions and suppressed breathing that can lead to death [1,2,3,4,5,6]
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