Porous silicon-modified electrode for electrochemical pesticide biosensor
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Porous silicon-modified electrode for electrochemical pesticide biosensor Maha Ayat , Katia Ayouz, Chafiaa Yaddadene, Malika Berouaken, Noureddine Gabouze
American Coatings Association 2020 Abstract An electrochemical biosensor for organophosphorus pesticides detection has been developed by immobilizing acetylcholinesterase (AChE) enzyme, through a multi-step functionalization process, on porous silicon (PSi) surface. The PSi surface was functionalized using thermal hydrosilylation creating acidic chains to stabilize the surface. The AChE was covalently attached on the PSi surface and exhibited a good enzyme activity in the presence of its substrate acetylthiocholine iodide (ATI) by forming thiocholine. The response of the device shows a linear evolution over a wide concentration range of ATI from 0.15 to 0.65 mM with a good correlation coefficient. Furthermore, AChE revealed high affinity to its substrate ATI from calculated Michaelis–Menten constant (Km), which is about 0.249 mM. The effect of the organophosphorus pesticide malathion was monitored by measuring the current oxidation in ATI solution. After incubation, it shows a drastic decrease in the electrochemical response in the presence of the pesticide at different concentrations (2–8 nM). Keywords Porous silicon, Enzyme immobilization, Enzyme activity, Pesticide, Electrochemical biosensor
Introduction During the two last decades, the use of pesticides by some developed countries in order to improve the production in agriculture has known a great boom. However, these chemical contaminants, through water, air or soil, pollute not only fruits, vegetables, fish, M. Ayat (&), K. Ayouz, C. Yaddadene, M. Berouaken, N. Gabouze Centre de Recherche en Technologie des Semi-conducteurs pour l’Energe´tique, Algiers, Algeria e-mail: [email protected], [email protected]
and meat, but also milk or eggs. These pesticides often have long half-lives and can remain for many years.1,2 The widely used pesticides are organophosphorus pesticides.3 Among the wide variety of pesticides based on existing organophosphates compounds, we can mention parathion, malathion, fenthion, diazinon, and dimpylate and chemical warfare agents, commonly known as nerve gases, such as sarin and tabun. Organophosphates pesticides are a class of insecticides, of which many are highly toxic.4 Organophosphtates are extremely potent inhibitors of the enzyme acetylcholinesterase (AChE) found in cholinergic neurons. Organophosphorus compounds have the property of being particularly strongly and stably fixed at the active site of this enzyme. Once fixed, the organophosphorus compound inhibits the AChE and causes the blocking of the nerve signal transference into the postsynaptic membrane.5,6 This can lead to paralysis of the central nervous system leading ultimately to death. Thereby, rapid determination of trace amounts of organophosphorous compounds is required. For this purpose, several methods and devices for detecting organophosphorus compounds have been developed. Among them, UV spectrophotometr
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