Abstract
A renewable, disposable, low cost, and sensitive sensor for the detection of organophosphorus pesticides was constructed by immobilizing the acetylcholinesterase enzyme (AChE), via glutaraldehyde, on magnetic iron nanoparticles (Fe3O4) previously synthesized and functionalized with chitosan (CS). The sensor was denoted AChE/CS/Fe3O4. The magnetic nanoparticles were characterized by Fourier transform infrared spectroscopy and transmission electron microscopy. Acetylthiocholine (ATCh) was incubated with AChE/CS/Fe3O4 and attached to a screen-printed electrode using a magnet. The oxidation of thiocholine (from ATCh hydrolysis) was monitored at an applied potential of +0.5 V vs. Ag/AgCl(KClsat) in 0.1 mol L−1 phosphate buffer solution (pH 7.5) as the supporting electrolyte. A mixture of the pesticide malathion and ATCh was investigated using the same procedure, and the results were compared and expressed as inhibition percentages. For determination of malathion, the proposed sensor presented a linear response in the range from 0.5 to 20 nmol L−1 (R = 0.9942). The limits of detection (LOD) and quantification (LOQ) were 0.3 and 0.8 nmol L−1, respectively. Real samples were also investigated, with recovery values of 96.0% and 108.3% obtained for tomato and pond water samples, respectively. The proposed sensor is a feasible option for malathion detection, offering a linear response, good sensitivity, and a low detection limit.
Highlights
Pesticides play an important role in increasing agricultural productivity [1,2]
The synthesized magnetic nanoparticles were characterized by Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM)
Magnetic Fe3 O4 nanoparticles coated with the natural polymer chitosan were successfully prepared and used for the immobilization of AChE, employing glutaraldehyde as a crosslinking reagent
Summary
Pesticides play an important role in increasing agricultural productivity [1,2]. the excessive use of carbamates and organophosphates results in large amounts of residues of pesticides and their metabolites, which are harmful to the environment and human health [3]. The organophosphates (OPs) are among the most widely used classes of pesticides [4], and their toxic effects in vertebrates are well documented [5] Their toxicity is due to inhibition of the activity of acetylcholinesterase (AChE), an enzyme that plays a role in controlling the transmission of nerve impulses to muscle and neuromuscular cells in living organisms [6]. MNPs have been used for removal and quantification of rhodamine [16], as a glucose sensor [17], for the diagnosis of malaria [18], and for enzyme immunoassay atrazine sensor [19], concerning both the inhibition of AChE for pesticide detection and the use of iron magnetic particles for the AChE immobilization, only two articles were found in the literature [12,20]
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