Sensor ultrasensível para detecção de malation baseado em acetilcolinesterase imobilizada em nanopartícula magnética funcionalizada com quitosana

The pesticides irreversibly inhibit acetylcholinesterase (AChE), key enzyme in the transmission of nerve impulses [1,2]. In this sense, the present work describes the development of an amperometric sensor for the detection of pesticide malathion. The iron magnetic nanoparticles were synthesized/characterized and functionalized with chitosan (CS) (Fe3O4/CS); the AChE was immobilized via glutaraldehyde on magnetic nanoparticle. After that, 30 μL of the suspension containing the functionalized magnetic nanoparticles were pre-concentrated on the screen-printed carbon electrode from Dropsens with the neodymium magnet assistence. The experimental conditions were optimized by using cyclic voltammetry and chronoamperometry techniques in order to found the best sensor response. Enzyme activity was monitored by inhibition of acetylthiocholine (ATCh) hydrolysis. The thiocholine oxidation (thiocholine from ATCh hydrolysis) at applied potential of 0.5 V vs Ag / AgCl was measured in 0.1 mol L-1 phosphate buffer solution at pH 7.5 as the electrolyte support. The effect of acetylthiocholine concentration on the biosensor response was also evaluated resulting in a best sensor response for 10 mmol L-1 ATCh (100 % of activity) and the current intensity was intitled I0. After optimization of analytical parameters, the pesticide was incubated with AChE/CS/Fe3O4 and after 6 minutes a new current intensity measurement was performed (It); enzyme inhibition (% I = (I0-It / I0) x 100) was calculated. The proposed sensor for Malathion pesticide presented linear response range from 0.01 up to 20 nmol L-1, with the following regression equation: ΔI (μA) = [71.8 (± 0.2) + 6.2 (± 0.2)] / [Malathion] / nmol L-1, R = 0.9914 and n = 7. From these results, limit of detection (LOD) and limit of quantification (LOQ) were obtained through mathematical calculations as 0.1 and 0.3 nmol L-1, respectively. The proposed sensor is a feasible alternative for Malathion detection with high linear response range, sensitivity and low detection limit.