Disposable electrochemical biosensor based on acetylcholinesterase for inhibition assays using a natural substance and plant extracts†

In general, insects are considered pests in agricultural areas, and their control is essential for high productivity of the cultivated areas. Control of these insects can be achieved by the inhibition of enzymes present in the insect's body. The enzyme acetylcholinesterase (AChE) is present in the neuromuscular junctions of vertebrates and invertebrates, and it is an important target for pest control. Herein, we present the development of a disposable electrochemical biosensor based on AChE (Bio-AChE) to rapidly evaluate the presence of new potential inhibitors in crude extracts of plants. Bio-AChE was constructed by modifying the disposable screen-printed carbon electrode (SPCE) with glutathione-decorated gold nanoparticles on which AChE was covalently immobilized. Electrochemical studies confirm the effective immobilization of the enzyme, and the Bio-AChE was applied to assess the inhibitory activity of azadirachtin, obtained from Azadirachta indica, which is a well-known AChE inhibitor. The proposed biosensor showed excellent results, demonstrating the inhibition activity of azadirachtin against AChE. The crude extracts of Picramnia riedelli, P. ciliata, and Toona ciliata were evaluated with the Bio-AChE, and all showed inhibition percentage values of around 50%. The extracts were evaluated by ¹H NMR spectra, which identified classes of natural compounds that could be responsible for the inhibition activity. The proposed disposable Bio-AChE was shown to be a reliable method for simple and rapid screening of new inhibitors in plant extracts, opening an avenue for the screening of new natural products with potential for pest control.