Duong_2023_Mikrochim.Acta_190_122

A liquid crystal-based assay (LC) was developed to monitor paraoxon by incorporating a Cu(2+) -coated substrate and the inhibitory effect of paraoxon with acetylcholinesterase (AChE). We observed that thiocholine (TCh), a hydrolysate of AChE and acetylthiocholine (ATCh), interfered with the alignment of 5CB films through a reaction between Cu(2+) ions and the thiol moiety of TCh. The catalytic activity of AChE was inhibited in the presence of paraoxon due to the irreversible interaction between TCh and paraoxon; consequently, no TCh molecule was available to interact with Cu(2+) on the surface. This resulted in a homeotropic alignment of the liquid crystal. The proposed sensor platform sensitively quantified paraoxon with a detection limit of 2.20 +/- 0.11 (n = 3) nM within a range of 6 to 500 nM. The specificity and reliability of the assay were verified by measuring paraoxon in the presence of various suspected interfering substances and spiked samples. As a result, the sensor based on LC can potentially be used as a screening tool for accurate evaluation of paraoxon and other organophosphorus compounds.