Surface-enhanced Raman scattering detection of cholinesterase inhibitors

A new sensitive surface-enhanced Raman scattering (SERS) assay for detection of cholinesterase inhibitors such as organophosphorous pesticides using silver colloidal nanoparticles was developed and optimized. Acetylcholinesterase (AChE) mediated the hydrolysis of acetylthiocholine to produce thiocholine, which interacted with the silver nanoparticles to give a specific SERS spectrum. Variation in enzyme activity due to inhibition was measured from changes in intensity of a characteristic peak (772 cm⁻¹) of the SERS spectrum that was directly correlated with the concentration of produced thiocholine. The method was demonstrated for the detection of paraoxon as reference AChE inhibitor. Limit of detection of paraoxon for 5 min incubation at 25 °C was 1.8 × 10⁻⁸ M. This assay can be utilized for the detection of trace amounts of any AChE inhibitor.