Acetylcholine and acetylcholinesterase inhibitors detection using gold nanoparticles coupled with dynamic light scattering

A novel sensitive method for the detection of acetylcholinesterase inhibitors is presented by using unmodified gold nanoparticle coupled with dynamic light scattering (DLS). The hydrolysis of acetylcholine (ACh) mediated by acetylcholinesterase (ACHE) yields the choline, which influences the gold nanoparticles (AuNPs) aggregation, and triggered the increase of their average diameter. The inhibition of the enzyme by pesticides (paraoxon) produces lower yields of choline, leading to less or no AuNP aggregate formation. This study is the first to describe a homogeneous AuNPs-based DLS nanosensor for ultrasensitive detection of paraoxon by measuring ACHE activity. The average diameter and count rate of unmodified AuNPs decreased with the increasing concentration of paraoxon, with a detection limit of 75.5 pmol.L−1. These results suggest that this DLS assay based on unmodified AuNPs could be used in the future for measuring ACHE activity and for non-selective detection of trace amounts of all ACHE inhibitors.