Application of a thiol-specific electrocatalytic electrode for real-time amperometric monitoring of enzymatic hydrolysis

Abstract

A pyrroloquinoline quinone (PQQ) modified electrode was investigated for the electrocatalytic oxidation and detection of thiocholine (SCh) at low concentrations. PQQ entrapped in a polypyrrole matrix on a glassy carbon electrode effectively mediated the amperometric detection of thiocholine at +500 mV vs.Ag/AgCl. The detection limit for thiocholine was determined to be 0.5 µM with a linear range from 0.5 to 50 µM. The PQQ electrode was then utilized as a thiol-specific sensor for the real-time monitoring of thiocholine generated from the hydrolysis of acetylthiocholine (ASCh) by acetylcholinesterase (AChE). The rapid and sensitive detection of thiocholine allowed monitoring the inhibition of acetylcholinesterase in the presence of the pesticide, carbofuran. These measurements demonstrated the versatility of this sensor for the detection of thiols and potentially for the development of assays to evaluate the enzymatic activity of acetylcholinesterase.