Acetylcholinesterase-catalyzed Silver Deposition for Ultrasensitive Electrochemical Biosensing of Organophosphorus Pesticide
Herein, an electrochemical biosensing platform with acetylcholinesterase (AChE)-catalyzed silver deposition was developed for ultrasensitive detection of organophosphorus pesticide (OP). The biosensing mechanism is based on the fact that AChE can catalyze the rapid hydrolysis of indoxyl acetate to form hydroxyindole, which in turn reduces silver ion to a deposition of metallic silver on the gold electrode. Upon sweeping positive voltages on gold electrode using linear sweep voltammetry (LSV), the deposited silver on gold electrode surface undergoes a rapid electrochemical oxidation reaction. Due to its lower oxidation potential under facile condition with a relatively sharp peak, a small amount of deposited silver generated from the AChE-catalysis could result in a significant change of LSV response. In the presence of OP, the AChE-catalyzed hydrolysis of indoxyl acetate is blocked, and then the silver deposition on gold electrode declines, leading to a remarkable decrease of LSV response and, thus, offering a large signal output for ultrasensitive detection of chlorpyrifos, a proof-of-concept OP in this work. The change of the LSV peak current intensity is linearly correlated with the logarithm value of chlorpyrifos concentration ranging from 10 pM to 10 nM with a low detection limit of 4.0 pM. To the best of our knowledge, this is the first example of a biosensing platform for ultrasensitive OP assay using AChE-controlled silver deposition to enhance the output of electronic signal.