A fluorometric assay for acetylcholinesterase activity and inhibitor detection based on DNA-templated copper/silver nanoclusters

A novel label-free, rapid, cost-effective, and highly sensitive fluorometric sensor has been constructed for the detection of acetylcholinesterase (AChE) activity and its inhibitor based on the fluorescence quenching of DNA-templated copper/silver nanoclusters (DNA-Cu/AgNCs). In this assay, AChE catalyzes the hydrolysis of acetylthiocholine (ATCh) to form thiocholine which induces fluorescence quenching of DNA-Cu/AgNCs. The AChE activity could be detected as low as 0.05 mU/mL and with a linear range from 0.05 to 2.0 mU/mL. This assay offers a very convenient “mix and detect” approach for AChE activity. On the other hand, tacrine and organophosphorus pesticides (OPPs) were employed to inhibit the hydrolysis of ATCh, which could eliminate the fluorescence quenching of DNA-Cu/AgNCs. The IC50 of tacrine and methamidophos were estimated to be 16.9 nM and 0.075 mg/L, respectively. This method was also used to detect spiked OPPs in agricultural products successfully. The present work may expand the use of DNA-Cu/AgNCs to the field of enzyme sensors.