Enhanced graphene quantum dot fluorescence nanosensor for highly sensitive acetylcholinesterase assay and inhibitor screening

A highly sensitive nanosensor based on the enhanced fluorescence of graphene quantum dots (GQDs) by 3-(ethyliminomethyleneamino)-N,N-dimethyl-propan-1-amine/N-hydroxysuccinimide was constructed to determine acetylcholinesterase (AChE) activity and to screen for its inhibitors. The approach relied on the fact that the enhanced fluorescence of GQDs could be effectively quenched by Hg2+, and that thiol compounds released by acetylthiocholine iodide (ATCh) under AChE catalytic hydrolysis could interact with Hg2+ through the formation of Hg-S bonds, resulting in the fluorescence recovery of GQDs. The fluorescence recovery ratio of GQDs was proportional to the dose of AChE, and an analytical method for detecting AChE was constructed with a limit of detection of 2.3 x 10(-6) U. A model for AChE inhibition was further established and two traditional AChE inhibitors were employed to verify the feasibility of the system. Because of the enhanced fluorescence and lower amount of GQDs, lower IC50 values of 63.76 and 14.07 nM were obtained for paraoxon and tacrine, respectively. The developed protocol provides a new and promising platform for assaying AChE activity and screening its inhibitors with low cost and high sensitivity. (C) 2015 Elsevier B.V. All rights reserved.