Simple and sensitive fluorescence assay for acetylcholinesterase activity detection and inhibitor screening based on glutathione-capped gold nanoclusters

A direct fluorescence turn-on method for simple and sensitive acetylcholinesterase (AChE) activity assay and AChE inhibitor screening has been developed by first using low-fluorescence glutathione-capped gold nanoclusters (GSH-AuNCs). The thiocholine produced by AChE-catalyzed hydrolysis of S-acetylthiocholine iodide could effectively enhance the fluorescence of GSH-AuNCs via AuS bond formation. In the presence of inhibitors, AChE activity was suppressed and thus fluorescence enhancement decreased. Therefore, AChE activity assay and inhibitor screening could be performed by measuring the fluorescence intensity of the system. The linear range of the AChE activity assay was 0-30 mU mL−1 with a limit of detection of 0.03 mU mL−1 (S/N = 3). The IC50 values of two inhibitors (tacrine and neostigmine bromide) were 42.92 nM and 37.04 nM, respectively. The developed protocol provides a simple and sensitive platform for assaying AChE activity and screening its inhibitors.