A Label-Free Fluorescent Sensor Based on Structure-Switching Oligonucleotides for the Detection of Ag+, Biothiols and Acetylcholinesterase Activity

A label-free, highly sensitive and specific fluorescent sensor was developed for the detection of Ag+, biothiolsand acetylcholinesterase (AChE) activity and for the screening of AChE inhibitors. The sensing approach was based on the conformational switch of human telomeric G-rich sequence. The present assay was capable of detecting Ag+ in the range of 0 to 6.0 mu M, with a detection limit of 34 nM. In addition, the proposed method was developed as a turn-on cysteine-sensing system, which presented a good response to cysteine in the range of 0 to 4.5 mu M, and the detection limit was 25 nM. The cysteine-sensing system could be used to detect the activity of AChE as low as 0.05 U/L in the range of 0.05 to 1.3 U/L. The proposed sensor was also promising in screening of AChE inhibitors. Furthermore, this method has been applied successfully to the sensing of Ag+ in tap water and lake water with satisfactory recovery.