Triple-mode sensing platform for acetylcholinesterase activity monitoring and anti-Alzheimer's drug screening based on a highly stable Cu (I) compound.

Acetylcholinesterase (AChE) and AChE inhibitors play critical roles in the early diagnosis and treatment of Alzheimer's disease (AD). Herein, a fluorescence/colorimetry/smartphone triple-mode sensing platform was constructed for both AChE activity monitoring and AChE inhibitor screening by exploring a Cu (I) compound, Cu3I (SR)2 (R = CH2CH2NH2), as a fluorescent probe. In comparison of most other fluorescent probes, Cu3I (SR)2 presented exceptional stability against pH, temperature, UV irradiation, redox agents, and metal ions, as well as good recyclability due to its unique chemical structure. We further found the fluorescence emission of Cu3I (SR)2 could be quenched by MnO2 nanosheet (NS) via inner filter effect, and restored by thiocholine (TCh) generated from the hydrolysis of acetylthiocholine iodide (ATCh) in the catalysis of AChE. On this basis, a fluorescence "turn-on" assay was developed for monitoring AChE activity with a detection limit of 0.03 U/L and a detection range of 0.25-50 U/L. This method demonstrates great potential for real-time detection of AChE activity in biological samples and screening of AChE inhibitors obtained from herbal extracts as anti-AD agents. Additionally, Cu3I (SR)2/MnO2 NS sensing system also exhibited a color change from brown to colorless as the increasing AChE activity, which allowed the colorimetric and smartphone detection of AChE activity.