Fluorescence and scattering based dual-optical signals ratiometric sensing and logic gate device for acetylcholinesterase activity assay

Abstract Acetylcholinesterase (AChE) plays a crucial role in regulating the levels of the neurotransmitters in organisms. In this study, a dual-optical signals ratiometric sensing system based on fluorescence and scattered light was constructed by using silicon quantum dots (SiQDs) and MnO2 nanosheets for AChE activity assay. The two independent signals of fluorescence and scattering can be collected at the same excitation wavelength, which not only improves the accuracy of detection but also greatly simplifies the experimental operation. In this study, the SiQDs with excellent optical properties were successfully prepared by one-step hydrothermal method and the optimal emission peak was located at 445 nm. The fluorescence signal of SiQDs could be suppressed via MnO2 nanosheets on account of the inner filter effect (IFE). In addition, MnO2 nanosheets could provide a size-regulated second-order scattering (SOS) signal at 725 nm. Therefore, MnO2 nanosheets could play the dual roles of fluorescence signal quencher and SOS signal donor. AChE could act on the substrate acetylthiocholine (ATCh) and make it to engender thiocholine (TCh), which will triggered the reduction of MnO2 nanosheets, resulting the decompostion of MnO2 nanosheets. At the same time, the fluorescence of SiQDs recovery and the SOS signal decline. Thus, the ratiometric sensing analysis of AChE activity was achieved according to the opposite responses of fluorescence and scattering dual signals. Under the optimal conditions, an excellent linearity for AChE from 0.5 to 80.0 U/L and high sensitivity with a detection limit of 0.16 U/L were achieved. The practical application of the established method was assessed and verified by analyzing of AChE activity in human serum, and obtained satisfactory results. The proposed dual-optical signals ratiometric analytical strategy exhibits the merits of simple operation, high sensitivity and excellent selectivity, indicating that it has great application potential in diagnosis the AChE-related diseases. Furthermore, an innovative logic gate device was designed based on dual-optical signals, which has great value for the development of artificial intelligence analysis equipment to monitor AChE activity.