Sensitivity Dependence on the Crystal Forms of a Fluorescence Quencher for Silicon Quantum Dots and Its Use in Acetylcholinesterase Assay

Acetylcholinesterase (AChE) plays crucial roles in the nervous system, and thus the reliable assay of its activity is of great significance for the diagnosis of nervous diseases. In this work, we report a fluorescent sensing platform with silicon quantum dots (Si-QDs) as a fluorescence oscillator and nano iron oxyhydroxide (alpha-, beta-, and gamma-FeOOH) as a quencher for the assay of AChE. FeOOH with alpha-, beta-, and gamma-crystal forms quenches the fluorescence of Si-QDs at lambda(ex)/lambda(em) = 350/438 nm, which is retrieved in the presence of AChE and its substrate acetylthiocholine (ATCh) to provide an off-on strategy with a high signal/noise ratio. It is interesting that the sensitivity of AChE sensing is closely related to the crystal forms of FeOOH, with the highest sensitivity by adopting alpha-FeOOH as the quencher. A linear calibration is achieved within 0.02-1.4 U/L along with a limit of detection of 0.016 U/L. The sensing strategy was demonstrated by the AChE assay in human blood, plasma, and hemocytes.

Automated summary

This study presents a fluorescent sensing platform using silicon quantum dots and nano iron oxyhydroxide for the detection of AChE activity. The sensing method achieved a high signal/noise ratio and sensitivity, with linear calibration and low detection limit in human blood samples.