A new optical fiber biosensor for acetylcholine detection based on pH sensitive fluorescent carbon quantum dots

Acetylcholine (Ach) is an important neurotransmitter and plays a vital role in the diagnosis and treatment of many neurological diseases. A new acetylcholine optical fiber biosensor is reported based on the nitrogen doped fluorescent carbon quantum dots/ acetylcholinesterase (N-CQDs/AchE) compound, where AchE was immobilized on the surface of N-CQDs by the cross-linking method. N-CQDs were synthesized by the hydrothermal method as fluorescent probe and can be responsible for pH value. The optical properties, morphology, particle size distribution and surface groups of N-CQDs were characterized by UV-Vis spectrophotometer, Fluorescence spectrometer, High-resolution transmission electron microscope (TEM) and Fourier transform infrared spectrometer (FTIR), respectively. The relationship between acetylcholine chloride solution and fluorescence intensity of N-CQDs/AchE complex was detected in detailed. Good linear relationship between fluorescence intensity and the concentration of acetylcholine from 20–200 µM and 1–100 nM with the lower detection limits of 16.28 µM and 0.29 nM, respectively. Compared with other sensors, this new optic fiber sensor immobilized (N-CQDs/AchE) complex is more simple and operable.