Photoluminescent C-dots@RGO Probe for Sensitive and Selective Detection of Acetylcholine

摘要

We have developed a sensitive and selective photoluminescence (PL) quenching assay for the detection of acetylcholine (ACh) that uses reduced graphene oxide decorated with carbon dots (C-dots@RGO). The highly stable C-dots@RGO synthesized from catechin and graphene oxide through a hydrothermal reaction displays excitation-wavelength dependence of PL. Acetylcholinesterase (AChE) converts ACh to choline, which in turn is oxidized by choline oxidase (ChOx) to produce betaine and H_2O_2 that generates the reactive oxygen species (ROS). The as-produced ROS induces PL quenching of the C-dots@RGO through an etching process. With respect to sensitivity, the optimal reaction/sensing temperature and pH are 37℃ and 9.0, respectively, using C-dots@RGO (0.4 mg·mL~(-1)) and AChE and ChOx at the activities of 0.5 and 0.1 unit·mL~(-1), respectively. The PL intensity (excitation/emission wavelengths 365/440 nm) of the C-dots@RGO is inversely proportional to the concentration of ACh over a range of 0.05-10 nM (r = 0.997), with a limit of detection (signal-to-noise ratio 3) of 30 pM. We have validated this assay by determination of concentrations of ACh in plasma and blood samples, with results of 2.6 ± 0.8 nM (n = 5) and 6.8 ± 0.4 nM (n = 5), respectively. Our study opens an avenue for the detection of various analytes by use of C-dots@RGO in conjunction with different enzymes, substrates, and/or inhibitors.