A ratiometric fluorescence probe based on graphene quantum dots and o -phenylenediamine for highly sensitive detection o
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ORIGINAL PAPER
A ratiometric fluorescence probe based on graphene quantum dots and o-phenylenediamine for highly sensitive detection of acetylcholinesterase activity Mingshu Ye 1 & Bixia Lin 1 & Ying Yu 1
&
He Li 1 & Yumin Wang 1 & Li Zhang 1 & Yujuan Cao 1 & Manli Guo 1
Received: 14 April 2020 / Accepted: 19 August 2020 # Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract By using graphene quantum dots (GQDs) and o-phenylenediamine (OPD), a ratiometric fluorescence probe was designed for the highly sensitive and selective detection of AChE. GQDs with strong fluorescence were synthesized by the one-step hydrothermal method. The optimal emission wavelength of GQDs was 450 nm at the excitation wavelength of 375 nm. MnO2 nanosheets with a wide absorption band of 300–600 nm were prepared at room temperature. Because of the extensive overlap between the absorption spectrum of MnO2 nanosheets and the excitation and emission spectra of GQDs, the fluorescence of GQDs at 450 nm was efficiently quenched by the inner-filter effect. Meanwhile, due to the peroxidase-like activity of MnO2 nanosheets, OPD was catalytically oxidized to 2,3-diaminophenazine (oxOPD), a yellow fluorescent substance with a new emission peak at 572 nm. When AChE was present, the substrate acetylthiocholine (ATCh) was hydrolyzed to thiocholine (TCh) that is capable of decomposing MnO2 nanosheets. Therefore, the quench of GQDs and the oxidation of OPD by MnO2 nanosheets were suppressed, resulting in the fluorescence recovery of GQDs at 450 nm, while the fluorescence decrease of oxOPD at 572 nm. Utilizing the fluorescence intensity ratio F450/F572 as the signal readout, the ratiometric fluorescence method was established to detect AChE activity. The ratio F450/F572 against the AChE concentration demonstrated two linear relationships in the range 0.1–2.0 and 2.0–4.5 mU mL−1 with a detection limit of 0.09 mU mL−1. The method was applied to the detection of positive human serum samples and the analysis of the inhibitor neostigmine. Due to the advantages of high sensitivity, favorable selectivity, and strong anti-interference, the method possesses an application prospect in clinical diagnosis of AChE and the screening of inhibitors. Keywords Acetylcholinesterase . Graphene quantum dots . MnO2 nanosheets . o-Phenylenediamine . Peroxidase-like enzymes . Ratiometric fluorescence detection
Introduction
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00604-020-04522-1) contains supplementary material, which is available to authorized users. * Bixia Lin [email protected] * Ying Yu [email protected] 1
School of Chemistry, Guangzhou Key Laboratory of Analytical Chemistry for Biomedicine, South China Normal University, Guangzhou 510006, China
Acetylcholinesterase (AChE, E.C. 3.1.1.7) is a critical hydrolytic enzyme that can decrease the level of acetylcholine through catalytic hydrolysis. Excessively low level of acetylcholine is closely related to diseases such as Parkinson’s disease, Alzheime
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