Turn-on fluorometric NADPH assay using orange emitting graphene oxide quantum dots

• Published in: Mikrochimica acta (1966) 2017-12, Vol.184 (12), p.4571-4578
• Main Authors: Na, Weidan, Hu, Tianyu, Su, Xingguang
• Format: Article
• Language: English
• Subjects: Analytical Chemistry; Benzene; Catalysis; Catalytic activity; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Dopamine; Enzymes; Fluorescence; Graphene; Graphite; Microengineering; Nanochemistry; Nanotechnology; Original Paper; Oxidation; Peroxidase; Quantum dots; Quenching (cooling)
• ISSN: 0026-3672; 1436-5073
• DOI: 10.1007/s00604-017-2490-y

The authors describe a method for synthesizing graphene oxide quantum dots (GOQDs) possessing orange fluorescence with emission wavelength that can be tuned over the range from 537 to 593 nm by variation of the excitation wavelength. The GOQD display peroxidase-mimicking catalytic activity. Specifically, they catalyze the oxidation of dopamine to produce 4-(2-aminoethyl)benzene-1,2-quinone (AQ) which is colored and can quench the fluorescence of GOQDs. However, quenching is reversed by addition of NADP + , but not by its reduced form (NADPH). Based on these findings, an assay was worked out to monitor enzymatic reactions involving NADP + . The method allows NADPH to be detected in the 2–175 μM concentration range, with a 0.6 μM detection limit. Graphical abstract Schematic of a top-down method for synthesizing fluorescent graphene oxide quantum dots (GOQD) by chemical degrading, exfoliation and self-assembly of graphene oxide (GO). The GOQDs display peroxidase-like activity and can oxidize dopamine to form a colored quinone that quenches the fluorescence of the GOQDs. The quenching efficiency is reduced, however, in the presence of NADP + .