Green fluorescent carbon quantum dots functionalized with polyethyleneimine, and their application to aptamer-based dete
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ORIGINAL PAPER
Green fluorescent carbon quantum dots functionalized with polyethyleneimine, and their application to aptamer-based determination of thrombin and ATP Ying Guo 1 & Juncai Zhang 1 & Weihong Zhang 1 & Daodao Hu 2 Received: 19 May 2019 / Accepted: 26 September 2019 # Springer-Verlag GmbH Austria, part of Springer Nature 2019
Abstract Brightly fluorescent carbon quantum dots coated with polyethylenimine (PEI-CDs) were prepared using malic acid and PEI as the precursors. The PEI-CDs have a high quantum yield (41%) and green emission (peaking at 502 nm under 430 nm excitation), both of which are not affected by high ionic strength. The PEI-CDs have a positive charge at physiological pH values and can electrostatically bind aptamers with their negative charge. This is shown for aptamers binding thrombin or ATP. Binding of aptamers results in quenching of fluorescence. If thrombin or ATP are introduced, the respective aptamer will bind them, and the complex is then released from the PEI-CDs. Fluorescence increases in proportion to the analyte concentration. Under optimized conditions, thrombin and ATP can be sensitively and selectively detected by fluorometry with lower detection limits of 1.2 and 13 nM, respectively. The assay was successfully applied to the determination of thrombin and of ATP in spiked serum samples. Keywords PEI-CDs . Apatmer sensor . Green luminescent . Fluorescence assay . Thrombin detection . ATP detection . Hydrothermal reaction . Malic acid . Polyethylenimine . Serum analysis
Introduction Carbon dots (CDs) have been widely investigated because of their many advantages including excellent optical properties, inexpensive synthetic routes, and low environmental impact as compared to other quantum dots and fluorescent dyes [1]. Many ways have been explored for the synthesis of CDs. However, most CDs fabricated by early chemical syntheses have a relatively low fluorescence quantum yields (QY), usually less than 10% in comparison to other fluorescent materials, which greatly impedes their practical application [2, 3]. In order to improve the fluorescence property of CDs, doped CDs were reported. To date, doping CDs with heteroatoms,
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00604-019-3874-y) contains supplementary material, which is available to authorized users. * Ying Guo [email protected] 1
College of Chemistry & Chemical Engineering, Xianyang Normal University, Xianyang 712000, China
2
School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710062, China
especially nitrogen and sulfur, are usually concerned. Doped CDs often hold high QY, but most of them show intense emissions at short blue wavelengths (λmax = 430-460 nm), and the long-wavelength emission is usually weak. These drawbacks severely hampered their further applications in the fields of biology, due to the blue autofluorescence of the biological matrix and photodamage of biological tissues caused by ultraviolet excitation light [4, 5]. So, t
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