Green fluorescent carbon quantum dots functionalized with polyethyleneimine, and their application to aptamer-based determination of thrombin and ATP.

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 502nm under 430nm 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 13nM, respectively. The assay was successfully applied to the determination of thrombin and of ATP in spiked serum samples. Graphical abstract Green fluorescent carbon quantum dots werefunctionalized with polyethyleneimine. They were applied to aptamer-based determination of thrombin and ATP. ThePEI-functionalized carbon quantum dots (PEI-CDs) have bright green fluorescence are weresynthesized by one-step hydrothermal treatment of malic acid and PEI. Employing the PEI-CDs, a fluorometric aptamer-based assay was developed for the determination of thrombin and ATP.