Analytical Sciences

Abstract − Analytical Sciences, 37(6), 833 (2021).

Fluorometric Aptasensor for Determination of Escherichia coli O157:H7 by FRET Effect between Aminated Carbon Quantum Dots and Graphene Oxide
Tao PAN, Xueling SHAN, Ding JIANG, Lu QI, Wenchang WANG, and Zhidong CHEN
Jiangsu Key Laboratory of Advanced Catalytic Materials and Technology, School of Petrochemical Engineering, Changzhou University, Changzhou 213164, China
A fluorometric aptasensor based on Escherichia coli O157:H7 (E. coli O157:H7) aptamer labeled aminated carbon quantum dots (NH2-CQDs) and graphene oxide (GO) for the determination of E. coli O157:H7 was developed. In this research, carboxyl group (–COOH) terminated E. coli O157:H7 aptamer was steadily labeled to NH2-CQDs by amidation reaction, and played the role of energy donor and was responsible for chemical recognition. Correspondingly, GO served as an energy acceptor. The introduction of NH2-CQDs not only made the aptamer bond stably through covalent bond, but also significantly enhanced the fluorescence intensity compared with general CQDs. The NH2-CQDs-aptamer is adsorbed on the surface of GO through π-π stacking and hydrophobic interaction. The fluorescence of NH2-CQDs-aptamer was quenched via fluorescence resonance energy transfer (FRET) between NH2-CQDs and GO. After adding E. coli O157:H7, the specific binding affinity between NH2-CQDs-aptamer and E. coli O157:H7 lead to desorption of NH2-CQDs-aptamer from GO, and recovery of the fluorescence intensity of NH2-CQDs-aptamer. Under the optimal conditions, the increased fluorescence intensity showed a good linear relationship to concentrations of E. coli O157:H7 in the range 102 – 107 cells/mL, with a detection limit of 89 cells/mL. Furthermore, the developed method was successfully applied to the determination of E. coli O157:H7 in commercial milk samples.