Zeinab Saberi , Behzad Rezaei , Mohammad Seyedhamzeh, and Ali Ashghar Ensafi

IEEE SENSORS JOURNAL, VOL. 21, NO. 15, AUGUST 1, 2021, https://ieeexplore.ieee.org/abstract/document/9424594/

Abstract—The development of a high-performance biosensor for potassium ion (K+) analysis is desirable for clinical diagnostics. In the present study, a sensitive and selective biosensor has been presented for the K+ determination using G-rich ssDNA as a recognition tool. A fluorimetric assay based on intermolecular G-quadruplex was introduced using metal sulfide (CoS and CuS) nanosheets as quenchers and carbon dots (CDs) as fluorescence probes conjugated to a G-rich ssDNA (CDs-aptamer). This biosensor was based on the adsorption CDs-aptamer on the surface of nanosheets via van der Waals forces, which resulted in reducing the fluorescence signal. By addition K+ to the system, CDs-aptamer folded into G-quadruplex structure that causes to detach from nanosheets. As a result, the fluorescence signal was increased proportionally to K+ concentration. The present biosensor can detect K+ sensitively and selectively with 12.3 nmol L−1 as a low detection limit. A linear range was achieved from 50.0 nmol L−1 to 1000 nmol L−1. Furthermore, this biosensor has been successfully applied for the detection of K+ in the real samples and was validated by comparing the data of analyzing real samples to results obtained by the ion-selective electrode (ISE).

Index Terms—G-rich ssDNA, carbon dots, potassium ions, G-quadruplex, CoS, and CuS nanosheets.