A new sensing strategy based on thymine bases–Hg²⁺–methylene blue coordination on the electrospun PES–QDs platform for detection of Hg²⁺ in fruit juice samples

A novel label-free and highly sensitive electrochemical aptasensor for highly sensitive mercury ion detection has been successfully fabricated in fruit juice samples using of electrospun nanofibers polyethersulfone and quantum dots (NFs–QDs) at the surface of carbon paste electrode (CPE). In addition to the T bases used in the designed aptasensor which can be strong and specific binding to the Hg²⁺, the methylene blue (MB) also can interact specifically with the Hg²⁺ (T–Hg²⁺–MB), as well as interact with the guanine bases in the DNA aptamer as an receiver site for interaction. According to this, the proposed sensor has more receiver sites for interaction with the Hg²⁺. Here, the electrochemical signal of MB was employed for Hg²⁺ measurements which this signal was amplified by NFs–QDs nanocomposites. The Apt–MB binding event easily investigated by the peak current variations in Apt–MB1–Hg²⁺–MB2/NFs–QDs/CPE through cyclic voltammetry, differential pulse voltammetry (DPV) measurement. Also, this study was evaluated with electrochemical impedance spectroscopy. Under optimized conditions, the constructed aptasensor illustrated a wide linear range using the DPVs, from 0.1 to 150 nM and an excellent low detection limit of 0.02 nM. The quality of carefully choosing, an excellent stability and specificity sensitivity of the designed aptasensor were accredited by spiked juice samples as real sample. Moreover, the aptasensor exhibits the good reproducibility as well as has high selectivity to other cations. The recoveries of the Hg²⁺ assay of the fruit juice samples were obtained satisfactorily which can use for measurement of Hg²⁺ in the laboratory.