Field-free electrochemical sensor: A novel inverted Y-type DNA conformation possessing specific self-transform capability for ultrasensitive determination of tetracycline

Abstract

Herein, a novel filed-free electrochemical sensor based on inverted Y-type DNA conformation was developed for the ultrasensitive determination of tetracycline (TC). In this sensor, a ferrocene was immobilized on a DNA strand near the interface and showing a signal as reference. Meanwhile, a methylene blue (MB) was modified on a DNA vertical away from the interface, presenting a little signal. When the target TC attracted the aptamer, the DNA modifying MB was released, and then exchanged another DNA near the interface via toe-hold strand displacement effect. This caused an obvious enhancement of the MB signal, and achieved a sensitive response to the TC amount. In comparison to other DNA sensors based on field-confined assembling mode, this sensor exploited the transform of self-structure to make signal response, which avoids the steric hinerance effect and achieving field-free conversion. Meanwhile, the immobile ferrocene provided a reference proportion, reducing the influence of nonspecific signal on measurement accuracy. The followed assays demonstrated when the base-pairs on the straight side were 1.5-fold to that on the hypotenuse, the strand transferring efficiency and signal response were optimal. It exhibited a linearity of 1.0 × 10-1–1.0 × 103 nM for TC with a detection limit of 28.4 pM. In practical assay, the measured result was matched to that of the contrast method. Meanwhile, the recovery rates ranged from 98.0% to 103.0% with the RSD of 1.4%∼2.5%, respectively. Indicating an expectant application prospect of the proposed sensor in antibiotic monitoring.