posted on 2022-01-11, 02:03authored byHaiyin Li, Qian Li, Suixin Zhao, Xuemei Wang, Feng Li
Given the significance of food safety,
it is highly urgent to develop
a sensitive yet reliable sensor for the practical analysis of algal
toxins. As most of the developed sensors are disturbed by interfering
substances and the target toxin is detected in a single-signal manner
based on the immunoassay technology. Herein, we developed an aptamer-based
dual-signal ratiometric electrochemical sensor for the sensitive and
accurate analysis of microcystin-LR (MC-LR), using it as a proof-of-concept
analyte. Methylene blue-tagged ssDNA (MB-ssDNA) was immobilized at
the gold electrode surface accompanied with the absence of ferrocene-tagged
ssDNA (Fc-ssDNA), resulting in a high differential pulse voltammetry
(DPV) current of MB and a low DPV current of Fc. The recognition of
MB-ssDNA by MC-LR stimulated the formation of MC-LR@MB-ssDNA, which
induced the removal of MB-ssDNA from the electrode and the exposure
of SH-ssDNA, enabling Fc-ssDNA to be captured at the electrode surface
via nucleic acid hybridization. In comparison with MC-LR deficiency,
the DPV signal of MB dropped along with an improved DPV signal of
Fc, contributing to the ratiometric detection of MC-LR, with the limit
of detection down to 0.0015 nM. Furthermore, this ratiometric electrochemical
sensor was successfully explored to assess the bioaccumulated amount
of MC-LR in the liver and meat of fish. The aptamer-based ratiometric
strategy to develop an electrochemical MC-LR assay will offer a promising
avenue to develop high-performance sensors, and the sensor will find
more useful application in MC-LR-related aquatic product safety studies.