QD-aptamer as a donor for a FRET-based chemosensor and evaluation of affinity between acetamiprid and its aptamer

Abstract

The sensitive and convenient detection of pesticides has become an important issue in food safety and environmental pollution. In this work, a unique aptamer biosensor for the detection of acetamiprid based on fluorescence resonance energy transfer (FRET) between complementary aptamer-modified CdTe quantum dots (QDs) and aptamer-modified Cy5.5 dye molecules was developed. Hybridization results in the transfer of excitation energy from the QDs to the dye. The Förster radius (R₀) and the distance between the donor and acceptor pair (r) were 4.815 nm and 5.134 nm, respectively, based on an analysis of the ratio of donor- to acceptor-dependent FRET efficiency. The K_d was 0.58 μmol L⁻¹ for the Cy5.5-aptamer with acetamiprid. In the presence of acetamiprid, the specific and strong interaction between the aptamer and target inhibited the conjugation of the donor and acceptor, thus leading to a decrease in energy transfer efficiency. A limit of detection (LOD) of 0.02 μM and a wide assay range from 0.01 μM to 10 μM for acetamiprid detection were achieved by fitting the dose-dependent energy transfer efficiency using a 4-parameter model. The proposed method was also successfully applied to measure acetamiprid in spiked water samples, demonstrating its reliability and repeatability.