Homogenous FRET-based fluorescent immunoassay for deoxynivalenol detection by controlling the distance of donor-acceptor couple.

Semiconductor quantum dots (QDs) are one of the most popular luminescent labels that are widely used in food and medical analysis. Their unique optical properties establish QDs as excellent tools for highly sensitive biosensors based on Förster resonance energy transfer (FRET). To provide a convenient analytical system with long-term optical stability, a FRET pair consisting of QDs as energy donor and gold nanoparticles (GNs) as energy acceptor was developed. Careful selection of donor and acceptor properties allowed to achieve a large Förster distance of 12.9 nm and to use full-size specific antibody. As the immunoreagents pair, mycotoxins were bound to proteins and then to GNs, while QDs were conjugated with specific antibodies. FRET was observed as a result of the immunocomplex formation. Contributions of FRET and inner filter effect on the quenching were evaluated separately. The quenching effect in the donor-acceptor pair was compared for proteins with different sizes. The developed homogeneous FRET-based immunoassay for the detection of deoxynivalenol (DON) is an example of a fast method for high-throughput control of mycotoxins. The quenching effect of FRET was observed with a limit of detection of 28 μg kg of DON in spiked wheat samples.