A lateral flow immunoassay (LFIA) was developed for the determination of fumonisin mycotoxins. The fluorescence of CdSe/ZnS quantum dots (QDs), observed at excitation/emission wavelengths of 365/525 nm, is suppressed by the addition of silver nanoparticles (SNPs) or gold nanoparticles (GNPs) because SNPs overlap the excitation bands of the QDs, and GNPs overlap the emission bands. The fluorescence of the QDs is recovered upon addition of fumonisins, allowing for the sensitive detection in "positive mode" of the target mycotoxin by monitoring the changes of the QDs fluorescence intensity. The SNPs are found to be the most effective quenchers, while the use of GNPs allows for an efficient recovery of fluorescence and can be employed in the LFIA. The method was successfully applied to the fluorometric determination of fumonisins in spiked maize flour samples. The visual detection limit is at the ng·mL-1 level. This is four times lower compared to the colorimetric LFIA based on the use of the conventional gold NPs. Graphical abstract Schematic of the fluorescence quenching lateral flow immunoassay that uses fluorescent quantum dots (QD) and metal nanoparticles (NP) as the quencher: the binding of NP-labelled antibody to the antigen (purple triangle) modulates QD luminescence at the Test line, allowing for 'positive mode' detection of fumonisins. The NP accumulation at Control line assures validity of the test.
Keywords: FRET; Gold nanoparticles; Immunochromatography; Inner filter effect; Silver nanoparticles; Strip test.