A test strip for ochratoxin A based on the use of aptamer-modified fluorescence upconversion nanoparticles.

An aptamer-based test strip is described for visual and instrumental determination of the mycotoxin ochratoxin A (OTA). It is based on the use of NaYF:Yb,Er upconversion nanoparticles (UCNPs) as a label for the aptamer and on the competition between OTA and its complementary sequence for an OTA-specific aptamer. To improve the analytical performance, the optical properties of the UCNPs, the fluidity of the UCNP-aptamer conjugate, and the migration rate on the nitrocellulose membranes were investigated. Under the optimal experimental conditions and by using a 980-nm laser, the relative fluorescence intensity (test line value/control line value) is proportional to the logarithm of the OTA concentration over a range from 5 to 100 ng·mL (R = 0.9955). The limit of the detection is 1.86 ng·mL. This aptamer based flow assay can be performed within 15 min and has no serious cross-sensitivity to potentially interfering species. It was successfully applied to the determination of OTA in spiked wheat and beer samples. Graphical abstract An aptamer-based upconversion fluorescent strip based on the use of NaYF:Yb,Er nanoparticles was developed for sensitive detection of Ochratoxin A. The limit of the detection was determined as 1.86 ng·mL. The assay can be performed within 15 min, indicating its great potential in point-of-care testing.