Portable optical aptasensor for rapid detection of mycotoxin with a reversible ligand-grafted biosensing surface

As food safety is gaining prominence as a global issue, the demand for developing rapid, simple, on-site, accurate and low-cost biosensor technologies will continue to grow. This study demonstrates an evanescent wave optical aptasensor with a reversible ligand-grafted biosensing surface for rapid, sensitive and highly selective detection of ochratoxin A (OTA) in food. In this system, the OTA molecules were covalently immobilized onto the surface of an optical fiber using glutaraldehyde and ethylenediamine as space linkers. An integrated evanescent wave all-fiber (EWA) biosensing platform was developed for investigating the binding kinetics between the tethered ligand and free OTA-aptamer, the performance of the aptamer-based bioassay and the reversibility of biosensing surface. The affinity constant (K-a) of aptamer with tethered OTA was measured to be 2.2 x 10(8) M-1 based on the EWA biosensing platform. With a competitive detection mode, the quantification of OTA over concentration ranges from 0.73 mu g L-1 to 12.50 mu g L-1 with a detection limit of 0.39 mu g L-1. The performance of the aptasensor with other interfering mycotoxins and spiked real wheat samples shows high specificity and selectivity, good recovery, precision, and accuracy, indicating that it can be applied for on-site, inexpensive and easy-to-use monitoring of OTA in real samples. Moreover, since the organic ligands are grafted onto the fiber surface, this strategy may avoid the potential disadvantages caused by immobilizing the nucleic acid biomolecules, such as weak restoration to the original DNA conformation after repeated uses. (C) 2015 Elsevier B.V. All rights reserved.