A reusable aptamer-based evanescent wave all-fiber biosensor for highly sensitive detection of Ochratoxin A.

Although aptamer-based biosensors have attracted ever-increasing attentions and found potential applications in a wide range of areas, they usually adopted the assay protocol of immobilizing DNA probe (e.g., aptamer, aptamer-complementary oligonucleotides) on a solid sensing surface, making it critical and challengeable to keep the integration of nucleic acid surface during the regeneration and the restoration to its original DNA probe form after repeated uses. In order to address the issue, we report a novel aptamer-based biosensing strategy based on an evanescent wave all-fiber (EWA) platform. In a simple target capturing step using aptamer-functionalized magnetic microbeads, signal probes conjugated with streptavidin are released and further detected by a EWA biosensor via a facial dethiobiotin-streptavidin recognition. Apart from the inherent advantages of aptamer-based evanescent wave biosensors (e.g. target versatility, sensitivity, selectivity and portability), the proposed strategy exhibits a high stability and remarkable reusability over other aptasensors. Under the optimized conditions, the typical calibration curve obtained for Ochratoxin A has a detection limit of 3nM with a linear response ranging from 6nM to 500nM. The dethiobiotin-streptavidin sensing surface instead of the traditional nucleic acid one can be reused for over 300 times without losing sensitivity.