An innovative ultrasensitive electrochemical aptamer-based sensor was developed for ochratoxin A (OTA) detection in cold brew coffee through revolutionary combination of nanofibers, electrochemical method, and aptamer technologies. The assembly of the aptasensor was based on the activation of silanized cellulose nanofibrous membranes as a supporting matrix for methylene blue (MB) redox probe-labeled aptamer tethering. Cellulose nanofibrous membranes were regenerated by deacetylating electrospun cellulose acetate nanofibrous membranes with deacetylation efficacy of 97%, followed by silanization of the nanofiber surfaces by using (3-aminopropyl)triethoxysilane (APTES). A replacement of conventionally casted membranes by the nanofibrous membranes increased the active surface area on the working electrode of a screen-printed three-electrode sensor by more than two times, consequently enhancing the fabricated aptasensor performance. The developed aptasensor demonstrated high sensitivity and specificity toward OTA in a range 0.002-2 ng mL-1, with a detection limit of 0.81 pg mL-1. Moreover, the assembled aptamer-based sensor successfully detected OTA in cold brew coffee samples without any pretreatment. The aptasensor exhibited good reusability and stability over long storage time. Graphical abstract.
Keywords: Aptamer; Cellulose nanofibers; Coffee analysis; Electrochemical aptasensor; Ochratoxin A; Point-of-use.