Immunologically Controlled Biofuel Cell as a Self‐Powered Biosensor for Antibiotic Residue Determination

A biofuel cell consisting of a self‐powered sulfonamide immunosensor as biocathode and a cellobiose dehydrogenase (CDH)‐based bioanode was developed for the determination of sulfonamide antibiotics in milk. A graphite‐rod electrode was modified with protein G for the immobilization of selective capture antibodies. A direct competitive immunoassay with a horseradish‐peroxidase‐labeled analog of the antibiotic and the 2,2′‐azino‐bis(3‐ethyl benzothiazoline‐6‐sulfonic acid) diammonium salt‐mediated reduction of H2O2 allows quantification of antibiotic residues. CDH was co‐immobilized with a toluidine‐blue‐modified redox polymer on a graphite electrode for the biocatalytic oxidation of lactose in milk. An open‐circuit voltage of 676 mV and a maximal power density of 6.9 µW cm−2 were obtained. The power densities measured at 550 mV (vs. the anode) as a function of antibiotic concentration in milk samples allowed the construction of a calibration curve with a detection limit for sulfapyridine as low as 2.4 ng mL−1.