Amperometric biosensor for aflatoxin B1 based on aflatoxin-oxidase immobilized on multiwalled carbon nanotubes

An amperometric aflatoxin biosensor developed by aflatoxin-oxidase (AFO), embedded in sol-gel, linked to multiwalled carbon nanotubes (MWCNTs)-modified Pt electrode was reported for the first time. The covalent linkage between AFO and MWCNTs retained enzyme activity and responsed to the oxidation of afltoxin B1 (AFB1). Its apparent Michaelis-Menten constant for AFB1 was 7.03 μmol•L−1, showing a good affinity. The sensor exhibited a linear range from 3.2 nmol•L−1 to 721 nmol•L−1 (1 ng/ml to 225 ng/ml) with limits of detection of 1.6 nmol•L−1 (signal-to-noise ratio = 3), an average response time of 44 s (less than 30 s when AFB1 Conc. is bigger than 45 ng/ml), and a high sensitivity of 0.33 × 102 A mol−1•L cm−2. The active energy was 18.8 kJ mol−1, demonstrating the significant catalyzation of AFO for oxidation of AFB1 in this biosensor.