Amperometric biosensor for aflatoxin B-1 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 B-1 (AFB(1)). Its apparent Michaelis-Menten constant for AFB(1) was 7.03 mu mol.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 AFB(1) Conc. is bigger than 45 ng/ml), and a high sensitivity of 0.33 x 10(2) A mol(-1).L cm(-2). The active energy was 18.8 kJ mol(-1), demonstrating the significant catalyzation of AFO for oxidation of AFB(1) in this biosensor. (C) 2010 Elsevier Ltd. All rights reserved.