The Development And Optimization Of Aflatoxin-detecting Biosensor Based On Immobilized Enzyme-MWNT Modified Pt Electrode

AFB₁ was a kind of mycotoxin having strong cancerigenic mutant abilities. Several methodsfor AFB₁ detecting had been reported in both domestic and foreign articles. Among the articles, thedetections of AFB₁ and its structural analogue ST with enzyme biosensor based on ADTZ was a newmethod firstly reported by our instititute.The objectives of our study were developing researches on improving the constancy, servicelife, detecting continuity and sensitivity of the assembled enzyme biosensor for AFB₁ and STdetections, so as to find out a method for the construction of an enzyme biosensor which coulddetect AFB₁ continuously.Methods: rADTZ with high purity and high special activity was used as a recognizing element toassemble and compare three biosensors constructed in three different waysâ‘ rADTZ/EDC&NHS/MWNT electrode (covalently cross linking rADTZ on MWNT modifiedelectrode)â‘¡rADTZ&sol-gel electrode(immobilizing the sol-gel which had embedded rADTZ inadvance directly on the surface of Pt electrode)â‘¢rADTZ&sol-gel/MWNT electrode(immobilizingsol-gel-embedded rADTZ on MWNT modified electrode). Cyclic voltammetry (CV), differentiatedpulse voltammetry (DPV) and single potential time base (TB) were employed to analyze electricalsignals detected, to characterize this modified electrode and to optimize detecting conditions of thebiosensor.Results:(1) rADTZ was purified with the special activity of 95.8U/g and the purity of 76.10% by atwo-step procedure using ordinary pressure purification system providing necessary materials for thepreparation of the enzyme-modified electrode.(2) rADTZ/sol-gel/MWNT modified electrode could resist the interference of methanol fairlywell, having good reproducibility and constancy. After being placed at 4℃for 28 days, the electrodehad a stable response current with a standard deviation of 2.1%.(3) The TB experiment showed that the enzyme-modified electrode had a rather sensitiveresponse with an average response time of 44s. Moreover when C_AFB1 is more than 45μg·L^-1, theresponse time will be less than 30s and the biosensor could last detecting stably for more than 5 hours. Two linear range of 5×10^-6g/L～2.5×10^-5g/L and 3×10^-5g/L～7×10^-5g/L were gotwhile AFB₁ was detected. The linear range was already within the detecting limit of AFB₁ allowedin feed and feed additives in China, which manifested that the rADTZ/sol-gel/MWNT modifiedelectrode was an ideal method and means to detect AFB1 online with the ability to combine withFIA.