▎ 摘　　要

NOVELTY - A composite biosensor for detecting aflatoxin B1, is prepared by: (1) preparing silver nanoparticles: dispersing silver nitrate in deionized water to obtain 0.01-1.0 wt.% aqueous solution of silver nitrate, and nitric acid; placing silver aqueous solution in a flask, installing a condensing reflux device, and heating the oil bath; (2) preparing graphene oxide-nanosilver composite material: taking 0.2-1.45 wt.% graphene oxide dispersion and silver nanoparticle sol in a light-shielded condition in the bottle; (3) preparing graphene oxide-nanosilver-aflatoxin B1 monoclonal antibody composite: taking aflatoxin B1 monoclonal antibody and fully dispersing it in phosphate buffer solution; (4) preparing modified electrode: polishing the alumina powder having a diameter of 0.02-0.10 mu m; and (5) preparing working electrode: dropping the graphene oxide-nanosilver-aflatoxin B1 monoclonal antibody composite on the surface of the activated gold electrode, and storing in a refrigerator. USE - The method is useful for preparing a composite biosensor for detecting aflatoxin B1 (claimed). ADVANTAGE - The nano-silver used in the method has lower cost than nano-gold, and the instrument used has lower cost than instruments used in high performance liquid chromatography method. The operation is simple, the analysis time is short, the detection cost is low, and the qualitative and quantitative detection of aflatoxin B1 has minimum detection limit of 7.19x 10-10 mu g/kg, and shows good linear relationship in 7.19x 10-10-2.47x 10-4 mu g /kg. The reaction is sensitive in the experiment without adding a signal amplification substance such as chitosan or potassium ferricyanide to increase the current response. DETAILED DESCRIPTION - A composite biosensor for detecting aflatoxin B1, is prepared by: (1) preparing silver nanoparticles: dispersing silver nitrate in deionized water to obtain 0.01-1.0 wt.% aqueous solution of silver nitrate, and nitric acid; placing silver aqueous solution in a flask, installing a condensing reflux device, and heating the oil bath; after the solution in the flask is boiled, 0.01-3% sodium citrate solution is added to continue boiling for 1-1.2 hours, stopping heating and cooling at room temperature, and allowing the mixture to stand for not greater than 150 hours in the dark, and obtaining silver nanoparticle sol; (2) preparing graphene oxide-nanosilver composite material: taking 0.2-1.45 wt.% graphene oxide dispersion and silver nanoparticle sol in a light-shielded condition in the bottle, where the mass ratio of the graphene oxide dispersion to the silver nanoparticle sol is 2:3, and stirring the mixture for 5-6 hours to be fully mixed and used; (3) preparing graphene oxide-nanosilver-aflatoxin B1 monoclonal antibody composite: taking aflatoxin B1 monoclonal antibody and fully dispersing it in phosphate buffer solution with pH of 7.0 to prepare a corresponding proportion of antibody dilution; (4) preparing modified electrode: polishing the alumina powder having a diameter of 0.02-0.10 mu m; and (5) preparing working electrode: dropping the graphene oxide-nanosilver-aflatoxin B1 monoclonal antibody composite on the surface of the activated gold electrode, and storing in a refrigerator at 3-6 degrees C until the surface of the electrode is a solid film, which is used for working electrode for detecting aflatoxin B1. An INDEPENDENT CLAIM is included for detecting aflatoxin B1 using the prepared biosensor which involves: (a) preparing 0.05 mol/L sodium dihydrogen phosphate buffer solution, preparing 0.05 mol/L dipotassium hydrogen phosphate buffer solution, mixing sodium dihydrogen phosphate buffer solution and dipotassium hydrogen phosphate buffer solution to prepare phosphoric acid salt buffer solution; (b) adding 0.1-2.0 mu g/kg antigen solution to the corresponding amount of phosphate buffer solution prepared in step (a) to prepare a corresponding concentration of the antigen dilution as a detection base; and (c) using the gold electrode modified with graphene oxide-nanosilver-aflatoxin B1 monoclonal antibody as working electrode, the platinum electrode as counter electrode, the saturated potassium chloride electrode as reference electrode, and mixing the phosphate buffer solution and the corresponding concentration of antigen; when the aflatoxin B1 monoclonal antibody specifically binds to the aflatoxin B1 antigen, electron transfer occurs, which is amplified by the electrochemical workstation through nano-silver conduction, and the detection result is presented in a cyclic voltammetry image.