Immunochemical methods for mycotoxin analysis: from radioimmunoassay to biosensors

Preparation for aflatoxin B(1)-cationized bovine serum albumin based on Mannich-type reaction

Aflatoxin B(1) (AFB(1)), which is commonly found in agricultural commodities, is one of the most potent carcinogenic mycotoxins. To ensure food safety, rapid and low-cost immunological methods have been applied to detect AFB(1) worldwide. A key step in these immunological methods is coupling AFB(1) to carrier proteins; AFB(1) is usually deviated to AFB(1)-oxime and coupled to carrier proteins to form the AFB(1)-oxime-protein conjugate. In the current research, AFB(1) was directly coupled with cationized bovine serum albumin (cBSA) using a method based on Mannich-type principles. The coupling effects were investigated with different initial molar ratios of AFB(1) to cBSA. The conjugate molar ratio was 6.4:1 when the initial molar ratio was 40:1. The cationized proteins and their conjugates were identified by UV-Vis and FT-IR spectra, which showed the characteristic bands of the ethylendiamine group and AFB(1), respectively. After BALB/c mice were immunized with AFB(1)-cBSA, a quicker immunological response and a similar sensitivity of antisera against AFB(1) were observed, compared with immunization by AFB(1)-oxime-BSA. This suggests that the Mannich-type reaction might be an alternative method of preparation for AFB(1)-protein.

Preparation of gold-labeled antibody probe and its use in immunochromatography assay for detection of aflatoxin B1

Preparation of an antibody-colloidal gold probe (conjugate) specific to aflatoxin B1 (AFB1) and its use in developing a rapid AFB1 diagnostic method was presented in this paper. Monodispersional nanogold colloid was synthesized and preparation of nanogold-labeled polyclonal antibody probe to aflatoxin B1 under friendly and optimal condition. Combination of antibody with nanogold particles was also characterized by UV-visible (UV-vis) light absorption spectra, transmission electron microscopy (TEM), fluorescence spectroscopy, titers, cross reactivity and stability measurements. Furthermore, nanogold-labeled probe was used to develop an immunochromatographic (IC) method for aflatoxin B1 analysis. With this method, analysis could be completed in less than 10 min. Detection time was reduced 6-10 times comparative with ELISA. With visual observation, lower test limit was found to be around 2.5 ng/ml aflatoxin B1 standard solution, which was increased to two times of ELISA.