Immunochromatographic strip development for ultrasensitive analysis of aflatoxin M1

A specific monoclonal antibody against aflatoxin (AF) M1 was prepared by a duo-immunogen immunization strategy. After two immunizations of Balb/c mice with AFB1 keyhole limpet hemocyanin (KLH) conjugates and followed by five subsequent immunizations of AFM-KLH, the mice secreting antibody against AFM1 were selected for cell fusion and a 7C6-H1 cell line was obtained to produce the antibody. The 50% inhibition rate of the prepared antibody was calculated as 0.034 +/- 0.002 mu g L-1. The anti-AFM1 antibody was characterized with high affinity to AFM1 (1.28 x 10(9) mol L-1) and low cross-reactivity to related AFs (<5%). With a competitive format, an immunochromatographic strip was developed using AFB1-bovine serum albumin as the immobilized antigen and anti-AFM1 antibody labeled with gold nanoparticles as tracers. Without any sample preparation, the strip could be directly applied to detect AFM1 contamination in liquid milk. The minimum cut-off concentrations were 0.2 mu g L-1 and 1.6 mu g kg(-1) in liquid milk and powdered milk, respectively, by assessment with the naked eye. Detection of real samples and spiked milk samples indicated the potential of this strip in routine AFM1 monitoring.