Dual Aptamer-DNAzyme based colorimetric assay for the detection of AFB1 from food and environmental samples

In the present study, a colorimetric biosensor strategy is devised in combination with apta-magnetic separation assisted with DNAzyme based colorimetric detection of Aflatoxin B1 (AFB1). The optimized analytical procedures consisted of the capture of AFB1 by biotinylated aptamer conjugated to streptavidin magnetic beads and detection by a colorimetric signal from a DNAzyme modified aptamer in presence hemin and H2O2/TMB (3', 3', 5, 5'- tetramethylbenzidine). The DNA concentration, incubation time, hemin, and NaCl concentrations were evaluated and optimized. The visual optical signal thus generated could determine the presence of AFB1 in the given sample. The selectivity of the method with other mycotoxins was evaluated. The linear range of AFB1 from 0 to 200 ppb was assessed and detected as low as 40 ppb visually. The absorbance of blue color generated by the catalytic reaction was in a linear correlation with AFB1 concentrations and was able to detect as low as 22.6 ppb (LOD). The suitability of the assay for AFB1 quantification in sorghum and natural samples was also evaluated. Thus, the developed assay could be a reliable, inexpensive, alternative tool for possible use as a screening method for aflatoxins and other mycotoxins.