Aflatoxins are naturally occurring mycotoxins that contaminate food and agro commodities, leading to acute and chronic health conditions in human and animals. In the present work, an attempt was made to generate high-affinity single stranded DNA aptamers that specifically bind to Aflatoxin B1 (AFB1) by a modified Systemic Evolution of Ligands by Exponential Enrichment (SELEX) procedure with the aid of Immunoaffinity columns. Ten rounds of SELEX and alternating three counter SELEX rounds with a cocktail of related and other mycotoxins were performed to enhance the specificity. Resultant 105 aptamers were clustered into 12 groups according to their primary sequence homology. Candidates with lowest Gibbs free energy (dG value) and unique stem loop structures were selected for further characterization. Aptamers, AFLA5, AFLA53, and AFLA71 exhibiting lower Kd values (50.45 ± 11.06, 48.29 ± 9.45, and 85.02 ± 25.74 nM) were chosen for development of ELONA and determination of purification ability of toxin. The detection limit (LOD) of AFLA5 and AFLA71 was 20 and 40 ng/ml, respectively. HPLC analysis implied that selected aptamers were able to recover and quantify 82.2 to 96.21% (LOQ – 53.74 ng) and 78.3 to 94.22% (LOQ – 66.75 ng) of AFB1 from spiked corn samples, respectively. These findings indicate, immunoaffinity based SELEX can pave an alternative approach to screen aptamers against mycotoxin detection and purification.

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Purpose A real-time immunocapture PCR (RT-IPCR) has been fabricated for the detection of Staphylococcus aureus enterotoxin B (SEB) from food and environmental samples. Methods Considering the fact, anti-SEB immunoglobulin G (IgG) has affinity towards protein A, produced by nearly all S. aureus, and generates false-positive read out in all immuno-based assay. We have employed avian anti-SEB antibody (SEB-IgY) as capture probe, since IgY interact less efficiently to protein A and biotinylated SEB-specific monoclonal antibody (SEB -MAb) conjugated with reporter DNA as revealing probe for real-time PCR amplification and signal generation. Sensitivity and selectivity of the assay were evaluated employing closely related enterotoxins and other toxins. Results The RT-IPCR is highly specific and sensitive (100 fg/mL). The practical applicability of the assay was tested using spiked food sample as well as naturally contaminated food samples. The sensitivity and specificity of RT-IPCR were not compromised by the foods tested and was able to detect SEB conveniently. Further, the assay was validated comparing with the in-house developed PCR, and plausible result was obtained. Conclusion The developed assay can be utilized as a low-cost detection system of SEB in routine food testing laboratories.