Fieldable Assay For Botulinum Neurotoxins

Background: The Botulinum neurotoxins (BoNTs) are a major threat in military settings. The mouse bioassay is the “gold standard” method, however, it has practical limitations. Purpose: To standardize a rapid, sensitive and fieldable optical immunoassay (OIA) for the detection of BoNTs A, B, E and F in food matrices. Materials and methods: The toxicity of BoNTs A, B, E and F was assessed by using a modified LD 50 assay. OIA was used to detect BoNTs in a variety of food matrices representing liquids, solids, and semisolid food. For specificity studies, the assay was used to test varying concentrations of epsilon toxin (ETX) from Clostridium perfringens, toxin A (TcdA) from C.difficile and staphylococcus enterotoxin B (SEB) from S.aureus in spiked assay buffer. To evaluate the OIA performance, five concentrations (serially five-fold diluted, viz. 20, 4, 0.8, 0.16 and 0.032 in ng/mL) of BoNT/A were made in orange juice and tested by both OIA and mouse bioassay. Results: The mouse intraperitoneal (i.p.) LD 50 values (in ng/kg) of BoNTs A, B, E and F were determined to be 1.6, 1.8, 1.3, and 2.4 respectively. OIA could readily detect 20ng/mL of BoNTs A, B, E and F in all the food samples tested. OIA demonstrate limits of detection lesser in range to the gold standard mouse bioassay. Conclusion: The OIA was found to