Development of a Structure-Switching Aptamer for Sensitive Colorimetric Detection of Botulinum Neurotoxin

Detection of botulinum neurotoxin (BoNT) is critical for public health and national security because of its high toxicity and potential use in bioterrorism. In this study, we aimed to identify an aptamer specific to BoNT via the BoNT structure switching systematic evolution of ligands by exponential enrichment (BOSS-SELEX) method. After confirming that a novel aptamer (BoNT-A4) undergoes structural changes upon binding to BoNT with high affinity (K_d = 3.482 nM), a sensitive colorimetric detection approach was developed using tyramide signal amplification. It determines BoNT as low as 5.72 ng/mL and does not respond to other toxins (ochratoxin, zearalenone, vomitoxin, aflatoxin) or to bovine serum albumin, confirming its high specificity against BoNT. The proposed system, which has an excellent performance, can be applied to various aptamer-based-sensing platforms and pave the way for the screening of other aptamers specific to biological risk factors that can threaten humans.