SNAP-25, SPR Background

Botulinum Neurotoxins (BoNTs) are causative agents of botulism and because of their extreme potency, lethality, ease of production, transport and the need for prolonged medical care they are classified as category A (the highest priority) bioterrorism agents/diseases by the Centers for Disease Control and Prevention [1]. Seven distinct serotypes of the BoNTs have been identified and are designated type A through G. Humans are usually exposed to the preformed neurotoxins produced by Clostridium botulinum through food poisoning, although there are rare incidents of wound botulism and colonizing infections in the small intestine of neonates known as infant botulism [2]. Once ingested or inhaled into the lung, BoNTs are taken up by the blood stream, target the peripheral cholinergic nerve endings resulting in flaccid muscle paralysis, which leads to death. In recent years, the development of in vitro assays for the detection of BoNTs has been accelerated with the aim of decreasing the Limit Of Detection (LOD) upto femtogram quantities. However, none of the assays developed to date has been validated to be robust enough to completely replace the mouse bioassay, the FDA-approved and widely accepted gold standard method for BoNT detection. The endopeptidase assays and its variants viz. fluorescence endopeptidase assays, Fluorescence Resonance Energy Transfer (FRET) assays which can detect the biologically active neurotoxin, are reported to be more sensitive than the mouse assay [3] and have the potential to replace the mouse lethality assay. Detection of the cleaved peptides by mass spectrometry further increases the sensitivity [4], but due to the requirement for expensive instrumentation, reagents and specialized skills, these techniques are not easily affordable for most laboratories. In the scenario of a bioterror attack, an economic technology compatible with a hand-held type of device would be preferred solution for field deployment and laboratory detection