Rapid detection and characterization of botulinum neurotoxin using porous silicon interferometer

The overall goal of this project is to develop a generic integrated biosensing platform for the detection of botulinum neurotoxins (BoNTs), one of the strongest toxins in nature, by assessing the serotype and its biological activity. The neurotoxins are produced by Clostridium botulinum (C. botulinum), a gram-positive spore-forming bacteria that inhabit the gastrointestinal tract of diverse animals, such as ruminants and others, and can be found hazardous contaminants in the environment. BoNTs mode of action is characterized by hindering the release of the neurotransmitter acetylcholine in the neuromuscular junctions, causing the botulism disease in humans and animals, and categorized by flaccid paralysis. The current diagnosis method for botulism is long (7-10 days), expensive, low throughput, uses mouse lethality assay and, in fact, does not directly detect BoNTs in samples rather the toxigenic bacteria. In the present work, we have designed a miniaturized label-free optical biosensing platform, porous Si microcavity modified with specific robust capture probes offering increased sensitivity for target analytes. The sensing performance of the device is performed through indicative protein-protein interaction between simulating target molecule and its specific antibody modified with horseradish peroxidase within the dynamic range of 0.01 to 100 µg mL^–1. The optical response of the porous nanostructure (pore diameter 30–60 nm) is monitored in real-time by reflective interferometric Fourier transform spectroscopy. Preliminary results depict low limit of quantification of 10 µg mL^–1 and 10 ng mL^–1 for direct and enzymatically amplified sensing approach, respectively. Overall, the presented optical concept offers means for systematic analysis of BoNTs at environmentally relevant concentrations for suspected samples serotype diagnosis.