Botulinum neurotoxins (BoNT) are one of the most potent toxins known to humankind. BoNT represents a significant bioterrorism threat, and if an attack event were to happen, then a detection method that combines speed, sensitivity, ease of use and the ability to be used in various environments would be required.
Currently, the field detection of BoNT is based on spectrometric methods (e.g., ultraviolet laser-induced fluorescence—UV-LIF and immunological methods (mainly lateral flow assay—LFA or enzyme-linked immunosorbent assay—ELISA). In the case of spectrometric methods, the undoubted advantage is the short analysis time and the possibility of detection in the stand-off mode. However, these methods are characterized by a low selectivity and are more suitable for the detection of a biological aerosol and its classification rather than for the identification of a biological agent (not to mention the identification of the toxin serotype).
Immunological methods have a significant advantage of high selectivity, which allows one to determine the serotype of the toxin, of great importance in the possible medical treatment of people exposed to this toxin. The disadvantages of immunological methods include a much longer analysis time, the need to perform a relatively complicated analytical protocol (in the case of ELISA), and a low sensitivity (in the case of LFA).
Researchers aimed to overcome these limitations by using a Love-type surface acoustic wave immunosensor for detecting BoNT Type A (light chain). The study results were recently published in the journal Sensors.
The sensor was prepared by immobilizing monoclonal antibodies specific for BoNT via a thiol monolayer deposited on a gold substrate. Changes in wave parameters are the analytical signal of acoustic wave sensors. The detection of antigens is carried out directly (label-less). Not needing to use labels simplifies the analytical procedure and significantly reduces the analysis time.
The sensor can be used several times (regeneration of the sensor is possible using a low pH buffer). In this study, the detectability of the analyte was relatively low compared to other analytical techniques that can be used for rapid detection of BoNT. These results constitute the proof of concept and can be used as a starting point in improving the technique.
Due to low equipment requirements, high potential for miniaturization, and the possibility of constructing devices that operate automatically, the technique of immunosensors based on acoustic wave transducers has a good chance of practical application in the on-site detection of BoNT, but only after addressing the issue of the low detectability of the analyte.
Surface Acoustic Wave Immunosensor for Detection of Botulinum Neurotoxin. Sensors, 6 September 2023.