Next, they mixed the antibody-coated nanoparticles with botulinum-contaminated orange juice. As expected, the coated nanoparticles stuck to the botulinum toxins in the orange juice.
After that, they put the orange juice sample onto a surface that was already covered in the same antibodies as the nanoparticles. When the orange juice sample came into contact with the surface, the antibodies there stuck to the other side of the nanoparticles, causing them to stay concentrated in one area. The clumping is important for analysis. Because the next step is to illuminate the surface with an ultraviolet light. Particles that clump together produce a strong UV signal, indicating the presence of the toxin. Without the toxins, the nanoparticles would roll around and spread out on the surface, producing a weaker and more diffuse UV signal.
The experiment was published in the journal Biosensors and Bioelectronics.
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Gangopadhyay told Discovery News that the big advantage of this method is simplicity, speed and the ability to detect small concentrations. Most methods for testing for botulinum involve getting a sample and injecting it into a mouse, and then checking if the mouse shows symptoms (or dies). That takes at least a couple of days, which can result in big monetary losses if the plant (or part of it) has to stay idle while managers wait for results, on top of having to find the source of the contamination if the result is positive.