Between worries about terrorism in the wake of the bombs in Boston and a new strain of bird flu, there’s some good news: a new method for testing food with glow-in-the-dark nanoparticles could give early warnings about food-borne infections or contamination.
A team at the University of Missouri started with cells called antibodies, which occur naturally in a person’s immune system. One side of an antibody latches onto a germ or toxic molecule. The other side can stick to other antibodies, or to other proteins as part of the signalling that acts like a big red flag telling other immune cells to come and help destroy a dangerous invader. Biotech companies can produce antibodies in a lab to seek out and kill specific germs or bacteria, or to study them.
In this case, electrical engineering professor Shubhra Gangopadhyay and his colleagues used antibodies that recognize botulinum toxin, a poison that shows up in contaminated food when it’s infected with a particular bacteria. The antibodies were coated onto one side of a bunch of nanometer-sized particles that encapsulated bits of dye designed to glow under an ultraviolet light.
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.
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.
The University of Missouri method would be a lot easier, since it can be made into a test kit and used on location at a meat processing plant to test samples in about an hour. That can save time and ultimately money, not to mention ensure that food products are safe.
Because there are commercially available antibodies to many toxins, viruses and bacteria, it’s possible to make nanoparticles tailored to a wide range of contaminants. Gangopadhyay noted that one application is detecting bioterrorism threats — if someone were to try to poison a food supply, these nanoparticles would tell anyone doing the testing right away.
Study co-author and Missouri University professor Keshab Gangopadhyay founded Nanos Technologies LLC to manufacture the nanoparticles on a commercial scale — and do so in Missouri.
Photo: Stock image of bacteria glowing under an ultraviolet light. Credit: Roger Ressmeyer/CORBIS