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Sensor detects bacteria in food

Bacteria adhered to magnetic nanoparticles (red arrow) on the bottom of the container

Rui Sintra/IFSC-USP

Brazilian researchers have developed a biosensor capable of quickly identifying bacteria in food and drink. They coated magnetic nanoparticles with a peptide called melitin, which is extracted from bee venom and has a high affinity for the cell walls of bacteria. The melittin-coated nanoparticles adhere to microorganisms separated from a drink or liquefied food sample by a magnet. Small volumes of the isolated material are then deposited on a film with silver electrodes, which identify the bacterial species based on changes in the electrical properties of the electrode. The biosensor was created by a research team led by physicist Osvaldo Novais de Oliveira, from the São Carlos Institute of Physics at the University of São Paulo (IFSC-USP). In initial tests, it identified water and apple juice contaminated by Escherichia coli, Staphylococcus aureus, and Salmonella typhimurium (Talanta, October 28, 2018). “As soon as they were added to the contaminated environment, the nanoparticles attracted the bacteria, which were at the bottom of the container within 25 minutes,” says Oliveira. If further studies confirm the efficacy and commercial viability of the biosensor, which is faster than other existing techniques, it could eventually be used in routine analyses by the food industry or during contamination outbreaks.