New technology could soon make it cheap and easy to identify food pathogens by tagging them with color-coded probes made out of synthetic tree-shaped DNA.
These tiny "nanobarcodes" fluoresce under ultraviolet light in a combination of colors that can then be read by a computer scanner or observed with a fluorescent light microscope.
The Cornell University research group behind the project likens the technology to a supermarket checkout computer, capable of identifying thousands of different items by scanning barcodes.
"We wanted something that could be done with inexpensive, readily available equipment," said Dan Luo, Cornell University assistant professor of biological engineering. He points out that other methods of identifying biological molecules currently available mostly involve expensive equipment.
The researchers have already tested their system using samples containing various combinations of E. coli and tularemia bacteria, and have found the color codes could clearly distinguish several different pathogens simultaneously.
The technology is similar to a new DNA-based test developed by the ARS (Agricultural Research Center) that makes it possible for the first time to simultaneously identify all of the major head blight pathogens in corn and predict their toxin profiles. At least 16 species of Fusarium can cause head blight, a disease that can reduce yields and contaminate cereals with toxins that can make grain unsafe for food or feed.
The new ARS scientists devised a test that pinpoints nucleotide variations that genetically distinguish one head blight species from another. When a probe matches the DNA in a head blight sample, the DNA is fluorescently labeled and detected using a special camera and a high-power laser, providing unambiguous identification of the head blight pathogen and its toxin potential.
Such developments are making food safer, a fact that is reflected in recent US government safety figures. From 1996 to 2004, the incidence of E. coli O157 infections decreased 42 percent, campylobacter infections fell 31 percent, cryptosporidium dropped 40 percent, and yersinia decreased 45 percent.
"Many [firms] have applied new technologies to reduce or eliminate pathogens and have increased their testing to ensure the effectiveness of control measures," claims the government report .
The development is also testament to the growing importance of nanotechnology in food safety. This emerging new science, which involves the use of materials the size of millionths of a millimetre, has opened new possibilities in monitoring never before imagined, and this latest discovery has the potential to dramatically increase food safety at every stage of the supply chain.
Food safety and the development of early warning systems is a growing area of study given the emphasis on food safety and the perceived threat of terrorism. This is a point emphasised by the Cornell University researchers, who suggest that their nanobarcode technology could also be used in genomic research, clinical diagnosis, drug testing and even monitoring for biological terrorism.
The research is described in a paper, "DNA fluorescence nanobarcodes for multiplexed pathogen detections," that will be published in the July 2005 issue of the journal Nature Biotechnology.