New Nanotech Foodborne Pathogen Detection

CodeWanker writes "Scientific American is reporting that scientists in China have developed a better, faster way to screen foodstuffs for infectious agent contamination. Bind antibodies to flourescent silica bits, mix with your hamburger, and turn on the black lights. Hilarity ensues."

Comments

Re:China?

[Anonymous Coward]

Nope, but the researcher has a Chinese name, and it would be too much for the submitter to read the whole article, when sweeping statements are so much easier. Besides, it is far more interesting (and thus more likely to be posted) when "scientists in China" do something, rather than researches at the University of Florida...

Re:What about unsaturated fats?

[amide_one]

The excitation wavelength/absorption spectrum for unsaturated organics depends on the number of consecutive double bonds. Single double bonds (ones by themselves, instead of long chains of double bonds) absorb starting around 210 nm - vacuum UV, with no visible emission to speak of at all. Long chains of double bonds shift the emission up to higher wavelengths (a result of conjguation). (This also happens with fused aromatic rings, found in most useful fluorescent dyes, including the ones that Tan's group uses.)

In ground beef, presumably the unsaturated fats that might interfere would be fairly evenly dispersed, giving a uniform low background fluorescence that's pretty easy to filter out and ignore, either during collection or after. The labeled antibodies show up as very bright spots, like in the pictures in the article. (In raw samples, the fat would be concentrated into fatty spots that can also be ignored by only looking at "meat" regions instead of "fat" bits.) It worked well for the stamping oil because, when there's not supposed to be any fluorescence in a part, it's very easy to see the glow of oily residues.

I'm not sure that this is really intended as a "quick consumer test" at the restaurant level (there'd have to be a LOT of E. coli on the burger before the whole surface glows), but it's much better than having to do amplification (PCR) before checking for E. coli DNA.

E coli, yeah... but which one?

[igollum]

Below is the full reference and abstract of the research paper in question, which I feel is much more interesting and informative than the three and a half words in the Science article, which fails to make some very important points - like the fact that it's not just any E. coli they're after, which are all over the place anyway, but mainly type O157:H7, which is the big nasty. There is a huge genetic diversity in the species, the name being more an umbrella term than anything - there is more genetic difference between two average E. coli subspecies than between close cousins Bacillus thuringiensis (biopesticide sprayed on crops) and Bacillus anthracis (responsible for anthrax). My point is, being able to quickly detect the bacteria in general is nice, but hardly new; the real challenge is to specifically detect the baddies, which is much tougher.
Addendum: I've just finished skimming through the PNAS paper and apparently the selectivity of this method is pretty good, which should minimize food-scare inducing false positives. More good news is they're also adapting it for other food contaminant like Salmonella (eggs, poultry etc) and Bacillus cereus (pasta, rice etc). Finally, after reading the Materials & Methods section, I can confirm that the plan is definitely not to illuminate burgers with blacklight - the method involves several sample preparation steps to bind the fluorescent particles and so on, and the reading is taken using a spectrophotometer set to specific excitation and emission wavelengths, solving the problem mentioned in another post of background signal due to fat and whatnot.

From the Cover: A rapid bioassay for single bacterial cell quantitation using bioconjugated nanoparticles. Zhao X, Hilliard LR, Mechery SJ, Wang Y, Bagwe RP, Jin S, Tan W. Center for Research at the Bio/Nano Interface, Department of Chemistry, and The Shands Cancer Center, University of Florida, Gainesville, FL 32611. The rapid and sensitive determination of pathogenic bacteria is extremely important in biotechnology, medical diagnosis, and the current fight against bioterrorism. Current methods either lack ultrasensitivity or take a long time for analysis. Here, we report a bioconjugated nanoparticle-based bioassay for in situ pathogen quantification down to single bacterium within 20 min. The bioconjugated nanoparticle provides an extremely high fluorescent signal for bioanalysis and can be easily incorporated with biorecognition molecules, such as antibody. The antibody-conjugated nanoparticles can readily and specifically identify a variety of bacterium, such as Escherichia coli O157:H7, through antibody-antigen interaction and recognition. The single-bacterium-detection capability within 20 min has been confirmed by the plate-counting method and realized by using two independent optical techniques. The two detection methods correlated extremely well. Furthermore, we were able to detect multiple bacterial samples with high throughput by using a 384-well microplate format. To show the usefulness of this assay, we have accurately detected 1-400 E. coli O157 bacterial cells in spiked ground beef samples. Our results demonstrate the potential for a broad application of bioconjugated nanoparticles in practical biotechnological and medical applications in various biodetection systems. The ultimate power of integrating bionanotechnology into complex biological systems will emerge as a revolutionary tool for ultrasensitive detection of disease markers and infectious agents.