NUROTOXINS DETECTED IN INKJET-PRINTERS , INK & PAPER

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NUROTOXINS DETECTED IN INKJET-PRINTERS , INK & PAPER

 user 2009-07-14 at 11:38:06 am Views: 49
  • #22355

    http://www.examiner.com/x-16026-Napa-County-Science-News-Examiner~y2009m7d13-
    NUROTOXINS DETECTED IN INKJET-PRINTERS , INK & PAPER
    It’s almost like something out of a James Bond movie. Fearing an assassination attempt using paraoxon (a potent organophosphate neurotoxin) Bond takes out a laptop computer and portable inkjet printer. Replacing the printer cartridges with some containing specially designed ink, he then pulls up a special program on the laptop and prints a small “dipstick” pattern. Cutting out the dipstick, he then dips it in a glass of vodka that was delivered to his room. The dipstick turns sickly yellow, showing that the vodka is safe to drink. Had there been paraoxon present the dipstick would have either remained white or turned only slightly yellow.

    This may sound far-fetched, but researchers at McMaster University’s Department of Chemistry, under the direction of Dr. John Brennan have just developed such a dipstick. Although not quite as easy to produce as the James Bond scenario implies, the key components of the process are paper, an inkjet printer and specially prepared inks.
    Using an inkjet printer to produce bioactive paper, the more technically correct term for this technology, is not a new idea. In 2008 researchers in the Department of Applied Chemistry at Keio University in Japan developed bioactive paper using an inkjet printer. Their paper could simultaneously test for serum albumen, glucose and pH, commonly measured parameters in urinalysis. Of course, dipsticks for urinalysis are already used, but being able to produce them so readily with just paper and an inkjet printer could represent a cost reduction innovation. Other similar applications have been studied by other researchers.

    Dr. Brennan’s hope was to take the basic science behind these previous successes and use it to develop dipsticks for detection of more challenging chemicals for which expensive instrumentation is currently required. A simple paper dipstick approach could save money, produce results much more rapidly and could be used in the field. Currently the expensive instruments used to detect neurotoxins like paraoxon and aflatoxin B1 are not particularly portable, often requiring that field samples be returned to the lab for analysis. More rapid, in the field, results would be far superior.In a paper published in the July 1, 2009 issue of Analytical Chemistry, the methods used by Dr. Brennan’s research team are outlined. It is a multi-step process in which first a layer of polyvinylamine (PVAm) is printed directly onto the paper. PVAm is used to bind negatively charged chemicals, and in the case of this assay it was used to keep the product of the color reaction bound to the paper. Secondly, a silica sol-gel layer was printed, followed by printing a layer of buffered acetylcholineesterase (AChE) solution. The AChE is a key component, as this enzyme is inhibited by neurotoxins. A final silica sol layer was printed to seal everything into a more durable matrix.To use the dipstick, it is first dipped in a sample that is being tested for a neurotoxin, such as Aflatoxin B1. After dipping, it is removed and is then dipped into a standard acetylcholine (ACh) solution. The assay is designed so that when AChE breaks down the ACh, a yellow color is produced. The darker the color of yellow, the more active the AChE is. If there was any neurotoxin in the solution being tested, it will inhibit the AChE, resulting in less breakdown of ACh and a less intense yellow color. Therefore, the higher the concentration of the neurotoxin, the less yellow the dipstick will turn.
     
    The elegance of this new procedure is that it works quickly (about 5 minutes), it is very accurate at detecting even small quantities of the neurotoxin and the results can be analyzed visually by comparing the intensity of the yellow color against a standard series of yellow bands. For greater accuracy the dipstick can be scanned into a computer and analyzed. As long as PVAm is used as the base layer, the color remains for several days with minimal change in intensity. Lastly, when stored at 4°C, the dipsticks worked even after 60 days of storage (possibly longer) and the same degree of accuracy was obtained.Although this approach is not yet in commercial production, it seems like it should be fairly easy to produce and the cost should be relatively low. Having such dipsticks readily available would make field testing for neurotoxins very simple. This same approach could likely be used for a variety of other assays for other toxins. It might even be possible incorporate multiple tests into one dipstick. There are still some technical hurdles to overcome for these to reach the marketplace, but this represents a much needed advance in field testing potential.