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AnonymousInactivehttp://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. -
AuthorJuly 14, 2009 at 11:53 AM
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