A paper on the biochip, "Micro-Scale Detection of Biological Species
in Micro-Fluidic Chips," was presented at the Nanoscience and
Nanotechnology: Shaping Biomedical Research conference at the National
Institutes of Health in Bethesda, Md., on June 25.
The first non-laboratory application of the new biochips will be to
develop sensors to detect the deadly pathogen Listeria monocytogenes
in foods.
According to 1999 statistics from the Centers for Disease Control and
Prevention, there are an estimated 2,500 cases of Listeria
monocytogenes infections annually. Unlike other foodborne pathogens, a
high number one out of five of the cases of Listeria are
fatal.
Better detection of this fatal food pathogen is a high priority for
the food industry, according to Arun Bhunia, associate professor of
food science at Purdue. "The problem is, however, that at the present
time we can only detect the pathogen if we have a large sample. To get
a large number, you have to let the bacterium grow in a
laboratory. You typically don't see levels that high in a food
system," he says. "It can take as much as five to seven days to grow,
test and confirm the presence of a specific pathogen."
The biochip could speed this process dramatically. It would contain
antibodies to Listeria monocytogenes obtained from rabbits or
mice. Antibodies are natural defense proteins that organisms use to
recognize and disable harmful proteins.
Because only Listeria monocytogenes could interact with the antibodies
on the chip, a definite determination of the absence or presence of
the bacterium could be made within minutes.
The work to develop a biochip sensor for the food industry is being
financed by the Purdue Food Safety Engineering Project with funds from
the U. S. Department of Agriculture.
"This is a good first use of this technology," Ladisch says. "To
detect Listeria monocytogenes, speed is needed, and the combination of
biotechnology with computer chips is a possible answer."
The biochips would require approval of the Food and Drug
Administration before they could be used in food production.
Researchers from several schools and disciplines at Purdue played key
roles in the development of the biochip.
"Microelectronic technology and life sciences have historically been
separate areas of research," Bashir says. "But applying micro- or even
nano-electronic technologies and devices, such as these biochips, to
life science problems will result in solutions that are low cost
compared to current testing methods, and will significantly reduce the
time needed for the detection of organisms and specific biological
materials."
Expertise on processing samples and interpreting their interactions is
being contributed by Rakesh Singh, professor of food science, and Mike
McElfresch, associate professor of physics and materials engineering.
Ladisch and Dr. Stephen Badylak, a senior research scientist in
Purdue's Department of Biomedical Engineering, originally proposed the
concept as a way to probe natural materials for therapeutic molecules.
"The real bottleneck in biological research is the lack of a way to
quickly interrogate the chemistry of various organisms to find out if
they contain any beneficial or harmful compounds," Ladisch says.
Scientists have long known that each species of plant or animal
produces unique chemical compounds, and that some of these compounds
can, like penicillin, become miracle drugs.
"There are estimates that there are about a million species of
organisms on earth, and through human history tens of thousands of
these have been used for medicinal purposes," Ladisch says. "Up to
now, we've been uncovering the actual proteins or molecules at the
rate of just a few a year. This research has the potential to increase
that number several fold.
"What we would have would be a high-tech litmus paper. It would tell
us the presence of molecules with specific properties and the
concentrations. There are a lot of secrets still being held by Mother
Nature. Maybe this will allow us to probe for some of the more obvious
ones."
