Protein-coated chip sniffs out bacteria

By Kimberly Patch, Technology Research News

Researchers at Purdue University have created a computer chip that contains just a hint of Star Trek Borg: it combines inorganic silicon, organic protein molecules, and microfluidic channels.

The protein biochip, which uses the proteins to identify specific molecules, is designed to be used in handheld devices that will quickly detect low levels of harmful or therapeutic chemicals and microbes.

The biochip contains tiny channels that allow fluids to pass by proteins that are attached to the chip using a process that leverages the proteins' naturally occurring electrical charges.

The proteins bind to specific molecules contained in the fluid via the same lock and key mechanism antibodies in organisms use to capture harmful microorganisms.

"The idea is to place the [protein] in the chip, expose a solution containing the cells to the chip, and then if the cells are present they would specifically bind with the [protein] and thereby we would detect them," said Michael Ladisch, Professor of agriculture and biological engineering and biomedical engineering at Purdue.

The researchers proof-of-concept chip, studded with the egg white protein avidin, picked up biotin molecules. In that case researchers verified the capture via florescence microscopy. "We have also shown we can detect the presence of the cells themselves electronically, so the next step is to put everything together," Ladisch said. "Our first target is of course food, and the possibility of the presence of food pathogens."

The researchers are working on a chip that would quickly detect very low levels of the bacteria Listeria and show the result electronically. "We apply an electric signal to the chip, we change the frequency of it, and depending on the spectrum of the frequency we will get a different signal back for a solution containing cells versus a solution not containing cells," said Ladisch

The researchers have identified a protein in the Listeria membrane that will bind with a specific protein antibody and are working on attaching the antibody to a chip.

"It sounds like they've been successful in bringing together a number of different technologies into an integrated system," said Charles L. Cooney, professor of chemical and biochemical engineering at MIT. And that's the sort of thing that's exciting these days.... miniaturization into chip technologies [is] a convergence of technologies that we're going to see more of," he added.

Microfluidic technology allows the researchers to miniaturize diagnostic tests, which means they need only small amounts of both the attached proteins and the sample to be tested Cooney said. In addition, "because the distances are short on these chip technologies you can do things very quickly."

Eventually the technology could be applied to handheld devices that could be used in the field to probe plant fluids for therapeutic molecules, said Ladisch.

"This is speculative... but one can imagine going out into a forest and having a device that has a receptor for a molecule that might be effective against infection, or against some type of cancer... [and finding] molecules that bind to these receptors [as candidates] for further investigation," said Ladisch.

The Listeria detector could be a viable product within two years; other detectors based on biochips may be available in three years or so, said Ladisch.

In addition to Ladisch and Bashir, the cross disciplinary project involved the following Purdue researchers: Biomedical Engineering Research Scientist Stephen Badylak, Physics and Materials Engineering Associate Professor Mike McElfresch, Food Science Associate Professor Arun Bhunia, Biomedical Engineering and Immunopharmacology Professor J. Paul Robinson and graduate student Rafael Gomez.

The researchers presented a poster on the subject at NIH on June 25th.

The research was funded by the U.S. Department of Agriculture and by Purdue's Agriculture Research Program's Food Safety Program.

Timeline:   < 2 years; > 3 years
Funding:  University; Government
TRN Categories:  Applied Computing; Integrated Circuits
Story Type:  News
Related Elements:  Photo


July 12, 2000

Page One

Bendable nanotubes store bits

Protein-coated chip sniffs out bacteria

The little light-sensitive molecule that could

Fault-tolerant free speech

Chemical reaction zips nanowires onto silicon


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