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Microfluidic chip detects diseases at less cost, time

Posted: 12 Jul 2007 ?? ?Print Version ?Bookmark and Share

Keywords:microfluidic chip? disease detection? tests?

Medical tests such as fluorescence in situ hybridization (FISH) provide early warnings for a variety of diseases that can be cured if caught in time. Unfortunately, only the wealthy can routinely have them performed, because the reagents used in such tests can cost as much as $1 million per gram.

Now an electrical engineer at Canada's University of Alberta has designed a programmable microfluidic chipreminiscent of the Star Trek "tricorder"that performs FISH and similar tests with a fraction of the reagents normally required. That can speed the time-to-results by at least tenfold and cut the costs from as much as $1,000 to as low as a dollar.

"Our microfluidic system allows us to process extremely small quantities of reagents," said professor Chris Backhouse. "The small quantities we use decrease both the cost and the time by a factor of 10 to 1,000, depending on the particular test being performed."

Cell-by-cell detection
The handheld device employs a novel method to immobilize blood cells inside its microfluidic channels using both mechanical and electrokinetic pumping. FISH and other sensitive diagnostic tests performed by these microfluidic chips can detect the telltale signs of many aggressive diseases on a cell-by-cell basis.

In the past, the high cost and slow turnaround of such tests have discouraged their routine use in clinical settings. But Backhouse, working with University of Alberta oncology professor Linda Pilarski, has developed a variety of microfluidic chips to perform such tests via handheld devices for a fraction of the cost of traditional tests. Specifically, using these chips, test results can be obtained 10 times faster and 10 times more cheaply, which the researchers hope to eventually improve to 1,000 times faster and cheaper.

"We are trying to build tricorders, like they have on Star Trek, which give inexpensive results immediately," said Backhouse. "A tricorder for the life sciences must perform many sequential steps, each of which takes hours to perform by a human, which can add up to several days to get the full results back. However, with our microfluidic chips, we can reduce that time to a couple of hours."

Backhouse added that "large companies like Siemens and Philips are starting to get interested in microfluidic devices like ours. In fact, the whole field of life sciences is getting more interested in applied electronics. It is a very interesting time to be an electrical engineer."

Clinical tests
Currently, Backhouse and Pilarski's microfluidic chips are being tested in a clinical setting at the Cross Cancer Institute in Edmonton, Canada as part of the Alberta Cancer Diagnostics Consortium (ACDC), an initiative to commercialize the chips for diagnostics.

Performing a complicated medical test on a microfluidic chip involves metering minute quantities of a patient sample down channels and into reaction chambers where reagents are pumped. Typically, several such tests must be performed on different chambers on the chip to obtain final test results. Detectors then determine the outcome of the test and what should be done next.

"Not only do you need to use the smallest quantities possible to speed up results and to make them cheaper, but you also need quite a bit of intelligence in your microfluidic device, because the procedures are very complex," said Backhouse. "You need micropumps, microvalves, microreservoirs and microdetectors, all automated and under computer control."

Today many medical laboratories are only set up to perform such tests manually, requiring a skilled technician to perform all the steps. Equipment is available to automate such tests, using robots to perform the steps of the technician. But such machines can cost up to $1 million each; can only operate in batch operations, in which many other identical tests are performed simultaneously on different samples; and can sometimes take days to get the final results.

With a microfluidic device, both the cost and time are cut by virtue of the small scale of the test. The smaller the scale, the less reagent needed. In addition, such tests often depend on diffusion over measurable distances; thus, the smaller the scale, the shorter the diffusion distance and the faster the test results can be obtained.

Automating the esoteric
So far, the microfluidic chips have automated the most tedious, time-consuming and labor-intensive elements of the tests. Before commercial versions of the experimental microfluidic chips can be marketed, however, the researchers plan to automate the more-esoteric elements of the tests, so that entire batteries of diagnostic procedures can be performed while the patient waits.

"We want physicians to be able to ask a question and get the answer quickly. The classic line is this: 'We want the surgeon to know when to stop cutting, rather than make a guess, wait and see, then operate again if their guess was wrong,' " said Backhouse. "So far, we have integrated the more arduous steps that are well established onto our microfluidic chips, but we still need an expert in a white coat to supervise its operation."

The team hopes to design a completely automated, CMOS-compatible microfluidic chip that is inexpensive enough to be sold in pharmacies and that does not require trained personnel, similar to a home-pregnancy test. Such end-user-operable chips would level the playing field, so that everyone, not just the wealthy, could have access to the most modern medical diagnostics available.

- R. Colin Johnson
EE Times

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