August 1, 2011
Lab-on-a-chip Could Streamline Blood Testing Worldwide
An inexpensive and portable blood test could provide a breakthrough in diagnosing infections and has been proven as accurate as expensive hospital-based testing in the detection of HIV, syphilis and other diseases, according to a new study released Sunday.
Samuel K. Sia, assistant professor of biomedical engineering at Columbia Engineering, has developed the innovative strategy for an integrated microfluidic-based diagnostic device. The mChip, as it is called, has been tested with hundreds of patients in Rwanda, with nearly 100 percent accuracy.
"The idea is to make a large class of diagnostic tests accessible to patients in any setting in the world, rather than forcing them to go to a clinic to draw blood and then wait days for their results," Sia told the AFP news agency.
With a projected production cost of $1 dollar per unit, the mChip would be far cheaper to administer than current lab-based tests.
Because the mChip can scan for multiple proteins, each corresponding to a particular disease, at the same time with a single blood sample, it is probably even cheaper than strips which work like store-bought pregnancy tests, and are more accurate to boot.
"Current rapid HIV tests require subjective interpretation of band intensity by the user that can result in false positives," that is, healthy individuals being misdiagnosed, the study noted.
The mChip, however, allows for measurement using a handheld instrument - which costs about $100 -- that is no more complicated to use than a cell phone, according to researchers. The device will produce accurate results within minutes rather than the standard days or weeks.
The device contains a microchip housed inside an injection-molded plastic casing, explained Vincent Linder, Chief Technological Officer at Claros Diagnostics, which owns or has licensed relevant patents.
A nano-sized gold "reagent" -- which detects a substance via a chemical reaction -- is injected, followed by a silver one that interacts with the gold to produce an ultra-thin film.
"The darkness of the film is proportional to the concentration of biomarker in the sample," said Linder, comparing the steps to the development process in non-digital photography. The results can be measured with a LED-based detector or can be viewed by the naked eye.
Sia and his colleagues tested the mChip prototype in Muhima Hospital in Kigali. From a total of 70 specimens with known HIV status, only one tested false, a result that rivals the accuracy of lab-based HIV testing.
Similar tests on more than 100 archived specimens yielded similarly reliable results, as did further trials based on samples from female sex workers known to be infected with both HIV and syphilis.
Sia hopes the mChip can be used to help pregnant woman in Rwanda who, while they may be suffering from AIDS and STDs, cannot be diagnosed with any certainty because they live too far from clinics or hospitals that have labs.
"Diagnosis of infectious diseases is very important in the developing world," Sia said. "When you're in these villages, you may have the drugs for many STDs, but you don't know who to give treatments to, so the challenge really comes down to diagnostics."
Currently, less than 25 percent of pregnant women in low- and middle-income countries are tested for HIV, a figure which provides limited hoping of reaching the UN goal of eliminating mother-to-child transmission of the disease by 2015, according to the 2010 UNAIDS Report on the Global AIDS Epidemic.
In Zambia and the Democratic Republic of Congo, for example, only nine and six percent, respectively, of pregnant women currently receive HIV testing, according to the report.
A version of the mChip that tests for prostate cancer has also been developed by Claros Diagnostics and was approved in 2010 for use in Europe.
Sia's work also focuses on developing new high-resolution tools to control the extra-cellular environments around cells, in order to study how they interact to form human tissues and organs. His lab uses techniques from a number of different fields, including biochemistry, molecular biology, microfabrication, microfluidics, materials chemistry, and cell and tissue biology.
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