Lab on a Chip

By Medical Discovery News

April 21, 2012

Lab on a Chip

One drop of blood can now reveal whether someone has liver damage. The novel invention of a stamp-sized piece of paper that can diagnose such things circumvents expensive lab equipment and travel time to diagnose over a dozen microbes and diseases at just pennies per test.

The “lab-on-a-chip” was developed by Dr. George Whitesides of Harvard University, who is considered one of America’s top chemists. He admits paper tests are not new, since for decades home pregnancy tests have been telling women whether they’re pregnant. But unlike the stick, Whitesides’ stamp-lab can detect complex diseases instantly and cheaply. And like the home pregnancy test, this lab-on-a-chip reliably without needing a doctor to interpret the results.

Surprisingly, this innovative test is produced using very simple equipment. Mainly, it’s filter paper, a $5,000 oven, and an office printer. That’s what keeps it cheap, but getting to this point took a $10 million research grant from the Bill and Melinda Gates Foundation.

The technology uses the concept of microfluidics, which is the science of moving fluids on a tiny scale. The process starts with feeding filter paper through a modified office printer that prints 132 stamp-sized patterns per sheet using melted black wax. The printed pages are then briefly heated in an oven to further melt the wax into the paper. When the wax dries, the patterns become channels that are key to guiding fluid samples along the test strip.  Along these channels, a variety of chemicals are applied, which react with specific biological substances.

One particular test detects aspartate transaminase (AST), which is released by dying liver cells. As a drop of blood is applied to the test strip, an outer membrane allows only the clear plasma to absorb into the paper. Several pieces of the test paper are stacked and taped, so that when the plasma enters the second layer, it encounters several chemicals. If AST is present, a reaction takes place, releasing sulfite ions that penetrate the last layer of paper. The presence of these ions causes a blue dye in the paper to turn colorless, giving a positive test result for liver damage.

The liver test is aimed at the millions of people in Africa who take powerful drugs for AIDS and tuberculosis that can damage the liver. AIDS patients there are 12 times more likely to die from liver failure than their American counterparts. But this test can also be used for the billions of people in developing countries are also at risk for aflatoxin poisoning. Aflatoxin is a mold that grows on crops such as corn and peanuts. High doses and long-term small doses cause liver cancer.

At $6, the cost of a current aflatoxin test is too expensive for farmers in Third World countries, so the British government has given Whitesides’ lab a $3 million grant to develop an inexpensive paper test for aflatoxin at no more than 50 cents a piece. But once the tests can diagnose everything from malaria to possibly even cancer, people won’t have to wait until they’re too sick before going to the doctor.

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