Sep 272011
 
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The diagnostic tests fit on a postage stamp and cost less than a penny.

While other scientists successfully shrank beakers, tubes and centrifuges into diagnostic laboratories that fit into aluminum boxes that cost $50,000, George Whitesides had smaller dreams.

The diagnostic tests designed in Dr. Whitesides’s Harvard University chemistry laboratory fit on a postage stamp and cost less than a penny.

His secret? Paper.

His colleagues miniaturized diagnostic tests so they could move into the field with tiny pumps and thread-thin tubes. Dr. Whitesides opted for a more novel approach, reasoning that a drop of blood or urine could wick its way through a square of filter paper without any help.

And if the paper could be etched with tiny channels so that the drop followed a path, and if that path were mined with dried proteins and chemically triggered dyes, the thumbnail-size square could be a mini-laboratory — one that could be run off by the thousands on a Xerox machine.

Diagnostics for All, the private company Dr. Whitesides founded four years ago here in Boston’s Brighton neighborhood to commercialize his inspirations, has already created such a test for liver damage.

It requires a single drop of blood, takes 15 minutes and can be read by an untrained eye: If a round spot the size of a sesame seed on the paper changes to pink from purple, the patient is probably in danger.

Using paper in diagnostic tests is not entirely new. It soaks up urine in home pregnancy kits and blood in home diabetes kits. But Dr. Whitesides has patented ways to control the flow through multiple layers for ever-more-complex diagnoses. His test has proved more than 90 percent accurate on blood samples previously screened by the laboratory of Beth Israel Deaconess Medical Center, a Harvard teaching hospital, said Una S. Ryan, chief executive of Diagnostics for All.

“They should be even more accurate on fresh blood,” added Dr. Ryan, a biologist. Field tests in India are set for later this year.

The initial target audience is AIDS patients with tuberculosis who must take powerful cocktails of seven or more drugs.

Some drugs damage the liver, and deaths from liver failure are 12 times as common among African AIDS patients as among American ones, Dr. Ryan said, because current liver tests are expensive and require tubes of blood.

The paper test was developed with a $10 million grant from the Bill and Melinda Gates Foundation.The foundation and the British government just donated $3 million toward creating three more paper tests to help small farmers. One is for aflatoxin, a poison produced by mold that grows on corn, peanuts and other crops. A large dose can lead to liver cancer, but even small amounts eaten regularly can leave children stunted. Farmers who can prove their crops are mold-free can protect their families and get higher prices. But current tests cost $6 each, far more than farmers can afford. A paper test that works on water washed over the grain could be made for as little as 50 cents, Dr. Ryan estimated. Volume production could drive the cost down to pennies.

The second test checks for milk spoilage caused by bacteria. Many small dairy farmers belong to cooperatives in which they pool their milk, and one sick cow can contaminate a whole batch.

The current test detects just the acidity caused by the bacteria, which is not very specific and can be defeated by adding a base like lime. A cheap enough test would help the cooperative find the offending farmer, and the farmer find the diseased cow.

The third proposed test detects hormones released into the urine when a cow is pregnant. Currently, farmers have to either watch their cows for behavior changes or perform physical exams that can be dangerous because they require reaching deep into the cow’s rectum to palpate the uterus.

“Raising cows is how farmers build wealth,” said Patrick Beattie, head of global health operations at Diagnostics for All. “They need better tests.”

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