Diagnostics tests almost at no cost – a possibility

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Many paper-based diagnostics are made from nitrocellulose, a sticky membrane used in pregnancy tests and by medical researchers to detect proteins, DNA or antibodies in the human immune system.

Ratner hopes to replace that specialized membrane with cheap, ubiquitous paper, and to use it for any type of medical test—not just the big, biological molecules.

Daniel Ratner is an assistant professor of bioengineering, Univ. of Washington and lead author of the paper recently published in the American Chemical Society journal Langmuir.

The new technique uses minimal equipment or know-how. The researchers used a cheap, industrial solvent called divinyl sulfone that can be bought by the gallon and has been used for decades as an adhesive. Ratner’s group discovered they could dilute the chemical in water, carefully control the acidity, then pour it into a Ziploc bag and add a stack of paper, shake for a couple of hours, and finally rinse the paper and let it dry.

Researchers coat the paper in an industrial solvent, use an inkjet printer to print on biomolecule sensing agents, then perform medical tests.

The dried paper feels smooth to the touch but is sticky to all kinds of chemicals that could be of medical interest: proteins, antibodies and DNA, for example, as well as sugars and the small-molecule drugs used to treat most medical conditions.

“We want to develop something to not just ask a single question but ask many personal health questions,” Ratner said. “‘Is there protein in the urine? Is this person diabetic? Do they have malaria or influenza?’”

To test their idea, the researchers ran the treated paper through an inkjet printer where the cartridge ink had been replaced with biomolecules, in this case a small sugar called galactose that attaches to human cells. They printed the biomolecules onto the sticky paper in an invisible pattern. Exposing that paper to fluorescent ricin, a poison that sticks to galactose, showed that the poison was present.

Now that they have proven their concept, Ratner said, they hope other groups will use the paper to develop actual diagnostic tests.

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