U. WASHINGTON (US) — A chemical trick turns regular paper into a device similar to a home-based pregnancy test, and it might work for malaria, diabetes, or other diseases.
“We wanted to go for the simplest, cheapest starting material, and give it more capability,” says Daniel Ratner, assistant professor of bioengineering at the University of Washington who developed a way to make the same paper available in office supply stores sticky to medically interesting molecules.
“We also wanted to make the system as independent of the end applications as possible, something any researcher could plug into.”
Researchers coat the paper in an industrial solvent, use an inkjet printer to print on biomolecule sensing agents, then perform medical tests. View larger. (Credit: Dan Ratner/U. Washington)
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.
As reported in the journal Langmuir, the new technique uses minimal equipment or know-how. 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.
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 says. “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 says they hope other groups will use the paper to develop actual diagnostic tests.
Researchers from the University of Minnesota, Temple University, and Dalian University of Technology in China contributed to the study, which was funded by the Washington Research Foundation and the UW’s Royalty Research Fund.
Source: University of Washington