Treated Paper Suitable for Diagnostics

Biomolecule sensing agents were printed onto paper that had been treated with a diluted chemical solvent. This offers a cheap, easy solution for paper-based diagnostics.

The scientists printed a biomolecule in the pattern of the University of Washington (Seattle, WA, USA) UW mascot; it bound to a toxic molecule, indicating that the toxin was present. “We wanted to go for the simplest, cheapest starting material, and give it more capability,” said Daniel Ratner, a UW assistant professor of bioengineering and lead author of a paper recently published in the June 18, 2012, edition of the American Chemical Society journal Langmuir. Prof. Ratner continued, “We also wanted to make the system as independent of the end applications as possible, something any researcher could plug into.”

The UW technique uses minimal equipment or knowhow. A cheap, industrial solvent called divinyl sulfone that has been used extensively as an adhesive was diluted in water, and the acidity carefully controlled. It was then poured into a Ziploc bag and a stack of paper was added. This was shaken for a couple of hours, and then the paper was rinsed and dried.

Once the paper was coated in the industrial solvent, an inkjet printer printed on it molecule sensing agents, then medical tests were performed. The dried paper 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.

To test their idea further, the scientists 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 the paper to fluorescent ricin, a poison that sticks to galactose, showed that the poison was present.

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.

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

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

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