Paper-based diagnostic platforms that can cheaply screen people for a variety of diseases are currently being investigated by research teams around the world. A common way to capture wanted molecules is to use a sticky nitrocellulose membrane as a screen, a technique used in pregnancy tests and other diagnostic tools.
Nitrocellulose is still expensive if paper-based diagnostics are to become ubiquitous in impoverished regions of the world. It is also limited to capturing relatively large biomolecules, reducing its role in a variety of applications. Daniel Ratner and colleagues at the University of Washington have come up with a method to replace nitrocellulose and at the same time create a new platform for the development of a wide range of cheap diagnostic tests.
From University of Washington:
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. 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. 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.