Twenty years ago, the Pentagon asked George M. Whitesides, a chemist at Harvard University, to invent a way to quickly detect anthrax and other biohazards in the field. His solution was a handheld device that used polymers to draw samples through a complex series of very small chemical baths. If biohazards were present, the chemicals would react. The device worked, but Whitesides was more excited about its civilian potential. Nearly a billion people live without access to hospitals or any reasonably sophisticated means of diagnosing illness; if he could transform the biohazard detector into a universal diagnostic tool, he could help save millions of lives. The design was straightforward. The only problem was that the Pentagon version was too expensive. For years, he and other researchers tried shrinking parts or using cheaper components. Then, four years ago, Whitesides had another idea. What if the whole thing was made out of paper?
Using an $800 printer, he selectively patterned sheets of paper with melted wax to create assay zones, similar to the circuits on a computer chip. He then added assay reagents that changed colour when exposed to certain chemicals. The paper would wick blood samples into the appropriate assay zones, where it would bind to the reagents and change colour to deliver a diagnosis. Mass-produced, his stamp could cost less than a penny.
But Whitesides needed help getting his paper out into the world. For this, he approached Una Ryan, a doctor who had just left her job as the CEO of a biopharmaceutical company that specialised in manufacturing vaccines and was looking to become involved in nonprofit work. She says her first reaction was that a simple diagnostic tool could not directly save as many lives as a vaccine. But, Whitesides countered, millions of patients die every year simply because physicians have an incomplete picture of their health. The blood work that could save them was too expensive and time-consuming. Diagnostic paper was cheap and quick, and its colour-coded system made it easy for even nonprofessionals to interpret. Moreover, the printing methods required to manufacture diagnostic tools by the millions could be replicated nearly anywhere. "Printing comic books is a very high-technology business that occurs everywhere," Whitesides says. Those same printers could be made to work in this case as well. "I realised then," Ryan says, "that if we could get this into the developing world, it would be game-changing."
Ryan now runs Diagnostics For All, which develops and distributes Whitesides's paper. She recently shipped a liver-function test to India and will soon send more to Vietnam. Ryan says the company is also working on tests for dengue fever, diabetes, anemia and hypertension. "The best outcome," Whitesides says, "is that paper diagnostics eventually emerge as the global standard.
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