Chemists at Ohio State University are developing paper strips that detect diseases, including cancer and malaria—for a cost of 50 cents per strip. The idea is that people could apply a drop of blood to the paper at home and mail it to a laboratory on a regular basis—and see a doctor only if the test comes out positive. The researchers found that the tests were accurate even a month after the blood sample was taken.
Since the antibody strips survive more than long enough to reach a lab by mail, they could open up a whole new world of medical care for people in rural communities—even in the United States, according to Dr. Abraham Badu-Tawiah, an assistant professor of chemistry and biochemistry at Ohio State. Even for people living in the city, testing themselves at home would save money compared to going to the doctor.
In the U.S., he said, the tests would be ideal for people who have a family history of cancer or have successfully undergone cancer treatment. Instead of waiting to visit a doctor every six months to confirm that they are still in remission, they could test themselves from home more frequently.
Badu-Tawiah conceived of the papers as a way to get cheap malaria diagnoses into the hands of people in rural Africa and Southeast Asia, where the disease kills hundreds of thousands of people and infects hundreds of millions every year. But in the Journal of the American Chemical Society, he and his colleagues report that the test can be tailored to detect any disease for which the human body produces antibodies, including ovarian cancer and cancer of the large intestine.
The patent-pending technology could bring disease diagnosis to people who need it most—those who don’t have regular access to a doctor or can’t afford regular in-person visits, Badu-Tawiah said.
The technology resembles today’s “lab on a chip” diagnostics, but instead of plastic, the “chip” is made from sheets of plain white paper stuck together with two-sided adhesive tape and run through a typical ink jet printer.
Instead of regular ink, however, the researchers use wax ink to trace the outline of channels and reservoirs on the paper. The wax penetrates the paper and forms a waterproof barrier to capture the blood sample and keep it between the layers. One 8.5-inch by 11-inch sheet of paper can hold dozens of individual tests, which can then be cut apart into strips, each a little larger than a postage stamp.
The technology works differently than other paper-based medical diagnostics, such as home pregnancy tests, which are coated with enzymes or gold nanoparticles to make the paper change color. Instead, the paper contains small synthetic chemical probes that carry a positive charge. These “ionic” probes allow ultrasensitive detection by a handheld mass spectrometer.
The chemists designed ionic probes to tag specific antibodies that extract the disease biomarker from the blood and onto the paper chip. Once they are extracted, the chemicals stay unchanged until the paper is dipped in an ammonia solution at the laboratory. There, someone peels the paper layers apart and holds them in front of a mass spectrometer, which detects the presence of the probes based on their atomic characteristics—and, by extension, the presence of biomarkers in an infected person’s blood.
Badu-Tawiah and his colleagues successfully detected the protein biomarker for ovarian cancer, known as cancer antigen 125, and the carcinoembryonic antigen, which is a marker for cancer of the large intestine, among other cancers.
Source: Ohio State University; June 29, 2016.