Low cost paper strips may detect malaria, cancers

 Scientists have developed low cost paper strips that may make detecting diseases such as cancer and malaria as easy as testing blood sugar or taking a home pregnancy test.

According to Abraham Badu-Tawiah from The Ohio State University in the US, 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, proving they could work for people living in remote areas.

They said 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 technology could bring disease diagnosis to people who do not have regular access to a doctor or can not afford regular in-person visits, Badu-Tawiah said.

The technology resembles "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, 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.

"To get tested, all a person would have to do is put a drop of blood on the paper strip, fold it in half, put it in an envelope and mail it," Badu-Tawiah said.

The technology works differently than other paper-based medical diagnostics like home pregnancy tests, which are coated with enzymes or gold nanoparticles to make the paper change colour.

Instead, the paper contains small synthetic chemical probes that carry a positive charge. It is these "ionic" probes that allow ultra-sensitive detection by a handheld mass spectrometer.

The researchers successfully demonstrated that they could detect protein biomarkers from the most common malaria parasite, Plasmodium falciparum, which is most prevalent in Africa.

They also 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.

After confirming that their tests worked, Badu-Tawiah and his team stored the strips away and re-tested them every few days to see if the signal detected by the mass spectrometer would fade over time.

They found that the signal was just as strong after 30 days as on day one, meaning that the disease proteins were stable and detectable even after a month.
The study was published in the Journal of the American Chemical Society.