by Lina Zeldovich
In 2010, Ethel Cesarman, a pathologist at New York City’s Weill Cornell Medical Center working with scientists running clinical trials on Kaposi sarcoma (KS). KS is a cancer of the connective tissue. Connective tissue characterized by bluish-red or purple bumps on the skin.
So in the Western world, KS affects older men of Mediterranean heritage. Consequently in Africa, though, it’s common in young adults and children. As a result it also has a high mortality rate. Especially in people under 40. This also often occurs as a side effect of AIDS. She also was part of the team that in the mid-1990s discovering KS. So it was originally identified by dermatologist Moritz Kaposi. That was over a century ago. However it is caused by a human herpes virus.
“For some reason, KS is endemic in Africa.”
With early diagnosis and treatment, the cancer’s progress will be significantly slowed. The technique used to detect viruses responsible for the cancer in biopsy samples. It as a result employs a thermal process called the polymerase chain reaction (PCR). Yet more importantly it is expensive and requires complex equipment.
But in Africa, medical centers don’t have the necessary machinery to diagnose the disease.
Miniature solution for big problem
Four years later, the Cornell team took their diagnostic tool for a test run. The miniature device they built consists of a smartphone. Yes an app, a lens and a tiny round chip. And it’s powered by the one nearly unlimited resource Africa has: the sun.
For starters, a standard PCR test uses a technique called DNA amplification. Double-helix viral DNA from a biopsy sample is combined with primers. Primers which are lab-synthesized single DNA strands. These strands mimic the sequence of viral DNA. The mix is put through a three-step thermal process. First, it is heated to 95 degrees Celsius, at which point the double-stranded viral DNA breaks down.
Consequently it’s then cooled to 65 degrees C. Seems that 65 degrees is what causes the single-stranded primers to link to the broken viral DNA.
Finally, it’s brought up to 72 degrees C. All when the DNA chain recombines, thereby doubling its amount.
The results of their effort were published at the end of February in the journal Scientific Reports.
Jiang and his colleagues field-tested the device in Kenya and Uganda in early 2014. The Cornell team and local doctors tested the same biopsy samples. All using both the solar PCR and traditional diagnostic methods. For example, examining them under the microscope (because the thermal PCR equipment wasn’t available). At the moment, the team is awaiting results from the clinics to compare the accuracy of the solar method to the traditional one.
Clouds can interfere with the test so the team is including a backup light that works just like the sun in the kit. The smartphone uses Android because it offers a better programming language, Jiang says. Then the phone’s battery supplies enough power for the whole system. All as a result to last through 70 hours of operation. Each test takes about half an hour to complete and uses 100 times less energy than the standard PCR. Besides the phone, the team expects the device to cost under $500. “It’s really not much,” Jiang says, adding that the entire kit fits into a case the size of a lunchbox. “It’s just some plastic, some metal and the lens.”
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