(...) I first saw Andraka present his discovery at a TED worldwide talent search inNew York two weeks ago. In only three minutes he had the audience dumbfounded with the results of his work: a paper test strip that uses minute changes in conductivity to detect targeted viruses or antigens faster, cheaper and more accurately than today’s standard diagnostics. It seems too good to be true, but the panel of judges at the Intel science fair are not rubes. For a teenager he is disarmingly forthright and direct in talking about complex chemistry, but he’s also good at making it understandable to the lay person.
Andraka’s diagnostic breakthrough is a humble piece of filter paper, except that it is dipped in a solution of carbon nanotubes, which are hollow cylinders with walls the thickness of a single atom, coated with a specific antibody designed to bind with the virus or protein you’re looking for. Andraka’s key insight is that there are noticeable changes in the electrical conductivity of the nanotubes when the distances between them changes. When the antibodies on the surface of the nanotubes come in contact with a target protein, the proteins bind to the tubes and spread them apart a tiny bit. That shift in the spaces between tubes can be detected by an electrical meter. Andraka used a $50 meter from the Home Depot to do the trick but, he says, doctors can just as easily insert his test-strips into the kinds of devices used by millions of diabetics around the world.
Andraka’s paper sensor is extremely sensitive. In a single-blinded test of 100 patient samples, it spotted the presence of mesothelin, a protein commonly used as a biomarker for pancreatic cancer, at a limit of 0.156 nano grams per milliliter, well below the 10 ng/mL considered an overexpression of mesothelin consistent with pancreatic cancer. It’s also 100 times more selective than existing diagnostic tests, which means no false positives or false negatives. It ignored healthy patient samples as well as those with mere pancreatitis. Compared with the 60-year-old diagnostic technique called enzyme-linked immunosorbent assay (or ELISA), used in pregnancy test strips and viral checks for HIV, West Nile and hepatitis B, Andraka’s sensor is 168 times faster, 26,667 times less expensive, and 400 times more sensitive. It can spot the presence of the cancer-linked protein well before the cancer itself becomes invasive. This could save the lives of thousands of pancreatic cancer victims each year. The sensor costs $3 (ELISA can cost up to $800) (...)