Gold leaf – gold metal hammered into thin sheets – is used by artists and craftsmen to gild picture frames, works of art and clothing. Despite its luxurious appearance, the material is affordable and available at most craft stores. Now researchers are reporting ACS Central Science developed gold foil electrodes that, in combination with a CRISPR-based assay, could sensitively detect human papillomavirus (HPV) DNA in human samples. The method could also be modified to diagnose other viral infections.
Previous research indicates that about 80% of new cases of sexually transmitted infections, such as HPV and human immunodeficiency virus (known as HIV), occur in low-resource settings. In addition, more than 90% of cervical cancer deaths, which are mainly caused by HPV, occur in these regions, according to the World Health Organization. But people living in low-resource settings lack the facilities, trained staff, and money to perform common diagnostic tests, including polymerase chain reaction (PCR) or antibody detection. Therefore, Ariel Furst, Catherine Klapperich and their colleagues wanted to develop a simple and affordable point-of-care test.
Using 24-karat gold foil, adhesive, stencil, and a razor blade, the researchers fabricated a three-electrode system that provided a reading in the presence of DNA from the HPV. On the surface of the electrodes, they attached strands of DNA labeled with a dye. Then, they amplified DNA from cervical swab samples with a technique called isothermal loop-mediated amplification, which doesn’t require expensive PCR machines. They added the amplified DNA, along with a CRISPR Cas12a enzyme designed to recognize an HPV sequence, to the surface of the electrode. In the presence of HPV DNA, Cas12a became activated, causing the enzyme to cut the dye-labeled DNA sequence, which changed the electrochemical signal. The test, which costs only about $ 2.30 in total per test (compared to $ 30-75 for existing tests), accurately detected HPV in cervical swabs from patients. The technology could be adapted to detect any viral infection, including SARS-CoV-2, the researchers say.
The authors acknowledge funding from the Dorf-Ebner Distinguished Faculty Fellow Award, the Boston University Precision Diagnostics Center, the Defense Advanced Research Projects Agency, and the National Science Foundation.
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