University of Pennsylvania engineers have created a $2 genetic test for Zika virus. The device doesn’t need electricity or special training to function, making it especially useful in the field.
The device is about the size and shape of a soda can and requires a sample of saliva for testing. A genetic assay then tests the sample for Zika virus. If present, a color-changing dye will turn blue. A rapid test for the virus would help combat the current outbreak as the only approved tests for Zika require lab equipment, the university said in a statement.
"[We] engineered a low-cost, point-of-care system that consists of a diagnostic cassette and a processor,” said Changchun Liu, a research assistant professor in the Department of Mechanical Engineering and Applied Mechanics at Penn, in the statement. “The cassette isolates, concentrates and purifies nucleic acids and carries out enzymatic amplification. The test results are indicated by the change in the color of a dye, which can be inspected visually." Once a saliva sample is put in the cartridge, the test takes 40 minutes, the team said.
A genetic test to detect Zika virus is more accurate than alternative tests, such as those that screen for antibodies the body produces in response to Zika infection. Some Zika-infected patients may turn up as false negatives because they haven’t had time to produce antibodies yet. Meanwhile, some noninfected patients may turn up as false positives if they have produced antibodies against other diseases that are similar to Zika.
However, currently approved tests that screen for Zika RNA using reverse transcriptase polymerase chain reaction (RT-PCR) require the genetic sequences to be copied numerous times until there is enough to detect. This has been a challenge for portable genetic tests as it depends on multiple temperature changes. The Penn team looked into using an alternative screening tool, RT-LAMP, which only requires the sample to be kept at one specific temperature, making it ideal for use outside a lab.
The device currently serves as a proof of concept and there are numerous steps ahead before it can be commercialized. The team said they will investigate a version of the test that will indicate Zika virus using a fluorescent dye and a smartphone camera. "Before the assay can be adapted for medical use, we must experiment with patients' samples and make assure that our assay and system match the performance of the gold standard and operate reproducibly and reliably,” said Haim Bau, a professor in the Department of Mechanical Engineering and Applied Mechanics, in the statement.
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