As seen with the COVID-19 pandemic, detection methods that are rapid, simple, accurate, and sensitive are vital for detecting viral pathogens and controlling the spread of infectious diseases. Unfortunately, laboratory methods often require trained personnel and involve complex procedures. In a new study, researchers at the University of Illinois at Urbana-Champaign joined forces to develop a tool that can be attached to a smartphone to rapidly test for the Zika virus in a single drop of blood.
Zika virus is primarily transmitted through Aedes aegypti mosquitoes. Although the disease is mostly asymptomatic or causes mild symptoms in adults, it causes developmental disorders in newborns if their mothers are infected early in pregnancy. The virus currently circulates in more than 87 countries, infecting thousands of people each year, requiring improved testing and control measures.
“Viruses transmitted by mosquitoes cause serious diseases, but they have similar symptoms. If you have Zika, malaria, dengue or chikungunya, you can just show up to the doctor with a fever and they won’t know why,” said Brian Cunningham (Director CGD/MMG), Department of Electrical and Computer Engineering Intel Alumni Endowed. “But it’s important to know if it’s Zika, especially if the patient is a pregnant woman, because the consequences for the developing fetus are really serious.”
Zika virus infections are currently detected by polymerase chain reaction tests performed in the laboratory, which can amplify the genetic material of the virus, allowing scientists to detect it. In the new study, researchers used isothermal loop-mediated amplification to detect the virus in blood samples, using an approach suitable for point-of-care clinics. While PCR requires 20-40 repeated temperature changes to amplify genetic material, LAMP requires only one temperature – 65 °C – which facilitates control. In addition, PCR tests are very sensitive to the presence of contaminants, especially other components in the blood sample. As a result, the sample is first cleaned before it can be used. LAMP, on the other hand, does not require such a cleanup step.
A cartridge containing the reagents needed to detect the virus is inserted into the device to perform the test while the device is attached to the smartphone. After a patient adds a drop of blood, one set of chemicals breaks down viruses and blood cells within five minutes. A heater under the cartridge heats it up to 65 °C. A second set of chemicals then amplify the virus’s genetic material, and the liquid in the cartridge fluoresces bright green if the blood sample contains the Zika virus. The whole process takes 25 minutes.
“The other cool aspect is that we’re doing a smartphone reading,” Cunningham said. “We designed a clip-on device so that the smartphone’s rear camera looks at the cartridge while amplification is taking place. If there is a positive reaction, you see small green fluorescent spots that eventually fill the entire cartridge with green light. “
Researchers are now developing similar devices to simultaneously detect other mosquito-borne viruses, and are working to make them even smaller. “Although our clip-on detector is quite small, batteries take up a lot of space. In the next version, it will be powered by the phone’s battery,” said Cunningham.
The study, “Smartphone mountable device and microfluidic processor for rapid sample-to-response detection of Zika virus in whole blood using spatial RT-LAMP,” was published in the journal an analyst and can be found at 10.1039/d2an00438k.
The work was conducted in collaboration with Rashid Bashir (CGD/M-CELS), the Abel Bliss Professor of Engineering; Enrique Valera, Associate Professor of Bioengineering; Min Do, the Thomas and Margaret Huang Professor of Electrical and Computer Engineering; and William King, professor of electrical and computer engineering. The research was funded by the Partnership for Innovation program of the National Institutes of Health and the National Science Foundation.