As seen with the COVID-19 pandemic, detection methods that are fast, 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 Urbana-Champaign combined their efforts to develop an instrument that can be connected to a smartphone to rapidly detect Zika virus in a single drop of blood.
Zika virus is transmitted primarily through Aedes aegypti mosquitoes Although the disease is largely asymptomatic or produces mild symptoms in adults, it causes developmental disorders in newborns if their mothers are infected during early pregnancy. The virus currently circulates in more than 87 countries, infecting thousands of people annually, requiring better testing and control measures.
“Mosquito-borne viruses cause serious illness, but have similar symptoms. If you have Zika, malaria, dengue, or chikungunya, you may show up to the doctor with a fever and not know why,” said Brian Cunningham (Director of CGD/MMG), Intel Alumni Endowed president of Electrical and Computer Engineering. “But it’s important to know if it’s Zika, especially if the patient is a pregnant woman, because the consequences for a developing fetus are really serious.”
Currently, Zika virus infections are detected using polymerase chain reaction tests performed in a laboratory, which can amplify the genetic material of the virus, allowing scientists to detect it. In the new study, the researchers used loop-mediated isothermal amplification to detect the virus in blood samples using an approach suitable for point-of-care clinics. While PCR requires 20 to 40 repeated temperature changes to amplify genetic material, LAMP requires only one temperature, 65°C, making it easy to control. Furthermore, PCR tests are very sensitive to the presence of contaminants, especially other components, in a blood sample. As a result, the sample is first purified before it can be used. On the other hand, LAMP does not require any such purification steps.
A cartridge, containing the reagents needed to detect the virus, is inserted into the instrument to perform the test while the instrument is attached to a smartphone. Once the patient adds a drop of blood, a set of chemicals breaks open the viruses and blood cells within five minutes. A heater below the cartridge heats it up to 65°C. A second set of chemicals then amplifies the viral genetic material, and the fluid inside the cartridge fluoresces bright green if the blood sample contains Zika virus. The whole process takes 25 minutes.
“The other interesting aspect is that we’re doing the reading with a smartphone,” Cunningham said. “We have designed a clip-on device so that the rear camera of the smartphone looks at the cartridge while the amplification is happening. When there is a positive reaction, you see little green flowers of fluorescence that eventually fill the entire cartridge with green light.”
The researchers are now developing similar devices to simultaneously detect other mosquito-borne viruses and are working to make them even smaller. “Although our clip detector is quite small, the batteries take up a lot of space. In the next version, it will be powered by the phone’s battery,” Cunningham said.
Reference: Jankelow AM, Lee H, Wang W, et al. Smartphone clip instrument with microfluidic processor for rapid sample-to-response detection of Zika virus in whole blood using spatial RT-LAMP. Analyst. 2022:10.1039.D2AN00438K. do: 10.1039/D2AN00438K
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