Mobile Device Rapidly Detects Zika and Related Viruses

The same platform can also be adapted to detect other human or animal pathogens.

Accurate testing for these viruses currently requires a laboratory with expensive instruments, making local testing unrealistic for limited-resource clinics where the viruses are prevalent. The team, from Sandia National Laboratories (Livermore, CA, USA), used smartphone technology as a key feature: “In addition to creating an app that serves as a simple interface to operate the device, we were able to adapt smartphone camera sensors to replace traditional laboratory sample analysis tools, allowing for unprecedented mobility,” said lead author Aashish Priye.

The “laboratory in a box” device is based on the loop-mediated isothermal amplification (LAMP) diagnostic method, which eliminates PCR thermal cycling as well as the need to process the biological sample (e.g. blood or urine) before testing. LAMP copies viral DNA/RNA but without the heating/cooling cycles of PCR, so a heavy-duty power source is not needed. The addition of a few carefully designed biochemical reagents allows a LAMP box to test a sample that is heated only once for 30 minutes.

“We’ve demonstrated that the chemistry we’re using can amplify viral RNA directly from raw, unprocessed samples,” said project lead Robert Meagher, “That is the ideal for a point-of-care testing scenario because you don’t want to have extra equipment for isolating DNA or RNA.” Meagher and team previously developed a method to combine LAMP with an additional detection technique so that multiple viruses could be tested simultaneously. This other technique, named quenching of unincorporated amplification signal reporters (QUASR), involves using synthetic virus-based primers tagged with fluorophores for the sample-DNA/RNA amplification step.

For the Zika project, Meagher’s team developed a novel algorithm that allows a smartphone sensor to act as a fluorimeter, detecting QUASR LAMP light signals if they appear. The user need only place the smartphone on top of the LAMP box and open an app that turns on the heater to initiate the LAMP reaction, after which the smartphone photographs the sample. The app then employs a novel image analysis algorithm to determine the color and brightness of the fluorescence emitted from the LAMP reaction.

Zika, dengue, and chikungunya are spread via the same mosquito vector and have similar early symptoms. The team’s prototype diagnostic tool could enable care providers to test quickly for all three at the same time, preventing misdiagnoses.

The cost of making a LAMP box prototype to test for these viruses depends largely on the cost of the phone selected for using it with. “There are billions of smartphones in the world, even in developing countries, and this tool doesn’t require the highest-end smartphone on the market,” said Priye, “It only needs to have an optical sensor and be able to run the app.” The smartphone used in Sandia’s successful tests of the current prototype costs only USD 20.

The study, by Priye A et al, was published online March 20, 2017, in the journal Scientific Reports.