Scientists have already used smartphones to combat the Zika virus, in the form of a grid computing system that puts idle processors to work searching for a cure, but new work from Sandia National Laboratories is a little more direct. A team there has developed a low-cost, portable device for quickly detecting Zika and similar viruses in a sample, driven by a smartphone app.

After an outbreak in late 2015 that lasted through most of 2016, Zika hasn't been grabbing as many headlines of late. The World Health Organization (WHO) declared back in November that the mosquito-borne virus was no longer a Public Health Emergency of International Concern, but stressed that it is still an ongoing issue that needs addressing.

Since it most commonly affects developing countries, Zika has been the target of several projects that are low-cost and portable. Simple, inexpensive tests use paper discs or 3D-printed cartridges, while traps made of tires or solar-powered fans can help prevent mosquitoes spreading the virus in the first place.

Generally, to test for a virus a lab needs to repeatedly heat up and cool down a sample in order to multiply the amount of DNA or RNA in it to a level that specialized instruments can detect. But the Sandia team's new method does much the same with just a box, a heater and a smartphone running a custom app.

A diagnostic method called loop-mediated isothermal amplification (LAMP) allows the team to spot traces of a virus in a sample without needing to repeatedly heat and cool it first. Instead, a few custom biochemical agents are added to a sample, which copy the viral RNA to high enough levels for it to be detected. DNA "primer" molecules are also added, which latch onto the target DNA or RNA and fluoresce.

"We've demonstrated that the chemistry we're using can amplify viral RNA directly from raw, unprocessed samples," says Robert Meagher, lead researcher on the project. "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."

To kick off the test, the doctor places the sample inside a LAMP box and sits the smartphone on top of that. Using the app, the sample is heated, just once, to 65° C (149° F), for about half an hour, before the phone snaps a photo of the sample. Thanks to the fluorescent molecules in the sample, which bind to the virus DNA or RNA, the more of that virus present in the sample, the brighter it will glow. An algorithm in the app is then able to analyze that fingerprint, as well as the color of the light, to determine the presence and type of virus in the sample.

Along with Zika, the test can also alert doctors to other mosquito-borne diseases, like dengue fever and chikungunya, at the same time, and the team says the process could be adapted to check for other pathogens in the future.

The smartphone is the most expensive part of the new device, but the team says that as long as it has a camera and a modicum of memory, low-end phones are sufficient – in fact, their own tests used one that rings up for just US$20.

"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," says Aashish Priye, lead author on the study. "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. It only needs to have an optical sensor and be able to run the app."

The research was published in the journal Scientific Reports.

Source: Sandia National Laboratories

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