Indian-American scientist develops electricity-free COVID-19 testing instrument

PTI

New York

Researchers, led by an Indian scientist, have developed a cheap, electricity-free centrifuge to separate components in patient saliva samples for the detection of the novel coronavirus, an innovation that may increase accessibility of COVID-19 diagnostics in poor regions of the world.

According to the scientists, including Manu Prakash from Stanford University in the US, the ‘Handyfuge’ device spins tubes containing patient saliva at very high speeds, enough to separate the virus genome from other components in the sample, without needing electricity.

They said the cheap centrifuge, described in a yet-to-be peer-reviewed study published in the platform medRxiv, can be assembled using readily available components for a cost less than five USD per unit.

It can allow clinicians and scientists to carry out a quick and cheap diagnostic technique called the LAMP assay to detect the presence of the novel coronavirus genome in patient saliva samples, the scientists noted. The LAMP protocol, according to Prakash and his team, “has the benefits of being simple, requiring no specialised equipment, rapid, requiring less than an hour from sample collection to readout, and cheap, costing around one dollar per reaction using commercial reagents.”

While the assay has several merits, the Stanford scientists said there could be a variability in output in diagnostic methods based on viral genome detection in saliva samples.

They explained that this is due to the saliva containing substances which can inhibit diagnostic reagents.

“Centrifugation to separate the reaction inhibitors from inactivated sample was shown to be an effective way to ensure reliable LAMP amplification,” the scientists wrote in the study.

However, they said a centrifuge capable of safely achieving the necessary speeds of 2000 rotations per minute (RPM), for several minutes, costs hundreds of dollars, also requiring a power supply.

With Handyfuge, this hurdle can be over come, believes Prakash — a professor of Bioengineering at Stanford University, whose lab had earlier developed a cheap “origami microscope” called ‘Foldscope’.

The scientists explained that the novel device uses a mechanical strategy similar to that seen in ‘Dyno-torch’ flashlights to generate centrifugal force using kinetic input from the user.

“The user repeatedly squeezes the handle to spin a small freewheel connected to a centrifuge spindle,” they wrote in the study.

After a designated amount of time, enough centrifugal force is applied to the sample-containing tubes, the scientists said, yielding a separated liquid layer that is free of chemicals that may inhibit the coronavirus genetic material, its RNA.

“This supernatant can then be reliably used for LAMP detection of SARS-CoV-2 or other viruses,” the researchers wrote.

According to the study, the Handyfuge-LAMP assay works based on protocol for the diagnostic method developed by scientists, Brian Rabe and Constance Cepko, from Harvard University in the US.

“This simple electricity-free LAMP protocol builds on fantastic work by Cepko lab at Harvard, but with a hand powered centrifuge to make this assay completely electricity free for resource constrained settings,” Prakash’s lab mentioned in a tweet.

“The advantage for handyfuge is increased stability and limited fluctuations in RPM and it matches covid test need,” the scientists noted on Twitter.