Manu Prakash, the Meerut-born Stanford bioengineering professor known for designing inexpensive paper-based microscope called Foldscope, and his colleagues have designed a low-cost, electricity-free centrifuge which would make detection of Covid-19 infections in low-resource settings cheaper and faster.

The Stanford team, which included Ethan Li, Adam Larson and Anesta Kothari, all of whom work in Prakash’s lab, posted the details of the hand-powered centrifuge (so called Handyfuge) in MedRxiv , the preprint server for non-peer reviewed papers in health sciences, early this week.

 

The paper explained how Handyfuge, when combined with a revolutionary molecular assay recently designed for SARS-CoV2 detection by two Harvard Medical School (HMS) researchers, can deliver a Covid-testing protocol that could be several times cheaper than those currently in use.

HMS Genetics professor Constance Cepko and her graduate student Brian Rabe announced in April a highly-sensitive but inexpensive protocol for inactivating, purifying and amplifying viral particles in human saliva samples collected for Covid testing. This molecular assay, which costs $0.07 per sample, not only uses readily available chemical reagents and is capable of detecting even a few viral RNA copies per microlitre in a sample under 30 minutes. Such an assay is called RT-LAMP, or Reverse Transcription Loop-mediated Isothermal Amplification.

Prakash, known for his work in frugal science, in a series of tweets on Saturday explained the workings of the low-cost, electricity-free centrifugation technology for isothermal SARS-CoV2 detection in saliva.

“We have been developing many frugal tools for applications in diagnostics – including other hand held centrifugation techniques for many years. The advantage of handyfuge is increased stability and limited fluctuations in RPM (revolutions per minute) and it matches covid test need,” he said in one tweet.

Explaining it further, the researchers said handyfuge uses a mechanical strategy similar to ‘Dyno-torch’ flashlights to generate centrifugal force by repeatedly squeezing the handle to spin a small freewheel connected to the centrifuge spindle. After a designated amount of time, enough centrifugal force is applied to the inactivated sample to provide inhibitor-free supernatant. This supernatant can then be reliably used for LAMP detection of SARS-CoV-2 or other viruses using the Rabe and Cepko assay, they said.

Handyfuge-LAMP assay

Prakash’s team, which has made the design of handyfuge available freely to anybody who wants to develop the low-cost tool, hoped that this would help bring LAMP assay to communities with limited resources.

The scientists tested the reliable working of the Handyfuge-LAMP assay using synthetic Covid RNA in minute quantities (10 to100 copies in microlitre). “To determine the effectiveness as a point of care tool however, it will need to be validated with actual patient samples. We are currently preparing to test this protocol and Handyfuge in field settings,” the Stanford team said in their paper.

“As the numbers keep rising both in our backyard and globally, this disease will also make tremendous negative impact on already weak healthcare systems,” Prakash said in the tweet. “We urgently need coherent global strategies instead of each country/state/county for itself. We need to re-engineer supply chain. Bring distributed manufacturing to table. Share solutions and IP (intellectual property) freely,” he said.

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