Stanford researchers create a highly automated device that can detect COVID-19 in 30 minutes

Reviewed by Emily Henderson, B.Sc.November 5, 2020

During the pandemic, infectious disease experts and frontline health workers demanded a faster, cheaper, and more reliable COVID-19 test. Now, leveraging so-called “lab on a chip” technology and the cutting-edge gene editing technique known as CRISPR, Stanford researchers have created a highly automated device that can identify the presence of the novel coronavirus in just half an hour.

“The microlab is a microfluidic chip just half the size of a credit card containing a complex network of channels smaller than the width of a human hair,” said study senior author Juan G. Santiago, professor of mechanics at Charles Lee Powell Foundation engineering at Stanford and an expert in microfluidics, a field dedicated to controlling fluids and molecules at the microscale using chips.

The new COVID-19 test is detailed in a study published Nov.4 in the journal Proceedings of the National Academy of Sciences. “Our test can identify an active infection relatively quickly and inexpensively. It also doesn’t rely on antibodies like many tests, which only indicate whether someone has had the disease and not whether they are currently infected and therefore contagious,” Ashwin explained. Ramachandran, a Stanford graduate student and first author of the study.

The microlab test takes advantage of the fact that coronaviruses like SARS-COV-2, the virus that causes COVID-19, leave behind tiny genetic fingerprints wherever they go in the form of strands of RNA, the genetic precursor of DNA. If coronavirus RNA is present in a swab sample, the person from whom the sample was taken is infected.

To initiate a test, liquid from a nasal swab sample is dropped into the microlab, which uses electric fields to extract and purify any nucleic acids such as RNA it may contain. The purified RNA is then converted to DNA and then replicated many times using a technique known as isothermal amplification.

Next, the team used an enzyme called CRISPR-Cas12 – a sibling of the CRISPR-Cas9 enzyme associated with this year’s Nobel Prize in Chemistry – to determine if any of the amplified DNA came from the coronavirus.

In that case, the activated enzyme triggers the fluorescent probes that make the sample glow. Here, too, electric fields play a crucial role by helping to concentrate all the important ingredients – the target DNA, the CRISPR enzyme and the fluorescent probes – together into a tiny space smaller than the width of a human hair, greatly increasing the chances that they will. to interact.

Our chip is unique in that it uses electric fields both to purify the nucleic acids from the sample and to speed up the chemical reactions that inform us of their presence. “

Juan G. Santiago, senior author of the study

The team created their device on a shoestring budget of around $ 5,000. For now, the DNA amplification step has to be done outside of the chip, but Santiago expects that within a few months his lab will integrate all the steps into one chip.

Several human-scale diagnostic tests use similar gene and enzymatic amplification techniques, but are slower and more expensive than the new test, which provides results in just 30 minutes. Other tests may require multiple manual steps and may take several hours.

The researchers say their approach is not specific to COVID-19 and could be adapted to detect the presence of other harmful microbes, such as E. coli in food or water samples, or tuberculosis and other diseases in the blood.

“If we want to look for a different disease, we simply design the appropriate nucleic acid sequence on a computer and e-mail it to a commercial synthetic RNA manufacturer. It sends us a vial with the molecule that completely reconfigures our new disease assay.” Ramachandran said.

The researchers are working with the Ford Motor Company to further integrate the stages and develop their prototype into a marketable product.