Using “lab on a chip” technology, Stanford engineers have created a microlab half the
size of a credit card that can detect COVID-19 in just 30 minutes.
Throughout the pandemic, infectious disease experts and frontline medical workers have
asked for a faster, cheaper and more reliable COVID-19 test.
Now, leveraging the so-called “lab on a chip” technology and the cutting-edge genetic
editing technique known as CRISPR, researchers at Stanford have created a highly automated
device that can identify the presence of the novel coronavirus in just a half-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.
The new COVID-19 test is detailed in a study published in the journal Proceedings of the
National Academy of Sciences.
This test can identify an active infection relatively quickly and cheaply.
It’s also not reliant on antibodies like many tests, which only indicates if someone
has had the disease, and not whether they are currently infected and therefore contagious.
The microlab test takes advantage of the fact that coronaviruses like SARS-COV-2, the virus
that causes COVID-19, leaves behind tiny genetic fingerprints wherever they go in the form
of strands of RNA, the genetic product of DNA.
If the coronavirus’s 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 like RNA that it might contain.
The purified RNA is then converted into DNA and then replicated many times over 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.
If so, the activated enzyme triggers fluorescent probes that cause the sample to glow.
Here also, electric fields play a crucial role by helping concentrate all of 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, dramatically increasing the
chances they will interact.
This chip is unique in that it uses electric fields to both purify nucleic acids from the
sample and to speed up chemical reactions.
The team created its device on a shoestring budget of about $5,000.
For now, the DNA amplification step must be performed outside of the chip, but the researchers
expect that within months they will integrate all the steps into a single chip.
Several human-scale diagnostic tests use similar gene amplification and enzyme techniques,
but they are slower and more expensive than the new test, which provides results in just
30 minutes.
Other tests can require more manual steps and can 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.
The researchers are working with the Ford Motor Company to further integrate the steps
and develop their prototype into a marketable product.