Researchers in the US have developed an automated microlab device that identifies the presence of the novel coronavirus in half an hour.
The breakthrough by a team at Stanford University in California leverages lab-on-a-chip technology and CRISPR, a genetic editing technique.
“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 the study’s senior author, Juan G Santiago, the Charles Lee Powell Foundation Professor of mechanical engineering at Stanford and an expert in microfluidics.
The new COVID-19 test is detailed in the journal Proceedings of the National Academy of Sciences.
“Our 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,” said Ashwin Ramachandran, a Stanford graduate student and the study’s first author.
The microlab test is said to take 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 precursor 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 placed 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 using isothermal amplification.
According to Stanford, the team then used an enzyme called CRISPR-Cas12 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 help to concentrate ingredients – such as the target DNA, the CRISPR enzyme and the fluorescent probes – together into a space smaller than the width of a human hair.
“Our chip is unique in that it uses electric fields to both purify nucleic acids from the sample and to speed up chemical reactions that let us know they are present,” Santiago said in a statement.
The team created its microlab device on a budget of about $5,000. For now, the DNA amplification step must be performed outside of the chip, but Santiago expects that within months his lab 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. 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 E. coli in food or water samples, or tuberculosis and other diseases in the blood. The team is also working with the Ford Motor Company to further integrate the steps and develop the prototype into a marketable product.