Inexpensive Chip Detects Covid-19, Other Pathogens

TriSilix chip (Imperial College London)

3 Dec. 2020. A small silicon lab-on-a-chip device costing about $0.35 to make is shown in lab tests to quickly detect SARS-CoV-2 viruses and infectious bacteria. Researchers from an engineering lab at Imperial College London in the U.K. describe the device in yesterday’s issue of the journal Nature Communications.

A team from the lab of Imperial College bioengineering professor Firat Güder aims to fill a need for an easy-to-use device to test for harmful bacteria and viruses in fluid samples, from human bodies but also in drinking water, animals, or crops. The need is particularly urgent for fast, accurate, and inexpensive diagnostics for SARS-CoV-2 viruses responsible for Covid-19 infections that today use either expensive table-top systems or require sending samples to a remote lab for analysis.

Güder and colleagues designed their device, called TriSilix, to analyze samples for nucleic acids such as RNA and DNA and return results in real time. TriSilix performs polymerase chain reaction, or PCR, analysis of the sample, a technique for quickly amplifying small specimens and reading DNA sequences, using few reagents. PCR conducted directly or after reverse transcription of RNA is considered the gold standard for sample analysis, particularly for detecting SARS-CoV-2 viruses.

The Imperial College team created TriSilix as a self-contained chip on silicon, about 10 millimeters square. However, the researchers devised techniques for fabricating TriSilix chips in a regular biology lab, rather than needing a clean-room foundry, the standard production method for semiconductor chips. The team produced the chips used in their study on four-inch wafers, at an estimated cost of $0.35 each, making them disposable. The researchers believe they can drive down the cost even further with larger wafers.

The chip, say the authors, requires little power, and can be configured on a hand-held device, powered with a battery comparable in capacity to one used in smartphones. Power from the battery heats the chip and fluid specimen sample stored a reservoir on the silicon chip. PCR analysis requires heating the sample.

The researchers tested TriSilix concept in the lab with Mycobacterium avium subspecies paratuberculosis, a bacterial parasite infecting cattle and sheep, and considered a possible cause of some human diseases. The team found a TriSilix chip can detect low concentrations of the bacteria, down to single microorganism in their samples, with results similar to testing on standard lab equipment.

The Imperial College team also tested TriSilix with a synthetic form of SARS-CoV-2 viral DNA, since they did not have access to clinical samples. The findings show the chip detects the presence of SARS-CoV-2 in samples, finding low concentrations of the virus and returning results in about 40 minutes. TriSilix also detects synthetic DNA from the 2003 SARS epidemic, and distinguishes it from today’s SARS-CoV-2 viruses.

The researchers envision a TriSilix device eventually used routinely at home to test for colds, flu, and common infections, like those in the urinary tract. “You would use the test,” says Güder in an Imperial College statement, “much like how people with diabetes use blood sugar tests, by providing a sample and waiting for results, except this time it’s for infectious diseases.”

The team plans to continue testing TriSilix with clinical samples, and automate the preparation and reporting processes. The university is seeking partners to develop the device further for use in homes and farms worldwide.

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