PCR (polymerase chain reaction) is a molecular diagnostic testing technique and is a gold standard diagnostic test for a variety of infectious pathogens, including bacteria and viruses, such as SARS-CoV-2. However, this type of test requires bulky and expensive lab equipment. Researchers at Imperial College London have developed a tiny lab-on-a-chip that is only 1 cm in diameter and can perform PCR diagnostics in just a few minutes.

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Known as TriSilix, the chip is made from silicon, the same material that is used to make electronic chips. Silicon itself is cheap, however, it is expensive to process into chips as this requires massive, extremely clean factories known as cleanrooms, reports Imperial College London.

Each TriSilix contains a DNA sensor, temperature detector, and heater to automate the testing process. A typical smartphone battery could power up to 35 tests on a single charge.

To make the new lab-on-chip, the researchers developed a series of methods to produce the chips in a standard laboratory, cutting the costs and time they take to fabricate, potentially allowing them to be produced anywhere in the world.

Lead researcher Dr. Firat Güder of Imperial’s Department of Bioengineering said: “Rather than sending swabs to the lab or going to a clinic, the lab could come to you on a fingernail-sized chip. You would use the test 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 researchers have so far used TriSilix to diagnose a bacterial infection mainly present in animals as well as a synthetic version of the genetic material from SARS-CoV-2, the virus behind COVID-19.

The researchers say the system could in the future be mounted onto handheld blood sugar test-style devices. This would let people test themselves and receive results at home for colds, flu, recurrent infections like those of the urinary tract (UTIs), and COVID-19.

If validated on human samples, this new test could provide results outside a clinic, at home or on-the-go within minutes.

Cutting costs

The researchers said a highly portable test could accelerate diagnosis of infections and reduce costs by eliminating the transportation of samples. Such tests could be performed by citizens in the absence of highly trained medical professionals – hence, if they need to self-isolate, they can start immediately without potentially infecting others.

Making testing more accessible and cheaper is especially important for people in rural areas of low-income countries, where clinics can be far away and expensive to travel to. If made available to patients, it could also be used to diagnose and monitor infections like UTIs, which often recur despite antibiotics.

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“Monitoring infections at home could even help patients, with the help of their doctor, to personalize and tailor their antibiotic use to help reduce the growing problem of antibiotic resistance, said first author Dr. Estefania Nunez-Bajo, also of the Department of Bioengineering.

Next, the researchers plan to validate their chip with clinical samples, automate the preparation of samples and advance their handheld electronics. They are looking for partners and funders to help accelerate the translation of the technology and deliver testing at resource-limited settings at homes, farms or remote locations in the developing world.

The paper is published in Nature Communications.