As the COVID-19 pandemic rolls on, rapid testing is likely to be an important element in opening up, even as vaccination rates lift.

However, one of the hurdles with non-lab-based testing is accuracy, something teams of researchers in labs around the world have been trying to solve.

A new diagnostic tool has now been developed that allows users to test themselves for SARS-CoV-2 and multiple variants of the virus using just a sample of their saliva themselves with no extra instrumentation needed, and the tool can be created with a 3D printer.

The device, known as ‘minimally instrumented SHERLOCK’ (miSHERLOCK), uses a scientific process known as CRISPR that deploy “molecular scissors” to snip SARS-CoV-2 RNA at a specific location.

This process creates a fluorescent signal when the saliva detects the virus and displays the results on the accompanying smartphone app within an hour.

It has also been engineered to detect the genetic variants, Alpha, Beta, and Gamma.

What’s more remarkable is that the test can be assembled using a 3D printer and commonly available components for about $30, and re-using the hardware brings the cost of individual tests down to $10 each, Helena de Puig, a postdoctoral researcher in James J. Collins' lab at the Wyss Institute for Biologically Inspired Engineering at Harvard University, explained to Information Age.

This is a significant development because miSHERLOCK is currently the only low-cost, non-laboratory COVID test capable of detecting and differentiating specific SARS-CoV-2 variants.

“It could be used to guide patient care as well as infection control or epidemiologically purposes,” said de Puig.

The diagnostic procedure from saliva to test result. Credit: Wyss Institute at Harvard University

Print-your-own COVID test

Seeing the pressure on global supply chains early in the pandemic that meant many materials such as nasopharyngeal swabs or RNA extraction kits were suddenly difficult to obtain, the researchers looked at ways to create an all-in-one testing and diagnostic unit.

“We decided to build miSHERLOCK when we realised many materials such as nasopharyngeal swabs or RNA extraction kits were suddenly difficult to obtain.”

The research team had wanted to design an easy-to-use, low-cost device that can democratise COVID-19 testing and strain-tracking.

It’s why the device’s hardware can be built by anyone with access to a 3D printer, with the files and circuitry designs all publicly available online.

The team added the smartphone app for resource-limited settings because mobile phone services are available virtually anywhere in the world, even in areas that are difficult to reach on foot.

The unit can be created using 3D printing and publicly available designs. Credit: Wyss Institute at Harvard University

Technology offers hope of test anywhere

This is not an antigen test, unlike rapid testing already being used in parts of the world, and offers accuracy at speed.

“While there are other home-based test kits, many are antigen-based tests, which are generally less sensitive than nucleic acid tests, and most of the tests capable of identifying SARS-CoV-2 genes are self-collection kits that are mailed back to a central testing facility,” she said.

To test for variants, current tests send samples to centralised sequencing centres, but nucleic acid sequencing is expensive and can only be done for a small subset of samples, even in resource-rich nations. These typically require up to 72 hours and cost several hundred dollars.

“There are no other point-of-care COVID tests capable of differentiating between specific variants. Our device provides direct confirmation of specific strains at the point of care,” she added.

The team is eager to work with manufacturers who are interested in producing miSHERLOCK at scale for global distribution.

Innovation in wearable disease protection

Working in the field of synthetic biology, the team is also innovating with Synbio, a disruptive technology that may hold solutions for global healthcare, agriculture, manufacturing and environmental challenges. They have also developed wearable biosensors technology that allows face masks to detect SARS-CoV-2 through the wearer’s breath.

In that project, the team demonstrated that it can freeze-dry a broad range of synthetic biology sensors to detect viral or bacterial nucleic acids, as well as toxic chemicals, including nerve toxins.

“It could enable next-generation wearable biosensors for first responders, health care personnel and military personnel,” de Puig added.