A facemask that can diagnose if its wearer has Covid-19 within about 90 minutes has been developed in the USA. It is embedded with tiny, disposable sensors that can be fitted into other facemasks and could also be adapted to detect other viruses.

The sensors are based on freeze-dried cellular machinery that researchers from MIT and Harvard University have previously developed for use in diagnostics for viruses such as Ebola and Zika. In a new study, the researchers have shown that the sensors could be incorporated into not only facemasks but also clothing such as lab coats, potentially offering a new way to monitor health care workers’ exposure to a variety of pathogens or other threats.

“We’ve demonstrated that we 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,” said Professor James Collins of the MIT’s Institute for Medical Engineering and Science (IMES) and Department of Biological Engineering. “We envisage that this platform could enable next-generation wearable biosensors for first responders, health care personnel and the military personnel.”

The facemask sensors are designed to be activated by the wearer when they’re ready to perform the test, and the results are only displayed on the inside of the mask, for user privacy.

Stable components

The cell-free circuit components are freeze-dried and remain stable for many months until they are rehydrated. When activated by water, they can interact with their target molecule, which can be any RNA or DNA sequence, as well as other types of molecules, and produce a signal such as a change in colour.

More recently, Collins and his colleagues began working on incorporating the sensors into textiles, with the goal of creating a lab coat.

Luis Soenksen at MIT’s Abdul Latif Jameel Clinic for Machine Learning in Health performed a screen of hundreds of different types of fabric, from cotton and polyester to wool and silk, to find out which might be compatible with this kind of sensor.

“We ended up identifying a couple that are very widely used in the fashion industry for making garments,” he said. “The one that was the best was a combination of polyester and other synthetic fibres.”

To make wearable sensors, the researchers embedded their freeze-dried components into a small section of this synthetic fabric, surrounding them with a ring of silicone elastomer. This compartmentalisation prevents the sample from evaporating or diffusing away from the sensor. To demonstrate the technology, the researchers created a jacket embedded with about 30 of the sensors.

They showed that a small splash of liquid containing viral particles, mimicking exposure to an infected patient, can hydrate the freeze-dried cell components and activate the sensor. The sensors can be designed to produce different types of signals, including a colour change that can be seen with the naked eye, or a fluorescent or luminescent signal, which can be read with a handheld spectrometer.

Spectrometer

A wearable spectrometer that can be integrated into the fabric, where it can read the results and wirelessly transmit them to a mobile device has also been developed.

“This gives you an information feedback cycle that can monitor your environmental exposure and alert you and others about the exposure and where it happened,” Collins said.

As the researchers were finishing up their work on the wearable sensors early in 2020, Covid-19 began spreading around the globe, so they quickly decided to try using their technology to create a diagnostic for the SARS-CoV-2 virus.

To produce their diagnostic facemask, the researchers embedded freeze-dried Sherlock sensors into a paper mask. As with the wearable sensors, the freeze-dried components were surrounded by silicone elastomer. In this case, the sensors are placed on the inside of the mask, so they can detect viral particles in the breath of the person wearing the mask.

The mask also includes a small reservoir of water that is released at the push of a button when the wearer is ready to perform the test. This hydrates the freeze-dried components of the SARS-CoV-2 sensor, which analyzes accumulated breath droplets on the inside of the mask and produces a result within 90 minutes.

Gold standard

“This test is as sensitive as the gold standard, highly sensitive PCR tests, but it’s as fast as the antigen tests that are used for quick analysis of Covid-19,” Collins said.

The prototypes developed have sensors on the inside of the mask to detect a user’s status, as well as sensors placed on the outside of garments, to detect exposure from the environment. The researchers can also swap in sensors for other pathogens, including influenza, Ebola, and Zika, or sensors they have developed to detect organophosphate nerve agents.

The researchers have filed for a patent on the technology and they are now hoping to work with a company to further develop them.

“I think the facemask is probably the most advanced and the closest to a product,” Collins said. “We have already had a lot of interest from outside groups that would like to take the prototype efforts we have and advance them to an approved, marketed product.”

www.mit.edu

www.harvard.edu