Engineers designed a novel facemask that can diagnose the wearer with COVID-19 within about 90 minutes. The masks are embedded with tiny, disposable sensors that can be fitted into other face-masks and could also be adapted to detect other viruses.
The sensors are based on freeze-dried cellular machinery that the research team previously developed for use in paper diagnostics for viruses such as Ebola and Zika. In a new study, the team showed that the sensors could be incorporated into not only facemasks but also clothing such as labcoats, potentially offering a new way to monitor health care workers’ exposure to a variety of pathogens or other threats.
The team demonstrated the ability to freeze-dry a broad range of synthetic biology sensors to detect viral or bacterial nucleic acids as well as toxic chemicals including nerve toxins. The facemask sensors are designed so that they can 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.
The proteins and nucleic acids needed to create synthetic gene networks that react to specific target molecules could be embedded into paper. Another cell-free sensor system, known as SHERLOCK, is based on CRISPR enzymes and allows highly sensitive detection of nucleic acids.
These 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 color. The researchers began working on incorporating these sensors into textiles, with the goal of creating a labcoat for healthcare workers or others with potential exposure to pathogens.
First, the team 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. The best was a combination of polyester and other synthetic fibers. To make wearable sensors, the researchers embedded their freeze-dried components into a small section of this synthetic fabric, where they are surrounded by a ring of silicone elastomer. This compartmentalization 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 these 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 color change that can be seen with the naked eye or a fluorescent or luminescent signal that can be read with a handheld spectrometer. They also designed a wearable spectrometer that could be integrated into the fabric, where it can read the results and wirelessly transmit them to a mobile device.
To produce the diagnostic facemask, the team embedded freeze-dried SHERLOCK sensors into a paper mask. As with the wearable sensors, the freeze-dried components are 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.
The prototypes 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.