Just Add Water

The gold standard method for detecting the presence of viral particles is quantitative PCR (qPCR). But qPCR requires that a sample be sent off to a laboratory for testing, which delays the results of the test. These delays can be far more than just a mere inconvenience when trying to contain the outbreak of an infectious pathogen.

Charting a new path forward, a team of researchers from Harvard University and the Massachusetts Institute of Technology have essentially shrunk a state-of-the-art molecular testing facility into a tiny biosensor that can be incorporated into fabrics. The biosensors contain freeze-dried, cell-free (FDCF) synthetic circuits that detect metabolites, chemicals, and signatures of pathogenic nucleic acids.

FDCF circuits contain all the biochemical machinery required for transcription and translation of nucleic acids. Being freeze dried, they are shelf-stable and easily distributed. Engineered genetic circuits are encoded into DNA or RNA, and are mixed in with the biochemical machinery. The circuits can then be activated by simply adding water. Sensors can be engineered that present the results through color change or fluorescence.

To get these devices where they are most needed, the team designed fabrics with integrated biosensors that can be formed into articles of clothing. One particularly interesting sensor they designed was a CRISPR-based nucleic acid detector. CRISPR-based methods offer high sensitivity, rapid output, and single base-pair resolution in recognizing specific sequences of DNA and RNA.

A sensor such as this was created with the ability to recognize nucleic acid sequences specific to SARS-CoV-2. These sensors were then embedded within a face mask. The test can be activated by the push of a button and will analyze breath droplets that accumulate inside the mask. Results are reported within 90 minutes; results will be visible only from the inside of the mask for the privacy of the wearer. It is also possible to reconfigure the mask such that the sensors are on the outside rather than the inside; such an arrangement would be helpful in providing warnings about environmental conditions, rather than the health status of the wearer.

This research represents a significant leap forward in diagnostics. No wearable devices previously existed that were able to detect nucleic acids in fluid samples with sensitivities rivaling those seen in state-of-the-art laboratory tests.

The possible applications of FDCF circuits extend far beyond the detection of SARS-CoV-2. The sensors are capable of detecting influenza, Ebola, and Zika, for example. Work has already been completed that shows the potential of these circuits to detect organophosphate nerve agents as well. By incorporating these circuits into other articles of clothing, this research could enable a new generation of wearable sensors for first responders, health care personnel, and military personnel. The researchers have filed for a patent and intend to work to incorporate FDCF-based wearable sensors into commercial products.