Using specialized carbon nanotubes,Engineers at MIT have designed a new type of sensor that can detect SARS-CoV-2 without any antibodies and give results within minutes. Researchers say that their new sensor is not only for Covid-19, but also for future pandemics.
Quick testing means you can open up travel earlier in future pandemics. You can screen people who got off the plane and determine if they should be quarantined. You can also screen people who enter the workplace. The diagnostic instrument is based on the carbon nanotube sensor technology previously developed by Stella Labs. Once the researchers started working on the Covid-19 sensor, it took them only 10 days to identify an improved carbon nanotube capable of selectively detecting viral proteins, then tested it and incorporated it into a working prototype. This method also eliminates the need for antibodies or other reagents, which are time-consuming to produce, purify, and widely use.
A few years ago, Strano Lab developed a new method to design sensors for various molecules. Their technology relies on carbon nanotubes, which are hollow, nanometer-thick cylinders made of carbon that naturally fluoresce when exposed to laser light. They have shown that by wrapping this tube in different polymers, they can create sensors that react by chemically identifying specific target molecules.
Their method, called Corona Phase Molecular Recognition (CoPhMoRe), takes advantage of a phenomenon that occurs when certain types of polymers are combined with nanoparticles. These molecules are called amphiphilic polymers. They have hydrophobic regions that lock to the tube like an anchor, and have hydrophilic regions that form a series of loops that extend from the tube. These rings form a layer called corona around the nanotubes. Different types of target molecules can be wedged into the space between cycles, and the combination of this target changes the intensity or peak wavelength of the fluorescence produced by the carbon nanotubes.
Researchers in the Strano Lab have developed strategies that allow them to predict which amphiphilic polymers will interact best with specific target molecules, so they can quickly generate a set for SARS-CoV-2 Of 11 strong candidate materials. In about 10 days after the start of the project, the researchers have identified accurate sensors for the nucleocapsid and spike protein of the SARS-CoV-2 virus. During that time, they were also able to incorporate the sensor into a prototype device with a fiber-optic tip that could detect changes in fluorescence in biological fluid samples in real time. This eliminates the need to send samples to the laboratory, which is required for the gold standard PCR diagnostic test for Covid-19.
The device produces results in about 5 minutes and can detect viral protein concentrations as low as 2.4 picograms per milliliter of sample. In more recent experiments done after this paper was submitted, the researchers achieved a lower detection limit than the rapid tests currently on the market. The researchers also showed that when SARS-CoV-2 nucleocapsid protein (but not spike protein) is dissolved in saliva, the device can detect it. Detection of viral proteins in saliva is often difficult because saliva contains sticky carbohydrates and digestive enzyme molecules that can interfere with protein detection, which is why most Covid-19 diagnoses require nasal swabs.