RapidPlex aims for swift home COVID-19 tests

The spread of COVID-19 by people who are asymptomatic could be thwarted with RapidPlex, a home test that returns results in under 10 minutes.  

When attached to supporting electronics, the sensor can wirelessly transmit data to the user's cell phone through Bluetooth (Image: Caltech)

This is the aim of researchers at Caltech who have developed a multiplexed test with a low-cost sensor that rapidly analyses small volumes of blood or saliva.


The research was conducted in the lab of Wei Gao, assistant professor in the Andrew and Peggy Cherng department of medical engineering.

To make the sensors, a plastic sheet etched with a laser generates a 3D graphene structure with pores that create a large amount of surface area. This makes it sensitive enough to detect, with high accuracy, compounds that are only present in very small amounts. In this sensor, the graphene structures are coupled with antibodies, immune system molecules that are sensitive to specific proteins, like those on the surface of a COVID virus.

Previous versions of the sensor were impregnated with antibodies for the hormone cortisol, which is associated with stress, and uric acid, which at high concentrations causes gout. The new version of the sensor, which Gao has named SARS-CoV-2 RapidPlex, contains antibodies and proteins that allow it to detect the presence of the virus itself; antibodies created by the body to fight the virus; and chemical markers of inflammation, which indicate the severity of the COVID-19 infection.

"This is the only telemedicine platform I've seen that can give information about the infection in three types of data with a single sensor," Gao said in a statement. "In as little as a few minutes, we can simultaneously check these levels, so we get a full picture about the infection, including early infection, immunity, and severity."

Established COVID-testing technologies usually take hours or even days to produce results. Those technologies also require expensive, complicated equipment, whereas Gao's system is simple and compact.

The device has been tested in the lab with a small number of blood and saliva samples obtained from individuals who have tested positive or negative for COVID-19. Though preliminary results indicate that the sensor is highly accurate, a larger-scale test with real-world patients rather than laboratory samples must be performed, Gao cautioned, to definitively determine its accuracy.

Gao plans to test how long the sensors last with regular use, and to begin testing them with hospitalised COVID-19 patients. Following in-hospital testing, he would like to study the suitability of the tests for in-home use.

"Our ultimate aim really is home use," he said. "In the following year, we plan to mail them to high-risk individuals for at-home testing. And in the future, this platform could be modified for other types of infectious disease testing at home."

The paper describing the research, titled, "SARS-CoV-2 RapidPlex: A Graphene-based Multiplexed Telemedicine Platform for Rapid and Low-Cost COVID-19 Diagnosis and Monitoring," has been published online and will appear in the December issue of Matter.