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Wireless Sensor Detects Multiple Covid-19 Indicators

RapidPlex sensor and circuits

RapidPlex sensor, in orange, and circuits (Caltech)

2 Oct. 2020. Biomedical engineers designed a lab-on-a-chip sensor that quickly detects SARS-CoV-2 viruses in saliva or blood, as well as antibodies and indicators of disease severity. The device, from the bioelectronics lab of California Institute of Technology professor Wei Gao, is described in yesterday’s issue of the journal Matter.

Gao and colleagues are seeking a portable device for fast point-of-care or home diagnostics of Covid-19 infections, but can also provide other important information about the status of the disease in the patient, such as the presence of antibodies to the virus and proteins indicating inflammation in the body from an infection. Gao’s lab studies bioelectronic devices, particularly materials and robotics for wearable systems providing real-time health monitoring. In November 2019, Science & Enterprise reported on wearable sensors developed by the lab to detect gout from sweat.

The researchers’ solution, called RapidPlex, is a microfluidics, or lab-on-a-chip device, with laser-cut graphene sensors. Graphene is very light, strong, chemically stable, and only one atom in thickness, arrayed in a hexagonal pattern. The material can conduct both heat and electricity, with many applications in electronics, energy, and health care. The lasers create tiny pores in the graphene that enable the sensor to require only a small quantity of specimen fluid, either saliva or blood serum.

The graphene sensors then are primed with proteins for detecting or measuring the relevant biological indicators. For detecting the SARS-CoV-2 virus itself, RapidPlex tests for the protein capsid or outer shell of the virus. To test for antibodies, the sensors measure immunoglobulin M and G, IgM and IgG, antibodies that appear in response to SARS-CoV-2 viruses. And to detect the severity of the disease, the sensors measure for the presence of c-reactive protein, made in the liver in response in inflammation, a characteristic response of the body to Covid-19 infections. The sensors then send their measures wirelessly over a Bluetooth link to an external reader, such as a smartphone app.

The Caltech team pilot-tested RapidPlex on blood and saliva samples from small numbers of patients hospitalized with Covid-19 infections, who were also tested with so-called gold-standard diagnostic methods, such as the RT-PCR test to detect SARS-CoV-2 viruses, and enzyme-linked immunosorbent assay or ELISA systems found in most licensed diagnostic labs that identify and measure the number of antigens in blood samples.

The researchers say RapidPlex returns results in about 10 minutes. The results show a high correlation between the RapidPlex findings and conventional test results. The strong correlations are found in all three test measures: SARS-CoV-2 virus detection, antibody measures, and inflammation biomarkers. And perhaps most encouraging, says the team, results for saliva samples match the findings for blood samples.

“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,” says Gao in a Caltech 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.”

The researchers plan to expand testing to larger numbers of Covid-19 patients, as well as assess the device’s durability for long-term use. “Our ultimate aim really is home use,” notes Gao. “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.”

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