Scientists have developed a stamp-sized chip that simplifies the COVID-19 test, and delivers results on a smartphone in less than 55 minutes. The microfluidic chip developed by researchers from Rice University in the U.S. measures the nucleocapsid (N) protein density of SARS-CoV-2, a biomarker for COVID-19, in blood serum from a normal fingerprogram.
According to the research published in the journal ACS Sensors, the nanobeads bind to the SARS-CoV-2 N protein in the chip and transport it to an electrochemical sensor that detects small levels of the biomarker. The researchers noted that their process simplifies sample handling compared to swab-based PCR tests that are widely used for the detection of COVID-19 and need to be studied in work- blade.
“The great thing about this machine is that it doesn’t require a laboratory,” said Rice Laboratory, mechanical engineer Peter Lillehoj. “You can do all the testing and generate the results at the collection site, health clinic or even pharmacy. The whole system is easy to carry and easy to use,” he said in a statement. The team, which includes Rice graduate student and lead author Jiran Li, took advantage of existing biosensing tools to develop a simple diagnosis, such as a microneedle patch that was introduced into the last year to diagnose malaria.
The new tool relies on a slightly more complex search scheme but will provide accurate, quantitative results in a short time. To test the device, the researchers relied on serum samples provided from healthy people and others who were COVID-19-posthumous. They said that a longer product gives more accurate results when using whole serum. The team found that 55 min was the optimal time for the microchip to detect SARS-CoV-2 N proteins at concentrations as low as 50 picograms (billions of grams) per milliliter in whole serum.
The microchip was able to detect protein N in an even lower density, at 10 picograms per milliliter, in just 25 minutes by diluting the serum five times. Fixed with a Google Pixel 2 phone and potentiostat plug-in – a device that controls voltage and steps that flow out of the stream – it was able to deliver advanced diagnostics with a density as low as 230 picograms per serum whole. “There are standard methods to modify the beads with antibody targeted at a specific biomarker,” Lillehoj said.
“When you combine them with a sample that contains the biomarker, in this case SARS-CoV-2 N proteins, they bind together,” he said. A capillary tube is used to deliver the sample to the chip, which is then mounted on a magnet that draws the beads toward an electrochemical sensor with a coating of capturing antibodies. The beads bind to the capture antibodies and generate a current that is proportional to the biomarker density in the sample. The potentiostat reads that stream and sends a signal to its phone app. If COVID-19 biomarkers are not present, the beads will not connect to the sensor and will be washed away inside the chip.
