Feb 25, 2021 |
Chip simplifies COVID-19 testing, delivers results on a phone
(Nanowerk News) COVID-19 can be diagnosed in 55 minutes or less with the help of programmed magnetic nanobeads and a diagnostic tool that plugs into an off-the-shelf cell phone, according to Rice University engineers. |
The Rice lab of mechanical engineer Peter Lillehoj has developed a stamp-sized microfluidic chip that measures the concentration of SARS-CoV-2 nucleocapsid (N) protein in blood serum from a standard finger prick. The nanobeads bind to SARS-CoV-2 N protein, a biomarker for COVID-19, in the chip and transport it to an electrochemical sensor that detects minute amounts of the biomarker.
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The researchers argued their process simplifies sample handling compared to swab-based PCR tests that are widely used to diagnose COVID-19 and need to be analyzed in a laboratory.
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“What’s great about this device is that doesn’t require a laboratory,” Lillehoj said. “You can perform the entire test and generate the results at the collection site, health clinic or even a pharmacy. The entire system is easily transportable and easy to use.”
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Programmed magnetic nanobeads paired with an off-the-shelf cellphone and plug-in diagnostic tool can diagnose COVID-19 in 55 minutes or less, according to Rice University engineers. (Image: Jeff Fitlow/Rice University)
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The research appears in the American Chemical Society journal ACS Sensors ("Microfluidic Magneto Immunosensor for Rapid, High Sensitivity Measurements of SARS-CoV-2 Nucleocapsid Protein in Serum").
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Lillehoj and Rice graduate student and lead author Jiran Li took advantage of existing biosensing tools and combined them with their own experience in developing simple diagnostics, like a microneedle patch introduced last year to diagnose malaria.
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The new tool relies on a slightly more complex detection scheme but delivers accurate, quantitative results in a short amount of time. To test the device, the lab relied on donated serum samples from people who were healthy and others who were COVID-19-positive.
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Lillehoj said a longer incubation yields more accurate results when using whole serum. The lab found that 55 minutes was an optimum amount of time for the microchip to sense SARS-CoV-2 N protein at concentrations as low as 50 picograms (billionths of a gram) per milliliter in whole serum. The microchip could detect N protein in even lower concentrations, at 10 picograms per milliliter, in only 25 minutes by diluting the serum fivefold.
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Paired with a Google Pixel 2 phone and a plug-in potentiostat, it was able to deliver a positive diagnosis with a concentration as low as 230 picograms for whole serum.
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“There are standard procedures to modify the beads with an antibody that targets a particular biomarker,” Lillehoj said. “When you combine them with a sample containing the biomarker, in this case SARS-CoV-2 N protein, they bond together.”
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A system developed by Rice University engineers employs a stamp-sized microfluidic chip that measures the concentration of SARS-CoV-2 nucleocapsid protein in blood serum to diagnose COVID-19 in less than an hour. The system uses an off-the-shelf cellphone and potentiostat to deliver the results. (Illustration by the Lillehoj Research Group)
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A capillary tube is used to deliver the sample to the chip, which is then placed on a magnet that pulls the beads toward an electrochemical sensor coated with capture antibodies. The beads bind to the capture antibodies and generate a current proportional to the concentration of biomarker in the sample.
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The potentiostat reads that current and sends a signal to its phone app. If there are no COVID-19 biomarkers, the beads do not bind to the sensor and get washed away inside the chip.
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Lillehoj said it would not be difficult for industry to manufacture the microfluidic chips or to adapt them to new COVID-19 strains if and when that becomes necessary.
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