The microfluidic chip attaches to a potentiostat that then plugs into a phone (Picture: Jeff Fitlow/Rice University)

Engineers at Rice University in Texas have developed a small device that plugs into a standard smartphone to help detect Covid-19.

Roughly the size of a stamp, the gadget is a sensor able to measure the concentration of Covid-19 nucleocapsid proteins in the blood from a regular finger prick.

Using ‘programmable magnetic nanobeads’ which bind to the protein biomarker of the virus, the sensor is able to pick up and diagnose a coronavirus infection in under an hour.

The researchers behind the invention say their process simplifies sample handling compared to swab-based PCR tests that are widely used to diagnose Covid and need to be analysed in a lab.

‘What’s great about this device is that doesn’t require a laboratory,’ explained mechanical engineer Peter Lillehoj, who developed the chip.

‘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.’

The stamp-sized microfluidic chip measures the concentration of SARS-CoV-2 nucleocapsid protein in blood serum (Lillehoj Research Group)
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. (Lillehoj Research Group)
The beads bind to the capture antibodies and generate a current proportional to the concentration of biomarker in the sample. The potentiostat reads that current and sends a signal to its phone app (Lillehoj Research Group)

To test the device, the lab relied on donated serum samples from people who were healthy and others who were Covid-19 positive.

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 the SARS-CoV-2 N protein at concentrations as low as 50 picograms (billionths of a gram) per milliliter in whole serum.

If there are no Covid-19 biomarkers, the beads do not bind to the sensor and get washed away inside the chip.

It was paired with a Google Pixel 2 phone from 2017 and a plug-in potentiostat. The chip was able to deliver a positive diagnosis with a concentration as low as 230 picograms for whole serum.

Rice University mechanical engineer Peter Lillehoj, left, and graduate student Jiran Li invented the device that works with a standard smartphone. (Credit: Jeff Fitlow/Rice University)

‘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.’

The engineer said that it wouldn’t be difficult for industry to manufacture these microfluidic chips or to adapt them to new Covid-19 strains if it became necessary.

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