PARIS: Scientists develop chip to deliver COVID-19 test results on smartphone

PARIS: Scientists have developed a
stamp-sized chip that simplifies Covid-19 testing and delivers results on a smartphone
in less than 55 minutes.

The microfluidic chip developed by researchers from Rice University in the US
measures the concentration of SARS-CoV-2 nucleocapsid (N) protein, a biomarker
for Covid-19, in blood serum from a standard finger prick.

According to the research published in the journal ACS Sensors, the nanobeads
bind to SARS-CoV-2 N protein in the chip and transport it to an electrochemical
sensor that detects minute amounts of the biomarker.

The researchers noted that their process simplifies sample handling compared to
swab-based PCR tests that are widely used to diagnose Covid-19 and need to be
analysed in a laboratory.

“What’s great about this device is that it doesn’t require a
laboratory,” said Rice lab of mechanical engineer Peter Lillehoj.

“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,” he said in a statement.

The team, including Rice graduate student and lead author Jiran Li, took
advantage of existing biosensing tools to develop simple diagnostics, like a
microneedle patch introduced last year to diagnose malaria.

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 researchers relied on donated serum samples from people
who were healthy and others who were Covid-19-positive.

They said a longer incubation yields more accurate results when using whole
serum.

The team 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 millilitre 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.

Paired with a Google Pixel 2 phone and a plug-in potentiostat — a device that
controls voltage and measures resulting current — it was able to deliver a
positive diagnosis with a concentration as low as 230 picograms for whole
serum.

“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,” he added.

A capillary tube is used to deliver the sample to the chip, which is then
placed on a magnet that pulls the beads towards 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.
The potentiostat reads that current and sends a signal to its phone app.