A team led by an Indian-born scientist has developed a rapid and ultra-sensitive test for Covid-19 using a paper electrochemical sensor that can detect the presence of the new coronavirus in less than five minutes.
Researchers at the University of Illinois in the US created a graphene-based electrochemical biosensor with an electrical readout setup to selectively detect the presence of SARS-CoV-2 genetic material.
According to research published in the journal ACS Nano, this biosensor has two components: a platform to measure an electrical reading and probes to detect the presence of viral RNA.
To create the platform, the researchers led by Professor Dipanjan Pan first coated filter paper with a layer of graphene nanoplates to create a conductive film.
They then placed a gold electrode with a predefined pattern on the graphene as a contact pad for electrical reading.
Both gold and graphene have high sensitivity and conductivity, making this platform ultrasensitive for detecting changes in electrical signals, the researchers noted.
“Graphene exhibits unique mechanical and electrochemical properties that make it ideal for developing sensitive electrochemical sensors,” said Maha Alafeef, a graduate student at the University of Illinois Grainger College of Engineering.
Current RNA-based Covid-19 tests detect the presence of the N (nucleocapsid phosphoprotein) gene in the SARS-CoV-2 virus, they said.
In the new research, the team designed antisense oligonucleotide (ASO) probes to target two regions of the N gene.
Targeting two regions ensures sensor reliability should one region suffer a genetic mutation, according to the researchers.
Gold nanoparticles (AuNP) are coated with these single-stranded nucleic acids (ssDNA), which represent an ultrasensitive detection probe for SARS-CoV-2 RNA.
The team tested the performance of this sensor using positive and negative Covid-19 samples.
The sensor showed a significant increase in the voltage of the positive samples compared to the negative ones and confirmed the presence of viral genetic material in less than five minutes.
The sensor was able to differentiate the viral RNA loads in these samples. Viral load is an important quantitative indicator of the progress of infection and a challenge to measure using existing diagnostic methods.
The researchers noted that this platform has powerful applications due to its portability and low cost.
The sensor, when integrated with microcontrollers and LED displays or with a smartphone via Bluetooth or Wi-Fi, could be used at the point of care in a doctor’s office or even at home, they said.
Beyond Covid-19, the research team also envision the system to be adaptable for the detection of many different diseases.
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