Washington: A team led by scientists from India developed a fast and highly sensitive COVID-19 test using paper-based electrochemical sensors that can detect the presence of the novel coronavirus in less than five minutes. Researchers at the University of Illinois, USA, created a graphene-based electrochemical biosensor with an electrical readout setup to selectively detect the presence of SARS-CoV-2 genetic material.
According to a study published in the journal ACS Nano, this biosensor has two components: a platform to measure electrical readings and a probe to detect the presence of viral RNA. To create this platform, researchers led by Professor Dipanjan Pan first coated a filter paper with a layer of graphene nanoplatelets to create a conductive film.
Then, a gold electrode of a predefined design was placed over the graphene as a contact pad for electrical readings. Both gold and graphene have high sensitivity and conductivity, making this platform very sensitive to detecting changes in electrical signals, the researchers pointed out.
“Graphene exhibits unique mechanical and electrochemical properties that are ideal for the development of sensitive electrochemical sensors,” said Maha Alafeef, graduate student at the University of Illinois Grainger Institute of Technology.
Current RNA-based COVID-19 tests test the presence of the N-gene (a protein that is a nucleocapsid) in the SARS-CoV-2 virus, they said.
In a new study, the team designed an antisense oligonucleotide (ASO) probe that targets two regions of the N-gene. Targeting both regions, according to the researchers, ensures the reliability of the sensor if one region undergoes a genetic mutation.
Gold nanoparticles (AuNPs) are covered with these single-stranded nucleic acids (ssDNA) representing ultra-sensitive sensing probes for SARS-CoV-2 RNA. The team tested the performance of this sensor using COVID-19 positive and negative samples.
The sensor showed a significant increase in voltage in the positive sample compared to the negative sample and confirmed the presence of viral genetic material within 5 minutes.
The sensor was able to differentiate the viral RNA load in these samples. Viral load is an important quantitative indicator of infection progression and is difficult to measure using conventional diagnostic methods. Researchers pointed out that this platform has a wide range of applications due to its portability and low cost.
When the sensor is integrated with a microcontroller and LED screen, or when integrated with a smartphone via Bluetooth or Wi-Fi, it can be used in the doctor’s office or even in the clinic at home, they said.
In addition to COVID-19, the research team expects this system to be adaptable to detect a variety of diseases.