Scientists have developed a new molecule that attaches to the surface of the SARS-CoV-2 virus and prevents it from entering human cells and spreading the COVID-19 infection.

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The researchers at Aarhus University in Denmark noted that the molecule is cheaper and easier to manufacture than the antibodies currently used to treat COVID-19, and to detect viral infection using rapid antigen tests. The molecule, described in the journal PNAS on 14 December, belongs to a class of compounds known as RNA aptamers and is based on the same type of building blocks that are used for mRNA vaccines.

An aptamer is a piece of genetic material DNA or RNA that folds into a three dimensional (3D) structure that can recognise a specific target molecule of interest. By attaching itself to the virus surface, the RNA aptamer prevents the spike protein from serving as a key that allows the virus to enter a cell, the researchers said.

The RNA aptamer is not a new type of vaccine but a compound that can potentially stop the virus from spreading in the body once someone is exposed to the virus, they said. The efficient binding to SARS-CoV-2 virus also means that the aptamer can be used to test for COVID-19 infection, according to the researchers.

"We have started testing the new aptamer in rapid tests and we expect to be able to detect very low concentrations of the virus," said study lead author Jorgen Kjems, a professor at Aarhus University. Studies in cell culture show that the aptamer works against the previous variants of coronavirus that the researchers tested.

"Since we submitted the article for peer review, we have continued our studies and been able to show that it also recognises the Delta variant," Kjems noted. "Now we are waiting for samples of the newly identified variant, Omicron, so we can test whether the aptamer also recognises that," he said.

Due to its small size and chemical stability, the newly developed aptamer holds potential as an alternative to antibodies and nanobodies targeting spike protein, the researchers added.