‘Nanosponges’ act as a decoy for the new coronavirus

A new study has found that nanosponges — tiny, bio-friendly plastics coated in lung and immune cell membranes — act as a decoy for SARS-CoV-2, neutralizing the virus.

A team of scientists has found that a new technology is effective at distracting and neutralizing SARS-CoV-2 in a laboratory setting.

The research, published in the journal Nano Letters, has implications not only for treating SARS-CoV-2 but also for other virulent viruses, such as influenza, Ebola, Marburg, and Lassa viruses.

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COVID-19 therapies

As the initial wave of the COVID-19 pandemic eases in some countries, attention is turning to therapies that may be of use in slowing the spread of the virus, reducing the risk of infection or saving the lives of people in intensive care.

In the absence of a vaccine — which could not be available for years, if at all — treatments and therapies that help reduce the negative effects of the pandemic are crucial.

In this context, lab results from researchers at Boston University’s National Emerging Infectious Diseases Laboratories (NEIDL) and the University of California, San Diego seem promising.

The researchers have made use of new technology to see whether SARS-CoV-2 can be drawn to nanoparticles that neutralize the virus.

Prof. Anna Honko, a NEIDL microbiologist and co-first author of the study, comments on the findings.

“I was skeptical at the beginning because it seemed too good to be true. But when I saw the first set of results in the lab, I was just astonished.”

– Prof. Anna Honko

Decoy polymers

The technology works by creating microscopic, bio-friendly polymers, which are then coated in cells from living lung tissue or the immune system.

“It looks like a nanoparticle coated in pieces of cell membrane,” says Prof. Honko. “The small polymer [droplet] mimics a cell having a membrane around it.”

SARS-CoV-2 is attracted to lung cell membranes. After attaching to the outside of the cell, the virus gains entry and uses the cell’s internal machinery to replicate itself. These new virus particles then exit the cell to continue the cycle of spreading and multiplying.

However, the researchers found that the polymers coated in lung cells did a better job of attracting the virus than the lung cells themselves.

According to Prof. Anthony Griffiths, a NEIDL microbiologist and co-corresponding author of the study, “Our guess is that it acts like a decoy, it competes with cells for the virus.”

“They are little bits of plastic, just containing the outer pieces of cells with none of the internal cellular machinery contained inside living cells. Conceptually, it’s such a simple idea. It mops up the virus like a sponge.”

As a consequence, the researchers have named the polymers “nanosponges.”

Once SARS-CoV-2 attaches to the nanosponges rather than lung cells, the virus quickly dies.

The researchers believe that if nanosponges were administered to the body, the immune system would clear away the dead cell debris, which is one of its key jobs.

Inflammation

As well as distracting and neutralizing SARS-CoV-2, the nanosponges were effective at reducing inflammation, the researchers found.

This is important, as the rapid spread of inflammation is central to severe cases of COVID-19 and can be a key factor in death from the illness.

Nanosponges covered in immune cells, the team discovered, “soak up” signals that increase inflammation.

For this reason, a combination of nanosponges — some covered in lung cells, some in immune cells — could both neutralize SARS-CoV-2 and treat the body’s reaction to COVID-19.

Next steps

Profs. Honko and Griffiths now intend to treat animals infected with a coronavirus using their new method, working closely with colleagues at the University of California, San Diego, who originally developed the technology. Their aim is to create a treatment that is safe and effective for humans.

According to Prof. Liangfang Zhang, a nanoengineer and leader of the California-based team, “Traditionally, drug developers for infectious diseases dive deep on the details of the pathogen in order to find druggable targets.”

“Our approach is different. We only need to know what the target cells are. And then, we aim to protect the targets by creating biomimetic decoys.”

After the emergence of SARS-CoV-2, Prof. Zhang realized that his technology could play a role in treating the disease. He reached out to NEIDL for help with implementing the technology in response to the pandemic.

The researchers believe that it should be possible to create nanosponges that can be implemented in humans. According to Prof. Griffiths, “We should be able to drop it right into the nose. In humans, it could be something like a nasal spray.”

“That would be an easy and safe administration method that should target the appropriate [respiratory] tissues,” agrees Prof. Honko. “And if you wanted to treat patients that are already intubated, you could deliver it straight into the lung.”

The treatment could also be repurposed to treat other viruses that are resistant to conventional treatments, or for which no effective vaccine has been found.

By changing the type of cell membranes covering the polymers, other viruses could be attracted to these, rather than human cells.

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