Scientists use 'nanosponges' to soak up, neutralise coronavirus in lab study

Ultrasmall sponge-like particles covered by human lung and immune cell membranes can attract, soak up, and neutralise the novel coronavirus, says a lab study that may lead to new therapies for COVID-19.

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According to the research, published in the journal Nano Letters, these "nanosponges," which are thousand times smaller than the width of a single human hair, are named so as they soak up harmful pathogens and toxins.

These particles were developed by engineers, including those from the University of California (UC) San Diego in the US, for their ability to prevent the novel coronavirus, SARS-CoV-2, from hijacking host cells.

Following incubation with the nanosponges, the researchers said, "SARS-CoV-2 is neutralized and unable to infect cells."

In experiments performed on lab-grown cells, they said nanosponges built with lung and immune cell membranes caused SARS-CoV-2 to lose nearly 90 per cent of its "viral infectivity" in a dose-dependent manner.

Viral infectivity, the scientists explained, is a measure of the ability of a virus to enter the host cell and exploit its resources to replicate and produce additional infectious copies of itself.

"Traditionally, drug developers for infectious diseases dive deep on the details of the pathogen in order to find druggable targets. Our approach is different," said study co-author Liangfang Zhang, a nanoengineering professor at the UC San Diego.

"We only need to know what the target cells are. And then we aim to protect the targets by creating biomimetic decoys," Zhang said.

The scientists explained that instead of targeting the virus itself, the nanosponges are designed to protect the healthy cells which the virus invades.

They said the nanosponges when engineered with fragments of the outer membranes of the human immune system's macrophage cells can also soak up inflammatory cell-cell signalling proteins called cytokines.

According to the scientists, the cytokines, which are sometimes overdriven by immune response to the infection, are implicated in some of the most dangerous, and sometimes deadly, aspects of COVID-19.

Describing the structure of the nanosponges, the researchers said they consist of a polymer core coated in membranes extracted from either the cells lining the lung's outer layer, or the immune system's macrophages.

They said these membranes cover the sponges with all the same protein receptors as the cells they impersonate, adding that this includes whatever receptors the novel coronavirus uses to enter cells in the human body.

In the research, the scientists prepared several different concentrations of nanosponges in solution to test against SARS-CoV-2.

They then tested the ability of various concentrations of each nanosponge type to reduce the infectivity of the virus behind the COVID-19 pandemic.

The researchers found that at a concentration of five milligrammes per milliliter (mg/mL), the lung cell membrane-cloaked sponges inhibited 93 per cent of the viral infectivity of SARS-CoV-2.

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According to the study, the macrophage-cloaked sponges inhibited 88 per cent of the viral infectivity.

"From the perspective of an immunologist and virologist, the nanosponge platform was immediately appealing as a potential antiviral because of its ability to work against viruses of any kind," said Anna Honko, study co-author from Boston University.

"This means that as opposed to a drug or antibody that might very specifically block SARS-CoV-2 infection or replication, these cell membrane nanosponges might function in a more holistic manner in treating a broad spectrum of viral infectious diseases," Honko explained.

In the next few months, the scientists plan to test the effectiveness of the nanosponges in neutralising the novel coronavirus in animal models.

"Another interesting aspect of our approach is that even as SARS-CoV-2 mutates, as long as the virus can still invade the cells we are mimicking, our nanosponge approach should still work," Zhang said.

"I'm not sure this can be said for some of the vaccines and therapeutics that are currently being developed," he added.