Viruses spread in a variety of media - from droplets and aerosols carried by air to being carried by water - and a new filter membrane shows promise in deactivating these pathogens.
Currently, filtration technologies have effectively removed viruses and other pathogens using nanoparticles or reverse osmosis methods. However, their effectiveness as a filter membrane is currently limited by their expensive costs and negative effect on the environment. One example is a nanofilter against viruses, which is made from petroleum-based raw materials. Meanwhile, reverse osmosis processes require an unusually large amount of energy, increasing the costs and carbon footprint involved.
A new design for a filter membrane, made from natural materials, is detailed in the report "An antiviral trap made of protein nanofibrils and iron oxyhydroxide nanoparticles." The new study appears in the latest Nature Nanotechnology.
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An Environmentally Friendly Filter Membrane
The filter membrane from the natural membrane is the result of an international collaborative effort led by Raffaele Mezzenga, ETH Zurich Professor of Food & Soft Materials. Together, their work resulted in the development of a water filter membrane that is both highly effective and environmentally friendly. Additionally, to create the new material, researchers used natural materials drawn from other raw items.
Its method of operation is similar to the same principle applied by Mezzenga and colleagues for removing heavy or precious metals that are present in water. The new filter membrane is drawn from denatured whey proteins - byproducts of milk processing - that are assembled into very small filaments known as amyloid fibrils. A previously released article in the journal Prion explains how amyloid fibrils are formed by otherwise soluble proteins but assembles to form insoluble fibers resistant to degradation.
In their study, the filter membrane is built from iron hydroxide nanoparticles. Researchers additionally claimed that the manufacturing process behind the new filter membrane is relatively simple. The whey proteins are mixed with acid and are heated to a temperature of 90 degrees Celsius, causing these proteins to connect with each other and form fibrils. The nanoparticles used are also formed in a similar process, raising the pH levels and adding iron salt. This causes the mixture to disintegrate into nanoparticles of iron hydroxide, which in turn connects to the amyloid fibrils. For their filter, researchers used cellulose to help support the membrane scaffold that forms the filter material.
Testing the New Filter Membrane
The new filter membrane, made from natural materials, works by having the positively charged iron oxide nanoparticle attract the negatively charged pathogens, canceling them out in the process. This is impossible with amyloid fibrils alone since the material is also intrinsically negatively charged. However, its structure makes for a perfect matrix to embed iron hydroxide nanoparticles.
Researchers tested the new material and discovered how it eliminates a number of water-borne viruses such as nonenveloped adenoviruses, enteroviruses, and retroviruses. Enteroviruses, according to the CDC, are particularly dangerous to humans as they cause gastrointestinal infections, especially in developing countries.
More importantly, the new filter membrane also works well in deactivating H1N1 flu viruses and even SARS-CoV-2, which causes COVID-19. In their filtered samples, researchers report having the viruses below the detection limit, which means that the new material almost completely eliminates the virus.
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