The antiviral potential of polymers

Polymers formed when smaller molecules link together could open new avenues in the fight against coronaviruses.

As the Covid-19 pandemic sweeps the globe, researchers are striving to find new ways to fight the coronavirus responsible for the infection. The major approaches are vaccines to stimulate immunity and small molecule antiviral drugs. However, larger molecules called polymers might also play an important role. Researchers in China, Singapore and Australia review research into using polymers to combat coronaviruses, including that responsible for Covid-19, in the journal Materials Today Advances.

“We wanted to provide antivirus researchers with new ideas, having found there were no reviews of the significant potential of polymers to assist the fight against coronaviruses,” says corresponding author Xian Jun Loh of the A*STAR Institute of Materials Research and Engineering in Singapore.

Polymers get their generic name from the Greek poly meros, meaning many parts. There are a huge variety of types, but all are large molecules formed when many smaller subunits called monomers become chemically bonded together. They are often long, chain-like molecules, but can also become branched, cross-linked or folded into compact globular structures. DNA, RNA and proteins are natural polymers, while most plastics and synthetic fibres are composed of manufactured polymers.

“Recently, many rationally designed biocompatible and biodegradable polymers, suitable for large-scale manufacture, have been developed that will hopefully to contribute to novel antiviral therapeutic approaches against coronavirus infection,” says Loh.

The authors consider that the most straightforward applications for polymers involve their incorporation into personal protective equipment (PPE), such as face masks, gloves and gowns. They describe how everyday polymers such as polypropylene, used to make plastic bottles, can be specially processed into non-woven fabrics that form a much more effective barrier to virus-laden droplets than woven cotton, polyester, nylon or silk.

They also discuss a variety of polymers that can bind to the surface of virus particles to interfere with the interactions between viruses and cells of the body. This could prevent viruses from attaching to and entering cells, which they must do in order to hijack the host cell and divert it into producing more virus particles. The authors see considerable promise in polyelectrolytes – polymers studded with electrically charged groups that allow them to be attracted to, and bind to, crucial viral proteins.

Polymers also hold potential for acting as vehicles that can transport drugs or drug precursors. Loh and colleagues suggest this could aid the delivery of drugs to the correct target tissues, and perhaps control the steady release of antiviral drugs to improve their effectiveness.

The active components of vaccines, or the materials called adjuvants that make vaccines more effective, might also be delivered by polymer-based carrier systems. The authors review research into several synthetic and natural polymers that show potential to form water-soluble nanocapsules to contain the active ingredients of vaccines. They explain that using biocompatible, biodegradable polymers that do not themselves provoke any undesired immune responses could offer significant advantages. One hope is that they might allow vaccines that must currently be injected to be delivered by the simpler, and perhaps safer, intranasal route.

The possibilities considered are largely in the early stage of laboratory research, but Loh and his colleagues hope the insights they summarise will help the potential being demonstrated in principle to make the transition into clinical practice.

Article details: Jiang, X. et al.: “Toward the prevention of coronavirus infection: what role can polymers play?Materials Today Advances (2021).