A D V A N C E D M A T E R I A L S & P R O C E S S E S | J U L Y / A U G U S T 2 0 2 1 2 8 MEASURING VIRUS INFECTIVITY ON MATERIAL SURFACES Various methods are available to evaluate the behavior of viruses on material surfaces, an important area of research for determining how long a virus can live on an inanimate object, and learning how to design and develop advanced antiviral materials. Hideyuki Kanematsu* and Risa Kawai, National Institute of Technology (KOSEN), Suzuka College, Japan Dana M. Barry, Clarkson University and SUNY Canton, New York Eri Nakajima and Yasuo Imoto, Japan Textile Products Quality and Technology Center MATERIALS SCIENCE AND CORONAVIRUS SERIES According to statistics investigated by the National Institute of Tech- nology (KOSEN) in Japan, the country’s antibacterial materials market value was around $8 billion in 2019. This category includes both antiviral and antifungal materials. By the end of 2020, the market had doubled[1]. As the battle against COVID-19 continues, we have learned that viruses not only spread from human to human directly through breathing shared air, but also via the surfaces of products[2]. Viruses remain infective on material surfaces, yet the duration of infectivity varies depending on the specific material. BACTERIAL VERSUS VIRAL INFECTION Bacteria and viruses do not share the same mechanism for infection[3]. Most bacteria produce toxic substances (toxins and enzymes) that destroy cells in human bodies (Fig. 1). In contrast, viral infections use a different mechanism. Viruses are mainly composed of nucleic acids (DNA or RNA) and proteins. The nucleic acid is in the center and is usually surrounded by a sheath of proteins called a capsid. Many viruses belong to the simple structural group of noroviruses, which are most common during winter and often cause gastroenteritis. Other viruses have an envelope outside of the capsid, which is composed of double lipid layers. *Member of ASM International Sometimes the bar-type glycoproteins look like spikes on the surface of the envelope. COVID-19 and influenza A belong to this group (Fig. 2). In the case of viruses, they first attach to host cells. In fact, the driving force of the virus is the interaction between the protein components on its surface and a specific receptor on the host cells. After adsorption of the virus on host cells, parts or entire viruses enter the cells. Next, the nucleic acid of the virus is incorporated into the host cells. Reproduction of the nucleic acids begins, as well as the synthesis of proteins in the host cell. Finally, new viruses are born and released from the host cell. In this manner, viruses spread from human to human. In the case of inanimate materials, virus growth cannot occur because there are no receptors on thematerial to act as a host. In addition, the collapse of viral structures, deformation, and reactions with environmental components could decrease or end the infectivity of the virus as it sits on the material. Further, because the infectivity of the virus decreases at different rates depending on the substrate, the collapse or change Fig. 1 — Infection and microbes. Fig. 2 — Schematic of viral structures.
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