key: cord-0836069-uigo9dxd
authors: Matsushima, Asako; Shibata, Shinichiro; Ohara, Hirotaka
title: Novel transparent copper film with antibacterial activity for environmental infection control
date: 2020-07-14
journal: Acute Med Surg
DOI: 10.1002/ams2.543
sha: 5c4324af4e106b9b94a4afc41a235166cea2a2a6
doc_id: 836069
cord_uid: uigo9dxd

nan

Dear Editor, The wide distribution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the air and object surfaces in hospital wards, which indicates a potential risk of nosocomial infection for medical staff and other close contacts, was reported from Wuhan, China. 1 In another report, van Doremalen et al. 2 showed that SARS-CoV-2 was not detectable on copper after 4 h, although it was stable and viable on plastic and stainless steel up to 72 h. Their results indicated that some metals, such as copper, could become an antiviral material to protect against environmental contamination from SARS-CoV-2.

We recently developed a novel transparent copper film using a spattering method (patent applied for; cooperative research with UACJ Corporation, Tokyo, Japan). According to the International Organization for Standardization (ISO) rules (available on line at the ISO website 3 ), we proved the antibacterial effect of this new film against Staphylococcus aureus and Escherichia coli. The strains used in this study were S. aureus (ATCC6538P) and E. coli (ATCC8739). We incubated the copper film with S. aureus or E. coli at 37°C and more than 90% relative humidity.

We examined two experimental conditions for copper film coatings (0 and 5 nm), with 0 nm being the control. All experimental measurements are reported as means across three replicates. With the 5-nm copper film, the bacterial colonies of S. aureus were exponentially reduced, and no viable bacteria were found after 50 min (Fig. 1A) . The colonies of E. coli diminished even more quickly, and no colonies were present after 30 min (Fig. 1B) . For the colonies of both bacterial species, no reduction in count was found on the 0-nm film.

The antimicrobial effect of soluble micro metal was first revealed 100 years ago. The antimicrobial effect of silver is the most well known in the medical field and is present in creams containing Ag + or medical equipment coated with Ag + . Copper, which has an antimicrobial effect more than 100 times stronger than that of silver, has been used in water pipes and as an industrial material, but it is not yet well known in the medical field. Recently, the strong antimicrobial effect of copper against methicillin-resistant S. aureus, multidrug-resistant Pseudomonas aeruginosa, and E. coli was revealed, which indicated the strong potential of copper for infection control including that of antimicrobial-resistant bacteria in the medical field. 4 Antiviral effect of copper was reported in norovirus, influenza virus, and SARS-CoV-2. 2,5 Infection control of these viruses with copper products is also expected in the future. However, copper itself is not transparent, which has made its antimicrobial effect difficult to introduce in the medical field. The novel transparent copper film reported here can be used as a face shield, partition, keyboard cover, or control panel cover on medical equipment without disturbing its operation. Although we have not examined its antiviral effect yet, we think this novel film could help to prevent nosocomial infection not only in hospitals but also nursing homes and nursery schools in which environmental contamination could easily cause a disease outbreak.

Aerosol and surface distribution of severe acute respiratory syndrome coronavirus 2 in hospital wards

Aerosol and surface stability of SARS-CoV-2 as compared with SARS-CoV-1

Measurement of antibacterial activity on plastics and other non-porous surfaces. Geneva: International Organization for Standardization

Antimicrobial activity of copper alloys against invasive multidrug-resistant nosocomial pathogens

Comparison of the antiviral effect of solid-state copper and silver compounds