BACKGROUND

Healthcare-associated infections (HAIs) are serious public health issues, and environmental surfaces contaminated with microorganisms have been reported to play an important role in their occurrence. We focused on copper, which is known to have excellent antimicrobial activity, as a measure to prevent contamination of environmental surfaces. In hospital environments, copper has been used on handrails and doorknobs. However, its use has been limited because of its opaque nature. Therefore, we developed a thin, highly transparent copper film via the sputtering method. This study examines the antimicrobial activity of this transparent film to expand the potential applications of copper to commonly used surfaces in healthcare settings.

METHODS

Polyethylene terephthalate film was coated with a copper layer of four different thicknesses via the sputtering method. The antimicrobial activity of the copper film was evaluated according to the ISO22196:2011 standards. The antimicrobial activity and the change in the viable bacteria count with contact time between the test bacteria and the copper film surface were evaluated.

RESULTS

For all copper layer thicknesses, the bacterial count decreased exponentially after contact with the copper film. For Escherichia coli, the count decreased 100-fold after 10 min, and no viable bacteria were observed within 30 min. For Staphylococcus aureus, the count decreased 100-fold after 20 min, and no viable bacteria were observed within 50 min. In these two bacterial species, the antibacterial activity did not differ according to the thickness of the copper layer.

CONCLUSION

All copper films showed sufficient antimicrobial activity against Escherichia coli and Staphylococcus aureus regardless of the copper layer thickness. The thinnest 5 nm copper film with high transparency was considered most useful for medical applications because of its visibility. Further study is needed to determine whether this transparent copper film reduces microbial contamination on environmental surfaces and contributes to reducing HAIs in hospitals and healthcare facilities.