Antimicrobial characterization of silver nanoparticle-coated surfaces by “touch test” method

Marianne Gunell,1,2 Janne Haapanen,3 Kofi J Brobbey,4 Jarkko J Saarinen,4 Martti Toivakka,4 Jyrki M Mäkelä,3 Pentti Huovinen,1 Erkki Eerola1,2 1Department of Medical Microbiology and Immunology, University of Turku, 2Department of Clinical Microbiology and Immunology, Microbiology and Genetics Service Area, Turku University Hospital, Turku, 3Aerosol Physics Laboratory, Department of Physics, Tampere University of Technology, Tampere, 4Laboratory of Paper Coating and Converting, Center for Functional Materials, Åbo Akademi University, Turku, Finland Abstract: Bacterial infections, especially by antimicrobial resistant (AMR) bacteria, are an increasing problem worldwide. AMR is especially a problem with health care-associated infections due to bacteria in hospital environments being easily transferred from patient to patient and from patient to environment, and thus, solutions to prevent bacterial transmission are needed. Hand washing is an effective tool for preventing bacterial infections, but other approaches such as nanoparticle-coated surfaces are also needed. In the current study, direct and indirect liquid flame spray (LFS) method was used to produce silver nanoparticle-coated surfaces. The antimicrobial properties of these nanoparticle surfaces were evaluated with the “touch test” method against Escherichia coli and Staphylococcus aureus. It was shown in this study that in glass samples one silver nanoparticle-coating cycle can inhibit E. coli growth, whereas at least two coating cycles were needed to inhibit S. aureus growth. Silver nanoparticle-coated polyethylene (PE) and PE terephthalate samples did not inhibit bacterial growth as effectively as glass samples: three nanoparticle-coating cycles were needed to inhibit E. coli growth, and more than 30 coating cycles were needed until S. aureus growth was inhibited. To conclude, with the LFS method, it is possible to produce nanostructured large-area antibacterial surfaces which show antibacterial effect against clinically relevant pathogens. Results indicate that the use of silver nanoparticle surfaces in hospital environments could prevent health care-associated infections in vivo. Keywords: silver, nanoparticle, E. coli, S. aureus, LFS, HAI&nbsp

Controlled time release and leaching of silver nanoparticles using a thin immobilizing layer of aluminum oxide

Silver nanoparticles are widely used as antibacterial agents in consumer products. There have been concerns about the environmental exposure and their toxic effect to organisms such as fish. Studies have quantified the release of silver from various products including textiles and plastics that use silver as an antibacterial agent, yet there is no unified standard for the measurement of silver release. Additionally, there is limited information about the release of silver from glass surfaces coated with silver nanoparticles. While immobilizing silver to substrates will ultimately reduce environmental exposure, deliberately controlling silver release will also reduce the amount of silver released into the environment. In this study, silver nanoparticles were synthesized and deposited onto glass using an aerosol pyrolysis process, i. e. the Liquid Flame Spray. The deposited silver nanoparticles were further coated with a thin layer of aluminum oxide that was fabricated by atomic layer deposition. The leaching of silver from the coated glass was measured in water over a period of six days. The results show that a 15 nm thin layer of aluminum oxide is able to inhibit the release of silver up to 48 h, thereby providing a way to control the release of silver in time