Environmental surfaces are increasingly recognized as important sources of transmission of hospital-acquired infections. The use of antibacterial surface coatings may constitute an effective solution to reduce the spread of contamination in healthcare settings, provided that they exhibit sufficient stability and a long-term antibacterial effect. In this study, silver-incorporated diamondlike carbon films (Ag-DLC) were prepared in a continuous, single-step plasma process using a hybrid, inductively coupled plasma reactor combined with a very-low-frequency sputtering setup. The average Ag concentration in the films, ranging from 0 to 2.4 at. %, was controlled by varying the sputtering bias on the silver target. The authors found that the activity of Escherichia coli was reduced by 2.5 orders of magnitude, compared with the control surface, after a 4-h contact with a 2.4 at. % Ag-DLC coating. The coatings displayed slow release kinetics, with a total silver ion release in the sub-ppb range after 4 h in solution, as measured by graphite furnace-atomic absorption spectroscopy. This was confirmed by Kirby–Bauer diffusion tests, which showed limited diffusion of biocidal silver with a localized antibacterial effect. As a slow and continuous release is mandatory to ensure a lasting antibacterial effect, the newly developed Ag-DLC coatings appears as promising materials for environmental hospital surfaces.
This work was supported by grants from the Canadian Space Agency (CSA) and the Natural Sciences and Engineering Research Council of Canada (NSERC). MC acknowledges funding from a NSERC Vanier scholarship. The authors are grateful to the people at Plasmionique Inc., and especially to Andranik Sarkissian, for their participation, technical support and valuable discussions. The authors would also like to express our thanks to Pascale Chevallier and Vicky Dodier for skilled assistance with the XPS and GF-AAS experiments, respectively. The authors declare that there are no conflicts of interest. All authors read and approved the final manuscript.
B. Plasma deposition of thin film
C. X-ray photoelectron spectroscopy
D. Silver release analysis
E. Bacterial strain and culture preparation
F. Antibacterial activity test
G. Live/dead bacterial viability assay
H. Modified Kirby–Bauer diffusion test
III. RESULTS AND DISCUSSION
A. Chemical composition
B. Antibacterial activity evaluation
C. Release of silver ions from the coating
- Sputter deposition
- Plasma materials processing
- Surface cleaning
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