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A series of plasma-mediated coatings, containing silver nanoparticles embedded in an organosilicon or silica-like matrix, were deposited onto stainless steel and chemically characterized. Their anti-adhesive properties were evaluated in vitro towards Escherichia coli by performing shear-flow induced detachment experiments. Increasing the wall shear stress facilitated E. coli cell detachment, irrespective of the coating characteristics. When nanosilver was incorporated, cell detachment was lower, probably due to the affinity of the embedded silver for biological components of the cell wall. The presence of methyl groups in the matrix network could also promote enhanced hydrophobic interactions. Within the population fraction remaining attached to the coating under increasing shear flow, different association phenotypes were observed, viz. progressively lying flat, moving laterally, remaining tethered, or rotating by a single anchoring point, until alignment with the flow direction. This re-orientation phenotype and its relation with detachment were dependent of the coating. The effects of such heterogeneities should be more deeply explored.

Abstract: Composite thin films (∼170nm) containing silver nanoclusters embedded in an organosilicon matrix were deposited by PE-CVD onto stainless steel in order to prevent microbial adhesion. The process originality relies on a dual strategy combining silver sputtering and simultaneous plasma polymerization in argon–hexamethyldisiloxane (HMDSO) plasma, using an asymmetrical RF glow discharge. The metal content in the film was controlled by varying the HMDSO flow rate. Investigation of the physico-chemical properties of the obtained films was conducted by X-ray photoelectron spectroscopy and transmission FTIR spectroscopy. Plasma-mediated coatings were composed of C, O, Si and Ag which was predominantly under metallic form, as indicated by XPS analysis. The presence of Si–H, Si–O–Si, Si–(CH) n –Si and C–H groups was established by FTIR. The yeast Saccharomyces cerevisiae was selected as the model for eukaryotic microorganisms. The maximal anti-adhesive efficiency was achieved for the organosilicon matrix alone. When nanosilver was incorporated into the organic matrix, the efficiency was reduced, especially for high metal contents. Silver antimicrobial property was assumed to be related to Ag+ progressive release from the embedded nanoparticles into the surrounding medium. This release was confirmed by ICP-MS measurements. Moreover, silver-containing film antifungal activity was observed towards sessile cells. [Copyright &y& Elsevier]