The oxidation state of Ag nanoparticles highly affects the release of Ag ions without compromising the mechanical performance and the safety of amorphous hydrogenated carbon coatings

• Published in: Diamond and related materials 2022-12, Vol.130, p.109430, Article 109430
• Main Authors: Bonilla-Gameros, Linda, Chevallier, Pascale, Copes, Francesco, Sarkissian, Andranik, Mantovani, Diego
• Format: Article
• Language: English
• Subjects: Amorphous hydrogenated carbon; Diamond-like carbon; Magnetron sputtering; Plasma-enhanced chemical vapor deposition; Silver; Silver oxide
• ISSN: 0925-9635; 1879-0062
• DOI: 10.1016/j.diamond.2022.109430

Antibacterial coatings play an important adjunct against hospital-acquired infections. More specifically, the use of silver nanoparticles (Ag NPs) incorporated on amorphous hydrogenated carbon (a-C:H) demonstrates a promising approach to reduce microbial contamination while maintaining excellent mechanical properties. However, their success as a long-term (e.g. years) antibacterial coating hinges on the control over Ag+ release. In this sense, if a continuous release is required, a driving force must exist to induce silver ionization. Thus, this research studies the influence of silver oxide (AgO) NPs in a-C:H film as a novel and a simple approach to activate the release of Ag+. Herein, Ag and AgO NPs were deposited on a-C:H films (with 2.8 and 2.5 at.% Ag, respectively) using low-pressure plasma. Their mechanical properties, release kinetics, and antibacterial activity were analyzed, with special attention to cell viability. Overall, a-C:H:Ag showed an increase in hardness, whereas a-C:H:AgO exhibited ameliorated mechanical properties with higher elastic deformation and wear resistance. Moreover, the coatings did not induce any cytotoxicity after 7 days. Regarding the release kinetics, a-C:H:Ag displayed a slow-release reaching a maximum of 22 μg/L, while a-C:H:AgO showed a fast continuous-release with a maximum of 148 μg/L. In this sense, a-C:H:AgO exhibited improved antibacterial activity in comparison with a-C:H:Ag. The use of AgO NPs in a-C:H film demonstrated to be a simple approach to activate the release of Ag+, without compromising the mechanical and the cytotoxic properties of the coating. These results highlight a new pathway towards coatings with lasting antibacterial and mechanical stability. [Display omitted] •Silver oxide nanoparticles of 17 nm do not alter the crystallinity of the coating.•The oxidation state of silver nanoparticles influences the release of silver ions.•Silver oxide enhances the mechanical properties of the amorphous carbon coating.•The modified coatings do not alter human dermal fibroblasts viability and behavior.•Low pressure plasma is shown as a versatile and reliable technique.