Multi-doped diamond like-carbon coatings (DLC-Si/Ag) for biomedical applications fabricated using the modified chemical vapour deposition method

• RF PACVD method was modified in order to allow the incorporation of two dopants at the same time.
• The Si and Ag contents were varied in order to tailor the properties of DLC coatings.
• Ag contained in DLC-Si/Ag coatings creates chemical bonds with silicon and oxygen forming Si–O–Ag groups.
• Higher Ag concentration causes higher bactericidal activity.
• Higher Si content improves hardness and biocompatibility.

In this study the Si/Ag-incorporated DLC layers were deposited on titanium alloy (Ti6Al7Nb) using modified radio frequency plasma assisted chemical vapour deposition (RF PACVD) method and examined in terms of chemical, mechanical and biological properties. The modified RF PACVD method allows to dope carbon coatings with silicon and silver during one process and in one chamber. In order to determine the chemical composition, morphology and structure of the manufactured coatings the XPS, FTIR and Raman spectroscopy, as well as SEM observation and EDS analysis were performed. The obtained results were correlated with the biological response of the coatings. The viability of cells in contact with the examined surfaces was evaluated using LIVE/DEAD test and endothelial cells, while the bactericidal activity was assessed using Escherichia coli. The XPS results showed that the Si content in the films ranged from 1.65 at.% up to 2.94 at.%, while the Ag content was from 1.36 at.% up to 2.09 at.%. SEM observation and EDS analysis proved that with the increasing Ag content, the number of Ag conglomerates increases. FTIR analysis confirmed that the Ag contained in the deposited carbon films is not in metallic state and it creates chemical bonds with silicon and oxygen (Si–O–Ag groups). Mechanical properties were measured using nanoindentation technique. The growing concentration of Ag causes the decrease in the concentration of Si, what ultimately results in decreased hardness, higher bactericidal activity and lower biocompatibility. Results demonstrated that the DLC coating containing 2.94 at.% of Si and 1.36 at.% of Ag is optimal in terms of medical applications as an antibacterial coating.

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