Implant Surface Modification with Silver Nanoparticles and Amorphous–Carbon Films

Objective: Microbial infection on implant surfaces has a strong influence on healing and long-term outcome. Prevention and control of biofilms can be achieved by reducing the initial bacterial adhesion on surfaces of modified metallic implants. Amorphous carbon (a-C) films have been studied as a surface modification for implant materials. These films could be applied to orthopedic and dental implants due to their biocompatibility, corrosion resistance, and antibacterial properties. In this work, we propose a modification of a-C films by inclusion of small percentages of silver nanoparticles (a-C:Ag) to prevent device-associated infections.

Method: The a-C:Ag films were deposited by dual co-sputtering using graphite and silver targets under an argon plasma, varying the power applied to the Ag target. Microstructure and composition of the a-C:Ag films was characterized by XRD, EDS, AFM, and SEM. Biocompatibility of a-C:Ag samples was evaluated using osteoblast-like cells (MG63). The anti-bacterial effect of the samples were tested at 24 hours by counting the number of colony forming units and the biofilm formation was observed by SEM and fluorescence microscopy during incubation periods of 1, 3 and 5 days using Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. 

Result: Biological tests showed that a-C:Ag films containing up to 6 at% Ag supported osteoblast proliferation and osteogenic local factor production, demonstrating that the biocompatability and osteoinduction properties of the surfaces were not modified by the addition of small percentages of silver. Bacteria attachment was reduced on a-C:Ag samples with Ag concentrations ranging from 0-10 at% in comparison to films without silver. 

Conclusion: The a-C:Ag films inhibit bacterial attachment and biofilm formation. In addition, a-C:Ag coatings support osteoblast maturation, demonstrating that they are suitable for use on biomedical devices.