Silver-Containing Titanium Dioxide Nanocapsules for Combating Multidrug-Resistant Bacteria

Background
Joint arthroplasty has improved the quality of life of patients worldwide, but infections of the prosthesis are frequent and cause significant morbidity. Antimicrobial coatings for implants promise to prevent these infections.Methods
We have synthesized nanocapsules of titanium dioxide in amorphous or anatase form containing silver as antibacterial agent and tested their impact on bacterial growth. Furthermore, we explored the possible effect of the nanocapsules on the immune system. First, we studied their uptake into macrophages using a combination of electron microscopy and energy-dispersive spectroscopy. Second, we exposed immune cells to the nanocapsules and checked their activation state by flow cytometry and enzyme-linked immunosorbent assay.Results
Silver-containing titanium dioxide nanocapsules show strong antimicrobial activity against both E. coli and S. aureus and even against a multidrug-resistant strain of S. aureus. We could demonstrate the presence of the nanocapsules in macrophages, but, importantly, the nanocapsules did not affect cell viability and did not activate proinflammatory responses at doses up to 20 μg/mL.Conclusion
Our bactericidal silver-containing titanium dioxide nanocapsules fulfill important prerequisites for biomedical use and represent a promising material for the coating of artificial implants.