Biocompatibility evaluation of antibacterial Ti-Ag alloys with nanotubular coatings.

BACKGROUND: Implant-related infection is a major problem postsurgery. As an alternative to a localized antibiotic release system, we used Ag to fabricate Ti-Ag alloys with nanotubular coatings (TiAg-NTs). Ag has excellent antibacterial properties, but its biological toxicity is a concern. Therefore, we performed biological experiments both in vitro and in vivo to evaluate the biocompatibility of TiAg-NTs with different concentrations of Ag (1%, 2%, and 4%). METHODS: For in vitro experiments, cytocompatibility, including cell attachment, viability, and proliferation, was tested, and genes and proteins related to osteogenic differentiation were also evaluated. For in vivo assays, the rat femoral condylar insertion model was used, and micro-computed tomography (micro-CT) and histological analysis were conducted to analyze bone formation around implants at 1, 2, and 4 weeks after surgery. RESULTS: Both in vitro and in vivo results indicate that Ti2%Ag-NT showed comparable cytocompatibility with commercially pure Ti (cp-Ti), and it could achieve good osseointegration with the surrounding bone tissue. CONCLUSION: We thus believe that Ti2%Ag-NT is a potential biomaterial for orthopedics.

Antibacterial activities and biocompatibilities of Ti-Ag alloys prepared by spark plasma sintering and acid etching.

In this work, Ti-Ag sintered alloys (Ti-Ag) with different Ag contents were prepared by a spark plasma sintering (SPS) technique, which is a new, efficient and convenient method of powder metallurgy. The Ti-Ag samples were then treated with a mixture of 40 wt% hydrofluoric acid (HF) and nitric acid (HNO3). The surface features, ion release, antibacterial activities and biocompatibilities of the acid-etched Ti-Ag (Ti-Ag(AE)) samples were systematically characterized. The surface characterization results revealed the formation of micropits and particles with high Ag contents. Antibacterial experiments demonstrated that the antibacterial ratios of the Ti-Ag samples increased significantly after the acid etching treatment, and the particles with high Ag contents are thought to play a key role in the antibacterial mechanism. Biocompatibility experiments indicated that the cell proliferation, cell morphology, and osteoblastic differentiation did not significantly differ between the pure titanium (cp-Ti) and Ti-Ag(AE) samples. The Ti-Ag(AE) samples with 3 wt% and 5 wt% Ag not only possessed sustained antibacterial activities for at least 30 days but also did not have impaired biocompatibility.

Antibacterial abilities and biocompatibilities of Ti-Ag alloys with nanotubular coatings.

PURPOSE: To endow implants with both short- and long-term antibacterial activities without impairing their biocompatibility, novel Ti-Ag alloy substrates with different proportions of Ag (1, 2, and 4 wt% Ag) were generated with nanotubular coverings (TiAg-NT). METHODS: Unlike commercial pure Ti and titania nanotube, the TiAg-NT samples exhibited short-term antibacterial activity against Staphylococcus aureus (S. aureus), as confirmed by scanning electron microscopy and double staining with SYTO 9 and propidium iodide. A film applicator coating assay and a zone of inhibition assay were performed to investigate the long-term antibacterial activities of the samples. The cellular viability and cytotoxicity were evaluated through a Cell Counting Kit-8 assay. Annexin V-FITC/propidium iodide double staining was used to assess the level of MG63 cell apoptosis on each sample. RESULTS: All of the TiAg-NT samples, particularly the nanotube-coated Ti-Ag alloy with 2 wt% Ag (Ti2%Ag-NT), could effectively inhibit bacterial adhesion and kill the majority of adhered S. aureus on the first day of culture. Additionally, the excellent antibacterial abilities exhibited by the TiAg-NT samples were sustained for at least 30 days. Although Ti2%Ag-NT had less biocompatibility than titania nanotube, its performance was satisfactory, as demonstrated by the higher cellular viability and lower cell apoptosis rate obtained with it compared with those achieved with commercial pure Ti. The Ti1%Ag-NT and Ti4%Ag-NT samples did not yield good cell viability. CONCLUSION: This study indicates that the TiAg-NT samples can prevent biofilm formation and maintain their antibacterial ability for at least 1 month. Ti2%Ag-NT exhibited better antibacterial ability and biocompatibility than commercial pure Ti, which could be attributed to the synergistic effect of the presence of Ag (2 wt%) and the morphology of the nanotubes. Ti2%Ag-NT may offer a potential implant material that is capable of preventing implant-related infection.