Fabrication And Evaluation Of Ag-loaded Implant Coatings Based On Titania Nanotubes

To reduce the probability of periimplantitis toward implants, antibacterial coatingsespecially antibacterial agent loading coatings of the dental implant trans-gingival havebeen widely studied. In addition, the TiO2nanotubular surface with a tube size of~120nm exhibits better electrochemical stability in artificial saliva as well as improvedadhesion and proliferation of human gingival fibroblasts (HGFs). Another good merit ofthe titania nanotubes is that they can serve as carriers for drugs such as antibacterial agentsthereby acquiring antibacterial ability. We believe that silver is better for antibacterialcoating application because it owns many advantages such as broad antibacterial spectrum,good bioactivity at suitable dose, good stability and low risk of resistance development.Because the effective dose of silver is every low, long-term antibacterial ability can beobtained by loading enough amount of silver and controlling its release. Ag nanoparticlesare subsequently electrodeposited on this nanotubular surface to form Ag-loaded TiO2nanotube array, and Ag-loaded TiO2nanotube array shows good biocompatibility in vitro.But there are still some controversy about cytotoxicity of the Ag. And the biocompatibilityhas aroused huge attentions with the implant technology. This study aims to evaluate the biocompatibility of the Ag-loaded TiO2nanotube array though the rat soft tissue model, tomeasure the distribution and concentration in the body and to provide more evidences forthe clinical application.MethodsTitanium samples were anodized at20V with Ti anode and graphite cathode to formTiO2nanotube array on the surface．Different AgNO3concentrations (0.030mol/L and0.003mol/L)are used to electrodeposit on this nanotubular surface to form Ag-loaded TiO2nanotube arrays．Energy Dispersive X-ray Detector (EDX)and Fe-sem are used to analyzethe surface microtopography and components of all samples. Rat soft tissue model ischoose according to ISO1093-6:2006(E). The host foreign body reactions of day2, day12and day28after the implantation were tested; cell spreading morphology of sample surfacewas observed using Field emission Scanning electron microscope (FE-SEM).ED1-positive cell densities in the capsule were measured using the Immunofluorescencestaining. The reactive capsule thickness are measured by histological staining;Furthermore, the expression of monocyte chemoattractant protein-1(MCP-1) mRNA wasmeasured by RT-PCR to evaluate the biocompatible properties. The concentration of Ag inblood, liver, kidneys and brain were measured by ICP-MS.Results1. The titania nanotubes (100nm) are fabricated by anodization; the surface energyand wettability are enhanced compared to PT.2. Ag nanoparticles with a diameter about10nm were electrodeposited on thisnanotubular surface to form Ag-loaded TiO2nanotube array and adhered to the tube walltightly. The Ag nanoparticles densities rised with the AgNO3concentration. But thesurface free energy and wettability showed no significant differences.3. Ag release of NAg-H in day2, day12and day28in the liquid extract were higherthan NAg-L. The former2days is the burst release, and the release slow down with thetime run. 4. There were no statistical differences in the accumulation of AgNPs in potential rattarget organs between the NAg-L and NT group. The concentrations of silver in the rattarget organs rise in2day and12day but decreased in28day, and the silver firstlygathered in the blood and liver.5. When cultured for2or28days, the four groups showed the similar cell topogrphy.But in12days, the PT group showed less spreading compared with other three surfaces.6. The NAg-L and NAg-H groups showed the more CD68-positive macrophages thanother two groups(P<0.05) in2day. In12day, the CD68-positive macrophages on theNAg-L and NAg-H surface reduced and showed no difference with the NT group（P>0.05）, but a slight increase of the PT group was observed. In28day, theCD68-positive macrophages on the the four surfaces all reduced obviously（P<0.05）, andthe NAg-H and PT groups were higher than NT and NAg-L group（P<0.05）.7. The MCP-1mRNA relative expression showed the similar trend of theCD68-positive macrophages densities.8. The reactive capsule thickness of the four goups showed no differences in2day. In12day and28day, the trend of the reactive capsule thickness was: PT>NAg-H>NAg-L>NT.ConclusionUniform TiO2nanotubes arrays were formed on Ti surface by anodization. Agnanoparticles were electrodeposited on this nanotubular surface to form Ag-loaded TiO2nanotube array. The Ag nanoparticles densities rised with the AgNO3concentration. TheTiO2nanotube array showed well biocompatibility in vivo. The Ag loaded arouse theforeign body reaction. But the appropriate amount of Ag release didn’t enhance the foreignbody reaction and the gatheration of Ag in the tissue. To find the feasible way to loadsilver into the titania nanotubes for long-term antibacterial ability could apply to the clinic.