Surface Treatments On Titanium Implants Via Nanostructured Ceria For Antibacterial And Anti-inflammatory Capabilities

Titanium dental implants have been widely used in dentistry for prosthetic rehabilitations of lost teeth.However,peri-implantitis is a common complication of implant repair,if not timely intervention,will lead to failure.Clinically,peri-implantitis is an inflammatory lesion with bacterial plaque infection as the driving factor.It is characterized by the inflammation of surrounding soft tissues and the absorption of supporting bones.When microorganisms,especially pathogenic bacteria,adhere to the surface of the implant to form a biofilm,the endogenous immune disorders caused by their virulence factors become a potential risk of peri-implantitis.Therefore,preparation of an implant surface that could inhibit bacterial attachment and reduce inflammation is the current research trend and hot spot.In recent years,cerium dioxide?CeO₂?nanoparticles?NPs?have the ability to mimic the enzyme activities of superoxide dismutase?SOD?and catalase?CAT?due to the coexistence of Ce³⁺and Ce⁴⁺.NPs have a strong ability to scavenge active oxygen free radicals?ROS?,while giving them effective antibacterial and anti-inflammatory properties.In the past decade,a large number of studies have shown that CeO₂ NPs could alleviate or reduce inflammation,accelerate wound healing and inhibit bacterial growth.Therefore,CeO₂ NPs could play an important role in the antibacterial and anti-inflammatory modification of the implant surface.In addition,related studies have shown that controlling the morphology of CeO₂ NPs could improve the catalytic activity of CeO₂ NPs.The different morphologies of CeO₂NPs could affect the number and mobility of Ce³⁺ions and oxygen vacancies on each crystal plane.But so far,there have been no reports on the antibacterial and anti-inflammatory capabilities of CeO₂ NPs modified titanium surfaces with different morphologies.In summary,we intend to synthesize three different morphologies of CeO₂ NPs in rod,cube,and octahedron by controlling the hydrothermal reaction conditions,and study its antibacterial and anti-inflammatory functions of the modified titanium implant surfaces in vivo and in vitro.Deeply reveal the relationship between different morphologies of the same substance and its antibacterial and anti-inflammatory effects.Further clarify the mechanism of CeO₂ NPs morphologie affecting its antibacterial and anti-inflammatory effects.The specific content of this research is divided into four parts:Experiment 1:Synthesis,Surface Treatment and Characterization of CeO₂NPs with Different MorphologiesCeO₂ NPs with different morphologies?rod,cube,octahedron?were synthesized by changing the concentration of alkali,the reaction temperature/time using hydrothermal synthesis.Coating CeO₂ NPs with different morphologies on the surface of pure titanium by spin coating method.X-ray diffraction?XRD?,transmission electron microscopy?TEM?,scanning electron microscopy?SEM?,X-ray photoelectron spectroscopy?XPS?,contact angle experiments,and Fourier transform infrared spectroscopy?FTIR?were used to evaluate the physical characteristics.Experiment 2:Evaluate the Nanozyme Activity and Biosafety of CeO₂ NPs with Different MorphologiesEnzyme activities of CeO₂ NPs with three different morphologies and their respective total antioxidant capacity were detected by total antioxidant capacity test kit,total SOD activity test kit,and catalase test kit.Cytotoxicity and hemolysis test were used to evaluate the biological safety and biocompatibility of three different morphologies of CeO₂ NPs and their coated titanium disks.Using qPCR experiments to evaluate the inflammatory response on the surface of three different morphologies CeO₂ NPs modified titanium disks.Experiment 3:Research on the Antibacterial Properties of CeO₂ NPs with Different Morphologies and their Modified Pure Titanium SurfaceCultivation of three representative peri-implantitis-associated pathogenic bacteria:Porphyromonas gingivalis?P.gingivalis?,Fusobacterium nucleatum?F.nucleatum?,Streptococcus sanguinis?S.sanguinis?.The early adhesion experiment was tested by Gram-positive bacteria S.sanguinis and Gram-negative bacteria F.nucleatum on the surface of titanium disks modified by three different morphologies of CeO₂ NPs.The antibacterial performance of three different morphologies of CeO₂ NPs modified titanium surface was detected by live/dead staining,scanning electron microscope?SEM?,bacterial metabolic activity detection,and colony forming unit?CFU?.Experiment 4:Research on the Anti-inflammatory Properties of CeO₂ NPs with Different Morphologies and their Modified Pure Titanium SurfaceIn vitro mouse macrophage inflammation model was established by P.gingivalis lipopolysaccharide?P.gingivalis-LPS?stimulation,and tumor necrosis factor??TNF-??,interleukin 1??IL-1??,interleukin 6?IL-6?were detected by qPCR.Explore whether the titanium surface modified by three different morphologies of CeO₂ NPs could inhibit the activation of NF-?B signaling pathway to play an anti-inflammatory role.Titanium disks loaded with three different morphologies of CeO₂ NPs were implanted on the back of rats to build a rat back inflammation model.Tissues surrounding the implanted titanium disks were excised 3 and 6 weeks later,respectively.Hematoxylin-eosin staining?H&E staining?,immunohistochemistry?IHC?,and immunofluorescence staining?IF?were used to evaluate its anti-inflammatory properties.Through the above 4 part experiments,the following results were obtained:1.All the three different morphologies of CeO₂ NPs modified pure titanium surfaces have certain antibacterial functions,and could inhibit about 2 logs for key pathogenic biofilms?P.gingivalis?.2.The total antioxidant capacity of octahedral CeO₂ NPs was the strongest.3.Cube and octahedral CeO₂ NPs modified titanium has better anti-inflammatory effects in vitro than rod CeO₂ NPs.4.All the three morphologies of CeO₂ NPs modified titanium could inhibit the activation of the pro-inflammatory NF-?B signaling pathway,but the inhibition effect of octahedron CeO₂ NPs was the most obvious.5.In vivo,the expression of pro-inflammatory factors was significantly reduced in all three groups.The octahedral CeO₂ NPs modification showed the strongest anti-inflammatory effect in all groups.