Biological Effect Of Ultraviolet Photocatalysis On Nanoscale Titanium With A Focus On Physicochemical Mechanism

BackgroundDental implants have been extensively used as one of the ideal restorations for replacing missing teeth in clinic.However,traditional titanium implants require 3-6 months of osseointegration after primary surgery,which will disturb patient masticatory function.Moreover,the risk of implant failure will increase with the longer duration of osseointegration due to the external force.At present,studies focus on immediate implant and early loading and attempt to accelerate the process of osseointegration by implant surface modification.In order to overcome limitations of the micro-scale implant surface,nano-scale titanium implants which can promote implant osseointegration by a better mimic hierarchical bone in vivo have been proposed recently.Moreover,age-related degradation of implant bioactivity is another clinical issue urged to be solved.Several studies demonstrated the bioactivity of traditional implants will degrade with the longer storage time.Inour previous work,we identified UV treatment can lead to a better surface energy of implant and improve bone-implant integration.Technically,the efficiency of UV photocatalysis is positive related to titanium surface areas.However,the bioactivity and physicochemical property of UV treatment on the titanium coating with the nanostructure remains to be elucidated,especially the change of hydroxyl group and electric charge on implant surface after UV treatment need to be further explored.ObjectiveTo investigate the biological and physicochemical effect of UV treatment on nanoscale titanium.MethodsThe surface characteristics were evaluated by field-emission scanning electron microscopy,X-ray photoelectron spectroscopy,surface profilometry,and contact angle assay.In addition,we applied the zeta-potential,a direct method to measure the electrostatic charge on UV-treated and UV-untreated titanium nanotube surfaces.The effect of above Ti surface on osteoblast-like MG-63 cells was determined by analyzing initial protein and cell early adhesion,morphology,cytoskeletal arrangement,proliferation and focal adhesion.ResultsTitanium nanotubes were successfully synthesized with diameters of approximately 80-100nm.The UV-treated titanium disks showed no obvious differences in extrinsic features under FE-SEM.Surface roughness(Sa,Rz,Fig.1E,F)did not differ markedly between the groups.UV irradiation altered the contact angles on the control surface from 51.5° to 6.2°.To determine the physicochemical properties of samples,we used X-ray photoelectron spectroscopy(XPS)analysis.UV irradiation removed the organic and inorganic contaminations on titanium surface,exposing more Ti3+?Ti4+.Notably,the content of acidic hydroxyls on surface is significantly decreased after UV-treatment.From the real-time zeta-potential results,we found the isoelectric point of UV-treated nanotube was significant lower compared with UV-untreated surface,which meant UV-treated titanium nanotubes carried a markedly less negative charge at physiological condition.In vitro,UV-treated nanotube had an enhanced capability to adsorb BSA.The amount of adsorbed protein on the UV-treated titanium nanotubes after 3 h was considerably higher than that on the UV-untreated nanotubes after 24 h.UV enhanced the cell activity at initial stage of cell-surface interaction.Both in the amount of attached cell and morphologic change were promoted by UV treatment on titanium nanotube,as a result of enhanced formation of focal adhesion.ConclusionThe results suggest that UV enhance the initial bioactivity of titanium nanotube.This results may related to the change of surface hydroxyl group on UV-treated titanium nanotube surface,which led to a reduction of negative charge on UV-treated nano-scale titanium surface,as well as electrostatic repulsion between biomaterials and biomolecules.