Regulation Roles Of Surface Chemistry Of Tantalum And Titanium Alloy To Protein Adsorption And Early Cell Behaviors

Tantalum and titanium(alloy)are among the most widely employed metallic orthopedic biomaterials.Tantalum-based implants are generally much more expensive than titanium(alloy)-based ones due to the higher density and higher melting point of tantalum and thus the more difficult manufacturing than titanium(alloy)implants.Therefore,a careful evaluation and comparison of the bone formation ability of tantalum and titanium(alloy)may help to guide the selection of clinical orthopedic biomaterials.However,despite the wide comparison of tantalum and titanium(alloy)in in vitro or in vivo bone formation ability,whether tantalum is better than titanium(alloy)is still in dispute.The primary reason is attributed to the divergent surface topography and pore structure between tantalum and titanium(alloy)which may significantly affect their biological performance.Therefore,to provide a more objective and effective comparison,it is crucial to choose a suitable processing method to exclude the effects of pore structure and surface topography and then explore the regulation of surface chemistry of tantalum and titanium(alloy)to biological performances.In this study,to exclue the effects of pore structure and surface topography,compact tantalum and titanium alloy(TC4)sheets were fabricated by usind identical technologies and the surface chemistries and properties were carefully characterized.In view of the fact that surface chemistries affect protein adsorption which then regulates cell behavior,the effects of surfaces chemistries on protein adsorption and then on early cellular behaviors of osteoblasts and macrophages were investigated by using bovine serum albumin(BSA)and human fibronectin(h FN)as model proteins.The main works and conclusions are summarized as follows:(1)Two types of compact tantalum and titanium alloy sheets were manufactured by roll forming technology(2D-Ta,2D-TC4)and laser selective melting technology(3D-Ta,3D-TC4).The results from scanning electron microscope,X-ray photoelectron spectroscopy,X-ray diffraction,water contact angle detection indicate that 2D-Ta and2D-TC4 have similar surface topography and obvious oxide layers and surface hydroxyl groups exist on both surfaces.2D-TC4 has slightly higher hydrophilicity and surface energy than 2D-Ta.On the other hand,obvious topographical difference was observed between 3D-Ta and 3D-TC4,with 3D-TC4 containing adhered global paritcles on surfaces.Compared with 2D-surfaces,more amorphorous structures were observed on the corresponding 3D-surfaces,suggesting that manufacture methods may result in change in crystal structures.(2)Mirco-BCA assay,enzyme linked immunosorbent assay and immune-fluorescence staining were employed to detect the adsorption of BSA and h FN on 2D-Ta and 2D-TC4.The results show that the surface chemistry of 2D-Ta and2D-TC4 leads to negligible differences in surface protein density and active sites density and distribution,suggesting that the surface chemistry of tantalum and TC4 has similar contribution to protein adsorption.(3)Rat osteoblasts and RAW 264.7 cells were seeded on tantalum and TC4 sheets with pre-adsorbed h FN.The results from immunofluorescence staining,wound healing assay and CCK-8 assay indicate that the adhesion,migration and proliferation of osteoblasts on 2D-Ta are similar to those on 2D-TC4,and osteoblasts can reorganize endogenous FN rather than the adsorbed h FN,suggesting the surface chemistry of tantalum and TC4 has similar effects on early osteoblasts behaviors.On the other hand,RAW 264.7 cells can obviously reorganize both the adsorbed h FN and endogeneous FN on 2D-Ta and 2D-TC4,and 2D-TC4 produces stronger activation of RAW 264.7 cells,implying that the surface chemistry of TC4 might induce potentially stronger in vivo immune reactions.In conclusion,based on the invetstigation via material-protein-cell system,we verify that,the surface chemistries of tantalum and titanium alloy do not affect the early osteoblasts behaviors but do cause different macrophage activation.These findings may help to guide the selection of clinical orthopaedic materials.