The Design Of Titanium-based Materials For Bone Repair And Biological Evaluations

After implantation into a host,titanium-based(Ti-based)orthopedic materials are facing two major clinical challenges:aseptic loosening and bacterial infection,which directly determine the long-term success and longevity of the implant.Aseptic loosening is derived from a variety of factors,including micromotion of the implant relative to the adjacent bone under physiological load,inflammatory reaction and bone resorption induced by the wear particles,“stress shielding”caused by the mechanical mismatch between Ti-based material and bone tissue,as well as poor osteointegration between the implant and the host bone tissue.In addition,bacterial infection is another major factor leading to implant failure and revision surgery.Considering that,excellent osteointegration and prevention of bacterial infection are essential for the survival of an implant.Therefore,it is of great significant to endow Ti-based orthopedic materials with multiple biological functions when designing implants.In this study,from the perspective of coupled osteogenesis and angiogenesis during bone development and remolding,we employed anodic oxidation and layer-by-layer assembly(LBL)technique to construct a drug-device combination system with pro-osteogenic/angiogenic differentiation potentials and antibacterial properties,to improve bone formation and osteointegration.Furthermore,inspired by the hierarchical micro/nano-structures of natural bone tissue,we used 3D printing technology to manufacture porous Ti6Al4V scaffolds with proper mechanical properties comparable to that of natural bone,and further produced triphase biomimetic composite scaffolds with antibacterial,anti-tumor and pro-osteogenesis abilities by lyophilization.The main contents and conclusions of this study are listed as follows:1.Deferoxamine loaded titania nanotubes substrates regulate osteogenic and angiogenic differentiation of MSCs via activation of HIF-1αsignaling.To develop biomaterials for inducing osteogenic and angiogenic differentiation of mesenchymal stem cells(MSCs)is crucial for bone repair.In this study,we employed titania nanotubes(TNT)as drug nanoreservoirs to load deferoxamine(DFO),and then deposited chitosan(Chi)and gelatin(Gel)multilayer as coverage structure via layer-by-layer(LBL)assembly technique,resulting in TNT-DFO-LBL substrates.Scanning electron microscopy(SEM),atomic force microscopy(AFM),X-ray photoelectron spectroscopy(XPS)and contact angle measurements were employed to characterize the physical and chemical properties of the substrates.The results proved the successful fabrication of multilayer coating on TNT array.DFO released from the TNT arrays in a sustained manner.The drug-device combination(DDC)titanium(Ti)substrates positively improved the adhesion,proliferation,osteogenic/angiogenic differentiation of MSCs and mediated the growth behavior of human umbilical vein endothelial cells(HUVECs).Moreover,the TNT-DFO-LBL substrates up-regulated osteogenic and angiogenic differentiation related genes expression of MSCs by activating HIF-1αsignaling pathway.The approach presents here has a potential impact on the development of high quality Ti-based orthopedic implants.2.Enzyme responsive titanium substrates with antibacterial property and osteo/angio-genic differentiation potentials.To endow Ti implant with self-defensive antibacterial properties and desirable osteo/angiogenesis potentials,gentamicin(Gen)was covalently grafted to hyaluronic acid(HA)molecules to obtain hyaluronidase(HAase)sensitive HA-Gen conjugate.The multilayer structure of chitosan(Chi)/hyaluronic acid-gentamicin conjugate(HA-Gen)was constructed onto DFO loading TNT substrates via LBL technique,termed as TNT/DFO/HA-Gen.The HA-Gen conjugates were characterized by Fourier transform infrared spectroscopy(FTIR)and nuclear magnetic resonance(~1H NMR).The physical and chemical properties of the substrates were characterized by field emission scanning electron microscopy(FE-SEM),AFM,XPS and contact angle measurements.The on-demand DFO release was associated with the degradation of multilayers triggering by exogenous hyaluronidase,which indicated enzymatic and bacterial responsiveness.The TNT/DFO/HA-Gen substrates displayed effective antifouling and antibacterial properties against Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus),while was favorable for the adhesion,proliferation and osteo/angio-genic differentiation of MSCs.The multifaceted drug-device combination(DDC)strategy showed potential applications in orthopedic and dental implants.3.Osteogenesis of 3D printed porous Ti6Al4V implants with different pore sizes.Selective laser melting(SLM)is one of the three-dimensional(3D)printing techniques that manufacturing versatile porous scaffolds with precise architectures for potential orthopedic application.To understand how the pore sizes of porous Ti6Al4V scaffolds affect their biological performances,we designed and fabricated porous Ti6Al4V implants with straightforward pore dimensions(500,700,and 900μm)via SLM,termed as p500,p700,and p900 respectively.The morphological characteristics of Ti6Al4V scaffolds were assessed.The results showed that the actual pore sizes of the scaffolds were 401±26μm,607±24μm,801±33μm,respectively.The mechanical properties of Ti6Al4V scaffolds were also evaluated,showing that they were comparable to that of bone tissues.Meanwhile,the effect of pore size on biological responses was systematically investigated in vitro and in vivo.It was verified that 3D printing technique was able to fabricate porous Ti6Al4V implants with proper mechanical properties analogous to human bone.The in vitro results revealed that scaffolds with appropriate pore dimension were conducive to cell adhesion,proliferation and early differentiation.Furthermore,the porous Ti6Al4V scaffolds were implanted into the rabbit femur to investigate bone regeneration performance.The in vivo experiment showed the p700 sample was in favor of bone ingrowth into implant pores and bone-implant fixation stability.Taken together,the biological performance of p700 group with actual pore size of about 600μm was superior to other two groups.The obtained findings provide scientific basis to individually design and fabricate suitable porous Ti6Al4V with specific geometries for orthopedic application.4.Biomimetic triphase composite scaffolds for bone repair with antibacterial and anti-tumor potentials.Clinically,the treatment of large bone defects caused by trauma,tumor resection and other bone diseases remains a significant challenge,especially bone defects at the load-bearing sites.To prevent tumor recurrence and bacterial infection after surgical resection of oteosarcoma,we designed biomimetic triphase composite scaffold comprised of porous Ti6Al4V,chitosan and Selenium(Se)doped hydroxyapatite nanoparticles,termed as pTi/CS/HAP-Se.The HAP-Se hydroxyapatite nanoparticles were characterized by transmission electron microscope(TEM).The morphology,chemical and phase composition were characterized by FE-SEM,FTIR and X-ray diffraction(XRD)respectively.The composite scaffold promoted osteoblast proliferation while inhibiting tumor cells(MDA-MB-231)growth and bacterial viability.The biomimetic triphase composite scaffold resembles natural bone with hierarchical porous structures,showing potential applications for resconstruction of bone defects result from surgical resection of osteosarcoma.