| Purpose: It has been a hot research topic to manufacture medical grade titanium(Ti)alloy with high strength,low elastic modulus,optimized microstructure and modified surface based on the the original excellent properties of titanium.This study aimed to explore the surface properties and biological activities of metal matrix nanocomposite(MMNC)modified by friction stir processing(FSP).The microstructure and mechanical properties were detected.In addition,the adhesion,proliferation and osteogenic differentiation of rat bone marrow stromal cells(BMSCs)on the nanocomposite surface were also investigated.Methods:(1)A constant traverse speed(υ)of 50 mm/min at a rotation rate(ω)of 500 r/min was adopted for fabricate Ti/Si C MMNC by FSP.The Ti base material was denoted as the control group,and the Ti/Si C nanocomposites,which underwent FSP at the different depths of the premade holes,were denoted as the FSP-1 group(1 mm)and the FSP-2 group(2 mm).(2)A constant traverse speed(υ)of 50 mm/min at a rotation rate(ω)of 300 r/min was adopted for fabricate TC4/Zn MMNC by FSP.The TC4 base material was denoted as the control group.The TC4 MMNC,which underwent FSP without Zn addition,was denoted as the FSP group.The TC4/Zn MMNC,which underwent FSP at the different depths of the premade holes,were denoted as the Zn-I-FSP group(1 mm)and the Zn-II-FSP group(0.5mm).(3)The MMNC microstructure was observed by metallographic techniques,scanning and transmission electron microscopy.Mechanical properties were characterized by nanoindentation and Vickers hardness testing.(4)Integrin β1 immunofluorescence,cell adhesion,and MTT assays were used to evaluate the effects of the nanocomposite on cell adhesion and proliferation.Osteogenic differentiation were evaluated by alkaline phosphatase(ALP)staining,ALP activity,PCR and osteocalcin immunofluorescence.(5)Micro-CT,sequential fluorescent labeling observation,and Van Gieson staining were used to evaluate the new bone formation around the TC4/Zn MMNC implant in vivo.Results:(1)The observed microstructures and mechanical properties clearly indicated that FSP is a very effective technique for modifying Ti/Si C MMNC to contain uniformly distributed nanoparticles.In the interiors of recrystallized grains,characteristics including twins,fine recrystallized grains,and dislocations formed concurrently.The elastic modulus of the Ti/Si C MMNC were decreased and the Vickers hardness were increased significantly when compared with base material.Ti/Si C MMNC surface showed the improved hydrophilicity.(2)Cell adhesion,proliferation,and osteogenic differentiation of rat BMSCs were all enhanced on the novel Ti/Si C MMNC surface.(3)TC4/Zn MMNC was successfully fabricated by FSP.In the interiors of recrystallized grains,characteristics including β region,refined acicular-α twins,coarsening acicular α and dislocations formed concurrently.The nano-Zn particles were uniformly distributed and had a metallurgical combination with Ti crystals.The elastic modulus of the TC4/Zn MMNC were decreased and the Vickers hardness were increased significantly when compared with base material.TC4/Zn MMNC surface showed the improved hydrophilicity.(4)Cell adhesion,proliferation,and osteogenic differentiation of rat BMSCs were all enhanced on the novel TC4/Zn MMNC surface.(5)The Zn-I-FSP group demonstrated higher Trabecular number(Tb.N)than other group.The Zn-II-FSP group demonstrated higher bone volume(BV),bone volume/total volume(BV/TV)and rate of new bone formation than other group.Both the Zn-I-FSP group and the Zn-II-FSP group showed the better bone-implant contact.Conclusion: In conclusion,both Ti/Si C MMNC and TC4/Zn MMNC surface modified using FSP technology not only have superior mechanical properties under stress-bearing conditions but also provide improved surface and physicochemical properties for cell attachment and osseointegration. |
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