| Biomedical metallic materials are widely used in biomedical fields because of their excellent mechanical properties and biocompatibility.However,metallic bare stents release harmful metal ions in the blood environment,and postoperative restenosis severely limits the long-term safety of coronary stents.At the same time,the bioinert layers(TiO2)on titanium alloy also limit the osseointegration between the surrounding natural bones,which increases the risk of displacement and loosening of the implant.Therefore,it is extremely important to modify the surface of the metallic platform.The surface microstructure of the implant plays an crucial role in regulating cell behavior.We have proposed two strategies to introduce cobalt-chromium alloy and titanium alloy with microstructure by biomimetic precipitation method and selective laser melting,and the biological function evaluation were further investgated in vitro or in vivo.The main research details and results were as follows:(1)The micro-nanostructured apatite coating was prepared on cobalt-chromium alloy by acid-alkali two-step treatment and biomimetic precipitation.The nanosheets and porous structure was observed on apatite through field emission scanning electron microscope(FE-SEM)and attenuated total reflection-fourier transform infrared spectroscopy(ATR-FTIR).In vitro release of Ca2+from apatite in physiological saline solution indicated that apatite can achieve a sustained and controlled degradation pattern.The adhesion and proliferation of smooth muscle cells(SMCs)and endothelial cells(ECs)on apatite proved that the apatite has multiple functions as anti-proliferation of SMCs and compatible of ECs.(2)We investigated the regulation mechanism of apatite nanosheets to inhibit restenosis.In vitro cytocompatibility studies indicated that the apatite was non-toxic.The FE-SEM observation of the cell morphology on the apatite showed that SMCs could be inserted by apatite nanosheets other than ECs.Further study on the cell behavior of smooth muscle cells on apatite nanosheets was investgated.It was found that released calcium ions from apatite nanosheets can triger SMC contraction and relexation violently to be inserted by apatite nanosheets.Therefore,the SMCs proliferation was inhibited,while ECs could survive.The construction of apatite coating has vital significance for the long-term and safety of drug-eluting stents,and also provides an important theoretical reference for the design of stent coatings.(3)Similar mechanical properties to native bone,excellent biocompatibility and osseointegration are key factors for interbody fusion cage.In the present study,porous Ti6A14V cage with computer designed macro-and micro-architecture was reproduced by selective laser melting(SLM).Dense Ti6A14V discs with six different angles were fabricated to investigate the effects of additive angle on surface properties and biocompatibility.As angle increased,both surface roughness and hydrophobicity increased due to increases in the number of unmelted metallic particles.Bullet-shaped Ti6Al4V cage with opened window,porosity of 70%and pore size of 600 ?m revealed elastic modulus of 0.51 ± 0.04 GPa and ultimate compressive load of 25000N at 2.62 mm displacement,which is comparable with the commercialized polyetheretherketone cage.(4)In vitro cytocompatibility studies indicated that the SLM Ti6A14V disc was non-toxic.In the early stage of cell culture,more elongated MC3T3E1 cells were observed at higher additive angle,but cell adhesion and proliferation with different angle did not show statistically differences.In vivo evaluation of Beagle tibia model through histological analysis showed that the cylindrical porous body with same porosity and pore size achieved similar bone ingrowth as commercialized porous tantalum implant at 4 and 12 weeks,indicating SLM fabricated porous Ti6A14V cage holds great potential for spinal fusion. |
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