| Background and Objection:On account of good Biocompatibility and properties of physical and chemical, Ti-alloy is extensively used as implant material in clinical practice like artificial joints, bone graft and dental implant. However, lack of strong chemical combination caused by poor bioactivity and paucity of osteoinduction confine the Ti-alloy beyond the demands to get powerful synosteosis. Currently, HA coating on Ti-alloy is also practical in promoting interface osseointegration, while there exist deficiences of non-Metallurgical connection between different metals, coating desquamation and weak chemical instability. Polyporous Tantalum came into our sight well-known for its reliable biocompatibility, chemical instability, appropriate elastic modulus between cortical bone and cancellous bone as well, which ameliorates osteointegration, practically making a difference in ONFH (Osteonecrosis of the Femoral Head), artificial joints and bone reconstruction therapy, etc. Nevertheless, the expenditure holds us back. This study is aimed at generating metallurgical alloy between Ta-coating and Ti-alloy as matrix by virture of laser Laser rapid prototyping technology. Whereafter influence on interface osseointegration by polyporous Ta-coating and its mechanical character is preliminarily ascertained by analyzing interface microstructure and in vitro biocompatibility. Moreover, another goal is to develop high-tech polyporous Ta-coating on Ti-alloy with intellectual property right in order to laying foundations for further industrialization and clinical practice.Methods and materials:With precision machine tools, two symmetrical longitudinal grooves were generated on the precisely opposite sides of Ti (Ti-6A1-4V) matrix (depth:1.5mm, width:2.5mm). The oxide layer on the surface was erased by being polished gradually with abrasive paper of different meshes, afterwards, Ti-alloy rods were dried after ultrasonic cleaning. Mixed powders which were composed of Nano-Tantalum powder of80nm diameter on average and TiH2powder no more than0.02%mass fraction use to increase porosity were precoated in the longitudinal grooves of Ti-alloy rod. In the protection of Argon gas, Nano-Ta powders were cladded into the symmetrical longitudinal grooves of Ti-alloy applying advanced laser cladding technology. Then, Ta-Ti alloys were dried after ultrasonic cleaning for further use. XRD (x ray diffractometer)(x’pert pro, PHILIPS CO,Ltd) was applied to analyze the components of different parts of intersecting surface. The experimental conditions for XRD were as follows:radiation:Cu-Ka·入(入=1.5406nm), tube voltage:40kV, tube current:150mA, scanning speed:8°/min). Afterwards, microhardnesses of Ti-matrix, Ta-Ti metallurgical layer and pure Ta-coating were respectively detected using micro Vickers machine supplied by Analytical&Testing Center of Gaungzhou Research institute of non-Ferrous Metals. At the same time, SEM (EVO MA10) furnitured with EDX (INCA ENERGY350) and EBSD(INCA Synergy) was adopted to observe morphology of Ta-coating surface and Ta-Ti metallurgical layer cross-section and analyze components of them. Working voltage was set at20kV. In order to reduce the impact from electron on the sample surface, we use carbon to absorb before SEM process. More over, a quite convenient free image analyzing program, Image J program, was introduced into calculating porosity of nano-Ta-coating. The main process was divided into these parts:Image import, filter and noise reduction, image binaryzation, data processing and outcome measure. The final porosity was represented by the area proportion of porosity in the whole nano-Ta-coating. Minor samples (15.Omm*5.0mm) of Ta-Ti alloy rods were produced employing general Linear cutting machine. Control group was set as Ti-aloy with symmetrical longitudinal grooves but lase cladding. Both groups were handled through precision linear cutting machine as to obtain sample slice (2.0mm*5.0mm)(n=6for each group). The preosteoblast MC3T3-E1cells were cultured on the metallurgical nano-Ta-Ti alloy sample slice. Ti-alloy slices without Ta-coating but only symmetrical longitudinal grooves only were set as group Ⅱ while nano-Ta-coated Ti alloy slices were group Ⅱ. After3and6hours of seeding, the attachment morphology and number of MC3T3-E1cells growing on all specimens was observed by scanning electron microscope. Meanwhile, blank control group was devised in the trial which included cell culture fluid only(without metal sample slices). After culturing of1,3and7days, the proliferation of MC3T3-E1cells was determined by CCK-8assay. The MC3T3-E1cells on two specimens were cultured in inducing culture medium. After7,14and21days, the alkaline phosphatase (ALP) activity of cells cultured on all specimens was evaluated to assess the differentiation of cells to osteoblasts. Two sample T-test was carried on by SPSS13.0(a=0.05).Results:With SEM, it showed as rough and porous, and this kind of structure offered advancing condition for cell adhesion and cells conceiving on the surface. There was significant High temperature sintering mark on the Ta-coating surface and visible pores generated according to preset parameters by computer and decomposition of T1H2during high temperature of laser cladding. Pore diameter lied between100and200nm. The whole cross-section could be categorized into three parts:Ti matrix, metallurgical Nano-Ta-Ti-alloy layer and Ta-coating. The depth of metallurgical Nano-Ta-Ti-alloy layer was300um, which also could be grouped into3parts as follows:melting zone, bonding zone and heat-affected zone. The XRD results were consistent with results from EDX:Ta was most prominent in Ta-coating; the main components of metallurgical Nano-Ta-Ti-alloy layer were combination of Ta powder and Ti-6A1-4V matrix; Ti matrix contained Ti only. Owing to different location, temperature and cooling velocity during laser cladding procedure, arborization, clot, flower and granule shape could be observed in metallurgical layer, which meant successful metallurgical combination between coating and matrix. By SEM, multi-Synaptic structure of different sizes attached to the surface of metallurgical Nano-Ta-Ti-alloy slice, while the cells on the surface of group II acted as spherome. After1hours of seeding, cell numbers of both groups were close while more cells were detected being attached to the metallurgical Nano-Ta-Ti-alloy sample slice after3hours of seeding. The best hatching time of MC3T3-E1cell was ascertained to be1.5h by CCK-8kit test. The MC3T3-E1cells grew well on the surface of all specimens. After1day of seeding, no significant difference was detected between control group and experimental group. Then after3days of seeding, slight but significant deference was attained between experimental group and control group(P<0.05).7days later, the results indicated that newly-designed nano-Ta-Ti alloy harbored much more significant auxo-action than simple Ti alloy(P<0.05). ALP tests showed that ALP activities of group I increased compared with group I without statistical difderence(P>0.05) after7days of seeding. However,14days and21days later, group I showed higher ALP activity significantly than group I(P<0.05).Conclusion:The metallurgical combination between Ta and medical Ti-alloy with excellent structure and function were successfully generated by laser cladding,. The attachment, proliferation and differentiation of preosteoblast MC3T3-E1cells cultured on the Ti-alloy with metallurgical nano-Ta-coating are significantly better than that of untreated Ti-alloy, which indicates that this Ti-alloy with metallurgical nano-Ta-coating can provide better good biocompatibility and bioactivity compared with untreated Ti-alloy. All above provided favorable premise for further stufy of interface osseointegration. |
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