| With the development and popularization of dental implant technology, an increasing number of anodontia patients have considered dental implant as the preferred way of repairing the missing teeth. The fast and stable osseointegration between the implant and the surrounding bone is the key to a successful dental implant and is also the main target of the implant surface modification.The surface morphology and chemical composition of the implant are the important factor to affect its osseointegration ability. The coating technology can effectively improve the implant surface physicochemical properties and form the material/cell interface beneficial to bone integration,which advance the integrated performance of implant. Hydroxyapatite (HA) is the common surface coating material for implants, but the good biological activity cannot make up for its inherent weakness such as brittleness, low fatigue strength and interfacial bonding strength. Adding the ingredients to prepare composite coatings is the important development direction to improve the mechanical properties of hydroxyapatite. Porous tantalum is regarded as the ideal bone implant material owing to its virtue of excellent biological propertiesis and has achieved significant clinical efficacy in the joint surgery. In recent years, tantalum, as the surface coating materials, has attracted much interest. It is presently a domestic and international hot point for designing the microstructure of biological materials to regulate the biological behavior of stem cell. From the perspective of bionics, micro/nanostructure could better simulate the cellular survival environment, which is advantageous to the bone tissue repair regeneration.In this study, plasma spraying technology was used to fabricate tantalum and tantalum/hydroxyapatite composite coating with micro/nano structure on the surface of medical pure titanium and its surfacical physicochemical properties were characterized.The the effect of the composite coating on the biological behavior of rat bone marrow mesenchymal stem cells was studied in vitro, which aimed to lay the foundation for the further study on osseointegration implant surface in vivo,and propose a new ideas to optimize the design of implant surficial modification,and provide a theoretical basis for the development of new implants.Partâ… Effects of micro/nano structured tantalum coating on the biological activity of bone marrow mesenchymal stem cellObjective:To characterize the surface properties of tantalum coating with micro/ nano structure on pure titanium and the ability of protein adsorption, and to study in vitro the effect of the composite coating on the biological behavior of BMSCs,including adhesion, proliferation and differentiation, which aims to assess its cellular biocompatibility and provide reference basis for surficial optimization design of implant.Methods:1. On the basis of our previous study,we adopted atmospheric plasma spraying technique to fabricate tantalum coating with micro/nano structure. After optimized parameters, the power is set at 25KW and the spraying distance at 130mm.2.The scanning electron microscope was used for observing the surfacial morphology of samples, X-ray diffraction for the phase composition, profilometer for the roughness, contact angle meter for the surfacial contact angle and the vertical tension method was adopted to measure the bonding strength between coating and substrate material.3.MicroBCA method was used for quantitative detection of protein adsorption on surface of the specimen.4.The primary bone marrow mesenchymal stem cells of rat were isolated,cultured purified and identified.5.The celluar skeleton and morphology of BMSCs cultured on the surface of the material were observed by scanning electron microscopy and confocal microscopy ,and the celluar proliferation was detected by MTS method.6.After osteoinductive culture, the alkaline phosphatase activity, extracellular matrix mineralization,collagen secretion and osteocalcin secretion of the BMSCs cultured on the samples were studied to assess its osteogenic differentiation The cellular effects of tantalum coating on the osteogenic differentiation were investigated in terms of alkaline phosphatase activity, collagen secretion, extracellular matrix mineralization, and osteocalcin production, as well as osteogenesis-related genes expression..7.The Rea-time PCR was used to detect the expression of the osteogenesis-related genes including RUNX2, ALP, BMP-2 and OPN.Results:1.Tantalum coating on the surface of pure titanium formed multi-structure of micron and nano pore hole.2.Comparison of pure titanium and titanium coating, the micro/nano structure of tantalum coating possess higher roughness,smaller surfacial contact angle and higher interfacial bonding strength.3.The protein adsorption capacity of tantalum coating with micro/nano structure is higher than pure titanium and titanium coating.4.There are more BMSCs adsorbing on the tantalum coating and spreading well,and the cytoskeleton arranged more orderly. After 4 days of culture, the cellular proliferative activity of BMSCs on the tantalum coating cells begin to be stronger than other samples.5.With respect to pure titanium, samples with micro/nano structure significantly promoted the activity of alkaline phosphatase, collagen secretion and extracellular matrix mineralization, and increase the expression of osteogenic differentiation related genes, especially tantalum coating was more obvious.Conclusion:1.Tantalum coating with micro/nano morphology on the surface of pure titanium facributed by plasma spraying technology is compact and bind well, which has good hydrophilicity and protein adsorption capacity.2.Tantalum coating with micro/nano morphology has good biocompatibility and it can promote celluar adhesion, proliferation and osteogenic differentiation.Part â…¡Effects of tantalum/hydroxyapatite composite coating with micro/nano structure on the bioactivity of bone marrow mesenchymal stem cellObjective:To fabricate Tantalum/hydroxyapatite composite coating with micro/ nano structure by atmospheric plasma spraying technology on the surface of pure titanium and characterize its surfacial properties,and to study the effect of Tantalum/hydroxyapatite composite coating on the biological behavior of bone marrow mesenchymal stem cell so as to evaluate its biocompatibility, and provide a theoretical basis for the development of new functional implants, and screen the composite coating with best cell compatibility.Methods:1. Adopting atmospheric plasma spraying technique, we fabricated tantalum/HA composite coating with micro/nano structure after optimizing parameters.2.The surfacial physicochemical property of samples were characterized by the microtopography, phase composition wettability and roughness using scanning electron microscope, X-ray diffraction, profilometer and contact angle meter.3.The bonding strength betwenn coating and body material was measured by mechanical testing machine and the adsorption behaviors of BSA and FN onto the samples were quantitatively detectied by BCA method4.The BMSCs adherent on the samples and its morphology were observed by scanning electron microscope and fluorescence microscope, and the cell activity was determined by MTS method.5.The cellular effects of tantalum/HA composite coating on the osteogenic differentiation were investigated in terms of alkaline phosphatase activity, collagen secretion, extracellular matrix mineralization, and osteocalcin production, as well as osteogenesis-related genes expression.Results:1.The tantalum/HA composite coating with micro/nano structure was uniform and compact, and bonded well with body metal.2. With the increase of the mass of tantalum, the roughness of composite coating rise,and the hydrophilicity gradually reduce,but the bonding strength also increase gradually,which was between that of tantalum coating and hydroxyapatite coating. The tantalum/HA coating also has good hydrophilicity and bonding strength,3.The protein adsorption ability of tantalum/HA coating is stronger than that of hydroxyapatite coating and pure titanium.But there is no statistical difference of protein adsorption ability among different groups of composite coating.4.The bone marrow mesenchymal stem cells have a lager number adhered to the surface of composite coating and spread well. After 3 days of culture,cells on the surface of the micro morphology of the composite coating was higher than that of the proliferation of pure titanium.5.With respect to the pure titanium, micro/nano structured coating significantly promoted the activity of alkaline phosphatase, Ca secretion, osteocalcin secretion and mineralization of extracellular matrix, and increased the expression of osteogenic differentiation related genes,especially tantalum/HA coating was more obvious.6.The composite coating promoted more obviously and has a regular order, HA1Ta9>HA2Ta8>HA3Ta7> HA4Ta6.Conclusion:1.The tantalum/HA coating with micro/nano structure has good biocompatibility and mechanical property. Its hydrophilicity and protein adsorption ability is also superior to tantalum coating,but the bonding strength is greater than HA coating.2.With respect to Ti and single coating, composite micro/nano coating has better biocompatibility, and it can significantly promote cell adhesion, proliferation and osteogenic differentiation of BMSCs.3. The ability of the micro/nano structured tantalum/HA promoting osteogenetic differentiation of BMSCs has a regular order,HA1Ta9>HA2Ta8>HA3Ta7>HA4Ta6. |
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