Attachment,spreading, and matrix formation by human gingival fibroblasts on porous-structured titanium alloy and calcium polyphosphate substrates

Porous calcium polyphosphate (CPP) structures represent promising resorbable implant systems that can promote anchorage to connective tissues. Previous studies focused on chondrocyte interactions with CPP, but there are limited data on interactions of soft connective tissue cells with these materials. We studied attachment, spreading, and matrix formation by human gingival fibroblasts when cultured on amorphous and crystalline CPP. Comparison with porous Ti6Al4V substrates of similar volume percent, porosity, and pore size distribution provided evaluations of fibroblast interactions with rapid, moderate, and nonbiodegradable systems, respectively. Cells were incubated on substrates in medium containing ascorbic acid and evaluated at 3, 24, 48, 72, and 96 h after plating. Attached cell counts, cytoplasmic actin filament area, and immunostained extracellular type 1 collagen or fibronectin were quantified by morphometric analyses using epifluorescence microscopy. Cell morphology and substrate interactions were evaluated by scanning electron microscopy. Spreading, attachment, and matrix production were similar for both CPP substrates. In contrast, titanium alloy substrates exhibited threefold more attachment and twofold more spreading than CPP substrates. The area per cell of immunostained extracellular collagen and fibronectin was similar for the three different substrates. The results indicate that the crystallinity and, hence, degradation rate of CPP substrates does not substantially affect the interactions of fibroblasts with CPP materials but that compared with titanium alloy substrates, spreading and attachment are inhibited.     

Mechanical characteristics of solid-freeform-fabricated porous calcium polyphosphate structures with oriented stacked layers

This study addresses the mechanical properties of calcium polyphosphate (CPP) structures formed by stacked layers using a powder-based solid freeform fabrication (SFF) technique. The mechanical properties of the 35% porous structures were characterized by uniaxial compression testing for compressive strength determination and diametral compression testing to determine tensile strength. Fracture cleavage surfaces were analyzed using scanning electron microscopy. The effects of the fabrication process on the microarchitecture of the CPP samples were also investigated. Results suggest that the orientation of the stacked layers has a substantial influence on the mechanical behavior of the SFF-made CPP samples. The samples with layers stacked parallel to the mechanical compressive load are 48% stronger than those with the layers stacked perpendicular to the load. However, the samples with different stacking orientations are not significantly different in tensile strength. The observed anisotropic mechanical properties were analyzed based on the physical microstructural properties of the CPP structures.     

Characterization of cartilagenous tissue formed on calcium polyphosphate substrates in vitro

Successful joint resurfacing by tissue-engineered cartilage has been limited, in part, by an inability to secure the implant to bone. To overcome this, we have developed the methodology to form a cartilage implant in vitro consisting of a layer of cartilagenous tissue overlying a porous, biodegradable calcium polyphosphate (CPP) substrate. As bone will grow into the CPP after implantation, it will result in anchorage of the cartilage. In this study, the cartilagenous tissue formed in vitro after 8 weeks in culture was characterized and compared to native articular cartilage. Light microscopic examination of histological sections showed that there was a continuous layer of cartilagenous tissue on, and integrated with the subsurface of, the CPP substrate. The in vitro-formed tissue achieved a similar thickness to native articular cartilage (mean +/- SEM: in vitro = 0.94 +/- 0.03 mm; ex vivo = 1.03 +/- 0.01 mm). The cells in the in vitro-formed tissue synthesized large proteoglycans (Kav +/- SEM: in vitro = 0.27 +/- 0.01; ex vivo = 0.27 +/- 0.01) and type II collagen similar to the chondrocytes in the ex-vivo cartilage. The in vitro-formed tissue had a similar amount of proteoglycan (GAG microg/mg dry wt.: in vitro = 198 +/- 10; ex vivo = 201 +/- 13) but less collagen than the native cartilage (hydroxyproline microg/mg dry wt.: in vitro = 21 +/- 1; ex vivo = 70 +/- 8). The in vitro-formed tissue had only about 3% of the load-bearing capacity and stiffness of the native articular cartilage, determined from unconfined mechanical compression testing. Although low, this was within the range of properties reported by others for tissue-engineered cartilage. It is possible that the limited load-bearing capacity is the result of the low collagen content and further studies are required to identify the conditions that will increase collagen synthesis.     

多孔复合掺杂聚磷酸钙支架骨修复材料的制备及其性能

背景：离子掺杂是生物陶瓷改性的一种重要方法。 目的：评估复合掺杂生物陶瓷作为骨修复材料的可行性。 方法：将钾离子和锶离子复合掺入聚磷酸钙中,制得一种新型骨修复材料—KSCPP。采用扫描电镜和X射线衍射检测分析聚磷酸钙和KSCPP的微观结构和结晶情况;采用抗压强度测试实验、体外降解实验、体外细胞培养实验表征KSCPP的性能,并且进行短期兔肌肉植入实验观察KSCPP的组织相容性。 结果与结论：与羟基磷灰石和聚磷酸钙相比较,KSCPP支架材料拥有更高的抗压强度和更快的降解速度及更低的细胞毒性和更好的组织相容性。     

3D打印钛合金骨小梁多孔结构的拉伸性能

文题释义：3D打印：3D打印技术开创了增材制造的生产方式,即依照3D设计蓝图可将金属粉末等原材料逐层堆积而制成最终产品,擅长构建形状结构复杂的产品与个体化定制,制作特异性假体或植入物,供植入以达到重建等目的,在骨科领域得到了广泛应用。 钛合金骨小梁：是以钛合金粉末为原材料,采用金属3D打印技术通过金属微粒逐层熔融叠加生成的一种类人体骨小梁三维空间网孔结构,其力学性能和生物学性能和人体的松质骨骨小梁极为相似,作为人工植入假体的表面结构,具有非常出色的骨长入效果。 背景：3D打印钛合金多孔结构以其良好的机械性能和生物相容性已经在骨科植入假体设计与临床应用方面得到了快速发展,与涂层假体相比,钛合金骨小梁结构具有骨长入快和骨长入好的优点。为了保证骨科植入物的安全,目前多采用实验方式确定骨小梁结构的拉伸、剪切疲劳和弯曲疲劳强度。 目的：通过力学实验和有限元数值模拟方法研究骨小梁多孔结构的力学性能。 方法：①3D打印钛合金骨小梁拉伸试件实验：设计并制备3D打印钛合金骨小梁拉伸试件,骨小梁结构的丝径为0.28-0.35 mm、孔径为0.71 mm、孔隙率为73%。检测钛合金骨小梁结构的拉伸强度,分析其失效机制,同时分析不同打印位置对骨小梁拉伸强度的影响。②数值模拟实验：利用有限元方法建立包括骨小梁理论结构的拉伸试件实体模型,模拟骨小梁试件的拉伸破坏过程。 结果与结论：①3D打印钛合金骨小梁拉伸试件的极限载荷分布在39.55-47.11 kN之间,等效极限拉伸应力分布在62.79-74.53 MPa之间,拉伸破坏的结果为网状结构断裂,说明钛合金骨小梁具有较高的拉伸强度;②3D打印钛合金骨小梁拉伸试件实验与数值模拟实验均显示,骨小梁试件受到拉伸破坏时的破坏形式为丝径断裂,不会在骨小梁与钛合金实体的结合面发生断裂;③数值模拟实验中骨小梁试件的拉伸破坏载荷低于3D打印钛合金骨小梁拉伸试件,造成该差异的原因主要为：3D打印骨小梁试件的丝径(280-350 μm之间)大于骨小梁的理论丝径(142 μm),而孔径(孔隙率75%)小于骨小梁的理论孔径(孔隙率96%)。 ORCID: 0000-0001-7000-2093(张兰) 中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程     

Electrochemically assisted co-precipitation of protein with calcium phosphate coatings on titanium alloy

A bovine serum albumin protein-containing calcium phosphate coating (BSA/brushite) was prepared by electrochemically assisted co-precipitation onto a hydroxyapatite (HA) coated Ti-6Al-4V surface. Electrochemically assisted co-precipitation of BSA/brushite coatings onto HA resulted in a 70-fold increase in BSA inclusion compared to simple adsorption, and was subsequently released by a slower mechanism (15% loss over 70 h). Thus, this electrochemically assisted co-precipitation technique provides an efficient method of protein incorporation at physiological temperature, with a potential for sustained release of therapeutic agents as may be required for metallic implant fixation.     

Initial interaction of rat bone marrow cells with non-coated and calcium phosphate coated titanium substrates

Initial interactions of rat bone marrow (RBM) cells with smooth titanium, rough titanium or calcium phosphate coated substrates were tested. Cells were seeded onto the substrates, and attachment, integrin expression and spreading and morphology were studied. We found no difference in attachment of RBM cells to the different materials. We did find differences in the percentage of attached cells within a certain time between replicate runs of the experiments. RBM cells on all materials express alpha1, alpha3, alpha5, alpha6 and beta1 subunits. Again there was a large difference in expression patterns on RBM cells in different runs. No difference was found in expression on the various materials. For alpha1, alpha5, alpha6 and beta1, no difference was found in expression between attached and unattached cells. Expression of alpha3 was similar on attached and unattached cells during early culture. At the end of culture, alpha3 expression was downregulated for attached cells and not for unattached cells. This resulted in a higher expression of alpha3 for unattached cells compared to attached cells. Cells did spread on all materials, and reached a larger cell size on smooth titanium than on the rough materials. Morphology of the cells on the materials differed. On smooth titanium, cells usually showed a compact cell body with short cellular extensions. On the rough materials, cells often showed elongated shapes, with many thin cellular extensions. From this we conclude that the substrate surface characteristics of the materials we used do not influence attachment or integrin expression during the initial cell-material interactions. On the other hand, spreading behavior and cell morphology do depend on substrate surface characteristics.     

Initial interaction of U2OS cells with noncoated and calcium phosphate coated titanium substrates

From previous studies, we know that calcium phosphate (CaP) coated implants stimulate bone formation compared to uncoated implants. Nevertheless, the mechanism by which substrate surface characteristics affect cell function is unclear. In this study, we examined the initial interaction (30 min to 24 h) of U2OS cells with titanium substrates with or without a CaP coating. The effect of substrate roughness was also studied. When cell attachment was studied, we found that cells attached more readily to rough than to smooth surfaces. Also, more cells attached to the uncoated than to the CaP coated surface. After 24 h, cell numbers were similar for all substrate surfaces. Further, cells spread to a larger area on noncoated titanium than on the CaP coated substrates. At 24 h, the sequence of cell size was smooth titanium > rough titanium > CaP coated titanium. Shape measurements showed differences in cell shape between the cells on the different materials only at 7 h, not at different culture times. Cells expressed alpha2, alpha3, alpha5, alpha6, alphav, and beta1 subunits. Expression of alpha1, alpha4, alphavbeta3, beta3, beta4, and beta7 was extremely low or was not found.The beta1 integrin expression was higher on the coated than on the noncoated titanium at 3 h, but not on the other studied times. Expression of alpha2, alpha5, alpha6, and alphav expression was found to be upregulated at 24 h compared to earlier culture times on coated titanium, but not on uncoated titanium substrates. From this we conclude that the surface characteristics of a material (roughness and composition) can affect the initial interaction of cells with the material.     

The significance of crystallographic texture of titanium alloy substrates on pre-osteoblast responses

The aim of this study is to investigate the effects of grain orientation in polycrystalline materials on cell-substrate interactions. Samples are prepared from rods and sheets of Ti-6Al-4V substrates with predominately two distinct crystallographic orientations. X-ray diffraction analysis indicates that 36% of the surfaces of rod samples consist of (1010) plane, while the predominant orientation in the surface of the sheet samples is (1120) plane (29%). Morphological studies and cell biological experiments including cell attachment, proliferation and differentiation are conducted using MC3T3 pre-osteoblast cells cultured on these two different samples. The number of attached cells on the rod Ti-(1010) samples (70% after 1 h and 50% after 2 h) is higher than on the sheet Ti-(1120) samples. Cell proliferation after 3 days is also significantly higher on the Ti-(1010) samples. Alkaline phosphatase activity, however, shows no significant difference between the two samples. Scanning electron microscopy (SEM) analysis of MC3T3 cells grown on samples with different crystallographic texture demonstrate significant differences in morphology with respect to attachment and growth pattern. This study shows that crystal orientation of the substrate can influence cell responses and, therefore, substrate engineering can be used to improve and control cell-substrate interactions.     

Microstructure and corrosion behavior of porous coatings on titanium alloy by vacuum-brazed method

The microstructural evolution and electrochemical characteristics of brazed porous-coated Ti-6Al-4V alloy were analyzed and compared with respect to the conventionally 1300 degrees C sintering method. The titanium filler metal of low-melting-point (934 degrees C) Ti-15Cu-15Ni was used to braze commercially pure (CP) titanium beads onto the substrate of Ti-6Al-4V alloy at 970 degrees C for 2 and 8 h. Optical microscopy, scanning and transmission electron microscopy, and X-ray diffractometry (XRD) were used to characterize the microstructure and phase of the brazed metal; also, the potentiostat was used for corrosion study. Experimental results indicate that the bead/substrate contact interface of the 970 degrees C brazed specimens show larger contact area and higher radius curvature in comparison with 1300 degrees C sintering method. The microstructure of brazed specimens shows the Widmanst?tten structure in the brazed zone and equiaxed alpha plus intergranular beta in the Ti-6Al-4V substrate. The intermetallic Ti2Ni phase existing in the prior filler metal diminishes, while the Ti2Cu phase can be identified for the substrate at 970 for 2 h, but the latter phase decrease with time. In Hank's solution at 37 degrees C, the corrosion rates of the 1300 degrees C sintering and the 970 degrees C brazed samples are similar at corrosion potential (E(corr)) in potentiodynamic test, and the value of E(corr) for the brazed sample is noble to the sintering samples. The current densities of the brazed specimens do not exceed 100 microA/cm2 at 3.5 V (SCE). These results suggest that the vacuum-brazed method exhibits the potentiality to manufacture the porous-coated specimens for biomedical application.     

Biomimetic coprecipitation of calcium phosphate and bovine serum albumin on titanium alloy

Titanium alloy implants were precoated biomimetically with a thin and dense layer of calcium phosphate and then incubated either in a supersaturated solution of calcium phosphate or in phosphate-buffered saline, each containing bovine serum albumin (BSA) at various concentrations, under physiological conditions for 48 h. Coated implants then underwent scanning electron microscopy, immunohistochemical evaluation, Fourier transform infrared spectroscopy, and X-ray diffraction. The quantity of BSA taken up by coatings and the kinetics of protein release were monitored colorimetrically. In coatings prepared by the coprecipitation of calcium phosphate and BSA, protein had become incorporated into the mineral crystal latticework. With increasing BSA concentration, matrices decreased in thickness, became more dense, showed lower crystallinity, and underwent a change in crystal geometry. The octacalcium phosphate structure manifested in the absence of protein was gradually transformed into a carbonated apatite form. Preformed mineral coatings became only superficially mantled with a layer of BSA, and the morphology of the mineral matrices themselves remained unchanged. At equivalent protein concentrations, coatings prepared by the coprecipitation of calcium phosphate released only a minute fraction of its protein component under physiological conditions, whereas preformed mineral matrices showed a "burst" release of their associated protein within a single 2-h period. The biomimetic coating can be a carrier for osteoinductive agents.     

成人成骨细胞与多孔钛联合培养观察

目的观察成人成骨细胞在多孔钛表面的生长情况，评价多孔钛的生物相容性。方法将成人骨髓来源的成骨细胞与多孔钛联合培养，以多孔羟基磷灰石（hydroxyapatite，HA）为对照，倒置显微镜、扫描电镜观察细胞生长情况，MTT法检测细胞活性。结果成骨细胞在钛微孔表面生长良好，MTT法检测细胞活性，两组吸光度值无显著性差异（P〉0．05）。结论多孔钛具有良好的生物相容性，是比较理想的成骨细胞载体。     

Rapid prototyped porous titanium coated with calcium phosphate as a scaffold for bone tissue engineering

High strength porous scaffolds and mesenchymal stem cells are required for bone tissue engineering applications. Porous titanium scaffolds (TiS) with a regular array of interconnected pores of 1000 microm in diameter and a porosity of 50% were produced using a rapid prototyping technique. A calcium phosphate (CaP) coating was applied to these titanium (Ti) scaffolds with an electrodeposition method. Raman spectroscopy and energy dispersive X-ray analysis showed that the coating consisted of carbonated hydroxyapatite. Cross-sectioned observations by scanning electron microscopy indicated that the coating evenly covered the entire structure with a thickness of approximately 25 microm. The bonding strength of the coating to the substrate was evaluated to be around 25 MPa. Rat bone marrow cells (RBMC) were seeded and cultured on the Ti scaffolds with or without coating. The Alamar Blue assay provided a low initial cell attachment (40%) and cell numbers were similar on both the uncoated and coated Ti scaffolds after 3 days. The Ti scaffolds were subsequently implanted subcutaneously for 4 weeks in syngenic rats. Histology revealed the presence of a mineralized collagen tissue in contact with the implants, but no bone formation. This study demonstrated that porous Ti scaffolds with high strength and defined geometry may be evenly coated with CaP layers and cultured mesenchymal stem cells for bone tissue engineering.     

Biological performance in goats of a porous titanium alloy-biphasic calcium phosphate composite

In this study, porous 3D fiber deposition titanium (3DFT) and 3DFT combined with porous biphasic calcium phosphate ceramic (3DFT+BCP) implants, both bare and 1 week cultured with autologous bone marrow stromal cells (BMSCs), were implanted intramuscularly and orthotopically in 10 goats. To assess the dynamics of bone formation over time, fluorochrome markers were administered at 3, 6 and 9 weeks and the animals were sacrificed at 12 weeks after implantation. New bone in the implants was investigated by histology and histomorphometry of non-decalcified sections. Intramuscularly, no bone formation was found in any of the 3DFT implants, while a very limited amount of bone was observed in 2 BMSC 3DFT implants. 3DFT+BCP and BMSC 3DFT+BCP implants showed ectopic bone formation, in 8 and 10 animals, respectively. The amount of formed bone was significantly higher in BMSC 3DFT+BCP as compared to 3DFT+BCP implants. Implantation on transverse processes resulted in significantly more bone formation in composite structure as compared to titanium alloy alone, both with and without cells. Unlike intramuscularly, the presence of BMSC did not have a significant effect on the amount of new bone either in metallic or in composite structure. Although the 3DFT is inferior to BCP for bone growth, the reinforcement of the brittle BCP with a 3DFT cage did not negatively influence osteogenesis, osteoinduction and osteoconduction as previously shown for the BCP alone. The positive effect of BMSCs was observed ectopically, while it was not significant orthotopically.     

Surface engineering of titanium alloy substrates with multilayered biomimetic hierarchical films to regulate the growth behaviors of osteoblasts

Osseointegration is essential for the long-term survival of orthopedic implants. Inspired by the hierarchical structure of natural bone, we fabricated a hierarchical structure with osteoinduction potential on titanium alloy (Ti6Al7Nb) substrates via a spin-assisted layer-by-layer assembly technique, with hydroxyapatite nanofibers as the intercalated materials and gelatin and chitosan as the polycation and polyanion, respectively. The as-synthesized hydroxyapatite nanofibers were characterized using scanning electron microscopy (SEM), transmission electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. The change of water contact angle corresponding to different layers indicated the formation of a multilayered structure, since different components have their inherent wettability natures. The multilayered lamellar structure was revealed by the cross-sectional view of SEM, suggesting that the film was successfully deposited onto Ti6Al7Nb substrates. Osteoblasts cultured on the hierarchical structure deposited Ti alloy substrates displayed significantly higher cell viability (P < 0.01) and better adhesion, a higher production level of alkaline phosphatase, mineralization, genes expressions of osteocalcin and osteopontin (P < 0.01 or P < 0.05) compared to those of native Ti6Al7Nb substrates after culture for 4, 7 or 14 days. These results indicated that the lamellar structure was beneficial for the biological functions of osteoblasts, establishing the basis for osseointegration of a titanium alloy implant.     

A comparative study of electrochemical deposition and biomimetic deposition of calcium phosphate on porous titanium

Coating porous titanium with calcium phosphate (Ca-P) is an effective way to enhance titanium's osteoinduction capability. This study investigated the effectiveness of two coating methods: biomimetic deposition (BD) and electrochemical deposition (ED) in aqueous solutions. The titanium surfaces were treated by acidic etching and alkaline before coating. Effects of the pre-coating treatments on Ca-P coating were also investigated. Both deposition methods could produce Ca-P coatings on the inner pore surfaces of the titanium. The BD coatings were thicker and more uniform than were the ED coatings. On the other hand, ED was less sensitive to the condition of the titanium surface, and much faster in the coating deposition. However, ED produces less uniform and thinner coating layers on the inner pore surfaces of the titanium than does BD. The crystal structure of the coating is octacalcium phosphate (OCP) regardless of the deposition method. The morphology of flake-like OCP crystals in the deposition layers is similar for both deposition methods, except that the crystal flakes rupture after ED.     

Biomimetic and electrolytic calcium phosphate coatings on titanium alloy: physicochemical characteristics and cell attachment

Biomimetically deposited octacalcium phosphate (OCP) and carbonate apatite (BCA) as well as electrolytically deposited carbonate apatite (ECA) were considered as promising alternatives to conventional plasma spraying hydroxyapatite. This study compared their physicochemical characteristics and cell attachment behavior. The physicochemical characteristics included scanning electron microscopy observation, X-ray diffraction analysis, Fourier transform infrared spectroscopy analysis, surface roughness, coating thickness, dissolution test and scratch test. Cell attachment tests included morphology observation with stereomicroscopy and scanning electron microscopy as well as cell number count with DNA content assay. The OCP coating had 100% crystallinity and was about 40 microm thick, composed of large plate-like crystals of 30 microm, with the lowest surface roughness (R(a)=2.33 microm). The BCA coating had 60% crystallinity and was approximately 30 microm in thickness, composed of small crystals of 1-2 microm in size, with the highest surface roughness (R(a)=4.83 microm). The ECA coating had intermediate characteristics, with 78% crystallinity, 45 microm thickness, crystals of 5-6 microm and an average roughness of 3.87 microm. All coatings could be seen by eyes dissolving quickly and completely into acidic simulated body fluid (simulated physiological solutions-SPS, pH 3.0) but slowly and incompletely into neutral SPS (pH 7.3). It was suggested that the main factor determining coating dissolution in acidic SPS was the solubility isotherm, while some other factors including crystallinity and crystal size joined to determine coating dissolution in neutral SPS. In regard to adhesive strength, results of scratch test showed the critical load at the first crack of coating (L(c1)) was tightly related to crystal size as well as their arrangement, while the critical load at the total delamination of coating (L(c2)) was also related to the coating thickness. The ECA coating had the highest values. Owing to higher dissolution rate and globular appearance, BCA coating demonstrated the best goat bone marrow stromal cells attachment at 1 day or 3 days, followed by OCP and ECA coating.     

Effect of strontium ions on the growth of ROS17/2.8 cells on porous calcium polyphosphate scaffolds

Preparation, characterization and cellular biocompatibility study of a series of calcium polyphosphate containing 0-100 mol% of Ca2+ replaced by Sr2+ were reported. The osteoblastic ROS17/2.8 cell line was used and seeded on the strontium-doped calcium polyphosphate (SCPP) scaffolds to estimate its optimal dose and to study its potential to support the growth of osteoblastic cells for bone tissue engineering. The effects of SCPP on cells' proliferation and differentiation were evaluated by MTT and ALP activity assay. The results showed that porous SCPP did not exert cytotoxic effect on the cells. In addition, the proliferation and differentiation of the growth of ROS17/2.8 cells on the SCPP containing a low dose of strontium showed a higher level compared to the control, and the SCPP containing 1% strontium was optimal according to the results of MTT and ALP activity assay. The cells on the porous SCPP formed a continuous layer on the outer and inner surface observed by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). The bunchy collagens were excreted from the cells and the calcium granules wrapped by collagens were sedimentated on the surface of cells. The results suggested that the biodegradable SCPP could stimulate the proliferation and differentiation of ROS17/2.8 cells in vitro after addition of proper dose of strontium. The porous SCPP may be a promising material for the bone tissue engineering.     

Tensile adhesion of type I collagen to titanium alloy and calcium phosphate coated surfaces with different roughness values

The purpose of total joint arthroplasty is to reduce pain and restore function. Its success depends on the formation of a new bone that stabilizes the prosthesis. The proposed solution for this important problem is to have bio-coated implant surfaces which are more conductive to bone growth. Additionally, collagen has long been used as a matrix for medical applications, because of its biocompatibility and adaptability. In this study, a test method for measuring the tensile adhesion strength of collagen to titanium alloy and calcium phosphate coated surfaces with different roughness values was developed, in order to evaluate how well the collagen adheres to the metallic and bio-coated surfaces. A precision motion system was used to stretch gels that were adherent to the plate surfaces. The tests were done in DMEM solution. The adhesive strength between the collagen gel and plate was significantly higher for calcium phosphate coated surfaces. Adhesive strength was highest in the sample with the highest roughness value.     

Influence of calcium ion deposition on apatite-inducing ability of porous titanium for biomedical applications

In the present study, the influence of calcium ion deposition on the apatite-inducing ability of porous titanium(Ti) was investigated in a modified simulated body fluid (m-SBF). Calcium hydroxide (Ca(OH)₂) solutions with five degrees of saturation were used to hydrothermally deposit Ca ions on porous Ti with a porosity of 80%. Apatite-inducing ability of the Ca-ion-deposited porous Ti was evaluated by soaking them in m-SBF for up to 14 days. Scanning electron microscopy (SEM) and X-ray diffractometry (XRD) confirmed that a thin layer of calcium titanate (CaTiO₃)/calcium oxide (CaO) mixture with a nanostructured porous network was produced on porous Ti substrates after hydrothermal treatment at 200 °C for 8 h. X-ray photoelectron spectroscopy results demonstrated that the content of the Ca ions deposited on Ti and the thickness of the CaTiO₃/CaO layer increased with increasing saturation degree of the Ca(OH)₂ solution. The thickest (over 10 nm) CaTiO₃/CaO layer with the highest Ca content was achieved on the Ti treated in an oversaturated Ca(OH)₂ solution (0.2 M). SEM, XRD, transmission electron microscopy and Fourier transformed infrared spectroscopy analysis indicated that the porous Ti samples deposited with the highest content of Ca ions exhibited the best apatite-inducing ability, producing a dense and complete carbonated apatite coating after a 14 day soaking in m-SBF. The present study illustrated the validity of using Ca ion deposition as a pre-treatment to endow desirable apatite-inducing ability of porous Ti for bone tissue engineering applications.