Bond strength of plasma-sprayed hydroxyapatite/Ti composite coatings

Multidirectional effects of Sr-, Mg-, and Si-containing bioceramic coatings with high bonding strength on inflammation, osteoclastogenesis, and osteogenesis

Ideal coating materials for implants should be able to induce excellent osseointegration, which requires several important parameters, such as good bonding strength, limited inflammatory reaction, and balanced osteoclastogenesis and osteogenesis, to gain well-functioning coated implants with long-term life span after implantation. Bioactive elements, like Sr, Mg, and Si, have been found to play important roles in regulating the biological responses. It is of great interest to combine bioactive elements for developing bioactive coatings on Ti-6Al-4 V orthopedic implants to elicit multidirectional effects on the osseointegration. In this study, Sr-, Mg-, and Si-containing bioactive Sr2MgSi2O7 (SMS) ceramic coatings on Ti-6Al-4 V were successfully prepared by the plasma-spray coating method. The prepared SMS coatings have significantly higher bonding strength (∼37 MPa) than conventional pure hydroxyapatite (HA) coatings (mostly in the range of 15-25 MPa). It was also found that the prepared SMS coatings switch the macrophage phenotype into M2 extreme, inhibiting the inflammatory reaction via the inhibition of Wnt5A/Ca(2+) and Toll-like receptor (TLR) pathways of macrophages. In addition, the osteoclastic activities were also inhibited by SMS coatings. The expression of osteoclastogenesis-related genes (RANKL and MCSF) in bone-marrow-derived mesenchymal cells (BMSCs) with the involvement of macrophages was decreased, whereas OPG expression was enhanced on SMS coatings compared to HA coatings, indicating that SMS coatings also downregulated the osteoclastogenesis. However, the osteogenic differentiation of BMSCs with the involvement of macrophages was comparable between SMS and HA coatings. Therefore, the prepared SMS coatings showed multidirectional effects, such as improving bonding strength, reducing inflammatory reaction, and downregulating osteoclastic activities, but maintaining a comparable osteogenesis, as compared with HA coatings. The combination of bioactive elements of Sr, Mg, and Si into bioceramic coatings can be a promising method to develop bioactive implants with multifunctional properties for orthopedic application.

Biomimetic and cell-mediated mineralization of hydroxyapatite by carrageenan functionalized graphene oxide

In bone tissue engineering, it is imperative to design multifunctional biomaterials that can induce and assemble bonelike apatite that is close to natural bone. In this study, graphene oxide (GO) was functionalized by carrageenan. The resulting GO-carrageenan (GO-Car) composite was further used as a substrate for biomimetic and cell-mediated mineralization of hydroxyapatite (HA). It was confirmed that carrageenan on the GO surface facilitated the nucleation of HA. The observation of the effect of the GO-Car on the adhesion, morphology, and proliferation of MC3T3-E1 cells was investigated. In vitro studies clearly show the effectiveness of GO-Car in promoting HA mineralization and cell differentiation. The results of this study suggested that the GO-Car hybrid will be a promising material for bone regeneration and implantation.

Surface-mediated bone tissue morphogenesis from tunable nanolayered implant coatings

The functional success of a biomedical implant critically depends on its stable bonding with the host tissue. Aseptic implant loosening accounts for more than half of all joint replacement failures. Various materials, including metals and plastic, confer mechanical integrity to the device, but often these materials are not suitable for direct integration with the host tissue, which leads to implant loosening and patient morbidity. We describe a self-assembled, osteogenic, polymer-based conformal coating that promotes stable mechanical fixation of an implant in a surrogate rodent model. A single modular, polymer-based multilayered coating was deposited using a water-based layer-by-layer approach, by which each element was introduced on the surface in nanoscale layers. Osteoconductive hydroxyapatite (HAP) and osteoinductive bone morphogenetic protein-2 (BMP-2) contained within the nanostructured coating acted synergistically to induce osteoblastic differentiation of endogenous progenitor cells within the bone marrow, without indications of a foreign body response. The tuned release of BMP-2, controlled by a hydrolytically degradable poly(β-amino ester), was essential for tissue regeneration, and in the presence of HAP, the modular coating encouraged the direct deposition of highly cohesive trabecular bone on the implant surface. In vivo, the bone-implant interfacial tensile strength was significantly higher than standard bioactive bone cement, did not fracture at the interface, and had long-term stability. Collectively, these results suggest that the multilayered coating system promotes biological fixation of orthopedic and dental implants to improve surgical outcomes by preventing loosening and premature failure.

Surface microstructure and in vitro analysis of nanostructured akermanite (Ca2MgSi2O7) coating on biodegradable magnesium alloy for biomedical applications

Magnesium (Mg) alloys, owing to their biodegradability and good mechanical properties, have potential applications as biodegradable orthopedic implants. However, several poor properties including low corrosion resistance, mechanical stability and cytocompatibility have prevented their clinical application, as these properties may result in the sudden failure of the implants during the bone healing. In this research, nanostructured akermanite (Ca2MgSi2O7) powder was coated on the AZ91 Mg alloy through electrophoretic deposition (EPD) assisted micro arc oxidation (MAO) method to modify the properties of the alloy. The surface microstructure of coating, corrosion resistance, mechanical stability and cytocompatibility of the samples were characterized with different techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), electrochemical corrosion test, immersion test, compression test and cell culture test. The results showed that the nanostructured akermanite coating can improve the corrosion resistance, mechanical stability and cytocompatibility of the biodegradable Mg alloy making it a promising material to be used as biodegradable bone implants for orthopedic applications.

Bioactive bredigite coating with improved bonding strength, rapid apatite mineralization and excellent cytocompatibility

Previous studies have shown that bredigite (Ca7MgSi4O16) bioceramics possessed excellent biocompatibility, apatite-mineralization ability and mechanical properties. In this paper, the bredigite coating on Ti-6Al-4 V substrate was prepared by plasma spraying technique. The main compositions of the coating were bredigite crystal phase with small parts of amorphous phases. The bonding strength of the coating to Ti-6Al-4 V substrate reached 49.8 MPa, which was significantly higher than that of hydroxyapatite coating and other silicate-based bioceramic coatings prepared by same method. After immersed in simulated body fluid for 2 days, a distinct apatite layer was deposited on the surface of bredigite coating, indicating that the prepared bredigite coating has excellent apatite-mineralization ability. The prepared bredigite coating supported the attachment and proliferation of rabbit bone marrow stem cells. The proliferation level of bone marrow stem cells was significantly higher than that on the hydroxyapatite coating. Our further study showed that the released SiO44– and Mg2+ ions from bredigite coating as well as the formed nano-apatite layer on the coating surface might mainly contribute to the improvement of cell proliferation. The results indicated that the bredigite coating may be applied on orthopedic implants due to its excellent bonding strength, apatite mineralization and cytocompatibility.

Preparation and in vitro evaluation of plasma-sprayed bioactive akermanite coatings

Bioactive ceramic coatings on titanium (Ti) alloys play an important role in orthopedic applications. In this study, akermanite (Ca(2)MgSi(2)O(7)) bioactive coatings are prepared through a plasma spraying technique. The bonding strength between the coatings and Ti-6Al-4V substrates is around 38.7-42.2 MPa, which is higher than that of plasma sprayed hydroxyapatite (HA) coatings reported previously. The prepared akermanite coatings reveal a distinct apatite-mineralization ability in simulated body fluid. Furthermore, akermanite coatings support the attachment and proliferation of rabbit bone marrow mesenchymal stem cells (BMSCs). The proliferation rate of BMSCs on akermanite coatings is obviously higher than that on HA coatings.

Materials Design for the Titanium Scaffold Based Implant

The main objective of here presented research is a design the scaffold/porous titanium (Ti) alloy based composite material demonstrating better biocompatibility, longer lifetime and bioactivity behaviour for load-bearing implants. The development of such material is proposed by making a number of consecutive tasks. Modelling the mechanical, biomechanical and biological behavior of porous titanium structure and an elaboration of results is performed by mathematical methods, including FEM and fuzzy logic. The development of selected Ti-13Zr-Nb alloy with designed porosity and no harmful effects is made by powder metallurgy (PM) with and without space holders, and by rapid prototyping with an use of selective laser melting (SLM). The development of an oxidation technology resulting in high corrosion resistance and bioactivity is carried out by electrochemical oxidation, gaseous oxidation and chemical oxidation, and their combination. The HA depositon is made by electrochemical and chemical (alternate immersion) methods. The core material is designed as a combination of natural polymer and bioceramics in order to allow slow dissolution followed by stepwise growth of bone tissue and angiogenesis, preventing local inflammation processes, and sustaining the mechanical strength close to that of non-porous material.

Electrophoretic deposition of porous CaO-MgO-SiO2 glass-ceramic coatings with B2O3 as additive on Ti-6Al-4V alloy

The sub-micron glass-ceramic powders in CaO-MgO-SiO(2) system with 10 wt% B(2)O(3) additive were synthesized by sol-gel process. Then bioactive porous CaO-MgO-SiO(2) glass-ceramic coatings on Ti-6Al-4V alloy substrates were fabricated using electrophoretic deposition (EPD) technique. After being calcined at 850°C, the above coatings with thickness of 10-150 μm were uniform and crack-free, possessing porous structure with sub-micron and micron size connected pores. Ethanol was employed as the most suitable solvent to prepare the suspension for EPD. The coating porous appearance and porosity distribution could be controlled by adjusting the suspension concentration, applied voltage and deposition time. The heat-treated coatings possessed high crystalline and was mainly composed of diopside, akermanite, merwinite, calcium silicate and calcium borate silicate. Bonelike apatite was formed on the coatings after 7 days of soaking in simulated body fluid (SBF). The bonding strength of the coatings was needed to be further improved.

Surface mineralization of Ti6Al4V substrates with calcium apatites for the retention and local delivery of recombinant human bone morphogenetic protein-2

Titanium alloys are prevalently used as orthopedic prosthetics. Inadequate bone-implant interactions can lead to premature prosthetic loosening and implant failure. Local delivery of osteogenic therapeutics promoting osteointegration of the implant is an attractive strategy to address this clinical challenge. Given the affinity of calcium apatites for bone matrix proteins we hypothesize that titanium alloys surface mineralized with calcium apatites should be explored for the retention and local delivery of osteogenic recombinant human bone morphogenetic protein-2 (rhBMP-2). Using a heterogeneous surface nucleation and growth process driven by the gradual pH elevation of an acidic solution of hydroxyapatite via thermal decomposition of urea, Ti6Al4V substrates were surface mineralized with calcium apatite domains exhibiting good affinity for the substrate. The microstructures, size and surface coverage of the mineral domains as a function of the in vitro mineralization conditions were examined by light and scanning electron microscopy and the surface calcium ion content quantified. An optimal mineralization condition was identified to rapidly (<10h) achieve surface mineral coverage far superior to those accomplished by week long incubation in simulated body fluids. In vitro retention-release profiles of rhBMP-2 from the mineralized and unmineralized Ti6Al4V, determined by an enzyme-linked immunosorbent assay, supported a higher degree of retention of rhBMP-2 on the mineralized substrate. The rhBMP-2 retained on the mineralized substrate after 24h incubation in phosphate-buffered saline remained bioactive, as indicated by its ability to induce osteogenic transdifferentiation of C2C12 myoblasts attached to the substrate. This mineralization technique could also be applied to the surface mineralization of calcium apatites on dense tantalum and titanium and porous titanium substrates.

The comparison of phosphate-titanate-silicate layers on the titanium and Ti6Al4V alloy base

The studied layers were composed of two parts: titanate-silicate underlayer for better adhesion and titanate-phosphate-silicate layers for potential bioparameters. The layers with different amounts of hydroxyapatite were deposited on titanium and Ti6Al4V alloy substrates using dipping sol-gel method and electrophoresis. The selection of sol/suspension composition, deposition time and heat treatment conditions have the decisive influence on the layers parameters. The obtained layers should be very thin and almost amorphous. The specific nature of ceramic layers on the metal substrates excludes the use of some measurements methods or makes it difficult to interpret the measurement results. All the obtained samples were compared using XRD analysis data (GID technique), SEM with EDX measurements and FTIR spectroscopy (transmission and reflection techniques) before and after soaking in simulated body fluid. FTIR spectroscopy with mathematical treatment of the spectra (BIO-RAD Win-IR program, Arithmetic-subtract function) was used to detect the increase or decrease of any phosphate phases during SBF soaking. Based on the FTIR results the processes of hydroxyapatite (HAp) growth or layer dissolution were estimated. The layers deposited on titanium substrate are more crystalline then the ones deposited on Ti6Al4V. During SBF soaking process the growth of small amount of microcrystalline carbonate hydroxyapatite was observed on titanium substrate. The layer on Ti6Al4V base contained amorphous carbonate apatite. During heating treatment above about 870-920 K this apatite transforms into carbonate hydroxyapatite. The Ti6Al4V substrate seems to be more advantageous in context of potentially bioactive materials obtaining.

Relative influence of surface topography and surface chemistry on cell response to bone implant materials. Part 1: physico-chemical effects

Knowledge of the complexity of cell-material interactions is essential for the future of biomaterials and tissue engineering, but we are still far from achieving a clear understanding, as illustrated in this review. Many factors of the cellular or the material aspect influence these interactions and must be controlled systematically during experiments. On the material side, it is essential to illustrate surface topography by parameters describing the roughness amplitude as well as the roughness organization, and at the scales pertinent for the cell response, i.e., from the nano-scale to the micro-scale. Authors interested in this field must be careful to develop surfaces or methods systematically, allowing perfect control of the relative influences of surface topography and surface chemistry.

Nanostructured glass-ceramic coatings for orthopaedic applications

Glass-ceramics have attracted much attention in the biomedical field, as they provide great possibilities to manipulate their properties by post-treatments, including strength, degradation rate and coefficient of thermal expansion. In this work, hardystonite (HT; Ca2ZnSi2O7) and sphene (SP; CaTiSiO5) glass-ceramic coatings with nanostructures were prepared by a plasma spray technique using conventional powders. The bonding strength and Vickers hardness for HT and SP coatings are higher than the reported values for plasma-sprayed hydroxyapatite coatings. Both types of coatings release bioactive calcium (Ca) and silicon (Si) ions into the surrounding environment. Mineralization test in cell-free culture medium showed that many mushroom-like Ca and phosphorus compounds formed on the HT coatings after 5 h, suggesting its high acellular mineralization ability. Primary human osteoblasts attach, spread and proliferate well on both types of coatings. Higher proliferation rate was observed on the HT coatings compared with the SP coatings and uncoated Ti-6Al-4V alloy, probably due to the zinc ions released from the HT coatings. Higher expression levels of Runx2, osteopontin and type I collagen were observed on both types of coatings compared with Ti-6Al-4V alloy, possibly due to the Ca and Si released from the coatings. Results of this study point to the potential use of HT and SP coatings for orthopaedic applications.

Effects of Dicalcium Silicate Coating Ionic Dissolution Products on Human Mesenchymal Stem-Cell Proliferation and Osteogenic Differentiation

This study investigated the effects of ionic dissolution products released from dicalcium silicate (DS) coatings on human mesenchymal stem cells (hMSC), cultured in the presence or absence of the dissolution products, with or without osteogenic supplements (OS). DS+ medium promoted cell proliferation during the first 4 days, but then inhibited proliferation. DS+OS− medium increased alkaline phosphatase (ALP) activity on day 14, and upregulated runt-related transcription factor 2 and osteonectin mRNA on days 7 and 14, respectively. The addition of osteogenic supplements (DS+OS+) led to a significant increase in ALP activity from days 7 to 21, upregulation of osteogenic markers on day 14, and formation of more mineralized nodules on day 28. The results demonstrated that the ionic dissolution products from DS coating alone can partly induce osteogenic differentiation of hMSC, and that the addition of osteogenic supplements further enhances osteoblast-specific gene expression and mineralization in hMSC.

Functional Coatings or Films for Hard-Tissue Applications

Metallic biomaterials like stainless steel, Co-based alloy, Ti and its alloys are widely used as artificial hip joints, bone plates and dental implants due to their excellent mechanical properties and endurance. However, there are some surface-originated problems associated with the metallic implants: corrosion and wear in biological environments resulting in ions release and formation of wear debris; poor implant fixation resulting from lack of osteoconductivity and osteoinductivity; implant-associated infections due to the bacterial adhesion and colonization at the implantation site. For overcoming these surface-originated problems, a variety of surface modification techniques have been used on metallic implants, including chemical treatments, physical methods and biological methods. This review surveys coatings that serve to provide properties of anti-corrosion and anti-wear, biocompatibility and bioactivity, and antibacterial activity.

Enhanced osteointegration of orthopaedic implant gradient coating composed of bioactive glass and nanohydroxyapatite

We conducted histologic and histomorphometric studies to evaluate the osteointegration of gradient coatings composed of bioactive glass and nanohydroxyapatite (BG-nHA) on titanium-alloy orthopaedic implants and surrounding bone tissue in vivo. Titanium-alloy implants with a gradient coating (gradient coating group), uncoated implants (uncoated group), and implants with a conventional hydroxyapatite (HA) coating (HA coating group) were randomly implanted in bilateral femoral condyles of 36 male New Zealand rabbits. The bone-implant contact at 12 and 24 weeks and the new bone volume in the notch created for observing bone ingrowth at 4, 12, and 24 weeks were found greater in the gradient coating group than those in both the uncoated group and the HA coating group (p < 0.05). Fluorescence micrographs showed active osteogenesis in the gradient coating group at 4 weeks after implantation. These findings indicated that BG-nHA gradient coatings could enhance the osteointegration of orthopaedic implant.

Biomimetic whisker-shaped apatite coating of titanium powder

Biomimetic apatite coatings on chemically modified titanium powder have been processed and the resulting coating layers evaluated in terms of morphology, composition and structure, using TF-XRD, XPS, SEM, TEM and FTIR analysis. After 7 days immersion in a simulated body fluid (SBF), nanometer-sized fine precipitates with an amorphous whisker-like phase and a Ca/P atomic ratio of 1.94 were obtained on the external surface of the titanium particles. When the immersion time in SBF was extended to 16 days, the coating layer consisted of the whisker-like nanostructured crystals of carbonated hydroxyapatite with a atomic ratio of 3; in such a case, a double coating layer was developed. The double layer could be divided into two regions and could be clearly distinguished: an inner dense region (approximately 200 nm in thickness) which may include hard agglomerated crystals and an outer less dense region (> 500 nm in thickness) in which crystals are loosely distributed.

Preparation and in vitro evaluation of plasma-sprayed Mg(2)SiO(4) coating on titanium alloy

In this paper, chemically synthesized Mg(2)SiO(4) (MS) powder was plasma-sprayed onto a titanium alloy substrate to evaluate its application potentials in biomedicine. The phase composition and surface morphology of the MS coating were analyzed. Results showed that the MS coating was composed mainly of Mg(2)SiO(4) phase, with a small amount of MgO and glass phases. Mechanical testing showed that the coating exhibited good adhesion strength to the substrate due to the close thermal expansion coefficient between the MS ceramic and the titanium alloy substrate. The measured bonding strength was as high as 41.5+/-5.3MPa, which is much higher than the traditional HA coating. In vitro cytocompatibility evaluation of the MS coating was performed using canine bone marrow stem cells (MSCs). The MSCs exhibited good adhesion, proliferation and differentiation behavior on the MS coating surface, which can be explained by the high protein adsorption capability of the MS coating, as well as the stimulatory effects of Mg and Si ions released from the coating. The proliferation rate of the MSCs on MS coating was very close to that on the hydroxylapatite (HA) coating. Alkaline phosphatase (ALP) activity analysis demonstrated that the ALP level of the MSCs on the MS coating remained high even after 21days, implying that the surface characteristics of the coating are beneficial for the differentiation of MSCs. In summary, our results suggest that MS coating might be a new approach to prepare bone implants.

The preparation, cytocompatibility, and in vitro biodegradation study of pure beta-TCP on magnesium

Biodegradable and bioactive beta-tricalcium phosphate (beta-TCP) coatings were prepared on magnesium (Mg) in order to improve its biocompatibility by a chemical method. The tensile bonding strength of beta-TCP coating and Mg substrate was measured by the standard adhesion test (ISO 13779-4). And the cytocompatibility of beta-TCP coated Mg was studied by using human osteoblast-like MG63 cells. It was found that the MG63 cells could grow well on the surface of beta-TCP coated Mg and the cell viability on beta-TCP coated Mg was above 80% during the cocultivation of MG63 cells and beta-TCP coated Mg for 10 days, indicating no cytotoxicity. It was concluded that the beta-TCP coated Mg had good cytocompatibility. The degradation of Mg substrate with beta-TCP coating in vitro was studied in detail by XRD, EDX, SEM, and ICP. The results showed that a bone-like apatite continually formed on the surface of the sample with the degradation of both Mg substrate and beta-TCP coating in Hank's solution (a simulated body fluid). The biodegradation mechanism was preliminarily analyzed in the paper.

Plasma-sprayed CaTiSiO5 ceramic coating on Ti-6Al-4V with excellent bonding strength, stability and cellular bioactivity

Novel Ca-Si-Ti-based sphene (CaTiSiO5) ceramics possess excellent chemical stability and cytocompatibility. The aim of this study was to prepare sphene coating on titanium alloy (Ti-6Al-4V) for orthopaedic applications using the plasma spray method. The phase composition, surface and interface microstructure, coating thickness, surface roughness and bonding strength of the plasma-sprayed sphene coating were analysed using X-ray diffraction, scanning electron microscopy, atomic force microscopy and the standard mechanical testing of the American Society for Testing and Materials, respectively. The results indicated that sphene coating was obtained with a uniform and dense microstructure at the interface of the Ti-6Al-4V surface and the thickness and surface roughness of the coating were approximately 150 and 10 microm, respectively. Plasma-sprayed sphene coating on Ti-6Al-4V possessed a significantly improved bonding strength and chemical stability compared with plasma-sprayed hydroxyapatite (HAp) coating. Plasma-sprayed sphene coating supported human osteoblast-like cell (HOB) attachment and significantly enhanced HOB proliferation and differentiation compared with plasma-sprayed HAp coating and uncoated Ti-6Al-4V. Taken together, plasma-sprayed sphene coating on Ti-6Al-4V possessed excellent bonding strength, chemical stability and cellular bioactivity, indicating its potential application for orthopaedic implants.

Bioactive borate glass coatings for titanium alloys

Bioactive borate glass coatings have been developed for titanium and titanium alloys. Glasses from the Na(2)O-CaO-B(2)O(3) system, modified by additions of SiO(2), Al(2)O(3), and P(2)O(5), were characterized and compositions with thermal expansion matches to titanium were identified. Infrared and X-ray diffraction analyses indicate that a hydroxyapatite surface layer forms on the borate glasses after exposure to a simulated body fluid for 2 weeks at 37 degrees C; similar layers form on 45S5 Bioglass((R)) exposed to the same conditions. Assays with MC3T3-E1 pre-osteoblastic cells show the borate glasses exhibit in vitro biocompatibility similar to that of the 45S5 Bioglass((R)). An enameling technique was developed to form adherent borate glass coatings on Ti6Al4V alloy, with adhesive strengths of 36 +/- 2 MPa on polished substrates. The results show these new borate glasses to be promising candidates for forming bioactive coatings on titanium substrates.

Calcium phosphate-based coatings on titanium and its alloys

Use of titanium as biomaterial is possible because of its very favorable biocompatibility with living tissue. Titanium implants having calcium phosphate coatings on their surface show good fixation to the bone. This review covers briefly the requirements of typical biomaterials and narrowly focuses on the works on titanium. Calcium phosphate ceramics for use in implants are introduced and various methods of producing calcium phosphate coating on titanium substrates are elaborated. Advantages and disadvantages of each type of coating from the view point of process simplicity, cost-effectiveness, stability of the coatings, coating integration with the bone, cell behavior, and so forth are highlighted. Taking into account all these factors, the efficient method(s) of producing these coatings are indicated finally.

Preparation of an electrodeposited hydroxyapatite coating on titanium substrate suitable for in-vivo applications

In this paper the porous hydroxyapatite coating on Ti implant materials was prepared by the process of electrodeposition, hydrothermal and sinter. The surface morphology, bond strength and thickness of HA coatings were investigated by SEM, AFM, and its biocompatibility was evaluated by cytotoxicity experiments and implant experiments, respectively. Results showed that (1) The HA coatings was 50 microm thickness and adhered on the Ti substrate strongly, which bond strength reached 38 MPa. AFM analysis showed that the HA coating was porous structure, in which the mean pore size was 236.5 microm, (2) Cytotoxicity experiments and implant experiments showed that HA-coated Ti implant materials has little cytotoxicity in vitro and little inflammatory reaction in vivo, and there were no statistically disparity between HA-coated Ti implant and titanium implant materials of clinical application (p>0.05), which demonstrated that HA-coated Ti has a good biocompatibility.

Characteristic and in vitro bioactivity of a microarc-oxidized TiO(2)-based coating after chemical treatment

Microarc oxidation (MAO) was used to prepare a TiO(2)-based coating containing Ca and P on titanium alloy. An alkali treatment was developed to modify the surface of the MAO coating to improve the apatite-forming ability of the coating. The chemically treated MAO coating exhibits a modified layer, with the main constituents being O, Ti, Ca and Na, showing anatase. The modified MAO coating shows a rough and porous morphology containing numerous nanoflakes of approximately 100nm thickness. During the alkali treatment process, P on the surface of the MAO coating shows a main dynamic process of dissolution; however, Ca exhibits a re-deposition process as well as dissolution. The formation of the modified layer could be explained by this mechanism: negatively charged HTiO(3)(-) ions are formed on the MAO coating due to the attack of OH(-) ions on the TiO(2) phase. The HTiO(3)(-) ions could incorporate sodium from the alkali solution and calcium from the alkali solution and MAO coating. The apatite-forming ability of the MAO coating is improved remarkably by the simple chemical treatment, since the surface of the alkali-treated MAO coating could provide abundant Ti-OH groups probably formed by ionic exchanges between (Ca2+, Na+) ions of the alkali-treated MAO coating and H3O+ ions of a simulated body fluid (SBF). Moreover, Ca released from the alkali-treated MAO coating increases the degree of supersaturation of SBF, promoting the formation of apatite. The apatite induced by the alkali-treated MAO coating possesses carbonated structure and pore networks on the nanometer scale.

Sol-Gel-derived TiO2-SiO2 implant coatings for direct tissue attachment. Part II: Evaluation of cell response

Silica-releasing sol-gel derived TiO2-SiO2 coatings with tailored nanostructure were evaluated in fibroblast and osteoblast cell cultures. The adhesion of both fibroblasts and osteoblasts proceeded within two hours. The highest fibroblast proliferation activities were observed on the TiO2-SiO2 (70:30) and (30:70) coatings. However, the cell layer on TiO2-SiO2 (30:70) coating was disordered. Prolonged osteoblast activity was observed on the coatings as a function of increased amount of released silica. At day 21 the surfaces were fully covered by the calcified nodules and extracellular matrix except for the coatings TiO2-SiO2 (10:90) i.e. having the highest SiO2 amount. The results suggested that TiO2-SiO2 (70:30) was the best for fibroblasts and TiO2-SiO2 (30:70) for osteoblasts. The applicability of the sol-gel derived TiO2 and TiO2-SiO2 coatings as an alternative for the calcium phosphate based implant coatings are discussed.