Apatite Growth Research Articles

Nanosized CaP-silk fibroin-PCL-PEG-PCL/PCL based bilayer membranes for guided bone regeneration

Guided bone regeneration (GBR) concept has been developed to prevent the formation of non-functional scar tissue layer on defect site by undertaking barrier role. In this study, a new bilayer membrane which consisted of one layer of electrospun silk fibroin/PCL-PEG-PCL incorporating nanocalcium phosphate (SPCA)11Silk fibroin/PCL-PEG-PCL incorporating nanocalcium phosphate (SPCA) and one layer of PCL membrane was developed for GBR. To improve the osteoconductivity of membranes, nanosized calcium phosphate particles synthesized by Flame Spray Pyrolysis method were incorporated into membranes at 10% (wt) (SPCA10) and 20% (wt) (SPCA20) of the polymer content. The structural and chemical analyses revealed the well-integrated two layers of membranes with a total thickness of ca 100μm. In the regenerative layer, the highly porous mesh structure had a thickness of 12.6μm with randomly oriented fibers having diameters around 760nm, and nanoparticles dispersed homogenously. The mechanical test results showed remarkable improvement on the tensile strength of membranes with incorporation of nanoparticles. Higher water affinity of nanoCaP included membranes was proved by lower contact angle values and higher percent water uptake capacity. Biomineralization assay revealed that nucleation and growth of apatites around fibers of SPCA10 and SPCA20 were apparent while on SPCA0 apatite minerals were barely detected after 10days. Human dental pulp stem cells (DPSC) were seeded on electrospun layer of the bilayer membranes for biocompatibility and osteo-compatibility study. Increasing nanoCaP amount resulted in higher cell adhesion, proliferation, ALP activity and calcium deposition on membranes. These overall results confirmed the biocompatibility and potential applicability of proposed membranes for GBR treatments.

Surface treatment and biomimetic mineralization of porous microspheres fabricated by calcium gluconate-g-poly(D,L-lactide)

Porous hybrid microspheres were fabricated by the synthesized calcium gluconate-g-poly(D,L-lactide) (CG-g-PDLLA) composites. These hybrid microspheres were treated with an alkaline solution for different period of time to control the amount of generated carboxylate groups and remained CG on the surface. The microspheres were then incubated in a supersaturated simulated body fluid (1.5 SBF) solution for different time to investigate their biomimetic mineralization behavior. The depositions were found to have a fine cluster morphology, a similar crystal structure and chemical structure to natural hydroxyapatite, and a medium Ca/P of approximately 1.30. The effect of surface treating time on the structure and mineralization behavior of these microspheres has been discussed in detail. The results indicate that the nucleation and growth of apatite on the surface are influenced by the induced carboxylate groups and the remained CG. The hybrid CG-g-PDLLA microspheres have the potential as a novel alternative in bone tissue engineering.

Strontium doped hydroxyapatite biomimetic coatings on Ti6Al4V plates

Abstract Titanium (Ti) and its alloys are the most attractive metallic biomaterials since their first introduction to the biomedical area. Their major drawback is that they do not promote complete osteointegration due to their low bioactivity; thus, it is necessary to perform a surface treatment or apply a surface coating to increase the initial formation of surrounding bone tissue. In this study, strontium (Sr)-doped hydroxyapatite (HA) coatings on Ti6Al4V substrates were prepared by biomimetic method in which 2 times concentrated simulated body fluid (2×SBF) solution was used as the apatite growth medium. The characterization studies with X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicated that as the amount of strontium ion (Sr2+) replacing with calcium ion (Ca2+) in the structure increases, crystallinity decreases without causing a significant change in morphology of the HA deposits. Incorporation of Sr2+ ions resulted in the disappearance of Fourier transform infrared (FTIR) bands of carbonate ion (CO32-) which was found in the structure of pure HA biomimetic coating. The biological results demonstrated that Sr-doped HAs presented no cytotoxicity on Saos-2 cells. This study showed that the incorporation of Sr into apatitic structure is possible by mimicking the natural route and this procedure yields a promising bioactive coating on Ti alloys to be used in bone replacement therapies especially associated with osteoporosis.

In vitro study of electrodeposited fluoridated hydroxyapatite coating on G-II titanium with a nanostructured TiO2 interlayer

Titanium and its alloys have been widely used as orthopedic and dental implants for several decades due to their superior mechanical properties, corrosion resistance and biocompatibility. Recently, many researches revealed that the hydroxyapatite coatings on biomedical materials can further improve their biocompatibility and bioactivity. However, hydroxyapatite coatings are easily decomposed, weakening the bonding between implants and bone tissues and resulting in a high dissolution rate in the biological environment. Prolonging the lifetime of hydroxyapatite in implants is valuable for improving postoperative quality. Hydroxyapatite is the primary inorganic component of bones and teeth. A suitable amount of fluoride ions would be beneficial for the formation of fluoridated hydroxyapatite, which can enhance bone-cell response and the acid resistance of enamel. In this study, G-II titanium substrate was anodized to form a TiO2 interlayer with a nanotube structure. An electrolyte composed of fluoride, calcium and phosphorus ions was prepared for electroplating fluoridated hydroxyapatite (FHA) coatings onto anodized G-II titanium substrates at a constant voltage. The obtained coatings were examined for their microstructure, mechanical properties; moreover, the changes of apatite structure, surface morphology and corrosion resistance were further investigated after immersion in simulated body fluid (SBF) for a number of weeks. The results show that FHA coatings have a higher surface roughness and hardness than plain hydroxyapatite. After immersion in SBF, the FHA coatings induced the nucleation and growth of apatite on the surface and increased their crystallinity. In a potentiodynamic polarization test, FHA coatings exhibited a better anti-corrosion ability than bare G-II titanium substrate in SBF. Additionally, the anodized TiO2 nanotube improved the adhesion and corrosion resistance of FHA as well.

Deposition of nanodiopside coatings on metallic biomaterials to stimulate apatite-forming ability

One of the drawbacks of metals and alloys in biomedical applications is their inefficient fixation to adjacent tissues which can be fairly addressed by applying bioactive ceramic coatings. In this work, colloidal suspensions based on coprecipitation-derived nanoparticulate diopside (CaMgSi2O6) were deposited on stainless steel 316L by dip-coating and subsequent low-temperature sintering. Afterwards, the structure, bioactivity and biodegradation of the samples were in vitro evaluated by spectroscopic and microscopic techniques. The apatite-forming ability of the surface was found to be improved by using the nanodiopside coating, while controlled by a typical ion-exchange reaction mechanism originating from the film's degradability. In this regard, after soaking the coated samples in a simulated body fluid, an integrated leaf-like precipitation of apatite at early stages and a following non-uniform rose-like growth of apatite with an increased level of the carbonate substitution for hydroxyl were detected. It is eventually concluded that nanodiopside coatings deserve further consideration and development in the biomedical field, where a bioactive fixation is needed along the implant/tissue interface.

Biomimetic Bone-Like Apatite Coating on Anodised Titanium in Simulated Body Fluid under UV Irradiation

Low temperature deposition techniques of bioceramics coatings are now being researched and developed to avoid deficiencies inherent in high temperature techniques. Biomimetic coatings is a solution-based method conducted at ambient temperature to deposit bioactive coatings on the surface. The current study aims to investigate the effect of ultraviolet (UV) irradiation on the coating of bone-like apatite on the anodised surface. High purity titanium foils were anodised with an applied voltage of 350 V, current density of 70 mA.cm-2 in mixture of 0.04 M β-glycerophosphate disodium salt pentahydrate (β-GP) and 0.4 M calcium acetate (CA) for 10 min. After anodic oxidation, UV light treatment was conducted in pH-adjusted distilled water for 12 hours with ultraviolet light A (UVA) irradiation. Subsequently, the UV-treated anodised titanium foils were soaked in SBF for 7 days with/without UVA irradiation. After SBF immersion for 7 days, anodised titanium with combination of UV light treatment and UV irradiation during in vitro testing was fully covered by highly crystalline bone-like apatite at maximal thickness of 2.8 μm. This occurred mainly due to the formation of large amounts of Ti-OH groups which act as nucleation sites for bone-like apatite. This study also revealed that UV irradiation during in vitro testing is superior in promoting growth of bone-like apatite compared to UV light treatment. The suggested mechanism for bone-like apatite formation on anodised titanium under different UV irradiation conditions is illustrated in this article. The findings of this study indicated that biomimetic bone-like apatite coating with assistance of UV irradiation is an effective method in accelerating the formation of bone-like apatite.

Grain structure dependent self-assembled bioactive coating on Mg-2Zn-2Gd alloy: Mechanism of degradation at biointerfaces

Metallic biomedical devices with ultrafine-sized grains (UFGs) provide surfaces that are different from their coarse-grained (CG) (tens of micrometer) counterpart in terms of increased fraction of grain boundaries (UFG>50%; CG<2–3%). A novel concept of severe plastic deformation involving multiaxial forging and annealing was used to obtain a wide range of grain structures, starting from the UFG regime to the CG regime, to elucidate that the grain structure significantly impacts bioactivity and degradation behavior at biointerfaces. Experiments on the interplay between grain structure from the UFG regime to CG regime and bioactivity in a magnesium alloy indicated that the fundamental mechanism associated with the biodegradation process was strongly governed by the grain structure such that the ultrafine-grained alloy with dendritic growth of apatite exhibited slowest degradation in comparison to the coarse-grained counterpart. The differences observed in the biodegradation behavior with respect to grain structure are attributed to differences in surface energy that led to the formation of a stable surface oxide and apatite layer with dendritic morphology, which suppressed surface degradation at longer times in the UFG alloy. The degradation rate expressed in terms of corrosion rate was observed to decrease from 10.74mm/year to 3.77mm/year, with decrease in grain size from ~44μm to ~0.7μm. The study underscores and lays the foundation of a new branch of ultrafine grained magnesium alloy for biomedical devices.⁎Corresponding author.

Development of Self-Assembled Titania Nanopore Arrays for Orthopedic Applications

Self-assembled TiO2 nanopore arrays (TNPA) were developed by electrochemical anodization. Microscopic studies revealed the presence of nanoporous surface with pore diameter and length of about 84 and 100 nm, respectively. Growth of apatite (HAp) on TNPA after immersion in Hank’s solution for different durations such as 3, 5, and 7 days was confirmed by various spectroscopic studies. Polarization study exhibited that the specimens after immersion in Hank’s solution showed high corrosion resistance which is attributed to the HAp growth on TNPA surface. Hence, TNPA is a viable material with required biocompatibility and corrosion resistance for use as orthopedic implants.

Enhancement of fluoride immobilization in apatite by Al3+ additives

Immobilization of fluoride (F−) in apatite using Ca(OH)2 as a mineralizer in the presence of phosphate is known to be accompanied by a stagnation period. This is caused by the formation of hydroxyapatite and/or fluoroapatite (HAp/FAp) on the surface of Ca(OH)2, which inhibits the dissolution of Ca(OH)2. Al3+ additives effectively eliminated the delay period, leading to the rapid formation of apatites by suppressing the formation of CaCO3. Zeta potential measurements clearly showed that increasing the quantity of Al3+ additives caused not only a decrease in the initial surface charge but also a decrease in the rate of the surface charge of the solid residues during the reaction, indicating that Al3+ additives enhanced the formation of HAp/FAp. 27Al-nuclear magnetic resonance (NMR) studies of the solid residues indicated that the predominant coordination number of Al was always hexagonal ([6]Al) and that the fraction of [6]Al increased with an increase in the molar ratio of F/Al in the solid residues, suggesting that the stable AlF63− complex was easily incorporated into the apatites. In addition, transmission electron microscope- energy dispersive X-ray spectroscopy (TEM-EDX) revealed a uniform distribution of Al in the apatites, which suggests that in the initial stages of the reaction, free Al3+ ions contribute to the formation of apatite crystal seeds independent of Ca(OH)2 particles, resulting in the efficient growth of apatites containing F−. This result is helpful for the treatment of F−-bearing industrial wastewaters in practical applications by using an Al-bearing Ca source, such as ground-granulated blast-furnace slag.

Fabrication of thick nanoporous oxide films on stainless steel via DC anodization and subsequent biofunctionalization

Abstract Remarkably thick nanoporous anodic films have been formed through simple DC anodization by adding hydrogen peroxide as an oxidant to a sulfuric acid electrolyte. This result was not possible when using the previously reported pulsed polarization technique. While this anodic film's growth was significantly promoted by DC anodization, having only sulfuric acid resulted in the preferential anodic dissolution of the substrate material. Transmission electron microscopy of the anodic film's cross-section confirmed that the film has numerous fine pores with a size distribution ranging from 5 nm to 20 nm. Energy-dispersive x-ray spectroscopic analysis of the anodized specimens revealed that the films were composed of a complex chromium-rich oxide. In addition, coating stainless steel with thick nanoporous oxide films through anodization in the optimized conditions confirmed that it could act as a highly suitable host for synthetic hydroxyapatite coating, resulting in the enhanced growth of natural apatite in a simulated body environment. The enhancement of the apatite deposition is attributed to the availability of the empty pore volume in the thick anodic porous films, formed on stainless steel surfaces. These findings suggest a novel functionality to stainless-steel surface modification.

Surface Modification of Ti-30Ta Alloy by Electrospun PCL Deposition

In this study, PCL electrospun fibers were deposited on the Ti-30Ta alloy for change the surface properties. Experimental Ti-30Ta alloy was obtained by melting titanium and tantalum in arc melting furnace with argon atmosphere. Ingots were homogenized and bars with 10 mm of diameter were obtained in rotative swagging. PCL fibers were deposited on disks of the alloy by electrospinning. Plasma treatment was carried out for change PCL electrospun superficial energy by using stainless steel plasma reactor. Samples were immersed in mineralization solution for apatite growth. Surfaces were evaluated by using SEM, X-rays diffraction and contact angle. Samples exhibited hydrophilic behavior after plasma treatment and mineralization. Results are very interesting for biomedical applications.

Fabrication and characterization of poly(vinyl alcohol)-TiO2 nanocomposite films for orthopedic applications

Poly(vinyl alcohol) (PVA) is reinforced with TiO2 nanoparticles in order to enhance thermo-mechanical stabilities, surface characteristics and osteoblastic cell adhesion. PVA–TiO2 nanocomposite films with desirable mechanical, thermal and biocompatible properties are fabricated through solution casting method followed by de-hydrothermal cross-linking treatment. The composition of TiO2 nanoparticles was standardized to achieve mechanically stable nanocomposite films, based on tensile strength measurements composition of TiO2 is determined as optimal at 3wt%. PVA–TiO2 nanocomposite films were characterized by Scanning electron microscopy, Energy dispersive spectroscopy, Atomic force microscopy, Ultra violet and Fourier transform infrared spectroscopic techniques. Elemental mapping studies substantiate incorporation of TiO2 nanoparticles within the PVA matrix. Dimensional stability evaluated by soaking films in SBF for 24h insinuates the role of TiO2 in the direction of controlling degree of swelling. In-vitro bioactivity test and cell adhesion results also predict that presence of TiO2 is advantageous to enhance apatite growth and promote cell-substrate interaction. SEM studies illustrate improved surface morphology of PVA–TiO2 nanocomposite film with homogenously distributed TiO2 nanoparticles, which help to enhance thermo-mechanical behavior. TiO2 nanoparticles construct cell-adhesive hydrophilic nano-domains that act as potential cell adhesion sites and promotes osteointegration. Bio compatibility studies proved that thermally cross-linked PVA is non-toxic in relation to PVA cross-linked with glutaraldehyde. Cytotoxicity and cell adhesion of nanocomposite films evaluated through cell viability (MMT) assay and crystal violet staining revealed that PVA-3wt% TiO2nanocomposite could act as an excellent composite and hence suitable to be used in bone implant applications.

Synthesis of porous Ce-doped titania coating containing CaTiO3 by MAO and its apatite inducing ability

Abstract Bioactive porous CaTiO 3 -contained titania coatings doped with cerium were prepared on CP-Ti surfaces by micro arc oxidation (MAO) process. The surface morphologies, chemical composition, wettability and the phase compositions of coatings were investigated by scanning electron microscopy (SEM), energy dispersion X-ray spectrometry (EDS), contact angle goniometer and X-ray diffraction (XRD), respectively. The results showed the surface phase compositions of the as-synthesized coatings are anatase, rutile TiO 2 and perovskite CaTiO 3 phases, as well as a few amorphous phases. The participation of Ce in the electrolyte during MAO is evidenced to benefit in crystallizing CaTiO 3 phase and enhancing the coating surface hydrophilicity. The results of simulated body fluid (SBF) immersion experiments indicate that the hydrolysis of CaTiO 3 during immersion could enhance the nucleation and growth of apatite. In comparison, the porous Ce-doped titania coating containing CaTiO 3 exhibits better bioactivity as more apatites were observed at the same immersion duration.

Effect of Mg content on the bioactivity and biocompatibility of Mg-substituted fluorapatite nanopowders fabricated via mechanical activation

The aim of this work was preparation, characterization, bioactivity and biocompatibility evaluation of Mg-substituted fluorapatite (Mg-FA) nanopowders. Mg-FA nanopowders with a chemical composition of Ca10−xMgx(PO4)6F2, with x=0, 0.5, 1, and 2 were prepared by mechanically activated method. The in vitro bioactivity was investigated by soaking the powders in simulated body fluid (SBF) for various time periods to analyze the nucleation and growth of bone-like apatite on the surface of the samples. Cell viability and cell attachment were studied by MTT assay. Results indicated that the bioactivity of all of samples with different Mg content was improved compared with the pure FA. However, the mechanism of bioactivity is different and depends on the amount of Mg substitution. Finally, cell culture suggested that the addition of Mg2+ has no adverse effect and Mg-FA samples have good biocompatibility. The Mg-FA material shows potential in satisfying the requirements of biomedical applications.

Fabrication and apatite inducing ability of different porous titania structures by PEO treatment

Plasma electrolytic oxidation (PEO) was employed to grow different porous titania structures on Ti6Al4V alloy (TC4) substrate using various parameters. It was found that the PEO voltage and working frequency could affect the morphology, the pore size, the pore density, the thickness and the phase composition of titania structures. Thereafter, three typical porous titania structures with nanosize pores, microsize pores and microsize grooves were respectively selected to estimate their bioactivity using SBF immersion test. After soaking at different durations (3–28d), the surface morphology, the chemical composition as well as the phase structure of deposited apatite layers on porous titania were evaluated using SEM, EDS, and XRD. The formation of various biomimetic apatite layers indicated the different influence due to the characteristics of porous titania structures. The porous titania structure with nanosize pores could induce a fast apatite growth at the early immersion stage (~7d), while the one with microsize pores exhibited the best apatite inducing ability at long term immersion (~28d). Based on the experimental results, the formation mechanism of biomimetic apatite affected by the pore structure of titania was discussed as well.

Petrographic and Mineral Chemical Characteristics of the Hoidas Lake Deposit, Northern Saskatchewan, Canada: Constraints on the Origin of a Distal Magmatic-Hydrothermal REE System

The diopside-allanite veins and apatite breccia veins of the Hoidas Lake light rare earth element (LREE) deposit in northern Saskatchewan, Canada, represent a complex magmatic-hydrothermal system unrelated to its strongly deformed Archean and Paleoproterozoic host rocks in the Rae subprovince. The veins were emplaced along the Hoidas-Nisikkatch fault, a subsidiary of the deeply rooted Black Bay fault system, which likely provided pathways for the melts and fluids. Allanite in the diopside-allanite veins is concentrically zoned, reflecting rare earth element (REE) depletion, followed by REE enrichment. Later apatite breccia veins comprise multiple apatite generations. Graphic-textured inclusions in the earliest red apatite indicate the presence of a melt during apatite growth. The average total rare earth oxide (TREO) content increases from 1.5 wt % in the red apatite to 5.5 wt % in the green apatite, both dominated by Ce. In contrast, the latest generation, coarse red apatite, contains about 1 wt % TREO and is Nd dominant. This shift from Ce- to Nd-dominant apatite might reflect a transition from magmatic to hydrothermal growth. Interaction with hydrothermal fluids resulted in chlorite-hematite alteration and REE redistribution into secondary monazite, REE carbonates, REE-Sr carbonates, and allanite, the last occurring in late quartz-carbonate veins and containing up to 32.9 wt % TREO. The chemistry of the REE-bearing phases and their connection with hyalophane-bearing pegmatites and later lamprophyre dikes indicate a mantle-derived, most probably carbonatitic or syenitic source for the mineralizing melts and fluids.

Biomimetic growth and substrate dependent mechanical properties of bone like apatite nucleated on Ti and magnetron sputtered TiO2 nanostructure

This report presents findings on biomimetic growth of hydroxyapatite (HAp) nanocrystals on Ti and sputtered TiO2 substrates. The possibility of TiO2 nanostructure as candidate materials for future biomedical applications has been explored through the comparison of microstructural and mechanical properties of bone like apatite grown on Ti and nano-TiO2 surfaces. Raman spectroscopy and x-ray diffraction studies reveal formation of carbonate apatite with apparent domain size in the nanoscale range. A better interaction at the nano-TiO2/nano-HAp interface due to higher interfacial area could promote the growth of bone like apatite. The crystal phases, crystallinity, and surface morphology of nano-TiO2 are considered as parameters to understand the nucleation and growth of apatite with different mechanical properties at the nanoscale. The methodology of x-ray line profile analysis encompasses deconvolution of merged peaks by preserving broadening due to nanosized HAp aggregates. The Young’s modulus of bone like apatite exhibits crystallographic directional dependence which suggests the presence of elastic anisotropy in bone like apatite. The lattice contraction in the c-direction is associated with the degree of carbonate substitution in the apatite lattice. The role of residual stress is critical for the lattice distortion of HAp deposited at physiological conditions of temperature and pH of human blood plasma. The ion concentration is crucial for the uniformity, crystallinity, and mechanical behaviour of the apatite.

Enhanced bone regeneration with carbon nanotube reinforced hydroxyapatite in animal model

In order to improve the inherently poor mechanical properties of hydroxyapatite (HAp) and to increase its feasibility as load bearing implant material, in the present investigation, functionalised (HFC1 and HFC2) and non-functionalized (HC1 and HC2) multi-walled carbon nanotubes were used as reinforcing material with HAp. Significant improvement with respect to fracture toughness, flexural strength and impact strength of the composites was noticed. In vitro biological properties of HAp–carbon nanotube (CNT) biocomposites have also favored uniform and systematic apatite growth on their surface. Subsequently, in vivo osseous ingrowth at bone defect of rabbit femur was evaluated and compared using radiology, push out test, fluorochrome labeling, histology and scanning electron microscopy after 2 and 4 months respectively. The results demonstrated growth of web like soft callus from the host bone towards the implant, ensuring strong host bone interaction. Toxicological studies of the liver and kidney cells exhibited no abnormality, thereby confirming non-toxicity of the CNT in the animal body. Host–implant biomechanical strength showed high interfacial strength of the composites, indicating their high potentials to be used for bone remodeling applications.

Preparation of chitosan-HAp composite fiber for artificial ligament

Event Abstract Back to Event Preparation of chitosan-HAp composite fiber for artificial ligament Takuma Okada1, Toshiki Miyazaki1*, Yuta Nobunaga2*, Toshiisa Konishi2*, Tomohiko Yoshioka2*, Satoshi Hayakawa2* and Yuki Shirosaki3* 1 Kyushu Institute of Technology, Graduate School of Life Science and System Engineering, Japan 2 Okayama University, Graduate School of Natural Science and Technology, Japan 3 Kyushu Institute of Technology, Frontier Research Academy for Young Researchers, Japan Introduction: Although autograft is clinically used for reconstructive surgery of anterior cruciate ligament, it has still some problems. For example, it is necessary to extract the ligament tissue from other healthy part of patient’s body[1][2]. This problem can be solved by using artificial ligament. For this purpose, we focus on chitosan and hydroxyapatite (HAp) composite fiber. Chitosan is biodegradable polymer and HAp is fundamental inorganic component for exhibiting bone-bonding ability. Therefore we expect that the composite fiber can bond to bone and play a role as a scaffold for ligament tissue regeneration. Tamura et al., reported that the chitosan-HAp fiber can be prepared by coagulation system using calcium chloride solution[3]. This method is suitable for biomaterial fabrication because of synthesis with low toxicity materials. However, the obtained fiber did not have sufficient mechanical strength for artificial ligament, since excessive calcium ion decreased crystallinity of chitosan. In this study, we attempted sodium hydroxide treatment of the chitosan fiber containing phosphate ion to form HAp on the fiber and remove the excessive calcium ion and acetic acid. Materials and Methods: Chitosan solution was prepared by dissolving 10.5 g of chitosan powder and the appropriate amount of sodium dihydrogen phosphate in 30 mL of 0.1 M acetic acid solution. The solution was pumped into coagulation bath from nozzle with hole 0.5 mm in diameter. Coagulation bath was prepared mixing the saturated calcium chloride aqueous solution and ethanol. The wet fiber was soaked in ethanol for 5 min, and subsequently soaked in 0.2 M sodium hydroxide solution for 30 min to remove the excessive calcium ion and acetic acid. The fiber was then stretched by two rollers at speed ratio of 2:3. Finally, the fiber was dried at room temperature. The structure of the fiber was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). Tensile strength of the fiber was measured by Creep meter. The fiber was soaked in simulated body fluid (SBF) for 3 days to examine apatite growth. Results and Discussion: Although HAp formation on the fiber was not confirmed just after the coagulation by XRD, HAp was formed after the subsequent sodium hydroxide treatment. Assemble of HAp nanoparticle was observed on the surface of the fiber by SEM. In addition, crystallinity of the chitosan was improved by the treatment. After soaking in SBF, intensity assigned to HAp in XRD pattern was increased. Tensile strength of the fiber showed tendency to increase with increase in crystallinity of the chitosan. It is assumed that calcium phosphate in the fiber transforms to HAp and excessive calcium ion chelated with carbonyl group of chitosan is removed by sodium hydroxide treatment. Therefore a lot of hydrogen bond is constructed between amino group and carbonyl group of chitosan. Consequently crystallinity and tensile strength are improved. Conclusion: Chitosan-HAp composite fiber was obtained by coagulation method. Sodium hydroxide treatment after the coagulation was effective for enhancement of not only HAp precipitation but also mechanical property. It is expected that the obtained fiber is suitable for artificial ligament.

Precipitation of bone-like apatite on anodised titanium in simulated body fluid under UV irradiation

Fabricating a photocatalytic oxide layer on biomaterial surfaces has recently attracted a great deal of attention owing to its effect in accelerating the osseointegration process. Anodic oxidation is a widely used electrochemical method to deposit ceramic coatings of photocatalytic titania on titanium metal substrates. The current study aims to investigate the effect of UV irradiation during in vitro testing on the precipitation of bone-like apatite on the anodised surface. High purity titanium foils were anodised with varying voltages (50–350 V) in a mixture of 0.04 M β-glycerophosphate disodium salt pentahydrate (β-GP) and 0.4 M calcium acetate monohydrate (CA) for 10 min. Subsequently, the anodised titanium foils were soaked in simulated body fluid (SBF) for 7 days with illumination under ultraviolet light C. The titanium foil produced using high voltage (350 V) appeared to be highly porous and demonstrated high crystallinity as well high hydrophilic properties. After soaking in SBF for 7 days, highly crystallised bone-like apatite was covered on the surface of anodised titanium. Interestingly, the smooth and partially porous surface of the anodised titanium was observed to be fully covered by the bone-like apatite layer, contradicting previous findings that smooth surfaces lack sufficient nucleation sites needed for the growth of bone-like apatite. The suggested mechanism for the formation of bone-like apatite under UV irradiation is illustrated in this article. The findings of this study indicate that UV irradiation is able to accelerate the formation of bone-like apatite on the surface of titanium.