Apatite Formation In Simulated Body Fluid Research Articles

Development of bioactive zirconium-tin alloy by combination of micropores formation and apatite nuclei deposition.

In previous studies, Zr gained apatite-forming ability by various methods; however, it took more than 7 days in simulated body fluid (SBF) to gain apatite-forming ability. In this study, the authors developed the method to achieve apatite-forming ability in Zr alloy within 1 day in SBF by a combination with apatite nuclei that promote apatite formation in SBF. First, Zr-Sn alloy was soaked in concentrated sulphuric acid, and pores in micro-level were formed on the surface of Zr-Sn alloy. To attain apatite forming ability in Zr-Sn alloy, second, apatite nuclei were formed in the micropores. To evaluate apatite-forming ability, thus-obtained Zr-Sn alloy with apatite nuclei was soaked in SBF; hydroxyapatite formation was observed on the whole surface of the Zr-Sn alloy plates. From this result, it was clarified that higher apatite-forming ability was attained on the apatite nuclei-treated Zr-Sn alloy with micropores in comparison with that without micropores. When adhesive strength of formed hydroxyapatite film with respect to Zr-Sn alloy plates was measured, high-adhesive strength of the formed apatite film was attained by forming micropores and subsequently precipitating apatite nuclei in the fabrication process because of an interlocking effect caused by hydroxyapatite formed in the micropores.

Biocomposites based on hydroxyapatite matrix reinforced with nanostructured monticellite (CaMgSiO4) for biomedical application: Synthesis, characterization, and biological studies

In this study, a simple and facile strategy was developed for the synthesis of novel hydroxyapatite (HA)/nanostructured monticellite ceramic composites by mechanical method. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive x-ray spectroscopy (EDS) were used to peruse the phase structure, and morphology of soaked ceramic composites in simulated body fluid (SBF). The in vitro bioactivity of HA-based ceramic composites with nanostructured monticellite ranging from 0 to 50 wt% was evaluated via investigating the formation ability of bone-like calcium phosphates in SBF and the effect of obtained extracts from composites dissolution on osteoblast-like G-292 cell line. Moreover, In vitro cytocompatibility of the HA/monticellite ceramic composites was investigated by MTT, cell growth & adhesion and alkaline phosphatase (ALP) activity assays, and quantitative real-time PCR analysis. The results showed that HA/nanostructured monticellite ceramic composites could induce apatite formation in SBF. The cell proliferation and growth exposed to ceramic composites extracts were significantly stimulated and promoted at a certain concentration range compared to control for various time periods of cell culture. The optimized composite extract enhanced considerably gene expression of G-292 type X collagen (COLX) at different days. Also, G-292 cells were spread and adhered well on the ceramic composite disc. Furthermore, ALP activity of G-292 cells exposed to ceramic composites extracts was dramatically enhanced in comparison with pure HA extract (as control) at different concentrations for various time periods of cell culture. The results suggest that the optimized HA/nanostructured monticellite composite is promising biomaterial for clinical applications such as orthopedic and dentistry.

Bone Response to Titanium Implants Coated with Double- or Single-Stranded DNA.

We aimed to evaluate in vivo bone response and in vitro apatite formation to titanium (Ti) implants, coated with double-stranded DNA (DNA-d) or single-stranded DNA (DNA-s), and to compare the influence in different structure of DNA, double strand and single strand on bone response and apatite formation. The bone responses to multilayered DNA-d/protamine or DNA-s/protamine coating implants were evaluated after implantation into the extracted sockets of rat maxillary molars. Apatite formation on either coating surface after immersion in simulated body fluid (SBF) was evaluated using the quartz crystal microbalance (QCM) method. DNA-d/protamine and DNA-s/protamine coatings produced more roughened and hydrophilic surfaces than untreated Ti. Animal experiments showed that higher bone-to-implant ratios were achieved 3 and 6 weeks after implantation using DNA-d/protamine and DNA-s/protamine coatings compared with Ti. QCM measurements revealed that each coating contributed to significant earlier apatite formation in SBF. We conclude that both DNA-d/protamine and DNA-s/protamine coatings enhanced early bone formation. We suggest that a DNA-multilayer coating is useful for the surface modification of a Ti implant.

Bioactive surface modification of carbon/carbon composites with multilayer SiC-SiC nanowire-Si doped hydroxyapatite coating

Multilayer SiC-SiC nanowire-Si doped hydroxyapatite (S-SN-SiH) coatings were applied on carbon/carbon composites (CC) for bone implant applications. The SiC, SiC nanowire(SN) and Si doped hydroxyapatite(SiH) were prepared using pack cementation, electrophoretic deposition(EPD) and electrochemical deposition(ECD), respectively. The morphology and composition of the S-SN-SiH coatings were investigated by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectrometer and X-ray photoelectron spectroscopy. The formation process of the coating was proposed. The bonding strength between S-SN-SiH coating and CC substrate was studied by testing the shear strength. The in-vitro bioactivity was evaluated by simulated body fluid(SBF) immersion test. The results showed that the SiC layer was in-situ formed on CC and exhibited dense and rough morphology. The SN layer was composed of random orientated SN and showed a porous structure on the surface of SiC modified CC. The amount of SN increased with increasing EPD voltages and EPD time. SiH coating demonstrated blade morphology with a width of 1–3 μm and a thickness of 30–50 nm. Moreover, SN could keep their random orientation and form uniform distribution inside the SiH layer. The formation process of SiH was affected by not only the nucleation points provided by both SiC layer and SN but also the OH− concentration near the nucleation points. The shear strength test showed the bonding strength between S-SN-SiH coating and CC reached to 17.20 MPa. The in-vitro bioactivity test showed that the morphology of S-SN-SiH coating transformed from blade shape to grainy shape, suggesting that S-SN-SiH coating had the ability of inducing apatite formation in SBF and exhibited good in-vitro bioactivity.

Effect of metallographic structure and machining process on the apatite-forming ability of sodium hydroxide- and heat-treatedtitanium.

Although titanium (Ti) is clinically used for hard tissue reconstruction, it has low bone-bonding ability, i.e. bioactivity. Materials able to deposit apatite on their surfaces within the body is considered to exhibit bioactivity. Effects of the metallographic structure and machining process of Ti on its apatite-forming ability remains unclear. In this study, Ti substrates subjected to various preheating and machining processes were then subjected to NaOH and heat treatments. The apatite-forming abilities of resulting Ti were examined in simulated body fluid (SBF). Preheating of the Ti decreased its reactivity with NaOH solution. When quenched or annealed Ti was subjected to NaOH and heat treatments, the induction period for apatite formation in SBF slightly increased. This was attributed to a decrease in sodium titanate and increase in rutile on the Ti surface after the treatments. Substrates subjected to wire-electrical-discharge machining did not form apatite. This was attributed to the inhibition of PO43- adsorption on their surfaces following Ca2+ adsorption, which is an essential process for apatite nucleation. Contamination of Ti surface by components of the brass wire used in the machining contributed to the inhibition. The bioactivity of surface-modified Ti was therefore significantly affected by its thermal treatment and machining process.

Quantitative Analysis of Apatite Formation on Titanium and Zirconia in a Simulated Body Fluid Solution Using the Quartz Crystal Microbalance Method

The bone-bonding ability of a material is evaluated by examining apatite formation on its surface in simulated body fluid (SBF). Partially stabilized zirconia (ZrO2) is currently attractive as an alternative to titanium (Ti) implants; however, no quantitative analysis of apatite formation between Ti and ZrO2 in SBF has been reported. In the present study, we quantitatively evaluated apatite formation onto Ti or ZrO2 in SBF using the 27 MHz quartz crystal microbalance method (QCM). In the QCM measurements, apatite formation was detected as a frequency decrease in the Ti or ZrO2 sensor. Frequency decreases were observed at around 1 hour for Ti and at around 2 hours for the ZrO2 sensor after the injection of SBF. This revealed that the Ti sensor showed faster apatite formation than ZrO2. There was no significant difference in the amounts of apatite formation between the Ti and ZrO2 sensors after 24 hours of apatite formation in SBF. In conclusion, the present quantitative study using QCM revealed that apatite formation on the Ti surface in the SBF was obviously faster than that on the ZrO2 surface. Faster apatite formation may predict faster initiation of bone formation on Ti compared with ZrO2.

Novel bioactive materials developed by simulated body fluid evaluation: Surface-modified Ti metal and its alloys.

Until the discovery of the bone-bonding activity of Bioglass by Hench et al. in the early 1970s, it had not been demonstrated that a synthetic material could bond to living bone without eliciting a foreign body reaction. Since then, various kinds of materials based on calcium phosphate, such as sintered hydroxyapatite and β-tricalcium phosphate have also been shown to bond to living bone. Until the discovery of the bone-bonding activity of Ti metal formed with a sodium titanate surface layer by the present authors in 1996, it had not been shown that a metallic material could bond to living bone. Since then, various kinds of surface-modified Ti metal and its alloys have been found to bond to living bone. Until the discovery of the osteoinduction of porous hydroxyapatite by Yamasaki in 1990, it was unknown whether a synthetic material could induce bone formation even in muscle tissue. Since then, various kinds of porous calcium phosphate ceramics have been shown to induce osteoinduction. Until the discovery of osteoinduction induced by a porous Ti metal formed with a titanium oxide surface layer by Fujibayashi et al. in 2004, it had been unclear whether porous metals would be able to induce osteoinduction. These novel bioactive materials have been developed by systematic research into the apatite formation that occurs on surface-modified Ti metal and its related materials in an acellular simulated body fluid (SBF) having ion concentrations almost equal to those of human blood plasma. Some of the novel bioactive materials based on Ti metal are already in clinical use or clinical trials, such as artificial hip joints and spinal fusion devices. In the present paper, we review how these novel bioactive materials based on Ti metal have been developed based on an evaluation of apatite formation in SBF. Without the SBF evaluation, these novel bioactive materials would most likely never have been developed. On the basis of systematic study of apatite formation on a material in a simulated body fluid, various kinds of novel bioactive materials possessing not only bone-bonding activity and but also various other functions such as bone growth promotion, antibacterial activity and osteoinduction have been developed. Some of them are already successfully applied to clinical applications or trials for artificial hip joints and spinal fusion devices. It is shown in the present paper how these novel bioactive materials have been developed.

Formation of bioactive N-doped TiO2 on Ti with visible light-induced antibacterial activity using NaOH, hot water, and subsequent ammonia atmospheric heat treatment

Titanium (Ti) treated with NaOH and hot water, and heated in an ammmonia (NH3) gas atmosphere for 1 or 3h exhibited in vitro apatite formation within 7days when soaked in simulated body fluid (SBF). Moreover, the treated Ti decomposed methylene blue and showed excellent bactericidal activity against Escherichia coli under visible light irradiation. The surface treatment resulted in the formation of a fine network of N-doped anatase-type titania (TiO2-xNx) on the Ti surface, which was responsible for both the apatite formation in SBF and the visible light-induced antibacterial activity. These preliminary results highlight the efficacy of our simple method for producing novel bioactive Ti with visible light-induced antibacterial activity, which could be applied to orthopaedic and dental implants without the risk of infection.

Role of electrolyte additives on in-vitro corrosion behavior of DC plasma electrolytic oxidization coatings formed on Cp-Ti

Abstract The present investigation reports the effect of different electrolyte additives on in-vitro corrosion behavior of the plasma electrolytic oxidation (PEO) coatings formed on commercially pure titanium (Cp-Ti). PEO coatings were produced using a pulsed DC power source at a constant current density of 70 mA/cm 2 and a treatment time of 8 min. Different coatings were developed with different additives (sodium sulfate, Tris, di-ammonium hydrogen phosphate and ammonium acetate) added to a base electrolyte consisting of TSOP and KOH. PEO coatings were characterized for phase composition, elemental composition, surface and cross-sectional microstructure, corrosion behavior, apatite forming ability and osteoblast cell adhesion. The corrosion resistance of the developed oxide coatings was evaluated in a Kokubo simulated body fluid (SBF) by potentiodynamic polarization test and EIS study. The in-vitro bioactivity of all the PEO coatings and the untreated substrate was studied by soaking the samples in an SBF environment for 21 days. The TiO 2 layer formed in phosphate, sulfate and nitrite containing electrolyte highly enhances the apatite formation in SBF. An in-vitro cell adhesion test was performed on all coatings using human osteosarcoma cells for 48 h. SEM images of cell adhesion test showed that human osteosarcoma cells were well adhered and spread on all PEO treated samples. Among all the additives, Tris has provided higher corrosion resistance in the SBF environment with good apatite forming ability and osteoblast cell adhesion.

Apatite-forming PEEK with TiO2 surface layer coating.

Polyetheretherketone (PEEK) is widely used in orthopedic implants, such as spinal fusion devices, because of its moderate elastic modulus, as well as relatively high mechanical strength. However, it does not bond to living bone, and hence it needs autograft to be fixed to the bone. In this study, we attempted to add bone-bonding properties to PEEK by coating with TiO2 synthesized by the sol-gel process. When a TiO2 sol solution consisting of titanium isopropoxide, water, ethanol, and nitric acid was deposited on a PEEK substrate without any pretreatment, the formed TiO2 gel layer was easily peeled off after subsequent treatments. However, when the same solution was deposited on PEEK that was preliminarily subjected to UV or O2 plasma treatment, the deposited TiO2 gel layer strongly adhered to the substrate even after subsequent treatments. The strong adhesion was attributed to the interaction among the C-O, C=O, and O-C=O groups on the PEEK owing to the UV or O2 plasma treatment and the Ti-O bond of the TiO2 gel. Apatite did not form on the as-formed TiO2 gel layer in a simulated body fluid (SBF) even within 3 days; however, apatite formed after soaking in 0.1 M HCl solution at 80 °C for 24 h. This apatite formation was attributed to positive surface charge of the TiO2 gel layer induced by the acid treatment. The PEEK with the TiO2 gel layer coating formed by the proposed process is expected to bond to living bone, because a positively charged titanium oxide which facilitates the formation of apatite in SBF within a short period is known to bond to living bone.

Effect of Ca contamination on apatite formation in a Ti metal subjected to NaOH and heat treatments

It has long been known that titanium (Ti) metal bonds to living bone through an apatite layer formed on its surface in the living body after it had previously been subjected to NaOH and heat treatments and as a result had formed sodium titanate on its surface. These treatments were applied to a porous Ti metal layer on a total hip joint and the resultant joint has been in clinical use since 2007. It has been also demonstrated that the apatite formation on the treated Ti metal in the living body also occurred in an acelullar simulated body fluid (SBF) with ion concentrations nearly equal to those of the human blood plasma, and hence bone-bonding ability of the treated Ti metal can be evaluated using SBF in vitro. However, it was recently found that certain Ti metals subjected to the same NaOH and heat treatments display apatite formation in SBF which is decreased with the increasing volume of the NaOH solution used in some cases. This indicates that bone-bonding ability of the treated Ti metal varies with the volume of the NaOH solution used. In the present study, this phenomenon was systematically investigated using commercial NaOH reagents and is considered in terms of the structure and composition of the surface layers of the treated Ti metals. It was found that a larger amount of the calcium contamination in the NaOH reagent is concentrated on the surface of the Ti metal during the NaOH treatment with an increasing volume of the NaOH solution, and that this inhibited apatite formation on the Ti metal in SBF by suppressing Na ion release from the sodium titanate into the surrounding fluid. Even a Ca contamination level of 0.0005 % of the NaOH reagent was sufficient to inhibit apatite formation. On the other hand, another NaOH reagent with a nominal purity of just 97 % did not exhibit any such inhibition, since it contained almost no Ca contamination. This indicates that NaOH reagent must be carefully selected for obtaining reliable bone-bonding implants of Ti metal by the NaOH and heat treatments.

In vitro apatite formation on organic–inorganic hybrids in the CaO–SiO2–PO5/2–poly(tetramethylene oxide) system

The osteoconduction potential of artificial materials is usually evaluated in vitro by apatite formation in a simulated body fluid (SBF) proposed by Kokubo and his colleagues. This paper reports the compositional dependence of apatite formation on organic-inorganic hybrids in the CaO-SiO(2)-PO(5/2)-poly(tetramethylene oxide) system, initiated from tetraethoxysilane (TEOS), triethyl phosphate (OP(OEt)(3)), calcium chloride (CaCl(2)) and poly(tetramethylene oxide)(PTMO) modified with alkoxysilane. Formation of an apatite layer was observed on the surface of the organic-inorganic hybrids with molar ratios of TEOS/OP(OEt)(3) ranging from 100/0 to 20/80. The rate of apatite formation remarkably decreased when the hybrids were synthesized with TEOS/OP(OEt)(3) ratios of 40/60 or less. Hybrids without TEOS showed no apatite formation in SBF for up to 14 days. Addition of small amounts of OP(OEt)(3) to TEOS in the hybrids led to the high dissolution of calcium and silicate, while addition of large amounts of OP(OEt)(3) decreased the dissolution of calcium and silicate ions and resulted in reduced apatite formation regardless of the dissolution of phosphate ions from the hybrids.

Effect of preparation conditions on the properties of bioactive glasses for testing SBF

A simulated body fluid (SBF) with ion concentrations similar to body fluid, proposed by Kokubo et al., is widely used to evaluate bone-bonding potential through the formation of an apatite layer. To be confident of the evaluation of the potential for the apatite formation in SBF, standard substrates are required. Although Na(2)O-CaO-SiO(2) glasses have been focused upon as candidate standard substrates, it has not been clarified whether the preparation conditions of the glasses affect their apatite formation potential in SBF. In this study, Na(2)O-CaO-SiO(2) glasses were prepared by a conventional melting-quenching method with different melting periods and annealing processes to examine their properties, including apatite formation in SBF. The Na(2)O-CaO-SiO(2) glasses show reproducible apatite-forming ability when prepared using moderate melting and annealing processes, and can be useful substrates to test the reproducibility of SBF.

A study of apatite formation on natural nano-hydroxyapatite/chitosan composite in simulated body fluid

This study is focused on the ability of apatite formation on the surface of nano-hydroxyapatite (HA)/chitosan (CH) composite in simulated body fluid (SBF) in vitro. At first, natural nano-HA was prepared according to a wet-balling method and the composite was prepared by combining the natural nano-hydroxyapatite and chitosan, and then in vitro biomineralization test of natural nano-HA/CH composite was carried out in standard SBF. Subsequently, the quantity of the weight of the particles formed on the composite surface in SBF was measured by analytical balance, and the morphology change on the surface of the composite was observed by a scanning electron microscope (SEM). Lastly, a Fourier transform infrared spectroscope (FTIR) was used to investigate the chemical components of the particles formed on the natural nano-HA/CH composite surface in SBF. The result of quantity assessment shows that the weight of the composite increased with the increase of soaking time. The SEM image shows that the particles were gradually formed on natural nano-HA/CH composite surface, and the FTIR spectrum of the particles on composite surface confirms that these particles were carbonate apatite. This study indicates that the nano-HA/CH composite has a good ability for apatite formation in SBF, which predicts the bone-inducing ability of natural nano-HA/CH composite in vivo.

Preparation and in vitro bioactivity of poly( d,l-lactide) composite containing hydroxyapatite nanocrystals

The nano-sized hydroxyapatite (n-HA) was incorporated into poly( d,l-Lactide) (PDLLA) to form a bioactive and biodegradable composite for application in hard tissue replacement and regeneration. Thin film of PDLLA composite containing 20 mass% of n-HA fillers was successfully developed through integration of solvent co-blending and hot pressing techniques. firstly, n-HA and PDLLA were chemically synthesized, respectively, then mixed together and homogeneously dispersed in N, N-dimethyl formamide(DMF) solvent, finally, the dried blended hybrid containing PDLLA matrix and n-HA fillers was put into the mould and compacted by hot-pressing machine under 8 MPa pressure at 110 °C for 15 min. In vitro studies were conducted using the simulated body fluid(SBF). Composite specimens were soaked in SBF from 1 day to 21 days prior to surface analysis. Results obtained from scanning electron microscopy(SEM) examination, Energy dispersive X-ray detector(EDX) analysis and X-ray diffraction (XRD) analysis showed that a layer of non-stoichiometric apatite formed within 7 days on HA/PDLLA composite surface after its immersion in SBF, demonstrating moderate in vitro bioactivity of n-HA/PDLLA composite, though a moderate rate of apatite formation in SBF was found on initial stage of immersion periods for n-HA/PDLLA composite, compared to the other biomaterial composite. This type of composite film exhibited certain desirable bioactive characteristics, and they are promising bone candidates to develop novel bioactive composites for biomedical application.

Evaluation of apatite-forming ability and mechanical property of pectin hydrogels

Apatite-polymer hybrids are expected as novel bone substitutes exhibiting bone-bonding ability, i.e. bioactivity, and mechanical performances analogous to those of natural bone. To fabricate such hybrids, biomimetic process has been paid much attention where bone-like apatite is deposited on organic polymers that have specific functional groups in simulated body fluid (SBF) or more concentrated solutions. Previous studies showed that carboxyl groups (-COOH) have a catalytic effect for heterogeneous apatite nucleation in SBF. In this study, we chose pectin as an organic polymer. Pectin is a natural polysaccharide containing carboxyl groups. Hydrogels were prepared from various pectins including pectic acid, apple-derived pectin and citrus-derived pectin by treatment with CaCl2 solution. Ability of apatite formation in SBF and mechanical properties of the gels were examined. The apatite-forming ability increased in the order (pectic acid)<(apple-derived pectin)<(citrus-derived pectin). It was suggested that the apatite-forming ability of the pectin gels is governed by not only the amount of carboxyl groups but also changes in Ca2+ concentration and pH in surrounding solutions. Young's modulus of the pectin gels was similar to natural bone, although tensile strength is a little lower.

Influence of film thickness on in vitro bioactivity of thin anatase films produced through direct deposition from an aqueous titanium tetrafluoride solution

With proper pre-treatment of the metal, well-crystallized thin anatase films of thicknesses varying from 0.12 to 0.79 μm were deposited on commercially available pure titanium (CPTi) substrate from a 25 mM titanium tetrafluoride aqueous solution. The deposition of anatase films took place at a low temperature of 60 °C between 1 to 48 h. After a heat treatment in air at 300 °C for 1 h to remove fluorine from the anatase films, the films of thicknesses above 0.41 μm induced apatite deposition in a simulated body fluid (SBF) within 5 days. The 0.12 μm thick anatase film required 21 days to induce apatite formation in SBF. There appeared to be a critical film thickness of anatase, above which the in vitro bioactivity improved greatly. But further increases in the film thickness of anatase did not have remarkable effect on in vitro bioactivity.

How useful is SBF in predicting in vivo bone bioactivity?

The bone-bonding ability of a material is often evaluated by examining the ability of apatite to form on its surface in a simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma. However, the validity of this method for evaluating bone-bonding ability has not been assessed systematically. Here, the history of SBF, correlation of the ability of apatite to form on various materials in SBF with their in vivo bone bioactivities, and some examples of the development of novel bioactive materials based on apatite formation in SBF are reviewed. It was concluded that examination of apatite formation on a material in SBF is useful for predicting the in vivo bone bioactivity of a material, and the number of animals used in and the duration of animal experiments can be reduced remarkably by using this method.

Effect of Concentrated Sulfuric Acid-Etching on Apatite-Forming Ability of Alkaline-Treated Titanium

Concentrated H2SO4 acid was applied to pretreatment for the alkaline treatment of commercially pure titanium, and the effect of acid-etching on apatite-forming ability of alkaline-treated titanium in a simulated body fluid (SBF) was investigated. Characterization analysis revealed that the concentrated H2SO4 etching formed much amount of sodium titanate, resulting a large amount of formation of apatite in SBF. It is confirmed that the etching in concentrated H2SO4 enhance apatite-forming ability of alkaline-treated titanium.

Preparation of bioactive titanium metal via anodic oxidation treatment

Titania with specific structures of anatase and rutile was found to induce apatite formation in vitro. In this study, anodic oxidation in H 2SO 4 solution, which could form anatase and rutile on titanium metal surface by conditioning the process, was employed to modify the structure and bioactivity of biomedical titanium. After the titanium metal was subjected to anodic oxidation treatment, thin film X-ray diffraction and scanning electron microscopy results showed the titanium metals surfaces were covered by porous titania of anatase and/or rutile. In simulated body fluid (SBF), the titanium anodically oxidized under the conditions with spark-discharge could induce apatite formation on its surface. The induction period of apatite formation was decreased with increasing amount of either anatase or rutile by conditioning the anodic oxidation. After the titanium metal, anodically oxidized under the conditions without spark-discharge, was subjected to heat treatment at 600°C for 1 h, it could also induce apatite formation in SBF because the amount of anatase and/or rutile was increased by the heat treatment. Our results showed that induction of apatite-forming ability on titanium metal could be attained by anodic oxidation conjoined with heat treatment. So it was believed that anodic oxidation in H 2SO 4 solution was an effective way to prepare bioactive titanium.