Highly pure brushite

Using ultraviolet (UV) irradiation of micro-arc oxidized (MAO) titania coating in distilled water for 0.5 and 2 h, we have achieved an enhanced bioactivity and cell response to titania surface. The MAO coating appears porous and predominantly consists of nanocrystallized anatase TiO2. Compared with the MAO coating, the UV-irradiated coatings do not exhibit any obvious change in surface roughness, morphology, grain size and phase component; however, they have more abundant basic Ti-OH groups and become more hydrophilic because the water contact angle decreases significantly from 17.9

Nanocrystalline titania films were prepared by plasma electrolytic oxidation of a titanium alloy at 200–350 V in a Na2CO3 electrolytic solution using a pulsed power supply. XRD, EDS and Field Emission (FE) SEM were employed to characterize the phase, composition, and microstructure of the films. Vickers indentation, nanoindentation and adhesion–tension test were used to evaluate the mechanical properties of the films. The phase, pore size and thickness of the films strongly depend on the applied voltage consistent with the previous reports. The films prepared at 350V were porous with; 1 mm pores and the pore walls were composed of 10-20 nm rutile crystallites. The hardness, Young's modulus and bond strength of the film were 0.9"0.2 GPa, 32"4 GPa and 37"3 MPa, respectively. The film exhibited a significant plasticity and ductility compared to the conventional coarse-grained titania ceramics.

Titania-based films on titanium were formed by micro-arc oxidation in electrolytic solutions containing sodium carbonate, sodium phosphate, acetate monohydrate and b-glycerophosphate disodium salt pentahydrate using a pulse power supply. The morphology, elemental composition and phase components of the films were investigated as a function of the electrolytes composition and the applied voltage (in the range of 200–500 V). In vitro bioactivity of the films was evaluated in a most commonly used simulated body fluid as proposed by Kokubo et al. The results showed that the films were porous with 1-8mm pores and nano-crystallized, without apparent interface to the titanium substrates. The phase components of the films could be anatase, rutile, CaTiO3, b-Ca2P2O7 and a-Ca3(PO4)2, strongly depending on the electrolytes composition and the applied voltage. The pore size and the content of Ca and P tended to increase with the applied voltage. Among the prepared titania-based films, only the film containing CaTiO3, b-Ca2P2O7 and a-Ca3(PO4)2 could induce an apatite layer on its surface, exhibiting bioactivity. The bioactive response of the micro-arc oxidized films to the structural factors and the apatite-induced mechanism were discussed.

Nanocrystalline titania films were synthesized by micro-arc oxidation of titanium substrates in an electrolytic solution using a pulsed power supply. X-ray diffraction (XRD) indicated that the deposited films consisted of a high crystalline anatase phase. Field emission scanning electron microscopy (FESEM) showed that the films were macro-porous with 1–2 Am pores and the matrix was composed of 10–20 nm grains. The adhesion–tension test showed that the films had an adhesive strength of 20F2MPa. Such firmly adhesive, porous and nanocrystalline anatase films are expected to have significant applications as orthopaedic/dental implants and catalysts.

Biomimetic apatite coatings on micro-arc oxidized titania films were investigated and their apatite-inducing ability was evaluated in a simulated body fluid (1.0SBF) as well as in a 1.5 times concentrated SBF (1.5SBF). Titania-based films on titanium were prepared by micro-arc oxidation at various applied voltages (250-500V) in an electrolytic solution containing b-glycerophosphate disodium salt pentahydrate (b-GP) and calcium acetate monohydrate (CA). Macro-porous,Ca- and P-containing titania-based films were formed on the titanium substrates. The phase,Ca and P content, morphology, and thickness of the films were strongly dependent on the applied voltage. In particular, Ca- and P-containing compounds such as CaTiO3, b-Ca2P2O7 and a-Ca3(PO4)2 were produced at higher voltages (>450 V). When immersed in 1.0SBF,a carbonated hydroxyapatite was induced on the surfaces of the films oxidized at higher voltages (>450 V) after 28 days,which is closely related to the Ca- and P-containing phases. The use of 1.5SBF shortened the apatite induction time and apatite formation was confirmed even on the surface of the films oxidized at 350 V, which suggests that the incorporated Ca and P in the titania films play a similar role to the Ca-and P-containing compounds in the SBF.

A new route was developed to synthesis a new type of strontium-containing hydroxyapatite (Sr-HAP) bone cement with precursors of tetracalcium phosphate (TTCP), strontium hydrogen phosphate (DSPA), dicalcium phosphate (DCPA), phosphate acid and water. The processing parameters and fundamental properties including pH value, setting time, compressive strength of final hardened bodyand the cytotoxicityfor serial extracts of each cements were investigated. The result shows that the final product of the cement after setting for 24 h is nonstoichiometic Sr-containing hydroxyapatite (Ca10mxSrxm(HPO4) y(PO4)6y(OH)22m2m, 0oxo1, nSr-HAP) and no other harmful impurities were detected. The pH value of Sr-containing cement pastes approaches to 7.0-7.6 when theyare mixed with a ratio of 1:1 of powder to liquid (P/L) in weight. The setting time of the cement pastes is 4-11 min for the initial one and 10-17 min for the final one when the concentration of diluted phosphate is in a range of 0.5-1.0mol/l. The compressive strengths of the hardened cements with different molar ratios of Sr/(Sr+Ca) after subjected an immersion in simulated body fluid (SBF) increase uniformly from 1 day to 5 days, where they get maximum values, respectively, but then decrease till to 2 weeks. Especiallyfor the CPC-1, with a Sr/(Sr+Ca) molar ratios of 5% in cement powder composition, the largest compressive strength gained at 5 days is 66.57MPa and the lowest one gained at 2 weeks is 44.75 MPa, which matches the value of human bones and can be expected to use in clinic application in repairing the nonloading sites on account of the positive result of cytotoxicity test of the extracts of Sr-containing calcium phosphate cement (Sr-CPC).

Carbon-carbon composite has mechanical properties similar to human bone, as well as good biocompatibility, but without bioactivity. TiOx film was deposited onto carbon-carbon composite by ion beam-enhanced deposition (IBED) technique, and a porous network was formed on the TiOx film after alkali treatment. The network induced the deposition of calcium phosphate layers with different morphologies and compositions from simulated body fluid and the fast calcification solution.