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A flow-micro-reactor system was employed to fabricate hydroxyapatite (HAp) in order to mimic the interface between calcium and phosphate solutions on a wet chemical procedure. The mixing ratio of calcium nitrate tetrahydrate and diammonium hydrogenphosphate solution was set to the stoichiometric atomic ratio HAp, 1.67, while pH value of the product suspension was varied from 6.4 to 10.0. The product morphology was changed from nano-sheet type to nano-particle type via nano-rod one, while their size was decreased from 100–500 nm to 50 nm. All as-prepared samples, irrespective of pH value of the resultant suspension, consisted of HAp, predominant phase, octacalcium phosphate (OCP), and dicalcium phosphate dihydrate (DCPD) or dicalcium phosphate anhydrate (DCPA). A batch system using the same solutions yielded very similar results, which confirmed that the reactions in this micro-reactor well reproduced a large-scale mixing system. Calcining sample obtained from pH 6.4 suspension for 2 h at lower temperatures (

Chitosan–γ-glycidoxypropyltrimethoxysilane (GPTMS)–tetraethoxysilane (TEOS) hybrid membranes were prepared by the sol–gel method. The effects of Si(IV) released from them on cell proliferation and differentiation were examined in terms of cell metabolic activity and the alkaline phosphatase (ALP) activity of MG63 osteoblastic cells. The amount of Si(IV) released from the hybrid membranes increased with the TEOS content. The released Si(IV) inhibited cell proliferation but promoted cell differentiation. Thus, the osteocompatibility of the chitosan hybrid membranes in the chitosan–GPTMS–TEOS system can be controlled by the amount of Si(IV) released from them when they are applied to cell culture.

We report on the effect of using a spatial gap on heterogeneous nucleation on the surface of thermally oxidized titanium substrates. Induction of heterogeneous nucleation of bone-like hydroxyapatite (BHAp) was evaluated in the spatial gaps between substrates that were thermally oxidized at temperatures of 100-800°C on exposure to a simulated body fluid (SBF). After soaking in a SBF for 7 d, BHAp spontaneously deposited inside the gap on the surface of samples that were thermally oxidized at temperatures above 400°C, but not on samples that were thermally oxidized at temperatures of 300°C or less. Among the substrates studied, BHAp particles were most readily deposited inside the gap on the surface of the samples that were thermally oxidized at 400°C after soaking in an SBF. A smaller gap led to a higher number of BHAp particles being deposited on the surface of the samples that were thermally oxidized at 400 or 500°C. Our results suggest that the formation of BHAp in a SBF is dependent on the temperature during thermal oxidization, and also on the spatial gap between the samples. The ease of formation of BHAp on thermally oxidized titanium increases with increasing thickness of the rutile phase and the number of Ti-OH groups, which are produced during the thermal oxidization process. In addition to the surface structure of the substrates, the spatial gap is regarded as an important parameter for enhancing the deposition of BHAp. Since the formation of BHAp allows osteoconduction to occur after implantation in a bony defect, it is possible to design titanium-based implants with a high biological affinity to bone by processing using an appropriate spatial design of the substrate.

Amino-modified TiO2 particles were derived from precursor mixtures of tetraethylorthotitanate and aminopropyltriethoxysilane (APTES) that both were dissolved in ethanol/water solution. Size, morphology, crystalline structures, and formation mechanism of the particles were discussed in terms of the APTES amount and the pH value in the solution. The addition of APTES resulted in amorphous amino-modified TiO2 particles. The low crystallinity in the final particles was attributed to the polar amino groups.

Ultraviolet (UV) light was irradiated in air for 1 h on titania (rutile) films prepared by thermal oxidation of titanium substrates from 300°C up to 800°C, coded as HT300UV, HT400UV, HT500UV, HT600UV, HT700UV, and HT800UV, respectively. All samples were then soaked in a simulated body fluid (SBF, Kokubo solution) and their in vitro apatite-forming ability was evaluated. It was found that bone-like apatite particles were deposited on HT500UV, HT600UV, and HT700UV within 7 d whereas that was not the case with others during the same period. Moreover, the apatite particles were deposited more on HT500UV than on the others. Therefore, the ultraviolet light irradiation enhanced the in vitro apatite-forming ability of the thermally oxidized titanium.

Titania layers were deposited on titanium substrates in titanylsulfate solutions under varied concentration (0.01 and 0.03M), pH (0.67-1.27) and temperature (60 and 80°C). They were rinsed and subsequently aged in water at 80°C for 3d. The layers consisted of only rutile or rutile with trace anatase, depending on the conditions. The X-ray diffraction intensity indicates that the rutile particles grew preferably in (101) plane, regardless of being aged or not. When aged, the anatase diffraction intensity increased, and anatase newly grew in the layer consisting only of rutile. When soaked in a simulated body fluid (SBF) of the Kokubo recipe, the rinsed layer with only rutile was weakly active to deposit apatite within 5 d, while the other two exhibited no deposition. The aging improved activity. Although anatase is reported in the literature to be more active than rutile, the present study indicates that the rutile layer is more active. Thus, it is concluded that topotaxy or epitaxy would not work well but other issues like the presence of Ti-OH affect apatite deposition.

y-Methacryloxypropyltrimethoxysilane (y-MPS) was grafted on a silicone elastomer by emulsion polymerization in order to improve cytocompatibiiity. The wettability of the grafted surface was evaluated with a contact angle toward distilled water. By grafting within 30 min at 60°C, the contact angle was reduced from 110° to about 70° while it remained almost constant for longer grafting. A larger number of osteoblastic cells (MC3T3-E1) and fibroblast cells (L929) proliferated on the surface modified with γ-MPS compared with the original silicone surface. After culturing for 7 d, the cells completely covered the grafted surface and even formed a cell layer.

A novel approach to fabricate sub-μm scale arrays is demonstrated with the growth of rutile TiO2 on titanium substrates. The fabrication process is template-free, simply involving coating of the titanium substrate with sodium tetraborate glass, Na2O•2B2O3: when the glass coating was removed by dissolution in distilled water at 80°C for about 5 h, random or well-ordered submicron-scale rod arrays of rutile were left on the substrate. A glass phase topotaxial (GPT) nucleation and growth mechanism is thought to operate in the crystal growth process.

A new approach is presented to prepare a rutile layer on titanium substrates. According to this approach, pulverized glass, composed of 3CaO•4B2O3•3TiO2, is first developed on the substrate, heated up to 700 to 850°C, and then removed by soaking in hot water. During the heating process, rutile grew at the glass coating-substrate interface to form nano-sized crystallites. The rutile layer induced apatite formation within 3 d when soaked in simulated body fluid of the Kokubo recipe. Such in vitro bioactivity was attributed to many Ti-OH groups on the crystallite surface derived from hydrolysis of bonds at the crystallite-flux (matrix) interface like (rutile)-Ti-O-B or Ti-O-Ca-(the borate matrix).

This study concerns with the adsorption of pathogenic substances on highly blood-compatible titania and the adsorption mechanism. Titania was prepared through a sol-gel procedure by hydrolyzing tetraethylorthotitanate and calcining up to 705°C for 3 h. Pore size distribution and surface charge density were measured as a function of calcining temperature. Adsorption of bilirubin, as a typical pathogenic substance, as well as albumin on the titania powder was studied. Bilirubin was adsorbed either in 4 to 8-nm pores or on the surface with a higher positive charge. Thus, either entrapping bilirubin in the pores or electrostatic interaction between bilirubin and titania surface was effective for the adsorption of bilirubin. The titania powder adsorbed a greater amount of bilirubin than the anion-exchange resin used in clinics, hence they have potential for blood purification therapy.

Synthesized were organically modified silicate (ORMOSILs) hybrids containing colloidal silica as an ingredient, starting from poly (dimethylsiloxane) (PDMS), tetrathoxysilane (TEOS) and calcium nitrate through sol-gel processing. The effects of pre-hydrolysis of TEOS on mechanical strength and viscoelasticity were examined. A sample of composition PDMS/TEOS = 0.60 (molar ratio) with pre-hydrolysis of TEOS showed about 65% maximum failure strain. Thus obtained hybrid exhibited a peak at around −75°C in the storage modulus-temperature curve of the hybrid, due to transverse movements of the PDMS chains. This hybrid, heated at 200°C deposited apatite within 1 d in the simulated body fluid of the Kokubo recipe.

Synthesized through sol-gel processing were Ormosil type hybrid gels containing varied mass fractions of colloidal silica, poly (dimethylsiloxane) (PDMS), tetraethoxysilane (TEOS) and calcium nitrate. Viscoelasticity, mechanical strength and 29 Si MAS NMR spectra were measured, and in vitro apatite deposition in a simulated body fluid (SBF) of the Kokubo recipe was examined. The relative height of a Tg peak at about -100°C in tan δ versus temperature curves grew with the colloidal silica content. This peak growth was accounted for the relative increase in PDMS-colloidal silica interactions. As the increase in the compressive strength followed the increase in colloidal silica content, the number of PDMS-silica bonds and hydrogen bond of colloidal silica increased due to the NMR spectra and tan δ curve. Thus, mechanical strength was dependent on PDMS-silica bonds and the hydrogen bond of colloidal silica. On the other hand, as the relative PDMS content increased, the number of PDMS-silica bonds was little influenced while PDMS chain structure increased. The gel (with a molar ratio TEDS:PDMS:H 2 O:HCl:Ca (NO 3 ) 2 .4H 2 O=1:0.48:5.0:0.9:0.10) containing 14 mass% colloidal silica (CS 14 P 0.48 Ca 0.10 ) exhibited the highest maximum failure strain (about 70%) among all samples. Thus, the relative content of PDMS chain structure depending on PDMS content influenced the maximum failure strain. CS 14 P 0.48 Ca 0.25 could not deposit apatite within 7 d after soaking in SBF, while PDMS/TEOS=0.24 (molar ratio) could deposit apatite within 3 d. The increase in PDMS content restrained the dissolution of Ca ions.

The in vitro bioactivity, in terms of apatite-forming ability, of calcium silicate glasses containing 10 mol% fluoride ions in the NaF-CaO-SiO 2 system was examined by soaking in Kokubo's simulated body fluid (SBF) at 36.5°C for 7 d. The surface structure of the glasses was examined by thin-film X-ray diffraction (TF-XRD) and Fourier transform infrared reflection spectroscopy (FT-IR) in order to confirm the apatite deposition. The structure of the calcium silicate glasses was examined by 29 Si magic angle spinning-nuclear magnetic resonance spectroscopy (MAS-NMR) and X-ray photoelectron spectroscopy (XPS). Three calcium silicate glasses containing 10 mol% fluoride ions had different apatite-forming abilities. In the case of CaO/SiO 2 = 1, the apatite-forming ability of 10NaF.45CaO.45SiO 2 was lower than that of 50CaO.50SiO 2 . This indicated that the addition of fluoride ions suppressed the apatite-forming ability, irrespective of the structural similarity of the silicate network based on the ratio of CaO/SiO 2 between the glasses.

Nucleation and crystal growth mechanism of apatite formation on porous silica gel derived by a sol-gel procedure was investigated by the use of several simulated body fluids (SBF's) that had different concentrations of Ca(II), P(V), and OH- but had the same degree of supersaturation for hydroxyapatite. Induction time of apatite crystallization in SBF's was evaluated by thin film X-ray diffractometry. The effect of each ion on the induction time increased in the order: Ca(II)-rich SBF

The structure of MO-TeO2 (M=Mg, Zn, Sr, Ba and Pb) glasses has been studied by means of 125Te static NMR technique. The fraction of TeO4 trigonal bipyramid (tbp), N4 decreased and that of TeO3 trigonal pyramid (tp), N3 increased almost linearly up to 33.3mol% MO and rapidly in the range of 33.3 to 40mol% MO, with increasing MO content. It was found that the glasses containing MO in the range of 40 to 45mol% MO consisted only of TeO3 tp. On the basis of the structural model proposed in a previous paper, the fractions of TeO4 tbp without a non-bridging oxygen (NBO) atom, TeO4/2 (N40), TeO4 tbp with an NBO atom, O3/2 Te-O- (N4-) and TeO3 tp with two NBO atoms, O1/2Te(=O)-O- (N3-) were calculated. The structural change for MO-TeO2 glasses in the range of 0 to 33.3mol% MO could be well represented by the model previously proposed for alkali tellurite binary glasses. A new model which represents the structural change for MO-TeO2 glasses containing more than 33.3mol% MO has been proposed.

31P MAS-NMR spectra were measured for pulverized binary and ternary glasses containing Ca2+ ions after soaking in a simulated body fluid (Kokubo solution; pH=7.25) for 1d, and the chemical state of adsorbed phosphate ions were examined. The 31P chemical shift indicated that orthophosphate ions, HxPO4-(3-x) (0

The structure of alkaline earth vanadate glasses, xMO⋅(100-x)V2O5 (M=Ca, Sr, Ba, x=30, 40, 45, 50, 55), has been investigated by means of 51V static and magic angle spinning (MAS) NMR spectroscopies. The 51V NMR spectral parameters of various constituent vanadate groups contained in the vanadate glasses were determined by the spectrum simulation with reference to those of various crystalline vanadates obtained previously. It was found that the structure of alkaline earth vanadate glasses consists mainly of VO4-tetrahedra in accordance with the authors' previous results based on the IR study. It was deduced that for x=50 the glass network is mainly constituted of one dimensional (VO3)n-single chains, and for x≤45 the decrease of the MO content yields a mixture of the V2O5-rich phase constituted of three dimensionally branched VO4-groups and the MO-rich phase constituted of the VO5-trigonal bipyramids, followed by the decrease of (VO3)n-single chains.

The structure of alkaline earth vanadate glasses of the compositions, xMO⋅(100-x)V2O5 (M=Mg, Ca, Sr, Ba, x=30, 40, 45, 50, 55), has been investigated by means of IR spectroscopy with reference to various crystalline alkaline earth vanadates structurally known. It is found that the structure of alkaline earth vanadate glasses is very similar to each other and mainly consists of VO4-tetrahedra which form either (VO3)n-sin-gle chains as found in Sr(VO3)2 and Ba(VO3)2 crystals or the three dimensional arrangement of the cornersharing branched VO4-tetrahedral groups as found in molten and amorphous V2O5. It is stressed that the glass network of the V2O5-rich glasses, 30MO⋅70V2O5, also mainly consists of VO4-tetrahedra.

Anatase of good crystallinity has been developed on titanium substrates by soaking in a 30 mass% hydrogen peroxide solution at 80°C for 8h, soaking in distilled water at ambient temperature for 12h, and subsequently aging in distilled water at 80°C for 3d. The anatase layers exhibit good bioactivity as inducing apatite deposition in Kokubo's simulated body fluid within 2d.