Abstract: Objectives: The aim of this study was to evaluate the mineralizing potential of ions released from surface pre-reacted glass-ionomer (S-PRG) fillers on mineral induction by phosphoprotein in vitro. Methods: Phosvitin was used as a model of dentin phosphoprotein in this study. Phosvitin was immobilized on agarose beads with divinyl sulfone. Five aliquots of phosvitin-immobilized agarose beads were incubated in control or experimental mineralizing solution. The experimental mineralizing solutions were made from eluates of resin filled with S-PRG fillers. The beads were incubated at 37 degrees C in a shaking water bath, and aliquots were taken at several time points during the incubation. Then the beads were analyzed for calcium by atomic absorption spectrometry. Results: Phosvitin-immobilized agarose beads induced mineral formation after incubation for 5.3 h in the metastable solution without ions eluted from S-PRG fillers. Undiluted eluates significantly reduced mineral induction time. SEM observation and X-ray diffraction revealed larger apatite crystals on the beads incubated with eluates of S-PRG fillers than with the control. Conclusions: S-PRG fillers may play a role in mineral induction. (C) 2010 Elsevier Ltd. All rights reserved.
Abstract: This study evaluated the effect of resin monomer composition on crystal growth at the interface between the resin/bioglass composites and water. Light-cured resin that contained 2-bis[4(2-hydroxy-3-methacryloyloxy-propyloxy)-phenyl], 2-hydroxyethyl methacrylate, and triethylene glycol dimethacrylate with different compositions were used. Resin/bioglass composites were prepared with 40 mass% bioglass and 60 mass% resin. The resin/bioglass composites were stored in deionized distilled water for 24 h (control group) or 3-12 months (experimental groups). After water storage, the disk surfaces were examined by light- and scanning electron microscopy. Chemical states of the crystals were analyzed by laser-Raman spectroscopy and micro-X-ray diffractometry. The microscopic analysis showed crystal on the resin disks surface after six months of water storage for hydrophilic resins. However, there was no crystal formation in the control and the experimental groups of specimens of hydrophobic resins. Raman analysis showed the chemical states of the crystals formed on the resin matrix and bioglass to be different. The micro-X-ray analysis of crystals on resin disks identified them to be calcium carbonate. This crystal formation occurred in water instead of simulated body fluid. In conclusion, the resin monomer compositions affected the ability to induce crystal growth on the surfaces of disks containing bioglass. (C) 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 94B:127-133, 2010.
Abstract: In biomaterial silane treated TiO2/high-density polyethylene(silane-TiO2/HDPE), silane connection structurally corresponds to acid phosphoprotein bond, which connects the noncalcified collagen fibril bands and the adjacent apatite crystals in natural bones. In order to explore the function and variation process of acid phosphoprotein under loading in natural bones, the microscopic variation mechanism of silane connection in silane-TiO2/HDPE was investigated through the compressive creep tests in air and saline solution. Through the analysis of creep rate curves under different stress loads, different creep mechanisms were proposed, in which silane connection plays a very important role. Through SEM observation of sample surfaces and the creep tests in saline solution, the important role of silane connection in creep process was further proved. That is, silane connection can not only support the loading stress but also hinder the failure process under loading effectively.
Abstract: In this study, polymethylmethacrylate-based composite cements containing 40-55.6 wt% micron-sized titania (titanium oxide) particles were developed, and their mechanical, setting, and biological properties evaluated. Three types of composite cement containing 40, 50, and 55.6 wt% silanized titania were designated ST2-40c, ST2-50c, and ST2-56c, respectively. In animal experiments, ST2-50c and ST2-56c were implanted into rat tibiae and solidified in situ. An affinity index was used to evaluate osteoconductivity. Compressive and bending strength of ST2-56c was 147.7 +/- 3.2 and 69.3 +/- 7.4; those of the other cements exceeded 100 MPa and 50 MPa, respectively. The affinity indices of ST2-56c were 42.1 +/- 12.9 at six weeks and 53.4 +/- 16.6 at 12 weeks, and were significantly higher than for ST2-50c and a commercial PMMA bone cement within 12 weeks. Our data indicate that bone cement containing micron-sized titania particles can be applied to prosthesis fixation as well as vertebroplasty, and ST2-56c is a good candidate cement.
Abstract: Composite materials consisting of TiO2 nanoparticles and high-density polyethylene (HDPE), designated hereafter as TiO2/HDPE, were prepared by a kneading and forming process. The effect of TiO2 content on the mechanical properties and apatite forming ability of these materials was studied. Increased TiO2 content resulted in an increase in bending strength, yield strength, Young's modulus and compressive strength (bending strength = 68 MPa, yield strength = 54 MPa, Young's modulus = 7 GPa, and compressive strength = 82 MPa) at 50 vol% TiO2. The composite with 50 vol% TiO2 shows a similar strength and Young's modulus to human cortical bone. The TiO2/HDPE composites with different TiO2 contents were soaked at 36.5 degrees C for up to 14 days in a simulated body fluid (SBF) whose ion concentrations were nearly equal to those of human blood plasma. The apatite forming ability, which is indicative of bioactivity, increased with TiO2 content. Little apatite formation was observed for the TiO2/HDPE composite with 20 vol% content. However, in the case of 40 vol% TiO2 content and higher, the apatite layers were formed on the surface of the composites within 7 days. The most potent TiO2 content for a bone-repairing material was 50 vol%, judging from the mechanical and biological results. This kind of bioactive material with similar mechanical properties to human cortical bone is expected to be useful as a load bearing bone substitute in areas such as the vertebra and cranium.
Abstract: Mechanical properties of composites made up of high-density polyethylene (HDPE) and silanated TiO2 particles for use as a bone-repairing material were investigated in comparison with those of the composites of HDPE with unsilanized TiO2 particles. The interfacial morphology and interaction between silanated TiO2 and HDPE were analyzed by means of Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). The absorption in spectral bands related to the carboxyl bond in the silane-coupling agent, the vinyl group in the HDPE, and the formation of the ether bond was studied in order to assess the influence of the silane-coupling agent. The SEM micrograph showed that the "bridging effect" between HDPE and TiO2 was brought about by the silane-coupling agent. The use of the silane-coupling agent and the increase of the hot-pressing pressure for shaping the composites facilitated the penetration of polymer into cavities between individual TiO2 particles, which increased the density of the composite. Therefore, mechanical properties such as bending yield strength and Young's modulus increased from 49 MPa and 7.5 GPa to 65 MPa and 10 GPa, respectively, after the silane-coupling treatment and increase in the hot-pressing pressure. (c) 2005 Elsevier Ltd. All rights reserved.
Abstract: Bioactive bone cement with mechanical properties higher than that of commercial polymethylmethacrylate (PMMA) bone cement are strongly desired to be developed. In the present study, PMMA-based cement incorporated with nano-sized rutile particles was prepared. The PMMA-based cement (rutile content was 50 wt%) shows the compressive strength (136 MPa) higher than that of commercial PMMA bone cement (88 MPa). The hardened cement formed apatite on the surface in a simulated body fluid within 3 days. Therefore, this PMMA-based cement incorporated with rutile particles might be useful as cement for fixation of prostheses as well as self-setting bone substitutes, because of its high apatite forming ability and mechanical strength.
Abstract: A newly improved simulated body fluid (n-SBF) was designed to have concentrations of ions equal to those of human blood plasma excepting that of HCO3-, the concentration of which is lower than the level of saturation with respect to calcite. The preparation process was modified and two different preparing processes such as powder dissolving and liquid mixing processes were attempted. The n-SBFs with nominal ion concentration can be prepared and its concentrations were unchanged over 4 weeks. The bioactive glasses showed almost same bioactivity in both n-SBFs and c-SBF. The n-SBFs is believed to produce apatite under quite similar condition to the body environment, thereby being useful for in vitro assessment of bioactivity of artificial material.
Abstract: Bioactive bone-substitutes with mechanical properties analogous to those of natural bone are strongly desired to be developed. In the present study, HDPE/TiO2 composites were prepared from titanium dioxide (TiO2) nano-powder with anatase structure and high density polyethylene (HDPE) with different melting flow rate (MFR) through a batch-kneader mixing. The composite with a uniform dispersion of TiO2 powder were prepared. The composite prepared from HDPE of MFR=8 shows the highest bending strength (about 50 MPa) and Young's modulus (about 7.5 GPa) within the range of the mechanical properties of human cortical bone. The composites formed apatite on their surfaces in a simulated body fluid within 7 days. Therefore, these PE/TiO2 composites with such mechanical properties and bioactivity are considered to be useful as bone-repairing materials.
Abstract: It has been reported that Ti-OH groups in a titania gel with an anatase structure are remarkably effective in inducing apatite formation. From these findings, bioactive polyethylene-titania (PE/TiO2) composites were prepared by hot pressing powders of titanium oxide with an anatase structure and ultra-high molecular weight polyethylene. In the present study, the effects of mixing, pressure and temperature during hot pressing on the mechanical property of the composites were investigated. It was found that their bending strength increased with increasing pressure and temperature and that Young's Modulus increased with increasing pressure. It was found that these composites can bend more than 6 mm without any cracks. These bioactive materials are considered to be useful as bone-repairing materials.
Abstract: Particulate titanium dioxide (crystalline phase is anatase) with an average size of 200 nm was incorporated into an ultra high molecular weight polyethylene (UHMWPE) for potential medical applications. Composites with titanium dioxide volumes of 10 and 40 % were produced by a manufacturing process consisting of blending in the theta-composer and compression molding with hot press. Titanium dioxide particles were well dispersed, and homogeneous distribution in the polymer matrix, achieved after compounding, was retained during subsequent composite processing. Thin-film X-ray diffraction pattern and Fourier transform infrared spectra, obtained from TiO2/UHMWPE samples exposed for up to 10 days at 36.5degreesC to a simulated body fluid (SBF), demonstrated that composites of all the compositions examined developed the surface biological apatite layer equivalent to that for bone-like apatite.
Abstract: Objective: Reactmer Bond (Shofu Inc., Kyoto, Japan) is a glass ionomer (GI) based, tri-curable, all-in-one, filled adhesive. Both fluoroaluminosilicate glass (FASG) and fully pre-reacted glass (F-PRG) are used as fillers. This study examined the ultrastructure and elemental composition of resin-dentine interfaces that were treated. with this adhesive. Methods: Dentine disks prepared from human third molars were abraded with either 600- or 60-grit SiC paper to create smear layers of different thickness. They were bonded using Reactmer Bond. Cryo-fraetured dentine surfaces devoid of smear layers were also bonded by chemical-activation and GI reaction without additional light-activation, or allowing the GI reaction to proceed for I min before the adhesive was applied and light-activated. Undemineralised and demineralised sections were processed for TEM examination and STEM/EDX analysis. Results: Resin-dentine interface from specimens with smear layers consisted of a mineral-dense surface layer that resided on top of a partially demineralised dentine. The partially demineralised zone was considerably, thicker in the 600-grit than the 60-grit specimens. In smear layer-free specimens that were cured by chemical-activation/GI modes. only, the surface layer concurred with the partially demineralised zone, and appeared as an electron-dense layer over the undemineralised intact dentine. Smear layer-free specimens that were cured by the light-activation of the partially neutralised adhesive contained incomplete amorphous surface layers only. Apart from colloidal silica, FASG fillers were the predominant filler type within the resin matrices. Peripheral hydrogel layers that contained electron-dense 'seeds' were found around the FASG fillers. F-PRG fillers were only sparsely observed. In specimens that were laboratory demineralised with formic acid, phase separation of the unstained resin matrices into electron-dense and electron-lucent domains occurred. Artefactual dendritic deposits were found within the electron-dense domains. Conclusions: The presence of a surface interaction layer on top of a partially demineralised zone along the resin-dentine interface suggests that either a GI-type reaction or precipitation of insoluble carboxylate salts around remnant apatite crystallites may occur when this single-step adhesive interacts with dentine. Appearance of artefactual dendritic deposits suggests that continuous ion movement is possible within the hydrophilic portion of the resin matrix in this fluoride-releasing adhesive. (C) 2001 Elsevier Science Ltd. All rights reserved.
Abstract: Self-assembled monolayers (SAMs) of alkanethiols having CH3, PO4H2, COOH, CONH2, OH, and NH2 terminal groups formed on a gold surface via sulfur attachment were soaked in a simulated body fluid (SBF), whose ion concentrations were nearly equal to those of human blood plasma, at 37 degrees C for up to 40 days. The effect of their terminal functional groups on apatite formation was assessed using X-ray photoelectron spectroscopic (XPS) measurement and a quartz crystal microbalance (QCM) technique. The Ca and P atoms were detected, of which element intensities increased with time, on SAMs except for the alkanethiol having the methyl terminal group. The Ca/P atomic ratios of the apatites formed on the SAMs ranged from around 1.0 to around 1.3. The most potent inducer for apatite formation, judged from the growth rate (micrometers per day) calculated from the weight change during QCM measurement, was the SAM of the alkanethiol with the PO4H2 group, followed by that of the alkanethiol with the COOH group. The SAMs of the alkanethiols with the CONH2, OH, and NH2 groups possessed much weaker inducing powers than the former two SAMs. Little weight change was observed for the methyl-group-terminated alkanethiol SAM. The growth rates increased with time, irrespective of the terminal group species among apatite formation-inducing groups. During the experimental observation period, the following relationship held. The growth rate decreased in the order PO4H2 > COOH much greater than CONH2 similar or equal to OH > NH2 much greater than CH3 similar or equal to 0. Since negatively charged groups strongly induced apatite formation but the positively charged group did not, it can be said that the apatite formation initiated via calcium ion-adsorption upon complexation with a negative surface-charged group may be dominant in biomaterial calcification where ionic species directly contact the biomaterial surface in body fluids. (C) 1997 John Wiley & Sons, Inc.
Abstract: A dense and uniform apatite layer about 20 mu m thick was formed on a poly(ether sulphone) (PESF) substrate treated with glow discharge in O-2 gas by a biomimetic process. The apatite-polymer composite obtained was implanted into a rabbit tibia and the structure of the PESF-apatite-bone interface was observed under a scanning and a transmission electron microscope 8 weeks after implantation. The apatite layer formed by the biomimetic process was confirmed to consist of small crystals of apatite with a structure similar to that of apatite in bone. The apatite layer remained on the substrate in the body, and bonded to the apatite in the bone directly. This type of apatite-organic polymer composite expected to be useful as bone-repairing material.
Abstract: Three types of calcium phosphate coating were formed on polyethersulphone (PES) rectangular plates using a biomimetic method: a 20 mu m thick amorphous calcium phosphate (ACP 20) coating, a 50 mu m thick amorphous calcium phosphate (ACP 50) coating, and a 50 mu m thick highly crystalline hydroxyapatite (hHA 50) coating. Uncoated PES plates were used as a control group. These materials were implanted in the tibiae of rabbits and subcutaneously in rats, and the samples were harvested 8 and 16 weeks thereafter, and were examined histologically. The tensile failure loads at the bone-implant interfaces were determined using the detaching test. Each ACP coating was more degradable than the hHA 50 coating. However, newly formed bone came into direct contact with underlying materials as the coating degraded. No coating degraded in subcutaneous tissue. Soft tissue intervening was seen in uncoated samples. Failure load of ACP 20-, ACP 50- and hHA 50-coated samples were all relatively higher than that of the uncoated samples at each period. Significant increase of failure load was seen in hHA 50-coated samples by 16 weeks, however, no increase was seen in either the uncoated or ACP-coated samples. If coating longevity is desired, then the hHA coating is preferable. However, if only the osteoconducive property of calcium phosphate coating is desired for initial fixation of porous materials, the ACP coating may be advantageous. (C) 1996 Elsevier Science Limited.
Abstract: A 20-mu m thick apatite layer was coated onto polyethersulfone (PES) rectangular plates by soaking them in simulated body fluid containing CaO-SiO2 based glass powder. Coated and uncoated PES plates (10 x 15 x 1.5 mm) were implanted in the tibiae of rabbits, which were sacrificed 8, 16, and 30 weeks thereafter, and the samples were examined histologically using contact microradiography (CMR), Giemsa surface staining, and a scanning electron microscope connected to an electron probe microanalyzer (SEM-EPMA). The tensile failure loads at the bone/implant interfaces were determined using the detaching test. The histological examinations showed excellent bone apposition on coated PES and the sign of degradation of the apatite layer at remodeling lacunae. The apatite layer underwent complete resorption and was replaced by bone in most areas of the bone/implant interface after 30 weeks. Bone did not bond directly to uncoated PES after each follow-up period. The failure loads between bone and coated PES at 8, 16, and 30 weeks after implantation were 1.17 +/- 0.35, 2.36 +/- 0.53, and 1.45 +/- 0.48 kg, respectively. Those between bone and uncoated PES were nearly 0 kg at each postimplantation period. Failure during the detaching test occurred at the bone/apatite interface or near it after 8 weeks. After 16 weeks, it usually occurred at the apatite/PES interface or near it, and occasionally in the middle of the apatite layer. The apatite layer was hardly detected at the failured interface after 30 weeks. In this study, an apatite-coated PES produced using a biomimetic method was demonstrated to bond directly to bone without any intervening soft tissue, which indicates that this material possesses excellent bioactivity. (C) 1996 John Wiley & Sons, Inc.
Abstract: Quantitative assessment of hydroxyapatite formation on a gold surface via the biomimetic method, composed of a nucleation step in a simulated body fluid (SBF) containing glass powders and a subsequent apatite growth step in glass powder-free SBF, was made using a quartz crystal microbalance (QCM) technique. The frequency change of the QCM linearly increased with increasing soaking time, and largely depended on the nucleation period. The growth rates, defined as daily increase in thickness, increased monotonicly with an increasing nucleation period of up to 96 h, thereafter being constant at 2.0 mu m/day. The growth rate of the apatite layer increased with increasing temperature of the SBF: 0.9, 2.0, and 3.8 mu m/day at 25, 37, and 50 degrees C, respectively. The Arrhenius-type activation energy for the growth of apatite was 47.3 kJ/mol. The QCM method was found to be a very powerful tool for quantitative, in situ measurement of precipitation and growth of apatite in real time. (C) 1996 John Wiley & Sons, Inc.
Abstract: A dense, uniform and highly biologically active bone-like apatite layer can be formed in arbitrary thickness on any kind and shape of solid substance by the following biomimetic method at normal temperature and pressure: first, a substrate is set in contact with particles of CaO-SiO2-based glass soaked in a simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma. Second, the substrate is soaked In another solution with ion concentrations 1.5 times those of SBF (1.5 SBF). In the present study, organic polymer substrates were treated with 1 M HCl solution, then subjected to the above mentioned biomimetic process. The induction periods for the apatite nucleation on polyethyleneterephthalate, polymethylmethacrylate, polyamide 6 and polyethersulfone substrates were reduced from 24 to 12 h with the HCl treatment. The adhesive strength of the formed apatite layer to the polyethyleneterephthalate, polymethylmethacrylate and polyamide 6 substrates were increased from 3.5 to 7.0 MPa from 1.1 to 2.8 MPa and from 0.6 to 3.1 MPa, respectively, with the HCl treatment. It is supposed that highly polar carboxyl group formed by the HCl hydrolysis reaction of ester group in polyethyleneterephthalate and polymethyl meth acrylate or amide group in polyamide 6 increased the affinity of the substrates with a silicate ion to decrease the induction period, and also increased the affinity of the substrate with the apatite to increase the adhesive strength. The apatite-organic polymer composites thus obtained are expected to be useful as bone-repairing materials as well as soft-tissue-repairing materials.
Abstract: A dense, uniform, and highly biologically active bone-like apatite layer can be formed in arbitrary thickness on any kind and shape of solid substrate surface by the following biomimetic method at ordinary temperature and pressure: First, a substrate is set in contact with particles of bioactive CaCrSiO2-based glass soaked in a simulated body fluid (SBF) with inorganic ion concentrations nearly equal to those of human blood plasma so that a number of apatite nuclei are formed on the substrate. Second, the substrate is soaked in another solution with ion concentrations 1.5 times those of SBF (1.5SBF) so that the apatite nuclei grow in situ. In the present study, organic polymer substrates were treated with glow-discharge in O-2 gas atmosphere, then subjected to the above-mentioned biomimetic process. The induction periods for the apatite nucleation on all the examined organic polymers were reduced from 24 to 6 h, with glow-discharge treatment. The adhesive strengths of the formed apatite layer to the substrates increased from about 4 to 10 MPa for poly(ethylene terephthalate) and poly-ether sulfone, and from 1 similar to 2 to 6 similar to 7 MPa even for poly(methyl methacrylate), polyamide 6 and polyethylene. It is supposed that highly polar groups such as carbonyl, ester, hydroxyl, and carboxyl ones formed by glow-discharge treatment increased the affinity of a silicate ion with the substrates to decrease the induction period, and also increased the affinity of the apatite with the substrate to increase the adhesive strength. The apatite-organic polymer composites thus obtained are expected to be useful as bone-repairing materials as well as soft tissue-repairing materials. (C) 1995 John Wiley & Sons, Inc.
Abstract: The present authors previously reported that a dense and uniform bone-like apatite layer with a desired thickness can be formed on any kind and shape of solid substance by the following biomimetic method at normal temperature and pressure. First, a substrate is set in contact with particles of CaO-SiO2-based glass soaked in a simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma. Second, the substrate is soaked in another solution highly supersaturated with respect to the apatite. In the present study, the CaO-SiO2-based glass as the nucleating agent was replaced by Na2O-SiO2 glasses, SiO2 glass and SiO2 gel. The induction periods for the apatite nucleation on poly-ethersulfone substrates were infinity, a little longer than 168, 96, 48, 1.5 and 0.5h for SiO2 glass, SiO2 gel, Na2O 10.SiO2 90, Na2O 20.SiO2 80, Na2O 30.SiO2 70 and Na2O 40.SiO2 60 mol% glasses, respectively, whereas 24h for MgO 4.6.CaO 44.7.SiO2 34.0.P2O5 16.2.CaF2 0.5 wt% glass G. The short induction period for the glasses with high Na2O contents is attributed to high dissolution rates of sodium and silicate ions from them. The adhesive strengths of the formed apatite layer to the poly(ethylene terephthalate), poly(methyl methacrylate), poly-ethersulfone and polyamide 6 were 5.37, 1.63, 6.80 and 2.91 MPa for Na2O 30.SiO2 70 mol% glass, whereas 3.48, 1.06, 4.40 and 0.63 MPa for glass G. It is considered that highly polar carboxyl or sulfinyl groups were formed on the polymer surfaces by the hydrolysis of their ester, amide or sulfonyl group in SBF with its pH considerably increased by the Na+ dissolution from the glass, and that these polar groups formed a fairly strong bond with the apatite. Thus formed apatite-organic polymer composites are expected to be useful as the bone-repairing as well as soft tissue-repairing materials.
Abstract: A dense, uniform and highly biologically active bone-like apatite layer can be formed in arbitrary thickness on any kind and shape of solid substrate surface by the following biomimetic method at ordinary temperature and pressure. First, a substrate is set in contact with particles of bioactive CaO SiO2 based glass soaked in a simulated body fluid (SBF) with inorganic ion concentrations nearly equal to those of human blood plasma. Second, the substrate is soaked in another solution with ion concentrations 1.5 times those of SBF (1.5 SBF). In the present study, organic polymer substrates treated with 5 M NaOH solution were subjected to the above mentioned biomimetic process. The induction periods for the apatite nucleation on polyethyleneterephthalate (PET), polymethylmethacrylate (PMMA), polyamide 6 (PA6), and polyethersulfone (PESF) substrates were reduced from 24 to 12 h with the NaOH treatment. The adhesive strength of the formed apatite layer were increased from 3.5 to 8.6 MPa, from 1.1 to 3.4 MPa, and from 0.6 to 5.3 MPa with the NaOH treatment, for PET, PMMA, and PA 6, respectively. It was assumed that highly polar groups, such as carboxyl and sulfinyl ones formed by the hydrolysis of an ester group on PET and PMMA and of an amide group on PA 6, or of a sulfonyl group on PESF with the NaOH treatment, attached a large number of hydrated silica dissolved from the glass particles, to accelerate the apatite nucleation, and also to form a strong bond with the apatite. The apatite-organic polymer composites thus obtained are expected to be useful as bone-repairing as well as soft tissue-repairing materials. (C) 1994 John Wiley & Sons, Inc.
Abstract: Dense and uniform layers of a biologically active carbonate-containing hydroxyapatite can be formed on various kinds of organic polymers by the following biomimetic method, First, a substrate is set in contact with particles of CaO-SiO2-based glass soaked in a simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma for forming the apatite nuclei on the substrate. Second, the substrate is soaked in another solution highly supersaturated with respect to the apatite, e.g., with ion concentrations 1.5 times those of SBF (1.5SBF) for making the apatite nuclei grow on the substrate in situ. The induction period for the apatite nucleation, which is defined as the time of the first treatment required for forming enough of the apatite nuclei to make the continuous layer after the second treatment, was almost 24 h for most of the examined polymers. The adhesive strength of the formed apatite layer to the polymers was as high as 3 to 4 MPa far poly(ethylene terephthalate), poly-ether sulfone, and poly (vinyl alcohol) hydrogel. This type of apatite-organic polymer composite is expected to be useful for repairing not only living hard tissues but also soft ones.
Abstract: In the preparation of fibrous hydroxyapatite (HAp), using the gel system consisting of agar gel containing calcium nitrate and over-layered (NH4)2HPO4 solution, the pH of the solution was found to greatly influence the growth rate and morphology of the resultant products. In particular, a pH value of about 9-10 produced straight fibrous HAp in the shortest time. Also, the Ca/P molar ratio of the product increased with the pH value of the starting solution. The growth rate and morphology of the product were correlated to the ion species present in the solution at different pHs.
