Abstract: Magnetic iron oxide nanoparticles (MIONPs) were synthesized in a FeClâ-NaNOâ-NaOH aqueous system under various initial Fe(2+)/NOâ»â molar ratios (α) and Fe(2+)/OH- molar ratios (β) in order to clarify the effects of the initial molar ratio of reactants on the reaction mechanism. The Fe(2+)/NOâ»â /OH(-) molar ratio of 3 : 1 : 5 led to the formation of magnetic nanoparticles mainly composed of magnetite (FeâOâ) and maghemite (γ-FeâOâ). The 36 nm sized γ-FeâOâ and 413 nm sized FeâOâ were obtained by changing the order in which NaNOâ was added to a NaOH solution. The in vitro heat generations of the resulting MIONPs in an agar phantom were measured under an alternating magnetic field (100 kHz, 23.9 kA/m). The temperature rise (ÎT) of the agar phantom for the 36 nm sized γ-FeâOâ was 55°C in the first 140 s, with a concentration of 58 mg Fe/mL. Our results showed that it is possible to prepare MIONPs with high heating efficiencies under optimal conditions using the present method.
Abstract: Porous Y2O3 microparticles 500 microm in size were obtained, when 1 wt%-ammonium alginate aqueous solution was dropped into 0.5 M-YCl3 aqueous solution by a Pasteur pipette and the resultant gel microparticles were heat-treated at 1100 degrees C. Small pores less than 1 microm were formed in the microparticles by the heat treatment. The bulk density of the heat-treated microparticle was as low as 0.66 g cm(-3). The chemical durability of the heat-treated microparticles in simulated body fluid at pH = 6 and 7 was high enough for clinical application of in situ radiotherapy. Although the size of the microparticles should be decreased to around 25 microm using atomizing device such as spray gun for clinical application, we found that the porous Y2O3 microparticles with high chemical durability and low density can be obtained by utilizing gelation of ammonium alginate in YCl3 aqueous solution in this study.
Abstract: Polymethylmethacrylate-based cements containing magnetite (Fe(3)O(4)) particles were prepared and their structure and properties were investigated. The Fe(3)O(4) particles were uniformly dispersed in the cement matrix and constituted a maximum of 60 wt.% of the total weight of cement. The setting time of the cement increased and the maximum temperature during the setting reaction decreased with increasing Fe(3)O(4) content. The compressive strength of cement increased with increasing Fe(3)O(4) content. Cement with 50 wt.% Fe(3)O(4) particles generated heat in alternating magnetic fields of 300 and 120 Oe at a frequency of 100 kHz.
Abstract: Calcium phosphate crystals were synthesized in polyacrylamide (PAAm) hydrogel, and the effects of the concentrations of calcium and phosphate ions on the crystalline phases and morphology were investigated. PAAm hydrogels containing diammonium hydrogen phosphate ((NH4)(2)HPO4) were transformed into calcified materials by diffusion of calcium ions from calcium nitrate (Ca(NO3)(2)) aqueous solution into the gels. Several kinds of calcium phosphate crystals were precipitated at various Ca(NO3)(2) concentrations (0.5-4.0 mol . dm(-3)), or (NH4)(2)HPO4 contents (3.6-21.6 mmol) in the gels. The crystalline phases were mainly determined by the (NH4)(2)HPO4 content in the gels. When the (NH4)(2)HPO4 content was >= 10.8 mmol, hydroxyapatite (HAp) formed near the interfaces between Ca(NO3)(2) solution and the gels, whereas octacalcium phosphate (OCP) formed in gels with <= 10.8 mmol (NH4)(2)HPO4. HAp crystals were granular in form and about 200 nm in diameter. and OCP crystals were spherulitic with diameter 10-70 mu m.
Abstract: We have prepared magnetic SiO(2) microspheres with a diameter of 20-30 µm as thermoseeds for hyperthermia of cancer. These were prepared by directly introducing preformed magnetic iron oxide nanoparticles (IONPs) into microspheres of a SiO(2) gel matrix derived from the hydrolysis of tetramethoxysilane (TMOS) in a water-in-oil (W/O) emulsion. Dimethylformamide (DMF) was used as a stabilizer, methanol (CH(3)OH) as a dispersant and ammonia (NH(4)OH) as the catalyst for the formation of the spherical particles in the aqueous phase of the W/O emulsion. The magnetic IONPs were synthesized hydrochemically in an aqueous system composed of ferrous chloride, sodium nitrate and sodium hydroxide. Mono-dispersed magnetic SiO(2) gel microspheres with a diameter of approximately 20 µm were successfully obtained by adding a determined amount of solution with a molar ratio of TMOS/DMF/CH(3)OH/H(2)O/NH(4)OH = 1:1.4:9:20:0.03 to kerosene with a surfactant (sorbitan monooleate/sorbitan monostearate = 3:1 by weight ratio) that was 30 wt% of the total amount of the oil phase. These were estimated to contain up to 60 wt% of IONPs that consisted mainly of Fe(3)O(4) and showed a higher specific absorption rate (SAR = 27.9-43.8 W g(-1)) than that of the starting IONPs (SAR = 25.3 W g(-1)) under an alternating current magnetic field of 300 Oe and 100 kHz.
Abstract: Silicone elastomer substrates were irradiated with acceleration voltages ranging from 3 to 9 kV and doses ranging from 1 x 10(14) to 2.5 x 10(15) ions cm(-2) by the simultaneous use of oxygen cluster and monomer (O(2) CM) ion beams, and then soaking in CaCl(2) solution. The apatite-forming ability of the substrates was examined using a metastable calcium phosphate solution that had 1.5 times the ion concentrations of normal simulated body fluid (1.5SBF). Silicon oxide clusters (SiO(x)) were formed at the silicone elastomer surfaces and the hydrophilicity of the substrates was remarkably improved by the irradiation. The irradiated silicone elastomer substrates formed apatite in 1.5SBF, whereas unirradiated ones did not. These results suggest that irradiation using O(2) CM ion beams is effective for inducing an apatite-forming ability on silicone elastomer substrates.
Abstract: OBJECTIVES: To research the crystal structure and surface morphology of anodic films on titanium metal in different electrolytes under various electrochemical conditions and investigate the effect of the crystal structure of the oxide films on apatite-forming ability in simulated body fluid (SBF). METHODS: Titanium oxide films were prepared using an anodic oxidation method on the surface of titanium metal in four different electrolytes: sulfuric acid, acetic acid, phosphoric acid and sodium sulfate solutions with different voltages for 1 min at room temperature. RESULTS: Anodic films that consisted of rutile and/or anatase phases with porous structures were formed on titanium metal after anodizing in H(2)SO(4) and Na(2)SO(4) electrolytes, while amorphous titania films were produced after anodizing in CH(3)COOH and H(3)PO(4) electrolytes. Titanium metal with the anatase and/or rutile crystal structure films showed excellent apatite-forming ability and produced a compact apatite layer covering all the surface of titanium after soaking in SBF for 7d, but titanium metal with amorphous titania layers was not able to induce apatite formation. SIGNIFICANCE: The resultant apatite layer formed on titanium metal in SBF could enhance the bonding strength between living tissue and the implant. Anodic oxidation is believed to be an effective method for preparing bioactive titanium metal as an artificial bone substitute even under load-bearing conditions.
Abstract: Bioactive polymeric microspheres can be prepared by means of coating them with a calcium silicate solution and subsequently soaking in a simulated body fluid (SBF). Such combination should allow for the development of bioactive microspheres for several applications in the medical field including tissue engineering carriers. Four types of polymeric microspheres, with different sizes, were used in this work: (i) ethylene-vinyl alcohol copolymer (20-30 mum), (ii) polyamide 12 with 10% magnetite (100 mum), (iii) polyamide 12 (10-30 mum) and (iv) polyamide 12 (300 mum). These microspheres were soaked in a calcium silicate solution at 36.5 degrees C for various periods of time under different conditions. Afterwards, they were dried in air at 60 and 100 degrees C for 24 hr. Then, the samples were soaked in SBF for 1, 3, and 7 days. Fourier transformed infrared spectroscopy, thin-film X-ray diffraction, and scanning electron microscopy showed that after the calcium silicate treatment and the subsequent soaking in SBF, the microspheres successfully formed an apatite layer on their surfaces in SBF within 7 days due to the formation of silanol groups, which are effective for apatite formation.
Abstract: A rectangular specimen of polyethylene terephthalate (PET) was soaked in a titania solution composed of titanium isopropoxide, water, ethanol and nitric acid at 25 degrees C for 1 h. An amorphous titanium oxide was formed uniformly on the surface of PET specimen, but did not form an apatite on its surface in a simulated body fluid (SBF) within 3 d. The PET plate formed with the amorphous titanium oxide was subsequently soaked in water or HCl solutions with different concentrations at 80 degrees C for different periods of time. The titanium oxide on PET was transformed into nano-sized anatase by the water treatment and into nano-sized brookite by 0.10 M HCl treatment at 80 degrees C for 8 d. The former did not form the apatite on its surface in SBF within 3 d, whereas the latter formed the apatite uniformly on its surface. Adhesive strength of the titanium oxide and apatite layers to PET plate was increased by pre-treatment of PET with 2 wt% NaOH solution at 40 degrees C for 2 h. A two-dimensional fabric of PET fibers 24 microm in diameter was subjected to the NaOH pre-treatment at 40 degrees C, titania solution treatment at 25 degrees C and subsequent 0.10 M HCl treatment at 80 degrees C. Thus treated PET fabric formed the apatite uniformly on surfaces of individual fibers constituting the fabric in SBF within 3 d. Two or three dimensional PET fabrics modified with the nano-sized brookite on surfaces of the individual fibers constituting the fabric by the present method are believed to be useful as flexible bone substitutes, since they could be integrated with living bone through the apatite formed on their constituent fibers.
Abstract: We have succeeded in producing liquid clusters such as ethanol and water clusters by an adiabatic expansion phenomenon, and the cluster size distribution was analyzed by using the time-of-flight method. For ethanol cluster ions, the size was distributed between a few hundreds and a few thousands, and the peak size was approximately 1200 molecules per cluster. For water cluster ions, the size distribution shifted to higher values, and the peak size was approximately 2500 molecules per cluster. Furthermore, the cluster size distribution was measured by changing the retarding voltage, and it was found that the minimum size increased with increase of the retarding voltage. In addition, the minimum size was larger than the critical size estimated by the theoretical calculation.
Abstract: Bioactive chitosan microparticles can be prepared successfully by treating them with a calcium silicate solution and then subsequently soaking them in simulated body fluid (SBF). Such a combination enables the development of bioactive microparticles that can be used for several applications in the medical field, including injectable biomaterial systems and tissue engineering carrier systems. Chitosan microparticles, 0.6microm in average size, were soaked either for 12h in fresh calcium silicate solution (condition I) or for 1h in calcium silicate solution that had been aged for 24h before use (condition II). Afterwards, they were dried in air at 60 degrees C for 24h. The samples were then soaked in SBF for 1, 3 and 7 days. After the condition I calcium silicate treatment and the subsequent soaking in SBF, the microparticles formed a dense apatite layer after only 7 days of immersion, which is believed to be due to the formation of silanol (Si-OH) groups effective for apatite formation. For condition II, the microparticles successfully formed an apatite layer on their surfaces in SBF within only 1 day of immersion.
Abstract: In order to clarify the interactions of ethanol cluster ion beams with solid surfaces, sputtering processes for Si, SiO(2) and Au surfaces were investigated by changing the acceleration voltage, the retarding voltage, and the incident angle. For the case of the normal incidence, the sputtered depth increased with increase of the acceleration voltage, and the sputtering ratio of Si to SiO(2) was approximately 10 at an acceleration voltage of 9 kV. Furthermore, with regard to the incident angle dependence, the sputtered depth for the Si surfaces had a maximum value at an incident angle between 10 degrees and 60 degrees . On the other hand, for the case of the physical sputtering by ethanol cluster ion irradiation on Au surfaces, the sputtered depth decreased with increase of the incident angle. With regard to the retarding voltage dependence, the sputtered depth had a maximum value for the Si surfaces, and the retarding voltage corresponding to the peak value changed according to the acceleration voltage applied. In addition, for the case of Au surfaces, the sputtered depth decreased with increase of the retarding voltage, and the physical sputtering was influenced by the minimum size of the cluster.
Abstract: An apatite layer was successfully formed on titanium substrates by electrochemical deposition in a metastable calcium phosphate solution, which had 1.5 times the ion concentrations of a normal simulated body fluid, but did not contain MgCl(2).6H(2)O, at 41 degrees C for 40 or 60 min at 13 mA. The current did not produce large effects on the crystalline size of the apatite, but the thickness of the apatite layer could be controlled by deposition conditions such as electrolyte temperature, current and deposition time. It is expected that the present electrochemical deposition will be useful to rapidly coat apatite on metallic materials.
Abstract: Titanium and its alloys have been widely used for orthopedic implants because of their good biocompatibility. We have previously shown that the crystalline titania layers formed on the surface of titanium metal via anodic oxidation can induce apatite formation in simulated body fluid, whereas amorphous titania layers do not possess apatite-forming ability. In this study, hot water and heat treatments were applied to transform the titania layers from an amorphous structure into a crystalline structure after titanium metal had been anodized in acetic acid solution. The apatite-forming ability of titania layers subjected to the above treatments in simulated body fluid was investigated. The XRD and SEM results indicated hot water and/or heat treatment could greatly transform the crystal structure of titania layers from an amorphous structure into anatase, or a mixture of anatase and rutile. The abundance of Ti-OH groups formed by hot water treatment could contribute to apatite formation on the surface of titanium metals, and subsequent heat treatment would enhance the bond strength between the apatite layers and the titanium substrates. Thus, bioactive titanium metals could be prepared via anodic oxidation and subsequent hot water and heat treatment that would be suitable for applications under load-bearing conditions.
Abstract: Ferrimagnetic materials can be expected to be useful as thermo seeds for hyperthermic treatment of cancer, especially where the cancer is located in deep parts of body, as they can generate heat by magnetic hysteretic loss when they are placed in an alternating magnetic field. Recently, it was reported that ferrimagnetic maghemite (gamma-Fe2O3) microspheres 20-30 microm in diameter prepared in aqueous solution can show excellent heat generating ability. However, these microspheres have many cracks on their surfaces. In this study, the preparation conditions for the microspheres was further optimized in order to obtain crack-free ferrimagnetic microspheres, and the in vitro heat generation of the obtained microspheres was measured in an agar phantom under an alternating magnetic field. Crack-free gamma-Fe2O3 microspheres 20-30 microm in diameter were obtained successfully. Their saturation magnetization and coercive force were 68 emu g(-1) and 198 Oe, respectively. Their heat generation under an alternating magnetic field of 300 Oe at 100 kHz was estimated to be 42 W g(-1). The microspheres showed in vitro heat generation when they were dispersed in an agar phantom and placed under an alternating magnetic field. It is believed that these microspheres may be useful for the in situ hyperthermic treatment of cancer.
Abstract: The present research aims to develop a new route for surface functionalization of biodegradable polymers. The method is based on a wet chemistry modification, resulting in etching and/or hydrolysis in order to increase the amount of polar groups, such as hydroxyl (--OH) and carboxylic (--COOH) groups on the surface of the polymer. The polymer used as substrate was a corn starch-ethylene vinyl alcohol biodegradable blend (SEVA-C). For that purpose it was used in two different types of activation: (a) calcium hydroxide solution [Ca(OH)(2)] and (b) sodium hydroxide solution (NaOH). These treatments lead to the formation carboxylic acid-rich SEVA-C surfaces. Then, the samples were soaked in simulated body fluid (SBF) for different time periods of time until 7 days. After 1 day in SBF, the surface of SEVA-C was fully covered with spherulite particles. As the soaking time increased, the particles increased and coalesced, leading to the formation of a dense and uniform layer. Furthermore, thin-film X-ray diffraction confirms that the layer formed on the surface of the polymer was an apatite-like layer. These results suggest that this rather simple treatment is a good method for surface functionalization and subsequent mineral nucleation and growth on biodegradable polymeric surfaces to be used for bone-related applications.
Abstract: Covalent coupling of sulfonic group (-SO 3H) was attempted on different polymers to evaluate efficacy of this functional group in inducing nucleation of apatite in body environment, and thereupon to design a simple biomimetic process for preparing bonelike apatite-polymer composites. Substrates of polyethylene terephthalate (PET), polycaprolactam (Nylon 6), high molecular weight polyethylene (HMWPE) and ethylene-vinyl alcohol co-polymer (EVOH) were subjected to sulfonation by being soaked in sulfuric acid (H2SO4) or chlorosulfonic acid (ClSO 3H) with different concentrations. In order to incorporate calcium ions, the sulfonated substrates were soaked in saturated solution of calcium hydroxide (Ca(OH)2). The treated substrates were soaked in a simulated body fluid (SBF). Fourier transformed infrared spectroscopy, thin-film X-ray diffraction, and scanning electron microscopy showed that the sulfonation and subsequent Ca(OH)2 treatments allowed formation of -SO3H groups binding Ca2+ ions on the surface of HMWPE and EVOH, but not on PET and Nylon 6. The HMWPE and EVOH could thus form bonelike apatite layer on their surfaces in SBF within 7 d. These results indicate that the -SO3H groups are effective for inducing apatite nucleation, and thereby that surface sulfonation of polymers are effective pre-treatment method for preparing biomimetic apatite on their surfaces.
Abstract: Polyethylene (PE) substrates were irradiated at a dose of 1 x 10(15) ions/cm(2) by the simultaneous use of oxygen (O(2)) cluster and monomer ion beams. The acceleration voltage for the ion beams was varied from 3 to 9 kV. Unirradiated and irradiated PE substrates were soaked for 7 days in a metastable calcium phosphate solution (1.5SBF) that had 1.5 times the ion concentrations of a normal simulated body fluid. The irradiated PE substrates formed apatite on their surfaces, irrespective of the acceleration voltage, whereas unirradiated substrates did not form apatite. This is attributed to the formation of functional groups that are effective for apatite nucleation, such as --COOH groups, on the substrate surface by the simultaneous use of O(2) cluster and monomer ion beams. The apatite-forming ability of the irradiated PE substrates was improved greatly by a subsequent CaCl(2) solution treatment. This suggests that Ca(2+) ions introduced on the substrate surface by the CaCl(2) solution treatment accelerated the apatite nucleation. It is concluded that apatite-forming ability can be induced on the surface of PE by the simultaneous use of O(2) cluster and monomer ion beams.
Abstract: Various kinds of inorganic substances doped with silver ions have been developed as antibacterial materials, and some have already been commercialized. Previously, we successfully prepared colorless silica glass microspheres doped with silver ions in combination with aluminum ions by a sol-gel method. However, the antibacterial activity of the microspheres was not maintained for long periods in an aqueous environment, since the silver ions were located only in a thin layer near the surface of the microspheres. In this study, silica glass microspheres in which silver ions are uniformly distributed were attempted to be prepared. A tetraethoxysilane ethanol solution was mixed with aqueous silver nitrate and aluminum nitrate solutions to be subjected to almost simultaneous hydrolysis and polycondensation. An ammonia solution was then added, to form microspheres. Monodispersed microspheres about 0.1 microm in diameter were obtained, which did not show coloring even after heat treatment at 600-1000 degrees C, indicating that the silver in the microspheres took the form of Ag(+) ions and not colloid, even after the heat treatments. Microspheres heat-treated at temperatures ranging from 700 to 800 degrees C showed much higher antibacterial activity than commercial antibacterial zeolites and maintained their high antibacterial activities for long periods in an aqueous environment. Polypropylene plates and films mixed with the microspheres heat-treated at 800 degrees C showed excellent antibacterial properties.
Abstract: Polyethylene (PE), polyethylene terephthalate (PET), ethylene-vinyl alcohol copolymer (EVOH), and poly(epsilon-caprolactam) (Nylon 6) were successfully modified with a thin crystalline titanium oxide layer on their surfaces by a simple dipping into a titanium alkoxide solution and a subsequent soak in hot HCl solution, without the aid of a silane-coupling agent. The surface modified polymers formed a bone-like apatite layer in a simulated body fluid (SBF) within a period of 2 days. PE, PET, and Nylon 6 formed an apatite layer faster and had a higher adhesive strength to the apatite. Three-dimensional fabrics with open spaces in various sizes containing such surface modified polymer fibers are expected to be useful as bone substitutes, since they may be able to form apatite on their constituent fibers in the living body, and thus, integrate with living bone.
Abstract: Poly(tetramethylene oxide) (PTMO)-CaO-Ta2O5 hybrids were prepared by hydrolysis and polycondensation of triethoxysilane-functionalized PTMO (Si-PTMO), tantalum ethoxide (Ta(OEt)5) and CaCl2. In the system CaO-free PTMO-Ta2O5, Si-PTMO/Ta(OEt)5 weight ratios were 30/70, 40/60 and 50/50 (hybrids PT30Ca0, PT40Ca0 and PT50Ca0, respectively). In the system PTMO-CaO-Ta2O5, the Si-PTMO/Ta(OEt)5 weight ratio was 40/60 and CaCl2/Ta(OEt)5 mole ratios were 0.05, 0.10 and 0.15 (hybrids PT40Ca5, PT40Ca10 and PT40Ca15, respectively). Crack-free transparent monolithic hybrids were obtained for all the examined compositions except for PT30Ca0. Even CaO-free hybrids PT40Ca0 and PT50Ca0 formed apatite on their surfaces in a simulated body fluid (SBF) within 14 days. Hybrid PT40Ca0 showed higher mechanical strength, which was increased by soaking in SBF, and larger strain to failure than human cancellous bone. The CaO-containing hybrids showed higher apatite-forming ability than the CaO-free hybrids, and its apatite-forming ability increased with increasing CaO content. Hybrids PT40Ca10 and PT40Ca15 formed apatite within 3 days. The mechanical strength of PT40Ca15 was, however, lower than PT40Ca0 and was decreased by soaking in SBF. Thus obtained flexible bioactive CaO-free PTMO-Ta2O5 hybrids are expected to be useful as bone substitutes.
Abstract: Ferrimagnetic materials can be expected to be useful as thermal seeds for hyperthermic treatment of cancer, especially where the cancer is located in deep parts of body, as they can generate heat by magnetic hysteretic loss when they are placed in an alternating magnetic field. In this study, hollow magnetite (Fe(3)O(4)) particles were prepared using an enzymatic reaction of urease. A hollow particle was obtained by using a Pasteur pipette. The particle was 500 microm in size and was composed of Fe(3)O(4). Its saturation magnetization and coercive force were 57 emuxg(-1) and 183 Oe, respectively. Its heat generation under an alternating magnetic field of 300 Oe at 100 kHz was estimated to be 45 Wxg(-1). Microspheres 30 microm in diameter were also successfully obtained by using a spray gun.
Abstract: Polyethylene terephthalate (PET), ethylene-vinyl alcohol copolymer (EVOH) and Nylon 6 in plate form were treated with silane-coupling agents, a titanium alkoxide-alcohol solution and a hot HCl solution to form a thin crystalline titanium oxide layer. When placed in a simulated body fluid with ion concentrations nearly equal to those of the human blood plasma, nanosized bone-like apatite formed uniformly on the surfaces of these treated polymers: within 2 days for PET and Nylon 6, and 7 days for EVOH. This indicates that such titania-modified polymers might form bone-like apatite in the living body, and bond to living bone through this apatite layer. Three-dimensional fabrics of these polymer fibers, with open spaces in various sizes, are expected to be useful as bone substitutes, as they will be integrated with the natural bone.
Abstract: Ferrimagnetic microspheres 20-30 microm in diameter are useful as thermoseeds for inducing hyperthermia in cancers, especially for tumors located deep inside the body. The microspheres are entrapped in the capillary bed of the tumors when they are implanted through blood vessels and heat cancers locally by their hysteresis loss when placed under an alternating magnetic field. In the present study, preparation of magnetite (Fe(3)O(4)) microspheres 20-30 microm in diameter was attempted by melting powders in high-frequency induction thermal plasma, and by precipitation from aqueous solution. The microspheres prepared by melting powders in high-frequency induction thermal plasma were composed of a large amount of Fe(3)O(4) and a small amount of wustite (FeO), and those subsequently heat treated at 600 degrees C for 1 h under 5.1 x 10(3) Pa were fully composed of Fe(3)O(4) 1 microm in size. The saturation magnetization and coercive force of the heat-treated microspheres were 92 emu g(-1) and 50 Oe, respectively. The heat generation of the heat-treated microspheres was estimated to be 10 Wg(-1), under 300 Oe and 100 kHz. The microspheres prepared by precipitation from aqueous solution consisted of beta-FeOOH, and those subsequently heat treated at 400 degrees C for 1 h in a 70% CO(2) + 30% H(2) atmosphere consisted of Fe(3)O(4) crystals 50 nm in size. The saturation magnetization and coercive force of the heat-treated microspheres were 53 emu g(-1) and 156 Oe, respectively. The heat generation of the heat-treated microspheres was estimated to be 41 Wg(-1), under 300 Oe and 100 kHz. The latter microspheres are believed to be promising thermoseeds for hyperthermic treatment of cancer.
Abstract: Three types of bioactive polymethylmethacrylate (PMMA)-based bone cement containing nano-sized titania (TiO2) particles were prepared, and their mechanical properties and osteoconductivity are evaluated. The three types of bioactive bone cement were T50c, ST50c, and ST60c, which contained 50 wt% TiO2, and 50 and 60 wt% silanized TiO2, respectively. Commercially available PMMA cement (PMMAc) was used as a control. The cements were inserted into rat tibiae and allowed to solidify in situ. After 6 and 12 weeks, tibiae were removed for evaluation of osteoconductivity using scanning electron microscopy (SEM), contact microradiography (CMR), and Giemsa surface staining. SEM revealed that ST60c and ST50c were directly apposed to bone while T50c and PMMAc were not. The osteoconduction of ST60c was significantly better than that of the other cements at each time interval, and the osteoconduction of T50c was no better than that of PMMAc. The compressive strength of ST60c was equivalent to that of PMMAc. These results show that ST60c is a promising material for use as a bone substitute.
Abstract: The mechanism of biomineralization of bone-like apatite on synthetic hydroxyapatite (HA) has been investigated in vitro, in which the HA surface was surveyed as a function of soaking time in simulated body fluid (SBF). In terms of surface structure by transmission electron microscopy with energy-dispersive X-ray spectrometry, the HA whose Ca/P atomic ratio was 1.67 revealed three different characteristic soaking periods in SBF, i.e. the first soaking period, in which the HA surface increased the Ca/P ratio up to 1.83 to form an amorphous phase of Ca-rich calcium phosphate; the second soaking period, in which the HA surface decreased the Ca/P ratio up to 1.47 to form an amorphous phase of Ca-poor calcium phosphate; and the third soaking period, in which the HA surface gradually increased the Ca/P ratio up to 1.65 to eventually produce the bone-like nano-cerystallites of apatite, which grew forming complex crystal assemblies with a further increase in immersion time. Analysis using electrophoresis spectroscopy indicated that, immediately after immersion in SBF, the HA revealed a highly negative surface potential, which increased to reach a maximum positive value in the first soaking period. The surface potential then decreased to again reach a negative value in the second soaking period and thereafter converge to a constant negative value in the third soaking period. This implies that the HA induces biomineralization of apatite by smartly varying its surface potential to trigger an electrostatic interaction, first with positive calcium ions and second with negative phosphate ions in the SBF.
Abstract: Composites which comprise a bioactive filler and ductile polymer matrix are desirable as implant materials since both their biological and mechanical properties can be tailored for a given application. In the present study three-point bending was used to characterise biomedical materials composed of glass-ceramic apatite-wollastonite (A-W) particulate reinforced polyethylene (PE) (denoted as AWPEX). The effects of filler volume fraction, varied from 10 to 50 vol%, and average particle size, 4.4 and 6.7 microm, on the bending strength, yield strength, mode of fracture, Young's modulus and strain to failure were investigated. HAPEX, a commercially used composite of hydroxyapatite and polyethylene, with a 40 vol% filler content, was used for comparison. Increasing the filler content caused an increase in Young's modulus, yield strength and bending strength, and a decreased strain to failure. When filler particle size was increased, the Young's modulus, yield and bending strengths were found to be slightly reduced. A transition in fracture behaviour from ductile to brittle behaviour was observed in samples containing between 30 and 40 vol% filler.
Abstract: Hydrolysis and polycondensation of triethoxysilane end-capped Poly (tetramethylene oxide) (Si-PTMO), tetraethoxysilane (TEOS), tetraisopropyltitanate (TiPT) and calcium nitrate (Ca(NO(3))(2)) gave transparent monolithics of PTMO-modified CaO-SiO(2)-TiO(2) hybrids. The samples with (TiPT)/(TEOS+TiPT) molar ratios from 0 to 0.20 under constant ratio of (Si-PTMO)/(TEOS+TiPT) of 2/3 in weight were prepared. It was found that the incorporation of TiO(2) component into a PTMO-CaO-SiO(2) hybrid results in an increase in the apatite-forming ability in a simulated body fluid: the hybrids with (TiPT)/(TEOS+TiPT) of 0.10 and 0.20 in mol formed an apatite on their surfaces within only 0.5 day. It seemed that, within the range of compositions studied, the TiO(2) content little affects the overall mechanical properties: Young's modulus were 52-55MPa, tensile strength, 7-9MPa, and strain at failure, about 30%. Thus, the organic-inorganic hybrids exhibiting both fairly high apatite-forming ability and high capability for deformation were obtained. These hybrid materials may be useful as new kind of bioactive bone-repairing materials.
Abstract: Chitin fibres constituting a non-woven fabric were carboxymethylated in monochloro acetic acid and treated with saturated Ca(OH)(2) aqueous solution. Within 3 days in a simulated body fluid with pH value and ion concentrations nearly equal to those of human blood plasma, a bonelike apatite layer formed on the surface of fibres of the treated fabric. The apatite-chitin fibre composite thus prepared is expected to be useful as a flexible bioactive bone-repairing material.
Abstract: Some ceramics, such as Bioglass, sintered hydroxyapatite, and glass-ceramic A-W, spontaneously form a bone-like apatite layer on their surface in the living body, and bond to bone through the apatite layer. These materials are called bioactive ceramics, and are clinically important for use as bone-repairing materials. However, they cannot be used at high-load sites, such as is found in femoral and tibial bones, because their fracture toughness values are not as high as that of human cortical bone. Titanium metal and its alloys have high fracture toughness, and form a sodium titanate layer on its surface when soaked in a 5 M-NaOH solution at 60 degrees C for 24 h, followed by a heat treatment at 600 degrees C for 1 h. On moving toward the metal interior, the sodium titanate layer gradually changes into the pure metal within a distance of 1 microm from the surface. The mechanical strength of the titanium metal or a titanium alloy is not adversely affected by these chemical and thermal treatments. The titanium metal and its alloys resulting from the above treatment can release Na+ ions from its surface into a surrounding body fluid via an ion exchange reaction with H3O+ ions, resulting in many Ti-OH groups forming on its surface. These Ti-OH groups initially combine with Ca2+ ions to form amorphous calcium titanate in the body environment, and later the calcium titanate combines with phosphate ions to form amorphous calcium phosphate. The amorphous calcium phosphate eventually transforms into bone-like apatite, and by this process the titanium metals are soon tightly bonded to the surrounding living bone through the bone-like apatite layer. The treated metals have already been subjected to clinical trials for applications in artificial total hip joints. Metallic tantalum has also been found to bond to living bone after it has been subjected to the NaOH and heat treatment to form a sodium tantalate layer on its surface.
Abstract: Calcium alginate fibers were prepared by extruding an aqueous sodium alginate solution into an aqueous calcium chloride solution. The fibers were treated with a saturated aqueous calcium hydroxide solution for various periods and their apatite-forming ability was examined in a simulated body fluid (SBF). The calcium alginate fibers were treated with the aqueous calcium hydroxide solution for periods longer than five days formed apatite on their surfaces in SBF, and their apatite-forming ability improved with increasing calcium hydroxide treatment time. The amount of calcium ions released from the fibers also increased with increasing calcium hydroxide treatment time, resulting in acceleration of nucleation and growth of apatite on the fiber surfaces. The resultant apatite-alginate fiber composite is expected to be useful as a flexible bioactive bone-repairing material.
Abstract: Polydimethylsiloxane (PDMS)-TiO(2) hybrids with PDMS (M=550)/tetraethylorthotitanate molar ratios at 0.27, 0.68 and 1.35, i.e. Si/Ti atomic ratios at 2, 5 and 10 (hybrids PD2, PD5 and PD10, respectively) were prepared by a sol-gel method. Hybrid PD2 formed many cracks. Hybrids PD5 and PD10 were subjected to hot-water treatment 80 degrees C for 7 d. Hybrid PD5 produced cracks, whereas hybrid PD10 was crack-free after the hot-water treatment. Hybrid PD10 took a homogeneous amorphous structure before the hot-water treatment, and precipitated anatase particles 10-20 nm in size after the hot-water treatment. Hybrid PD10 did not form apatite on its surface in a simulated body fluid before the hot-water treatment, but formed it after the hot-water treatment. The obtained hybrid showed elastic deformation as large as 200% after the hot-water treatment. This kind of hybrid could be useful as a new type of bone-repairing material.
Abstract: Carboxymethylated chitin, gellan gum, and curdlan gels were soaked in a simulated body fluid (SBF) having ion concentrations nearly equal to those of human blood plasma. Some of the gels had been soaked in a saturated Ca(OH)(2) solution, while others had not. The carboxymethylated chitin and gellan gum gels have carboxyl groups, while the curdlan gel has hydroxyl groups. None of the gels formed apatite on their surfaces in the SBF when they had not been subjected to the Ca(OH)(2) treatment, whereas the carboxymethylated chitin and gellan gum gels formed apatite on their surfaces when they had been subjected to the Ca(OH)(2) treatment. The curdlan gel did not form an apatite deposit even after the Ca(OH)(2) treatment. Apatite formation on the carboxymethylated chitin and gellan gum gels was attributed to the catalytic effect of their carboxyl groups for apatite nucleation, and acceleration of apatite nucleation from released Ca(2+) ions. This result provides a guiding principle for obtaining apatite-organic polymer fiber composites. This composite is expected to have an analogous structure to that of natural bone.
Abstract: Radiotherapy is one of the most effective treatments for cancers. However, external irradiation provides only small doses to deep-seated cancers, and often causes damage to healthy tissues. It has been reported that 20-30 microm diameter 17Y(2)O(3)-19Al(2)O(3)-64SiO(2) (mol%) glass microspheres are useful for the in situ irradiation of cancers. Yttrium-89 (89Y) in this glass can be neutron bombarded to form the beta-emitter 90Y (half-life=64.1h). When injected in the vicinity of the cancer, such activated glass microspheres can provide a large localized dose of beta-radiation. The Y(2)O(3) content of the glass in the microspheres is limited to only 17 mol%. Chemically durable microspheres with a higher Y(2)O(3) content need to be developed. Phosphorus-31 (31P) with 100% natural abundance can also be activated by neutron bombardment to form the beta-emitter 32P (half-life=14.3d). Chemically durable microspheres containing a high phosphorus content are expected to be more effective for cancer treatment. We prepared pure Y(2)O(3) and YPO(4) microspheres using a high-frequency induction thermal plasma melting technique, and investigated the resulting structure and chemical durability. We successfully prepared smooth, highly spherical polycrystalline Y(2)O(3) and YPO(4) microspheres with diameters in the range 20-30 microm. Both the Y(2)O(3) and YPO(4) microspheres showed high chemical durability in saline solutions buffered at pH=6 and 7. These microspheres are expected to be more effective than the conventional glass microspheres for the in situ radiotherapy of cancer.
Abstract: Bioactive glass-ceramic apatite-wollastonite (A-W) has been incorporated into polyethylene in particulate form to create new bioactive composites for potential maxillofacial applications. The effects of varying the volume fraction of glass-ceramic A-W filler and the glass-ceramic A-W particle size were investigated by measuring the bonding strength of the bonelike apatite layer formed on the surface of glass-ceramic A-W-polyethylene composites. The bonding strength was evaluated via a modified ASTM C-333 standard in which a tensile stress was applied to the substrate and the strength of the bioactive layer was compared with that formed on commercially available hydroxyapatite-polyethylene composite samples, HAPEX. The composites demonstrated greater bonding strength with increased filler content and reduced filler particle size (maximum 6.9 +/- 0.5 MPa) and a marginally greater bonding strength as compared with HAPEX (2.8 +/- 0.5 MPa), when glass-ceramic A-W-polyethylene composite samples with the same filler content were tested. The higher bonding strength of the apatite layer formed on the A-W-polyethylene composite samples suggests that, in addition to maxillofacial applications, these composites might also be utilized in applications involving higher levels of load bearing.
Abstract: Bioactive titanium metal can be prepared by NaOH and heat treatments that present the metal with a graded bioactive surface layer of amorphous sodium titanate. This study used laser electrophoresis together with transmission electron microscopy (TEM) and energy-dispersive X-ray microanalysis (EDX) to relate the surface potential change of the bioactive titanium metal with its surface structural change in simulated body fluid (SBF). The surface potential of the metal was highly negative immediately after immersion in SBF. With increasing soaking time, the surface potential increased, revealing a maximum positive value, and then decreased to a constant negative value. TEM-EDX showed that immediately after immersion in SBF, the metal surface formed Ti-OH groups by exchanging Na(+) ions in the surface sodium titanate with H3O(+) ions in the fluid. Thereafter, with increasing soaking time the metal surface formed an amorphous calcium titanate, then an amorphous calcium phosphate, and, finally, apatite with bone-like composition and structure. These results indicate that the process of apatite formation on bioactive titanium metal is initiated by the formation of Ti-OH groups with negative charges that interact with calcium ions with positive charges to form calcium titanate. The calcium titanate gains a positive charge and later interacts with phosphate ions with negative charges, forming amorphous calcium phosphate. The amorphous calcium phosphate eventually transforms and stabilizes into bone-like crystalline apatite with a negative charge.
Abstract: Various types of inorganic substances doped with silver ions have been developed as antibacterial materials, and some have already been commercialized. Colorless and chemically durable materials that slowly release silver ions are, however, still need to be developed. The present authors have previously shown that when a silica glass doped with silver and aluminium ions is prepared using the sol-gel method, the resultant product is colorless, chemically durable, and slowly releases silver ions into water over a long period. The doped silica glass takes a form of microspheres <1 microm in diameter, it is easily mixed with organic polymers, and the mixture can be formed into a thin film or fine fibers, etc. We report on the preparation of silver doped silica glass microspheres having a diameter =1 microm, using the sol-gel method. Initially, tetraethoxysilane was partially prehydrolyzed by water in ethanol, and then aluminium triisopropoxide was added to the solution to form Si-O-Al bonds. Finally, an ammonia solution containing silver nitrate was added to form silica microspheres doped with silver ion together with aluminium ions. The results show monodispersed microspheres 0.4-0.6 microm in diameter were obtained with nominal compositions of Si/Al/Ag = 1/0.01-0.03/0.003-0.03, with a molar ratio of Al/Ag = 1-3.3. The microspheres were colorless, showed a high chemical durability, and slowly released silver ions into water at 37 degrees C. Microspheres with the composition Si/Al/Ag = 1/0.01/0.01 showed excellent antibacterial activity against Escherichia coli. The minimum inhibitory concentration (MIC) of the microspheres was 400, which is less than the MIC value (800) of commercial antibacterial materials.
Abstract: The bioactivity of a range of glass-ceramic apatite-wollastonite (A-W) - polyethylene composites (AWPEXs) with glass-ceramic A-W volume percentages ranging from 10 to 50, has been investigated in an acellular simulated body fluid (SBF) with ion concentrations similar to those of human blood plasma. The formation of a biologically active apatite layer on the composite surface after immersion in SBF was demonstrated by thin-film X-ray diffraction (TF-XRD) and field-emission scanning electron microscopy (FE-SEM). An apatite layer was formed on all the composites, with the rate of formation increasing with an increase in glass-ceramic A-W percentage. For composites with glass-ceramic A-W filler contents >or=30 vol %, the apatite layer was formed within 12 h of immersion, which is a comparable time for apatite formation on monolithic glass-ceramic A-W. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) demonstrated that the apatite formation on AWPEX samples with 50 vol % filler content occurred in a manner similar to that seen on pure glass-ceramic A-W, in that the calcium, silicon, and magnesium ion concentrations increased and, conversely, a decrease was observed in the phosphate ion concentration. These results indicate that a suitable in vitro response was achieved on a composite incorporating particulate glass-ceramic A-W with a particularly favorable response being observed on the AWPEX sample with 50 vol % filler content.
Abstract: An ethylene-vinyl alcohol copolymer (EVOH) was treated with a silane coupling agent and calcium silicate solutions, and then soaked in a simulated body fluid (SBF) with ion concentrations approximately equal to those of human blood plasma. A smooth and uniform bonelike apatite layer was successfully formed on both the EVOH plate and the EVOH-knitted fibers in SBF within 2 days. Part of the structure of the resulting apatite-EVOH fiber composite was similar to that of natural bone. If this kind of composite can be fabricated into a three-dimensional structure similar to natural bone, the resultant composite is expected to exhibit both mechanical properties analogous to those of natural bone and bone-bonding ability. Hence, it has great potential as a bone substitute.
Abstract: Some ceramics, such as Bioglass, sintered hydroxyapatite, and glass-ceramic A-W, spontaneously bond to living bone. They are called bioactive materials and are already clinically used as important bone substitutes. However, compared with human cortical bone, they have lower fracture toughness and higher elastic moduli. Therefore, it is desirable to develop bioactive materials with improved mechanical properties. All the bioactive materials mentioned above form a bone-like apatite layer on their surfaces in the living body, and bond to bone through this apatite layer. The formation of bone-like apatite on artificial material is induced by functional groups, such as Si-OH, Ti-OH, Zr-OH, Nb-OH, Ta-OH, -COOH, and PO(4)H(2). These groups have specific structures revealing negatively charge, and induce apatite formation via formations of an amorphous calcium compound, e.g., calcium silicate, calcium titanate, and amorphous calcium phosphate. These fundamental findings provide methods for preparing new bioactive materials with different mechanical properties. Tough bioactive materials can be prepared by the chemical treatment of metals and ceramics that have high fracture toughness, e.g., by the NaOH and heat treatments of titanium metal, titanium alloys, and tantalum metal, and by H(3)PO(4) treatment of tetragonal zirconia. Soft bioactive materials can be synthesized by the sol-gel process, in which the bioactive silica or titania is polymerized with a flexible polymer, such as polydimethylsiloxane or polytetramethyloxide, at the molecular level to form an inorganic-organic nano-hybrid. The biomimetic process has been used to deposit nano-sized bone-like apatite on fine polymer fibers, which were textured into a three-dimensional knit framework. This strategy is expected to ultimately lead to bioactive composites that have a bone-like structure and, hence, bone-like mechanical properties.
Abstract: Poly(tetramethylene oxide) (PTMO)-TiO(2) hybrids were prepared by a sol-gel method from triethoxysilane-functionalized PTMO (Si-PTMO) and tetraisopropyltitanate with weight ratios of 30/70, 40/60 and 50/50 (hybrids PT30, PT40 and PT50, respectively), and subsequently subjected to a hot-water treatment at 95 degrees C for 2 d. All the obtained hybrids were amorphous before the hot-water treatment, and precipitated nanosized anatase after the hot-water treatment. The amount of precipitated anatase increased with decreasing PTMO content. Apatite was not formed on the surfaces of the hybrids in a simulated body fluid before the hot-water treatment, but was formed after the hot-water treatment, and its amount increased with decreasing PTMO content. Hybrid PT40 showed strength and Young's modulus analogous to those of human cancellous bones, and high ductility after the hot-water treatment. This kind of hybrid is expected to be useful as a new type of bone-repairing material.
Abstract: Radiotherapy is one of the effective treatments of cancers. External irradiation, however, often causes damages to healthy tissues. It has been reported that chemically durable 17Y(2)O(3)-19Al(2)O(3)-64SiO(2) (mol%) glass microspheres 20-30 mum in diameter are useful for in situ irradiation of cancers. This glass microsphere is already clinically used for treatment of liver cancer in USA, Canada and China. The number of yttrium. ions present in this glass microsphere is, however, not very large. On the other hand, P-31 can be activated to beta-emitter P-32 with a little longer half-life of 14.3 days by neutron bombardment. Therefore, it is expected that chemically durable microspheres containing a large amount of yttrium or phosphorus 20-30 mum in diameter are useful for in situ radiotherapy, when they were previously activated to beta-emitter by neutron bombardment. In the present study, Y2O3 and YPO4 microspheres were prepared by high-frequency induction thermal plasma melting method, and their structure, chemical durability and distribution in organs of rabbit were examined. The Y2O3 and YPO4 microspheres not only contained a large amount of yttrium or phosphorus but also showed high chemical durability. The Y2O3 microspheres were uniformly distributed only in their target organ and did not distribute in other organs. Therefore, they are believed to be useful for in situ radiotherapy of cancer.
Abstract: Polydimethylsiloxane (PDMS)-CaO-SiO(2) hybrids with starting compositions containing PDMS/(Si(OC(2)H(5))(4)+PDMS) weight ratio=0.30, H(2)O/Si(OC(2)H(5))(4) molar ratio=2, and Ca(NO(3))(2)/Si(OC(2)H(5))(4) molar ratios=0-0.2, were prepared by the sol-gel method. The apatite-forming ability of the hybrids increased with increasing calcium content in the Ca(NO(3))(2)/Si(OC(2)H(5))(4) molar ratio range 0-0.1. The hybrids with a Ca(NO(3))(2)/Si(OC(2)H(5))(4) molar ratio range 0.1-0.2 formed apatite on their surfaces in a simulated body fluid (SBF) within 12 h. The hybrid with a Ca(NO(3))(2)/Si(OC(2)H(5))(4) molar ratio of 0.10 showed an excellent apatite-forming ability in SBF with a low release of silicon into SBF. It also showed mechanical properties analogous to those of human cancellous bones. This hybrid is expected to be useful as a new type of bioactive material.
Abstract: Transparent monolithics of triethoxysilane end-capped poly(tetramethylene oxide) (Si-PTMO)-modified CaO-SiO2 hybrids were successfully synthesized by hydrolysis and polycondensation of Si-PTMO, tetraethoxysilane (TEOS) and calcium nitrate. As for the samples with varying (Ca(NO3)2)/(TEOS) molar ratios under constant ratio of (Si-PTMO)/(TEOS) of 2/3 in weight. the apatite-forming ability in a simulated body fluid (SBF) which is indicative of bioactivity. remarkably increased with increasing CaO content, although the tensile strength and Young's modulus decreased. The hybrid with (Ca(NO3)2)/(TEOS) = 0.15 in mol formed an apatite on its surface within only 1 day. For this series of samples, the strain at failure which is a measure of capability for deformation of material, was found to be about 30% and almost independent of CaO content. As for the samples with varying (Si-PTMO)/(TEOS) weight ratios under constant ratio of (Ca(NO3)2)/(TEOS) of 0.15 in mol, the strain at failure increased with increasing Si-PTMO content, but the apatite-forming ability, tensile strength and Young's modulus decreased. Thus, the synthesis of the hybrids exhibiting both high apatite-forming ability and high extensibility can be achieved by selecting suitable CaO and Si-PTMO contents. These new kind of hybrid materials may be useful as bioactive bone-repairing materials.
Abstract: Glass-ionomer cements, which consist of CaO-Al2O3-SiO2-CaF2 glass powders and a polyalkenoic acid solution, such as polyacrylic acid (PAA), have been widely used in dentistry. They set rapidly without any shrinkage, the lack of temperature increase on reaction, and develop high mechanical strength. Therefore, if bioactive glass-ionomer cements can be obtained, such cements are expected to be useful as cements for fixing orthopaedic implants to the surrounding bone. In the present study, to examine the possibility of obtaining bioactive glass-ionomer cements, the effect of PAA on the apatite formation on bioactive ceramics in a simulated body fluid was investigated. It was revealed that presence of even a small quantity of PAA inhibits the apatite formation in the body environment. It is speculated that when glass-ionomer cements are implanted into the body, PAA can be released from the glass-ionomer cements and inhibits the apatite formation on their surfaces. It is reasonable to suppose that this will occur with any glass-ionomer cement that contains PAA. Therefore, it might be considered difficult to obtain bioactive glass-ionomer cements.
Abstract: CaO, SiO2-based glasses form the bonelike apatite on their surfaces in an acellular simulated body fluid (SBF) with ion concentrations nearly equal to those of the human blood plasma. The apatite formation of the former glasses is attributed to the catalytic effect of the Si-OH groups, which are formed on their surfaces in SBF, for the apatite nucleation. The gels of SiO2, TiO2, ZrO2, Ta2O5, and Nb2O5 formed the apatite on their surfaces in SBF, but Al2O3 gel did not. This indicates that the Ti-OH, Zr-OH, Ta-OH, and Nb-OH groups besides the Si-OH groups are also effective for the apatite nucleation, but Al-OH groups are not effective. Apatite formation on self-assembled monolayer terminated with various functional groups in SBF showed that COOH and H2PO4 groups are also effective for the apatite nucleation. All these groups are negatively charged around pH 7.40. Their apatite nucleating ability is varied with their arrangements. Among the Ti-OH groups, those in anatase structure are most effective for the apatite nucleation. Transmission electron microscope attached with energy dispersive X-ray spectrometer showed that these functional groups induce the apatite nucleation not directly, but through formation of their calcium compounds and subsequent formation of amorphous calcium phosphate with low Ca/P atomic ratios.
Abstract: PURPOSE: To evaluate the histologic distribution of nonradioactive microspheres when intra-arterially infused into normal kidneys, and to evaluate the histologic changes after the infusion. MATERIALS AND METHODS: The glass microspheres were SiO2 microspheres with a smooth spherical shape measuring 20-30 micrometers in diameter with a specific gravity of 2.2 g/cm3. After the microspheres were mixed with contrast medium, they were infused into the renal artery. Twelve rabbits were sacrificed at 1 day, 3 days, 1 week, and 8 weeks after the treatment, respectively. The specimen was fixed with 10% buffered formalin, specially embedded in methyl methacrylate (MMA) resin and was stained by hematoxylin-eosin. The distribution of the microspheres in the kidney was analyzed microscopically, and histologic changes were also evaluated. RESULTS: The microspheres were found in arterioles whose diameters were about 20-30 micrometers, within normal kidneys. All vessels containing microspheres were confined to arterioles or arteries. No migration of microspheres was detected in the normal lung or the contralateral kidney. Severe ischemic changes were observed in kidneys, developing within 8 weeks of the infusion. CONCLUSION: Glass microspheres seemed to be a useful embolic material for intra-arterial radiation therapy.
Abstract: Recently, various inorganic antibacterial materials containing silver have been developed and some of them are in commercial use. Colorless and more chemically durable materials which slowly release the silver ion for a long period are, however, desirable to be developed for medical applications such as composite resin for dental restoration. In the present study, Si(OC2H5)4, Al(NO3)3 x 9H2O, AgNO3, HNO3, C2H5OH and H2O solutions with various Al/Ag atomic ratios under a constant Si/Ag atomic ratio of 1/0.023 were kept at 40 degrees C for gelation and drying. Thus obtained gels were pulverized into fine powders with average particle size of approximately 10 microm and then heat-treated at 900-1000 degrees C for 2 h. For the composition Al/Ag = 0, a yellow-colored glass was formed, since the silver existed in the form of metallic colloids in the glass. However, for the compositions Al/Ag > or = 1, colorless glasses were successfully obtained, since the silver existed in the form of Ag+ ions in the glasses. For the composition Al/Ag = 0, the silver ions got released rapidly into the water, whereas, for the compositions Al/Ag > or = 1, they gradually got released into the water at a controlled rate. A composite of the obtained powders with Al/Ag atomic ratio of 1 with Bis-GMA/TEGDMA in 70:30 weight ratio showed excellent antibacterial property. The sol-gel derived silica glass powders containing silver with compositions Al/Ag > or = 1 are believed to be useful as an antibacterial material for medical applications such as filler of composite resin for dental restoration.
Abstract: The essential requirement for an artificial material to bond to living bone is the formation of a bonelike apatite layer on its surface in the living body. The present paper shows that some functional groups such as SI-OH, TI-OH, Zr-OH, Ta-OH and Nb-OH on a material are effective for the apatite nucleation in body environment. These functional groups induce the apatite nucleation not directly but through formation of a calcium compound such as calcium silicate or titanate. Once the apatite nuclei are formed, they can grow spontaneously by consuming the calcium and phosphate ions from the surrounding fluid. Their growth is controlled not by ion diffusion in the fluid, but by the mass transport across the solid-liquid interface. These fundamental findings provide us principles for developing various kinds of bioactive materials with different mechanical properties.
Abstract: A chemically durable glass microsphere containing a large amount of phosphorus is useful for in situ irradiation of cancers, since they can be activated to be a beta-emitter with a half-life of 14.3 d by neutron bombardment. When the activated microspheres are injected to the tumors, they can irradiate the tumors directly with beta-rays without irradiating neighboring normal tissues. In the present study, P+ ion was implanted into silica glass microspheres of 25 microm in average diameter at 50 keV with nominal doses of 2.5 x 10(16) and 3.35 x 10(1)6 cm(-2). The glass microspheres were put into a stainless container and the container was continuously shaken during the ion implantation so that P+ ion was implanted into them uniformly. The implanted phosphorus was localized in deep regions of the glass microsphere with the maximum concentration at about 50 nm depth without distributing up to the surface even for a nominal dose of 3.35 x 10(16) cm(-2). Both samples released phosphorus and silicon into water at 95 degrees C for 7 d. On the basis of the previous study on P+-implanted silica glass plates, the silica glass microspheres containing more phosphorus which is desired for actual treatment could be obtained, without losing high chemical durability, if P+ ion would be implanted at higher energy than 50 keV to be localized in deeper region.
Abstract: A chemically durable glass that contains a large amount of phosphorus is useful for in situ irradiation of cancers. It can be activated to be a beta-emitter with a half-life of 14.3 d by using neutron bombardment. Microspheres of the activated glass that are injected to tumors can irradiate the tumors directly with beta-rays without irradiating neighboring normal tissues. In the present study, P+ ions in various doses have been implanted into a pure silica glass in a plate form at 200 keV. Almost all the implanted phosphorus is present in the inner region of the glass rather than in the surface region, taking the form of phosphorus colloids for all the doses in the range of 5 x 10(16)-1 x 10(18) cm(-2). A large number of amorphous phosphorus colloid particles with diameters of 10-150 nm are formed in the silica glass that has been implanted with a dose of 1 x 10(18) cm(-2); these colloid particles are distributed widely in a layer that is centered at a depth of 200-250 nm, All the investigated glasses hardly release any phosphorus and silicon into water at a temperature of 95 degrees C, even after 7 d. A silica glass that has been implanted with P+ ions at 200 keV with a dose of 1 x 10(18) cm(-2) is believed to be useful as a radiotherapy glass with sufficient phosphorus content and high chemical durability.
Abstract: A chemically durable glass containing a large amount of phosphorus is useful for in situ irradiation of cancers. It can be activated to be a beta emitter (half-life of 14.3 days) by neutron bombardment. Microspheres of the activated glass injected into the tumors can irradiate the tumors directly with beta rays without irradiating neighboring normal tissues. In the present study a P+ ion was implanted into a pure silica glass in a plate form at 100 keV in order to find the fundamental conditions for obtaining such a glass. Little phosphorus was present in the surface region, at least to a depth of 2.4 nm for doses of 5 x 10(16) and 1 x 10(17) cm-2, whereas an appreciable amount of it was distributed on the glass surface and a part of it was oxidized for doses above 5 x 10(17) cm-2. The glasses implanted with doses of 5 x 10(16) and 1 x 10(17) cm-2 hardly released the P and Si into water at 95 degrees C, even after 7 days, whereas the glasses implanted with doses above 5 x 10(17) cm-2 released appreciable amounts of these elements. Implantation energies of 20 and 50 keV (even at doses of 5 x 10(16) and 1 x 10(17) cm-2, respectively), formed oxidized phosphorus on the glass surfaces and gave appreciable release of the P and Si into the hot water. This indicates that a chemically durable glass containing a larger amount of phosphorus could be obtained if a P+ ion is implanted at higher energies to localize in a deeper region of the glass surface.
Abstract: A chemically durable glass containing a large amount of phosphorus is useful for in situ irradiation of cancers, It can be activated to beta-emitter with 14.3d half-life by neutron bombardment. Microspheres of the activated glass injected to the tumors can irradiate beta-ray directly to the tumors without giving radiation to neighboring normal tissues, In order to examine possibility for obtaining such a glass by ion implantation, P+ ion was implanted into a pure silica glass in a plate form under 50 keV to different doses, This implantation energy is estimated to give the maximum concentration of P+ ion at 18.6 nm in depth from the surface, Structural damage was produced near the surface of the glass by the ion implantation for all the doses in the range from 5 x 10(16) to 1 x 10(18) cm(-2). The phosphorus was localized only in the regions deeper than 1.2 nm from the surface, taking a form of phosphorus colloids, for a dose of 5 x 10(16) cm(-2), whereas it was distributed up to the glass surface and a part of it near the surface was oxidized for doses above 1 x 10(17) cm(-2), The former glass little released both P and Si into water at 95 degrees C even after 7d, whereas the latter glasses released appreciable amounts of these elements, At implantation energy of 20 keV, even a dose of 5 x 10(16) cm(-2) formed an oxidized phosphorus at the glass surface and gave appreciable releases of P and Si from the glass into water, This indicates that a chemically durable glass containing a larger amount of phosphorus could be obtained if P+ ion is implanted at higher energies and localized in a deeper region, even if the surface structure of the glass is damaged by the ion implantation.
Abstract: P-31 can be activated to beta-emitter P-32 by neutron bombardment. Chemically durable glasses containing a large amount of phosphorus is believed to be useful for in situ irradiation of cancers. A silica glass was implanted with phosphorus ion, heat-treated at 400 degrees C in H-2 to make phosphorus colloids grow, then heat-treated at 900 degrees C in O-2 in order to encapsulate the colloids with thin SiO2-P2O5 glass layer. Thus treated glass showed little dissolution even in hot water and is expected to be useful for radiotherapy.
