Structure of Yttrium and Phosphorus-Containing Microspheres Prepared by Spray Dry Method

Microspheres containing yttrium (Y) and/or phosphorus (P) around 25 µm are useful for radioembolization therapy because they are activated to β-emitter by neutron bombardment and infused in blood vessels in the neighborhood of tumors to irradiateβ-rays to the tumors. In this study, we attempt to prepare Y and P-containing microspheres by spray drying method. Starting solution containing yttrium nitrate and phosphoric acid in equimolar ratio was spray dried under various conditions. Microspheres 5-30 µm in size are obtained when the starting solution with polyvinyl alcohol (PVA) binder was spray-dried at the atomizing pressure of 0.05 MPa. When the microspheres were heated at 1100ºC for 1 h, they precipitated Y-containing crystals such as yttrium phosphate (YPO4), yttrium oxide (Y2O3), yttrium polyphosphate (Y(PO3)3) and yttrium tetraphosphate (Y2P4O13) but most of them were ruptured. Without the PVA binder, small microspheres around 5 µm in size were formed but their shape remained even after the heat treatment. We found that the atomizing pressure of spray dryer remarkably affects the size of microspheres and PVA binder is essential to obtain microspheres around 25 µm, but addition of pH adjuster to starting solution is not essential. This study proposed the criterion of conditions to prepare Y and P-containing microspheres by spray drying method

Yttrium phosphate microspheres with enriched phosphorus content prepared for radiotherapy of deep-seated cancer

Ceramic microspheres composed of β-emitters are useful for in situ radiotherapy of deep-seated cancer by implantation around the tumor. In addition, microspheres 20–30 µm in diameter can combine β-emission with the embolization effect. Yttrium phosphate is an attractive candidate material for such microspheres, because both Y and P play roles as β-emitters. The half-life of 31P is known to be much larger than that of 90Y. Therefore, it is expected that yttrium phosphate microspheres with high P content can maintain a longer radiotherapy effect. In the present study, preparation of microspheres with enriched P content has been attempted by water-in-oil emulsions using polyphosphate as a starting material. Yttrium phosphate microspheres with a higher P/Y molar ratio (2.5) than in previously reported YPO4 microspheres were obtained. It was found that emulsification for sufficient time (more than 10 min) is necessary to obtain microspheres that are 20–30 µm in size. Although the microspheres released Y sparingly, they released larger amounts of P than previously reported YPO4 microspheres in a simulated body environment. Heat treatment at moderate temperature can suppress P release to some extent. Further improvement in chemical durability through surface modification is essential for long-term clinical use

Атмосфера секретности как один из факторов формирования менталитета населения закрытых городов Урала

Apatite films were deposited onto titanium (Ti) metal substrates by an electrodeposition method under a pulse current. Metastable calcium phosphate solution was used as the electrolyte. The ion concentration of the solution was 1.5 times that of human body fluid, but the solution did not contain magnesium ions at 36.5 °C. We used an average current density of 0.01 A/cm2 and current-on time (TON) equal to current-off time (TOFF) of 10 ms, 100 ms, 1 s, and 15 s. The adhesive strength between apatite and Ti substrates were relatively high at TON = TOFF = 10 ms. It is considered that small calcium phosphate (C–P) crystals with low crystallinity were deposited on the Ti surface without reacting with other C–P crystals, H2O, and HCO3- in the surrounding environment. This resulted in relaxation of the lattice mismatch and enhancement of the adhesive strength between the apatite crystals and Ti substrates

Fabrication of Yttrium Phosphate Microcapsules by an Emulsion Route for in situ Cancer Radiotherapy

Radiotherapy is a novel, non-invasive cancer treatment. Radioactive hollow microspheres, i.e., microcapsules, are attractive for in situ cancer radiotherapy because they can effectively reach tumors without settling in blood vessels. In particular, microcapsules 20-30 µm in size are expected to exhibit not only a radiotherapy effect but also embolization that blocks the nutrient supply to cancer cells. β-ray irradiation is the most suitable source for in situ radiotherapy because of its moderate range. Several kinds of β-emitting yttria (Y2O3) microcapsules have therefore been developed. Yttrium phosphate (YPO4) should have a longer irradiation effect than that of Y2O3 because the half-life of 31P (14.3days) is longer than that of 90Y (64.1 hours). However, the preparation of YPO4 microcapsules has not been reported to date. In the present study, YPO4 microcapsules were fabricated using a water/oil (W/O) emulsion prepared by first dispersing a YPO4 sol into toluene containing a surfactant, with mechanical homogenization. The emulsion was then added into butanol to dehydrate the water phase and precipitate microcapsules. These were then heat-treated to improve their mechanical strength and chemical stability. Microcapsule fragility at low YPO4 sol concentrations in the water phase was attributed to the thinness of the microcapsule shell. The size of the microcapsules decreased with increasing emulsification speed. The chemical stability of the prepared microcapsules is similar to those of previously reported YPO4 and Y2O3 microspheres in weakly acidic conditions. Thus, little leakage of radioactive species into nearby healthy tissues is expected. The obtained microcapsules are expected to be highly effective for cancer radiotherapy

Effect of Ammonia or Nitric Acid Treatment on Surface Structure, in vitro Apatite Formation, and Visible-Light Photocatalytic Activity of Bioactive Titanium Metal

Ti metal treated with NaOH, NH4OH, and heat and then soaked in simulated body fluid (SBF) showed in vitro apatite formation whereas that treated with NaOH, HNO3, and heat and then soaked in SBF did not. The anatase TiO2 precipitate and/or the fine network structure formed on the surface of the Ti metal treated with NaOH, NH4OH, and heat and then soaked in SBF might be responsible for the formation of apatite on the surface of the metal. The NaOH, NH4OH, and heat treatments might produce nitrogen-doped TiO2 on the surface of the Ti metal, and the concentration of methylene blue (MB) in the Ti metal sample treated with NaOH, NH4OH, and heat decreased more than in the untreated and NaOH- and heat-treated ones. This preliminary result suggests that Ti metal treated with NaOH, NH4OH, and heat has the potential to show photocatalytic activity under visible light

Fabrication of Yttrium Phosphate Microcapsules by an Emulsion Route for in situ Cancer Radiotherapy

Radiotherapy is a novel, non-invasive cancer treatment. Radioactive hollow microspheres, i.e., microcapsules, are attractive for in situ cancer radiotherapy because they can effectively reach tumors without settling in blood vessels. In particular, microcapsules 20-30 µm in size are expected to exhibit not only a radiotherapy effect but also embolization that blocks the nutrient supply to cancer cells. β-ray irradiation is the most suitable source for in situ radiotherapy because of its moderate range. Several kinds of β-emitting yttria (Y2O3) microcapsules have therefore been developed. Yttrium phosphate (YPO4) should have a longer irradiation effect than that of Y2O3 because the half-life of 31P (14.3days) is longer than that of 90Y (64.1 hours). However, the preparation of YPO4 microcapsules has not been reported to date. In the present study, YPO4 microcapsules were fabricated using a water/oil (W/O) emulsion prepared by first dispersing a YPO4 sol into toluene containing a surfactant, with mechanical homogenization. The emulsion was then added into butanol to dehydrate the water phase and precipitate microcapsules. These were then heat-treated to improve their mechanical strength and chemical stability. Microcapsule fragility at low YPO4 sol concentrations in the water phase was attributed to the thinness of the microcapsule shell. The size of the microcapsules decreased with increasing emulsification speed. The chemical stability of the prepared microcapsules is similar to those of previously reported YPO4 and Y2O3 microspheres in weakly acidic conditions. Thus, little leakage of radioactive species into nearby healthy tissues is expected. The obtained microcapsules are expected to be highly effective for cancer radiotherapy

Effects of organic polymer addition in magnetite synthesis on its crystalline structure

Magnetite (Fe3O4) nanoparticles and magnetite-based inorganic–organic hybrids are attracting attention in biomedical fields as thermoseeds for hyperthermia and a contrast medium in magnetic resonance imaging. Size control of Fe3O4 thermoseeds is important as the particle size affects the heat generation properties. Fe3O4 can be easily synthesized via aqueous processes and the presence of organic substances during synthesis can affect the size and crystalline phase of the Fe3O4 formed. In this study, various polymers with different functional groups and surface charges were added to the precursor solution of Fe3O4 to clarify the relationship between the chemical structure of the organic substances and the crystal structure of Fe3O4. At first, coexistence effects of the organic substances in the solutions were clarified. As a result, crystalline Fe3O4 was precipitated even after addition of neutral polyethylene glycol and cationic poly(diallyldimethylammonium chloride). The poly(sodium-4-styrene sulfonate) addition significantly decreased the particle size, while polyacrylic acid addition inhibited Fe3O4 nucleation to afford an amorphous phase. These differences were related to the ease of complex formation from iron ions and coexisting organic polymers. In order to clarify this assumption, a modified experimental procedure was applied for the polyacrylic acid. Namely, the iron oxide precipitation by the NaOH solution was followed by the polyacrylic acid addition. Notably, Fe3O4 nucleation was not inhibited. Hence, the size and crystalline phase of the iron oxide prepared by the aqueous process were drastically affected by organic polymers

In vitro apatite formation and visible-light photocatalytic activity of Ti metal subjected to chemical and thermal treatments

In this study, we investigated the surface structure, apatite formation in simulated body fluid (SBF), and visible-light photocatalytic activity of Ti metal subjected to chemical and thermal treatments. Ti metal samples treated with NaOH, a nitrogen-containing solution (0.1 M HNO3, 0.1–1.0 M (H2N)2Cdouble bond; length as m-dashO, or 0.1–1.0 M NH4Cl), and heat showed apatite formation on their surfaces in SBF, whereas those treated with NaOH, 0.5 or 1.0 M HNO3, and heat did not. In the former case, apatite formation may be attributable to the fine network structure of anatase-type TiO2 doped with a small amount of nitrogen on the surface of the Ti metal. The Ti metal treated with the latter treatment showed higher methylene blue decomposition than the untreated sample and the one treated with the former treatment. This preliminary result suggests that Ti metal treated with NaOH, 0.1 M HNO3, and heat can potentially show visible-light-induced antibacterial property as well as bone-bonding ability

In vitro apatite formation and drug loading/release of porous TiO2 microspheres prepared by sol-gel processing with different SiO2 nanoparticle contents

Bioactive titania (TiO2) microparticles can be used as drug-releasing cement fillers for the chemotherapeutic treatment of metastatic bone tumors. Porous anatase-type TiO2 microspheres around 15 μm in diameter were obtained through a sol–gel process involving a water-in-oil emulsion with 30:70 SiO2/H2O weight ratio and subsequent NaOH solution treatment. The water phase consisted of methanol, titanium tetraisopropoxide, diethanolamine, SiO2 nanoparticles, and H2O, while the oil phase consisted of kerosene, Span 80, and Span 60. The resulting microspheres had a high specific surface area of 111.7 m2·g− 1. Apatite with a network-like surface structure formed on the surface of the microspheres within 8 days in simulated body fluid. The good apatite-forming ability of the microspheres is attributed to their porous structure and the negative zeta potential of TiO2. The release of rhodamine B, a model for a hydrophilic drug, was rapid for the first 6 h of soaking, but diffusion-controlled thereafter. The burst release in the first 6 h is problematic for clinical applications; nonetheless, the present results highlight the potential of porous TiO2 microspheres as drug-releasing cement fillers able to form apatite

Adsorption of Laminin on Hydroxyapatite and Alumina and the MC3T3-E1 Cell Response

Artificial hydroxyapatite (HAp) is osteoconductive, but the mechanism is still unclear. It is likely that some serum proteins are adsorbed onto HAp and influence its osteoconductivity. We investigated the adsorption behavior of laminin (LN), which was isolated from murine Engelbreth–Holm–Swarm sarcoma, onto HAp and compared it with nonosteoconductive alpha-type alumina (α-Al2O3). Cell adhesion, spreading, and proliferation on native and LN-adsorbed discs of HAp or α-Al2O3 were examined using murine MC3T3-E1 osteoblastic cells. A larger amount of LN adsorbed onto HAp than α-Al2O3 despite the electrostatic repulsion between LN and HAp, suggesting the specific adsorption of LN onto HAp. The LN adsorbed onto HAp remarkably enhanced initial attachment and spreading of MC3T3-E1 cells, but subsequent proliferation of MC3T3-E1 cells was influenced by the type of material rather than LN adsorption. These fundamental findings imply that LN adsorbed on HAp could trigger osteoconductivity in vivo, aiding in the development of novel biomaterials that specifically adsorb LN and effectively enhance cell attachment and spreading