Apatite-forming ability of vinylphosphonic acid-based copolymer in simulated body fluid: effects of phosphate group content

Phosphate groups on materials surfaces are known to contribute to apatite formation upon exposure of the materials in simulated body fluid and improved affinity of the materials for osteoblast-like cells. Typically, polymers containing phosphate groups are organic matrices consisting of apatite–polymer composites prepared by biomimetic process using simulated body fluid. Ca2+ incorporation into the polymer accelerates apatite formation in simulated body fluid owing because of increase in the supersaturation degree, with respect to apatite in simulated body fluid, owing to Ca2+ release from the polymer. However, the effects of phosphate content on the Ca2+ release and apatite-forming abilities of copolymers in simulated body fluid are rather elusive. In this study, a phosphate-containing copolymer prepared from vinylphosphonic acid, 2-hydroxyethyl methacrylate, and triethylene glycol dimethacrylate was examined. The release of Ca2+ in Tris-NaCl buffer and simulated body fluid increased as the additive amount of vinylphosphonic acid increased. However, apatite formation was suppressed as the phosphate groups content increased despite the enhanced release of Ca2+ from the polymer. This phenomenon was reflected by changes in the surface zeta potential. Thus, it was concluded that the apatite-forming ability of vinylphosphonic acid-2-hydroxyethyl methacrylate-triethylene glycol dimethacrylate copolymer treated with CaCl2 solution was governed by surface state rather than Ca2+ release in simulated body fluid

Apatite formation on a hydrogel containing sulfinic acid group under physiological conditions

Natural bone consists of apatite and collagen fiber. Bioactive materials capable to bonding to bone tissue are clinically used as bone-repairing materials. Apatite-organic polymer composites exhibit bone-bonding abilities and mechanical properties similar to those of natural bone, and these materials can be prepared using biomimetic processes in simulated body fluid (SBF). Specific functional groups such as sulfonic and carboxylic acid groups are known to induce the heterogeneous nucleation of apatite in SBF. However, it remains unclear whether structurally related sulfinic acid groups can contribute to apatite formation in the same way, despite sodium sulfonate being used in biomedical applications as a radical polymerization promoter in adhesive dental resin. Herein, we report the preparation of a new hydrogel containing sulfinic acid groups from sodium 4-vinylbenzenesulfinate and 2-hydroxyethyl methacrylate using a radical polymerization reaction and the subsequent incorporation of Ca2+ ions into this material. We also investigated the apatite-forming behavior of these hydrogels in SBF. Hydrogels containing sulfinic acid groups showed higher apatite-forming ability than those without sulfinic acid groups. In addition, the apatite layer formed on the former showed tight adhesion to the hydrogel. This phenomenon was attributed to the heterogeneous nucleation of apatite, induced by the sulfinic acid groups

Quasi-Phase-Matched Second-Harmonic Generation in Thermally Poled Twin-Hole Silica-Glass Optical Fiber: Comparison between Mercury Lamp and Excimer Laser Exposures

The 8th International Symposium on Transparent Oxide and Related Materials for Electronics and Optics (TOEO-8), May 13-15, 2013, International Conference Center, Waseda University, Tokyo, Japa

Biomineralization behavior of a vinylphosphonic acid-based copolymer added with polymerization accelerator in simulated body fluid

AbstractApatite-polymer composites have been evaluated in terms of its potential application as bone substitutes. Biomimetic processes using simulated body fluid (SBF) are well-known methods for preparation of such composites. They are reliant on specific functional groups to induce the heterogeneous apatite nucleation and phosphate groups possess good apatite-forming ability in SBF. Improving the degree of polymerization is important for obtaining phosphate-containing polymers, because the release of significant quantities of monomer or low molecular weight polymers can lead to suppression of the apatite formation. To date, there have been very few studies pertaining to the effect of adding a polymerization accelerator to the polymerization reaction involved in the formation of these composite materials under physiological conditions. In this study, we have prepared a copolymer from triethylene glycol dimethacrylate and vinylphosphonic acid (VPA) in the presence of different amounts of sodium p-toluenesulfinate (p-TSS) as a polymerization accelerator. The effects of p-TSS on the chemical durability and apatite formation of the copolymers were investigated in SBF. The addition of 0.1–1.0wt% of p-TSS was effective for suppressing the dissolution of the copolymers in SBF, whereas larger amount had a detrimental effect. A calcium polyvinylphosphate instead of the apatite was precipitated in SBF

Estimating the Elasticity of Taxable Income: Evidence from Top Japanese Taxpayers

This study measures the elasticity of taxable income (ETI) using data on top Japanese taxpayers between 1986 and 1989. During these years, Japan decreased the income tax rates of the top-to-bottom income earners and number of income brackets drastically. We construct a panel dataset of top taxpayers in Japan in this period, using Japanese tax return data and estimate the ETI. We find that the ETI with regard to the net-of-tax rate is approximately 0.074–0.055, considerably lower than those for the United States and most European countries but nearly equal to that for Denmark

Lumbar motor control & perceptual awareness

Purpose : The purpose of this study was to clarify the differences in lumbar spine and hip joint motor control ability (MCA) in prone hip extension (PHE) between individuals with and without low back pain (LBP). It also aimed to determine the relationship between lumbar spine and hip joint MCA and lumbar perceptual awareness in individuals with LBP. Methods : In total, 78 university students (20 with LBP and 58 without) were included in the study. The MCA of the lumbar spine and hip joint in PHE and perceptual awareness were evaluated. The MCA of the lumbar spine and hip joint was measured using a wearable sensor. Subsequently, a comparison of the MCA of the lumbar spine and hip joints of the participants and the relationship between MCA and lumbar perceptual awareness were examined. Results : The MCA of the LBP group was higher than that of the non-LBP group in motion on the sagittal plane. In addition, perceptual awareness was negatively correlated with MCA in the sagittal plane in the lumbar spine. Conclusion : People with LBP had higher lumbar spine and hip joint MCA than those without LBP. Perceptual awareness was associated with lumbar spine and hip joint MCA in people with LBP

電子レンジを利用して生成したプラズマの分光解析

A mechanical pencil lead or a dress pin absorbs electromagnetic waves emitted from a kitchen microwave as an antenna, both ends of which emit electrons. They ionize the surrounding gas molecules, and microwave-excited plasma is produced. The statistical properties (level statistics) of the energy-level spacing of spectroscopy of this plasma are discussed. It is known that different geometrical structures of the phase space in a classical system (for example, "islands" indicating periodicity and chaotic "seas") correspond to different statistical properties of energylevel spacing in a quantum system. The characteristics of level repulsions and attractions are reflected in a functional form of probability distribution functions of level spacing. From this viewpoint of quantum chaos, the energy spectra of the microwaveexcited plasma are considered.シャープペンの芯や待ち針は電子レンジのマイクロ波をよく吸収し, 加速された電子は両端から飛び出す. それは周囲の気体分子を電離させ, プラズマが生じる. このプラズマの分光解析を行う. 古典系の相空間の幾何学的構造(周期性を表す「島」やカオスの「海」)が対応する量子系のエネルギー準位の統計性に反映されることが知られているが, その観点を踏まえ, このプラズマの準位間隔の分布関数を求める

Structural effects of phosphate groups on apatite formation in a copolymer modified with Ca2+ in a simulated body fluid

Organic–inorganic composites are novel bone substitutes that can ameliorate the mismatch of Young\u27s moduli between natural bone and implanted ceramics. Phosphate groups contribute to the formation of apatite in a simulated body fluid (SBF) and the adhesion of osteoblast-like cells. Therefore, modification of a polymer with these functional groups is expected to enhance the ability of the organic–inorganic composite to bond with bone. Two phosphate groups have been used, phosphonic acid (–C–PO3H2) and phosphoric acid (–O–PO3H2). However, the effects of structural differences between these phosphate groups have not been clarified. In this study, the apatite formation of copolymers modified with Ca2+ and either –C–PO3H2 or –O–PO3H2 was examined. The mechanism of apatite formation is discussed based on analytical and computational approaches. The copolymers containing –O–PO3H2, but not those containing –C–PO3H2, formed apatite in the SBF, although both released similar amounts of Ca2+ into the SBF. Adsorption of HPO42− from –O–PO3H2 in the SBF following Ca2+ adsorption was confirmed by zeta-potential measurement and X-ray photoelectron spectroscopy. The measurement of the complex formation constant revealed that the –O–PO32−⋯Ca2+ complex was thermodynamically unstable enough to convert into CaHPO4, which was not the case with –C–PO32−⋯Ca2+. The formation of CaHPO4-based clusters was found to be a key factor for apatite nucleation. In conclusion, this study revealed that modification with –O–PO3H2 was more effective for enhancing apatite formation compared with –C–PO3H2

Structural effects of sulfur-containing functional groups on apatite formation on Ca2+-modified copolymers in a simulated body environment

Chemical modification with specific functional groups has been the conventional method to develop bone-bonding bioactive organic–inorganic hybrids. These materials are attractive as bone substitutes because they are flexible and have a Young’s modulus similar to natural bone. Immobilization of sulfonic acid groups (−SO3H) onto the polymer chain is expected to produce such hybrids because these groups induce apatite formation in a simulated body fluid (SBF) and enhance the activity of osteoblast-like cells. Sulfinic acid groups (−SO2H), which are derivatives of −SO3H, can also induce apatite nucleation. However, the structural effects of such sulfur-containing functional groups on apatite formation have not been elucidated. In the present study, apatite formation on Ca2+-modified copolymers containing −SO2H or −SO3H was investigated in a simulated body environment. The copolymer containing Ca2+ and −SO3H promoted Ca2+ release into the SBF and formed apatite faster (1 day) than the copolymer containing Ca2+ and −SO2H (14 days). In contrast, when they were not modified with Ca2+, the copolymer containing only −SO2H deposited the apatite faster (7 days) than that containing only −SO3H (>7 days) in the solution with Ca2+ concentration 1.5 times that of SBF. The former adsorbed larger amounts of Ca2+ than the latter. The measured stability constant of the complex indicated that the interaction of −SO2–···Ca2+ was more stable than that of −SO3–···Ca2+. It was found that both the release and adsorption of Ca2+ governed by the stability played an important role in induction of the apatite formation and that the apatite-forming ability of sulfur-containing functional groups drastically changed by the coexistence of Ca2+