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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.

The glass ionomer cement as one of the dental cements has been subjected to be widespread application in restoring tooth structure. Most of glass ionomer cements employ the poly(acrylic acid) (PAA) as the liquid phase, but the presence of PAA inhibits the apatite formation on the surface in the body environment, which is an essential requirement for exhibiting bone-bonding ability (bioactivity). In this study, poly(γ-glutamic acid) (γ-PGA), a kind of biopolymer, was utilized for cement preparation. The effort of preparation parameters including the glass powders/liquid ratio (P/L) and the concentration ofγ-PGA on diametral tensile strength were investigated. A maximum diametral tensile strength value of11.88±1.43MPa was obtained when the cement sample was prepared by P/L ratio of 1 : 1 and theγ-PGA concentration of 30% after aging for 3 days. The TF-XRD patterns, SEM images, and EDX spectra suggested that the cement induced a precipitation of calcite on the surface after 7 days of immersion in stimulated body fluid (SBF), although the apatite formation was not observed. The present results suggest that the cement has potential to show bioactivityin vivo, because calcite is also reported to be bioactive.

This study is concerning hybrid materials composed of the magnetite and the organic polymer such as dextran. They are useful for hyperthermia of cancer. In the preparation of this material, chemical structure or molecular weight of the added polymer is expected to affect ionic interaction between polymer and iron salts, and consequently the grain size and morphology of the prepared magnetite core. Therefore, we have synthesized magnetite-polymer hybrids using various polymers. Various polymers were dissolved in iron (II) chloride aqueous solution, and then NaOH aqueous solution was added to this mixed solution. As a result, in the case of neutral and cationic polymer crystalline magnetite was precipitated in the hybrid. On the other hand, in the case of anionic polyacrylic acid, lepidocrocite was precipitated rather than magnetite. It is known that the magnetite formation progresses through intermediate Fe (OH)2 formation and oxidation of the Fe (OH)2 by dissolved O2. Therefore it is considered that tight ionic interaction is constructed between the iron ions and the carboxyl group in the polyacrylic acid to form a complex, and the Fe (OH)2 formation is inhibited. When the hybrid was prepared by addition of NaOH aqueous solution to iron (II) chloride solution, and subsequent addition of the different polymers, magnetite formation was not inhibited irrespective of kind of polymer. The present results indicate that crystalline structure of the magnetite phase in magnetite-polymer hybrid is strongly affected by the chemical structure of polymer additives or the order of addition.