This paper reviews the studies achieved by the author and his research group on functional inorganic phosphorus materials, in commemoration of the distinguished contribution award from The Japanese Association of Inorganic Phosphorus Chemistry (JAIPC) in 2019. The focus of the review is on the development both of electrically functionalized hydroxyapatite and new Na⁺ conduction ceramics and glass-ceramics. It is therefore to be stated here that the present review clearly differs from conventional journal-reviews which summarize related papers and collect their related references with critical comments.

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Magnesium is an essential element to the human body, and Mg²⁺ ion can work to enhance cell adhesion, proliferation, differentiation, and mineralization. From the viewpoint of inorganic glass formation, MgO can be classified as an intermediate, that improves the glass-forming and ion-releasing abilities. The present work reports fundamental data for designing MgO-containing bioactive phosphate glasses with manipulated ion-releasability. MgO-CaO-P₂O₅-TiO₂ invert glasses were prepared, in which TiO₂ was substituted by MgO, and their structure and dissolution behavior were examined. Magnesium in the glasses was preferentially bonded to orthophosphate groups. The glass-forming ability and chemical durability of the glasses decreased with increasing MgO content, since P-O-Mg bonds are weaker than P-O-Ti bonds. In contrast, the ion-releasing ability of the glasses improved with increasing MgO content, and the released amount of Mg²⁺ ion was expected to be within the range suitable to stimulate cell adhesion and proliferation.

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A comparative study of polyvinylidene fluoride (PVDF) and polycaprolactone (PCL) incorporated with particles of amorphous calcium phosphate on the induction of apatite formation ability in simulated body fluid (SBF)-biomimetic environment has been investigated. PVDF and PCL films containing amorphous calcium phosphate particles were fabricated using the solvent casting method. These amorphous calcium phosphate particles were highly active in inducing apatite formation. Results showed that both PCL and PVDF successfully resulted in apatite formation in SBF. However, it was found that the amount of amorphous calcium phosphate particles and the induction period of the apatite formation in SBF significantly varied for PVDF and PCL. These types of bioactive polymeric composite materials are attractive candidates as bone restorative materials with flexibility as well as high apatite forming ability.

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Novel violet pigments were synthesized from manganese oxide and phosphoric acid by heating at several temperatures. The obtained materials were investigated by X-ray diffraction (XRD) analysis, infrared (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet-visible (UV-Vis) reflectance spectroscopy, and L*a*b* color space. Samples synthesized in this study did not show the XRD peak pattern for certain compounds. At P/Mn = 2/3 and 1/1, samples heated at 500 °C showed high a* value and low b* value, corresponding to violet color. On the other hand, at P/Mn = 2/1, the sample heated at 400 °C had the most violet powder.

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The phosphonylations of 5’-deoxy-5-fluorouridine (5’-DFUR) and 1-β-D-arabinofuranosylcytosine (Ara C) in aqueous solution were successfully performed using disodium diphosphonate (DP, Na2P2O5H2). The former reaction resulted in the synthesis of both 3’-phosphonyl-5’-DFUR and 2’-phosphonyl-5’-DFUR, with an overall yield of 100%. The reaction of 1-β-D-arabinofuranosylcytosine (Ara C) with DP gave 5’-phosphonyl-Ara C, 3’-phosphonyl-Ara C and 2’-phosphonyl-Ara C in a total yield of more than 35%. The optimal condition for the phosphonylation of either 5’-DFUR or Ara C with DP was determined to be a 1:10 ratio of 5’-DFUR or Ara C to DP and a solution pH of 11. The phosphonylated products of 5’-DFUR and Ara C were stable at 10 °C and 25 °C, respectively, over the pH range of 7 to 9. A proposed mechanism for the reactions of 5’-DFUR and Ara C with DP was developed.

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