A series of antibacterial ions-containing hydrotalcite-like compounds with various combination of divalent and trivalent matal ions were prepared by wet mothod and their MnO₄^- ion-derivatives were also obtained by the ion exchange of these hydrotalcite-like compounds with MnO₄^- ion in low concentration KMnO₄ solution. Their bactericidal behavior against Escherichia coli and the influence of content of antibacterial ions were investigated. The products exhibited strong bacteridal activity in aqueous solutions to E. coli, especially hydrotalcite-like compounds obtained after ion-exchange reaction with MnO₄^- ion. It was suggested that the high bactericidal effect was due to inactivation of E. coli by both Cu²⁺ ion and/or Zn²⁺ ion contained in the host layers and MnO₄^- ion loaded in the interlayer spaces. The eluted amounts of Cu²⁺, Zn²⁺ and MnO₄^- ion from hydrotalcite-like compounds into pure water were so low that they are not harmful to water environment. Therefore, the products are promising as a new antimicrobial water treatment agent for E. coli.

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The silver-doped ceramics is the whitewares coated with low-temperature lime zinc glaze containing silver, and has bactericidal activity. In this study, the mechanism of the bactericidal action of the silver-doped ceramics against bacteria, mainly Escherichia coli K12 W3110, was investigated. The silver-doped ceramics had high bactericidal activity when it was irradiated by visible light. Since the eluted silver ions from the surface of ceramics were not detected by ICP measurement and the supernatant had no bactericidal activity, it was proved that the eluted silver ions do not contribute to the bactericidal action of the ceramics. The bactericidal activity was extremely inhibited in the presence of radical scavengers such as L-cysteine, L-alanine or I^-. After the silver-doped ceramics was removed from the cell suspension irradiated for 60 min, the bactericidal activity was still maintained, and was inhibited by L-cysteine. The silver-doped ceramics also had bactericidal activity against Bacillus subtilis ATCC6633.
These results suggest that the bactericidal action of silver-doped ceramics is caused by the hydroxyl radical which is generated on the surface of the ceramics by light irradiation and is converted to a living radical in bacterial cells.

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Anodic oxidation coating of aluminum impregnated with iodine compound was prepared by electrochemical method and its bactericidal activity against Escherichia coli, Staphylococcus aureus and various molds was investigated. Iodine existed as I₂ in the anodic oxidation coating of aluminum and it was stipulated the iodine form iodophor having an amorphous structure. The bactericidal activity of anodic oxidation coating of aluminum impregnated with iodine compound was high against various molds and bacterial bodies. It was thought that the high bactericidal activity is due to I₂ eluted from anodic oxidation coating. The anodic oxidation coating is useful as a new antimicrobial material.

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Noble metal-and its oxide- particulates dispersed hydroxyapatite (HAp) composite powders were prepared by ultrasonic spray-pyrolysis method. The morphology of the resulting particles was spherical; these fine powders consisted of the primary particle with sizes of about 100 nm. The particle size of the powders increased with the amount of noble metal ions in the starting solution. The obtained powders were composed of stichiometric HAp without Ca²⁺ ions-deficiency. In case of Au and Ag additives, noble metal (Au, Ag) particulates dispersed HAp was formed. In case of Pt additive, however, oxide (PtO) particulates dispersed HAp was formed.

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