We have the purpose of evaluating fluorescent imaging for orthodontic bonding materials doped with a europium β-diketonate complex. Tris(1,3-diphenyl-1,3-propanedionato) (1,10-phenanthroline)Eu(III) [Eu(DBM)₃Phen]–doped poly(methyl methacrylate) (PMMA) adhesives were prepared by two kinds of radical in situ polymerization methods at room temperature, a benzoyl peroxide/tertiary amine (BPO/amine) redox method, and radical generation by oxygen coordination to partially oxidized tri-n-butyl borane (TBBO) method. However, the photoluminescence of the composites obtained by the latter system was inadequate. The reason for this phenomenon is speculated to be steric hindrance of DBM by TBBO. In contrast, fluorescent Eu(DBM)₃Phen/PMMA composites were successfully prepared by the BPO/amine redox method. The transparent and almost colorless appearance of these composites under natural light is favorable for application as an esthetic dental product. Strong emission of Eu³⁺ at 613 nm was observed to gradually increase as the concentration of the complex increased. Based on the results obtained, we can conclude that this Eu(DBM)₃Phen/PMMA adhesive can be used for developing photoluminescent orthodontic bonding materials.

Scaffold selection is critical for regenerative medicine. Mammalian (porcine) collagen has been extensively studied as a scaffold. However, collagens derived from mammals close to humans may pose problems associated with viruses contained in scaffolds upon tissue and organ transplantation into humans. Therefore, fish scale collagen from tilapia, which inhabits tropical and subtropical regions, may be more suitable than porcine collagen as a scaffold for regenerative medicine. Tilapia collagen can be utilized in a biological safety test on biomaterials for regenerative medicine.

No report has been published on nanomaterials with tilapia collagen. Therefore, we investigated cell differentiation using tilapia collagen in a nanomaterial insoluble in body fluids. Specifically, the differentiation of ES-D3 cells exposed to multi-walled carbon nanotubes (MWCNTs) was examined in two-dimensional culture with tilapia collagen. As a result, ES-D3 cells were differentiated with tilapia collagen in the same manner as porcine collagen. MWCNTs had significant effects on the differentiation of ES-D3 cells.

The Embryo Stem Cell Test (EST) protocol is an in vitro embryotoxicity test that has been internationally recognized as a screening protocol capable of predicting the risks of chemicals in normal human newborns through large-scale international validation. Mouse iPS cells are known to have characteristics similar to those of ES-D3 cells used in the EST protocol. We examined whether mouse iPS cells can be substituted for ES-D3 cells by investigating their differentiation and viability with C60 fullerenes, demonstrating that C60 fullerenes could be classified as "non-embryotoxicity." In addition, we compared the results with those obtained with conventional ES cells, revealing that mouse iPS cells could be employed because we obtained the same results as those with ES-D3, EL M3, and ES-R1 cells. C60 fullerenes are insoluble in culture solution, and, therefore, are inapplicable to the EST protocol, which requires solubility in culture medium. No embryotoxicity test has been developed for nanomaterials phagocytosed into cells. Therefore, a embryotoxicity test specialized for nanomaterials is expected.

Reproduction of tumor microenvironment in vivo using the conventional 2- or 3-dimensional culture method is difficult because of the lack of extracellular matrix (ECM) and intercellular interaction. In this study, we tried to establish a 3-dimensional tumor environment using spheroids of oral cancer-derived cells. The Interleukin-6 (IL-6) expression level was high in the spheroids on measurement using the real-time RT-PCR method showing a difference from that in single cells. A representative inflammatory cytokine, IL-6, increases the activity of many types of cancer-derived cells, being involved in tumor formation and metastasis, and similar findings were noted in HSC-4 cells derived from human squamous cell carcinoma of the tongue, for which analysis of phenomena in the cellular interface in 3-dimensionally formed masses is expected. It is highly possible that this method is applicable for studies on the carcinogenicity of nanomaterials represented by asbestos.

When a gold leaf or gold foil is ingested, it is considered to be excreted through the digestive organ without reaction with digestive juices, such as gastric acid. Since the standard thickness of gold leaves is about 0.1 μm, when a small gold leaf stays in the human digestive tract for a prolonged period without being gradually dissolved, the possibility of chronic inflammatory and carcinogenesis in the digestive tract through a mechanism similar to asbestos-induced carcinogenesis cannot be ruled out. Edible gold leaf has no nutritional usefulness for humans other than a luxury appearance and it has a high risk of safety; however, development of safe edible gold leaf of gold foil as an alloy completely dissolved in the digestive tract is necessary.