Using the pupillary reaction adopted in the autonomic function test as an index, we have investigated autonomic reactions to taste stimuli and clarified that the sympathetic nerve activity increases as the bitter substance concentration increases. Thus, to make the relation between a reaction of the nano level to the taste stimulus and a recognition threshold clear. we investigated autonomic reactions to a low-concentration stimulus at a bitter taste recognition threshold level. It was suggested that a non-sensible stimulus at a concentration lower than the bitter taste recognition threshold has a certain influence on the autonomic nerve.

Usability of high-purity silica fibers as a 3-dimensional carrier of ES cell differentiation-inducing culture has not yet been reported. CellBed^® has been reported to have high chemical stability and superior affinity to cells as a 3-dimensional culture carrier. In addition, cells are not detached during medium change, being another characteristic. Accordingly, there may be no interference with ES cell proliferation. We have reported no interference of various types of collagen with ES cell differentiation. However, the influence of high-purity silica fibers on normal ES cell differentiation as a 3-dimensional culture carrier is unclear.

In this study, the cell proliferation and differentiation levels of ES-D3 cells cultured in CellBed^® were measured and these were comparable with those using pig-derived collagen gel and fish (Tilapia)-derived collagen sponge. The influence of actual biological materials and drugs on ES cell differentiation may be evaluated using CellBed^®.

Metal nanoparticles (NPs) have the potential for use in infection control in the oral environment by killing bacteria or preventing plaque formation. However, little is known about their antibacterial properties against oral bacteria. The purpose of this study was to evaluate the antibacterial and biofilm inhibitory effects of gold (Au) and silver (Ag) NPs against S. mutans. Two NPs stabilized by metal-carbon σ-bonds between their core metal surfaces and the aromatic ring moieties were tested. This study evaluated the effect of NPs with the same surface chemistry but with two different core metal compositions (Au and Ag) on antibacterial activity. The antibacterial activity of both NPs was relatively weak. AgNPs exhibited a biofilm inhibitory effect against S. mutans; however, no inhibitory effect was found in AuNPs.

To improve the degradability and operability of conventional bone graft materials, we fabricated a water-oil emulsion based on α-tricalcium phosphate (α-TCP) bone paste. Simvastatin, a lipophilic hyperlipidemia treatment agent, reportedly enhances the expression of bone morphogenetic protein-2 and subsequent bone formation. Accordingly, we assessed the bone forming effects of α-TCP bone-paste containing simvastatin in rat cranial bone defects.

Bone paste exhibited porous structure and generation of hydroxyapatite after solidification. X-ray image analysis and histological examination were carried out after implantation of bone paste into rat skull defect. The results showed that new bone was formed after implantation of bone paste containing simvastatin. In particular, bone volume in the 0.1 mg simvastatin group was significantly promoted when compared to controls (no implantation). No bone paste residue was observed in the bone defect at 4 weeks after surgery. Therefore, α-TCP bone paste containing simvastatin is degradable and beneficial for bone tissue engineering.

Metal nanoparticles (NPs) exhibit increasing potential in infection control of oral bacteria, as well as in prevention of plaque formation. However, the detailed antibacterial effects of a variety of NPs are not known. The objective of this study was to evaluate the biofilm formation and bacterial viability of the oral bacterium, Streptococcus mutans (S. mutans), upon exposure to platinum NPs (PtNPs). In addition, micromorphological analyses were performed to evaluate the biological interaction between PtNPs and S. mutans bacteria, using a transmission electron microscope (TEM). PtNPs stabilized by polyacrylic acid (3.7 nm diameter) were used in this study. S. mutans was exposed to PtNPs at various concentrations in growth medium. After the 24 h, biofilm formation and bacterial viability were measured. TEM examinations showed that the presence of PtNPs was sporadic in the biofilm. However, PtNPs adhered to the bacterial surfaces. PtNPs exhibited an inhibitory effect on biofilm formation.

Interest in esthetics has increased in recent years, and demand for tooth coloration treatments is increasing. Since proteolytic enzymes, such as papain (papaya proteinase I), have been used in toothpastes to prevent tooth discoloration, this study investigated the mechanism by which papain prevents tooth discoloration. Various concentrations of papain (0.005, 0.05, and 0.5 mg/mL) were added to saliva, salivary proteins were subjected to electrophoresis, and changes in protein properties were examined by Coomassie Brilliant Blue staining. In addition, saliva specimens containing hydroxyapatite (HA) powder were mixed with papain (0.5 mg/mL) to examine changes in the proteins adsorbed onto HA. As a result, papain was found to degrade salivary proteins in a concentration-dependent manner. Papain also degraded salivary proteins that had adsorbed onto HA. Treatment with papain suppressed discoloration by decomposing the pellicles on tooth surfaces.

Implant fixtures are likely to be corroded by fluoride and the safety of corroded chemical substances is attracting interest. The possibility of developmental toxicity of products of titanium corrosion by fluoride has been pointed out. In this study, we investigated mutagenicity of corrosion products of titanium plates treated with hydrofluoric acid solution using the umu-test. The products of corroding titanium with hydrofluoric acid solution did not show strong mutagenicity. It was possible that the ratio of corroded powder against purified water was low in the corrosion product- dissolving technique and corroded chemical substances were not sufficiently dissolved in purified water. Improvement of these problems with the sample preparation method may be necessary.

Angiogenesis is essential for tumor growth. Control of angiogenesis is expected as a new therapy for cancer. It is possible that a part of effect on radiation therapy for cancer inhibits angiogenesis, but this mechanism is not clear. The purposes of this study was to investigate the effects of radiation on vascular endothelial cells including expression level of integrin family and to compare the effect by X-ray irradiation with carbon ion beam irradiation. Human endothelial cells, HUVEC and ECV304, were irradiated by carbon ion beam at Heavy Ion Medical Accelerator in Chiba and 4MV X-ray. We evaluated the effects of irradiation in cell motility, cell adhesion to extracellular matrix, tube formation and expression of integrin molecules. Both high dose X-ray and carbon ion irradiation decreased cell motility and tube formation. Adhesion abilities of cells irradiated with high dose X-ray and carbon ion beam were up-regulated. Also integrin α6 and β1 which associated with cell-extracellular matrix adhesion were up-regulated with high dose X-ray and carbon ion beam in mRNA and protein level. High dose irradiation of X-ray and carbon ion beam inhibited function of endothelial cells including the cell motility and tube formation, and up-regulated the capabilities of adhesion and the expression of integrin α6 and β1. These results suggest that high dose radiations might inhibit angiogenesis through integrin expression changes.

Designing a preoperative tissue engineering vascular graft (TEVG) that is immunologically compatible with the host is one of the goals of vascular tissue engineering. Angiogenesis is an important early step in wound healing, and the three-dimensional formation of capillaries using scaffold contributes greatly to the success of bone regeneration therapy. In this study, aragonite particles derived from exoskeleton of Montipora digitata (a kind of hard coral) as a scaffold of TEVG were applied to three-dimensional culture of normal human dermal skin fibroblasts and normal human umbilical cord vein endothelial cells, and the effect was observed morphologically. As a result, the particles promoted cell proliferation and capillary differentiation three-dimensionally in vitro. Also, incorporation of calcium from the aragonite particles into co-cultured normal human dermal skin fibroblasts and normal human umbilical vein endothelial cells was observed. Thus, aragonite particles were inferred to be a useful scaffold for 3 dimensional capillary culture.

In this study, we investigated the controlled release behavior of a model drug from nanoporous silica microparticles (NPSM) contained in dental glass ionomer cement (GIC). NPSM released model drug molecules gradually in water for 2 weeks when they were contained in GIC. In contrast, GIC-only specimens released the molecule rapidly. To estimate the cytocompatibility of NPSM, osteoblastic cells were exposed to particles with various concentrations. At a concentration of 30 ppm, cell viability remained identical to that without exposure. In addition, mixing the particles did not affect their mechanical properties. These results suggest that NPSM can be used as a sustainable drug-release dental material.