Ko Nakanishi

Electric Charge Dependence of Controlled Dye-Release Behavior in Glass Ionomer Cement Containing Nano-Porous Silica Particles

We investigated in controlled dye-release behavior of nanosized silica particles containing nanocavities (Nanoporous silica, NPS). To determine this, NPS were mixed with glass ionomer cement (GIC), which is a medical material used as a matrix. The dye-release behavior was observed using a UV-visible spectrometer. After cationic dye was charged into GIC pellet containing NPS, the pellet could gradually release cationic dye for up to two weeks. To understand the dependence of electric charge on the dye-release behavior, three types of dyes with different charge were also investigated. Dyes having a neutral or negative electric charge were quickly released from the pellet within a couple of days. These results suggest that the nanocavities present in NPS can selectively bind cationic dyes and allow for their gradual release. This result reveals the excellent sustained dye-release property of NPS.

Controlled Drug Release Property of Nano-Porous Silica Micro Particles and their Cytocompatibility

In this study, we investigated in cytocompativility and controlled release behavior of a model drug from nanoporous silica microparticles (NPSM). When Mouse osteoblastic cells (MC3T3-E1) were exposed to NPMSs, they indicated excellent cell viability. From NPSM contained in dental glass ionomer cement (NPMS-GIC), they can release cationic model drug molecules gradually in water for 2 weeks when they were contained in GIC. In contrast, GIC without NPSM specimens released the molecule only a couple of days. In the case of inionic molecules, their release were alos determined only a couple of days. These results suggest that NPSM can be used as a sustainable drug-release system in dental and medical fields

Effects of Surface Properties of Montmorillonite for their Cytocompatibility

We modified the surface of organically modified montmorillonite (OMMT) with the carboxyl group using the silane coupling reaction and assessed its characteristics and cytocompatibility. Scanning electron microscope observations show that while the size and morphology of the obtained OMMT (OMMT-COOH) was unchanged, the surface of OMMT-COOH was coarser than that of OMMT. Fourier transform infrared spectra showed characteristic strong peaks at 1210 and 1630 cm−1, corresponding to the peaks of the carboxyl group. X-ray diffraction analysis showed that the diffraction peak of OMMT-COOH corresponding to the (001) reflection was located at higher a 2θ value than that of OMMT. Results of the proliferation ratio and cell viability measurements indicated that the OMMT-COOH cytocompatibility is higher than that of OMMT. Based on these results, we conclude that cytocompatibility of montmorillonite would be improved by tuning the properties of the surface.

Cytocompatiblity of Ceramic Nanoparticles to Various Types of Cells

In this study, we investigated the cytocompatibility of ceramic nanoparticles on different types of cells. All ceramics nanoparticles investigated in this study except Copper oxide (CuO) exhibited good cytocompatibility and cell viability (90% or more) even at 20 ppm concentration. In contrast, CuO nanoparticles caused cell inflammation, and their effect depended on their particle size. Confocal fluorescence microscopy measurements indicated that some particles had penetrated into the cells. These results indicate that except CuO nanoparticles, all other ceramic nanoparticles reported herein exhibited excellent cytocompatibility even for lung epithelial cells.

Controlled Ion Release Property of Glass Ionomer Cement Containing Nanoporous Silica Particles

Controlled ion release property of nanoporous silica particles (NPS) were investigated using cationic fluorescent dye, rhodamine B. The dye was charged into a glass ionomer cements (GIC) pellet containing the particles and then the pellet were immersed into distilled water. The dye-release behavior was observed using a UV-vis. spectrophotometer. GIC containing NPS can release the dye for a couple of weeks, where as other samples released it only a few days. This result suggests that NPS has excellent sustained dye-release property.

Preparation of a Poly(Lactic Acid)/Montmorillonite Nanocomposite

Poly (L-lactic acid)/organically modified montmorillonite (PLLA/OMMT) nanocomposites were fabricated by a solution intercalation method. OMMT, modified with quaternary alkylammonium ion, was prepared by alkyltrialkoxysilane. The differential scanning calorimetry measurement revealed that the crystallization temperatures of PLLA/OMMT nanocomposites were at around 110 °C regardless of the existence of OMMT or the weight fraction of them. X-ray diffraction patterns suggested that the (001) diffraction was around 2θ = 2.5°. The TEM image showed variously expanded interlayer galleries of OMMT and partially exfoliated silicate layer unit in the matrix. Board-shaped specimens for mechanical property tests were fabricated by compression-molding at 190 °C (including 30 min annealing at 110 °C). The flexural modulus of the nanocomposites increased with increasing content of OMMT. Vickers hardness of the nanocomposites were almost same independent on weight fraction of OMMT.