Junji Yamakawa

Novel transdermal drug delivery system with polyhydroxyalkanoate and starburst polyamidoamine dendrimer.

In search of an efficient transdermal drug delivery system (TDDS), a polyhydroxyalkanoate (PHA)-based system with a polyamidoamine dendrimer was examined. Tamsulosin was used as the model drug. The dendrimer was found to act as the weak enhancer. By adding the dendrimer, the dendrimer-containing PHA matrix achieved the clinically required amount of tamsulosin permeating through the skin model. This is also the first report of the application of PHA and dendrimer to the TDDS.

Mechanism of Enhancement Effect of Dendrimer on Transdermal Drug Permeation through Polyhydroxyalkanoate Matrix

The possible application of polyhydroxyalkanoate (PHA) in transdermal drug delivery systems (TDDSs) for tamsulosin was previously reported. PHAs containing the drugs, ketoprofen, clonidine and tamsulosin showed good adhesiveness to the skin model used, that is, shed snake skin, and dispersed well all model drugs tested. The model drugs hardly permeated through snake skin in solution form. However, these drugs permeated well through snake skin from the PHA matrix. It was previously reported that the addition of a dendrimer, a polymeric permeation enhancer, is effective for the TDDS for tamsulosin to establish an effective clinical TDDS. The effect of dendrimer addition was examined in TDDSs for ketoprofen and clonidine. The dendrimer added did not show an enhancement effect on the TDDSs for the two drugs. To investigate the mechanism of the enhancement effect of a dendrimer on the tamsulosin TDDS, X-ray analyses were performed. With dendrimer addition, drug crystallization in PHA was promoted. The crystal in PHA had highly ordered and changed its space group. These findings are very important for exploiting high-performance PHA-based TDDSs.

Effects of the counterion on dielectric spectroscopy of a montmorillonite suspension over the frequency range 105-1010 Hz

Dielectric measurements were carried out on suspensions of montmorillonite clay exchanged with three different counterions: sodium, ammonium, and tetramethylammonium (TMA). Only two dielectric absorption peaks could be identified for the clay sample with the TMA counterion, whereas three peaks were found for the two inorganic counterions. The dielectric process observed at around 10 GHz is due to the orientation of bulk water molecules, judging from the relaxation time and relaxation strength. The relaxation strength of the process occurring at around 10 MHz was compared with the coefficient of adiabatic compressibility obtained from ultrasound velocity measurements. The increase in the relaxation strength with decreasing compressibility indicates that the process at around 10 MHz is caused by the orientation of bound water molecules on the clay samples. The relaxation strength of the process occurring at around 10 MHz for the TMA sample was remarkably small. Furthermore, the network structure of the bound water molecules can be characterized by a property peculiar to the TMA sample, taking into account the value of its Cole-Cole parameter. Results for the relaxation strength of the process occurring at around 100 kHz were compared with those for electrophoretic mobility. This comparison revealed that discrimination between bound ions and ions in the diffuse double layer is important, and both the relaxation and electrophoretic results could be satisfactorily explained by surface polarization of the clay.

Structure d'un Diphosphate Synthetique de Cobalt: Co2P2O7

The title compound, a new polymorphic phase of dicobalt diphosphate, Co2P2O7, was prepared by hydrothermal methods. The structure contains CoO6 coordination octahedra and P2O7 radicals. The CoO6 radicals, connected by edge sharing, form six-membered rings, which are further interconnected to form two-dimensional zigzag sheets parallel to (001). The P2O7 groups link these sheets to build three-dimensional networks.

Un Monophosphate Synthétique de Sodium et de Cobalt: Na4Co7(PO4)6

Tetrasodium heptacobalt hexaphosphate, a new monophosphate prepared by hydrothermal methods, comprises CoO 6 and CoO 4 coordination polyhedra connected to each other by corner and edge sharing to form zigzag layers parallel to the ab plane. These layers are interconnected by Co-O polyhedra and P-O tetrahedra via corner sharing to form a three-dimensional network. The Na + ions are located in the tunnels running parallel to the a axis. This compound is isostructural with Na 4 Ni 7 (PO 4 ) 6 .

High-Pressure Phase Relationships for FeS

Phase relationships for FeS polymorph have been studied at the pressure of 16-20 GPa and temperature of 300-1350 K by in situ X-ray observation using a large volume high-pressure apparatus and a synchrotron radiation. Contrary to Feis prediction [1], we found the stability field of NiAs-type phase of FeS extending at least to 18 GPa. Results of in situ X-ray observation correspond with the NiAs-hexagonal phase boundary determined by Kusaba et al . [2, 3]. Assuming the straight NiAs-hexagonal phase boundary, we estimate that the NiAs-hexagonal-liquid triple junction is located at 39.5 GPa and 2300 K.

Synthetic Magnesium Sodium Hydrogen Monophosphate: MgNa3H(PO4)2

The structure belongs to the monophosphate group and contains one type of PO 4 tetrahedra connected to one type of MgO 6 octahedra by corner sharing. These PO 4 -MgO 6 groups are connected along the two shorter a and b axes to form two-dimensional zigzag sheets. Two sheets are connected along the longer c axis by two types of Na-O polyhedra. Pairs of PO 4 tetrahedra in the sheets are connected by H atoms situated at the centres of symmetry, forming short hydrogen bonds.