Toshiyuki Mashino

Functional magnetic nanoparticles for use in a drug delivery system

γ-Fe2O3 nanoparticles encapsulated in amorphous SiO2 were prepared by the wet chemical method and carboxyl-modified functionalized nanoparticles were produced. The prepared samples were examined by X-ray diffraction measurements and TEM images. Particles sizes in the range 4-20 nm were determined from the Scherrer formula. Magnetization was measured by a SQUID magnetometer under a ±50-kOe magnetic field. The magnetization curves showed ferromagnetic or superparamagnetic behaviour depending on particle size. Functionalized nanoparticles were confirmed by Fourier transform infrared spectroscopy (FT-IR) measurements. The typical C=O peak was detected in the spectrum of functionalized nanoparticles. These magnetic nanoparticles are expected to be used as carriers in drug delivery systems (DDS), hyperthermia treatment, and other biomedical applications.

Production of Co-Ti ferrite nanoparticles for use as agents in hyperthermia treatment

Co-Ti ferrite (Co1+xTixFe2−2xO4, 0.2 ≤ x ≤ 0.5) nanoparticles with average diameters ranging from 6 to 12 nm were produced by using our novel wet chemical method. The crystal structures and magnetic properties of the obtained samples were investigated by X-ray diffraction and superconducting quantum interference device (SQUID) magnetometer measurements. DC magnetization measurements showed that the coercive force Hc and saturation magnetization Ms decreased as the composite parameter x increased. This phenomenon suggests that Ti4+ ions located on B-sites weaken the superexchange interaction between A and B sites. For x= 0.3, the value of Hc decreased drastically. The AC magnetic susceptibility of these samples was also investigated, and it was concluded that the sample with a diameter of 12 nm and composition given by x= 0.3 is the most appropriate sample for use as an agent in hyperthermia treatment.

AC magnetic susceptibility of Co-Ti-Zn ferrite nanoparticles for hyperthermia agents

CoTi-Zn ferrite nanoparticles were produced in order to carry out hyperthermia treatment and ac magnetic susceptibility measurements were performed. From the analyses of temperature and frequency dependence, Néel relaxation in this system was concluded.

Synthesis of multiferroic BiFeO3 nanoparticles

BiFeO3 nanoparticles with an average diameter of approximately 40 nm were synthesized by a wet chemical method. The annealing temperature and annealing time were controlled to obtain single-phase BiFeO3 nanoparticles. The behavior of magnetization curves of the nanoparticles is similar to that of a spin-glass system suggesting that the nanoparticles have antiferromagnetic properties. It is suggested that superexchange interaction is more dominant than RKKY interaction in this system. The ferromagnetic behavior of the nanoparticles at low temperatures could be explained by the uncompensated spins in each domain in this system.

Ionization Ability of Manganese Nanoparticles

Manganese oxide nanoparticles (Mn‐O NPs) were prepared through our novel method as reagents for laser desorption/ionization mass spectrometry (LDI‐MS). Through the control of the reaction time in the chemical preparation method (0.5, 1, and 5 h), we succeeded in preparing three different types of manganese oxide particles. The particles were characterized by X‐ray diffraction, Fourier transform infrared spectroscopy, and DC magnetization measurements. These characterization results indicated that the manganese ions oxidized in aqueous alkaline solution, and that the spinel structure was retained for the Mn3O4 phase, which then gradually changed into the MnO2 phase. The mass spectra of substance P (MW = 1347.6) were measured by MALDI‐TOF mass spectrometry with Mn‐O NPs. The Mn‐O NPs that reacted with 3‐aminopropyltriethoxysilane(γ‐APTES) for 1 h or 5 h had higher ionization abilities than those reacted for 0.5 h. These different abilities are attributed to the different crystal structures of the prepared m...

Ionization ability of manganese oxide nanoparticles

Manganese oxide nanoparticles(Mn-O NPs) were prepared by our novel method as reagents for the laser desorption/ionization mass spectrometry (MS) analytes. Reaction times by chemical preparation were controlled as 0.5, 1 and 5 hours, as the result, we succeeded preparing three different types of particles. Particles were characterized by measuring x-ray diffraction pattern (Fig. 1), Fourier transform infrared spectra (Fig. 2), and DC magnetization (Fig. 3). These characterization results indicated that Mn3O4 maintained spinel sturactures but manganese ions got oxidized under the alkaline water solution, that is Mn3O4 phase gradually translated into MnO2 phase.