Kazuchika Tamura

Effects of Micro/Nano Particle Size on Cell Function and Morphology

The cytotoxicity of micro/nano particles in Ti, TiO and carbon nanotube was investigated by in vitro biochemical analyses using human neutrophils. The particles smaller and larger than the neutrophils were used to determine the relationship between cell and pa rticle size with respect to cytotoxicity. As the particle size decreased, the cell survival rate was decreased and, with the good corresponding relation to this, the value of lactate dehydrogenase (LDH ), which is the indication of cell disruption, was increased. The release of superoxide anion showed t he increasing tendency. Proinflammatory cytokines were detected distinctly for 3μm or sm aller particles and very little in more than 10μm, which is closely related to the phagocytosis by neutrophil s. ICP elemental analysis showed that the dissolution from Ti particles was below detection li mit. Micro and nano particles stimulated the cell reactions according to the results of the huma n neutrophil functional tests. As the particle size was smaller, the inflammation was pronounced. The fine particl es less than 3μm caused distinctly the inflammation in the surrounding tissue. All these results i ndicated that the cytotoxicity was induced due to the physical size effect of particles, which is different from the ionic dissolution effect. The clinical phenomenon confirmed the result obtained in vitro ce ll tests. The neutrophils stimulated by fine particles may cause the inflammatory cascade and harm the surrounding tissue.

Strict preparation and evaluation of water-soluble hat-stacked carbon nanofibers for biomedical application and their high biocompatibility: influence of nanofiber-surface functional groups on cytotoxicity

Water-soluble H-CNFs modified with a carboxyl group possessed the ability to induce TNF-alpha, whereas CHAPS-treated H-CNFs possessed significantly greater activity and were also found to activate NF-kappaB reporter activity, to a significantly greater level than H-CNFs; furthermore the functional group modified or coated on the surface of H-CNFs was a significant cytotoxic factor that affected cell activation.

Internal Diffusion of Micro/Nanoparticles Inside Body

Both biochemical cell functional test and animal implantation test were done to investigate the reaction to fine particles. Particles cause nonspecifically phagocytosis to cells and inflammation to tissue for the size below 10m. With the size below 50nm particles may invade into the internal body through the respiratory or digestive system and diffuse inside body. Ti mapping by XSAM after the compulsory exposure test to the respiratory system showed the internal diffusion of 30nm TiO2 particles. They diffused with time course to lung, liver and spleen after injection from caudal vein. Nanoparticles might be the objects whose existence has not been assumed by the biophylactic system.

Synthesis and size classification of metal oxide nanoparticles for biomedical applications

Magnetic nanoparticles are considered for biomedical applications, such as the medium in magnetic resonance imaging, hyperthermia, drug delivery, and for the purification or classification of DNA or virus. The performance of magnetic nanoparticles in biomedical application such as hyperthermia depends very much on the magnetic properties, size and size distribution. We briefly described the basic idea behind their use in drug delivery, magnetic separation and hyperthermia and discussed the prerequisite properties magnetic particles for biomedical applications. Finally reported the synthesis and classification scheme to prepare magnetite (Fe3O4) nanoparticles with narrow size distribution for magnetic fluid hyperthermia.

Biocompatibility of carbon nanotube disk

We report the preparation, properties and biocompatibility of multi-walled carbon nanotube (MWCNT) disk. Sintered Multi-walled carbon nanotube disk was fabricated by spark plasma sintering the MWCNT and phenol resin mixture by using the Spark Plasma System (SPS) under 1273 K and 80 MPa in vacuum. As the concentration of phenol resin in the sintered MWCNT disk increases, the bending strength and Young’s modulus increased. However, the inflammatory response was observed in the tissue exposed to the surface of the sintered MWCNT disk. This was believed due to the residual phenol resin in the disk. The result indicates that the disk has to be annealed at higher temperatures under inert gas atmosphere to perfectly convert phenol resin to graphitic materials.

Preparation of magnetic nanoparticles for magnetic fluid hyperthermia

In this paper, the determination and preparation of suitable magnetic material for magnetic fluid hyperthermia (MFH) is presented. It was suggested that the highest heating rate could be obtained by using maghemite with particle diameter of 15 nm. The heating rate of magnetite particle with diameter less than 10 nm was found to generate heat higher than that of cobalt and barium ferrites. Therefore, the magnetite with diameters ranging from 11-13 nm was selected for MFH. The magnetite nanoparticles with diameter of 12 nm was synthesized using standard coprecipitation method. The heat dissipation of magnetic particles with varying average diameters was also reported.

Size separation of carbon nanotubes for biomedical applications

In this paper, we report the results of an attempt to disperse MWCNTs in water and determine their biocompatibilities. The length of the MWCNTs was reduced by treating the acidic nanotube suspension with ultrasonic irradiation. Then, the cut nanotubes were size-separated into 670, 550 and 220 nm length by filtration using polycarbonate membrane filters. The neutrophils activity (TNF-α) of size-separated MWCNTs was low and confirmed biocompatible.