Yoshinori Kuboki

In vivo internal diffusion of several inorganic microparticles through oral administration

We observed the internal diffusion behavior of inorganic micro/nano particles through oral administration. By oral exposure, the fed particles were absorbed through the digestive system then reached some organs after internal diffusion in the body. For example, TiO2 particles fed to mice were detected in the lung, liver, and spleen after 10 days of feeding. Whereas, the absorption efficiency was extremely low compared with intravenous injection. In a comparison of the simple amount of administration, oral exposure required 102 times or more amount by intravenous injection for detection by an X-ray scanning analytical microscope. During dental treatment, micro/nano particles from tooth or dental materials would generate in the oral cavity, and some of the particles had a possibility to be swallowed, absorbed through the digestive system, and then diffuse into the body. However, our results suggest that biocompatible microparticles that are naturally taken orally affect animals only rarely because of the low absorption efficiency.

Interaction of collagen triple-helix with carbon nanotubes: Geometric property of rod-like molecules

The interactions between carbon nanotubes and important biomolecules, above all collagen molecules, have not been studied in detail. This situation is partly due to the fact that CNT are solid entities, while most of the biomolecules can be prepared in solution. We used turbidity as a means of evaluating the interaction between CNT and collagen molecules. To a stable suspension of CNT (10 ppm in 0.1% Triton), collagen solution was added to obtain a final concentration of 25 ppm. The degree of aggregation was evaluated by measuring the turbidity of the suspension at 660 nm. It was found that native collagen induced distinct aggregation with CNT, while denaturation of this protein at 60 degrees C for 1 hr deprived the molecules of their ability to aggregate with CNT. Also other globular molecules, albumin and lysozyme, did not induce aggregation of CNT. These results indicate that the rigid rod-like structure of the native collagen triple helix is essential for interaction with CNT to cause aggregation. The mechanisms are considered to be dependent upon geometric properties of rod-like collagen molecules. The findings in this paper will open a new avenue to clarify the detailed mechanism of the interaction between collagen molecules and CNT.

Biodistribution imaging of magnetic particles in mice: X-ray scanning analytical microscopy and magnetic resonance imaging

Nano-sized particles have received much attention in view of their varied application in a wide range of fields. For example, magnetite (Fe(3)O(4)) nanoparticles have been investigated for various medical applications. In this study, we visualized the distribution of administered magnetic nanoparticles in mice using both X-ray scanning analytical microscopy (XSAM) and magnetic resonance imaging (MRI). After administration, the nanoparticles were rapidly dispersed via the blood circulation, and reached the liver, kidney and spleen. Using the XSAM and MRI methods in a complementary fashion, the biodistribution of nano-sized magnetite particles was successfully visualized.

Bone enhancing effect of titanium-binding proteins isolated from bovine bone and implanted into rat calvaria with titanium scaffold.

Based on our previous finding that a chromatography with titanium beads selectively binds phosphoproteins, including caseins, phosvitin and dentin phosphoproteins, we investigated whether bone phosphoproteins also bind to titanium. Bovine bone matrix proteins were extracted with 2 M urea/PBS after demineralization. The 2 M urea extract was directly applied to the titanium chromatography column as reported. The chromatogram showed an initial large peak at breakthrough position (non-binding fraction) and a smaller second peak eluted later (titanium-binding fraction). Both peaks were analyzed by SDS polyacrylamide gel electrophoresis. Stains-all staining which preferentially identifies phospho-proteins revealed that the first peak contained no positively stained band, while the second peak showed 4 or 5 distinctive bands indicative of bone phosphoproteins. To investigate the biological functions of the titanium-binding bone proteins (TiBP), we implanted them into calvaria of rats, combined with titanium web (TW), a highly porous titanium scaffold of thin titanium-fibers. Bone TiBP induced significantly enhanced bone formation, and new bone appeared connected directly to titanium fibers, accompanied by active blood vessel formations. Control TW alone did not induce bone formation within the titanium framework. These results demonstrate that the bone titanium-binding proteins include phosphoproteins which enhance bone formation when implanted into bone with titanium.

Honeycomb form β-tricalcium phosphate induces osteogenesis by geometrical property with BMSC

To establish an effective method for bone augmentation, we introduced a new honeycomb-like β-tricalcium phosphate (H-β-TCP) with BMP-2 as a scaffold, whose unique geometrical properties induce osteoblastic differentiation of autologous bone marrow mesenchymal stem cells (BMSCs). A total of six beagle dogs from 6 to 7 years old were used for this study. BMSCs were cultured with autologous serum and BMP-2 on H-β-TCP. Differentiation to osteoblasts was demonstrated in vitro and exo vivo. Scanning electron microscopy revealed formation and calcification of a matrix-like structure within the H-β-TCP tunnels in BMSC culture. Moreover, treatment of BMP-2 promoted osteoblastic differentiation of BMSCs in H-β-TCP in a diffusion chamber. These results indicated that H-β-TCP may be a useful tool for construction of functional artificial bone.