A 3D biodegradable protein based matrix for cartilage tissue engineering and stem cell differentiation to cartilage

A protein based 3D porous scaffold is fabricated by blending gelatin and albumin. The biomimetic biodegradable gelatin, promoted good cell adhesion and its hydrophilic nature enabled absorption of culture media. Albumin is proposed to serve as a nontoxic foaming agent and also helped to attain a hydrophobic-hydrophilic balance. The hydrophobic-hydrophilic balance and appropriate crosslinking of the scaffold avoided extensive swelling, as well as retained the stability of scaffold in culture medium for long period. The scaffold is found to be highly porous with open interconnected pores. The adequate swelling and mechanical property of the scaffold helped to withstand the loads imparted by the cells during in vitro culture. The scaffold served as a nontoxic material to monolayer of fibroblast cells and is found to be cell compatible. The suitability of scaffold for chondrocyte culture and stem cell differentiation to chondrocytes is further explored in this work. The scaffold provided appropriate environment for chondrocyte culture, resulting in deposition of cartilage specific matrix molecules that completely masked the pores of the porous scaffold. The scaffold promoted the proliferation and differentiation of mesenchymal stem cells to chondrocytes in presence of growth factors. The transforming growth factor, TGFbeta3 promoted better chondrogenic differentiation than its isoform TGFbeta1 in this scaffold.     

Importance of H2 gas for growth of hot-wire CVD nanocrystalline 3C-SiC from SiH4/CH4/H2

Silicon carbide (SiC) thin films were prepared by hot-wire chemical vapor deposition from SiH₄/CH₄/H₂ and the influence of H₂ gas flow rate (F(H₂)) on the film properties was investigated. The SiH₄ gas flow rate was 1 sccm. At the CH₄ gas flow rate (F(CH₄)) of 1 sccm, nanocrystalline cubic SiC (nc-3C-SiC) grew even without H₂. On the other hand, at F(CH₄) = 2 sccm, amorphous SiC grew without H₂ and nc-3C-SiC grew above F(H₂) = 50 sccm. As F(H₂) was increased, the crystallinity improved both at F(CH₄) = 1 and 2 sccm. However, the mean crystallite size decreased at F(CH₄) = 1 sccm and increased at F(CH₄) = 2 sccm. We discuss growth mechanisms of nc-3C-SiC.     

Growth of silicon carbide thin films by hot-wire chemical vapor deposition from SiH4/CH4/H2

Silicon carbide (SiC) thin films were prepared by hot-wire chemical vapor deposition from SiH₄/CH₄/H₂ and their structural properties were investigated by X-ray diffraction, Fourier transform infrared absorption and Raman scattering spectroscopies. At 2 Torr, Si-crystallite-embedded amorphous SiC (a-Si_1 − xC_x:H) grew at filament temperatures (T_f) below 1600 °C and nanocrystalline cubic SiC (nc-3C-SiC:H) grew above T_f = 1700 °C. On the other hand, At 4 Torr, a-Si_1 − xC_x:H grew at T_f = 1400 °C and nc-3C-SiC grew above T_f = 1600 °C. When the intakes of Si and C atoms into the film per unit time are almost the same and H radicals with a high density are generated, which takes place at high T_f, nc-3C-SiC grows. On the other hand, at low T_f the intake of Si atoms is larger than that of C atoms and, consequently, Si-rich a-Si_1 − xC_x:H or Si-crystallite-embedded a-Si_1 − xC_x:H grow.     

Cellular automaton simulation of micropowder blasting with mask erosion

Development of a two‐dimensional (2D) micropowder blasting simulator for microfabrication of a glass substrate with a patterned polymer mask is reported. In order to investigate the effect of mask erosion on a processed glass profile, a cellular automaton simulation in which erosion of the glass and the polymer mask were taken into account was applied to the micropowder blasting process for the first time. From a comparison of the simulation result with the processed glass profile in the experiment, it was demonstrated that the processed glass profile with the mask erosion could be simulated using our simulator. Furthermore, it was confirmed that the processed profile in the glass depended on the mask profile and the ratio of the deformation wear and the cutting wear of a mask. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Hepatocyte growth factor is involved in the morphogenesis of tooth germ in murine molars

The patterns of gene expression for hepatocyte growth factor (HGF) and its receptor, c-Met, were revealed in the tooth germ of rat mandibular molars using RT-PCR. In situ hybridization demonstrated that the HGF gene was expressed only in the cells of the dental papilla of the tooth germ in vivo. The characteristic temporospatial distribution of HGF and c-Met during germ development was revealed using immunohistochemical studies in vivo. In order to demonstrate the functional role played by HGF in tooth development, HGF translation arrest by antisense phosphorothioate oligodeoxynucleotide (ODN) was carried out in vitro. In the control experiment, explants of tooth germs from embryonic 14 day mice were cultured in a modification of Trowell's system under serum-free and chemically defined conditions for two weeks. Other explants were cultured with 15mer antisense or sense ODN targeted to the HGF mRNA. Both the control and the sense-treated explants showed normal histological structure, as observed in vivo. On the other hand, antisense-treated explants exhibited an abnormal structure in which the enamel organs were surrounded by a thin layer of dentin and dental papilla, appearing 'inside-out' compared to the control and sense-treated explants, although the cytodifferentiation of ameloblasts and odontoblasts was not inhibited. The explants treated with recombinant human HGF combined with antisense ODN showed normal development, indicating that exogenous HGF rescued the explants from the abnormal structure caused by antisense ODN. The findings of a BrdU incorporation experiment suggested that the imbalance between the proliferation activity of the inner enamel epithelium and that of the dental papilla caused by HGF translation arrest results in the abnormal structure of the tooth germ. These results indicate that HGF is involved in the morphogenesis of the murine molar.     

Catalytic properties and surface states of La1−x (Th,Sr) x CoO3

The surface chemical states of the perovskite-type thorium- or strontium-doped lanthanum cobalt oxides (La_1–x Th _x CoO₃, La_1–x Sr _x CoO₃) have been investigated using X-ray photoelectron spectroscopy. Catalytic oxidations of CO have been also investigated by flow methods. The ionicity between cobalt and lattice oxygen was increased by substituting thorium for lanthanum, and had a peak atx = 0.02. The catalytic activity also had a peak atx = 0.02. However, the ionicity decreased for the case of strontium substitution, and the activity also decreased.     

Prediction of postoperative pulmonary hemodynamics for the second lobectomy after the contralateral lobectomy

We presented 7 cases who were performed the second lobectomy for the second lung cancer after the first successful lobectomy on the contralateral lung (3 cases for right upper lobectomy + left lower lobectomy and 4 cases for right upper lobectomy + left lower lobectomy). In 6 patients, the predicted postoperative FEV1 estimated by multiplying the preoperative FEV1 by the fraction of perfusion to the contralateral lung was less than 800 ml/m2BSA, which is our first cut-off for identifying lung resection candidates. Unilateral pulmonary arterial occlusion test (UPAO) revealed that total pulmonary vascular resistance (TPVRI) in 3 of those 6 patients was lower than 700 dyne.sec.cm-5/m2BSA, our second cut-off for lung resection. More precise postlobectomy pulmonary hemodynamics in another 3 of those 6 patients were then estimated by adapting selective pulmonary occlusion test (SPAO). Since TPVRI during SPAO was lower than the cut-off value, it was suggested that second lobectomy would be feasible with low incidence of post operative cardiopulmonary complication. There was no serious complications in all 7 cases during their postoperative course. We believe that more precise prediction of postoperative pulmonary hemodynamics by adapting UPAO and SPAO could be one of the tools to minimumize postoperative cardiopulmonary complications in those patients needed second lobectomy for the second lung cancer after the first successful lobectomy on the contralateral lung even though their impaired lung fung function.     

Tumor accumulation of poly(vinyl alcohol) of different sizes after intravenous injection

The body distribution and tumor accumulation of polymers were evaluated using poly(vinyl alcohol) (PVA) which has the simplest chemical structure among water-soluble polymers, similar to poly(ethylene glycol). To study the effect of polymer size on the tumor accumulation, we used not only water-soluble PVA with different molecular weights but also PVA microgels prepared through gamma-irradiation of aqueous PVA solutions. The PVA specimens in the aqueous solution were intravenously injected to mice carrying a tumor mass at their footpad. Both types of PVA (water-soluble and microgel) of larger size were retained in the blood circulation for longer time periods and excreted more slowly from the kidney than those of smaller size. The plasma half-life period of PVA became longer with increasing size both for the water-soluble and microgel PVA, indicating that the body fate of PVA is governed only by the size. Both the water-soluble PVA and PVA microgels were accumulated in tumor tissue to a significantly greater extent than in normal tissue. The size dependence of the plasma half-life period and tumor accumulation was similar between the water-soluble PVA and the PVA microgels and the tumor accumulation became maximum around the size of 60 nm both for water-soluble and microgel PVA. A pharmacokinetical study demonstrated that the tumor uptake rate index of PVA decreased with the increase in PVA size. On the other hand, the greater the size, the larger the value of the area under the blood concentration-time curve (AUC). In addition, the PVA around 60 nm in diameter showed the smallest liver clearance. It was concluded that the balance between the uptake rate and the AUC as well as the liver clearance resulted in the maximum accumulation of PVA with the size of 60 nm.     

Light-intensity dependence in photocatalytic decomposition of water over K4Nb6O17 catalyst

We have measured, for the first time, the light-intensity dependence in photocatalytic decomposition of water over K₄Nb₆O₁₇ In higher light-intensity region, the rate of reaction is proportional to the square root of the light intensity. In lower light-intensity region, on the contrary, the rate is almost linearly proportional to the light intensity. We propose a reaction model whose main path of the reaction loss is the recombination of the charges generated under b and -gap radiation. This model describes the light-intensity dependence of this reaction well.     

Rhombic‐Shaped Nanostructures and Mechanical Properties of 2D DNA Origami Constructed with Different Crossover/Nick Designs

DNA origami methods enable the fabrication of various nanostructures and nanodevices, but their effective use depends on an understanding of their structural and mechanical properties and the effects of basic structural features. Frequency‐modulation atomic force microscopy is introduced to directly characterize, in aqueous solution, the crossover regions of sets of 2D DNA origami based on different crossover/nick designs. Rhombic‐shaped nanostructures formed under the influence of flexible crossovers placed between DNA helices are observed in DNA origami incorporating crossovers every 3, 4, or 6 DNA turns. The bending rigidity of crossovers is determined to be only one‐third of that of the DNA helix, based on interhelical electrostatic forces reported elsewhere, and the measured pitches of the 3‐turn crossover design rhombic‐shaped nanostructures undergoing negligible bending. To evaluate the robustness of their structural integrity, they are intentionally and simultaneously stressed using force‐controlled atomic force microscopy. DNA crossovers are verified to have a stabilizing effect on the structural robustness, while the nicks have an opposite effect. The structural and mechanical properties of DNA origami and the effects of crossovers and nicks revealed in this paper can provide information essential for the design of versatile DNA origami structures that exhibit specified and desirable properties.