Intestinal absorption and biological effects of orally administered amorphous silica particles

Although amorphous silica nanoparticles are widely used in the production of food products (e.g., as anticaking agents), there is little information available about their absorption and biological effects after oral exposure. Here, we examined the in vitro intestinal absorption and in vivo biological effects in mice of orally administered amorphous silica particles with diameters of 70, 300, and 1,000 nm (nSP70, mSP300, and mSP1000, respectively) and of nSP70 that had been surface-modified with carboxyl or amine groups (nSP70-C and nSP70-N, respectively). Analysis of intestinal absorption by means of the everted gut sac method combined with an inductively coupled plasma optical emission spectrometer showed that the intestinal absorption of nSP70-C was significantly greater than that of nSP70. The absorption of nSP70-N tended to be greater than that of nSP70; however, the results were not statistically significant. Our results indicate that silica nanoparticles can be absorbed through the intestine and that particle diameter and surface properties are major determinants of the degree of absorption. We also examined the biological effects of the silica particles after 28-day oral exposure in mice. Hematological, histopathological, and biochemical analyses showed no significant differences between control mice and mice treated with the silica particles, suggesting that the silica nanoparticles evaluated in this study are safe for use in food production.     

Fabrication of wrinkled carbon nano-films with excellent field emission characteristics

B-doped nano-structured carbon films were deposited on Si substrates by means of chemical-vapour-deposition with 3.8-kW microwave-plasma. Scanning electron microscope images show that the deposited films were composed of wrinkled graphitic nano-sheets with considerable disorder structures. Field emission (FE) characteristics measured from such films yielded considerably high FE currents, being larger than 50 mA/cm² at a macroscopic electric field of 9.5 V/μm. A possible mechanism of the observed FEs is discussed in relation to a modified Fowler–Nordheim equation considering field-dependent parameters. As a result, it is found that the structure of the surface geometry mainly increased the FE current densities. Adding a suitable amount of B-component gas to the carbon source gas resulted in a considerable increase in the FE areas of the wrinkled carbon nano-films.     

Amorphous nanosilicas induce consumptive coagulopathy after systemic exposure

We previously reported that well-dispersed amorphous nanosilicas with particle size 70 nm (nSP70) penetrate skin and produce systemic exposure after topical application. These findings underscore the need to examine biological effects after systemic exposure to nanosilicas. The present study was designed to examine the biological effects. BALB/c mice were intravenously injected with amorphous nanosilicas of sizes 70, 100, 300, 1000 nm and then assessed for survival, blood biochemistry, and coagulation. As a result, injection of nSP70 caused fatal toxicity, liver damage, and platelet depletion, suggesting that nSP70 caused consumptive coagulopathy. Additionally, nSP70 exerts procoagulant activity in vitro associated with an increase in specific surface area, which increases as diameter reduces. In contrast, nSP70-mediated procoagulant activity was absent in factor XII-deficient plasma. Collectively, we revealed that interaction between nSP70 and intrinsic coagulation factors such as factor XII, were deeply related to nSP70-induced harmful effects. In other words, it is suggested that if interaction between nSP70 and coagulation factors can be suppressed, nSP70-induced harmful effects may be avoided. These results would provide useful information for ensuring the safety of nanomaterials (NMs) and open new frontiers in biological fields by the use of NMs.     

Effect of surface properties of silica nanoparticles on their cytotoxicity and cellular distribution in murine macrophages

In this study, complexes composed of poly-l-tyrosine (pLT) and single-walled carbon nanotubes (SWCNTs) were produced and the dispersibility of the pLT/SWCNT complexes in water by measuring the ζ potential of the complexes and the turbidity of the solution were investigated. It is found that the absolute value of the ζ potential of the pLT/SWCNT complexes is as high as that of SWCNTs modified with double-stranded DNA (dsDNA) and that the complexes remain stably dispersed in the water at least for two weeks. Thermogravimetry analysis (TGA) and visualization of the surface structures of pLT/SWCNT complexes using an atomic force microscope (AFM) were also carried out.     

Flexible Cu(In,Ga)Se2 solar cell on stainless steel substrate deposited by multi‐layer precursor method: its photovoltaic performance and deep‐level defects

Cu(In,Ga)Se₂ (CIGS) films on soda‐lime glass and stainless steel (SUS) substrates with several [Ga]/([Ga] + [In]), GGI, and Fe concentrations are fabricated by so‐called “multi‐layer precursor method”. From optical deep‐level transient spectroscopy, deep‐level defect located at 0.8 eV from valence band maximum (E_V) is observed. This defect becomes recombination center when GGI is over 0.4, thereby decreasing cell performances. Fe‐related deep‐level defect is moreover detected in CIGS film on SUS substrate situated at 0.45 eV from E_V. Its density is consistent with Fe concentration in CIGS films. According to SCAPS simulation and experimental results, Fe concentration of above threshold (1.0 × 10¹⁶ atom/cm³) decreases carrier lifetime and carrier density and has more harmful influence on cell performances with GGI of above 0.4. On the other hand, Fe concentration of below threshold (1.0 × 10¹⁶ atom/cm³) has no detrimental impact on cell performances. Namely, conversion efficiency (η) is slightly changed by below 2%. CIGS solar cell on SUS substrate with η of 17.5% is fabricated by decreasing Fe concentration to approximately 5.2 × 10¹⁶ atom/cm³ although higher than the threshold value. Copyright © 2016 John Wiley & Sons, Ltd.     

Promotion of allergic immune responses by intranasally-administrated nanosilica particles in mice

With the increase in use of nanomaterials, there is growing concern regarding their potential health risks. However, few studies have assessed the role of the different physical characteristics of nanomaterials in allergic responses. Here, we examined whether intranasally administered silica particles of various sizes have the capacity to promote allergic immune responses in mice. We used nanosilica particles with diameters of 30 or 70 nm (nSP30 or nSP70, respectively), and conventional micro-sized silica particles with diameters of 300 or 1000 nm (nSP300 or mSP1000, respectively). Mice were intranasally exposed to ovalbumin (OVA) plus each silica particle, and the levels of OVA-specific antibodies (Abs) in the plasma were determined. Intranasal exposure to OVA plus smaller nanosilica particles tended to induce a higher level of OVA-specific immunoglobulin (Ig) E, IgG and IgG1 Abs than did exposure to OVA plus larger silica particles. Splenocytes from mice exposed to OVA plus nSP30 secreted higher levels of Th2-type cytokines than mice exposed to OVA alone. Taken together, these results indicate that nanosilica particles can induce allergen-specific Th2-type allergic immune responses in vivo. This study provides the foundations for the establishment of safe and effective forms of nanosilica particles.     

Size and surface modification of amorphous silica particles determine their effects on the activity of human CYP3A4 in vitro

Because of their useful chemical and physical properties, nanomaterials are widely used around the world - for example, as additives in food and medicines - and such uses are expected to become more prevalent in the future. Therefore, collecting information about the effects of nanomaterials on metabolic enzymes is important. Here, we examined the effects of amorphous silica particles with various sizes and surface modifications on cytochrome P450 3A4 (CYP3A4) activity by means of two different in vitro assays. Silica nanoparticles with diameters of 30 and 70 nm (nSP30 and nSP70, respectively) tended to inhibit CYP3A4 activity in human liver microsomes (HLMs), but the inhibitory activity of both types of nanoparticles was decreased by carboxyl modification. In contrast, amine-modified nSP70 activated CYP3A4 activity. In HepG2 cells, nSP30 inhibited CYP3A4 activity more strongly than the larger silica particles did. Taken together, these results suggest that the size and surface characteristics of the silica particles determined their effects on CYP3A4 activity and that it may be possible to develop silica particles that do not have undesirable effects on metabolic enzymes by altering their size and surface characteristics.     

Development of a charge-carrier drift velocity measurement system in diamonds by using a UV pulse laser

There are continuing efforts of developing faster FETs and diamond is one of the strong candidates as a base semiconductor. Since the upper-limit-frequency of diamond FETs determines saturated drift velocities of charge-carriers, we need to first characterize diamond to develop better FETs. It is, however, not easy to measure the velocities with response time of less than 20 ns. Therefore, we developed a drift velocity measurement system using a time-of-flight (TOF) technique with a UV laser with 100 ps pulse width. In order to realize response times faster than 20 ns, we employed a 50 Ω coaxial cable as a load, with which we could effectively reduce the stray capacitance and inductance, and also, suppress reflections in the signal which gives false signals. As a result, we can measure carrier-transit times shorter than 10 ns.     

Effect of amorphous silica nanoparticles on in vitro RANKL-induced osteoclast differentiation in murine macrophages

Amorphous silica nanoparticles (nSP) have been used as a polishing agent and/or as a remineralization promoter for teeth in the oral care field. The present study investigates the effects of nSP on osteoclast differentiation and the relationship between particle size and these effects. Our results revealed that nSP exerted higher cytotoxicity in macrophage cells compared with submicron-sized silica particles. However, tartrate-resistant acid phosphatase (TRAP) activity and the number of osteoclast cells (TRAP-positive multinucleated cells) were not changed by nSP treatment in the presence of receptor activator of nuclear factor κB ligand (RANKL) at doses that did not induce cytotoxicity by silica particles. These results indicated that nSP did not cause differentiation of osteoclasts. Collectively, the results suggested that nanosilica exerts no effect on RANKL-induced osteoclast differentiation of RAW264.7 cells, although a detailed mechanistic examination of the nSP70-mediated cytotoxic effect is needed.     

Schottky diode architectures on p-type diamond for fast switching, high forward current density and high breakdown field rectifiers

The electrical properties of Schottky contacts on the (100) surface of Boron doped diamond films epitaxially grown on Ib substrates are investigated in this work. The role of Boron doping concentration and extended defects detected by cathodoluminescence is correlated to current voltage characteristics, rectifying efficiency and high voltage performance of the diodes up to 1 kV and more. The influence of surface treatment prior to metal deposition is highlighted and the choice of metal for the Schottky contact is discussed. The paramount importance of using an oxidised diamond surface at the Schottky contacts and outside is demonstrated. Decreasing the series resistance of diodes is obtained with a stack of two layers, the upper one being lightly doped while the deeper one contains Boron concentrations close to the metallic conductivity threshold (4 × 10²⁰ B/cm³). Several architectures are studied. The ohmic contact directly laid on the heavily doped layer permits forward current densities of 66 A/cm² under 4 V at room temperature and switching times in the nanosecond range. This set of results shows that p-type diamond is an adequate semiconductor for implementing high speed, high power and high voltage electronic rectifiers.