Enhancement of keratinocyte survival and migration elicited by interleukin 24 upregulation in dermal microvascular endothelium upon welding-fume exposure.

Occupational exposure to welding fumes constitutes a serious health concern. Although the effects of fumes on the respiratory tract have been investigated, few apparent reports were published on their effects on the skin. The purpose of this study was to investigate the effects of exposure to welding fumes on skin cells, focusing on interleukin-24 (IL-24), a cytokine involved in the pathophysiology of skin conditions, such as atopic dermatitis and psoriasis. Treatment with welding fumes increased IL-24 expression and production levels in human dermal microvascular endothelial cells (HDMEC) which were higher than that in normal human epidermal keratinocytes. IL-24 levels in Trolox and deferoxamine markedly suppressed welding fume-induced IL-24 expression in HDMEC, indicating that oxidative stress may be involved in this cytokine expression. IL-24 released from HDMEC protected keratinocytes from welding fume-induced damage and enhanced keratinocyte migration. Serum IL-24 was higher in welding workers than in general subjects and was positively correlated with elevated serum levels of 8-hydroxy-2'-deoxyguanosine, an oxidative stress marker. In summary, welding fumes enhanced IL-24 expression in HDMEC, stimulating keratinocyte survival and migration. IL-24 expression in endothelial cells may act as an adaptive response to welding-fume exposure in the skin.

Polycyclic aromatic hydrocarbons in urban particle matter exacerbate movement disorder after ischemic stroke via potentiation of neuroinflammation.

BACKGROUND: A recent epidemiological study showed that air pollution is closely involved in the prognosis of ischemic stroke. We and others have reported that microglial activation in ischemic stroke plays an important role in neuronal damage. In this study, we investigated the effects of urban aerosol exposure on neuroinflammation and the prognosis of ischemic stroke using a mouse photothrombotic model. RESULTS: When mice were intranasally exposed to CRM28, urban aerosols collected in Beijing, China, for 7 days, microglial activation was observed in the olfactory bulb and cerebral cortex. Mice exposed to CRM28 showed increased microglial activity and exacerbation of movement disorder after ischemic stroke induction. Administration of core particles stripped of attached chemicals from CRM28 by washing showed less microglial activation and suppression of movement disorder compared with CRM28-treated groups. CRM28 exposure did not affect the prognosis of ischemic stroke in null mice for aryl hydrocarbon receptor, a polycyclic aromatic hydrocarbon (PAH) receptor. Exposure to PM2.5 collected at Yokohama, Japan also exacerbated movement disorder after ischemic stroke. CONCLUSION: Particle matter in the air is involved in neuroinflammation and aggravation of the prognosis of ischemic stroke; furthermore, PAHs in the particle matter could be responsible for the prognosis exacerbation.

Heat trapping in a nano-layered microenvironment: estimation of temperature by thermal sensing molecules.

We have previously found reversible photo-induced expansion and contraction of organic/inorganic clay hybrids, and even sliding of niobate nano-sheets at the macroscopic level of organic/inorganic niobate hybrids, induced by the molecular photo-isomerization of the polyfluoroalkylated azobenzene derivative (C3F-Azo-C6H) intercalated within the interlayer, which is viewed as an artificial muscle model unit. Based on systematic investigations of the steady state photo-isomerization and transient behavior of the reaction, we comprehended that the phenomena is caused by trapping of excess energy liberated during the isomerization, as well as the relaxation processes upon excitation of azobenzene chromophores in the interlayers of the hybrid. In this paper, quantitative estimation of transient 'heat' trapped in various microenvironments has been studied by each co-intercalation of temperature sensing dye molecules - rhodamine B (RhB) or tris(bipyridine)ruthenium(ii) chloride (Rubpy) with C3F-Azo-C6H within clay (SSA) nano-layers. The amount of dye molecules co-intercalated was kept to trace amounts that did not alter the bi-layered structure of the hybrid. The temperature of the microenvironment surrounding the probe molecules was estimated from the emission lifetime analysis. The evidently reduced emission lifetimes in C3F-Azo-C6H/SSA and C3H-Azo-C6H/SSA hybrids in the film state, indicated the elevation of temperature of the microenvironment upon excitation of the chromophores, which demonstrated our previous hypothesis rationalizing that the high reactivity of isomerization in the hybrid film state is caused by heat trapping via multi-step dissipation of the excess energy. With the hybrid of a hydrocarbon analogue (C3H-Azo-C6H), a distinct difference in temperature gradient was found to show the crucial role of the perfluoroalkyl chain of the surfactant that traps the excess energy to retard its dissipation leading to three-dimensional morphological motion.

Synthesis of a photo-responsive single-walled nanoscroll and its photo-reactivity in a nano-layered microenvironment.

A photo-responsive nanoscroll composed of niobate nanosheets and a polyfluoroalkyl azobenzene derivative (C3F-Azo-C6H) is one of the most interesting layered materials because the reversible winding and unwinding motion could be efficiently induced by photo-irradiations. Previously, we have studied a double-walled nanoscroll (DWNS) of niobate that could be synthesized by the intercalation of a cationic polyfluorinated surfactant only into the interlayer I of the layered niobate among the two interlayers, I and II. In this study, we have successfully synthesized another novel photo-responsive single-walled nanoscroll (SWNS) of niobate by a stepwise guest-guest ion-exchange method. All niobate nanosheets that were exfoliated at both interlayers I and II were efficiently converted to nanoscrolls by the intercalation of C3F-Azo-C6H. The synthetic yield has been quantitatively estimated. Though the photo-isomerization reaction of C3F-Azo-C6H was induced in the SWNS, its photo-reactivity was the lowest when compared with those of the nanosheet-stacked film and the DWNS. The photo-reactivity of C3F-Azo-C6H decreased in the order of DWNS > nanosheet-stacked film > SWNS. The different flexibility of the layered miroenvironment might influence the photo-reactivity of C3F-Azo-C6H in the niobate hybrid. The SWNS exhibited a reversible expansion and shrinkage of its interlayer spaces upon photo-irradiation, while the winding and unwinding motion was not observed, contrary to the DWNS. The direction of the expansion and shrinkage of the interlayer of the SWNS was opposite to those of the nanosheet-stacked film and the DWNS. Based on the experimental results, the tilt angle of C3F-Azo-C6H against the nanosheet surface and the matching structures of the top and bottom surfaces of the nanosheet could be the probable key factors that control the photo-reactivity of C3F-Azo-C6H in the layered microenvironment; the morphological changes of the nano hybrids was also discussed.

Synthesis of double-wall nanoscrolls intercalated with polyfluorinated cationic surfactant into layered niobate and their magnetic alignment.

The orientation of nanomaterials with an anisotropic nature such as nanoscrolls is very important for realizing their efficient and sophisticated functions in devices, including nanostructured electrodes in artificial photosynthetic cells. In this study, we successfully synthesized a nanoscroll by intercalation of a cationic polyfluorinated surfactant into the interlayer spaces of layered niobate and successfully controlled its orientation by applying an external magnetic field in water. The exfoliated niobate nanosheets were efficiently rolled-up to form nanoscrolls, which have a fine layered structure (d020 = 3.64 nm), by mixing with heptafluorobutanoylaminoethylhexadecyldimethylammonium bromide (C3F-S) in water, whereas the corresponding hydrocarbon analogue (C3H-S) did not form nanoscrolls. The synthetic yield for the purified and isolated nanoscrolls from the nanosheets was estimated to be 62% by weight. It was confirmed by atomic force microscopy (AFM) that most of the niobate nanosheets (98%) were converted to nanoscrolls. An external magnetic field was applied to the nanoscrolls to force them to align. After the magnetic treatment, the orientation of the nanoscrolls was investigated by small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The non-uniform ring distribution of the SAXS patterns indicates that the nanoscrolls dispersed in water were aligned well on applying the magnetic field. The long axis of the nanoscroll was oriented in the direction of the applied field and long nanoscrolls were aligned more efficiently. When the intercalated C3F-S molecules were removed from the nanoscrolls by treating with an acid, the resultant nanoscrolls did not exhibit magnetic alignment, strongly suggesting that C3F-S plays an important role in the orientation control of the nanoscrolls by the magnetic field.

Direct detection of key reaction intermediates in photochemical CO2 reduction sensitized by a rhenium bipyridine complex.

Photochemical CO2 reduction sensitized by rhenium-bipyridyl complexes has been studied through multiple approaches during the past several decades. However, a key reaction intermediate, the CO2-coordinated Re-bipyridyl complex, which should govern the activity of CO2 reduction in the photocatalytic cycle, has never been detected in a direct way. In this study on photoreduction of CO2 catalyzed by the 4,4'-dimethyl-2,2'-bipyridine (dmbpy) complex, [Re(dmbpy)(CO)3Cl] (1), we successfully detect the solvent-coordinated Re complex [Re(dmbpy)(CO)3DMF] (2) as the light-absorbing species to drive photoreduction of CO2. The key intermediate, the CO2-coordinated Re-bipyridyl complex, [Re(dmbpy)(CO)3(COOH)], is also successfully detected for the first time by means of cold-spray ionization spectrometry (CSI-MS). Mass spectra for a reaction mixture with isotopically labeled (13)CO2 provide clear evidence for the incorporation of CO2 into the Re-bipyridyl complex. It is revealed that the starting chloride complex 1 was rapidly transformed into the DMF-coordinated Re complex 2 through the initial cycle of photoreduction of CO2. The observed induction period in the time profile of the CSI-MS signals can well explain the subsequent formation of the CO2-coordinated intermediate from the solvent-coordinated Re-bipyridyl complex. An FTIR study of the reaction mixture in dimethyl sulfoxide clearly shows the appearance of a signal at 1682 cm(-1), which shifts to 1647 cm(-1) for the (13)CO2-labeled counterpart; this is assigned as the CO2-coordinated intermediate, Re(II)-COOH. Thus, a detailed understanding has now been obtained for the mechanism of the archetypical photochemical CO2 reduction sensitized by a Re-bipyridyl complex.

Hydrogen evolution coupled with the photochemical oxygenation of cyclohexene with water sensitized by tin(IV) porphyrins by visible light.

Hydrogen evolution coupled with the photochemical oxygenation of cyclohexene with water was observed in the system sensitized by Sn(IV)-porphyrin adsorbed on Pt loaded TiO2 nano-particles in aqueous acetonitrile solution upon visible light irradiation.

Remarkable enhancement of the photoreactivity of a polyfluoroalkyl azobenzene derivative in an organic-inorganic nano-layered microenvironment.

Organic-inorganic hybrids composed of polyfluoroalkyl azobenzene surfactant (abbreviated as C3F-Azo-C6H) and inorganic layered compounds are able to undergo reversible three-dimensional morphology changes such as interlayer space changes and nanosheet sliding in a giant scale due to reversible trans-cis isomerization of the azobenzene moiety upon photo-irradiation. In this paper, we have systematically studied the relationship between the layered hybrid microstructures of C3F-Azo-C6H-clay and their photoreactivity for understanding the mechanism of the photo-induced morphology change. The photoreactivity was found to be very much affected by the surrounding microenvironments. As compared with it in solution, the cis-trans photo-isomerization in C3F-Azo-C6H-clay nano-layered film was substantially enhanced with the quantum yield exceeding unity (Φ = 1.9), while the trans-cis isomerization was rather retarded. The corresponding hydrocarbon analogue of the azobenzene surfactant (C3H-Azo-C6H) did not show such an enhancement. The enhancement was discussed in terms of a cooperative effect among adjacent azobenzene moieties along with polyfluoroalkyl chains and the inorganic clay nanosheet to prevent a dissipation of the excess energy being liberated during the photo-isomerization within the nano-layered microenvironment.

Hydrophilicity control of visible-light hydrogen evolution and dynamics of the charge-separated state in dye/TiO2/Pt hybrid systems.

Visible-light-driven H(2) evolution based on Dye/TiO(2)/Pt hybrid photocatalysts was investigated for a series of (E)-3-(5'-{4-[bis(4-R(1)-phenyl)amino]phenyl}-4,4'-(R(2))(2)-2,2'-bithiophen-5-yl)-2-cyanoacrylic acid dyes. Efficiencies of hydrogen evolution from aqueous suspensions in the presence of ethylenediaminetetraacetic acid as electron donor under illumination at λ>420 nm were found to considerably depend on the hydrophilic character of R(1), varying in the order MOD (R(1)=CH(3)OCH(2), R(2)=H)≈MO4D (R(1)=R(2)=CH(3)OCH(2))>HD (R(1)=R(2)=H)>PD (R(1)=C(3)H(7), R(2)=H). In the case of MOD/TiO(2)/Pt, the apparent quantum yield for photocatalyzed H(2) generation at 436 nm was 0.27±0.03. Transient absorption measurements for MOD- or PD-grafted transparent films of TiO(2) nanoparticles dipped into water at pH 3 commonly revealed ultrafast formation (<100 fs) of the dye radical cation (Dye(·+) ) followed by multicomponent decays, which involve minor fast decays (<5 ps) almost independent of R(1) and major slower decays with significant differences between the two samples: 1) the early decay of the major components for MOD is about 2.5 times slower than that for PD and 2) a redshift of the spectrum occurred for MOD with a time constant of 17 ps, but not for PD. The substituent effects on H(2) generation as well as on transient behavior have been discussed in terms substituent-dependent charge recombination (CR) of Dye(·+) with electrons in bulk, inner-trap, and/or interstitial-trap states, arising from different solvent reorganization.

A photoactivated artificial muscle model unit: reversible, photoinduced sliding of nanosheets.

A novel photoactivated artificial muscle model unit is reported. Here we show that organic/inorganic hybrid nanosheets reversibly slide horizontally on a giant scale and the interlayer spaces in the layered hybrid structure shrink and expand vertically by photoirradiation. The sliding movement of the system on a giant scale is the first example of an artificial muscle model unit having much similarity with that in natural muscle fibrils. In particular, our layered hybrid molecular system exhibits a macroscopic morphological change on a giant scale (~1500 nm) relative to the molecular size of ~1 nm by means of a reversible sliding mechanism.

One Electron-Initiated Two-Electron Oxidation of Water by Aluminum Porphyrins with Earth's Most Abundant Metal.

We report herein a new molecular catalyst for efficient water splitting, aluminum porphyrins (tetra-methylpyridiniumylporphyrinatealuminum: AlTMPyP), containing earth's most abundant metal as the central ion. One-electron oxidation of the aluminum porphyrin initiates the two-electron oxidation of water to form hydrogen peroxide as the primary reaction product with the lowest known overpotential (97 mV). The aluminum-peroxo complex was detected by a cold-spray ionization mass-spectrometry in high-resolution MS (HRMS) mode and the structure of the intermediate species was further confirmed using laser Raman spectroscopy, indicating the hydroperoxy complex of AlTMPyP to be the key intermediate in the reaction. The two-electron oxidation of water to form hydrogen peroxide was essentially quantitative, with a Faradaic efficiency of 99 %. The catalytic reaction was found to be highly efficient, with a turnover frequency up to ∼2×104  s-1 . A reaction mechanism is proposed involving oxygen-oxygen bond formation by the attack of a hydroxide ion on the oxyl-radical-like axial ligand oxygen atom in the one-electron-oxidized form of AlTMPyP(O- )2 , followed by a second electron transfer to the electrode.

Selective optical trapping and deposition of polymer and aromatic molecules from binary mixed solution.

We have demonstrated size-selective optical trapping and deposition of polymer and aromatic molecules from binary mixed solution. As a near-infrared laser beam is tightly focused in polystyrene and perylene mixed solution and dropped on a glass substrate, a molecular assembly is deposited at the laser focus and fixed on the substrate. The fluorescence spectrum of the deposited microassembly depends on the laser power; perylene monomer fluorescence is dominant in the case of high laser power, whereas excimer emission of perylene crystal is observed in the case of low laser power. This suggests that polystyrene molecules are preferentially deposited by focusing a higher laser power so that the ratio of polystyrene and perylene in the assembly can be controlled by laser power. This mechanism can be explained in view of the molecular size selectivity in optical trapping.

Photo-induced morphological winding and unwinding motion of nanoscrolls composed of niobate nanosheets with a polyfluoroalkyl azobenzene derivative.

Photo-responsive nanoscrolls can be successfully fabricated by mixing a polyfluoroalkyl azobenzene derivative and a niobate nanosheet, which is exfoliated from potassium hexaniobate. In this study, we have found that the photo-responsive nanoscroll shows a morphological motion of winding and unwinding, which is basically due to the nanosheet sliding within the nanoscroll, by efficient photo-isomerization reactions of the intercalated azobenzene in addition to the interlayer distance change of the nanoscrolls. The relative nanosheet sliding of the nanoscroll is estimated to be ca. 280 nm from the AFM morphology analysis. The distance of the sliding motion is over 20 times that of the averaged nanosheet sliding in the azobenzene/niobate hybrid film reported previously. Photo-responsive nanoscrolls can be expected to be novel photo-activated actuators and artificial muscle model materials.

Synthesis of water-soluble silicon-porphyrin: protolytic behaviour of axially coordinated hydroxy groups.

A new water-soluble silicon(IV)-tetra(4-carboxyphenyl)porphyrin (SiTCPP) with silicon(iv), the second most abundant element on Earth, in the center of porphyrin was synthesized. Fundamental properties including protolytic behaviour of axially coordinating hydroxy groups, and electrochemical behaviour were characterized. The properties were compared with those of silicon(IV)-tetra(2,4,6-trimethylphenyl)porphyrin (SiTMP) and silicon(IV)-tetra(4-trifluoromethylphenyl)porphyrin (SiTFMPP) and discussed in respect to the electron donating/withdrawing effect of the substituents. Two axially coordinating hydroxy groups of SiTCPP exhibit a four-step protolytic behaviour under the acidic conditions along with a single step protolysis of peripheral carboxyl groups. Though SiTCPP and SiTFMPP did not show any reactivity in the photochemical oxygenation of a substrate with K2PtCl6 as a sacrificial electron acceptor, the first oxidation wave in the electrochemical process of SiTCPP and SiTFMPP showed catalytic behaviour in aqueous acetonitrile solution at any pH condition, in contrast to SiTMP which has only a reversible oxidation wave under neutral and weakly acidic conditions. The criteria for the electrochemical oxidative activation of water and the photooxygenation of the substrate were obtained. The higher oxidation wave of Si-porphyrins than ∼0.86 volt vs. SHE is required for the electrochemical oxidation of water, while suitable protecting groups such as a methyl substituent is a requisite for the photochemical oxygenation with K2PtCl6 as a sacrificial electron acceptor.

An artificial muscle model unit based on inorganic nanosheet sliding by photochemical reaction.

From the viewpoint of developing photoresponsive supramolecular systems in microenvironments to exhibit more sophisticated photo-functions even at the macroscopic level, inorganic/organic hybrid compounds based on clay or niobate nanosheets as the microenvironments were prepared, characterized, and examined for their photoreactions. We show here a novel type of artificial muscle model unit having much similarity with that in natural muscle fibrils. Upon photoirradiation, the organic/inorganic hybrid nanosheets reversibly slide horizontally on a giant scale, and the interlayer spaces in the layered hybrid structure shrink and expand vertically. In particular, our layered hybrid molecular system exhibits a macroscopic morphological change on a giant scale (~1500 nm) compared with the molecular size of ~1 nm, based on a reversible sliding mechanism.

How is the water molecule activated on metalloporphyrins? Oxygenation of substrates induced through one-photon/two-electron conversion in artificial photosynthesis by visible light.

The reaction mechanism of the highly efficient (phi = 0.60), selective photochemical epoxidation of alkenes sensitized by CO-coordinated tetra(2,4,6-trimethyl)phenylporphyrinatoruthenium(II) (Ru(II)TMP(CO)), with water acting both as an electron and oxygen atom donor, was investigated. The steady-state light irradiation of the reaction mixture indicated the formation of the Ru(II)TMP (CO) cation radical under neutral conditions, which was effectively trapped by an hydroxide ion to regenerate the starting sensitizer. By means of a laser flash photolysis experiment, the formation of the cation radical as the primary process from the triplet excited state of Ru(II)TMP(CO) was clearly observed. Four kinds of transients were detected in completely different ranges of the delay time: the excited triplet state of Ru(II)TMP(CO) [delay time region <20 micros], the cation radical of Ru(II)TMP(CO)(CH3CN) [20-50 micros], the hydroxyl-coordinated Intermediate [I] [50-200 micros], and the cyclohexane-attached Intermediate [II] [200 micros-8 ms]. A reaction mechanism was revealed that involves RuTMP(CO) cation radical formation from the triplet excited state of the sensitizer, followed by attack of an hydroxide ion to form an hydroxyl-coordinated Ru-porphyrin (Intermediate [I]) and subsequent reaction with cyclohexene to form Intermediate [II]. The kinetics for each step of the successive processes was carefully analyzed and their rate constants were determined. The two-electron oxidation of water by one-photon irradiation, as revealed in the photochemical epoxidation, is proposed to be one of the more promising candidates to get through the bottleneck of water oxidation in artificial photosynthesis.

The water oxidation bottleneck in artificial photosynthesis: how can we get through it? An alternative route involving a two-electron process.

The state-of-the-art of research on artificial photosynthesis is briefly reviewed. Insights into how Nature takes electrons from water, the photon-flux density of sunlight, the time scale for the arrival of the next photon (electron-hole) at the oxygen-evolving complex, how Nature solves the photon-flux-density problem, and how we can get through the bottleneck of water oxidation are discussed. An alternate route for a two-electron process induced by one-photon excitation is postulated for getting through the bottleneck of water oxidation.

Effects of optical trapping and liquid surface deformation on the laser microdeposition of a polymer assembly in solution.

A polymer microassembly is formed by focusing a near-infrared (NIR) laser beam in a thin film of a polymer solution. We have investigated the mechanism of laser microdeposition of a polyfluorene assembly by measuring the surface deformation of the solution film and the morphology of the deposited assembly. It is clearly observed that a rupture is formed at the laser focus in the solution film by using laser interferometric imaging. The time necessary for the rupture formation and the volume of the deposited microassembly are analyzed as a function of laser power. Experimental results suggest that the solution surface deformation induced by local laser heating and optical trapping effects determined the volume of the laser microdeposition. By combining this method with multiple optical trapping, a polymer microassembly with a polygonal morphology is formed on the glass substrate.