Acoustic Cavitation Enhances Focused Ultrasound Ablation with Phase-Shift Inorganic Perfluorohexane Nanoemulsions: An In Vitro Study Using a Clinical Device.

Purpose. To investigate whether acoustic cavitation could increase the evaporation of a phase-shift inorganic perfluorohexane (PFH) nanoemulsion and enhance high intensity focused ultrasound (HIFU) ablation. Materials and Methods. PFH was encapsulated by mesoporous silica nanocapsule (MSNC) to form a nanometer-sized droplet (MSNC-PFH). It was added to a tissue-mimicking phantom, whereas phosphate buffered saline (PBS) was added as a control (PBS-control). HIFU (P ac = 150 W, t = 5/10 s) exposures were performed in both phantoms with various duty cycles (DC). US images, temperature, and cavitation emissions were recorded during HIFU exposure. HIFU-induced lesions were measured and calculated. Results. Compared to PBS-control, MSNC-PFH nanoemulsion could significantly increase the volume of HIFU-induced lesion (P < 0.01). Peak temperatures were 78.16 ± 5.64°C at a DC of 100%, 70.17 ± 6.43°C at 10%, 53.17 ± 4.54°C at 5%, and 42.00 ± 5.55°C at 2%, respectively. Inertial cavitation was much stronger in the pulsed-HIFU than that in the continuous-wave HIFU exposure. Compared to 100%-DC exposure, the mean volume of lesion induced by 5 s exposure at 10%-DC was significantly larger, but smaller at 2%-DC. Conclusions. MSNC-PFH nanoemulsion can significantly enhance HIFU ablation. Appropriate pulsed-HIFU exposure could significantly increase the volume of lesion and reduce total US energy required for HIFU ablation.

DNA damage caused by inorganic particulate matter on Raji and HepG2 cell lines exposed to ultraviolet radiation.

Epidemiological studies have correlated exposure to ultraviolet-irradiated particulate matter with cardiovascular, respiratory, and lung diseases. This study investigated the DNA damage induced by two major inorganic particulate matter compounds found in diesel exhaust, ammonium nitrate and ammonium sulfate, on Burkitt's lymphoma (Raji) and hepatocellular carcinoma (HepG2) cell lines. We found a dose-dependent positive correlation of accumulated DNA damage at concentrations of ammonium nitrate (25 µg/ml, 50 µg/ml, 100 µg/ml, 200 µg/ml, 400 µg/ml) with ultraviolet exposure (250 J/m(2), 400 J/m(2), 600 J/m(2), 850 J/m(2)), as measured by the comet assay in both cell lines. There was a significant difference between the treated ammonium nitrate samples and negative control samples in Raji and HepG2 cells (p<0.001). Apoptosis was shown in Raji and HepG2 cells when exposed to high concentrations of ammonium nitrate (200 µg/ml and 400 µg/ml) for 1h in samples without ultraviolet exposure, as assessed by the comet assay. However, the level of apoptosis greatly diminished after ultraviolet exposure at these concentrations. Over a 24h period, at intervals of 1, 4, 8, 12, 18, and 24h, we also observed that ammonium nitrate decreased viability in Raji and HepG2 cell lines and inhibited cell growth. Ammonium sulfate-induced DNA damage was minimal in both cell lines, but there remained a significant difference (p<0.05) between the ultraviolet radiation treated and negative control samples. These results indicate that the inorganic particulate compound, ammonium nitrate, induced DNA strand breaks at all concentrations, and indications of apoptosis at high concentrations in Raji and HepG2 cells, with ultraviolet radiation preventing apoptosis at high concentrations. We hypothesize that ultraviolet radiation may inhibit an essential cellular mechanism, possibly involving p53, thereby explaining this phenomenon. Further studies are necessary to characterize the roles of apoptosis inhibition induced by DNA damage caused by inorganic particulate matter.

Designing artificial photosynthetic devices using hybrid organic-inorganic modules based on polyoxometalates.

Artificial photosynthesis aims at capturing solar energy and using it to produce storable fuels. However, while there is reason to be optimistic that such approaches can deliver higher energy conversion efficiencies than natural photosynthetic systems, many serious challenges remain to be addressed. Perhaps chief among these is the issue of device stability. Almost all approaches to artificial photosynthesis employ easily oxidized organic molecules as light harvesters or in catalytic centres, frequently in solution with highly oxidizing species. The 'elephant in the room' in this regard is that oxidation of these organic moieties is likely to occur at least as rapidly as oxidation of water, meaning that current device performance is severely curtailed. Herein, we discuss one possible solution to this problem: using self-assembling organic-polyoxometalate hybrid structures to produce compartments inside which the individual component reactions of photosynthesis can occur without such a high incidence of deleterious side reactions.

Flexible, transparent contacts for inorganic nanostructures and thin films.

A transparent, flexible contact is developed using Ni nanoparticles and Ag nanowires and demonstrated on free-standing, polymer embedded, Si microwire solar cells. Contact yields of over 99% and a series resistance of 14 Ω cm² are demonstrated.

Transformation of organic-inorganic hybrid films obtained by molecular layer deposition to photocatalytic layers with enhanced activity.

We present the transformation of organic-inorganic hybrid titanicone films formed by TiCl(4) as metal precursor and ethylene glycol (EG) using solvent-free MLD to highly active photocatalytic films. The photocatalytic activities of the films were investigated using hydroxyl-functionalized porphyrin as a spectroscopic marker. TEM imaging and electron diffraction, XPS, UV-vis spectroscopy, and spectroscsopic ellipsometry were employed for structural and composition analyses of the films. The photocatalytic activity of Ti-EG films was investigated for different anneal temperatures and compared to TiO(2) films prepared by ALD using TiCl(4) as metal precursor and H(2)O (TiO(2) films). Overall, our results indicate that the photocatalytic activity of the thermally annealed Ti-EG film is about 5-fold increased compared to that of the TiO(2) film prepared by ALD for optimal process conditions. The combined results indicate that the structural and photocatalytic properties can be assigned to three states: (I) amorphous state, intermediate dye loading, low photocatalytic activity, (II) intermediate film state with both crystalline and amorphous regions, high dye loading, high catalytic activity, and (III) highly crystalline film with low dye loading and low photocatalytic activity. The formation of photocatalytic nanotubes (NTs) is demonstrated using sacrificial Ge nanowires (NWs) scaffolds to yield Ti-EG NT structures with controllable wall thickness structures and enhanced dye loading capacity. Our results demonstrate the feasibility and high potential of MLD to form metal oxides with high photocatalytic activity.

Optical encoding by plasmon-based patterning: hard and inorganic materials become photosensitive.

The photosensitivity of nanocomposite AlN films with embedded silver nanospheres is reported. It stems from localized surface plasmon resonances (LSPR) whose modulation is photoinduced by laser annealing that induces a combined effect of metallic nanoparticle enlargement and dielectric matrix recrystallization; the photoindunced changes of the refractive index of the matrix result in strong spectral shift of LSPR. We demonstrate the utilization of this process for spectrally selective optical encoding into hard, durable, and chemically inert films.

UV-embossed inorganic-organic hybrid nanopillars for bioapplications.

We demonstrate rapid and maskless wafer-scale fabrication of inorganic-organic hybrid nanopillars for microfluidic and mass spectrometric applications. The nanopillar features are transferred from a black silicon master to the hybrid material by UV-embossing with a composite stamp made of polydimethylsiloxane (PDMS)/hard-PDMS (h-PDMS), which allows accurate transfer of structures in the 100 nm size range. The nanopillar embossing process is extremely simple and well suited for cheap wafer-scale prototyping, as the process does not require expensive masks or stamps and even works with a standard office lamp as the exposure source. The pillars can also be fabricated on a wide variety of substrates because the hybrid material is solvent-free. The use of the hybrid nanopillars as a hydrophobic/philic platforms and as sample plates in surface assisted laser desorption ionization mass spectrometry is demonstrated.

Nanostructuring of organic-inorganic hybrid materials for distributed feedback laser resonators by two-photon polymerization.

With two-photon absorption induced polymerization arbitrary three dimensional nano- and microstructures can be patterned directly into photoresists. We report on the fabrication of a low threshold organic semiconductor distributed feedback laser using the technique of two-photon absorption induced polymerization. A surface grating with 400 nm periodicity and 40 nm height modulation was fabricated by two-photon absorption induced polymerization in the organic-inorganic hybrid material ORMOCER. With structuring several stacked layers acting as a planar basis for the nanostructure microscopic substrate tilt can be compensated simply. This enabled us to uniformly nano-structure the surface grating over an area of 200 x 200 microm(2).

The Influence of a gradient static magnetic field on an unstirred Belousov-Zhabotinsky reaction.

It is believed that static magnetic fields (SMF) cannot affect the pattern formation of the Belousov-Zhabotinsky (BZ) reaction, which has been frequently studied as a simplified experimental model of a nonequilibrium open system, because SMF produces no induced current and the magnetic force of SMF far below 1 T is too low to expect the effects on electrons in the BZ reaction. In the present study, we examined whether the velocity of chemical waves in the unstirred BZ reaction can be affected by a moderate-intensity SMF exposure depending on the spatial magnetic gradient. The SMF was generated by a parallel pair of attracting rectangular NdFeB magnets positioned opposite each other. The respective maximum values of magnetic flux density (B(max)), magnetic flux gradient (G(max)), and the magnetic force product of the magnetic flux density its gradient (a magnetic force parameter) were 206 mT, 37 mT/mm, and 3,000 mT(2)/mm. The ferroin-catalyzed BZ medium was exposed to the SMF for up to 16 min at 25 degrees C. The experiments demonstrated that the wave velocity was significantly accelerated primarily by the magnetic gradient. The propagation of the fastest wave front indicated a sigmoid increase along the peak magnetic gradient line, but not along the peak magnetic force product line. The underlying mechanisms of the SMF effects on the anomalous wave propagation could be attributed primarily to the increased concentration gradient of the paramagnetic iron ion complexes at the chemical wave fronts induced by the magnetic gradient.

A combination of ultrasound and inorganic catalyst: removal of 2-chlorophenol from aqueous solution.

Removal of 2-chlorophenol by ultrasonic waves (sonolysis), inorganic catalyst, and a combination of the two processes was tested and compared with each technique. In sonolysis, 2-chlorophenol mostly degraded indirectly in the bulk of solution by the radicals produced in the cavitation process. In catalyst treatment, the removal was performed in the presence of Al2O3, TiO2 and CuO. The highest removal was achieved in the presence of TiO2 for this pollutant. In the combined method an enhancement was observed for the removal of 2-chlorophenol. This could be attributed primarily to the continuous cleaning and chemical activation of the catalyst by acoustic cavitation. The mass transfer between the liquid phase and the catalyst and also the surface area of the catalyst are accelerated by the ultrasonic waves. The removal of 2-chlorophenol was performed under different intensities of irradiation, temperatures and quantities of catalyst. Some experiments were conducted in the presence of a Fenton reagent. In kinetic point of view, the removal of pollutant showed a pseudo-first order behavior. The combined method had a higher rate coefficient than sonolysis and catalyst treatment individually. Under some conditions, the presence of ultrasound has increased the rate coefficient of removal to about 10 times that in the absence of ultrasound.