Toxicological consequences of TiO<Subscript>2</Subscript>, SiC nanoparticles and multi-walled carbon nanotubes exposure in several mammalian cell types: an in vitro study

The development of nanotechnologies may lead to dissemination of potentially toxic nanoparticles in the environment. Toxicology of these nano-sized particles is thus attracting attention of public and governments worldwide. Our research is focused on the in vitro response of eukaryotic cells to nanoparticles exposure. For this purpose, we used cellular models of primary target organs (lung: A549 alveolar epithelial cells), or secondary target organs (liver: WIF-B9, Can-10 and kidneys: NRK-52E, LLC-PK1 proximal cells), i.e., organs exposed if nanoparticles are translocated through epithelial barriers. These cells were exposed to TiO₂, SiC nanoparticles or multi-walled carbon nanotubes (MWCNT). The influence of nanoparticles physico-chemical characteristics on various toxicological endpoints (cytotoxicity, reactive oxygen species generation, genotoxicity) was specified. Our data demonstrate that nanoparticles toxicity depend on their size, morphology, and chemical composition, the finest, spherical shaped, and anatase TiO₂ nanoparticles being the more cytotoxic to NRK-52E cells, while SiC nanoparticles exert almost no cytotoxicity. MWCNT cytotoxicity neither depended on their length, nor on the presence of metal impurities. Nanoparticles cytotoxicity also depended on the exposed cell line. All the tested nanoparticles were uptaken by cells and caused intracellular reactive oxygen species generation. Relative to genotoxic effects, DNA strand breaks were detected in NRK-52E cells via the alkaline comet assay after exposure of cells to TiO₂ nanoparticles and to a lesser extent after exposure to MWCNT, but no double strand breaks were detected. The originality of this study lies on the panel of nanomaterials which were tested on a variety of cell lines. All these data may lead to a better understanding of nanomaterial toxicity and hazards for health.     

Detective quantum efficiency,modulation transfer function and energy resolution comparison between CdTe and silicon sensors bump‐bonded to XPAD3S

XPAD3S is a single‐photon‐counting chip developed in collaboration by SOLEIL Synchrotron, the Institut Louis Néel and the Centre de Physique de Particules de Marseille. The circuit, designed in the 0.25 µm IBM technology, contains 9600 square pixels with 130 µm side giving a total size of 1 cm × 1.5 cm. The main features of each pixel are: single threshold adjustable from 4.5 keV up to 35 keV, 2 ms frame rate, 10⁷ photons s^?1 mm^?2 maximum local count rate, and a 12‐bit internal counter with overflow allowing a full 27‐bit dynamic range to be reached. The XPAD3S was hybridized using the flip‐chip technology with both a 500 µm silicon sensor and a 700 µm CdTe sensor with Schottky contacts. Imaging performances of both detectors were evaluated using X‐rays from 6 keV up to 35 keV. The detective quantum efficiency at zero line‐pairs mm^?1 for a silicon sensor follows the absorption law whereas for CdTe a strong deficit at low photon energy, produced by an inefficient entrance layer, is measured. The modulation transfer function was evaluated and it was shown that both detectors present an ideal modulation transfer function at 26 keV, limited only by the pixel size. The influence of the Cd and Te K‐edges of the CdTe sensor was measured and simulated, establishing that fluorescence photons reduce the contrast transfer at the Nyquist frequency from 60% to 40% which remains acceptable. The energy resolution was evaluated at 6% with silicon using 16 keV X‐rays, and 8% with CdTe using 35 keV X‐rays. A 7 cm × 12 cm XPAD3 imager, built with eight silicon modules (seven circuits per module) tiled together, was successfully used for X‐ray diffraction experiments. A first result recently obtained with a new 2 cm × 3 cm CdTe imager is also presented.     

Evaluation of antiangiogenic treatment effects on tumors' microcirculation by Bayesian physiological pharmacokinetic modeling and magnetic resonance imaging

A physiological pharmacokinetic (PBPK) model was used to estimate tumor microcirculation in nude mice with a grafted tumor. The kinetics of a rapid clearance blood pool agent, Vistarem, were investigated by dynamic MRI after bolus administration. Signal enhancements were recorded in arterial blood and in tumor tissue. To analyze these data, we developed a whole-body mathematical model of the agent's biodistribution using physiological parameters. The model included six compartments: arterial and venous plasma, tumor (split into capillaries and interstitium), and the rest of the body (also split into capillaries and interstitium). As an application, changes in tumor microcirculation parameters were evaluated in mice receiving either an antiangiogenic treatment (ZD4190) or a placebo. The analysis was performed in a Bayesian framework, and the model was fitted to experimental data using Markov Chain Monte Carlo techniques. Results showed a significant difference in tumor microcirculation between the two groups of mice when the microcirculation parameters are considered together. This whole-body physiological model enables to analyze jointly data in tumor tissue and in arterial blood. This leads to accurate estimates of microcirculation parameters and the evaluation of their uncertainty.     

Optimized focusing properties of photonic crystal slabs

We propose an optimization procedure for focusing operation in finite two dimensional photonic crystal slabs. The device consists of a triangular lattice air holes etched in a semiconductor matrix at a nanometer scale to operate at 1.55 μm. To reach simultaneously an effective refractive index equal to −1 along with a very high transmission coefficient whatever optical wave incidence, the parameters as the lattice period and/or filling factor are precisely adjusted depending on the slab thickness. The method relies on Fabry-Perot resonances engineering in the air/crystal/air cavity constituting the lens.     

Optical near-field microscopy of light focusing through a photonic crystal flat lens

We report here the direct observation by using a scanning near-field microscopy technique of the light focusing through a photonic crystal flat lens designed and fabricated to operate at optical frequencies. The lens is fabricated using a III-V semiconductor slab, and we directly visualize the propagation of the electromagnetic waves by using a scanning near-field optical microscope. We directly evidence spatially, as well as spectrally, the focusing operating regime of the lens. At last, in light of the experimental scanning near-field optical microscope pictures, we discuss the lens ability to focus light at a subwavelength scale.     

Acoustic characterization of a new trisacryl contrast agent. Part II: Flow phantom study and in vivo quantification

The biocompatible trisacryl particles (TMP) are made of a cross-linked acrylic copolymer. Their inherent acoustic properties, studied for a contrast agent application, have been previously demonstrated in a in vitro Couette device. To measure their acoustic behaviour under circulating blood conditions, the TMP backscatter enhancement was further evaluated on a home-made flow phantom at different TMP doses (0.12-15.6 mg/ml) suspended in aqueous and blood media, and in nude mice (aorta and B16 grafted melanoma). Integrated backscatter (IB) was measured by spectral analysis of the Doppler signals recorded from an ultrasound system (Aplio^®) combined with a 12-MHz probe. Doppler phantom experiments revealed a maximal IB of 17 ± 0.88 dB and 7.5 ± 0.7 dB in aqueous and blood media, respectively. IB measured on mice aorta, in pulsed Doppler mode, confirmed a constant maximal value of 7.29 ± 1.72 dB over the first minutes after injection of a 7.8 mg/ml TMP suspension. Following the injection, a 60% enhancement of intratumoral vascularization detection was observed in power Doppler mode. A preliminary histological study revealed inert presence of some TMP in lungs 8 and 16 days after injection.Doppler phantom experiments on whole blood allowed to anticipate the in vivo acoustic behaviour. Both protocols demonstrated TMP effectiveness in significantly increasing Doppler signal intensity and intratumoral vascularization detection. However, it was also shown that blood conditions seemed to shadow the TMP contrast effect, as compared to in vitro observations. These results encourage further investigations on the specific TMP targeting and on their bio-distribution in the different tissues.     

Biodegradable Materials from Agro-Based By-Products

Summary: A new biodegradable thermoplastic material based on a wheat flour by-product has been developed. The influence of various additives (glycerol, silica) and fibers (flax, cotton, hemp) on the mechanical properties of the material has been investigated. The development of expanded materials is also presented.     

Ascending Runs in Dependent Uniformly Distributed Random Variables: Application to Wireless Networks

We analyze in this paper the longest increasing contiguous sequence or maximal ascending run of random variables with common uniform distribution but not independent. Their dependence is characterized by the fact that two successive random variables cannot take the same value. Using a Markov chain approach, we study the distribution of the maximal ascending run and we develop an algorithm to compute it. This problem comes from the analysis of several self-organizing protocols designed for large-scale wireless sensor networks, and we show how our results apply to this domain.     

Inorganic WS<Subscript>2</Subscript> nanotubes revealed atom by atom using ultra-high-resolution transmission electron microscopy

The characterization of nanostructures to the atomic dimensions becomes more important, as devices based on a single particle are being produced. In particular, inorganic nanotubes were shown to host interesting properties making them excellent candidates for various devices. The WS₂ nanotubes outperform the bulk in their mechanical properties offering numerous applications especially as part of high strength nanocomposites. In contrast, their electrical properties are less remarkable. The structure–function relationship can be investigated by aberration-corrected high-resolution transmission electron microscopy (HRTEM), which enables the insight into their atomic structure as well as performing spectroscopic measurements down to the atomic scale. In the present work, the deciphering of atomic structure and the chiral angle of the different shells in a multiwall WS2 nanotube is demonstrated. In certain cases, the helicity of the structure can also be deduced. Finally, first electron energy loss spectra (EELS) of a single tube are presented, acquired by a new acquisition technique that allows for high spatial resolution (denoted StripeSTEM). The measured band gap values correspond with the values found in literature for thin films, obtained by spectroscopic techniques, and are higher than the values resulting from STM measurements.     

Derivatization,molecular docking and in vitro acetylcholinesterase inhibitory activity of glycyrrhizin as a selective anti-Alzheimer agent

Acetylcholinesterase inhibitors (AChE-Is) increase both level and duration of action of acetylcholine (ACh); thus, alleviate symptoms of Alzheimer’s disease (AD). Glycyrrhizin, is the main active compound in liquorice root. Its aglycone, glycyrrhetinic acid, has shown several beneficial pharmacological activities. This study reports the synthesis and screening of a series of glycyrrhetinic acid analogs as AChE-Is. Fourteen derivatives were prepared, of which five derivatives are recorded as new viz., 3-phenyl-carbamoyl-18β-glycyrrhetinic acid (J9), 3-acetyl-18β-glycyrrhetinic-30-anilinamide (J10), 3-acetyl-18β-glycyrrhetinic-30-ethanolamide (J11), 3-acetyl-18β-glycyrrhetinic-30-n-butylamide (J12) and 18β-glycyrrhetinic acid-30-prenyl ester (J14), in addition to nine known derivatives (J1-J8 & J13). Compounds J12, J11, J0 and J3 showed remarkable AChE-I activity with IC₅₀ values of 3.43, 5.39, 6.27 and 8.68 μM, respectively. These results are in full agreement with the docking study. The active compounds were non-cytotoxic to normal cells (WI-38).