Simple and low-cost fabrication of PDMS microfluidic round channels by surface-wetting parameters optimization

Convenient for both biologists and MEMS designers, Polydimethylsiloxane (PDMS) polymer is intensively investigated for its biocompatibility, transparency, high resistance under plasma treatment, flexibility and resistance to high temperature. However, for microfluidic applications, the fabrication of PDMS circular channels is difficult to achieve except by wire moulding. In this article, we present a simple, fast and low-cost fabrication method which can be applied out of clean-room environment. It is based on the deposition of alginic acid sodium salt aqueous solution, enabling the formation of a liquid cylinder on the most hydrophilic part of a hydrophilic/hydrophobic patterned surface. We experimentally studied the interaction between liquid rivulets and surfaces presenting a contrast of wettability and/or a stepwise texture. Subsequent moulding of the half-cylinder of liquid produces round PDMS microfluidic channels. The optimal parameters for hydrophilic/hydrophobic patterns have then been applied to produce the roundest possible channels. The realisation of both straight channels 300–500 μm wide, 1 cm long and 75° tangent chord angle at best, and Y-shaped channels with the same dimensions and 55° TCA is demonstrated.     

Comparison of 2D simultaneous multi-slice and 3D GRASE readout schemes for pseudo-continuous arterial spin labeling of cerebral perfusion at 3 T

Objective

In this perfusion magnetic resonance imaging study, the performances of different pseudo-continuous arterial spin labeling (PCASL) sequences were compared: two-dimensional (2D) single-shot readout with simultaneous multislice (SMS), 2D single-shot echo-planar imaging (EPI) and multishot three-dimensional (3D) gradient and spin echo (GRASE) sequences combined with a background-suppression (BS) module.

Materials and methods

Whole-brain PCASL images were acquired from seven healthy volunteers. The performance of each protocol was evaluated by extracting regional cerebral blood flow (rCBF) measures using an inline morphometric segmentation prototype. Image data postprocessing and subsequent statistical analyses enabled comparisons at the regional and sub-regional levels.

Results

The main findings were as follows: (i) Mean global CBF obtained across methods was were highly correlated, and these correlations were significantly higher among the same readout sequences. (ii) Temporal signal-to-noise ratio and gray-matter-to-white-matter CBF ratio were found to be equivalent for all 2D variants but lower than those of 3D-GRASE.

Discussion

Our study demonstrates that the accelerated SMS readout can provide increased acquisition efficiency and/or a higher temporal resolution than conventional 2D and 3D readout sequences. Among all of the methods, 3D-GRASE showed the lowest variability in CBF measurements and thus highest robustness against noise.

     

RFID behavior study in enclosed marine container for real time temperature tracking

The performance of radio waves in open environments has been studied for years. In contrast, the behavior of Radio Frequency Identification (RFID) inside metal enclosed areas is not yet understood. This research project focuses on the 3-D mapping of RFID signal strength inside a 12 m refrigerated marine container instrumented with three different types of radio frequency (RF) emitters: 915 MHz reader; 2.45 GHz reader and 433 MHz RF transmitter. The main goal is to find a frequency/configuration that would allow real time reading of the temperature in a shipment of perishable products using RFID. Only one frequency and one antenna were used at a time. The RF transmitter antenna was mounted at two different places inside the container; at the top of the front wall (facing back) and on the ceiling in the middle of the container (facing down). The signal strength was acquired by a spectrum analyzer and its antenna was mounted on a small electric cart inside the container. The cart was programmed to move along the length of the container and stop repeatedly, allowing three automated measures per position. All data were analyzed in terms of power level and attenuation. The maps showed that the RFID antenna positioned at the front of the container delivered slightly better results than the one in the middle of the ceiling. The results showed a significantly higher performance at the 433 MHz level. This article was presented at Food Processing Automation Conference, American Society of Agricultural and Biological Engineering (ASABE), Providence, RI, June 28–29 2008.     

Design of poly(N‐acryloylglycine) materials for incorporation of microorganisms

To incorporate microorganisms and to preserve their integrity, new matrices of poly(N‐acryloylglycine) have been designed under appropriate conditions. To understand the interactions between the microorganisms and the organic part of the matrices, different conetworks of poly(N‐acryloylglycine) have been synthesized and characterized. Copolymerization with two crosslinkers was performed with different compositions. The thermal and swelling properties of conetworks are specifically controlled and compared. These investigations show that the swelling ratio of these materials is compatible with the incorporation of biomolecules in these matrices. They successfully permit Pseudomonasspecies 1625 bacteria incorporation. The biological activity of bacteria is also preserved, allowing the use of these materials for innovative biological applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 835‐841, 2013     

Common pattern of gene expression in response to hypoxia or cadmium in the gills of the European glass eel (Anguilla anguilla)

European eel (Anguilla anguilla) populations are in decline. Glass eel recruitment has fallen 10-fold since the early 1980s. Estuaries play a fundamental role in the life history of eels because glass eels must pass through them to reach freshwater ecosystems. Unfortunately, because of their geographical position at the upstream basin slopes, estuaries accumulate metals like cadmium and are important sites of hypoxia events. In this context, we studied the effect of the oxygen level on the ventilation of the glass eel. In parallel, glass eels were submitted to different dissolved cadmium concentrations (0, 2, and 10 microg L(-1)) under two oxygen levels (normoxia PO2 = 21 kPa and Hypoxia PO2 = 6 kPa). The expression level of various genes involved in the mitochondrial respiratory chain, in the cellular response to metal and oxidative stresses, was investigated. Our results showed that hypoxia enhances (1) ventilation of the postlarval stage and (2) Cd accumulation in gills only at the lowest metal water concentration tested (2 microg Cd L(-1)). At the gene level, Cd exposure mimics the effect of hypoxia since we observed a decrease in expression of genes involved in the respiratory chain and in the defense against oxidative stress.     

Optimization of Advanced Live-Cell Imaging through Red/Near-Infrared Dye Labeling and Fluorescence Lifetime-Based Strategies

Fluorescence microscopy is essential for a detailed understanding of cellular processes; however, live-cell preservation during imaging is a matter of debate. In this study, we proposed a guide to optimize advanced light microscopy approaches by reducing light exposure through fluorescence lifetime (τ) exploitation of red/near-infrared dyes. Firstly, we characterized key instrumental elements which revealed that red/near-infrared laser lines with an 86x (Numerical Aperture (NA) = 1.2, water immersion) objective allowed high transmission of fluorescence signals, low irradiance and super-resolution. As a combination of two technologies, i.e., vacuum tubes (e.g., photomultiplier) and semiconductor microelectronics (e.g., avalanche photodiode), type S, X and R of hybrid detectors (HyD-S, HyD-X and HyD-R) were particularly adapted for red/near-infrared photon counting and τ separation. Secondly, we tested and compared lifetime-based imaging including coarse τ separation for confocal microscopy, fitting and phasor plot analysis for fluorescence lifetime microscopy (FLIM), and lifetimes weighting for enhanced stimulated emission depletion (STED) nanoscopy, in light of red/near-infrared multiplexing. Mainly, we showed that the choice of appropriate imaging approach may depend on fluorochrome number, together with their spectral/lifetime characteristics and STED compatibility. Photon-counting mode and sensitivity of HyDs together with phasor plot analysis of fluorescence lifetimes enabled the flexible and fast imaging of multi-labeled living H28 cells. Therefore, a combination of red/near-infrared dyes labeling with lifetime-based strategies offers new perspectives for live-cell imaging by enhancing sample preservation through acquisition time and light exposure reduction.     

Optimization of star-oriented and layer-oriented wavefront sensing concepts for ground layer adaptive optics

Multiconjugate adaptive optics is one of the major challenges in adaptive optics. It requires the measurement of the volumic distribution of the turbulence. Two wavefront sensing (WFS) concepts have been proposed to perform the wavefront analysis for such systems: the star-oriented and layer-oriented approaches. We give a performance analysis and a comparison of these two concepts in the framework of the simplest of the multi-guide-star adaptive optics systems, that is, ground layer adaptive optics. A phase-related criterion is proposed to assess analytically the performance of both concepts. This study highlights the main advantages and drawbacks of each WFS concept and shows how it is possible to optimize the concepts with respect to the signal to noise ratio on the phase measurement. A comparison of their optimized versions is provided and shows that one can expect very similar performance with the two optimized concepts.     

Design and Synthesis of Dihydroxamic Acids as HDAC6/8/10 Inhibitors

We report the synthesis and evaluation of a class of selective multitarget agents for the inhibition of HDAC6, HDAC8, and HDAC10. The concept for this study grew out of a structural analysis of the two selective inhibitors Tubastatin A (HDAC6/10) and PCI-34051 (HDAC8), which we recognized share the same N-benzylindole core. Hybridization of the two inhibitor structures resulted in dihydroxamic acids with benzyl-indole and -indazole core motifs. These substances exhibit potent activity against HDAC6, HDAC8, and HDAC10, while retaining selectivity over HDAC1, HDAC2, and HDAC3. The best substance inhibited the viability of the SK-N-BE(2)C neuroblastoma cell line with an IC₅₀ value similar to a combination treatment with Tubastatin A and PCI-34051. This compound class establishes a proof of concept for such hybrid molecules and could serve as a starting point for the further development of enhanced HDAC6/8/10 inhibitors.