Direct patterning of composite biocompatible microstructures using microfluidics

This study demonstrates a versatile and fast method for patterning three-dimensional (3D) monolithic microstructures made of multiple (up to 24 demonstrated) types of materials, all spatially aligned, inside a microchannel. This technique uses confocal scanning or conventional fluorescence microscopy to polymerize selected regions of a photocurable material, and microfluidics to automate the delivery of a series of washes and photocurable reagents. Upon completion of lithographic cycles, the aligned 3D microstructures are suitable for microfluidic manipulation and analysis. We demonstrated the fabrication of composite 3D microstructures with various geometries, size scales (up to 1 mm2), spatial resolution (down to 3 microm), and materials. For a typical multi-cycle process, the total fabrication time was tens of minutes, compared to tens of hours for conventional methods. In the case of 3D hydrogels, a potential use is the direct patterning of inhomogeneous 3D microenvironments for studying cell behavior.     

Core-modified, meso-alkylidenyl porphyrins and their expanded analogues: a new family of nonplanar porphyrinoids

New core-modified, meso-alkylidenyl porphyrinoids bearing multiple exocyclic double bonds were synthesized and characterized. The synthesis was accomplished using a typical "3 + 1"-type condensation approach. Stable exocyclic tautomers bearing double bonds at the meso positions, as well the corresponding endocyclic tautomers, were isolated in the case of both thiabenziporphyrin and thiapyriporphyrin products prepared in the course of this study. On the other hand, only the exocyclic tautomer was isolated in the case of the congeneric oxapyriporphyrin and oxabenziporphyrin. Expanded analogues of the exocyclic forms of oxabenziporphyrin and thiabenziporphyrin were also isolated as minor products. A single-crystal X-ray diffraction analysis of the expanded thiabenziporphyrin (20) revealed that all four pyrrole rings displayed an inverted geometry, presumably reflecting the strong hydrogen-bonding extant between the pyrrole N-H proton and the carbonyl group of the malonate moiety in the solid state. On the other hand, the expanded oxabenziporphyrin (14) was found to possess a severely distorted geometry with only one pyrrole ring being inverted. Careful analysis of the structure revealed that the solid-state geometry of the expanded macrocycles correlates well with the internal angle defined by the 2- and 5 substituents and the centers of the furan (14) or thiophene (20) subunits.     

Determination of trace level chemical warfare agents in water and slurry samples using hollow fibre-protected liquid-phase microextraction followed by gas chromatography-mass spectrometry

A simple and solvent-minimised sample preparation technique based on hollow fibre-protected liquid-phase microextraction was investigated for the gas chromatography/mass spectrometric analysis of chemical warfare agents in water and slurry samples. The chemical warfare agents included four nerve agents and a blister agent. Parameters such as extraction solvent, salt concentration, stirring speed and extraction time were optimised using spiked deionised water samples. The technique provided a linear range of two orders of magnitude, good repeatability (RSDs < 10%, n = 6), good linearity (r2 >or= 0.995) and limits of detection (LODs) in the range of 0.02-0.09 microg l(-1) (S/N = 3) under full scan mode. The optimised technique was also applied to more complex slurry samples and similar precision (RSD < 15%, n = 3) and limits of detection (0.02-0.2 microgl(-1), S/N = 3) were obtained.     

Continuous flow microextraction combined with high-performance liquid chromatography for the analysis of pesticides in natural waters

Continuous flow microextraction (CFME) combined with high-performance liquid chromatography-ultraviolet (HPLC-UV) detection has been applied to the analysis of five widely used pesticides, simazine, fensulfothion, etridiazole, mepronil and bensulide, present at trace levels in water samples. CFME employs a single organic solvent drop positioned at the tip of a polyether ether ketone (PEEK) tubing, which is immersed in a continuous flowing aqueous sample solution in a 0.5-ml glass chamber. The PEEK tubing acts as the organic drop holder and fluid delivery duct. Analytes are partitioned between the organic drop and the bulk sample solution. Important extraction factors including type of solvent, its volume, sample solution flow rate, extraction time, its pH and addition of salt were investigated. All pesticides exhibit good linearity in the investigated concentration range of 25-250 ng ml(-1) with coefficients of determination (R2) ranging from 0.9879 to 0.9999 under the optimized conditions. Detection limits lower than 4 ng ml(-1) were obtained for all analytes. The method was evaluated by analyzing natural water sample collected from a reservoir in Singapore. This study for the first time demonstrated the compatibility of CFME procedure and HPLC separation.     

Functional magnetic resonance cholangiography with Gd-EOB-DTPA: A study in healthy volunteers

Purpose

To describe the patterns of bile distribution in the biliary tree, duodenum, jejunum, and stomach, and to determine the gallbladder ejection fraction (GBEF) by using functional magnetic resonance cholangiography (MRC) with gadolinium-ethoxybenzyl-diethylenetriamine penta-acetic acid (Gd-EOB-DTPA) in healthy volunteers.

Materials and Methods

Forty subjects were included in this study. After conventional MRC, pre-fatty meal MRC (PRFM) was obtained at 30, 40, 50, and 60 min after contrast agent injection. Then, post-fatty meal MRC (POFM) was obtained every 10 min for 1 h. We assessed the PRFM and POFM for opacification of contrast agent in the first- and second-order intrahepatic ducts (IHDs) and the common bile duct (CBD). Contrast agent opacification in the cystic duct was assessed, and the percentage volume of contrast agent filling in the gallbladder (GB) was calculated on PRFM. We calculated the GBEF and assessed the presence of contrast agent in the GB, duodenum, jejunum, and stomach.

Results

Thirty-six (90%) subjects showed grade 3 CBD opacification (visible contrast and well-defined bile duct border) on 60-min PRFM. Thirty-four (85%) subjects showed grade 3 first-order IHD opacification on 60-min PRFM. All (100%) subjects showed cystic duct opacification of contrast agent, and the average percentage volume of contrast agent filling in the GB was 68.81% ± 16.84% on 60-min PRFM. The GBEF at 30-min POFM was 35.00% ± 18.26%. Ten (25%) subjects had no contrast agent in the stomach and small bowel on all PRFMs. Twelve (30%) subjects had contrast medium in the stomach on PRFM and/or POFM.

Conclusions

Functional MRC with Gd-EOB-DTPA can allow determining the distribution of bile in the biliary tree and small intestine, as well as the GBEF.     

Deposition of osmium and ruthenium thin films from organometallic cluster precursors

Single‐source organometallic precursors based on a number of homometallic clusters as well as heterometallic cluster RuOs₃(CO)₁₃(µ‐H)₂ have been used for the chemical vapor deposition of osmium films and osmium–ruthenium alloy films, respectively. Copyright © 2009 John Wiley & Sons, Ltd.     

Investigation of the scanning tunneling microscopy image, the stacking pattern, and the bias-voltage-dependent structural instability of 1,10'-phenanthroline molecules adsorbed on Au(111) in terms of electronic structure calculations

A self-assembled monolayer of 1,10'-phenanthroline (phen) molecules on Au(111) was found to undergo a structural phase transition when the bias voltage is switched in scanning tunneling microscopy (STM) experiments (Phys. Rev. Lett. 1995, 75, 2376; Surf. Sci. 1997, 389, 19). The nature of two bright spots representing each phen molecule in the high-resolution STM images of phen molecules on Au(111) was identified by calculating the partial density plots for a monolayer of phen molecules adsorbed on Au(111) with tight-binding electronic structure calculations. The stacking pattern of chains of phen molecules on Au(111) was explained by studying the intermolecular interactions between phen molecules on the basis of first-principles electronic structure calculations for a phen dimer, (phen)(2). The structural instability of phen molecule arrangement caused by the bias-voltage switch was probed by estimating the adsorbate-surface interaction energy with the point-charge approximation for Au(111).     

Dynamic hollow fiber-supported headspace liquid-phase microextraction

With the increasing concern over deteriorating environmental quality, the analysis of organic pollutants in air, water, and soil has become critically important. The development of simple, efficient, and inexpensive analytical sample pretreatment is crucial for monitoring and evaluating the environment. In this work, a dynamic hollow-fiber supported headspace liquid-phase microextraction (DHF-HS-LPME) approach was developed. In dynamic LPME, the extracting solvent is held within a hollow fiber, affixed to a syringe needle and immersed in the sample solution, and is moved to-and-fro by using a programmable syringe pump. The movement facilitates mass transfer from the sample to the solvent. Here, a similar approach was adopted, except that extraction was from the headspace rather than by direct immersion. Analysis of the extract was carried out by gas chromatography-mass spectrometry. The effect of sampling temperature, water, salt, dwelling time were investigated. Results indicated that this novel headspace microextraction method gave good analyte-enrichment factors, linear range, limits of detection and repeatability, all of which were evaluated by extracting PAHs from soil samples. This technique represents an inexpensive, convenient, fast and simple sample preparation of this class of semi-volatile organic compounds.