Influence of microgel architecture and oil polarity on stabilization of emulsions by stimuli-sensitive core-shell poly(N-isopropylacrylamide-co-methacrylic acid) microgels: Mickering versus Pickering behavior?

Charged poly(N-isopropylacrylamide-co-methacrylic acid) [P(NiPAM-co-MAA)] microgels can stabilize thermo- and pH-sensitive emulsions. By placing charged units at different locations in the microgels and comparing the emulsion properties, we demonstrate that their behaviors as emulsion stabilizers are very different from molecular surfactants and rigid Pickering stabilizers. The results show that the stabilization of the emulsions is independent of electrostatic repulsion although the presence and location of charges are relevant. Apparently, the charges facilitate emulsion stabilization via the extent of swelling and deformability of the microgels. The stabilization of these emulsions is linked to the swelling and structure of the microgels at the oil-water interface, which depends not only on the presence of charged moieties and on solvent polarity but also on the microgel (core-shell) morphology. Therefore, the internal soft and porous structure of microgels is important, and these features make microgel-stabilized emulsions characteristically different from classical, rigid-particle-stabilized Pickering emulsions, the stability of which depends on the surface properties of the particles.     

Development of a microfluidic platform for single-cell secretion analysis using a direct photoactive cell-attaching method

A precise understanding of individual cellular processes is essential to meet the expectations of most advanced cell biology. Therefore single-cell analysis is considered to be one of possible approach to overcome any misleading of cell characteristics by averaging large groups of cells in bulk conditions. In the present work, we modified a newly designed microchip for single-cell analysis and regulated the cell-adhesive area inside a cell-chamber of the microfluidic system. By using surface-modification techniques involving a silanization compound, a photo-labile linker and the 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer were covalently bonded on the surface of a microchannel. The MPC polymer was utilized as a non-biofouling compound for inhibiting non-specific binding of the biological samples inside the microchannel, and was selectively removed by a photochemical reaction that controlled the cell attachment. To achieve the desired single-macrophage patterning and culture in the cell-chamber of the microchannel, the cell density and flow rate of the culture medium were optimized. We found that a cell density of 2.0 × 10(6) cells/ml was the appropriate condition to introduce a single cell in each cell chamber. Furthermore, the macrophage was cultured in a small size of the cell chamber in a safe way for 5 h at a flow rate of 0.2 μl/min under the medium condition. This strategy can be a powerful tool for broadening new possibilities in studies of individual cellular processes in a dynamic microfluidic device.     

Comparison between 2-hydroxypropyl-��-cyclodextrin and 2-hydroxypropyl-��-cyclodextrin for inclusion complex formation with danazol

Complexation in solution between danazol and two different cyclodextrins [2-hydroxypropyl-??-cyclodextrin (HP-??-CD) and 2-hydroxypropyl-??-cyclodextrin (HP-??-CD)] was studied using phase solubility analysis, and one- and two-dimensional ¹H-NMR. The increase of danazol solubility in the aqueous cyclodextrin solutions showed a linear relationship (A_L profile). The apparent stability constant, K _1:1, of each complex was calculated and found to be 51.7 × 10³ and 7.3 × 10³ M^?1 for danazol?CHP-??-CD and danazol?CHP-??-CD, respectively. ¹H-NMR spectroscopic analysis of varying ratios of danazol and the different cyclodextrins in a mixture of EtOD?CD₂O confirmed the 1:1 stoichiometry. Cross-peaks, from 2D ROESY ¹H-NMR spectra, between protons of danazol and H3?? and H5??of cyclodextrins, which stay inside the cyclodextrin cavity, proved the formation of an inclusion complex between danazol and the cyclodextrins. For HP-??-CD, the inclusion complex is formed by entrance of the isooxazole and the A rings of danazol in the cyclodextrin cavity. For HP-??-CD, two different inclusion structures may exist simultaneously in solution: one with the isooxazole and A ring in the cavity and the other with the C and D ring inside the cavity. DLS showed that self-aggregation of the CD??s was absent in the danazol HP-??-CD system up to a CD concentration of 10% and in the danazol HP-??-CD system up to a CD concentration of 5%.     

TPR investigations on the reducibility of Cu supported on Al2O3, zeolite Y and SAPO-5

Reducibility of Cu supported on Al₂O₃, zeolite Y and silicoaluminophosphate SAPO-5 has been investigated in dependence on the Cu content using a method combining conventional temperature programmed reduction (TPR) by hydrogen with reoxidation in N₂O followed by a second the so-called surface-TPR (s-TPR). The method enables discrimination and a quantitative estimation of the Cu oxidation states +2, +1 and 0. The quantitative results show that the initial oxidation state of Cu after calcination in air at 400 °C, independent on the nature of the support, is predominantly +2. Cu²⁺ supported on Al₂O₃ is quantitatively reduced by hydrogen to metallic Cu⁰. Comparing the TPR of the samples calcined in air and that of samples additionally pre-treated in argon reveals that in zeolite Y and SAPO-5 Cu²⁺ cations are stabilized as weakly and strongly forms. In both systems, strongly stabilized Cu²⁺ ions are not auto-reduced by pre-treatment in argon at 650 °C, but are reduced in hydrogen to form Cu⁺. The weakly stabilized Cu²⁺ ions, in contrast, may be auto-reduced by pre-treatment in argon at 650 °C forming Cu⁺ but are reduced in hydrogen to metallic Cu⁰.     

Barrier effect and coupled transport in the electrodialysis of metal complexonate solutions

The electrodialysis of an aqueous solution of an alkaline earth complex with ethylenediaminetetraacetic acid (EDTA) was studied in a wide range of current densities. The curve of the complexonate flow across an anionite membrane versus current density has three characteristic sections. The first section corresponds to a linear increase in the flow as a function of current density, the second to a decrease in the flow and decomposition of the complex (barrier effect), and the third to an increase in the complexonate flow due to the transport coupled with the flow of hydroxyl ions formed in the dissociation of water molecules at the interface of the solution and the anionite membrane. Conditions for complete separation of the singly and doubly charged cations were found.     

Droplet synthesis of well-defined block copolymers using solvent-resistant microfluidic device

Well-defined diblock copolymers were synthesized via an exothermic RAFT route by a droplet microfluidic process using a solvent-resistant and thermally stable fluoropolymer microreactor fabricated by a non-lithographic embedded template method. The resulting polymers were compared to products obtained from continuous flow capillary reactor and conventional bulk synthesis. The droplet based microreactor demonstrated superior molecular weight distribution control by synthesizing a higher molecular weight product with higher conversion and narrow polydispersity in a much shorter reaction time. The high quality of the as-synthesized block copolymer PMMA-b-PS led to a generation of micelles with a narrow size distribution that could be used as a template for well-ordered mesoporous silica with regular frameworks and high surface areas.     

On-chip multi-electrochemical sensor array platform for simultaneous screening of nitric oxide and peroxynitrite

In this work we report on the design, microfabrication and analytical performances of a new electrochemical sensor array (ESA) which allows for the first time the simultaneous amperometric detection of nitric oxide (NO) and peroxynitrite (ONOO(-)), two biologically relevant molecules. The on-chip device includes individually addressable sets of gold ultramicroelectrodes (UMEs) of 50 μm diameter, Ag/AgCl reference electrode and gold counter electrode. The electrodes are separated into two groups; each has one reference electrode, one counter electrode and 110 UMEs specifically tailored to detect a specific analyte. The ESA is incorporated on a custom interface with a cell culture well and spring contact pins that can be easily interconnected to an external multichannel potentiostat. Each UME of the network dedicated to the detection of NO is electrochemically modified by electrodepositing thin layers of poly(eugenol) and poly(phenol). The detection of NO is performed amperometrically at 0.8 V vs. Ag/AgCl in phosphate buffer solution (PBS, pH = 7.4) and other buffers adapted to biological cell culture, using a NO-donor. The network of UMEs dedicated to the detection of ONOO(-) is used without further chemical modification of the surface and the uncoated gold electrodes operate at -0.1 V vs. Ag/AgCl to detect the reduction of ONOOH in PBS. The selectivity issue of both sensors against major biologically relevant interfering analytes is examined. Simultaneous detection of NO and ONOO(-) in PBS is also achieved.     

High-throughput profiling of N-linked oligosaccharides in therapeutic antibodies using a microfluidic CD platform and MALDI-MS

Recombinant therapeutic antibodies have shown a great potential in the treatment of several severe medical conditions such as cancer and autoimmune diseases. Glycosylation plays a critical role in biological activity and immunogenic properties of these compounds. The analysis of glycan profiles is therefore necessary in many steps of the development and manufacturing process from early development to quality control of the final product. In this paper, a fast, parallel, and robust sample preparation platform for glycosylation profiling using a microfluidic compact disc (CD) is presented. A sequential process including selective capture of antibody from a crude cell supernatant using protein A beads, enzymatic release of glycans, purification with a graphitized carbon black column, and crystallisation for MALDI-TOF analysis were performed on the CD. Glycosylation profiles of an antibody intended for therapeutic use produced in two different cell lines were compared.     

Noninvasive assessment of hepatic fibrosis in patients with chronic hepatitis C using serum Fourier transform infrared spectroscopy

Assessment of liver fibrosis is of paramount importance to guide the therapeutic strategy in patients with chronic hepatitis C (CHC). In this pilot study, we investigated the potential of serum Fourier transform infrared (FTIR) spectroscopy for differentiating CHC patients with extensive hepatic fibrosis from those without fibrosis. Twenty-three serum samples from CHC patients were selected according to the degree of hepatic fibrosis as evaluated by the FibroTest: 12 from patients with no hepatic fibrosis (F0) and 11 from patients with extensive fibrosis (F3–F4). The FTIR spectra (ten per sample) were acquired in the transmission mode and data homogeneity was tested by cluster analysis to exclude outliers. After selection of the most discriminant wavelengths using an ANOVA-based algorithm, the support vector machine (SVM) method was used as a supervised classification model to classify the spectra into two classes of hepatic fibrosis, F0 and F3–F4. Given the small number of samples, a leave-one-out cross-validation algorithm was used. When SVM was applied to all spectra (n = 230), the sensitivity and specificity of the classifier were 90.1% and 100%, respectively. When SVM was applied to the subset of 219 spectra, i.e., excluding the outliers, the sensitivity and specificity of the classifier were 95.2% and 100%, respectively. This pilot study strongly suggests that the serum from CHC patients exhibits infrared spectral characteristics, allowing patients with extensive fibrosis to be differentiated from those with no hepatic fibrosis.     

An improvement of the Nevanlinna-Gundersen theorem

A well-known result of Nevanlinna states that for two nonconstant meromorphic functions f and g on the complex plane C and for four distinct values aj∈C∪{∞}, if νf−aj=νg−aj for all 1?j?4, then g is a Möbius transformation of f. In 1983, Gundersen generalized the result of Nevanlinna to the case where the above condition is replaced by: min{νf−aj,1}=min{νg−aj,1} for j=1,2 and νf−aj=νg−aj for j=3,4. In this paper, we prove that the theorem of Gundersen remains valid to the case where min{νf−aj,1}=min{νg−aj,1} for j=1,2, and min{νf−aj,2}=min{νg−aj,2} for j=3,4. Furthermore, we work on the case where {aj} are small functions.