The Effect of Enantiomer Elution Order on the Determination of Minor Enantiomeric Impurity in Ketoprofen and Enantiomeric Purity Evaluation of Commercially Available Dexketoprofen Formulations

In a recent study, opposite enantiomer elution order was observed for ketoprofen enantiomers on two amylose-phenylcarbamate-based chiral columns with the same chemical composition of the chiral selector but in one case with coated while in the other with an immobilized chiral selector. In the present study, the influence of this uncommon effect on method validation parameters for the determination of minor enantiomeric impurity in dexketoprofen was studied. The validated methods with two alternative elution orders for enantiomers were applied for the evaluation of enantiomeric impurity in six marketed dexketoprofen formulations from various vendors. In most of these formulations except one the content of enantiomeric impurity exceeded 0.1% (w/w).     

Sensitive Nucleic Acid Detection at NH2‐MWCNTs Modified Glassy Carbon Electrode and its Application for Monitoring of Gemcitabine‐DNA Interaction

An electrochemical dsDNA nanobiosensor was fabricated using amino‐functionalized multi walled carbon nanotubes modified glassy carbon electrode (NH₂fMWCNTs/GCE) for the sensitive detection of DNA bases and electrochemical monitoring of drug‐DNA interaction. The influence of functional groups on MWCNT was studied by MWCNT functionalized with NH₂ (NH₂fMWCNTs) and COOH (COOHfMWCNT) groups based on the signal of DNA bases. The modified electrodes were characterized by scanning electron microscopy. One layer of calf thymus double stranded deoxyribonucleic acid (ct‐dsDNA) was immobilized onto the NH₂fMWCNTs/GCE (dsDNA/NH₂fMWCNTs/GCE). The dsDNA/NH₂fMWCNTs/GCE were used to investigate the interaction between the dsDNA and the anticancer drug gemcitabine by differential pulse voltammetry in acetate buffer of pH 4.70. For the confirmation of interaction, the lowering in intensity of the current signals of guanine and adenine was considered as an indicator. Electrochemical impedance spectroscopy studies were performed for the comparison of the modified surfaces. In order to define and visualize the interaction mechanism between gemcitabine and dsDNA/NH₂fMWCNTs/GCE at the molecular level, in silico methods including docking and molecular dynamics simulations were employed.     

New Approaches to Synthesizing Electroactive Polymers

The chemical oxidative polymerization of aniline in a heterophase system is studied. In the presence of a solid substrate, the aniline polymerization involves two kinetically and chemically independent processes, namely, the polymerization in the bulk solution and at the substrate surface. The growth of the polyaniline coating at the substrate surface includes three successive processes: interfacial polymerization, adsorptive polymerization, and destruction of the polymer chain. The interfacial oxidative polymerization of diphenylamine and phenothiazine is examined. The yield and chemical structure of polymers is shown to depend on the polymerization conditions.     

New Methacrylate Copolymers Based on the Benzofurane Ring: Synthesis,Characterization, Monomer Reactivity Ratios and Biological Activity

The free radical copolymerization of (5-bromo-1-Benzofuran-2-yl)(phenyl)-O-methacrylketoxime (BPMKO) with 2-(4-acetylphenoxy)-2-oxoethyl-2-methylacrylate(AOEMA) has been carried out in 1, 4-dioxane at 65°C ± 1 and was analyzed by Fourier transform infrared, ¹H-NMR, ¹³C-NMR and gel permeation chromatography. Elemental analysis was used to determine the molar fractions of BPMKO and AOEMA in the copolymers. The monomer–reactivity ratios were calculated according to the general copolymerization equation using Kelen-Tüdõs and Finemann-Ross linearization methods. The reactivity ratios indicated a tendency toward random copolymerization. The polydispersity indices of the polymers were determined by gel permeation chromatography and suggested a strong tendency for chain termination by disproportionation. The thermal behaviors of copolymers with various compositions were investigated by differential scanning calorimetry and thermogravimetric analysis. The glass-transition temperature of the copolymers increased with increasing BPMKO content in the copolymers. All the products showed moderate activity against different strains of bacteria and fungi.     

Massively parallel low-cost pick-and-place of optoelectronic devices by electrochemical fluidic processing

We describe a novel electrochemical technique for the nonlithographic, fluidic pick-and-place assembly of optoelectronic devices by electrical and optical addressing. An electrochemical cell was developed that consists of indium tin oxide (ITO) and n -type silicon substrates as the two electrode materials and deionized water (R = 18 MOmega) as the electrolytic medium between the two electrodes. 0.8-20-microm-diameter negatively charged polystyrene beads, 50-100-microm-diameter SiO(2) pucks, and 50-microm LED's were successfully integrated upon a patterned silicon substrate by electrical addressing. In addition, 0.8-microm-diameter beads were integrated upon a homogeneous silicon substrate by optical addressing. This method can be applied to massively parallel assembly (>1000 x 1000 arrays) of multiple types of devices (of a wide size range) with very fast (a few seconds) and accurate positioning.     

Monitoring of oil-based polyurethane synthesis by FTIR-ATR

Oil-based polyurethanes were synthesized from triglyceride oil-based hydroxyl containing material and toluene diisocyanate or hexamethylene diisocyanate for wound dressing applications. The reactions were carried out with or without catalyst at 90 °C. The amount of free isocyanate during the reaction was determined by a FTIR-ATR method, and the results were compared with those from a back-titration method. The data obtained were used for determination of kinetic parameters.     

Oxidative polymerization of diphenylamine-2-carboxylic acid: Synthesis, structure, and properties of polymers

Polymers of diphenylamine-2-carboxylic acid are synthesized for the first time via chemical oxidative polymerization. The effects of the concentration of reagents, their ratio, and the temperature and time of reaction on the yield and chemical structure of poly(diphenylamine-2-carboxylic acid) are studied by IR and UV spectroscopy. It is shown that the growth of polymer chains proceeds through the C-C addition in the para position of phenyl rings relative to nitrogen. During the thermal oxidation of poly(diphenylamine-2-carboxylic acid), COOH groups and dopant molecules are successively eliminated; with a further increase in temperature, the polymer behaves as polydiphenylamine. The main processes of thermooxidative degradation of poly(diphenylamine-2-carboxylic acid) begin at 570°C. This value is 120°C higher than the corresponding parameter in the case of polydiphenylamine.     

Boundary-value problem for a class of second-order parameter-dependent dynamic equations on a time scale

In this study, we consider a boundary value problem generated by a second-order dynamic equation on a time scale and boundary conditions depending on the spectral parameter. We give some properties of the solutions and obtain a formulation of the number of eigenvalues of the problem.     

Separation of brombuterol enantiomers in capillary electrophoresis with cyclodextrin‐type chiral selectors and investigation of structure of selector‐selectand complexes using nuclear magnetic resonance spectroscopy

The major goal of this study was to determine the affinity pattern of brombuterol (BB) enantiomers toward various cyclodextrins (CD) and to evaluate the potential of NMR spectroscopy for understanding fine mechanisms of interactions between CDs and BB enantiomers. Separation of BB enantiomers was performed in a fused‐silica capillary using a phosphate buffer, pH 2.5, at the room temperature in the normal polarity mode. It was shown once again that CE in combination with NMR spectroscopy represents a very sensitive tool for studies of affinity patterns and structure of CD complexes with chiral guests. Although opposite affinity patterns of BB enantiomers were observed toward native β‐ and γ‐CDs, no significant differences between the structures of the complexes of these two CDs with BB were detected by NMR spectroscopy. In contrary to this, the opposite affinity pattern of BB enantiomers toward β‐CD and its two sulfated derivatives, heptakis (2,3‐O‐diacetyl‐6‐sulfo)‐β‐CD (HDAS‐β‐CD) and heptakis (2‐O‐methyl‐3,6‐di‐O‐sulfo)‐β‐CD (HMDS‐β‐CD) was associated with major differences in the structure of the complexes. In addition, it was shown again that HMDS‐β‐CD provides separation of enantiomers without formation of inclusion‐type complex with the chiral analyte.