Surface Activity of the Triflate Ion at the Air/Water Interface and Properties of N,N,N-Trimethyl-N-Dodecylammonium Triflate Aqueous Solutions

The surface activity of salts added to water is Air orders of magnitude lower than that of surfactants. Sodium trifluoromethanesulfonate (NaTf) produced a change in surface tension. with concentration, Delta gamma/Delta c, of -13.2 mN.L/m.mol. This value is ca. 4-fold larger than those of simple salts and that of methanesulfonate. This unexpected surface effect suggested that positively charged micelles containing Tf could exhibit interesting properties. Dodecyltrimethylammonium triflate (DTATf) had a higher Kraft temperature (37 degrees C) and a lower cmc (5 x 10(-3)M) and degree of dissociation (0.11) than the chloride and bromide salts of DTA. Above the Kraft temperature, at a characteristic temperature t(1), the addition of NaTf above 0.05 M. to a DTATf solution induced phase separation. By increasing the temperature of the two-phase system to above t(1), a homogeneous, transparent solution was obtained at a characteristic temperature t(2). These results, together with well-known triflate properties, led us to suggest that the Tf ion pairs With DTA and that the -CF(3) group may be dehydrated in the interfacial region, resulting in new and interesting self-aggregated structures.

Detection and Characterization of Cholesterol-Oxidized Products Using HPLC Coupled to Dopant Assisted Atmospheric Pressure Photoionization Tandem Mass Spectrometry

Oxidation of cholesterol (Ch) by a variety of reactive oxygen species gives rise mainly to hydroperoxides and aldehydes. Despite the growing interest in Ch-oxidized products, the detection and characterization of these products is still a matter of concern. In this work, the main Ch-oxidized products, namely, 3 beta-hydroxycholest-5-ene-7 alpha-hydroperoxide (7 alpha-OOH), 3 beta-5 alpha-cholest-6-ene-5-hydroperoxide (5 alpha-OOH), 3 beta-hydroxycholest-4-ene-6 alpha-hydroperoxide (6 alpha-OOH), 3 beta-hydroxycholest-4-ene-6 beta-hydroperoxide (6 beta-OOH), and 3 beta-hydroxy-5 beta-hydroxy-B-norcholestane-6 beta-carboxaldehyde (ChAld), were detected in the same analysis using high-performance liquid chromatography (HPLC) coupled to dopant assisted atmospheric pressure photoionization tandem mass spectrometry. The use of selected reaction monitoring mode (SRM) allowed a sensitive detection of each oxidized product, while the enhanced product ion mode (EPI) helped to improve the confidence of the analyses. Isotopic labeling experiments enabled one to elucidate mechanistic features during fragmentation processes. The characteristic fragmentation pattern of Ch-oxidized products is the consecutive loss of 1120 molecules, yielding cationic fragments at m/z 401, 383, and 365. Homolytic scissions of the peroxide bond are also seen. With (18)O-labeling approach, it was possible to establish a fragmentation order for each isomer. The SRM transitions ratio along with EPI and (18)O-labeled experiments give detailed information about differences for water elimination, allowing a proper discrimination between the isomers:Phis is of special interest considering the emerging role of Ch-oxidized products in the development of diseases.

1,4-Dioxane enhances properties and biocompatibility of polyanionic collagen for tissue engineering applications

Polyanionic collagen obtained from bovine pericardial tissue submitted to alkaline hydrolysis is an acellular matrix with strong potential in tissue engineering. However, increasing the carboxyl content reduces fibril formation and thermal stability compared to the native tissues. In the present work, we propose a chemical protocol based on the association of alkaline hydrolysis with 1,4-dioxane treatment to either attenuate or revert the drastic structural modifications promoted by alkaline treatments. For the characterization of the polyanionic membranes treated with 1,4-dioxane, we found that (1) scanning electron microscopy (SEM) shows a stronger reorientation and aggregation of collagen microfibrils; (2) histological evaluation reveals recovering of the alignment of collagen fibers and reassociation with elastic fibers; (3) differential scanning calorimetry (DSC) shows an increase in thermal stability; and (4) in biocompatibility assays there is a normal attachment, morphology and proliferation associated with high survival of the mouse fibroblast cell line NIH3T3 in reconstituted membranes, which behave as native membranes. Our conclusions reinforce the ability of 1,4-dioxane to enhance the properties of negatively charged polyanionic collagen associated with its potential use as biomaterials for grafting, cationic drug- or cell-delivery systems and for the coating of cardiovascular devices.

On the use of 2,1,3-benzothiadiazole derivatives as selective live cell fluorescence imaging probes

Newly designed 2,1,3-benzothiadiazole-containing fluorescent probes with four excited state intramolecular proton transfer (ESIPT) sites were successfully tested in live cell-imaging assays using a confluent monolayer of human stem-cells (tissue). All tested dyes were compared with the commercially available DAPI and gave far better results. (c) 2010 Elsevier Ltd. All rights reserved.

Electrostatic and Hydrophobic Interactions Involved in CNT Biofunctionalization with Short ss-DNA

This work is aimed at studying the adsorption mechanism of short chain 20-mer pyrimidinic homoss-DNA (oligodeoxyribonucleotide, ODN: polyC(20) and polyT(20)) onto CNT by reflectometry. To analyze the experimental data, the effective-medium theory using the Bruggemann approximation represents a Suitable optical model to account for the surface properties (roughness, thickness, and optical constants) and the size of the adsorbate. Systematic information about the involved interactions is obtained by changing the physicochemical properties of the system. Hydrophobic and electrostatic interactions are evaluated by comparing the adsorption oil hydrophobic CNT and oil hydrophilic silica and by Modulating the ionic Strength With and without Mg(2+). The ODN adsorption process oil CNT is driven by hydrophobic interactions only when the electrostatic repulsion is Suppressed. The adsorption mode results in ODN molecules in a side-on orientation with the bases (nonpolar region) toward the surface. This unfavorable orientation is partially reverse by adding Mg(2+). On the other hand, the adsorption oil silica is dominated by the strong repulsive electrostatic interaction that is screened at high ionic strength or mediated by Mg(2+). The cation-mediated process induces the interaction of the phosphate backbone (polar region) with the surface, leaving the bases free for hybridization. Although the general adsorption behavior of the pyrimidine bases is the same, polyC(20) presents higher affinity for the CNT Surface due to its acid-base properties.

Sequential injection analysis (SIA) and response surface methodology: A versatile small volume approach for optimization of photo-Fenton processes

Optimization of photo-Fenton degradation of copper phthalocyanine blue was achieved by response surface methodology (RSM) constructed with the aid of a sequential injection analysis (SIA) system coupled to a homemade photo-reactor. Highest degradation percentage was obtained at the following conditions [H(2)O(2)]/[phthalocyanine] = 7, [H(2)O(2)]/[FeSO(4)] = 10, pH = 2.5, and stopped flow time in the photo reactor = 30 s. The SIA system was designed to prepare a monosegment containing the reagents and sample, to pump it toward the photo-reactor for the specified time and send the products to a flow-through spectrophotometer for monitoring the color reduction of the dye. Changes in parameters such as reagent molar ratios. residence time and pH were made by modifications in the software commanding the SI system, without the need for physical reconfiguration of reagents around the selection valve. The proposed procedure and system fed the statistical program with degradation data for fast construction of response surface plots. After optimization, 97% of the dye was degraded. (C) 2009 Elsevier B.V. All rights reserved.

A new micro/nanoencapsulated porphyrin formulation for PDT treatment

The highly hydrophobic 5,10,15-triphenyl-20-(3-N-methylpyridinium-yl)porphyrin(3MMe)cationic species was synthesized, characterized and encapsulated in marine atelocollagen/xanthane gum microcapsules by the coacervation method. Further reduction in the capsule size, from several microns down to about 300-400 nm, was carried out successfully by ultrasonic processing in the presence of up to 1.6% Tween 20 surfactant, without affecting the distribution of 3MMe in the oily core. The resulting creamlike product exhibited enhanced photodynamic activity but negligible cytotoxicity towards HeLa cells. The polymeric micro/nanocapsule formulation was found to be about 4 times more phototoxic than the respective phosphatidylcholine lipidic emulsion, demonstrating high potentiality for photodynamic therapy applications. (C) 2009 Elsevier B.V. All rights reserved.

Peat as a natural solid-phase for copper preconcentration and determination in a multicommuted flow system coupled to flame atomic absorption spectrometry

The physical and chemical characteristics of peat were assessed through measurement of pH, percentage of organic matter, cationic exchange capacity (CEC), elemental analysis, infrared spectroscopy and quantitative analysis of metals by ICP OES. Despite the material showed to be very acid in view of the percentage of organic matter, its CEC was significant, showing potential for retention of metal ions. This characteristic was exploited by coupling a peat mini-column to a flow system based on the multicommutation approach for the in-line copper concentration prior to flame atomic absorption spectrometric determination. Cu(II) ions were adsorbed at pH 4.5 and eluted with 0.50 mol L(-1) HNO(3). The influence of chemical and hydrodynamic parameters, such as sample pH, buffer concentration, eluent type and concentration, sample flow-rate and preconcentration time were investigated. Under the optimized conditions, a linear response was observed between 16 and 100 mu g L(-1), with a detection limit estimated as 3 mu g L(-1) at the 99.7% confidence level and an enrichment factor of 16. The relative standard deviation was estimated as 3.3% (n = 20). The mini-column was used for at least 100 sampling cycles without significant variation in the analytical response. Recoveries from copper spiked to lake water or groundwater as well as concentrates used in hemodialysis were in the 97.3-111 % range. The results obtained for copper determination in these samples agreed with those achieved by graphite furnace atomic absorption spectrometry (GFAAS) at the 95% confidence level. (C) 2009 Elsevier B.V. All rights reserved.

Probing the binding of tetraplatinum(pyridyl)porphyrin complexes to DNA by means of surface plasmon resonance

Tetrapyridylporphyrins containing four chloro(2,2`-bipyridine)platinum(II) complexes attached at the meta (3-H(2)TPtPyP) and para (4-H(2)TPtPyP) positions of the peripheral pyridine ligands were synthesized and their interaction with DNA investigated. The compounds were isolated in the solid state and characterized by means of spectroscopic and analytical techniques. According to molecular simulations, the two isomers exhibit contrasting structural characteristics, consistent with a saddle shape configuration for 3-H(2)TPtPyP and a planar geometry for 4-H(2)TPtPyP. Surface plasmon resonance studies were carried out on the interaction of the complexes with calf thymus DNA, revealing a preferential binding of 3-H(2)TPtPyP, presumably at the DNA major grooves. (C) 2008 Elsevier Inc. All rights reserved.

Electroluminescent devices based on rare-earth tetrakis beta-diketonate complexes

In this paper the synthesis, photo luminescence and electroluminescence investigation of the novel tetrakis beta-diketonate of rare-earth complexes such as M[Eu(dbM)(4)] and M[Tb(acac)(4)] with a variety of cationic ligands, M=Li(+), Na(+) and K(+) have been investigated. The emission spectra of the Eu(3+) and Tb(3+) complexes displayed characteristic narrow bands arising from intraconfigurational transitions of trivalent rare-earth ions and exhibited red color emission for the Eu(3+) ion ((5)D(0) -> F(J), J=0-6) and green for the Tb(3+) ion ((5)D(4) -> (7)F(J), J = 6-0). The lack of the broaden emission bands arising from the ligands suggests the efficient intramolecular energy transfer from the dbm and acac ligands to Eu(3+) and Tb(3+) ions, respectively. In accordance to the expected, the values of PL quantum efficiency (eta) of the emitting (5)D(0) state of the tetrakis(beta-diketonate) complexes of Eu(3+) were higher compared with those tris-complexes. Therefore, organic electroluminescent (EL) devices were fabricated with the structure as follows: indium tin oxide (ITO)/hole transport layer (HTL) NPB or MTCD/emitter layer M[RE(beta-diketonate)(4)] complexes)/Aluminum (Al). All the films were deposited by thermal evaporation carried out in a high vacuum environment system. The OLED light emission was independent of driving voltage, indicating that the combination of charge carriers generates excitons within the M[RE(beta-diketonate)(4)] layers, and the energy is efficiently transferred to RE(3+) ion. As a best result, a pure red and green electroluminescent emission was observed from the Eu(3+) and Tb(3+) devices, confirmed by (X,Y) color coordinates. (C) 2008 Elsevier B.V. All rights reserved.

Oxidation of anilinium ions intercalated in montmorillonite clay by electrochemical route

Resonance Raman, FTIR, X-ray diffraction, UV-vis-NIR, electron paramagnetic resonance, X-ray absorption at Si K-edge and electron microscopy were employed for characterizing the products formed through electrochemical oxidation of intercalated anilinium ions inside the cationic montmorillonite (MMT) clay. The layer silicate structure was not affected by the anilinium oxidation between the layers. The intercalated products present only an electronic absorption band at 400 nm, very low conductivity (ca. 10(-7) S cm(-1)) and their Raman spectrum displays bands, with high relative intensities, assigned to the benzidine dication, indicating that this product was formed in high amount. Nevertheless, bands that can be correlated to phenazine-like segments and 1,4-phenylenediamine repeat units (PANI like segments) are also observed. The very low EPR signal indicates that diamagnetic species are predominant. All results are compared to those obtained by anilinium-MMT chemically oxidized by persulfate and the differences are pointed out. (C) 2008 Elsevier B.V. All rights reserved.

Chemiluminescence as a PDT light source for microbial control

The photodynamic therapy (PDT) is a combination of using a photosensitizer agent, light and oxygen that can cause oxidative cellular damage. This technique is applied in several cases, including for microbial control. The most extensively studied light sources for this purpose are lasers and LED-based systems. Few studies treat alternative light sources based PDT. Sources which present flexibility, portability and economic advantages are of great interest. In this study, we evaluated the in vitro feasibility for the use of chemiluminescence as a PDT light source to induce Staphylococcus aureus reduction. The Photogem (R) concentration varied from 0 to 75 mu g/ml and the illumination time varied from 60 min to 240 min. The long exposure time was necessary due to the low irradiance achieved with chemiluminescence reaction at mu W/cm(2) level. The results demonstrated an effective microbial reduction of around 98% for the highest photosensitizer concentration and light dose. These data suggest the potential use of chemiluminescence as a light source for PDT microbial control, with advantages in terms of flexibility, when compared with conventional sources. (C) 2011 Elsevier B.V. All rights reserved.

Surface-enhanced Raman study of electrochemical and photocatalytic degradation of the azo dye Janus Green B

The photocatalytic degradation of Janus Green B azo dye over silver modified titanium dioxide films was investigated by surface-enhanced Raman spectroscopy (SERS). An optimized SERS-active substrate was employed to study the photodegradation reaction of Janus Green B. Considering that photocatalytic degradation processes of organic molecules adsorbed on TiO2 might involve either their oxidation or reduction reaction, the vibrational spectroelectrochemical study of the dye was also performed, in order to clarify the transformations involved in initial steps of its photochemical decomposition. In order to understand the changes in Raman spectra of Janus Green B after photodegradation and/or electrochemical processes, a vibrational assignment of the main Raman active modes of the dye was carried out, based on a detailed resonance Raman profile. Products formed by electrochemical and photochemical degradation processes were compared. The obtained results revealed that the first steps of the degradation process of Janus Green B involve a reductive mechanism. (C) 2007 Published by Elsevier B.V.

Determination of ciclopirox olamine in pharmaceutical products by capillary electrophoresis with capacitively coupled contactless conductivity detection

This paper describes the determination of ciclopirox olamine in pharmaceutical formulations using capillary electrophoresis with capacitively coupled contactless conductivity detection. In an alkaline medium, ciclopirox olamine is converted into an anionic species and its detection is possible in capillary electrophoresis with capacitively coupled contactless conductivity detection without an electroosmotic flow modifier, because it is a low-mobility species. A linear working range from 2.64 to 264 mu g/mL in sodium hydroxide electrolyte as well as low detection limit (0.39 mu g/mL) and a good repeatability (RSD = 3.4% for 264 mu g/mL ciclopirox solution (n = 10)) were achieved. It was also possible to determine olamine in its cationic form when acetic acid was used as the electrolyte solution. The results obtained include a linear range from 26.4 to 184.8 mu g/mL and a detection limit of 2.6 mu g/mL olamine. The proposed methods were applied to the analysis of commercial pharmaceutical products and the results were compared with the values indicated by the manufacturer as well as those obtained using a titrimetric method recommended by American Pharmacopoeia.

Spectroscopic study of the polymerization of intercalated anilinium ions in different montmorillonite clays

The polymerization of the intercalated aniline ions was studied in three different clays, Swy2-montmorillonite (MMT), synthetic mica-montmorillonite (Synl) and pillarized Swy2-montmorillonite (PILC). PANI is formed between the MMT and Syn1 clay layers, being confirmed by the shift of d(001) peak in the X-ray pattern. X-ray Absorption near to Si K edge (Si K XANES) data show that the structures of clays are preserved after the polymerization process and in addition to the SEM images show that morphologies of the clays are maintained after polymerization, indicating no polymerization in their external surface. UV-vis-NIR and resonance Raman data display that the PANI formed in Syn1 galleries has higher amount of phenazinic rings than observed for PANI intercalated in montmorillonite (MMT) clay. No polymer formation was detected in the PILC. N K XANES and EPR spectroscopies show the presence of azo and radical nitrogen in intercalated PAN! chains. Hence, the results are rationalized considering the structural differences between the clays for understanding the role of the anilinium polymerization within the clays galleries. (C) 2011 Elsevier B.V. All rights reserved.