Langmuir and Langmuir-Blodgett (LB) films of poly [(2-methoxy,5-n-octadecyl)-p-phenylenevinylene] (OC1OC18-PPV)

A PPV derivative, poly(2-methoxy,5-(n-octadecyl)-p-phenylenevinylene) (OC1OC18-PPV), has been synthesized via the Gilch route and used to fabricate Langmuir and Langmuir-Blodgett (LB) films. True monomolecular films were formed at the air/water interface, which were successfully transferred onto different types of substrate. Using UV-visible absorption, FTIR, fluorescence and Raman scattering spectroscopies we observed that the polymer molecules were randomly distributed in the LB film, with no detectable anisotropy. This is in contrast to the anisotropic LB films of a previously reported PPV derivative, poly(2-methoxy-5-n-hexyloxy)-p-phenylenevinylene (OC1OC6-PPV), which is surprising because the longer chain of OC1OC18-PPV investigated here was expected to lead to more ordered films. As a consequence of the lack of order, LB films of OC1OC18-PPV exhibit lower photoconductivity and require higher operating voltage in a polymer light-emitting diode (PLED) in comparison with LB films of OC1OC6-PPV. This result confirms the importance of molecular organization in the LB film to obtain efficient PLEDs. (c) 2005 Elsevier Ltd. All rights reserved.

Fabrication, structural characterization, and applications of Langmuir and Langmuir-Blodgett films of a poly(azo)urethane

The synthesis of a poly(azo)urethane by fixing CO2 in bis-epoxide followed by a polymerization reaction with an azodiamine is presented. Since isocyanate is not used in the process, it is termed clean method and the polymers obtained are named NIPUs (non-isocyanate polyurethanes). Langmuir films were formed at the air-water interface and were characterized by surface pressure vs mean molecular area per met unit (Pi-A) isotherms. The Langmuir monolayers were further studied by running stability tests and cycles of compression/expansion (possible hysteresis) and by varying the compression speed of the monolayer formation, the subphase temperature, and the solvents used to prepare the spreading polymer solutions. The Langmuir-Blodgett (LB) technique was used to fabricate ultrathin films of a particular polymer (PAzoU). It is possible to grow homogeneous LB films of up to 15 layers as monitored using UV-vis absorption spectroscopy. Higher number of layers can be deposited when PAzoU is mixed with stearic acid, producing mixed LB films. Fourier transform infrared (FTIR) absorption spectroscopy and Raman scattering showed that the materials do not interact chemically in the mixed LB films. The atomic force microscopy (AFM) and micro-Raman technique (optical microscopy coupled to Raman spectrograph) revealed that mixed LB films present a phase separation distinguishable at micrometer or nanometer scale. Finally, mixed and neat LB films were successfully characterized using impedance spectroscopy at different temperatures, a property that may lead to future application as temperature sensors. Principal component analysis (PCA) was used to correlate the data.

Electrical characterization of poly(amide-imide) for application in organic field effect devices

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Determining the interfacial density of states in metal-insulator-semiconductor devices based on poly(3-hexylthiophene)

Low frequency admittance measurements are used to determine the density of interface states in metal-insulator-semiconductor diodes based on the unintentionally doped, p-type semiconductor poly(3-hexylthiophene). After vacuum annealing at 90 degrees C, interface hole trapping states are shown to be distributed in energy with their density decreasing approximately linearly from similar to 20x10(10) to 5x10(10) cm(-2) eV(-1) over an energy range extending from 0.05 to 0.25 eV above the bulk Fermi level. (c) 2008 American Institute of Physics.

Fabrication and characterization of chemical sensors made from nanostructured films of poly(o-ethoxyaniline) prepared with different doping acids

Chemical sensors made from nanostructured films of poly(o-ethoxyaniline) POEA and poly(sodium 4-styrene sulfonate) PSS are produced and used to detect and distinguish 4 chemicals in solution at 20 mM, including sucrose, NaCl, HCl, and caffeine. These substances are used in order to mimic the 4 basic tastes recognized by humans, namely sweet, salty, sour, and bitter, respectively. The sensors are produced by the deposition of POEA/PSS films at the top of interdigitated microelectrodes via the layer-by-layer technique, using POEA solutions containing different dopant acids. Besides the different characteristics of the POEA/PSS films investigated by UV-Vis and Raman spectroscopies, and by atomic force microscopy.. it is observed that their electrical response to the different chemicals in liquid media is very fast, in the order of seconds, systematical, reproducible, and extremely dependent on the type of acid used for film fabrication. The responses of the as-prepared sensors are reproducible and repetitive after many cycles of operation. Furthermore, the use of an "electronic tongue" composed by an array of these sensors and principal component analysis as pattern recognition tool allows one to reasonably distinguish test solutions according to their chemical composition. (c) 2007 Published by Elsevier B.V.

Molecular architecture of thin films fabricated via physical vapor deposition and containing a poly(azo)urethane

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Inhibitory Effect of Gallic Acid and Its Esters on 2,2 '-Azobis(2-amidinopropane)hydrochloride (AAPH)-Induced Hemolysis and Depletion of Intracellular Glutathione in Erythrocytes

The protective effect of gallic acid and its esters, methyl, propyl, and lauryl gallate, against 2,2'-azobis(2-amidinopropane)hydrochloride (AAPH)-induced hemolysis and depletion of intracellular glutathione (GSH) in erythrocytes was studied. The inhibition of hemolysis was dose-dependent, and the esters were significantly more effective than gallic acid. Gallic acid and its esters were compared with regard to their reactivity to free radicals, using the DPPH and AAPH/pyranine free-cell assays, and no significant difference was obtained. Gallic acid and its esters not only failed to inhibit the depletion of intracellular GSH in erythrocytes induced by AAPH but exacerbated it. Similarly, the oxidation of GSH by AAPH or horseradish peroxidase/H(2)O(2) in cell-free systems was exacerbated by gallic acid or gallates. This property could be involved in the recent findings on proapoptotic and pro-oxidant activities of gallates in tumor cells. We provide evidence that lipophilicity and not only radical scavenger potency is an important factor regarding the efficiency of antihemolytic substances.

Loss of nuclear poly(A)-binding protein 1 causes defects in myogenesis and mRNA biogenesis

The nuclear poly(A)-binding protein 1 (PABPN1) is a ubiquitously expressed protein that plays a critical role in polyadenylation. Short expansions of the polyalanine tract in the N-terminus of PABPN1 lead to oculopharyngeal muscular dystrophy (OPMD), which is an adult onset disease characterized by eyelid drooping, difficulty in swallowing and weakness in the proximal limb muscles. Although significant data from in vitro biochemical assays define the function of PABPN1 in control of poly(A) tail length, little is known about the role of PABPN1 in mammalian cells. To assess the function of PABPN1 in mammalian cells and specifically in cells affected in OPMD, we examined the effects of PABPN1 depletion using siRNA in primary mouse myoblasts from extraocular, pharyngeal and limb muscles. PABPN1 knockdown significantly decreased cell proliferation and myoblast differentiation during myogenesis in vitro. At the molecular level, PABPN1 depletion in myoblasts led to a shortening of mRNA poly(A) tails, demonstrating the cellular function of PABPN1 in polyadenylation control in a mammalian cell. In addition, PABPN1 depletion caused nuclear accumulation of poly(A) RNA, revealing that PABPN1 is required for proper poly(A) RNA export from the nucleus. Together, these experiments demonstrate that PABPN1 plays an essential role in myoblast proliferation and differentiation, suggesting that it is required for muscle regeneration and maintenance in vivo.

Determination of amfepramone hydrochloride, fenproporex, and diazepam in so-called natural capsules used in the treatment of obesity

A simple and rapid method was developed for the determination of amfepramone hydrochloride, fenprorex, and diazepam in capsules using high performance liquid chromatography (HPLC) with UV detection. This procedure provided conditions for the separation of the active ingredient from the complex matrices of the dosage forms by extraction in methanol. Isocratic reversed phase chromatography was performed using acetonitrile, methanol, and aqueous 0,1% ammonium carbonate (50:10:40) as a mobile phase, LiChrospher 100 RP 18 column (125 x 5 mm id, 5 mu m), a column temperature of 25 +/- 1 degrees C and detection at 230 nm.The calibration curves were linear over a wide concentration range (20-2000 mu g.mL(-1) to amfepramone hydrochloride, 8-800 mu g.mL(-1) to fenproporex, and 4-200 mu g.mL(-1) to diazepam) and good analytical recovery (87.1 to 107.8%) was obtained. The method is accurate and precise, as well as having advantages such as simplicity and short duration of analysis. Twenty samples of pharmaceutical preparations labelled as natural products were analysed. Anorectics and diazepam, were detected in 40% of the samples.

Potential tuberculostatic agents: Micelle-forming copolymer poly(ethylene glycol)-poly(aspartic acid) prodrug with isoniazid

With the objective of obtaining slow-acting isoniazid derivatives, of potential use as chemoprophylactics or chemotherapeutics in tuberculosis, the micelle-forming copolymer of poly(ethylene glycol)-poly(aspartic acid) prodrug with isoniazid was synthesized. The derivative obtained was found to be active in Mycobacterium Il(tuberculosis culture, with a minimal inhibitory concentration (MIC) 5.6 times lower than that of the tuberculostatic drug.

High-performance liquid chromatographic determination of amfepramone hydrochloride, mazindol, and diazepam in tablets

Simple and rapid procedures were developed for the quantification of amfepramone hydrochloride and diazepam and mazindol and diazepam in tablets using high performance liquid chromatography (HPLC) with UV detection. These techniques provided conditions for the separation of each active ingredient from the complex matrices of the dosage forms by dilution or extraction in methanol. Isocratic reversed phase chromatography was performed using acetonitrile, methanol, and aqueous 0,1% ammonium carbonate (70:10:20, v/v/v) as a mobile phase, Radial-Pak C-18 column (100 x 8 mm id, 4 mu m), a column temperature of 25+/-1 degrees C and detection at 255 nm. The calibration curves were linear over a wide concentration range (100-1000 mu g.mL(-1) to amfepramone hydrochloride and mazindol and 10-100 mu g.mL(-1) to diazepam) with good correlation factors of 0.9978, 0.9956 and 0.9997 for amfepramone hydrochloride, mazindol, and diazepam, respectively.Mean recoveries obtained from the two kinds of samples ranged from 83.2 to 102.5%, with coefficients of variation ranging from 1.0 to 6.1.These results demonstrated the efficiency of the proposed methods, as well as advantages such as simplicity and short duration of analysis.

Nanoencapsulation and Characterization of Zidovudine on Poly(L-lactide) and Poly(L-lactide)-Poly(ethylene glycol)-Blend Nanoparticles

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

LC Assay for Ciprofloxacin Hydrochloride Ophthalmic Solution

The objective of the current study was to develop and subsequently validate a simple, sensitive and precise reversed-phase LC method for the determination of ciprofloxacin hydrochloride in ophthalmic solution form. The chromatographic separation of ciprofloxacin hydrochloride was achieved on a Symmetry Waters C(18) column using UV detection at 275 nm. The optimized mobile phase consisted of 2.5% acetic acid solution: methanol:acetonitrile (70:15:15, v/v/v). The proposed method provided linear responses within the concentration range 1.0-6.0 mu g mL(-1) for ciprofloxacin hydrochloride. Correlation coefficient (r) for the ciprofloxacin hydrochloride was 0.9994. The precision of the method was demonstrated using intra- and inter-day assay RSD% values which were less than 5% in all instances. No interference from any components of pharmaceutical dosage forms was observed.

Development and validation of an analytical method by RP-HPLC for quantification of sibutramine hydrochloride in pharmaceutical capsules

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Development and validation of a dissolution test for diltiazem hydrochloride in immediate release capsules

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)