Thermal stability of ionene polymers

Two different cationic polymers of the same chemical type and with very similar chemical structures were reacted with a natural bentonite over a wide range of polymer/clay ratios. This study involved the synthesis of cationic aliphatic ammonium polyionenes, specifically 3,6-ionene and 3,6-dodecylionene. Ionenes are ion-containing polymers that contain quaternary nitrogen atoms in the main macromolecular chain as opposed to a pendant chain. The CHN content, basal spacing, and elemental composition of each of the polymer-clay complexes were analyzed by X-ray diffraction, X-ray fluorescence, and thermogravimetry. All the polycations reacted to form interlayer complexes with clay, which displaced more Na+ and little Ca2+. Sodium and calcium were both present as interlayer cations in the clay and its complexes. The TG/DTG curves show that both polymers underwent thermal degradation in more than one stage. Specifically, 3,6-ionene was found to undergo two stages of decomposition and 3,6-dodecylionene undergo three stages. The behavior of the TG/DTG curves and the activation energy values suggest that 3,6-dodecylionene (E = 174,85 kJ mol-1) complexes have greater thermal stability than 3,6-ionene (E = 115,52 kJ mol-1) complexes. The mechanism of degradation suggests a direct interaction with the dodecyl chain containing 12 carbons, which are present in 3,6-dodecylionene but not in 3,6-ionene. © 2012 Akadémiai Kiadó, Budapest, Hungary.

Polycation-Based Gene Therapy: Current Knowledge and New Perspectives

At present, gene transfection insufficient efficiency is a major drawback of non-viral gene therapy. The 2 main types of delivery systems deployed in gene therapy are based on viral or non-viral gene carriers. Several non-viral modalities can transfer foreign genetic material into the human body. To do so, polycation-based gene delivery methods must achieve sufficient efficiency in the transportation of therapeutic genes across various extracellular and intracellular barriers. These barriers include interactions with blood components, vascular endothelial cells and uptake by the reticuloendothelial system. Furthermore, the degradation of therapeutic DNA by serum nucleases is a potential obstacle for functional delivery to target cells. Cationic polymers constitute one of the most promising approaches to the use of viral vectors for gene therapy. A better understanding of the mechanisms by which DNA can escape from endosomes and traffic to enter the nucleus has triggered new strategies of synthesis and has revitalized research into new polycation-based systems. The objective of this review is to address the state of the art in gene therapy with synthetic and natural polycations and the latest advances to improve gene transfer efficiency in cells.

Synthetic and natural polycations for gene therapy: State of the art and new perspectives

Currently, the major drawback of gene therapy is the gene transfection rate. The two main types of vectors that. are used in gene therapy are based on viral or non-viral gene delivery systems. There are several non-viral systems that can be used to transfer foreign genetic material into the human body. In order to do so, the DNA to be transferred must escape the processes that affect the disposition of macromolecules. These processes include the interaction with blood components, vascular endothelial cells and uptake by the reticuloendothelial system. Furthermore, the degradation of therapeutic DNA by serum nucleases is also a potential obstacle for functional delivery to the target cell. Cationic polymers have a great potential for DNA complexation and may be useful as non-viral vectors for gene therapy applications. The objective of this review was to address the state of the art in gene therapy using synthetic and natural polycations and the latest strategies to improve the efficiency of gene transfer into the cell.

Clarificação por flotação com ar dissolvido (FAD) da calda de açúcar cristal para produção de açúcar refinado

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

The Interaction Between N-Isopropylacrylamide-Acrylic Acid-Ethyl Methacrylate Thermosensitive Polymers and Cationic Surfactants

The interaction between cationic surfactants and isopropylacrylamide-acrylic acid-ethyl methacrylate (IPA:AA:EMA) terpolymers has been investigated using steady-state fluorescence and spectrophotometric measurements to assess the effect of the polymer composition on the aggregation process and terpolymers' thermosensitivities. Micropolarity studies using pyrene show that the interaction of cationic surfactants with IPA:AA:EMA terpolymers occurs at surfactant concentrations much smaller than that observed for the pure surfactant in aqueous solution. The critical aggregation concentration (CAC) values decrease with both the hydrocarbon length of the surfactant and the content of ethyl methacrylate. These results were interpreted as a manifestation of the increasing contribution of attractive hydrophobic and electrostatic forces between negatively charged polymer chains and positively charged surfactant molecules. The increase of ethyl methacrylate in the copolymers lowers the CAC due to the larger hydrophobic character of the polymer backbone. The cloud point determination reveals that the lower critical solution temperatures (LCST) depend strongly on the copolymer composition and surfactant nature. The binding of surfactants molecules to the polymer chain screens the electrostatic repulsion between the carboxylic groups inducing a conformational transition and the dehydration of the polymer chain.

Tailoring the Structural Properties of PVDF and P(VDF-TrFE) by Using Natural Polymers as Additives

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

Inclusion complex of piroxicam with beta-cyclodextrin and incorporation in cationic microemulsion. In vitro drug release and in vivo topical anti-inflammatory effect

Topical formulations of piroxicam were evaluated by determination of their in vitro release and in vivo anti-inflammatory effect. The in vitro release assay demonstrated that the microemulsion (ME) systems provided a reservoir effect for piroxicam release. However, the incorporation of the ME into carboxyvinilic gel provoked a greater reduction in the release of piroxicam than the ME system alone. Anti-inflammatory activity was carried out by the cotton pellet granuloma inhibition bioassay. Topical anti-inflammatory effect of the piroxicam inclusion complex/ME contained in carboxyvinilic gel showed significant inhibition of the inflammation process (36.9%, P < 0.05). Subcutaneous administration of the drug formulations showed a significant effect on the inhibition of inflammation, 68.8 and 70.5%, P <0.05, when the piroxicam was incorporated in ME and in the combined system beta -cyclodextrin (B-CD)/ME, respectively, relative to the buffered piroxicam (42.2%). These results demonstrated that the ME induced prolonged effects, providing inhibition of the inflammation for 9 days after a single dose administration. (C) 2001 Elsevier B.V. B.V. All rights reserved.

On the incorporation of the non-steroidal anti-inflammatory naproxen into cationic O/W microemulsions

Microemulsions (ME) containing hexadecyltrimethylammonium bromide (HTAB)/ethanol as surfactant, isopropylmyristate (IM) or butylstearate (BS) as oil phase and aqueous buffer were studied. Pseudo-ternary phase diagrams of the investigated systems were obtained at constant surfactant/cosurfactant molar ratio (1:5) by titration in order to characterize the proportions between the components to obtain clear systems. Oil in water microemulsions were prepared in a wide range of phase volume (phi). UV-vis absorption spectra of naproxen at pH 5.5 showed that the solubility of Np increases significantly in the presence of O/W ME in high phase volumes. For both, IM and BS microemulsions, the dynamic light scattering experiments showed that the size of the oil droplets remains constant in low values of phi, increasing abruptly in high phi values. Phase solubility study revealed that for both IM and BS microemulsions, the drug incorporation followed a straight-line profile in all range of phi. The data could be analyzed through the phase-separation model and the association constants (K) calculated varied from 27 to 90 M-1, depending on the pH and on the microemulsion oil phase. (c) 2005 Elsevier B.V. All rights reserved.

Effect of cationic micelles on the decomposition of alpha-aminophenyl cephalosporins

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

Chitosan-pectin multiparticulate systems associated with enteric polymers for colonic drug delivery

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Hyperfine interaction in Zn-Al layered double hydroxides intercalated with conducting polymers

Organic-inorganic hybrid materials based on the assembly between inorganic 2D host structure and polymer have received considerable attention in the last few years. This emerging class of materials presents several applications according to their structural and functional properties. Particularly, among others, layered double hydroxides (LDHs) provide the opportunity of preparing new organically modified 2D nanocomposites. Pyrrole carboxylic acid derivatives, namely 4-(lH-pyrrol-1-yl)benzoate, 3-(pyrrol-i-yl)-propanoate,7-(pyrrol-1-yl)-heptanoate, and aniline carboxylic acid derivative, namely 3-aminobenzoic acid, have been intercalated in LDHs of intralamellar composition Zn2Al(OH)(6). The LDHs were synthesized by the co-precipitation method at constant pH followed by hydrothermal treatment for 72 h. The materials were characterized by powder X-ray diffraction patterns (PXRD), transmission electron microscopy (TEM) thermogravimetric analysis (TGA), and electron spin resonance (ESR). The basal spacing found by the PXRD technique gives evidence of the formation of bilayers of the intercalated anions. ESR spectra present a typical signal with a superhyperfine structure with 6 + 1 lines (g = 2.005 +/- 0.0004), which is assigned to the interaction between a carboxylate radical from the guest molecules and a nearby aluminium nucleus (I = 5/2) from the host structure. Additionally, the ESR data suggest that the monomers are connected to each other in limited number after thermal treatment. (c) 2007 Elsevier Ltd. All rights reserved.

Structural and optical properties of chlorinated plasma polymers

Amorphous hydrogenated chlorinated carbon (a-C:H:Cl) films were produced by the plasma polymerization of chloroform-acetylene-argon mixtures in a radiofrequency plasma enhanced chemical vapor deposition system. The main parameter of interest was the proportion of chloroform in the feed, R(C), which was varied from 0 to 80%. Deposition rates of 80 nm min (1) were typical for the chlorinated films. Infrared reflection-absorption spectroscopy revealed the presence of C-Cl groups in all the films produced with chloroform in the feed. X-ray photoelectron spectroscopy confirmed this finding, and revealed a saturation of the chlorine content at similar to 47 at.% for R(C)>= 40%. The refractive index and optical gap, E(04), of the films were roughly in the 1.6 to 1.7, and the 2.8 to 3.7 eV range. These values were calculated from transmission ultraviolet-visible-near infrared spectra. Chlorination leads to an increase in the water surface contact angle from similar to 40 degrees to similar to 77 degrees. (C) 2011 Elsevier B.V. All rights reserved.

Optical and structural properties of PEO-like plasma polymers

This paper deals with the study of optical, structural and biocompatible properties of PEO-like plasma polymerized films resulting from RF excited diethylene glycol dimethyl ether (CH3O(CH2CH2O)(2)CH3 diglyme) glow discharges. The study was carried out using visible-ultraviolet and FTIR spectroscopies and contact angle measurements. FTIR spectra of plasma polymerized diglyme showed a stronger presence of ethylene glycol groups in film structure for lower RF power levels. The contact angle measurements for water revealed an increasing from 30degrees to 62,5degrees when the RF power was varied from 2 to 45 W, indicating the decreasing of the hydrophilic character of diglyme films with the increasing of RF power. This trend is in agreement with FTIR results. The data from visible-ultraviolet reflectance and transmittance spectra revealed alterations on optical properties of plasma polymerized diglyme films. The film's optical gap varied from 3.8 to 3 eV for RF power running from 5 to 45 W.

Argon ion implantation inducing modifications in the properties of benzene plasma polymers

Benzene plasma polymer films were bombarded with Ar ions by plasma immersion ion implantation. The treatments were performed using argon pressure of 3 Pa and 70 W of applied power. The substrate holder was polarized with high voltage negative pulses (25 kV, 3 Hz). Exposure time to the immersion plasma, t, was varied from 0 to 9000 s. Optical gap and chemical composition of the samples were determined by ultraviolet-visible and Rutherford backscattering spectroscopies, respectively. Film wettability was investigated by the contact angle between a water drop and the film surface. Nanoindentation technique was employed in the hardness measurements. It was observed growth in carbon and oxygen concentrations while there was decrease in the concentration of H atoms with increasing t. Furthermore, film hardness and wettability increased and the optical gap decreased with t. Interpretation of these results is proposed in terms of the chain crosslinking and unsaturation. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Treatment of PET and PU polymers by atmospheric pressure plasma generated in dielectric barrier discharge in air

Plasma treatments are frequently employed to modify surface properties of materials such as adhesivity, hydrophobicity, oleophobicity etc. Present work deals with surface modification of common commercial polymers such as polyethylene terephthalate (PET) and polyurethane (PU) by an air dielectric barrier discharge (DBD) at atmospheric pressure. The DBD treatment was performed in a plain reactor in wire-duct geometry (non-uniform field reactor), which was driven by a 60 Hz power supply. Material characterization was carried out by water contact angle measurements, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The plasma-induced modifications are associated with incorporation of polar oxygen and nitrogen containing groups on the polymer surface. The AFM analysis reveals that the plasma treatment roughens the material surface. Due to these structural and morphological changes the surface of DBD-treated polymers becomes more hydrophilic resulting in enhanced adhesion properties. (C) 2010 Elsevier B.V. All rights reserved.