Electrospun nanofibers of polyCD/PMAA polymers and their potential application as drug delivery system

Herein, we used an electrospinning process to develop highly efficacious and hydrophobic coaxial nanofibers based on poly-cyclodextrin (polyCD) associated with poly(methacrylic acid) (PMAA) that combines polymeric and supramolecular features for modulating the release of the hydrophilic drug, propranolol hydrochloride (PROP). For this purpose, polyCD was synthesized and characterized, and its biocompatibility was assessed using fibroblast cytotoxicity tests. Moreover, the interactions between the guest PROP molecule and both polyCD and $\beta$CD were found to be spontaneous. Subsequently, PROP was encapsulated in uniaxial and coaxial polyCD/ PMAA nanofibers. A lower PROP burst effect (reduction of approximately 50%) and higher modulation were observed from the coaxial than from the uniaxial fibers. Thus, the coaxial nanofibers could potentially be a useful strategy for developing a controlled release system for hydrophilic molecules.Comment: 10 pages, 8 figures + Supplementary Data (4 pages, 6 figures

Microcalorimetric and SAXS determination of PEO−SDS interactions: The effect of cosolutes formed by ions

The effect of different ionic cosolutes (NaCl, Na2SO4, Li2SO4, NaSCN, Na2[Fe(CN)5NO], and Na3[Co(NO)6]) on the interaction between sodium dodecyl sulfate (SDS) and poly(ethylene oxide) (PEO) was examined by small-angle X-ray scattering (SAXS) and isothermal titration calorimetric techniques. The critical aggregation concentration values (cac), the saturation concentration (C2), the integral enthalpy change for aggregate formation (ΔHagg(int)) and the standard free energy change of micelle adsorption on the macromolecule chain (ΔΔGagg) were derived from the calorimetric titration curves. In the presence of 1.00 mmol L−1 cosolute, no changes in the parameters were observed when compared with those obtained for SDS−PEO interactions in pure water. For NaCl, Na2SO4, Li2SO4, and NaSCN at 10.0 and 100 mmol L−1, the cosolute presence lowered cac, increased C2, and the PEO−SDS aggregate became more stable. In the presence of Na2[Fe(CN)5NO], the calorimetric titration curves changed drastically, showing a possible reduction in the PEO−SDS degree of interaction, possibility disrupting the formed nanostructure; however, the SAXS data confirmed, independent of the small energy observed, the presence of aggregates adsorbed on the polymer chain

Diffusion par dispersions diluées de ferrofluides dans des gels polymériques

Les ferrofluides sont des solutions colloïdales de particules nanométriques associées à un dipôle magnétique permanent. La dispersion des ferrofluides dans un gel polymère produit un autre type de matériau connu sous le nom de gel magnétique ou ferrogel. Nous présentons, dans ce travail, les résultats expérimentaux de diffusion de rayonnement par des solutions diluées de ferrofluides de magnétite dispersées dans des gels de poly(acrylamide)/méthylène-bisacrylamide en utilisant des techniques de diffusion de la lumière, diffusion des rayons X aux petits angles (SAXS) et diffusion des neutrons aux petits angles (SANS). Les résultats de l'intensité diffusée I(q), en fonction du vecteur de diffusion, q, montrent que les particules magnétiques forment des amas fractales denses avec environ 200 à 300 particules par amas et dont la dimension fractale D est approximativement 2.9. Selon nous, ces résultats sont une conséquence de la disparition du surfactant de la surface des particules par le gel conduisant ainsi à l'agrégation irréversible des particules. Nous avons également étudié l'effet sur l'intensité diffusée de l'application d'un champ magnétique perpendiculaire au faisceau incident. Les résultats expérimentaux par SAXS coïncident avec le modèle des amas ellipsoïdaux dans lequel le moment magnétique effectif est une fonction de la concentration du gel. Pour la diffusion de la lumière les effets des interactions entre les particules sont importants et l'anisotropie de l'intensité diffusée est inversée par rapport à celle mesurée par SAXS. Finalement nous avons étudié la dynamique des ferrogels en utilisant la technique de corrélation de photons où les particules agissent comme des traceurs. Les résultats coïncident avec le modèle de diffusion des réseaux de Rouse avec une diffusion initialement libre suivie d'un régime anomal. Le temps caractéristique du passage d'un régime à l'autre dépend du vecteur de diffusion comme [to]- q-2.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Simulation of a perfectly dielectric drop in electro-osmotic flow of an electrolyte through a microchannel

A Digital Object Identifier (DOI) disponibilizada pela revista não correspondeThis research uses a computational fluid dynamic model to simulate motion and deformation of a dielectric drop in electrolyte solution in a microchannel. Different values of wall charge density, the Debye-Hückel parameter and the Weber number (We) were used for uncharged, positively and negatively charged drop interfaces. Drop flow and deformation were analysed and the effects of charge distribution, electric field and permittivity jump were discussed. For a positively charged channel wall, negatively charged drops moved faster and positively charged drops moved slower than an uncharged drop. This effect increased for a higher We. Vortex flows were observed inside the drop. For a low surface tension, the drops were elongated due to electric forces acting on its surface with the charged drops deforming more than the uncharged one. When the permittivity component of the force was removed, the drop had a horizontal deformation that was sufficiently high to cause the negatively charged drop to break up

SIMULATION OF A PERFECT DIELECTRIC DROP IN ELECTRO-OSMOTIC FLOW OF AN ELECTROLYTE THROUGH A MICROCHANNEL

This research uses a computational fluid dynamic model to simulate motion and deformation of a dielectric drop in electrolyte solution in a microchannel. Wall charge density, the Debye-Hückel parameter and the Weber number are varied for uncharged, positively and negatively charged drop interfaces. Drop flow and deformation were analysed and the effects of charge distribution, electric field and permittivity jump were discussed. For a positively charged channel wall, negatively charged drops moved faster and positively charged drops moved slower than an uncharged drop. This effect increased for a higher We. Vortex flow was observed inside the drop.  For a low surface tension, the drops were elongated due to electric forces acting on its surface with the charged drops deforming more than the uncharged one. When the permittivity component of the force was removed, the drop had a horizontal deformation that was sufficiently high to cause the negatively charged drop to break up

Combined effect of transglutaminase and sodium citrate on the microstructure and rheological properties of acid milk gel

Combined effects of trisodium citrate (TSC), transglutaminase (Tgase) and heating were studied withrelation to the mechanical properties of acid milk gels. Acidification of skimmed microfiltered milksamples was performed at 30 C by addition of glucono e d lactone to achieve final pH of 4.6 in 4 h.Increasing levels of TSC (0, 10 and 20mM) were added to the samples, followed by addition of a constantlevel of Tgase (3 U/g of protein), and subsequent heating to 85 C for 30 min. Prior to acidification,suspensions were analyzed in terms of amount of sedimentable material, hydration, hydrodynamicdiameter (Dh) and z-potential (z) of the particles. Acid-induced gelation was studied using smalldeformation rheology followed by large deformation test. The water holding capacity of the gels (WHC)was performed at pH 4.6. Gels microstructure were investigated by confocal laser scanning microscopy atpH 4.6 and determination of mean pore size was performed by 2D-correlation analysis. Results showedthat combined Tgase and TSC treatments had significant effect on rheological properties, WHC and gelmicrostructure. Higher stiffness of the gels was observed with Tgase and TSC at 10 mM, whereas a homogenousnetwork distribution with smaller pore size was observed in the presence of Tgase and TSC at20 m

Insights on physicochemical aspects of chitosan dispersion in aqueous solutions of acetic, glycolic, propionic or lactic acid

Chitosan is a polysaccharide well-known for its applicability as a biocompatible, biodegradable, and non-toxic material to produce drugs excipients and food coatings. Acidic media are required to disperse chitosan, and aqueous solutions of acetic acid have been typically used for this purpose. However, this acid has several sensory drawbacks. In this study, chitosan was dispersed [0.1 g·(100 mL)−1] in aqueous media containing acetic (AA), glycolic (GA), propionic (PA), or lactic (LA) acid, at 10, 20, 30, 40, or 50 mmol·L−1. The increase of acid concentration reduced pH and viscosity of the dispersions, and |ζ potential| of dispersed particles. Conversely, it increased electrical conductivity and density of the dispersions, and hydrodynamic diameter of dispersed particles. At a given concentration, these effects were slightly more pronounced for dispersions formed with GA or LA, compared to AA or PA. FT-IR data suggested more intense attractive interactions of chitosan chains with glycolate and lactate anions, than with acetate and propionate. Chitosan chains interacted more strongly with hydroxylated acids counter-anions than with their non-hydroxylated counterparts, leading to slight quantitative changes of physicochemical properties of these systems. Then, in physicochemical terms, GA, LA or PA are suitable to replace AA when preparing aqueous chitosan dispersions for technological applications

Formation and characterization of supramolecular structures of β-lactoglobulin and lactoferrin proteins

Combination of β-lactoglobulin (β-Lg) and lactoferrin (Lf), biomacromolecules derived from bovine whey, was used in the formation of supramolecular structures by thermal gelation technique to adjust the pH. Furthermore, the influence of the molar ratio, temperature, pH, and heating time in the formation of supramolecular structures were also studied. The characterization of the protein supramolecular structures was performed using dynamic light scattering, zeta potential measurements, molecular spectrofluorimetry, and circular dichroism spectroscopy. The thermal behavior of the pure proteins was investigated by differential scanning calorimetry. The protein denaturation temperatures were of around 85 °C for the β-Lg and around 52 °C and 85 °C (a small portion) for the Lf. The protein molar ratio of 2:1 Lf/β-Lg was used to form the structures, whose characterization showed that the best conditions of supramolecular structure formation occurred at pH 6.5 and at temperatures of 62.5 °C. In those conditions, more stable systems with reduced hydrophobic surface and average sizes between 30 and 100 nm were generated. The correlation between pH and temperature suggests that the method of preparation of the supramolecular structure affects its size during storage