Osmotic conditions in rheologic properties of erytrocites

Abstract The decreasing viability and in vivo survival of red blood cells, RBCs, observed in blood bank-storage are due to alterations in their rheologic properties and metabolic status. However, there is a lack of electrokinetic experiments with erythrocytes by the screening produced by the high concentration of buffer required to keep the isoosmotic conditions. Electrokinetic measurements in a wide range of sodium chloride and tetrasodium pyrophosphate are undertaken on liposomes as cell models, and in order to get an aqueous media suitable for maintaining osmotic conditions and allowing electrophoretic mobility measurements as well, advantage has been taken of dextrose properties. Measur…

Composite soy lecithin–decylpolyglucoside vesicles: A theoretical and experimental study

In the present work, vesicles made with soy lecithin and a commercial mixture of alkyl polyglucosides were prepared and characterized. Vesicles with a constant amount of soy lecithin and an increasing amount of a decylpolyglucoside surfactant, (OrNS10), were formulated and their physicochemical properties were studied with the aim to design a drug delivery system suitable for different applications. To this purpose, morphology, size distribution, ζ-potential and apparent viscosity of the prepared vesicles were studied. Vesicles were also characterized by using optical and light polarized microscopy, transmission electron microscopy and photon correlation spectroscopy. A stability study was …

Biopolymer coating of soybean lecithin liposomes via layer-by-layer self-assembly as novel delivery system for ellagic acid

Abstract The formulation of a novel delivery system for ellagic acid formulated via layer-by-layer (L-b-L) electrostatic deposition of biopolymers onto soybean lecithin liposomes was achieved. Optimization of parameters affecting the formulation of biopolymer-coated liposomes was carried out by monitoring changes on its size, surface charge and morphology. Ellagic acid was loaded into the liposome core and loading properties were analyzed. Release profiles for ellagic acid from optimized biopolymer-coated liposomes were evaluated as a function of time, temperature and pH of the media. The L-b-L electrostatic deposition of biopolymers succeeded in building nanosized, spherical and stable lip…

Theoretical and experimental evaluation of decypolyglucoside vesicles as potential drug delivery systems

The aim of this work was to ascertain the capability of a commercial mixture of decylpolyglucoside (Orami.x NS10) to form vesicle structures in water, either alone or in association with cholesterol. To this purpose, we compared results obtained from a theoretical model with those acquired from the experimental characterization of different Orami.x NS10/cliolesterol mixtures. The germen vesicular formation theory was used to predict the formation process of vesicular structures. To this purpose, the energy balance involved in the vesicle formation was calculated using critical concentration for vesicle formation (ccf), surface tension and molecular area of decylpolyglucoside. The ccf was me…

Interaction of ionic compounds with multilamellar liposomes. An electrokinetic model

Abstract We have proposed a theoretical model of interaction of ionic compounds (ionic adsorbate or ionic drugs), with multilamellar-liposomes, by means of their electrokinetic property variation with the ionic compound concentration. In this work, we show the complete development of the model proposed. Its theoretical results have been analysed to study the influence on the zeta-potential value of the following: number of membranes, size, shear-plane situation, critical concentration of formation (ccf), and the ionic compound concentration which annuls the zeta-potential value of the multilamellar-liposomes formed.

In vitrouptake of lysozyme-loaded liposomes coated with chitosan biopolymer as model immunoadjuvants

Chitosan binds to negatively charged soy lecithin liposomes by an electrostatic interaction driven by its cationic amino group. This interaction allows developing stable coated vesicles suitable as a targeted carrier and controlled release system for drugs and vaccines. In this work, we studied the effect of chitosan-coated liposomes on the uptake and antigen presentation of hen egg-white lysozyme (HEL) in Peyer's patches peritoneal macrophages isolated from mice. Chitosan-coated liposomes were characterized according to size, zeta potential, and antigen-loading and release properties. Results showed an increase in the positive net charge and size of the liposomes as the concentration of ch…

Geometric and thermodynamic considerations about the lipid vesicles formation in water (I. Unilamellar vesicles)

Abstract A parametrization based on the differential geometry and on the thermodynamics of dispersed systems has been developed in order to explain the processes leading to the formation of lipid vesicles in water. Several factors of known importance such as aqueous interlayer, chain-length, lipid chain-packing and membrane asymmetry, as well as the existence of two different surfaces in the vesicular bilayer have been considered. The barrier which amphiphile molecules need to surpass in order to the vesicle be formed has three contributions related to the surface energy, the mechanical energy due to overpressure and the excess of chemical potential. The theoretical results define the condi…

Effect of several electrolytes on the rheopectic behaviour of concentrated soy lecithin dispersions

Abstract Concentrated dispersions of soy lecithin (60 g/L) prepared by sonication-freezing–unfreezing method show a non-newtonian behaviour and a significant rheopexy. Shear stress versus shear rate plots shows a loop hysteresis area, which have been studied in soy lecithin dispersions prepared with aqueous solutions of various electrolytes (NaCl, CaCl2, MgCl2 and AlCl3) with concentrations in the range 10−5 to 10−2 mol/L. Also we have studied the effect of different pH on soy lecithin dispersions. The results have revealed a very sensitive influence of nature, valence and concentration of the respective cations and the pH value on the loop hysteresis area values. It seems to indicate that …

Polymer-liposome nanoparticles obtained by the electrostatic bio-adsorption of natural polymers onto soybean lecithin liposomes

This work is focused on the formulation of polymer-liposome nanoparticles based on the electrostatic bio-adsorption of natural polymers onto soybean lecithin liposomes, with potential as novel delivery system for macromolecules, such as proteins. The building up of the polymer-liposome nanoparticles was achieved through the alternating bio-adsorption of natural cationic (chitosan) and neutral (dextran) or anionic (dextran sulphate or alginate) polymer layers on a core composed by anionic nanosized soybean lecithin liposomes. The electrostatic bio-adsorption of natural polymers succeeded in building nanosized, spherical, monodisperse and stable polymer-liposome nanoparticles with cumulative …

Development and characterization of liposomes containing glycols as carriers for diclofenac

® Propylene glycol Permeation enhancer vesicles abstract This paper focuses on the preparation and characterization of new, stable phospholipid formulations as carriers for dermal delivery of diclofenac (DCF). To prepare these vesicles two water miscible permeation enhancers (PE) with glycol group: diethyleneglycol monoethyl ether (Transcutol ® , Trc) and propylene glycol (PG), were added at different concentrations (10%, 20%, 30%, 40%, 50%) during the preparation of diclofenac loaded soy lecithin (SL) liposomes. We added Transcutol ® or propylene glycol to the hydrophilic phase in order to obtain new systems able to enhance the skin delivery of diclofenac thanks to the synergic effect of g…

Modified hydrodynamic chromatography and its applications to liposomes

Transcutol containing vesicles for topical delivery of minoxidil

The aim of this work was to evaluate the ability of Transcutol (Trc) to produce elastic vesicles with soy lecithin (SL) and study the influence of the obtained vesicles on in vitro (trans)dermal delivery of minoxidil. To this purpose, so-called penetration enhancer-containing vesicles (PEVs) were prepared using Trc aqueous solutions (5-10-20-30% v/v) as hydrophilic phase. SL liposomes, without Trc, were used as control. Prepared formulations were characterized in terms of size distribution, morphology, zeta potential, deformability, and rheological behavior. The influence of the obtained PEVs on (trans)dermal delivery of minoxidil was studied by in vitro diffusion experiments through pig sk…

Penetration enhancer containing vesicles as carriers for dermal delivery of tretinoin.

The ability of a recently developed novel class of liposomes to promote dermal delivery of tretinoin (TRA) was evaluated. New penetration enhancer-containing vesicles (PEVs) were prepared adding to conventional phosphatidylcholine vesicles (control liposomes) different hydrophilic penetration enhancers: Oramix® NS10 (OrNS10), Labrasol® (Lab), Transcutol® P (Trc), and propylene glycol (PG). Vesicles were characterized by morphology, size distribution, zeta potential, incorporation efficiency, stability, rheological behaviour, and deformability. Small, negatively charged, non-deformable, multilamellar vesicles were obtained. Rheological studies showed that PEVs had fluidity higher than conven…

Chitosomes loaded with cranberry proanthocyanidins attenuate the bacterial lipopolysaccharide-induced expression of iNOS and COX-2 in raw 264.7 macrophages

Chitosan binds to negatively charged soy lecithin liposomes by an electrostatic interaction driven by its positively charged amino group. This interaction allows stable covered vesicles (chitosomes) to be developed as a suitable targeted carrier and controlled release system. This study investigated the effect of chitosomes on the activation of cranberry proanthocyanidins (PAC) in Raw 264.7 macrophages. Chitosomes were characterized according to size, zeta potential, PAC-loading, and release properties. Results showed an increase in the net positive charge and size of the liposomes as the concentration of chitosan was increased, suggesting an effective covering of the vesicles by means of e…

Influence of the electrical interface properties on the rheological behavior of sonicated soy lecithin dispersions

A significant effect, on the rheological behavior, due to the electrical properties of vesicles formed from concentrated soy lecithin dispersions have been studied in this work. The rheopectic behavior of concentrated soy lecithin dispersions (120, 150, 180, 210 and 240 g L−1) prepared by swelling–light sonication–freezing–unfreezing procedure is studied and it is specially emphasized on the transition under steady shear from lamellar phase of planar sheets to closed structures as multilamellar vesicles. Samples have been exposed to a different number of sonication cycles (from 0 to 100) and the changes in the hysteresis loop area, the apparent viscosity and the electrophoretic mobility hav…

Viscoelastic properties of concentrated dispersions in water of soy lecithin

Abstract Viscoelastic properties of soy lecithin dispersions at 60, 120, 180 and 240 g l−1 in water have been studied as a function of ionic strength (NaCl concentrations in the range 10−5–10−2 mol l−1) and of preparation method (sonication, freezing–unfreezing). Viscosity measurements of sonicated dispersions in a rotatory viscometer show Newtonian and plastic (Bingham) behavior, whereas the frozen–unfrozen dispersions show a spectacular change in their viscoelastic properties, that is, a non-Newtonian behavior with pseudoplastic characteristics and rheopexy. These properties have been related to electrokinetic characteristics of the segregated vesicles in each case. A decrease in ζ-potent…

An approach to rheological and electrokinetic behaviour of lipidic vesicles covered with chitosan biopolymer

The rheological and electrokinetic properties of soybean lecithin vesicles prepared from concentrated soy lecithin dispersions (250 g/L) obtained by slow swelling under shear conditions and mixed with chitosan biopolymer solutions were studied. The rheological behaviour of lecithin-chitosan vesicles was determined by shear stress against shear rate measurements, as well as by the variation on the hysteresis loop area. The results were compared with the rheopectic behaviour of soy lecithin dispersions without chitosan. An important change on the rheological properties of the complex dispersion was observed, depicting in a thixotropic behaviour with a plastic character in the presence of chit…

Thermodynamical aspects regarding the formation of self-assembly decylpolyglucoside structures

In this study, we used a generalized form of a recently reported parametrization based on the differential geometry and the thermodynamics of dispersed systems to ascertain the capability of decylpolyglucoside alone or in association with cholesterol to form vesicle structures (niosomes). The theoretical calculation of the energy balance involved in the vesicles formation was carried out using values of the critical concentration of formation (ccf), surface tension and the molar surface area of the non-ionic surfactant. Furthermore, in order to confirm the theoretical results found in this work, we prepared and characterized vesicles made with decylpolyglucoside and cholesterol. The vesicle…

Estimation of the size of liposomes by modified HDC

Internal calibration in modified hydrodynamic chromatography has been realized by the approach of Prieve and Hoysan, i.e. the use of polystyrene monodisperse latexes to evaluate the equivalent capillary radius, R. The value obtained has been used to estimate the average sizes of a variety of liposome samples from egg yolk lecithin.