Study of the diclofenac/phospholipid interactions with liposomes and monolayers

Interaction between Pharmaceutical Drugs and Polymer-Coated Fe3O4 Magnetic Nanoparticles with Langmuir Monolayers as Cellular Membrane Models

Surface modification of magnetic nanoparticles (MNPs) has been reported to play a significant role in determining their interactions with cell membranes. In this research, the interactions between polymer functionalized (chitosan, CHI or diethylamino-ethyl dextran, DEAE-D) Fe₃O₄ MNPs, pharmaceutical drugs and model cell membranes were investigated by Langmuir isotherms and adsorption measurements. In this study, 1,2-distearoyl-sn-glycerol-3-phosphate (DSPA) phospholipid monolayers were used as cell membrane models. Insertion experiments demonstrate that diclofenac (DCFN) is not absorbed at the air-water interface, whereas triflupromazine (TFPZ) has a MIP (maximum insertion pressure) of 35 m Nm^-1. The insertion of composites MNPs:TFPZ or DCFN has larger MIP values, indicating that the MNPs are adsorbed on the monolayer with the drugs. An Fe₃O₄@CHI:DCFN composite presented an MIP of 39 m Nm^-1 and Fe₃O₄@DEAE-D:DCFN presented an impressive MIP of 67 mNm^-1. In the case of TFPZ, the enhancement in the MIP values is also evident, being 42 mNm^-1 for Fe₃O₄@CHI:TFPZ and 40 mNm^-1 for Fe₃O₄@DEAE-D:DCFN composite. All MNPs:drugs composites have MIP values greater than commonly accepted membrane pressure values, indicating that MNPs:drugs can penetrate a cellular membrane. The fact that the composite MNPs:drugs present greater MIP values than separated compounds indicates that polymer-coated MNPs can act as good drug delivery systems.

Chitosan-covered liposomes as a promising drug transporter: nanoscale investigations

Liposomes are small artificial vesicles spherical shaped of 50-1000 nm in diameter. They are created from natural non-toxic phospholipids membranes. Externally, they are decorated with biocompatible polymers. Chitosan, a natural polymer, demonstrates exceptional advantages in drug delivery, in particular, as liposome cover. In this paper, Molecular Dynamics simulations (MD) are performed in the coupled NPT-NPH and NVT-NVE statistical ensembles to study the static and dynamic properties of DPPC membrane-bilayer with grafted cationic chitosan chains, with added Cl- anions to neutralize the environment, using the Martini coarse-grained force-field. From the NPT-NPH MD simulations we found a chitosan layer L DM ranging from 3.2 to 6.6 nm for graft chains of a degree of polymerization n p = 45 and different grafting molar fractions X p = 0.005, X p = 0.014 and X p = 0.1. Also, the chitosan chains showed three essential grafting regimes: mushroom, critic, and brush depending on X p. The DPPC bilayer thickness D B and the area per lipid A l increased proportionally to X p. From the NVT-NVE MD simulations, the analysis of the radial distribution function showed that the increase of X p gives a more close-packed and rigid liposome. The analysis of the mean square displacement revealed that the diffusion of lipids is anomalous. In contrast, the diffusion of chitosan chains showed a normal diffusion, just after 100 ps. The diffusion regime of ions is found to be normal and independent of time. For the three identified regimes, the chitosan showed a tendency to adhere to the membrane surface and therefore affect the properties of the liposomal membrane.

A Molecular Biophysical Approach to Diclofenac Topical Gastrointestinal Damage

Diclofenac (DCF), the most widely consumed non-steroidal anti-inflammatory drug (NSAID) worldwide, is associated with adverse typical effects, including gastrointestinal (GI) complications. The present study aims to better understand the topical toxicity induced by DCF using membrane models that mimic the physiological, biophysical, and chemical environments of GI mucosa segments. For this purpose, phospholipidic model systems that mimic the GI protective lining and lipid models of the inner mitochondrial membrane were used together with a wide set of techniques: derivative spectrophotometry to evaluate drug distribution at the membrane; steady-state and time-resolved fluorescence to predict drug location at the membrane; fluorescence anisotropy, differential scanning calorimetry (DSC), dynamic light scattering (DLS), and calcein leakage studies to evaluate the drug-induced disturbance on membrane microviscosity and permeability; and small- and wide-angle X-ray scattering studies (SAXS and WAXS, respectively), to evaluate the effects of DCF at the membrane structure. Results demonstrated that DCF interacts chemically with the phospholipids of the GI protective barrier in a pH-dependent manner and confirmed the DCF location at the lipid headgroup region, as well as DCF’s higher distribution at mitochondrial membrane contact points where the impairment of biophysical properties is consistent with the uncoupling effects reported for this drug.

Effect of polymer charge on the formation and stability of anti-inflammatory drug loaded nanostructured lipid carriers: physicochemical approach

Proposed model of NSAID-loaded and polymer-coated NLC along with its size dependence (), PDI (), release rate (), and absorption maxima () as well as its morphology and antibacterial activity.

Formulation and characterization of hydrophilic drug diclofenac sodium-loaded solid lipid nanoparticles based on phospholipid complexes technology

To successfully prepare the diclofenac sodium (DS)-loaded solid lipid nanoparticles (SLNs), phospholipid complexes (PCs) technology was applied here to improve the liposolubility of DS. Solid lipid nanoparticles (SLNs) loaded with phospholipid complexes (PCs) were prepared by the modified emulsion/solvent evaporation method. DS could be solubilized effectively in the organic solvents with the existence of phospholipid and apparent partition coefficient of DS in PCs increased significantly. X-ray diffraction analysis suggested that DS in PCs was either molecularly dispersed or in an amorphous form. However, no significant difference was observed between the Fourier transform infrared spectroscopy (FT-IR) spectra of physical mixture and that of PCs. Particles with small sizes, narrow polydispersity indexes and high entrapment efficiencies could be obtained with the addition of PCs. Furthermore, according to the transmission electron microscopy, a core-shell structure was likely to be formed. The presence of PCs caused the change of zeta potential and retarded the drug release of SLNs, which indicated that phospholipid formed multilayers around the solid lipid core of SLNs. Both FT-IR and differential scanning calorimetry analysis also illustrated that some weak interactions between DS and lipid materials might take place during the preparation of SLNs. In conclusion, the model hydrophilic drug-DS can be formulated into the SLNs with the help of PCs.

Enhanced transdermal delivery of diclofenac sodium via conventional liposomes, ethosomes, and transfersomes

The aim of this study was to improve the transdermal permeation of Diclofenac sodium, a poorly water-soluble drug, employing conventional liposomes, ethosomes, and transfersomes. The prepared formulations had been characterized for the loaded drug amount and vesicle size. The prepared vesicular systems were incorporated into 1% Carbopol 914 gel, and a survey of in vitro drug release and drug retention into rat skin has been done on them using a modified Franz diffusion cell. The cumulative amount of drug permeated after 24 h, flux, and permeability coefficient were assessed. Stability studies were performed for three months. The size of vesicles ranged from 145 to 202 nm, and the encapsulation efficiency of the Diclofenac sodium was obtained between 42.61% and 51.72%. The transfersomes and ethosomes provided a significantly higher amount of cumulative permeation, steady state flux, permeability coefficient, and residual drug into skin compared to the conventional liposomes, conventional gel, or hydroethanolic solution. The in vitro release data of all vesicular systems were well fit into Higuchi model (RSD > 0.99). Stability tests indicated that the vesicular formulations were stable over three months. Results revealed that both ethosome and transfersome formulations can act as drug reservoir in skin and extend the pharmacologic effects of Diclofenac sodium.

Gel formulation containing mixed surfactant and lipids associating with carboplatin

The interaction of amphiphilic molecules such as lipids and surfactants with the hydrophilic drug carboplatin was investigated to identify suitable self-assembling components for a potential gel-based delivery formulation. (1) H-NMR Studies in sodium bis(2-ethylhexyl) sulfosuccinate (aerosol-OT, AOT)-based reverse micelles show that carboplatin associates and at least partially penetrates the surfactant interface. Langmuir monolayers formed by dipalmitoyl(phosphatidyl)choline are penetrated by carboplatin. Carboplatin was found to also penetrate the more rigid monolayers containing cholesterol. A combined mixed surfactant gel formulation containing carboplatin and cholesterol for lymphatic tissue targeting was investigated for the intracavitary treatment of cancer. This formulation consists of a blend of the surfactants lecithin and AOT (1 : 3 ratio), an oil phase of isopropyl myristate, and an aqueous component. The phases of the system were defined within a pseudo-ternary phase diagram. At low oil content, this formulation produces a gel-like system over a wide range of H(2) O content. The carboplatin release from the formulation displays a prolonged discharge with a rate three to five times slower than that of the control. Rheological properties of the formulation exhibit pseudoplastic behavior. Microemulsion and Langmuir monolayer studies support the interactions between carboplatin and amphiphilic components used in this formulation. To target delivery of carboplatin, two formulations containing cholesterol were characterized. These two formulations with cholesterol showed that, although cholesterol does little to alter the phases in the pseudo-ternary system or to increase the initial release of the drug, it contributes significantly to the structure of the formulation under physiological temperature, as well as increases the rate of steady-state discharge of carboplatin.

Dermaseptin 01 as antimicrobial peptide with rich biotechnological potential: study of peptide interaction with membranes containing Leishmania amazonensis lipid-rich extract and membrane models

This article addresses the interactions of the synthetic antimicrobial peptide dermaseptin 01 (GLWSTIKQKGKEAAIAAA- KAAGQAALGAL-NH(2) , DS 01) with phospholipid (PL) monolayers comprising (i) a lipid-rich extract of Leishmania amazonensis (LRE-La), (ii) zwitterionic PL (dipalmitoylphosphatidylcholine, DPPC), and (iii) negatively charged PL (dipalmitoylphosphatidylglycerol, DPPG). The degree of interaction of DS 01 with the different biomembrane models was quantified from equilibrium and dynamic liquid-air interface parameters. At low peptide concentrations, interactions between DS 01 and zwitterionic PL, as well as with the LRE-La monolayers were very weak, whereas with negatively charged PLs the interactions were stronger. For peptide concentrations above 1 µg/ml, a considerable expansion of negatively charged monolayers occurred. In the case of DPPC, it was possible to return to the original lipid area in the condensed phase, suggesting that the peptide was expelled from the monolayer. However, in the case of DPPG, the average area per lipid molecule in the presence of DS 01 was higher than pure PLs even at high surface pressures, suggesting that at least part of DS 01 remained incorporated in the monolayer. For the LRE-La monolayers, DS 01 also remained in the monolayer. This is the first report on the antiparasitic activity of AMPs using Langmuir monolayers of a natural lipid extract from L. amazonensis.

Meloxicam and meloxicam-beta-cyclodextrin complex in model membranes: effects on the properties and enzymatic lipolysis of phospholipid monolayers in relation to anti-inflammatory activity

Meloxicam, a nonsteroidal anti-inflammatory drug (NSAID), is known as a selective cyclooxygenase-2 inhibitor. Cyclooxygenase-2 is a membrane protein, functionally coupled to an interfacial enzyme, phospholipase A2. Consequently, it may be supposed that the interactions of NSAIDs with lipid membranes play a role in the anti-inflammatory process. In order to investigate the mechanism of this process, Langmuir films formed with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, 1,2-dilauroyl-sn-glycero-3-phosphocholine, 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine, or 1,2-myristoyl-sn-glycero-3-phosphoethanolamine were exposed to meloxicam and its beta-cyclodextrin inclusion complex. The monolayers were studied by measuring surface pressure, electric surface potential, Brewster angle micrographs, polarization-modulation infrared reflection-absorption spectra, and phospholipase A2 activity; the inclusion complex was studied using molecular modeling. The results obtained show that the monolayers formed in the presence of meloxicam and its complex are expanded and more liquid-like compared to pure lipids. Both compounds modify hydration of the lipid polar heads, orientation of the molecules, morphology of the domains, and the rate of lipolysis catalyzed by phospholipase A2. The latter effect may be involved in the anti-inflammatory activity of meloxicam. Importantly, the effects observed with the meloxicam-beta-cyclodextrin complex are more pronounced compared to those of the free meloxicam. This observation may be relevant for developing new meloxicam preparations with increased bioavailability.

The influence of fatty acids on model cholesterol/phospholipid membranes

The aim of this work was to verify the influence of the saturated (SFA) (stearic acid) and the unsaturated (UFA) (oleic and alpha-linolenic) fatty acids on model cholesterol/phospholipid membranes. The experiments were based on the Langmuir monolayer technique. Cholesterol and phospholipid were mixed in the molar ratio that corresponds to the proportion of these lipids in the majority of natural human membranes. Into the binary cholesterol/phospholipid monolayers, various amounts of fatty acids were incorporated. Our investigations were based on the analysis of the interactions between molecules in ternary (cholesterol/phospholipids/fatty acid) mixtures, however, also binary (cholesterol/fatty acid and phospholipids/fatty acid) mixed system were examined. It was concluded that the influence of the fatty acids on model cholesterol/phospholipid membrane is closely connected with the shape of the fatty acid molecule, resulting from the saturation degree of the hydrocarbon chain. It was found that the saturated fatty acid makes the model membrane more rigid, while the presence of unsaturated fatty acid increases its fluidity. The increasing amount of stearic acid gradually destabilizes model membrane, however, this effect is the weakest at low content of SFA in the mixed monolayer. Unsaturated fatty acids in a small proportion make the membrane thermodynamically more stable, while higher content of UFA decreases membrane stability. This explains low proportion of the free fatty acids to other lipids in natural membrane.

Thermodynamic description of the interactions between lipids in ternary Langmuir monolayers: the study of cholesterol distribution in membranes

The aim of this work was to get insight into cholesterol distribution between two leaflets of a phospholipids bilayer. In this order, the thermodynamic analysis of the interactions between membrane lipids in binary (cholesterol/phospholipid) and ternary (phospholipid/ phospholipid/cholesterol) mixed Langmuir monolayers has been performed. For our investigation, phosphatidylcholine and phosphatidylethanolamine, which are the main types of phospholipids determining the distribution of cholesterol in membrane leaflets, were chosen and mixed in proportions corresponding to their molar ratios in the inner and outer layers of the natural human erythrocyte membrane. Into these mixed systems, various amount of cholesterol were incorporated. It has been found that despite strong differences in the phospholipid composition of both investigated ternary mixed systems, the influence of cholesterol is very similar, which indicates that cholesterol is symmetrically distributed between the inner and outer leaflets of the human erythrocytes membrane.

Nystatin in Langmuir monolayers at the air/water interface

The paper presents a thorough characteristics of Langmuir monolayers formed at the air/water interface by a polyene macrolide antibiotic-nystatin. The investigations are based on the analysis of pi/A isotherms recorded for monolayers formed by this antibiotic at different experimental conditions. A significant part of this work is devoted to the stability and relaxation phenomena. It has been found that nystatin forms at the air/water interface monolayers of the LE state. A plateau region, observed during the course of the isotherm compression, is suggested to be due to the orientational change of nystatin molecules from horizontal to vertical position. Quantitative analysis of the desorption of the monolayer material into bulk water indicates that the solubility of nystatin monolayers increases with surface pressure. At low surface pressures, the desorption of nystatin from a monolayer is controlled both by dissolution and by diffusion. However, at the plateau and in the post-plateau region, the desorption does not achieve a steady state and the monolayer is less stable than in the pre-plateau region. However, the presence of membrane lipids, even at a low mole fraction, considerably increases the stability of nystatin monolayers. This enables the application of the Langmuir monolayer technique to study nystatin in mixture with cellular membrane components, aiming at verifying its mode of action and the mechanism of toxicity.

Doxorubicin biocompatible O/W microemulsion stabilized by mixed surfactant containing soya phosphatidylcholine

Microemulsions (ME) containing soya phosphatidylcholine (SPC)/polyoxyethylenglycerol trihydroxystearate 40 (EU)/sodium oleate (SO) as surfactant cholesterol (CHO) as oil phase and aqueous buffer were studied. Pseudo-ternary phase diagrams of the investigated systems were obtained at constant SPC/EU/SO weight ratio 3.5:3.5:3.0 by titration, in order to characterize the proportions between the components to form clear systems. The dynamic light scattering results showed that the size of the oil droplets decreases significantly with the ratio of surfactant/oil phase added to system. Depending on the composition ME system could exhibit a thixotropic behavior. The apparent viscosity increased 25- and 13-folds with cholesterol concentration for drug-free and drug-load ME, respectively. It was also verified that the octanol/aqueous buffer partition coefficient (KO/B) of doxorubicin (DOX) was pH dependent increasing abruptly above pH 6.0. It was possible to incorporate 2.24 mg/ml of DOX into ME. The incorporation of DOX in the ME systems increased the droplets size for all surfactant concentrations used in the system. The results suggest that DOX interacts with the microstructure of the ME at the studied pH increasing significantly the drug solubility. It was possible to conclude that the investigated ME can be a very promising vehicle as drug-carrier for administration of doxorubicin.

Interactions of amphotericin B derivative of low toxicity with biological membrane components—the Langmuir monolayer approach

Amphotericin B (AmB)--a polyene macrolide antibiotic--exhibits strong antifungal activity, however, is known to be very toxic to mammalian cells. In order to decrease AmB toxicity, a number of its derivatives have been synthesized. Basing on in vitro and in vivo research, it was evidenced that one of AmB derivatives, namely N-methyl-N-D-fructopyranosylamphotericin B methyl ester (in short MF-AME) retained most of the antifungal activity of the parent antibiotic, however, exhibited dramatically lower animal toxicity. Therefore, MF-AME seems to be a very promising modification product of AmB. However, further development of this derivative as potential new antifungal drug requires the elucidation of its molecular mechanism of reduced toxicity, which was the aim of the present investigations. Our studies were based on examining the binding energies by determining the strength of interaction between MF-AME and membrane sterols (ergosterol-fungi sterol, and cholesterol-mammalian sterol) and DPPC (model membrane phospholipid) using the Langmuir monolayer technique, which serves as a model of cellular membrane. Our results revealed that at low concentration the affinity of MF-AME to ergosterol is considerably stronger as compared to cholesterol, which correlates with the improved selective toxicity of this drug. It is of importance that the presence of phospholipids is essential since--due to very strong interactions between MF-AME and DPPC--the antibiotic used in higher concentration is "immobilized" by DPPC molecules, which reduces the concentration of free antibiotic, thus enabling it to selectively interact with both sterols.

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.

Studies on the encapsulation of diclofenac in small unilamellar liposomes of soya phosphatidylcholine

The encapsulation of acid (AD) and sodium diclofenac (SD) in small unilamellar liposomes (SUV) as well as the interactions of the drug with the bilayer was studied. SUV was prepared by sonication from multilamellar liposomes containing soya phosphatidylcholine and diclofenac at various proportions. The size distribution obtained from dynamic light scattering showed that the incorporation of SD decreases significantly the size of the liposomes suggesting that the drug interacts with the bilayer of the liposomes. This size decrease is related with the phase transition of liposomes to mixed micelar solution. The encapsulation of the hydrophilic dye indocyanine green in the aqueous compartment of liposomes showed that the rate of captured dye decreases with SD concentration suggesting the transition of liposomes to mixed micelles. The (31)P NMR analysis indicates that SD interacts with the phosphate of phosphatidylcholine head groups. A schematic model for interaction of SD with phosphatidylcholine of the liposomes in which the diclofenac anion interacts with the ammonium group of the phospholipid and the dichlorophenyl ring occupies a more internal site of bilayer near phosphate group was proposed.