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PubMed1990

Bile salt-fatty acid mixed micelles as nasal absorption promoters of peptides. II. In vivo nasal absorption of insulin in rats and effects of mixed micelles on the morphological integrity of the nasal mucosa.

The effectiveness of mixed micelles in promoting nasal absorption of peptides has been demonstrated in vivo by employing insulin as a model compound. Insulin in the absence of adjuvants was not absorbed following intranasal administration. The results confirmed previous findings by others that absorption of insulin via alternative routes required absorption enhancers. Mixed micelles between NaGC and linoleic acid were found to rapidly deliver insulin into systemic circulation, with a concomitant decrease in plasma glucose. The extent of the hypoglycemic response was significantly greater than that produced by NaGC alone (55 vs 47%, P less than 0.05). Emulsion of linoleic acid, on the other hand, did not produce any significant insulin absorption. The findings thus supported previous in situ data that mixed micelles were more effective than NaGC or linoleic acid in promoting nasal absorption of peptides. Histopathologic examination of the rat nasal mucosa revealed that the extent of morphological alterations caused by mixed micelles was of mild to moderate severity even after 5 hr of exposure. However, studies involving more frequent and prolonged exposures are necessary to assess the practicality of these adjuvants before any clinical application can be attempted.

Absorption↗

PubMed1996

Micropolarity of Reversed Micelles: Comparison between Anionic, Cationic, and Nonionic Reversed Micelles

The interface polarity of benzyl-n-hexadecyldimethylammonium chloride (BHDC) cationic reversed micelles in benzene was studied and compared with those of the anionic systems of sodium 1,4-bis-2-ethylhexylsulfosuccinate (AOT) in benzene and hexane. The nonionic reversed micelles of the poly(oxyethylene)n dodecyl ethers type surfactants Brij 30 in benzene, cyclohexane, and decane and C12E5 in hexane, heptane, and decane were also investigated. 1-Methyl-8-oxyquinolinium betaine (QB) was used as optical probe. The influence of surfactant concentration and W = [H2O]/[surfactant] were analyzed as a function of the absorption bands shifts in the visible, B1, and in the UV, B2, and the absorbances ratio of these bands. At W = 0 the polarity sensed in the micelle interfaces of AOT-hexane and AOT-benzene is entirely similar while for BHDC-benzene is quite smaller. The detected interaction between the QB and BHDC may favor the entrance of QB into the oil side of the micelle interface thus sensing a less polar environment. At W >/= 10 once the polar heads of the surfactants are completed hydrated, the anionic as well as the cationic surfactants show the same behavior. The polarity of Brij 30 and C12E5 in the aliphatic hydrocarbons is comparable. However at W = 0 their micropolarity is higher than that of AOT-hexane, showing that the formation of hydrogen bond between QB and the free OH groups of these surfactants is the major factor affecting the microenvironment. In all the studied systems even at the maximum possible W, the polarity sensed by QB never reaches the value of pure water, that is, never reaches the bulk water phase prevailing in the micellar core.

Journal Article↗

PubMed1974

Thermodynamics of micelle formation: prediction of micelle size and size distribution.

This paper presents a simple theory for the calculation of micelle size and other properties of micelleforming systems. The theory is based on the separate estimation of the components of the free energy arising from hydrophobic attraction and from head group repulsion, each as a function of micelle size. The difficult problem of an a priori calculation of the repulsive factor is circumvented by using experimental values of this parameter, derived from pressure-area curves of monolayers at an interface between an aqueous solution and liquid hydrocarbon. Though some parameters of the theory are still somewhat uncertain, self-consistent and physically realistic values can be assigned that lead to almost exact prediction of experimental micelle sizes and critical micelle concentrations for two distinctly different ionic detergents.

Lipids↗

PubMed2002

Drug delivery in pluronic micelles: effect of high-frequency ultrasound on drug release from micelles and intracellular uptake.

The effect of high-frequency ultrasound on doxorubicin (DOX) release from Pluronic micelles and intracellular DOX uptake was studied for promyelocytic leukemia HL-60 cells, ovarian carcinoma drug-sensitive and multidrug-resistant (MDR) cells (A2780 and A2780/ADR, respectively), and breast cancer MCF-7 cells. Cavitation events initiated by high-frequency ultrasound were recorded by radical trapping. The onset of transient cavitation and DOX release from micelles were observed at much higher power densities than at low-frequency ultrasound (20-100 kHz). Even a short (15-30 s) exposure to high-frequency ultrasound significantly enhanced the intracellular DOX uptake from PBS, RPMI 1640, and Pluronic micelles. The mechanisms of the observed effects are discussed.

Algorithms↗

PubMed1989

Micelle-mediated transport of vitamin K1 through porous membranes: contribution of phosphatidylcholine-bile salt mixed micelles.

Diffusion of vitamin K1 solubilized by phosphatidylcholine-sodium deoxycholate mixed micelles through porous membranes having various pore characteristics was examined. The membranes include Nuclepore, Duragard and nitrocellulose membranes, which were intended to mimic the narrow channels in the vicinity of absorptive brush border. The diffusion coefficient of the mixed micelles was 4.6-5.5 x 10(-7) cm2/s, from which the hydrodynamic radius was calculated to be about 50 A. The dependence of the diffusivity on pore size showed that the transport of the micelles is hindered by pores having a radius ratio of the diffusate to the pore of about 0.05 or larger.

Bile Acids and Salts↗

PubMed1992

Pluronic micelles as a tool for low-molecular compound vector delivery into a cell: effect of Staphylococcus aureus enterotoxin B on cell loading with micelle incorporated fluorescent dye.

Micelles of pluronic P85 (poly(oxyethylene)-poly(oxypropylene) block copolymer) are used as microcontainers for in vitro delivery of fluorescein into Jurkat and MDCK cells. In order to target the fluorescein containing micelles into the cell, Staphylococcus aureus enterotoxin B (SEB) is covalently conjugated with a pluronic molecule and the conjugate is incorporated into the micelle content. The incorporation of SEB capable of receptor-mediated endocytosis results in a drastic enhancement of the efficiency of cell loading with the fluorescent dye. This effect is not observed under the conditions (4 degrees C) when endocytosis is abolished.

Animals↗

PubMed2006

[Dependence of antimicrobial effect of micelle-capsulated therapeutics on the micelle size].

With the method of dynamic light scattering it was shown that the average size of micelles in the series of formulations based on various clindamycin salts, i. e. ClindHCl+Tween-20, ClindBz+Tween-20, ClindHCl+Cremafor-EL and ClindBz+Cremafor-EL increased from 6 to 20 nm. Investigations with the agar diffusion method revealed that the bactericidic action of the micelle-capsulated therapeutics did not depend on the micelle size within 6 to 20 mn. The concentration of the micellar clindamycin or gentamicin equal to 0.05 mcg/ml was bacteriostatic with respect to Micrococcus (Sarsina) luteus.

Anti-Bacterial Agents↗

PubMed2003

Charge variance of ionic micelles: a significant parameter to account for and to predict changes in degrees of micelle ionization and in aggregation numbers.

In the context of the thermodynamics of self-assembling systems, which predicts that both the number-average number of aggregation, N(n), of the ionic surfactants and the number-average degree of ionic dissociation of the micelles, alpha(n), depend on the concentrations of micellized surfactant and counterion in the bulk, it is shown that a key parameter is the ratio between sigma(Q), the standard deviation of the micelle charge distribution of the micelles, and sigma(N), that of the aggregation numbers. In the case of hexadecyltrimethylammonium acetate-acetic acid (1:1) solutions, this ratio is calculated as ca. 0.1 from conductivity and aggregation number data.

Journal Article↗

PubMed2002

Interaction of UO2 2+ with sodium dodecyl sulfate micelles: association of phenols to micelles through fluorescence quenching data.

Time-resolved laser-induced fluorescence (TRLIF) has been used to study the interaction of uranyl ion with sodium dodecyl sulfate (SDS) micelles in H(3)PO(4) 1 M. The titration curve consists of two curved regions with different slopes, one of them more pronounced at low concentration of SDS and the other, with a less pronounced positive slope at larger [SDS] until a plateau is reached. The fluorescence quenching of uranyl ion by para-substituted phenol compounds was studied by TRLIF and steady-state emission intensity measurements. The results were interpreted in terms of binding of phenolic compounds to the micelle. The binding constant (K(Q)) as well as the entrance and exit rate constants were determined for all the quenchers used.

Micelles↗

PubMed1989

The neuroleptic activity of haloperidol increases after its solubilization in surfactant micelles. Micelles as microcontainers for drug targeting.

It has been suggested to use surfactant micelles as microcontainers for increasing the efficiency of neuroleptic targeting from blood flow into the brain. The neuroleptic action of haloperidol, intraperitoneally injected into mice in micellar solution of non-ionic block copolymer surfactant (pluronic P-85) in water, increased several-fold if compared with that observed for haloperidol aqueous solution. Incorporation of brain-specific antibodies into haloperidol-containing micelles resulted in additional drastic increase (more than by 2 orders of magnitude) in the drug effect.

Animals↗

PubMed1993

Protein-protein interactions in reverse micelles: trypsin shows superactivity towards a protein substrate alpha-chymotrypsinogen A in reverse micelles of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) in isooctane.

Protein-protein interactions in reverse micelles of sodium bis(2-ethylhexyl)sulfosuccinate (AOT), in isooctane containing varying amounts of Tris buffer are studied by using activation of alpha-chymotrypsinogen A by trypsin (EC 3.4.21.4) to alpha-chymotrypsin (EC 3.4.21.1) as a model reaction. It has been found that protein-protein interactions are strongly dependent on the water content of the medium. At an optimum water content the activation reaction in reverse micelles is faster than reaction in water by a factor of 21.3. At lower water content both reaction rates and the conversion of alpha-chymotrypsinogen A into alpha-chymotrypsin decrease with decrease in water content of the reaction medium.

Catalysis↗

PubMed1988

Experimental confirmation of the change of water structure in the critical range of micelle formation: a new method of critical micelle concentration (CMC) determination.

The decrease in the water structure in the critical range of micelle formation, which had been deduced theoretically, was confirmed by means of a new determination method. The method was based upon the dependence of the gelatin helicity on the water structure and the correlation between the helix-coil equilibrium and the disintegration of gelatin microcapsules. The significant rise in the disintegration rate, indicating a decay of water structure, represents also a new method of critical micelle concentration (CMC) determination.

Capsules↗

PubMed1997

Two-dimensional 1H NMR experiments show that the 23-residue magainin antibiotic peptide is an alpha-helix in dodecylphosphocholine micelles, sodium dodecylsulfate micelles, and trifluoroethanol/water solution.

Magainin2 is a 23-residue antibiotic peptide that disrupts the ionic gradient across certain cell membranes. Two-dimensional 1H NMR spectroscopy was used to investigate the structure of the peptide in three of the membrane environments most commonly employed in biophysical studies. Sequence-specific resonance assignments were determined for the peptide in perdeuterated dodecylphosphocholine (DPC) and sodium dodecylsulfate micelles and confirmed for the peptide in 2,2,2-trifluoroethanol solution. The secondary structure is shown to be helical in all of the solvent systems. The NMR data were used as a set of restraints for a simulated annealing protocol that generated a family of three-dimensional structures of the peptide in DPC micelles, which superimposed best between residues 4 and 20. For these residues, the mean pairwise rms difference for the backbone atoms is 0.47 +/- 0.10 A from the average structure. The calculated peptide structures appear to be curved, with the bend centered at residues Phe12 and Gly13.

Amino Acid Sequence↗

PubMed1992

Micelles of poly(oxyethylene)-poly(oxypropylene) block copolymer (pluronic) as a tool for low-molecular compound delivery into a cell: phosphorylation of intracellular proteins with micelle incorporated [gamma-32P]ATP.

Pluronic P85 (poly(oxyethylene)-poly(oxypropylene) block copolymer) was used for in vitro delivery of [gamma-32P]ATP into intact Jurkat cells. Negatively charged ATP molecules are not able to penetrate cell plasma membrane. Hence, exogenous [gamma-32P]ATP added to a cell culture does not participate in phosphorylation of intracellular proteins. The addition to cells of [gamma-32P]ATP solubilized in positively charged (containing dodecylamine) pluronic micelles results in considerable increase of protein phosphorylation. In this case the treatment of intact cells with alkaline phosphatase (resulting in dephosphorylation of external proteins) causes no essential decrease of [32P]-incorporation in cell proteins. That gives an evidence of delivery of solubilized ATP into a cell. Under the experimental conditions used, pluronic micelles neither influence the viability of cells nor permeabilize cell plasma membrane.

Adenosine Triphosphate↗

PubMed2004

Thermodynamic study of the protonation of dimethyldodecylamine N-oxide micelles in aqueous solution at 298 K. Establishment of a theoretical relationship linking critical micelle concentrations and pH.

Dodecyldimethylamine N-oxide (DDAO) is a zwitterionic surfactant with acid-base properties. The proton dissociation constant of this surfactant was determined by a novel potentiometric method at "controlled chemical potential" of the proton using a classical pH-glass electrode. When the DDAO was in its monomeric form, the pKa was about 5, consistent with the value commonly reported in the literature. However, a unique proton dissociation constant specific to the micellar form of this surfactant could not be obtained. We found that the acid-base behavior of the DDAO micelles depended on their environment. Indeed, we were able to establish thermodynamic relations linking the critical micellar concentration to the degree of protonation of the micelles. The experimental values were in good accordance with this model.

Journal Article↗

PubMed2004

Acceleration of nucleophilic attack on an organophosphorothioate neurotoxin, fenitrothion, by reactive counterion cationic micelles. Regioselectivity as a probe of substrate orientation within the micelle.

31P NMR and UV-vis spectrometric evidence has revealed an unexpected regioselectivity in the reaction of fenitrothion, 1, an organophosphorus pesticide, with the cetyltrimethylammonium (CTA) surfactants CTAOH and CTAMINA, that incorporate the reactive counterions OH- and MINA- (the anti-pyruvaldehyde 1-oximate anion). While both micellar solutions accelerate decomposition of 1 compared to aqueous OH- alone, CTAMINA produced the largest rate enhancement (ca. 10(5)) at a pH (8.39) appropriate for environmental applications. In the absence of surfactant, reaction proceeds solely via the SN2(P) pathway. In the presence of surfactant but below the critical micelle concentration (cmc), a competitive SN2(C) pathway was observed in addition to SN2(P). Above the cmc, however, the CTAOH reaction again proceeded solely via the SN2(P) pathway while both pathways were operative with CTAMINA. The changes in reactivity and mechanistic pathway are discussed in terms of premicellar and micellar influences on rates and regioselectivity. A proposal that would account for the observed regioselectivity in the micellar system is that the aromatic ring and aliphatic side-chains of 1 are oriented toward the micellar interior, while the P=S moiety faces the aqueous pseudophase.

Cations↗

PubMed1995

Kinetic analysis of phospholipase C beta isoforms using phospholipid-detergent mixed micelles. Evidence for interfacial catalysis involving distinct micelle binding and catalytic steps.

Phosphatidylinositol 4,5-bisphosphate (PtdIns (4,5)-P2) hydrolysis by three different beta-isoforms of phospholipase C (PLC) was examined to investigate the catalytic action of these extracellular signal-regulated enzymes. Depletion of phospholipase C from solution by incubation with sucrose-loaded vesicles of differing compositions followed by ultracentrifugation demonstrated stable attachment of PLC to the vesicles from which an equilibrium association constant of PLC with PtdIns (4,5)P2 could be determined. A mixed micellar system was established to assay PLC activity using dodecyl maltoside, which behaved as an essentially inert diluent of PtdIns (4,5)P2 with respect to PLC beta activity. Kinetic analyses were performed to test whether PLC beta activity was dependent on both bulk PtdIns (4,5)P2 concentration and surface concentration in the micelles as has been shown for other lipid metabolising enzymes. Each of the PLC beta isoforms behaved similarly in these analyses, which indicated the involvement of at least two binding events. Interfacial Michaelis constants were calculated to be between 0.1-0.2 mol fraction for all three enzymes, and Ks (the equilibrium dissociation constant of PLC for lipid) ranged between 100-200 microM. The apparent multiple interfacial binding events did not appear to result from lipid-induced PLC beta oligomerization implying that PLC beta monomers possess more than one lipid-binding site. Surface dilution of PLC-catalyzed PtdIns (4,5)P2 hydrolysis was assessed in the presence of increasing concentrations of various nonsubstrate phospholipids, which profoundly reduced PLC activity, suggesting that these lipids may inhibit enzyme action. The data indicate that G protein-regulated isoforms of PLC operate with separate lipid binding and catalytic steps and imply that under physiological conditions, PLC beta isoforms operate under first-order conditions. These findings may have implications for the mechanisms of regulation of PLC beta s by G protein subunits.

Animals↗

PubMed2004

Micelles and reverse micelles in the nickel bis(2-ethylhexyl) sulfosuccinate/water/isooctane microemulsion.

The ternary system Ni(2+)(AOT)(2) (nickel 2-bis[2-ethylhexyl] sulfosuccinate)/water/isooctane presents w/o and o/w microemulsions with a Winsor progression (2Phi-3Phi-2Phi), without the addition of salt; the "fish diagram" was obtained for alpha=0.5 and gamma=0.02-0.22. Using static and dynamic light scattering the micellar size, the ratio of water to surfactant, and the density of micelles for this system were estimated. In addition, the mean interfacial curvature as a function of temperature was obtained.

Journal Article↗