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Sample records for des micelles inverses

  1. Preparatiion of metal colloids in inverse micelles

    SciTech Connect

    Wilcoxon, J.P.

    1990-11-23

    A method is provided for preparing catalytic elemental metal colloidal particles (e.g., gold, palladium, silver, rhodium, nickel, iron, platinum, molybdenum) or colloidal alloy particles (silver/iridium or platinum/gold). A homogenous inverse micelle solution of a metal salt is first formed in a metal-salt solvent comprised of a surfactant (e.g. a nonionic or cationic surfactant) and an organic solvent. The size and number of inverse micelles is controlled by the proportions of the surfactant and the solvent. Then, the metal salt is reduced (by chemical reduction or by a pulsed or continuous wave UV laser) to colloidal particles of elemental metal. After their formation, the colloidal metal particles can be stabilized by reaction with materials that permanently add surface stabilizing groups to the surface of the colloidal metal particles. The sizes of the colloidal elemental metal particles and their size distribution is determined by the size and number of the inverse micelles. A second salt can be added with further reduction to form the colloidal alloy particles. After the colloidal elemental metal particles are formed, the homogeneous solution distributes to two phases, one phase rich in colloidal elemental metal particles and the other phase rich in surfactant. The colloidal elemental metal particles from one phase can be dried to form a powder useful as a catalyst.

  2. Characterizing generated charged inverse micelles with transient current measurements.

    PubMed

    Strubbe, Filip; Prasad, Manoj; Beunis, Filip

    2015-02-01

    We investigate the generation of charged inverse micelles in nonpolar surfactant solutions relevant for applications such as electronic ink displays and liquid toners. When a voltage is applied across a thin layer of a nonpolar surfactant solution between planar electrodes, the generation of charged inverse micelles leads to a generation current. From current measurements it appears that such charged inverse micelles generated in the presence of an electric field behave differently compared to those present in equilibrium in the absence of a field. To examine the origin of this difference, transient current measurements in which the applied voltage is suddenly increased are used to measure the mobility and the amount of generated charged inverse micelles. The mobility and the corresponding hydrodynamic size are found to be similar to those of charged inverse micelles present in equilibrium, which indicates that other properties determine their different behavior. The amplitude and shape of the transient currents measured as a function of the surfactant concentration confirm that the charged inverse micelles are generated by bulk disproportionation. A theoretical model based on bulk disproportionation with simulations and analytical approximations is developed to analyze the experimental transient currents. PMID:25580883

  3. Formation of catalysts in inverse micelles

    SciTech Connect

    Wilcoxon, J.P.; Baughmann, R.J.; Williamson, R.L.

    1990-01-01

    We report formation of several small colloidal metal catatlysts in inverted micelle (oil-continuous) systems. These materials have demonstrated catalytic activity in situ (i.e. unsupported). The range of solvents possible in this process is large, including all saturated hydrocarbons, cyclic hydrocarbons (e.g. cyclohexane) and aromatics (e.g. toluene, xylene). Three classes of micelle system were investigated, nonionic, anionic, and cationic. Nonionic types allow precise size control but in general do not act as strong stabilizing agents at high temperatures. Cationics can be chosen to provide this permanent stability, providing both charge and steric stabilization. Metal systems formed include Rh, Ni, NiB, MoO{sub 2}, Pd, Au and Ag and alloys. Selected examples are given. 4 figs.

  4. Transport of charged Aerosol OT inverse micelles in nonpolar liquids.

    PubMed

    Karvar, Masoumeh; Strubbe, Filip; Beunis, Filip; Kemp, Roger; Smith, Ashley; Goulding, Mark; Neyts, Kristiaan

    2011-09-01

    Surfactants such as Aerosol OT (AOT) are commonly used to stabilize and electrically charge nonpolar colloids in devices such as electronic ink displays. The electrical behavior of such devices is strongly influenced by the presence of charged inverse micelles, formed by excess surfactant that does not cover the particles. The presence of charged inverse micelles results in increased conductivity of the solution, affecting both the energy consumption of the device and its switching characteristics. In this work, we use transient current measurements to investigate the electrical properties of suspensions of the surfactant Aerosol OT in dodecane. No particles are added, to isolate the effect of excess surfactant. The measured currents upon application of a voltage step are found to be exponentially decaying, and can be described by an analytical model based on an equivalent electric circuit. This behavior is physically interpreted, first by the high generation rate of charged inverse micelles giving the suspension resistor like properties, and second by the buildup of layers of charged inverse micelles at both electrodes, acting as capacitors. The model explains the measurements over a large range of surfactant concentrations, applied voltages, and device thicknesses. PMID:21728309

  5. Synthesis and characterization of FE colloid catalysts in inverse micelle solutions

    SciTech Connect

    Martino, A.; Sault, A.G.; Kawola, J.S.; Stoker, M.; Hicks, M.; Bartholomew, C.H.

    1995-02-01

    Formation of Fe clusters in inverse micelles was studied. Iron salts are solubilized within the polar interior of inverse micelles, and addition of LiBH{sub 4} initiates reduction to produce monodisperse, nanometer-sized Fe based particles. The reaction sequence is sustained by material exchange between inverse micelles. Surfactant interface provides a spatial constraint on reaction volume, and reactions carried out in these micro-heterogeneous solutions produce colloidal sized particles (10--100 {Angstrom}) stabilized in solution against flocculation by surfactant. In this paper, the clusters were characterized using TEM, Moessbauer spectroscopy, electron diffraction, and x-ray photoelectron spectroscopy.

  6. Switching of charged inverse micelles in non-polar liquids.

    PubMed

    Prasad, Manoj; Beunis, Filip; Neyts, Kristiaan; Strubbe, Filip

    2015-11-15

    The electrodynamics of micellar ions in nonpolar liquids are well understood for the case that a voltage is applied or switched off. In this work, the electrodynamics of charged inverse micelles (CIMs) are studied when the applied voltage is switched to the opposite polarity, which is relevant for applications such as electrophoretic displays and liquid toner printing. Transient current measurements are used to characterize the switching of CIMs formed in a solution of surfactant polyisobutylene succinimide in n-dodecane. For reverse voltages with amplitude below 10V the measurements are in good agreement with a drift and diffusion model, confirming the established understanding of CIMs in nonpolar liquids. When the charge content is high, the reversal current shows a characteristic peak which is explained on the basis of dynamic space-charge effects. However, for reverse voltages larger than 10V, the transient currents are influenced by electrohydrodynamic flow in the liquid causing the CIMs to switch faster than predicted by the model. The occurrence of electrohydrodynamic flow is verified by optical tracking of tracer particles. Also, when the polarizing voltage is applied for longer times, an additional current peak emerges which is due to the accumulation of newly generated charges at the electrodes. PMID:26203590

  7. Different Types of Charged-Inverse Micelles in Nonpolar Media.

    PubMed

    Prasad, Manoj; Strubbe, Filip; Beunis, Filip; Neyts, Kristiaan

    2016-06-14

    Over the last few years, the electrodynamics of charged inverse micelles (CIMs) in nonpolar liquids and the generation mechanism and properties of newly generated CIMs have been studied extensively for the model system of polyisobutylene succinimide in dodecane. However, the newly generated CIMs, which accumulate at the electrodes when a continuous voltage is applied, behave differently compared to the regular CIMs present in equilibrium in the absence of a field. In this work, we use transient current measurements to investigate the behavior of the newly generated CIMs when the field is reduced to zero or reversed. We demonstrate that the newly generated CIMs do not participate in the diffuse double layer near the electrode formed by the regular CIMs but form an interface layer at the electrode surface. A fraction of the newly generated negative CIMs can be released from this interface layer when the field there becomes zero. The findings of this study provide a better understanding of fundamental processes in nonpolar liquids and are relevant for applications such as electronic ink displays and liquid toner printing. PMID:27231768

  8. Synthesis and characterization of Fe colloid catalysts in inverse micelle solutions

    SciTech Connect

    Martino, A.; Stoker, M.; Hicks, M.

    1995-12-31

    Surfactant molecules, possessing a hydrophilic head group and a hydrophobic tail group, aggregate in various solvents to form structured solutions. In two component mixtures of surfactant and organic solvents (e.g., toluene and alkanes), surfactants aggregate to form inverse micelles. Here, the hydrophilic head groups shield themselves by forming a polar core, and the hydrophobic tails groups are free to move about in the surrounding oleic phase. The formation of Fe clusters in inverse miscelles was studied.Iron salts are solubilized within the polar interior of inverse micelles, and the addition of the reducing agent LiBH{sub 4} initiates a chemical reduction to produce monodisperse, nanometer sized Fe based particles. The reaction sequence is sustained by material exchange between inverse micelles. The surfactant interface provides a spatial constraint on the reaction volume, and reactions carried out in these micro-heterogeneous solutions produce colloidal sized particles (10-100{Angstrom}) stabilized in solution against flocculation of surfactant. The clusters were stabilized with respect to size with transmission electron microscopy (TEM) and with respect to chemical composition with Mossbauer spectroscopy, electron diffraction, and x-ray photoelectron spectroscopy (XPS). In addition, these iron based clusters were tested for catalytic activity in a model hydrogenolysis reaction. The hydrogenolysis of naphthyl bibenzyl methane was used as a model for coal pyrolysis.

  9. Encapsulation of nanoclusters in dried gel materials via an inverse micelle/sol gel synthesis

    DOEpatents

    Martino, Anthony; Yamanaka, Stacey A.; Kawola, Jeffrey S.; Showalter, Steven K.; Loy, Douglas A.

    1998-01-01

    A dried gel material sterically entrapping nanoclusters of a catalytically active material and a process to make the material via an inverse micelle/sol-gel synthesis. A surfactant is mixed with an apolar solvent to form an inverse micelle solution. A salt of a catalytically active material, such as gold chloride, is added along with a silica gel precursor to the solution to form a mixture. To the mixture are then added a reducing agent for the purpose of reducing the gold in the gold chloride to atomic gold to form the nanoclusters and a condensing agent to form the gel which sterically entraps the nanoclusters. The nanoclusters are normally in the average size range of from 5-10 nm in diameter with a monodisperse size distribution.

  10. Encapsulation of nanoclusters in dried gel materials via an inverse micelle/sol gel synthesis

    DOEpatents

    Martino, A.; Yamanaka, S.A.; Kawola, J.S.; Showalter, S.K.; Loy, D.A.

    1998-09-29

    A dried gel material sterically entrapping nanoclusters of a catalytically active material and a process to make the material via an inverse micelle/sol-gel synthesis are disclosed. A surfactant is mixed with an apolar solvent to form an inverse micelle solution. A salt of a catalytically active material, such as gold chloride, is added along with a silica gel precursor to the solution to form a mixture. To the mixture are then added a reducing agent for the purpose of reducing the gold in the gold chloride to atomic gold to form the nanoclusters and a condensing agent to form the gel which sterically entraps the nanoclusters. The nanoclusters are normally in the average size range of from 5--10 nm in diameter with a monodisperse size distribution. 1 fig.

  11. Space charge limited release of charged inverse micelles in non-polar liquids.

    PubMed

    Prasad, Manoj; Strubbe, Filip; Beunis, Filip; Neyts, Kristiaan

    2016-07-28

    Charged inverse micelles (CIMs) generated during a continuous polarizing voltage between electrodes in the model system of polyisobutylene succinimide in dodecane do not populate a diffuse double layer like CIMs present in equilibrium (regular CIMs), but instead end up in interface layers. When the applied voltage is reversed abruptly after a continuous polarizing voltage step, two peaks are observed in the transient current. The first peak is due to the release of regular CIMs from the diffuse double layers formed during the polarizing voltage step, which is understood on the basis of the Poisson-Nernst-Planck equations. The second peak is due to the release of a small fraction of generated negative CIMs from the interface layer. A model based on space charge limited release of the generated negative CIMs from the interface layer is presented and the results of the model are compared with several types of measurements. For the situation in which the bulk is deprived of regular CIMs and neutral inverse micelles, the results of the model are in agreement with the experimental results. However, for the situation in which regular CIMs and neutral inverse micelles are present, the model shows discrepancies with the experiment for high voltages and high charge contents. These discrepancies are attributed to electrohydrodynamic flow caused by local variations in the electric field at the vicinity of the electrodes, which occur during the reversal voltage. Also the long term decrease of the amount of released generated CIMs is studied and it is found that the presence of regular CIMs and neutral inverse micelles speeds up the decrease. This study provides a deeper insight in the electrodynamics of CIMs and is relevant for various applications in non-polar liquids. PMID:27374418

  12. Method for the preparation of metal colloids in inverse micelles and product preferred by the method

    DOEpatents

    Wilcoxon, Jess P.

    1992-01-01

    A method is provided for preparing catalytic elemental metal colloidal particles (e.g. gold, palladium, silver, rhodium, iridium, nickel, iron, platinum, molybdenum) or colloidal alloy particles (silver/iridium or platinum/gold). A homogeneous inverse micelle solution of a metal salt is first formed in a metal-salt solvent comprised of a surfactant (e.g. a nonionic or cationic surfactant) and an organic solvent. The size and number of inverse micelles is controlled by the proportions of the surfactant and the solvent. Then, the metal salt is reduced (by chemical reduction or by a pulsed or continuous wave UV laser) to colloidal particles of elemental metal. After their formation, the colloidal metal particles can be stabilized by reaction with materials that permanently add surface stabilizing groups to the surface of the colloidal metal particles. The sizes of the colloidal elemental metal particles and their size distribution is determined by the size and number of the inverse micelles. A second salt can be added with further reduction to form the colloidal alloy particles. After the colloidal elemental metal particles are formed, the homogeneous solution distributes to two phases, one phase rich in colloidal elemental metal particles and the other phase rich in surfactant. The colloidal elemental metal particles from one phase can be dried to form a powder useful as a catalyst. Surfactant can be recovered and recycled from the phase rich in surfactant.

  13. Solving the Structure of Size-Selected Pt Nanocatalysts Synthesized by Inverse Micelle Encapsulation

    SciTech Connect

    Cuenya, B.; Croy, J; Mostafa, S; Behafarid, F; Li, L; Zhang, Z; Yang, J; Wang, Q; Frenkel, A

    2010-01-01

    The structure, size, and shape of {gamma}-Al{sub 2}O{sub 3}-supported Pt nanoparticles (NPs) synthesized by inverse micelle encapsulation have been resolved via a synergistic combination of imaging and spectroscopic tools. It is shown that this synthesis method leads to 3D NP shapes even for subnanometer clusters, in contrast to the raft-like structures obtained for the same systems via traditional deposition-precipitation methods. Furthermore, a high degree of atomic ordering is observed for the micellar NPs in H{sub 2} atmosphere at all sizes studied, possibly due to H-induced surface reconstruction in these high surface area clusters. Our findings demonstrate that the influence of NP/support interactions on NP structure can be diminished in favor of NP/adsorbate interactions when NP catalysts are prepared by micelle encapsulation methods.

  14. Encapsulated metal nanocluster materials prepared by a novel inverse micelle/sol-gel technique

    SciTech Connect

    Yamanaka, S.A.; Martino, A.; Kawola, J.S.

    1995-12-31

    A wide variety of manometer sized metal and semiconductor particles (Au, Ag, Pd, Pt, Rh, Fe, Ni, CdS, MoS{sub 2} and FeS{sub 2}) can be prepared using an inverse micelle technique. Such materials are of great interest for their potential use in catalytic, photochemical, electrochemical and optical applications but their practicality is often hindered by the agglomeration of the particles. Agglomeration may be prevented by using a porous support matrix where the nanoclusters are sterically trapped within the pores. The sol-gel process results in the formation of such a porous support material. We have thus combined the technique of forming metal nanoclusters in inverse micelle solutions with the technique of forming sol-gel materials. Using our novel method, we have succeeded in preparing manometer sized metal colloids encapsulated in both xerogel and aerogel materials. Characterization of these materials has been carried out by TEM, SEM, UV/Vis, NMR and nitrogen sorption porosimetry.

  15. Synthesis and characterization of Fe colloid catalysts in inverse micelle solutions

    SciTech Connect

    Martino, A.; Stoker, M.; Hicks, M.

    1995-10-01

    We have studied the formation of Fe clusters in inverse micelles. We have characterized the clusters with respect to size with transmission electron microscopy (TEM) and with respect to chemical composition with Mossbauer spectroscopy, electron diffraction, and x-ray photoelectron spectroscopy (XPS). In addition, we have tested these iron based clusters for catalytic activity in a model hydrogenolysis reaction. The formation of ultra-small metal particles is of particular interest in the area of chemical catalysis. The clusters are high surface area, highly dispersed, unsupported materials. In addition, catalytic enhancement due to unique material properties (i.e. quantum size effects) is possible. Metal clusters prepared by a number of techniques have been studied as potential catalysts. Reactant adsorption and the reactivity in various processes depends strongly on particle size. We are studying iron clusters as potential catalysts in hydrogenation reactions, Fischer-Tropsch synthesis, and coal liquefaction.

  16. Optical and Electronic Properties of Si Nanoclusters Synthesized in Inverse Micelles

    SciTech Connect

    Provencio, P.N.; Samara, G.A.; Wilcoxon, J.P.

    1998-12-14

    Highly crystalline, size-selected silicon (Si) nanocrystals in the size range 2-10 nm were grown in inverse micelles and their optical absorption and photoluminescence (PL) properties were studied. High resolution TEM and electron diffraction results show that these nanocrystals retain their cubic diamond stuctures down to sizes {approximately}4 nm in diameter, and optical absorption data suggest that this structure and bulk-like properties are retained down to the smallest sizes produced ({approximately}1.8 nm diameter containing about 150 Si atoms). High pressure liquid chromatography techniques with on-line optical and electrical diagnostics were developed to purify and separate the clusters into pure, monodisperse populations. The optical absorption revealed features associated with both the indirect and direct bandgap transitions, and these transitions exhibited different quantum confinement effects. The indirect bandgap shifts from 1.1 eV in the bulk to {approximately}2.1 eV for nanocrystals {approximately}2 nm in diameter and the direct transition at r(l_"X - r15) blue shifts by 0.4 eV from its 3.4 eV bulk value over the same size range. Tailorable, visible, room temperature PL in the range 700-350 nm (1.8 - 3.5 eV) was observed from these nanocrystals. The most intense PL was in the violet region of the spectrum ({approximately}400 nm) and is attributed to direct electron-hole recombination. Other less intense PL peaks are attributed to surface state and to indirect bandgap recombination. The results are compared to earlier work on Si clusters grown by other techniques and to the predictions of various model calculations. Currently, the wide variations in the theoretical predictions of the various models along with considerable uncertainties in experimental size determination for clusters less than 3-4 nm, make it difficult to select among competing models.

  17. Splitting of Surface-Immobilized Multicompartment Micelles into Clusters upon Charge Inversion.

    PubMed

    Dewald, Inna; Gensel, Julia; Betthausen, Eva; Borisov, Oleg V; Müller, Axel H E; Schacher, Felix H; Fery, Andreas

    2016-05-24

    We investigate a morphological transition of surface-immobilized triblock terpolymer micelles: the splitting into well-defined clusters of satellite micelles upon pH changes. The multicompartment micelles are formed in aqueous solution of ABC triblock terpolymers consisting of a hydrophobic polybutadiene block, a weak polyanionic poly(methacrylic acid) block, and a weak polycationic poly(2-(dimethylamino)ethyl methacrylate) block. They are subsequently immobilized on silicon wafer surfaces by dip-coating. The splitting process is triggered by a pH change to strongly basic pH, which goes along with a charge reversal of the micelles. We find that the aggregation number of the submicelles is well-defined and that larger micelles have a tendency to split into a larger number of submicelles. Furthermore, there is a clear preference for clusters consisting of doublets and triplets of submicelles. The morphology of surface-immobilized clusters can be "quenched" by returning to the original pH. Thus, such well-defined micellar clusters can be stabilized and are available as colloidal building blocks for the formation of hierarchical surface structures. We discuss the underlying physicochemical principles of the splitting process considering changes in charge and total free energy of the micelles upon pH change. PMID:27101441

  18. Highly Dispersed Pseudo-Homogeneous and Heterogeneous Catalysts Synthesized via Inverse Micelle Solutions for the Liquefaction of Coal

    SciTech Connect

    Hampden-Smith, M.; Kawola, J.S.; Martino, A.; Sault, A.G.; Yamanaka, S.A.

    1999-01-05

    The mission of this project was to use inverse micelle solutions to synthesize nanometer sized metal particles and test the particles as catalysts in the liquefaction of coal and other related reactions. The initial focus of the project was the synthesis of iron based materials in pseudo-homogeneous form. The frost three chapters discuss the synthesis, characterization, and catalyst testing in coal liquefaction and model coal liquefaction reactions of iron based pseudo-homogeneous materials. Later, we became interested in highly dispersed catalysts for coprocessing of coal and plastic waste. Bifunctional catalysts . to hydrogenate the coal and depolymerize the plastic waste are ideal. We began studying, based on our previously devised synthesis strategies, the synthesis of heterogeneous catalysts with a bifunctional nature. In chapter 4, we discuss the fundamental principles in heterogeneous catalysis synthesis with inverse micelle solutions. In chapter 5, we extend the synthesis of chapter 4 to practical systems and use the materials in catalyst testing. Finally in chapter 6, we return to iron and coal liquefaction now studied with the heterogeneous catalysts.

  19. Inverse-Micelle-Encapsulated Water-Enabled Bond Breaking of Dialkyl Diselenide/Disulfide: A Critical Step for Synthesizing High- Quality Gold Nanoparticles

    SciTech Connect

    Zaluzhna, Oksana; Li, Ying; Allison, Thomas C.; Tong, Yu ye J.

    2012-10-09

    Inverse-micelle-encapsulated water formed in the two-phase Brust-Schiffrin method (BSM) synthesis of Au nanoparticles (NPs) is identified as essential for dialkyl diselenide/disulfide to react with the Au(III) complex in which the Se-Se/S-S bond is broken, leading to formation of higher-quality Au NPs.

  20. NMR solution structure of the glucagon antagonist [desHis1, desPhe6, Glu9]glucagon amide in the presence of perdeuterated dodecylphosphocholine micelles.

    PubMed

    Ying, Jinfa; Ahn, Jung-Mo; Jacobsen, Neil E; Brown, Michael F; Hruby, Victor J

    2003-03-18

    Glucagon, a 29-residue peptide hormone, plays an important role in glucose homeostasis and in diabetes mellitus. Several glucagon antagonists and agonists have been developed, but limited structural information is available to clarify the basis of their biological activity. The solution structure of the potent glucagon antagonist, [desHis1, desPhe6, Glu9]glucagon amide, was determined by homonuclear 2D NMR spectroscopy at pH 6.0 and 37 degrees C in perdeuterated dodecylphosphocholine micelles. The overall backbone root-mean-square deviation (rmsd) for the structured portion (residues 7-29, glucagon numbering) of the micelle-bound 27-residue peptide is 1.36 A for the 15 lowest-energy structures, after restrained molecular dynamics simulation. The structure consists of four regions (segment backbone rmsd in A): an unstructured N-terminal segment between residues 2 and 5 (1.68), an irregular helix between residues 7 and 14 (0.79), a hinge region between residues 15 and 18 (0.54), and a well-defined alpha-helix between residues 19 and 29 (0.33). The two helices form an L-shaped structure with an angle of about 90 degrees between the helix axes. There is an extended hydrophobic cluster, which runs along the inner surface of the L-structure and incorporates the side chains of the hydrophobic residues of each of the amphipathic helices. The outer surface contains the hydrophilic side chains, with two salt bridges (D15-R18 and R17-D21) implied from close approach of the charged groups. This result is the first clear indication of an overall tertiary fold for a glucagon analogue in the micelle-bound state. The relationship of the two helical structural elements may have important implications for the biological activity of the glucagon antagonist. PMID:12627948

  1. pH-Triggered reversible morphological inversion of orthogonally-addressable poly(3-acrylamidophenylboronic acid)-block-poly(acrylamidoethylamine) micelles and their shell crosslinked nanoparticles

    PubMed Central

    Zou, Jiong; Zhang, Shiyi; Shrestha, Ritu; Seetho, Kellie; Donley, Carrie L.

    2012-01-01

    Functionally-responsive amphiphilic core-shell nanoscopic objects, capable of either complete or partial inversion processes, were produced by the supramolecular assembly of pH-responsive block copolymers, without or with covalent crosslinking of the shell layer, respectively. A new type of well-defined, dual-functionalized boronic acid- and amino-based diblock copolymer poly(3-acrylamidophenylboronic acid)30-block-poly(acrylamidoethylamine)25 (PAPBA30-b-PAEA25) was synthesized by sequential reversible addition-fragmentation chain transfer (RAFT) polymerization and then assembled into cationic micelles in aqueous solution at pH 5.5. The micelles were further cross-linked throughout the shell domain comprised of poly(acrylamidoethylamine) by reaction with a bis-activated ester of 4,15-dioxo-8,11-dioxa-5,14-diazaoctadecane-1,18-dioic acid, upon increase of the pH to 7, to different cross-linking densities (2%, 5% and 10%), forming well-defined shell cross-linked nanoparticles (SCKs) with hydrodynamic diameters of ca. 50 nm. These smart micelles and SCKs presented switchable cationic, zwitterionic and anionic properties, and existed as stable nanoparticles with high positive surface charge at low pH (pH = 2, zeta potential ~ +40 mV) and strong negative surface charge at high pH (pH = 12, zeta potential ~ −35 mV). 1H NMR spectroscopy, X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS), transmission electron microscopy (TEM), atomic force microscopy (AFM), and zeta potential, were used to characterize the chemical compositions, particle sizes, morphologies and surface charges. Precipitation occurred near the isoelectric points (IEP) of the polymer/particle solutions, and the IEP values could be tuned by changing the shell cross-linking density. The block copolymer micelles were capable of full reversible morphological inversion as a function of pH, by orthogonal protonation of the PAEA and hydroxide association with the PAPBA units, whereas the

  2. The Photovoltaic Effect of CdS Quantum Dots Synthesized in Inverse Micelles and R-Phycoerythrin Tunnel Cavities.

    PubMed

    Bekasova, Olga D; Revina, Alexandra A; Kornienko, Ekaterina S; Kurganov, Boris I

    2015-06-01

    CdS quantum dots (CdS QDs) 4.3 nm in diameter synthesized in an AOT/isooctane/water microemulsion and in R-phycoerythrin tunnel cavities (3.5 × 6.0 nm) were analyzed for photoelectrochemical properties. The CdS QDs preparations were applied onto a platinum electrode to obtain solid films. Experiments were performed in a two-section vessel, with one section filled with ethanol and the other, with 3 M KCl. The sections were connected through an agar stopper. It was found that illumination of the films resulted in a change of the electrode potential. The magnitude of this change and the kinetics of the appearance and disappearance of the photopotential, i.e., the difference between the electrode potential on the light and in dark, depended on the nature of the QD shell. The photovoltaic effect of CdS QDs in R-phycoerythrin, compared to that of CdS QDs in AOT/isooctane micelles, is three to four times greater due to the photosensitizing action of R-phycoerythrin. The photosensitized effect was markedly higher than the photoelectric sensitivity of R-phycoerythrin and had the opposite polarity. Changes in the potential upon turning the light on and off could be observed repeatedly. PMID:25935221

  3. Inversions

    ERIC Educational Resources Information Center

    Brown, Malcolm

    2009-01-01

    Inversions are fascinating phenomena. They are reversals of the normal or expected order. They occur across a wide variety of contexts. What do inversions have to do with learning spaces? The author suggests that they are a useful metaphor for the process that is unfolding in higher education with respect to education. On the basis of…

  4. Bactericidal block copolymer micelles.

    PubMed

    Vyhnalkova, Renata; Eisenberg, Adi; van de Ven, Theo

    2011-05-12

    Block copolymer micelles with bactericidal properties were designed to deactivate pathogens such as E. coli bacteria. The micelles of PS-b-PAA and PS-b-P4VP block copolymers were loaded with biocides TCMTB or TCN up to 20 or 30 wt.-%, depending on the type of antibacterial agent. Bacteria were exposed to loaded micelles and bacterial deactivation was evaluated. The micelles loaded with TCN are bactericidal; bacteria are killed in less than two minutes of exposure. The most likely interpretation of the data is that the biocide is transferred to the bacteria by repeated micelle/bacteria contacts, and not via the solution. PMID:21275041

  5. Musk Oxen and Micelles

    NASA Astrophysics Data System (ADS)

    Hill, John W.

    1996-09-01

    Musk oxen behavior provides an analogy to micelle formation by amphipathic substances. Mature male musk oxen protect their young and females from wolves by forming a protective circle around them. The males stand with their tails to the inside and their heads facing outward. Amphipathic substances such as soap form micelles. The hydrophobic hydrocarbon tails of the soap are turned to the inside of the micelle and the hydrophilic carboxylate heads are on the outside at the interface with the polar water molecules.

  6. Complex coacervate core micelles.

    PubMed

    Voets, Ilja K; de Keizer, Arie; Cohen Stuart, Martien A

    2009-01-01

    In this review we present an overview of the literature on the co-assembly of neutral-ionic block, graft, and random copolymers with oppositely charged species in aqueous solution. Oppositely charged species include synthetic (co)polymers of various architectures, biopolymers - such as proteins, enzymes and DNA - multivalent ions, metallic nanoparticles, low molecular weight surfactants, polyelectrolyte block copolymer micelles, metallo-supramolecular polymers, equilibrium polymers, etcetera. The resultant structures are termed complex coacervate core/polyion complex/block ionomer complex/interpolyelectrolyte complex micelles (or vesicles); i.e., in short C3Ms (or C3Vs) and PIC, BIC or IPEC micelles (and vesicles). Formation, structure, dynamics, properties, and function will be discussed. We focus on experimental work; theory and modelling will not be discussed. Recent developments in applications and micelles with heterogeneous coronas are emphasized. PMID:19038373

  7. Giant rodlike reversed micelles

    SciTech Connect

    Yu, Z.J.; Neuman, R.D. )

    1994-05-04

    Herein we report that sodium bis(2-ethylhexyl)phosphate, which is similar in structure to the classical surfactant sodium bis(2-ethylhexyl)sulfosuccinate (AOT), forms very large rodlike reversed micelles and that their size can be even much larger if water is removed from the apolar solution. We further suggest that long-range electrostatic interactions are the primary driving force for the formation of giant reversed micelles. 19 refs., 3 figs.

  8. Polymerization of anionic wormlike micelles.

    PubMed

    Zhu, Zhiyuan; González, Yamaira I; Xu, Hangxun; Kaler, Eric W; Liu, Shiyong

    2006-01-31

    Polymerizable anionic wormlike micelles are obtained upon mixing the hydrotropic salt p-toluidine hydrochloride (PTHC) with the reactive anionic surfactant sodium 4-(8-methacryloyloxyoctyl)oxybenzene sulfonate (MOBS). Polymerization captures the cross-sectional radius of the micelles (approximately 2 nm), induces micellar growth, and leads to the formation of a stable single-phase dispersion of wormlike micellar polymers. The unpolymerized and polymerized micelles were characterized using static and dynamic laser light scattering, small-angle neutron scattering, 1H NMR, and stopped-flow light scattering. Stopped-flow light scattering was also used to measure the average lifetime of the unpolymerized wormlike micelles. A comparison of the average lifetime of unpolymerized wormlike micelles with the surfactant monomer propagation rate was used to elucidate the mechanism of polymerization. There is a significant correlation between the ratio of the average lifetime to the monomer propagation rate and the average aggregation number of the polymerized wormlike micelles. PMID:16430253

  9. Glyco-Nanoparticles Made from Self-Assembly of Maltoheptaose-block-Poly(methyl methacrylate): Micelle, Reverse Micelle, and Encapsulation.

    PubMed

    Zepon, Karine M; Otsuka, Issei; Bouilhac, Cécile; Muniz, Edvani C; Soldi, Valdir; Borsali, Redouane

    2015-07-13

    The synthesis and the solution-state self-assembly of the "hybrid" diblock copolymers, maltoheptaose-block-poly(methyl methacrylate) (MH-b-PMMA), into large compound micelles (LCMs) and reverve micelle-type nanoparticles, are reported in this paper. The copolymers were self-assembled in water and acetone by direct dissolution method, and the morphologies of the nanoparticles were investigated by dynamic light scattering (DLS), nanoparticle tracking analysis (NTA), transmission electron microscopy (TEM), atomic force microscopy (AFM), proton nuclear magnetic resonance ((1)H NMR), and fluorescence spectroscopy as a function of the volume fraction of the copolymer hydrophobic block, copolymer concentration, stirring speed, and solvent polarity. The DLS measurements and TEM images showed that the hydrodynamic radius (Rh) of the LCMs obtained in water increases with the copolymer concentration. Apart from that, increasing the stirring speed leads to polydispersed aggregations of the LCMs. On the other hand, in acetone, the copolymers self-assembled into reverse micelle-type nanoparticles having Rh values of about 6 nm and micellar aggregates, as revealed the results obtained from DLS, AFM, and (1)H NMR analyses. The variation in micellar structure, that is, conformational inversion from LCMs to reverse micelle-type structures in response to polarity of the solvent, was investigated by apparent water contact angle (WCA) and (1)H NMR analyses. This conformational inversion of the nanoparticles was further confirmed by encapsulation and release of hydrophobic guest molecule, Nile red, characterized by fluorescence spectroscopy. PMID:25974198

  10. Rheology of giant micelles

    NASA Astrophysics Data System (ADS)

    Cates, M. E.; Fielding, S. M.

    2006-12-01

    Giant micelles are elongated, polymer-like objects created by the self-assembly of amphiphilic molecules (such as detergents) in solution. Giant micelles are typically flexible, and can become highly entangled even at modest concentrations. The resulting viscoelastic solutions show fascinating flow behaviour (rheology) which we address theoretically in this article at two levels. First, we summarize advances in understanding linear viscoelastic spectra and steady-state nonlinear flows, based on microscopic constitutive models that combine the physics of polymer entanglement with the reversible kinetics of self-assembly. Such models were first introduced two decades ago, and since then have been shown to explain robustly several distinctive features of the rheology in the strongly entangled regime, including extreme shear thinning. We then turn to more complex rheological phenomena, particularly involving spatial heterogeneity, spontaneous oscillation, instability and chaos. Recent understanding of these complex flows is based largely on grossly simplified models which capture in outline just a few pertinent microscopic features, such as coupling between stresses and other order parameters such as concentration. The role of ‘structural memory’ (the dependence of structural parameters such as the micellar length distribution on the flow history) in explaining these highly nonlinear phenomena is addressed. Structural memory also plays an intriguing role in the little-understood shear thickening regime, which occurs in a concentration regime close to but below the onset of strong entanglement, and which is marked by a shear-induced transformation from an inviscid to a gelatinous state.

  11. Supercritical fluid reverse micelle separation

    DOEpatents

    Fulton, J.L.; Smith, R.D.

    1993-11-30

    A method of separating solute material from a polar fluid in a first polar fluid phase is provided. The method comprises combining a polar fluid, a second fluid that is a gas at standard temperature and pressure and has a critical density, and a surfactant. The solute material is dissolved in the polar fluid to define the first polar fluid phase. The combined polar and second fluids, surfactant, and solute material dissolved in the polar fluid is maintained under near critical or supercritical temperature and pressure conditions such that the density of the second fluid exceeds the critical density thereof. In this way, a reverse micelle system defining a reverse micelle solvent is formed which comprises a continuous phase in the second fluid and a plurality of reverse micelles dispersed in the continuous phase. The solute material is dissolved in the polar fluid and is in chemical equilibrium with the reverse micelles. The first polar fluid phase and the continuous phase are immiscible. The reverse micelles each comprise a dynamic aggregate of surfactant molecules surrounding a core of the polar fluid. The reverse micelle solvent has a polar fluid-to-surfactant molar ratio W, which can vary over a range having a maximum ratio W[sub o] that determines the maximum size of the reverse micelles. The maximum ratio W[sub o] of the reverse micelle solvent is then varied, and the solute material from the first polar fluid phase is transported into the reverse micelles in the continuous phase at an extraction efficiency determined by the critical or supercritical conditions. 27 figures.

  12. Supercritical fluid reverse micelle separation

    DOEpatents

    Fulton, John L.; Smith, Richard D.

    1993-01-01

    A method of separating solute material from a polar fluid in a first polar fluid phase is provided. The method comprises combining a polar fluid, a second fluid that is a gas at standard temperature and pressure and has a critical density, and a surfactant. The solute material is dissolved in the polar fluid to define the first polar fluid phase. The combined polar and second fluids, surfactant, and solute material dissolved in the polar fluid is maintained under near critical or supercritical temperature and pressure conditions such that the density of the second fluid exceeds the critical density thereof. In this way, a reverse micelle system defining a reverse micelle solvent is formed which comprises a continuous phase in the second fluid and a plurality of reverse micelles dispersed in the continuous phase. The solute material is dissolved in the polar fluid and is in chemical equilibrium with the reverse micelles. The first polar fluid phase and the continuous phase are immiscible. The reverse micelles each comprise a dynamic aggregate of surfactant molecules surrounding a core of the polar fluid. The reverse micelle solvent has a polar fluid-to-surfactant molar ratio W, which can vary over a range having a maximum ratio W.sub.o that determines the maximum size of the reverse micelles. The maximum ratio W.sub.o of the reverse micelle solvent is then varied, and the solute material from the first polar fluid phase is transported into the reverse micelles in the continuous phase at an extraction efficiency determined by the critical or supercritical conditions.

  13. Glycation Reactions of Casein Micelles.

    PubMed

    Moeckel, Ulrike; Duerasch, Anja; Weiz, Alexander; Ruck, Michael; Henle, Thomas

    2016-04-13

    After suspensions of micellar casein or nonmicellar sodium caseinate had been heated, respectively, in the presence and absence of glucose for 0-4 h at 100 °C, glycation compounds were quantitated. The formation of Amadori products as indicators for the "early" Maillard reaction were in the same range for both micellar and nonmicellar caseins, indicating that reactive amino acid side chains within the micelles are accessible for glucose in a comparable way as in nonmicellar casein. Significant differences, however, were observed concerning the formation of the advanced glycation end products (AGEs), namely, N(ε)-carboxymethyllysine (CML), pyrraline, pentosidine, and glyoxal-lysine dimer (GOLD). CML could be observerd in higher amounts in nonmicellar casein, whereas in the micelles the pyrraline formation was increased. Pentosidine and GOLD were formed in comparable amounts. Furthermore, the extent of protein cross-linking was significantly higher in the glycated casein micelles than in the nonmicellar casein samples. Dynamic light scattering and scanning electron microscopy showed that glycation has no influence on the size of the casein micelles, indicating that cross-linking occurs only in the interior of the micelles, but altered the surface morphology. Studies on glycation and nonenzymatic cross-linking can contribute to the understanding of the structure of casein micelles. PMID:27018258

  14. Regulation of charged reverse micelles on particle charging in nonpolar media.

    PubMed

    Cao, Huiying; Lu, Naiyan; Ding, Baiyong; Qi, Ming

    2013-08-01

    By considering the mechanism of preferential adsorption, we systemically investigated the charging behavior of spherical particles in nonpolar media by the regulation of charged inverse micelles. Using the nonlinear Poisson-Boltzmann equation, we simulated the effects of micelle concentrations, particle concentrations, and particle sizes on the surface potential of spheres at the thermodynamic equilibrium of the system. As a result, we found two different micelle concentration-dependent regions for the surface potential of spheres which can be explained in terms of the mechanism of preferential adsorption and the electrostatic properties of charged reverse micelles between the particle surface and the double layer. Additionally, similar results were observed in an experiment for studying zeta potential of colloidal particles dispersed in AOT (sodium di-2-ethylhexyl sulfosuccinate)-dodecane solution. PMID:23770915

  15. Investigation of water-containing inverted micelles by fluorescence polarization determination of size and internal fluidity

    SciTech Connect

    Keh, E.; Valeur, B.

    1981-02-01

    Water-containing inverted micelles of sodium di(2-ethylhexyl) sulfosuccinate (AOT) have been investigated by fluorescence polarization using fluorescent hydrophilic probes localized in the aqueous core of the micelles. Measurements of the stationary polarization in two apolar solvents of different viscosity but of the same chemical nature permit rapid determination of both micellar hydrodynamic volume and water pool fluidity as a function of water content up to (H/sub 2/O)/(AOT) = 11. The characteristics of AOT micelles appear to be unchanged in the n-alkane series from hexane to dodecane and slightly affected in various apolar solvents. Solvents of high polarizability such as benzene, toluene, and carbon tetrachloride penetrate into the amphiphile layer, presumably up to the water core boundary. No significant effect of sodium chloride was observed up to a concentration of 0.4 M. The inverse micelle size is independent of surfactant concentration below 0.3 M.

  16. Evidence for a critical micelle concentration of surfactants in hydrocarbon solvents.

    PubMed

    Smith, Gregory N; Brown, Paul; Rogers, Sarah E; Eastoe, Julian

    2013-03-12

    The concentration-dependent aggregation of two surfactants, anionic sodium dioctylsulfosuccinate (Aerosol OT or AOT) and nonionic pentaethylene glycol monododecyl ether (C12E5), has been studied in cyclohexane-D12 using small-angle neutron scattering (SANS). A clear monomer-to-aggregate transition has been observed for both surfactants, spherical inverse micelles for AOT and hank-like micelles for C12E5. This suggests that a critical micelle concentration exists for surfactants of these kinds in nonpolar solvents. The nature of the transition is different for the two surfactants. AOT aggregates are the same size and shape with decreasing concentration until a sharp critical micelle concentration, after which they cannot be detected. However, C12E5 aggregates gradually decrease in size. These differences demonstrate that the strength of the solvophobic effect can influence the formation of surfactant aggregates in nonaqueous solvents. PMID:23410112

  17. Branching mechanisms in surfactant micelles

    NASA Astrophysics Data System (ADS)

    Dhakal, Subas; Sureshkumar, Radhakrishna

    The mechanisms of branch formation in surfactant micelles of cetyltrimethylammonium chloride (CTAC) in presence of sodium salicylate (NaSal) counter ions in water are studied using molecular dynamics simulations. The curvature energy associated with the formation of micelle branches and the effect of branching on the solution viscosity are quantified. Highly curved surfaces are energetically stabilized by a higher density of binding counter ions near the branch points. Simulations show that micellar branches result in a significant reduction in the solution viscosity as observed in experiments [Dhakal & Sureshkumar, J. Chem. Phys. 143, 024905 (2015)]. This reduction in viscosity has long been attributed to the sliding motion of micelle branches across the main chain. However, to date, such dynamics of micelle branches have never been visualized in either experiments or simulations. Here, we explicitly illustrate and quantify, for the first time, how branches slide along the micelle contour to facilitate stress relaxation. We acknowledged the computational resources provided by XSEDE which is supported by NSF Grant Number OCI-1053575 and the financial support by National Science Foundation under Grants 1049489 and 1049454.

  18. Biochemical characterization of the interactions between doxorubicin and lipidic GM1 micelles with or without paclitaxel loading.

    PubMed

    Leonhard, Victoria; Alasino, Roxana V; Bianco, Ismael D; Garro, Ariel G; Heredia, Valeria; Beltramo, Dante M

    2015-01-01

    Doxorubicin (Dox) is an anthracycline anticancer drug with high water solubility, whose use is limited primarily due to significant side effects. In this study it is shown that Dox interacts with monosialoglycosphingolipid (GM1) ganglioside micelles primarily through hydrophobic interactions independent of pH and ionic strength. In addition, Dox can be incorporated even into GM1 micelles already containing highly hydrophobic paclitaxel (Ptx). However, it was not possible to incorporate Ptx into Dox-containing GM1 micelles, suggesting that Dox could be occupying a more external position in the micelles. This result is in agreement with a higher hydrolysis of Dox than of Ptx when micelles were incubated at alkaline pH. The loading of Dox into GM1 micelles was observed over a broad range of temperature (4°C-55°C). Furthermore, Dox-loaded micelles were stable in aqueous solutions exhibiting no aggregation or precipitation for up to 2 months when kept at 4°C-25°C and even after freeze-thawing cycles. Upon exposure to blood components, Dox-containing micelles were observed to interact with human serum albumin. However, the amount of human serum albumin that ended up being associated to the micelles was inversely related to the amount of Dox, suggesting that both could share their binding sites. In vitro studies on Hep2 cells showed that the cellular uptake and cytotoxic activity of Dox and Ptx from the micellar complexes were similar to those of the free form of these drugs, even when the micelle was covered with albumin. These results support the idea of the existence of different nano-domains in a single micelle and the fact that this micellar model could be used as a platform for loading and delivering hydrophobic and hydrophilic active pharmaceutical ingredients. PMID:26005348

  19. Biochemical characterization of the interactions between doxorubicin and lipidic GM1 micelles with or without paclitaxel loading

    PubMed Central

    Leonhard, Victoria; Alasino, Roxana V; Bianco, Ismael D; Garro, Ariel G; Heredia, Valeria; Beltramo, Dante M

    2015-01-01

    Doxorubicin (Dox) is an anthracycline anticancer drug with high water solubility, whose use is limited primarily due to significant side effects. In this study it is shown that Dox interacts with monosialoglycosphingolipid (GM1) ganglioside micelles primarily through hydrophobic interactions independent of pH and ionic strength. In addition, Dox can be incorporated even into GM1 micelles already containing highly hydrophobic paclitaxel (Ptx). However, it was not possible to incorporate Ptx into Dox-containing GM1 micelles, suggesting that Dox could be occupying a more external position in the micelles. This result is in agreement with a higher hydrolysis of Dox than of Ptx when micelles were incubated at alkaline pH. The loading of Dox into GM1 micelles was observed over a broad range of temperature (4°C–55°C). Furthermore, Dox-loaded micelles were stable in aqueous solutions exhibiting no aggregation or precipitation for up to 2 months when kept at 4°C–25°C and even after freeze–thawing cycles. Upon exposure to blood components, Dox-containing micelles were observed to interact with human serum albumin. However, the amount of human serum albumin that ended up being associated to the micelles was inversely related to the amount of Dox, suggesting that both could share their binding sites. In vitro studies on Hep2 cells showed that the cellular uptake and cytotoxic activity of Dox and Ptx from the micellar complexes were similar to those of the free form of these drugs, even when the micelle was covered with albumin. These results support the idea of the existence of different nano-domains in a single micelle and the fact that this micellar model could be used as a platform for loading and delivering hydrophobic and hydrophilic active pharmaceutical ingredients. PMID:26005348

  20. Equilibrium and Kinetics of Block Copolymers Micelles

    NASA Astrophysics Data System (ADS)

    Mysona, Joshua; Morse, David

    Both equilibrium properties of micelles, such as the critical micelle concentration (CMC), and dynamical properties such as the micelle lifetime are difficult to study in simulations because of the slow dynamics of the processes by which micelles are created and destroyed. We first discuss a method of precisely identifying the CMC in a simple model of block copolymer micelles in a homopolymer matrix, which makes use of thermodynamic integration to compute the free energy of formation. We then examine the free energy barriers to competing mechanisms for creating and destroying micelles, which could occur predominantly either by a step-wise process involving insertion and extraction of single molecules or by fission and fusion of entire micelles.

  1. Ultrafast dynamics of water in cationic micelles

    NASA Astrophysics Data System (ADS)

    Dokter, Adriaan M.; Woutersen, Sander; Bakker, Huib J.

    2007-03-01

    The effect of confinement on the dynamical properties of liquid water is investigated for water enclosed in cationic reverse micelles. The authors performed mid-infrared ultrafast pump-probe spectroscopy on the OH-stretch vibration of isotopically diluted HDO in D2O in cetyltrimethylammonium bromide (CTAB) reverse micelles of various sizes. The authors observe that the surfactant counterions are inhomogeneously distributed throughout the reverse micelle, and that regions of extreme salinity occur near the interfacial Stern layer. The authors find that the water molecules in the core of the micelles show similar orientational dynamics as bulk water, and that water molecules in the counterion-rich interfacial region are much less mobile. An explicit comparison is made with the dynamics of water confined in anionic sodium bis(2-ethythexyl) sulfosuccinate (AOT) reverse micelles. The authors find that interfacial water in cationic CTAB reverse micelles has a higher orientational mobility than water in anionic AOT reverse micelles.

  2. Micelle Structure and Hydrophobic Hydration.

    PubMed

    Long, Joshua A; Rankin, Blake M; Ben-Amotz, Dor

    2015-08-26

    Despite the ubiquity and utility of micelles self-assembled from aqueous surfactants, longstanding questions remain regarding their surface structure and interior hydration. Here we combine Raman spectroscopy with multivariate curve resolution (Raman-MCR) to probe the hydrophobic hydration of surfactants with various aliphatic chain lengths, and either anionic (carboxylate) or cationic (trimethylammonium) head groups, both below and above the critical micelle concentration. Our results reveal significant penetration of water into micelle interiors, well beyond the first few carbons adjacent to the headgroup. Moreover, the vibrational C-D frequency shifts of solubilized deuterated n-hexane confirm that it resides in a dry, oil-like environment (while the localization of solubilized benzene is sensitive to headgroup charge). Our findings imply that the hydrophobic core of a micelle is surrounded by a highly corrugated surface containing hydrated non-polar cavities whose depth increases with increasing surfactant chain length, thus bearing a greater resemblance to soluble proteins than previously recognized. PMID:26222042

  3. Micelles of enzymatically synthesized PEG-poly(amine-co-ester) block copolymers as pH-responsive nanocarriers for docetaxel delivery.

    PubMed

    Zhang, Xiaofang; Liu, Bo; Yang, Zhe; Zhang, Chao; Li, Hao; Luo, Xingen; Luo, Huiyan; Gao, Di; Jiang, Qing; Liu, Jie; Jiang, Zhaozhong

    2014-03-01

    A series of PEGylated poly(amine-co-ester) terpolymers were successfully synthesized in one step via lipase-catalyzed copolymerization of ω-pentadecalactone (PDL), diethyl sebacate (DES), and N-methyldiethanolamine (MDEA) comonomers in the presence of poly(ethylene glycol) methyl ether as a chain-terminating agent. The resultant amphiphilic poly(ethylene glycol)-poly(PDL-co-MDEA-co-sebacate) (PEG-PPMS) block copolymers consisted of hydrophilic PEG chain segments and hydrophobic random PPMS chain segments, which self-assembled in aqueous medium to form stable, nanosized micelles at physiological pH of 7.4. Upon decreasing the medium pH from 7.4 to 5.0, the copolymer micelles swell significantly due to protonation of the amino groups in the micelle PPMS cores. Correspondingly, docetaxel (DTX)-encapsulated PEG2K-PPMS copolymer micelles showed gradual sustained drug release at pH of 7.4, but remarkably accelerated DTX release at acidic pH of 5.0. The drug-loaded micelle particles were readily internalized by SK-BR-3 cancer cells and, compared to free DTX drug, DTX-loaded micelles of the copolymers with optimal compositions exhibited enhanced potency against the cells. Biodegradable PEG-PPMS copolymer micelles represent a new type of promising, pH-responsive nanocarriers for anticancer drug delivery, and the drug release rate from the micelles can be systematically controlled by both pH and the copolymer composition. PMID:24398083

  4. Ultrasound-Mediated Polymeric Micelle Drug Delivery.

    PubMed

    Xia, Hesheng; Zhao, Yue; Tong, Rui

    2016-01-01

    The synthesis of multi-functional nanocarriers and the design of new stimuli-responsive means are equally important for drug delivery. Ultrasound can be used as a remote, non-invasive and controllable trigger for the stimuli-responsive release of nanocarriers. Polymeric micelles are one kind of potential drug nanocarrier. By combining ultrasound and polymeric micelles, a new modality (i.e., ultrasound-mediated polymeric micelle drug delivery) has been developed and has recently received increasing attention. A major challenge remaining in developing ultrasound-responsive polymeric micelles is the improvement of the sensitivity or responsiveness of polymeric micelles to ultrasound. This chapter reviews the recent advance in this field. In order to understand the interaction mechanism between ultrasound stimulus and polymeric micelles, ultrasound effects, such as thermal effect, cavitation effect, ultrasound sonochemistry (including ultrasonic degradation, ultrasound-initiated polymerization, ultrasonic in-situ polymerization and ultrasound site-specific degradation), as well as basic micellar knowledge are introduced. Ultrasound-mediated polymeric micelle drug delivery has been classified into two main streams based on the different interaction mechanism between ultrasound and polymeric micelles; one is based on the ultrasound-induced physical disruption of the micelle and reversible release of payload. The other is based on micellar ultrasound mechanochemical disruption and irreversible release of payload. PMID:26486348

  5. CTAB/water/chloroform reverse micelles: a closed or open association model?

    PubMed

    Klíčová, L'ubica; Sebej, Peter; Štacko, Peter; Filippov, Sergey K; Bogomolova, Anna; Padilla, Marc; Klán, Petr

    2012-10-30

    The micellization of cetyltrimethylammonium bromide (CTAB) in chloroform in the presence of water was examined. Three scenarios of the reverse micelle formation, the closed, open and Eicke's association models, were considered in the interpretation of the experimental data. The growth of the aggregates was observed through the changes of NMR signals of associated water, probing the microenvironment of the premicellar aggregates and the interior of reverse micelles. This technique if combined with isothermal titration calorimetry (ITC) revealed that hydrated surfactant premicellar aggregates are already present at ∼6 mM CTAB. NMR, ITC and conductometry were used to determine the critical micelle concentration (cmc) to be ∼40 mM CTAB. It is suggested that the variation of the cmc values reflects the fact that the NMR analysis indicated the beginning of the reverse micelle formation, whereas conductometry and ITC measurements provided the upper limit and an average value of a so-called apparent cmc, respectively. The cmc values were found to be unaffected by the water content. The presence of reverse micelles, the existence of multiple equilibria, and high polydispersity of the samples were evidenced by DOSY NMR spectroscopy. As a result, we validated Eicke's association model, according to which cyclic inverse micelles are formed by a structural reorganization of linear associates within a narrow concentration range, called the apparent cmc. New experimental results have also been gained for micellization of cetyltrimethylammonium chloride (CTAC) in chloroform in the presence of water; a similar mechanism of reverse micelle formation has been suggested. PMID:23072317

  6. The Distribution of Solubilized Molecules among Micelles.

    ERIC Educational Resources Information Center

    Miller, Dennis J.

    1978-01-01

    Conflicting views have been put forward on the derivation of the distribution of solubilized molecules among micelles. This stems from failure to consider the arrangement of the solubilized molecules in the micelles. In the treatment presented enthalpy effects are ignored as they are not amenable to a simple general theory. (Author/BB)

  7. Rapid (1 hour) high performance gel filtration chromatography resolves coexisting simple micelles, mixed micelles, and vesicles in bile.

    PubMed

    Cohen, D E; Carey, M C

    1990-11-01

    We describe the use and validation of Superose 6, a high performance gel filtration medium for rapid, high resolution separation and sizing of coexisting simple micelles, mixed micelles, and vesicles in bile. We fractionated model biles (1.7-4.2 g/dl total lipid concentration, 0.15 M NaCl) composed of lecithin (L), cholesterol (Ch), and the common bile salt taurocholate (TC) using Superose 6 gel filtration columns (1.0 cm diameter, 30 cm length, 0.5 ml model bile application, 1.0 ml fractions) pre-equilibrated and eluted with 2.5-10.0 mM TC. Lipid particle sizes were determined by quasielastic light scattering and lipid compositions by conventional analyses. In the absence of L and Ch, pure TC "biles" (32.2 mM), when eluted in the presence of 7.5 mM TC, yielded a single peak of particles (mean hydrodynamic radii, Rh values of 11-15 A), consistent with simple TC micelles. Model biles containing L and TC ([L] = 13.8 mM, [TC] = 32.2 mM) were fractionated with baseline resolution into TC-L mixed micelles, (Rh values of 30-40 A) and simple TC micelles. In agreement with the ternary TC-L-H2O phase diagram (Mazer, N. A., et al. 1980. Biochemistry. 19: 601-615), the proportions of simple and mixed micelles were inversely related to L concentrations ([L] = 0-32.2 mM) and correlated positively with eluant TC concentration. Superose 6 gel fractionation of model biles "super-saturated" with Ch (TC:L:Ch molar ratio 27:63:10, total lipid concentration 3 g/dl) yielded high resolution separation of vesicles (Rh value of 320 A) from mixed micelles of TC-L-Ch (Rh values of 40-50 A) and simple TC micelles (Rh values of 11-15 A). At an eluant TC concentration of 7.5 mM, Ch-rich vesicles (Ch/L molar ratio = 1.6) separated that contained 40% of total Ch, 9% of total L, and no TC, accurately reflecting predictions of the quaternary L-Ch-TC-H2O metastable phase diagram (Mazer, N. A., and M. C. Carey. 1983 Biochemistry. 22: 426-442). This suggested that a 7.5 mM TC concentration

  8. Selective Recognition of d-Aldohexoses in Water by Boronic Acid-Functionalized, Molecularly Imprinted Cross-Linked Micelles.

    PubMed

    Awino, Joseph K; Gunasekara, Roshan W; Zhao, Yan

    2016-08-10

    Molecular imprinting within cross-linked micelles using 4-vinylphenylboronate derivatives of carbohydrates provided water-soluble nanoparticle receptors selective for the carbohydrate templates. Complete differentiation of d-aldohexoses could be achieved by these receptors if a single inversion of hydroxyl occurred at C2 or C4 of the sugar or if two or more inversions took place. Glycosides with a hydrophobic aglycan displayed stronger binding due to increased hydrophobic interactions. PMID:27442012

  9. Casein Micelle Dispersions under Osmotic Stress

    PubMed Central

    Bouchoux, Antoine; Cayemitte, Pierre-Emerson; Jardin, Julien; Gésan-Guiziou, Geneviève; Cabane, Bernard

    2009-01-01

    Abstract Casein micelles dispersions have been concentrated and equilibrated at different osmotic pressures using equilibrium dialysis. This technique measured an equation of state of the dispersions over a wide range of pressures and concentrations and at different ionic strengths. Three regimes were found. i), A dilute regime in which the osmotic pressure is proportional to the casein concentration. In this regime, the casein micelles are well separated and rarely interact, whereas the osmotic pressure is dominated by the contribution from small residual peptides that are dissolved in the aqueous phase. ii), A transition range that starts when the casein micelles begin to interact through their κ-casein brushes and ends when the micelles are forced to get into contact with each other. At the end of this regime, the dispersions behave as coherent solids that do not fully redisperse when osmotic stress is released. iii), A concentrated regime in which compression removes water from within the micelles, and increases the fraction of micelles that are irreversibly linked to each other. In this regime the osmotic pressure profile is a power law of the residual free volume. It is well described by a simple model that considers the micelle to be made of dense regions separated by a continuous phase. The amount of water in the dense regions matches the usual hydration of proteins. PMID:19167314

  10. Chemical reactions in reverse micelle systems

    DOEpatents

    Matson, Dean W.; Fulton, John L.; Smith, Richard D.; Consani, Keith A.

    1993-08-24

    This invention is directed to conducting chemical reactions in reverse micelle or microemulsion systems comprising a substantially discontinuous phase including a polar fluid, typically an aqueous fluid, and a microemulsion promoter, typically a surfactant, for facilitating the formation of reverse micelles in the system. The system further includes a substantially continuous phase including a non-polar or low-polarity fluid material which is a gas under standard temperature and pressure and has a critical density, and which is generally a water-insoluble fluid in a near critical or supercritical state. Thus, the microemulsion system is maintained at a pressure and temperature such that the density of the non-polar or low-polarity fluid exceeds the critical density thereof. The method of carrying out chemical reactions generally comprises forming a first reverse micelle system including an aqueous fluid including reverse micelles in a water-insoluble fluid in the supercritical state. Then, a first reactant is introduced into the first reverse micelle system, and a chemical reaction is carried out with the first reactant to form a reaction product. In general, the first reactant can be incorporated into, and the product formed in, the reverse micelles. A second reactant can also be incorporated in the first reverse micelle system which is capable of reacting with the first reactant to form a product.

  11. Dynamic Processes in Diblock Copolymer Micelles

    NASA Astrophysics Data System (ADS)

    Robertson, Megan; Singh, Avantika

    2013-03-01

    Diblock copolymers, which form micelle structures in selective solvents, offer advantages of robustness and tunability of micelle characteristics as compared to small molecule surfactants. Diblock copolymer micelles in water have been a subject of great interest in drug delivery applications based on their high loading capacity and targeted drug delivery. The aim of this work is to understand the dynamic processes which underlie the self-assembly of diblock copolymer micelle systems which have a semi-crystalline core. Due to the large size of the molecules, the self-assembly of block copolymer micelles occurs on significantly longer time scales than small molecule analogues. The present work focuses on amphiphilic diblock copolymers containing blocks of poly(ethylene oxide) (a hydrophilic polymer) and polycaprolactone (a hydrophobic, semi-crystalline polymer), which spontaneously self-assemble into spherical micelles in water. A variety of experimental techniques are used to probe the kinetic processes relevant to micelle self-assembly, including time-resolved neutron scattering, dynamic light scattering, pulsed field gradient nuclear magnetic resonance, and fluorescence resonance energy transfer experiments.

  12. Ultrafast photoinduced electron transfer in the micelle and the gel phase of a PEO-PPO-PEO triblock copolymer

    SciTech Connect

    Mandal, Ujjwal; Ghosh, Subhadip; Dey, Shantanu; Adhikari, Aniruddha; Bhattacharyya, Kankan

    2008-04-28

    Ultrafast photoinduced electron transfer (PET) from N,N-dimethylaniline (DMA) to coumarin dyes is studied in the micelle and the gel phase of a triblock copolymer, (PEO){sub 20}-(PPO){sub 70}-(PEO){sub 20} (Pluronic P123) by picosecond and femtosecond emission spectroscopies. The rate of PET in a P123 micelle and gel is found to be nonexponential and faster than the slow components of solvation dynamics. In a P123 micelle and gel, PET occurs on multiple time scales ranging from a subpicosecond time scale to a few nanoseconds. In the gel phase, the highest rate constant (9.3x10{sup 9} M{sup -1} s{sup -1}) of ET for C152 is about two times higher than that (3.8x10{sup 9} M{sup -1} s{sup -1}) observed in micelle phase. The ultrafast components of electron transfer (ET) exhibits a bell shaped dependence with the free energy change which is similar to the Marcus inversion. Possible reasons for slower PET in P123 micelle compared to other micelles and relative to P123 gel are discussed.

  13. Determination of the aggregation number and charge of ionic surfactant micelles from the stepwise thinning of foam films.

    PubMed

    Anachkov, Svetoslav E; Danov, Krassimir D; Basheva, Elka S; Kralchevsky, Peter A; Ananthapadmanabhan, Kavssery P

    2012-11-15

    The stepwise thinning (stratification) of liquid films, which contain micelles of an ionic surfactant, depends on the micelle aggregation number, N(agg), and charge, Z. Vice versa, from the height of the step and the final film thickness one can determine N(agg), Z, and the degree of micelle ionization. The determination of N(agg) is based on the experimental fact that the step height is equal to the inverse cubic root of the micelle concentration. In addition, Z is determined from the final thickness of the film, which depends on the concentration of counterions dissociated from the micelles in the bulk. The method is applied to micellar solutions of six surfactants, both anionic and cationic: sodium dodecylsulfate (SDS), cetyl trimethylammonium bromide (CTAB), cetylpyridinium chloride (CPC), sodium laurylethersulfates with 1 and 3 ethylene oxide groups (SLES-1EO and SLES-3EO), and potassium myristate. The method has the following advantages: (i) N(agg) and Z are determined simultaneously, from the same set of experimental data; (ii) N(agg) and Z are determined for each given surfactant concentration (i.e. their concentration dependence is obtained), and (iii) N(agg) and Z can be determined even for turbid solutions, like those of carboxylates, where the micelles coexist with acid-soap crystallites, so that the application of other methods is difficult. The results indicate that the micelles of greater aggregation number have a lower degree of ionization, which can be explained with the effect of counterion binding. The proposed method is applicable to the concentration range, in which the films stratify and the micelles are spherical. This is satisfied for numerous systems representing scientific and practical interest. PMID:22935484

  14. Polysaccharide-Based Micelles for Drug Delivery

    PubMed Central

    Zhang, Nan; Wardwell, Patricia R.; Bader, Rebecca A.

    2013-01-01

    Delivery of hydrophobic molecules and proteins has been an issue due to poor bioavailability following administration. Thus, micelle carrier systems are being investigated to improve drug solubility and stability. Due to problems with toxicity and immunogenicity, natural polysaccharides are being explored as substitutes for synthetic polymers in the development of new micelle systems. By grafting hydrophobic moieties to the polysaccharide backbone, self-assembled micelles can be readily formed in aqueous solution. Many polysaccharides also possess inherent bioactivity that can facilitate mucoadhesion, enhanced targeting of specific tissues, and a reduction in the inflammatory response. Furthermore, the hydrophilic nature of some polysaccharides can be exploited to enhance circulatory stability. This review will highlight the advantages of polysaccharide use in the development of drug delivery systems and will provide an overview of the polysaccharide-based micelles that have been developed to date. PMID:24300453

  15. Micelle Catalysis of an Aromatic Substitution Reaction

    ERIC Educational Resources Information Center

    Corsaro, Gerald; Smith J. K.

    1976-01-01

    Describes an experiment in which the iodonation of aniline reaction is shown to undergo catalysis in solution of sodium lauryl sulfate which forms micelles with negatively charged pseudo surfaces. (MLH)

  16. Colloidal Wormlike Micelles with Highly Ferromagnetic Properties.

    PubMed

    Zhao, Wenrong; Dong, Shuli; Hao, Jingcheng

    2015-10-20

    For the first time, a new fabrication method for manipulating the ferromagnetic property of molecular magnets by forming wormlike micelles in magnetic-ionic-liquid (mag-IL) complexes is reported. The ferromagnetism of the mag-IL complexes was enhanced 4-fold because of the formation of wormlike micelles, presenting new evidence for the essence of magnetism generation at a molecular level. Characteristics such as morphology and magnetic properties of the wormlike micelle gel were investigated in detail by cryogenic transmission electron microscopy (Cryo-TEM), rheological measurements, circular dichroism (CD), FT-IR spectra, and the superconducting quantum interference device method (SQUID). An explanation of ferromagnetism elevation from the view of the molecular (ionic) distribution is also given. For the changes of magnetic properties (ferromagnetism elevation) in the wormlike micelle systems, the ability of CTAFe in magnetizing AzoNa4 (or AzoH4) can be ascribed to an interplay of the magnetic [FeCl3Br](-) ions both in the Stern layer and in the cores of the wormlike micelles. Formation of colloidal aggregates, i.e., wormlike micelles, provides a new strategy to tune the magnetic properties of novel molecular magnets. PMID:26411638

  17. Polymeric Micelles for Acyclovir Drug Delivery

    PubMed Central

    Sawdon, Alicia J.; Peng, Ching-An

    2014-01-01

    Polymeric prodrug micelles for delivery of acyclovir (ACV) were synthesized. First, ACV was used directly to initiate ring-opening polymerization of ε-caprolactone to form ACV-polycaprolactone (ACV-PCL). Through conjugation of hydrophobic ACV-PCL with hydrophilic methoxy poly(ethylene glycol) (MPEG) or chitosan, polymeric micelles for drug delivery were formed. 1H NMR, FTIR, and gel permeation chromatography were employed to show successful conjugation of MPEG or chitosan to hydrophobic ACV-PCL. Through dynamic light scattering, zeta potential analysis, transmission electron microscopy, and critical micelle concentration (CMC), the synthesized ACV-tagged polymeric micelles were characterized. It was found that the average size of the polymeric micelles was under 200 nm and the CMCs of ACV-PCLMPEG and ACV-PCL-chitosan were 2.0 mg L−1 and 6.6 mg L−1, respectively. The drug release kinetics of ACV was investigated and cytotoxicity assay demonstrates that ACV-tagged polymeric micelles were non-toxic. PMID:25193154

  18. Cellular uptake and trafficking of polydiacetylene micelles

    NASA Astrophysics Data System (ADS)

    Gravel, Edmond; Thézé, Benoit; Jacques, Isabelle; Anilkumar, Parambath; Gombert, Karine; Ducongé, Frédéric; Doris, Eric

    2013-02-01

    Polydiacetylene (PDA) micelles coated with either carboxylate-, ammonium-, or methoxy-polyethyleneglycol (PEG) chains were assembled and loaded with a fluorescent dye (DiO). Their interaction with MCF-7 human breast tumor cells was investigated by epi-fluorescence microscopy and fluorescence-activated cell sorting (FACS) to determine their internalization pathway and intracellular fate. It was found that the ionic character of the micelles influenced their internalization kinetics through a caveolae-mediated pathway and that all micelle types behaved somewhat similarly inside cells.Polydiacetylene (PDA) micelles coated with either carboxylate-, ammonium-, or methoxy-polyethyleneglycol (PEG) chains were assembled and loaded with a fluorescent dye (DiO). Their interaction with MCF-7 human breast tumor cells was investigated by epi-fluorescence microscopy and fluorescence-activated cell sorting (FACS) to determine their internalization pathway and intracellular fate. It was found that the ionic character of the micelles influenced their internalization kinetics through a caveolae-mediated pathway and that all micelle types behaved somewhat similarly inside cells. Electronic supplementary information (ESI) available: Detailed synthetic procedures and supplementary figures. See DOI: 10.1039/c2nr34149b

  19. Generation of a Chiral Giant Micelle.

    PubMed

    Ito, Thiago H; Salles, Airton G; Priebe, Jacks P; Miranda, Paulo C M L; Morgon, Nelson H; Danino, Dganit; Mancini, Giovanna; Sabadini, Edvaldo

    2016-08-23

    Over the past few years, chiral supramolecular assemblies have been successfully used for recognition, sensing and enantioselective transformations. Several approaches are available to control chirality of discrete assemblies (e.g., cages and capsules), but few are efficient in assuring chirality for micellar aggregates. Optically active amino acid-derived surfactants are commonly used to generate chiral spherical micelles. To circumvent this limitation, we benefited from the uniaxial growth of spherical micelles into long cylindrical micelles usually called wormlike or giant micelles, upon the addition of cosolutes. This paper describes the unprecedented formation of chiral giant micelles in aqueous solutions of cetyltrimethylammonium bromide (CTAB) upon increasing addition of enantiopure sodium salt of 1,1'-bi-2-naphthol (Na-binaphtholate) as a cosolute. Depending on the concentrations of CTAB and Na-binaphtholate, chiral gel-like systems are obtained. The transition from spherical to giant micellar structures was probed using rheology, cryo-transmission electron microscopy, polarimetry, and electronic circular dichroism (CD). CD can be effectively used to monitor the incorporation of Na-binaphtholate into the micelle palisade as well as to determine its transition to giant micellar structures. Our approach expands the scope for chirality induction in micellar aggregates bringing the possibility to generate "smart" chiral systems and an alternative asymmetric chiral environment to perform enantioselective transformations. PMID:27499127

  20. FTIR study of horseradish peroxidase in reverse micelles.

    PubMed

    Chen, J; Xia, C; Niu, J; Li, S

    2001-04-20

    Fourier transform infrared (FTIR) method was used to study the secondary structures of horseradish peroxidase (HRP) in aqueous solution and in reverse micelles for the first time. Results indicated that the structure of HRP in sodium bis(2-ethylhexy)sulfosuccinate (AOT) reverse micelles was close to that in aqueous solution. In cetyltrimethylammonium bromide (CTAB) and sodium dodecylfate (SDS) reverse micelles the position of some bands changed. Results indicated that the secondary structure had a close relationship with the surfactant species of the reverse micelles. Among the three types of reverse micelles, the system of AOT reverse micelles was probably the most beneficial reaction media to HRP. PMID:11302746

  1. Molecular Exchange in Ordered Diblock Copolymer Micelles

    NASA Astrophysics Data System (ADS)

    Choi, Soo-Hyung; Lodge, Timothy; Bates, Frank

    2011-03-01

    Previously, molecular exchange between spherical micelles in dilute solution (1 vol% polymer) was investigated using time-resolved small-angle neutron scattering (TR-SANS). As the concentration of spherical micelles formed by the diblock copolymers increases, the micelles begin to overlap and eventually pack onto body-centered cubic (BCC) lattice. In this study, concentrated, ordered micelles (15 vol% polymers) prepared by dispersing isotopically labeled poly(styrene- b -ethylene-alt-propylene) in an isotopic squalane mixture was investigated to understand the micellar concentration dependence of the molecular exchange. Perfectly random mixing of isotopically labeled micelles on the BCC lattice was confirmed by SANS patterns where the interparticle contribution vanishes, resulting in an intensity that directly relates to the exchange kinetics. The measured molecular exchange process for the concentrated, ordered system is qualitatively consistent with the previous observations, but the rate is more than an order of magnitude slower than that for the dilute, disordered system. Infineum(IPrime), MRSEC(NSF), NIST.

  2. Adsorption of pH-responsive amphiphilic copolymer micelles and gel on membrane surface as an approach for antifouling coating

    NASA Astrophysics Data System (ADS)

    Muppalla, Ravikumar; Rana, Harpalsinh H.; Devi, Sadhna; Jewrajka, Suresh K.

    2013-03-01

    A new approach for the surface modification of polymer membranes prepared by phase inversion technique for antifouling properties is reported. Direct deposition of poly(2-dimethylaminoethyl methacrylate)-b-poly(methyl methacrylate)-b-poly(2-dimethylaminoethyl methacrylate) (PDMA-b-PMMA-b-PDMA) copolymer micelles (core-shell) and gel formed from mixture of polyvinyl alcohol (PVA) and PDMA-b-PMMA-b-PDMA on the polysulfone (PSf-virgin) ultrafiltration membrane surface successfully provides modified membranes with improved antifouling properties and pH-responsive behaviour during both water and protein filtrations. Successful deposition and adsorption of such type of micelle and gel particles on the membrane surface was assessed by combination of SEM, AFM, contact angle, ATR-IR, and zeta potential measurements. The micelle and gel particles preferentially remained on the membranes surface due to their bigger size than the pores on the skin layer and also due to adsorption on the membrane surface by hydrophobic interaction. The modified membranes exhibited much higher rejection of macromolecules and almost steady trend in flux compared to corresponding virgin membranes during filtration operation. The major advantage of this protocol is that the deposited micelles and gel remained on the membrane surface even after filtration and storage of the membrane in water and the modified membranes retained similar performance. The effect of all the micelles and gel components on the membrane performance has been elucidated.

  3. Stability of casein micelles in milk

    NASA Astrophysics Data System (ADS)

    Tuinier, R.; de Kruif, C. G.

    2002-07-01

    Casein micelles in milk are proteinaceous colloidal particles and are essential for the production of flocculated and gelled products such as yogurt, cheese, and ice-cream. The colloidal stability of casein micelles is described here by a calculation of the pair potential, containing the essential contributions of brush repulsion, electrostatic repulsion, and van der Waals attraction. The parameters required are taken from the literature. The results are expressed by the second osmotic virial coefficient and are quite consistent with experimental findings. It appears that the stability is mainly attributable to a steric layer of κ-casein, which can be described as a salted polyelectrolyte brush.

  4. Statistical crystallography of surface micelle spacing

    NASA Technical Reports Server (NTRS)

    Noever, David A.

    1992-01-01

    The aggregation of the recently reported surface micelles of block polyelectrolytes is analyzed using techniques of statistical crystallography. A polygonal lattice (Voronoi mosaic) connects center-to-center points, yielding statistical agreement with crystallographic predictions; Aboav-Weaire's law and Lewis's law are verified. This protocol supplements the standard analysis of surface micelles leading to aggregation number determination and, when compared to numerical simulations, allows further insight into the random partitioning of surface films. In particular, agreement with Lewis's law has been linked to the geometric packing requirements of filling two-dimensional space which compete with (or balance) physical forces such as interfacial tension, electrostatic repulsion, and van der Waals attraction.

  5. Indirect inversions

    NASA Astrophysics Data System (ADS)

    Sergienko, Olga

    2013-04-01

    Since Doug MacAyeal's pioneering studies of the ice-stream basal traction optimizations by control methods, inversions for unknown parameters (e.g., basal traction, accumulation patterns, etc) have become a hallmark of the present-day ice-sheet modeling. The common feature of such inversion exercises is a direct relationship between optimized parameters and observations used in the optimization procedure. For instance, in the standard optimization for basal traction by the control method, ice-stream surface velocities constitute the control data. The optimized basal traction parameters explicitly appear in the momentum equations for the ice-stream velocities (compared to the control data). The inversion for basal traction is carried out by minimization of the cost (or objective, misfit) function that includes the momentum equations facilitated by the Lagrange multipliers. Here, we build upon this idea, and demonstrate how to optimize for parameters indirectly related to observed data using a suite of nested constraints (like Russian dolls) with additional sets of Lagrange multipliers in the cost function. This method opens the opportunity to use data from a variety of sources and types (e.g., velocities, radar layers, surface elevation changes, etc.) in the same optimization process.

  6. Micelle depletion-induced vs. micelle-mediated aggregation in nanoparticles

    SciTech Connect

    Ray, D. Aswal, V. K.

    2015-06-24

    The phase behavior anionic silica nanoparticle (Ludox LS30) with non-ionic surfactants decaethylene glycol monododecylether (C12E10) and cationic dodecyltrimethyl ammonium bromide (DTAB) in aqueous electrolyte solution has been studied by small-angle neutron scattering (SANS). The measurements have been carried out for fixed concentrations of nanoparticle (1 wt%), surfactants (1 wt%) and electrolyte (0.1 M NaCl). Each of these nanoparticle–surfactant systems has been examined for different contrast conditions where individual components (nanoparticle or surfactant) are made visible. It is observed that the nanoparticle-micelle system in both the cases lead to the aggregation of nanoparticles. The aggregation is found to be micelle depletion-induced for C12E10 whereas micelle-mediated aggregation for DTAB. Interestingly, it is also found that phase behavior of mixed surfactant (C12E10 + DTAB) system is similar to that of C12E10 (unlike DTAB) micelles with nanoparticles.

  7. Polymeric micelles as drug carriers: their lights and shadows.

    PubMed

    Yokoyama, Masayuki

    2014-08-01

    In this review, polymeric micelles as drug-targeting carriers are concisely explained. In the first introduction part, I describe a brief history of polymer micelle's research for drug targeting, and then I explain this review's focus. Since most other review articles concerning polymeric micelle carriers explain only what was achieved in the polymeric micelle's research, I describe this review by focusing on what was not done. In the second part, I take up three characteristics of polymeric micelle carriers by comparing their advantages and disadvantages, what was done and what was not done in the past studies, and what is easily achieved and what is difficult to be achieved with polymeric micelles. In the last part, I discuss three common problems of nano-sized drug carrier systems including polymeric micelles, and then I add a few comments on these problems. PMID:25012065

  8. Galactosylated fluorescent labeled micelles as a liver targeting drug carrier.

    PubMed

    Wu, De-Qun; Lu, Bo; Chang, Cong; Chen, Chang-Sheng; Wang, Tao; Zhang, Yuan-Yuan; Cheng, Si-Xue; Jiang, Xue-Jun; Zhang, Xian-Zheng; Zhuo, Ren-Xi

    2009-03-01

    Galactosylated and fluorescein isothiocyanate (FITC) labeled polycaprolactone-g-dextran (Gal-PCL-g-Dex-FITC) polymers were synthesized. The grafted polymers can self-assemble into stable micelles in aqueous medium and in serum. Transmission electron microscopy (TEM) images showed that the self-assembled micelles were regularly spherical in shape. Micelle size determined by size analysis was around 120 nm. The anti-inflammation drug prednisone acetate as a model drug was loaded in the polymeric micelles, and the in vitro drug release was investigated. The galactosylated micelles could be selectively recognized by HepG2 cells and subsequently accumulate in HepG2 cells. The in vivo study demonstrated the relative uptake of the micelles by liver is much higher than the other tissues, indicating that the galactosylated micelles have great potential as a liver targeting drug carrier. PMID:19100617

  9. Temperature Effect on the Nanostructure of SDS Micelles in Water

    PubMed Central

    Hammouda, Boualem

    2013-01-01

    Sodium dodecyl sulfate (SDS) surfactants form micelles when dissolved in water. These are formed of a hydrocarbon core and hydrophilic ionic surface. The small-angle neutron scattering (SANS) technique was used with deuterated water (D2O) in order to characterize the micelle structure. Micelles were found to be slightly compressed (oblate ellipsoids) and their sizes shrink with increasing temperature. Fits of SANS data to the Mean Spherical Approximation (MSA) model yielded a calculated micelle volume fraction which was lower than the SDS surfactant (sample mixing) volume fraction; this suggests that part of the SDS molecules do not participate in micelle formation and remain homogeneously mixed in the solvent. A set of material balance equations allowed the estimation of the SDS fraction in the micelles. This fraction was found to be high (close to one) except for samples around 1 % SDS fraction. The micelle aggregation number was found to decrease with increasing temperature and/or decreasing SDS fraction. PMID:26401428

  10. Antibacterial polyelectrolyte micelles for coating stainless steel.

    PubMed

    Falentin-Daudré, Céline; Faure, Emilie; Svaldo-Lanero, Tiziana; Farina, Fabrice; Jérôme, Christine; Van De Weerdt, Cécile; Martial, Joseph; Duwez, Anne-Sophie; Detrembleur, Christophe

    2012-05-01

    In this study, we report on the original synthesis and characterization of novel antimicrobial coatings for stainless steel by alternating the deposition of aqueous solutions of positively charged polyelectrolyte micelles doped with silver-based nanoparticles with a polyanion. The micelles are formed by electrostatic interaction between two oppositely charged polymers: a polycation bearing 3,4-dihydroxyphenylalanine units (DOPA, a major component of natural adhesives) and a polyanion (poly(styrene sulfonate), PSS) without using any block copolymer. DOPA units are exploited for their well-known ability to anchor to stainless steel and to form and stabilize biocidal silver nanoparticles (Ag(0)). The chlorine counteranion of the polycation forms and stabilizes biocidal silver chloride nanoparticles (AgCl). We demonstrate that two layers of micelles (alternated by PSS) doped with silver particles are enough to impart to the surface strong antibacterial activity against gram-negative E. coli. Moreover, micelles that are reservoirs of biocidal Ag(+) can be easily reactivated after depletion. This novel water-based approach is convenient, simple, and attractive for industrial applications. PMID:22506542

  11. On the composition fluctuations of reverse micelles.

    PubMed

    Tovstun, Sergey A; Razumov, Vladimir F

    2010-11-15

    The polydispersity of the reverse micelles is determined mainly by the fluctuations of their composition. The composition of the reverse micelle is a two-dimensional random variable whose components are the numbers of water (i) and surfactant (j) molecules. In this study the fluctuations of the composition of the reverse micelles are considered in the Gaussian approximation. It is shown that the standard deviation of the quantity w=i/j may be calculated from the dependence of the water vapor pressure above the microemulsion on the molar ratio W=[water]/[surfactant]. The estimation based on the literature data for microemulsion system sodium bis(2-ethylhexyl)sulfosuccinate/water/isooctane at 37°C in the range W=0-18 has shown that the relative standard deviation of the quantity w is about 10%. It is shown that the value of the composition fluctuations is related to the dependence of average composition on the concentration of reverse micelles at constant parameter W. PMID:20800237

  12. Secondary structure formation in peptide amphiphile micelles

    NASA Astrophysics Data System (ADS)

    Tirrell, Matthew

    2012-02-01

    Peptide amphiphiles (PAs) are capable of self-assembly into micelles for use in the targeted delivery of peptide therapeutics and diagnostics. PA micelles exhibit a structural resemblance to proteins by having folded bioactive peptides displayed on the exterior of a hydrophobic core. We have studied two factors that influence PA secondary structure in micellar assemblies: the length of the peptide headgroup and amino acids closest to the micelle core. Peptide length was systematically varied using a heptad repeat PA. For all PAs the addition of a C12 tail induced micellization and secondary structure. PAs with 9 amino acids formed beta-sheet interactions upon aggregation, whereas the 23 and 30 residue peptides were displayed in an apha-helical conformation. The 16 amino acid PA experienced a structural transition from helix to sheet, indicating that kinetics play a role in secondary structure formation. A p53 peptide was conjugated to a C16 tail via various linkers to study the effect of linker chemistry on PA headgroup conformation. With no linker the p53 headgroup was predominantly alpha helix and a four alanine linker drastically changed the structure of the peptide headgroup to beta-sheet, highlighting the importance of hydrogen boding potential near the micelle core.

  13. Colloidal Electrolytes and the Critical Micelle Concentration

    ERIC Educational Resources Information Center

    Knowlton, L. G.

    1970-01-01

    Describes methods for determining the Critical Micelle Concentration of Colloidal Electrolytes; methods described are: (1) methods based on Colligative Properties, (2) methods based on the Electrical Conductivity of Colloidal Electrolytic Solutions, (3) Dye Method, (4) Dye Solubilization Method, and (5) Surface Tension Method. (BR)

  14. Casein micelles and their internal structure

    SciTech Connect

    De Kruif, Cornelis G; Huppertz, Thom; Urban, Volker S; Petukhov, Andrei V

    2012-01-01

    The internal structure of casein micelles was studied by calculating the small-angle neutron and X-ray scattering and static light scattering spectrum (SANS, SAXS, SLS) as a function of the scattering contrast and composition. We predicted experimental SANS, SAXS, SLS spectra self consistently using independently determined parameters for composition size, polydispersity, density and voluminosity. The internal structure of the casein micelles, i.e. how the various components are distributed within the casein micelle, was modeled according to three different models advocated in the literature; i.e. the classical sub-micelle model, the nanocluster model and the dual binding model. In this paper we present the essential features of these models and combine new and old experimental SANS, SAXS, SLS and DLS scattering data with new calculations that predict the spectra. Further evidence on micellar substructure was obtained by internally cross linking the casein micelles using transglutaminase, which led to casein nanogel particles. In contrast to native casein micelles, the nanogel particles were stable in 6 M urea and after sequestering the calcium using trisodium citrate. The changed scattering properties were again predicted self consistently. An important result is that the radius of gyration is independent of contrast, indicating that the mass distribution within a casein micelle is homogeneous. Experimental contrast is predicted quite well leading to a match point at a D{sub 2}O volume fraction of 0.41 ratio in SANS. Using SANS and SAXS model calculations it is concluded that only the nanocluster model is capable of accounting for the experimental scattering contrast variation data. All features and trends are predicted self consistently, among which the 'famous' shoulder at a wave vector value Q = 0.35 nm{sup -1}. In the nanocluster model, the casein micelle is considered as a (homogeneous) matrix of caseins in which the colloidal calcium phosphate (CCP

  15. Inverse problem in hydrogeology

    NASA Astrophysics Data System (ADS)

    Carrera, Jesús; Alcolea, Andrés; Medina, Agustín; Hidalgo, Juan; Slooten, Luit J.

    2005-03-01

    The state of the groundwater inverse problem is synthesized. Emphasis is placed on aquifer characterization, where modelers have to deal with conceptual model uncertainty (notably spatial and temporal variability), scale dependence, many types of unknown parameters (transmissivity, recharge, boundary conditions, etc.), nonlinearity, and often low sensitivity of state variables (typically heads and concentrations) to aquifer properties. Because of these difficulties, calibration cannot be separated from the modeling process, as it is sometimes done in other fields. Instead, it should be viewed as one step in the process of understanding aquifer behavior. In fact, it is shown that actual parameter estimation methods do not differ from each other in the essence, though they may differ in the computational details. It is argued that there is ample room for improvement in groundwater inversion: development of user-friendly codes, accommodation of variability through geostatistics, incorporation of geological information and different types of data (temperature, occurrence and concentration of isotopes, age, etc.), proper accounting of uncertainty, etc. Despite this, even with existing codes, automatic calibration facilitates enormously the task of modeling. Therefore, it is contended that its use should become standard practice. L'état du problème inverse des eaux souterraines est synthétisé. L'accent est placé sur la caractérisation de l'aquifère, où les modélisateurs doivent jouer avec l'incertitude des modèles conceptuels (notamment la variabilité spatiale et temporelle), les facteurs d'échelle, plusieurs inconnues sur différents paramètres (transmissivité, recharge, conditions aux limites, etc.), la non linéarité, et souvent la sensibilité de plusieurs variables d'état (charges hydrauliques, concentrations) des propriétés de l'aquifère. A cause de ces difficultés, le calibrage ne peut êtreséparé du processus de modélisation, comme c'est le

  16. Fabrication of multiresponsive shell cross-linked micelles possessing pH-controllable core swellability and thermo-tunable corona permeability.

    PubMed

    Jiang, Xiaoze; Ge, Zhishen; Xu, Jian; Liu, Hao; Liu, Shiyong

    2007-10-01

    A double hydrophilic ABC triblock copolymer, poly(2-(diethylamino)ethyl methacrylate)-b-poly(2-(dimethylamino)ethyl methacrylate)-b-poly(N-isopropylacrylamide) (PDEA-b-PDMA-b-PNIPAM), containing the well-known pH-responsive PDEA block and thermoresponsive PNIPAM block, was synthesized by atom transfer radical polymerization via sequential monomer addition using ethyl 2-chloropropionate as the initiator. The obtained triblock copolymer exhibits interesting "schizophrenic" micellization behavior in aqueous solution, and supramolecularly self-assembles into three-layer "onion-like" PNIPAM-core micelles at acidic pH's and elevated temperatures and PDEA-core micelles with "inverted" structures at alkaline pH's and room temperature. In both cases, dynamic laser light scattering (LLS) and optical transmittance reveal the presence of near-monodisperse micelles, and the micelle formation/inversion process is fully reversible. Novel shell cross-linked (SCL) micelles with pH-responsive PDEA cores and thermoresponsive PNIPAM coronas were then facilely fabricated from the PDEA-b-PDMA-b-PNIPAM triblock copolymer by cross-linking the PDMA inner shells with 1,2-bis(2-iodoethoxy)ethane. The reversible pH-dependent swelling/shrinking of PDEA cores and thermosensitive collapse/aggregation of PNIPAM coronas of the obtained SCL micelles were investigated in detail by dynamic LLS, optical transmittance, and transmission electron microscopy. As the structurally stable SCL micelles possess pH-controllable core swellability and thermo-tunable corona permeability, the release profile of a model hydrophobic drug, dipyridamole, initially loaded within the hydrophobic PDEA core, can be dually controlled by both the solution pH and the temperature. This represents the first report of SCL micelles with multiresponsive cores and coronas, which may find practical applications in fields such as drug delivery and smart release. PMID:17887794

  17. Structural changes in block copolymer micelles induced by cosolvent mixtures

    SciTech Connect

    Kelley, Elizabeth G.; Smart, Thomas P.; Jackson, Andrew J.; Sullivan, Millicent O.; Epps, III, Thomas H.

    2012-11-26

    We investigated the influence of tetrahydrofuran (THF) addition on the structure of poly(1,2-butadiene-b-ethylene oxide) [PB-PEO] micelles in aqueous solution. Our studies showed that while the micelles remained starlike, the micelle core-corona interfacial tension and micelle size decreased upon THF addition. The detailed effects of the reduction in interfacial tension were probed using contrast variations in small angle neutron scattering (SANS) experiments. At low THF contents (high interfacial tensions), the SANS data were fit to a micelle form factor that incorporated a radial density distribution of corona chains to account for the starlike micelle profile. However, at higher THF contents (low interfacial tensions), the presence of free chains in solution affected the scattering at high q and required the implementation of a linear combination of micelle and Gaussian coil form factors. These SANS data fits indicated that the reduction in interfacial tension led to broadening of the core-corona interface, which increased the PB chain solvent accessibility at intermediate THF solvent fractions. We also noted that the micelle cores swelled with increasing THF addition, suggesting that previous assumptions of the micelle core solvent content in cosolvent mixtures may not be accurate. Control over the size, corona thickness, and extent of solvent accessible PB in these micelles can be a powerful tool in the development of targeting delivery vehicles.

  18. Interaction of lactoferrin and lysozyme with casein micelles.

    PubMed

    Anema, Skelte G; de Kruif, C G Kees

    2011-11-14

    On addition of lactoferrin (LF) to skim milk, the turbidity decreases. The basic protein binds to the caseins in the casein micelles, which is then followed by a (partial) disintegration of the casein micelles. The amount of LF initially binding to casein micelles follows a Langmuir adsorption isotherm. The kinetics of the binding of LF could be described by first-order kinetics and similarly the disintegration kinetics. The disintegration was, however, about 10 times slower than the initial adsorption, which allowed investigating both phenomena. Kinetic data were also obtained from turbidity measurements, and all data could be described with one equation. The disintegration of the casein micelles was further characterized by an activation energy of 52 kJ/mol. The initial increase in hydrodynamic size of the casein micelles could be accounted for by assuming that it would go as the cube root of the mass using the adsorption and disintegration kinetics as determined from gel electrophoresis. The results show that LF binds to casein micelles and that subsequently the casein micelles partly disintegrate. All micelles behave in a similar manner as average particle size decreases. Lysozyme also bound to the casein micelles, and this binding followed a Langmuir adsorption isotherm. However, lysozyme did not cause the disintegration of the casein micelles. PMID:21932853

  19. Preparation and evaluation of inhalable itraconazole chitosan based polymeric micelles

    PubMed Central

    2012-01-01

    Background This study evaluated the potential of chitosan based polymeric micelles as a nanocarrier system for pulmonary delivery of itraconazole (ITRA). Methods Hydrophobically modified chitosan were synthesized by conjugation of stearic acid to the hydrophilic depolymerized chitosan. FTIR and 1HNMR were used to prove the chemical structure and physical properties of the depolymerized and the stearic acid grafted chitosan. ITRA was entrapped into the micelles and physicochemical properties of the micelles were investigated. Fluorescence spectroscopy, dynamic laser light scattering and transmission electron microscopy were used to characterize the physicochemical properties of the prepared micelles. The in vitro pulmonary profile of polymeric micelles was studied by an air-jet nebulizer connected to a twin stage impinger. Results The polymeric micelles prepared in this study could entrap up to 43.2±2.27 μg of ITRA per milliliter. All micelles showed mean diameter between 120–200 nm. The critical micelle concentration of the stearic acid grafted chitosan was found to be 1.58×10-2 mg/ml. The nebulization efficiency was up to 89% and the fine particle fraction (FPF) varied from 38% to 47%. The micelles had enough stability to remain encapsulation of the drug during nebulization process. Conclusions In vitro data showed that stearic acid grafted chitosan based polymeric micelles has a potential to be used as nanocarriers for delivery of itraconazole through inhalation. PMID:23351398

  20. Structure of β-casein micelles

    NASA Astrophysics Data System (ADS)

    Leclerc, E.; Calmettes, P.

    β-casein is a flexible milk protein which forms micelles. Up to now their structure was controversial. Small-angle neutron scattering was used to determine the protein conformation in the aggregates. Whatever the mean aggregation number, the scattering profiles show that β-casein micelles are spherical and keep an almost constant radius of 135 Å. They consist of a relatively large and dense core surrounded by a shell of much lower density. In the latter, hydrophilic protein strands and loops protrude in the solvent as polymers grafted on a surface. The core contains most of the hydrophobic residues and some hydrophilic ones. Though its density increases with the aggregation number it is never compact.

  1. Micelle Morphology and Mechanical Response of Triblock Gels

    SciTech Connect

    Seitz, Michelle E.; Burghardt, Wesley R.; Shull, Kenneth R.

    2010-01-12

    The effect of polymer concentration on mechanical response and micelle morphology of ABA and AB copolymers in B-selective solvents has been systematically studied. Micelle morphology was determined using a combination of small-angle X-ray scattering, shear, and birefringence while mechanical response at low and high strains was determined using indentation techniques. Self-consistent field theory calculations were used to determine micelle volume fraction profiles and to construct an equilibrium phase map. The transition from spherical to cylindrical micelles increases the triblock gel modulus and energy dissipation. Combining knowledge of gel relaxation time, which determines the rate at which the gel can equilibrate its micelle structure, with the equilibrium phase map allows estimation of the experimental temperatures and time scales over which kinetic trapping will arrest micelle structure evolution. Kinetic trapping enables cylindrical morphologies to be obtained at significantly lower polymer fractions than is possible in equilibrated systems.

  2. Implicit solvent simulations of DPC micelle formation.

    PubMed

    Lazaridis, Themis; Mallik, Buddhadeb; Chen, Yong

    2005-08-11

    The formation of micelles by dodecylphosphocholine (DPC) is modeled by treating the surfactants in atomic detail and the solvent implicitly, in the spirit of the EEF1 solvation model for proteins. The solvation parameters of the DPC atoms are carried over from those of similar atoms in proteins. A slight adjustment of the parameters for the headgroup was found necessary for obtaining an aggregation number consistent with experiment. Molecular dynamics simulations of 960 DPC molecules at different concentrations are used to obtain the aggregation number, the micelle size distribution, and the CMC. At 20 mM concentration we obtain an aggregation number of 53-56 and a CMC of 1.25 mM, values close to the experimental ones. At 100 mM the aggregation number increases to 90. Simulations of individual micelles of varying size show that the effective energy per surfactant molecule is initially a decreasing function of aggregation number but stabilizes at about 60 molecules. The van der Waals term and the desolvation of nonpolar groups contribute to micellization, whereas the desolvation of polar groups opposes it. From the difference between the effective energy and the free energy (calculated from the CMC), the translational and rotational entropy contributions to the free energy are estimated at about 7 kcal/mol per monomer. The micelles obtained here are more irregular than those obtained in explicit water simulations. This modeling approach allows the study of larger surfactant aggregates for longer times and the extraction of thermodynamic in addition to structural information. PMID:16852911

  3. Chain exchange in triblock copolymer micelles

    NASA Astrophysics Data System (ADS)

    Lu, Jie; Lodge, Timothy; Bates, Frank

    2015-03-01

    Block polymer micelles offer a host of technological applications including drug delivery, viscosity modification, toughening of plastics, and colloidal stabilization. Molecular exchange between micelles directly influences the stability, structure and access to an equilibrium state in such systems and this property recently has been shown to be extraordinarily sensitive to the core block molecular weight in diblock copolymers. The dependence of micelle chain exchange dynamics on molecular architecture has not been reported. The present work conclusively addresses this issue using time-resolved small-angle neutron scattering (TR-SANS) applied to complimentary S-EP-S and EP-S-EP triblock copolymers dissolved in squalane, a selective solvent for the EP blocks, where S and EP refer to poly(styrene) and poly(ethylenepropylene), respectively. Following the overall SANS intensity as a function of time from judiciously deuterium labelled polymer and solvent mixtures directly probes the rate of molecular exchange. Remarkably, the two triblocks display exchange rates that differ by approximately ten orders of magnitude, even though the solvophobic S blocks are of comparable size. This discovery is considered in the context of a model that successfully explains S-EP diblock exchange dynamics.

  4. Structured Hydrogels using Micelles as Templates

    NASA Astrophysics Data System (ADS)

    Lee, Wonjoo; Kofinas, Peter; Briber, Robert M.

    2008-03-01

    Molecularly imprinted polymers can be created by crosslinking polymers in the presence of molecular templates. If the pores generated after the removing of templates have almost the same size and shape as the template, the material has a potential to be used for separation, biosensor and drug delivery applications. In this work, micelles were used as the template as they can be easily removed from the hydrogel and a range of structures are accessible by combining a (linear) polyelectrolyte and an oppositely charged surfactant. Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) was synthesized and quaternized using methyl iodide. We have performed small angle neutron scattering (SANS) on solutions and hydrogels of PDMAEMA with sodium dodecylsulfate (SDS) under different contrast matching conditions. A structured hydrogel was then formed by chemically crosslinking the semi-dilute PDMAEMA solution which contained SDS. It was confirmed that spherical micelle-like structures were associated along the polymer chain in a bead-and-necklace structure consistent with what has been observed in the (uncharged) poly(ethylene oxide)/SDS system. Furthermore, it was shown that the interaction between PDMAEMA and micelles is strong enough to maintain the nanoscale structure formed along the PDMAEMA chain, even after crosslinking, leading to a structured hydrogel.

  5. Toward a Standard Protocol for Micelle Simulation.

    PubMed

    Johnston, Michael A; Swope, William C; Jordan, Kirk E; Warren, Patrick B; Noro, Massimo G; Bray, David J; Anderson, Richard L

    2016-07-01

    In this paper, we present protocols for simulating micelles using dissipative particle dynamics (and in principle molecular dynamics) that we expect to be appropriate for computing micelle properties for a wide range of surfactant molecules. The protocols address challenges in equilibrating and sampling, specifically when kinetics can be very different with changes in surfactant concentration, and with minor changes in molecular size and structure, even using the same force field parameters. We demonstrate that detection of equilibrium can be automated and is robust, for the molecules in this study and others we have considered. In order to quantify the degree of sampling obtained during simulations, metrics to assess the degree of molecular exchange among micellar material are presented, and the use of correlation times are prescribed to assess sampling and for statistical uncertainty estimates on the relevant simulation observables. We show that the computational challenges facing the measurement of the critical micelle concentration (CMC) are somewhat different for high and low CMC materials. While a specific choice is not recommended here, we demonstrate that various methods give values that are consistent in terms of trends, even if not numerically equivalent. PMID:27096611

  6. Preparation and Characterization of Lipophilic Doxorubicin Pro-drug Micelles.

    PubMed

    Li, Feng; Snow-Davis, Candace; Du, Chengan; Bondarev, Mikhail L; Saulsbury, Marilyn D; Heyliger, Simone O

    2016-01-01

    Micelles have been successfully used for the delivery of anticancer drugs. Amphiphilic polymers form core-shell structured micelles in an aqueous environment through self-assembly. The hydrophobic core of micelles functions as a drug reservoir and encapsulates hydrophobic drugs. The hydrophilic shell prevents the aggregation of micelles and also prolongs their systemic circulation in vivo. In this protocol, we describe a method to synthesize a doxorubicin lipophilic pro-drug, doxorubicin-palmitic acid (DOX-PA), which will enhance drug loading into micelles. A pH-sensitive hydrazone linker was used to conjugate doxorubicin with the lipid, which facilitates the release of free doxorubicin inside cancer cells. Synthesized DOX-PA was purified with a silica gel column using dichloromethane/methanol as the eluent. Purified DOX-PA was analyzed with thin layer chromatography (TLC) and (1)H-Nuclear Magnetic Resonance Spectroscopy ((1)H-NMR). A film dispersion method was used to prepare DOX-PA loaded DSPE-PEG micelles. In addition, several methods for characterizing micelle formulations are described, including determination of DOX-PA concentration and encapsulation efficiency, measurement of particle size and distribution, and assessment of in vitro anticancer activities. This protocol provides useful information regarding the preparation and characterization of drug-loaded micelles and thus will facilitate the research and development of novel micelle-based cancer nanomedicines. PMID:27584689

  7. Mesoscale crystallization of calcium phosphate nanostructures in protein (casein) micelles

    NASA Astrophysics Data System (ADS)

    Thachepan, Surachai; Li, Mei; Mann, Stephen

    2010-11-01

    Aqueous micelles of the multi-protein calcium phosphate complex, casein, were treated at 60 °C and pH 7 over several months. Although partial dissociation of the micelles into 12 nm sized amorphous calcium phosphate (ACP)/protein nanoparticles occurred within a period of 14 days, crystallization of the ACP nanoclusters into bundles of hydroxyapatite (HAP) nanofilaments was not observed until after 12 weeks. The HAP nanofilaments were formed specifically within the partially disrupted protein micelles suggesting a micelle-mediated pathway of mesoscale crystallization. Similar experiments using ACP-containing synthetic micelles prepared from β-casein protein alone indicated that co-aligned bundles of HAP nanofilaments were produced within the protein micelle interior after 24 hours at temperatures as low as 35 °C. The presence of Mg2+ ions in the casein micelles, as well as a possible synergistic effect associated with the multi-protein nature of the native aggregates, could account for the marked inhibition in mesoscale crystallization observed in the casein micelles compared with the single-component β-casein constructs.Aqueous micelles of the multi-protein calcium phosphate complex, casein, were treated at 60 °C and pH 7 over several months. Although partial dissociation of the micelles into 12 nm sized amorphous calcium phosphate (ACP)/protein nanoparticles occurred within a period of 14 days, crystallization of the ACP nanoclusters into bundles of hydroxyapatite (HAP) nanofilaments was not observed until after 12 weeks. The HAP nanofilaments were formed specifically within the partially disrupted protein micelles suggesting a micelle-mediated pathway of mesoscale crystallization. Similar experiments using ACP-containing synthetic micelles prepared from β-casein protein alone indicated that co-aligned bundles of HAP nanofilaments were produced within the protein micelle interior after 24 hours at temperatures as low as 35 °C. The presence of Mg2+ ions in

  8. Diclofenac/biodegradable polymer micelles for ocular applications

    NASA Astrophysics Data System (ADS)

    Li, Xingyi; Zhang, Zhaoliang; Li, Jie; Sun, Shumao; Weng, Yuhua; Chen, Hao

    2012-07-01

    In this paper, methoxypoly(ethylene glycol)-poly(ε-caprolactone) (MPEG-PCL) micelle formulations as promising nano-carriers for poorly water soluble drugs were investigated for the delivery of diclofenac to the eye. Diclofenac loaded MPEG-PCL micelles were prepared by a simple solvent-diffusion method and characterized by dynamic light scattering (DLS), atomic force microscopy (AFM), Fourier transform infra-red (FTIR), X-ray diffraction (XRD), differential scanning calorimetery (DSC), etc. With the analysis of XRD and DSC, the diclofenac was present as an amorphous state in the formulation. The in vitro release profile indicated a sustained release manner of diclofenac from the micelles. Meanwhile, in vivo studies on eye irritation were performed with blank MPEG-PCL micelles (200 mg ml-1). The results showed that the developed MPEG-PCL micelles were non-irritants to the eyes of rabbits. In vitro penetration studies across the rabbit cornea demonstrated that the micelle formulations exhibited a 17-fold increase in penetration compared with that of diclofenac phosphate buffered saline (PBS) solution. The in vivo pharmacokinetics profile of the micelle parent drug in the aqueous humor of the rabbit was evaluated and the data showed that the diclofenac loaded MPEG-PCL micelles exhibited a 2-fold increase in AUC0-24 h than that of the diclofenac PBS solution eye drops. These results suggest a great potential of our micelle formulations as a novel ocular drug delivery system to improve the bioavailability of the drugs.

  9. Dynamic light scattering of cutinase in AOT reverse micelles.

    PubMed

    Melo, E P; Fojan, P; Cabral, J M; Petersen, S B

    2000-08-01

    The fungal lipolytic enzyme cutinase, incorporated into sodium bis-(2ethylhexyl) sulfosuccinate reversed micelles has been investigated using dynamic light scattering. The reversed micelles form spontaneously when water is added to a solution of sodium bis-(2ethylhexyl) sulfosuccinate in isooctane. When an enzyme is previously dissolved in the water before its addition to the organic phase, the enzyme will be incorporated into the micelles. Enzyme encapsulation in reversed micelles can be advantageous namely to the conversion of water insoluble substrates and to carry out synthesis reactions. However protein unfolding occurs in several systems as for cutinase in sodium bis-(2ethylhexyl) sulfosuccinate reversed micelles. Dynamic light scattering measurements of sodium bis-(2ethylhexyl) sulfosuccinate reversed micelles with and without cutinase were taken at different water to surfactant ratios. The results indicate that cutinase was attached to the micellar wall and that might cause cutinase unfolding. The interactions between cutinase and the bis-(2ethylhexyl) sulfosuccinate interface are probably the driving force for cutinase unfolding at room temperature. Twenty-four hours after encapsulation, when cutinase is unfolded, a bimodal distribution was clearly observed. The radii of reversed micelles with unfolded cutinase were determined and found to be considerable larger than the radii of the empty reversed micelles. The majority of the reversed micelles were empty (90-96% of mass) and the remainder (4-10%) containing unfolded cutinase were larger by 26-89 A. PMID:10930568

  10. Inverse Floatation

    NASA Astrophysics Data System (ADS)

    Nath, Saurabh; Mukherjee, Anish; Chatterjee, Souvick; Ganguly, Ranjan; Sen, Swarnendu; Mukhopadhyay, Achintya; Boreyko, Jonathan

    2014-11-01

    We have observed that capillarity forces may cause floatation in a few non-intuitive configurations. These may be divided into 2 categories: i) floatation of heavier liquid droplets on lighter immiscible ones and ii) fully submerged floatation of lighter liquid droplets in a heavier immiscible medium. We call these counter-intuitive because of the inverse floatation configuration. For case (i) we have identified and studied in detail the several factors affecting the shape and maximum volume of the floating drop. We used water and vegetable oil combinations as test fluids and established the relation between Bond Number and maximum volume contained in a floating drop (in the order of μL). For case (ii), we injected vegetable oil drop-wise into a pool of water. The fully submerged configuration of the drop is not stable and a slight perturbation to the system causes the droplet to burst and float in partially submerged condition. Temporal variation of a characteristic length of the droplet is analyzed using MATLAB image processing. The constraint of small Bond Number establishes the assumption of lubrication regime in the thin gap. A brief theoretical formulation also shows the temporal variation of the gap thickness. Jadavpur University, Jagadis Bose Centre of Excellence, Virginia Tech.

  11. FTIR spectroscopic study of the acrylamide states in AOT reversed micelles

    NASA Astrophysics Data System (ADS)

    Guo, Yilu; Wu, Peiyi

    2008-07-01

    The state of acrylamide (AM) confined within the hydrophilic core of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reversed micelles has been investigated by Fourier transform infrared spectroscopy with an attenuated total reflection (ATR) accessory. 2D correlation spectroscopy and curve fitting revealed that the acrylamide molecule was carried into the micellar core by one of the two long tails of the AOT through H-bonding between the amide group and the carbonyl group of AOT. The acrylamide tended to stick at the interface of the inverse emulsion at lower acrylamide-to-AOT molar ratio value ( X); when X increased to some higher values, the acrylamide would tend to congregate in the micellar core. Therefore, it is important to choose the suitable initiator for the inverse emulsion polymerization under different experimental conditions.

  12. Contributions a l'etude des lidars a champs visuels multiples

    NASA Astrophysics Data System (ADS)

    Roy, Gilles

    On presente un modele, base sur la diffraction et l'optique geometrique, liant les signaux lidar a champs multiples a la densite de distribution de la taille des particules. On ecrit la relation sous forme matricielle ce qui permet d'obtenir la densite de distribution apparente de la taille des particules par inversion matricielle avec contrainte. On interprete la perturbation causee par la contribution de l'optique geometrique au signal lidar comme de la diffraction causee par une particule de diametre d'environ un micron. La densite de distribution apparente est corrigee a posteriori en calculant la contribution relative des differents ordres de diffusion a l'elargissement de la fonction de phase des particules. La validite du modele est supportee par des simulations Monte Carlo et par des resultats experimentaux obtenus sous des conditions controlees. Finalement, on applique avec succes, la technique d'inversion aux mesures lidar multichamps obtenues sur des nuages.

  13. Photophysical properties of amphiphilic ruthenium(II) complexes in micelles.

    PubMed

    Rajkumar, Eswaran; Mareeswaran, Paulpandian Muthu; Rajagopal, Seenivasan

    2014-09-01

    Amphiphilic ruthenium(II) complexes II–IV were synthesized and their photophysical properties were investigated in the presence of anionic (SDS), cationic (CTAB) and neutral (Triton X-100) micelles. The absorption and emission spectral data in the presence of micelles show that these Ru(II) complexes are incorporated in the micelles. There are two types of interaction between complexes I–IV and the micelles: hydrophobic and electrostatic. In the case of cationic micelles (CTAB), the hydrophobic interactions are predominant over electrostatic repulsion for the binding of cationic complexes II–IV with CTAB. In the case of anionic micelles (SDS), electrostatic interactions seem to be important in the binding of II–IV to SDS. Hydrophobic interactions play a dominant role in the binding of II–IV to the neutral micelles, Triton X-100. Based on the steady state and luminescence experiments, the enhancement of luminescence intensity and lifetime in the presence of micelles is due to the protection of the complexes from exposure to water in this environment. PMID:24976590

  14. PLA2-responsive and SPIO-loaded phospholipid micelles

    PubMed Central

    Gao, Qiang; Yan, Lesan; Chiorazzo, Michael; Delikatny, E. James; Tsourkas, Andrew; Cheng, Zhiliang

    2015-01-01

    A PLA2-responsive and superparamagnetic iron oxide (SPIO) nanoparticle-loaded phospholipid micelle was developed. The release of phospholipid-conjugated dye from these micelles was triggered due to phospholipid degradation by phospholipase A2. High relaxivity of the encapsulated SPIO could enable non-invasive magnetic resonance imaging. PMID:26139589

  15. Electron solvation in aqueous reverse micelles: Equilibrium properties

    NASA Astrophysics Data System (ADS)

    Laria, Daniel; Kapral, Raymond

    2002-10-01

    Microscopic aspects of electron solvation in aqueous reverse micelles are investigated using molecular dynamics simulation techniques. Two micelle sizes, with water/surfactant ratios of 3 and 7.5, are examined. The electron is treated quantum mechanically using Feynman path integral methods while the water, surfactant head groups, and counter ions are treated classically. Through computations of the free energy as a function of the radial distance, the electron is found to be preferentially solvated in the interior of the micelle in the "bulk" water pool. For small micelles, the presence of the electron leads to a depletion of water in the central region of the micelle and thus strongly disrupts the water equilibrium structure. Contact and solvent-separated ion pairs between the electron and Na+ counter ions are found to play an important role in the equilibrium structure. For the two micelle sizes investigated, the most stable solvation structures correspond to contact ion pairs. The localization of the electronic charge distribution is found to increase with micelle size, signaling more efficient solvation in larger micelles.

  16. Chirality-mediated polypeptide micelles for regulated drug delivery.

    PubMed

    Ding, Jianxun; Li, Chen; Zhang, Ying; Xu, Weiguo; Wang, Jincheng; Chen, Xuesi

    2015-01-01

    Two kinds of triblock poly(ethylene glycol)-polyleucine (PEG-PLeu) copolymers were synthesized through the ring-opening polymerization of L-Leu N-carboxyanhydride (NCA), or equivalent D-Leu NCA and L-Leu NCA with amino-terminated PEG as a macroinitiator. The amphiphilic copolymers spontaneously self-assembled into spherical micellar aggregations in an aqueous environment. The micelle with a racemic polypeptide core exhibited smaller critical micelle concentration and diameter compared to those with a levorotatory polypeptide core. A model anthracycline antineoplastic agent, i.e., doxorubicin (DOX), was loaded into micelles through nanoprecipitation, and the PEG-P(D,L-Leu) micelle exhibited higher drug-loading efficacy than that with a P(L-Leu) core-this difference was attributed to the flexible and compact P(L-Leu) core. Sustained in vitro DOX release from micelles with both levorotatory and racemic polypeptide cores was observed, and the DOX-loaded PEG-P(D,L-Leu) micelle exhibited a slower release rate. More interestingly, DOX-loaded micelles exhibited chirality-mediated antitumor efficacy in vitro and in vivo, which are all better than that of free DOX. Furthermore, both enhanced tumor inhibition and excellent security in vivo were confirmed by histopathological or in situ cell apoptosis analyses. Therefore, DOX-loaded PEG-PLeu micelles appear to be an interesting nanoscale polymeric formulation for promising malignancy chemotherapy. PMID:25278445

  17. Designing Dendrimers to Offer Micelle-Type Nanocontainers

    ERIC Educational Resources Information Center

    King, Angela G.

    2005-01-01

    The properties of a dendrimer with hydrophobic and hydrophilic substituents on an orthogonal plane is synthesized and studied. The resulting polymer contains one of the substituents in its concave interior and the other at the convex surface and the design promotes micelle-like behavior in polar solvent and inverted micelle arrangement in…

  18. Magainin II modified polydiacetylene micelles for cancer therapy

    NASA Astrophysics Data System (ADS)

    Yang, Danling; Zou, Rongfeng; Zhu, Yu; Liu, Ben; Yao, Defan; Jiang, Juanjuan; Wu, Junchen; Tian, He

    2014-11-01

    Polydiacetylene (PDA) micelles have been widely used to deliver anticancer drugs in the treatment of a variety of tumours and for imaging living cells. In this study, we developed an effective strategy to directly conjugate magainin II (MGN-II) to the surface of PDA micelles using a fluorescent dye. These stable and well-defined PDA micelles had high cytotoxicity in cancer cell lines, and were able to reduce the tumour size in mice. The modified PDA micelles improved the anticancer effects of MGN-II in the A549 cell line only at a concentration of 16.0 μg mL-1 (IC50). In addition, following irradiation with UV light at 254 nm, the PDA micelles gave rise to an energy transfer from the fluorescent dye to the backbone of PDA micelles to enhance the imaging of living cells. Our results demonstrate that modified PDA micelles can not only be used in the treatment of tumors in vitro and in vivo in a simple and directed way, but also offer a new platform for designing functional liposomes to act as anticancer agents.Polydiacetylene (PDA) micelles have been widely used to deliver anticancer drugs in the treatment of a variety of tumours and for imaging living cells. In this study, we developed an effective strategy to directly conjugate magainin II (MGN-II) to the surface of PDA micelles using a fluorescent dye. These stable and well-defined PDA micelles had high cytotoxicity in cancer cell lines, and were able to reduce the tumour size in mice. The modified PDA micelles improved the anticancer effects of MGN-II in the A549 cell line only at a concentration of 16.0 μg mL-1 (IC50). In addition, following irradiation with UV light at 254 nm, the PDA micelles gave rise to an energy transfer from the fluorescent dye to the backbone of PDA micelles to enhance the imaging of living cells. Our results demonstrate that modified PDA micelles can not only be used in the treatment of tumors in vitro and in vivo in a simple and directed way, but also offer a new platform for

  19. Configurations of the amphiphilic molecules in micelles

    SciTech Connect

    Dill, K.A.

    1982-04-29

    Several theoretic models aim to account for the properties of micelles in terms of the configurations of the constituent amphiphilic chain molecules. Recent /sup 13/C NMR measurement of one property of the configuration distribution of the the hydrocarbon chain segments allows critical evaluation of these theories. It is concluded that the interphase and singly-bent chain theories, which fully account for chain continuity and for intermolecular constraints imposed by hydrophobic and steric forces, give a more satisfactory description of micellar molecular organization than models in which chains are ordered and radially aligned, or in which they have the complete disorder characteristic of an amorphous hydrocarbon liquid.

  20. A novel temperature-responsive micelle for enhancing combination therapy

    PubMed Central

    Peng, Cheng-Liang; Chen, Yuan-I; Liu, Hung-Jen; Lee, Pei-Chi; Luo, Tsai-Yueh; Shieh, Ming-Jium

    2016-01-01

    A novel thermosensitive polymer p(N-isopropylacrylamide-co-poly[ethylene glycol] methyl ether acrylate)-block-poly(epsilon-caprolactone), p(NIPAAM-co-PEGMEA)-b-PCL, was synthesized and developed as nanomicelles. The hydrophobic heat shock protein 90 inhibitor 17-allylamino-17-demethoxygeldanamycin and the photosensitizer cyanine dye infrared-780 were loaded into the core of the micelles to achieve both chemotherapy and photothermal therapy simultaneously at the tumor site. The release of the drug could be controlled by varying the temperature due to the thermosensitive nature of the micelles. The micelles were less than 200 nm in size, and the drug encapsulation efficiency was >50%. The critical micelle concentrations were small enough to allow micelle stability upon dilution. Data from cell viability and animal experiments indicate that this combination treatment using photothermal therapy with chemotherapy had synergistic effects while decreasing side effects. PMID:27524894

  1. Effects of depletion interactions on block copolymer micelles

    NASA Astrophysics Data System (ADS)

    Abbas, Sayeed; Lodge, Timothy P.

    2008-03-01

    Block copolymer micelles exhibit two levels of hierarchical self-assembly: the process of micellization itself, and the ordering of these micelles onto a lattice. By a combination of small angle x-ray scattering and neutron scattering, we show that both levels of self-assembly are affected when non-adsorbing homopolymer is added to the solutions. The phenomena are analogous to depletion interactions in colloid/polymer mixtures. We have chosen poly(styrene-b-isoprene) micelles dissolved in diethyl phthalate as the model system. To these solutions polystyrene homopolymer was added. The effects strongly depend on the molecular weight and concentration of the added homopolymer. We find an induced attraction between micelles at moderate micelle concentrations, and a preference for fcc over bcc lattices in more concentrated solutions.

  2. A novel temperature-responsive micelle for enhancing combination therapy.

    PubMed

    Peng, Cheng-Liang; Chen, Yuan-I; Liu, Hung-Jen; Lee, Pei-Chi; Luo, Tsai-Yueh; Shieh, Ming-Jium

    2016-01-01

    A novel thermosensitive polymer p(N-isopropylacrylamide-co-poly[ethylene glycol] methyl ether acrylate)-block-poly(epsilon-caprolactone), p(NIPAAM-co-PEGMEA)-b-PCL, was synthesized and developed as nanomicelles. The hydrophobic heat shock protein 90 inhibitor 17-allylamino-17-demethoxygeldanamycin and the photosensitizer cyanine dye infrared-780 were loaded into the core of the micelles to achieve both chemotherapy and photothermal therapy simultaneously at the tumor site. The release of the drug could be controlled by varying the temperature due to the thermosensitive nature of the micelles. The micelles were less than 200 nm in size, and the drug encapsulation efficiency was >50%. The critical micelle concentrations were small enough to allow micelle stability upon dilution. Data from cell viability and animal experiments indicate that this combination treatment using photothermal therapy with chemotherapy had synergistic effects while decreasing side effects. PMID:27524894

  3. Micelle structure in a deep eutectic solvent: a small-angle scattering study.

    PubMed

    Sanchez-Fernandez, A; Edler, K J; Arnold, T; Heenan, R K; Porcar, L; Terrill, N J; Terry, A E; Jackson, A J

    2016-05-18

    In recent years many studies into green solvents have been undertaken and deep eutectic solvents (DES) have emerged as sustainable and green alternatives to conventional solvents since they may be formed from cheap non-toxic organic precursors. In this study we examine amphiphile behaviour in these novel media to test our understanding of amphiphile self-assembly within environments that have an intermediate polarity between polar and non-polar extremes. We have built on our recently published results to present a more detailed structural characterisation of micelles of sodium dodecylsulfate (SDS) within the eutectic mixture of choline chloride and urea. Here we show that SDS adopts an unusual cylindrical aggregate morphology, unlike that seen in water and other polar solvents. A new morphology transition to shorter aggregates was found with increasing concentration. The self-assembly of SDS was also investigated in the presence of water; which promotes the formation of shorter aggregates. PMID:27157993

  4. NMR study about solubilization of phenyl alkyl alcohol in sodium dodecyl sulfate micelle and in BRIJ 35 micelle

    SciTech Connect

    Miyagishi, S.; Nishida, M.

    1980-11-01

    This work examines the NMR spectra of surfactant solutions solubilizing phenyl alkyl alcohols and the effect of holmium ion on them. More detailed information was obtained about the solubilization site. In addition, it was found that the solubilization in BRIJ 35 micelle was different from that in sodium dodecyl sulfate micelle. 16 references.

  5. Des Moines.

    ERIC Educational Resources Information Center

    Gore, Deborah, Ed.

    1988-01-01

    This document, intended for elementary students, contains articles and activities designed to acquaint young people with the history of Des Moines, Iowa. The articles are short, and new or difficult words are highlighted and defined for young readers. "The Raccoon River Indian Agency" discusses the archeological exploration of the indian…

  6. Micelles Protect and Concentrate Activated Acetic Acid

    NASA Astrophysics Data System (ADS)

    Todd, Zoe; House, C.

    2014-01-01

    As more and more exoplanets are discovered and the habitability of such planets is considered, one can turn to searching for the origin of life on Earth in order to better understand what makes a habitable planet. Activated acetic acid, or methyl thioacetate, has been proposed to be central to the origin of life on Earth, and also as an important energy currency molecule in early cellular evolution. We have investigated the hydrolysis of methyl thioacetate under various conditions. Its uncatalyzed rate of hydrolysis is about three orders of magnitude faster (K = 0.00663 s^-1; 100°C, pH 7.5, concentration = 0.33mM) than published rates for its catalyzed production making it unlikely to accumulate under prebiotic conditions. However, we also observed that methyl thioacetate was protected from hydrolysis when inside its own hydrophobic droplets. We found that methyl thioacetate protection from hydrolysis was also possible in droplets of hexane and in the membranes of nonanoic acid micelles. Thus, the hydrophobic regions of prebiotic micelles and early cell membranes could have offered a refuge for this energetic molecule increasing its lifetime in close proximity to the reactions for which it would be needed. Methyl thioacetate could thus be important for the origin of life on Earth and perhaps for better understanding the potential habitability of other planets.

  7. Therapeutic surfactant-stripped frozen micelles

    NASA Astrophysics Data System (ADS)

    Zhang, Yumiao; Song, Wentao; Geng, Jumin; Chitgupi, Upendra; Unsal, Hande; Federizon, Jasmin; Rzayev, Javid; Sukumaran, Dinesh K.; Alexandridis, Paschalis; Lovell, Jonathan F.

    2016-05-01

    Injectable hydrophobic drugs are typically dissolved in surfactants and non-aqueous solvents which can induce negative side-effects. Alternatives like `top-down' fine milling of excipient-free injectable drug suspensions are not yet clinically viable and `bottom-up' self-assembled delivery systems usually substitute one solubilizing excipient for another, bringing new issues to consider. Here, we show that Pluronic (Poloxamer) block copolymers are amenable to low-temperature processing to strip away all free and loosely bound surfactant, leaving behind concentrated, kinetically frozen drug micelles containing minimal solubilizing excipient. This approach was validated for phylloquinone, cyclosporine, testosterone undecanoate, cabazitaxel and seven other bioactive molecules, achieving sizes between 45 and 160 nm and drug to solubilizer molar ratios 2-3 orders of magnitude higher than current formulations. Hypertonic saline or co-loaded cargo was found to prevent aggregation in some cases. Use of surfactant-stripped micelles avoided potential risks associated with other injectable formulations. Mechanistic insights are elucidated and therapeutic dose responses are demonstrated.

  8. Therapeutic surfactant-stripped frozen micelles

    PubMed Central

    Zhang, Yumiao; Song, Wentao; Geng, Jumin; Chitgupi, Upendra; Unsal, Hande; Federizon, Jasmin; Rzayev, Javid; Sukumaran, Dinesh K.; Alexandridis, Paschalis; Lovell, Jonathan F.

    2016-01-01

    Injectable hydrophobic drugs are typically dissolved in surfactants and non-aqueous solvents which can induce negative side-effects. Alternatives like ‘top-down' fine milling of excipient-free injectable drug suspensions are not yet clinically viable and ‘bottom-up' self-assembled delivery systems usually substitute one solubilizing excipient for another, bringing new issues to consider. Here, we show that Pluronic (Poloxamer) block copolymers are amenable to low-temperature processing to strip away all free and loosely bound surfactant, leaving behind concentrated, kinetically frozen drug micelles containing minimal solubilizing excipient. This approach was validated for phylloquinone, cyclosporine, testosterone undecanoate, cabazitaxel and seven other bioactive molecules, achieving sizes between 45 and 160 nm and drug to solubilizer molar ratios 2–3 orders of magnitude higher than current formulations. Hypertonic saline or co-loaded cargo was found to prevent aggregation in some cases. Use of surfactant-stripped micelles avoided potential risks associated with other injectable formulations. Mechanistic insights are elucidated and therapeutic dose responses are demonstrated. PMID:27193558

  9. Therapeutic surfactant-stripped frozen micelles.

    PubMed

    Zhang, Yumiao; Song, Wentao; Geng, Jumin; Chitgupi, Upendra; Unsal, Hande; Federizon, Jasmin; Rzayev, Javid; Sukumaran, Dinesh K; Alexandridis, Paschalis; Lovell, Jonathan F

    2016-01-01

    Injectable hydrophobic drugs are typically dissolved in surfactants and non-aqueous solvents which can induce negative side-effects. Alternatives like 'top-down' fine milling of excipient-free injectable drug suspensions are not yet clinically viable and 'bottom-up' self-assembled delivery systems usually substitute one solubilizing excipient for another, bringing new issues to consider. Here, we show that Pluronic (Poloxamer) block copolymers are amenable to low-temperature processing to strip away all free and loosely bound surfactant, leaving behind concentrated, kinetically frozen drug micelles containing minimal solubilizing excipient. This approach was validated for phylloquinone, cyclosporine, testosterone undecanoate, cabazitaxel and seven other bioactive molecules, achieving sizes between 45 and 160 nm and drug to solubilizer molar ratios 2-3 orders of magnitude higher than current formulations. Hypertonic saline or co-loaded cargo was found to prevent aggregation in some cases. Use of surfactant-stripped micelles avoided potential risks associated with other injectable formulations. Mechanistic insights are elucidated and therapeutic dose responses are demonstrated. PMID:27193558

  10. Surfactant micelles containing solubilized oil decrease foam film thickness stability.

    PubMed

    Lee, Jongju; Nikolov, Alex; Wasan, Darsh

    2014-02-01

    Many practical applications involving three-phase foams (aqueous foams containing oil) commonly employ surfactants at several times their critical micelle concentration (CMC); in these applications, the oil can exist in two forms: (1) oil drops or macroemulsions and (2) oil solubilized within the micelles. We have recently observed that in the case of aqueous foams stabilized with sodium dodecyl sulfate (SDS) and n-dodecane as an oil, the oil drops did not alter the foam stability but the solubilized oil (swollen micelles) greatly influenced the foam's stability. In order to explain the effect of oil solubilized in the surfactant micelles on foam stability, we studied the stability of a single foam film containing swollen micelles of SDS using reflected light microinterferometry. The film thinning occurs in stepwise manner (stratification). In addition, we obtained data for the film-meniscus contact angle versus film thickness (corresponding to the different number of micellar layers) and used it to calculate the film structural energy isotherm. The results of this study showed that the structural energy stabilization barrier decreased in the presence of swollen micelles in the film, thereby decreasing the foam stability. These results provide a better understanding of the role of oil solubilized by the micelles in affecting foam stability. PMID:24267325

  11. Free-energy analysis of solubilization in micelle

    NASA Astrophysics Data System (ADS)

    Matubayasi, Nobuyuki; Liang, Kuo Kan; Nakahara, Masaru

    2006-04-01

    A statistical-mechanical treatment of the solubilization in micelle is presented in combination with molecular simulation. The micellar solution is viewed as an inhomogeneous and partially finite, mixed solvent system, and the method of energy representation is employed to evaluate the free-energy change for insertion of a solute into the micelle inside with a realistic set of potential functions. Methane, benzene, and ethylbenzene are adopted as model hydrophobic solutes to analyze the solubilization in sodium dodecyl sulfate micelle. It is shown that these solutes are more favorably located within the micelle than in bulk water and that the affinity to the micelle inside is stronger for benzene and ethylbenzene than for methane. The micellar system is then divided into the hydrophobic core, the head-group region in contact with water, and the aqueous region outside the micelle to assess the relative importance of each region in the solubilization. In support of the pseudophase model, the aqueous region is found to be unimportant to determine the extent of solubilization. The contribution from the hydrophobic-core region is shown to be dominant for benzene and ethylbenzene, while an appreciable contribution from the head-group region is observed for methane. The methodology presented is not restricted to the binding of a molecule to micelle, and will be useful in treating the binding to such nanoscale structures as protein and membrane.

  12. Redox-Responsive Micelles with Cores Crosslinked via Click Chemistry.

    PubMed

    Zhang, Xiaojin; Dong, Hui; Fu, Shuangli; Zhong, Zhenlin; Zhuo, Renxi

    2016-06-01

    Redox-responsive micelles with cores crosslinked via click chemistry are developed to improve the stability of polymer micelles. Amphiphilic block copolymer mPEG-b-P(DTC-ADTC) with pendant azido groups on the hydrophobic chains is synthesized by the ring-opening polymerization of 2,2-bis(azidomethyl)trimethylene carbonate (ADTC) and 2,2-dimethyltrimethylene carbonate (DTC) with monomethoxy poly(ethylene glycol) (mPEG) as an initiator. mPEG-b-P(DTC-ADTC) self-assemble to form the micelles in aqueous solution and the cores of the micelles are crosslinked via click chemistry to afford redox-responsive core-crosslinked micelles. Core-crosslinking enhances the stability of the micelles in aqueous solution and improve the drug-loading property. The redox-responsive core-crosslinked micelles can be reduced by the addition of reducing agents such as dithiothreitol (DTT), and thus release the loaded drug quickly in the presence of DTT. PMID:27150437

  13. Ultrasonic transformation of micelle structures: effect of frequency and power.

    PubMed

    Yusof, Nor Saadah Mohd; Ashokkumar, Muthupandian

    2015-05-01

    A comprehensive investigation on the effect of ultrasonic frequency and power on the structural transformation of CTABr/NaSal micelles has been carried out. Sonication of this micelle system at various ultrasonic frequencies and power resulted in the formation and separation of two types of micelles. High viscoelastic threadlike micelles of ∼ 2 nm in diameter and several μm in length and tubular micelles possessing a viscosity slightly above that of water with ∼ 30-50 nm diameter and few hundred nm length. The structural transformation of micelles was induced by the shear forces generated during acoustic cavitation. At a fixed acoustic power of 40 W, the structural transformation was found to decrease from 211 to 647 kHz frequency due to the decreasing shear forces generated, as evidenced by rheological measurements and cryo-TEM images. At 355 kHz, an increase in the structural transformation was observed with an increase in acoustic power. These findings provide a knowledge base that could be useful for the manipulation of viscosity of micelles that may have applications in oil industry. PMID:25465878

  14. Solvent kinetic isotope effects of human placental alkaline phosphatase in reverse micelles.

    PubMed Central

    Huang, T M; Hung, H C; Chang, T C; Chang, G G

    1998-01-01

    the pH of the solution was raised. At pL 11.0, the piT was 1.07 in reverse micelles, which corresponds to the inverse-isotope effect of the reaction in this solvent system. Normal viscosity effects on kcat and kcat/Km were observed in aqueous solution, corresponding to a diffusional controlled physical step as the rate-limiting step. We propose that the rate-limiting step of the hydrolytic reaction changes from phosphate releasing in aqueous solution to a covalent phosphorylation or dephosphorylation step in reverse micelles. PMID:9461520

  15. Stereocomplex micelle from nonlinear enantiomeric copolymers efficiently transports antineoplastic drug

    NASA Astrophysics Data System (ADS)

    Wang, Jixue; Shen, Kexin; Xu, Weiguo; Ding, Jianxun; Wang, Xiaoqing; Liu, Tongjun; Wang, Chunxi; Chen, Xuesi

    2015-05-01

    Nanoscale polymeric micelles have attracted more and more attention as a promising nanocarrier for controlled delivery of antineoplastic drugs. Herein, the doxorubicin (DOX)-loaded poly(D-lactide)-based micelle (PDM/DOX), poly(L-lactide)-based micelle (PLM/DOX), and stereocomplex micelle (SCM/DOX) from the equimolar mixture of the enantiomeric four-armed poly(ethylene glycol)-polylactide (PEG-PLA) copolymers were successfully fabricated. In phosphate-buffered saline (PBS) at pH 7.4, SCM/DOX exhibited the smallest hydrodynamic diameter ( D h) of 90 ± 4.2 nm and the slowest DOX release compared with PDM/DOX and PLM/DOX. Moreover, PDM/DOX, PLM/DOX, and SCM/DOX exhibited almost stable D hs of around 115, 105, and 90 nm at above normal physiological condition, respectively, which endowed them with great potential in controlled drug delivery. The intracellular DOX fluorescence intensity after the incubation with the laden micelles was different degrees weaker than that incubated with free DOX · HCl within 12 h, probably due to the slow DOX release from micelles. As the incubation time reached to 24 h, all the cells incubated with the laden micelles, especially SCM/DOX, demonstrated a stronger intracellular DOX fluorescence intensity than free DOX · HCl-cultured ones. More importantly, all the DOX-loaded micelles, especially SCM/DOX, exhibited potent antineoplastic efficacy in vitro, excellent serum albumin-tolerance stability, and satisfactory hemocompatibility. These encouraging data indicated that the loading micelles from nonlinear enantiomeric copolymers, especially SCM/DOX, might be promising in clinical systemic chemotherapy through intravenous injection.

  16. Stereocomplex micelle from nonlinear enantiomeric copolymers efficiently transports antineoplastic drug.

    PubMed

    Wang, Jixue; Shen, Kexin; Xu, Weiguo; Ding, Jianxun; Wang, Xiaoqing; Liu, Tongjun; Wang, Chunxi; Chen, Xuesi

    2015-12-01

    Nanoscale polymeric micelles have attracted more and more attention as a promising nanocarrier for controlled delivery of antineoplastic drugs. Herein, the doxorubicin (DOX)-loaded poly(D-lactide)-based micelle (PDM/DOX), poly(L-lactide)-based micelle (PLM/DOX), and stereocomplex micelle (SCM/DOX) from the equimolar mixture of the enantiomeric four-armed poly(ethylene glycol)-polylactide (PEG-PLA) copolymers were successfully fabricated. In phosphate-buffered saline (PBS) at pH 7.4, SCM/DOX exhibited the smallest hydrodynamic diameter (D h) of 90 ± 4.2 nm and the slowest DOX release compared with PDM/DOX and PLM/DOX. Moreover, PDM/DOX, PLM/DOX, and SCM/DOX exhibited almost stable D hs of around 115, 105, and 90 nm at above normal physiological condition, respectively, which endowed them with great potential in controlled drug delivery. The intracellular DOX fluorescence intensity after the incubation with the laden micelles was different degrees weaker than that incubated with free DOX · HCl within 12 h, probably due to the slow DOX release from micelles. As the incubation time reached to 24 h, all the cells incubated with the laden micelles, especially SCM/DOX, demonstrated a stronger intracellular DOX fluorescence intensity than free DOX · HCl-cultured ones. More importantly, all the DOX-loaded micelles, especially SCM/DOX, exhibited potent antineoplastic efficacy in vitro, excellent serum albumin-tolerance stability, and satisfactory hemocompatibility. These encouraging data indicated that the loading micelles from nonlinear enantiomeric copolymers, especially SCM/DOX, might be promising in clinical systemic chemotherapy through intravenous injection. PMID:26058504

  17. Redox-Responsive, Core Cross-Linked Polyester Micelles

    PubMed Central

    Zhang, Zhonghai; Yin, Lichen; Tu, Chunlai; Song, Ziyuan; Zhang, Yanfeng; Xu, Yunxiang; Tong, Rong; Zhou, Qin; Ren, Jie; Cheng, Jianjun

    2013-01-01

    Monomethoxy poly(ethylene glycol)-b-poly(Tyr(alkynyl)-OCA), a biodegradable amphiphilic block copolymer, was synthesized by means of ring-opening polymerization of 5-(4-(prop-2-yn-1-yloxy)benzyl)-1,3-dioxolane-2,4-dione (Tyr(alkynyl)-OCA) and used to prepare core cross-linked polyester micelles via click chemistry. Core cross-linking not only improved the structural stability of the micelles but also allowed controlled release of cargo molecules in response to the reducing reagent. This new class of core cross-linked micelles can potentially be used in controlled release and drug delivery applications. PMID:23536920

  18. Water equivalence of micelle gels for x-ray beams

    NASA Astrophysics Data System (ADS)

    Gorjiara, T.; Hill, R.; Kuncic, Z.; Bosi, S.; Baldock, C.

    2013-06-01

    Micelle gel is a radiochromic hydrogel with the potential to be used as a three dimensional (3D) radiation dosimeter. Since an ideal dosimeter should present water equivalent properties, in this study the water equivalence of two formulations of micelle gel has been investigated by calculating electron density, effective atomic number, fractional interaction probabilities, mass attenuation coefficient. The depth doses for kilovoltage and megavoltage x-ray beams have also modelled using Monte Carlo code. Based on the results of this work, micelle gels can be considered as water equivalent dosimeters.

  19. Iron Oxide Nanoparticle-Micelles (ION-Micelles) for Sensitive (Molecular) Magnetic Particle Imaging and Magnetic Resonance Imaging

    PubMed Central

    Starmans, Lucas W. E.; Burdinski, Dirk; Haex, Nicole P. M.; Moonen, Rik P. M.; Strijkers, Gustav J.; Nicolay, Klaas; Grüll, Holger

    2013-01-01

    Background Iron oxide nanoparticles (IONs) are a promising nanoplatform for contrast-enhanced MRI. Recently, magnetic particle imaging (MPI) was introduced as a new imaging modality, which is able to directly visualize magnetic particles and could serve as a more sensitive and quantitative alternative to MRI. However, MPI requires magnetic particles with specific magnetic properties for optimal use. Current commercially available iron oxide formulations perform suboptimal in MPI, which is triggering research into optimized synthesis strategies. Most synthesis procedures aim at size control of iron oxide nanoparticles rather than control over the magnetic properties. In this study, we report on the synthesis, characterization and application of a novel ION platform for sensitive MPI and MRI. Methods and Results IONs were synthesized using a thermal-decomposition method and subsequently phase-transferred by encapsulation into lipidic micelles (ION-Micelles). Next, the material and magnetic properties of the ION-Micelles were analyzed. Most notably, vibrating sample magnetometry measurements showed that the effective magnetic core size of the IONs is 16 nm. In addition, magnetic particle spectrometry (MPS) measurements were performed. MPS is essentially zero-dimensional MPI and therefore allows to probe the potential of iron oxide formulations for MPI. ION-Micelles induced up to 200 times higher signal in MPS measurements than commercially available iron oxide formulations (Endorem, Resovist and Sinerem) and thus likely allow for significantly more sensitive MPI. In addition, the potential of the ION-Micelle platform for molecular MPI and MRI was showcased by MPS and MRI measurements of fibrin-binding peptide functionalized ION-Micelles (FibPep-ION-Micelles) bound to blood clots. Conclusions The presented data underlines the potential of the ION-Micelle nanoplatform for sensitive (molecular) MPI and warrants further investigation of the FibPep-ION-Micelle platform for

  20. Solar energy storage using surfactant micelles

    NASA Astrophysics Data System (ADS)

    Srivastava, R. C.; Marwadi, P. R.; Latha, P. K.; Bhise, S. B.

    1982-09-01

    The results of experiments designed to test the soluble reduced form of thionine dye as a suitable solar energy storage agent inside the hydrophobic core of surfactant micelles are discussed. Aqueous solutions of thionine, methylene blue, cetyl pyridinium bromide, sodium lauryl sulphate, iron salts, and iron were employed as samples of anionic, cationic, and nonionic surfactants. The solutions were exposed to light until the dye disappeared, and then added drop-by-drop to surfactant solutions. The resultant solutions were placed in one cell compartment while an aqueous solution with Fe(2+) and Fe(3+) ions were placed in another, with the compartments being furnished with platinum electrodes connected using a saturated KCl-agar bridge. Data was gathered on the short circuit current, maximum power, and internal resistance encountered. Results indicate that dye-surfactant systems are viable candidates for solar energy storage for later conversion to electrical power.

  1. Multicompartmental Microcapsules from Star Copolymer Micelles

    SciTech Connect

    Choi, Ikjun; Malak, Sidney T.; Xu, Weinan; Heller, William T.; Tsitsilianis, Constantinos; Tsukruk, Vladimir V.

    2013-02-26

    We present the layer-by-layer (LbL) assembly of amphiphilic heteroarm pH-sensitive star-shaped polystyrene-poly(2-pyridine) (PSnP2VPn) block copolymers to fabricate porous and multicompartmental microcapsules. Pyridine-containing star molecules forming a hydrophobic core/hydrophilic corona unimolecular micelle in acidic solution (pH 3) were alternately deposited with oppositely charged linear sulfonated polystyrene (PSS), yielding microcapsules with LbL shells containing hydrophobic micelles. The surface morphology and internal nanopore structure of the hollow microcapsules were comparatively investigated for shells formed from star polymers with a different numbers of arms (9 versus 22) and varied shell thickness (5, 8, and 11 bilayers). The successful integration of star unimers into the LbL shells was demonstrated by probing their buildup, surface segregation behavior, and porosity. The larger arm star copolymer (22 arms) with stretched conformation showed a higher increment in shell thickness due to the effective ionic complexation whereas a compact, uniform grainy morphology was observed regardless of the number of deposition cycles and arm numbers. Small-angle neutron scattering (SANS) revealed that microcapsules with hydrophobic domains showed different fractal properties depending upon the number of bilayers with a surface fractal morphology observed for the thinnest shells and a mass fractal morphology for the completed shells formed with the larger number of bilayers. Moreover, SANS provides support for the presence of relatively large pores (about 25 nm across) for the thinnest shells as suggested from permeability experiments. The formation of robust microcapsules with nanoporous shells composed of a hydrophilic polyelectrolyte with a densely packed hydrophobic core based on star amphiphiles represents an intriguing and novel case of compartmentalized microcapsules with an ability to simultaneously store different hydrophilic, charged, and hydrophobic

  2. Furoxan-Bearing Micelles for Nitric Oxide Delivery.

    PubMed

    Hasegawa, Urara; Wang, Tengjiao; Chen, Jerry J Y; Uyama, Hiroshi; van der Vlies, André J

    2016-07-01

    Furoxans, or 1,2,5-oxadiazole-N-oxides, are a class of nitric oxide (NO)-donating compounds that release NO in response to thiol-containing molecules. In this study, polymeric micelles bearing furoxan moieties are prepared from an amphiphilic block copolymer consisting of a hydrophobic furoxan-bearing block and a hydrophilic poly(N-acryloylmorpholine) block. The block copolymer is prepared using a combination of the reversible addition-fragmentation chain transfer polymerization and the copper-catalyzed Huisgen cycloaddition techniques. The block copolymers form spherical micelles with a diameter of 50 nm by self-assembly in water. The micelles release NO in response to cysteine and show improved stability against hydrolytic decomposition. Furthermore, the micelles show a synergistic anti-proliferative effect with ibuprofen in human colon cancer cells. PMID:26953715

  3. Progress of drug-loaded polymeric micelles into clinical studies.

    PubMed

    Cabral, Horacio; Kataoka, Kazunori

    2014-09-28

    Targeting tumors with long-circulating nano-scaled carriers is a promising strategy for systemic cancer treatment. Compared with free small therapeutic agents, nanocarriers can selectively accumulate in solid tumors through the enhanced permeability and retention (EPR) effect, which is characterized by leaky blood vessels and impaired lymphatic drainage in tumor tissues, and achieve superior therapeutic efficacy, while reducing side effects. In this way, drug-loaded polymeric micelles, i.e. self-assemblies of amphiphilic block copolymers consisting of a hydrophobic core as a drug reservoir and a poly(ethylene glycol) (PEG) hydrophilic shell, have demonstrated outstanding features as tumor-targeted nanocarriers with high translational potential, and several micelle formulations are currently under clinical evaluation. This review summarizes recent efforts in the development of these polymeric micelles and their performance in human studies, as well as our recent progress in polymeric micelles for the delivery of nucleic acids and imaging. PMID:24993430

  4. Rheology and phase behavior of dense casein micelle dispersions

    NASA Astrophysics Data System (ADS)

    Bouchoux, A.; Debbou, B.; Gésan-Guiziou, G.; Famelart, M.-H.; Doublier, J.-L.; Cabane, B.

    2009-10-01

    Casein micelle dispersions have been concentrated through osmotic stress and examined through rheological experiments. In conditions where the casein micelles are separated from each other, i.e., below random-close packing, the dispersions have exactly the flow and dynamic properties of the polydisperse hard-sphere fluid, demonstrating that the micelles interact only through excluded volume effects in this regime. These interactions cause the viscosity and the elastic modulus to increase by three orders of magnitude approaching the concentration of random-close packing estimated at Cmax≈178 g/l. Above Cmax, the dispersions progressively turn into "gels" (i.e., soft solids) as C increases, with elastic moduli G' that are nearly frequency independent. In this second regime, the micelles deform and/or deswell as C increases, and the resistance to deformation results from the formation of bonds between micelles combined with the intrinsic mechanical resistance of the micelles. The variation in G' with C is then very similar to that observed with concentrated emulsions where the resistance to deformation originates from a set of membranes that separate the droplets. As in the case of emulsions, the G' values at high frequency are also nearly identical to the osmotic pressures required to compress the casein dispersions. The rheology of sodium caseinate dispersions in which the caseins are not structured into micelles is also reported. Such dispersions have the behavior of associative polymer solutions at all the concentrations investigated, further confirming the importance of structure in determining the rheological properties of casein micelle systems.

  5. New self-assembled nanocrystal micelles for biolabels and biosensors.

    SciTech Connect

    Tallant, David Robert; Wilson, Michael C. (University of New Mexico, Albuquerque, NM); Leve, Erik W. (University of New Mexico, Albuquerque, NM); Fan, Hongyou; Brinker, C. Jeffrey; Gabaldon, John (University of New Mexico, Albuquerque, NM); Scullin, Chessa (University of New Mexico, Albuquerque, NM)

    2005-12-01

    The ability of semiconductor nanocrystals (NCs) to display multiple (size-specific) colors simultaneously during a single, long term excitation holds great promise for their use in fluorescent bio-imaging. The main challenges of using nanocrystals as biolabels are achieving biocompatibility, low non-specific adsorption, and no aggregation. In addition, functional groups that can be used to further couple and conjugate with biospecies (proteins, DNAs, antibodies, etc.) are required. In this project, we invented a new route to the synthesis of water-soluble and biocompatible NCs. Our approach is to encapsulate as-synthesized, monosized, hydrophobic NCs within the hydrophobic cores of micelles composed of a mixture of surfactants and phospholipids containing head groups functionalized with polyethylene glycol (-PEG), -COOH, and NH{sub 2} groups. PEG provided biocompatibility and the other groups were used for further biofunctionalization. The resulting water-soluble metal and semiconductor NC-micelles preserve the optical properties of the original hydrophobic NCs. Semiconductor NCs emit the same color; they exhibit equal photoluminescence (PL) intensity under long-time laser irradiation (one week) ; and they exhibit the same PL lifetime (30-ns). The results from transmission electron microscopy and confocal fluorescent imaging indicate that water-soluble semiconductor NC-micelles are biocompatible and exhibit no aggregation in cells. We have extended the surfactant/lipid encapsulation techniques to synthesize water-soluble magnetic NC-micelles. Transmission electron microscopy results suggest that water-soluble magnetic NC-micelles exhibit no aggregation. The resulting NC-micelles preserve the magnetic properties of the original hydrophobic magnetic NCs. Viability studies conducted using yeast cells suggest that the magnetic nanocrystal-micelles are biocompatible. We have demonstrated, for the first time, that using external oscillating magnetic fields to manipulate

  6. Preparation and characterization of magnetic thermosensitive fluorouracil micelles.

    PubMed

    Zhang, Min; Jin, Xueqin; Gou, Guojing

    2016-06-01

    In this study, we synthesized P(NIPAM-co-DMAM)-b-PLA polymers with free radical polymerization and ring-opening addition polymerization, and immediately assembled 'dextran magnetic layered double hydroxide fluorouracil' (DMF) magnetic particles into the core of the amphiphilic polymer micelles with synchronous hydration and dialysis, to generate a magnetic thermosensitive fluorouracil drug delivery system. The basic properties of the micelle particles, such as the core-shell-type structure, size, and zeta potential, were studied with (1)H-NMR, FTIR, TEM, TGA, laser nanoparticle size analysis, and other characterization techniques. The thermosensitivity of the micelles was investigated by measuring parameters such as the lower critical solution temperature (LCST) and the relationship between the particle size variation and temperature. The drug release curves for the micelles at different temperatures were constructed with a dialysis method. The LCST of the triblock polymers was 42 °C. The particle sizes of the blank micelles and DMF-loaded micelles were 493.6 ± 1.8 nm and 464.9 ± 4.1 nm, respectively, at 25 °C. When the temperature was higher than LSCT, a contraction phase change in the micelle structure occurred, a significant characteristic of the core-shell-type structure, and reversible phase transition phenomena. The release behavior of the drug-loaded micelles showed obvious variations with temperature. Therefore, the magnetic thermosensitive fluorouracil drug delivery system has a good magnetic response and excellent temperature controlled release characteristics, so it can be used as a drug delivery system in magnetically and thermally targeted chemotherapy for tumors. PMID:26948946

  7. Nucleation of polyaniline nano-/macrotubes from anilinium composed micelles.

    PubMed

    Wang, Ruijuan; Wang, Chensen; Liu, Kong; Bei, Fengli; Lu, Lude; Han, Qiaofeng; Wu, Xiaodong

    2014-03-01

    A mechanistic study on the nucleation of polyaniline nanotubes (PANI-NT) through template-free method is explored by in situ solution-state (1)H NMR experiments via a careful analysis of the spectral evolution of the major species in the course of the reaction. Before polymerization, aniline and salicylic acid have assembled into loosely packed micelles due to electrostatic interactions and the proton exchange reaction between aniline and anilinium. A three-stage polymerization with a formation, accumulation of aniline dimers, as well as a generation of phenazine-like oligomers is observed, which can be attributed to the monomer transformation from neutral aniline molecules to anilinium cations and the significantly lowered pH in the reaction. Strong π-π stacking interactions from the phenazine-like oligomers facilitate the intermolecular aggregation which initiates the formation of PANI-NT. At first, such aggregates, locating at the outermost layer of anilinium composed micelles, shield in situ formed protons from releasing into the aqueous bulk but into the micelle instead. Due to the continuously increased charge in the micelle, a sphere-to-rod structural transition occurs which leads the oligomer aggregates to be sheathed at the exterior of the rod. Further consumption of anilinium in the micelle leaves the internal cavity while the fusion between the micelles elongates the length of the tubes. Our work demonstrates that (i) loosely packed anilinium composed micelles, highly mobile monomers within the micelle, and efficient blockage of the proton-releasing to the aqueous bulk are three key factors for the generation of tubular structures; and (ii) dynamic NMR line shape analysis provides a new perspective for resolving the formation profile of nanostructured polymers. PMID:24568544

  8. Preparation and optimization of media using Pluronic® micelles for solubilization of sirolimus and release from the drug eluting stents.

    PubMed

    Raval, Ami; Parmar, Arpan; Raval, Ankur; Bahadur, Pratap

    2012-05-01

    Understanding the in-vitro release profile of drugs from drug eluting devices such as cardiac stent is crucial in designing and optimizing the drug embedded matrices. Sirolimus (SRL), a widely used anti-inflammatory/antiproliferative/immunosuppressive hydrophobic drug undergoes irreversible changes such as hydrolysis leading to erroneous assessment of the release profile. The release profile mainly depends on the drug release medium. The present study aims to develop and optimize the aqueous medium for the solubilization of SRL and in-vitro release method from drug eluting stent (DES). In the first stage of study several release media containing different buffer compositions, pH, and a series of micelle forming PEO-PPO-PEO block copolymers (known as Pluronic(®)) were examined for solubility and stability of SRL by reversed phase high performance liquid chromatography (RP-HPLC). SRL showed good solubility and stability at pH 4.0 (both in acetate buffer as well in phosphate buffer) in the presence of block copolymers. Solubilization of SRL was remarkably higher in P103 and P123 micelles than more hydrophilic F68 and F127. To get further insight into the underlying drug dissolution mechanisms, critical micellization temperature (CMT), and hydrodynamic size of micelles with and without drug incorporation were determined by UV-visible spectroscopy and dynamic light scattering (DLS) respectively. The micelle-water partition coefficient (P) and location of solubilized drug were also evaluated from a thermodynamics viewpoint. Finally, the optimized media were examined for the release of SRL from drug eluting stent; the data suggest that a release medium consisting of 0.1% P123 in phosphate buffer pH 4.0 is most suitable for evaluation of in-vitro release of SRL from DES. PMID:22265756

  9. Simvastatin Prodrug Micelles Target Fracture and Improve Healing

    PubMed Central

    Dusad, Anand; Yuan, Hongjiang; Ren, Ke; Li, Fei; Fehringer, Edward V.; Purdue, P. Edward; Goldring, Steven R.; Daluiski, Aaron; Wang, Dong

    2014-01-01

    Simvastatin (SIM), a widely used anti-lipidaemic drug, has been identified as a bone anabolic agent. Its poor water solubility and the lack of distribution to the skeleton, however, have limited its application in the treatment of bone metabolic diseases. In this study, an amphiphilic macromolecular prodrug of SIM was designed and synthesized to overcome these limitations. The polyethylene glycol (PEG)-based prodrug can spontaneously self-assemble to form micelles. The use of SIM trimer as the prodrug’s hydrophobic segment allows easy encapsulation of additional free SIM. The in vitro studies showed that SIM/SIM-mPEG micelles were internalized by MC3T3 cells via lysosomal trafficking and consistently induced expression of both BMP2 and DKK1 mRNA, suggesting that the prodrug micelle retains the biological functions of SIM. After systemic administration, optical imaging suggests that the micelles would passively target to bone fracture sites associated with hematoma and inflammation. Furthermore, flow cytometry study revealed that SIM/SIM-mPEG micelles had preferred cellular uptake by inflammatory and resident cells within the fracture callus tissue. The treatment study using a mouse osteotomy model validated the micelles’ therapeutic efficacy in promoting bone fracture healing as demonstrated by micro-CT and histological analyses. Collectively, these data suggest that the macromolecular prodrug-based micelle formulation of SIM may have great potential for clinical management of impaired fracture healing. PMID:25542644

  10. Superlattice Formation in Binary Mixtures of Block Copolymer Micelles

    SciTech Connect

    Abbas, Sayeed; Lodge, Timothy P.

    2008-08-26

    Two distinct diblock copolymers, poly(styrene-b-isoprene) (SI) and poly(styrene-b-dimethylsiloxane) (SD), were codissolved at various concentrations in the polystyrene selective solvent diethyl phthalate. Two SI diblocks, with block molar masses of 12000-33000 and 30000-33000, and two SD diblocks, with block molar masses of 19000-6000 and 16000-9000, were employed. The size ratio of the smaller SD micelles (S) to the larger SI micelles (L) varied from approximately 0.5 to 0.6, based on hydrodynamic radii determined by dynamic light scattering on dilute solutions containing only one polymer component. Due to incompatibility between the polyisoprene and polydimethylsiloxane blocks, a binary mixture of distinct SI and SD micelles was formed in each mixed solution, as confirmed by cryogenic transmission electron microscopy. When the total concentration of polymer was increased to 20--30%, the micelles adopted a superlattice structure. Small angle X-ray scattering revealed the lattice to be the full LS{sub 13} superlattice (space group Fm{sub 3}c) in all cases, with unit cell dimensions in excess of 145 nm. A coexistent face-centered cubic phase composed of SD micelles was also observed when the number ratio of S to L micelles was large.

  11. Polymer Micelles with Crystalline Cores for Thermally Triggered Release

    PubMed Central

    Glover, Amanda L.; Nikles, Sarah M.; Nikles, Jacqueline A.; Brazel, Christopher S.; Nikles, David E.

    2012-01-01

    Interest in the use of poly(ethylene glycol)-b-polycaprolactone diblock copolymers in a targeted, magnetically triggered drug delivery system has led to this study of the phase behavior of the polycaprolactone core. Four different diblock copolymers were prepared by the ring opening polymerization of caprolactone from the alcohol terminus of poly(ethylene glycol) monomethylether, Mn ~ 2,000. The critical micelle concentration depended on the degree of polymerization for the polycaprolactone block and was in the range of 2.9 to 41 mg/L. Differential scanning calorimetry curves for polymer solutions with a concentration above the critical micelle concentration showed a melting endotherm in the range of 40 to 45°C, indicating the polycaprolactone core was semicrystalline. Pyrene was entrapped in the micelle core without interfering with the ability of the polycaprolactone to crystallize. When the polymer solution was heated above the melting point of the micelle core, the pyrene was free to leave the core. Temperature dependent measurements of the critical micelle concentration and temperature dependent dynamic light scattering showed the micelles remain intact at temperatures above the melting point of the polycaprolactone core. PMID:22726124

  12. Activation of lignin peroxidase in organic media by reversed micelles.

    PubMed

    Kimura, Masayuki; Michizoe, Junji; Oakazaki, Shin-Ya; Furusaki, Shintaro; Goto, Masahiro; Tanaka, Hiroo; Wariishi, Hiroyuki

    2004-11-20

    Activation of lignin peroxidase (LIP) in an organic solvent by reversed micelles was investigated. Bis(2-ethylhexyl)sulfosuccinate sodium salt (AOT) was used as a surfactant to form a reversed micelle. Lyophilized LIP from an optimized aqueous solution exhibited no enzymatic activity in any organic solvents examined in this study; however, LIP was catalytically active by being entrapped in the AOT reversed micellar solution. LIP activity in the reversed micelle was enhanced by optimizing either the preparation or the operation conditions, such as water content and pH in water pools of the reversed micelle and the reaction temperature. Stable activity was obtained in isooctane because of the stability of the reversed micelle. The optimal pH was 5 in the reversed micellar system, which shifted from pH 3 in the aqueous solution. The degradation reaction of several environmental pollutants was attempted using LIP hosted in the AOT reversed micelle. Degradation achieved after a 1-h reaction reached 81%, 50%, and 22% for p-nonylphenol, bisphenol A, and 2,4-dichlorophenol, respectively. This is the first report on the utilization of LIP in organic media. PMID:15459910

  13. Structural modifications in polymeric micelles to impart multifunctionality for improved drug delivery.

    PubMed

    Mittal, Anupama; Chitkara, Deepak

    2016-01-01

    Polymeric micelles are macromolecular nanoconstructs which are formed by self-assembly of synthetic amphiphilic block copolymers. These copolymers could be chemically modified to expand their functionality and hence obtain a multifunctional micelle which could serve several functions simultaneously, for example, long circulation time along with active targeting, smart polymeric micelles providing on-demand drug release for example, pH responsive micelles, redox- and light-sensitive micelles, charge-conversion micelles and core/shell cross-linked micelles. Additionally, micelles could be tailored to carry a contrast agent or siRNA/miRNA along with the drug for greater clinical benefit. The focus of the current commentary would be to highlight such chemical modifications which impart multifunctionality to a single carrier and discuss challenges involved in clinical translation of these multifunctional micelles. PMID:26769002

  14. Sizing of reverse micelles in microemulsions using NMR measurements of diffusion.

    PubMed

    Law, Susan J; Britton, Melanie M

    2012-08-14

    This paper reports the size of reverse micelles (RMs) in AOT/octane/H(2)O and CTAB/hexanol/H(2)O microemulsions using magnetic resonance (MR) pulsed field gradient (PFG) measurements of diffusion. Diffusion data were measured using the pulsed gradient stimulated echo (PGSTE) experiment for surfactant molecules residing in the RM interface. Inverse Laplace transformation of these data generated diffusion coefficients for the RMs, which were converted into hydrodynamic radii using the Stokes-Einstein relation. This technique is complementary to those previously used to size RMs, such as dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS), but also offers several advantages, which are discussed. RM sizes, determined using the PGSTE method, in the AOT (sodium bis(2-ethylhexyl) sulfosuccinate) and CTAB (cetyltrimethylammonium bromide) microemulsions were compared with previous DLS and SAXS data, showing good agreement. Methods for determining number distributions from the PGSTE data, through the use of scaling factors, were investigated. PMID:22794150

  15. Dielectric Analysis for the Spherical and Rodlike Micelle Aggregates Formed from a Gemini Surfactant: Driving Forces of Micellization and Stability of Micelles.

    PubMed

    Wang, Shanshan; Zhao, Kongshuang

    2016-08-01

    The self-aggregation behavior of Gemini surfactant 12-2-12 (ethanediyl-1,2-bis(dimethyldodecylammonium bromide)) in water was investigated by dielectric relaxation spectroscopy (DRS) over a frequency range from 40 Hz to 110 MHz. Dielectric determination shows that well-defined spherical micelles formed when the concentration of the surfactant was above a critical micelle concentration CMC1 of 3 mM and rodlike micelles formed above CMC2, 16 mM. The formation mechanism of the spherical micelles and their transition mechanism to clubbed micelles were proposed by calculating the degree of counterion binding of the micelles. The interactions between the head groups and the hydrophobic chains of the surfactant led to the formation of the micelles, whereas the transition is mainly attributed to the interaction among the hydrophobic chains. By analyzing the dielectric relaxation observed at about 10(7) Hz based on the interface polarization theory, the permittivity and conductivity of micelle aggregates (spherical and clubbed) and volume fraction of micelles were calculated theoretically as well as the electrical properties of the solution medium. Furthermore, we also calculated the electrokinetic parameters of the micelle particle surface, surface conductivity, surface charge density, and zeta potential, using the relaxation parameters and phase parameters. On the basis of these results, the balance of forces controlling morphological transitions, interfacial electrokinetic properties, and the stability of the micelle aggregates was discussed. PMID:27396495

  16. Acetal-linked polymeric prodrug micelles for enhanced curcumin delivery.

    PubMed

    Li, Man; Gao, Min; Fu, Yunlan; Chen, Chao; Meng, Xuan; Fan, Aiping; Kong, Deling; Wang, Zheng; Zhao, Yanjun

    2016-04-01

    On-demand curcumin delivery via stimuli-responsive micellar nanocarriers holds promise for addressing its solubility and stability problem. Polymer-curcumin prodrug conjugate micelle is one of such nanosystems. The diversity of linker and conjugation chemistry enabled the generation and optimization of different curcumin micelles with tunable stimuli-responsiveness and delivery efficiency. The aim of the current work was to generate and assess acetal-linked polymeric micelles to enrich the pH-responsive curcumin delivery platforms. Curcumin was slightly modified prior to conjugating to amphiphilic methoxy poly(ethylene glycol)-poly(lactic acid) (mPEG-PLA) copolymer via an acetal bond, whereas an ester bond-linked conjugate was used as the control. The acetal-containing micelles showed a hydrodynamic diameter of 91.1 ± 2.9(nm) and the accompanying core size of 63.5 ± 7.1 (nm) with a zeta potential of -10.9 ± 0.7(mV). Both control and pH-labile micelles displayed similar critical micelle concentration at 1.6 μM. The acetal-containing nanocarriers exhibited a pH-dependent drug release behavior, which was faster at lower pH values. The cytotoxicity study in HepG2 cells revealed a significantly lower IC50 at 51.7 ± 9.0(μM) for acetal-linked micelles in contrast to the control at 103.0 ± 17.8(μM), but the polymer residue showed no cytotoxicity upon drug release. The acetal-linked micellar nanocarrier could be a useful addition to the spectrum of currently available stimuli-responsive curcumin nano-formulations. PMID:26731193

  17. The Use of Dodecylphosphocholine Micelles in Solution NMR

    NASA Astrophysics Data System (ADS)

    Kallick, D. A.; Tessmer, M. R.; Watts, C. R.; Li, C. Y.

    Dodecylphosphocholine (DPC) micelles are useful as a model membrane system for solution NMR. Several new observations on dodecylphosphocholine micelles and their interactions with opioid peptides are described. The optimal lipid concentration has been investigated for small peptide NMR studies in DPC micelles for two opioid peptides, a 5-mer and a 17-mer. In contrast to reports in the literature, identical 2D spectra have been observed at low and high lipid concentrations. The chemical shift of resolved peptide proton resonances has been followed as a function of added lipid and indicates that there are changes in the chemical shifts above the critical micelle concentration and up to a ratio of 7:1 (lipid:peptide) for the 17-mer, and 9.6:1 for the 5-mer. These results suggest that conformational changes occur in the peptide significantly above the critical micelle concentration, up to a lipid:peptide ratio which is dependent upon the peptide, here ranging from 7:1 to 9.6:1. To address the stoichiometry more directly, the diffusion coefficients of the lipid alone and the lipid with peptide have been measured using pulsed-field gradient spin-echo NMR experiments. These data have been used to calculate the hydrodynamic radius and the aggregation number of the micelle with and without peptide and show that the aggregation number of the peptide-lipid complex increases at high lipid concentrations without a concomitant change in the peptide conformation. Last, several protonated impurities have been observed in the commercial preparation of DPC which resonate in the amide proton region of the NMR spectrum. These results are significant for researchers using DPC micelles and illustrate that both care in sample preparation and the stoichiometry are important issues with the use of DPC as a model membrane.

  18. Micelles as Soil and Water Decontamination Agents.

    PubMed

    Shah, Afzal; Shahzad, Suniya; Munir, Azeema; Nadagouda, Mallikarjuna N; Khan, Gul Shahzada; Shams, Dilawar Farhan; Dionysiou, Dionysios D; Rana, Usman Ali

    2016-05-25

    Contaminated soil and water pose a serious threat to human health and ecosystem. For the treatment of industrial effluents or minimizing their detrimental effects, preventive and remedial approaches must be adopted prior to the occurrence of any severe environmental, health, or safety hazard. Conventional treatment methods of wastewater are insufficient, complicated, and expensive. Therefore, a method that could use environmentally friendly surfactants for the simultaneous removal of both organic and inorganic contaminants from wastewater is deemed a smart approach. Surfactants containing potential donor ligands can coordinate with metal ions, and thus such compounds can be used for the removal of toxic metals and organometallic compounds from aqueous systems. Surfactants form host-guest complexes with the hydrophobic contaminants of water and soil by a mechanism involving the encapsulation of hydrophobes into the self-assembled aggregates (micelles) of surfactants. However, because undefined amounts of surfactants may be released into the aqueous systems, attention must be paid to their own environmental risks as well. Moreover, surfactant remediation methods must be carefully analyzed in the laboratory before field implementation. The use of biosurfactants is the best choice for the removal of water toxins as such surfactants are associated with the characteristics of biodegradability, versatility, recovery, and reuse. This Review is focused on the currently employed surfactant-based soil and wastewater treatment technologies owing to their critical role in the implementation of certain solutions for controlling pollution level, which is necessary to protect human health and ensure the quality standard of the aquatic environment. PMID:27136750

  19. Basic investigations on LCV micelle gel

    NASA Astrophysics Data System (ADS)

    Ebenezer, S. B.; Rafic, M. K.; Ravindran, P. B.

    2013-06-01

    The aim of this study was to investigate the feasibility of using Leuco Crystal Violet (LCV) based micelle gel dosimeter as a quality assurance tool in radiotherapy applications. Basic properties such as absorption coefficient and diffusion of LCV gel phantom over time were evaluated. The gel formulation consisted of 25 mM Trichloroacetic acid, 1mM LCV, 4 mM Triton X-100, 4% gelatin by mass and distilled water. The advantages of using this gel are its tissue equivalence, easy and less preparation time, lower diffusion rate and it can be read with an optical scanner. We were able to reproduce some of the results of Babic et al. The peak absorption was found to be at 600 nm and hence a matrix of yellow LEDs was used as light source. The profiles obtained from projection images confirmed the diffusion of LCV gel after 6 hours of irradiation. Hence the LCV gel phantom should be read before 6 hours post irradiation to get accurate dose information as suggested previously.

  20. Nickel-aluminum layered double hydroxides prepared via inverse micelles formation

    SciTech Connect

    Perez-Bernal, Maria E.; Ruano-Casero, Ricardo J.; Benito, Fatima; Rives, Vicente

    2009-06-15

    Nickel-aluminum layered double hydroxides have been prepared by conventional coprecipitation and by coprecipitation in the presence of a surfactant. The solids have been characterised by several physicochemical techniques. Calcination leads to formation of homogeneously dispersed mixed oxides, which have been characterised as well. The colour properties (lightness and chromaticity coordinates) of both series of solids (layered precursors and calcined ones) have been measured. It has been found that both the preparation method and the calcination treatment have an important effect on the luminosity (whiteness/darkness) of the solids, although the effect on the precise chromaticity coordinates (green/red and blue/yellow) is less marked. - Graphical abstract: Nickel-aluminum layered double hydroxides have been prepared by conventional coprecipitation and by coprecipitation in the presence of a surfactant. It has been found that both the preparation method and the calcination treatment have an important effect on the luminosity (whiteness/darkness) of the solids, although the effect on the precise chromaticity coordinates (green/red and blue/yellow) is less marked.

  1. A "voice inversion effect?".

    PubMed

    Bédard, Catherine; Belin, Pascal

    2004-07-01

    Voice is the carrier of speech but is also an "auditory face" rich in information on the speaker's identity and affective state. Three experiments explored the possibility of a "voice inversion effect," by analogy to the classical "face inversion effect," which could support the hypothesis of a voice-specific module. Experiment 1 consisted of a gender identification task on two syllables pronounced by 90 speakers (boys, girls, men, and women). Experiment 2 consisted of a speaker discrimination task on pairs of syllables (8 men and 8 women). Experiment 3 consisted of an instrument discrimination task on pairs of melodies (8 string and 8 wind instruments). In all three experiments, stimuli were presented in 4 conditions: (1) no inversion; (2) temporal inversion (e.g., backwards speech); (3) frequency inversion centered around 4000 Hz; and (4) around 2500 Hz. Results indicated a significant decrease in performance caused by sound inversion, with a much stronger effect for frequency than for temporal inversion. Interestingly, although frequency inversion markedly affected timbre for both voices and instruments, subjects' performance was still above chance. However, performance at instrument discrimination was much higher than for voices, preventing comparison of inversion effects for voices vs. non-vocal stimuli. Additional experiments will be necessary to conclude on the existence of a possible "voice inversion effect." PMID:15177788

  2. Synthesis and Self-Aggregation of Poly(2-ethyl-2-oxazoline)-Based Photocleavable Block Copolymer: Micelle, Compound Micelle, Reverse Micelle, and Dye Encapsulation/Release.

    PubMed

    Jana, Somdeb; Saha, Anupam; Paira, Tapas K; Mandal, Tarun K

    2016-02-01

    We report on the synthesis of photocleavable poly(2-ethyl-2-oxazoline)-block-poly(2-nitrobenzyl acrylate) (PEtOx-b-PNBA) block copolymers (BCPs) with varying compositions via combination of microwave-assisted cationic ring-opening polymerization (CROP) and atom transfer radical polymerization (ATRP) using α-bromoisobutyryl bromide as an orthogonal initiator. The amphiphilic nature of this BCP causes them to self-assemble into primary micelles in THF/H2O, which further undergo secondary aggregation into nanostructured compound micelles as established through DLS, FESEM, and TEM. Upon UV irradiation (λ = 350 nm), the photocleavage of the PNBA block of the PEtOx-b-PNBA BCP takes place, and that leads to the formation of the doubly hydrophilic poly(2-ethyl-2-oxazoline)-b-poly(acrylic acid) (PEtOx-b-PAA) BCP causing the rupture of compound micelles as confirmed by spectroscopic and microscopic techniques. Encapsulation of a model hydrophobic guest molecule, nile red (NR), into the photocleavable BCP micellar core in aqueous solution and its UV-induced release is also investigated by fluorescence emission measurements. PEtOx-b-PNBA BCP amphiphiles are also shown to self-assemble into spherical nanostructures (∼90 nm) in dichloromethane as established by DLS and TEM analysis. These are referred to as reverse micelles and are able to encapsulate anionic hydrophilic dye, Eosin B, and facilitate its solubilization in organic media. PMID:26735171

  3. Structural investigation of diglycerol polyisostearate reverse micelles in organic solvents.

    PubMed

    Shrestha, Lok Kumar; Shrestha, Rekha Goswami; Oyama, Keiichi; Matsuzawa, Makoto; Aramaki, Kenji

    2009-09-24

    The structure of glycerol-based reverse micelles in the surfactant/oil binary system without external water addition has been investigated using a small-angle X-ray scattering technique, and different tunable parameters for the structure control of reverse micelles are determined. The scattering data were evaluated by the generalized indirect Fourier transformation (GIFT) method and complemented by model fitting. It was found that diglycerol polyisostearates (abbreviated as (iso-C18)nG2, n=2-4, where n represents the number of isosterate chains per surfactant molecule) form reverse micelles in a variety of organic solvents such as cyclohexane, n-decane, and n-hexadecane without the addition of water from outside, and their structure (shape and size) depends on solvent properties (alkyl chain length), tail architecture of the surfactant, temperature, and added water. Small globular types of micelles were observed in the (iso-C18)2G2/cyclohexane system at 25 degrees C. The micellar size and the aggregation number were increased with increasing the alkyl chain length of the oils resulting in elongated ellipsoidal prolate or rodlike type micelles in the (iso-C18)2G2/hexadecane system. This structural evolution is caused by the different penetration tendency depending on the chain length of oils to the lipophilic chain of the surfactant. At fixed oil, composition, and temperature, the tail architecture of the surfactant played a crucial role in the micellar structure. The micellar size and, hence, the aggregation number decreased monotonically with increasing number of isostearate chain per surfactant molecule due to the voluminous lipophilic part of the surfactant. Composition could not modulate the structure of micelles but led to strong repulsive interactions among the micelles due to reduced osmotic compressibility of the system at higher concentrations. Increasing temperature decreased the micellar size, while the cross-section structure remains essentially the

  4. Novel micelle formulations to increase cutaneous bioavailability of azole antifungals.

    PubMed

    Bachhav, Y G; Mondon, K; Kalia, Y N; Gurny, R; Möller, M

    2011-07-30

    Efficient topical drug administration for the treatment of superficial fungal infections would deliver the therapeutic agent to the target compartment and reduce the risk of systemic side effects. However, the physicochemical properties of the commonly used azole antifungals make their formulation a considerable challenge. The objective of the present investigation was to develop aqueous micelle solutions of clotrimazole (CLZ), econazole nitrate (ECZ) and fluconazole (FLZ) using novel amphiphilic methoxy-poly(ethylene glycol)-hexyl substituted polylactide (MPEG-hexPLA) block copolymers. The CLZ, ECZ and FLZ formulations were characterized with respect to drug loading and micelle size. The optimal drug formulation was selected for skin transport studies that were performed using full thickness porcine and human skin. Penetration pathways and micellar distribution in the skin were visualized using fluorescein loaded micelles and confocal laser scanning microscopy. The hydrodynamic diameters of the azole loaded micelles were between 70 and 165nm and the corresponding number weighted diameters (d(n)) were 30 to 40nm. Somewhat surprisingly, the lowest loading efficiency (<20%) was observed for CLZ (the most hydrophobic of the three azoles tested); in contrast, under the same conditions, ECZ was incorporated with an efficiency of 98.3% in MPEG-dihexPLA micelles. Based on the characterization data and preliminary transport experiments, ECZ loaded MPEG-dihexPLA micelles (concentration 1.3mg/mL; d(n)<40nm) were selected for further study. ECZ delivery was compared to that from Pevaryl® cream (1% w/w ECZ), a marketed liposomal formulation for topical application. ECZ deposition in porcine skin following 6h application using the MPEG-dihexPLA micelles was >13-fold higher than that from Pevaryl® cream (22.8±3.8 and 1.7±0.6μg/cm(2), respectively). A significant enhancement was also observed with human skin; the amounts of ECZ deposited were 11.3±1.6 and 1.5±0.4μg/cm(2

  5. Precise hierarchical self-assembly of multicompartment micelles

    PubMed Central

    Gröschel, André H.; Schacher, Felix H.; Schmalz, Holger; Borisov, Oleg V.; Zhulina, Ekaterina B.; Walther, Andreas; Müller, Axel H.E.

    2012-01-01

    Hierarchical self-assembly offers elegant and energy-efficient bottom-up strategies for the structuring of complex materials. For block copolymers, the last decade witnessed great progress in diversifying the structural complexity of solution-based assemblies into multicompartment micelles. However, a general understanding of what governs multicompartment micelle morphologies and polydispersity, and how to manipulate their hierarchical superstructures using straightforward concepts and readily accessible polymers remains unreached. Here we demonstrate how to create homogeneous multicompartment micelles with unprecedented structural control via the intermediate pre-assembly of subunits. This directed self-assembly leads to a step-wise reduction of the degree of conformational freedom and dynamics and avoids undesirable kinetic obstacles during the structure build-up. It yields a general concept for homogeneous populations of well-defined multicompartment micelles with precisely tunable patchiness, while using simple linear ABC triblock terpolymers. We further demonstrate control over the hierarchical step-growth polymerization of multicompartment micelles into micron-scale segmented supracolloidal polymers as an example of programmable mesoscale colloidal hierarchies via well-defined patchy nanoobjects. PMID:22426231

  6. Phase behavior and local dynamics of concentrated triblock copolymer micelles

    NASA Astrophysics Data System (ADS)

    Yardimci, H.; Chung, B.; Harden, J. L.; Leheny, R. L.

    2005-12-01

    We report a neutron-scattering study to characterize the ordering and local dynamics of spherical micelles formed by the triblock copolymer polyethylene oxide (PEO) - polypropylene oxide (PPO) - polyethylene oxide (Pluronic) in aqueous solution. The study focuses on two Pluronic species, F68 and F108, that have the same weight fraction of PEO but that differ in chain length by approximately a factor of 2. At sufficiently high concentration, both species undergo a sequence of phase changes with increasing temperature from dissolved chains to micelles with liquidlike order to a cubic crystal phase and finally back to a micelle liquid phase. A comparison of the phase diagrams constructed from small-angle neutron scattering indicates that crystallization is suppressed for shorter chain micelles due to fluctuation effects. The intermediate scattering function I(Q,t)/I(Q,0) determined by neutron spin echo displays a line shape with two distinct relaxations. Comparisons between I(Q,t)/I(Q,0) for fully hydrogenated F68 chains in D2O and for F68 with deuterated PEO blocks reveal that the slower relaxation corresponds to Rouse modes of the PPO segments in the concentrated micelle cores. The faster relaxation is identified with longitudinal diffusive modes in the PEO corona characteristic of a polymer brush.

  7. Polymeric micelles in mucosal drug delivery: Challenges towards clinical translation.

    PubMed

    Sosnik, Alejandro; Menaker Raskin, Maya

    2015-11-01

    Polymeric micelles are nanostructures formed by the self-aggregation of copolymeric amphiphiles above the critical micellar concentration. Due to the flexibility to tailor different molecular features, they have been exploited to encapsulate motley poorly-water soluble therapeutic agents. Moreover, the possibility to combine different amphiphiles in one single aggregate and produce mixed micelles that capitalize on the features of the different components substantially expands the therapeutic potential of these nanocarriers. Despite their proven versatility, polymeric micelles remain elusive to the market and only a few products are currently undergoing advanced clinical trials or reached clinical application, all of them for the therapy of different types of cancer and administration by the intravenous route. At the same time, they emerge as a nanotechnology platform with great potential for non-parenteral mucosal administration. However, for this, the interaction of polymeric micelles with mucus needs to be strengthened. The present review describes the different attempts to develop mucoadhesive polymeric micelles and discusses the challenges faced in the near future for a successful bench-to-bedside translation. PMID:25597531

  8. Supersaturated polymeric micelles for oral cyclosporine A delivery.

    PubMed

    Yu, Hongzhen; Xia, Dengning; Zhu, Quanlei; Zhu, Chunliu; Chen, Dan; Gan, Yong

    2013-11-01

    Polymeric micelles provide a promising platform for improving oral absorption of poorly soluble drugs. However, improved understanding of how drug retention within the hydrophobic micelle core can reduce drug absorption is required. We designed supersaturated polymeric micelles (Super-PMs) to increase molecularly dissolved drug concentration and gain an insight into the effect of the degree of supersaturation on oral absorption of cyclosporine A (CsA) in rats. The drug release from Super-PMs increased with an increase in initial supersaturation degrees in micelles. The cellular uptake of coumarin-6 was reduced by the retention of drug in polymer micelles. The transport flux of CsA across Caco-2 monolayer was increased with initial supersaturation degrees of 0.81-3.53 (p < 0.05). However, increase in supersaturation to 5.64 actually resulted in decreased CsA transport. The same trend was observed in a rat in vivo absorption study, in which the highest bioavailability of 134.6 ± 24.7% (relative to a commercial product, Sandimmun Neoral®, p<0.01) was achieved when the supersaturation degree was 3.53. These results demonstrated that Super-PMs were a promising drug delivery system for compounds with low aqueous solubility. This study also provided an experimental proof for the hypothesis that moderately supersaturated formulations are valuable alternative to high supersaturation formulations, resulting in optimal in vivo performance, and the degree of supersaturation should be carefully controlled to optimize drug absorption. PMID:23954511

  9. Paclitaxel isomerisation in polymeric micelles based on hydrophobized hyaluronic acid.

    PubMed

    Smejkalová, Daniela; Nešporová, Kristina; Hermannová, Martina; Huerta-Angeles, Gloria; Cožíková, Dagmar; Vištejnová, Lucie; Safránková, Barbora; Novotný, Jaroslav; Kučerík, Jiří; Velebný, Vladimír

    2014-05-15

    Physical and chemical structure of paclitaxel (PTX) was studied after its incorporation into polymeric micelles made of hyaluronic acid (HA) (Mw=15 kDa) grafted with C6 or C18:1 acyl chains. PTX was physically incorporated into the micellar core by solvent evaporation technique. Maximum loading capacity for HAC6 and HAC18:1 was determined to be 2 and 14 wt.%, respectively. The loading efficiency was higher for HAC18:1 and reached 70%. Independently of the derivative, loaded HA micelles had spherical size of approximately 60-80 nm and demonstrated slow and sustained release of PTX in vitro. PTX largely changed its form from crystalline to amorphous after its incorporation into the micelle's interior. This transformation increased PTX sensitivity towards stressing conditions, mainly to UV light exposure, during which the structure of amorphous PTX isomerized and formed C3C11 bond within its structure. In vitro cytotoxicity assay revealed that polymeric micelles loaded with PTX isomer had higher cytotoxic effect to normal human dermal fibroblasts (NHDF) and human colon carcinoma cells (HCT-116) than the same micelles loaded with non-isomerized PTX. Further observation indicated that PTX isomer influenced in different ways cell morphology and markers of cell cycle. Taken together, PTX isomer loaded in nanocarrier systems may have improved anticancer activity in vivo than pure PTX. PMID:24614580

  10. Fluorescence dynamics of green fluorescent protein in AOT reversed micelles.

    PubMed

    Uskova, M A; Borst, J W; Hink, M A; van Hoek, A; Schots, A; Klyachko, N L; Visser, A J

    2000-09-15

    We have used the enhanced green fluorescent protein (EGFP) to investigate the properties of surfactant-entrapped water pools in organic solvents (reversed micelles) with steady-state and time-resolved fluorescence methods. The surfactant used was sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and the organic solvents were isooctane and (the more viscous) dodecane, respectively. The water content of the water pools could be controlled through the parameter w0, which is the water-to-surfactant molar ratio. With steady-state fluorescence, it was observed that subtle fluorescence changes could be noted in reversed micelles of different water contents. EGFP can be used as a pH-indicator of the water droplets in reversed micelles. Time-resolved fluorescence methods also revealed subtle changes in fluorescence decay times when the results in bulk water were compared with those in reversed micelles. The average fluorescence lifetimes of EGFP scaled with the relative fluorescence intensities. Time-resolved fluorescence anisotropy of EGFP in aqueous solution and reversed micelles yielded single rotational correlation times. Geometrical considerations could assign the observed correlation times to dehydrated protein at low w0 and internal EGFP rotation within the droplet at the highest w0. PMID:11036971

  11. Oxidative refolding of reduced, denatured lysozyme in AOT reverse micelles.

    PubMed

    Fan, Jun-Bao; Chen, Jie; Liang, Yi

    2008-06-01

    The refolding kinetics of the reduced, denatured hen egg white lysozyme in sodium bis(2-ethylhexyl)sulfosuccinate (AOT)-isooctane-water reverse micelles at different water-to-surfactant molar ratios has been investigated by fluorescence spectroscopy and UV spectroscopy. The oxidative refolding of the confined lysozyme is biphasic in AOT reverse micelles. When the water-to-surfactant molar ratio (omega 0) is 12.6, the relative activity of encapsulated lysozyme after refolding for 24 h in AOT reverse micelles increases 46% compared with that in bulk water. Furthermore, aggregation of lysozyme at a higher concentration (0.2 mM) in AOT reverse micelles at omega 0 of 6.3 or 12.6 is not observed; in contrast, the oxidative refolding of lysozyme in bulk water must be at a lower protein concentration (5 microM) in order to avoid a serious aggregation of the protein. For comparison, we have also investigated the effect of AOT on lysozyme activity and found that the residual activity of lysozyme decreases with increasing the concentration of AOT from 1 to 5 mM. When AOT concentration is larger than 2 mM, lysozyme is almost completely inactivated by AOT and most of lysozyme activity is lost. Together, our data demonstrate that AOT reverse micelles with suitable water-to-surfactant molar ratios are favorable to the oxidative refolding of reduced, denatured lysozyme at a higher concentration, compared with bulk water. PMID:18377920

  12. Determination of polymeric micelles' structural characteristics, and effect of the characteristics on pharmacokinetic behaviors.

    PubMed

    Shiraishi, Kouichi; Sanada, Yusuke; Mochizuki, Shinichi; Kawano, Kumi; Maitani, Yoshie; Sakurai, Kazuo; Yokoyama, Masayuki

    2015-04-10

    We evaluated structural factors characterizing PEG-b-P(Asp-Bzl) micelles including core size, aggregation number (Nagg), and core surface PEG density by means of small-angle X-ray scattering (SAXS), field flow fractionation with multi-angle light scattering (FFF-MALS) analysis, and DLS. Furthermore, we evaluated the stability of PEG-b-P(Asp-Bzl) micelles by means of GPC. This paper reports the correlation between the evaluated micelles' structural factors and the micelles' behaviors including the micelles' in vivo pharmacokinetic behaviors. One micelle PEG(12)-b-P(Asp-Bzl) (PEG=12,000) exhibited a high core surface density (~0.99 chain/nm(2)). In these circumstances, PEG(12)-b-P(Asp-Bzl) micelles exhibited a highly stretched PEG brush form. However, the evaluated core surface PEG densities could not fully explain the micelles' in vivo pharmacokinetic behaviors. In contrast, GPC will become a strong tool for predicting PEG(12)-b-P(Asp-Bzl) micelles' in vivo behaviors, as well as the micelles' in vitro behaviors. The stability results correlated strongly with the area-under-the-curve (AUC) values of PEG-b-P(Asp-Bzl) micelles' in vivo pharmacokinetics. Finally, we evaluated PEG(12)-b-P(Asp-Bzl) micelles' most effective structural factor for determining the micelles' behaviors, and the micelles' outermost shell surface's PEG density (DOS, PEG) correlated with the micelles' behaviors. We revealed that the evaluated DOS, PEG is the most important factor for understanding PEG(12)-b-P(Asp-Bzl) micelles' behaviors. PMID:25687307

  13. Curcumin-Loading-Dependent Stability of PEGMEMA-Based Micelles Affects Endocytosis and Exocytosis in Colon Carcinoma Cells.

    PubMed

    Chang, Teddy; Trench, David; Putnam, Joshua; Stenzel, Martina H; Lord, Megan S

    2016-03-01

    Polymeric micelles were formed from poly(poly(ethylene glycol) methyl ether methacrylate)-block-poly(styrene) (P(PEGMEMA)-b-PS) block copolymer of two different chain lengths. The micelles formed were approximately 16 and 46 nm in diameter and used to encapsulate curcumin. Upon loading of the curcumin into the micelles, their size increased to approximately 34 and 80 nm in diameter, respectively, with a loading efficiency of 58%. The unloaded micelles were not cytotoxic to human colon carcinoma cells, whereas only the smaller loaded micelles were cytotoxic after 72 h of exposure. The micelles were rapidly internalized by the cells within minutes of exposure, with the loaded micelles internalized to a greater extent owing to their enhanced stability compared to that of the unloaded micelles. The larger micelles were more rapidly internalized and exocytosed than the smaller micelles, demonstrating the effect of micelle size and drug loading on drug delivery and cytotoxicity. PMID:26755445

  14. Biomimetic oral mucin from polymer micelle networks

    NASA Astrophysics Data System (ADS)

    Authimoolam, Sundar Prasanth

    Mucin networks are formed by the complexation of bottlebrush-like mucin glycoprotein with other small molecule glycoproteins. These glycoproteins create nanoscale strands that then arrange into a nanoporous mesh. These networks play an important role in ensuring surface hydration, lubricity and barrier protection. In order to understand the functional behavior in mucin networks, it is important to decouple their chemical and physical effects responsible for generating the fundamental property-function relationship. To achieve this goal, we propose to develop a synthetic biomimetic mucin using a layer-by-layer (LBL) deposition approach. In this work, a hierarchical 3-dimensional structures resembling natural mucin networks was generated using affinity-based interactions on synthetic and biological surfaces. Unlike conventional polyelectrolyte-based LBL methods, pre-assembled biotin-functionalized filamentous (worm-like) micelles was utilized as the network building block, which from complementary additions of streptavidin generated synthetic networks of desired thickness. The biomimetic nature in those synthetic networks are studied by evaluating its structural and bio-functional properties. Structurally, synthetic networks formed a nanoporous mesh. The networks demonstrated excellent surface hydration property and were able capable of microbial capture. Those functional properties are akin to that of natural mucin networks. Further, the role of synthetic mucin as a drug delivery vehicle, capable of providing localized and tunable release was demonstrated. By incorporating antibacterial curcumin drug loading within synthetic networks, bacterial growth inhibition was also demonstrated. Thus, such bioactive interfaces can serve as a model for independently characterizing mucin network properties and through its role as a drug carrier vehicle it presents exciting future opportunities for localized drug delivery, in regenerative applications and as bio

  15. Tunable depletion potentials driven by shape variation of surfactant micelles

    NASA Astrophysics Data System (ADS)

    Gratale, Matthew D.; Still, Tim; Matyas, Caitlin; Davidson, Zoey S.; Lobel, Samuel; Collings, Peter J.; Yodh, A. G.

    2016-05-01

    Depletion interaction potentials between micron-sized colloidal particles are induced by nanometer-scale surfactant micelles composed of hexaethylene glycol monododecyl ether (C12E6 ), and they are measured by video microscopy. The strength and range of the depletion interaction is revealed to arise from variations in shape anisotropy of the surfactant micelles. This shape anisotropy increases with increasing sample temperature. By fitting the colloidal interaction potentials to theoretical models, we extract micelle length and shape anisotropy as a function of temperature. This work introduces shape anisotropy tuning as a means to control interparticle interactions in colloidal suspensions, and it shows how the interparticle depletion potentials of micron-scale objects can be employed to probe the shape and size of surrounding macromolecules at the nanoscale.

  16. Modification of Encapsulation Pressure of Reverse Micelles in Liquid Ethane

    PubMed Central

    Peterson, Ronald W.; Nucci, Nathaniel V.; Wand, A. Joshua

    2011-01-01

    Encapsulation of within reverse micelles dissolved in low viscosity fluids offers a potential solution to the slow tumbling problem presented by large soluble macromolecules to solution NMR spectroscopy. The reduction in effective macromolecular tumbling is directly dependent upon the viscosity of the solvent. Liquid ethane is of sufficiently low viscosity at pressures below 5,000 p.s.i. to offer a significant advantage. Unfortunately, the viscosity of liquid ethane shows appreciable pressure dependence. Reverse micelle encapsulation in liquid ethane often requires significantly higher pressures, which obviates the potential advantages offered by liquid ethane over liquid propane. Addition of co-surfactants or co-solvents can be used to manipulate the minimum pressure required to obtain stable, well-behaved solutions of reverse micelles prepared in liquid ethane. A library of potential additives is examined and several candidates suitable for use with encapsulated proteins are described. PMID:21764613

  17. Superdiffusion of concentration in wormlike-micelle solutions

    NASA Astrophysics Data System (ADS)

    Ganapathy, R.; Sood, A. K.; Ramaswamy, S.

    2007-01-01

    Our dynamic light scattering studies of viscoelastic wormlike-micelle solutions of surfactant cetyltrimethylammonium tosylate (CTAT) show superdiffusive relaxation of concentration fluctuations: relaxation rate ~qz at wavenumber q, with z<2, at concentrations just past overlap. Linear rheology experiments show that the micellar recombination kinetics in this system is diffusion-controlled (micelles break and recombine with their original partners). Addition of 10 mM to 100 mM of sodium chloride (NaCl), takes the system from the diffusion-controlled (DC) regime to mean-field recombination kinetics regime where micellar ends combine with ends belonging to other micelles. In the mean-field regime, the concentration fluctuations decay in a purely diffusive manner. We suggest a qualitative explanation for the observed superdiffusive behaviour in the DC regime.

  18. Topology, length scales, and energetics of surfactant micelles.

    PubMed

    Dhakal, Subas; Sureshkumar, Radhakrishna

    2015-07-14

    We study the morphology, energetics, and kinetics of a self-associating model cationic surfactant in water using large-scale coarse-grained molecular dynamics simulations over time scales that allow for probing micelle recombination dynamics. We develop an algorithm to track micelle contours and quantify various microstructural features such as contour length distribution, persistence length, and mesh size. We predict reliably the end-cap energy and recombination time of micelles, directly from molecular simulations for the first time. We further consider the variation of solution viscosity as a function of salt concentration and show that branched and multiconnected structures govern the experimentally observed anomalous dependence of zero-shear viscosity on salt concentration. Overall, simulation predictions are in good agreement with experiments. PMID:26178125

  19. From micelle supramolecular assemblies in selective solvents to isoporous membranes.

    PubMed

    Nunes, Suzana P; Karunakaran, Madhavan; Pradeep, Neelakanda; Behzad, Ali Reza; Hooghan, Bobby; Sougrat, Rachid; He, Haoze; Peinemann, Klaus-Viktor

    2011-08-16

    The supramolecular assembly of PS-b-P4VP copolymer micelles induced by selective solvent mixtures was used to manufacture isoporous membranes. Micelle order in solution was confirmed by cryo-scanning electron microscopy in casting solutions, leading to ordered pore morphology. When dioxane, a solvent that interacts poorly with the micelle corona, was added to the solution, polymer-polymer segment contact was preferential, increasing the intermicelle contact. Immersion in water gave rise to asymmetric porous membranes with exceptional pore uniformity and high porosity. The introduction of a small number of carbon nanotubes to the casting solution improved the membrane stability and the reversibility of the gate response in the presence of different pH values. PMID:21710987

  20. Charged micelle depletion attraction and interfacial colloidal phase behavior.

    PubMed

    Iracki, Tara D; Beltran-Villegas, Daniel J; Eichmann, Shannon L; Bevan, Michael A

    2010-12-21

    Ensemble total internal reflection microscopy (TIRM) is used to directly measure the evolution of colloid-surface depletion attraction with increasing sodium dodecyl sulfate (SDS) concentration near the critical micelle concentration (CMC). Measured potentials are well described by a modified Asakura-Oosawa (AO) depletion potential in addition to electrostatic and van der Waals contributions. The modified AO potential includes effects of electrostatic interactions between micelles and surfaces via effective depletant dimensions in an excluded volume term and partitioning in an osmotic pressure term. Directly measured colloid-surface depletion potentials are used in Monte Carlo (MC) simulations to capture video microscopy (VM) measurements of micelle-mediated quasi-two-dimensional phase behavior including fluid, crystal, and gel microstructures. Our findings provide information to develop more rigorous and analytically simple models of depletion attraction in charged micellar systems. PMID:21077612

  1. Electron spin echo modulation study of AOT reverse micelles

    SciTech Connect

    Baglioni, P. ); Nakamura, Hiroshi ); Kevan, L. )

    1991-05-02

    Electron spin echo deuterium modulation studies have been carried out for x-doxylstearic acid spin probes in frozen reversed micellar solutions of sodium bis(2-ethyl-1-hexyl) sulfosuccinate (AOT)/isooctane as a function of the water pool size with deuterium located in the isooctane or in the water. The results determine the probe location and conformation in the reverse micelle and the amount of water and isooctane penetration into the AOT interface. Modulation effects due to the interaction of the unpaired electron with deuterated isooctane or deuterated water show that the probes are in an extended conformation and are located at the interface of the reverse micelle. The results obtained are in good agreement with the current view of the structure of AOT reversed micelles in liquids and demonstrate at a molecular level that the micellar structure is retained upon fast freezing.

  2. Photosensitized production of hydrogen by hydrogenase in reversed micelles

    PubMed Central

    Hilhorst, Riet; Laane, Colja; Veeger, Cees

    1982-01-01

    Hydrogenase (hydrogen:ferricytochrome c3 oxidoreductase, EC 1.12.2.1) from Desulfovibrio vulgaris was encapsulated in reversed micelles with cetyltrimethylammonium bromide as surfactant and a chloroform/octane mixture as solvent. Reducing equivalents for hydrogenase-catalyzed hydrogen production were provided by vectorial photosensitized electron transfer from a donor (thiophenol) in the organic phase through a surfactant-Ru2+ sensitizer located in the interphase to methyl viologen concentrated in the aqueous core of the reversed micelle. The results show that reversed micelles provide a microenvironment that (i) stabilizes hydrogenase against inactivation and (ii) allows an efficient vectorial photosensitized electron and proton flow from the organic phase to hydrogenase in the aqueous phase. Images PMID:16593204

  3. Modification of encapsulation pressure of reverse micelles in liquid ethane.

    PubMed

    Peterson, Ronald W; Nucci, Nathaniel V; Wand, A Joshua

    2011-09-01

    Encapsulation within reverse micelles dissolved in low viscosity fluids offers a potential solution to the slow tumbling problem presented by large soluble macromolecules to solution NMR spectroscopy. The reduction in effective macromolecular tumbling is directly dependent upon the viscosity of the solvent. Liquid ethane is of sufficiently low viscosity at pressures below 5000 psi to offer a significant advantage. Unfortunately, the viscosity of liquid ethane shows appreciable pressure dependence. Reverse micelle encapsulation in liquid ethane often requires significantly higher pressures, which obviates the potential advantages offered by liquid ethane over liquid propane. Addition of co-surfactants or co-solvents can be used to manipulate the minimum pressure required to obtain stable, well-behaved solutions of reverse micelles prepared in liquid ethane. A library of potential additives is examined and several candidates suitable for use with encapsulated proteins are described. PMID:21764613

  4. Micelle to trapping solution stacking in micellar electrokinetic chromatography.

    PubMed

    Liu, Lihong; Deng, Xinxian; Chen, Xingguo

    2010-01-01

    An analytical strategy micelle to trapping solution stacking (MSS) was developed in acidic buffer in micellar electrokinetic chromatography (MEKC). The stacking mechanism is based on the transport, release, capturing of molecules bound to micelle carriers that are made to collapse into trapping solution (TS) to serve as the medium to contain and stacking the analytes. Tetrandrine and fangchinoline were selected as model mixture using sodium dodecyl sulfate (SDS) micelles as carrier to demonstrate this stacking method. The experiments by MSS-MEKC were carried out and further compared with those by normal MEKC. The results reveal that 113-123-fold improvements in the detection sensitivity was obtained for the analytes, and separation and determination of tetrandrine and fangchinoline in Stephaniae tetrandrae S. Moore and Fengtongan capsules were finished under optimum conditions using the sample matrix containing 8.0mM SDS and TS containing 50mM H(3)PO(4)-55% (v/v) ethanol. PMID:19945115

  5. Alternating Vorticity Bands in a Solution of Wormlike Micelles

    SciTech Connect

    Herle, Vishweshwara; Pfister, Bruno; Fischer, Peter; Windhab, Erich J; Kohlbrecher, Joachim

    2007-10-12

    We report on structural characterization of vorticity bands formed in a wormlike micellar solution by Rheo-small-angle neutron scattering and video imaging experiments. Below a critical shear stress {tau}{sub c} in Newtonian and shear-thinning regime, only a minor flow alignment of the micelles is observed. Above {tau}{sub c}, in the shear-thickening regime, alternating transparent and turbid bands are formed. Triggered small-angle neutron scattering shows different anisotropic patterns in both bands indicating strongly aligned structures. By high-speed video imaging, we show that such an alignment of micelles does not correspond to a phase of lower viscosity.

  6. Fluorescent supramolecular micelles for imaging-guided cancer therapy

    NASA Astrophysics Data System (ADS)

    Sun, Mengmeng; Yin, Wenyan; Dong, Xinghua; Yang, Wantai; Zhao, Yuliang; Yin, Meizhen

    2016-02-01

    A novel smart fluorescent drug delivery system composed of a perylene diimide (PDI) core and block copolymer poly(d,l-lactide)-b-poly(ethyl ethylene phosphate) is developed and named as PDI-star-(PLA-b-PEEP)8. The biodegradable PDI-star-(PLA-b-PEEP)8 is a unimolecular micelle and can self-assemble into supramolecular micelles, called as fluorescent supramolecular micelles (FSMs), in aqueous media. An insoluble drug camptothecin (CPT) can be effectively loaded into the FSMs and exhibits pH-responsive release. Moreover, the FSMs with good biocompatibility can also be employed as a remarkable fluorescent probe for cell labelling because the maximum emission of PDI is beneficial for bio-imaging. The flow cytometry and confocal laser scanning microscopy analysis demonstrate that the micelles are easily endocytosed by cancer cells. In vitro and in vivo tumor growth-inhibitory studies reveal a better therapeutic effect of FSMs after CPT encapsulation when compared with the free CPT drug. The multifunctional FSM nanomedicine platform as a nanovehicle has great potential for fluorescence imaging-guided cancer therapy.A novel smart fluorescent drug delivery system composed of a perylene diimide (PDI) core and block copolymer poly(d,l-lactide)-b-poly(ethyl ethylene phosphate) is developed and named as PDI-star-(PLA-b-PEEP)8. The biodegradable PDI-star-(PLA-b-PEEP)8 is a unimolecular micelle and can self-assemble into supramolecular micelles, called as fluorescent supramolecular micelles (FSMs), in aqueous media. An insoluble drug camptothecin (CPT) can be effectively loaded into the FSMs and exhibits pH-responsive release. Moreover, the FSMs with good biocompatibility can also be employed as a remarkable fluorescent probe for cell labelling because the maximum emission of PDI is beneficial for bio-imaging. The flow cytometry and confocal laser scanning microscopy analysis demonstrate that the micelles are easily endocytosed by cancer cells. In vitro and in vivo tumor growth

  7. Proton transfer in ionic and neutral reverse micelles.

    PubMed

    Lawler, Christian; Fayer, Michael D

    2015-05-14

    Proton-transfer kinetics in both ionic and neutral reverse micelles were studied by time-correlated single-photon counting investigations of the fluorescent photoacid 8-hydroxypyrene-1,3,6-trisulfonate (HPTS). Orientational dynamics of dissolved probe molecules in the water pools of the reverse micelles were also investigated by time-dependent fluorescence anisotropy measurements of MPTS, the methoxy derivative of HPTS. These experiments were compared to the same experiments in bulk water. It was found that in ionic reverse micelles (surfactant Aerosol OT, AOT), orientational motion (fluorescence anisotropy decay) of MPTS was relatively unhindered, consistent with MPTS being located in the water core of the reverse micelle away from the water-surfactant interface. In nonionic reverse micelles (surfactant Igepal CO-520, Igepal), however, orientational anisotropy displayed a slow multiexponential decay consistent with wobbling-in-a-cone behavior, indicating MPTS is located at the water-surfactant interface. HPTS proton transfer in ionic reverse micelles followed kinetics qualitatively like those in bulk water, albeit slower, with the long-time power law time dependence associated with recombination of the proton with the dissociated photoacid, suggesting a modified diffusion-controlled process. However, the power law exponents in the ionic reverse micelles are smaller (∼ -0.55) than that in bulk water (-1.1). In neutral reverse micelles, proton-transfer kinetics did not show discernible power law behavior and were best represented by a two-component model with one relatively waterlike population and a population with a faster fluorescence lifetime and negligible proton transfer. We explain the Igepal results on the basis of close association between the probe and the neutral water-surfactant interface, with the probe experiencing a distribution of more and less waterlike environments. In addition, the observation in bulk water of a power law t(-1.1) for diffusion

  8. A ''Voice Inversion Effect?''

    ERIC Educational Resources Information Center

    Bedard, Catherine; Belin, Pascal

    2004-01-01

    Voice is the carrier of speech but is also an ''auditory face'' rich in information on the speaker's identity and affective state. Three experiments explored the possibility of a ''voice inversion effect,'' by analogy to the classical ''face inversion effect,'' which could support the hypothesis of a voice-specific module. Experiment 1 consisted…

  9. Seismic Inversion Methods

    SciTech Connect

    Jackiewicz, Jason

    2009-09-16

    With the rapid advances in sophisticated solar modeling and the abundance of high-quality solar pulsation data, efficient and robust inversion techniques are crucial for seismic studies. We present some aspects of an efficient Fourier Optimally Localized Averaging (OLA) inversion method with an example applied to time-distance helioseismology.

  10. Inverse structure functions

    SciTech Connect

    Pearson, Bruce R.; Water, Willem van de

    2005-03-01

    While the ordinary structure function in turbulence is concerned with the statistical moments of the velocity increment {delta}u measured over a distance r, the inverse structure function is related to the distance r where the turbulent velocity exits the interval {delta}u. We study inverse structure functions of wind-tunnel turbulence which covers a range of Reynolds numbers Re{sub {lambda}}=400-1100. We test a recently proposed relation between the scaling exponents of the ordinary structure functions and those of the inverse structure functions [S. Roux and M. H. Jensen, Phys. Rev. E 69, 16309 (2004)]. The relatively large range of Reynolds numbers in our experiment also enables us to address the scaling with Reynolds number that is expected to highlight the intermediate dissipative range. While we firmly establish the (relative) scaling of inverse structure functions, our experimental results fail both predictions. Therefore, the question of the significance of inverse structure functions remains open.

  11. One-Step Way to Form Prodrug Micelles with High Amount Drug Loading.

    PubMed

    Zhang, Jing; Wu, Dan; Feng, Jie

    2016-06-01

    Prodrug micelles with high amount drug loading were obtained via one-step way. Antineoplastic drug doxorubicin (DOX), used as hydrophobic tail, was conjugated to hydrophilic head mPEG via hydrazone bonds, allowing drug release under intracellular condition. Free DOX was loaded into the hydrophobic core of micelles during the conjugation step simultaneously. Total drug content of the prodrug micelles was up to 61.2%. Endocytosis experiments confirmed that the prodrug micelles achieved good cellular-uptake ability. In vitro experiments indicated that the prodrug micelles showed better therapy efficacy than free drug in cancerous cells. PMID:27427600

  12. Plasma inverse transition acceleration

    SciTech Connect

    Xie, Ming

    2001-06-18

    It can be proved fundamentally from the reciprocity theorem with which the electromagnetism is endowed that corresponding to each spontaneous process of radiation by a charged particle there is an inverse process which defines a unique acceleration mechanism, from Cherenkov radiation to inverse Cherenkov acceleration (ICA) [1], from Smith-Purcell radiation to inverse Smith-Purcell acceleration (ISPA) [2], and from undulator radiation to inverse undulator acceleration (IUA) [3]. There is no exception. Yet, for nearly 30 years after each of the aforementioned inverse processes has been clarified for laser acceleration, inverse transition acceleration (ITA), despite speculation [4], has remained the least understood, and above all, no practical implementation of ITA has been found, until now. Unlike all its counterparts in which phase synchronism is established one way or the other such that a particle can continuously gain energy from an acceleration wave, the ITA to be discussed here, termed plasma inverse transition acceleration (PITA), operates under fundamentally different principle. As a result, the discovery of PITA has been delayed for decades, waiting for a conceptual breakthrough in accelerator physics: the principle of alternating gradient acceleration [5, 6, 7, 8, 9, 10]. In fact, PITA was invented [7, 8] as one of several realizations of the new principle.

  13. Glyceroglycolipids Affect Uptake of Carotenoids Solubilized in Mixed Micelles by Human Intestinal Caco-2 Cells.

    PubMed

    Kotake-Nara, Eiichi; Yonekura, Lina; Nagao, Akihiko

    2015-09-01

    We previously reported that phospholipids markedly affected the uptake of carotenoids solubilized in mixed micelles by human intestinal Caco-2 cells. In the present study, we found that two classes of dietary glyceroglycolipids and the corresponding lysoglyceroglycolipids affected uptake of β-carotene and lutein by differentiated Caco-2 cells. The levels of carotenoid uptake from micelles containing digalactosyldiacylglycerol or sulfoquinovosyldiacylglycerol were significantly lower than that from control micelles. On the other hand, the uptakes from micelles containing digalactosylmonoacylglycerol or sulfoquinovosylmonoacylglycerol were significantly higher than that from control micelles. In dispersed cells and Caco-2 cells with poor cell-to-cell adhesion, however, the levels of uptake from micelles containing these lyso-lipids were much lower than that from control micelles. The uptake levels from control micelles were markedly decreased depending on the development of cell-to-cell/cell-matrix adhesion in Caco-2 cells, but the uptake levels from the micelles containing these lyso-lipids were not substantially changed, suggesting that the intercellular barrier formed by cell-to-cell/cell-matrix adhesion inhibited the uptake from control micelles, but not from the lyso-lipid-containing micelles. The lyso-lipids appeared to enhance carotenoid uptake by decreasing the intercellular barrier integrity. The results showed that some types of glyceroglycolipids have the potential to modify the intestinal uptake of carotenoids. PMID:26012480

  14. Biodegradable polymeric micelle-encapsulated doxorubicin suppresses tumor metastasis by killing circulating tumor cells

    NASA Astrophysics Data System (ADS)

    Deng, Senyi; Wu, Qinjie; Zhao, Yuwei; Zheng, Xin; Wu, Ni; Pang, Jing; Li, Xuejing; Bi, Cheng; Liu, Xinyu; Yang, Li; Liu, Lei; Su, Weijun; Wei, Yuquan; Gong, Changyang

    2015-03-01

    Circulating tumor cells (CTCs) play a crucial role in tumor metastasis, but it is rare for any chemotherapy regimen to focus on killing CTCs. Herein, we describe doxorubicin (Dox) micelles that showed anti-metastatic activity by killing CTCs. Dox micelles with a small particle size and high encapsulation efficiency were obtained using a pH-induced self-assembly method. Compared with free Dox, Dox micelles exhibited improved cytotoxicity, apoptosis induction, and cellular uptake. In addition, Dox micelles showed a sustained release behavior in vitro, and in a transgenic zebrafish model, Dox micelles exhibited a longer circulation time and lower extravasation from blood vessels into surrounding tissues. Anti-tumor and anti-metastatic activities of Dox micelles were investigated in transgenic zebrafish and mouse models. In transgenic zebrafish, Dox micelles inhibited tumor growth and prolonged the survival of tumor-bearing zebrafish. Furthermore, Dox micelles suppressed tumor metastasis by killing CTCs. In addition, improved anti-tumor and anti-metastatic activities were also confirmed in mouse tumor models, where immunofluorescent staining of tumors indicated that Dox micelles induced more apoptosis and showed fewer proliferation-positive cells. There were decreased side effects in transgenic zebrafish and mice after administration of Dox micelles. In conclusion, Dox micelles showed stronger anti-tumor and anti-metastatic activities and decreased side effects both in vitro and in vivo, which may have potential applications in cancer therapy.

  15. Thermodynamics of micelle formation in a water-alcohol solution of sodium tetradecyl sulfate

    NASA Astrophysics Data System (ADS)

    Shilova, S. V.; Tret'yakova, A. Ya.; Barabanov, V. P.

    2016-01-01

    The effects of addition of ethanol and propan-1-ol on sodium tetradecyl sulfate micelle formation in an aqueous solution are studied via microprobe fluorescence microscopy and conductometry. The critical micelle concentration, quantitative characteristics of micelles, and thermodynamic parameters of micelle formation are determined. Addition of 5-15 vol % of ethanol or 5-10 vol % of propan-1-ol is shown to result in a lower critical micelle concentration than in the aqueous solution, and in the formation of mixed spherical micelles whose sizes and aggregation numbers are less than those for the systems without alcohol. The contribution from the enthalpy factor to the free energy of sodium tetradecyl sulfate micelle formation is found to dominate in mixed solvents, in contrast to aqueous solutions.

  16. Molecular dynamics simulation strategies for protein-micelle complexes.

    PubMed

    Cheng, Xi; Kim, Jin-Kyoung; Kim, Yangmee; Bowie, James U; Im, Wonpil

    2016-07-01

    The structure and stability of membrane proteins can vary widely in different detergents and this variability has great practical consequences for working with membrane proteins. Nevertheless, the mechanisms that operate to alter the behavior of proteins in micelles are poorly understood and not predictable. Atomic simulations could provide considerable insight into these mechanisms. Building protein-micelle complexes for simulation is fraught with uncertainty, however, in part because it is often unknown how many detergent molecules are present in the complex. Here, we describe several convenient ways to employ Micelle Builder in CHARMM-GUI to rapidly construct protein-micelle complexes and performed simulations of the isolated voltage-sensor domain of voltage-dependent potassium-selective channel and an antimicrobial peptide papiliocin with varying numbers of detergents. We found that once the detergent number exceeds a threshold, protein-detergent interactions change very little and remain very consistent with experimental observations. Our results provide a platform for future studies of the interplays between protein structure and detergent properties at the atomic level. This article is part of a Special Issue entitled: Membrane Proteins edited by J.C. Gumbart and Sergei Noskov. PMID:26679426

  17. Micelles as Delivery Vehicles for Oligofluorene for Bioimaging

    PubMed Central

    Su, Fengyu; Alam, Ruhaniyah; Mei, Qian; Tian, Yanqing; Meldrum, Deirdre R.

    2011-01-01

    With the successful development of organic/polymeric light emitting diodes, many organic and polymeric fluorophores with high quantum efficiencies and optical stability were synthesized. However, most of these materials which have excellent optical properties are insoluble in water, limiting their applications in biological fields. Herein, we used micelles formed from an amino-group-containing poly(ε-caprolactone)-block-poly(ethylene glycol) (PCL-b-PEG-NH2) to incorporate a hydrophobic blue emitter oligofluorene (OF) to enable its application in biological conditions. Although OF is completely insoluble in water, it was successfully transferred into aqueous solutions with a good retention of its photophysical properties. OF exhibited a high quantum efficiency of 0.84 in a typical organic solvent of tetrahydrofuran (THF). In addition, OF also showed a good quantum efficiency of 0.46 after being encapsulated into micelles. Two cells lines, human glioblastoma (U87MG) and esophagus premalignant (CP-A), were used to study the cellular internalization of the OF incorporated micelles. Results showed that the hydrophobic OF was located in the cytoplasm, which was confirmed by co-staining the cells with nucleic acid specific SYTO 9, lysosome specific LysoTracker Red®, and mitochondria specific MitoTracker Red. MTT assay indicated non-toxicity of the OF-incorporated micelles. This study will broaden the application of hydrophobic functional organic compounds, oligomers, and polymers with good optical properties to enable their applications in biological research fields. PMID:21915324

  18. Biochemical characterization of GM1 micelles-Amphotericin B interaction.

    PubMed

    Leonhard, Victoria; Alasino, Roxana V; Bianco, Ismael D; Garro, Ariel G; Heredia, Valeria; Beltramo, Dante M

    2015-01-01

    In this work a thorough characterization of the GM1 micelle-Amphotericin B (AmB) interaction was performed. The micelle formation as well as the drug loading occurs spontaneously, although influenced by the physicochemical conditions, pH and temperature. The chromatographic profile of GM1-AmB complexes at different molar ratios shows the existence of two populations. The differential absorbance of GM1, monomeric and aggregate AmB, allowed us to discriminate the presence of all of them in both fractions. Thus, we noted that at higher proportion of AmB in the complex, increases the larger population which is composed mainly of aggregated AmB. The physical behavior of these micelles shows that both GM1- AmB complexes were stable in solution for at least 30 days. However upon freeze-thawing or lyophilization-solubilization cycles, only the smallest population, enriched in monomeric AmB, showed a complete solubilization. In vitro, GM1-AmB micelles were significantly less toxic on cultured cells than other commercial micellar formulations as Fungizone, but had a similar behavior to liposomal formulations as Ambisome. Regarding the antifungal activity of the new formulation, it was very similar to that of other formulations. The characterization of these GM1-AmB complexes is discussed as a potential new formulation able to improve the antifungal therapeutic efficiency of AmB. PMID:25772153

  19. Formation of micelles in homopolymer-copolymer mixtures

    NASA Astrophysics Data System (ADS)

    Müller, Marcus; Cavallo, Anna; Binder, Kurt

    2007-03-01

    Using Monte Carlo (MC) simulations of the bond fluctuation model and self-consistent field (SCF) calculations, we study the formation of micelles in a mixture of homopolymers and asymmetric AB-diblock copolymers with composition, fA=1/8. We work in the semi--grandcanonical ensemble, i.e., we fix the monomer density and incompatibility, χN˜100, and control the composition of the mixture via the exchange chemical potential, δμ between the copolymer and homopolymer solvent. The MC simulation comprises moves that allow homopolymers to mutate into AB-diblock copolymers and vice versa. These moves are very efficient in equilibrating the configurations. We accurately locate the critical micelle concentration, study the micellar size distribution and characterize the shape of the micelles by the tensor of gyration and radial density profiles. The simulation results are quantitatively compared to predictions of the SCF theory in the grandcanonical ensemble without adjustable parameter. Only in the limit of high molecular weight the simulation results gradually approach the theoretical predictions. The structure and phase behavior of mixed micelles is investigated by SCF calculations.

  20. Vibrational energy relaxation of water in Aerosol OT reverse micelle

    NASA Astrophysics Data System (ADS)

    Pang, Yoonsoo; Deak, John; Dlott, Dana

    2005-03-01

    An IR-Raman technique with mid-IR pump and anti-Stokes Raman probe is used to investigate reverse micelle mixture of Aerosol OT, water, and carbon tetrachloride, where polar water phase and nonpolar oil phase is separated by a monolayer of surfactant molecules. Anti-Stokes Raman scattering is only dependent on the population of vibrationally excited states, thus time-dependent population changes of parent/daughter vibrations can be monitored with this technique. Vibrational energy from nanodroplet of water is transferred to the surfactant head group in 1.8 ps and then out to solvent in 10 ps. Vibrational energy directly pumped into the surfactant tail group results in a slower 20-40 ps energy transfer to solvent. This energy transfer cannot be explained by ordinary heat transfer, but the specific vibrational energy relaxation pathway such as sulfonate stretch of surfactant molecules should be used. We can change the water-to-solvent energy transfer rate by adopting different size of reverse micelles or changing pump frequency over the broad OH stretch mode of water due to hydrogen bond network. Water molecules confined in nanometer scale reverse micelles have very different properties from bulk water and we have found many differences between the vibrational dynamics of water in these reverse micelles and those of bulk water.

  1. CASEIN MICELLE STRUCTURE: THE PAST AND THE PRESENT

    Technology Transfer Automated Retrieval System (TEKTRAN)

    At the heart of the milk system are the colloidal casein–calcium–transport complexes termed the casein micelles. The application of physical chemical techniques such as light, neutron, and X-ray scattering, and Electron Microscopy (EM) has yielded a wealth of experimental detail concerning the struc...

  2. Sialoganglioside Micelles for Enhanced Paclitaxel Solubility: In Vitro Characterization.

    PubMed

    Heredia, Valeria; Alasino, Roxana V; Leonhard, Victoria; Garro, Ariel G; Maggio, Bruno; Beltramo, Dante M

    2016-01-01

    Efficiency of mono-sialogangliosides to load Paclitaxel (Ptx) has recently been found to depend on the structure of the polysaccharide chain. In this study, we demonstrated that incorporation of only one more sialic acid into the ganglioside molecule, independently of its position, causes a 4-fold increase in Ptx-loading capacity, the maximum being at a 5:1 molar ratio (di-sialoganglioside/Paclitaxel, GD/Ptx). These complexes are stable in solution for at least 3 months, and over 90% of Ptx remains loaded in the micelles after extreme stress conditions such as high-speed centrifugation, lyophilization, or freeze-thaw cycles. Ganglioside micelles protect 50% of the initially loaded Ptx from alkaline hydrolysis after 24 h at pH 10. Dynamic light scattering studies revealed that GD micelles increase their size from 9 to 12 nm when loaded with Ptx. Transmission electron microscopy shows a homogeneous population of spherical micelles either with or without Ptx. In vitro biological activity was similar to that of the free drug. These results provide further options of self-assembled nanostructures of di- and tri-sialogangliosides with a higher loading capacity. PMID:26852858

  3. Fluorescent supramolecular micelles for imaging-guided cancer therapy.

    PubMed

    Sun, Mengmeng; Yin, Wenyan; Dong, Xinghua; Yang, Wantai; Zhao, Yuliang; Yin, Meizhen

    2016-03-01

    A novel smart fluorescent drug delivery system composed of a perylene diimide (PDI) core and block copolymer poly(d,l-lactide)-b-poly(ethyl ethylene phosphate) is developed and named as PDI-star-(PLA-b-PEEP)8. The biodegradable PDI-star-(PLA-b-PEEP)8 is a unimolecular micelle and can self-assemble into supramolecular micelles, called as fluorescent supramolecular micelles (FSMs), in aqueous media. An insoluble drug camptothecin (CPT) can be effectively loaded into the FSMs and exhibits pH-responsive release. Moreover, the FSMs with good biocompatibility can also be employed as a remarkable fluorescent probe for cell labelling because the maximum emission of PDI is beneficial for bio-imaging. The flow cytometry and confocal laser scanning microscopy analysis demonstrate that the micelles are easily endocytosed by cancer cells. In vitro and in vivo tumor growth-inhibitory studies reveal a better therapeutic effect of FSMs after CPT encapsulation when compared with the free CPT drug. The multifunctional FSM nanomedicine platform as a nanovehicle has great potential for fluorescence imaging-guided cancer therapy. PMID:26881415

  4. Characterisation of chlorophyll a solubilised in sodium lauryl sulphate micelles

    NASA Astrophysics Data System (ADS)

    Mukherjee, T.; Sapre, A. V.; Mittal, Jai P.

    1980-01-01

    Poisson statistics has been applied to the problem of solubilisation of chlorophyll a in sodium lauryl sulphate micelles. Dilution experiments have been carried out to support the finding that each unit of chlorophyll a contributing to the 740 nm band contains just one chlorophyll a molecule.

  5. Degradation patterns of tetracycline antibiotics in reverse micelles and water.

    PubMed

    Sah, Hongkee

    2006-11-01

    The objective of this study was to determine the chemical stability of tetracycline and oxytetracycline hydro-chlorides in reverse micelles. Their reverse micellar solutions were prepared using cetyltrimethylammonium bromide, water and ethyl formate. The aqueous solutions of the tetracycline antibiotics were also prepared for comparison. The reverse micellar and aqueous solutions were stored at 37 degrees C. Samples were analyzed by high performance liquid chromatography. When evaluation was performed on an aqueous tetracycline HCl solution, its half-life was estimated to be 329 h. Its chemical stability was not improved after being dissolved in the reverse micelles, and a similar half-life of 330 h was observed. However, there were noticeable differences between the two systems in terms of degradation kinetics and degradation byproducts. On the other hand, oxytetracycline HCl was unstable in water so that its half-life was only 34 h. Very interestingly, pronounced improvement in stability was attained with the reverse micellar system: upon dissolving in the reverse micelles, its half-life was increased to 2402 h. There were also marked differences in degradation patterns and mechanisms of oxytetracycline HCl in water and the reverse micelles. Our study indicates that the reverse micellar system has potential applications in solubilizing and stabilizing oxytetracycline HCl, thereby contributing to the development of its dosage forms. PMID:16729272

  6. PH responsive polypeptide based polymeric micelles for anticancer drug delivery.

    PubMed

    Zhao, Dongping; Li, Bingqiang; Han, Jiaming; Yang, Yue; Zhang, Xinchen; Wu, Guolin

    2015-09-01

    A pH-responsive polymeric micelle based on poly(aspartamide) derivative was explored as an efficient acid-triggered anticancer drug delivery system. Poly(α,β-l-asparthydrazide) (PAHy) was prepared by aminolysis reaction of polysuccinimide with hydrazine hydrate. Poly(ethylene glycol) and aliphatic chain (C18) were conjugated onto PAHy to afford an amphiphilic copolymer with acid-liable hydrazone bonds. The structure of the resulting copolymer and its self-assembled micelles were confirmed by (1) H NMR, FTIR, DLS, and TEM. Furthermore, doxorubicin (DOX) was loaded into the polymeric micelles via the hydrophobic interaction between the C18 group and DOX molecules, and the π-π staking between the hydrazone conjugated DOX and free DOX molecules. Results showed that the DOX loaded nanoparticle (NP) was relatively stable under physiological conditions, while the DOX was quickly released in response to acidity due to the shedding of mPEG shells and dissociating of C18 segments because of the pH-cleavage of intermediate hydrazone bonds. In addition, the DOX loaded micelles presented a high cytotoxic activity against tumor cells in vitro. This pH responsive NP has appeared highly promising for the targeted intracellular delivery of hydrophobic chemotherapeutics in cancer therapy. PMID:25689362

  7. Quenching mechanism of exciplex fluorescence by inverted micelles

    SciTech Connect

    Sato, Chika; Kikuchi, Koichi

    1992-06-25

    Using an emission-absorption laser photolysis method, the quenching mechanism of the pyrene-N,N-dimethylaniline exciplex fluorscence by inverted micelles is studied. The rate of enhanced intersystem crossing depends upon water pool size and is reduced by external magnetic fields. 15 refs., 3 figs., 2 tabs.

  8. Micelle hydrogels for three-dimensional dose verification

    NASA Astrophysics Data System (ADS)

    Babic, S.; Battista, J.; Jordan, K.

    2009-05-01

    Gelatin hydrogels form a transparent and colourless matrix for polymerization or chromic reactions initiated by absorption of ionizing radiation. Generally, hydrogel chemistries have been limited to water soluble reactants. Work to adapt a water insoluble colourless leuco dye to coloured dye conversion reaction in hydrogels, led to the idea that micelles (i.e. tiny aggregates of surfactant molecules) may provide the necessary polar and nonpolar hybrid environment. Both leucomalachite green and leuco crystal violet radiochromic gels have been developed as three-dimensional (3-D) radiochromic dosimeters for optical computed tomography (CT) scanners. It has been found that the post-irradiation diffusion rates strongly correlate with the solubility of the leuco dyes. Since the crystal violet dye is more soluble in the micelle than in the surrounding water, the dose distribution degrades at the slower rate of micelle diffusion, thus yielding stable images of dose. A dosimetric characterization of leucomalachite green and leuco crystal violet gels, respectively, reveals that tissue equivalent micelle hydrogels are promising dosimeters for radiation therapy 3-D dose verification.

  9. [Optimization and in vitro characterization of resveratrol-loaded poloxamer 403/407 mixed micelles].

    PubMed

    Li, Jin-feng; Gao, Ming-yue; Wang, Hui-min; Liu, Qiao-yu; Mao, Shi-rui

    2015-08-01

    The objectives of this study are to prepare resveratrol loaded mixed micelles composed of poloxamer 403 and poloxamer 407, and optimize the formulation in order to achieve higher drug solubility and sustained drug release. Firstly, a thin-film hydration method was utilized to prepare the micelles. By using drug-loading, encapsulation yield and particle size of the micelles as criteria, influence of three variables, namely poloxamer 407 mass fraction, amount of water and feeding of resveratrol, on the quality of the micelles was optimized with a central composite design method. Steady fluorescence measurement was carried out to evaluate the critical micelle concentration of the carriers. Micelle stability upon dilution with simulated gastric fluid and simulated intestinal fluid was investigated. The in vitro release of resveratrol from the mixed micelles was monitored by dialysis method. It was observed that the particle size of the optimized micelle formulation was 24 nm, with drug-loading 11.78%, and encapsulation yield 82.51%. The mixed micelles increased the solubility of resveratrol for about 197 times. Moreover, the mixed micelles had a low critical micelle concentration of 0.05 mg · mL(-1) in water and no apparent changes in particle size and drug content were observed upon micelles dilution, indicating improved kinetic stability. Resveratrol was released from the micelles in a controlled manner for over 20 h, and the release process can be well described by Higuchi equation. Therefore, resveratrol-loaded poloxamer 403/407 mixed micelles could improve the solubility of resveratrol significantly and sustained drug release behavior can be achieved. PMID:26669007

  10. Casein polymorphism heterogeneity influences casein micelle size in milk of individual cows.

    PubMed

    Day, L; Williams, R P W; Otter, D; Augustin, M A

    2015-06-01

    Milk samples from individual cows producing small (148-155 nm) or large (177-222 nm) casein micelles were selected to investigate the relationship between the individual casein proteins, specifically κ- and β-casein phenotypes, and casein micelle size. Only κ-casein AA and β-casein A1A1, A1A2 and A2A2 phenotypes were found in the large casein micelle group. Among the small micelle group, both κ-casein and β-casein phenotypes were more diverse. κ-Casein AB was the dominant phenotype, and 3 combinations (AA, AB, and BB) were present in the small casein micelle group. A considerable mix of β-casein phenotypes was found, including B and I variants, which were only found in the small casein micelle group. The relative amount of κ-casein to total casein was significantly higher in the small micelle group, and the nonglycosylated and glycosylated κ-casein contents were higher in the milks with small casein micelles (primarily with κ-casein AB and BB variants) compared with the large micelle group. The ratio of glycosylated to nonglycosylated κ-casein was higher in the milks with small casein micelles compared with the milks with large casein micelles. This suggests that although the amount of κ-casein (both glycosylated and nonglycosylated) is associated with micelle size, an increased proportion of glycosylated κ-casein could be a more important and favorable factor for small micelle size. This suggests that the increased spatial requirement due to addition of the glycosyl group with increasing extent of glycosylation of κ-casein is one mechanism that controls casein micelle assembly and growth. In addition, increased electrostatic repulsion due to the sialyl residues on the glycosyl group could be a contributory factor. PMID:25828659

  11. Effect of micelles and mixed micelles on efficiency and selectivity of antibiotic-based capillary electrophoretic enantioseparations

    SciTech Connect

    Rundlett, K.L.; Armstrong, D.W.

    1995-07-01

    Vancomycin (an oligophenolic, glycopeptide, macrocyclic antibiotic) has been shown to be a superb chiral selector for anionic and neutral compounds. It was found that adding sodium dodecyl sulfate to the run buffer increased efficiency by over 1 order of magnitude, decreased analysis times, and reversed the elution order of the enantiomers. This allows for control of the retention order as well as the resolution of enantiomers in complex mixtures in a single run. A mechanism is proposed which explains all of the observed effects and is verified experimentally. Since vancomycin is present in both the micelle and in free solution, previously proposed micelle-selector models are, at best, limiting cases. A general equation is derived which can be used to describe all possible interactions, including those with the capillary wall, if needed. Also, it is shown that electrophoretic mobilities and not migration times must be used to calculate binding constants of a solute to the micelle, the chiral selector, or both. Furthermore, it is shown that a neutral marker molecule cannot be used to accurately correct mobilities that have been altered due to changes in solution viscosity. While this work utilizes the practical vancomycin-micelle system, the general conclusions and theory apply to most other analogous CE systems as well. 48 refs., 4 figs., 5 tabs.

  12. Generalized emissivity inverse problem.

    PubMed

    Ming, DengMing; Wen, Tao; Dai, XianXi; Dai, JiXin; Evenson, William E

    2002-04-01

    Inverse problems have recently drawn considerable attention from the physics community due to of potential widespread applications [K. Chadan and P. C. Sabatier, Inverse Problems in Quantum Scattering Theory, 2nd ed. (Springer Verlag, Berlin, 1989)]. An inverse emissivity problem that determines the emissivity g(nu) from measurements of only the total radiated power J(T) has recently been studied [Tao Wen, DengMing Ming, Xianxi Dai, Jixin Dai, and William E. Evenson, Phys. Rev. E 63, 045601(R) (2001)]. In this paper, a new type of generalized emissivity and transmissivity inverse (GETI) problem is proposed. The present problem differs from our previous work on inverse problems by allowing the unknown (emissivity) function g(nu) to be temperature dependent as well as frequency dependent. Based on published experimental information, we have developed an exact solution formula for this GETI problem. A universal function set suggested for numerical calculation is shown to be robust, making this inversion method practical and convenient for realistic calculations. PMID:12005916

  13. The inverse electroencephalography pipeline

    NASA Astrophysics Data System (ADS)

    Weinstein, David Michael

    The inverse electroencephalography (EEG) problem is defined as determining which regions of the brain are active based on remote measurements recorded with scalp EEG electrodes. An accurate solution to this problem would benefit both fundamental neuroscience research and clinical neuroscience applications. However, constructing accurate patient-specific inverse EEG solutions requires complex modeling, simulation, and visualization algorithms, and to date only a few systems have been developed that provide such capabilities. In this dissertation, a computational system for generating and investigating patient-specific inverse EEG solutions is introduced, and the requirements for each stage of this Inverse EEG Pipeline are defined and discussed. While the requirements of many of the stages are satisfied with existing algorithms, others have motivated research into novel modeling and simulation methods. The principal technical results of this work include novel surface-based volume modeling techniques, an efficient construction for the EEG lead field, and the Open Source release of the Inverse EEG Pipeline software for use by the bioelectric field research community. In this work, the Inverse EEG Pipeline is applied to three research problems in neurology: comparing focal and distributed source imaging algorithms; separating measurements into independent activation components for multifocal epilepsy; and localizing the cortical activity that produces the P300 effect in schizophrenia.

  14. Direct and indirect inversions

    NASA Astrophysics Data System (ADS)

    Virieux, Jean; Brossier, Romain; Métivier, Ludovic; Operto, Stéphane; Ribodetti, Alessandra

    2016-06-01

    A bridge is highlighted between the direct inversion and the indirect inversion. They are based on fundamental different approaches: one is looking after a projection from the data space to the model space while the other one is reducing a misfit between observed data and synthetic data obtained from a given model. However, it is possible to obtain similar structures for model perturbation, and we shall focus on P-wave velocity reconstruction. This bridge is built up through the Born approximation linearizing the forward problem with respect to model perturbation and through asymptotic approximations of the Green functions of the wave propagation equation. We first describe the direct inversion and its ingredients and then we focus on a specific misfit function design leading to a indirect inversion. Finally, we shall compare this indirect inversion with more standard least-squares inversion as the FWI, enabling the focus on small weak velocity perturbations on one side and the speed-up of the velocity perturbation reconstruction on the other side. This bridge has been proposed by the group led by Raul Madariaga in the early nineties, emphasizing his leading role in efficient imaging workflows for seismic velocity reconstruction, a drastic requirement at that time.

  15. Improving antiangiogenesis and anti-tumor activity of curcumin by biodegradable polymeric micelles.

    PubMed

    Gong, Changyang; Deng, Senyi; Wu, Qinjie; Xiang, Mingli; Wei, Xiawei; Li, Ling; Gao, Xiang; Wang, Bilan; Sun, Lu; Chen, Yishan; Li, Yuchen; Liu, Lei; Qian, Zhiyong; Wei, Yuquan

    2013-01-01

    For developing aqueous formulation and improving anti-tumor activity of curcumin (Cur), we prepared Cur encapsulated MPEG-PCL micelles by solid dispersion method without using any surfactants or toxic organic solvent. Cur micelles could be lyophilized into powder form without any cryoprotector or excipient, and the re-dissolved Cur micelles are homogenous and stable. Molecular modeling study suggested that Cur tended to interact with PCL serving as a core embraced by PEG as a shell. After Cur was encapsulated into polymeric micelles, cytotoxicity and cellular uptake were both increased. Cur micelles had a stronger inhibitory effect on proliferation, migration, invasion, and tube formation of HUVECs than free Cur. Besides, Cur micelles showed a sustained in vitro release behavior and slow extravasation from blood vessels in transgenic zebrafish model. Embryonic angiogenesis and tumor-induced angiogenesis were both dramatically inhibited by Cur micelles in transgenic zebrafish model. Furthermore, Cur micelles were more effective in inhibiting tumor growth and prolonged survival in both subcutaneous and pulmonary metastatic LL/2 tumor models. In pharmacokinetic and tissue distribution studies, Cur micelles showed higher concentration and longer retention time in plasma and tumors. Our findings suggested that Cur micelles may have promising applications in pulmonary carcinoma therapy. PMID:23164423

  16. Cytotoxicity and internalization of Pluronic micelles stabilized by core cross-linking.

    PubMed

    Arranja, Alexandra; Schroder, André P; Schmutz, Marc; Waton, Gilles; Schosseler, François; Mendes, Eduardo

    2014-12-28

    A UV-cross-linkable agent was incorporated and polymerized in Pluronic micelle core to create an interpenetrating polymer network (IPN) of poly(pentaerythritol tetraacrylate). This stabilization prevented micelle disruption below the critical micelle temperature (CMT) and concentration (CMC), while maintaining the integrity of the PEO corona and the hydrophobic properties of the PPO core. The prepared stabilized spherical micelles of Pluronic P94 and F127 presented hydrodynamic diameters ranging from 40 to 50 nm. The stability of cross-linked Pluronic micelles at 37 °C in the presence of serum proteins was studied and no aggregation of the micelles was observed, revealing the colloidal stability of the system. Cytotoxicity experiments in NIH/3T3 mouse fibroblasts revealed that the presence of the cross-linking agent did not induce any further toxicity in comparison to the respective pure polymer solutions. Furthermore, stabilized micelles of Pluronic P94 were shown to be less toxic than the polymer itself. A hydrophobic fluorescent probe (Nile red) was absorbed in the cross-linked core of pre-stabilized micelles to mimic the incorporation of a poorly water-soluble drug, and the internalization and intracellular localization of Nile red was studied by confocal microscopy at different incubation times. Overall, the results indicate that Pluronic micelles stabilized by core cross-linking are capable of delivering hydrophobic components physically entrapped in the micelles, thus making them a potential candidate as a delivery platform for imaging or therapy of cancer. PMID:25307996

  17. Mesoscale Simulations and Experimental Studies of pH-Sensitive Micelles for Controlled Drug Delivery.

    PubMed

    Wang, Yan; Li, Qiu Yu; Liu, Xu Bo; Zhang, Can Yang; Wu, Zhi Min; Guo, Xin Dong

    2015-11-25

    The microstructures of doxorubicin-loaded micelles prepared from block polymers His(x)Lys10 (x = 0, 5, 10) conjugated with docosahexaenoic acid (DHA) are investigated under different pH conditions, using dissipative particle dynamics (DPD) simulations. The conformation of micelles and the DOX distributions in micelles were obviously influenced by pH values and the length of the histidine segment. At pH >6.0, the micelles self-assembled from the polymers were dense and compact. The drugs were entrapped well within the micellar core. The particle size increases as the histidine length increases. With the decrease of pH value to be lower than 6.0, there was no distinct difference for the micelles self-assembled from the polymer without histidine residues. However, the micelles prepared from the polymers with histidine residues shows a structural transformation from dense to swollen conformation, leading to an increased particle size from 10.3 to 14.5 DPD units for DHD-His10Lys10 micelles. This structural transformation of micelles can accelerate the DOX release from micelles under lower pH conditions. The in vitro drug release from micelles is accelerated by the decrease of pH value from 7.4 (physiological environment) to 5.0 (lysosomal environment). The integration of simulation and experiments might be a valuable method for the optimization and design of biomaterials for drug delivery with desired properties. PMID:26539742

  18. Characterizing interfacial friction in bis(2-ethylhexyl) sodium sulfosuccinate reverse micelles from photoisomerization studies of carbocyanine derivatives

    SciTech Connect

    Gangamallaiah, V.; Dutt, G. B.

    2011-01-14

    Photoisomerization of two carbocyanine derivatives has been examined in bis(2-ethylhexyl) sodium sulfosuccinate (AOT) reverse micelles to understand the factors that govern this process in the interfacial region of organized assemblies. To this effect, fluorescence lifetimes and quantum yields of 3,3{sup '}-diethyloxadicarbocyanine iodide and merocyanine 540 have been measured in AOT/isooctane/water and AOT/cyclohexane/water reverse micellar systems as a function of the mole ratio of water to the surfactant, W. The nonradiative rate constants, which have been identified as the rates of photoisomerization for these solutes, were obtained from the experimentally measured parameters. The steady rise and subsequent saturation observed in the nonradiative rate constants upon increasing W has been rationalized in terms of micellar packing. An inverse correlation has been obtained between the nonradiative rate constants and the critical packing parameter, indicating that the interfacial friction experienced by the solute molecule is essentially described by this parameter.

  19. Characterizing interfacial friction in bis(2-ethylhexyl) sodium sulfosuccinate reverse micelles from photoisomerization studies of carbocyanine derivatives.

    PubMed

    Gangamallaiah, V; Dutt, G B

    2011-01-14

    Photoisomerization of two carbocyanine derivatives has been examined in bis(2-ethylhexyl) sodium sulfosuccinate (AOT) reverse micelles to understand the factors that govern this process in the interfacial region of organized assemblies. To this effect, fluorescence lifetimes and quantum yields of 3,3(')-diethyloxadicarbocyanine iodide and merocyanine 540 have been measured in AOT∕isooctane∕water and AOT∕cyclohexane∕water reverse micellar systems as a function of the mole ratio of water to the surfactant, W. The nonradiative rate constants, which have been identified as the rates of photoisomerization for these solutes, were obtained from the experimentally measured parameters. The steady rise and subsequent saturation observed in the nonradiative rate constants upon increasing W has been rationalized in terms of micellar packing. An inverse correlation has been obtained between the nonradiative rate constants and the critical packing parameter, indicating that the interfacial friction experienced by the solute molecule is essentially described by this parameter. PMID:21241145

  20. Characterizing interfacial friction in bis(2-ethylhexyl) sodium sulfosuccinate reverse micelles from photoisomerization studies of carbocyanine derivatives

    NASA Astrophysics Data System (ADS)

    Gangamallaiah, V.; Dutt, G. B.

    2011-01-01

    Photoisomerization of two carbocyanine derivatives has been examined in bis(2-ethylhexyl) sodium sulfosuccinate (AOT) reverse micelles to understand the factors that govern this process in the interfacial region of organized assemblies. To this effect, fluorescence lifetimes and quantum yields of 3,3'-diethyloxadicarbocyanine iodide and merocyanine 540 have been measured in AOT/isooctane/water and AOT/cyclohexane/water reverse micellar systems as a function of the mole ratio of water to the surfactant, W. The nonradiative rate constants, which have been identified as the rates of photoisomerization for these solutes, were obtained from the experimentally measured parameters. The steady rise and subsequent saturation observed in the nonradiative rate constants upon increasing W has been rationalized in terms of micellar packing. An inverse correlation has been obtained between the nonradiative rate constants and the critical packing parameter, indicating that the interfacial friction experienced by the solute molecule is essentially described by this parameter.

  1. Polymeric micelles and nanoemulsions as drug carriers: Therapeutic efficacy, toxicity, and drug resistance.

    PubMed

    Gupta, Roohi; Shea, Jill; Scafe, Courtney; Shurlygina, Anna; Rapoport, Natalya

    2015-08-28

    The manuscript reports the side-by-side comparison of therapeutic properties of polymeric micelles and nanoemulsions generated from micelles. The effect of the structure of a hydrophobic block of block copolymer on the therapeutic efficacy, tumor recurrence, and development of drug resistance was studied in pancreatic tumor bearing mice. Mice were treated with paclitaxel (PTX) loaded poly(ethylene oxide)-co-polylactide micelles or corresponding perfluorocarbon nanoemulsions. Two structures of the polylactide block differing in a physical state of micelle cores or corresponding nanodroplet shells were compared. Poly(ethylene oxide)-co-poly(d,l-lactide) (PEG-PDLA) formed micelles with elastic amorphous cores while poly(ethylene oxide)-co-poly(l-lactide) (PEG-PLLA) formed micelles with solid crystalline cores. Micelles and nanoemulsions stabilized with PEG-PDLA copolymer manifested higher therapeutic efficacy than those formed with PEG-PLLA copolymer studied earlier. Better performance of PEG-PDLA micelles and nanodroplets was attributed to the elastic physical state of micelle cores (or droplet shells) allowing adequate rate of drug release via drug diffusion and/or copolymer biodegradation. The biodegradation of PEG-PDLA stabilized nanoemulsions was monitored by the ultrasonography of nanodroplets injected directly into the tumor; the PEG-PDLA stabilized nanodroplets disappeared from the injection site within 48h. In contrast, nanodroplets stabilized with PEG-PLLA copolymer were preserved at the injection site for weeks and months indicating extremely slow biodegradation of solid PLLA blocks. Multiple injections of PTX-loaded PEG-PDLA micelles or nanoemulsions to pancreatic tumor bearing mice resulted in complete tumor resolution. Two of ten tumors treated with either PEG-PDLA micellar or nanoemulsion formulation recurred after the completion of treatment but proved sensitive to the second treatment cycle indicating that drug resistance has not been developed. This

  2. Electromagnetic inverse scattering

    NASA Technical Reports Server (NTRS)

    Bojarski, N. N.

    1972-01-01

    A three-dimensional electromagnetic inverse scattering identity, based on the physical optics approximation, is developed for the monostatic scattered far field cross section of perfect conductors. Uniqueness of this inverse identity is proven. This identity requires complete scattering information for all frequencies and aspect angles. A nonsingular integral equation is developed for the arbitrary case of incomplete frequence and/or aspect angle scattering information. A general closed-form solution to this integral equation is developed, which yields the shape of the scatterer from such incomplete information. A specific practical radar solution is presented. The resolution of this solution is developed, yielding short-pulse target resolution radar system parameter equations. The special cases of two- and one-dimensional inverse scattering and the special case of a priori knowledge of scatterer symmetry are treated in some detail. The merits of this solution over the conventional radar imaging technique are discussed.

  3. Protein structures in SDS micelle-protein complexes.

    PubMed Central

    Parker, W; Song, P S

    1992-01-01

    Sodium dodecyl sulfate (SDS) is used more often than any other detergent as an excellent denaturing or "unfolding" detergent. However, formation of ordered structure (alpha-helix or beta-sheet) in certain peptides is known to be induced by interaction with SDS micelles. The SDS-induced structures formed by these peptides are amphiphilic, having both a hydrophobic and a hydrophilic face. Previous work in this area has revealed that SDS induces helical folding in a wide variety of non-helical proteins. Here, we describe the interaction of several structurally unrelated proteins with SDS micelles and the correlation of these structures to helical amphiphilic regions present in the primary sequence. It is likely that the ability of native nonordered protein structures to form induced amphiphilic ordered structures is rather common. PMID:1600087

  4. A Pyrene@Micelle Sensor for Fluorescent Oxygen Sensing

    PubMed Central

    Yuan, Yan-xia; Peng, Hong-shang; Ping, Jian-tao; Wang, Xiao-hui; You, Fang-tian

    2015-01-01

    For most fluorescent oxygen sensors developed today, their fabrication process is either time-consuming or needs specialized knowledge. In this work, a robust fluorescent oxygen sensor is facilely constructed by dissolving pyrene molecules into CTAB aqueous solution. The as-prepared pyrene@micelle sensors have submicron-sized diameter, and the concentration of utilized pyrene can be reduced as low as 0.8 mM but still can exhibit dominant excimer emission. The excimer fluorescence is sensitive to dissolved oxygen in both intensity and lifetime, and the respective Stern-Volmer plot follows a nonlinear behavior justified by a two-site model. Because of the merits of large Stokes shift (~140 nm), easy fabrication, and robustness, the pyrene@micelle sensors are very attractive for practical determination of oxygen. PMID:26539471

  5. SYNTHESIS AND CHARACTERIZATION OF SUBSTITUTED POLY(STYRENE)-b-POLY(ACRYLIC ACID) BLOCK COPOLYMER MICELLES

    SciTech Connect

    Pickel, Deanna L; Pickel, Joseph M; Devenyi, Jozsef; Britt, Phillip F

    2009-01-01

    Block copolymer micelle synthesis and characterization has been extensively studied. In particular, most studies have focused on the properties of the hydrophilic corona due to the micelle corona structure s impact on the biodistribution and biocompatibility. Unfortunately, less attention has been given to the effect of the core block on the micelle stability, morphology, and the rate of diffusion of small molecules from the core. This investigation is focused on the synthesis of block copolymers composed of meta-substituted styrenes and acrylic acid by Atom Transfer Radical Polymerization. Micelles with cores composed of substituted styrenes having Tgs ranging from -30 to 100 oC have been prepared and the size and shape of these micelles were characterized by Static and Dynamic Light Scattering and TEM. In addition, the critical micelle concentration and rate of diffusion of small molecules from the core were determined by fluorimetry using pyrene as the probe.

  6. Time-resolved SANS studies on block copolymer micelles with varying core-solvent interactions

    NASA Astrophysics Data System (ADS)

    Cooksey, Tyler; Singh, Avantika; Marquez, Maria; Robertson, Megan

    The self-assembly of block copolymer micelles occurs through a relaxation process dominated by the exchange of individual polymer chains. The objective of this work is to probe the single chain exchange of block copolymer micelles with varying core-solvent interactions, utilizing time-resolved neutron scattering (TR-SANS). The interactions between the core-forming polymer and the solvent has many implications for the micelle structure, including the aggregation number, micelle size, and interfacial tension. However, few studies have investigated the effect of the core polymer-solvent interactions on the dynamics of micelle formation. We will focus our study on poly(epsilon-caprolactone-block-ethylene oxide) block copolymers forming micelle structures in mixtures of water and tetrahydrofuran (THF). It was observed that changing the THF concentration, which varies the degree of repulsion between the core and solvent, greatly influences the single chain exchange rate in this system.

  7. Synthesis and Biological Properties of Porphyrin-Containing Polymeric Micelles with Different Sizes.

    PubMed

    Zhang, Jialiang; Zhang, Zhengkui; Yu, Bo; Wang, Chen; Wu, Wei; Jiang, Xiqun

    2016-03-01

    To understand the size effect of polymeric micelles on their biological properties, such as cellular uptake, biodistribution, tumor accumulation, and so on, we prepared a series of doxorubicin (DOX)-loaded protoporphyrin (PP)-poly(ε-caprolactone) (PCL)-poly(ethylene glycol) (PEG) micelles with different diameters (40, 70, 100, and 130 nm). The incorporation of the protoporphyrin moiety enhanced the stability of the micelles and provided luminescent capability that is useful in the investigation of the cellular uptake of the micelles by fluorescence imaging. The biodistributions of the micelles in mice bearing tumors were evaluated by near-infrared fluorescence imaging and DOX concentration measurements in different tissues. The in vitro and in vivo investigations demonstrated the pronounced dependence of the cellular uptake, biodistribution, and antitumor effectiveness of the micelles on their size. PMID:26894502

  8. Efficient inhibition of colorectal peritoneal carcinomatosis by drug loaded micelles in thermosensitive hydrogel composites

    NASA Astrophysics Data System (ADS)

    Gong, Changyang; Wang, Cheng; Wang, Yujun; Wu, Qinjie; Zhang, Doudou; Luo, Feng; Qian, Zhiyong

    2012-05-01

    In this work, we aim to develop a dual drug delivery system (DDDS) of self-assembled micelles in thermosensitive hydrogel composite to deliver hydrophilic and hydrophobic drugs simultaneously for colorectal peritoneal carcinomatosis (CRPC) therapy. In our previous studies, we found that poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) (PCEC) copolymers with different molecular weight and PEG/PCL ratio could be administered to form micelles or thermosensitive hydrogels, respectively. Therefore, the DDDS was constructed from paclitaxel (PTX) encapsulated PCEC micelles (PTX-micelles) and a fluorouracil (Fu) loaded thermosensitive PCEC hydrogel (Fu-hydrogel). PTX-micelles were prepared by self-assembly of biodegradable PCEC copolymer (Mn = 3700) and PTX without using any surfactants or excipients. Meanwhile, biodegradable and injectable thermosensitive Fu-hydrogel (Mn = 3000) with a lower sol-gel transition temperature at around physiological temperature was also prepared. The obtained PTX-micelles in thermosensitive Fu-hydrogel (PTX-micelles-Fu-hydrogel) composite is a free-flowing sol at ambient temperature and rapidly turned into a non-flowing gel at physiological temperature. In addition, the results of cytotoxicity, hemolytic study, and acute toxicity evaluation suggested that the PTX-micelles-Fu-hydrogel was non-toxic and biocompatible. In vitro release behaviors of PTX-micelles-Fu-hydrogel indicated that both PTX and Fu have a sustained release behavior. Furthermore, intraperitoneal application of PTX-micelles-Fu-hydrogel effectively inhibited growth and metastasis of CT26 peritoneal carcinomatosis in vivo (p < 0.001), and induced a stronger antitumor effect than that of Taxol® plus Fu (p < 0.001). The pharmacokinetic study indicated that PTX-micelles-Fu-hydrogel significantly increased PTX and Fu concentration and residence time in peritoneal fluids compared with Taxol® plus Fu group. Thus, the results suggested the micelles-hydrogel DDDS may

  9. Development of the simple and sensitive method for lipoxygenase assay in AOT/isooctane reversed micelles.

    PubMed

    Park, Kyung Min; Kim, Yu Na; Choi, Seung Jun; Chang, Pahn-Shick

    2013-06-01

    In this study, we investigated the possibility of reversed micelles, widely used as an enzyme reactor for lipases, for the determination of lipoxygenase activity. Although it is rapid and simple, reversed micelles have some limitations, such as interference by UV-absorbing materials and surfactant. Lipoxygenase activity in the reversed micelles was determined by reading the absorbance of the lipid hydroperoxidation product (conjugated diene) at 234 nm. Among surfactants and organic media, AOT and isooctane were most effective for the dioxygenation of linoleic acid in reversed micelles. The strong absorbance of AOT in the UV region is a major obstacle for the direct application of the AOT/isooctane reversed micelles to lipoxygenase activity determination. To prevent interference by AOT, we added an AOT removal step in the procedure for lipoxygenase activity determination in reversed micelles. The lipoxygenase activity was dependent on water content, and maximum activity was obtained at an R-value of 10. PMID:23411168

  10. PEGylated Albumin-Based Polyion Complex Micelles for Protein Delivery.

    PubMed

    Jiang, Yanyan; Lu, Hongxu; Chen, Fan; Callari, Manuela; Pourgholami, Mohammad; Morris, David L; Stenzel, Martina H

    2016-03-14

    An increasing amount of therapeutic agents are based on proteins. However, proteins as drug have intrinsic problems such as their low hydrolytic stability. Delivery of proteins using nanoparticles has increasingly been the focus of interest with polyion complex micelles, prepared from charged block copolymer and the oppositely charged protein, as an example of an attractive carrier for proteins. Inspired by this approach, a more biocompatible pathway has been developed here, which replaces the charged synthetic polymer with an abundant protein, such as albumin. Although bovine serum albumin (BSA) was observed to form complexes with positively charged proteins directly, the resulting protein nanoparticle were not stable and aggregated to large precipitates over the course of a day. Therefore, maleimide functionalized poly(oligo (ethylene glycol) methyl ether methacrylate) (MI-POEGMEMA) (Mn = 26000 g/mol) was synthesized to generate a polymer-albumin conjugate, which was able to condense positively charged proteins, here lysozyme (Lyz) as a model. The PEGylated albumin polyion complex micelle with lysozyme led to nanoparticles between 15 and 25 nm in size depending on the BSA to Lyz ratio. The activity of the encapsulated protein was tested using Sprouty 1 (C-12; Spry1) proteins, which can act as an endogenous angiogenesis inhibitor. Condensation of Spry1 with the PEGylated albumin could improve the anticancer efficacy of Spry1 against the breast cancer cells lowering the IC50 value of the protein. Furthermore, the high anticancer efficacy of the POEGMEMA-BSA/Spry1 complex micelle was verified by effectively inhibiting the growth of three-dimensional MCF-7 multicellular tumor spheroids. The PEGylated albumin complex micelle has great potential as a drug delivery vehicle for a new generation of cancer pharmaceuticals. PMID:26809948

  11. Interplay between micelle formation and waterlike phase transitions

    NASA Astrophysics Data System (ADS)

    Heinzelmann, G.; Figueiredo, W.; Girardi, M.

    2010-02-01

    A lattice model for amphiphilic aggregation in the presence of a structured waterlike solvent is studied through Monte Carlo simulations. We investigate the interplay between the micelle formation and the solvent phase transition in two different regions of temperature-density phase diagram of pure water. A second order phase transition between the gaseous (G) and high density liquid (HDL) phases that occurs at very high temperatures, and a first order phase transition between the low density liquid (LDL) and (HDL) phases that takes place at lower temperatures. In both cases, we find the aggregate size distribution curve and the critical micellar concentration as a function of the solvent density across the transitions. We show that micelle formation drives the LDL-HDL first order phase transition to lower solvent densities, while the transition G-HDL is driven to higher densities, which can be explained by the markedly different degrees of micellization in both cases. The diffusion coefficient of surfactants was also calculated in the LDL and HDL phases, changing abruptly its behavior due to the restructuring of waterlike solvent when we cross the first order LDL-HDL phase transition. To understand such behavior, we calculate the solvent density and the number of hydrogen bonds per water molecule close to micelles. The curves of the interfacial solvent density and the number of hydrogen bonds per water molecule in the first hydration signal a local phase change of the interfacial water, clarifying the diffusion mechanism of free surfactants in the solvent.

  12. Thermoresponsive magnetic micelles for simultaneous magnetic hyperthermia and drug delivery.

    SciTech Connect

    Kim, D.-H.; Rozhkova, E. A.; Rajh, T.; Bader, S. D.; Novosad, V.

    2009-05-18

    Hyperthermia has been shown to be a potentially effective therapeutic modality in cancer treatment as it intensifies the efficacy of chemotherapy. The hyperthermia has a good synergic effect with chemotherapy. Their sensitivity to chemotherapy after hyperthermia treatment is increased. Therefore, a simultaneous hyperthermia and chemotherapy can be a new approach for cancer treatment. Multifunctional magnetic nanoparticles with thermoresponsive polymer allowed the simultaneous cancer therapy because the functions of thermo triggered drug release and heating for hyperthermia can be performed simultaneously by applied magnetic field. In our study, magnetic nanoparticles loaded thermoresponsive micelles were synthesized for the simultaneous magnetic hyperthermia and chemotherapy. The micelles made of amphiphilic block copolymer of poly(N-isopropylacrylamide-co-acrylamide)-block-poly(e-caprolaction), P(NIPAAm-co-AAm)-b-PCL, were combined with magnetic nanoparticles and drug which are self-assembled at the hydrophobic core. We synthesized iron oxide nanoparticles having a narrow size distribution of 6 nm by the high-temperature diol reduction in benzyl ether. The amphiphilic block copolymer, P(NIPAAm-co-AAm)-b-PCL was synthesized by radical polymerization for copolymer and ring opening polymerization for block copolymer, respectively. Iron oxide loaded thermoresponsive micelles were formed by solvent-evaporation method. Simultaneous heating and drug release was demonstrated with the anticancer drug doxorubicin.

  13. Predicting proton titration in cationic micelle and bilayer environments

    SciTech Connect

    Morrow, Brian H.; Shen, Jana K.; Eike, David M.; Murch, Bruce P.; Koenig, Peter H.

    2014-08-28

    Knowledge of the protonation behavior of pH-sensitive molecules in micelles and bilayers has significant implications in consumer product development and biomedical applications. However, the calculation of pK{sub a}’s in such environments proves challenging using traditional structure-based calculations. Here we apply all-atom constant pH molecular dynamics with explicit ions and titratable water to calculate the pK{sub a} of a fatty acid molecule in a micelle of dodecyl trimethylammonium chloride and liquid as well as gel-phase bilayers of diethyl ester dimethylammonium chloride. Interestingly, the pK{sub a} of the fatty acid in the gel bilayer is 5.4, 0.4 units lower than that in the analogous liquid bilayer or micelle, despite the fact that the protonated carboxylic group is significantly more desolvated in the gel bilayer. This work illustrates the capability of all-atom constant pH molecular dynamics in capturing the delicate balance in the free energies of desolvation and Coulombic interactions. It also shows the importance of the explicit treatment of ions in sampling the protonation states. The ability to model dynamics of pH-responsive substrates in a bilayer environment is useful for improving fabric care products as well as our understanding of the side effects of anti-inflammatory drugs.

  14. Chain exchange kinetics of block copolymer micelles in ionic liquids

    NASA Astrophysics Data System (ADS)

    Ma, Yuanchi; Lodge, Timothy

    The chain exchange kinetics of block copolymer micelles has been studied using time-resolved small-angle neutron scattering (TR-SANS), a key tool in determining the average micelle composition in contrast-matched solvents. In this work, PMMA-block-PnBMA was selected as the model block copolymer, which has a LCST behavior in the common ionic liquids, [EMIM][TFSI] and [BMIM][TFSI]. We examined the chain exchange kinetics of three PMMA-block-PnBMA copolymers, with identical PMMA block length (MPMMA = 25000) and different PnBMA block lengths (MPnBMA = 24000, 35000 and 53000); the Flory-Huggins interaction parameter (χ) between the core (PnBMA) and the solvent were varied by mixing [EMIM][TFSI] and [BMIM][TFSI] in different ratios. We found that the relaxation of the initial segregation of h- and d- micelles followed the same form with the time as previously developed by our group. Assuming that single chain expulsion is the rate limiting step, the thermal barrier was found to depend linearly on the core block length (Ncore) . Furthermore, the effect of χ on the chain exchange kinetics will also be discussed.

  15. Micelles and Nanoparticles for Ultrasonic Drug and Gene Delivery

    PubMed Central

    Husseini, Ghaleb A.; Pitt, William G.

    2008-01-01

    Drug delivery research employing micelles and nanoparticles has expanded in recent years. Of particular interest is the use of these nanovehicles that deliver high concentrations of cytotoxic drugs to diseased tissues selectively, thus reducing the agent’s side effects on the rest of the body. Ultrasound, traditionally used in diagnostic medicine, is finding a place in drug delivery in connection with these nanoparticles. In addition to their non-invasive nature and the fact that they can be focused on targeted tissues, acoustic waves have been credited with releasing pharmacological agents from nanocarriers, as well as rendering cell membranes more permeable. In this article, we summarize new technologies that combine the use of nanoparticles with acoustic power both in drug and gene delivery. Ultrasonic drug delivery from micelles usually employs polyether block copolymers, and has been found effective in vivo for treating tumors. Ultrasound releases drug from micelles, most probably via shear stress and shock waves from collapse of cavitation bubbles. Liquid emulsions and solid nanoparticles are used with ultrasound to deliver genes in vitro and in vivo. The small packaging allows nanoparticles to extravasate into tumor tissues. Ultrasonic drug and gene delivery from nano-carriers has tremendous potential because of the wide variety of drugs and genes that could be delivered to targeted tissues by fairly non-invasive means. PMID:18486269

  16. Polymeric micelles encapsulating photosensitizer: structure/photodynamic therapy efficiency relation.

    PubMed

    Gibot, Laure; Lemelle, Arnaud; Till, Ugo; Moukarzel, Béatrice; Mingotaud, Anne-Françoise; Pimienta, Véronique; Saint-Aguet, Pascale; Rols, Marie-Pierre; Gaucher, Mireille; Violleau, Frédéric; Chassenieux, Christophe; Vicendo, Patricia

    2014-04-14

    Various polymeric micelles were formed from amphiphilic block copolymers, namely, poly(ethyleneoxide-b-ε-caprolactone), poly(ethyleneoxide-b-d,l-lactide), and poly(ethyleneoxide-b-styrene). The micelles were characterized by static and dynamic light scattering, electron microscopy, and asymmetrical flow field-flow fractionation. They all displayed a similar size close to 20 nm. The influence of the chemical structure of the block copolymers on the stability upon dilution of the polymeric micelles was investigated to assess their relevance as carriers for nanomedicine. In the same manner, the stability upon aging was assessed by FRET experiments under various experimental conditions (alone or in the presence of blood proteins). In all cases, a good stability over 48 h for all systems was encountered, with PDLLA copolymer-based systems being the first to release their load slowly. The cytotoxicity and photocytotoxicity of the carriers were examined with or without their load. Lastly, the photodynamic activity was assessed in the presence of pheophorbide a as photosensitizer on 2D and 3D tumor cell culture models, which revealed activity differences between the 2D and 3D systems. PMID:24552313

  17. Dose rate dependency of micelle leucodye 3D gel dosimeters

    NASA Astrophysics Data System (ADS)

    Vandecasteele, J.; Ghysel, S.; De Deene, Y.

    2010-11-01

    Recently a novel 3D radiochromic gel dosimeter was introduced which uses micelles to dissolve a leucodye in a gelatin matrix. Experimental results show that this 3D micelle gel dosimeter was found to be dose rate dependent. A maximum difference in optical dose sensitivity of 70% was found for dose rates between 50 cGy min-1 and 400 cGy min-1. A novel composition of 3D radiochromic dosimeter is proposed composed of gelatin, sodium dodecyl sulphate, chloroform, trichloroacetic acid and leucomalachite green. The novel gel dosimeter formulation exhibits comparable radio-physical properties in respect to the composition previously proposed. Nevertheless, the novel formulation was found to be still dose rate dependent. A maximum difference of 33% was found for dose rates between 50 cGy min-1 and 400 cGy min-1. On the basis of these experimental results it is concluded that the leucodye micelle gel dosimeter is still unsatisfactory for clinical radiation therapy dose verifications. Some insights in the physico-chemical mechanisms were obtained and are discussed.

  18. Negative adsorption due to electrostatic exclusion of micelles.

    PubMed

    Somasundaran, P; Ananthapadmanabhan, K P; Deo, Puspendu

    2005-10-15

    Interactions of surfactants with solid substrates are important in the controlling of processes such as flotation, coating, flocculation and sedimentation. These interactions usually lead to adsorption on solids, but can also result in an exclusion of the reagents with dire consequences. In this work electrostatic exclusion of negatively charged dodecylbenzene sulfonate micelles from quartz/water, Bio-Sil/water and alumina/water interfaces has been investigated as a function of pH and ionic strength. Measurable negative adsorption of these surfactants from similarly charged solid/liquid interface was observed in the micellar region. In the case of porous samples with large surface area, comparison of pore size with the micelle size is necessary to avoid any erroneous conclusions regarding the role of electrostatic exclusion in a given system. A theoretical model for the electrostatic exclusion of micelles is developed and used to calculate the adsorption of negatively charged dodecylbenzene sulfonate on negatively charged quartz (pH 7), silica (Bio-Sil A, pH 3) and alumina (pH 11) in the micellar concentration region. The micellar exclusion values calculated using the model are in excellent agreement with the experimental results. PMID:16153903

  19. Light-responsive viscoelastic fluids based on anionic wormlike micelles.

    PubMed

    Lu, Yechang; Zhou, Tengfei; Fan, Qing; Dong, Jinfeng; Li, Xuefeng

    2013-12-15

    A new class of light-responsive viscoelastic fluids based on anionic wormlike micelles is reported. The key components are sodium oleate (NaOA) and a cationic azobenzene dye, 1-[2-(4-phenylazo-phenoxy)-ethyl]-3-methylimidazolium bromide (C0AZOC2IMB). These binary systems are gel-like fluids at certain concentration ratios of [C0AZOC2IMB]/[NaOA], e.g. 35/100, owing to the formation of long, entangled wormlike micelles. The viscosity of these fluids can be controlled reversibly by light due to photo isomerization between trans-C0AZOC2IMB and cis-C0AZOC2IMB. For example, the zero-shear viscosity (η0) of an originally gel-like sample is high up to ~1300 Pa s when C0AZOC2IMB is in its trans from, whereas the mixture becomes a Newtonian fluid with η0 about 0.01 Pa s after UV light irradiation. For the post-irradiated cis-C0AZOC2IMB, short cylindrical micelles form, hence accounting for the lower viscosity. Evidence for the structural transition is provided by UV-vis spectra, rheology, (1)H NMR and cryo-transmission electronic microscopy measurements. PMID:24144381

  20. Beyond Spherical Micelles in Styrene-Isoprene Block Copolymer Solutions

    NASA Astrophysics Data System (ADS)

    Bang, Joona; Lodge, Timothy P.

    2004-03-01

    As macromolecular surfactants, block copolymers have been shown to self-assemble into various microstructures. Many studies have focused on aqueous systems, in which the strongly amphiphilic characteristics of the polymers lead to various micellar shapes (worms, vesicles, compound micelles, etc). However, such micellar shape changes are apparently very rare in organic systems. We report systematic shape changes of the micelles in styrene-isoprene block copolymer solutions. Remarkably, such changes could be accomplished in a single block copolymer by varying the solvent selectivity. We studied two asymmetric poly(styrene-b-isoprene) diblock copolymers with the styrene volume fractions of approximately 0.15 in a series of solvents with varying styrene selectivity, dibuthyl phthalate, diethyl phthalate, and dimethyl phthalate. The degree of the solvent selectivity was adjusted by mixing two solvents. With increasing solvent selectivity, the micellar shape changes from cylindrical micelles to bilayer vesicles, and then phase-separates, reflecting the changing interfacial curvature induced by solvent selectivity. The detailed micellar morphologies were characterized by dynamic light scattering, rheology, electron microscopy, and small angle x-ray scattering.

  1. Nanoparticle Contrast Agents for Computed Tomography: A Focus on Micelles

    PubMed Central

    Cormode, David P.; Naha, Pratap C.; Fayad, Zahi A.

    2014-01-01

    Computed tomography (CT) is an X-ray based whole body imaging technique that is widely used in medicine. Clinically approved contrast agents for CT are iodinated small molecules or barium suspensions. Over the past seven years there has been a great increase in the development of nanoparticles as CT contrast agents. Nanoparticles have several advantages over small molecule CT contrast agents, such as long blood-pool residence times, and the potential for cell tracking and targeted imaging applications. Furthermore, there is a need for novel CT contrast agents, due to the growing population of renally impaired patients and patients hypersensitive to iodinated contrast. Micelles and lipoproteins, a micelle-related class of nanoparticle, have notably been adapted as CT contrast agents. In this review we discuss the principles of CT image formation and the generation of CT contrast. We discuss the progress in developing non-targeted, targeted and cell tracking nanoparticle CT contrast agents. We feature agents based on micelles and used in conjunction with spectral CT. The large contrast agent doses needed will necessitate careful toxicology studies prior to clinical translation. However, the field has seen tremendous advances in the past decade and we expect many more advances to come in the next decade. PMID:24470293

  2. Predicting proton titration in cationic micelle and bilayer environments

    NASA Astrophysics Data System (ADS)

    Morrow, Brian H.; Eike, David M.; Murch, Bruce P.; Koenig, Peter H.; Shen, Jana K.

    2014-08-01

    Knowledge of the protonation behavior of pH-sensitive molecules in micelles and bilayers has significant implications in consumer product development and biomedical applications. However, the calculation of pKa's in such environments proves challenging using traditional structure-based calculations. Here we apply all-atom constant pH molecular dynamics with explicit ions and titratable water to calculate the pKa of a fatty acid molecule in a micelle of dodecyl trimethylammonium chloride and liquid as well as gel-phase bilayers of diethyl ester dimethylammonium chloride. Interestingly, the pKa of the fatty acid in the gel bilayer is 5.4, 0.4 units lower than that in the analogous liquid bilayer or micelle, despite the fact that the protonated carboxylic group is significantly more desolvated in the gel bilayer. This work illustrates the capability of all-atom constant pH molecular dynamics in capturing the delicate balance in the free energies of desolvation and Coulombic interactions. It also shows the importance of the explicit treatment of ions in sampling the protonation states. The ability to model dynamics of pH-responsive substrates in a bilayer environment is useful for improving fabric care products as well as our understanding of the side effects of anti-inflammatory drugs.

  3. Enhancing oral bioavailability of quercetin using novel soluplus polymeric micelles

    NASA Astrophysics Data System (ADS)

    Dian, Linghui; Yu, Enjiang; Chen, Xiaona; Wen, Xinguo; Zhang, Zhengzan; Qin, Lingzhen; Wang, Qingqing; Li, Ge; Wu, Chuanbin

    2014-12-01

    To improve its poor aqueous solubility and stability, the potential chemotherapeutic drug quercetin was encapsulated in soluplus polymeric micelles by a modified film dispersion method. With the encapsulation efficiency over 90%, the quercetin-loaded polymeric micelles (Qu-PMs) with drug loading of 6.7% had a narrow size distribution around mean size of 79.00 ± 2.24 nm, suggesting the complete dispersibility of quercetin in water. X-ray diffraction (XRD) patterns illustrated that quercetin was in amorphous or molecular form within PMs. Fourier transform infrared spectroscopy (FTIR) indicated that quercetin formed intermolecular hydrogen bonding with carriers. An in vitro dialysis test showed the Qu-PMs possessed significant sustained-release property, and the formulation was stable for at least 6 months under accelerated conditions. The pharmacokinetic study in beagle dogs showed that absorption of quercetin after oral administration of Qu-PMs was improved significantly, with a half-life 2.19-fold longer and a relative oral bioavailability of 286% as compared to free quercetin. Therefore, these novel soluplus polymeric micelles can be applied to encapsulate various poorly water-soluble drugs towards a development of more applicable therapeutic formulations.

  4. Multicompartment Core Micelles of Triblock Terpolymers in Organic Media

    SciTech Connect

    Schacher, Felix; Walther, Andreas; Ruppel, Markus A; Drechsler, Markus; Muller, Axel

    2009-01-01

    The formation of multicompartment micelles featuring a spheres on sphere core morphology in acetone as a selective solvent is presented. The polymers investigated are ABC triblock terpolymers, polybutadieneb-poly(2-vinyl pyridine)-b-poly(tert-butyl methacrylate) (BVT), which were synthesized via living sequential anionic polymerization in THF. Two polymers with different block lengths of the methacrylate moiety were studied with respect to the formation of multicompartmental aggregates. The micelles were analyzed by static and dynamic light scattering as well as by transmission electron microscopy. Cross-linking of the polybutadiene compartment could be accomplished via two different methods, cold vulcanization and with photopolymerization after the addition of a multifunctional acrylate. In both cases, the multicompartmental character of the micellar core is fully preserved, and the micelles could be transformed into core-stabilized nanoparticles. The successful cross-linking of the polybutadiene core is indicated by 1H NMR and by the transfer of the aggregates into nonselective solvents such as THF or dioxane.

  5. Docetaxel-loaded pluronic p123 polymeric micelles: in vitro and in vivo evaluation.

    PubMed

    Liu, Zhihong; Liu, Donghua; Wang, Lili; Zhang, Juan; Zhang, Na

    2011-01-01

    In this work, novel docetaxel (DTX) -loaded Tween 80-free Pluronic P123 (P123) micelles with improved therapeutic effect were developed. The freeze-dried DTX-loaded P123 micelles (DTX-micelles) were analyzed by HPLC, TEM and DLS to determine the DTX loading, micelle morphology, size, respectively. The in vitro cytotoxic activity of DTX-micelles in HepG2, A549 and malignant melanoma B16 cells were evaluated by MTT assay. The corresponding in vivo antitumor efficacy was assessed in Kunming mice bearing B16 tumor after intravenous administration. The DTX-loading and efficiency into the micelles were 2.12 ± 0.09% and 86.34 ± 3.32%, respectively. The DTX-micelles were spherical with a mean particle size of 50.7 nm and size distribution from 22 to 84 nm, which suggested that they should be able to selectively accumulate in solid tumors by means of EPR effect, with a zeta potential of -12.45 ± 3.24 mV. The in vitro release behavior of DTX from DTX-micelles followed the Weibull equation. Compared with Duopafei(®), DTX-micelles showed higher cytotoxicity against HepG2 (P < 0.01), A549 (P < 0.05) and B16 (P < 0.01) cells. In addition, DTX-micelles exhibited remarkable antitumor activity and reduced toxicity on B16 tumor in vivo. The tumor inhibition rates (TIR) of DTX-micelles was 91.6% versus 76.3% of Duopafei(®) (P < 0.01). These results suggested that P123 micelles might be considered as an effective DTX delivery system. PMID:21673916

  6. Mucoadhesive acrylated block copolymers micelles for the delivery of hydrophobic drugs.

    PubMed

    Eshel-Green, Tal; Bianco-Peled, Havazelet

    2016-03-01

    Blockpolymer micelles having acrylated end groups were fabricated for the development of mucoadhesive drug loaded vehicle. The critical micelle concentration (CMC) of Pluronic(®) F127 modified with acrylate end groups (F127DA) was found to be similar to that of the unmodified Pluronic(®) F127 (F127). Small angle X-ray scattering verified existence of micelles with an inner core of 4.9±0.2 and 5.5±0.3 for F127 and F127DA respectively. Indomethacin, a hydrophobic drug, was incorporated into the micelles using the thin-film hydration method. In vitro drug release assay demonstrated that the micelles sustained the release of the drug in comparison with free drug in solution. Several methods were used for mucoadhesion evaluation. Viscosity profiling was performed by shear rate sweep experiment of hydrated commercial mucin, F127 or F127DA, and combination of both mucin and a copolymer. Elevated viscosity was achieved for acrylated micelles with mucin compared to mixtures of non-acrylated micelles with mucin. The mucoadhesivity of the acrylated micelles was further characterized using nuclear magnetic resonance (NMR); data affirmed the Michael type addition reaction occurred between acrylates on the micelles corona and thiols present in the mucin. SAXS scattering data further showed a modification in the scattering of F127DA micelles with the addition of pig gastric mucin. Cryo-transmission electron microscopy (cryo-TEM) and dynamic light scattering (DLS) data detected increase in the aggregates size while using acrylated micelles enhance mucoadhesion. Thus acrylated F127DA micelles were found to be mucoadhesive, and a suitable and preferred candidate for micellar drug delivery to mucosal surfaces. PMID:26700232

  7. Atomistic Simulation of Solubilization of Polycyclic Aromatic Hydrocarbons in a Sodium Dodecyl Sulfate Micelle.

    PubMed

    Liang, Xujun; Marchi, Massimo; Guo, Chuling; Dang, Zhi; Abel, Stéphane

    2016-04-19

    Solubilization of two polycyclic aromatic hydrocarbons (PAHs), naphthalene (NAP, 2-benzene-ring PAH) and pyrene (PYR, 4-benzene-ring PAH), into a sodium dodecyl sulfate (SDS) micelle was studied through all-atom molecular dynamics (MD) simulations. We find that NAP as well as PYR could move between the micelle shell and core regions, contributing to their distribution in both regions of the micelle at any PAH concentration. Moreover, both NAP and PYR prefer to stay in the micelle shell region, which may arise from the greater volume of the micelle shell, the formation of hydrogen bonds between NAP and water, and the larger molecular volume of PYR. The PAHs are able to form occasional clusters (from dimer to octamer) inside the micelle during the simulation time depending on the PAH concentration in the solubilization systems. Furthermore, the micelle properties (i.e., size, shape, micelle internal structure, alkyl chain conformation and orientation, and micelle internal dynamics) are found to be nearly unaffected by the solubilized PAHs, which is irrespective of the properties and concentrations of PAHs. PMID:27049522

  8. Polymer Micelles with Cross-Linked Polyanion Core for Delivery of a Cationic Drug Doxorubicin

    PubMed Central

    Kim, Jong Oh; Kabanov, Alexander V.; Bronich, Tatiana K.

    2009-01-01

    Polymer micelles with cross-linked ionic cores were prepared by using block ionomer complexes of poly(ethylene oxide)-b-poly(methacrylic acid) (PEO-b-PMA) copolymer and divalent metal cations as templates. Doxorubicin (DOX), an anthracycline anticancer drug, was successfully incorporated into the ionic cores of such micelles via electrostatic interactions. A substantial drug loading level (up to 50 w/w %) was achieved and it was strongly dependent on the structure of the cross-linked micelles and pH. The drug-loaded micelles were stable in aqueous dispersions exhibiting no aggregation or precipitation for a prolonged period of time. The DOX-loaded polymer micelles exhibited noticeable pH-sensitive behavior with accelerated release of DOX in acidic environment due to the protonation of carboxylic groups in the cores of the micelles. The attempt to protect the DOX-loaded core with the polycationic substances resulted in the decrease of loading efficacy and had a slight effect on the release characteristics of the micelles. The DOX-loaded polymer micelles exhibited a potent cytotoxicity against human A2780 ovarian carcinoma cells. These results point to a potential of novel polymer micelles with cross-linked ionic cores to be attractive carriers for the delivery of DOX. PMID:19386272

  9. Solubilization of docetaxel in poly(ethylene oxide)-block-poly(butylene/styrene oxide) micelles.

    PubMed

    Elsabahy, Mahmoud; Perron, Marie-Eve; Bertrand, Nicolas; Yu, Ga-Er; Leroux, Jean-Christophe

    2007-07-01

    Poly(ethylene oxide)-block-poly(styrene oxide) (PEO-b-PSO) and PEO-b-poly(butylene oxide) (PEO-b-PBO) of different chain lengths were synthesized and characterized for their self-assembling properties in water by dynamic/static light scattering, spectrofluorimetry, and transmission electron microscopy. The resulting polymeric micelles were evaluated for their ability to solubilize and protect the anticancer drug docetaxel (DCTX) from degradation. The drug release kinetics as well as the cytotoxicity of the loaded micelles were assessed in vitro. All polymers formed micelles with a highly viscous core at low critical association concentrations (<10 mg/L). Micelle morphology depended on the nature of the hydrophobic block, with PBO- and PSO-based micelles yielding monodisperse spherical and cylindrical nanosized aggregates, respectively. The maximum solubilization capacity for DCTX ranged from 0.7 to 4.2% and was the highest for PSO micelles exhibiting the longest hydrophobic segment. Despite their high affinity for DCTX, PEO-b-PSO micelles were not able to efficiently protect DCTX against hydrolysis under accelerated stability testing conditions. Only PEO-b-PBO bearing 24 BO units afforded significant protection against degradation. In vitro, DCTX was released slower from the latter micelles, but all formulations possessed a similar cytotoxic effect against PC-3 prostate cancer cells. These data suggest that PEO-b-P(SO/BO) micelles could be used as alternatives to conventional surfactants for the solubilization of taxanes. PMID:17579476

  10. Investigation of ultrafiltration rejection of surfactant micelles by dynamic light scattering

    SciTech Connect

    Singh, R.

    1996-05-01

    The absence of nonionic surfactant micelles in ultrafiltration membrane (molecular weight cut-off = 10,000) permeates is verified with the aid of a dynamic light-scattering (DLS) technique. DLS is also used to determine the hydrodynamic radii of micelles at concentrations above the critical micelle concentration. An empirical relationship between the micelle diameter, diffusion coefficient, and a pseudomolecular weight is plotted. The relationship can be used to screen high molecular weight cut-off membranes for surfactant-based UF applications.

  11. Mixed Micelles of Doxorubicin Overcome Multidrug Resistance by Inhibiting the Expression of P-Glycoprotein.

    PubMed

    Jin, Yan; Zhang, Zhijie; Zhao, Tie; Liu, Xiaodong; Jian, Lingyan

    2015-08-01

    With the goal of overcoming multidrug resistance, DSPE-PEG (polyethylene glycol 2000 grafted with distearoyl phosphatidylethanolamine) and TPGS (d-alpha-tocopheryl polyethylene glycol 1000 succinate) were combined, each with a different inhibiting mechanism for P-glycoprotein (P-gp) expression, to create mixed micelles with the purpose of encapsulating the water-soluble drug, doxorubicin (Dox). As the molar ratio of Dox/DSPE-PEG/TPGS was 1:1:0.2, the encapsulation efficiency and particle size of the micelles were 98.2% and 12.8 nm respectively. Compared to Dox/DSPE-PEG micelles, Dox/DSPE-PEG/TPGS mixed micelles demonstrated enhanced in vitro cytotoxicity, drug uptake, and apoptosis for drug resistant H460/TaxR cancer cells. Western blot results showed that the expression level of P-gp significantly decreased as H460/TaxR cells were incubated with Dox/DSPE-PEG/TPGS mixed micelles. The anti-tumor efficacy in vivo was evaluated using H460/TaxR-bearing mice and showed that Dox/DSPE-PEG/TPGS mixed micelles were more effective at inhibiting tumor growth than Dox/DSPE-PEG micelles and free Dox solution. It was also found that the high efficacy of mixed micelles was associated with the ability to induce dramatic apoptosis of the tumor cells. In summary, through combining different P-gp inhibiting mechanisms, mixed micelles could be a promising nanocarrier for anti-cancer drugs in overcoming multidrug resistance. PMID:26295136

  12. Fabrication of novel coumarin derivative functionalized polypseudorotaxane micelles for drug delivery

    NASA Astrophysics Data System (ADS)

    Chang, Jing; Li, Yuan; Wang, Gang; He, Bin; Gu, Zhongwei

    2012-12-01

    The fabrication and drug delivery of novel polypseudorotaxane micelles with small molecule coumarin derivative as hydrophobic segment were reported. 7-Carboxymethoxy coumarin was immobilized on the terminal hydroxyl groups of poly(ethylene glycol) (PEG). The modified PEG chains were threaded in α-cyclodextrins (α-CDs) to form polypseudorotaxanes. The polypseudorotaxanes self-assembled into supramolecular micelles driven by hydrophobic interaction and polypseudorotaxane crystallization. Anti-tumor drug doxorubicin (DOX) was trapped in the micelles. The structure, morphology, drug release profile and cytotoxicity of the micelles were investigated. The in vitro anti-tumor studies including cellular uptake and inhibition efficiency were performed on mice cancer cell lines of TC1 lung cancer cells and B16 melanoma cells. The results revealed that the 7-carboxymethoxy coumarin modified PEG could thread into the cavity of α-CDs to form necklace-like polypseudorotaxanes. The polypseudorotaxanes self-assembled into spherical micelles with the mean size of 30 nanometers, and the size was increased to about 80 nanometers after the drug was loaded. The drug loading content of the micelles was decreased with increasing the chain length of PEG. The sustaining release of DOX could last for 32 hours. The polypseudorotaxane micelles were non-toxic to both TC1 and B16 cells. The IC50 of the DOX loaded polypseudorotaxane micelles with PEG2k was lower than that of micelles with PEG4k or PEG6k both in TC1 and B16 cells.

  13. Dynamic light scattering measurements of reverse micelle phases in liquid and supercritical ethane

    SciTech Connect

    Blitz, J.P.; Fulton, J.L.; Smith, R.D.

    1988-05-19

    Dynamic light scattering of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in liquid and supercritical ethane provides the first direct evidence of reverse micelles in a supercritical fluid (dense gas). Micellar hydrodynamic diameters are only slightly larger in ethane than in liquid isooctane at the same concentrations and temperature, but diffusion coefficients are more than 10 times greater. Measurements of micelle diffusion coefficient and hydrodynamic diameter versus pressure in liquid and supercritical ethane show that density has a strong effect on hydrodynamic size and suggest that micelle clustering may be significant and highly sensitive to pressure. The utility of dynamic light scattering for studying reverse micelle phases in a dense gas is demonstrated.

  14. Cy3 in AOT reverse micelles II. Probing intermicellar interactions using fluorescence correlation spectroscopy.

    PubMed

    McPhee, Jeffrey T; Scott, Eric; Levinger, Nancy E; Van Orden, Alan

    2011-08-11

    Cyanine-3 (Cy3) fluorescent dye molecules confined in sodium di-2-ethylhexyl sulfosuccinate (AOT) reverse micelles were examined using dynamic light scattering and fluorescence correlation spectroscopy to probe the kinetics of Cy3 dye and reverse micelle aggregation. This study explored a range of reverse micelle sizes, defined as w(0) = [H(2)O]/[AOT], in which the occupation number ranged from one Cy3 molecule per ∼10(5) to ∼10(6) reverse micelles. These measurements reveal that in the smallest reverse micelle, w(0) = 1, the Cy3 molecules aggregate to form H-aggregate dimers, and the Cy3 dimerization is accompanied by the formation of a transient dimer between reverse micelles. Transient reverse micelle dimer particles are only observed in the small fraction of Cy3-labeled reverse micelles probed by fluorescence correlation spectroscopy and are not observed in the bulk solution probed by dynamic light scattering. Furthermore, fluorescence correlation spectroscopy makes it possible to probe the size and shape of these dimers, revealing prolate ellipsoid-shaped particles with twice the volume and surface area of a single reverse micelle. PMID:21761943

  15. Surfactant-assisted synthesis of water-soluble and biocompatible semiconductor quantum dot-micelles.

    SciTech Connect

    Brinker, C. Jeffrey; Bunge, Scott D.; Gabaldon, John; Fan, Hongyou; Scullin, Chessa; Leve, Erik W.; Wilson, Michael C.; Tallant, David Robert; Boyle, Timothy J.

    2005-04-01

    We report a simple, rapid approach to synthesize water-soluble and biocompatible fluorescent quantum dot (QD) micelles by encapsulation of monodisperse, hydrophobic QDs within surfactant/lipid micelles. Analyses of UV-vis and photo luminescence spectra, along with transmission electron microscopy, indicate that the water-soluble semiconductor QD micelles are monodisperse and retain the optical properties of the original hydrophobic QDs. The QD micelles were shown to be biocompatible and exhibited little or no aggregation when taken up by cultured rat hippocampal neurons.

  16. Solution structure of detergent micelles at conditions relevant to membrane protein crystallization.

    SciTech Connect

    Littrell, K.; Thiyagarajan, P.; Tiede, D.; Urban, V.

    1999-07-02

    In this study small angle neutron scattering was used to characterize the formation of micelles in aqueous solutions of the detergents DMG and SPC as a function of detergent concentration and ionic strength of the solvent. The effects on the micelle structure of the additives glycerol and PEG, alone as well as in combination typical for actual membrane protein crystallization, were also explored. This research suggests that the micelles are cigar-like in form at the concentrations studied. The size of the micelles was observed to increase with increasing ionic strength but decrease with the addition of glycerol or PEG.

  17. Inverse temperature in Superstatistics

    NASA Astrophysics Data System (ADS)

    Loguercio, Humberto; Davis, Sergio

    2016-05-01

    In this work, it is shown that there are (at least) three alternative definitions of the inverse temperature for a non-canonical ensemble. These definitions coincide in expectation but, in general, not in their higher moments. We explore in detail the application to the recent formalism of Superstatistics (C. Beck, 2003), and, in particular, to the configurational probability distribution in the microcanonical ensemble.

  18. Higher order structure of proteins solubilized in AOT reverse micelles.

    PubMed

    Naoe, Kazumitsu; Noda, Kazuki; Kawagoe, Mikio; Imai, Masanao

    2004-11-15

    The higher order structure of proteins solubilized in an bis(2-ethylhexyl) sulfosuccinate sodium (AOT) reverse micellar system was investigated. From circular dichroic (CD) measurement, CD spectra of cytochrome c, which is solubilized at the interface of reverse micelles, markedly changed on going from buffer solution to the reverse micellar solution, and the ellipticity values in the far- and near-UV regions decreased with decreasing the water content (W0: molar ratio of water to AOT), indicating that the secondary and tertiary structures of cytochrome c changed with the water content. The ellipticity of ribonuclease A, which is solubilized in the center of micellar water pool, in the near-UV region was dependent on W0 and became minimum when W0 of ca. 8 while the ellipticity in the far-UV region was almost constant, indicating that the tertiary structure of ribonuclease A was affected by the water content, but the secondary structure was conserved. The degree of curvature of the micellar interface appears to influence the protein structure because the reverse micelle size is linearly proportional to the W0 value. As evidence of this, when the micelle size was comparable to the protein's dimensions, the structures were more affected by the water content. Judging from the dependence of the factor influencing the protein structure on the protein species, the location of solubilized protein in reverse micelles is significantly related to whether the protein structure in the system is affected by the micellar interface. In the cases of cytochrome c and lysozyme, the ellipticity against W0 was dependent on the AOT concentration. In contrast, ribonuclease A gave very similar ellipticity values whatever the AOT concentration. In the n-hexane micellar system, cytochrome c exhibited lower ellipticity values and ribonuclease A in the lower W0 range (W0

  19. AVO inversion based on inverse operator estimation in trust region

    NASA Astrophysics Data System (ADS)

    Yin, Xing-Yao; Deng, Wei; Zong, Zhao-Yun

    2016-04-01

    Amplitude variation with offset (AVO) inversion is widely utilized in exploration geophysics, especially for reservoir prediction and fluid identification. Inverse operator estimation in the trust region algorithm is applied for solving AVO inversion problems in which optimization and inversion directly are integrated. The L1 norm constraint is considered on the basis of reasonable initial model in order to improve effciency and stability during the AVO inversion process. In this study, high-order Zoeppritz approximation is utilized to establish the inversion objective function in which variation of {{v}\\text{p}}/{{v}\\text{s}} with time is taken into consideration. A model test indicates that the algorithm has a relatively higher stability and accuracy than the damp least-squares algorithm. Seismic data inversion is feasible and inversion values of three parameters ({{v}\\text{p}},{{v}\\text{s}},ρ ) maintain good consistency with logging curves.

  20. Curcumin-loaded biodegradable polymeric micelles for colon cancer therapy in vitro and in vivo

    NASA Astrophysics Data System (ADS)

    Gou, Maling; Men, Ke; Shi, Huashan; Xiang, Mingli; Zhang, Juan; Song, Jia; Long, Jianlin; Wan, Yang; Luo, Feng; Zhao, Xia; Qian, Zhiyong

    2011-04-01

    Curcumin is an effective and safe anticancer agent, but its hydrophobicity inhibits its clinical application. Nanotechnology provides an effective method to improve the water solubility of hydrophobic drug. In this work, curcumin was encapsulated into monomethoxy poly(ethylene glycol)-poly(ε-caprolactone) (MPEG-PCL) micelles through a single-step nano-precipitation method, creating curcumin-loaded MPEG-PCL (Cur/MPEG-PCL) micelles. These Cur/MPEG-PCL micelles were monodisperse (PDI = 0.097 +/- 0.011) with a mean particle size of 27.3 +/- 1.3 nm, good re-solubility after freeze-drying, an encapsulation efficiency of 99.16 +/- 1.02%, and drug loading of 12.95 +/- 0.15%. Moreover, these micelles were prepared by a simple and reproducible procedure, making them potentially suitable for scale-up. Curcumin was molecularly dispersed in the PCL core of MPEG-PCL micelles, and could be slow-released in vitro. Encapsulation of curcumin in MPEG-PCL micelles improved the t1/2 and AUC of curcuminin vivo. As well as free curcumin, Cur/MPEG-PCL micelles efficiently inhibited the angiogenesis on transgenic zebrafish model. In an alginate-encapsulated cancer cell assay, intravenous application of Cur/MPEG-PCL micelles more efficiently inhibited the tumor cell-induced angiogenesisin vivo than that of free curcumin. MPEG-PCL micelle-encapsulated curcumin maintained the cytotoxicity of curcumin on C-26 colon carcinoma cellsin vitro. Intravenous application of Cur/MPEG-PCL micelle (25 mg kg-1curcumin) inhibited the growth of subcutaneous C-26 colon carcinoma in vivo (p < 0.01), and induced a stronger anticancer effect than that of free curcumin (p < 0.05). In conclusion, Cur/MPEG-PCL micelles are an excellent intravenously injectable aqueous formulation of curcumin; this formulation can inhibit the growth of colon carcinoma through inhibiting angiogenesis and directly killing cancer cells.

  1. Doxorubicin-incorporated polymeric micelles composed of dextran-b-poly(DL-lactide-co-glycolide) copolymer

    PubMed Central

    Jeong, Young-Il; Kim, Do Hyung; Chung, Chung-Wook; Yoo, Jin-Ju; Choi, Kyung Ha; Kim, Cy Hyun; Ha, Seung Hee; Kang, Dae Hwan

    2011-01-01

    Background Polymeric micelles using amphiphilic macromolecules are promising vehicles for antitumor targeting. In this study, we prepared anticancer agent-incorporated polymeric micelles using novel block copolymer. Methods We synthesized a block copolymer composed of dextran and poly (DL-lactide-co-glycolide) (DexbLG) for antitumor drug delivery. Doxorubicin was selected as the anticancer drug, and was incorporated into polymeric micelles by dialysis. Polymeric micelles were observed by transmission electron microscopy to be spherical and smaller than 100 nm, with a narrow size distribution. The particle size of doxorubicin-incorporated polymeric micelles increased with increasing drug content. Higher initial drug feeding also increased the drug content. Results During the drug-release study, an initial burst release of doxorubicin was observed for 10 hours, and doxorubicin was continuously released over 4 days. To investigate the in vitro anticancer effects of the polymeric micelles, doxorubicin-resistant HuCC-T1 cells were treated with a very high concentration of doxorubicin. In an antiproliferation study, the polymeric micelles showed higher cytotoxicity to doxorubicin-resistant HuCC-T1 cells than free doxorubicin, indicating that the polymeric micelles were effectively engulfed by tumor cells, while free doxorubicin hardly penetrated the tumor cell membrane. On confocal laser scanning microscopy, free doxorubicin expressed very weak fluorescence intensity, while the polymeric micelles expressed strong red fluorescence. Furthermore, in flow cytometric analysis, fluorescence intensity of polymeric micelles was almost twice as high than with free doxorubicin. Conclusion DexbLG polymeric micelles incorporating doxorubicin are promising vehicles for antitumor drug targeting. PMID:21796244

  2. Evaluation of Iron Oxide Nanoparticle Micelles for Magnetic Particle Imaging (MPI) of Thrombosis

    PubMed Central

    Aussems-Custers, Erica; Daemen, Mat J. A. P.; Strijkers, Gustav J.; Nicolay, Klaas; Grüll, Holger

    2015-01-01

    Magnetic particle imaging (MPI) is an emerging medical imaging modality that directly visualizes magnetic particles in a hot-spot like fashion. We recently developed an iron oxide nanoparticle-micelle (ION-Micelle) platform that allows highly sensitive MPI. The goal of this study was to assess the potential of the ION-Micelles for MPI-based detection of thrombi. To this aim, an in vivo carotid artery thrombosis mouse model was employed and ex vivo magnetic particle spectrometer (MPS) measurements of the carotid arteries were performed. In addition, we studied the effect of functionalization of the ION-Micelle nanoplatform with fibrin-binding peptides (FibPeps) with respect to nanoparticle thrombus uptake and hence thrombus detection. In vivo quantitative MR imaging pre- and post-ION-Micelle injection was performed as reference for visualization of ION-micelle uptake. ION-Micelles significantly decreased T2 values in the thrombi with respect to pre-injection T2 values (p < 0.01) and significantly increased ex vivo MPS thrombus signal with respect to the noninjured, contralateral carotid (p < 0.01). Functionalization of the ION-Micelles with the FibPep peptides did not result in an increased MPS thrombus signal with respect to the non-fibrin binding ION-Micelles. The lack of a significant increased thrombus uptake for the FibPep-ION-Micelles indicates that (non-fibrin-specific) entrapment of nanoparticles in the mesh-like thrombi is the key contributor to thrombus nanoparticle uptake. Therefore, (nontargeted) ION-Micelles might be of value for noninvasive MPI-based diagnosis, characterization and treatment monitoring of thrombosis. PMID:25746677

  3. Fluorescent Block Copolymer Micelles That Can Self-Report on Their Assembly and Small Molecule Encapsulation

    PubMed Central

    2016-01-01

    Block copolymer micelles have been prepared with a dithiomaleimide (DTM) fluorophore located in either the core or shell. Poly(triethylene glycol acrylate)-b-poly(tert-butyl acrylate) (P(TEGA)-b-P(tBA)) was synthesized by RAFT polymerization, with a DTM-functional acrylate monomer copolymerized into either the core forming P(tBA) block or the shell forming P(TEGA) block. Self-assembly by direct dissolution afforded spherical micelles with Rh of ca. 35 nm. Core-labeled micelles (CLMs) displayed bright emission (Φf = 17%) due to good protection of the fluorophore, whereas shell-labeled micelles (SLMs) had lower efficiency emission due to collisional quenching in the solvated corona. The transition from micelles to polymer unimers upon dilution could be detected by measuring the emission intensity of the solutions. For the core-labeled micelles, the fluorescence lifetime was also responsive to the supramolecular state, the lifetime being significantly longer for the micelles (τAv,I = 19 ns) than for the polymer unimers (τAv,I = 9 ns). The core-labeled micelles could also self-report on the presence of a fluorescent hydrophobic guest molecule (Nile Red) as a result of Förster resonance energy transfer (FRET) between the DTM fluorophore and the guest. The sensitivity of the DTM fluorophore to its environment therefore provides a simple handle to obtain detailed structural information for the labeled polymer micelles. A case will also be made for the application superiority of core-labeled micelles over shell-labeled micelles for the DTM fluorophore. PMID:27065494

  4. Molecular inversion probe assay.

    PubMed

    Absalan, Farnaz; Ronaghi, Mostafa

    2007-01-01

    We have described molecular inversion probe technologies for large-scale genetic analyses. This technique provides a comprehensive and powerful tool for the analysis of genetic variation and enables affordable, large-scale studies that will help uncover the genetic basis of complex disease and explain the individual variation in response to therapeutics. Major applications of the molecular inversion probes (MIP) technologies include targeted genotyping from focused regions to whole-genome studies, and allele quantification of genomic rearrangements. The MIP technology (used in the HapMap project) provides an efficient, scalable, and affordable way to score polymorphisms in case/control populations for genetic studies. The MIP technology provides the highest commercially available multiplexing levels and assay conversion rates for targeted genotyping. This enables more informative, genome-wide studies with either the functional (direct detection) approach or the indirect detection approach. PMID:18025701

  5. Silk inverse opals

    NASA Astrophysics Data System (ADS)

    Kim, Sunghwan; Mitropoulos, Alexander N.; Spitzberg, Joshua D.; Tao, Hu; Kaplan, David L.; Omenetto, Fiorenzo G.

    2012-12-01

    Periodic nanostructures provide the facility to control and manipulate the flow of light through their lattices. Three-dimensional photonic crystals enable the controlled design of structural colour, which can be varied by infiltrating the structure with different (typically liquid) fillers. Here, we report three-dimensional photonic crystals composed entirely of a purified natural protein (silk fibroin). The biocompatibility of this protein, as well as its favourable material properties and ease of biological functionalization, present opportunities for otherwise unattainable device applications such as bioresorbable integration of structural colour within living tissue or lattice functionalization by means of organic and inorganic material doping. We present a silk inverse opal that demonstrates a pseudo-photonic bandgap in the visible spectrum and show its associated structural colour beneath biological tissue. We also leverage silk's facile dopability to manufacture a gold nanoparticle silk inverse opal and demonstrate patterned heating mediated by enhancement of nanoparticle absorption at the band-edge frequency of the photonic crystal.

  6. Intersections, ideals, and inversion

    SciTech Connect

    Vasco, D.W.

    1998-10-01

    Techniques from computational algebra provide a framework for treating large classes of inverse problems. In particular, the discretization of many types of integral equations and of partial differential equations with undetermined coefficients lead to systems of polynomial equations. The structure of the solution set of such equations may be examined using algebraic techniques.. For example, the existence and dimensionality of the solution set may be determined. Furthermore, it is possible to bound the total number of solutions. The approach is illustrated by a numerical application to the inverse problem associated with the Helmholtz equation. The algebraic methods are used in the inversion of a set of transverse electric (TE) mode magnetotelluric data from Antarctica. The existence of solutions is demonstrated and the number of solutions is found to be finite, bounded from above at 50. The best fitting structure is dominantly onedimensional with a low crustal resistivity of about 2 ohm-m. Such a low value is compatible with studies suggesting lower surface wave velocities than found in typical stable cratons.

  7. Des ballons pour demain

    NASA Astrophysics Data System (ADS)

    Régipa, R.

    A partir d'une théorie sur la détermination des formes et des contraintes globales d'un ballon de révolution, ou s'en rapprochant, une nouvelle famille de ballons a été définie. Les ballons actuels, dits de ``forme naturelle'', sont calculés en général pour une tension circonférencielle nulle. Ainsi, pour une mission donnée, la tension longitudinale et la forme de l'enveloppe sont strictement imposées. Les ballons de la nouvelle génération sont globalement cylindriques et leurs pôles sont réunis par un câble axial, chargé de transmettre une partie des efforts depuis le crochet (pôle inférieur), directement au pôle supérieur. De plus, la zone latérale cylindrique est soumise à un faible champ de tensions circonférencielles. Ainsi, deux paramètres permettent de faire évoluer la distribution des tensions et la forme de l'enveloppe: - la tension du câble de liaison entre pôles (ou la longueur de ce câble) - la tension circonférencielle moyenne désirée (ou le rayon du ballon). On peut donc calculer et réaliser: - soit des ballons de forme adaptée, comme les ballons à fond plat pour le bon fonctionnement des montgolfières infrarouge (projet MIR); - soit des ballons optimisés pour une bonne répartition des contraintes et une meilleure utilisation des matériaux d'enveloppe, pour l'ensemble des programmes stratosphériques. Il s'ensuit une économie sensible des coûts de fabrication, une fiabilité accrue du fonctionnement de ces ballons et une rendement opérationnel bien supérieur, permettant entre autres, d'envisager des vols à très haute altitude en matériaux très légers.

  8. Positively charged micelles based on a triblock copolymer demonstrate enhanced corneal penetration

    PubMed Central

    Li, Jingguo; Li, Zhanrong; Zhou, Tianyang; Zhang, Junjie; Xia, Huiyun; Li, Heng; He, Jijun; He, Siyu; Wang, Liya

    2015-01-01

    Purpose The cornea is a main barrier to drug penetration after topical application. The aim of this study was to evaluate the abilities of micelles generated from a positively charged triblock copolymer to penetrate the cornea after topical application. Methods The triblock copolymer poly(ethylene glycol)-poly(ε-caprolactone)-g-polyethyleneimine was synthesized, and the physicochemical properties of the self-assembled polymeric micelles were investigated, including hydrodynamic size, zeta potential, morphology, drug-loading content, drug-loading efficiency, and in vitro drug release. Using fluorescein diacetate as a model drug, the penetration capabilities of the polymeric micelles were monitored in vivo using a two-photon scanning fluorescence microscopy on murine corneas after topical application. Results The polymer was successfully synthesized and confirmed using nuclear magnetic resonance and Fourier transform infrared. The polymeric micelles had an average particle size of 28 nm, a zeta potential of approximately +12 mV, and a spherical morphology. The drug-loading efficiency and drug-loading content were 75.37% and 3.47%, respectively, which indicates that the polymeric micelles possess a high drug-loading capacity. The polymeric micelles also exhibited controlled-release behavior in vitro. Compared to the control, the positively charged polymeric micelles significantly penetrated through the cornea. Conclusion Positively charged micelles generated from a triblock copolymer are a promising vehicle for the topical delivery of hydrophobic agents in ocular applications. PMID:26451109

  9. Folated Synperonic-Cholesteryl Hemisuccinate Polymeric Micelles for the Targeted Delivery of Docetaxel in Melanoma

    PubMed Central

    Varshosaz, Jaleh; Taymouri, Somayeh; Hassanzadeh, Farshid; Haghjooy Javanmard, Shaghayegh; Rostami, Mahboobeh

    2015-01-01

    The objective of this study was the synthesis of folic acid- (FA-) targeted polymeric micelles of Synperonic PE/F 127-cholesteryl hemisuccinate (PF127-Chol) for specific delivery of docetaxel (DTX). Targeted or nontargeted micelles loaded with DTX were prepared via dialysis method. The effects of processing variables on the physicochemical properties of targeted micelles were evaluated using a full factorial design. After the optimization of the polymer/drug ratio, the organic solvent type used for the preparation of the micelles, and the temperature of dialyzing medium, the in vitro cytotoxicity and cellular uptake of the optimized micelles were studied on B16F10 melanoma cells by flow cytometry and fluorescent microscopy. The anticancer efficacy of DTX-loaded FA-PF127-Chol was evaluated in mice bearing melanoma tumor. Optimized targeted micelles had the particle size of 171.3 nm, zeta potential of −7.8 mV, PDI of 0.325, and a high encapsulation efficiency that released the drug within 144 h. The MTT assay indicated that targeted micelles carrying DTX were significantly more cytotoxic, had higher cellular uptake, and reduced the tumor volume significantly more than the nontargeted micelles and the free drug. FA-PF127-Chol could be, therefore, a promising biomaterial for tumors overexpressing folate receptors. PMID:25839040

  10. Synchrotron Small-Angle X-ray Scattering Study of Cross-Linked Polymeric Micelles.

    PubMed

    Kim, Hyun-Chul; Jin, Kyeong Sik; Lee, Se Guen; Kim, Eunjoo; Lee, Sung Jun; Jeong, Sang Won; Lee, Seung Woo; Kim, Kwang-Woo

    2016-06-01

    Polymeric micelles of methoxypoly(ethylene glycol)-b-poly(lactide) containing lysine units (mPEG-PLA-Lys4) were cross-linked by reacting of lysine moieties with a bifunctional bis(N-hydroxy-succinimide ester). The micelles were characterized in aqueous solution using dynamic light scattering, transmission electron microscopy, and synchrotron small-angle X-ray scattering. The mPEG-PLA-Lys4 was synthesized through the ring-opening polymerization of N6-carbobenzyloxy-L-lysine N-carboxyanhydride with amine-terminated mPEG-PLA and subsequent deprotection. The polymeric micelles showed enhanced micelle stability after cross-linking, which was confirmed by adding sodium dodecyl sulfate as a destabilizing agent. The average diameters measured via dynamic light scattering were 19.1 nm and 29.2 nm for non-cross-linked polymeric micelles (NCPMs) and cross-linked polymeric micelles (CPMs), respectively. The transmission electron microscopy images showed that the size of the polymeric micelles increased slightly due to cross-linking, which was in good agreement with the DLS measurements. The overall structures and internal structural changes of NCPMs and CPMs in aqueous solution were studied in detail using synchrotron X-ray scattering method. According to the structural parameters of X-ray scattering analysis, CPMs with a more densely packed core structure were formed by reacting bifunctional cross-linking agents with lysine amino groups located in the innermost core of the polymeric micelles. PMID:27427731

  11. The association of low-molecular-weight hydrophobic compounds with native casein micelles in bovine milk.

    PubMed

    Cheema, M; Mohan, M S; Campagna, S R; Jurat-Fuentes, J L; Harte, F M

    2015-08-01

    The agreed biological function of the casein micelles in milk is to carry minerals (calcium, magnesium, and phosphorus) from mother to young along with amino acids for growth and development. Recently, native and modified casein micelles were used as encapsulating and delivery agents for various hydrophobic low-molecular-weight probes. The ability of modified casein micelles to bind certain probes may derive from the binding affinity of native casein micelles. Hence, a study with milk from single cows was conducted to further elucidate the association of hydrophobic molecules into native casein micelles and further understand their biological function. Hydrophobic and hydrophilic extraction followed by ultraperformance liquid chromatography-high resolution mass spectrometry analysis were performed over protein fractions obtained from size exclusion fractionation of raw skim milk. Hydrophobic compounds, including phosphatidylcholine, lyso-phosphatidylcholine, phosphatidylethanolamine, and sphingomyelin, showed strong association exclusively to casein micelles as compared with whey proteins, whereas hydrophilic compounds did not display any preference for their association among milk proteins. Further analysis using liquid chromatography-tandem mass spectrometry detected 42 compounds associated solely with the casein-micelles fraction. Mass fragments in tandem mass spectrometry identified 4 of these compounds as phosphatidylcholine with fatty acid composition of 16:0/18:1, 14:0/16:0, 16:0/16:0, and 18:1/18:0. These results support that transporting low-molecular-weight hydrophobic molecules is also a biological function of the casein micelles in milk. PMID:26074238

  12. Preparation and evaluation of novel mixed micelles as nanocarriers for intravenous delivery of propofol.

    PubMed

    Li, Xinru; Zhang, Yanhui; Fan, Yating; Zhou, Yanxia; Wang, Xiaoning; Fan, Chao; Liu, Yan; Zhang, Qiang

    2011-01-01

    Novel mixed polymeric micelles formed from biocompatible polymers, poly(ethylene glycol)-poly(lactide) (mPEG-PLA) and polyoxyethylene-660-12-hydroxy stearate (Solutol HS15), were fabricated and used as a nanocarrier for solubilizing poorly soluble anesthetic drug propofol. The solubilization of propofol by the mixed micelles was more efficient than those made of mPEG-PLA alone. Micelles with the optimized composition of mPEG-PLA/Solutol HS15/propofol = 10/1/5 by weight had particle size of about 101 nm with narrow distribution (polydispersity index of about 0.12). Stability analysis of the mixed micelles in bovine serum albumin (BSA) solution indicated that the diblock copolymer mPEG efficiently protected the BSA adsorption on the mixed micelles because the hydrophobic groups of the copolymer were efficiently screened by mPEG, and propofol-loaded mixed micelles were stable upon storage for at least 6 months. The content of free propofol in the aqueous phase for mixed micelles was lower by 74% than that for the commercial lipid emulsion. No significant differences in times to unconsciousness and recovery of righting reflex were observed between mixed micelles and commercial lipid formulation. The pharmacological effect may serve as pharmaceutical nanocarriers with improved solubilization capacity for poorly soluble drugs. PMID:21711808

  13. Preparation and evaluation of novel mixed micelles as nanocarriers for intravenous delivery of propofol

    NASA Astrophysics Data System (ADS)

    Li, Xinru; Zhang, Yanhui; Fan, Yating; Zhou, Yanxia; Wang, Xiaoning; Fan, Chao; Liu, Yan; Zhang, Qiang

    2011-12-01

    Novel mixed polymeric micelles formed from biocompatible polymers, poly(ethylene glycol)-poly(lactide) (mPEG-PLA) and polyoxyethylene-660-12-hydroxy stearate (Solutol HS15), were fabricated and used as a nanocarrier for solubilizing poorly soluble anesthetic drug propofol. The solubilization of propofol by the mixed micelles was more efficient than those made of mPEG-PLA alone. Micelles with the optimized composition of mPEG-PLA/Solutol HS15/propofol = 10/1/5 by weight had particle size of about 101 nm with narrow distribution (polydispersity index of about 0.12). Stability analysis of the mixed micelles in bovine serum albumin (BSA) solution indicated that the diblock copolymer mPEG efficiently protected the BSA adsorption on the mixed micelles because the hydrophobic groups of the copolymer were efficiently screened by mPEG, and propofol-loaded mixed micelles were stable upon storage for at least 6 months. The content of free propofol in the aqueous phase for mixed micelles was lower by 74% than that for the commercial lipid emulsion. No significant differences in times to unconsciousness and recovery of righting reflex were observed between mixed micelles and commercial lipid formulation. The pharmacological effect may serve as pharmaceutical nanocarriers with improved solubilization capacity for poorly soluble drugs.

  14. Dual pH-responsive 5-aminolevulinic acid pseudopolyrotaxane prodrug micelles for enhanced photodynamic therapy.

    PubMed

    Tong, Hongxin; Wang, Yin; Li, Huan; Jin, Qiao; Ji, Jian

    2016-03-11

    Novel 5-aminolevulinic acid (ALA) pseudopolyrotaxane prodrug micelles with dual pH-responsive properties were prepared by the host-guest interaction of α-cyclodextrin (α-CD) and poly(ethylene glycol) (PEG). The micelles exhibited pH dependent cellular uptake and pH-sensitive ALA release, enabling enhanced photodynamic therapy. PMID:26882232

  15. Photopolymerized micelles of diacetylene amphiphile: physical characterization and cell delivery properties.

    PubMed

    Neuberg, Patrick; Perino, Aurélia; Morin-Picardat, Emmanuelle; Anton, Nicolas; Darwich, Zeinab; Weltin, Denis; Mely, Yves; Klymchenko, Andrey S; Remy, Jean-Serge; Wagner, Alain

    2015-07-25

    A series of polydiacetylene (PDA) - based micelles were prepared from diacetylenic surfactant bearing polyethylene glycol, by increasing UV-irradiation times. These polymeric lipid micelles were analyzed by physicochemical methods, electron microscopy and NMR analysis. Cellular delivery of fluorescent dye suggests that adjusting the polymerization state is vital to reach the full in vitro potential of PDA-based delivery systems. PMID:26095460

  16. Terminal modification of polymeric micelles with π-conjugated moieties for efficient anticancer drug delivery.

    PubMed

    Liang, Yan; Deng, Xin; Zhang, Longgui; Peng, Xinyu; Gao, Wenxia; Cao, Jun; Gu, Zhongwei; He, Bin

    2015-12-01

    High drug loading content is the critical factor to polymeric micelles for efficient chemotherapy. Small molecules of cinnamic acid, 7-carboxymethoxy coumarin and chrysin with different π-conjugated moieties were immobilized on the terminal hydroxyl groups of PCL segments in mPEG-PCL micelles to improve drug loading content via the evocation of π-π stacking interaction between doxorubicin (DOX) and polymeric micelles. The modification of π-conjugated moieties enhanced the capability of crystallization of mPEG-PCL block copolymers. The drug loading content increased dramatically from 12.9% to 25.5% after modification. All the three modified mPEG-PCL micelles were nontoxic to cells. Chrysin modified polymeric micelles exhibited the most efficient anticancer activity. The in vivo anticancer activity of 10 mg/kg DOX dose of chrysin modified micelle formulation for twice injections was comparable to that of 5 mg/kg dose of free DOX·HCl for four injections under the circumstance of same total DOX amount. The systemic toxicity of DOX loaded chrysin modified micelles was significantly reduced. This research provided a facile strategy to achieve polymeric micelles with high drug loading content and efficient anticancer activity both in vitro and in vivo. PMID:26310358

  17. Controlled hydrophobic functionalization of natural fibers through self-assembly of amphiphilic diblock copolymer micelles.

    PubMed

    Aarne, Niko; Laine, Janne; Hänninen, Tuomas; Rantanen, Ville; Seitsonen, Jani; Ruokolainen, Janne; Kontturi, Eero

    2013-07-01

    The functionalization of natural fibers is an important task that has recently received considerable attention. We investigated the formation of a hydrophobic layer from amphiphilic diblock copolymer micelles [polystyrene-block-poly(N-methyl-4-vinyl pyridinium iodide)] on natural fibers and on a model surface (mica). A series of micelles were prepared. The micelles were characterized by using cryoscopic TEM and light scattering, and their hydrophobization capability was studied through contact angle measurements, water adsorption, and Raman imaging. Mild heat treatment (130 °C) was used to increase the hydrophobization capability of the micelles. The results showed that the micelles could not hydrophobize a model surface, but could render the natural fibers water repellent both with and without heat treatment. This effect was systematically studied by varying the composition of the constituent blocks. The results showed that the micelle size (and the molecular weight of the constituent diblock copolymers) was the most important parameter, whereas the cationic (hydrophilic) part played only a minor role. We hypothesized that the hydrophobization effect could be attributed to a combination of the micelle size and the shrinkage of the natural fibers upon drying. The shrinking caused the roughness to increase on the fiber surface, which resulted in a rearrangement of the self- assembled layer in the wet state. Consequently, the fibers became hydrophobic through the roughness effects at multiple length scales. Mild heat treatment melted the micelle core and decreased the minimum size necessary for hydrophobization. PMID:23687082

  18. Versatile polyion complex micelles for peptide and siRNA vectorization to engineer tolerogenic dendritic cells.

    PubMed

    Mebarek, Naila; Vicente, Rita; Aubert-Pouëssel, Anne; Quentin, Julie; Mausset-Bonnefont, Anne-Laure; Devoisselle, Jean-Marie; Jorgensen, Christian; Bégu, Sylvie; Louis-Plence, Pascale

    2015-05-01

    Dendritic cells (DCs) are professional antigen-presenting cells that play a critical role in maintaining the balance between immunity and tolerance and, as such are a promising immunotherapy tool to induce immunity or to restore tolerance. The main challenge to harness the tolerogenic properties of DCs is to preserve their immature phenotype. We recently developed polyion complex micelles, formulated with double hydrophilic block copolymers of poly(methacrylic acid) and poly(ethylene oxide) blocks and able to entrap therapeutic molecules, which did not induce DC maturation. In the current study, the intrinsic destabilizing membrane properties of the polymers were used to optimize endosomal escape property of the micelles in order to propose various strategies to restore tolerance. On the first hand, we showed that high molecular weight (Mw) copolymer-based micelles were efficient to favor the release of the micelle-entrapped peptide into the endosomes, and thus to improve peptide presentation by immature (i) DCs. On the second hand, we put in evidence that low Mw copolymer-based micelles were able to favor the cytosolic release of micelle-entrapped small interfering RNAs, dampening the DCs immunogenicity. Therefore, we demonstrate the versatile use of polyionic complex micelles to preserve tolerogenic properties of DCs. Altogether, our results underscored the potential of such micelle-loaded iDCs as a therapeutic tool to restore tolerance in autoimmune diseases. PMID:25796349

  19. Preparation and Characterization of Individual and Multi-drug Loaded Physically Entrapped Polymeric Micelles.

    PubMed

    Rao, Deepa A; Nguyen, Duc X; Mishra, Gyan P; Doddapaneni, Bhuvana Shyam; Alani, Adam W G

    2015-01-01

    Amphiphilic block copolymers like polyethyleneglycol-block-polylactic acid (PEG-b-PLA) can self-assemble into micelles above their critical micellar concentration forming hydrophobic cores surrounded by hydrophilic shells in aqueous environments. The core of these micelles can be utilized to load hydrophobic, poorly water soluble drugs like docetaxel (DTX) and everolimus (EVR). Systematic characterization of the micelle structure and drug loading capabilities are important before in vitro and in vivo studies can be conducted. The goal of the protocol described herein is to provide the necessary characterization steps to achieve standardized micellar products. DTX and EVR have intrinsic solubilities of 1.9 and 9.6 µg/ml respectively Preparation of these micelles can be achieved through solvent casting which increases the aqueous solubility of DTX and EVR to 1.86 and 1.85 mg/ml, respectively. Drug stability in micelles evaluated at room temperature over 48 hr indicates that 97% or more of the drugs are retained in solution. Micelle size was assessed using dynamic light scattering and indicated that the size of these micelles was below 50 nm and depended on the molecular weight of the polymer. Drug release from the micelles was assessed using dialysis under sink conditions at pH 7.4 at 37 (o)C over 48 hr. Curve fitting results indicate that drug release is driven by a first order process indicating that it is diffusion driven. PMID:26382662

  20. Dissipative particle dynamics simulation study of poly(2-oxazoline)-based multicompartment micelle nanoreactor.

    PubMed

    Chun, Byeong Jae; Fisher, Christina Clare; Jang, Seung Soon

    2016-02-17

    We investigate multicompartment micelles consisting of poly(2-oxazoline)-based triblock copolymers for nanoreactor applications, using the DPD simulation method to characterize the internal structure of the micelles and the distribution of reactant. The DPD simulation parameters are determined from the Flory-Huggins interaction parameter (χFH). From the snapshots of the micellar structures and radial distribution function of polymer blocks, it is clearly presented that the micelle is multicompartmental. In addition, by implementing the DPD simulations in the presence of reactants, it is found that Reac-C4 and Reac-OPh are associate well with the hydrophilic shell of the micelle, whereas the other two reactants, Reac-Ph and Reac-Cl, are not incorporated into the micelle. From our DPD simulations, we confirm that the miscibility (solubility) of reactant with the micelle has a strong correlation with the rate of hydrolysis kinetic resolution. Utilizing accurate methods evaluating accurate χFH parameters for molecular interactions in micelle system, this DPD simulation can have a great potential to predict the structures of micelles consisting of designed multiblock copolymers for useful reactions. PMID:26853511

  1. Amphiphile micelle structures in the protic ionic liquid ethylammonium nitrate and water.

    PubMed

    Chen, Zhengfei; Greaves, Tamar L; Caruso, Rachel A; Drummond, Calum J

    2015-01-01

    Micelles formed by amphiphiles in a protic ionic liquid (PIL), ethylammonium nitrate (EAN), were investigated using synchrotron small-angle X-ray scattering and contrasted with those that formed in water. The amphiphiles studied were cationic hexadecyltrimethylammonium chloride (CTAC) and hexadecylpyridinium bromide (HDPB) and nonionic poly(oxyethylene) (10) oleyl ether (Brij 97) and Pluronic ethylene oxide-propylene oxide-ethylene oxide block copolymer (P123). The scattering patterns were analyzed using spherical, core-shell, and cylindrical scattering models. The apparent micelle shape and size of the surfactants and the block copolymer in the PIL have been reported. At low amphiphile concentrations (<10 wt %) spherical micelles were preferentially formed for all the amphiphiles in EAN. The micelles formed by the two cationic amphiphiles in EAN and water were similar, though different scattering models were required predominantly due to the ionic nature of EAN. The two nonionic amphiphiles formed micelles with similar core radii in water and in EAN. However, the micelle shells composed of ethylene oxide groups fitted to a significantly thicker layer in water compared to EAN. At high concentrations (>10 wt %) in EAN and water, there was a preference for cylindrical micelles for CTAC, HDPB, and Brij 97; however, the P123 micelles remained spherical. PMID:25490177

  2. Image-guided and tumor-targeted drug delivery with radiolabeled unimolecular micelles

    PubMed Central

    Chen, Guojun; Shi, Sixiang; Zheng, Qifeng; Zhang, Yin; Theuer, Charles P.; Barnhart, Todd E.; Cai, Weibo; Gong, Shaoqin

    2013-01-01

    Unimolecular micelles formed by dendritic amphiphilic block copolymers poly(amidoamine)–poly(l-lactide)-b-poly(ethylene glycol) conjugated with anti-CD105 monoclonal antibody (TRC105) and 1,4,7-triazacyclononane-N, N’, N-triacetic acid (NOTA, a macrocyclic chelator for 64Cu) (abbreviated as PAMAM–PLA-b-PEG–TRC105) were synthesized and characterized. Doxorubicin (DOX), a model anti-cancer drug, was loaded into the hydrophobic core of the unimolecular micelles formed by PAMAM and PLA via physical encapsulation. The unimolecular micelles exhibited a uniform size distribution and pH-sensitive drug release behavior. TRC105-conjugated unimolecular micelles showed a CD105-associated cellular uptake in human umbilical vein endothelial cells (HUVEC) compared with non-targeted unimolecular micelles, which was further validated by cellular uptake in CD105-negative MCF-7 cells. In 4T1 murine breast tumor-bearing mice, 64Cu-labeled targeted micelles exhibited a much higher level of tumor accumulation than 64Cu-labeled non-targeted micelles, measured by serial non-invasive positron emission tomography (PET) imaging and confirmed by biodistribution studies. These unimolecular micelles formed by dendritic amphiphilic block copolymers that synergistically integrate passive and active tumor-targeting abilities with pH-controlled drug release and PET imaging capabilities provide the basis for future cancer theranostics. PMID:23932288

  3. Image-guided and tumor-targeted drug delivery with radiolabeled unimolecular micelles.

    PubMed

    Guo, Jintang; Hong, Hao; Chen, Guojun; Shi, Sixiang; Zheng, Qifeng; Zhang, Yin; Theuer, Charles P; Barnhart, Todd E; Cai, Weibo; Gong, Shaoqin

    2013-11-01

    Unimolecular micelles formed by dendritic amphiphilic block copolymers poly(amidoamine)-poly(L-lactide)-b-poly(ethylene glycol) conjugated with anti-CD105 monoclonal antibody (TRC105) and 1,4,7-triazacyclononane-N, N', N-triacetic acid (NOTA, a macrocyclic chelator for (64)Cu) (abbreviated as PAMAM-PLA-b-PEG-TRC105) were synthesized and characterized. Doxorubicin (DOX), a model anti-cancer drug, was loaded into the hydrophobic core of the unimolecular micelles formed by PAMAM and PLA via physical encapsulation. The unimolecular micelles exhibited a uniform size distribution and pH-sensitive drug release behavior. TRC105-conjugated unimolecular micelles showed a CD105-associated cellular uptake in human umbilical vein endothelial cells (HUVEC) compared with non-targeted unimolecular micelles, which was further validated by cellular uptake in CD105-negative MCF-7 cells. In 4T1 murine breast tumor-bearing mice, (64)Cu-labeled targeted micelles exhibited a much higher level of tumor accumulation than (64)Cu-labeled non-targeted micelles, measured by serial non-invasive positron emission tomography (PET) imaging and confirmed by biodistribution studies. These unimolecular micelles formed by dendritic amphiphilic block copolymers that synergistically integrate passive and active tumor-targeting abilities with pH-controlled drug release and PET imaging capabilities provide the basis for future cancer theranostics. PMID:23932288

  4. Compression-Induced Fusion of Glassy Core Polymer Micelles at the Air-Water Interface

    NASA Astrophysics Data System (ADS)

    Kim, Hyun Chang; Won, You-Yeon

    The surface mechanical and morphological properties of glassy core polymer micelles at the air-water interface were investigated. Asymmetric PS-PEG and PtBMA-PEG block copolymers with PEG weight fractions larger than 0.5 were formulated in the form of aqueous micelles and spread onto water. Compressed films of PS-PEG and PtBMA-PEG micelles reach high dynamic surface pressures. On the detailed level, however, PS-PEG and PtBMA-PEG micelles exhibit different surface pressure-area profiles. The PtBMA-PEG isotherm shows a transition to a plateau around a surface pressure of 24 mN/m, which is attributed to the PtBMA block as it forms a continuous film; this interpretation is supported by the fact that the surface pressure at the plateau transition is identical to the value of the spreading coefficient for PtBMA. This presents evidence that the core domains of PtBMA-PEG micelles melt and merge into a film when the micellar monolayer is laterally compressed. Such behavior was not observed with PS-PEG micelles. We suspect that under lateral compression, PtBMA-PEG micelles undergo fusion into a continuous film because PtBMA has the natural tendency to spread on the water surface, whereas PS-PEG micelles does not because the dewetting tendency of PS preventing formation of a uniform layer.

  5. Triclosan-loaded Tooth-binding Micelles for Prevention and Treatment of Dental Biofilm

    PubMed Central

    Chen, Fu; Rice, Kelly C.; Liu, Xin-Ming; Reinhardt, Richard A.; Bayles, Kenneth W.; Wang, Dong

    2010-01-01

    The purpose of the present study was to develop tooth-binding micelle formulations and evaluate their ability to both inhibit initial biofilm formation as well as decrease the viability of preformed biofilm using an in vitro dental biofilm model. Alendronate (ALN, a bisphosphonate) was covalently attached to the ends of different Pluronic copolymers to confer tooth-binding ability to the micelles, and triclosan was used as a model drug. Based on different micelle preparation methods, Pluronic copolymers and ALN-terminated Pluronic copolymers were used to prepare triclosan-loaded tooth-binding micelles. The formulation was optimized for triclosan solubility, particle size, hydroxyapatite (HA) binding capacity and kinetics, and in vitro drug release behavior. In vitro biofilm treatment studies demonstrated that the triclosan-loaded tooth-binding micelles were able to inhibit initial biofilm growth of Streptococcus mutans UA159 by 6-log CFU/HA disc compared to the untreated control. These tooth-binding micelles were also capable of reducing the viability of preformed biofilm by 4-log CFU/HA disc compared to untreated control biofilm. In summary, triclosan-loaded tooth-binding micelles have been successfully developed and optimized in this study. These micelles demonstrated promising anti-biofilm capabilities that have the potential for use in the future treatment and prevention of dental diseases. PMID:20387099

  6. Inverse avalanches on Abelian sandpiles

    SciTech Connect

    Chau, H.F. Department of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801-3080 )

    1994-11-01

    A simple and computationally efficient way of finding inverse avalanches for Abelian sandpiles, called the inverse particle addition operator, is presented. In addition, the method is shown to be optimal in the sense that it requires the minimum amount of computation among methods of the same kind. The method is also conceptually succinct because avalanche and inverse avalanche are placed in the same footing.

  7. Reversible precipitation of casein micelles with a cationic hydroxyethylcellulose.

    PubMed

    Ausar, Salvador F; Bianco, Ismael D; Castagna, Leonardo F; Alasino, Roxana V; Narambuena, Claudio F; Leiva, Ezequiel P M; Beltramo, Dante M

    2005-11-16

    The cationic hydroxyethylcellulose Polyquaternium 10 (PQ10) was found to produce a dose-dependent destabilization of casein micelles from whole or skim milk without affecting the stability of most of the whey proteins. The anionic phosphate residues on caseins were not determinant in the observed interaction since the destabilization was also observed with dephosphorylated caseins to the same extent. However, the precipitation process was completely inhibited by rising NaCl concentration, indicating an important role of electrostatic interactions. Furthermore, the addition of 150 mM NaCl solubilized preformed PQ10-casein complexes, rendering a stable casein suspension without a disruption of the internal micellar structure as determined by dynamic light scattering. This casein preparation was found to contain most of the Ca2+ and only 10% of the lactose originally present in milk and remained as a stable suspension for at least 4 months at 4 degrees C. The final concentration of PQ10 determined both the size of the casein-polymer aggregates and the amount of milkfat that coprecipitates. The presence of PQ10 in the aggregates did not inhibit the activity of rennet or gastrointestinal proteases and lipases, nor did it affect the growth of several fermentative bacteria. The cationic cellulose PQ10 may cause a reversible electrostatic precipitation of casein micelles without disrupting their internal structure. The reversibility of the interaction described opens the possibility of using this cationic polysaccharide to concentrate and resuspend casein micelles from whole or skim milk in the production of new fiber-enriched lactose-reduced calcium-caseinate dairy products. PMID:16277399

  8. Micelle-derived catalysts for extended Schulz-Flory

    SciTech Connect

    Not Available

    1985-01-01

    The reduced C-73-1-101 iron catalyst was retested in Run 10, under the third set of reference conditions: 208[degree]C, 500 psig, 0.9 (molar) H[sub 2]/CO feed ratio, [approximately] 35% initial CO conversion. The analysis of the products collected during the entire 252-hour run, including the wax recovered from the catalyst, resulted in [alpha] = 0.78 for carbon numbers 1 to 15 and [alpha] = 0.88 for carbon numbers 16 to 45. The results of Run 10 are satisfactory and will be used in the future as reference performance. No further tests with the reference catalyst are going to be conducted until a method for testing experimental catalysts is established and new reference performance under different conditions is necessitated. Ruthenium particles, mostly in the 40 to 60 [Angstrom] size range, were prepared on the [gamma]-alumina by using a micelle technique. The narrow size distribution of ruthenium particles was not maintained and some very large particles up to 1000 [Angstrom] resulted when the catalyst preparation was upscaled from 2 g to [approximately] 30 g. The causes of the maldistribution that occurred during the scaling up of the catalyst preparation are under investigation. The catalyst which showed broad size distribution of ruthenium particles showed rapid deactivation during a test in Plant 700. Investigations are under way to improve the catalytic stability. Small angle X-ray scattering was used to characterize the reversed micelle solution used in the preparation of ruthenium catalysts. The volume averaged diameter of the water core for the reversed micelles is between 75 and 90 [Angstrom].

  9. Lysosomal delivery of a lipophilic gemcitabine prodrug using novel acid-sensitive micelles improved its antitumor activity

    PubMed Central

    Zhu, Saijie; Lansakara-P, Dharmika S.P.; Li, Xinran; Cui, Zhengrong

    2012-01-01

    Stimulus-sensitive micelles are attractive anticancer drug delivery systems. Herein we reported a novel strategy to engineer acid-sensitive micelles using a amphiphilic material synthesized by directly conjugating the hydrophilic polyethylene glycol (PEG) with a hydrophobic stearic acid derivative (C18) using an acid-sensitive hydrazone bond (PHC). An acid-insensitive PEG-amide-C18 (PAC) compound was also synthesized as a control. 4-(N)-stearoyl gemcitabine (GemC18), a prodrug of the nucleoside analog gemcitabine, was loaded into the micelles, and they were found to be significantly more cytotoxic to tumor cells than GemC18 solution, likely due to the lysosomal delivery of GemC18 by micelles. Moreover, GemC18 in the acid-sensitive PHC micelles was more cytotoxic than in the acid-insensitive PAC micelles, which may be attributed to the acid-sensitive release of GemC18 from the PHC micelles in lysosomes. In B16-F10 melanoma-bearing mice, GemC18-loaded PHC or PAC micelles showed a stronger antitumor activity than GemC18 or gemcitabine solution, likely because of the prolonged circulation time and increased tumor accumulation of the GemC18 by the micelles. Importantly, the in vivo antitumor activity of GemC18-loaded PHC micelles was significantly stronger than that of the PAC micelles, demonstrating the potential of the novel acid-sensitive micelles as an anticancer drug delivery system. PMID:22471294

  10. Brain-targeting study of stearic acid–grafted chitosan micelle drug-delivery system

    PubMed Central

    Xie, Yi-Ting; Du, Yong-Zhong; Yuan, Hong; Hu, Fu-Qiang

    2012-01-01

    Purpose Therapy for central nervous system disease is mainly restricted by the blood–brain barrier. A drug-delivery system is an effective approach to overcome this barrier. In this research, the potential of polymeric micelles for brain-targeting drug delivery was studied. Methods Stearic acid–grafted chitosan (CS-SA) was synthesized by hydrophobic modification of chitosan with stearic acid. The physicochemical characteristics of CS-SA micelles were investigated. bEnd.3 cells were chosen as model cells to evaluate the internalization ability and cytotoxicity of CS-SA micelles in vitro. Doxorubicin (DOX), as a model drug, was physically encapsulated in CS-SA micelles. The in vivo brain-targeting ability of CS-SA micelles was qualitatively and quantitatively studied by in vivo imaging and high-performance liquid chromatography analysis, respectively. The therapeutic effect of DOX-loaded micelles in vitro was performed on glioma C6 cells. Results The critical micelle concentration of CS-SA micelles with 26.9% ± 1.08% amino substitute degree was 65 μg/mL. The diameter and surface potential of synthesized CS-SA micelles in aqueous solution was 22 ± 0.98 nm and 36.4 ± 0.71 mV, respectively. CS-SA micelles presented excellent cellular uptake ability on bEnd.3 cells, the IC50 of which was 237.6 ± 6.61 μg/mL. DOX-loaded micelles exhibited slow drug-release behavior, with a cumulative release up to 72% within 48 hours in vitro. The cytotoxicity of DOX-loaded CS-SA micelles against C6 was 2.664 ± 0.036 μg/mL, compared with 0.181 ± 0.066 μg/mL of DOX · HCl. In vivo imaging results indicated that CS-SA was able to transport rapidly across the blood–brain barrier and into the brain. A maximum DOX distribution in brain of 1.01%/g was observed 15 minutes after administration and maintained above 0.45%/g within 1 hour. Meanwhile, free DOX · HCl was not detected in brain. In other major tissues, DOX-loaded micelles were mainly distributed into lung, liver, and

  11. Shaping and patterning gold nanoparticles via micelle templated photochemistry

    NASA Astrophysics Data System (ADS)

    Kundrat, F.; Baffou, G.; Polleux, J.

    2015-09-01

    Shaping and positioning noble metal nanostructures are essential processes that still require laborious and sophisticated techniques to fabricate functional plasmonic interfaces. The present study reports a simple photochemical approach compatible with micellar nanolithography and photolithography that enables the growth, arrangement and shaping of gold nanoparticles with tuneable plasmonic resonances on glass substrates. Ultraviolet illumination of surfaces coated with gold-loaded micelles leads to the formation of gold nanoparticles with micro/nanometric spatial resolution without requiring any photosensitizers or photoresists. Depending on the extra-micellar chemical environment and the illumination wavelength, block copolymer micelles act as reactive and light-responsive templates, which enable to grow gold deformed nanoparticles (potatoids) and nanorings. Optical characterization reveals that arrays of individual potatoids and rings feature a localized plasmon resonance around 600 and 800 nm, respectively, enhanced photothermal properties and high temperature sustainability, making them ideal platforms for future developments in nanochemistry and biomolecular manipulation controlled by near-infrared-induced heat.Shaping and positioning noble metal nanostructures are essential processes that still require laborious and sophisticated techniques to fabricate functional plasmonic interfaces. The present study reports a simple photochemical approach compatible with micellar nanolithography and photolithography that enables the growth, arrangement and shaping of gold nanoparticles with tuneable plasmonic resonances on glass substrates. Ultraviolet illumination of surfaces coated with gold-loaded micelles leads to the formation of gold nanoparticles with micro/nanometric spatial resolution without requiring any photosensitizers or photoresists. Depending on the extra-micellar chemical environment and the illumination wavelength, block copolymer micelles act as

  12. Radiochromic leuco dye micelle hydrogels: I. Initial investigation

    NASA Astrophysics Data System (ADS)

    Jordan, Kevin; Avvakumov, Nikita

    2009-11-01

    This investigation reports the use of surfactants and colorless leuco triarylmethane dyes to form a new class of radiochromic micelle hydrogels for three-dimensional (3D) water-equivalent dosimetry. Gelatin gel samples with several surfactants and leuco dyes were prepared and evaluated for optical transparency, dose sensitivity and diffusion rates. The addition of Triton X-100, a non-ionic surfactant, at levels exceeding the critical micelle concentration provides a transparent hydrogel in which the water insoluble leuco Malachite Green (LMG) can dissolve. During irradiation, the LMG dye precursor converts to Malachite Green (MG+). The most sensitive reported LMG gel formulation contains 0.3 mM LMG leuco dye, 16 mM trichloroacetic acid, 7 mM Triton X-100 and 4% w/w gelatin. A diffusion coefficient of 0.14 mm2 h-1 was determined for MG+ in this gel by fitting the time-dependent degradation of the transmission profile after irradiating half of the sample. The diffusion rate was three times lower than the standard radiochromic ferrous xylenol-orange (FX) gel. The primary feature of this 3D hydrogel is that it introduces transparent, radiochromic, micelle hydrogels. The radiochromic response to dose is instantaneous and images are stable for several hours. A dosimetric characterization revealed that the dose response is reproducible to within 10% over five separate batches and independent of both energy and dose rate. Uniform pre-irradiation of samples to 5 Gy provided a subsequent near linear response to greater than 110 Gy. LMG gels when read with a fast optical CT scanner can provide full 3D dose distributions in less than 30 min post-irradiation. LMG micelle gels scanned with a 633 nm light source are a promising system for quantitative water- or tissue-equivalent 3D dose verification in the 5-100 Gy dose range. These gels are useful for the scanning of larger volume dosimeters (i.e. >15 cm diameter) since they are easily prepared with inexpensive ingredients, are

  13. Folding Behaviors of Protein (Lysozyme) Confined in Polyelectrolyte Complex Micelle.

    PubMed

    Wu, Fu-Gen; Jiang, Yao-Wen; Chen, Zhan; Yu, Zhi-Wu

    2016-04-19

    The folding/unfolding behavior of proteins (enzymes) in confined space is important for their properties and functions, but such a behavior remains largely unexplored. In this article, we reported our finding that lysozyme and a double hydrophilic block copolymer, methoxypoly(ethylene glycol)5K-block-poly(l-aspartic acid sodium salt)10 (mPEG(5K)-b-PLD10), can form a polyelectrolyte complex micelle with a particle size of ∼30 nm, as verified by dynamic light scattering and transmission electron microscopy. The unfolding and refolding behaviors of lysozyme molecules in the presence of the copolymer were studied by microcalorimetry and circular dichroism spectroscopy. Upon complex formation with mPEG(5K)-b-PLD10, lysozyme changed from its initial native state to a new partially unfolded state. Compared with its native state, this copolymer-complexed new folding state of lysozyme has different secondary and tertiary structures, a decreased thermostability, and significantly altered unfolding/refolding behaviors. It was found that the native lysozyme exhibited reversible unfolding and refolding upon heating and subsequent cooling, while lysozyme in the new folding state (complexed with the oppositely charged PLD segments of the polymer) could unfold upon heating but could not refold upon subsequent cooling. By employing the heating-cooling-reheating procedure, the prevention of complex formation between lysozyme and polymer due to the salt screening effect was observed, and the resulting uncomplexed lysozyme regained its proper unfolding and refolding abilities upon heating and subsequent cooling. Besides, we also pointed out the important role the length of the PLD segment played during the formation of micelles and the monodispersity of the formed micelles. Furthermore, the lysozyme-mPEG(5K)-b-PLD10 mixtures prepared in this work were all transparent, without the formation of large aggregates or precipitates in solution as frequently observed in other protein

  14. Mechano-responsive hydrogels crosslinked by reactive block copolymer micelles

    NASA Astrophysics Data System (ADS)

    Xiao, Longxi

    Hydrogels are crosslinked polymeric networks that can swell in water without dissolution. Owing to their structural similarity to the native extracelluar matrices, hydrogels have been widely used in biomedical applications. Synthetic hydrogels have been designed to respond to various stimuli, but mechanical signals have not incorporated into hydrogel matrices. Because most tissues in the body are subjected to various types of mechanical forces, and cells within these tissues have sophisticated mechano-transduction machinery, this thesis is focused on developing hydrogel materials with built-in mechano-sensing mechanisms for use as tissue engineering scaffolds or drug release devices. Self-assembled block copolymer micelles (BCMs) with reactive handles were employed as the nanoscopic crosslinkers for the construction of covalently crosslinked networks. BCMs were assembled from amphiphilic diblock copolymers of poly(n-butyl acrylate) and poly(acrylic acid) partially modified with acrylate. Radical polymerization of acrylamide in the presence of micellar crosslinkers gave rise to elastomeric hydrogels whose mechanical properties can be tuned by varying the BCM composition and concentration. TEM imaging revealed that the covalently integrated BCMs underwent strain-dependent reversible deformation. A model hydrophobic drug, pyrene, loaded into the core of BCMs prior to the hydrogel formation, was dynamically released in response to externally applied mechanical forces, through force-induced reversible micelle deformation and the penetration of water molecules into the micelle core. The mechano-responsive hydrogel has been studied for tissue repair and regeneration purposes. Glycidyl methacrylate (GMA)-modified hyaluronic acid (HA) was photochemically crosslinked in the presence of dexamethasone (DEX)-loaded crosslinkable BCMs. The resultant HA gels (HAxBCM) contain covalently integrated micellar compartments with DEX being sequestered in the hydrophobic core. Compared

  15. Vibrational Energy Transfer Across a Reverse Micelle Surfactant Layer

    NASA Astrophysics Data System (ADS)

    Deàk, John C.; Pang, Yoonsoo; Sechler, Timothy D.; Wang, Zhaohui; Dlott, Dana D.

    2004-10-01

    In a suspension of reverse micelles, in which the surfactant sodium dioctyl sulfosuccinate (AOT) separates a water nanodroplet from a bulk nonpolar CCl4 phase, ultrafast vibrational spectroscopy was used to study vibrational energy transfer from the nanodroplet through the AOT interfacial monolayer to the surrounding CCl4. Most of the vibrational energy from the nanodroplet was transferred to the polar AOT head group within 1.8 picoseconds and then out to the CCl4 within 10 picoseconds. Vibrational energy pumped directly into the AOT tail resulted in a slower 20- to 40-picosecond transfer of energy to the CCl4.

  16. Vibrational energy transfer across a reverse micelle surfactant layer.

    PubMed

    Deàk, John C; Pang, Yoonsoo; Sechler, Timothy D; Wang, Zhaohui; Dlott, Dana D

    2004-10-15

    In a suspension of reverse micelles, in which the surfactant sodium dioctyl sulfosuccinate (AOT) separates a water nanodroplet from a bulk nonpolar CCl4 phase, ultrafast vibrational spectroscopy was used to study vibrational energy transfer from the nanodroplet through the AOT interfacial monolayer to the surrounding CCl4. Most of the vibrational energy from the nanodroplet was transferred to the polar AOT head group within 1.8 picoseconds and then out to the CCl4 within 10 picoseconds. Vibrational energy pumped directly into the AOT tail resulted in a slower 20- to 40-picosecond transfer of energy to the CCl4. PMID:15388896

  17. Self-assembled penetratin-deferasirox micelles as potential carriers for hydrophobic drug delivery.

    PubMed

    Goswami, Dibakar; Vitorino, Hector Aguilar; Machini, M Teresa; Espósito, Breno P

    2015-11-01

    There has been a growing interest in the use of micelles with nanofiber geometry as nanocarriers for hydrophobic drugs. Here we show that the conjugate of penetratin, a cell-penetrating peptide (CPP) with blood-brain barrier (BBB) permeability, and deferasirox (DFX), a hydrophobic iron chelator, self-assembles to form micelles at a very low concentration (∼15 mg/L). The critical micelle concentration (CMC) was determined, and the micelles were used for solubilizing curcumin, a hydrophobic anti-neurodegenerative drug, for successful delivery across RBE4 cells, a BBB model. Transmission Electron Microscope images of the curcumin-loaded micelles confirmed the formation of nanofibers. These results indicate the potential of CPP-drug conjugates for use as nanocarriers. PMID:25973759

  18. Process of forming compounds using reverse micelle or reverse microemulsion systems

    DOEpatents

    Linehan, John C.; Fulton, John L.; Bean, Roger M.

    1998-01-01

    The present invention is directed to a process for producing a nanometer-sized metal compound. The process comprises forming a reverse micelle or reverse microemulsion system comprising a polar fluid in a non-polar or low-polarity fluid. A first reactant comprising a multi-component, water-soluble metal compound is introduced into the polar fluid in a non-polar or low-polarity fluid. This first reactant can be introduced into the reverse micelle or reverse microemulsion system during formation thereof or subsequent to the formation of the reverse micelle or microemulsion system. The water-soluble metal compound is then reacted in the reverse micelle or reverse microemulsion system to form the nanometer-sized metal compound. The nanometer-sized metal compound is then precipitated from the reverse micelle or reverse microemulsion system.

  19. DNA polymerase beta reveals enhanced activity and processivity in reverse micelles.

    PubMed

    Anarbaev, Rashid O; Rogozina, Anastasia L; Lavrik, Olga I

    2009-04-01

    Water is essential for the stability and functions of proteins and DNA. Reverse micelles are simple model systems where the structure and dynamics of water are controlled. We have estimated the size of complex reverse micelles by light scattering technique and examined the local microenvironment using fluorescein as molecular probe. The micelle size and water polarity inside reverse micelles depend on water volume fraction. We have investigated the different hydration and confinement effects on activity, processivity, and stability of mammalian DNA polymerase beta in reverse micelles. The enzyme displays high processivity on primed single-stranded M13mp19 DNA with maximal activity at 10% of water content. The processivity and activity of DNA polymerase strongly depend on the protein concentration. The enzyme reveals also the enhanced stability in the presence of template-primer and at high protein concentration. The data provide direct evidence for strong influence of microenvironment on DNA polymerase activity. PMID:19138815

  20. Macroscopic alignment of nanoparticle arrays in soft crystals of cubic and cylindrical polymer micelles

    NASA Astrophysics Data System (ADS)

    Pozzo, D. C.; Walker, L. M.

    2008-05-01

    We describe a method to organize nanometer-sized hydrophilic particles into ordered arrays by templating them in the soft, micelle-crystal phases (spherical and cylindrical) of a thermoreversible block copolymer. Small-angle neutron scattering (SANS) with contrast variation is used to show that the dispersed particles (in this case, proteins or silica) form structured arrays by being constrained in the interstitial cavities between the polymer micelles in the ordered micelle crystal. Simple shear is used to macroscopically align both phases of the nanocomposites (micelles and particles) into macro-domains. The temperature-induced order-order transition between templates of spherical and cylindrical micelles is demonstrated as a reversible technique to modify the structure of the templated nanoparticle arrays.

  1. Methoxy poly(ethylene glycol) conjugated doxorubicin micelles for effective killing of cancer cells.

    PubMed

    Zhang, Liming; Xia, Kai; Deng, Yan; Li, Song; Zhang, Chuanxiang; Lu, Zhuoxuan; He, Nongyue

    2014-08-01

    Methoxy poly(ethylene glycol) conjugated doxorubicin (mPEG-DOX) micelles are prepared for delivering drug effectively. The core of the unimolecular micelle is a DOX (doxorubicin) which is an anti-cancer chemotherapy drug, while the outer hydrophilic shell is composed of poly(ethylene glycol) (PEG) segments. Dynamic light scattering (DLS) analysis shows that the unimolecular micelles are uniform with a mean hydrodynamic diameter around 250 nm. The mPEG-DOX micelles can be internalized by the cancer cells and exhibit good cell uptake by the fluorescence microscopy. Obvious cytotoxicity is also observed when the concentration (count on DOX) is over 1 μg/mL. These findings indicate that these unique unimolecular micelles may offer a very promising approach for targeted cancer therapy. PMID:25936136

  2. Effect of water on the local electric potential of simulated ionic micelles.

    PubMed

    Brodskaya, Elena N; Vanin, Alexander A

    2015-07-28

    Ionic micelles in an aqueous solution containing single-charged counter-ions have been simulated by molecular dynamics. For both cationic and anionic micelles, it has been demonstrated that explicit description of solvent has strong effect on the micelle's electric field. The sign of the local charge alters in the immediate vicinity of the micellar crown and the electric potential varies nonmonotonically. Two micelle models have been examined: the hybrid model with a rigid hydrocarbon core and the atomistic model. For three molecular models of water (Simple Point Charge model (SPC), Transferable Intermolecular Potential 5- Points (TIP5P) and two-centered S2), the results have been compared with those for the continuum solvent model. The orientational ordering of solvent molecules has strong effect on the local electric field surprisingly far from the micelle surface. PMID:26233157

  3. Kinetics of formation of bile salt micelles from coarse-grained Langevin dynamics simulations.

    PubMed

    Vila Verde, Ana; Frenkel, Daan

    2016-06-21

    We examine the mechanism of formation of micelles of dihydroxy bile salts using a coarse-grained, implicit solvent model and Langevin dynamics simulations. We find that bile salt micelles primarily form via addition and removal of monomers, similarly to surfactants with typical head-tail molecular structures, and not via a two-stage mechanism - involving formation of oligomers and their subsequent aggregation to form larger micelles - originally proposed for bile salts. The free energy barrier to removal of single bile monomers from micelles is ≈2kBT, much less than what has been observed for head-tail surfactants. Such a low barrier may be biologically relevant: it allows for rapid release of bile monomers into the intestine, possibly enabling the coverage of fat droplets by bile salt monomers and subsequent release of micelles containing fats and bile salts - a mechanism that is not possible for ionic head-tail surfactants of similar critical micellar concentrations. PMID:27199094

  4. Spectrometric study on the binding of curcumin with AOT: effect of micelle-to-vesicle transition.

    PubMed

    Zhou, Haibo; Yang, Qianqian; Wang, Xiaoyong

    2014-10-15

    In this work, the role of micelle-to-vesicle transition of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in the binding, stability and antioxidant activity of curcumin has been studied using absorption and fluorescence measurements. As AOT molecules aggregate into micelles and vesicles, curcumin bound with AOT often gives higher intensities of absorption and fluorescence than that of free curcumin. The most enhanced absorption and fluorescence of curcumin induced by AOT vesicles, are attributed to the location of curcumin in their lipid bilayer. The measurement of curcumin anisotropy suggests that the bilayer of AOT vesicles provides curcumin with a more hydrophobic microenvironment than the palisade layer of AOT micelles. The binding constant (Kb) of curcumin with AOT vesicles is three times that of curcumin with AOT micelles. Moreover, AOT vesicles are found to be superior to AOT micelles for enhancing the stability and radical scavenging ability of curcumin. PMID:24837931

  5. Effective repair of traumatically injured spinal cord by nanoscale block copolymer micelles

    NASA Astrophysics Data System (ADS)

    Shi, Yunzhou; Kim, Sungwon; Huff, Terry B.; Borgens, Richard B.; Park, Kinam; Shi, Riyi; Cheng, Ji-Xin

    2010-01-01

    Spinal cord injury results in immediate disruption of neuronal membranes, followed by extensive secondary neurodegenerative processes. A key approach for repairing injured spinal cord is to seal the damaged membranes at an early stage. Here, we show that axonal membranes injured by compression can be effectively repaired using self-assembled monomethoxy poly(ethylene glycol)-poly(D,L-lactic acid) di-block copolymer micelles. Injured spinal tissue incubated with micelles (60 nm diameter) showed rapid restoration of compound action potential and reduced calcium influx into axons for micelle concentrations much lower than the concentrations of polyethylene glycol, a known sealing agent for early-stage spinal cord injury. Intravenously injected micelles effectively recovered locomotor function and reduced the volume and inflammatory response of the lesion in injured rats, without any adverse effects. Our results show that copolymer micelles can interrupt the spread of primary spinal cord injury damage with minimal toxicity.

  6. Micelle structural studies on oil solubilization by a small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Putra, Edy Giri Rachman; Seong, Baek Seok; Ikram, Abarrul

    2009-02-01

    A small-angle neutron scattering (SANS) technique was applied to reveal the micelle structural changes. The micelle structural changes of 0.3 M sodium dodecyl sulfate (SDS) concentration by addition of various oil, i.e. n-hexane, n-octane, and n-decane up to 60% (v/v) have been investigated. It was found that the size, aggregation number and the structures of the micelles changed exhibiting that the effective charge on the micelle decreases with an addition of oil. There was a small increase in minor axis of micelle while the correlation peak shifted to a lower momentum transfer Q and then to higher Q by a further oil addition.

  7. Effect of water on the local electric potential of simulated ionic micelles

    NASA Astrophysics Data System (ADS)

    Brodskaya, Elena N.; Vanin, Alexander A.

    2015-07-01

    Ionic micelles in an aqueous solution containing single-charged counter-ions have been simulated by molecular dynamics. For both cationic and anionic micelles, it has been demonstrated that explicit description of solvent has strong effect on the micelle's electric field. The sign of the local charge alters in the immediate vicinity of the micellar crown and the electric potential varies nonmonotonically. Two micelle models have been examined: the hybrid model with a rigid hydrocarbon core and the atomistic model. For three molecular models of water (Simple Point Charge model (SPC), Transferable Intermolecular Potential 5- Points (TIP5P) and two-centered S2), the results have been compared with those for the continuum solvent model. The orientational ordering of solvent molecules has strong effect on the local electric field surprisingly far from the micelle surface.

  8. Cisplatin-loaded core cross-linked micelles: comparative pharmacokinetics, antitumor activity, and toxicity in mice

    PubMed Central

    Oberoi, Hardeep S; Nukolova, Natalia V; Laquer, Frederic C; Poluektova, Larisa Y; Huang, Jiangeng; Alnouti, Yazen; Yokohira, Masanao; Arnold, Lora L; Kabanov, Alexander V; Cohen, Samuel M; Bronich, Tatiana K

    2012-01-01

    Polymer micelles with cross-linked ionic cores are shown here to improve the therapeutic performance of the platinum-containing anticancer compound cisplatin. Biodistribution, antitumor efficacy, and toxicity of cisplatin-loaded core cross-linked micelles of poly(ethylene glycol)-b-poly(methacrylic acid) were evaluated in a mouse ovarian cancer xenograft model. Cisplatin-loaded micelles demonstrated prolonged blood circulation, increased tumor accumulation, and reduced renal exposure. Improved antitumor response relative to free drug was seen in a mouse model. Toxicity studies with cisplatin-loaded micelles indicate a significantly improved safety profile and lack of renal abnormalities typical of free cisplatin treatment. Overall, the study supports the fundamental possibility of improving the potential of platinum therapy using polymer micelle-based drug delivery. PMID:22745537

  9. Vitamin E containing polymer micelles for reducing normal cell cytotoxicity and enhancing chemotherapy efficacy.

    PubMed

    Lee, Kuan-Yi; Chiang, Yi-Ting; Hsu, Ning-Yu; Yang, Chieh-Yu; Lo, Chun-Liang; Ku, Chen-An

    2015-09-01

    An α-tocopheryl succinate (α-TOS) containing diblock copolymer micellar system was used to deliver doxorubicin (Dox), an anticancer drug, for HCT116 colon cancer therapy. The α-TOS containing diblock copolymers were synthesized by conjugation of α-TOS molecules and a mPEG-b-PHEMA hydrophilic diblock copolymer by ester bonds. The Dox-loaded polymeric micelles were then obtained by solvent exchange process. In acidic surroundings such as endosomes or secondary lysosomes, the structures of the Dox-loaded polymeric micelles deformed and released the drug loads. Additionally, Dox-loaded polymeric micelles enhanced the cytotoxicity of Dox and α-TOS to cancer cells in vitro. Dox-loaded polymeric micelles also showed an exceptional tumor inhibiting effect in vivo. This study indicates that the α-TOS containing polymeric micelle system can be used as a drug carrier for cancer therapy. PMID:26087112

  10. Amputation des quatre membres

    PubMed Central

    Feruzi, Maruis Kitembo; Milindi, Cédrick Sangwa; Zabibu, Mireille Kakinga; Mulefu, Jules Panda; Katombe, Francois Tshilombo

    2014-01-01

    Les auteurs présentent les cas d'amputation des quatre membres réalisée chez trois patients différents. Ce sont des amputations réalisées pour chaque patient au cours d'une seule hospitalisation et en un seul temps opératoire. Deux patients pour gangrène sèche infectée et un pour amputation traumatique des quatre membres. L'amputation d'urgence a été pratiquée en premier temps suivie de remodelage des moignons d'amputation en second temps. L’évolution de tous les patients a été bonne. PMID:25469177

  11. Vitamin E succinate-conjugated F68 micelles for mitoxantrone delivery in enhancing anticancer activity

    PubMed Central

    Liu, Yuling; Xu, Yingqi; Wu, Minghui; Fan, Lijiao; He, Chengwei; Wan, Jian-Bo; Li, Peng; Chen, Meiwan; Li, Hui

    2016-01-01

    Mitoxantrone (MIT) is a chemotherapeutic agent with promising anticancer efficacy. In this study, Pluronic F68-vitamine E succinate (F68-VES) amphiphilic polymer micelles were developed for delivering MIT and enhancing its anticancer activity. MIT-loaded F68–VES (F68–VES/MIT) micelles were prepared via the solvent evaporation method with self-assembly under aqueous conditions. F68–VES/MIT micelles were found to be of optimal particle size with the narrow size distribution. Transmission electron microscopy images of F68–VES/MIT micelles showed homogeneous spherical shapes and smooth surfaces. F68–VES micelles had a low critical micelle concentration value of 3.311 mg/L, as well as high encapsulation efficiency and drug loading. Moreover, F68–VES/MIT micelles were stable in the presence of fetal bovine serum for 24 hours and maintained sustained drug release in vitro. Remarkably, the half maximal inhibitory concentration (IC50) value of F68–VES/MIT micelles was lower than that of free MIT in both MDA-MB-231 and MCF-7 cells (two human breast cancer cell lines). In addition, compared with free MIT, there was an increased trend of apoptosis and cellular uptake of F68–VES/MIT micelles in MDA-MB-231 cells. Taken together, these results indicated that F68–VES polymer micelles were able to effectively deliver MIT and largely improve its potency in cancer therapy. PMID:27471384

  12. Enhancement of triptolide-loaded micelles on tumorigenicity inhibition of human ovarian cancer.

    PubMed

    Wang, You; Liu, Ting; Li, He

    2016-05-01

    Triptolide (TP), a diterpenoid obtained from Tripterygium wilfordii Hook.f, has shown its antitumor activities against a variety of cancers in vitro in recent years. Unfortunately, TP has a small margin between the therapeutic and toxic doses and shows serious toxicity which limits its uses in antitumor treatment. In our previous study, Triptolide-loaded micelles (TP micelles), a TP drug delivery system with a sustained release behavior, had been reported to decrease TP uptake in the liver to relieve its toxicity, and increase TP distribution in the ovary to enhance its effects. This work therefore aimed at evaluating the inhibitory ability of TP micelles in the proliferation, apoptosis, invasion, and migration, and compared with free TP in SKOV3 cells. Our results showed that TP micelles inhibited the proliferation of SKOV3 in a time- and dose-dependent manner, and exhibited enhanced inhibition following 48 and 72 h treatment compared to TP. Cell cycle analysis revealed that TP and TP micelles inhibited cell proliferation by blocking their progression from the G2/M phase to the S phase. Although TP induced a significant increase in cell apoptosis, TP micelles showed a superior effect following 48 and 72 h treatment. Induction of caspase-dependent way and inhibition of NF-κB activation were found to be involved in the mechanism of TP micelles-induced apoptosis. Furthermore, the wound healing assay and transwell assay showed that both TP and TP micelles could obviously inhibit SKOV3 cells migration and invasion. Overall, TP micelles exhibited enhanced therapeutic efficacy in ovarian cancer in vitro due to its prolonged release and redistribution compared with the free TP. TP micelles might lead to an increase in tumorigenicity inhibition and a decrease in resistance and incidence simultaneously, indicating that it offers a new strategy with promising characteristics for TP chemotherapy application for ovarian cancer. PMID:26786618

  13. Stimulated release of photosensitizers from graft and diblock micelles for photodynamic therapy.

    PubMed

    Tsai, Hsieh-Chih; Tsai, Cheng-Hung; Lin, Shuian-Yin; Jhang, Chang-Rong; Chiang, Yung-Sheng; Hsiue, Ging-Ho

    2012-02-01

    To understand the effect of photosensitizer (PS) release from graft copolymer based micelles in photodynamic therapy (PDT), the two pH-sensitive and non-pH-sensitive graft copolymers, (poly(N-vinyly caprolactam)-g-poly(D,L-lactide) and poly(N-vinyly caprolactam-co-N-vinyl imidazole)-g-poly(D,L-lactide)), were synthesized and utilized for the encapsulation of protoporphyrin IX (PPIX) for in vitro and in vivo PDT studies. Photochemical internalization (PCI) was utilized to study the localization of pH- and non-pH-sensitive micelles uptake in the lysosome. After non-toxic light treatment, PPIX was found in the nucleus with pH-sensitive micelles, while PPIX was still localized in the lysosomal organism with the non-pH-sensitive micelles, as observed by confocal microscopy. Because the formation of singlet oxygen was observed for the block and graft micelles, dramatic differences in the cell viability could be ascribed to the damage occurring at the region where the PPIX was located. An in vivo study revealed that PPIX-loaded graft and diblock micelles presented prolonged blood circulation and enhanced tumor targeting ability. The PPIX released from g-CIM micelles on tumor site was further proved by ex vivo confocal image. In addition, non-pH-sensitive micelle-treated mice showed a better repression of tumor growth than PPIX-treated mice, which was likely due to the larger amount of PS localized in the tumor region still exhibiting therapeutic effects. Finally, effective PDT-induced inhibition of tumor growth was found in pH-sensitive micelle-treated mice. This work provides insight into PS-loaded graft and diblock micelles for the PDT of tumors. PMID:22142770

  14. Tuning Cationic Block Copolymer Micelle Size by pH and Ionic Strength.

    PubMed

    Sprouse, Dustin; Jiang, Yaming; Laaser, Jennifer E; Lodge, Timothy P; Reineke, Theresa M

    2016-09-12

    The formation, morphology, and pH and ionic strength responses of cationic block copolymer micelles in aqueous solutions have been examined in detail to provide insight into the future development of cationic micelles for complexation with polyanions such as DNA. Diblock polymers composed of a hydrophilic/cationic block of N,N-dimethylaminoethyl methacrylate (DMAEMA) and a hydrophobic/nonionic block of n-butyl methacrylate (BMA) were synthesized [denoted as DMAEMA-b-BMA (X-Y), where X = DMAEMA molecular weight and Y = molecular weight of BMA in kDa]. Four variants were created with block molecular weights of 14-13, 14-23, 27-14, 27-29 kDa and low dispersities less than 1.10. The amphiphilic polymers self-assembled in aqueous conditions into core-shell micelles that ranged in size from 25-80 nm. These cationic micelles were extensively characterized in terms of size and net charge in different buffers over a wide range of ionic strength (0.02-1 M) and pH (5-10) conditions. The micelle core is kinetically trapped, and the corona contracts with increasing pH and ionic strength, consistent with previous work on micelles with glassy polystyrene cores, indicating that the corona properties are independent of the dynamics of the micelle core. The contraction and extension of the corona scales with solution ionic strength and charge fraction of the amine groups. The aggregation numbers of the micelles were obtained by static light scattering, and the Rg/Rh ratios are close to that of a hard sphere. The zeta potentials of the micelles were positive up to two pH units above the corona pKa, suggesting that applications relying on micelle charge for stability should be viable over a wide range of solution conditions. PMID:27487088

  15. Molecular dynamics study of solubilization of immiscible solutes by a micelle: Free energy of transfer of alkanes from water to the micelle core by thermodynamic integration method.

    PubMed

    Fujimoto, K; Yoshii, N; Okazaki, S

    2010-08-21

    Free energy of transfer, DeltaG(w-->m), from water phase to a sodium dodecyl sulfate (SDS) micelle core has been calculated for a series of hydrophobic solutes originally immiscible with water by thermodynamic integration method combined with molecular dynamics calculations. The calculated free energy of transfer is in good correspondence to the experiment as well as the theoretical free energy of transfer. The calculated DeltaG(w-->m)'s are all negative, implying that the alkane molecules are more stable in the micelle than in the water phase. It decreases almost linearly as a function of the number of carbon atoms of the alkanes longer than methane with a decrement of 3.3 kJ mol(-1) per one methylene group. The calculated free energy of transfer indicates that, for example, at the micelle concentration of 50 CMC (critical micelle concentration), about only 1 of 6 micelles or 1 of 32 000 micelles does not contain a solute methane or n-octane molecule, respectively. PMID:20726656

  16. Molecular dynamics study of solubilization of immiscible solutes by a micelle: Free energy of transfer of alkanes from water to the micelle core by thermodynamic integration method

    NASA Astrophysics Data System (ADS)

    Fujimoto, K.; Yoshii, N.; Okazaki, S.

    2010-08-01

    Free energy of transfer, ΔGw→m, from water phase to a sodium dodecyl sulfate (SDS) micelle core has been calculated for a series of hydrophobic solutes originally immiscible with water by thermodynamic integration method combined with molecular dynamics calculations. The calculated free energy of transfer is in good correspondence to the experiment as well as the theoretical free energy of transfer. The calculated ΔGw→m's are all negative, implying that the alkane molecules are more stable in the micelle than in the water phase. It decreases almost linearly as a function of the number of carbon atoms of the alkanes longer than methane with a decrement of 3.3 kJ mol-1 per one methylene group. The calculated free energy of transfer indicates that, for example, at the micelle concentration of 50 CMC (critical micelle concentration), about only 1 of 6 micelles or 1 of 32 000 micelles does not contain a solute methane or n-octane molecule, respectively.

  17. Multiscale full waveform inversion

    NASA Astrophysics Data System (ADS)

    Fichtner, Andreas; Trampert, Jeannot; Cupillard, Paul; Saygin, Erdinc; Taymaz, Tuncay; Capdeville, Yann; Villaseñor, Antonio

    2013-07-01

    We develop and apply a full waveform inversion method that incorporates seismic data on a wide range of spatio-temporal scales, thereby constraining the details of both crustal and upper-mantle structure. This is intended to further our understanding of crust-mantle interactions that shape the nature of plate tectonics, and to be a step towards improved tomographic models of strongly scale-dependent earth properties, such as attenuation and anisotropy. The inversion for detailed regional earth structure consistently embedded within a large-scale model requires locally refined numerical meshes that allow us to (1) model regional wave propagation at high frequencies, and (2) capture the inferred fine-scale heterogeneities. The smallest local grid spacing sets the upper bound of the largest possible time step used to iteratively advance the seismic wave field. This limitation leads to extreme computational costs in the presence of fine-scale structure, and it inhibits the construction of full waveform tomographic models that describe earth structure on multiple scales. To reduce computational requirements to a feasible level, we design a multigrid approach based on the decomposition of a multiscale earth model with widely varying grid spacings into a family of single-scale models where the grid spacing is approximately uniform. Each of the single-scale models contains a tractable number of grid points, which ensures computational efficiency. The multi-to-single-scale decomposition is the foundation of iterative, gradient-based optimization schemes that simultaneously and consistently invert data on all scales for one multi-scale model. We demonstrate the applicability of our method in a full waveform inversion for Eurasia, with a special focus on Anatolia where coverage is particularly dense. Continental-scale structure is constrained by complete seismic waveforms in the 30-200 s period range. In addition to the well-known structural elements of the Eurasian mantle

  18. Dynamic multicompartment-core micelles in aqueous media.

    PubMed

    Schacher, Felix; Walther, Andreas; Müller, Axel H E

    2009-09-15

    We investigate micellar aggregates of amphiphilic block terpolymers, polybutadiene-block-poly(2-vinyl pyridine)-block-poly(methacrylic acid) (PB800P2VP190PMAA550) and their quaternized analogues polybutadiene-block-poly(N-methyl-2-vinylpyridinium)-block-poly(methacrylic acid) (PB800P2VPq190PMAA550) in aqueous solution using light scattering (DLS, SLS) and cryogenic transmission electron microscopy (cryo-TEM). At high pH, PB800P2VP190PMAA550 forms core--shell--corona micelles with a hydrodynamic radius Rh approximately 100 nm and a continuous shell of P2VP. However, at pH 4 partial intramicellar interpolyelectrolyte complex (im-IPEC) formation between P2VP and PMAA results in a patchy, collapsed shell. This is far more pronounced for the quaternized analogue, PB800P2VPq190PMAA550, which forms aggregates of similar size, also exhibiting a noncontinuous, patchy shell. Here, these im-IPECs of the positively charged P2VPq and the partially negatively charged PMAA are present over the whole investigated pH range (4-10). We further demonstrate that size and charge of the corona can be tuned through the block terpolymer composition, in particular, the ratio between P2VPq and PMAA. These micelles are dynamic and able to react to changes in pH or salinity in terms of corona diameter and aggregation number. PMID:19537738

  19. pH-Responsive Micelle Sequestrant Polymers Inhibit Fat Absorption.

    PubMed

    Qian, Jian; Sullivan, Bradley P; Berkland, Cory

    2015-08-10

    Current antiobesity therapeutics are associated with side effects and/or poor long-term patient compliance, necessitating development of more efficacious and safer alternatives. Herein, we designed and engineered a new class of orally acting pharmaceutical agents, or micelle sequestrant polymers (MSPs), that could respond to the pH change in the gastrointestinal (GI) tract and potentially sequester lipid micelles; inhibiting lipid absorption through a pH-triggered flocculation process. These MSPs, derived from poly(2-(diisopropylamino)ethyl methacrylate) and poly(2-(dibutylamino)ethyl methacrylate), were soluble in acidic media, but they transitioned to become insoluble around pH 7.2 and 6.1, respectively. MSPs showed substantial bile acid and triglyceride sequestration capacity with fast pH response tested in vitro. In vivo study showed that orally dosed MSPs significantly enhanced fecal elimination of triglycerides and bile acids. Several MSPs increased fecal elimination of triglycerides by 9-10 times compared with that of the control. In contrast, fecal concentration of bile acids, but not triglycerides, was increased by cholestyramine or Welchol. Importantly, fecal elimination of bile acids and triglycerides was unaltered by addition of control dietary fibers. MSPs may serve as a novel approach to weight loss that inhibits excess caloric intake by preventing absorption of excess dietary triglycerides. PMID:26133544

  20. Micelle assisted structural conversion with fluorescence modulation of benzophenanthridine alkaloids.

    PubMed

    Pradhan, Ankur Bikash; Bhuiya, Sutanwi; Haque, Lucy; Tiwari, Richa; Das, Suman

    2017-01-01

    In this study we have reported the anionic surfactant (Sodium dodecyl sulfate, SDS) driven structural conversion of two benzophenanthridine plant alkaloids namely Chelerythrine (herein after CHL) and Sanguinarine (herein after SANG). Both the alkaloids exist in two forms: the charged iminium and the neutral alkanolamine form. The iminium form is stable at low pH (<6.5) and the alkanolamine form exists at higher pH (>10.1). The fluorescence intensity of the alkanolamine form is much stronger than the iminium form. The iminium form of both the alkaloids remains stable whereas the alkanolamine form gets converted to the iminium form in the SDS micelle environment. The iminium form possesses positive charge and it seems that electrostatic interaction between the positively charged iminium and negatively charged surfactant leads to the stabilization of the iminium form in the Stern layer of the anionic micelle. Whereas the conversion of the alkanolamine form into the iminium form takes place and that can be monitored in naked eye since the iminium form is orange in colour and the alkanolamine form has blue violet emission. Such a detail insight about the photophysical properties of the benzophenanthridine alkaloids would be a valuable addition in the field of alkaloid-surfactant interaction. PMID:27419642

  1. Skin delivery by block copolymer nanoparticles (block copolymer micelles).

    PubMed

    Laredj-Bourezg, Faiza; Bolzinger, Marie-Alexandrine; Pelletier, Jocelyne; Valour, Jean-Pierre; Rovère, Marie-Rose; Smatti, Batoule; Chevalier, Yves

    2015-12-30

    Block copolymer nanoparticles often referred to as "block copolymer micelles" have been assessed as carriers for skin delivery of hydrophobic drugs. Such carriers are based on organic biocompatible and biodegradable materials loaded with hydrophobic drugs: poly(lactide)-block-poly(ethylene glycol) copolymer (PLA-b-PEG) nanoparticles that have a solid hydrophobic core made of glassy poly(d,l-lactide), and poly(caprolactone)-block-poly(ethylene glycol) copolymer (PCL-b-PEG) nanoparticles having a liquid core of polycaprolactone. In vitro skin absorption of all-trans retinol showed a large accumulation of retinol in stratum corneum from both block copolymer nanoparticles, higher by a factor 20 than Polysorbate 80 surfactant micelles and by a factor 80 than oil solution. Additionally, skin absorption from PLA-b-PEG nanoparticles was higher by one order of magnitude than PCL-b-PEG, although their sizes (65nm) and external surface (water-swollen PEG layer) were identical as revealed by detailed structural characterizations. Fluorescence microscopy of histological skin sections provided a non-destructive picture of the storage of Nile Red inside stratum corneum, epidermis and dermis. Though particle cores had a different physical states (solid or liquid as measured by (1)H NMR), the ability of nanoparticles for solubilization of the drug assessed from their Hildebrand solubility parameters appeared the parameter of best relevance regarding skin absorption. PMID:26602293

  2. Purification of a membrane protein with conjugated engineered micelles.

    PubMed

    Patchornik, Guy; Danino, Dganit; Kesselman, Ellina; Wachtel, Ellen; Friedman, Noga; Sheves, Mordechai

    2013-07-17

    A novel method for purifying membrane proteins is presented. The approach makes use of engineered micelles composed of a nonionic detergent, β-octylglucoside, and a hydrophobic metal chelator, bathophenanthroline. Via the chelators, the micelles are specifically conjugated, i.e., tethered, in the presence of Fe(2+) ions, thereby forming micellar aggregates which provide the environment for separation of lipid-soluble membrane proteins from water-soluble proteins. The micellar aggregates (here imaged by cryo-transmission electron microscopy) successfully purify the light driven proton pump, bacteriorhodopsin (bR), from E. coli lysate. Purification takes place within 15 min and can be performed both at room temperature and at 4 °C. More than 94% of the water-soluble macromolecules in the lysate are excluded, with recovery yields of the membrane protein ranging between 74% and 85%. Since this approach does not require precipitants, high concentrations of detergent to induce micellar aggregates, high temperature, or changes in pH, it is suggested that it may be applied to the purification of a wide variety of membrane proteins. PMID:23758098

  3. Reverse Micelle Based Synthesis of Microporous Materials in Microgravity

    NASA Technical Reports Server (NTRS)

    Dutta, Prabir K.

    1995-01-01

    Formation of zincophosphates from zinc and phosphate containing reverse micelles (water droplets in hexane) has been examined. The frameworks formed resemble that made by conventional hydrothermal synthesis. Dynamics of crystal growth are however quite different, and form the main focus of this study. In particular, the formation of zincophosphate with the sodalite framework was examined in detail. The intramicellar pH was found to have a strong influence on crystal growth. Crystals with a cubic morphology were formed directly from the micelles, without an apparent intermediate amorphous phase over a period of four days by a layer-bylayer growth at the intramicellar pH of 7.6. At a pH of 6.8, an amorphous precipitate rapidly sediments in hours. Sodalite was eventually formed from this settled phase via surface diffusion and reconstruction within four days. With a rotating cell, it was possible to minimize sedimentation and crystals were found to grow epitaxially from the spherical, amorphous particles. Intermediate pH's of 7.2 led to formation of aggregated sodalite crystals prior to settling, again without any indication of an intermediate amorphous phase. These diverse pathways were possible due to changes in intramicellar supersaturation conditions by minor changes in pH. In contrast, conventional syntheses in this pH range all proceeded by similar crystallization pathways through an amorphous gel. This study establishes that synthesis of microporous frameworks is not only possible in reverse micellar systems, but they also allow examination of possible crystallization pathways.

  4. Nonionic surfactants enhancing bactericidal activity at their critical micelle concentrations.

    PubMed

    Tobe, Seiichi; Majima, Toshiaki; Tadenuma, Hirohiko; Suekuni, Tomonari; Sakai, Kenichi; Sakai, Hideki; Abe, Masahiko

    2015-01-01

    Bactericidal activities of benzalkonium chloride [also known as alkyldimethylbenzylammonium chloride (ADBAC)] containing nonionic surfactants such as methyl ester ethoxylates (MEE) with the alkyl group C8-C14 and oxyethylene (EO) group of average adduct number 3-15 were measured against Escherichia coli and Staphylococcus aureus. Sample solutions containing MEE in the vicinity of the critical micelle concentration exhibited a dramatic decrease in viable bacterial counts. MEE with an alkyl group of C12 and an oxyethylene group of lower adduct number exhibited little viable bacterial counts than those having higher EO adduct numbers. MEE with reduced EO adduct numbers increased fluorescence intensity in E. coli using the viability stain SYTO 9. Our results show that MEE molecules with low EO adduct numbers exhibited bactericidal activity by increasing the permeability of the E. coli cell membrane. Sample solution containing ADBAC and MEE molecules with lower EO adduct numbers also displayed higher zeta potentials. Moreover, ADBAC molecules incorporated into micelles of MEE with lower EO adduct numbers were adsorbed onto the surface of E. coli, which augmented bactericidal activity. PMID:25492231

  5. Thermodynamics of mixed micelles: Determination of the aggregate composition.

    PubMed

    Letellier, Pierre; Mayaffre, Alain; Turmine, Mireille

    2008-11-01

    In most studies concerning surfactant mixtures, the determination of the composition of mixed micelles is often tricky. This composition can be obtained by different ways. One of them, undoubtedly the most used, supposes, a priori, that the surfactant in the micelle follows the regular solution model. This poses a problem on the thermodynamic point of view because in these studies, a model of behavior is first admitted for deducing a composition. In a correct thermodynamic approach, a composition should first be determined and then, a model of behavior which accounts for the observed physicochemical properties can be found. This approach is all the more questionable since the application of the Gibbs-Duhem relationship to the pseudo-phase allows aggregate composition to be determined simply, without using a solution model, because the composition of the bulk at the threshold of aggregation is known. In this article, we describe and validate a simple procedure, which supplements that proposed by Rodenas et al. [E. Rodenas, M. Valiente, M.D. Villafruela, J. Phys. Chem. B 103 (1999) 4549], and which allows determination of the activities of the components of the micellar aggregate and its composition. The results are compared to those obtained with other approaches such as molecular-thermodynamic model. PMID:18723182

  6. Fractionation of salivary micelle-like structures by gel chromatography.

    PubMed

    Rykke, M; Young, A; Devold, T; Smistad, G; Rölla, G

    1997-10-01

    Globular structures have been demonstrated in human parotid saliva by transmission electron microscopy and photon correlation spectroscopy. The aim of this study was to fractionate these salivary globular structures for analytical and preparative purposes using a gel-filtration material capable of separating spherical particles up to 300-400 nm in diameter. Freshly obtained parotid saliva was applied to a Sephacryl S-1000 column. Peak fractions were collected and prepared for transmission electron microscopy (TEM) or for amino acid analysis. Bovine milk was included as the casein micelles by TEM appear to be similar to the salivary aggregates and their elution profiles are known. The salivary globular structures were eluted in one major peak. TEM of negatively stained samples from the peak fractions demonstrated globular protein aggregates consistent with the salivary structures in parotid saliva. Amino acid analysis showed characteristic amino acid profiles with unusual high levels of proline, 40-45%. The casein micelles were eluted in one major peak and separated from the whey proteins. This study indicates that the salivary globular structures can be isolated by gel chromatography. The amino acid analysis indicates that proline-rich proteins may be an important fraction of the salivary globular structures. PMID:9395115

  7. Neighborhood inverse consistency preprocessing

    SciTech Connect

    Freuder, E.C.; Elfe, C.D.

    1996-12-31

    Constraint satisfaction consistency preprocessing methods are used to reduce search effort. Time and especially space costs limit the amount of preprocessing that will be cost effective. A new form of consistency preprocessing, neighborhood inverse consistency, can achieve more problem pruning than the usual arc consistency preprocessing in a cost effective manner. There are two basic ideas: (1) Common forms of consistency enforcement basically operate by identifying and remembering solutions to subproblems for which a consistent value cannot be found for some additional problem variable. The space required for this memory can quickly become prohibitive. Inverse consistency basically operates by removing values for variables that are not consistent with any solution to some subproblem involving additional variables. The space requirement is at worst linear. (2) Typically consistency preprocessing achieves some level of consistency uniformly throughout the problem. A subproblem solution will be tested against each additional variable that constrains any subproblem variable. Neighborhood consistency focuses attention on the subproblem formed by the variables that are all constrained by the value in question. By targeting highly relevant subproblems we hope to {open_quotes}skim the cream{close_quotes}, obtaining a high payoff for a limited cost.

  8. Biodegradable self-assembled PEG-PCL-PEG micelles for hydrophobic honokiol delivery: I. Preparation and characterization

    NASA Astrophysics Data System (ADS)

    Gong, ChangYang; Wei, XiaWei; Wang, XiuHong; Wang, YuJun; Guo, Gang; Mao, YongQiu; Luo, Feng; Qian, ZhiYong

    2010-05-01

    This study aims to develop self-assembled poly(ethylene glycol)-poly(ɛ-caprolactone)-poly(ethylene glycol) (PEG-PCL-PEG, PECE) micelles to encapsulate hydrophobic honokiol (HK) in order to overcome its poor water solubility and to meet the requirement of intravenous administration. Honokiol loaded micelles (HK-micelles) were prepared by self-assembly of PECE copolymer in aqueous solution, triggered by its amphiphilic characteristic assisted by ultrasonication without any organic solvents, surfactants and vigorous stirring. The particle size of the prepared HK-micelles measured by Malvern laser particle size analyzer were 58 nm, which is small enough to be a candidate for an intravenous drug delivery system. Furthermore, the HK-micelles could be lyophilized into powder without any adjuvant, and the re-dissolved HK-micelles are stable and homogeneous with particle size about 61 nm. Furthermore, the in vitro release profile showed a significant difference between the rapid release of free HK and the much slower and sustained release of HK-micelles. Moreover, the cytotoxicity results of blank micelles and HK-micelles showed that the PECE micelle was a safe carrier and the encapsulated HK retained its potent antitumor effect. In short, the HK-micelles were successfully prepared by an improved method and might be promising carriers for intravenous delivery of HK in cancer chemotherapy, being effective, stable, safe (organic solvent and surfactant free), and easy to produce and scale up.

  9. Extraction of lysozyme, alpha-chymotrypsin, and pepsin into reverse micelles formed using an anionic surfactant, isooctane, and water.

    PubMed

    Chang, Q; Liu, H; Chen, J

    1994-11-01

    The extraction of lysozyme, alpha-chymotrypsin, and pepsin from buffered salt solutions into reverse micelles was examined at different pH values and surfactant concentrations. The reverse micelles was formed by mixing aqueous buffer supplemented with KCl and an organic phase of isooctane(2,2,4-trimethylpentane), containing the anionic surfactant, Aerosol O. T. (dioctyl ester of sodium sulfosuccinic acid). The technique of dynamic laser scattering was used to measure the size of reverse micelles which were in equilibrium with the aqueous phase. It was found that the size of the reverse micelles decreased with increasing ionic strength but increased with increasing AOT concentration. In the process of extraction, the reverse micelles might have rearranged themselves to host the protein. The sizes of protein-filled and -unfilled reverse micelles were different, and an open equilibrium could be reached between them. Under the extraction conditions, only a small number of micelles were found to contain protein. PMID:7522474

  10. Biodegradable polymeric micelles encapsulated JK184 suppress tumor growth through inhibiting Hedgehog signaling pathway

    NASA Astrophysics Data System (ADS)

    Zhang, Nannan; Liu, Shichang; Wang, Ning; Deng, Senyi; Song, Linjiang; Wu, Qinjie; Liu, Lei; Su, Weijun; Wei, Yuquan; Xie, Yongmei; Gong, Changyang

    2015-01-01

    JK184 can specially inhibit Gli in the Hedgehog (Hh) pathway, which showed great promise for cancer therapeutics. For developing aqueous formulation and improving anti-tumor activity of JK184, we prepared JK184 encapsulated MPEG-PCL micelles by the solid dispersion method without using surfactants or toxic organic solvents. The cytotoxicity and cellular uptake of JK184 micelles were both increased compared with the free drug. JK184 micelles induced more apoptosis and blocked proliferation of Panc-1 and BxPC-3 tumor cells. In addition, JK184 micelles exerted a sustained in vitro release behavior and had a stronger inhibitory effect on proliferation, migration and invasion of HUVECs than free JK184. Furthermore, JK184 micelles had stronger tumor growth inhibiting effects in subcutaneous Panc-1 and BxPC-3 tumor models. Histological analysis showed that JK184 micelles improved anti-tumor activity by inducing more apoptosis, decreasing microvessel density and reducing expression of CD31, Ki67, and VEGF in tumor tissues. JK184 micelles showed a stronger inhibition of Gli expression in Hh signaling, which played an important role in pancreatic carcinoma. Furthermore, circulation time of JK184 in blood was prolonged after entrapment in polymeric micelles. Our results suggested that JK184 micelles are a promising drug candidate for treating pancreatic tumors with a highly inhibitory effect on Hh activity.JK184 can specially inhibit Gli in the Hedgehog (Hh) pathway, which showed great promise for cancer therapeutics. For developing aqueous formulation and improving anti-tumor activity of JK184, we prepared JK184 encapsulated MPEG-PCL micelles by the solid dispersion method without using surfactants or toxic organic solvents. The cytotoxicity and cellular uptake of JK184 micelles were both increased compared with the free drug. JK184 micelles induced more apoptosis and blocked proliferation of Panc-1 and BxPC-3 tumor cells. In addition, JK184 micelles exerted a sustained in

  11. Thermodynamic parameters and counterion binding to the micelle in binary anionic surfactant systems.

    PubMed

    Maneedaeng, Atthaphon; Haller, Kenneth J; Grady, Brian P; Flood, Adrian E

    2011-04-15

    Competitive counterion binding of sodium and calcium to micelles, and mixed micellization have been investigated in the systems sodium dodecylsulfate (NaDS)/sodium decylsulfate (NaDeS) and NaDS/sodium 4-octylbenzenesulfonate (NaOBS) in order to accurately model the activity of the relevant species in solution. The critical micelle concentration (CMC) and equilibrium micelle compositions of mixtures of these anionic surfactants, which is necessary for determining fractional counterion binding measurements, is thermodynamically modeled by regular solution theory. The mixed micelle is ideal (the regular solution parameter β(M)=0) for the NaDS/NaOBS system, while the mixed micelle for NaDS/NaDeS has β(M)=-1.05 indicating a slight synergistic interaction. Counterion binding of sodium to the micelle is influenced by the calcium ion concentration, and vice versa. However, the total degree of counterion binding is essentially constant at approximately 0.65 charge negation at the micelle's surface. The counterion binding coefficients can be quantitatively modeled using a simple equilibrium model relating concentrations of bound and unbound counterions. PMID:21292278

  12. Curcumin-encapsulated polymeric micelles suppress the development of colon cancer in vitro and in vivo.

    PubMed

    Yang, Xi; Li, Zhaojun; Wang, Ning; Li, Ling; Song, Linjiang; He, Tao; Sun, Lu; Wang, Zhihan; Wu, Qinjie; Luo, Na; Yi, Cheng; Gong, Changyang

    2015-01-01

    To develop injectable formulation and improve the stability of curcumin (Cur), Cur was encapsulated into monomethyl poly (ethylene glycol)-poly (ε-caprolactone)-poly (trimethylene carbonate) (MPEG-P(CL-co-TMC)) micelles through a single-step solid dispersion method. The obtained Cur micelles had a small particle size of 27.6 ± 0.7 nm with polydisperse index (PDI) of 0.11 ± 0.05, drug loading of 14.07 ± 0.94%, and encapsulation efficiency of 96.08 ± 3.23%. Both free Cur and Cur micelles efficiently suppressed growth of CT26 colon carcinoma cells in vitro. The results of in vitro anticancer studies confirmed that apoptosis induction and cellular uptake on CT26 cells had completely increased in Cur micelles compared with free Cur. Besides, Cur micelles were more effective in suppressing the tumor growth of subcutaneous CT26 colon in vivo, and the mechanisms included the inhibition of tumor proliferation and angiogenesis and increased apoptosis of tumor cells. Furthermore, few side effects were found in Cur micelles. Overall, our findings suggested that Cur micelles could be a stabilized aqueous formulation for intravenous application with improved antitumor activity, which may be a potential treatment strategy for colon cancer in the future. PMID:25980982

  13. Enzyme activity and structural dynamics linked to micelle formation: a fluorescence anisotropy and ESR study.

    PubMed

    Chin, Michael; Somasundaran, Ponisseril

    2014-01-01

    Activities of the enzymes, protease subtilisin and horse radish peroxidase (HRP) have been increased 50 and 40%, respectively, in the presence of the nonionic surfactant, alkyl polyglucoside, compared with the activities in buffer alone. This enzyme hyperactivity reaches a peak at 3.0 mm of surfactant. Investigation into the structure of surfactant aggregates indicates "giant" micelle superstructures at this range of surfactant concentration of 1.7 μm in diameter--dramatically decreasing to 60 and 70 nm at higher surfactant concentrations, while surface tension measurements indicate two critical micelle concentration inflection points at 0.2 and 5.0 mm, which suggests transitions in micelle structure with respect to concentration. Furthermore, electron spin resonance (ESR) indicates that the micelles in first critical micelle concentration regime are loosely packed relative to the second aggregate phase. We hypothesize that this loose packing results in diminished hydration shell repulsion between the micelles, leading to the large, micrometer-sized aggregates. We further hypothesize that it is the interaction with these loosely packed micelles that affects the flexibility of the HRP and protease enzyme structure. Time-resolved fluorescence anisotropy of subtilisin in Brij-30 indicates increasing flexibility of catalytic active site with surfactant concentration. This is correlated with an increase in enzymatic activity. PMID:24303849

  14. Bone-Targeted Acid-Sensitive Doxorubicin Conjugate Micelles as Potential Osteosarcoma Therapeutics

    PubMed Central

    2015-01-01

    Osteosarcoma is a malignancy of the bone that primarily affects adolescents. Current treatments retain mortality rates, which are higher than average cancer mortality rates for the adolescent age group. We designed a micellar delivery system with the aim to increase drug accumulation in the tumor and potentially reduce side effects associated with chemotherapy. The design features are the use of the hydrophilic d-aspartic acid octapeptide as both the effective targeting agent as well as the hydrophilic micelle corona. Micelle stabilization was accomplished by binding of model drug (doxorubicin) via an acid-sensitive hydrazone bond and incorporating one to four 11-aminoundecanoic acid (AUA) moieties to manipulate the hydrophobic/hydrophilic ratio. Four micelle-forming unimers have been synthesized and their self-assembly into micelles was evaluated. Size of the micelles could be modified by changing the architecture of the unimers from linear to branched. The stability of the micelles increased with increasing content of AUA moieties. Adsorption of all micelles to hydroxyapatite occurred rapidly. Doxorubicin release occurred at pH 5.5, whereas no release was detected at pH 7.4. Cytotoxicity toward human osteosarcoma Saos-2 cells correlated with drug release data. PMID:25291150

  15. Measurement and Control of pH in the Aqueous Interior of Reverse Micelles

    PubMed Central

    2015-01-01

    The encapsulation of proteins and nucleic acids within the nanoscale water core of reverse micelles has been used for over 3 decades as a vehicle for a wide range of investigations including enzymology, the physical chemistry of confined spaces, protein and nucleic acid structural biology, and drug development and delivery. Unfortunately, the static and dynamical aspects of the distribution of water in solutions of reverse micelles complicate the measurement and interpretation of fundamental parameters such as pH. This is a severe disadvantage in the context of (bio)chemical reactions and protein structure and function, which are generally highly sensitive to pH. There is a need to more fully characterize and control the effective pH of the reverse micelle water core. The buffering effect of titratable head groups of the reverse micelle surfactants is found to often be the dominant variable defining the pH of the water core. Methods for measuring the pH of the reverse micelle aqueous interior using one-dimensional 1H and two-dimensional heteronuclear NMR spectroscopy are described. Strategies for setting the effective pH of the reverse micelle water core are demonstrated. The exquisite sensitivity of encapsulated proteins to the surfactant, water content, and pH of the reverse micelle is also addressed. These results highlight the importance of assessing the structural fidelity of the encapsulated protein using multidimensional NMR before embarking upon a detailed structural and biophysical characterization. PMID:24506449

  16. Simulation of non-ionic surfactant micelle formation across a range of temperature and pressure

    NASA Astrophysics Data System (ADS)

    Custer, Gregory; Das, Payel; Matysiak, Silvina

    Non-ionic surfactants can, at certain concentrations and thermodynamic conditions, aggregate into micelles due to their amphiphilic nature. Our work looks at the formation and behavior of micelles at extremes of temperature and pressure. Due to the large system size and simulation time required to study micelle formation, we have developed a coarse-grained (CG) model of our system. This CG model represents each heavy atom with a single CG bead. We use the multibody Stillinger-Weber potential, which adds a three-body angular penalty to a two-body potential, to emulate hydrogen bonds in the system. We simulate the linear surfactant C12E5 , which has a nonpolar domain of 12 carbons and a polar domain of 5 ethers. Our CG model has been parameterized to match structural properties from all-atom simulations of single and dimer surfactant systems. Simulations were performed using a concentration above the experimental critical micelle concentration at 300K and 1atm. We observe an expected region of stable micelle formation at intermediate temperature, with a breakdown at high and low temperature, as well as at high pressure. The driving forces behind the destabilization of micelles and the mechanism of micelle formation at different thermodynamic conditions will be discussed.

  17. Green Tea Catechin-Based Complex Micelles Combined with Doxorubicin to Overcome Cardiotoxicity and Multidrug Resistance

    PubMed Central

    Cheng, Tangjian; Liu, Jinjian; Ren, Jie; Huang, Fan; Ou, Hanlin; Ding, Yuxun; Zhang, Yumin; Ma, Rujiang; An, Yingli; Liu, Jianfeng; Shi, Linqi

    2016-01-01

    Chemotherapy for cancer treatment has been demonstrated to cause some side effects on healthy tissues and multidrug resistance of the tumor cells, which greatly limits therapeutic efficacy. To address these limitations and achieve better therapeutic efficacy, combination therapy based on nanoparticle platforms provides a promising approach through delivering different agents simultaneously to the same destination with synergistic effect. In this study, a novel green tea catechin-based polyion complex (PIC) micelle loaded with doxorubicin (DOX) and (-)-Epigallocatechin-3-O-gallate (EGCG) was constructed through electrostatic interaction and phenylboronic acid-catechol interaction between poly(ethylene glycol)-block-poly(lysine-co-lysine-phenylboronic acid) (PEG-PLys/PBA) and EGCG. DOX was co-loaded in the PIC micelles through π-π stacking interaction with EGCG. The phenylboronic acid-catechol interaction endowed the PIC micelles with high stability under physiological condition. Moreover, acid cleavability of phenylboronic acid-catechol interaction in the micelle core has significant benefits for delivering EGCG and DOX to same destination with synergistic effects. In addition, benefiting from the oxygen free radicals scavenging activity of EGCG, combination therapy with EGCG and DOX in the micelle core could protect the cardiomyocytes from DOX-mediated cardiotoxicity according to the histopathologic analysis of hearts. Attributed to modulation of EGCG on P-glycoprotein (P-gp) activity, this kind of PIC micelles could effectively reverse multidrug resistance of cancer cells. These results suggested that EGCG based PIC micelles could effectively overcome DOX induced cardiotoxicity and multidrug resistance. PMID:27375779

  18. Production of Fluconazole-Loaded Polymeric Micelles Using Membrane and Microfluidic Dispersion Devices.

    PubMed

    Lu, Yu; Chowdhury, Danial; Vladisavljević, Goran T; Koutroumanis, Konstantinos; Georgiadou, Stella

    2016-01-01

    Polymeric micelles with a controlled size in the range between 41 and 80 nm were prepared by injecting the organic phase through a microengineered nickel membrane or a tapered-end glass capillary into an aqueous phase. The organic phase was composed of 1 mg·mL(-1) of PEG-b-PCL diblock copolymers with variable molecular weights, dissolved in tetrahydrofuran (THF) or acetone. The pore size of the membrane was 20 μm and the aqueous/organic phase volumetric flow rate ratio ranged from 1.5 to 10. Block copolymers were successfully synthesized with Mn ranging from ~9700 to 16,000 g·mol(-1) and polymeric micelles were successfully produced from both devices. Micelles produced from the membrane device were smaller than those produced from the microfluidic device, due to the much smaller pore size compared with the orifice size in a co-flow device. The micelles were found to be relatively stable in terms of their size with an initial decrease in size attributed to evaporation of residual solvent rather than their structural disintegration. Fluconazole was loaded into the cores of micelles by injecting the organic phase composed of 0.5-2.5 mg·mL(-1) fluconazole and 1.5 mg·mL(-1) copolymer. The size of the drug-loaded micelles was found to be significantly larger than the size of empty micelles. PMID:27231945

  19. Curcumin-Encapsulated Polymeric Micelles Suppress the Development of Colon Cancer In Vitro and In Vivo

    PubMed Central

    Yang, Xi; Li, Zhaojun; Wang, Ning; Li, Ling; Song, Linjiang; He, Tao; Sun, Lu; Wang, Zhihan; Wu, Qinjie; Luo, Na; Yi, Cheng; Gong, Changyang

    2015-01-01

    To develop injectable formulation and improve the stability of curcumin (Cur), Cur was encapsulated into monomethyl poly (ethylene glycol)-poly (ε-caprolactone)-poly (trimethylene carbonate) (MPEG-P(CL-co-TMC)) micelles through a single-step solid dispersion method. The obtained Cur micelles had a small particle size of 27.6 ± 0.7 nm with polydisperse index (PDI) of 0.11 ± 0.05, drug loading of 14.07 ± 0.94%, and encapsulation efficiency of 96.08 ± 3.23%. Both free Cur and Cur micelles efficiently suppressed growth of CT26 colon carcinoma cells in vitro. The results of in vitro anticancer studies confirmed that apoptosis induction and cellular uptake on CT26 cells had completely increased in Cur micelles compared with free Cur. Besides, Cur micelles were more effective in suppressing the tumor growth of subcutaneous CT26 colon in vivo, and the mechanisms included the inhibition of tumor proliferation and angiogenesis and increased apoptosis of tumor cells. Furthermore, few side effects were found in Cur micelles. Overall, our findings suggested that Cur micelles could be a stabilized aqueous formulation for intravenous application with improved antitumor activity, which may be a potential treatment strategy for colon cancer in the future. PMID:25980982

  20. Therapeutic and scintigraphic applications of polymeric micelles: combination of chemotherapy and radiotherapy in hepatocellular carcinoma.

    PubMed

    Shih, Ying-Hsia; Peng, Cheng-Liang; Chiang, Ping-Fang; Lin, Wuu-Jyh; Luo, Tsai-Yueh; Shieh, Ming-Jium

    2015-01-01

    This study evaluated a multifunctional micelle simultaneously loaded with doxorubicin (Dox) and labeled with radionuclide rhenium-188 ((188)Re) as a combined radiotherapy and chemotherapy treatment for hepatocellular carcinoma. We investigated the single photon emission computed tomography, biodistribution, antitumor efficacy, and pathology of (188)Re-Dox micelles in a murine orthotopic luciferase-transfected BNL tumor cells hepatocellular carcinoma model. The single photon emission computed tomography and computed tomography images showed high radioactivity in the liver and tumor, which was in agreement with the biodistribution measured by γ-counting. In vivo bioluminescence images showed the smallest size tumor (P<0.05) in mice treated with the combined micelles throughout the experimental period. In addition, the combined (188)Re-Dox micelles group had significantly longer survival compared with the control, (188)ReO4 alone (P<0.005), and Dox micelles alone (P<0.01) groups. Pathohistological analysis revealed that tumors treated with (188)Re-Dox micelles had more necrotic features and decreased cell proliferation. Therefore, (188)Re-Dox micelles may enable combined radiotherapy and chemotherapy to maximize the effectiveness of treatment for hepatocellular carcinoma. PMID:26719687

  1. Preparation and evaluation of reduction-responsive nano-micelles for miriplatin delivery.

    PubMed

    Zhang, Ying; Hu, Dejian; Han, Shangcong; Yan, Guowen; Ma, Chao; Wei, Chen; Yu, Miao; Li, Dongmei; Sun, Yong

    2016-06-01

    A reduction-responsive amphiphilic core-shell micelle for miriplatin delivery was prepared and evaluated. A pyrene-terminated poly(2-(dimethylamino) ethyl acrylate) was synthesized through reversible addition-fragmentation chain transfer polymerization with 4-cyano-4-(ethylthiocarbonothioylthio) pentanoic acid as reversible addition-fragmentation chain transfer reagent and further modified by 2,2'-dithiodiethanol and 1-pyrenebutyric acid. Self-assembled blank micelles and drug-loaded micelles were obtained by dialysis method, and the particle size was proved to be about 40 nm with narrow dispersity by dynamic laser light scattering. Morphology results showed that blank micelles and drug-loaded micelles were spherical nanoparticles confirmed by transmission electron microscope, and the critical micelle concentration was as low as 6.09 µg/mL via pyrene fluorescence probe method. The reductive sensitivity of disulfide bond in BMs was further verified by changes in particle size, pyrene fluorescence intensity ratio (I338/I333), and morphology after treatment by dithiothreitol. Moreover, drug release rate in vitro of drug-loaded micelles was evaluated and the results suggested that this amphiphilic pyrene-modified poly(2-(dimethylamino) ethyl acrylate) can be used as reduction-triggered controlled release drug delivery carrier for hydrophobic drug. PMID:26743756

  2. Influence of serum albumin on intracellular delivery of drug-loaded hyaluronan polymeric micelles.

    PubMed

    Nešporová, Kristina; Šógorková, Jana; Šmejkalová, Daniela; Kulhánek, Jaromír; Huerta-Angeles, Gloria; Kubala, Lukáš; Velebný, Vladimír

    2016-09-10

    Polymeric micelles are attractive drug delivery systems for intravenously administered nonpolar drugs. Although physical parameters like size, shape and loading capacity are considered as the most important for their efficiency, here we demonstrate that the effects of serum protein interaction and characteristics of loaded compound cannot be neglected during the micelle development and design of experimental set up. Polymeric micelles prepared from amphiphilic hyaluronic acid grafted with short (hexanoic) and long fatty acids (oleic) were tested after loading with two different hydrophobic models, Nile red and curcumin. The composition of micelles affected mainly the loading capacity. Both encapsulated compounds behaved differently in the in vitro cell uptake, which was also influenced by serum concentration, where serum albumin was found to be the primary destabilizing component. This destabilization was found to be influenced by polymeric micelle concentration. Thus, the chemical structure of micelle, the properties of non-covalently loaded substance and serum albumin/polymeric micelle ratio modulate the in vitro intracellular uptake of drugs loaded in nanocarriers. PMID:27473277

  3. Structure of diglycerol polyisostearate nonionic surfactant micelles in nonpolar oil hexadecane: a SAXS study.

    PubMed

    Shrestha, Lok Kumar; Shrestha, Rekha Goswami; Oyama, Keiichi; Matsuzawa, Makoto; Aramaki, Kenji

    2010-01-01

    Using a small-angle X-ray scattering technique, shape and size, and internal structure of diglycerol polyisostearate nonionic surfactant micelles in nonpolar oil n-hexadecane (HD) were investigated at 25 degrees C. Furthermore, the effect of added water on the structure of host reverse micelles was also investigated. The scattering data were evaluated by the generalized indirect Fourier transformation (GIFT) method and model fittings. It was found that diglycerol polyisostearate (abbreviated as (iso-C18)nG2, where n=2-4 represent the number of isostearate chain per surfactant molecule) spontaneously form reverse micelles in HD at 25 degrees C and their geometry (shape and size, and internal structure) could flexibly be controlled by a small change in the lipophilic tail architecture of the surfactant, temperature, and water addition. Increasing number of isostearate chain per surfactant molecule decreases the micelles size favoring prolate-to-sphere type transition. This phenomenon could be best understood due to voluminous lipophilic part of the surfactant. Increasing temperature decreases the size of the reverse micelles due to enhanced inter-penetration of the surfactant chain and the oil and also due to dominant hydrophobic character of the surfactant at higher temperatures. In the studies of effect of added water on the structure of micelles, it was found that the reverse micelles swell with water causing two dimensional micellar growths. PMID:20513967

  4. Production of Fluconazole-Loaded Polymeric Micelles Using Membrane and Microfluidic Dispersion Devices

    PubMed Central

    Lu, Yu; Chowdhury, Danial; Vladisavljević, Goran T.; Koutroumanis, Konstantinos; Georgiadou, Stella

    2016-01-01

    Polymeric micelles with a controlled size in the range between 41 and 80 nm were prepared by injecting the organic phase through a microengineered nickel membrane or a tapered-end glass capillary into an aqueous phase. The organic phase was composed of 1 mg·mL−1 of PEG-b-PCL diblock copolymers with variable molecular weights, dissolved in tetrahydrofuran (THF) or acetone. The pore size of the membrane was 20 μm and the aqueous/organic phase volumetric flow rate ratio ranged from 1.5 to 10. Block copolymers were successfully synthesized with Mn ranging from ~9700 to 16,000 g·mol−1 and polymeric micelles were successfully produced from both devices. Micelles produced from the membrane device were smaller than those produced from the microfluidic device, due to the much smaller pore size compared with the orifice size in a co-flow device. The micelles were found to be relatively stable in terms of their size with an initial decrease in size attributed to evaporation of residual solvent rather than their structural disintegration. Fluconazole was loaded into the cores of micelles by injecting the organic phase composed of 0.5–2.5 mg·mL−1 fluconazole and 1.5 mg·mL−1 copolymer. The size of the drug-loaded micelles was found to be significantly larger than the size of empty micelles. PMID:27231945

  5. Hyaluronic acid based micelle for articular delivery of triamcinolone, preparation, in vitro and in vivo evaluation.

    PubMed

    Saadat, Ebrahim; Shakor, Naeeme; Gholami, Mehdi; Dorkoosh, Farid A

    2015-07-15

    A novel triamcinolone loaded polymeric micelle was synthesized based on hyaluronic acid and phospholipid for articular delivery. The newly developed micelle was characterized for physicochemical properties including size, zeta potential, differential scanning calorimetry (DSC) analysis and also morphology by means of transmission electron microscopy. The biocompatibility of micelle was explored by histopathological experiment in rat model. Also biological fate of micelle was investigated in rat by means of real time in vivo imaging system. Triamcinolone loaded micelle was in the size range of 186 nm with negative zeta potential charge. Micelles were spherical in shape with core shell like structure. Triamcinolone was released from micelle during 76 h with almost low burst effect. DSC analysis showed the conversion of crystalline triamcinolone from its crystalline state. Histopathological analysis showed no evidence of tissue damage or phagocytic accumulation in knee joint of rat. The real time in vivo imaging analysis suggested at least three days retention time of micellar system in knee joint post injection. PMID:25956051

  6. Reduction-Triggered Breakable Micelles of Amphiphilic Polyamide Amine-g-Polyethylene Glycol for Methotrexate Delivery

    PubMed Central

    Huang, Yihang; Liu, Jun; Cui, Yani; Li, Huanan; Sun, Yong; Fan, Yujiang; Zhang, Xingdong

    2014-01-01

    Reduction-triggered breakable polymeric micelles incorporated with MTX were prepared using amphiphilic PAA-g-PEG copolymers having S–S bonds in the backbone. The micelles were spherical with diameters less than 70 nm. The micelles could encapsulate the hydrophobic MTX in the hydrophobic core. The drug loading content and drug loading efficiency of the micelles were highly dependent on the copolymer chemical structure, ranging from 2.9 to 7.5% and 31.9 to 82.5%, respectively. Both the drug loading content and drug loading efficiency increased along with more hydrophobic segments in the copolymers. In normal circumstance, these micelles were capable of keeping stable and hold most of the MTX in the core, stabilizing the incorporated MTX through the π-π stacking with the phenyl groups in the backbone of the copolymers. In reductive environments that mimicked the intracellular compartments, the entire MTX payload could be quickly released due to the reduction-triggered breakage of the micelles. These micelles showed good antiproliferative activity against several cancer cell lines, including KB, 4T-1 and HepG2, especially within the low drug concentration scope. PMID:24895626

  7. Octreotide-functionalized and resveratrol-loaded unimolecular micelles for targeted neuroendocrine cancer therapy

    NASA Astrophysics Data System (ADS)

    Xu, Wenjin; Burke, Jocelyn F.; Pilla, Srikanth; Chen, Herbert; Jaskula-Sztul, Renata; Gong, Shaoqin

    2013-09-01

    Medullary thyroid cancer (MTC) is a neuroendocrine tumor (NET) that is often resistant to standard therapies. Resveratrol suppresses MTC growth in vitro, but it has low bioavailability in vivo due to its poor water solubility and rapid metabolic breakdown, as well as lack of tumor-targeting ability. A novel unimolecular micelle based on a hyperbranched amphiphilic block copolymer was designed, synthesized, and characterized for NET-targeted delivery. The hyperbranched amphiphilic block copolymer consisted of a dendritic Boltorn® H40 core, a hydrophobic poly(l-lactide) (PLA) inner shell, and a hydrophilic poly(ethylene glycol) (PEG) outer shell. Octreotide (OCT), a peptide that shows strong binding affinity to somatostatin receptors, which are overexpressed on NET cells, was used as the targeting ligand. Resveratrol was physically encapsulated by the micelle with a drug loading content of 12.1%. The unimolecular micelles exhibited a uniform size distribution and spherical morphology, which were determined by both transmission electron microscopy (TEM) and dynamic light scattering (DLS). Cellular uptake, cellular proliferation, and Western blot analyses demonstrated that the resveratrol-loaded OCT-targeted micelles suppressed growth more effectively than non-targeted micelles. Moreover, resveratrol-loaded NET-targeted micelles affected MTC cells similarly to free resveratrol in vitro, with equal growth suppression and reduction in NET marker production. These results suggest that the H40-based unimolecular micelle may offer a promising approach for targeted NET therapy.

  8. Therapeutic and scintigraphic applications of polymeric micelles: combination of chemotherapy and radiotherapy in hepatocellular carcinoma

    PubMed Central

    Shih, Ying-Hsia; Peng, Cheng-Liang; Chiang, Ping-Fang; Lin, Wuu-Jyh; Luo, Tsai-Yueh; Shieh, Ming-Jium

    2015-01-01

    This study evaluated a multifunctional micelle simultaneously loaded with doxorubicin (Dox) and labeled with radionuclide rhenium-188 (188Re) as a combined radiotherapy and chemotherapy treatment for hepatocellular carcinoma. We investigated the single photon emission computed tomography, biodistribution, antitumor efficacy, and pathology of 188Re-Dox micelles in a murine orthotopic luciferase-transfected BNL tumor cells hepatocellular carcinoma model. The single photon emission computed tomography and computed tomography images showed high radioactivity in the liver and tumor, which was in agreement with the biodistribution measured by γ-counting. In vivo bioluminescence images showed the smallest size tumor (P<0.05) in mice treated with the combined micelles throughout the experimental period. In addition, the combined 188Re-Dox micelles group had significantly longer survival compared with the control, 188ReO4 alone (P<0.005), and Dox micelles alone (P<0.01) groups. Pathohistological analysis revealed that tumors treated with 188Re-Dox micelles had more necrotic features and decreased cell proliferation. Therefore, 188Re-Dox micelles may enable combined radiotherapy and chemotherapy to maximize the effectiveness of treatment for hepatocellular carcinoma. PMID:26719687

  9. Parenterally administrable nano-micelles of 3,4-difluorobenzylidene curcumin for treating pancreatic cancer.

    PubMed

    Kesharwani, Prashant; Banerjee, Sanjeev; Padhye, Subhash; Sarkar, Fazlul H; Iyer, Arun K

    2015-08-01

    Pancreatic cancer remains one of the most devastating diseases in terms of patient mortality rates for which current treatment options are very limited. 3,4-Difluorobenzylidene curcumin (CDF) is a nontoxic analog of curcumin (CMN) developed in our laboratory, which exhibits extended circulation half-life, while maintaining high anticancer activity and improved pancreas specific accumulation in vivo, compared with CMN. CDF however has poor aqueous solubility and its dose escalation for systemic administration remains challenging. We have engineered self-assembling nano-micelles of amphiphilic styrene-maleic acid copolymer (SMA) with CDF by non-covalent hydrophobic interactions. The SMA-CDF nano-micelles were characterized for size, charge, drug loading, release, serum stability, and in vitro anticancer activity. The SMA-CDF nano-micelles exhibited tunable CDF loading from 5 to 15% with excellent aqueous solubility, stability, favorable hemocompatibility and sustained drug release characteristics. The outcome of cytotoxicity testing of SMA-CDF nano-micelles on MiaPaCa-2 and AsPC-1 pancreatic cancer cell lines revealed pronounced antitumor response due to efficient intracellular trafficking of the drug loaded nano-micelles. Additionally, the nano-micelles are administrable via the systemic route for future in vivo studies and clinical translation. The currently developed SMA based nano-micelles thus portend to be a versatile carrier for dose escalation and targeted delivery of CDF, with enhanced therapeutic margin and safety. PMID:26037703

  10. An Activatable Theranostic Nanomedicine Platform Based on Self-Quenchable Indocyanine Green-Encapsulated Polymeric Micelles.

    PubMed

    Liu, Lanxia; Ma, Guilei; Zhang, Chao; Wang, Hai; Sun, Hongfan; Wang, Chun; Song, Cunxian; Kong, Deling

    2016-06-01

    Self-quenchable indocyanine green (ICG)-encapsulated micelles with folic acid (FA)-targeting specificity (FA-ICG-micelles) were developed for biologically activatable photodynamic theranostics. FA-ICG-micelles were successfully prepared using the thin-film hydration method, which allows ICG to be encapsulated with a high drug loading that induces an efficient ICG-based quenched state. FA-ICG-micelles are initially in the "OFF" state with no fluorescence signal or phototoxicity, but they become highly fluorescent and phototoxic in cellular degradative environments. Importantly, via folate receptor-mediated endocytosis, the FA targeting of FA-ICG-micelles enhanced intracellular uptake and photodynamic therapy (PDT) efficacy. Systematic administration of FA-ICG-micelles to folate receptor-positive tumor-bearing mice elicited prolonged blood circulation, enhanced tumor accumulation and improved therapeutic efficiency compared to free ICG. Therefore, based on the FA-targeted specificity and switchable photoactivity, FA-ICG-micelles have potential for photodynamic theranostics in cancer. PMID:27319216

  11. Characterization of Cetyltrimethylammonium Bromide/Hexanol Reverse Micelles by Experimentally Benchmarked Molecular Dynamics Simulations.

    PubMed

    Fuglestad, Brian; Gupta, Kushol; Wand, A Joshua; Sharp, Kim A

    2016-02-23

    Encapsulation of small molecules, proteins, and other macromolecules within the protective water core of reverse micelles is emerging as a powerful strategy for a variety of applications. The cationic surfactant cetyltrimethylammonium bromide (CTAB) in combination with hexanol as a cosurfactant is particularly useful in the context of solution NMR spectroscopy of encapsulated proteins. Small-angle X-ray and neutron scattering is employed to investigate the internal structure of the CTAB/hexanol reverse micelle particle under conditions appropriate for high-resolution NMR spectroscopy. The scattering profiles are used to benchmark extensive molecular dynamics simulations of this reverse micelle system and indicate that the parameters used in these simulations recapitulate experimental results. Scattering profiles and simulations indicate formation of homogeneous solutions of small approximately spherical reverse micelle particles at a water loading of 20 composed of ∼150 CTAB and 240 hexanol molecules. The 3000 waters comprising the reverse micelle core show a gradient of translational diffusion that reaches that of bulk water at the center. Rotational diffusion is slowed relative to bulk throughout the water core, with the greatest slowing near the CTAB headgroups. The 5 Å thick interfacial region of the micelle consists of overlapping layers of Br(-) enriched water, CTAB headgroups, and hexanol hydroxyl groups, containing about one-third of the total water. This study employs well-parametrized MD simulations, X-ray and neutron scattering, and electrostatic theory to illuminate fundamental properties of CTAB/hexanol reverse micelle size, shape, partitioning, and water behavior. PMID:26840651

  12. Mixed Micelles for Targeted and Efficient Doxorubicin Delivery to Multidrug-Resistant Breast Cancer Cells.

    PubMed

    Jung, Heesun; Mok, Hyejung

    2016-05-01

    For efficient treatment of multidrug-resistance (MDR) breast cancer cells, design of biocompatible mixed micelles with diverse functional moieties and superior stability is needed for targeted delivery of chemical drugs. In this study, polypropylene glycol (PPG)-grafted hyaluronic acid (HA) copolymers (PPG-g-HA) are used to make mixed micelles with different amounts of pluronic L61, named PPG-g-HA/L61 micelles. Optimized PPG-g-HA/L61 micelles with 3% pluronic L61 exhibit great stability in aqueous solution, superior biocompatibility, and significantly increased uptake into MCF-7 MDR cells via HA-CD44-specific interactions when compared to free doxorubicin (DOX) and other types of micelles. In addition, DOX in PPG-g-HA/L61 micelles with 3% pluronic L61 have toxicity in MCF-7 MDR cells but significantly lower toxicity in fibroblast L929 cells compared to free DOX. Thus, PPG-g-HA/L61 micelles with 3% pluronic L61 content can be a promising nanocarrier to overcome MDR and release DOX in a hyaluronidase-sensitive manner without any toxicity to normal cells. PMID:26806493

  13. Enhanced transcellular penetration and drug delivery by crosslinked polymeric micelles into pancreatic multicellular tumor spheroids.

    PubMed

    Lu, Hongxu; Utama, Robert H; Kitiyotsawat, Uraiphan; Babiuch, Krzysztof; Jiang, Yanyan; Stenzel, Martina H

    2015-07-01

    Many attempts have been made in the application of multicellular tumor spheroids (MCTS) as a 3D tumor model to investigate their biological responses upon introduction of polymeric micelles as nanocarriers for therapeutic applications. However, the micelle penetration pathways in MCTS are not yet known. In this study, micelles (uncrosslinked, UCM) were prepared by self-assembly of block copolymer poly(N-(2-hydroxypropyl) methacrylamide-co-methacrylic acid)-block-poly(methyl methacrylate) (P(HPMA-co-MAA)-b-PMMA). Subsequently, the shells were crosslinked to form relatively stable micelles (CKM). Both UCM and CKM penetrated deeper and delivered more doxorubicin (DOX) into MCTS than the diffusion of the free DOX. Additionally, CKM revealed higher delivery efficiency than UCM. The inhibition of caveolae-mediated endocytosis, by Filipin treatment, decreased the uptake and penetration of the micelles into MCTS. Treatment with Exo1, an exocytosis inhibitor, produced the same effect. Furthermore, movement of the micelles through the extracellular matrices (ECM), as modelled using collagen micro-spheroids, appeared to be limited to the peripheral layer of the collagen spheroids. Those results indicate that penetration of P(HPMA-co-MAA)-b-PMMA micelles depended more on transcellular transport than on diffusion through ECM between the cells. DOX-loaded CKM inhibited MCTS growth more than their UCM counterpart, due to possible cessation of endocytosis and exocytosis in the apoptotic peripheral cells, caused by faster release of DOX from UCM. PMID:26221942

  14. Water purification from organic pollutants by optimized micelle-clay systems.

    PubMed

    Polubesova, Tamara; Nir, Shlomo; Zadaka, Dikla; Rabinovitz, Onn; Serban, Carina; Groisman, Ludmila; Rubin, Baruch

    2005-04-01

    Removal of anionic pollutants (imazaquin, sulfentrazone, sulfosulfuron) and neutral pollutants (alachlor, acetochlor, chlorotoluron, bromacil) from water by micelles preadsorbed on montmorillonite was studied. Micelles of octadecyltrimethylammonium and benzyldimethylhexadecylammonium (BDMHDA) were used. The micelle-clay systems (1% w/w) removed 87-99% of the pollutants from their water solutions containing 1-33 mg/L of herbicide. The nature of the headgroup of the organic cation, which forms the micelles, is critical. Desorption of imazaquin and acetochlor from 0.3% (w/w) suspension of BDMHDA-clay complex after 24 h was around 7% in the range of adsorbed amounts from 0.6 to 15.3 mg/g. These results indicate rather slow rates and small extents of release of pollutants from micelle-clay complexes. Column filters (25 cm) made of a mixture of quartz sand and BDMHDA micelle-clay complex at 100:1 w/w ratio removed at least 99% of above pollutants from initial solutions containing 10 mg/L; 99.5 and 97% of sulfosulfuron and alachlor were removed from their initial solutions containing 200 and 5 microg/L, respectively. These data indicate that micelle-clay complexes are very efficient for water purification from organic contaminants. PMID:15871274

  15. Probing the structure and dynamics of confined water in AOT reverse micelles.

    PubMed

    Martinez, Anna Victoria; Dominguez, Laura; Małolepsza, Edyta; Moser, Adam; Ziegler, Zack; Straub, John E

    2013-06-20

    Reverse micelles are attractive nanoscale systems used for the confinement of molecules in studies of structure and chemical reactions, including protein folding, and aggregation. The simulation of reverse micelles, in which a water "pool" is separated from a nonpolar bulk phase by a surfactant layer, poses significant challenges to empirical force fields due to the diversity of interactions between nonpolar, polar, and charged groups. We have explored the dependence of system density, reverse micelle structure, and water configurational relaxation times as a function of reverse micelle composition, including water:surfactant ratio, absolute number of water molecules, and force field using molecular dynamics simulations. The resulting structures and dynamics are found to depend more on the force field used than on varying interpretations of the water:surfactant ratio in terms of absolute size of the reverse micelle. Substantial deviations from spherical reverse micelle geometries are observed in all unrestrained simulations. Rotational anisotropy decay times and water residence times show a strong dependence on force field and water model used, but power-law relaxation in time is observed independent of the force field. Our results suggest the need for further experimental study of reverse micelles that can provide insight into the distribution and dynamics of shape fluctuations in these complex systems. PMID:23687916

  16. Probing the Structure and Dynamics of Confined Water in AOT Reverse Micelles

    PubMed Central

    Martinez, Anna Victoria; Dominguez, Laura; Małolepsza, Edyta; Moser, Adam; Ziegler, Zack; Straub, John E.

    2013-01-01

    Reverse micelles are attractive nanoscale systems used for the confinement of molecules in studies of structure and chemical reactions, including protein folding and aggregation. The simulation of reverse micelles, in which a water “pool” is separated from a non-polar bulk phase by a surfactant layer, poses significant challenges to empirical force fields due to the diversity of interactions between non-polar, polar, and charged groups. We have explored the dependence of system density, reverse micelle structure, and water configurational relaxation times as a function of reverse micelle composition, including water:surfactant ratio, absolute number of water molecules, and force field using molecular dynamics simulations. The resulting structures and dynamics are found to depend more on the force field used than on varying interpretations of the water:surfactant ratio in terms of absolute size of the reverse micelle. Substantial deviations from spherical reverse micelle geometries are observed in all unrestrained simulations. Rotational anisotropy decay times and water residence times show a strong dependence of force field and water model used, but power-law relaxation in time is observed independent of the force field. Our results suggest the need for further experimental study of reverse micelles that can provide insight into the distribution and dynamics of shape fluctuations in these complex systems. PMID:23687916

  17. Bone-targeted acid-sensitive doxorubicin conjugate micelles as potential osteosarcoma therapeutics.

    PubMed

    Low, Stewart A; Yang, Jiyuan; Kopeček, Jindřich

    2014-11-19

    Osteosarcoma is a malignancy of the bone that primarily affects adolescents. Current treatments retain mortality rates, which are higher than average cancer mortality rates for the adolescent age group. We designed a micellar delivery system with the aim to increase drug accumulation in the tumor and potentially reduce side effects associated with chemotherapy. The design features are the use of the hydrophilic D-aspartic acid octapeptide as both the effective targeting agent as well as the hydrophilic micelle corona. Micelle stabilization was accomplished by binding of model drug (doxorubicin) via an acid-sensitive hydrazone bond and incorporating one to four 11-aminoundecanoic acid (AUA) moieties to manipulate the hydrophobic/hydrophilic ratio. Four micelle-forming unimers have been synthesized and their self-assembly into micelles was evaluated. Size of the micelles could be modified by changing the architecture of the unimers from linear to branched. The stability of the micelles increased with increasing content of AUA moieties. Adsorption of all micelles to hydroxyapatite occurred rapidly. Doxorubicin release occurred at pH 5.5, whereas no release was detected at pH 7.4. Cytotoxicity toward human osteosarcoma Saos-2 cells correlated with drug release data. PMID:25291150

  18. Formation of thermo-sensitive polyelectrolyte complex micelles from two biocompatible graft copolymers for drug delivery.

    PubMed

    Li, Guiying; Meng, Yanfeng; Guo, Lei; Zhang, Ting; Liu, Junshen

    2014-07-01

    Thermo-sensitive polyelectrolyte complex (PEC) micelles assembled from two biocompatible graft copolymers chitosan-g-poly(N-isopropylacrylamide) (CS-g-PNIPAM) and carboxymethyl cellulose-g-poly(N-isopropylacrylamide) (CMC-g-PNIPAM) were prepared for delivery of 5-fluorouracil (5-FU). The PEC micelles showed a narrow size distribution with core-shell structure, in which the core formed from positively charged CS and negatively charged CMC by electrostatic interactions and the shell formed from thermo-sensitive PNIPAM. The synthesized PEC micelles have lower critical solution temperatures (LCST) in the region of 37°C, which is favorable for smart drug delivery applications. The hydrogen bondings between PEC micelles and 5-FU increased the drug loading. Changing temperature, pH or ionic strength, a sustained and controlled release was observed due to the deformation of PEC micelles. Adding glutaraldehyde, a chemical crosslinking reagent, was an efficient way to reinforce the micelles structure and decrease the initial burst release. Cytotoxicity assays showed that drug-loaded PEC micelles retained higher cell inhibition efficiency in HeLa cells. PMID:23894021

  19. Antibody fragment-conjugated polymeric micelles incorporating platinum drugs for targeted therapy of pancreatic cancer.

    PubMed

    Ahn, Jooyeon; Miura, Yutaka; Yamada, Naoki; Chida, Tsukasa; Liu, Xueying; Kim, Ahram; Sato, Ryuta; Tsumura, Ryo; Koga, Yoshikatsu; Yasunaga, Masahiro; Nishiyama, Nobuhiro; Matsumura, Yasuhiro; Cabral, Horacio; Kataoka, Kazunori

    2015-01-01

    Antibody-mediated therapies including antibody-drug conjugates (ADCs) have shown much potential in cancer treatment by tumor-targeted delivery of cytotoxic drugs. However, there is a limitation of payloads that can be delivered by ADCs. Integration of antibodies to drug-loaded nanocarriers broadens the applicability of antibodies to a wide range of therapeutics. Herein, we developed antibody fragment-installed polymeric micelles via maleimide-thiol conjugation for selectively delivering platinum drugs to pancreatic tumors. By tailoring the surface density of maleimide on the micelles, one tissue factor (TF)-targeting Fab' was conjugated to each carrier. Fab'-installed platinum-loaded micelles exhibited more than 15-fold increased cellular binding within 1 h and rapid cellular internalization compared to non-targeted micelles, leading to superior in vitro cytotoxicity. In vivo, Fab'-installed micelles significantly suppressed the growth of pancreatic tumor xenografts for more than 40 days, outperforming non-targeted micelles and free drugs. These results indicate the potential of Fab'-installed polymeric micelles for efficient drug delivery to solid tumors. PMID:25477168

  20. Tumor-targeting multifunctional micelles for imaging and chemotherapy of advanced bladder cancer

    PubMed Central

    Lin, Tzu-yin; Li, Yuan-Pei; Zhang, Hongyong; Luo, Juntao; Goodwin, Neal; Gao, Tingjuan; de Vere White, Ralph; Lam, Kit S; Pan, Chong-Xian

    2013-01-01

    Aim This work aimed to determine if the treatment outcomes of bladder cancer could be improved by targeting micelles that are decorated with bladder cancer-specific ligands on the surface and loaded with the chemotherapeutic drug paclitaxel. Materials & methods Targeting efficacy and specificity was determined with cell lines. An in vivo targeting and anti-tumor efficacy study was conducted in mice carrying patient-derived xenografts. Results & discussion Targeting micelles were more efficient than nontargeting micelles in delivering the drug load into bladder cancer cells both in vitro and in vivo (p < 0.05). The micelle formulation of paclitaxel was less toxic than free paclitaxel in Cremophor® (Sigma, MO, USA) and allowed administration of three-times the maximum tolerated dose without increasing the toxicity. Targeting micelles were more effective than the nontargeting micelles in controlling cancer growth (p = 0.0002) and prolonging overall survival (p = 0.002). Conclusion Targeting micelles loaded with paclitaxel offer strong potential for clinical applications in treating bladder cancer. PMID:23199207

  1. Micelle-templated composite quantum dots for super-resolution imaging.

    PubMed

    Xu, Jianquan; Fan, Qirui; Mahajan, Kalpesh D; Ruan, Gang; Herrington, Andrew; Tehrani, Kayvan F; Kner, Peter; Winter, Jessica O

    2014-05-16

    Quantum dots (QDs) have tremendous potential for biomedical imaging, including super-resolution techniques that permit imaging below the diffraction limit. However, most QDs are produced via organic methods, and hence require surface treatment to render them water-soluble for biological applications. Previously, we reported a micelle-templating method that yields nanocomposites containing multiple core/shell ZnS-CdSe QDs within the same nanocarrier, increasing overall particle brightness and virtually eliminating QD blinking. Here, this technique is extended to the encapsulation of Mn-doped ZnSe QDs (Mn-ZnSe QDs), which have potential applications in super-resolution imaging as a result of the introduction of Mn(2+) dopant energy levels. The size, shape and fluorescence characteristics of these doped QD-micelles were compared to those of micelles created using core/shell ZnS-CdSe QDs (ZnS-CdSe QD-micelles). Additionally, the stability of both types of particles to photo-oxidation was investigated. Compared to commercial QDs, micelle-templated QDs demonstrated superior fluorescence intensity, higher signal-to-noise ratios, and greater stability against photo-oxidization,while reducing blinking. Additionally, the fluorescence of doped QD-micelles could be modulated from a bright 'on' state to a dark 'off' state, with a modulation depth of up to 76%, suggesting the potential of doped QD-micelles for applications in super-resolution imaging. PMID:24762566

  2. Targeted therapy of colorectal neoplasia with rapamycin in peptide-labeled pegylated octadecyl lithocholate micelles.

    PubMed

    Khondee, Supang; Rabinsky, Emily F; Owens, Scott R; Joshi, Bishnu P; Qiu, Zhen; Duan, Xiyu; Zhao, Lili; Wang, Thomas D

    2015-02-10

    Many powerful drugs have limited clinical utility because of poor water solubility and high systemic toxicity. Here, we formulated a targeted nanomedicine, rapamycin encapsulated in pegylated octadecyl lithocholate micelles labeled with a new ligand for colorectal neoplasia, LTTHYKL peptide. CPC;Apc mice that spontaneously develop colonic adenomas were treated with free rapamycin, plain rapamycin micelles, and peptide-labeled rapamycin micelles via intraperitoneal injection for 35days. Endoscopy was performed to monitor adenoma regression in vivo. We observed complete adenoma regression at the end of therapy. The mean regression rate for peptide-labeled rapamycin micelles was significantly greater than that for plain rapamycin micelles, P<0.01. On immunohistochemistry, we observed a significant reduction in phospho-S6 but not β-catenin expression and reduced tumor cell proliferation, suggesting greater inhibition of downstream mTOR signaling. We observed significantly reduced renal toxicity for peptide-labeled rapamycin micelles compared to that of free drug, and no other toxicities were found on chemistries. Together, this unique targeted micelle represents a potential therapeutic for colorectal neoplasia with comparable therapeutic efficacy to rapamycin free drug and significantly less systemic toxicity. PMID:25483425

  3. Relative free energy of binding between antimicrobial peptides and SDS or DPC micelles.

    PubMed

    Sayyed-Ahmad, Abdallah; Khandelia, Himanshu; Kaznessis, Yiannis N

    2009-09-01

    We present relative binding free energy calculations for six antimicrobial peptide-micelle systems, three peptides interacting with two types of micelles. The peptides are the scorpion derived antimicrobial peptide (AMP), IsCT and two of its analogues. The micelles are dodecylphosphatidylcholine (DPC) and sodium dodecylsulphate (SDS) micelles. The interfacial electrostatic properties of DPC and SDS micelles are assumed to be similar to those of zwitterionic mammalian and anionic bacterial membrane interfaces, respectively. We test the hypothesis that the binding strength between peptides and the anionic micelle SDS can provide information on peptide antimicrobial activity, since it is widely accepted that AMPs function by binding to and disrupting the predominantly anionic lipid bilayer of the bacterial cytoplasmic membrane. We also test the hypothesis that the binding strength between peptides and the zwitterionic micelle DPC can provide information on peptide haemolytic activities, since it is accepted that they also bind to and disrupt the zwitterionic membrane of mammalian cells. Equilibrium structures of the peptides, micelles and peptide-micelle complexes are obtained from more than 300 ns of molecular dynamics simulations. A thermodynamic cycle is introduced to compute the binding free energy from electrostatic, non-electrostatic and entropic contributions. We find relative binding free energy strengths between peptides and SDS to correlate with the experimentally measured rankings for peptide antimicrobial activities, and relative free energy binding strengths between peptides and DPC to correlate with the observed rankings for peptide haemolytic toxicities. These findings point to the importance of peptide-membrane binding strength for antimicrobial activity and haemolytic activity. PMID:21113423

  4. A study of the thermodynamic properties of surfactant mixtures: Mixed micelle formation and mixed surfactant adsorption

    SciTech Connect

    Lopata, J.J.

    1992-12-31

    The volumetric mixing in anionic/nonionic, cationic/nonionic, and anionic/cationic mixed micelles was determined by examining the total surfactant apparent molar volumes at total surfactant concentrations much greater than the mixture critical micelle concentration. The mixed surfactant systems investigated were: sodium dodecyl sulfate and a polyethoxylated nonylphenol, at 0.15 M NaCl and with no added NaCl; cetyl pyridinium chloride and polyethoxylated nonylphenol, at 0.03 M NaCl; and sodium dodecyl sulfate and dodecyl pyridinium chloride, at 0.15 M NaCl. The results of this study suggest that the electrostatic interactions in the mixed micelles do no significantly effect the molar volume of the mixed micelle. Therefore, the micelle hydrophobic core dominates the volumetric mixing in mixed micelles. The adsorption of sodium dodecyl sulfate and a polyethoxylated nonylphenol and well defined mixtures thereof was measured on gamma alumina. A pseudo-phase separation model to describe mixed anionic/nonionic admicelle (adsorbed surfactant aggregate) formation was developed. In this model, regular solution theory was used to describe the anionic/nonionic surfactant interactions in the mixed admicelle and a patch-wise adsorption model was used to describe surfactant adsorption on a heterogeneous surface. Regular solution theory was tested on specific homogeneous surface patches by examining constant total surfactant adsorption levels. For the adsorption of binary surfactant mixtures adsorbing at total equilibrium concentrations above the mixture critical micelle concentration, simultaneous solution of the pseudo-phase separation models for mixed admicelle and mixed micelle formation predicts that the surfactant compositions in the monomer, micelle, and admicelle pseudo-phases are constant at a constant total adsorption level.

  5. The Effect of Hydrophilic and Hydrophobic Structure of Amphiphilic Polymeric Micelles on Their Transportation in Rats.

    PubMed

    Deng, Feiyang; Yu, Chao; Zhang, Hua; Dai, Wenbing; He, Bing; Zheng, Ying; Wang, Xueqing; Zhang, Qiang

    2016-01-01

    In the previous study, we have clarified how the hydrophilic and hydrophobic structures of amphiphilic polymers impact the transport of their micelles (PEEP-PCL, PEG-PCL and PEG-DSPE micelles) in epithelial MDCK cells (Biomaterials 2013, 34: 6284-6298). In this study, we attempt to clarify the behavior of the three micelles in rats. Coumarin-6 loaded micelles were injected into different sections of intestine of rats and observed by confocal laser scanning microscope (CLSM) or orally administrated and conducted pharmacokinetic study. All of the three kinds of micelles were able to cross the intestinal epithelial cells and enter blood circulation. The PEEP-PCL micelles demonstrated the fastest distribution mainly in duodenum, while the PEGDSPE micelles showed the longest distribution with the highest proportion in ileum of the three. No significant difference was observed among the pharmacokinetic parameters of the three micelles. The results were consistent in the two analysis methods mentioned above, yet there were some differences between in vivo and in vitro results reported previously. It might be the distinction between the environments in MDCK model and intestine that led to the discrepancy. The hydrophobicity of nanoparticles could both enhance uptake and hinder the transport across the mucus. However, there was no intact mucus in MDCK model, which preferred hydrophobic nanoparticles. PEEP was the most hydrophilic material constructing the micelles in the study and its uptake would be increased in rats compared to that in MDCK model, while DSPE was more hydrophobic than the others and MDCK model would be more ideal for its uptake. Considering the inconsistency of the results in the two models, whether the methods researchers were generally using at present were reasonable needs further investigation. PMID:26201346

  6. Hydrogen Sulfide Triggered Charge-Reversal Micelles for Cancer-Targeted Drug Delivery and Imaging.

    PubMed

    Zhang, Haitao; Kong, Xiuqi; Tang, Yonghe; Lin, Weiying

    2016-06-29

    Currently, the development of polymeric micelles combining diagnosis and targeted therapy is theoretically and practically significant in cancer treatment. In addition, it has been reported that cancer cells can produce large amounts of hydrogen sulfide (H2S) and their survival depends on the content of H2S. In this study, a series of N-(2-hydroxyethyl)-4-azide-1,8-naphthalimide ended amphiphilic diblock copolymer poly(2-hydroxyethyl methacrylate)-block-poly(methyl methacrylate) (N3-Nap-PHEMA-b-PMMA-N3) micelles were prepared. Around cancer tissues, the N3-Nap-PHEMA45-b-PMMA42-N3 micelles exhibited dual characteristics of monitoring H2S and H2S triggered charge reversal with the reduction of the azido group. The surface charge of N3-Nap-PHEMA45-b-PMMA42-N3 micelles reversed from negative to positive after monitoring H2S. With H2S triggered charge reversal, the cellular uptake of DOX-loaded N3-Nap-PHEMA45-b-PMMA42-N3 micelles was effectively enhanced through electrostatic attraction mediated targeting, and a fast doxorubicin (DOX) release rate was observed. The MTT assay demonstrated that N3-Nap-PHEMA45-b-PMMA42-N3 micelles were biocompatible to HeLa cells, and DOX-loaded N3-Nap-PHEMA45-b-PMMA42-N3 micelles showed enhanced cytotoxicity in HeLa cells in the presence of H2S. Furthermore, in vivo fluorescence imaging and biodistribution experiments revealed that DOX-loaded N3-Nap-PHEMA45-b-PMMA42-N3 micelles could provide good tumor imaging and accumulate in tumor tissue. Therefore, N3-Nap-PHEMA45-b-PMMA42-N3 micelles can be used as a promising platform for tumor diagnosis and therapy. PMID:27280335

  7. A biophysical characterization of the interaction of a hepatitis C virus membranotropic peptide with micelles.

    PubMed

    Alves, N S; Mendes, Y S; Souza, T L F; Bianconi, M L; Silva, J L; Gomes, A M O; Oliveira, A C

    2016-04-01

    Membrane fusion is a highly regulated process that allows enveloped viruses to enter cells and replicate. Viral glycoproteins trigger membrane fusion by means of internal sequences known as fusion peptides. The hepatitis C virus (HCV) genome encodes the envelope glycoproteins E1 and E2, but their specific roles in the fusion step and the localization of the fusion peptide remain uncharacterized. Here, we studied the biophysics of the interactions between the glycoprotein E2 peptide HCV421-445 and four different micellar systems providing ionic, non-ionic and zwitterionic surfaces to investigate the importance of electrostatic interactions for peptide-membrane binding. Circular dichroism, fluorescence spectroscopy and calorimetry were used to characterize peptide-micelle interactions and structural changes. Fluorescence quenching showed that HCV421-445 interacts with SDS or CTAB ionic, n-OGP non-ionic and DPC zwitterionic micelles. The indole ring of Trp seems to anchor the peptide in micelles. Trp residues seem to be more deeply inserted in ionic and non-ionic micelles where peptide interactions are more stable than with DPC zwitterionic micelles. The interaction with zwitterionic micelles appears to occur at the surface. Both interaction types are exothermic because of peptide-micelle interactions and a gain of secondary structure in the helical conformation. HCV421-445 interacts with detergent monomers and micelles. Peptide-micelle interaction is pH-independent. HCV421-445 interacts with membranes, promoting aggregation and coalescence of vesicles with content leakage, suggesting that HCV421-445 may participate in membrane fusion. This structural characterization contributes to our understanding of the molecular process that promotes fusion, which is important in the further development of new antiviral therapies. PMID:26773352

  8. Inverse Compton for Compton

    NASA Astrophysics Data System (ADS)

    Suortti, Pekka

    2016-04-01

    A novel concept for a high resolution Compton spectrometer is introduced. 88 keV radiation from an Inverse Compton Compact Source is focused using crossed cylindrically bent Laue-type Si perfect crystals, and dispersed on the sample with a constant energy gradient. Dispersion is compensated exactly at a Ge crystal analyzer, so that the same wavelength shift is observed for all wavelengths of the incident beam. The ThomX source is used as a concrete example. Detailed dimensions and flux estimates at successive locations of the spectrometer are given, and the performance is compared with the dispersion compensating spectrometer at ID15 of the ESRF. The momentum resolution is better than 0.1 atomic units in both cases. The intensity of scattering with the compact source is an order of magnitude smaller, but still adequate for high resolution Compton profile measurements.

  9. Inverse magnetorheological fluids.

    PubMed

    Rodríguez-Arco, L; López-López, M T; Zubarev, A Y; Gdula, K; Durán, J D G

    2014-09-01

    We report a new kind of field-responsive fluid consisting of suspensions of diamagnetic (DM) and ferromagnetic (FM) microparticles in ferrofluids. We designate them as inverse magnetorheological (IMR) fluids for analogy with inverse ferrofluids (IFFs). Observations on the particle self-assembly in IMR fluids upon magnetic field application showed that DM and FM microparticles were assembled into alternating chains oriented along the field direction. We explain such assembly on the basis of the dipolar interaction energy between particles. We also present results on the rheological properties of IMR fluids and, for comparison, those of IFFs and bidispersed magnetorheological (MR) fluids. Interestingly, we found that upon magnetic field application, the rheological properties of IMR fluids were enhanced with respect to bidispersed MR fluids with the same FM particle concentration, by an amount greater than the sum of the isolated contribution of DM particles. Furthermore, the field-induced yield stress was moderately increased when up to 30% of the total FM particle content was replaced with DM particles. Beyond this point, the dependence of the yield stress on the DM content was non-monotonic, as expected for FM concentrations decreasing to zero. We explain these synergistic results by two separate phenomena: the formation of exclusion areas for FM particles due to the perturbation of the magnetic field by DM particles and the dipole-dipole interaction between DM and FM particles, which enhances the field-induced structures. Based on the second phenomenon, we present a theoretical model for the yield stress that semi-quantitatively predicts the experimental results. PMID:25022363

  10. Specific tumor delivery of paclitaxel using glycolipid-like polymer micelles containing gold nanospheres.

    PubMed

    You, Jian; Wang, Zuhua; Du, Yongzhong; Yuan, Hong; Zhang, Peizun; Zhou, Jialin; Liu, Fei; Li, Chun; Hu, Fuqiang

    2013-06-01

    It is difficult for most of the drug delivery systems to really display a temporal and spatial release of entrapped drug once the systems are iv administrated. We hypothesized that the photothermal effect, mediated by a near-infrared (NIR) laser and hollow gold nanospheres (HAuNS), can modulate paclitaxel (PTX) release from polymer micelles, and further result in the enhanced antitumor activity of the micelles. We loaded PTX and HAuNS, which display strong plasmon absorption in the NIR region, into glycolipid-like polymer micelles with an excellent cell internalization capability. The surface of the micelles was conjugated successfully with a peptide, which has the specific-binding with EphB4, a member of the Eph family of receptor tyrosine kinases overexpressed on cell membrane of numerous tumors, to increase the delivery of PTX into tumor cells. Rapid and repetitive drug release from our polymer (HP-TCS) micelles could be readily achieved upon NIR laser irradiation. Our data demonstrated the specific delivery of HP-TCS micelles into positive-EphB4 tumors using a duel-tumor model after iv administration during the whole experiment process (1-48 h). Interestingly, significantly higher uptake of the micelles by SKOV3 tumors (positive-EphB4) than A549 tumors (negtive-EphB4) was observed, with increased ratio on experiment time. However, the specific cell uptake was observed only during the short incubation time (1-4 h) in vitro. Our data also indicated the treatment of tumor cells with the micelles followed by NIR laser irradiation showed significantly greater toxicity activity than the treatment with the micelles alone, free PTX and the micelles (without PTX loading) plus NIR laser irradiation. The enhanced toxicity activity to tumor cells should be attributed to the enhanced drug cellular uptake mediated by the glycolipid-like micelles, chemical toxicity of the released drug from the micelles due to the trigger of NIR laser, and the photothermal ablation under NIR

  11. Formulation of Acid-Sensitive Micelles for Delivery of Cabazitaxel into Prostate Cancer Cells.

    PubMed

    Aydin, Omer; Youssef, Ibrahim; Yuksel Durmaz, Yasemin; Tiruchinapally, Gopinath; ElSayed, Mohamed E H

    2016-04-01

    We report the synthesis of an amphiphilic triblock copolymer composed of a hydrophilic poly(ethylene glycol) (PEG) block, a central poly(acrylic acid) (PAA) block, and a hydrophobic poly(methyl methacrylate) (PMMA) block using atom transfer radical polymerization technique. We examined the self-assembly of PEG-b-PAA-b-PMMA copolymers in aqueous solutions forming nanosized micelles and their ability to encapsulate hydrophobic guest molecules such as Nile Red (NR) dye and cabazitaxel (CTX, an anticancer drug). We used 2,2β'-(propane-2,2-diylbis(oxy))-diethanamine to react with the carboxylic acid groups of the central PAA block forming acid-labile, shell cross-linked micelles (SCLM). We investigated the loading efficiency and release of different guest molecules from non-cross-linked micelles (NSCLM) and shell cross-linked micelles (SCLM) prepared by reacting 50% (SCLM-50) and 100% (SCLM-100) of the carboxylic acid groups in the PAA in physiologic (pH 7.4) and acidic (pH 5.0) buffer solutions as a function of time. We examined the uptake of NR-loaded NSCLM, SCLM-50, and SCLM-100 micelles into PC-3 and C4-2B prostate cancer cells and the effect of different micelle compositions on membrane fluidity of both cell lines. We also investigated the effect of CTX-loaded NSCLM, SCLM-50, and SCLM-100 micelles on the viability of PC-3 and C4-2B cancer cells compared to free CTX as a function of drug concentration. Results show that PEG-b-PAA-b-PMMA polymers form micelles at concentrations ≥11 μg/mL with an average size of 40-50 nm. CTX was encapsulated in PEG-b-PAA-b-PMMA micelles with 55% loading efficiency in NSCLM. In vitro release studies showed that 30% and 85% of the loaded CTX was released from SCLM-50 micelles in physiologic (pH 7.4) and acidic (pH 5.0) buffer solutions over 30 h, confirming micelles' sensitivity to solution pH. Results show uptake of NSCLM and SCLM into prostate cancer cells delivering their chemotherapeutic cargo, which triggered efficient cancer

  12. Binding of Sulfonamide Antibiotics to CTABr Micelles Characterized Using (1)H NMR Spectroscopy.

    PubMed

    Sarker, Ashish K; Cashin, Patrick J; Balakrishnan, Vimal K; Exall, Kirsten; Buncel, Erwin; Brown, R Stephen

    2016-08-01

    Interactions of nine sulfonamide antibiotics (sulfadoxine, sulfathiazole, sulfamethoxazole, sulfamerazine, sulfadiazine, sulfamethazine, sulfacetamide, sulfaguanidine, and sulfanilamide) with cetyltrimethylamonium bromide (CTABr) micelles were examined using (1)H NMR spectroscopy. Seven of the nine provided a significant change in the (1)H NMR chemical shift such that the magnitude and direction (upfield vs downfield) of the chemical shift could be used to propose a locus and orientation of the sulfonamide within the micelle structure. The magnitude of the chemical shift was used to estimate the binding constant for seven sulfonamides with CTABr micelles, providing values and an overall pattern consistent with previous studies of these sulfonamides. PMID:27391918

  13. DNA Micelle Flares for Intracellular mRNA Imaging and Gene Therapy

    PubMed Central

    Chen, Tao; Sam Wu, Cuichen; Jimenez, Elizabeth; Zhu, Zhi; Dajac, Joshua G.; You, Mingxu; Han, Da

    2013-01-01

    Multifunctional DNA micelles: Molecular beacon micelle flares (MBMFs), based on diacyllipid-molecular beacon conjugate (L-MB) self-assembly, have been developed for combined mRNA detection and gene therapy. The advantages of these micelle flares include easy probe synthesis, efficient cellular uptake, enhanced enzymatic stability, high signal-to-background ratio, excellent target selectivity, and superior biocompatibility. In addition, these probes possess a hydrophobic cavity that can be used for additional hydrophobic agents, holding great promise for constructing an all-in-one nucleic acid probe. PMID:23319350

  14. Wavelet Sparse Approximate Inverse Preconditioners

    NASA Technical Reports Server (NTRS)

    Chan, Tony F.; Tang, W.-P.; Wan, W. L.

    1996-01-01

    There is an increasing interest in using sparse approximate inverses as preconditioners for Krylov subspace iterative methods. Recent studies of Grote and Huckle and Chow and Saad also show that sparse approximate inverse preconditioner can be effective for a variety of matrices, e.g. Harwell-Boeing collections. Nonetheless a drawback is that it requires rapid decay of the inverse entries so that sparse approximate inverse is possible. However, for the class of matrices that, come from elliptic PDE problems, this assumption may not necessarily hold. Our main idea is to look for a basis, other than the standard one, such that a sparse representation of the inverse is feasible. A crucial observation is that the kind of matrices we are interested in typically have a piecewise smooth inverse. We exploit this fact, by applying wavelet techniques to construct a better sparse approximate inverse in the wavelet basis. We shall justify theoretically and numerically that our approach is effective for matrices with smooth inverse. We emphasize that in this paper we have only presented the idea of wavelet approximate inverses and demonstrated its potential but have not yet developed a highly refined and efficient algorithm.

  15. Inverse problem for Bremsstrahlung radiation

    SciTech Connect

    Voss, K.E.; Fisch, N.J.

    1991-10-01

    For certain predominantly one-dimensional distribution functions, an analytic inversion has been found which yields the velocity distribution of superthermal electrons given their Bremsstrahlung radiation. 5 refs.

  16. Formation of Polyion Complex (PIC) Micelles and Vesicles with Anionic pH-Responsive Unimer Micelles and Cationic Diblock Copolymers in Water.

    PubMed

    Ohno, Sayaka; Ishihara, Kazuhiko; Yusa, Shin-Ichi

    2016-04-26

    A random copolymer (p(A/MaU)) of sodium 2-(acrylamido)-2-methylpropanesulfonate (AMPS) and sodium 11-methacrylamidoundecanate (MaU) was prepared via conventional radical polymerization, which formed a unimer micelle under acidic conditions due to intramolecular hydrophobic interactions between the pendant undecanoic acid groups. Under basic conditions, unimer micelles were opened up to an expanded chain conformation by electrostatic repulsion between the pendant sulfonate and undecanoate anions. A cationic diblock copolymer (P163M99) consisting of poly(3-(methacrylamido)propyl)trimethylammonium chloride (PMAPTAC) and hydrophilic polybetaine, 2-(methacryloyloxy)ethylphosphorylcholine (MPC), blocks was prepared via controlled radical polymerization. Mixing of p(A/MaU) and P163M99 in 0.1 M aqueous NaCl under acidic conditions resulted in the formation of spherical polyion complex (PIC) micelles and vesicles, depending on polymer concentration before mixing. Shapes of the PIC micelles and vesicles changed under basic conditions due to collapse of the charge balance between p(A/MaU) and P163M99. The PIC vesicles can incorporate nonionic hydrophilic guest molecules, and the PIC micelles and vesicles can accept hydrophobic guest molecules in the hydrophobic core formed from p(A/MaU). PMID:27048989

  17. Solute partitioning in aqueous surfactant assemblies: comparison of hydrophobic-hydrophilic interactions in micelles, alcohol-swollen micelles, microemulsions, and synthetic vesicles

    SciTech Connect

    Russell, J.C.; Whitten, D.G.

    1982-11-03

    The structures of anionic assemblies including sodium lauryl sulfate (SLS) micelles, alcohol-swollen SLS micelles, microemulsions, and vesicles of a mixture of dipalmitoyllecithin and dicetyl phosphate are investigated by using the ground-state complexation of a hydrophilic quencher (methyl viologen) with several hydrophobic fluorescent probes, including surfactant stilbenes and 1,4-diphenylbutadiene. In SLS micelles this complexation can be decreased nearly an order of magnitude by addition of 1-heptanol, indicating that the structure of the micelle can be adjusted from the highly open structure of the pure micelle to a much more closed structure in which hydrophobic solubilizates can be sequestered from hydrophilic reagents bound to the surface. The fluorescence quenching process in anionic vesicles is strongly dependent on temperature; at low temperatures quenching occurs, while at higher temperatures addition of methyl viologen appears to increase the stilbene fluorescence, indicating that the dicationic quencher binds to the vesicle surface, increasing the order of the system. These results indicate that the degree of organization of surfactant systems can be adjusted by simple changes in composition. 33 references.

  18. Reverse micelles for the removal of dyes from aqueous solutions.

    PubMed

    Majhi, S; Sharma, Y C; Upadhyay, S N

    2009-08-01

    The ability of reverse micelles to solvate organic dyes in the aqueous core was investigated with methyl orange (MO) and methylene blue (MB) using hexadecyl trimethyl ammonium bromide (HTAB) and sodium dodecyl benzene sulphonate (SDBS) surfactants in a polar amyl alcohol medium. The removal trend of the dyes from water was studied with different concentrations of the dyes. The effects of NaCl and CaCl2 salts on removal efficiency of the surfactants were investigated and results were compared. It was observed that the separation of dyes from the aqueous phase to the organic phase depends on the electrostatic interaction between the dye molecule and surfactant head groups. In the case of NaCl, with increasing salt concentration, the removal (%) of dye decreases. For CaCl2, removal of methyl orange shows a gradual increase with increasing dye concentration, whereas, for methylene blue, its removal decreases with increasing dye concentration. PMID:19803326

  19. Synthetic Oral Mucin Mimic from Polymer Micelle Networks

    PubMed Central

    2015-01-01

    Mucin networks are formed in the oral cavity by complexation of glycoproteins with other salivary proteins, yielding a hydrated lubricating barrier. The function of these networks is linked to their structural, chemical, and mechanical properties. Yet, as these properties are interdependent, it is difficult to tease out their relative importance. Here, we demonstrate the ability to recreate the fibrous like network through a series of complementary rinses of polymeric worm-like micelles, resulting in a 3-dimensional (3D) porous network that can be deposited layer-by-layer onto any surface. In this work, stability, structure, and microbial capture capabilities were evaluated as a function of network properties. It was found that network structure alone was sufficient for bacterial capture, even with networks composed of the adhesion-resistant polymer, poly(ethylene glycol). The synthetic networks provide an excellent, yet simple, means of independently characterizing mucin network properties (e.g., surface chemistry, stiffness, and pore size). PMID:24992241

  20. The elasticity of soap bubbles containing wormlike micelles.

    PubMed

    Sabadini, Edvaldo; Ungarato, Rafael F S; Miranda, Paulo B

    2014-01-28

    Slow-motion imaging of the rupture of soap bubbles generally shows the edges of liquid films retracting at a constant speed (known as the Taylor-Culick velocity). Here we investigate soap bubbles formed from simple solutions of a cationic surfactant (cetyltrimethylammonium bromide - CTAB) and sodium salicylate. The interaction of salicylate ions with CTAB leads to the formation of wormlike micelles (WLM), which yield a viscoelastic behavior to the liquid film of the bubble. We demonstrate that these elastic bubbles collapse at a velocity up to 30 times higher than the Taylor-Culick limit, which has never been surpassed. This is because during the bubble inflation, the entangled WLM chains stretch, storing elastic energy. This extra energy is then released during the rupture of the bubble, yielding an additional driving force for film retraction (besides surface tension). This new mechanism for the bursting of elastic bubbles may have important implications to the breakup of viscoelastic sprays in industrial applications. PMID:24401119

  1. Rational strategy for shaped nanomaterial synthesis in reverse micelle reactors

    PubMed Central

    Wei, Zengyan; Matsui, Hiroshi

    2014-01-01

    The shape-controlled synthesis of nanoparticles was established in single-phase solutions by controlling growth directions of crystalline facets on seed nanocrystals kinetically; however, it was difficult to rationally predict and design nanoparticle shapes. Here we introduce a methodology to fabricate nanoparticles in smaller sizes by evolving shapes thermodynamically. This strategy enables a more rational approach to fabricate shaped nanoparticles by etching specific positions of atoms on facets of seed nanocrystals in reverse micelle reactors where the surface energy gradient induces desorption of atoms on specific locations on the seed surfaces. From seeds of 12 nm palladium nanocubes, the shape is evolved to concave nanocubes and finally hollow nanocages in the size ~10 nm by etching the center of {200} facets. The high surface area-to-volume ratio and the exposure of a large number of palladium atoms on ledge and kink sites of hollow nanocages are advantageous to enhance catalytic activity and recyclability. PMID:24828960

  2. Homopolymers and Micelles in Supercritical CO2 : a SANS Study

    NASA Astrophysics Data System (ADS)

    Chillura-Martino, D.; McClain, J. B.; Canelas, D.; Betts, D.; Samulski, E. T.; Desimone, J. M.; Wignall, G. D.; Londono, J. D.; Triolo, R.

    1996-03-01

    Supercritical Carbon Dioxide (SC-CO_2) is becoming an attractive alternative to the liquid solvents traditionally used as polymerization media. We have applied small-angle neutron scattering (SANS) to characterize homopolymers and micellar systems in SC-CO_2. Although polymerizations are carried out at high pressures, the penetrating power of the neutron beam means that typical cell windows are virtually transparent. Homopolymers studied include polyfluoro-octyl acrylate (PFOA), hexafluoro-polypropylene oxide and Polydimethyl-siloxane. Also, copolymers of amphiphilic character in CO_2, were characterized via SANS. Systems studied were PFOA-polystyrene diblocks and PFOA-polyethyleneoxide (PFOA-PEO) graft copolymers, which swell as the CO2 medium is saturated with water. This work illustrates the utility of SANS to measure molecular dimensions, thermodynamic variables, molecular weights, micelle structures etc. in supercritical CO_2.

  3. Reverse micelle synthesis of nanoscale metal containing catalysts

    SciTech Connect

    Darab, J.G.; Fulton, J.L.; Linehan, J.C.

    1993-03-01

    The need for morphological control during the synthesis of catalyst precursor powders is generally accepted to be important. In the liquefaction of coal, for example, iron-bearing catalyst precursor particles containing individual crystallites with diameters in the 1-100 nanometer range are believed to achieve good dispersion through out the coal-solvent slurry during liquefaction 2 runs and to undergo chemical transformations to catalytically active iron sulfide phases. The production of the nanoscale powders described here employs the confining spherical microdomains comprising the aqueous phase of a modified reverse micelle (MRM) microemulsion system as nanoscale reaction vessels in which polymerization, electrochemical reduction and precipitation of solvated salts can occur. The goal is to take advantage of the confining nature of micelles to kinetically hinder transformation processes which readily occur in bulk aqueous solution in order to control the morphology and phase of the resulting powder. We have prepared a variety of metal, alloy, and metal- and mixed metal-oxide nanoscale powders from appropriate MRM systems. Examples of nanoscale powders produced include Co, Mo-Co, Ni{sub 3}Fe, Ni, and various oxides and oxyhydroxides of iron. Here, we discuss the preparation and characterization of nickel metal (with a nickel oxide surface layer) and iron oxyhydroxide MRM nanoscale powders. We have used extended x-ray absorption fine structure (EXAFS) spectroscopy to study the chemical polymerization process in situ, x-ray diffraction (XRD), scanning and transmission electron microcroscopies (SEM and TEM), elemental analysis and structural modelling to characterize the nanoscale powders produced. The catalytic activity of these powders is currently being studied.

  4. Enzymatic synthesis of phosphatidylserine using bile salt mixed micelles.

    PubMed

    Pinsolle, Alexandre; Roy, Philippe; Buré, Corinne; Thienpont, Anne; Cansell, Maud

    2013-06-01

    Phosphatidylserine (PS) rich in polyunsaturated fatty acids of the n-3 series was obtained by enzymatic synthesis with phospholipase D (PLD) and a marine lipid extract as substrate. Synthesis was performed using mixed micelles composed of either sodium deoxycholate (SDC) or sodium cholate (SC). To limit the use of surfactant and to monitor the performance of PLD, the mixed micelles were characterized both in terms of bile salt/lipid molar ratio in the aggregates and of mean diameter. A fractional factorial experiment was selected to study the effect of pH, temperature, enzyme, L-serine concentrations, bile salt/lipid molar ratio and Ca(2+) content (in the case of SC only) on PS synthesis. The amount of L-serine was the main factor governing the equilibrium between transphosphatidylation and hydrolysis reaction. Increasing the bile salt/lipid molar ratio decreased PS synthesis yield. In contrast, pH (6.5-8) and temperature (35-45°C) did not affect PLD activity in the tested conditions. This statistical approach allowed determining a combination of parameters (pH, temperature, bile salt/lipid molar ratio, enzyme and alcohol acceptor concentrations) for PS synthesis. After 24 h, the transphosphatidylation reaction led to 57±2% and 56±3% of PS in the phospholipid mixtures with SDC and SC, respectively. In both cases, about 10% of phosphatidic acid was present as a side-product. On the whole, this work provided fundamental basis for a possible development of enzymatic PLD technology using food-grade emulsifiers to produce PS complying with industrial constraints for nutritional applications. PMID:23434712

  5. Mechanism of YF3 nanoparticle formation in reverse micelles.

    PubMed

    Lemyre, Jean-Luc; Lamarre, Sébastien; Beaupré, Ariane; Ritcey, Anna M

    2011-10-01

    This article reports an investigation of the mechanism of YF(3) nanoparticle formation in two variants of the reverse microemulsion precipitation method. These two variants involve the addition of F(-), either as a microemulsion or directly as an aqueous solution, to Y(3+) dispersed in nonionic reverse micelles. The two methods yield amorphous and single-crystal nanoparticles, respectively. The kinetics of reagent mixing are studied by (19)F NMR and colorimetric model reactions, and the particle growth is monitored by TEM. Mixing and nucleation are shown to occur within seconds to minutes whereas particle growth continues for 4 to 48 h, depending on the particle type. Moreover, the growth rate remains constant during most of the growth period, indicating that Ostwald ripening is the most probable growth mechanism. The single-emulsion method also produces a minority amorphous population that exhibits significantly different growth kinetics, attributed to a coagulation mechanism. Secondary growth experiments, involving the addition of precursor ions to mature particles, have been conducted to evaluate the relative importance of nucleation and the competitive growth of existing particle populations. The key differences between the two methods reside in the nucleation step. In the case of the classical method, nucleation occurs upon intermicellar collisions and under conditions of comparable concentrations of Y(3+) and F(-). This method generates more numerous stable nuclei and smaller particles. In the single-microemulsion method, nucleation occurs in the presence of excess F(-) through the interaction of Y(3+)-containing micelles with microdroplets of aqueous F(-). These conditions lead to the formation of crystalline particles and a wider size distribution of unstable nuclei. PMID:21842856

  6. Examination of Gossypol-Pluronic Micelles as Potential Radiosensitizers.

    PubMed

    Tomoda, Keishiro; Chiang, Carol; Kozak, Kevin R; Kwon, Glen S

    2015-11-01

    Chemoradiotherapy, the combination of chemotherapy and radiotherapy to treat cancer, has the potential to enhance local therapeutic effects and simultaneously treat systemic disease. However, chemoradiotherapy may also enhance normal tissue effects leading to both acute and late toxicities. Furthermore, subtherapeutic chemoradiotherapy may result in aggressive tumor repopulation. Tumor-specific radiosensitizing chemotherapy may yield a synergistic therapeutic effect and avoid augmentation of normal tissue toxicity. In this study, the radiosensitizing effects of gossypol were investigated. Also, Pluronics were studied for gossypol solubilization and co-radiosensitization effects. Gossypol inhibits Bcl-2 and Bcl-XL, antiapoptotic proteins that are overexpressed in various cancer cells. Pluronic micelles (P85, F88, L35, and P123) effectively encapsulated gossypol, raising its water solubility by more than 1000-fold. Cytotoxic, anticlonogenic, and radiosensitizing effects were evaluated to characterize gossypol and Pluronic combinations. Gossypol and P85 had the strongest antiproliferative effect on A549 human lung adenocarcinoma cells in a cell viability assay. The IC50 value was seven times lower than gossypol only treatment (330 ± 70 nM vs 2400 ± 400 nM, (mean ± SE)). Gossypol and P85 showed significant inhibition of clonogenic survival, approximately 30% inhibition, compared to treatment with gossypol alone. An experimental sequencing study demonstrated greater inhibition of clonogenic survival when drug treatment followed radiation compared to a sequence of drug treatment followed by radiation. These results suggest that Pluronic micelles readily solubilize gossypol and that the combination of gossypol and P85 may augment the therapeutic effects of ionizing radiation. PMID:26246329

  7. In vitro degradation behavior of poly(lactide)-poly(ethylene glycol) block copolymer micelles in aqueous solution.

    PubMed

    Yang, Liu; El Ghzaoui, Abdeslam; Li, Suming

    2010-11-15

    Self-assembling micelles were prepared from polylactide-poly(ethylene glycol) (PLA-PEG) block copolymer by using two different methods: direct dissolution and dialysis. The in vitro degradation properties of the micelles were investigated at 37°C and monitored by using various techniques. During the investigated degradation time, the size of micelles by dialysis remains stable, while that of micelles by direct dissolution first increases, followed by a collapse of micellar structure. The composition of PLA-PEG copolymers greatly affects the degradation of micelles. Micelles with longer hydrophobic PLA blocks exhibit less size changes due to more compact structure. On the other hand, the structural integrity of L/D mixed micelles is preserved for longer time than that of single micelles, in agreement with the stereocomplexation effect between L-PLA and D-PLA blocks. As degradation proceeds, the average molar mass of copolymer decreases and the distribution becomes wider, especially for micelles by dialysis and L/D mixed micelles with a more compact structure. Additionally, the PEG content in the copolymer chains increases during degradation, leading to a decrease of glass transition and crystallization temperature of the copolymers. However, the residual LA fragments produced by degradation disfavors the crystallization of PEG blocks, thus resulting in the decrease of melting temperature and melting enthalpy. PMID:20816736

  8. Biodegradable polymeric micelle-encapsulated quercetin suppresses tumor growth and metastasis in both transgenic zebrafish and mouse models

    NASA Astrophysics Data System (ADS)

    Wu, Qinjie; Deng, Senyi; Li, Ling; Sun, Lu; Yang, Xi; Liu, Xinyu; Liu, Lei; Qian, Zhiyong; Wei, Yuquan; Gong, Changyang

    2013-11-01

    Quercetin (Que) loaded polymeric micelles were prepared to obtain an aqueous formulation of Que with enhanced anti-tumor and anti-metastasis activities. A simple solid dispersion method was used, and the obtained Que micelles had a small particle size (about 31 nm), high drug loading, and high encapsulation efficiency. Que micelles showed improved cellular uptake, an enhanced apoptosis induction effect, and stronger inhibitory effects on proliferation, migration, and invasion of 4T1 cells than free Que. The enhanced in vitro antiangiogenesis effects of Que micelles were proved by the results that Que micelles significantly suppressed proliferation, migration, invasion, and tube formation of human umbilical vein endothelial cells (HUVECs). Subsequently, transgenic zebrafish models were employed to investigate anti-tumor and anti-metastasis effects of Que micelles, in which stronger inhibitory effects of Que micelles were observed on embryonic angiogenesis, tumor-induced angiogenesis, tumor growth, and tumor metastasis. Furthermore, in a subcutaneous 4T1 tumor model, Que micelles were more effective in suppressing tumor growth and spontaneous pulmonary metastasis, and prolonging the survival of tumor-bearing mice. Besides, immunohistochemical and immunofluorescent assays suggested that tumors in the Que micelle-treated group showed more apoptosis, fewer microvessels, and fewer proliferation-positive cells. In conclusion, Que micelles, which are synthesized as an aqueous formulation of Que, possess enhanced anti-tumor and anti-metastasis activity, which can serve as potential candidates for cancer therapy.

  9. Characteristic of core materials in polymeric micelles effect on their micellar properties studied by experimental and dpd simulation methods.

    PubMed

    Cheng, Furong; Guan, Xuewa; Cao, Huan; Su, Ting; Cao, Jun; Chen, Yuanwei; Cai, Mengtan; He, Bin; Gu, Zhongwei; Luo, Xianglin

    2015-08-15

    Polymeric micelles are one important class of nanoparticles for anticancer drug delivery, but the impact of hydrophobic segments on drug encapsulation and release is unclear, which deters the rationalization of drug encapsulation into polymeric micelles. This paper focused on studying the correlation between the characteristics of hydrophobic segments and encapsulation of structurally different drugs (DOX and β-carotene). Poly(ϵ-caprolactone) (PCL) or poly(l-lactide) (PLLA) were used as hydrophobic segments to synthesize micelle-forming amphiphilic block copolymers with the hydrophilic methoxy-poly(ethylene glycol) (mPEG). Both blank and drug loaded micelles were spherical in shape with sizes lower than 50 nm. PCL-based micelles exhibited higher drug loading capacity than their PLLA-based counterparts. Higher encapsulation efficiency of β-carotene was achieved compared with DOX. In addition, both doxorubicin and β-carotene were released much faster from PCL-based polymeric micelles. Dissipative particle dynamics (DPD) simulation revealed that the two drugs tended to aggregate in the core of the PCL-based micelles but disperse in the core of PLLA based micelles. In vitro cytotoxicity investigation of DOX loaded micelles demonstrated that a faster drug release warranted a more efficient cancer-killing effect. This research could serve as a guideline for the rational design of polymeric micelles for drug delivery. PMID:26196277

  10. Interaction of 6-methoxyquinoline with anionic sodium dodecylsulfate micelles: Photophysics and rotational relaxation dynamics at different pH.

    PubMed

    Varma, Y Tej; Pant, Debi D

    2016-04-01

    Interactions of different species of 6-methoxyquinoline (6MQ) with anionic micelles have been studied at different pre-micellar, micellar and post-micellar concentrations using steady state, time resolved fluorescence and fluorescence anisotropy techniques. The sensitivity of fluorescence of 6MQ to change in its local environment was used to probe sodium dodecylsulfate (SDS) micelles. At post-micellar concentrations of SDS, the observed blue shift in the fluorescence spectrum and increase in quantum yield are attributed to the incorporation of solute molecule to micelles. 6MQ has been found to bind to the surface of the anionic micelles instead of penetrating inside the core of micelles. The binding constant (Kb) calculated for 6MQ revealed that the electrostatic forces mediate charged probe-micelle association, whereas, hydrophobic interaction allowed neutral 6MQ to associate with SDS micelles. The charged 6MQ gets inserted deeper into the micelle surface than its neutral form. The fluorescence anisotropy decay of 6MQ in SDS micelles studied at different pH allowed determination of restriction of motion of the fluorophore. The location of the probe molecule in micellar systems is justified by a variety of spectral parameters such as refractive index, dielectric constant, ET(30), average fluorescence decay time, radiative and non-radiative rate constants, and rotational relaxation time. The micro-environment around the fluorophore reveals that the photophysics of 6MQ is very sensitive to the microenvironment of SDS and probe molecules reside at the water-micelle interface. PMID:26775098

  11. Interaction of 6-methoxyquinoline with anionic sodium dodecylsulfate micelles: Photophysics and rotational relaxation dynamics at different pH

    NASA Astrophysics Data System (ADS)

    Varma, Y. Tej; Pant, Debi D.

    2016-04-01

    Interactions of different species of 6-methoxyquinoline (6MQ) with anionic micelles have been studied at different pre-micellar, micellar and post-micellar concentrations using steady state, time resolved fluorescence and fluorescence anisotropy techniques. The sensitivity of fluorescence of 6MQ to change in its local environment was used to probe sodium dodecylsulfate (SDS) micelles. At post-micellar concentrations of SDS, the observed blue shift in the fluorescence spectrum and increase in quantum yield are attributed to the incorporation of solute molecule to micelles. 6MQ has been found to bind to the surface of the anionic micelles instead of penetrating inside the core of micelles. The binding constant (Kb) calculated for 6MQ revealed that the electrostatic forces mediate charged probe-micelle association, whereas, hydrophobic interaction allowed neutral 6MQ to associate with SDS micelles. The charged 6MQ gets inserted deeper into the micelle surface than its neutral form. The fluorescence anisotropy decay of 6MQ in SDS micelles studied at different pH allowed determination of restriction of motion of the fluorophore. The location of the probe molecule in micellar systems is justified by a variety of spectral parameters such as refractive index, dielectric constant, ET(30), average fluorescence decay time, radiative and non-radiative rate constants, and rotational relaxation time. The micro-environment around the fluorophore reveals that the photophysics of 6MQ is very sensitive to the microenvironment of SDS and probe molecules reside at the water-micelle interface.

  12. Nanostructured Oxygen Sensor - Using Micelles to Incorporate a Hydrophobic Platinum Porphyrin

    PubMed Central

    Su, Fengyu; Alam, Ruhaniyah; Mei, Qian; Tian, Yanqing; Youngbull, Cody; Johnson, Roger H.; Meldrum, Deirdre R.

    2012-01-01

    Hydrophobic platinum(II)-5,10,15,20-tetrakis-(2,3,4,5,6-pentafluorophenyl)-porphyrin (PtTFPP) was physically incorporated into micelles formed from poly(ε-caprolactone)-block-poly(ethylene glycol) to enable the application of PtTFPP in aqueous solution. Micelles were characterized using dynamic light scattering (DLS) and atomic force microscopy (AFM) to show an average diameter of about 140 nm. PtTFPP showed higher quantum efficiency in micellar solution than in tetrahydrofuran (THF) and dichloromethane (CH2Cl2). PtTFPP in micelles also exhibited higher photostability than that of PtTFPP suspended in water. PtTFPP in micelles exhibited good oxygen sensitivity and response time. This study provided an efficient approach to enable the application of hydrophobic oxygen sensors in a biological environment. PMID:22457758

  13. Interactions of myelin basic protein with mixed dodecylphosphocholine/palmitoyllysophosphatidic acid micelles

    SciTech Connect

    Mendz, G.L. ); Brown, L.R. ); Martenson, R.E. )

    1990-03-06

    The interactions of myelin basic protein and peptides derived from it with detergent micelles of lysophosphatidylglycerol, lysophosphatidylserine, palmitoyllysophosphatidic acid, and sodium lauryl sulfate, and with mixed micelles of the neutral detergent dodecylphosphocholine and the negatively charged detergent palmitoyllysophosphatidic acid, were investigated by {sup 1}H NMR spectroscopy and circular dichroic spectropolarimetry. The results with single detergents suggested that there are discrete interaction sites in the protein molecule for neutral and anionic detergent micelles and that at least some of these sites are different for each type of detergent. The data on the binding of the protein and peptides to mixed detergent micelles suggested that intramolecular interactions in the intact protein and in one of the longer peptides limited the formation of helices and also that a balance between hydrophobic and ionic forces is achieved in the interactions of the peptides with the detergents. At high detergent/protein molar ratios, hydrophobic interactions appeared to be favored.

  14. CD and 31P NMR studies of tachykinin and MSH neuropeptides in SDS and DPC micelles

    NASA Astrophysics Data System (ADS)

    Schneider, Sydney C.; Brown, Taylor C.; Gonzalez, Javier D.; Levonyak, Nicholas S.; Rush, Lydia A.; Cremeens, Matthew E.

    2016-02-01

    Secondary structural characteristics of substance P (SP), neurokinin A (NKA), neurokinin B (NKB), α-melanocyte stimulating hormone peptide (α-MSH), γ1-MSH, γ2-MSH, and melittin were evaluated with circular dichroism in phosphite buffer, DPC micelles, and SDS micelles. CD spectral properties of γ1-MSH and γ2-MSH as well as 31P NMR of DPC micelles with all the peptides are reported for the first time. Although, a trend in the neuropeptide/micelle CD data appears to show increased α-helix content for the tachykinin peptides (SP, NKA, NKB) and increased β-sheet content for the MSH peptides (α-MSH, γ1-MSH, γ2-MSH) with increasing peptide charge, the lack of perturbed 31P NMR signals for all neuropeptides could suggest that the reported antimicrobial activity of SP and α-MSH might not be related to a membrane disruption mode of action.

  15. Synergistic Combinations of Multiple Chemotherapeutic Agents in High Capacity Poly(2-oxazoline) Micelles

    PubMed Central

    Han, Yingchao; He, Zhijian; Schulz, Anita; Bronich, Tatiana K.; Jordan, Rainer; Luxenhofer, Robert; Kabanov, Alexander V.

    2012-01-01

    Many effective drugs for cancer treatment are poorly water-soluble. In combination chemotherapy, needed excipients in additive formulations are often toxic and restrict their applications in clinical intervention. Here, we report on amphiphilic poly(2-oxazoline)s (POx) micelles as a promising high capacity delivery platform for multi-drug cancer chemotherapy. A variety of binary and ternary drugs combinations of paclitaxel (PTX), docetaxel (DTX), 17-allylamino-17-demethoxygeldanamycin (17-AAG), etoposide (ETO) and bortezomib (BTZ) were solubilized in defined polymeric micelles achieving unprecedented high total loading capacities of up to 50 wt.% drug per final formulation. Multi-drug loaded POx micelles showed enhanced stability in comparison to single-drug loaded micelles. Drug ratio dependent synergistic cytotoxicity of micellar ETO/17-AAG was observed in MCF-7 cancer cells and of micellar BTZ/17-AAG in MCF-7, PC3, MDA-MB-231 and HepG2 cells. PMID:22681126

  16. Carbohydrate-Specific Uptake of Fucosylated Polymeric Micelles by Different Cancer Cell Lines.

    PubMed

    Babiuch, Krzysztof; Dag, Aydan; Zhao, Jiacheng; Lu, Hongxu; Stenzel, Martina H

    2015-07-13

    Inspired by upregulated levels of fucosylated proteins on the surfaces of multiple types of cancer cells, micelles carrying β-l-fucose and β-d-glucose were prepared. A range of block copolymers were synthesized by reacting a mixture of 2-azidoethyl β-l-fucopyranoside (FucEtN3) and 2-azideoethyl β-d-glucopyranoside (GlcEtN3) with poly(propargyl methacrylate)-block-poly(n-butyl acrylate) (PPMA-b-PBA) using copper-catalyzed azide-alkyne cycloaddition (CuAAC). Five block copolymers were obtained ranging from 100 mol % fucose to 100% glucose functionalization. The resulting micelles had hydrodynamic diameters of around 30 nm. In this work, we show that fucosylated micelles reveal an increased uptake by pancreatic, lung, and ovarian carcinoma cell lines, whereas the uptake by the healthy cell lines (CHO) is negligible. This finding suggests that these micelles can be used for targeted drug delivery toward cancer cells. PMID:26057004

  17. An improved procedure for determination of the mean aggregation number of micelles

    NASA Astrophysics Data System (ADS)

    Wu, Shuangyan; Tachiya, Masanori; Yan, Zhenning

    2015-03-01

    In this paper, a theory of fluorescence quenching in micelles which enables a dynamic approach to the evaluation of the aggregation numbers of micelles is presented. This method is based on a detailed kinetic model of quenching of fluorescent probe developed by Tachiya (1975, 1982) and takes into account that a part of quenchers are associated with micelles but the remaining quenchers are in the aqueous phase. The approach presented is an improvement on a previous fluorescence quenching method (Turro and Yekta, 1978) and is applied to determine the aggregation number of sodium dodecyl sulfonate (SAS) in aqueous dipeptide solution using cetylpyridinium chloride as quencher. The values of aggregation number and association constant for quencher-micelle association are presented.

  18. Molecular dynamics simulations of a membrane protein-micelle complex in vacuo.

    PubMed

    Friemann, Rosmarie; Larsson, Daniel S D; Wang, Yaofeng; van der Spoel, David

    2009-11-25

    We report the first molecular dynamics simulations of an integral membrane protein in a detergent micelle under vacuum conditions. To mimic the dehydration process in electrospray ionization, the N-terminal outer membrane protein A transmembrane domain (OmpA171) from Escherichia coli embedded in a dodecylphosphocholine (DPC) detergent micelle has been simulated with water shells of varying thickness. Removal of the water molecules leaves the membrane protein relatively unaffected by the vacuum conditions. The major structural change occurs in the surrounding micelle, where the DPC molecules structurally rearrange from a normal-phase micelle with DPC detergents radiating spherically from OmpA171 to a structure where the DPC molecules form a layered onion structure in which the head groups, which strive to interact with each other, form an intermediate layer between the inner layer of tail groups that are expelled to the surface, protruding into the void. PMID:19877613

  19. Removal of Cr(VI) from Aqueous Environments Using Micelle-Clay Adsorption

    PubMed Central

    Qurie, Mohannad; Khamis, Mustafa; Manassra, Adnan; Ayyad, Ibrahim; Nir, Shlomo; Scrano, Laura; Bufo, Sabino A.; Karaman, Rafik

    2013-01-01

    Removal of Cr(VI) from aqueous solutions under different conditions was investigated using either clay (montmorillonite) or micelle-clay complex, the last obtained by adsorbing critical micelle concentration of octadecyltrimethylammonium ions onto montmorillonite. Batch experiments showed the effects of contact time, adsorbent dosage, and pH on the removal efficiency of Cr(VI) from aqueous solutions. Langmuir adsorption isotherm fitted the experimental data giving significant results. Filtration experiments using columns filled with micelle-clay complex mixed with sand were performed to assess Cr(VI) removal efficiency under continuous flow at different pH values. The micelle-clay complex used in this study was capable of removing Cr(VI) from aqueous solutions without any prior acidification of the sample. Results demonstrated that the removal effectiveness reached nearly 100% when using optimal conditions for both batch and continuous flow techniques. PMID:24222757

  20. Stimulus-responsive polymeric micelles for the light-triggered release of drugs.

    PubMed

    Wang, Bin; Chen, Kefu; Yang, Rendang; Yang, Fei; Liu, Jin

    2014-03-15

    Ethyl cellulose macroinitiator was firstly synthesized by direct acylation of ethyl cellulose with 2-bromopropionyl bromide in a room temperature. And a light-responsive triblock copolymer of ethyl cellulose-g-poly(2-hydroxyethyl methacrylate)-g-poly(spiropyran ether methacrylate) (EC-g-PHEMA-g-PSPMA) was prepared by atom transfer radial polymerization. The amphiphilic structure of the copolymer enabled it to aggregate into spherical micelles in aqueous solution with an average diameter of 100 nm. The micelles exhibited light-responsive performance because of the SPMA monomer. The hydrophobic side chain of PSPMA became hydrophilic under UV light, which decreased the average size of the micelles. Additionally, the diameters of the micelles can be recovered when subsequently irradiated with visible light. The loading and light-triggered release profiles of model drugs were also investigated, and results showed that the release behavior can be controlled by changing the light wavelength. PMID:24528761

  1. A 1H-n.m.r. study of casein micelles.

    PubMed Central

    Griffin, M C; Roberts, G C

    1985-01-01

    The 1H-n.m.r. spectrum of casein micelles consists of a small number of moderately sharp (linewidth approx. 60 Hz) resonances superimposed on the envelope of very broad lines expected for particles of this size. These sharp lines resemble, in chemical shift and relative intensity, the spectrum of the isolated 'macropeptide' released from the micelles by treatment with chymosin. The sharp lines in the casein micelle spectrum are further sharpened by addition of chymosin and broadened markedly by addition of ethanol. These observations are consistent with the proposal that the 'macropeptide' (the C-terminal 64 residues of K-casein) forms flexible 'hairs' on the surface of the micelles. PMID:3924034

  2. Poly(ethylene glycol)-polypeptide Copolymer Micelles for Therapeutic Agent Delivery.

    PubMed

    Cheng, Yilong

    2016-01-01

    Poly(ethylene glycol)-polypeptide (PEG-polypeptide) based polymeric micelles as therapeutic agent carriers have received considerable interest due to their advanced achievements in clinical trials. Polypeptides not only show well-defined secondary structure (alfa-helix and beta-sheet) and good biocompatibility, but can also be functionalized with various groups by direct N-carboxyanhydrides (NCAs) polymerization or further modification. Additionally, the ionizable side chains enable them to deliver diverse therapeutic agents, such as negative nucleic acid and positive doxorubicin. In this review, we firstly summarized the synthetic methods of amphiphilic copolymers PEG-polypeptide, and emphatically discussed recent progress on their applications as nanocarriers for therapeutic agents from following aspects: PEG-nonionic polypeptide copolymer micelles, PEG-anionic polypeptide micelles, and PEGcationic polypeptide micelles. PMID:26696015

  3. Electron processes in AOT reverse micelles. Part 2. Influence of oil phase. Pulse radiolysis study

    NASA Astrophysics Data System (ADS)

    Gebicki, J. L.; Bednarek, P.

    2000-11-01

    Reverse micellar systems formed of AOT, i.e. sodium bis(2-ethyl-1-hexyl) sulfo-succinate, in different hydrocarbons, without water, dry micelles, and in the presence of water, wet micelles, have been studied by means of pulse radiolysis. Different localization sites of hydrated electron within wet reverse micelle including a triad e aq-/Na +/SO 3- rad (absorption band peaking around 610 nm) are proposed and discussed to explain the influence of the ratio [water]/[AOT] and of the kind of alkane on the position and half-width of the absorption spectrum of the hydrated electron. Sulfite radical, necessary to form such triad, is released as a result of electron interaction with AOT molecule within reverse micelles (RM) containing water. A product of direct electron attachment to AOT molecule, AOT radical anion, has been observed spectrophotometrically only in dry AOT RM at ambient temperature (absorption band peaking around 330 nm).

  4. Smart polymeric micelles as nanocarriers for oligonucleotides and siRNA delivery.

    PubMed

    Kataoka, Kazunori; Itaka, Keiji; Nishiyama, Nobuhiro; Yamasaki, Yuichi; Oishi, Motoi; Nagasaki, Yukio

    2005-01-01

    The development of in vivo delivery systems for oligonucleotides and siRNA is strongly desired to achieve their clinical applications. Recently, polyplex micelles, which are formed through an electrostatic interaction between nucleic acid compounds (DNA and RNA) and poly(ethylene glycol) (PEG)-polycation block copolymers, have received much attention due to their nanometric-scaled size and excellent biocompatibility. Here, three types of newly engineered block copolymers were developed to construct polyplex micelles useful for oligonucleotides and siRNA delivery: (1) PEG-polycation diblock copolymers possessing diamine side-chain with distinctive pKa for siRNA encapsulation into polyplex micelles with high endosomal escaping ability, (2) Lactosylated PEG-(oligonucleotide or siRNA) conjugate through acid-labile beta-thiopropionate linkage to construct pH-sensitive PIC micelles, and (3) PEG-poly(methacrylic acid) block copolymer for the construction of organic/inorganic hybrid nanoparticles encapsulating siRNA. PMID:17150611

  5. The impact of PEGylation patterns on the in vivo biodistribution of mixed shell micelles.

    PubMed

    Gao, Hongjun; Liu, Jinjian; Yang, Cuihong; Cheng, Tangjian; Chu, Liping; Xu, Hongyan; Meng, Aimin; Fan, Saijun; Shi, Linqi; Liu, Jianfeng

    2013-01-01

    Polyethylene glycol (PEG)-ylation is a widely used strategy to fabricate nanocarriers with a long blood circulation time. Further elaboration of the contribution of the surface PEGylation pattern to biodistribution is highly desirable. We fabricated a series of polyion complex (PIC) micelles PEGylated with different ratios (PEG2k and PEG550). The plasma protein adsorption, murine macrophage uptake, and in vivo biodistribution with iodine-125 as the tracer were systematically studied to elucidate the impact of PEGylation patterns on the biodistribution of micelles. We demonstrated that the PEGylated micelles with short hydrophilic PEG chains mixed on the surface were cleared quickly by the reticuloendothelial system (RES), and the single PEG2k PEGylated micelles could efficiently prolong the blood circulation time and increase their deposition in tumor sites. The present study extends the understanding of the PEGylation strategy to further advance the development of ideal nanocarriers for drug delivery and imaging applications. PMID:24235825

  6. Polymeric Micelles with Uniform Surface Properties and Tunable Size and Charge: Positive Charges Improve Tumor Accumulation.

    PubMed

    Shen, Tong; Guan, Shuli; Gan, Zhihua; Zhang, Guan; Yu, Qingsong

    2016-05-01

    The influence of surface charge on biodistribution and tumor accumulation remains debatable because most research has been carried out by changing the surface functional groups of nanocarriers. In this work, to avoid the interference of different surface properties such as chemical composition and hydrophilicity, polymeric micelles with uniform PEG coatings and continuously tunable sizes or zeta potentials were developed via a facile route. Therefore, the influence of surface charge on the biological functions of micelles with the same size and surface properties could be well-explored. In this case, positive charge was found to enhance both tumor cellular uptake and tumor accumulation. Immunofluorescence staining indicated that the improved tumor accumulation was mainly due to the tumor vasculature targeting of positively charged micelles. It is predicted that efficient drug delivery systems for both tumor vasculature and cancer cell targeting can be realized based on positively charged micelles. PMID:27008333

  7. Application of active-phase plot to the kinetic analysis of lipoxygenase in reverse micelles.

    PubMed Central

    Perez-Gilabert, M; Sanchez-Ferrer, A; Garcia-Carmona, F

    1992-01-01

    A new plot for explaining the complex expression of the enzymic activity in reverse micelles has been developed as an extension of the theoretical model described by our group [Bru, Sánchez-Ferrer & García-Carmona (1990) Biochem. J. 268, 679-684]. The plot describes the changes in the relative volume, amount of enzyme (mumoles), enzyme concentration (microM) and substrate concentration (microM) in the phase where the enzyme is active. To illustrate the usefulness of this plot, the complex activity of soya bean lipoxygenase in reverse micelles acting on its interfacial substrate, octadecadienoic acid, was studied. It showed the key parameters ruling the activity profiles of lipoxygenase with respect to micelle size (omega 0), micelle concentration (theta) and the substrate/surfactant molar ratio (rho), which have never been described before. PMID:1281978

  8. Effect of water on the local electric potential of simulated ionic micelles

    SciTech Connect

    Brodskaya, Elena N.; Vanin, Alexander A.

    2015-07-28

    Ionic micelles in an aqueous solution containing single-charged counter-ions have been simulated by molecular dynamics. For both cationic and anionic micelles, it has been demonstrated that explicit description of solvent has strong effect on the micelle’s electric field. The sign of the local charge alters in the immediate vicinity of the micellar crown and the electric potential varies nonmonotonically. Two micelle models have been examined: the hybrid model with a rigid hydrocarbon core and the atomistic model. For three molecular models of water (Simple Point Charge model (SPC), Transferable Intermolecular Potential 5- Points (TIP5P) and two-centered S2), the results have been compared with those for the continuum solvent model. The orientational ordering of solvent molecules has strong effect on the local electric field surprisingly far from the micelle surface.

  9. Simple model for the growth behaviour of mixed lecithin-bile salt micelles.

    PubMed

    Madenci, Dilek; Salonen, Anniina; Schurtenberger, Peter; Pedersen, Jan Skov; Egelhaaf, Stefan U

    2011-02-28

    Mixed lecithin-bile salt micelles are known to have a cylindrical or worm-like structure. We investigated their shape, length, flexibility and cross-sectional structure using small-angle neutron scattering (SANS). A broad range of sample compositions was studied varying both the total amphiphile concentration and the molar ratio of bile salt (sodium taurochenodeoxycholate, NaTCDC) to lecithin (egg yolk phosphatidylcholine, EYL). The length of the micelles was quantitatively linked to the micellar composition by introducing a simple model. The model takes into account the partitioning of lecithin and bile salt between the bulk, cylindrical parts and the end caps of the micelles. The model also sheds light on the organization of the micelles, both in their cylindrical regions and end caps. PMID:21135948

  10. Inverse Problems of Thermoelectricity

    NASA Astrophysics Data System (ADS)

    Anatychuk, L. I.; Luste, O. J.; Kuz, R. V.; Strutinsky, M. N.

    2011-05-01

    Classical thermoelectricity is based on the use of the Seebeck and Thomson effects that occur in the near-contact areas between n- and p-type materials. A conceptually different approach to thermoelectric power converter design that is based on the law of thermoelectric induction of currents is also known. The efficiency of this approach has already been demonstrated by its first applications. More than 10 basically new types of thermoelements were discovered with properties that cannot be achieved by thermocouple power converters. Therefore, further development of this concept is of practical interest. This paper provides a classification and theory for solving the inverse problems of thermoelectricity that form the basis for devising new thermoelement types. Computer methods for their solution for anisotropic and inhomogeneous media are elaborated. Regularities related to thermoelectric current excitation in anisotropic and inhomogeneous media are established. The possibility of obtaining eddy currents of a particular configuration through control of the temperature field and material parameters for the creation of new thermo- element types is demonstrated for three-dimensional (3D) models of anisotropic and inhomogeneous media.

  11. Alendronate-decorated biodegradable polymeric micelles for potential bone-targeted delivery of vancomycin.

    PubMed

    Cong, Yingying; Quan, Changyun; Liu, Meiqing; Liu, Jie; Huang, Gang; Tong, Guoquan; Yin, Yihua; Zhang, Chao; Jiang, Qing

    2015-01-01

    Osteomyelitis is a bone infection disease which is caused by bacteria or other germs, and could cause serious impact on the health and working capacity of the patients. Alendronate (ALN) can chelate strongly with the calcium ion of hydroxyapatite (HA) which is commonly used to treat osteoporosis. Nanomedicine has attracted a lot of attention in that the nano-sized carrier can deliver drug molecules to specific site of interest with the aid of targeting moiety and achieve sustained release, resulting in improved therapeutic effect and reduced side effect. In this study, micelles self-assembled from poly(lactic acid-co-glycolic acid)-block-poly(ethylene glycol)-alendronate (PLGA-PEG-ALN) copolymer were prepared for bone-targeted delivery of vancomycin (Van). The chemical structure of PLGA-PEG-ALN was confirmed by proton nuclear magnetic resonance ((1)H-NMR) spectroscopy. The formation of the nanoparticles was characterized by dynamic light scattering, transmission electronic microscopy as well as the critical micelle concentration measurement. Release profiles from the micelles revealed that the conjugation of ALN to the surface of micelle did not pose adverse effect on the drug-loading capacity and release behaviors. The cytotoxicity of Van-loaded PLGA-PEG-ALN micelles as well as the blank micelles was evaluated via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay toward rat bone marrow stromal cells (rBMSCs) and human embryonic hepatocytes (L02 cells), and results showed that this Van-loaded micelle possesses appropriate cytotoxicity and is safe in the potential treatment of osteomyelitis. The in vitro affinity of PLGA-PEG-ALN micelles to the HA was also confirmed in vitro. The antibacterial effect of Van-loaded PLGA-PEG-ALN micelles was tested against Staphylococcus aureus (SA) which is the main pathogenic bacteria in osteomyelitis, and the results showed that the Van-loaded micelles can effectively inhibit the growth of SA. These results

  12. Des Vents et des Jets Astrophysiques

    NASA Astrophysics Data System (ADS)

    Sauty, C.

    well expected result from the theory. Although, collimation may be conical, paraboloidal or cylindrical (Part 4), cylindrical collimation is the more likely to occur. The shape of outflows may then be used as a tool to predict physical conditions on the flows or on their source. L'éjection continue de plasma autour d'objets massifs est un phénomène largement répandu en astrophysique, que ce soit sous la forme du vent solaire, de vents stellaires, de jets d'étoiles en formation, de jets stellaires autour d'objets compacts ou de jets extra-galactiques. Cette zoologie diversifiée fait pourtant l'objet d'un commun effort de modélisation. Le but de cette revue est d'abord de présenter qualitativement le développement, depuis leur origine, des diverses théories de vents (Partie 1) et l'inter disciplinarité dans ce domaine. Il s'agit d'une énumération, plus ou moins exhaustive, des idées proposées pour expliquer l'accélération et la morphologie des vents et des jets, accompagnée d'une présentation sommaire des aspects observationnels. Cette partie s'abstient de tout aspect faisant appel au formalisme mathématique. Ces écoulements peuvent être décrits, au moins partiellement, en résolvant les équations magnétohydrodynamiques, axisymétriques et stationnaires. Ce formalisme, à la base de la plupart des théories, est exposé dans la Partie 2. Il permet d'introduire quantitativement les intégrales premières qu'un tel système possède. Ces dernières sont amenées à jouer un rôle important dans la compréhension des phénomènes d'accélération ou de collimation, en particulier le taux de perte de masse, le taux de perte de moment angulaire ou l'énergie du rotateur magnétique. La difficulté de modélisation réside dans l'existence de points critiques, propres aux équations non linéaires, qu'il faut franchir. La nature physique et la localisation de ces points critiques fait l'objet d'un débat important car ils sont la clef de voute de la r

  13. Multifunctional polymeric micelles for delivery of drugs and siRNA

    PubMed Central

    Jhaveri, Aditi M.; Torchilin, Vladimir P.

    2014-01-01

    Polymeric micelles, self-assembling nano-constructs of amphiphilic copolymers with a core-shell structure have been used as versatile carriers for delivery of drugs as well as nucleic acids. They have gained immense popularity owing to a host of favorable properties including their capacity to effectively solubilize a variety of poorly soluble pharmaceutical agents, biocompatibility, longevity, high stability in vitro and in vivo and the ability to accumulate in pathological areas with compromised vasculature. Moreover, additional functions can be imparted to these micelles by engineering their surface with various ligands and cell-penetrating moieties to allow for specific targeting and intracellular accumulation, respectively, to load them with contrast agents to confer imaging capabilities, and incorporating stimuli-sensitive groups that allow drug release in response to small changes in the environment. Recently, there has been an increasing trend toward designing polymeric micelles which integrate a number of the above functions into a single carrier to give rise to “smart,” multifunctional polymeric micelles. Such multifunctional micelles can be envisaged as key to improving the efficacy of current treatments which have seen a steady increase not only in hydrophobic small molecules, but also in biologics including therapeutic genes, antibodies and small interfering RNA (siRNA). The purpose of this review is to highlight recent advances in the development of multifunctional polymeric micelles specifically for delivery of drugs and siRNA. In spite of the tremendous potential of siRNA, its translation into clinics has been a significant challenge because of physiological barriers to its effective delivery and the lack of safe, effective and clinically suitable vehicles. To that end, we also discuss the potential and suitability of multifunctional polymeric micelles, including lipid-based micelles, as promising vehicles for both siRNA and drugs. PMID:24795633

  14. Multifunctional polymeric micelles for delivery of drugs and siRNA.

    PubMed

    Jhaveri, Aditi M; Torchilin, Vladimir P

    2014-01-01

    Polymeric micelles, self-assembling nano-constructs of amphiphilic copolymers with a core-shell structure have been used as versatile carriers for delivery of drugs as well as nucleic acids. They have gained immense popularity owing to a host of favorable properties including their capacity to effectively solubilize a variety of poorly soluble pharmaceutical agents, biocompatibility, longevity, high stability in vitro and in vivo and the ability to accumulate in pathological areas with compromised vasculature. Moreover, additional functions can be imparted to these micelles by engineering their surface with various ligands and cell-penetrating moieties to allow for specific targeting and intracellular accumulation, respectively, to load them with contrast agents to confer imaging capabilities, and incorporating stimuli-sensitive groups that allow drug release in response to small changes in the environment. Recently, there has been an increasing trend toward designing polymeric micelles which integrate a number of the above functions into a single carrier to give rise to "smart," multifunctional polymeric micelles. Such multifunctional micelles can be envisaged as key to improving the efficacy of current treatments which have seen a steady increase not only in hydrophobic small molecules, but also in biologics including therapeutic genes, antibodies and small interfering RNA (siRNA). The purpose of this review is to highlight recent advances in the development of multifunctional polymeric micelles specifically for delivery of drugs and siRNA. In spite of the tremendous potential of siRNA, its translation into clinics has been a significant challenge because of physiological barriers to its effective delivery and the lack of safe, effective and clinically suitable vehicles. To that end, we also discuss the potential and suitability of multifunctional polymeric micelles, including lipid-based micelles, as promising vehicles for both siRNA and drugs. PMID:24795633

  15. Patchy micelles based on coassembly of block copolymer chains and block copolymer brushes on silica particles.

    PubMed

    Zhu, Shuzhe; Li, Zhan-Wei; Zhao, Hanying

    2015-04-14

    Patchy particles are a type of colloidal particles with one or more well-defined patches on the surfaces. The patchy particles with multiple compositions and functionalities have found wide applications from the fundamental studies to practical uses. In this research patchy micelles with thiol groups in the patches were prepared based on coassembly of free block copolymer chains and block copolymer brushes on silica particles. Thiol-terminated and cyanoisopropyl-capped polystyrene-block-poly(N-isopropylacrylamide) block copolymers (PS-b-PNIPAM-SH and PS-b-PNIPAM-CIP) were synthesized by reversible addition-fragmentation chain transfer polymerization and chemical modifications. Pyridyl disulfide-functionalized silica particles (SiO2-SS-Py) were prepared by four-step surface chemical reactions. PS-b-PNIPAM brushes on silica particles were prepared by thiol-disulfide exchange reaction between PS-b-PNIPAM-SH and SiO2-SS-Py. Surface micelles on silica particles were prepared by coassembly of PS-b-PNIPAM-CIP and block copolymer brushes. Upon cleavage of the surface micelles from silica particles, patchy micelles with thiol groups in the patches were obtained. Dynamic light scattering, transmission electron microscopy, and zeta-potential measurements demonstrate the preparation of patchy micelles. Gold nanoparticles can be anchored onto the patchy micelles through S-Au bonds, and asymmetric hybrid structures are formed. The thiol groups can be oxidized to disulfides, which results in directional assembly of the patchy micelles. The self-assembly behavior of the patchy micelles was studied experimentally and by computer simulation. PMID:25811763

  16. Integral physicochemical properties of reverse micelles of sodium bis(2-ethylhexyl) sulfosuccinate (AOT)

    NASA Astrophysics Data System (ADS)

    Fedyaeva, O. A.; Shubenkova, E. G.; Poshelyuzhnaya, E. G.; Lutaeva, I. A.

    2016-08-01

    The effect the degree of hydration has on optical and electrophysical properties of water/AOT/ n-hexane system is studied. It is found that AOT reverse micelles form aggregates whose dimensions grow along with the degree of hydration and temperature. Aggregation enhances their electrical conductivity and shifts the UV spectrum of AOT reverse emulsions to the red region. Four states of water are found in the structure of AOT reverse micelles.

  17. A 502-Base Free-Solution Electrophoretic DNA Sequencing Method Using End-Attached Wormlike Micelles.

    PubMed

    Istivan, Stephen B; Bishop, Daniel K; Jones, Angela L; Grosser, Shane T; Schneider, James W

    2015-11-17

    We demonstrate that the use of wormlike nonionic micelles as drag-tags in end-labeled free-solution electrophoresis ("micelle-ELFSE") provides single-base resolution of Sanger sequencing products up to 502 bases in length, a nearly 2-fold improvement over reported ELFSE separations. "CiEj" running buffers containing 48 mM C12E5, 6 mM C10E5, and 3 M urea (32.5 °C) form wormlike micelles that provide a drag equivalent to an uncharged DNA fragment with a length (α) of 509 bases (effective Rh = 27 nm). Runtime in a 40 cm capillary (30 kV) was 35 min for elution of all products down to the 26-base primer. We also show that smaller Triton X-100 micelles give a read length of 103 bases in a 4 min run, so that a combined analysis of the Sanger products using the two buffers in separate capillaries could be completed in 14 min for the full range of lengths. A van Deemter analysis shows that resolution is limited by diffusion-based peak broadening and wall adsorption. Effects of drag-tag polydispersity are not observed, despite the inherent polydispersity of the wormlike micelles. We ascribe this to a stochastic size-sampling process that occurs as micelle size fluctuates rapidly during the runtime. A theoretical model of the process suggests that fluctuations occur with a time scale less than 10 ms, consistent with the monomer exchange process in nonionic micelles. The CiEj buffer has a low viscosity (2.7 cP) and appears to be semidilute in micelle concentration. The large drag-tag size of the CiEj buffers leads to steric segregation of the DNA and tag for short fragments and attendant mobility shifts. PMID:26455271

  18. Esterase-activatable β-lapachone prodrug micelles for NQO1-targeted lung cancer therapy

    PubMed Central

    Ma, Xinpeng; Huang, Xiumei; Moore, Zachary; Huang, Gang; Kilgore, Jessica A.; Wang, Yiguang; Hammer, Suntrea; Williams, Noelle S.; Boothman, David A.; Gao, Jinming

    2016-01-01

    Lung cancer is one of the most lethal forms of cancer and current chemotherapeutic strategies lack broad specificity and efficacy. Recently, β-lapachone (β-lap) was shown to be highly efficacious in killing non-small cell lung cancer (NSCLC) cells regardless of their p53, cell cycle and caspase status. Pre-clinical and clinical use of β-lap (clinical form, ARQ501 or 761) is hampered by poor pharmacokinetics and toxicity due to hemolytic anemia. Here, we report the development and preclinical evaluation of β-lap prodrug nanotherapeutics consisting of diester derivatives of β-lap encapsulated in biocompatible and biodegradable poly(ethylene glycol)-b-poly(d,l-lactic acid) (PEG-b-PLA) micelles. Compared to the parent drug, diester derivatives of β-lap showed higher drug loading densities inside PEG-b-PLA micelles. After esterase treatment, micelle-delivered β-lap-dC3 and -dC6 prodrugs were converted to β-lap. Cytotoxicity assays using A549 and H596 lung cancer cells showed that both micelle formulations maintained NAD(P)H:quinone oxidoreductase 1 (NQO1)-dependent cytotoxicity. However, antitumor efficacy study of β-lap-dC3 micelles against orthotopic A549 NSCLC xenograft-bearing mice showed significantly greater long-term survival over β-lap-dC6 micelles or β-lap-HPβCD complexes. Improved therapeutic efficacy of β-lap-dC3 micelles correlated with higher area under the concentration-time curves of β-lap in tumors, and enhanced pharmacodynamic endpoints (e.g., PARP1 hyperactivation, γH2AX, and ATP depletion). β-Lap-dC3 prodrug micelles provide a promising strategy for NQO1-targeted therapy of lung cancer with improved safety and antitumor efficacy. PMID:25542645

  19. Liquid marbles prepared from pH-responsive self-assembled micelles.

    PubMed

    Sun, Jianhua; Wei, Wei; Zhao, Donghua; Hu, Qiong; Liu, Xiaoya

    2015-03-14

    In this study, we report the assembly of amphiphilic polymeric micelles at the liquid/air interface to prepare liquid marbles for the first time. The polymeric micelles were synthesized from the self-assembly of a fluoropolymer, poly(styrene-co-acrylic acid-co-2,2,3,4,4,4-hexafluorobutyl methacrylate), in a selective solvent. The particle size, morphology and chemical composition of the micelles were determined by dynamic light scattering (DLS), transmission electron microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. DLS and aqueous electrophoresis revealed the pH-responsiveness of the micelles in aqueous dispersion. Liquid marbles with water volumes varying from 10 μL to 1 mL were formed by rolling water droplets on the micelle powder bed. The increase in water volume led to the shape transition of the liquid marbles from quasi-spherical to a puddle-like shape because of gravity. Fluorescence microscopy was used to observe the morphology of the formed liquid marbles, which confirmed that the micelles were adsorbed at the interface of water and air. The effective surface tension of the liquid marbles decreased with the increasing concentration of NaOH, which was added to the interior water phase. This agreed with the results of droplet roller experiments: the mechanical integrity of the liquid marbles prepared from alkaline solution (pH 10) was relatively poorer than those prepared from acidic solution (pH 2). Moreover, these liquid marbles coated with micelles showed pH-responsiveness when transferred onto the surfaces of aqueous solutions with different pH values. The liquid marbles were relatively stable on the acidic solution, whereas they burst immediately on the alkaline solution with a pH of 10. In addition, apart from water, Gellan gum solution and glycerol could be also successfully encapsulated by the fluorinated micelles to form stable liquid marbles. PMID:25621854

  20. Reverse micelles and microemulsions in near-critical and supercritical fluids

    SciTech Connect

    Smith, R.D.; Fulton, J.L.; Blitz, J.P.; Tingey, J.M. )

    1990-01-25

    Reverse micelle and water-in-oil (w/o) microemulsion phases can be formed in near-critical and supercritical fluids, giving rise to uniquely pressure dependent phase behavior. The solvating power of reverse micelles formed from the surfactant sodium bis(2-ethylhexyl) sulfosuccinate (AOT) in fluids with moderate critical temperatures (e.g., ethane, propane, or xenon) depends largely upon the water-to-surfactant ratio of the micelle phase (W{sub m}), which at large W{sub m} can approach that of bulk water. The maximum water-to-surfactant ratio (W{sub 0}), which defines the boundary between a one-phase and a two-phase fluid system (where a second, predominantly aqueous phase exists), is strongly pressure dependent. The physical size of a reverse micelle in one-phase AOT/H{sub 2}O systems at constant W{sub m} has been shown to be nearly independent of the continuous-phase identity and pressure. In contrast, the apparent hydrodynamic size increases dramatically as W{sub 0} is approached due to increased micelle-micelle attractive interactions (e.g., clustering). The maximum reverse micelle size (W{sub m} {proportional to} diameter) increases with pressure for fluids such as ethane and propane, approaching W{sub m} = 40, corresponding to a droplet size of {approximately} 17 nm. Significant micelle densities are obtained for two phase systems, even at relatively low pressure (< 100 bar). These systems can be used to efficiently extract hydrophilic substances, including proteins, from dilute aqueous solution with substantial selectivity without the need for any chemical change to the system.

  1. Micellar lipid composition affects micelle interaction with class B scavenger receptor extracellular loops.

    PubMed

    Goncalves, Aurélie; Gontero, Brigitte; Nowicki, Marion; Margier, Marielle; Masset, Gabriel; Amiot, Marie-Josèphe; Reboul, Emmanuelle

    2015-06-01

    Scavenger receptors (SRs) like cluster determinant 36 (CD36) and SR class B type I (SR-BI) play a debated role in lipid transport across the intestinal brush border membrane. We used surface plasmon resonance to analyze real-time interactions between the extracellular protein loops and various ligands ranging from single lipid molecules to mixed micelles. Micelles mimicking physiological structures were necessary for optimal binding to both the extracellular loop of CD36 (lCD36) and the extracellular loop of SR-BI (lSR-BI). Cholesterol, phospholipid, and fatty acid micellar content significantly modulated micelle binding to and dissociation from the transporters. In particular, high phospholipid micellar concentrations inhibited micelle binding to both receptors (-53.8 and -74.4% binding at 0.32 mM compared with 0.04 mM for lCD36 and lSR-BI, respectively, P < 0.05). The presence of fatty acids was crucial for micelle interactions with both proteins (94.4 and 81.3% binding with oleic acid for lCD36 and lSR-BI, respectively, P < 0.05) and fatty acid type substitution within the micelles was the component that most impacted micelle binding to the transporters. These effects were partly due to subsequent modifications in micellar size and surface electric charge, and could be correlated to micellar vitamin D uptake by Caco-2 cells. Our findings show for the first time that micellar lipid composition and micellar properties are key factors governing micelle interactions with SRs. PMID:25833688

  2. Controlling the Size and Shape of the Elastin-Like Polypeptide based Micelles

    NASA Astrophysics Data System (ADS)

    Streletzky, Kiril; Shuman, Hannah; Maraschky, Adam; Holland, Nolan

    Elastin-like polypeptide (ELP) trimer constructs make reliable environmentally responsive micellar systems because they exhibit a controllable transition from being water-soluble at low temperatures to aggregating at high temperatures. It has been shown that depending on the specific details of the ELP design (length of the ELP chain, pH and salt concentration) micelles can vary in size and shape between spherical micelles with diameter 30-100 nm to elongated particles with an aspect ratio of about 10. This makes ELP trimers a convenient platform for developing potential drug delivery and bio-sensing applications as well as for understanding micelle formation in ELP systems. Since at a given salt concentration, the headgroup area for each foldon should be constant, the size of the micelles is expected to be proportional to the volume of the linear ELP available per foldon headgroup. Therefore, adding linear ELPs to a system of ELP-foldon should result in changes of the micelle volume allowing to control micelle size and possibly shape. The effects of addition of linear ELPs on size, shape, and molecular weight of micelles at different salt concentrations were studied by a combination of Dynamic Light Scattering and Static Light Scattering. The initial results on 50 µM ELP-foldon samples (at low salt) show that Rh of mixed micelles increases more than 5-fold as the amount of linear ELP raised from 0 to 50 µM. It was also found that a given mixture of linear and trimer constructs has two temperature-based transitions and therefore displays three predominant size regimes.

  3. Caractérisation des convertisseurs matriciels : II. Synthèse des fonctions de connexion

    NASA Astrophysics Data System (ADS)

    François, B.; Cambronne, J. P.; Hautier, J. P.

    1996-05-01

    Knowing the wished conversion levels (-1,0,1) of a power converter, this paper describes a particular method for setting the corresponding states of switches into the matrix converter. In a first step, a mathematical analysis establishes the relations linking the states of switches with the conversion functions. Afterwards, the presented method gives the inverse relations which constitute the sequential part of the converter control. The turn-on and the turn-off sequences are designed by considering the on-line wished level conversions. This general method enhances the idea that a converter functionnality must be defined by its structure and its control. Cet article propose une méthode originale pour définir la séquence de commande d'un convertisseur à partir de la fonction de conversion globalement souhaitée. Les auteurs procèdent d'abord à une analyse mathématique précise des relations qui existent entre les états des interrupteurs et les fonctions de conversion obtenues. À partir de cette analyse, la méthode developpée permet d'établir systématiquement les relations inverses qui constituent alors le module séquentiel de la commande rapprochée du convertisseur. Les ordres d'ouverture et de fermeture des interrupteurs sont élaborés en considérant à tout instant les niveaux de conversion souhaités pour les grandeurs électriques. Cette méthode générale renforce l'idée que la fonction remplie par un convertisseur moderne doit être définie à la fois par sa structure et sa commande.

  4. Microfibres and macroscopic films from the coordination-driven hierarchical self-assembly of cylindrical micelles.

    PubMed

    Lunn, David J; Gould, Oliver E C; Whittell, George R; Armstrong, Daniel P; Mineart, Kenneth P; Winnik, Mitchell A; Spontak, Richard J; Pringle, Paul G; Manners, Ian

    2016-01-01

    Anisotropic nanoparticles prepared from block copolymers are of growing importance as building blocks for the creation of synthetic hierarchical materials. However, the assembly of these structural units is generally limited to the use of amphiphilic interactions. Here we report a simple, reversible coordination-driven hierarchical self-assembly strategy for the preparation of micron-scale fibres and macroscopic films based on monodisperse cylindrical block copolymer micelles. Coordination of Pd(0) metal centres to phosphine ligands immobilized within the soluble coronas of block copolymer micelles is found to induce intermicelle crosslinking, affording stable linear fibres comprised of micelle subunits in a staggered arrangement. The mean length of the fibres can be varied by altering the micelle concentration, reaction stoichiometry or aspect ratio of the micelle building blocks. Furthermore, the fibres aggregate on drying to form robust, self-supporting macroscopic micelle-based thin films with useful mechanical properties that are analogous to crosslinked polymer networks, but on a longer length scale. PMID:27538877

  5. DNA aptamer–micelle as an efficient detection/delivery vehicle toward cancer cells

    PubMed Central

    Wu, Yanrong; Sefah, Kwame; Liu, Haipeng; Wang, Ruowen; Tan, Weihong

    2010-01-01

    We report the design of a self-assembled aptamer–micelle nanostructure that achieves selective and strong binding of otherwise low-affinity aptamers at physiological conditions. Specific recognition ability is directly built into the nanostructures. The attachment of a lipid tail onto the end of nucleic acid aptamers provides these unique nanostructures with an internalization pathway. Other merits include: extremely low off rate once bound with target cells, rapid recognition ability with enhanced sensitivity, low critical micelle concentration values, and dual-drug delivery pathways. To prove the potential detection/delivery application of this aptamer–micelle in biological living systems, we mimicked a tumor site in the blood stream by immobilizing tumor cells onto the surface of a flow channel device. Flushing the aptamer–micelles through the channel demonstrated their selective recognition ability under flow circulation in human whole-blood sample. The aptamer–micelles show great dynamic specificity in flow channel systems that mimic drug delivery in the blood system. Therefore, our DNA aptamer–micelle assembly has shown high potential for cancer cell recognition and for in vivo drug delivery applications. PMID:20080797

  6. Microfibres and macroscopic films from the coordination-driven hierarchical self-assembly of cylindrical micelles

    PubMed Central

    Lunn, David J.; Gould, Oliver E. C.; Whittell, George R.; Armstrong, Daniel P.; Mineart, Kenneth P.; Winnik, Mitchell A.; Spontak, Richard J.; Pringle, Paul G.; Manners, Ian

    2016-01-01

    Anisotropic nanoparticles prepared from block copolymers are of growing importance as building blocks for the creation of synthetic hierarchical materials. However, the assembly of these structural units is generally limited to the use of amphiphilic interactions. Here we report a simple, reversible coordination-driven hierarchical self-assembly strategy for the preparation of micron-scale fibres and macroscopic films based on monodisperse cylindrical block copolymer micelles. Coordination of Pd(0) metal centres to phosphine ligands immobilized within the soluble coronas of block copolymer micelles is found to induce intermicelle crosslinking, affording stable linear fibres comprised of micelle subunits in a staggered arrangement. The mean length of the fibres can be varied by altering the micelle concentration, reaction stoichiometry or aspect ratio of the micelle building blocks. Furthermore, the fibres aggregate on drying to form robust, self-supporting macroscopic micelle-based thin films with useful mechanical properties that are analogous to crosslinked polymer networks, but on a longer length scale. PMID:27538877

  7. Binary-component micelle and vesicle: Free energy and asymmetric distributions of amphiphiles between vesicle monolayers

    NASA Astrophysics Data System (ADS)

    Zhang, Qi-Yi; Xiang, Xun

    2013-03-01

    The real-space two-dimensional self-consistent field theory (SCFT) is employed to study the free energies of micelles and vesicles constituted by binary amphiphilic diblock copolymer AB in homopolymer A. With an increasing volume fraction of copolymer AB, there are morphological transitions from circle micelles to oblate circle-like micelles, to a compound structure with inverted micelles in the inner center and micelles outer layer, and to vesicles. Special attention is paid to the role of the copolymer AB in controlling the free energies of the micelles and vesicles by examining the effect of the length ratio of A/B with the fixed whole chain length of the AB copolymer, the length effect of A or B block with the corresponding fixed length of B or A block, for one component of copolymer, and the effect of different amphiphile compositions for a binary-component copolymer system. The quantity η is provided to describe the asymmetric density distribution of amphiphiles between the inner and outer monolayers of vesicles, and to quantify the relative asymmetric extent of the density distribution between two species of copolymers in binary component vesicles.

  8. Influence of Corona Structure on Binding of an Ionic Surfactant in Oppositely Charged Amphiphilic Polyelectrolyte Micelles.

    PubMed

    Delisavva, Foteini; Uchman, Mariusz; Škvarla, Juraj; Woźniak, Edyta; Pavlova, Ewa; Šlouf, Miroslav; Garamus, Vasil M; Procházka, Karel; Štěpánek, Miroslav

    2016-04-26

    Interaction of polystyrene-block-poly(methacrylic acid) micelles (PS-PMAA) with cationic surfactant N-dodecylpyridinium chloride (DPCl) in alkaline aqueous solutions was studied by static and dynamic light scattering, SAXS, cryogenic transmission electron microscopy (cryo-TEM), isothermal titration calorimetry (ITC), and time-resolved fluorescence spectroscopy. ITC and fluorescence measurements show that there are two distinct regimes of surfactant binding in the micellar corona (depending on the DPCl content) caused by different interactions of DPCl with PMAA in the inner and outer parts of the corona. The compensation of the negative charge of the micellar corona by DPCl leads to the aggregation of PS-PMAA micelles, and the micelles form colloidal aggregates at a certain critical surfactant concentration. SAXS shows that the aggregates are formed by individual PS-PMAA micelles with intact cores and collapsed coronas interconnected with surfactant micelles by electrostatic interactions. Unlike polyelectrolyte-surfactant complexes formed by free polyelectrolyte chains, the PMAA/DPCl complex with collapsed corona does not contain surfactant micelles. PMID:27054848

  9. Structure, dynamics, and insertion of a chloroplast targeting peptide in mixed micelles.

    PubMed

    Wienk, H L; Wechselberger, R W; Czisch, M; de Kruijff, B

    2000-07-18

    Nuclear-encoded, chloroplast-destined proteins are synthesized with transit sequences that contain all information to get them inside the organelle. Different proteins are imported via a general protein import machinery, but their transit sequences do not share amino acid homology. It has been suggested that interactions between transit sequence and chloroplast envelope membrane lipids give rise to recognizable, structural motifs. In this study a detailed investigation of the structural, dynamical, and topological features of an isolated transit peptide associated with mixed micelles is described. The structure of the preferredoxin transit peptide in these micelles was studied by circular dichroism (CD) and multidimensional NMR techniques. CD experiments indicated that the peptide, which is unstructured in aqueous solution, obtained helical structure in the presence of the micelles. By NMR it is shown that the micelles introduced ill-defined helical structures in the transit peptide. Heteronuclear relaxation experiments showed that the whole peptide backbone is very flexible. The least dynamic segments are two N- and C-terminal helical regions flanking an unstructured proline-rich amino acid stretch. Finally, the insertion of the peptide backbone in the hydrophobic interior of the micelle was investigated by use of hydrophobic spin-labels. The combined data result in a model of the transit peptide structure, backbone dynamics, and insertion upon its interaction with mixed micelles. PMID:10889029

  10. Complete regression of xenograft tumors using biodegradable mPEG-PLA-SN38 block copolymer micelles.

    PubMed

    Lu, Lu; Zheng, Yan; Weng, Shuqiang; Zhu, Wenwei; Chen, Jinhong; Zhang, Xiaomin; Lee, Robert J; Yu, Bo; Jia, Huliang; Qin, Lunxiu

    2016-06-01

    7-Ethyl-10-hydroxy-comptothecin (SN38) is an active metabolite of irinotecan (CPT-11) and the clinical application of SN38 is limited by its hydrophobicity and instability. To address these issues, a series of novel amphiphilic mPEG-PLA-SN38-conjugates were synthesized by linking SN38 to mPEG-PLA-SA, and they could form micelles by self-assembly. The effects of mPEG-PLA composition were studied in vitro and in vivo. The mean diameters of mPEG2K-PLA-SN38 micelles and mPEG4K-PLA-SN38 micelles were 10-20nm and 120nm, respectively, and mPEG2K-PLA-SN38 micelles showed greater antitumor efficacy than mPEG4K-PLA-SN38 micelles both in vitro and in vivo. These data suggest that the lengths of mPEG and PLA chains had a major impact on the physicochemical characteristics and antitumor activity of SN38-conjugate micelles. PMID:26994941

  11. Biodegradable micelles enhance the antiglioma activity of curcumin in vitro and in vivo

    PubMed Central

    Zheng, Songping; Gao, Xiang; Liu, Xiaoxiao; Yu, Ting; Zheng, Tianying; Wang, Yi; You, Chao

    2016-01-01

    Curcumin (Cur), a natural polyphenol of Curcuma longa, has been recently reported to possess antitumor activities. However, due to its poor aqueous solubility and low biological availability, the clinical application of Cur is quite limited. The encapsulation of hydrophobic drugs into nanoparticles is an effective way to improve their pharmaceutical activities. In this research, nanomicelles loaded with Cur were formulated by a self-assembly method with biodegradable monomethoxy poly(ethylene glycol)-poly(lactide) copolymers (MPEG-PLAs). After encapsulation, the cellular uptake was increased and Cur could be released from MPEG-PLA micelles in a sustained manner. The Cur-loaded MPEG-PLA micelles (Cur/MPEG-PLA micelles) exhibited an enhanced toxicity on C6 and U251 glioma cells and induced more apoptosis on C6 glioma cells compared with free Cur. Moreover, the therapy efficiency of Cur/MPEG-PLA micelles was evaluated at length on a nude mouse model bearing glioma. The Cur/MPEG-PLA micelles were more effective on suppressing tumor growth compared with free Cur, which indicated that Cur/MPEG-PLA micelles improved the antiglioma activity of Cur in vivo. The results of immunohistochemical and immunofluorescent analysis indicated that the induction of apoptosis, antiangiogenesis, and inhibition of cell proliferation may contribute to the improvement in antiglioma effects. Our data suggested that Cur/MPEG-PLA may have potential clinic applications in glioma therapy. PMID:27354801

  12. Biodegradable micelles enhance the antiglioma activity of curcumin in vitro and in vivo.

    PubMed

    Zheng, Songping; Gao, Xiang; Liu, Xiaoxiao; Yu, Ting; Zheng, Tianying; Wang, Yi; You, Chao

    2016-01-01

    Curcumin (Cur), a natural polyphenol of Curcuma longa, has been recently reported to possess antitumor activities. However, due to its poor aqueous solubility and low biological availability, the clinical application of Cur is quite limited. The encapsulation of hydrophobic drugs into nanoparticles is an effective way to improve their pharmaceutical activities. In this research, nanomicelles loaded with Cur were formulated by a self-assembly method with biodegradable monomethoxy poly(ethylene glycol)-poly(lactide) copolymers (MPEG-PLAs). After encapsulation, the cellular uptake was increased and Cur could be released from MPEG-PLA micelles in a sustained manner. The Cur-loaded MPEG-PLA micelles (Cur/MPEG-PLA micelles) exhibited an enhanced toxicity on C6 and U251 glioma cells and induced more apoptosis on C6 glioma cells compared with free Cur. Moreover, the therapy efficiency of Cur/MPEG-PLA micelles was evaluated at length on a nude mouse model bearing glioma. The Cur/MPEG-PLA micelles were more effective on suppressing tumor growth compared with free Cur, which indicated that Cur/MPEG-PLA micelles improved the antiglioma activity of Cur in vivo. The results of immunohistochemical and immunofluorescent analysis indicated that the induction of apoptosis, antiangiogenesis, and inhibition of cell proliferation may contribute to the improvement in antiglioma effects. Our data suggested that Cur/MPEG-PLA may have potential clinic applications in glioma therapy. PMID:27354801

  13. Induced redox responsiveness and electroactivity for altering the properties of micelles without external stimuli.

    PubMed

    Glavas, Lidija; Odelius, Karin; Albertsson, Ann-Christine

    2014-06-14

    Control over micelle properties is vital in the field of drug delivery, and the ability to modify these properties in order to trigger dissociation is highly desirable. We prepared polymeric micelles with the ability to undergo dissociation over time without the need for external stimulation by incorporating an electroactive and redox responsive segment into amphiphilic copolymers. The incorporation of this segment also provides the ability to tailor the critical micelle concentration (CMC) and micelle size of the copolymers. Amphiphilic PEG-PLA copolymers were functionalized by coupling to an aniline pentamer in two different oxidation states (leucoemeraldine and emeraldine state). The incorporation of the electroactive and redox responsive aniline pentamer decreased the CMCs and the micelle size, independent of the oxidation state. However, the copolymers with the aniline pentamer in the leucoemeraldine state had significantly lower CMCs than the copolymers with the aniline pentamer in the emeraldine state. Simultaneously, stability tests performed on the functionalized micelles demonstrated the oxidation of the aniline segment, from the leucoemeraldine to the emeraldine state, over time. The oxidation led to an increase in the CMC, and the copolymers could thereby represent an excellent starting point for triggering drug release without external stimuli. PMID:24737104

  14. Pluronic mixed micelles overcoming methotrexate multidrug resistance: in vitro and in vivo evaluation

    PubMed Central

    Chen, Yanzuo; Sha, Xianyi; Zhang, Wei; Zhong, Weitong; Fan, Zhuoyang; Ren, Qiuyue; Chen, Liangcen; Fang, Xiaoling

    2013-01-01

    A Pluronic polymeric mixed micelle delivery system was developed in this study by using Pluronic P105 and F127 block copolymers to encapsulate the antitumor compound, methotrexate (MTX). The MTX-loaded Pluronic P105/F127 mixed micelle exhibited the spherical shape with about 22 nm in diameter, high encapsulation efficiency (about 85%) and pH-dependent in vitro drug release. In this study, A-549 and KBv cell lines were selected as multidrug resistance tumor cell models, while H-460 and KB cell lines were chosen as sensitive tumor cells. The MTX-loaded Pluronic P105/F127 mixed micelle exhibited significant higher in vitro cytotoxicity in multidrug resistant tumor cells than that of control (MTX injection) mainly because of higher cellular uptake of MTX. The pharmacokinetic studies indicated that the Pluronic micelles significantly prolonged systemic circulation time of MTX compared to MTX injection. Moreover, a much stronger antitumor efficacy in KBv tumor xenografts nude mice was observed in the MTX-loaded Pluronic P105/F127 mixed micelle group, than MTX. Collectively, Pluronic P105/F127 mixed micelles could significantly enhance the antitumor activity of MTX and might be a promising drug delivery platform for multidrug resistance modulation. PMID:23620663

  15. [Construction of biotin-modified polymeric micelles for pancreatic cancer targeted photodynamic therapy].

    PubMed

    Deng, Chun-yue; Long, Ying-ying; Liu, Sha; Chen, Zhang-bao; Li, Chong

    2015-08-01

    In this study, we explored the feasibility of biotin-mediated modified polymeric micelles for pancreatic cancer targeted photodynamic therapy. Poly (ethylene glycol)-distearoyl phosphatidyl ethanolamine (mPEG2000-DSPE) served as the drug-loaded material, biotin-poly(ethylene glycol)-distearoyl phosphatidyl ethanolamine (Biotin-PEG3400-DSPE) as the functional material and the polymeric micelles were prepared by a thin-film hydration method. The targeting capability of micelles was investigated by cell uptake assay in vitro and fluorescence imaging in vivo and the amounts of Biotin-PEG-DSPE were optimized accordingly. Hypocrellin B (HB), a novel photosensitizer was then encapsulated in biotinylated polymeric micelles and the anti-tumor efficacy was evaluated systemically in vitro and in vivo. The results showed that micelles with 5 mol % Biotin-PEG-DSPE demonstrated the best targeting capability than those with 20 mol % or 0.5 mol % of corresponding materials. This formulation has a small particle size [mean diameter of (36.74 ± 2.16) nm] with a homogeneous distribution and high encapsulation efficiency (80.06 ± 0.19) %. The following pharmacodynamics assays showed that the biotinylated micelles significantly enhanced the cytotoxicity of HB against tumor cells in vitro and inhibited tumor growth in vivo, suggesting a promising potential of this formulation for treatment of pancreatic cancer, especially those poorly permeable, or insensitive to radiotherapy and chemotherapy. PMID:26669006

  16. Disulfide cross-linked phosphorylcholine micelles for triggered release of camptothecin

    PubMed Central

    McRae Page, Samantha; Martorella, Molly; Parelkar, Sangram; Kosif, Irem

    2013-01-01

    A series of block copolymers based on 2-methacryloyloxyethyl phosphorylcholine (MPC) were synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization. Incorporation of dihydrolipoic acid (DHLA) into the hydrophobic block led to formation of block copolymer micelles in water. The micelles were between 15 and 30 nm in diameter, as characterized by dynamic light scattering (DLS), with some size control achieved by adjusting the hydrophobic/hydrophilic balance. Cross-linked micelles were prepared by disulfide formation, and observed to be stable in solution for weeks. The micelles proved amenable to disassembly when treated with a reducing agent, such as dithiothreitol (DTT), and represent a potential delivery platform for chemotherapeutic agents. As a proof-of-concept, camptothecin (CPT) was conjugated to the polymer scaffold through a disulfide linkage, and release of the drug from the micelle was monitored by fluorescence spectroscopy. These CPT-loaded prodrug micelles showed a reduction in release rate compared to physically encapsulated CPT. The use of disulfide conjugation facilitated drug release under reducing conditions, with a half-life (t1/2) of 5.5 hours in the presence of 3 mM DTT, compared to 28 hours in PBS. The toxicity of the micellar prodrugs was evaluated in cell culture against human breast (MCF7) and colorectal (COLO205) cancer cell lines. PMID:23742055

  17. Association of chlorophyll with inverted micelles of dodecylpyridinium iodide in toluene

    SciTech Connect

    Seely, G.R.; Ma, X.C.; Nieman, R.A.; Gust, D. )

    1990-02-22

    Dodecylpyridinium iodide forms inverted micelles in water-containing toluene at concentrations higher than 10{sup {minus}4} M, as it reportedly does in other nonpolar solvents. Micelle formation is characterized by changes in the charge-transfer absorption band, and in the chemical shifts of protons, especially those on or near the pyridinium group. The micelles associate with chlorophyll a, also dissolved in the toluene, as evidenced by large changes in the chemical shift of some of the surfactant and the chlorophyll resonances. The fluorescence quantum yield of chlorophyll is little reduced by the presence of 10{sup {minus}3} M 2,2{prime}-dithiobis(5-nitropyridine), a quencher which is soluble in toluene and probably associates weakly with the micelles, but is strongly reduced by the presence of the bis(tetramethylammonium) salt of 5,5{prime}-dithiobis(2-nitrobenzoic acid), which is solubilized only in the presence of the inverted micelles, and furthermore forms a complex with chlorophyll. These cationic inverted micelles constitute a new environment for the pursuit of chlorophyll model system investigations.

  18. Influence of surfactant structure on reverse micelle size and charge for nonpolar electrophoretic inks.

    PubMed

    Parent, Mary E; Yang, Jun; Jeon, Yoocharn; Toney, Michael F; Zhou, Zhang-Lin; Henze, Dick

    2011-10-01

    Electrophoretic inks, which are suspensions of colorant particles that are controllably concentrated and dispersed by applied electric fields, are the leading commercial technology for high-quality reflective displays. Extending the state of the art for high-fidelity color in these displays requires improved understanding and control of the colloidal systems. In these inks, reverse micelles in nonpolar media play key roles in media and particle charging. Here we investigate the effect of surfactant structure on reverse micelle size and charging properties by synthesizing different surfactants with variations in polyamine polar head groups. Small-angle X-ray scattering (SAXS) and dynamic light scattering (DLS) were used to determine the micelle core plus shell size and micelle hydrodynamic radius, respectively. The results from SAXS agreed with DLS and showed that increasing polyamines in the surfactant head increased the micelle size. The hydrodynamic radius was also calculated on the basis of transient current measurements and agreed well with the DLS results. The transient current technique further determined that increasing polyamines increased the charge stabilization capability of the micelles and that an analogous commercial surfactant OLOA 11000 made for a lower concentration of charge-generating ions in solution. Formulating magenta inks with the various surfactants showed that the absence of amine in the surfactant head was detrimental to particle stabilization and device performance. PMID:21863832

  19. Thailandepsin A-loaded and octreotide-functionalized unimolecular micelles for targeted neuroendocrine cancer therapy.

    PubMed

    Jaskula-Sztul, Renata; Xu, Wenjin; Chen, Guojun; Harrison, April; Dammalapati, Ajitha; Nair, Renu; Cheng, Yiqiang; Gong, Shaoqin; Chen, Herbert

    2016-06-01

    Due to the overexpression of somatostatin receptors in neuroendocrine (NE) cancers, drug nanocarriers conjugated with somatostatin analogs, such as octreotide (OCT), for targeted NE cancer therapy may offer increased therapeutic efficacies and decreased adverse effects. In this study, OCT-functionalized unimolecular micelles were prepared using individual hyperbranched polymer molecules consisting of a hyperbranched polymer core (Boltorn(®) H40) and approximately 25 amphiphilic polylactide-poly(ethlyene glycol) (PLA-PEG) block copolymer arms (H40-PLA-PEG-OCH3/OCT). The resulting micelles, exhibiting a uniform core-shell shape and an average hydrodynamic diameter size of 66 nm, were loaded with thailandepsin-A (TDP-A), a relatively new naturally produced histone deacetylase (HDAC) inhibitor. In vitro studies using flow cytometry and confocal laser scanning microscopy (CLSM) demonstrated that OCT conjugation enhanced the cellular uptake of the unimolecular micelles. Consequently, TDP-A-loaded and OCT-conjugated micelles exhibited the highest cytotoxicity and caused the highest reduction of NE tumor markers. Finally, the in vivo studies on NE cancer bearing nude mice demonstrated that TDP-A-loaded and OCT-conjugated micelles possessed superior anticancer activity in comparison with other TDP-A formulations or drug alone, while showing no detectable systemic toxicity. Thus, these TDP-A-loaded and OCT-conjugated micelles offer a promising approach for targeted NE cancer therapy. PMID:26994874

  20. Growth control of nonionic reverse micelles by surfactant and solvent molecular architecture and water addition.

    PubMed

    Shrestha, Lok Kumar; Shrestha, Rekha Goswami; Aramaki, Kenji

    2011-06-01

    This paper describes a facile route to the shape, size, and structure control of reversed micelles by surfactant and solvent molecular architecture and water addition. Nonionic reverse micellar size is found to increase with increase in hydrophilic headgroup size of surfactant, whose scheme is understood in terms of decrease in the critical packing parameter (cpp). On the other hand, an opposite trend is observed with increase in lipophilicity of the surfactant. This is caused by the repulsive excluded volume interactions, which increases with the volume of lipophilic moiety of surfactant; as a result, the micelle interface tends to become more curved and micelles shrink. Solvent molecular structure has played a crucial role; increasing hydrocarbon chain length of alkanes favored one dimensional micellar growth. We note that long chain oil has a poor penetration tendency to lipophilic tail of surfactant and decreases the cpp. Solvent polarity is also crucial; globular micelles are formed in short chain oil cyclohexane. We note that decreasing chain length of oil mimic the decrease in the headgroup size of surfactant; rod-to-sphere type transition in the micellar structure. Addition of trace water favors micellar growth; maximum dimension and micellar cross section increases with increase in water concentration. The sizes of the water incorporated reverse micelles (or w/o microemulsion) are much bigger than the empty micelles. Micellar structure was confirmed by small angle X-ray scattering (SAXS) and supported by rheology. PMID:21770115

  1. Thermosensitive PNIPAM-b-HTPB block copolymer micelles: molecular architectures and camptothecin drug release.

    PubMed

    Luo, Yan-Ling; Yang, Xiao-Li; Xu, Feng; Chen, Ya-Shao; Zhang, Bin

    2014-02-01

    Two kinds of thermo-sensitive poly(N-isoproplacrylamide) (PNIPAM) block copolymers, AB4 four-armed star multiblock and linear triblock copolymers, were synthesized by ATRP with hydroxyl-terminated polybutadiene (HTPB) as central blocks, and characterization was performed by (1)H NMR, FT-IR and SEC. The multiblock copolymers could spontaneously assemble into more regular spherical core-shell nanoscale micelles than the linear triblock copolymer. The physicochemical properties were detected by a surface tension technique, nano particle analyzer, TEM, DLS and UV-vis measurements. The multiblock copolymer micelles had lower critical micelle concentration than the linear counterpart, TEM size from 100 to 120 nm and the hydrodynamic diameters below 150 nm. The micelles exhibited thermo-dependent size change, with low critical solution temperature about 33-35 °C. The characteristic parameters were affected by the composition ratios, length of PNIPAM blocks and molecular architectures. The camptothecin release demonstrated that the drug release was thermo-responsive, accompanied by the temperature-induced structural changes of the micelles. MTT assays were performed to evaluate the biocompatibility or cytotoxicity of the prepared copolymer micelles. PMID:24184534

  2. Hyaluronic acid-quercetin conjugate micelles: synthesis, characterization, in vitro and in vivo evaluation.

    PubMed

    Pang, Xin; Lu, Zhen; Du, Hongliang; Yang, Xiaoye; Zhai, Guangxi

    2014-11-01

    A tumor cell-targeted prodrug was developed for quercetin, using hyaluronic acid as polymeric carrier. Hyaluronic acid-quercetin (HA-QT) bioconjugates were synthesized by linking the hydroxy of quercetin via a succinate ester to adipic dihydrazide-modified hyaluronic acid. The mirco-morphology demonstrated that the prepared prodrug could form self-assembled micelles possessing spherical shape, 172.1 nm average diameter and -20.30 mV surface potential. The HA-QT micelles exhibited significant sustained and pH-dependent drug release behaviors without dramatic initial burst. Compared to free quercetin solution, the HA-QT micelles were found a 4 times increase in cytotoxicity on MCF-7 cells (CD44-overexpressing cell lines), while weak enhancement in inhibitory activity was observed towards L929 cells (CD44 deficient cell lines). Promisingly, 20.1-fold increase in the half-life and 4.9-fold increase in the area-under-the-curve (AUC) of quercetin were achieved for the HA-QT micelles compared with the parent drug. In addition, the HA-QT micelles also showed excellent inhibition effect on tumor growth in H22 tumor-bearing mice. Hemolytic toxicity and vein irritation assay further suggested that the HA-QT micelles were a safe and potent drug delivery system for targeted antitumor therapy. PMID:25454664

  3. Magnetothermally responsive star-block copolymeric micelles for controlled drug delivery and enhanced thermo-chemotherapy

    NASA Astrophysics Data System (ADS)

    Deng, Li; Ren, Jie; Li, Jianbo; Leng, Junzhao; Qu, Yang; Lin, Chao; Shi, Donglu

    2015-05-01

    Magnetothermally responsive drug-loaded micelles were designed and prepared for cancer therapy. These specially designed micelles are composed of the thermo-responsive star-block copolymer poly(ε-caprolactone)-block-poly(2-(2-methoxyethoxy)ethyl methacrylate-co-oligo(ethylene glycol)methacrylate) and Mn, Zn doped ferrite magnetic nanoparticles (MZF-MNPs). The thermo-responses of 6sPCL-b-P(MEO2MA-co-OEGMA) copolymers were shown to be dependent on the MEO2MA to OEGMA ratio. The lower critical solution temperature (LCST) of the star-block copolymers was controlled at 43 °C by adjusting the feed molar ratios of MEO2MA/OEGMA at 92 : 8. With the anti-tumor drug doxorubicin (DOX) self-assembling into the carrier system, the thermo-responsive micelles exhibited excellent temperature-triggered drug release behavior. In vitro cytotoxicity results showed high biocompatibility of the polymer micelles. Efficient cellular proliferation inhibition by the drug-loaded micelles was found on the HepG2 cells under different treatments. The thermo-responsive polymer micelles are promising for controlled drug delivery in tumor therapy under an alternating magnetic field.

  4. Development of lycopene micelle and lycopene chylomicron and a comparison of bioavailability

    NASA Astrophysics Data System (ADS)

    Jyun Chen, Yi; Inbaraj, Baskaran Stephen; Shiau Pu, Yeong; Chen, Bing Huei

    2014-04-01

    The objectives of this study were to develop lycopene micelles and lycopene chylomicrons from tomato extracts for the enhancement and comparison of bioavailability. Lycopene micelles and chylomicrons were prepared by a microemulsion technique involving tomato extract, soybean oil, water, vitamin E and surfactant Tween 80 or lecithin in different proportions. The encapsulation efficiency of lycopene was 78% in micelles and 80% in chylomicrons, with shape being roughly spherical and mean particle size being 7.5 and 131.5 nm. A bioavailability study was conducted in rats by both gavage and i.v. administration, with oral bioavailability of lycopene, phytoene and phytofluene being 6.8, 4.3 and 3.1% in micelles and 9.5, 9.4 and 7.1% in chylomicrons, respectively. This outcome reveals higher lycopene bioavailability through incorporation into micelle or chylomicron systems. Both size and shape should be considered for oral bioavailability determination. For i.v. injection, lycopene micelles should be more important than lycopene chylomicrons for future clinical applications.

  5. Development of lycopene micelle and lycopene chylomicron and a comparison of bioavailability.

    PubMed

    Chen, Yi Jyun; Inbaraj, Baskaran Stephen; Pu, Yeong Shiau; Chen, Bing Huei

    2014-04-18

    The objectives of this study were to develop lycopene micelles and lycopene chylomicrons from tomato extracts for the enhancement and comparison of bioavailability. Lycopene micelles and chylomicrons were prepared by a microemulsion technique involving tomato extract, soybean oil, water, vitamin E and surfactant Tween 80 or lecithin in different proportions. The encapsulation efficiency of lycopene was 78% in micelles and 80% in chylomicrons, with shape being roughly spherical and mean particle size being 7.5 and 131.5 nm. A bioavailability study was conducted in rats by both gavage and i.v. administration, with oral bioavailability of lycopene, phytoene and phytofluene being 6.8, 4.3 and 3.1% in micelles and 9.5, 9.4 and 7.1% in chylomicrons, respectively. This outcome reveals higher lycopene bioavailability through incorporation into micelle or chylomicron systems. Both size and shape should be considered for oral bioavailability determination. For i.v. injection, lycopene micelles should be more important than lycopene chylomicrons for future clinical applications. PMID:24651082

  6. Worm-like micelles of CTAB and sodium salicylate under turbulent flow.

    PubMed

    Rodrigues, Roberta K; da Silva, Marcelo A; Sabadini, Edvaldo

    2008-12-16

    Polymers with high molecular weight and worm-like micelles are drag-reducing agents under turbulent flow. However, in contrast to the polymeric systems, the worm-like micelles do not undergo mechanical degradation due to the turbulence, because their macromolecular structure can be spontaneously restored. This very favorable property, together with their drag-reduction capability, offer the possibility to use such worm-like micelles in heating and cooling systems to recirculate water while expending less energy. The formation, growth, and stability of worm-like micelles formed by cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal) were investigated using the self-fluorescence of salicylate ions and the ability of the giant micelles to promote hydrodynamic drag reduction under turbulent flow. The turbulence in solutions of CTAB-Sal was produced within the double-gap cell of a rotational rheometer. Detailed diagrams were obtained for different ratios of Sal and CTAB, which revealed transitions associated with the thermal stability of giant micelles under turbulent flow. PMID:19053646

  7. Thailandepsin A-loaded and octreotide-functionalized unimolecular micelles for targeted neuroendocrine cancer therapy

    PubMed Central

    Jaskula-Sztul, Renata; Xu, Wenjin; Chen, Guojun; Harrison, April; Dammalapati, Ajitha; Nair, Renu; Cheng, Yiqiang; Gong, Shaoqin; Chen, Herbert

    2016-01-01

    Due to the overexpression of somatostatin receptors in neuroendocrine (NE) cancers, drug nanocarriers conjugated with somatostatin analogs, such as octreotide (OCT), for targeted NE cancer therapy may offer increased therapeutic efficacies and decreased adverse effects. In this study, OCT-functionalized unimolecular micelles were prepared using individual hyperbranched polymer molecules consisting of a hyperbranched polymer core (Boltorn® H40) and approximately 25 amphiphilic polylactide-poly(-ethlyene glycol) (PLA-PEG) block copolymer arms (H40-PLA-PEG-OCH3/OCT). The resulting micelles, exhibiting a uniform core-shell shape and an average hydrodynamic diameter size of 66 nm, were loaded with thailandepsin-A (TDP-A), a relatively new naturally produced histone deacetylase (HDAC) inhibitor. In vitro studies using flow cytometry and confocal laser scanning microscopy (CLSM) demonstrated that OCT conjugation enhanced the cellular uptake of the unimolecular micelles. Consequently, TDP-A-loaded and OCT-conjugated micelles exhibited the highest cytotoxicity and caused the highest reduction of NE tumor markers. Finally, the in vivo studies on NE cancer bearing nude mice demonstrated that TDP-A-loaded and OCT-conjugated micelles possessed superior anticancer activity in comparison with other TDP-A formulations or drug alone, while showing no detectable systemic toxicity. Thus, these TDP-A-loaded and OCT-conjugated micelles offer a promising approach for targeted NE cancer therapy. PMID:26994874

  8. Recent advances in polymeric micelles for anti-cancer drug delivery.

    PubMed

    Biswas, Swati; Kumari, Preeti; Lakhani, Prit Manish; Ghosh, Balaram

    2016-02-15

    Block co-polymeric micelles receive increased attention due to their ability to load therapeutics, deliver the cargo to the site of action, improve the pharmacokinetic of the loaded drug and reduce off-target cytotoxicity. While polymeric micelles can be developed with improved drug loading capabilities by modulating hydrophobicity and hydrophilicity of the micelle forming block co-polymers, they can also be successfully cancer targeted by surface modifying with tumor-homing ligands. However, maintenance of the integrity of the self-assembled system in the circulation and disassembly for drug release at the site of drug action remain a challenge. Therefore, stimuli-responsive polymeric micelles for on demand drug delivery with minimal off-target effect has been developed and extensively investigated to assess their sensitivity. This review focuses on discussing various polymeric micelles currently utilized for the delivery of chemotherapeutic drugs. Designs of various stimuli-sensitive micelles that are able to control drug release in response to specific stimuli, either endogenous or exogenous have been delineated. PMID:26747018

  9. Transport of nanoparticulate material in self-assembled block copolymer micelle solutions and crystals.

    PubMed

    Cheng, Vicki A; Walker, Lynn M

    2016-04-12

    Water soluble poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) [PEO-PPO-PEO] triblock copolymers self-assemble into thermoreversible micellar crystals comprised of periodically spaced micelles. The micelles have PPO cores surrounded by hydrated PEO coronas and the dimensions of the unit cell of the organized micelles is on the order of several to tens of nanometers. Fluorescence recovery after photobleaching (FRAP) is used to quantify nanoparticle transport in these nanostructured polymer micelle systems. Diffusivity of bovine serum albumin (BSA, Dh ∼ 7 nm) is quantified across a wide range of polymer, or micelle, concentrations covering both the disordered fluid as well as the structured micellar crystal to understand the effects of nanoscale structure on particle transport. Measured particle diffusivity in these micellar systems is reduced by as much as four orders of magnitude when compared to diffusivity in free solution. Diffusivity in the disordered micellar fluid is best understood in terms of diffusion through a polymeric solution, while transport in the structured micellar phase is possibly due to hopping between interstitial sites. These results not only show that the nanoscale structures of the micelles have a measureable impact on particle diffusivity, but also demonstrate the ability to tune nanoscale transport in self-assembled materials. PMID:26796632

  10. Ultrafast fluorescence resonance energy transfer in a reverse micelle: Excitation wavelength dependence

    NASA Astrophysics Data System (ADS)

    Mondal, Sudip Kumar; Ghosh, Subhadip; Sahu, Kalyanasis; Mandal, Ujjwal; Bhattacharyya, Kankan

    2006-12-01

    Fluorescence resonance energy transfer (FRET) from coumarin 480 (C480) to fluorescein 548 (F548) in a sodium dioctyl sulfosuccinate (AOT) reverse micelle is studied by picosecond and femtosecond emission spectroscopy. In bulk water, at the low concentration of the donor (C480) and the acceptor (F548), no FRET is observed. However, when the donor (C480) and the acceptor (F548) are confined in a AOT reverse micelle very fast FRET is observed. The time constants of FRET were obtained from the rise time of the emission of the acceptor (F548). In a AOT microemulsion, FRET is found to occur in multiple time scales—3, 200, and 2700ps. The 3ps component is assigned to FRET in the water pool of the reverse micelle with a donor-acceptor distance, 16Å. The 200ps component corresponds to a donor-acceptor distance of 30Å and is ascribed to the negatively charged acceptor inside the water pool and the neutral donor inside the alkyl chains of AOT. The very long 2700ps component may arise due to FRET from a donor outside the micelle to an acceptor inside the water pool and also from diffusion of the donor from bulk heptane to the reverse micelle. With increase in the excitation wavelength from 375to405nm the relative contribution of the FRET due to C480 in the AOT reverse micelle (the 3 and 200ps components) increases.

  11. Gold nanoparticles tune the activity of laccase in anionic reverse micelles.

    PubMed

    Yu, Xinxin; Zou, Feixue; Yao, Peipei; Huang, Xirong; Qu, Yinbo

    2014-09-14

    The interfacial property of reverse micelles is an important factor affecting the catalytic activity of enzymes hosted in the micelles. In this article, the effect of gold nanoparticles (GNPs) on the catalytic activity of laccase (non-surface-active enzyme) and the related mechanism are reported. It was found that laccase activity was dependent on the size of the particle and its concentration as well as on the water content and the concentration of AOT. It was shown that there existed several types of micelles in the present reverse micellar system in the presence of GNPs. The population of the various micelles depended on the concentrations of both GNPs and AOT. Fluorescence and circular dichroism spectra of laccase at different water contents and GNP concentrations indicated that the conformation of laccase and its activity were tuned by GNPs via changing the structure of the reverse micelles. Analysis showed that changes in the thickness of the water layer (Lw) and in the apparent occupied area of individual AOT molecules (AAOT) caused by GNPs were the main parameters affecting the activity of laccase. The present work extends and deepens the understanding of the tuning mechanism of GNPs on enzymatic performance in reverse micelles and provides guidance for rational design of the optimal microenvironment of laccase. PMID:25046816

  12. Ultrafast fluorescence resonance energy transfer in a reverse micelle: excitation wavelength dependence.

    PubMed

    Mondal, Sudip Kumar; Ghosh, Subhadip; Sahu, Kalyanasis; Mandal, Ujjwal; Bhattacharyya, Kankan

    2006-12-14

    Fluorescence resonance energy transfer (FRET) from coumarin 480 (C480) to fluorescein 548 (F548) in a sodium dioctyl sulfosuccinate (AOT) reverse micelle is studied by picosecond and femtosecond emission spectroscopy. In bulk water, at the low concentration of the donor (C480) and the acceptor (F548), no FRET is observed. However, when the donor (C480) and the acceptor (F548) are confined in a AOT reverse micelle very fast FRET is observed. The time constants of FRET were obtained from the rise time of the emission of the acceptor (F548). In a AOT microemulsion, FRET is found to occur in multiple time scales--3, 200, and 2700 ps. The 3 ps component is assigned to FRET in the water pool of the reverse micelle with a donor-acceptor distance, 16 A. The 200 ps component corresponds to a donor-acceptor distance of 30 A and is ascribed to the negatively charged acceptor inside the water pool and the neutral donor inside the alkyl chains of AOT. The very long 2700 ps component may arise due to FRET from a donor outside the micelle to an acceptor inside the water pool and also from diffusion of the donor from bulk heptane to the reverse micelle. With increase in the excitation wavelength from 375 to 405 nm the relative contribution of the FRET due to C480 in the AOT reverse micelle (the 3 and 200 ps components) increases. PMID:17176157

  13. Influencing the structure of block copolymer micelles with small molecule additives

    NASA Astrophysics Data System (ADS)

    Robertson, Megan; Singh, Avantika; Cooksey, Tyler; Kidd, Bryce; Piemonte, Rachele; Wang, Shu; Mai Le, Kim; Madsen, Louis

    Amphiphilic block copolymer micelles in water are under broad exploration for drug delivery applications due to their high loading capacity and targeted drug delivery. We aim to understand the kinetic and thermodynamic processes that underlie the self-assembly of diblock copolymer micelle systems. The present work focuses on diblock copolymers containing poly(ethylene oxide) (a hydrophilic polymer) and polycaprolactone (a hydrophobic polymer), which spontaneously self-assemble into spherical micelles in water. Addition of a common good solvent (a co-solvent) for both of the constituting blocks, such as tetrahydrofuran (THF), reduces the interfacial tension at the core-corona interface. We are currently investigating the effect of this phenomenon on the micelle structural properties, using small-angle scattering and nuclear magnetic resonance. We have characterized the hydrodynamic radius, core radius, corona thickness, aggregation number, degree of swelling of the micelle core with the co-solvent, and unimer (free chain) concentration, as a function of the co-solvent concentration. Fundamental knowledge from these studies will inform design of drug delivery systems by allowing us to tailor micelle properties for optimal cargo loading.

  14. Structure of block copolymer micelles in the presence of co-solvents

    NASA Astrophysics Data System (ADS)

    Robertson, Megan; Wang, Shu; Le, Kim Mai; Piemonte, Rachele; Madsen, Louis

    2015-03-01

    Amphiphilic block copolymer micelles in water are under broad exploration for drug delivery applications due to their high loading capacity and targeted drug delivery. We aim to understand the kinetic and thermodynamic processes that underlie the self-assembly of diblock copolymer micelle systems. The present work focuses on diblock copolymers containing poly(ethylene oxide) (a hydrophilic polymer) and polycaprolactone (a hydrophobic polymer), which spontaneously self-assemble into spherical micelles in water. Addition of a common good solvent (a co-solvent) for both of the constituting blocks, such as tetrahydrofuran (THF), reduces the interfacial tension at the core-corona interface. We are currently investigating the effect of this phenomenon on the micelle structural properties, using scattering experiments and nuclear magnetic resonance. We have characterized the hydrodynamic radius, core radius, corona thickness, aggregation number, degree of swelling of the micelle core with the co-solvent, and unimer (free chain) concentration, as a function of the co-solvent concentration. Fundamental knowledge from these studies will inform design of drug delivery systems by allowing us to tailor micelle properties for optimal cargo loading.

  15. New shell crosslinked micelles from dextran with hydrophobic end groups and their interaction with bioactive molecules.

    PubMed

    Mocanu, Georgeta; Nichifor, Marieta; Stanciu, Magdalena C

    2015-03-30

    Micelles formed in aqueous solution by dextran with hydrophobic (alkyl) end-groups were stabilized through divinyl sulfone crosslinking of the dextran shell. The efficacy of the crosslinking reaction was influenced by the divinyl sulfone amount, the pH and micelle concentration. Crosslinked micelles with a moderate crosslinking degree were further functionalized by attachment of 10 and 17 moles% N-(2-hydroxypropyl)-N,N-dimethyl-N-benzylammonium chloride groups along the dextran chain. The size and shape of both crosslinked micelles and their cationic derivatives were analyzed by DLS and TEM. The prepared micelles were able to bind anionic diclofenac (60-370 mg/g), hydrophobic anionic indometacin (70-120 mg/g), and hydrophobic alpha-tocopherol (170-220 mg/g) or ergocalciferol (90-110 mg/g) by hydrophobic or/and electrostatic forces. The release experiments and the antioxidant activity of bound alpha-tocopherol highlighted the potential of the new nano-sized micelles mainly as carriers for prolonged and controlled delivery of hydrophobic drugs. PMID:25563964

  16. A molecular model for the free energy, bending elasticity, and persistence length of wormlike micelles.

    PubMed

    Asgari, Meisam

    2015-09-01

    An expression for the elastic free-energy density of a wormlike micelle is derived taking into account interactions between its constituent molecules. The resulting expression is quadratic in the curvature and torsion of the centerline of micelle and thus resembles free-energy density functions for polymer chains and helical filaments such as DNA. The model is applied on a wormlike micelle in the shape of a circular arc, open or closed. Conditions under which linear chains in dilute systems transform into toroidal rings are analyzed. Two concrete anisotropic soft-core interaction potentials are used to calculate the elastic moduli present in the derived model, in terms of the density of the molecules and their dimensions. Expressions for the persistence length of the wormlike micelle are found based on the flexural rigidities so obtained. Similar to previous observations, our results indicate that the persistence length of a wormlike micelle increases as the aspect ratio of its constituent molecules increases. A detailed application of the model on wormlike micelles of toroidal geometry, along with employing statistical-thermodynamical concepts of self-assembly is performed, and the results are found to be well consistent with the literature. Steps to obtain the material parameters through possible experiments are discussed. PMID:26362658

  17. Molecular dynamics simulation and NMR investigation of the association of the β-blockers atenolol and propranolol with a chiral molecular micelle

    NASA Astrophysics Data System (ADS)

    Morris, Kevin F.; Billiot, Eugene J.; Billiot, Fereshteh H.; Hoffman, Charlene B.; Gladis, Ashley A.; Lipkowitz, Kenny B.; Southerland, William M.; Fang, Yayin

    2015-08-01

    Molecular dynamics simulations and NMR spectroscopy were used to compare the binding of two β-blocker drugs to the chiral molecular micelle poly-(sodium undecyl-(L)-leucine-valine). The molecular micelle is used as a chiral selector in capillary electrophoresis. This study is part of a larger effort to understand the mechanism of chiral recognition in capillary electrophoresis by characterizing the molecular micelle binding of chiral compounds with different geometries and charges. Propranolol and atenolol were chosen because their structures are similar, but their chiral interactions with the molecular micelle are different. Molecular dynamics simulations showed both propranolol enantiomers inserted their aromatic rings into the molecular micelle core and that (S)-propranolol associated more strongly with the molecular micelle than (R)-propranolol. This difference was attributed to stronger molecular micelle hydrogen bonding interactions experienced by (S)-propranolol. Atenolol enantiomers were found to bind near the molecular micelle surface and to have similar molecular micelle binding free energies.

  18. Microwave inverse Cerenkov accelerator

    SciTech Connect

    Zhang, T.B.; Marshall, T.C.; LaPointe, M.A.; Hirshfield, J.L.

    1997-03-01

    A Microwave Inverse Cerenkov Accelerator (MICA) is currently under construction at the Yale Beam Physics Laboratory. The accelerating structure in MICA consists of an axisymmetric dielectrically lined waveguide. For the injection of 6 MeV microbunches from a 2.856 GHz RF gun, and subsequent acceleration by the TM{sub 01} fields, particle simulation studies predict that an acceleration gradient of 6.3 MV/m can be achieved with a traveling-wave power of 15 MW applied to the structure. Synchronous injection into a narrow phase window is shown to allow trapping of all injected particles. The RF fields of the accelerating structure are shown to provide radial focusing, so that longitudinal and transverse emittance growth during acceleration is small, and that no external magnetic fields are required for focusing. For 0.16 nC, 5 psec microbunches, the normalized emittance of the accelerated beam is predicted to be less than 5{pi}mm-mrad. Experiments on sample alumina tubes have been conducted that verify the theoretical dispersion relation for the TM{sub 01} mode over a two-to-one range in frequency. No excitation of axisymmetric or non-axisymmetric competing waveguide modes was observed. High power tests showed that tangential electric fields at the inner surface of an uncoated sample of alumina pipe could be sustained up to at least 8.4 MV/m without breakdown. These considerations suggest that a MICA test accelerator can be built to examine these predictions using an available RF power source, 6 MeV RF gun and associated beam line. {copyright} {ital 1997 American Institute of Physics.}

  19. Etude des phenomenes dynamiques ultrarapides et des caracteristiques impulsionnelles d'emission terahertz du supraconducteur YBCO

    NASA Astrophysics Data System (ADS)

    Savard, Stephane

    choisi, nous avons mesure les proprietes intrinseques du meme echantillon de YBa2Cu3O7- delta avec la technique pompe-visible et sonde-terahertz donnant, elle aussi, acces aux temps caracteristiques regissant l'evolution hors-equilibre de ce materiau. Dans le meilleur scenario, ces temps caracteristiques devraient correspondre a ceux evalues grace a la modelisation des antennes. Un bon controle des parametres de croissance des couches minces supraconductrices et de fabrication du dispositif nous a permis de realiser des antennes d'emission terahertz possedant d'excellentes caracteristiques en terme de largeur de bande d'emission (typiquement 3 THz) exploitables pour des applications de spectroscopie resolue dans le domaine temporel. Le modele developpe et retenu pour le lissage du spectre terahertz decrit bien les caracteristiques de l'antenne supraconductrice pour tous les parametres d'operation. Toutefois, le lien avec la technique pompe-sonde lors de la comparaison des proprietes intrinseques n'est pas direct malgre que les deux techniques montrent que le temps de relaxation des porteurs augmente pres de la temperature critique. Les donnees en pompe-sonde indiquent que la mesure du temps de relaxation depend de la frequence de la sonde, ce qui complique la correspondance des proprietes intrinseques entre les deux techniques. De meme, le temps de relaxation extrait a partir du spectre de l'antenne terahertz augmente en s'approchant de la temperature critique (T c) de YBa2Cu 3O7-delta. Le comportement en temperature du temps de relaxation correspond a une loi de puissance qui est fonction de l'inverse du gap supraconducteur avec un exposant 5 soit 1/Delta 5(T). Le travail presente dans cette these permet de mieux decrire les caracteristiques des antennes supraconductrices a haute temperature critique et de les relier aux proprietes intrinseques du materiau qui les compose. De plus, cette these presente les parametres a ajuster comme le courant applique, la puissance de

  20. Adsorption behavior of pH-dependent phytic acid micelles at the copper surface observed by Raman and electrochemistry

    NASA Astrophysics Data System (ADS)

    Shen, Shu; Du, Juan; Guo, Xiao-yu; Wen, Ying; Yang, Hai-Feng

    2015-02-01

    As heated at 90 °C, phytic acid (PA) molecules in the solution self-organized to form the PA micelles. The size of PA micelles could be tuned by varying pH of the solutions. The adsorption behavior of the different micelles at the copper surface and their corrosion inhibition mechanisms in 0.5 M H2SO4 solution were studied by using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and surface-enhanced Raman scattering (SERS) spectroscopy. Raman studies showed that the bigger micelles anchoring on the copper surface via P27sbnd O28, P43sbnd O42 and P35sbnd O36 groups, while the smaller PA micelles formed at pH 9 adsorbed at the surface through P35sbnd O36 group. The electrochemical measurements demonstrated that the copper modified with the smaller micelles presented the best inhibition efficiency in 0.5 M H2SO4 solution.

  1. Preparation and evaluation of poly(ethylene glycol)-poly(lactide) micelles as nanocarriers for oral delivery of cyclosporine a.

    PubMed

    Zhang, Yanhui; Li, Xinru; Zhou, Yanxia; Wang, Xiaoning; Fan, Yating; Huang, Yanqing; Liu, Yan

    2010-01-01

    A series of monomethoxy poly(ethylene glycol)-poly(lactide) (mPEG-PLA) diblock copolymers were designed according to polymer-drug compatibility and synthesized, and mPEG-PLA micelle was fabricated and used as a nanocarrier for solubilization and oral delivery of Cyclosporine A (CyA). CyA was efficiently encapsulated into the micelles with nanoscaled diameter ranged from 60 to 96 nm with a narrow size distribution. The favorable stabilities of CyA-loaded polymeric micelles were observed in simulated gastric and intestinal fluids. The in vitro drug release investigation demonstrated that drug release was retarded by polymeric micelles. The enhanced intestinal absorption of CyA-loaded polymeric micelles, which was comparable to the commercial formulation of CyA (Sandimmun Neoral®), was found. These suggested that polymeric micelles might be an effective nanocarrier for solubilization of poorly soluble CyA and further improving oral absorption of the drug. PMID:20671795

  2. Preparation and Evaluation of Poly(Ethylene Glycol)-Poly(Lactide) Micelles as Nanocarriers for Oral Delivery of Cyclosporine A

    NASA Astrophysics Data System (ADS)

    Zhang, Yanhui; Li, Xinru; Zhou, Yanxia; Wang, Xiaoning; Fan, Yating; Huang, Yanqing; Liu, Yan

    2010-06-01

    A series of monomethoxy poly(ethylene glycol)-poly(lactide) (mPEG-PLA) diblock copolymers were designed according to polymer-drug compatibility and synthesized, and mPEG-PLA micelle was fabricated and used as a nanocarrier for solubilization and oral delivery of Cyclosporine A (CyA). CyA was efficiently encapsulated into the micelles with nanoscaled diameter ranged from 60 to 96 nm with a narrow size distribution. The favorable stabilities of CyA-loaded polymeric micelles were observed in simulated gastric and intestinal fluids. The in vitro drug release investigation demonstrated that drug release was retarded by polymeric micelles. The enhanced intestinal absorption of CyA-loaded polymeric micelles, which was comparable to the commercial formulation of CyA (Sandimmun Neoral®), was found. These suggested that polymeric micelles might be an effective nanocarrier for solubilization of poorly soluble CyA and further improving oral absorption of the drug.

  3. Drug-loaded pseudo-block copolymer micelles with a multi-armed star polymer as the micellar exterior.

    PubMed

    Xie, Chen; Zhang, Peng; Zhang, Zhengkui; Yang, Chenchen; Zhang, Jialiang; Wu, Wei; Jiang, Xiqun

    2015-08-01

    Supramolecular constructed pseudo block copolymer micelles based on β-cyclodextrin terminated 4 and 7 armed star poly(N-vinylpyrrolidone) and adamantane terminated linear poly(ε-caprolactone) were prepared. The size, morphology, stability and protein adsorption were experimentally examined. The micelles with 7 armed PVP chains as the micellar exterior showed the lowest amount of protein adsorption and the best stability in media. When cabazitaxel, a new taxane, was loaded into the micelles, 14.4% drug loading content and 85% encapsulation efficacy were achieved. In vitro cytotoxicity studies demonstrated that the cabazitaxel-loaded micelles show significant cytotoxicity against drug-resistant A2780/T cell lines. Biodistribution studies showed that the micelles can almost double the content of cargo in tumor sites compared with the free cargo. In vivo antitumor activity examinations indicated that cabazitaxel-loaded micelles show superior antitumor activity over free paclitaxel and free cabazitaxel. PMID:26144838

  4. A generalized inversion method: Simultaneous source localization and environmental inversion

    NASA Astrophysics Data System (ADS)

    Neilsen, Tracianne B.; Knobles, David P.

    2002-05-01

    The problem of localizing and tracking a source in the shallow ocean is often complicated by uncertainty in the environmental parameters. Likewise, the estimates of environmental parameters in the shallow ocean obtained by inversion methods can be degraded by incorrect information about the source location. To overcome both these common obstacles-environmental mismatch in matched field processing and incorrect source location in geoacoustic inversions-a generalized inversion scheme is developed that includes both source and environmental parameters as unknowns in the inversion. The new technique called systematic decoupling using rotated coordinates (SDRC) expands the original idea of rotated coordinates [M. D. Collins and L. Fishman, J. Acoust. Soc. Am. 98, 1637-1644 (1995)] by using multiple sets of coherent broadband rotated coordinates, each corresponding to a different set of bounds, to systematically decouple the unknowns in a series of simulated annealing inversions. The results of applying the SDRC inversion method to data from the Area Characterization Test II experiment performed on the New Jersey continental shelf are presented. [Work supported by ONR.

  5. Drug-loaded pseudo-block copolymer micelles with a multi-armed star polymer as the micellar exterior

    NASA Astrophysics Data System (ADS)

    Xie, Chen; Zhang, Peng; Zhang, Zhengkui; Yang, Chenchen; Zhang, Jialiang; Wu, Wei; Jiang, Xiqun

    2015-07-01

    Supramolecular constructed pseudo block copolymer micelles based on β-cyclodextrin terminated 4 and 7 armed star poly(N-vinylpyrrolidone) and adamantane terminated linear poly(ε-caprolactone) were prepared. The size, morphology, stability and protein adsorption were experimentally examined. The micelles with 7 armed PVP chains as the micellar exterior showed the lowest amount of protein adsorption and the best stability in media. When cabazitaxel, a new taxane, was loaded into the micelles, 14.4% drug loading content and 85% encapsulation efficacy were achieved. In vitro cytotoxicity studies demonstrated that the cabazitaxel-loaded micelles show significant cytotoxicity against drug-resistant A2780/T cell lines. Biodistribution studies showed that the micelles can almost double the content of cargo in tumor sites compared with the free cargo. In vivo antitumor activity examinations indicated that cabazitaxel-loaded micelles show superior antitumor activity over free paclitaxel and free cabazitaxel.Supramolecular constructed pseudo block copolymer micelles based on β-cyclodextrin terminated 4 and 7 armed star poly(N-vinylpyrrolidone) and adamantane terminated linear poly(ε-caprolactone) were prepared. The size, morphology, stability and protein adsorption were experimentally examined. The micelles with 7 armed PVP chains as the micellar exterior showed the lowest amount of protein adsorption and the best stability in media. When cabazitaxel, a new taxane, was loaded into the micelles, 14.4% drug loading content and 85% encapsulation efficacy were achieved. In vitro cytotoxicity studies demonstrated that the cabazitaxel-loaded micelles show significant cytotoxicity against drug-resistant A2780/T cell lines. Biodistribution studies showed that the micelles can almost double the content of cargo in tumor sites compared with the free cargo. In vivo antitumor activity examinations indicated that cabazitaxel-loaded micelles show superior antitumor activity over free

  6. Enhanced solubilization and desorption of organochlorine pesticides (OCPs) from soil by oil-swollen micelles formed with a nonionic surfactant.

    PubMed

    Zheng, Guanyu; Selvam, Ammaiyappan; Wong, Jonathan W C

    2012-11-01

    The effect of oil-swollen micelles formed with nonionic surfactant polyoxyethylene sorbitan monooleate (Tween 80), cosurfactant 1-pentanol, and linseed oil on the solubilization and desorption of organochlorine pesticides (OCPs) including DDT and γ-HCH from both loam soil and clay soil were investigated. Results showed that the solubilizing capacities of oil-swollen micelles were dependent on the critical micelle concentration (CMC) of Tween 80. Once the concentrations of oil-swollen micelles exceeded the CMC of Tween 80, the oil-swollen micelles exhibited much higher solubilizing capacity than empty Tween 80 micelles for the two OCPs. Desorption tests revealed that oil-swollen micelles could successfully enhance desorption of OCPs from both loam soil and clay soil. However, compared with the efficiencies achieved by empty Tween 80 micelles, oil-swollen micelles exhibited their superiority to desorb OCPs only in loam soil-water system while was less effective in clay soil-water system. Distribution of Tween 80, 1-pentanol and linseed oil in soil-water system revealed that the difference in the sorption behavior of linseed oil onto the two soils is responsible for the different effects of oil-swollen micelles on the desorption of OCPs in loam soil and clay soil systems. Therefore, oil-swollen micelles formed with nonionic surfactant Tween 80 are better candidates over empty micelle counterparts to desorb OCPs from soil with relatively lower sorption capacity for oil fraction, which may consequently enhance the availability of OCPs in soil environment during remediation processes of contaminated soil. PMID:22998366

  7. Modulation of excited-state proton-transfer reactions of 7-hydroxy-4-methylcoumarin in ionic and nonionic reverse micelles.

    PubMed

    Choudhury, Sharmistha Dutta; Pal, Haridas

    2009-05-14

    The prototropic behavior of the dye, 7-hydroxy-4-methylcoumarin (7H4MC), has been studied in cationic benzyldimethylhexadecylammonium chloride (BDHC) and nonionic poly(oxyethylene)(tetramethylbutyl)phenyl ether (TritonX-100, TX-100) reverse micelles using ground-state absorption and steady-state and time-resolved fluorescence measurements. The results have been compared with the previous results in the anionic sodium 1,4-bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles. Although the probe dye, 7H4MC, is indicated to reside in the interfacial region in all of the reverse micelles studied, significant differences have been observed in the evolution of the different prototropic species. In BDHC reverse micelles, the anionic form is favored over the tautomeric form at the higher w0 values, which is contrary to the observation in AOT reverse micelles where both of these forms are almost equally produced. The higher propensity for the formation of the anionic form in BDHC reverse micelles has been explained on the basis of the additional electrostatic stabilization of the anionic species in the cationic BDHC reverse micelles compared to that in the anionic AOT reverse micelles. On the other hand, in TX-100 reverse micelles, the anionic form is not very evident, but interestingly, the tautomer form begins to appear beyond w0=2. The appearance of the tautomeric species apparently coincides with the formation of the water pool in the TX-100 reverse micelles. However, due to the more restricted nature of the water molecules within this reverse micelle (mostly dispersed around the oxyethylene chains), deprotonation of the 7H4MC dye and the consequential stabilization of the anionic form are considerably reduced. The results clearly reveal that the aqueous environment in the vicinity of the probe is quite different for the reverse micelles considered, and these differences largely modulate the prototropic processes of the excited dye. PMID:19374362

  8. pH-Sensitive Micelles Based on Double-Hydrophilic Poly(methylacrylic acid)-Poly(ethylene glycol)-Poly(methylacrylic acid) Triblock Copolymer

    NASA Astrophysics Data System (ADS)

    Tao, Youhua; Liu, Ren; Liu, Xiaoya; Chen, Mingqing; Yang, Cheng; Ni, Zhongbin

    2009-04-01

    pH-sensitive micelles with hydrophilic core and hydrophilic corona were fabricated by self-assembling of triblock copolymer of poly(methylacrylic acid)-poly(ethylene glycol)-poly(methylacrylic acid) at lower solution pH. Transmission electron microscopy and laser light scattering studies showed micelles were in nano-scale with narrow size distribution. Solution pH value and the micelles concentration strongly influenced the hydrodynamic radius of the spherical micelles (48-310 nm). A possible mechanism for the formation of micelles was proposed. The obtained polymeric micelle should be useful for biomedical materials such as carrier of hydrophilic drug.

  9. Theranostic reduction-sensitive gemcitabine prodrug micelles for near-infrared imaging and pancreatic cancer therapy

    NASA Astrophysics Data System (ADS)

    Han, Haijie; Wang, Haibo; Chen, Yangjun; Li, Zuhong; Wang, Yin; Jin, Qiao; Ji, Jian

    2015-12-01

    A biodegradable and reduction-cleavable gemcitabine (GEM) polymeric prodrug with in vivo near-infrared (NIR) imaging ability was reported. This theranostic GEM prodrug PEG-b-[PLA-co-PMAC-graft-(IR820-co-GEM)] was synthesized by ring-opening polymerization and ``click'' reaction. The as-prepared reduction-sensitive prodrug could self-assemble into prodrug micelles in aqueous solution confirmed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). In vitro drug release studies showed that these prodrug micelles were able to release GEM in an intracellular-mimicking reductive environment. These prodrug micelles could be effectively internalized by BxPC-3 pancreatic cancer cells, which were observed by confocal laser scanning microscopy (CLSM). Meanwhile, a methyl thiazolyl tetrazolium (MTT) assay demonstrated that this prodrug exhibited high cytotoxicity against BxPC-3 cells. The in vivo whole-animal near-infrared (NIR) imaging results showed that these prodrug micelles could be effectively accumulated in tumor tissue and had a longer blood circulation time than IR820-COOH. The endogenous reduction-sensitive gemcitabine prodrug micelles with the in vivo NIR imaging ability might have great potential in image-guided pancreatic cancer therapy.A biodegradable and reduction-cleavable gemcitabine (GEM) polymeric prodrug with in vivo near-infrared (NIR) imaging ability was reported. This theranostic GEM prodrug PEG-b-[PLA-co-PMAC-graft-(IR820-co-GEM)] was synthesized by ring-opening polymerization and ``click'' reaction. The as-prepared reduction-sensitive prodrug could self-assemble into prodrug micelles in aqueous solution confirmed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). In vitro drug release studies showed that these prodrug micelles were able to release GEM in an intracellular-mimicking reductive environment. These prodrug micelles could be effectively internalized by BxPC-3 pancreatic cancer cells, which

  10. A folate-integrated magnetic polymer micelle for MRI and dual targeted drug delivery

    NASA Astrophysics Data System (ADS)

    Ao, Lijiao; Wang, Bi; Liu, Peng; Huang, Liang; Yue, Caixia; Gao, Duyang; Wu, Chunlei; Su, Wu

    2014-08-01

    This paper devotes a novel micellar structure for cancer theranostics by incorporating magnetic and therapeutic functionalities into a natural sourced targeting polymer vehicle. Heparin-folic acid micelles taking advantage of both excellent loading capability and cancer targeting ability have been employed to simultaneously incorporate superparamagnetic iron oxide nanoparticles (SPIONs) and doxorubicin through an ultrasonication-assisted microemulsion method. In this system, folic acids not only take the responsibility of micelle construction, but also facilitate cellular uptake due to their specific reorganization by MCF-7 cells over-expressing folate receptors. The obtained micelles exhibit good colloidal stability, a high magnetic content, considerable drug loading and sustained in vitro drug release. These clustered SPIONs exhibited high r2 relaxivity (243.65 mM-1 s-1) and further served as efficient probes for MR imaging. Notably, the transport efficiency of these micelles could be significantly improved under an external magnetic field, owing to their quick magnetic response. As a result, the as-proposed micelle shows great potential in multimodal theranostics, including active targeting, MRI diagnosis and drug delivery.This paper devotes a novel micellar structure for cancer theranostics by incorporating magnetic and therapeutic functionalities into a natural sourced targeting polymer vehicle. Heparin-folic acid micelles taking advantage of both excellent loading capability and cancer targeting ability have been employed to simultaneously incorporate superparamagnetic iron oxide nanoparticles (SPIONs) and doxorubicin through an ultrasonication-assisted microemulsion method. In this system, folic acids not only take the responsibility of micelle construction, but also facilitate cellular uptake due to their specific reorganization by MCF-7 cells over-expressing folate receptors. The obtained micelles exhibit good colloidal stability, a high magnetic content

  11. Structural transitions of CTAB micelles in the presence of n-octylamine: A small angle neutron scattering study

    SciTech Connect

    Prasad, C.D.; Singh, H.N. ); Goyal, P.S.; Rao, K.S. )

    1993-02-01

    Small angle neutron scattering (SANS) was used to characterize the micelles of cetyltrimethylammonium bromide (CTAB) in D[sub 2]O solutions, with or without added n-octylamine. SANS data have been analyzed using various models. Micellar parameters, such as mean aggregation numbers, micelle dimensions, and fractional charge on the micelles, are reported from the analysis of SANS spectra for the CTAB/n-octylamine system as a function of octylamine concentration and temperature. Results are interpreted in terms of micellar sphere-to-rod transition prompted by amine concentration in CTAB micellar solution. The size of the micelle decreases as the temperature increases.

  12. pH-Responsive Poly(ethylene glycol)/Poly(L-lactide) Supramolecular Micelles Based on Host-Guest Interaction.

    PubMed

    Zhang, Zhe; Lv, Qiang; Gao, Xiaoye; Chen, Li; Cao, Yue; Yu, Shuangjiang; He, Chaoliang; Chen, Xuesi

    2015-04-29

    pH-responsive supramolecular amphiphilic micelles based on benzimidazole-terminated poly(ethylene glycol) (PEG-BM) and β-cyclodextrin-modified poly(L-lactide) (CD-PLLA) were developed by exploiting the host-guest interaction between benzimidazole (BM) and β-cyclodextrin (β-CD). The dissociation of the supramolecular micelles was triggered in acidic environments. An antineoplastic drug, doxorubicin (DOX), was loaded into the supramolecular micelles as a model drug. The release of DOX from the supramolecular micelles was clearly accelerated as the pH was reduced from 7.4 to 5.5. The DOX-loaded PEG-BM/CD-PLLA supramolecular micelles displayed an enhanced intracellular drug-release rate in HepG2 cells compared to the pH-insensitive DOX-loaded PEG-b-PLLA counterpart. After intravenous injection into nude mice bearing HepG2 xenografts by the tail vein, the DOX-loaded supramolecular micelles exhibited significantly higher tumor inhibition efficacy and reduced systemic toxicity compared to free DOX. Furthermore, the DOX-loaded supramolecular micelles showed a blood clearance rate markedly lower than that of free DOX and comparable to that of the DOX-loaded PEG-b-PLLA micelles after intravenous injection into rats. Therefore, the pH-responsive PEG-BM/CD-PLLA supramolecular micelles hold potential as a smart nanocarrier for anticancer drug delivery. PMID:25856564

  13. Heparin modification enhances the delivery and tumor targeting of paclitaxel-loaded N-octyl-N-trimethyl chitosan micelles.

    PubMed

    Zhang, Feiran; Fei, Jia; Sun, Minjie; Ping, Qineng

    2016-09-10

    Polycations have been widely used as efficient drug and gene carriers. However, the further application of polycation nanocarriers is greatly hampered by the serious cytotoxicity caused by exposed positive charges. Despite recent progress towards the therapeutic delivery of nucleic acids, there remains a compelling need for development of novel delivery systems for various types of drug. Here, we created mixed micelles based on N-octyl-N-trimethyl chitosan (OTMC) and coated them with an anionic polymer for delivery of paclitaxel (PTX). OTMC/PEG-100 stearate (S-100) micelles (PTX-SN) were firstly prepared by a dialysis method with a high drug loading efficiency and positive charge. PTX-SN micelles were then coated with two anionic polymers, heparin sodium (PTX-HSN) and sodium carboxymethyl cellulose (PTX-CSN) to shield positive charges. Both PTX-HSN and PTX-CSN micelles showed decreased cytotoxicity and hemolysis while retaining high uptake efficiency. PTX-HSN micelles were taken up more effectively than PTX-CSN by HeLa cells, which over-express heparanase. PTX-HSN micelles persisted longer in the circulation of rats than free drug in pharmacokinetic studies. DIR-HSN micelles accumulated strongly in tumors, and PTX-HSN micelles significantly inhibited tumor growth in tumor-bearing mice. Overall, the results validate heparin-coated OTMC micelles as safe and effective tumor-targeting carriers that are suitable for anti-tumor drug delivery. PMID:27426109

  14. Transferrin receptor-targeted vitamin E TPGS micelles for brain cancer therapy: preparation, characterization and brain distribution in rats.

    PubMed

    Sonali; Agrawal, Poornima; Singh, Rahul Pratap; Rajesh, Chellappa V; Singh, Sanjay; Vijayakumar, Mahalingam R; Pandey, Bajrangprasad L; Muthu, Madaswamy Sona

    2016-06-01

    The effective treatment of brain cancer is hindered by the poor transport across the blood-brain barrier (BBB) and the low penetration across the blood-tumor barrier (BTB). The objective of this work was to formulate transferrin-conjugated docetaxel (DTX)-loaded d-alpha-tocopheryl polyethylene glycol 1000 succinate (vitamin E TPGS or TPGS) micelles for targeted brain cancer therapy. The micelles with and without transferrin conjugation were prepared by the solvent casting method and characterized for their particle size, polydispersity, drug encapsulation efficiency, drug loading, in vitro release study and brain distribution study. Particle sizes of prepared micelles were determined at 25 °C by dynamic light scattering technique. The external surface morphology was determined by transmission electron microscopy analysis and atomic force microscopy. The encapsulation efficiency was determined by spectrophotometery. In vitro release studies of micelles and control formulations were carried out by dialysis bag diffusion method. The particle sizes of the non-targeted and targeted micelles were <20 nm. About 85% of drug encapsulation efficiency was achieved with micelles. The drug release from transferrin-conjugated micelles was sustained for >24 h with 50% of drug release. The in vivo results indicated that transferrin-targeted TPGS micelles could be a promising carrier for brain targeting due to nano-sized drug delivery, solubility enhancement and permeability which provided an improved and prolonged brain targeting of DTX in comparison to the non-targeted micelles and marketed formulation. PMID:26431064

  15. Temperature Inversions Have Cold Bottoms.

    ERIC Educational Resources Information Center

    Bohren, Craig F.; Brown, Gail M.

    1982-01-01

    Uses discussion and illustrations of several demonstrations on air temperature differences and atmospheric stability to explain the phenomena of temperature inversions. Relates this to the smog in Los Angeles and discusses the implications. (DC)

  16. Donor states in inverse opals

    NASA Astrophysics Data System (ADS)

    Mahan, G. D.

    2014-09-01

    We calculate the binding energy of an electron bound to a donor in a semiconductor inverse opal. Inverse opals have two kinds of cavities, which we call octahedral and tetrahedral, according to their group symmetry. We put the donor in the center of each of these two cavities and obtain the binding energy. The binding energies become very large when the inverse opal is made from templates with small spheres. For spheres less than 50 nm in diameter, the donor binding can increase to several times its unconfined value. Then electrons become tightly bound to the donor and are unlikely to be thermally activated to the semiconductor conduction band. This conclusion suggests that inverse opals will be poor conductors.

  17. Donor states in inverse opals

    SciTech Connect

    Mahan, G. D.

    2014-09-21

    We calculate the binding energy of an electron bound to a donor in a semiconductor inverse opal. Inverse opals have two kinds of cavities, which we call octahedral and tetrahedral, according to their group symmetry. We put the donor in the center of each of these two cavities and obtain the binding energy. The binding energies become very large when the inverse opal is made from templates with small spheres. For spheres less than 50 nm in diameter, the donor binding can increase to several times its unconfined value. Then electrons become tightly bound to the donor and are unlikely to be thermally activated to the semiconductor conduction band. This conclusion suggests that inverse opals will be poor conductors.

  18. Inversion layer MOS solar cells

    NASA Technical Reports Server (NTRS)

    Ho, Fat Duen

    1986-01-01

    Inversion layer (IL) Metal Oxide Semiconductor (MOS) solar cells were fabricated. The fabrication technique and problems are discussed. A plan for modeling IL cells is presented. Future work in this area is addressed.

  19. Uterine Inversion; A case report.

    PubMed

    Bouchikhi, C; Saadi, H; Fakhir, B; Chaara, H; Bouguern, H; Banani, A; Melhouf, Ma

    2008-01-01

    The puerperal uterine inversion is a rare and severe complication occurring in the third stage of labour. The mechanisms are not completely known. However, extrinsic factors such as oxytocic arrests after a prolonged labour, umbilical cord traction or abdominal expression are pointed. Other intrinsic factors such as primiparity, uterine hypotonia, various placental localizations, fundic myoma or short umbilical cord were also reported. The diagnosis of the uterine inversion is mainly supported by clinical symptoms. It is based on three elements: haemorrhage, shock and a strong pelvic pain. The immediate treatment of the uterine inversion is required. It is based on a medical reanimation associated with firstly a manual reduction then surgical treatment using various techniques. We report an observation of a 25 years old grand multiparous patient with a subacute uterine inversion after delivery at home. PMID:21516244

  20. Uterine Inversion; A case report

    PubMed Central

    Bouchikhi, C; Saadi, H; Fakhir, B; Chaara, H; Bouguern, H; Banani, A; Melhouf, MA

    2008-01-01

    The puerperal uterine inversion is a rare and severe complication occurring in the third stage of labour. The mechanisms are not completely known. However, extrinsic factors such as oxytocic arrests after a prolonged labour, umbilical cord traction or abdominal expression are pointed. Other intrinsic factors such as primiparity, uterine hypotonia, various placental localizations, fundic myoma or short umbilical cord were also reported. The diagnosis of the uterine inversion is mainly supported by clinical symptoms. It is based on three elements: haemorrhage, shock and a strong pelvic pain. The immediate treatment of the uterine inversion is required. It is based on a medical reanimation associated with firstly a manual reduction then surgical treatment using various techniques. We report an observation of a 25 years old grand multiparous patient with a subacute uterine inversion after delivery at home. PMID:21516244

  1. Computation of inverse magnetic cascades

    NASA Technical Reports Server (NTRS)

    Montgomery, D.

    1981-01-01

    Inverse cascades of magnetic quantities for turbulent incompressible magnetohydrodynamics are reviewed, for two and three dimensions. The theory is extended to the Strauss equations, a description intermediate between two and three dimensions appropriate to Tokamak magnetofluids. Consideration of the absolute equilibrium Gibbs ensemble for the system leads to a prediction of an inverse cascade of magnetic helicity, which may manifest itself as a major disruption. An agenda for computational investigation of this conjecture is proposed.

  2. Computation of inverse magnetic cascades

    SciTech Connect

    Montgomery, D.

    1981-10-01

    Inverse cascades of magnetic quantities for turbulent incompressible magnetohydrodynamics are reviewed, for two and three dimensions. The theory is extended to the Strauss equations, a description intermediate between two and three dimensions appropriate to tokamak magnetofluids. Consideration of the absolute equilibrium Gibbs ensemble for the system leads to a prediction of an inverse cascade of magnetic helicity, which may manifest itself as a major disruption. An agenda for computational investigation of this conjecture is proposed.

  3. Self-Assembled Thermoresponsive Nanogels Prepared by Reverse Micelle → Positive Micelle Method for Ophthalmic Delivery of Muscone, a Poorly Water-Soluble Drug.

    PubMed

    Wang, Guohua; Nie, Qixia; Zang, Chen; Zhang, Baoxian; Zhu, Qiong; Luo, Gan; Wang, Shuang

    2016-09-01

    This study aimed to design a nanocarrier ophthalmic delivery system of muscone, a poorly water-soluble drug. The muscone thermoresponsive nanogels were self-assembled by reverse micelle → positive micelle method. Muscone was demonstrated to have uniform narrow particle size distribution in nanogel by the dynamic light scattering test. The developed nanocomposite hydrogel had a high muscone loading, and the rheology results showed that the phase transition temperature was 34.05°C. Thixotropy test indicated that the nanogel was able to resist the blinking of eyes because of the thixotropy recovery time, which is <5 s. Compared with muscone eye drops, muscone nanogels showed longer retention time on the corneal surface using fluorescent labeling technology and produced a 3.4-fold increase in apparent permeability coefficients (Papp). Draize testing showed that the developed nanogel caused no eye irritation. In vivo pharmacokinetic study indicated that the nanogel could significantly increase the bioavailability of muscone after administration compared with eye drops. These results indicate that self-assembled thermoresponsive nanogel prepared by reverse micelle → positive micelle method has potential for the ophthalmic delivery of poorly water-soluble drugs. PMID:27041413

  4. Light Scattering Characterization of Salt Dependent Thermoreversible Micelles Synthesized from Elastin-Like Polypeptides

    NASA Astrophysics Data System (ADS)

    Vandemark, Kaitlin; Ghoorchian, Ali; Streletzky, Kiril; Holland, Nolan

    2012-02-01

    Environmentally responsive nanoparticles synthesized from Elastin-Like Polypeptides (ELP) present a promising system for applications such as biosensors, drug delivery vehicles, and viscosity modifiers. These nanoparticles undergo a transition from a soluble state at Troom to micellar aggregates above the transition. The ELP micelles have been found to be sensitive to various outside stimuli including pH, salt concentration, and solvent. Dynamic and Static Light Scattering were used to study structure and dynamics of ELP nanoparticles below the transition and of formed ELP micelles above the transition. Micelles were found to generally depend strongly on solution pH, however, in the pH window of 10.1-10.4 their size stayed constant. The apparent radius and molecular weight of micelles in this pH range strongly depend on salt concentration with three apparent regimes. At low salt (0-15mM), largely spherical micelles were found with Rh=15nm, which corresponds to the size of folded ELP hydrophilic tail; and molecular weight of 5000-6000kg/mol. At the intermediate salt (15-30mM) the observed particles are spherical micelles that increase in size (by about 3 fold) and molecular weight (by about 50 fold) as salt concentration increases. At high salt concentrations (30-60mM), Rg/Rh˜ 1.3, indicating the micelles behave as elongated particles with Rh˜75nm that corresponds to the size of a stretched ELP chain with an apparent molecular weight of 300000-600000kg/mol.

  5. Cytotoxicity Study on Luminescent Nanocrystals Containing Phospholipid Micelles in Primary Cultures of Rat Astrocytes.

    PubMed

    Latronico, Tiziana; Depalo, Nicoletta; Valente, Gianpiero; Fanizza, Elisabetta; Laquintana, Valentino; Denora, Nunzio; Fasano, Anna; Striccoli, Marinella; Colella, Matilde; Agostiano, Angela; Curri, M Lucia; Liuzzi, Grazia Maria

    2016-01-01

    Luminescent colloidal nanocrystals (NCs) are emerging as a new tool in neuroscience field, representing superior optical probes for cellular imaging and medical diagnosis of neurological disorders with respect to organic fluorophores. However, only a limited number of studies have, so far, explored NC applications in primary neurons, glia and related cells. Indeed astrocytes, as resident cells in the central nervous system (CNS), play an important pathogenic role in several neurodegenerative and neuroinflammatory diseases, therefore enhanced imaging tools for their thorough investigation are strongly amenable. Here, a comprehensive and systematic study on the in vitro toxicological effect of core-shell type luminescent CdSe@ZnS NCs incorporated in polyethylene glycol (PEG) terminated phospholipid micelles on primary cultures of rat astrocytes was carried out. Cytotoxicity response of empty micelles based on PEG modified phospholipids was compared to that of their NC containing counterpart, in order to investigate the effect on cell viability of both inorganic NCs and micelles protecting NC surface. Furthermore, since the surface charge and chemistry influence cell interaction and toxicity, effect of two different functional groups terminating PEG-modified phospholipid micelles, namely amine and carboxyl group, respectively, was evaluated against bare micelles, showing that carboxyl group was less toxic. The ability of PEG-lipid micelles to be internalized into the cells was qualitatively and quantitatively assessed by fluorescence microscopy and photoluminescence (PL) assay. The results of the experiments clearly demonstrate that, once incorporated into the micelles, a low, not toxic, concentration of NCs is sufficient to be distinctly detected within cells. The overall study provides essential indications to define the optimal experimental conditions to effectively and profitably use the proposed luminescent colloidal NCs as optical probe for future in vivo

  6. Modulation of partition and localization of perfume molecules in sodium dodecyl sulfate micelles.

    PubMed

    Fan, Yaxun; Tang, Haiqiu; Strand, Ross; Wang, Yilin

    2016-01-01

    The influence of perfume molecules on the self-assembly of the anionic surfactant sodium dodecyl sulfate (SDS) and their localization in SDS micelles have been investigated by ζ potential, small angle X-ray scattering (SAXS), one- and two-dimensional NMR and isothermal titration microcalorimetry (ITC). A broad range of perfume molecules varying in octanol/water partition coefficients P are employed. The results indicate that the surface charge, size and aggregation number of the SDS micelles strongly depend on the hydrophobicity/hydrophilicity degree of perfume molecules. Three distinct regions along the log P values are identified. Hydrophilic perfumes (log P < 2.0) partially incorporate into the SDS micelles and do not lead to micelle swelling, whereas hydrophobic perfumes (log P > 3.5) are solubilized close to the end of the hydrophobic chains in the SDS micelles and enlarge the micelles with higher ζ potential and a larger aggregation number. The incorporated fraction and micelle properties show increasing tendency for the perfumes in the intermediate log P region (2.0 < log P < 3.5). Besides, the molecular conformation of perfume molecules also affects these properties. The perfumes with a linear chain structure or an aromatic group can penetrate into the palisade layer and closely pack with the SDS molecules. Furthermore, the thermodynamic parameters obtained from ITC show that the binding of the perfumes in the intermediate log P region is more spontaneous than those in the other two log P regions, and the micellization of SDS with the perfumes is driven by entropy. PMID:26458054

  7. Tailor-made dimensions of diblock copolymer truncated micelles on a solid by UV irradiation.

    PubMed

    Liou, Jiun-You; Sun, Ya-Sen

    2015-09-28

    We investigated the structural evolution of truncated micelles in ultrathin films of polystyrene-block-poly(2-vinylpyridine), PS-b-P2VP, of monolayer thickness on bare silicon substrates (SiOx/Si) upon UV irradiation in air- (UVIA) and nitrogen-rich (UVIN) environments. The structural evolution of micelles upon UV irradiation was monitored using GISAXS measurements in situ, while the surface morphology was probed using atomic force microscopy ex situ and the chemical composition using X-ray photoelectron spectroscopy (XPS). This work provides clear evidence for the interpretation of the relationship between the structural evolution and photochemical reactions in PS-b-P2VP truncated micelles upon UVIA and UVIN. Under UVIA treatment, photolysis and cross-linking reactions coexisted within the micelles; photolysis occurred mainly at the top of the micelles, whereas cross-linking occurred preferentially at the bottom. The shape and size of UVIA-treated truncated micelles were controlled predominantly by oxidative photolysis reactions, which depended on the concentration gradient of free radicals and oxygen along the micelle height. Because of an interplay between photolysis and photo-crosslinking, the scattering length densities (SLD) of PS and P2VP remained constant. In contrast, UVIN treatments enhanced the contrast in SLD between the PS shell and the P2VP core as cross-linking dominated over photolysis in the presence of nitrogen. The enhancement of the SLD contrast was due to the various degrees of cross-linking under UVIN for the PS and P2VP blocks. PMID:26251976

  8. Intrinsic parameters for the structure control of nonionic reverse micelles in styrene: SAXS and rheometry studies.

    PubMed

    Shrestha, Lok Kumar; Shrestha, Rekha Goswami; Aramaki, Kenji

    2011-05-17

    Shape, size, and internal structure of nonionic reverse micelle in styrene depending on surfactant chain length, concentration, temperature, and water addition have been investigated using a small-angle X-ray scattering (SAXS) technique. The generalized indirect Fourier transformation (GIFT) method has been employed to deduce real-space structural information. The consistency of the GIFT method has been tested by the geometrical model fittings, and the micellar aggregation number (N(agg)) has been determined. It was found that diglycerol monocaprate (C(10)G(2)), diglycerol monolaurate (C(12)G(2)), and diglycerol monomyristate (C(14)G(2)), spontaneously self-assemble into reverse micelles in organic solvent styrene under ambient conditions. The micellar size and the N(agg) decrease with an increase in surfactant chain length, a scenario that could be understood from the modification of the critical packing parameter (cpp). A clear picture of one-dimensional (1-D) micellar growth was observed with an increase in surfactant weight fraction (W(s)) in the C(10)G(2) system, which eventually formed rodlike micelles at W(s) ≥ 15%. On the other hand, micelles shrunk favoring a rod-to-sphere type transition upon heating. Reverse micelles swelled with water, forming a water pool at the micellar core; the size of water-incorporated reverse micelles was much bigger than that of the empty micelles. Model fittings showed that water addition not only increase the micellar size but also increase the N(agg). Zero-shear viscosity was found to decrease with surfactant chain but increase with W(s), supporting the results derived from SAXS. PMID:21488609

  9. Zwitterionic-Modified Starch-Based Stealth Micelles for Prolonging Circulation Time and Reducing Macrophage Response.

    PubMed

    Ye, Lei; Zhang, Yabin; Yang, Boguang; Zhou, Xin; Li, Junjie; Qin, Zhihui; Dong, Dianyu; Cui, Yuanlu; Yao, Fanglian

    2016-02-01

    Over the last few decades, nanoparticles have been emerging as useful means to improve the therapeutic efficacy of drug delivery and medical diagnoses. However, the heterogeneity and complexity of blood as a medium is a fundamental problem; large amounts of protein can be adsorbed onto the surface of nanoparticles and cause their rapid clearance before reaching their target sites, resulting in the failure of drug delivery. To overcome this challenge, we present a rationally designed starch derivative (SB-ST-OC) with both a superhydrophilic moiety of zwitterionic sulfobetaine (SB) and a hydrophobic segment of octane (OC) as functional groups, which can self-assemble into "stealth" micelles (SSO micelles). The superhydrophilic SB kept the micelles stable against aggregation in complex media and imbued them with "stealth" properties, eventually extending their circulation time in blood. In stability and hemolysis tests the SSO micelles showed excellent protein resistance properties and hemocompatibility. Moreover, a phagocytosis test and cytokine secretion assay confirmed that the SSO micelles had less potential to trigger the activation of macrophages and were more suitable as a drug delivery candidate in vivo. On the basis of these results, doxorubicin (DOX), a hydrophobic drug, was used to investigate the potential application of this novel starch derivative in vivo. The results of the pharmacokinetic study showed that the values of the plasma area under the concentration curve (AUC) and elimination half-life (T1/2) of the SSO micelles were higher than those of micelles without SB modifications. In conclusion, the combination of excellent protein resistance, lower macrophage activation, and longer circulation time in vivo makes this synthesized novel starch derivative a promising candidate as a hydrophobic drug carrier for long-term circulation in vivo. PMID:26835968

  10. Oscillatory structural forces due to nonionic surfactant micelles: data by colloidal-probe AFM vs theory.

    PubMed

    Christov, Nikolay C; Danov, Krassimir D; Zeng, Yan; Kralchevsky, Peter A; von Klitzing, Regine

    2010-01-19

    Micellar solutions of nonionic surfactants Brij 35 and Tween 20 are confined between two surfaces in a colloidal-probe atomic-force microscope (CP-AFM). The experimentally detected oscillatory forces due to the layer-by-layer expulsion of the micelles agree very well with the theoretical predictions for hard-sphere fluids. While the experiment gives parts of the stable branches of the force curve, the theoretical model allows reconstruction of the full oscillatory curve. Therewith, the strength and range of the ordering could be determined. The resulting aggregation number from the fits of the force curves for Brij 35 is close to 70 and exhibits a slight tendency to increase with the surfactant concentration. The last layer of micelles cannot be pressed out. The measured force-vs-distance curve has nonequilibrium portions, which represent "jumps" from one to another branch of the respective equilibrium oscillatory curve. In the case of Brij 35, at concentrations <150 mM spherical micelles are present and the oscillation period is close to the micelle diameter, slightly decreasing with the rise of concentration. For elongated micelles (at concentration 200 mM), no harmonic oscillations are observed anymore; instead, the period increases with the decrease of film thickness. In the case of Tween 20, the force oscillations are almost suppressed, which implies that the micelles of this surfactant are labile and are demolished by the hydrodynamic shear stresses due to the colloidal-probe motion. The comparison of the results for the two surfactants demonstrates that in some cases the micelles can be destroyed by the CP-AFM, but in other cases they can be stable and behave as rigid particles. This behavior correlates with the characteristic times of the slow micellar relaxation process for these surfactants. PMID:20067306

  11. Novel Redox-Responsive Amphiphilic Copolymer Micelles for Drug Delivery: Synthesis and Characterization.

    PubMed

    Bae, Jungeun; Maurya, Abhijeet; Shariat-Madar, Zia; Murthy, S Narasimha; Jo, Seongbong

    2015-11-01

    A novel redox-responsive amphiphilic polymer was synthesized with bioreductive trimethyl-locked quinone propionic acid for a potential triggered drug delivery application. The aim of this study was to synthesize and characterize the redox-responsive amphiphilic block copolymer micelles containing pendant bioreductive quinone propionic acid (QPA) switches. The redox-responsive hydrophobic block (polyQPA), synthesized from QPA-serinol and adipoyl chloride, was end-capped with methoxy poly(ethylene glycol) of molecular weight 750 (mPEG750) to achieve a redox-responsive amphiphilic block copolymer, polyQPA-mPEG750. PolyQPA-mPEG750 was able to self-assemble as micelles to show a critical micelle concentration (CMC) of 0.039% w/v (0.39 mg/ml, 0.107 mM) determined by a dye solubilization method using 1,6-diphenyl-1,3,5-hexatriene (DPH) in phosphate-buffered saline (PBS). The mean diameter of polymeric micelles was found to be 27.50 nm (PI = 0.064) by dynamic light scattering. Furthermore, redox-triggered destabilization of the polymeric micelles was confirmed by (1)H-NMR spectroscopy and particle size measurements in a simulated redox state. PolyQPA-mPEG750 underwent triggered reduction to shed pendant redox-responsive QPA groups and its polymeric micelles were swollen to be dissembled in the presence of a reducing agent, thereby enabling the release of loaded model drug, paclitaxel. The redox-responsive polyQPA-mPEG750 polymer micelles would be useful as a drug delivery system allowing triggered drug release in an altered redox state such as tumor microenvironments with an altered redox potential and/or redox enzyme upregulation. PMID:26122497

  12. PEG-PDLLA Micelle Treatment Improves Axonal Function of the Corpus Callosum following Traumatic Brain Injury

    PubMed Central

    Ping, Xingjie; Jiang, Kewen; Lee, Seung-Young; Cheng, Ji-Xing

    2014-01-01

    Abstract The initial pathological changes of diffuse axonal injury following traumatic brain injury (TBI) include membrane disruption and loss of ionic homeostasis, which further lead to dysfunction of axonal conduction and axon disconnection. Resealing the axolemma is therefore a potential therapeutic strategy for the early treatment of TBI. Monomethoxy poly (ethylene glycol)-poly (D, L–lactic acid) di-block copolymer micelles (mPEG-PDLLA) have been shown to restore depressed compound action potentials (CAPs) of spinal axons and promote functional recovery after spinal cord injury. Here, we evaluate the effect of the micelles on repairing the injured cortical axons following TBI. Adult mice subjected to controlled cortical impact (CCI) were treated with intravenous injection of the micelles at 0 h or 4 h after injury. Evoked CAPs were recorded from the corpus callosum of coronal cortical slices at 2 days after injury. The CCI caused significant decreases in the amplitudes of two CAP peaks that were respectively generated by the faster myelinated axons and slower unmyelinated axons. Micelle treatment at both 0 h and 4 h after CCI resulted in significant increases in both CAP peak amplitudes. Injection of fluorescent dye-labeled micelles revealed high fluorescent staining in cortical gray and white matters underneath the impact site. Labeling membrane-perforated neurons by injecting a membrane impermeable dye Texas Red-labeled dextran into lateral ventricles at 2 h post-CCI revealed that immediate micelle injection after CCI did not reduce the number of dye-stained cortical neurons and dentate granule cells of the hippocampus, indicating its ineffectiveness in repairing plasma membrane of neuronal somata. We conclude that intravenous administration of mPEG-PDLLA micelles immediately or at 4 h after TBI allows brain penetration via the compromised blood brain–barrier, and thereby improves the function of both myelinated and unmyelinated axons of the

  13. Cytotoxicity Study on Luminescent Nanocrystals Containing Phospholipid Micelles in Primary Cultures of Rat Astrocytes

    PubMed Central

    Valente, Gianpiero; Fanizza, Elisabetta; Laquintana, Valentino; Denora, Nunzio; Fasano, Anna; Striccoli, Marinella; Colella, Matilde; Agostiano, Angela; Curri, M. Lucia; Liuzzi, Grazia Maria

    2016-01-01

    Luminescent colloidal nanocrystals (NCs) are emerging as a new tool in neuroscience field, representing superior optical probes for cellular imaging and medical diagnosis of neurological disorders with respect to organic fluorophores. However, only a limited number of studies have, so far, explored NC applications in primary neurons, glia and related cells. Indeed astrocytes, as resident cells in the central nervous system (CNS), play an important pathogenic role in several neurodegenerative and neuroinflammatory diseases, therefore enhanced imaging tools for their thorough investigation are strongly amenable. Here, a comprehensive and systematic study on the in vitro toxicological effect of core-shell type luminescent CdSe@ZnS NCs incorporated in polyethylene glycol (PEG) terminated phospholipid micelles on primary cultures of rat astrocytes was carried out. Cytotoxicity response of empty micelles based on PEG modified phospholipids was compared to that of their NC containing counterpart, in order to investigate the effect on cell viability of both inorganic NCs and micelles protecting NC surface. Furthermore, since the surface charge and chemistry influence cell interaction and toxicity, effect of two different functional groups terminating PEG-modified phospholipid micelles, namely amine and carboxyl group, respectively, was evaluated against bare micelles, showing that carboxyl group was less toxic. The ability of PEG-lipid micelles to be internalized into the cells was qualitatively and quantitatively assessed by fluorescence microscopy and photoluminescence (PL) assay. The results of the experiments clearly demonstrate that, once incorporated into the micelles, a low, not toxic, concentration of NCs is sufficient to be distinctly detected within cells. The overall study provides essential indications to define the optimal experimental conditions to effectively and profitably use the proposed luminescent colloidal NCs as optical probe for future in vivo

  14. Dynamic response of block copolymer wormlike micelles to shear flow

    NASA Astrophysics Data System (ADS)

    Lonetti, B.; Kohlbrecher, J.; Willner, L.; Dhont, J. K. G.; Lettinga, M. P.

    2008-10-01

    The linear and nonlinear dynamic response to an oscillatory shear flow of giant wormlike micelles consisting of Pb-Peo block copolymers is studied by means of Fourier transform rheology. Experiments are performed in the vicinity of the isotropic-nematic phase transition concentration, where the location of isotropic-nematic phase transition lines is determined independently. Strong shear-thinning behaviour is observed due to critical slowing down of orientational diffusion as a result of the vicinity of the isotropic-nematic spinodal. This severe shear-thinning behaviour is shown to result in gradient shear banding. Time-resolved small-angle neutron scattering experiments are used to obtain an insight into the microscopic phenomena that underlie the observed rheological response. An equation of motion for the order parameter tensor and an expression of the stress tensor in terms of the order parameter tensor are used to interpret the experimental data, both in the linear and nonlinear regimes. Scaling of the dynamic behaviour of the orientational order parameter and the stress is found when critical slowing down due to the vicinity of the isotropic-nematic spinodal is accounted for.

  15. Revisiting the interpretation of casein micelle SAXS data.

    PubMed

    Ingham, B; Smialowska, A; Erlangga, G D; Matia-Merino, L; Kirby, N M; Wang, C; Haverkamp, R G; Carr, A J

    2016-08-17

    An in-depth, critical review of model-dependent fitting of small-angle X-ray scattering (SAXS) data of bovine skim milk has led us to develop a new mathematical model for interpreting these data. Calcium-edge resonant soft X-ray scattering data provides unequivocal evidence as to the shape and location of the scattering due to colloidal calcium phosphate, which is manifested as a correlation peak centred at q = 0.035 Å(-1). In SAXS data this feature is seldom seen, although most literature studies attribute another feature centred at q = 0.08-0.1 Å(-1) to CCP. This work shows that the major SAXS features are due to protein arrangements: the casein micelle itself; internal regions approximately 20 nm in size, separated by water channels; and protein structures which are inhomogeneous on a 1-3 nm length scale. The assignment of these features is consistent with their behaviour under various conditions, including hydration time after reconstitution, addition of EDTA (a Ca-chelating agent), addition of urea, and reduction of pH. PMID:27491477

  16. Ecotoxicological assessment of the micelle encapsulator F-500.

    PubMed

    Pane, Luigi; Mariottini, Gian Luigi; Giacco, Elisabetta

    2015-08-01

    Surfactants are synthetic chemicals utilized as detergents and cleaning products or as dispersants and emulsifiers to face water pollution. In spite of this, due to their wide diffusion, surfactants can induce water and soil pollution, notably in developed countries, and can be toxic to organisms. Taking into account that the assessment of new compounds is mandatory in the European Union, in this research the ecotoxicity of fire-fighting micelle encapsulator F-500, newly utilized as dispersant in seawaters polluted with oil dumping, was evaluated. The assessment was carried out on a battery of test-organisms (freshwater algae, crustaceans, and larval fish; seawater algae, crustaceans, and bivalves; soil earthworms, and seeds) as well as on cultured cells (L-929 mouse fibroblasts), which were exposed to F-500 concentrations. According to the toxicity thresholds provided by GESAMP, F-500 resulted to be slightly or moderately toxic to all test-organisms, excluding the freshwater alga Pseudokirchneriella subcapitata that suffered highly toxic effects with IC50 values ranging from 0.21 to 0.49mg/L. The IC50 for mouse fibroblasts was 5.41µg/L after 24h treatment. PMID:25938697

  17. Biochemical synthesis of gold and zinc nanoparticles in reverse micelles

    NASA Astrophysics Data System (ADS)

    Egorova, E. M.

    2010-04-01

    Gold and zinc nanoparticles were obtained in AOT reverse micelles in isooctane by reduction of the corresponding metal ions by the natural pigment quercetin (the biochemical synthesis technique). Gold and zinc ions were introduced into the micellar solution of quercetin in the form of aqueous solutions, HAuCl4 and [Zn(NH3)4]SO4, to the water to AOT molar ratios 1-3 and 3-4, respectively. The process of nanoparticle formation was investigated by spectrophotometry. Nanoparticle size and shape were determined by transmission electron microscopy. The data obtained allow to conclude that there are two steps in metal ion-quercetin interaction: (1) complex formation, and (2) complex dissociation with subsequent formation of nanoparticles and a second product, presumably oxidized quercetin. Gold nanoparticles were found to be of various shapes (spheres, hexahedrons, triangles, and cylinders) and sizes, mainly in the 10-20 nm range; zinc nanoparticles are chiefly spherical and ˜5 nm in size. In both cases, the nanoparticles are stable in the air in micellar solution over long periods of time (from a several months to a several years).

  18. Ultrafast energy transfer in water-AOT reverse micelles.

    PubMed

    Cringus, Dan; Bakulin, Artem; Lindner, Jörg; Vöhringer, Peter; Pshenichnikov, Maxim S; Wiersma, Douwe A

    2007-12-27

    A spectroscopic investigation of the vibrational dynamics of water in a geometrically confined environment is presented. Reverse micelles of the ternary microemulsion H2O/AOT/n-octane (AOT = bis-2-ethylhexyl sulfosuccinate or aerosol-OT) with diameters ranging from 1 to 10 nm are used as a model system for nanoscopic water droplets surrounded by a soft-matter boundary. Femtosecond nonlinear infrared spectroscopy in the OH-stretching region of H2O fully confirms the core/shell model, in which the entrapped water molecules partition onto two molecular subensembles: a bulk-like water core and a hydration layer near the ionic surfactant headgroups. These two distinct water species display different relaxation kinetics, as they do not exchange vibrational energy. The observed spectrotemporal ultrafast response exhibits a local character, indicating that the spatial confinement influences approximately one molecular layer located near the water-amphiphile boundary. The core of the encapsulated water droplet is similar in its spectroscopic properties to the bulk phase of liquid water, i.e., it does not display any true confinement effects such as droplet-size-dependent vibrational lifetimes or rotational correlation times. Unlike in bulk water, no intermolecular transfer of OH-stretching quanta occurs among the interfacial water molecules or from the hydration shell to the bulk-like core, indicating that the hydrogen bond network near the H2O/AOT interface is strongly disrupted. PMID:18047308

  19. Reverse micelle and microemulsion phases in supercritical fluids

    SciTech Connect

    Fulton, J.L.; Smith, R.D.

    1988-05-19

    The surfactant sodium bis(2-ethylhexyl) sulfosuccinate (AOT) was used to form reverse micelle and microemulsion phases in supercritical ethane and propane for systems consisting of 80-100% alkane by weight. Phase diagrams obtained from view cell studies of microemulsion phases formed in supercritical fluids are reported and shown to be strongly dependent on pressure. The properties of these solutions were also characterized by conductivity, density, and surfactant solubility measurements. The solubility of AOT in ethane and propane over a range of pressures shows behavior typical of solids in supercritical fluids. The maximum water-to-surfactant ratio (W/sub 0/) increased dramatically in both ethane and propane systems as pressure was increased. At 300 bar and 103/sup 0/C, the supercritical propane-surfactant system is capable of solubilizing much more water (W/sub 0/ = 12) than the supercritical ethane-surfactant system (W/sub 0/ = 4) at 300 bar and 37/sup 0/C. Some of the important thermodynamic contributions that are likely responsible for this pressure-dependent phase behavior are discussed, and potential applications of this new class of solvents are considered.

  20. Multidimensional NMR inversion without Kronecker products: Multilinear inversion.

    PubMed

    Medellín, David; Ravi, Vivek R; Torres-Verdín, Carlos

    2016-08-01

    Multidimensional NMR inversion using Kronecker products poses several challenges. First, kernel compression is only possible when the kernel matrices are separable, and in recent years, there has been an increasing interest in NMR sequences with non-separable kernels. Second, in three or more dimensions, the singular value decomposition is not unique; therefore kernel compression is not well-defined for higher dimensions. Without kernel compression, the Kronecker product yields matrices that require large amounts of memory, making the inversion intractable for personal computers. Finally, incorporating arbitrary regularization terms is not possible using the Lawson-Hanson (LH) or the Butler-Reeds-Dawson (BRD) algorithms. We develop a minimization-based inversion method that circumvents the above problems by using multilinear forms to perform multidimensional NMR inversion without using kernel compression or Kronecker products. The new method is memory efficient, requiring less than 0.1% of the memory required by the LH or BRD methods. It can also be extended to arbitrary dimensions and adapted to include non-separable kernels, linear constraints, and arbitrary regularization terms. Additionally, it is easy to implement because only a cost function and its first derivative are required to perform the inversion. PMID:27209370

  1. Multidimensional NMR inversion without Kronecker products: Multilinear inversion

    NASA Astrophysics Data System (ADS)

    Medellín, David; Ravi, Vivek R.; Torres-Verdín, Carlos

    2016-08-01

    Multidimensional NMR inversion using Kronecker products poses several challenges. First, kernel compression is only possible when the kernel matrices are separable, and in recent years, there has been an increasing interest in NMR sequences with non-separable kernels. Second, in three or more dimensions, the singular value decomposition is not unique; therefore kernel compression is not well-defined for higher dimensions. Without kernel compression, the Kronecker product yields matrices that require large amounts of memory, making the inversion intractable for personal computers. Finally, incorporating arbitrary regularization terms is not possible using the Lawson-Hanson (LH) or the Butler-Reeds-Dawson (BRD) algorithms. We develop a minimization-based inversion method that circumvents the above problems by using multilinear forms to perform multidimensional NMR inversion without using kernel compression or Kronecker products. The new method is memory efficient, requiring less than 0.1% of the memory required by the LH or BRD methods. It can also be extended to arbitrary dimensions and adapted to include non-separable kernels, linear constraints, and arbitrary regularization terms. Additionally, it is easy to implement because only a cost function and its first derivative are required to perform the inversion.

  2. Pharmacokinetics and antitumor efficacy of micelles assembled from multiarmed amphiphilic copolymers with drug conjugates in comparison with drug-encapsulated micelles.

    PubMed

    Luo, Xiaoming; Chen, Maohua; Zhang, Yun; Chen, Zhoujiang; Li, Xiaohong

    2016-01-01

    The premature drug release and structural dissociation before reaching pathological sites have posed major challenges for self-assembled micelles. To address these challenges, star-shaped amphiphilic copolymers derived from 4-armed poly(ethylene glycol) (PEG) were proposed for chemical conjugation of chemotherapeutic drugs and assembly into drug-conjugated micelles (DCM) with reductive sensitivity. The current study aimed to elucidate the in vitro and in vivo performance of DCM and a comparison with conventional drug-encapsulated micelles (DEM) was initially launched. DEM carriers were constructed with a similar structure to DCM from 4-armed PEG, and disulfide linkages were located between the hydrophilic and hydrophobic segments. Both DCM and DEM had an average size of around 130 nm, camptothecin (CPT) loadings of around 7.7% and critical micelle concentrations of around 0.95 μg/ml. Compared with DEM, DCM showed a lower initial drug release, a lower sensitivity of drug release to glutathione, and a higher structural stability after incubation with human serum albumin (HSA). The CPT derivatives (CPT-SH) released from DCM indicated cytotoxicities similar to CPT and remained a higher lactone stability than CPT in the presence of HSA. DCM showed slightly higher cytotoxicities to 4T1 cells and significantly lower cytotoxicities to normal cells than DEM. Pharmacokinetic analyses after intravenous administration of DCM indicated around 2.65 folds higher AUC0-∞, 2.66 folds lower clearance, and 1.87 folds higher tumor accumulation than those of DEM. In addition to a less disturbance to hematological and biochemical parameters and a lower acute toxicity to small intestines, DCM showed more significant tumor suppression efficacy and less tumor metastasis to lungs than DEM. It is suggested that DCM could overcome the limitation of conventional micelles by alleviating the premature drug release during blood circulation, relieving the systemic toxicity and promoting the

  3. Self-assembled micelles of amphiphilic poly(l-phenylalanine)-b-poly(l-serine) polypeptides for tumor-targeted delivery

    PubMed Central

    Zhao, Ziming; Wang, Yu; Han, Jin; Wang, Keli; Yang, Dan; Yang, Yihua; Du, Qian; Song, Yuanjian; Yin, Xiaoxing

    2014-01-01

    The aim of this work was to design, synthesize, and characterize self-assembled micelles based on polypeptides as a potential antitumor drug carrier. Amphiphilic poly(l-phenylalanine)-b-poly(l-serine) (PFS) polypeptides were obtained through the polymerization of N-carboxyanhydride. As a novel hydrophilic segment, poly(l-serine) was utilized to enhance tumor targeting due to a large demand of tumors for serine. PFS could self-assemble into micelles with an average diameter of 110–240 nm and a slightly negative charge. PFS polypeptides adopted random coil in pH 7.4 phosphate-buffered saline and could partly transform to α-helix induced by trifluoroethanol. PFS micelles with a low critical micelle concentration of 4.0 μg mL−1 were stable in pH 5–9 buffers and serum albumin solution. PFS micelles had a loading capacity of 3.8% for coumarin-6 and exhibited a sustained drug release. Coumarin-6 loaded rhodamine B isothiocyanate-labeled PFS micelles were incubated with Huh-7 tumor cells to study the correlation between drugs and carriers during endocytosis. The uptake of drugs was consistent with the micelles, illustrating that the intracellular transport of drugs highly depended on the micelles. PFS micelles diffused in whole cytoplasm while coumarin-6 assumed localized distribution, suggesting that the micelles could release the loaded drugs in particular areas. The internalization mechanism of PFS micelles was involved with clathrin-mediated endocytosis and macropinocytosis. Excess serine inhibited the uptake of PFS micelles, which demonstrated that serine receptors played a positive role in the internalization of PFS. The more interesting thing was that the uptake inhibition impacted on normal cells but not on tumor cells at the physiological concentration of serine. The difference in the uptake of PFS micelles was fourfold as high between the tumor cells and the normal cells, which indicated that PFS micelles had good tumor targeting in vitro. In conclusion

  4. Amphiphilic Copolymeric Micelles for Doxorubicin and Curcumin Co-Delivery to Reverse Multidrug Resistance in Breast Cancer.

    PubMed

    Lv, Li; Qiu, Kaifeng; Yu, Xiaoxia; Chen, Chuxiong; Qin, Fengchao; Shi, Yonghui; Ou, Jiebin; Zhang, Tao; Zhu, Hua; Wu, Junyan; Liu, Chunxia; Li, Guocheng

    2016-05-01

    Development of multidrug resistance against chemotherapeutic drugs is one of the major obstacles to successful cancer therapy in the clinic. Thus far, amphiphilic polymeric micelles and chemosensitizers have been used to overcome multidrug resistance in cancer. The goals of this study were to prepare poly(ethylene glycol)-bock-poly(lactide) (PEG(2k)-PLA(5k)) micelles for co-delivery of the chemotherapeutic drug doxorubicin (DOX) with a chemosensitizer curcumin (CUR), investigate the potential of the dual drug-loaded micelles ((DOX+CUR)-Micelles) to reverse multidrug resistance, and explore the underlying mechanisms. (DOX + CUR)-Micelles were prepared using an emulsion solvent evaporation method. The cellular uptake, drug efflux, down-regulation of P-glycoprotein expression and inhibition of ATP activity of (DOX+ CUR)-Micelles were studied in drug-resistant MCF-7/ADR cells. In vitro analyses demonstrated that (DOX + CUR)-Micelles were superior to free DOX, free drug combination (DOX + CUR), and DOX-loaded micelles in inhibiting proliferation of MCF-7/ADR cells. This effect of (DOX + CUR)-Micelles was partially attributable to their highest cellular uptake, lowest efflux rate of DOX, and strongest effects on down-regulation of P-glycoprotein and inhibition of ATP activity. Additionally, (DOX+CUR)-Micelles showed increased tumor accumulation and strong inhibitory effect on tumor growth in the xenograft model of drug-resistant MCF-7/ADR cells compared to that of other drug formulations. These results indicate that (DOX + CUR)-Micelles display potential for application in the therapy of drug-resistant breast carcinoma. PMID:27305819

  5. Selective intracellular delivery of proteasome inhibitors through pH-sensitive polymeric micelles directed to efficient antitumor therapy.

    PubMed

    Quader, S; Cabral, H; Mochida, Y; Ishii, T; Liu, X; Toh, K; Kinoh, H; Miura, Y; Nishiyama, N; Kataoka, K

    2014-08-28

    The ubiquitin-proteasome system is central in the regulation of cellular proteins controlling cell cycle progression and apoptosis, drawing much interest for developing effective targeted cancer therapies. Herein, we developed a novel pH-responsive polymeric-micelle-based carrier system to effectively deliver the proteasome inhibitor MG132 into cancer cells. MG132 is covalently bound to the block copolymer composed of polyethylene glycol (PEG) and polyaspartate through an acid-labile hydrazone bond. This bond is stable at physiological condition, but hydrolytically degradable in acidic compartments in the cell, such as late-endosomes and lysosomes, and thus, it was used for controlled release of MG132 after EPR-mediated preferential accumulation of the micelles into the tumor. MG132-loaded micelles have monodispersed size distribution with an average diameter of 45nm, and critical micelle concentration is well below 10(-7)M. In vitro studies against several cancer cell lines confirmed that MG132-loaded micelles retained the cytotoxic effect, and this activity was indeed due to the inhibition of proteasome by released MG132 from the micelles. Real-time in vitro confocal-microscopy experiments clearly indicated that MG132-conjugated micelles disintegrated only inside the target cells. By intravital confocal micro-videography, we also confirmed the prolonged circulation of MG132 loaded micelles in the bloodstream, which lead to tumor specific accumulation of micelles, as confirmed by in vivo imaging 24h after injection. These micelles showed significantly lower in vivo toxicity than free MG132, while achieving remarkable antitumor effect against a subcutaneous HeLa-luc tumor model. Our findings create a paradigm for future development of polymeric-micelle-based carrier system for other peptide aldehyde type proteasome inhibitors to make them effective cohort of the existing cancer therapeutic regiments. PMID:24892974

  6. Prediction inverse d'un front de solidification dans un four de transformation a haute temperature

    NASA Astrophysics Data System (ADS)

    Marois, Marc-Andre

    Ce projet de recherche porte sur une methode numerique permettant de predire l'evolution du profil 2D de la couche solide qui recouvre l'interieur des parois de plusieurs fours de transformation a haute temperature. Un modele mathematique base sur la formulation faible de l'energie est d'abord developpe et valide. Une methode de transfert thermique inverse reposant sur ce modele est ensuite developpee afin d'obtenir une mesure rapide et continue de l'evolution du profil de cette couche solide. Vu la grande inertie thermique du systeme a l'etude, differentes strategies sont proposees afin de faciliter la mise en uvre de cette methode numerique. Finalement, cette approche inverse est confrontee aux resultats experimentaux obtenus a l'aide d'un reacteur metallurgique. Une etude preliminaire montre que les fours de transformation presentent une tres grande inertie thermique qui limite grandement l'utilisation des methodes inverses. En effet, la sensibilite de cette methode numerique repose essentiellement sur le delai temporel observe entre la variation du profil du banc et la fluctuation de la temperature a la surface externe de la paroi du four. Les resultats obtenus demontrent qu'une partie de ce delai est proportionnel a la chaleur latente de fusion lorsque le materiau a changement de phase est constitue d'un melange non eutectique. Afin de limiter l'impact de ce delai temporel, deux astuces numeriques sont proposees : reutiliser plus d'une fois les mesures de temperature et modifier le probleme thermique dans les regions pateuse et liquide. D'une part, le concept de chevauchement propose permet de reduire le temps d'acquisition des donnees entre chacune des predictions. D'autre part, l'approche virtuelle developpee permet de reduire l'inertie thermique du systeme et, par le fait meme, le delai temporel associe a la diffusion de la chaleur. Ces deux strategies ont permis de predire efficacement l'evolution 1D de l'epaisseur de la couche de gelee qui se solidifie a

  7. Nanotoxicity comparison of four amphiphilic polymeric micelles with similar hydrophilic or hydrophobic structure

    PubMed Central

    2013-01-01

    Background Nanocarriers represent an attractive means of drug delivery, but their biosafety must be established before their use in clinical research. Objectives Four kinds of amphiphilic polymeric (PEG-PG-PCL, PEEP-PCL, PEG-PCL and PEG-DSPE) micelles with similar hydrophilic or hydrophobic structure were prepared and their in vitro and in vivo safety were evaluated and compared. Methods In vitro nanotoxicity evaluations included assessments of cell morphology, cell volume, inflammatory effects, cytotoxicity, apoptosis and membrane fluidity. An umbilical vein cell line (Eahy.926) and a kind of macrophages (J774.A1) were used as cell models considering that intravenous route is dominant for micelle delivery systems. In vivo analyses included complete blood count, lymphocyte subset analysis, detection of plasma inflammatory factors and histological observations of major organs after intravenous administration to KM mice. Results All the micelles enhanced inflammatory molecules in J774.A1 cells, likely resulting from the increased ROS levels. PEG-PG-PCL and PEEP-PCL micelles were found to increase the J774.A1 cell volume. This likely correlated with the size of PEG-PG-PCL micelles and the polyphosphoester structure in PEEP-PCL. PEG-DSPE micelles inhibited the growth of Eahy.926 cells via inducing apoptosis. This might relate to the structure of DSPE, which is a type of phospholipid and has good affinity with cell membrane. No evidence was found for cell membrane changes after treatment with these micelles for 24 h. In the in vivo study, during 8 days of 4 time injection, each of the four nanocarriers altered the hematic phase differently without changes in inflammatory factors or pathological changes in target organs. Conclusions These results demonstrate that the micelles investigated exhibit diverse nanotoxicity correlated with their structures, their biosafety is different in different cell model, and there is no in vitro and in vivo correlation found. We believe

  8. Reticulation des fibres lignocellulosiques

    NASA Astrophysics Data System (ADS)

    Landrevy, Christel

    Pour faire face à la crise économique la conception de papier à valeur ajoutée est développée par les industries papetières. Le but de se projet est l'amélioration des techniques actuelles de réticulation des fibres lignocellulosiques de la pâte à papier visant à produire un papier plus résistant. En effet, lors des réactions de réticulation traditionnelles, de nombreuses liaisons intra-fibres se forment ce qui affecte négativement l'amélioration anticipée des propriétés physiques du papier ou du matériau produit. Pour éviter la formation de ces liaisons intra-fibres, un greffage sur les fibres de groupements ne pouvant pas réagir entre eux est nécessaire. La réticulation des fibres par une réaction de « click chemistry » appelée cycloaddition de Huisgen entre un azide et un alcyne vrai, catalysée par du cuivre (CuAAC) a été l'une des solutions trouvée pour remédier à ce problème. De plus, une adaptation de cette réaction en milieux aqueux pourrait favoriser son utilisation en milieu industriel. L'étude que nous désirons entreprendre lors de ce projet vise à optimiser la réaction de CuAAC et les réactions intermédiaires (propargylation, tosylation et azidation) sur la pâte kraft, en milieu aqueux. Pour cela, les réactions ont été adaptées en milieu aqueux sur la cellulose microcristalline afin de vérifier sa faisabilité, puis transférée à la pâte kraft et l'influence de différents paramètres comme le temps de réaction ou la quantité de réactifs utilisée a été étudiée. Dans un second temps, une étude des différentes propriétés conférées au papier par les réactions a été réalisée à partir d'une série de tests papetiers optiques et physiques. Mots Clés Click chemistry, Huisgen, CuAAC, propargylation, tosylation, azidation, cellulose, pâte kraft, milieu aqueux, papier.

  9. Novel polymeric micelles for drug delivery: Material characterization and formulation screening.

    PubMed

    Janas, Christine; Mostaphaoui, Zouhair; Schmiederer, Ludwig; Bauer, Johann; Wacker, Matthias G

    2016-07-25

    A rising number of new chemical entities that exhibit only poor aqueous solubility are identified in drug discovery processes. Polymeric micelles composed of block copolymers (BP) facilitate the delivery of such lipophilic molecules in drug therapy. Consequently, a rational screening and selection procedure for novel BP was established. Further, the interplay of polymer structure, micelle formation and drug binding was studied. Therefore seven polymers (BP001 to BP007) were synthesized from different monomer compositions resulting in nanocarriers varying in surface decoration and lipophilicity. These polymers were characterized by H(1)-NMR and SEC. The molecular weight was ranging between 13 and 37kDa. The critical micelle concentration and micellar integrity in presence of human plasma were determined. Micelles were loaded with dexamethasone and characterized with regards to their size, morphology and surface charge. Polymeric micelles with a size of 49.21-236.37nm were obtained. A half-life of 11h was determined for five of the copolymers in presence of human plasma. Two nanocarrier formulations (BP006 and BP007) were exhibiting optimal micellar integrity in vitro and a modified release profile under biorelevant conditions. Strongest drug-polymer interaction was observed for nanocarrier compositions providing benzyl and carboxylic groups and were composed of BP006 and BP007. PMID:27234698

  10. Antisense precision polymer micelles require less poly(ethylenimine) for efficient gene knockdown.

    PubMed

    Fakhoury, Johans J; Edwardson, Thomas G; Conway, Justin W; Trinh, Tuan; Khan, Farhad; Barłóg, Maciej; Bazzi, Hassan S; Sleiman, Hanadi F

    2015-12-28

    Therapeutic nucleic acids are powerful molecules for shutting down protein expression. However, their cellular uptake is poor and requires transport vectors, such as cationic polymers. Of these, poly(ethylenimine) (PEI) has been shown to be an efficient vehicle for nucleic acid transport into cells. However, cytotoxicity has been a major hurdle in the development of PEI-DNA complexes as clinically viable therapeutics. We have synthesized antisense-polymer conjugates, where the polymeric block is completely monodisperse and sequence-controlled. Depending on the polymer sequence, these can self-assemble to produce micelles of very low polydispersity. The introduction of linear poly(ethylenimine) to these micelles leads to aggregation into size-defined PEI-mediated superstructures. Subsequently, both cellular uptake and gene silencing are greatly enhanced over extended periods compared to antisense alone, while at the same time cellular cytotoxicity remains very low. In contrast, gene silencing is not enhanced with antisense polymer conjugates that are not able to self-assemble into micelles. Thus, using antisense precision micelles, we are able to achieve significant transfection and knockdown with minimal cytotoxicity at much lower concentrations of linear PEI then previously reported. Consequently, a conceptual solution to the problem of antisense or siRNA delivery is to self-assemble these molecules into 'gene-like' micelles with high local charge and increased stability, thus reducing the amount of transfection agent needed for effective gene silencing. PMID:26597764

  11. Water-induced micelle formation of block copoly(oxyethylene-oxypropylene-oxyethylene) in o-xylene

    SciTech Connect

    Wu, Guangwei; Zhou, Zukang; Chu, B. )

    1993-04-12

    Static and dynamic light scattering, viscometry, NMR, and vapor pressure osmometry techniques have been employed to study the water-induced micellization behavior of poly(oxyethylene-oxypropylene-oxyethylene) block copolymer, Pluronic L64, in o-xylene solution. Results show that Pluronic L64 does not form polymolecular micelles in the absence of water or in the presence of a small amount of water (molar ratio water/EO < 0.15). Micelles, consisting of a PPO shell and a PEO and H[sub 2]O core, are formed when the water to EO molar ratio (Z) in the micelle is greater than 0.2. For Z < 1.3, spherical micelles with an average hydrodynamic radius R[sub h] of ca. 9.2 nm are formed, with R[sub h] almost independent of Z. For Z > 1.3, both the aggregation number and the hydrodynamic radius become dependent on the Z value, then the micelle shape could be nonspherical. As experimentally evidenced by NMR spectra, the solubilized water can be classified into bound water and free water. Most likely, water is not evenly distributed in the core, as the environments of EO units at different positions in the block copolymer are not identical.

  12. Synergistic effect of pH-responsive wormlike micelles based on a simple amphiphile.

    PubMed

    Wu, Xuepeng; Wu, Yining; Yang, Shuai; Zhao, Mingwei; Gao, Mingwei; Li, Hao; Dai, Caili

    2016-05-18

    Imagine a novel solution that can be switched reversibly from low viscosity to high viscosity with only one additive, upon different commands. To this end, we have developed a simple and effective route to form smart, multi-response wormlike micelles based on a synthesized surfactant, N-cetyl-N,N-diisopropanolammonium bromide (CDIAB). Moreover, we provide new insight into the effects of synergy on this smart wormlike micelle. Rheological measurements were used to study the morphology of the wormlike micelles; (1)H NMR spectroscopy and density functional theory (DFT) calculations were employed to investigate the molecular arrangements and mechanism of the synergy involved in the reversible reactions of pH-response and CO2-response of the micelles in solution. Based on the abovementioned results, it is encouraging to discover that binding energy and electrostatic interaction are the basic driving forces in the formation of wormlike micelles. Moreover, stable viscoelastic behavior was observed in the CDIAB system, with strong binding energy and electrostatic interactions. It is highly anticipated that the synergy observed in this surfactant will be of particular interest due to its novel mechanism and unique properties. PMID:27094804

  13. Depletion Interactions: Effects of Added Homopolymer on Ordered Phases Formed by Spherical Block Copolymer Micelles

    SciTech Connect

    Abbas, Sayeed; Lodge, Timothy P.

    2008-12-09

    Three distinct poly(styrene-b-isoprene) (SI) diblock copolymers with molecular weights of 16-16, 38-14, and 50-13 kDa for styrene and isoprene, respectively, formed spherical micelles when dissolved in diethyl phthalate (DEP). Since DEP is a styrene-selective solvent, micelles with polyisoprene in the core and polystyrene in the corona were formed. At block copolymer concentrations of 20%, 16%, and 14% in DEP, the spherical micelles of SI(16-16), SI(38-14), and SI(50-13) pack onto a face-centered cubic (FCC) lattice, a mixture of FCC and body-centered cubic (BCC) lattices, and a BCC lattice, respectively. Polystyrene homopolymers with molecular weights of 4, 48, and 180 kDa were added to these ordered solutions. The following general trends were observed: the FCC phase tended to disorder, and samples that originally behaved like soft solids exhibited liquidlike flow behavior. The effect increased strongly with both the molecular weight and concentration of homopolymer in the solution. Furthermore, the BCC lattice tended to be displaced by the FCC lattice, or to disorder, when homopolymer was added. These results can be explained by invoking depletion interactions, which have been studied extensively in colloid/polymer mixtures. However, the phenomenon differs in certain details from colloidal systems because the addition of homopolymer can also influence the aggregation number of the micelles, which in turn affects the lattice packing of the micelles.

  14. Rotational reorientation dynamics of Aerosol-OT reverse micelles formed in near-critical propane

    SciTech Connect

    Heitz, M.P.; Bright, F.V.

    1996-06-01

    The rotational reorientation kinetics of two fluorescent solutes (rhodamine 6G, R6G, and rhodamine 101, R101) have been determined in sodium bis(2-ethylhexyl) sulfosuccinate (Aerosol-OT, AOT) reverse micelles formed in liquid and near-critical propane. We show that the amount of water loading ([water]/[AOT], R), continuous phase density, and temperature all influence the solute rotational dynamics. In all cases, the decay of anisotropy data (i.e., frequency-dependent differential polarized phase angle and polarized modulation ratio) are well described by a bi-exponential decay law. We find that the faster rotational correlation times are similar to but slightly less than the values predicted for an individual AOT reverse micelle rotating in propane. The recovered rotational correlation times range from 200 to 500 ps depending on experimental conditions. This faster rotational process is explained in terms of lateral diffus