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Sample records for micelle environments investigated

  1. 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.

  2. 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.

  3. 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.

  4. Predicting proton titration in cationic micelle and bilayer environments

    PubMed Central

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

    2014-01-01

    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. PMID:25173037

  5. Micelle dynamic simulation and physicochemical characterization of biorelevant media to reflect gastrointestinal environment in fasted and fed states.

    PubMed

    Xie, XiaoYu; Cardot, Jean-Michel; Garrait, Ghislain; Thery, Vincent; El-Hajji, Mohamed; Beyssac, Eric

    2014-10-01

    The characterization of biorelevant media simulating the upper part of the gastrointestinal tract in the fasted and fed states was investigated by classical determination of physicochemical parameters such as pH, osmolality, surface tension and results were compared to in vivo physiological data. Incorporation of fatty material, in order to better simulate the influence of high fat meal was also performed. Stability and characterization of this medium was studied and compared to classical FeSSIF. Micelle characterization and computer dynamic simulation were performed in order to understand the interaction between lecithin and taurocholate and possible interactions between mixed micelle and drugs. The addition of NaTc, lecithin, and/or fatty materials has no influence on pH and osmolality, whereas the presence of fatty material modifies the surface tension. Values of FaSSIF and FeSSIF are in accordance with in vivo parameters and the presence of micelles can simulate the gastrointestinal environment. Modelization of micelles by computer simulation led to a model of mixed micelles in which structures of NaTc interact either by their hydrophilic or hydrophobic phase to give a bilayer stable model in which the lecithin molecule can insert its long carbon chain. The micelle structure is stable and can enhance dissolution of hydrophobic molecules by hydrophobic interaction with the numerous hydrophobic spaces available in the multilayer hydrophilic/hydrophobic layer.

  6. 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

  7. Further investigation of the mechanism of Doxorubicin release from P105 micelles using kinetic models

    PubMed Central

    Stevenson-Abouelnasr, Dana; Husseini, Ghaleb A.; Pitt, William G.

    2007-01-01

    The kinetics of the release of Doxorubicin from Pluronic P105 micelles during ultrasonication and its subsequent re-encapsulation upon cessation of insonation were investigated. Four mechanisms are proposed to explain the acoustically-triggered Doxorubicin (Dox) release and re-encapsulation from Pluronic P105 micelles. The four mechanisms are: micelle destruction; destruction of cavitating nuclei; reassembly of micelles, and the re-encapsulation of Dox. The first mechanism, the destruction of micelles during insonation, causes the release of Dox into solution. The micelles are destroyed because of cavitation events produced by collapsing nuclei, or bubbles in the insonated solution. The second mechanism, the slow destruction of cavitating nuclei, results in a slow partial recovery phase, when a small amount of Dox is re-encapsulated. The third and fourth mechanisms, the reassembly of micelles and the re-encapsulatin of Dox, are independent of ultrasound. These two mechanism are responsible for maintaining the drug release at a partial level, and for recovery after insonation ceases. A normal distribution was used to describe micellar size. Parameters for the model were determined based upon the best observed fit to experimental data. The resulting model provides a good approximation to experimental data for the release of Dox from Pluronic P105 micelles. PMID:17207611

  8. 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

  9. Brij-micelle and polyacrylic acid interaction investigated by Cu 2+-induced pyrene fluorescence: Effect of brij-micelle structure

    NASA Astrophysics Data System (ADS)

    Bandyopadhyay, Prasun; Ghosh, Amit K.; Bandyopadhyay, Sayan

    2009-07-01

    Fluorescence response of pyrene has been studied in the presence of polyacrylic acid (PAA) and brij surfactant micelles with Cu 2+ as an ionic quencher. The quenched pyrene emission is completely recovered with the addition of PAA (conc. 2.4 × 10 -4 M) for brij 35 (poly-oxyethylene-23 lauryl ether) micelle indicating PAA-Cu 2+ complex formation at the micelle-water interface. This could be due to the relatively easier accessibility of PAA polymer chains near poly-oxyethylene chain of brij 35 micelle compared to brij 30 (poly-oxyethylene-4 lauryl ether) micelle. The interaction between brij-micelle and polymer is confirmed by turbidimetry and NMR spectroscopy.

  10. Light scattering investigation of phase separation in a micelle system

    SciTech Connect

    Wilcoxon, J.P.; Martin, J.E.; Odinek, J.

    1993-12-31

    We report a real-time, two-dimensional light scattering study of the evolution of structure in a two component nonionic micelle system during phase separation via spinodal decomposition. Our principal finding is that domain growth proceeds much slower than the cube root of time prediction for simple binary fluids. In fact, the growth kinetics can be empirically described as a stretched exponential approach to a pinned domain size. Although the kinetics are not yet understood, this anomalous behavior may be due to the ability of the spherical micelles to reorganize into more complex structures. The domain structure also shows some anomalies. Although at short times the expected structure factor for a critical quench is observed, at long times the structure factor crosses over to the off-critical form. However, in all cases the average scattered intensity is proportional to the cube of the domain size. These findings are discussed in comparison to standard theories of and experimental work on binary fluids.

  11. Luminescent nanocrystals in phospholipid micelles for bioconjugation: an optical and structural investigation.

    PubMed

    Depalo, Nicoletta; Mallardi, Antonia; Comparelli, Roberto; Striccoli, Marinella; Agostiano, Angela; Curri, Maria Lucia

    2008-09-15

    Organic capped luminescent CdSe@ZnS nanocrystals (NCs) have been incorporated in block copolymer micelles, formed by polyethylene glycol modified phospholipids (PEG lipids). The obtained water soluble NC including PEG lipid micelles have been conjugated with bovine serum albumine (BSA). The entire process has been investigated by using optical, structural and electrophoretic complementary techniques. Such an integrated approach has allowed to elucidate critical issues, such as the time and temperature effects on the phase behavior of the PEG lipid/NC aggregate structures, the emitting properties of the NCs before and after micelle formation and bio-conjugation and the effect of conjugation on the biological moiety. The overall results provide relevant insight on the fabrication of the bio-conjugates, on their stability and on preparative procedure reproducibility, in view of the use of the resulting protein decorated NCs as multifunctional hybrid building blocks for the fabrication of a variety of supramolecular assemblies to exploit in biological sensing and diagnostic applications.

  12. Investigating Your Environment.

    ERIC Educational Resources Information Center

    Forest Service (USDA), Washington, DC.

    The goal of this interdisciplinary curriculum is to enable students to make informed and responsible decisions about natural resources management by promoting an understanding of natural, social, and economic environments and the student's role in affecting all three. The included investigations utilize processes and techniques that help people…

  13. pH-Sensitive Polymeric Micelle-based pH Probe for Detecting and Imaging Acidic Biological Environments

    PubMed Central

    Lee, Young Ju; Kang, Han Chang; Hu, Jun; Nichols, Joseph W.; Jeon, Yong Sun; Bae, You Han

    2012-01-01

    To overcome the limitations of monomeric pH probes for acidic tumor environments, this study designed a mixed micelle pH probe composed of polyethylene glycol (PEG)-b- poly(L-histidine) (PHis) and PEG-b-poly(L-lactic acid) (PLLA), which is well-known as an effective antitumor drug carrier. Unlike monomeric histidine and PHis derivatives, the mixed micelles can be structurally destabilized by changes in pH, leading to a better pH sensing system in nuclear magnetic resonance (NMR) techniques. The acidic pH-induced transformation of the mixed micelles allowed pH detection and pH mapping of 0.2–0.3 pH unit differences by pH-induced “on/off”-like sensing of NMR and magnetic resonance spectroscopy (MRS). The micellar pH probes sensed pH differences in non-biological phosphate buffer and biological buffers such as cell culture medium and rat whole blood. In addition, the pH-sensing ability of the mixed micelles was not compromised by loaded doxorubicin. In conclusion, PHis-based micelles could have potential as a tool to simultaneously treat and map the pH of solid tumors in vivo. PMID:22861824

  14. 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.

  15. Reconstitution of KCNE1 into lipid bilayers: comparing the structural, dynamic, and activity differences in micelle and vesicle environments.

    PubMed

    Coey, Aaron T; Sahu, Indra D; Gunasekera, Thusitha S; Troxel, Kaylee R; Hawn, Jaclyn M; Swartz, Max S; Wickenheiser, Marilyn R; Reid, Ro-jay; Welch, Richard C; Vanoye, Carlos G; Kang, Congbao; Sanders, Charles R; Lorigan, Gary A

    2011-12-20

    KCNE1 (minK), found in the human heart and cochlea, is a transmembrane protein that modulates the voltage-gated potassium KCNQ1 channel. While KCNE1 has previously been the subject of extensive structural studies in lyso-phospholipid detergent micelles, key observations have yet to be confirmed and refined in lipid bilayers. In this study, a reliable method for reconstituting KCNE1 into lipid bilayer vesicles composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho(1'-rac-glycerol) (sodium salt) (POPG) was developed. Microinjection of the proteoliposomes into Xenopus oocytes expressing the human KCNQ1 (K(V)7.1) voltage-gated potassium channel led to nativelike modulation of the channel. Circular dichroism spectroscopy demonstrated that the percent helicity of KCNE1 is significantly higher for the protein reconstituted in lipid vesicles than for the previously described structure in 1.0% 1-myristoyl-2-hydroxy-sn-glycero-3-phospho(1'-rac-glycerol) (sodium salt) (LMPG) micelles. SDSL electron paramagnetic resonance spectroscopic techniques were used to probe the local structure and environment of Ser28, Phe54, Phe57, Leu59, and Ser64 of KCNE1 in both POPC/POPG vesicles and LMPG micelles. Spin-labeled KCNE1 cysteine mutants at Phe54, Phe57, Leu59, and Ser64 were found to be located inside POPC/POPG vesicles, whereas Ser28 was found to be located outside the membrane. Ser64 was shown to be water inaccessible in vesicles but found to be water accessible in LMPG micelle solutions. These results suggest that key components of the micelle-derived structure of KCNE1 extend to the structure of this protein in lipid bilayers but also demonstrate the need to refine this structure using data derived from the bilayer-reconstituted protein to more accurately define its native structure. This work establishes the basis for such future studies.

  16. Investigation of laundering and dispersion approaches for silica and calcium phosphosilicate composite nanoparticles synthesized in reverse micelles

    NASA Astrophysics Data System (ADS)

    Tabakovic, Amra

    Nanotechnology, the science and engineering of materials at the nanoscale, is a booming research area with numerous applications in electronic, cosmetic, automotive and sporting goods industries, as well as in biomedicine. Composite nanoparticles (NPs) are of special interest since the use of two or more materials in NP design imparts multifunctionality on the final NP constructs. This is especially relevant for applications in areas of human healthcare, where the use of dye or drug doped composite NPs is expected to improve the diagnosis and treatment of cancer and other serious illnesses. Since the physicochemical properties of NP suspensions dictate the success of these systems in biomedical applications, especially drug delivery of chemotherapeutics, synthetic routes which offer precise control of NP properties, especially particle diameter and colloidal stability, are utilized to form a variety of composite NPs. Formation of NPs in reverse, or water-in-oil, micelles is one such synthetic approach. However, while the use of reverse micelles to form composite NPs offers precise control over NP size and shape, the post-synthesis laundering and dispersion of synthesized NP suspensions can still be a challenge. Reverse micelle synthetic approaches require the use of surfactants and low dielectric constant solvents, like hexane and cyclohexane, as the oil phase, which can compromise the biocompatibility and colloidal stability of the final composite NP suspensions. Therefore, appropriate dispersants and solvents must be used during laundering and dispersion to remove surfactant and ensure stability of synthesized NPs. In the work presented in this dissertation, two laundering and dispersion approaches, including packed column high performance liquid chromatography (HPLC) and centrifugation (sedimentation and redispersion), are investigated for silver core silica (Ag-SiO2) and calcium phosphosilicate (Caw(HxPO4)y(Si(OH)zOa) b · cH2O, CPS) composite NP suspensions

  17. Opportunities for improving the performance of LCV micelle gel dosimeters: I. Preliminary investigation

    NASA Astrophysics Data System (ADS)

    Nasr, A. T.; Alexander, K. M.; Schreiner, L. J.; McAuley, K. B.

    2015-01-01

    The effects of the various components of leuco crystal violet (LCV) micelle gels on dose sensitivity and initial colour are tested. Dose sensitivity and gel turbidity are influenced by tri-chloro acetic acid (TCAA) concentration, with the highest dose sensitivity obtained at ~21.5 mM. Increasing Triton x-100 (Txl00) concentration improved dose sensitivity but, unfortunately, increased initial colour of the gel. Using Cetyl Trimethyl Ammonium Bromide (CTAB) in place of Tx100 produces gels that are nearly colourless prior to irradiation, but reduces the dose sensitivity. The effects of chlorinated species on dose sensitivity are tested using 2,2,2-trichloroethanol (TCE), chloroform, and 1,1,1-trichloro-2-methyl-2-propanol hemihydrate (TCMPH). TCE gives the largest improvement in dose sensitivity and is recommended for use in micelle gel dosimeters because it is less volatile and safer to use than chloroform. A new gel containing CTAB as the surfactant and TCE gives improved dose sensitivity compared to previous LCV micelle gels.

  18. Structural investigation of nonionic fluorinated micelles by SANS in relation to mesoporous silica materials.

    PubMed

    Michaux, Florentin; Blin, Jean-Luc; Teixeira, José; Stébé, Marie José

    2012-01-12

    In an attempt to answer the question if there is dependence between the pore ordering of the mesoporous silica, obtained through the cooperative template mechanism, and the shape of the micellar aggregates of the surfactant solutions, the micellar structures of two nonionic fluorinated surfactant based-systems are studied by SANS. By fitting the experimental spectra with theoretical models, the structural evolution of the molecular aggregates can be described, and some important parameters can be obtained, such as the water and eventually oil penetration into the surfactant film, the aggregation number, the area per polar head of the surfactant, and the surfactant chain conformations. We have shown that for the C(8)F(17)C(2)H(4)(OC(2)H(4))(9)OH system, the micelles are prolate spheroids. The increase of the surfactant concentration in water does not change the characteristics of the interfacial film, but the aggregation number raises and the particles become more elongated. By contrast, the experimental curves of C(7)F(15)C(2)H(4)(OC(2)H(4))(8)OH cannot be fitted considering a small particle model. However, progressive incorporation of fluorocarbon induces a change of size and shape of the globules, which become smaller and more and more spherical. Regarding the material mesopore ordering, it appears that the micelles that lead to hexagonal mesoporous silica materials are described with a model of quasi-spherical globules. On the contrary, when large micelles are found, only wormhole-like structures are obtained.

  19. 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

  20. 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.

  1. Viscoelasticity and interface bending properties of lecithin reverse wormlike micelles studied by diffusive wave spectroscopy in hydrophobic environment.

    PubMed

    Martiel, Isabelle; Sagalowicz, Laurent; Mezzenga, Raffaele

    2014-09-01

    Upon the addition of minute quantities of water into a phosphatidylcholine (PC) solution in certain organic solvents, PC micelles elongate into giant reverse wormlike micelles that entangle and form highly viscous microemulsions, called lecithin organogels. We investigated the microrheological properties of concentrated PC-cyclohexane reverse wormlike micellar systems by diffusive wave spectroscopy (DWS) in apolar medium, combined with bulk shear rheology. We applied DWS to our oil-continuous system by using hydrophobic poly(hydroxystearic acid)-grafted PMMA particles as monodisperse tracer particles. Relevant parameters such as the micellar scission energy and persistence length were extracted from the microrheology data and interpreted according to the sphere-to-rod-to-sphere structural transition. On the basis of these quantities, we calculated the bending and saddle-splay moduli of the PC-covered water-cyclohexane interface. This approach represents a new method for the quantitative estimation of these fundamental parameters, which are thought to underpin the self-assembly of surfactants.

  2. Calorimetric and Light Scattering Investigations of the Transition from Spherical to Wormlike Micelles of C₁₄TAB Triggered by Salicylate.

    PubMed

    Ito, Thiago Heiji; Rodrigues, Roberta Kamei; Loh, Watson; Sabadini, Edvaldo

    2015-06-01

    Although wormlike micelles (WLM) were first described more than 30 years ago, many aspects of their formation process are still unclear. Herein, a systematic experimental investigation of the process for wormlike micelle (WLM) formation in mixtures of tetradecyltrimethylammonium bromide (C14TAB) and salicylate (2-hydroxybenzoate) was carried out. This system was used as a model to investigate the conditions for the formation of the giant aggregate. For comparison, the other two isomers of salicylate (3- and 4-hydroxybenzoate) were also investigated, once in these cases wormlike micelles are not formed. The studies were based on calorimetric titration, static light scattering, and rheological measurements. Enthalpy changes upon titration of C14TAB into 2-hydroxybenzoate solutions revealed a highly cooperative and exothermic process that was associated with micelle growth. The size of the aggregates, obtained by static light scattering measurements, confirms the shape transition. In addition, the correlation of these two sets of results with measurements of micelle charge surface indicates that this transition occurs around the point of charge neutralization.

  3. TR-ESR Investigation on Reaction of Vitamin C with Excited Triplet of 9,10-phenanthrenequinone in Reversed Micelle Solutions

    NASA Astrophysics Data System (ADS)

    Xu, Xin-sheng; Shi, Lei; Liu, Yi; Ji, Xue-han; Cui, Zhi-feng

    2011-04-01

    Time-resolved electron spin resonance has been used to study quenching reactions between the antioxidant Vitamin C (VC) and the triplet excited states of 9,10-phenanthrenequinone (PAQ) in ethylene glycol-water (EG-H2O) homogeneous and inhomogeneous reversed micelle solutions. Reversed micelle solutions were used to be the models of physiological environment of biological cell and tissue. In PAQ/EG-H2O homogeneous solution, the excited triplet of PAQ (3PAQ*) abstracts hydrogen atom from solvent EG. In PAQ/VC/EG-H2O solution, 3PAQ* abstracts hydrogen atom not only from solvent EG but also from VC. The quenching rate constant of 3PAQ* by VC is close to the diffusion-controlled value of 1.41 × 108 L/(mol ·s). In hexadecyltrimethylammonium bromide (CTAB)/EG-H2O and aerosol OT (AOT)/EG-H2O reversed micelle solutions, 3PAQ* and VC react around the water-oil interface of the reversed micelle. Exit of 3PAQ* from the lipid phase slows down the quenching reaction. For Triton X-100 (TX-100)/EG-H2O reversed micelle solution, PAQ and VC coexist inside the hydrophilic polyethylene glycol core, and the quenching rate constant of 3PAQ* by VC is larger than those in AOT/EG-H2O and CTAB/EG-H2O reversed micelle solutions, even a little larger than that in EG-H2O homogeneous solution. The strong emissive chemically induced dynamic electron polarization of As.- resulted from the effective TM spin polarization transfer in hydrogen abstraction of 3PAQ* from VC.

  4. Distance dependence of magnetic field effect inside confined environment of reverse micelles

    NASA Astrophysics Data System (ADS)

    Sarangi, Manas Kumar; Basu, Samita

    2013-06-01

    In this article, we emphasize on the distance dependence of the magnetic field effect (MFE) on the donoracceptor (D-A) pair inside the confined environment of AOT/H2O/n-heptane reverse micellar (RMs) system. For this study N, N-dimethyl aniline (DMA) is used as an electron donor while the protonated form of Acr is treated as an electron acceptor. We report of the occurrence of an associated excited state proton transfer with the photoinduced electron transfer between Acr and DMA forming corresponding radical pair (RP) and radical ion pairs (RIP). The fate of these reaction products has been tested in the presence of an external magnetic field (˜0.08T) by varying the size of the RMs. The MFE between Acr and DMA has been compared to the results with the earlier reported interactions between Acr and TEA (Chemical Physics Letters, 2011, 506, 205-210). We accentuate the importance of the localization of the D and A inside the RMs, and the intervening distance between the pair to be the critical component for observing substantial MFE.

  5. 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.

  6. Investigating Web Searching Behavior in Home Environments.

    ERIC Educational Resources Information Center

    Rieh, Soo Young

    2003-01-01

    Investigates situational elements of the home as a Web use environment, examining how domestic settings influenced people's Web search activities and behaviors. The subjects, 12 participants in 10 households, were found to search on the Web more frequently, more briefly, and less intensely for broader and more diverse information. Results have…

  7. Using Ants to Investigate the Environment

    ERIC Educational Resources Information Center

    Hagevik, Rita A.

    2005-01-01

    The best place for students to begin to understand complex environmental relationships is in their own back yards. Doing investigations of ants allows students to establish a baseline survey of ant fauna, test the importance of ants in nutrient cycling and soil structure maintenance, and increase their understanding of the environment and their…

  8. Investigating Your Environment--Intermountain Region.

    ERIC Educational Resources Information Center

    Forest Service (USDA), Washington, DC.

    This resource notebook contains over 100 activities in which students investigate different aspects of the environment. The activities are presented in 21 sections covering the following environmental topics and issues: (1) soil; (2) water; (3) forests; (4) plant relationships; (5) wildlife; (6)measurement; (7) urban communities; (8) deserts; (9)…

  9. Molecular Dynamics Simulation and NMR Investigation of the Association of the β-Blockers Atenolol and Propranolol with a Chiral Molecular Micelle

    PubMed Central

    Morris, Kevin F.; Billiot, Eugene J.; Billiot, Fereshteh H.; Hoffman, Charlene B.; Gladis, Ashley A.; Lipkowitz, Kenny B.; Southerland, William M.; Fang, Yayin

    2015-01-01

    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. PMID:26257464

  10. 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.

  11. Investigations of Methane Production in Hypersaline Environments

    NASA Technical Reports Server (NTRS)

    Bebout, Brad M.

    2015-01-01

    The recent reports of methane in the atmosphere of Mars, as well as the findings of hypersaline paleo-environments on that planet, have underscored the need to evaluate the importance of biological (as opposed to geological) trace gas production and consumption. Methane in the atmosphere of Mars may be an indication of life but might also be a consequence of geologic activity and/or the thermal alteration of ancient organic matter. Hypersaline environments have now been reported to be extremely likely in several locations in our solar system, including: Mars, Europa, and Enceladus. Modern hypersaline microbial mat communities, (thought to be analogous to those present on the early Earth at a period of time when Mars was experiencing very similar environmental conditions), have been shown to produce methane. However, very little is known about the physical and/or biological controls imposed upon the rates at which methane, and other important trace gases, are produced and consumed in these environments. We describe here the results of our investigations of methane production in hypersaline environments, including field sites in Chile, Baja California Mexico, California, USA and the United Arab Emirates. We have measured high concentrations of methane in bubbles of gas produced both in the sediments underlying microbial mats, as well as in areas not colonized by microbial mats in the Guerrero Negro hypersaline ecosystem, Baja California Mexico, in Chile, and in salt ponds on the San Francisco Bay. The carbon isotopic (d13C) composition of the methane in the bubbles exhibited an extremely wide range of values, (ca. -75 per mille ca. -25 per mille). The hydrogen isotopic composition of the methane (d2H) ranged from -60 to -30per mille and -450 to -350per mille. These isotopic values are outside of the range of values normally considered to be biogenic, however incubations of the sediments in contact with these gas bubbles reveals that the methane is indeed being

  12. SISGR: Water dynamics in heterogeneous and confined environments: Salt solutions, reverse micelles, and lipid multi-bilayers

    SciTech Connect

    Skinner, James

    2013-11-05

    Our goal is to understand the structure and dynamics of water, in its different phases, at the interfaces between these phases, and in confined and heterogeneous environments. To this end, linear and nonlinear vibrational spectroscopy is playing a very important role. We have developed techniques for calculating spectroscopic observables, and then used our results to analyze and interpret experiment.

  13. Dendrimeric micelles for controlled drug release and targeted delivery

    PubMed Central

    Ambade, Ashootosh V.; Savariar, Elamprakash N.; Thayumanavan, S.

    2008-01-01

    This review highlights the developments in dendrimer-based micelles for drug delivery. Dendrimers, the perfectly branched monodisperse macromolecules, have certain structural advantages that make them attractive candidates as drug carriers for controlled release or targeted delivery. As polymeric micelle-based approaches precede the work in dendrimers, these are also discussed briefly. The review concludes with a perspective on possible applications of biaryl-based dendrimeric micelles that exhibit environment-dependent conformations, in drug delivery. PMID:16053329

  14. Investigative Science Learning Environment: Motivation and Outcomes

    NASA Astrophysics Data System (ADS)

    Etkina, Eugenia

    2007-04-01

    The National Science Foundation's ``Shaping the Future 1996'' warns that: ``the national work force is changing dramatically, as high-paying but relatively unskilled factory jobs disappear in the face of foreign competition and technological advances; consequently the educational needs of the prospective work force are now vastly different.'' This report and many others indicate that science education should place much more emphasis on helping students acquire the process abilities used in the practice of science, abilities such as model building, designing experiments, analyzing real world problems, justifying assumptions, evaluating work, and communicating. This presentation will illustrate how Investigative Science Learning Environment used in introductory physics courses helps achieve these goals in large and small college classrooms and describe the results in terms of student learning of these abilities and of physics content.

  15. Dependence of micelle size and shape on detergent alkyl chain length and head group.

    PubMed

    Oliver, Ryan C; Lipfert, Jan; Fox, Daniel A; Lo, Ryan H; Doniach, Sebastian; Columbus, Linda

    2013-01-01

    Micelle-forming detergents provide an amphipathic environment that can mimic lipid bilayers and are important tools for solubilizing membrane proteins for functional and structural investigations in vitro. However, the formation of a soluble protein-detergent complex (PDC) currently relies on empirical screening of detergents, and a stable and functional PDC is often not obtained. To provide a foundation for systematic comparisons between the properties of the detergent micelle and the resulting PDC, a comprehensive set of detergents commonly used for membrane protein studies are systematically investigated. Using small-angle X-ray scattering (SAXS), micelle shapes and sizes are determined for phosphocholines with 10, 12, and 14 alkyl carbons, glucosides with 8, 9, and 10 alkyl carbons, maltosides with 8, 10, and 12 alkyl carbons, and lysophosphatidyl glycerols with 14 and 16 alkyl carbons. The SAXS profiles are well described by two-component ellipsoid models, with an electron rich outer shell corresponding to the detergent head groups and a less electron dense hydrophobic core composed of the alkyl chains. The minor axis of the elliptical micelle core from these models is constrained by the length of the alkyl chain, and increases by 1.2-1.5 Å per carbon addition to the alkyl chain. The major elliptical axis also increases with chain length; however, the ellipticity remains approximately constant for each detergent series. In addition, the aggregation number of these detergents increases by ∼16 monomers per micelle for each alkyl carbon added. The data provide a comprehensive view of the determinants of micelle shape and size and provide a baseline for correlating micelle properties with protein-detergent interactions.

  16. 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

  17. 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

  18. An Investigation of Person-Environment Congruence

    ERIC Educational Resources Information Center

    McMurray, Marissa Johnstun

    2013-01-01

    This study tested a hypothesis derived from Holland's (1997) theory of personality and environment that congruence between person and environment would influence satisfaction with doctoral training environments and career certainty. Doctoral students' (N = 292) vocational interests were measured using questions from the Interest Item Pool, and…

  19. 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

  20. 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.

  1. Mesoscopic simulation studies on the formation mechanism of drug loaded polymeric micelles.

    PubMed

    Wang, Yan; Zhu, Dan Dan; Zhou, Jian; Wang, Qi Lei; Zhang, Can Yang; Liu, Yue Jin; Wu, Zhi Min; Guo, Xin Dong

    2015-12-01

    In this work, the formation of polymeric micelles as drug delivery vehicles in an aqueous environment is investigated by dissipative particle dynamics (DPD) simulations. Doxorubicin (DOX) is selected as the model drug, whereas docosahexaenoic acid (DHA) conjugated His10Lys10 (DHA-His10Lys10) as the drug carrier. It is shown from DPD simulation that drug molecules and DHA-His10Lys10 molecules could aggregate and form micelles under a defined composition recipe; drug molecules are homogeneously distributed inside the carrier matrix, on whose surface the stabilizer lysine segments are absorbed. Under different compositions of drug and water, aggregate morphologies of polymeric micelles are observed as spherical, columnar, and lamellar structures. We finally proposed the formation mechanism of drug loaded polymeric micelles and apply it in practice by analyzing the simulated phenomena. All the results can effectively guide the experimental preparation of drug delivery system with desired properties or explore a novel polymeric micelle with high performance. PMID:26454543

  2. pH responsive micelle self-assembled from a new amphiphilic peptide as anti-tumor drug carrier.

    PubMed

    Liang, Ju; Wu, Wen-Lan; Xu, Xiao-Ding; Zhuo, Ren-Xi; Zhang, Xian-Zheng

    2014-02-01

    An acid-responsive amphiphilic peptide that contains KKGRGDS sequence in hydrophilic head and VVVVVV sequence in hydrophobic tail was designed and prepared. In neutral or basic medium, this amphiphilic peptide can self-assemble into micelles through hydrogen bonding and hydrophobic interactions. If changing the solution pH to an acidic environment, the electrostatic repulsion interaction among the ionized lysine (K) residues will prevent the self-assembly of the amphiphilic peptide, leading to the dissociation of micelles. The anti-tumor drug of doxorubicin (DOX) was chosen and loaded into the self-assembled micelles of the amphiphilic peptide to investigate the influence of external pH change on the drug release behavior. As expected, the micelles show a sustained DOX release in neutral medium (pH 7.0) but fast release behavior in acidic medium (pH 5.0). When incubating these DOX-loaded micelles with HeLa and COS7 cells, due to the over-expression of integrins on cancer cells, the micelles can efficiently use the tumor-targeting function of RGD sequence to deliver the drug into HeLa cells. Combined with the low cytotoxicity of the amphiphilic peptide against both HeLa and COS7 cells, the amphiphilic peptide reported in this work may be promising in clinical application for targeted drug delivery.

  3. 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

  4. Polymeric micelles for acyclovir drug delivery.

    PubMed

    Sawdon, Alicia J; Peng, Ching-An

    2014-10-01

    Polymeric prodrug micelles for delivery of acyclovir (ACV) were synthesized. First, ACV was used directly to initiate ring-opening polymerization of ɛ-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. (1)H 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 200nm and the CMCs of ACV-PCL-MPEG and ACV-PCL-chitosan were 2.0mgL(-1) and 6.6mgL(-1), respectively. The drug release kinetics of ACV was investigated and cytotoxicity assay demonstrates that ACV-tagged polymeric micelles were non-toxic.

  5. 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

  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.

  7. 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.

  8. Do the physical properties of water in mixed reverse micelles follow a synergistic effect: a spectroscopic investigation.

    PubMed

    Das, Arindam; Patra, Animesh; Mitra, Rajib Kumar

    2013-04-01

    In this contribution we have tried to investigate whether the mechanical properties of the reverse micellar (RM) interface dictate the physical properties of entrapped water molecules in the RM waterpool. We choose AOT/Igepal-520/cyclohexane (Cy) mixed RM as a model system which exhibits synergistic water solubilization behavior as a function of interfacial stoichiometry. Such a phenomenon associates systematic modification of the interface curvature. Dynamic light scattering (DLS) studies reveal linear increase in the droplet size and aggregation number of the RMs with increasing XIgepal (mole fraction of Igepal in the surfactant mixture). FTIR study in the 3000-3800 cm(-1) region identifies that the relative population of the surface-bound water molecules is higher in AOT RM compared to that in Igepal RM, and in mixed systems it also follows a linear trend with XIgepal. Water relaxation dynamics as probed by time-resolved fluorescence spectroscopy using Coumarin-500 also reveals an overall linear trend with no characteristic feature around the solubilization inflation point. Our study clearly identifies that the physical properties of water in RM are mostly governed by the interfacial stoichiometry and water content, and merely bares any dependence on the mechanical properties of the interface.

  9. Unique influence of cholesterol on modifying the aggregation behavior of surfactant assemblies: investigation of photophysical and dynamical properties of 2,2'-bipyridine-3,3'-diol, BP(OH)2 in surfactant micelles, and surfactant/cholesterol forming vesicles.

    PubMed

    Ghosh, Surajit; Kuchlyan, Jagannath; Roychowdhury, Subhajit; Banik, Debasis; Kundu, Niloy; Roy, Arpita; Sarkar, Nilmoni

    2014-08-01

    The binding and rotational properties of an excited-state intramolecular proton transfer (ESIPT) fluorophore, 2,2'-bipyridine-3,3'-diol, BP(OH)2 has been investigated in alkyltrimethylammonium bromide containing (CnTAB, n = 12, 14, and 16) micelles and alkyltrimethylammonium bromide/cholesterol (CnTAB (n = 14 and 16)/cholesterol) forming vesicles using fluorescence-based spectroscopy techniques. The formation of thermodynamically stable unilamellar self-assemblies of alkyltrimethylammonium bromide/cholesterol are characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements. Individually, aqueous solutions of all these alkyltrimethylammonium bromide form micelles after certain surfactant concentration (critical micelle concentration, cmc) of surfactant, whereas cholesterol molecules are insoluble in water. But with the variation of the cholesterol-to-surfactant molar ratio (Q = [cholesterol]/[surfactant]), uniform distribution of vesicular aggregates in aqueous solution can be obtained. The micelle-to-vesicle transition of surfactant solution upon addition of cholesterol also influences the steady state emission profile, fluorescence lifetime, and rotational dynamics of BP(OH)2 molecule. The diketo tautomer of BP(OH)2 molecule gets stabilized as the concentration of surfactant increases in aqueous solution. Fluorescence lifetime and rotational time constant of the BP(OH)2 molecule are also influenced by the variation of alkyl chain length of surfactant molecule. The emission quantum yield (Φ) is also found to be sensitive with surfactant concentration, variation in chain length of surfactants, and it saturates after the cmc of surfactants. The rigid and restricted microenvironment of vesicle bilayer enhance the lifetime and also rotational relaxation of BP(OH)2 significantly. The rotational behavior of BP(OH)2 in surfactant/cholesterol self-assemblies is also explained by using analytical parameters related to time

  10. Crystal nucleation of zincophosphate open frameworks in reverse micelle nanoreactors

    NASA Astrophysics Data System (ADS)

    Castagnola, Mario J.

    The synthesis of microporous zincophosphates was studied through a novel synthetic route based on reactants encapsulated in reverse micelles. The zincophosphate analog of sodalite had been previously synthesized in a reverse micelle system using Aerosol OT (AOT) as surfactant. The synthesis of open framework zincophosphates using this detergent proved unsuccessful. By studying the conventional synthesis of zincophosphates and the AOT reverse micelle aqueous environment through Raman microscopy, FTIR, NMR and XRD, it was found that the relatively high concentrations of sodium ions and the disordered structure of water present in the AOT reverse micelles prevented the synthesis of open framework structures. Based on these results, a system containing reverse micelles of the cationic surfactant dioctyldimethylammonium chloride (DODMAC) was developed. Zn 2+- and PO43--containing DODMAC reverse micelles were characterized by dynamic light scattering and conductivity measurements, indicating a rod-like shape for the former and a spherical shape for the latter reverse micelles. Combination of the two reverse micelle solutions led to the first successful reverse micelle based synthesis of the zincophosphate analog of Zeolite-X, ZnPO-X. The size of the crystals was controlled by modifying the volume ratio between the individual reagent micellar solutions. Nanocrystals of the order of 20 nm were obtained by interrupting the reaction at early stages. Studies of both the conventional aqueous and the reverse micelle based syntheses of ZnPO-X revealed that the morphology of the ZnPO-X crystals was controlled by the concentration of tetramethylammonium ions (TMA+). The ZnPO-X crystals synthesized via the reverse micelles were obtained as a single phase. Using Raman spectroscopy, it was determined that, during conventional synthesis, H+ ions promote the hydrolysis of the ZnPO-X crystals that leads to hopeite formation. Ion-exchange by monovalent cations indicated that the crystal

  11. 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.

  12. Investigating Our Environment. Science: Grade 6.

    ERIC Educational Resources Information Center

    New York City Board of Education, Brooklyn, NY. Bureau of Curriculum Development.

    Intended mainly for use in the intermediate grades, this document provides demonstrations, field trips and laboratory experiences designed to help students investigate the role that people play in problems associated with environmental quality, pollution, and ecology in general. The book was developed as an alternative program to the regular sixth…

  13. Using Ants To Investigate the Environment.

    ERIC Educational Resources Information Center

    Hagevik, Rita A.

    2003-01-01

    Describes three inquiry-based activities designed for students to begin to understand complex environmental relationships in their own backyard. Includes investigations of ants, which allow students to establish a baseline survey of ant fauna, test the importance of ants in nutrient cycling and soil structure maintenances, and increase student…

  14. Targeted antithrombotic protein micelles.

    PubMed

    Kim, Wookhyun; Haller, Carolyn; Dai, Erbin; Wang, Xiowei; Hagemeyer, Christoph E; Liu, David R; Peter, Karlheinz; Chaikof, Elliot L

    2015-01-26

    Activated platelets provide a promising target for imaging inflammatory and thrombotic events along with site-specific delivery of a variety of therapeutic agents. Multifunctional protein micelles bearing targeting and therapeutic proteins were now obtained by one-pot transpeptidation using an evolved sortase A. Conjugation to the corona of a single-chain antibody (scFv), which binds to the ligand-induced binding site (LIBS) of activated GPIIb/IIIa receptors, enabled the efficient detection of thrombi. The inhibition of thrombus formation was subsequently accomplished by incorporating the catalytically active domain of thrombomodulin (TM) onto the micelle corona for the local generation of activated protein C, which inhibits the formation of thrombin. An effective strategy has been developed for the preparation of protein micelles that can be targeted to sites of activated platelets with broad potential for treatment of acute thrombotic events. PMID:25504546

  15. Mechanism of Molecular Exchange in Copolymer Micelles

    NASA Astrophysics Data System (ADS)

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

    2010-03-01

    Compared to thermodynamic structure, much less has been known about the kinetics of block copolymer micelles which should underlay the attainment of thermodynamic equilibrium. In this presentation, molecular exchange between spherical micelles formed by isotopically labeled diblock copolymers was investigated using time-resolved small-angle neutron scattering. Two pairs of structurally matched poly(styrene-b-ethylene-alt-propylene) (PS-PEP) were synthesized and dispersed in isotopic mixture of squalane, highly selective to PEP block. Each pair includes polymers with fully deuterated (dPS-PEP) and a normal (hPS-PEP) PS blocks. Temperature dependence of the micelle exchange rate R(t) is consistent with melt dynamics for the core polymer. Furthermore, R(t) is significantly sensitive to the core block length N due to the thermodynamic penalty associated with ejecting a core block into the solvent. This hypersensitivity, combined with modest polydispersity in N, leads to an approximately logarithmic decay in R(t).

  16. Antigen-antibody binding in reverse micelles: interaction of monoclonal antibodies with a myelin basic protein peptide.

    PubMed

    Groome, N P; Vacher, M; Nicot, C; Waks, M

    1990-01-01

    Reverse micelles can be used to mimic biological processes occurring at interfaces. To investigate antigen-antibody binding in a membrane-like environment, we first obtained Fab fragments from monoclonal antibodies against bovine myelin basic protein (MBP), an encephalitogenic protein. The binding of the fragments to a dansylated synthetic human MBP peptide gly(119)-gly(131), presenting sequence homologies with a viral protein, was measured in buffer and for the first time in reverse micelles of sodium bis(2-ethylhexyl) sulfosuccinate, in isooctane. Analysis of the fluorescence polarisation titration curves discloses that the Fab fragments in reverse micelles have retained the high affinity for the peptide found in buffer, and similar to that for intact MBP.

  17. 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

  18. Triggered disassembly of hierarchically assembled onion-like micelles into the pristine core-shell micelles via a small change in pH.

    PubMed

    Cai, Guoqiang; Zhang, Haiwen; Liu, Peng; Wang, Liqun; Jiang, Hongliang

    2011-10-01

    The size and surface property of nanomaterial-based delivery systems administered intravenously play important roles in their cell uptake and in vivo distribution. Both of them should be capable of self-evolution in order to achieve efficient targeting performance. A facile strategy was proposed to manipulate both the size and surface property of polymeric micelles. It was found that the hierarchical assembly between trimethylated chitosan-g-poly(ε-caprolactone) (TMC-PCL) micelles and carboxyethyl chitosan-g-poly(ethylene glycol) (CEC-PEG) could produce onion-like micelles with enlarged size and PEGylated surface. The onion-like micelles could withstand the ionic strength of plasma and competitive exchange with BSA, and abruptly disassemble into the pristine TMC-PCL micelles via a small change in pH. By varying the degree of carboxyethylation, the disassembly pH could be modulated to the range of the tumoral microclimate pH. In contrast with TMC-PCL micelles, which displayed high cytotoxicity and endocytic ability towards C6 glioma cells, the onion-like micelles were cell-friendly and internalized by the cells at a very low level. Doxorubicin was used as a model chemotherapeutic agent and incorporated within TMC-PCL micelles. Dox release from both TMC-PCL micelles and the onion-like micelles was very slow under normal physiological conditions and displayed excellent pH sensitivity. Cell viability of Dox-loaded micelles was also investigated.

  19. Evaluation of Doxorubicin-loaded 3-Helix Micelles as Nanocarriers

    PubMed Central

    Dube, Nikhil; Shu, Jessica Y.; Dong, He; Seo, Jai W.; Ingham, Elizabeth; Kheirolomoom, Azadeh; Chen, Pin-Yuan; Forsayeth, John; Bankiewicz, Krystof; Ferrara, Katherine W.; Xu, Ting

    2013-01-01

    Designing stable drug nanocarriers, 10-30 nm in size, would have significant impact on their transport in circulation, tumor penetration and therapeutic efficacy. In the present study, biological properties of 3-helix micelles loaded with 8 wt% doxorubicin (DOX), ~15 nm in size, were characterized to validate their potential as a nanocarrier platform. DOX-loaded micelles exhibited high stability in terms of size and drug retention in concentrated protein environments similar to conditions after intravenous injections. DOX-loaded micelles were cytotoxic to PPC-1 and 4T1 cancer cells at levels comparable to free DOX. 3-helix micelles can be disassembled by proteolytic degradation of peptide shell to enable drug release and clearance to minimize long-term accumulation. Local administration to normal rat striatum by convection enhanced delivery (CED) showed greater extent of drug distribution and reduced toxicity relative to free drug. Intravenous administration of DOX-loaded 3-helix micelles demonstrated improved tumor half-life and reduced toxicity to healthy tissues in comparison to free DOX. In vivo delivery of DOX-loaded 3-helix micelles through two different routes clearly indicates the potential of 3-helix micelles as safe and effective nanocarriers for cancer therapeutics. PMID:24050265

  20. Novel pluronic-chitosan micelle as an ocular delivery system.

    PubMed

    Lin, Hong-Ru; Chang, Pei-Csang

    2013-07-01

    Pluronic micelles were prepared for ophthalmic delivery by incorporation of ethyl acetate as a dispersion agent and their surfaces were modified by chitosan to improve their bioavailability. The micelles disperse well in the solution and have a core-shell like structure with a particle size ranging from 93 to 181 nm for drug unloaded, 123-232 nm for drug-loaded, and a zeta potential between 6.1 and 9.2 mV, indicating very suitable use as ophthalmic carrier. The in vitro serum stability tests indicate the particle size of the micelles was very stable during the serum absorption. The turbidity test reveals that the prepared micelles were very stable under phosphate buffered saline environment, which can prevent the blurred vision. The loading efficiency of metipranolol in micelles can be as high as 83%. Finally, the in vitro and in vivo studies indicate the pluronic micelles modified by chitosan have sustained release behavior and good pharmacological response. As the results, the pluroic-chitosan micelles system provides a potential opportunity in decreasing frequency of administration and improving patient compliance for ocular drug delivery.

  1. 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.

  2. 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

  3. Smart wormlike micelles.

    PubMed

    Chu, Zonglin; Dreiss, Cécile A; Feng, Yujun

    2013-09-01

    A major scientific challenge of the past decade pertaining to the field of soft matter has been to craft 'adaptable' materials, inspired by nature, which can dynamically alter their structure and functionality on demand, in response to triggers produced by environmental changes. Amongst these, 'smart' surfactant wormlike micelles, responsive to external stimuli, are a particularly recent area of development, yet highly promising, given the versatility of the materials but simplicity of the design-relying on small amphiphilic molecules and their spontaneous self-assembly. The switching 'on' and 'off' of the micellar assembly structures has been reported using electrical, optical, thermal or pH triggers and is now envisaged for multiple stimuli. The structural changes, in turn, can induce major variations in the macroscopic characteristics, affecting properties such as viscosity and elasticity and sometimes even leading to a spontaneous and effective 'sol-gel' transition. These original smart materials based on wormlike micelles have been successfully used in the oil industry, and offer a significant potential in a wide range of other technological applications, including biomedicine, cleaning processes, drag reduction, template synthesis, to name but a few. This review will report results in this field published over the last few years, describe the potential and practical applications of stimuli-responsive wormlike micelles and point out future challenges.

  4. Structural Analysis of Hydrophobe-Uptake Micelle of an Amphiphilic Alternating Copolymer in Aqueous Solution.

    PubMed

    Morishima, Ken; Terao, Ken; Sato, Takahiro

    2016-08-01

    We investigated the structure of the hydrophobe-uptake micelle of an alternating amphiphilic copolymer in aqueous solutions, by combining light scattering and small-angle X-ray scattering (SAXS). When the copolymer micelle includes the hydrophobe (1-dodecanol), the unicore flower micelle transforms into the multicore flower necklace, and the flower necklace is slightly stiffer than the hydrophobe-free flower necklace of the same copolymer. Moreover, the hydrophobe is included not in the hydrophobic core region but in the intermingled region of the hydrophobic group and the loop chain of the unit flower micelle. Therefore, the structure of the hydrophobe-uptake micelle of the amphiphilic alternating copolymer is quite different from that of hydrophobe-uptake spherical micelles of low molar mass surfactants and of amphiphilic block copolymers, where the hydrophobe is included in the hydrophobic region of the micelles.

  5. On the stability and morphology of complex coacervate core micelles: from spherical to wormlike micelles.

    PubMed

    van der Kooij, Hanne M; Spruijt, Evan; Voets, Ilja K; Fokkink, Remco; Cohen Stuart, Martien A; van der Gucht, Jasper

    2012-10-01

    We present a systematic study of the stability and morphology of complex coacervate core micelles (C3Ms) formed from poly(acrylic acid) (PAA) and poly(N-methyl-2-vinylpyridinium)-b-poly(ethylene oxide) (PM2VP-b-PEO). We use polarized and depolarized dynamic and static light scattering, combined with small-angle X-ray scattering, to investigate how the polymer chain length and salt concentration affect the stability, size, and shape of these micelles. We show that C3Ms are formed in aqueous solution below a critical salt concentration, which increases considerably with increasing PAA and PM2VP length and levels off for long chains. This trend is in good agreement with a mean-field model of polyelectrolyte complexation based on the Voorn-Overbeek theory. In addition, we find that salt induces morphological changes in C3Ms when the PAA homopolymer is sufficiently short: from spherical micelles with a diameter of several tens of nanometers at low salt concentration to wormlike micelles with a contour length of several hundreds of nanometers just before the critical salt concentration. By contrast, C3Ms of long PAA homopolymers remain spherical upon addition of salt and shrink slightly. A critical review of existing literature on other C3Ms reveals that the transition from spherical to wormlike micelles is probably a general phenomenon, which can be rationalized in terms of a classical packing parameter for amphiphiles.

  6. 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.

  7. Impact of urea on detergent micelle properties.

    PubMed

    Broecker, Jana; Keller, Sandro

    2013-07-01

    Co-solvents, such as urea, can entail drastic changes in the micellization behavior of detergents. We present a systematic quantification of the impact of urea on the critical micellar concentration, the micellization thermodynamics, and the micelle size in three homologous series of commonly used non-ionic alkyl detergents. To this end, we performed demicellization experiments by isothermal titration calorimetry and hydrodynamic size measurements by dynamic light scattering on alkyl maltopyranosides, cyclohexyl alkyl maltopyranosides, and alkyl glucopyranosides at urea concentrations of 0-8 M. For all detergents studied, we found that the critical micellar concentration increases exponentially because the absolute Gibbs free energy of micellization decreases linearly over the entire urea concentration range, as does the micelle size. In contrast, the enthalpic and entropic contributions to micellization reveal more complex, nonlinear dependences on urea concentration. Both free energy and size changes are more pronounced for long-chain detergents, which bury more apolar surface area upon micelle formation. The Gibbs free energy increments per methylene group within each detergent series depend on urea concentration in a linear fashion, although they result from the entropic term for alkyl maltosides but are of enthalpic origin for cyclohexyl alkyl maltosides. We compare our results to transfer free energies of amino acid side chains, relate them to protein-folding data, and discuss how urea-induced changes in detergent micelle properties affect in vitro investigations on membrane proteins.

  8. Light responsive thin films of micelles of PS-b-PVP complexed with diazophenol chromophore

    NASA Astrophysics Data System (ADS)

    Saiz, Luciana M.; Oyanguren, Patricia A.; José Galante, María; Zucchi, Ileana A.

    2014-02-01

    We have incorporated push-pull azobenzene units into diblock-copolymer micelles by supramolecular assembly. Specifically, we encapsulated a phenol-functionalized chromophore, DO13, within PS-b-P4VP micelles in toluene by means of H-bond interactions developed between DO13 molecules and pyridine groups of P4VP block. The solutions were spin-coated onto glass substrates resulting in multi- or mono-layered thin films of micelles with P4VP(DO13) core and PS corona. We show that the use of DO13 as a building block of micellar aggregates allowed us to manipulate the developed nanostructures. Spherical to cylindrical micellar transition was found when we increased the degree of chromophore complexation. Also, it was found that the polymer concentration in the solution plays an important role in determining the micellar nanostructures. The chain extension and change in composition of the P4VP core in the presence of the chromophore may be responsible for the structural changes observed in the micelles. The optical properties of the thin films have been investigated focusing on the effect of the micellar morphology over the photoinduced birefringence. The optical anisotropy (Δn) increased with respect to the analogous homogeneous system P4VP(DO13), indicating that the protective micelle environment can enhance the optical properties of the embedded chromophores significantly. Furthermore, we show very interesting new results in which we have related changes in optical properties to the film morphology (spheres to cylinders). This can be exploited for producing optical devices having improved optoelectronic properties and stability.

  9. Enhanced solubility and targeted delivery of curcumin by lipopeptide micelles.

    PubMed

    Liang, Ju; Wu, Wenlan; Lai, Danyu; Li, Junbo; Fang, Cailin

    2015-01-01

    A lipopeptide (LP)-containing KKGRGDS as the hydrophilic heads and lauric acid (C12) as the hydrophobic tails has been designed and prepared by standard solid-phase peptide synthesis technique. LP can self-assemble into spherical micelles with the size of ~30 nm in PBS (phosphate buffer saline) (pH 7.4). Curcumin-loaded LP micelles were prepared in order to increase the water solubility, sustain the releasing rate, and improve the tumor targeted delivery of curcumin. Water solubility, cytotoxicity, in vitro release behavior, and intracellular uptake of curcumin-loaded LP micelles were investigated. The results showed that LP micelles can increase the water solubility of curcumin 1.1 × 10(3) times and sustain the release of curcumin in a low rate. Curcumin-loaded LP micelles showed much higher cell inhibition than free curcumin on human cervix carcinoma (HeLa) and HepG2 cells. When incubating these curcumin-loaded micelles with HeLa and COS7 cells, due to the over-expression of integrins on cancer cells, the micelles can efficiently use the tumor-targeting function of RGD (functionalized peptide sequences: Arg-Gly-Asp) sequence to deliver the drug into HeLa cells, and better efficiency of the self-assembled LP micelles for curcumin delivery than crude curcumin was also confirmed by LCSM (laser confocal scanning microscope) assays. Combined with the enhanced solubility and higher cell inhibition, LP micelles reported in this study may be promising in clinical application for targeted curcumin delivery.

  10. Pharmacokinetics of core-polymerized, boron-conjugated micelles designed for boron neutron capture therapy for cancer.

    PubMed

    Sumitani, Shogo; Oishi, Motoi; Yaguchi, Tatsuya; Murotani, Hiroki; Horiguchi, Yukichi; Suzuki, Minoru; Ono, Koji; Yanagie, Hironobu; Nagasaki, Yukio

    2012-05-01

    Core-polymerized and boron-conjugated micelles (PM micelles) were prepared by free radical copolymerization of a PEG-b-PLA block copolymer bearing an acetal group and a methacryloyl group (acetal-PEG-b-PLA-MA), with 1-(4-vinylbenzyl)-closo-carborane (VB-carborane), and the utility of these micelles as a tumor-targeted boron delivery system was investigated for boron neutron capture therapy (BNCT). Non-polymerized micelles (NPM micelles) that incorporated VB-carborane physically showed significant leakage of VB-carborane (ca. 50%) after 12 h incubation with 10% fetal bovine serum (FBS) at 37 °C. On the other hand, no leakage from the PM micelles was observed even after 48 h of incubation. To clarify the pharmacokinetics of the micelles, (125)I (radioisotope)-labeled PM and NPM micelles were administered to colon-26 tumor-bearing BALB/c mice. The (125)I-labeled PM micelles showed prolonged blood circulation (area under the concentration curve (AUC): 943.4) than the (125)I-labeled NPM micelles (AUC: 495.1), whereas tumor accumulation was similar for both types of micelles (AUC(PM micelle): 249.6, AUC(NPM micelle): 201.1). In contrast, the tumor accumulation of boron species in the PM micelles (AUC: 268.6) was 7-fold higher than the NPM micelles (AUC: 37.1), determined by ICP-AES. Thermal neutron irradiation yielded tumor growth suppression in the tumor-bearing mice treated with the PM micelles without reduction in body weight. On the basis of these data, the PM micelles represent a promising approach to the creation of boron carrier for BNCT.

  11. [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.

  12. 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

  13. [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

  14. Applications of polymer micelles for imaging and drug delivery.

    PubMed

    Movassaghian, Sara; Merkel, Olivia M; Torchilin, Vladimir P

    2015-01-01

    Polymeric micelles, self-assembling nano-constructs of amphiphilic copolymers, are widely considered as convenient nano-carriers for a variety of applications, such as diagnostic imaging, and drug and gene delivery. They have demonstrated a variety of favorable properties including biocompatibility, longevity, high stability in vitro and in vivo, capacity to effectively solubilize a variety of poorly soluble drugs, changing the release profile of the incorporated pharmaceutical agents, and the ability to accumulate in the target zone based on the enhanced permeability and retention effect. Moreover, additional functions can be imparted to the micelle-based delivery systems by engineering their surface for specific applications. Various targeting ligands can be attached for cell or intracellular accumulation at a site of interest. Also, the chelation or incorporation of imaging moieties into the micelle structure enables in vivo biodistribution studies. Moreover, pH-, thermo-, ultrasound-, enzyme- and light-sensitive block-copolymers allow for controlled micelle dissociation and triggered drug release in response to the pathological environment-specific stimuli and/or externally applied signals. The combination of these approaches can further improve specificity and efficacy of micelle-based drug delivery to promote the development of smart multifunctional micelles. PMID:25683687

  15. 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.

  16. Reverse micelles directed synthesis of TiO{sub 2}-CeO{sub 2} mixed oxides and investigation of their crystal structure and morphology

    SciTech Connect

    Matejova, Lenka; Vales, Vaclav; Fajgar, Radek; Matej, Zdenek; Holy, Vaclav; Solcova, Olga

    2013-02-15

    The synthesis of TiO{sub 2}-CeO{sub 2} mixed oxides based on the sol-gel process controlled within reverse micelles of non-ionic surfactant Triton X-114 in cyclohexane is reported. The crystallization, phase composition, trends in nanoparticles growth and porous structure properties are studied as a function of Ti:Ce molar composition and annealing temperature by in-situ X-ray diffraction, Raman spectroscopy and physisorption. The brannerite-type CeTi{sub 2}O{sub 6} crystallizes as a single crystalline phase at Ti:Ce molar composition of 70:30 and in the mixture with cubic CeO{sub 2} and anatase TiO{sub 2} for composition 50:50. At Ti:Ce molar ratios 90:10 and 30:70 the mixtures of TiO{sub 2} anatase, rutile and cubic CeO{sub 2} appear. In these mixtures TiO{sub 2} rutile is formed at higher temperatures than conventionally. Additionally, the amount of a present amorphous phase in individual mixtures was estimated from diffraction data. The porous structure morphology depends both on molar composition and annealing temperature. This is correlated with the presence of carbon impurities of different character. - Graphical abstract: The phase composition of Ti90--Ce10 and Ti50--Ce50 oxide mixtures as a function of annealing temperature. The amount of the amorphous phase was estimated and attributed to TiO{sub 2}. Highlights: Black-Right-Pointing-Pointer Ti/Ce oxides were prepared using reverse micelles of Triton X-114. Black-Right-Pointing-Pointer Crystallization of TiO{sub 2}, CeO{sub 2} or CeTi{sub 2}O{sub 6} depends on Ti:Ce molar ratio. Black-Right-Pointing-Pointer Amorphous phase attributed to TiO{sub 2} was identified. Black-Right-Pointing-Pointer Metal oxides surface area is influenced by the character of present carbon impurities.

  17. Preliminary results from Radiation Environment Investigations on GIOVE-A

    NASA Astrophysics Data System (ADS)

    Underwood, C. I.; Taylor, B.; Ryden, K. A.; Rodgers, D. J.; Dyer, C. S.; Evans, H. D. R.; Daly, E. J.

    GIOVE-A is a small satellite build by SSTL UK for the European Space Agency as a first element of its Galileo satellite navigation programme GIOVE-A s primary payload is a navigation payload to secure use of the frequencies allocated by the International Telecommunications Union ITU for the Galileo system and to demonstrate critical technologies for the navigation payload of future operational Galileo satellites It also includes radiation environments and effects experiments constructed by the University of Surrey CEDEX and QinetiQ MERLIN to characterise the hazardous MEO environment GIOVE-A was launched 28 December 2005 into a 24000 km circular orbit with 56 degree inclination The environment experiments contain detectors to register the electron proton and ion signals and also to investigate the resulting total dose and charging environments The payloads will be described and preliminary results will be presented

  18. Reverse micelles directed synthesis of TiO2-CeO2 mixed oxides and investigation of their crystal structure and morphology

    NASA Astrophysics Data System (ADS)

    Matějová, Lenka; Valeš, Václav; Fajgar, Radek; Matěj, Zdeněk; Holý, Václav; Šolcová, Olga

    2013-02-01

    The synthesis of TiO2-CeO2 mixed oxides based on the sol-gel process controlled within reverse micelles of non-ionic surfactant Triton X-114 in cyclohexane is reported. The crystallization, phase composition, trends in nanoparticles growth and porous structure properties are studied as a function of Ti:Ce molar composition and annealing temperature by in-situ X-ray diffraction, Raman spectroscopy and physisorption. The brannerite-type CeTi2O6 crystallizes as a single crystalline phase at Ti:Ce molar composition of 70:30 and in the mixture with cubic CeO2 and anatase TiO2 for composition 50:50. At Ti:Ce molar ratios 90:10 and 30:70 the mixtures of TiO2 anatase, rutile and cubic CeO2 appear. In these mixtures TiO2 rutile is formed at higher temperatures than conventionally. Additionally, the amount of a present amorphous phase in individual mixtures was estimated from diffraction data. The porous structure morphology depends both on molar composition and annealing temperature. This is correlated with the presence of carbon impurities of different character.

  19. 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.

  20. 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.

  1. Co-delivery of hydrophobic paclitaxel and hydrophilic AURKA specific siRNA by redox-sensitive micelles for effective treatment of breast cancer.

    PubMed

    Yin, Tingjie; Wang, Lei; Yin, Lifang; Zhou, Jianping; Huo, Meirong

    2015-08-01

    In this study, a novel redox-sensitive micellar system constructed from a hyaluronic acid-based amphiphilic conjugate (HA-ss-(OA-g-bPEI), HSOP) was successfully developed for tumor-targeted co-delivery of paclitaxel (PTX) and AURKA specific siRNA (si-AURKA). HSOP exhibited excellent loading capacities for both PTX and siRNA with adjustable dosing ratios and desirable redox-sensitivity independently verified by morphological changes of micelles alongside in vitro release of both drugs in different reducing environments. Moreover, flow cytometry and confocal microscopy analysis confirmed that HSOP micelles were capable of simultaneously delivering PTX and siRNA into MDA-MB-231 breast cancer cells via HA-receptor mediated endocytosis followed by rapid transport of cargoes into the cytosol. Successful delivery and transport amplified the synergistic effects between the drugs while leading to substantially greater antitumor efficacy when compared with single drug-loaded micelles and non-sensitive co-loaded micelles. In vivo investigation demonstrated that HSOP micelles could effectively accumulate in tumor sites and possessed the greatest antitumor efficacy over non-sensitive co-delivery control and redox-sensitive single-drug controls. These findings indicated that redox-sensitive HSOP co-delivery system holds great promise for combined drug/gene treatment for targeted cancer therapy.

  2. Morphology and local organization of water-containing (1R,2S)-dodecyl(2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium bromide reverse micelles dispersed in toluene.

    PubMed

    Longo, Alessandro; Giannici, Francesco; Portale, Giuseppe; Banerjee, Dipanjan; Calandra, Pietro; Turco Liveri, Vincenzo

    2014-08-28

    The structure of (1R,2S)-dodecyl(2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium bromide (DMEB) reverse micelles, at various water-to-surfactant molar ratio (Rw, Rw = [water]/[DMEB]) and DMEB concentrations, has been investigated by small angle X-ray scattering (SAXS) and extended X-ray absorption fine structure spectroscopy (EXAFS). SAXS data of dry reverse micelles are consistent with a model of spherical hydrophilic core surrounded by DMEB alkyl chains whose polydispersity decreases significantly with surfactant concentration. By adding water, a sphere to cylinder transition occurs leading to a one-dimensional growth of reverse micellar cores with Rw and surfactant concentration. The observed behavior was taken as an indication that water molecules are confined in the core of DMEB reverse micelles, quite uniformly distributed among them and mainly located among surfactant head groups. EXAFS data allow to focus within the hydrophilic micellar core to solve the short range local environment around the Br(-) counterion and to follow its changing with surfactant concentration and Rw. Analysis of Fourier transform of the EXAFS spectra indicates the existence of a local order nearby the bromide ions; pointing toward a quite structured hydrophilic core of DMEB reverse micelles. However, as a consequence of the fluid nature of reverse micelles, such local order is lower than that found in the lamellar structure of solid DMEB. Water confinement within the reverse micellar cores induces an increase of the local disorder suggesting an enhancement of the micellar core dynamics.

  3. Morphology and local organization of water-containing (1R,2S)-dodecyl(2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium bromide reverse micelles dispersed in toluene

    NASA Astrophysics Data System (ADS)

    Longo, Alessandro; Giannici, Francesco; Portale, Giuseppe; Banerjee, Dipanjan; Calandra, Pietro; Liveri, Vincenzo Turco

    2014-08-01

    The structure of (1R,2S)-dodecyl(2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium bromide (DMEB) reverse micelles, at various water-to-surfactant molar ratio (Rw, Rw = [water]/[DMEB]) and DMEB concentrations, has been investigated by small angle X-ray scattering (SAXS) and extended X-ray absorption fine structure spectroscopy (EXAFS). SAXS data of dry reverse micelles are consistent with a model of spherical hydrophilic core surrounded by DMEB alkyl chains whose polydispersity decreases significantly with surfactant concentration. By adding water, a sphere to cylinder transition occurs leading to a one-dimensional growth of reverse micellar cores with Rw and surfactant concentration. The observed behavior was taken as an indication that water molecules are confined in the core of DMEB reverse micelles, quite uniformly distributed among them and mainly located among surfactant head groups. EXAFS data allow to focus within the hydrophilic micellar core to solve the short range local environment around the Br- counterion and to follow its changing with surfactant concentration and Rw. Analysis of Fourier transform of the EXAFS spectra indicates the existence of a local order nearby the bromide ions; pointing toward a quite structured hydrophilic core of DMEB reverse micelles. However, as a consequence of the fluid nature of reverse micelles, such local order is lower than that found in the lamellar structure of solid DMEB. Water confinement within the reverse micellar cores induces an increase of the local disorder suggesting an enhancement of the micellar core dynamics.

  4. Production Scaleup of Reverse Micelle Synthesis

    SciTech Connect

    Morrison,S.; Cahill, C.; Carpenter, E.; Harris, V.

    2006-01-01

    A wide range of techniques for the successful synthesis of nanosized materials have been developed recently. These procedures are sufficient for normal scientific investigation; however, for these materials to be incorporated into any practical application, the process for making them must be scalable to a larger volume. In this work, we focus on a published recipe for manganese zinc ferrite (MZFO) nanoparticles, which uses the reverse micelle synthesis technique. The normal bench-top synthesis has been scaled by a factor of 40 and successfully adapted to a 30-L pilot plant. The product of this synthesis is similar to the bench-top sample, which is also comparable to a ceramic MZFO standard. Through this work, we have demonstrated that the reverse micelle process is scalable to larger volumes.

  5. Preparation and characterization of magnetic thermosensitive fluorouracil micelles.

    PubMed

    Zhang, Min; Jin, Xueqin; Gou, Guojing

    2016-01-01

    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

  6. 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.

  7. Comparative Fluorescence Resonance Energy-Transfer Study in Pluronic Triblock Copolymer Micelle and Niosome Composed of Biological Component Cholesterol: An Investigation of Effect of Cholesterol and Sucrose on the FRET Parameters.

    PubMed

    Roy, Arpita; Kundu, Niloy; Banik, Debasis; Sarkar, Nilmoni

    2016-01-14

    The formation of pluronic triblock copolymer (F127)-cholesterol-based niosome and its interaction with sugar (sucrose) molecules have been investigated. The morphology of F127-cholesterol -based niosome in the presence of sucrose has been successfully demonstrated using dynamic light scattering (DLS) and transmission electron microscopic (TEM) techniques. The DLS profiles and TEM images clearly suggest that the size of the niosome aggregates increases significantly in the presence of sucrose. In addition to structural characterization, a detailed comparative fluorescence resonance energy transfer (FRET) study has been carried out in these F127-containing aggregates, involving coumarin 153 (C153) as donor (D) and rhodamine 6G (R6G) as an acceptor (A) to monitor the dynamic heterogeneity of the systems. Besides, time-resolved anisotropy and fluorescence correlation spectroscopy measurements have been carried out to monitor the rotational and lateral diffusion motion in these F127-cholesterol-based aggregates using C153 and R6G, respectively. During the course of FRET study, we have observed multiple time constants of FRET inside the F127-cholesterol-based niosomes in contrast with the F127 micelle. This corresponds to the presence of more than one preferential donor-acceptor (D-A) distance in niosomes than in F127 micelle. FRET has also been successfully used to probe the effect of sucrose on the morphology of F127-cholesterol-based niosome. In the presence of sucrose, the time constant of FRET further increases as the D-A distances increase in sucrose-decorated niosome. Finally, the excitation-wavelength-dependent FRET studies have indicated that as the excitation of donor molecules varies from 408 to 440 nm the contribution of the faster rise component of the acceptor enhances considerably, which clearly establishes the dynamics heterogeneity of both systems. Our findings also indicate that FRET is completely intravesicular in nature in these block copolymer

  8. Comparative Fluorescence Resonance Energy-Transfer Study in Pluronic Triblock Copolymer Micelle and Niosome Composed of Biological Component Cholesterol: An Investigation of Effect of Cholesterol and Sucrose on the FRET Parameters.

    PubMed

    Roy, Arpita; Kundu, Niloy; Banik, Debasis; Sarkar, Nilmoni

    2016-01-14

    The formation of pluronic triblock copolymer (F127)-cholesterol-based niosome and its interaction with sugar (sucrose) molecules have been investigated. The morphology of F127-cholesterol -based niosome in the presence of sucrose has been successfully demonstrated using dynamic light scattering (DLS) and transmission electron microscopic (TEM) techniques. The DLS profiles and TEM images clearly suggest that the size of the niosome aggregates increases significantly in the presence of sucrose. In addition to structural characterization, a detailed comparative fluorescence resonance energy transfer (FRET) study has been carried out in these F127-containing aggregates, involving coumarin 153 (C153) as donor (D) and rhodamine 6G (R6G) as an acceptor (A) to monitor the dynamic heterogeneity of the systems. Besides, time-resolved anisotropy and fluorescence correlation spectroscopy measurements have been carried out to monitor the rotational and lateral diffusion motion in these F127-cholesterol-based aggregates using C153 and R6G, respectively. During the course of FRET study, we have observed multiple time constants of FRET inside the F127-cholesterol-based niosomes in contrast with the F127 micelle. This corresponds to the presence of more than one preferential donor-acceptor (D-A) distance in niosomes than in F127 micelle. FRET has also been successfully used to probe the effect of sucrose on the morphology of F127-cholesterol-based niosome. In the presence of sucrose, the time constant of FRET further increases as the D-A distances increase in sucrose-decorated niosome. Finally, the excitation-wavelength-dependent FRET studies have indicated that as the excitation of donor molecules varies from 408 to 440 nm the contribution of the faster rise component of the acceptor enhances considerably, which clearly establishes the dynamics heterogeneity of both systems. Our findings also indicate that FRET is completely intravesicular in nature in these block copolymer

  9. Structure and stability of complex coacervate core micelles with lysozyme.

    PubMed

    Lindhoud, Saskia; Vries, Renko de; Norde, Willem; Stuart, Martien A Cohen

    2007-07-01

    Encapsulation of enzymes by polymers is a promising method to influence their activity and stability. Here, we explore the use of complex coacervate core micelles for encapsulation of enzymes. The core of the micelles consists of negatively charged blocks of the diblock copolymer PAA42PAAm417 and the positively charged homopolymer PDMAEMA150. For encapsulation, part of the positively charged homopolymer was replaced by the positively charged globular protein lysozyme. We have studied the formation, structure, and stability of the resulting micelles for three different mixing ratios of homopolymer and lysozyme: a system predominantly consisting of homopolymer, a system predominantly consisting of lysozyme, and a system where the molar ratio between the two positively charged molecules was almost one. We also studied complexes made of only lysozyme and PAA42PAAm417. Complex formation and the salt-induced disintegration of the complexes were studied using dynamic light-scattering titrations. Small-angle neutron scattering was used to investigate the structures of the cores. We found that micelles predominantly consisting of homopolymer are spherical but that complex coacervate core micelles predominantly consisting of lysozyme are nonspherical. The stability of the micelles containing a larger fraction of lysozyme is lower.

  10. Tuning micelle dimensions and properties with binary surfactant mixtures.

    PubMed

    Oliver, Ryan C; Lipfert, Jan; Fox, Daniel A; Lo, Ryan H; Kim, Justin J; Doniach, Sebastian; Columbus, Linda

    2014-11-11

    Detergent micelles are used in many areas of research and technology, in particular, as mimics of the cellular membranes in the purification and biochemical and structural characterization of membrane proteins. Applications of detergent micelles are often hindered by the limited set of properties of commercially available detergents. Mixtures of micelle-forming detergents provide a means to systematically obtain additional micellar properties and expand the repertoire of micelle features available; however, our understanding of the properties of detergent mixtures is still limited. In this study, the shape and size of binary mixtures of seven different detergents commonly used in molecular host-guest systems and membrane protein research were investigated. The data suggests that the detergents form ideally mixed micelles with sizes and shapes different from those of pure individual micelles. For most measurements of size, the mixtures varied linearly with detergent mole fraction and therefore can be calculated from the values of the pure detergents. We propose that properties such as the geometry, size, and surface charge can be systematically and predictably tuned for specific applications.

  11. Synthesis and agglomeration of gold nanoparticles in reverse micelles

    NASA Astrophysics Data System (ADS)

    Herrera, Adriana P.; Resto, Oscar; Briano, Julio G.; Rinaldi, Carlos

    2005-07-01

    Reverse micelles prepared in the system water, sodium bis-(2-ethylhexyl) sulfoccinate (AOT), and isooctane were investigated as a templating system for the production of gold nanoparticles from Au(III) and the reducing agent sulfite. A core-shell Mie model was used to describe the optical properties of gold nanoparticles in the reverse micelles. Dynamic light scattering of gold colloids in aqueous media and in reverse micelle solution indicated agglomeration of micelles containing particles. This was verified theoretically with an analysis of the total interaction energy between pairs of particles as a function of particle size. The analysis indicated that particles larger than about 8 nm in diameter should reversibly flocculate. Transmission electron microscopy measurements of gold nanoparticles produced in our reverse micelles showed diameters of 8-10 nm. Evidence of cluster formation was also observed. Time-correlated UV-vis absorption measurements showed a red shift for the peak wavelength. This was interpreted as the result of multiple scattering and plasmon interaction between particles due to agglomeration of micelles with particles larger than 8 nm.

  12. 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.

  13. Design and synthesis of pH-sensitive polymeric micelles for oral delivery of poorly water-soluble drugs.

    PubMed

    Yang, Xiaolan; Fan, Rongrong; Wang, Wenlong; Wang, Jiexin; Le, Yuan

    2016-09-01

    pH-sensitive polymer poly (polylactide-co-methacrylic acid)-b-poly (acrylic acid) was synthesized using atom transfer radical polymerization and ring-opening polymerization and characterized by gel permeation chromatography and (1)H NMR. The polymers can self-assemble to form micelles in aqueous medium, which respond rapidly to pH change within the gastrointestinal relevant pH range. Critical micelle concentrations and pH response behavior of the polymeric micelle were investigated. Water-insoluble drug nifedipine was loaded and the drug-loading content can be controlled by tuning the composition of the polymers. The in vitro release studies indicate pH sensitivity enabled rapid drug release at the environment of simulated intestinal fluid (pH 7.36), the cumulative released amount of NFD reached more than 80% within 24 h, while only 35% in the simulated gastric fluid (pH 1.35). All the results showed that the pH-sensitive P(PLAMA-co-MAA)-b-PAA micelle may be a prospective candidate as oral drug delivery carrier for hydrophobic drugs with controlled release behavior. PMID:27342342

  14. Design and synthesis of pH-sensitive polymeric micelles for oral delivery of poorly water-soluble drugs.

    PubMed

    Yang, Xiaolan; Fan, Rongrong; Wang, Wenlong; Wang, Jiexin; Le, Yuan

    2016-09-01

    pH-sensitive polymer poly (polylactide-co-methacrylic acid)-b-poly (acrylic acid) was synthesized using atom transfer radical polymerization and ring-opening polymerization and characterized by gel permeation chromatography and (1)H NMR. The polymers can self-assemble to form micelles in aqueous medium, which respond rapidly to pH change within the gastrointestinal relevant pH range. Critical micelle concentrations and pH response behavior of the polymeric micelle were investigated. Water-insoluble drug nifedipine was loaded and the drug-loading content can be controlled by tuning the composition of the polymers. The in vitro release studies indicate pH sensitivity enabled rapid drug release at the environment of simulated intestinal fluid (pH 7.36), the cumulative released amount of NFD reached more than 80% within 24 h, while only 35% in the simulated gastric fluid (pH 1.35). All the results showed that the pH-sensitive P(PLAMA-co-MAA)-b-PAA micelle may be a prospective candidate as oral drug delivery carrier for hydrophobic drugs with controlled release behavior.

  15. Micelle Formation in Liquid Ammonia.

    PubMed

    Griffin, Joseph M; Atherton, John H; Page, Michael I

    2015-07-17

    Perfluorinated long chain alkyl amides aggregate in liquid ammonia with increasing concentration which reflects micelle-type formation based on changes in (19)F NMR chemical shifts. The critical micelle concentrations (cmc) decrease with increasing chain length and give Kleven parameters A = 0.18 and B = 0.19. The micelles catalyze the ammonolysis of esters in liquid ammonia. The corresponding perfluorinated long chain alkyl carboxylates form ion pairs in liquid ammonia, but the equilibrium dissociation constants indicate favorable interactions between the chains in addition to the electrostatic forces. These perfluorinated carboxylates form micelles in aqueous solution, and their cmc's generate a Kleven B-value = 0.52 compared with 0.30 for the analogous alkyl carboxylates. The differences in hydrophobicity of CH2 and CF2 units in water and liquid ammonia are discussed, as is the possible relevance to life forms in liquid ammonia.

  16. 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.

  17. 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.

  18. Structural changes of a sodium dodecyl sulfate (SDS) micelle induced by alcohol molecules.

    PubMed

    Méndez-Bermúdez, Jose G; Dominguez, Hector

    2016-01-01

    Coarse-grained dynamical simulations have been performed to investigate the behavior of a surfactant micelle in the presence of six different alcohols: hexanol, octanol, decanol, dodecanol, tetradecanol, and hexadecanol. The self-assembly of sodium dodecyl sulfate (SDS) is modified by the alcohol molecules into cylindrical and bilayer micelles as a function of the alcohol/SDS mass ratio. Therefore, in order to understand, from a molecular point of view, how SDS and alcohol molecules self-organize to form the new micelles, different studies were carried out. Analysis of micelle structures, density profiles, and parameters of order were conducted to characterize the shape and size of those micelles. The density profiles revealed that the alcohol molecules were located at the water-micelle interface next to the SDS molecules at low alcohol/SDS mass ratio. At high alcohol/SDS mass ratios, alcohol molecules moved to the middle of the micelle by increasing their size and by producing a structural change. Moreover, micelle structures and sizes were influenced not only by the alcohol/SDS mass ratio but also by the order of the SDS and alcohol tails. Finally, the size of the micelles and enthalpy calculations were used as order parameters to determine a structural phase diagram of alcohol/SDS mixtures in water. Graphical Abstract Structural transition of SDS/alcohol mixtures. PMID:26768159

  19. Facile fabrication of core cross-linked micelles by RAFT polymerization and enzyme-mediated reaction.

    PubMed

    Wu, Yukun; Lai, Quanyong; Lai, Shuqi; Wu, Jing; Wang, Wei; Yuan, Zhi

    2014-06-01

    Polymeric micelles formed in aqueous solution by assembly of amphiphilic block copolymers have been extensively investigated due to their great potential as drug carriers. However, the stability of polymeric assembly is still one of the major challenges in delivering drugs to tissues and cells. Here, we report a facile route to fabricate core cross-linked (CCL) micelles using an enzymatic polymerization as the cross-linking method. We present synthesis of poly(ethylene glycol)-block-poly(N-isopropyl acrylamide-co-N-(4-hydroxyphenethyl) acrylamide) diblock copolymer PEG-b-P(NIPAAm-co-NHPAAm) via reversible addition-fragmentation chain transfer (RAFT) polymerization. The diblock copolymer was then self-assembled into non-cross-linked (NCL) micelles upon heating above the lower critical solution temperature (LCST), and subsequently cross-linked using horseradish peroxidase (HRP) and hydrogen peroxide (H2O2) as enzyme and oxidant. The characterization of the diblock copolymer and micelles were studied by NMR, DLS, UV-vis, and fluorescence spectroscopy. The fluorescence study reveals that the cross-linking process endows the micelles with much lower critical micelle concentration (CMC). In addition, the drug release study shows that the CCL micelles have lower release amount of doxorubicin (DOX) than the NCL micelles due to the enhanced stability of the CCL micelles by core cross-linking process. PMID:24768266

  20. Investigation of high voltage spacecraft system interactions with plasma environments

    NASA Technical Reports Server (NTRS)

    Stevens, N. J.; Berkopec, F. D.; Purvis, C. K.; Grier, N.; Staskus, J.

    1978-01-01

    The exposure of high voltage spacecraft systems to the charged particle environment of space can produce interactions that will influence system operation. An experimental investigation of these interactions has been undertaken for insulator and conductor test surfaces biased up to plus or minus 1 kV in a simulated low earth orbit charged particle environment. It has been found that these interactions are controlled by the insulator surfaces surrounding the biased conductors. For positive applied voltages the electron current collection can be enhanced by the insulators. For negative applied voltages the insulator surface confines the voltage to the conductor region; this can cause arcing. Understanding these interactions and the technology to control their impact on system operation is essential to the design of solar cell arrays for ion drive propulsion applications that use direct drive power processing.

  1. Application of air remote sensing in investigation of engineering environment

    SciTech Connect

    Kejie, L.

    1996-11-01

    Engineering environment is a research field with broad scope in which air remote sensing can play an important role. Longtan Reservoir is located in a mountainous region with high ridges and deep canyons. Air remote sensing technique was used to evaluate engineering environment of the reservoir area. Various types of land use were interpreted and mapped on a scale of 1:10000 by using infrared color orthophoto, and selecting training samples, meanwhile types and dimensions of slumps and landslides were recognized and measured within the reservoir area. Furthermore an evaluation and regionalization of slope stability of reservoir bank were carried out. Finally a precision over 90% was given for the results of this investigation by field sampling checking. 3 refs., 1 fig., 2 tabs.

  2. Investigation of high voltage spacecraft system interactions with plasma environments

    NASA Technical Reports Server (NTRS)

    Stevens, N. J.; Berkopec, F. D.; Purvis, C. K.; Grier, N.; Staskus, J. V.

    1978-01-01

    An experimental investigation was undertaken for insulator and conductor test surfaces biased up to + or - 1kV in a simulated low earth orbit charged particle environment. It was found that these interactions are controlled by the insulator surfaces surrounding the biased conductors. For positive applied voltages the electron current collection can be enhanced by the insulators. For negative applied voltages the insulator surface confines the voltage to the conductor region. Understanding these interactions and the technology to control their impact on system operation is essential to the design of solar cell arrays for ion drive propulsion applications that use direct drive power processing.

  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. 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.

  5. Spectroscopic investigation of the binding interactions of a membrane potential molecule in various supramolecular confined environments: contrasting behavior of surfactant molecules in relocation or release of the probe between nanocarriers and DNA surface.

    PubMed

    Ghosh, Surajit; Banik, Debasis; Roy, Arpita; Kundu, Niloy; Kuchlyan, Jagannath; Sarkar, Nilmoni

    2014-12-01

    The fluorescence and optical properties of membrane potential probes are widely used to measure cellular transmembrane potentials. Hemicyanine dyes are also able to bind to membranes. The spectral properties of these molecules depend upon the charge shift from the donor moiety to the acceptor moiety. Changes in their spectral properties, i.e. absorption and emission maxima or intensities, are helpful in characterizing model membranes, microheterogeneous media, etc. In this article, we have demonstrated the binding interaction of a membrane potential probe, 1-ethyl-2-(4-(p-dimethylaminophenyl)-1,3-butadienyl)-pyridinium perchlorate (LDS 698), with various supramolecular confined environments. The larger dipole moment in the ground state compared to the excited state is a unique feature of hemicyanine dyes. Due to this unique feature, red shifts in the absorption maxima are observed in hydrophobic environments, compared with bulk solvent. On addition of surfactants and CT DNA to an aqueous solution containing LDS 698, significant increase in the emission intensity along with the quantum yield and lifetime indicate partition of the probe molecules into organized assemblies. In the case of the sodium dodecyl sulfate (SDS)-water system, due to interactions between the cationic LDS 698 and the anionic dodecyl sulfate moiety, the fluorescence intensity at ∼666 nm decreases and an additional peak at ∼590 nm appears at premicellar concentration (∼0.20 mM-4.50 mM). But at ∼5.50 mM SDS concentration, the absorbance in the higher wavelength region increases again, indicating encapsulation of the probe in micellar aggregates. This observation indicates that the premicellar aggregation behavior of SDS can also be judged by observing the changes in the UV-vis and fluorescence spectral patterns. The temperature dependent study also indicates that non-radiative deactivation of the dye molecules is highly restricted in the DNA micro-environment, compared with micelles

  6. Microbiology of subsurface environments: Proceedings second investigators' meeting

    SciTech Connect

    Not Available

    1986-01-01

    The agenda of this meeting was to provide for: (1) general reports by the principal investigators on the initial scientific findings from the Savannah River Site cores; (2) a feedback session during which the principal investigators and others in attendance can provide a critique on how the program can be improved; (3) presentations by scientists on research that may be related to the program. The preliminary scientific results indicate that a diverse, metabolically active microbial community is present in unconsolidated materials to depths of 400 meters below the surface of the Savannah River study site. A thorough characterization of samples revealed that deep subsurface environments are inhabited by microorganisms that range from denitrifying, sulfate-reducing, and methanogenic bacteria to aerobic heterotrophs, autotrophs, fungi, and protozoa. These results have implications in the use of indigenous microorganisms for biological decontamination of deep aquifers or as a biobarrier to contaminant movement, development of strategies to cope with health problems arising from contamination of aquifers by pathogenic microorganisms, reduction of biocorrosion of waste containers planned for storage in deep subsurface environments, and as a source of new organisms or metabolic capabilities for biotechnological applications.

  7. 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

  8. Intracellular Doxorubicin Delivery of a Core Cross-linked, Redox-responsive Polymeric Micelles.

    PubMed

    Lili, Yu; Ruihua, Mu; Li, Li; Fei, Liang; Lin, Yao; Li, Su

    2016-02-10

    Redox-responsive micelles based on amphiphilic polyethylene glycol-polymethyl methacrylate with the introduction of disulfide containing cross-linked agent (mPEG-PMMA-SS) were developed for intracellular drug release. Benefiting from the amphiphilicity, mPEG-PMMA-SS could self-assembled into core cross-linked micelles in aqueous medium with tunable sizes (85-151 nm), appropriate zeta potential (-24.8 mV), and desirable critical micelle concentration (CMC) (0.18 mg/mL). Doxorubicin (DOX) could efficiently load into the micelles with satisfactory entrapment efficiency. As expected, the in vitro release studies displayed that DOX release from mPEG-PMMA-SS micelles was about 75% within 10h under tumor-relevant reductive condition, whereas only about 25% DOX was released in non-reductive medium. SRB assays indicated that these mPEG-PMMA-SS micelles were biocompatible and nontoxic up to a concentration of 50 μg/mL. The cytotoxicity studies and the intracellular drug delivery demonstrated that the drug release behavior in cells was related to the concentration of GSH in cytoplasm. Furthermore, the cell experiments using fluorescence microscopy showed clearly that DOX was delivered by micelles to the cytoplasm, released in cytoplasm under reductive environment, and then accumulated in cell nucleus. These results suggest that such redox-responsive micelles may develop into an efficient cytoplasmic delivery for hydrophobic anticancer drugs.

  9. 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

  10. Tumor homing indocyanine green encapsulated micelles for near infrared and photoacoustic imaging of tumors.

    PubMed

    Uthaman, Saji; Bom, Joon-suk; Kim, Hyeon Sik; John, Johnson V; Bom, Hee-Seung; Kim, Seon-Jong; Min, Jung-Joon; Kim, Il; Park, In-Kyu

    2016-05-01

    Photoacoustic imaging (PAI) is an emerging analytical modality that is under intense preclinical development for the early diagnosis of various medical conditions, including cancer. However, the lack of specific tumor targeting by various contrast agents used in PAI obstructs its clinical applications. In this study, we developed indocyanine green (ICG)-encapsulated micelles specific for the CD 44 receptor and used in near infrared and photoacoustic imaging of tumors. ICG was hydrophobically modified prior to loading into hyaluronic acid (HA)-based micelles utilized for CD 44 based-targeting. We investigated the physicochemical characteristics of prepared HA only and ICG-encapsulated HA micelles (HA-ICG micelles). After intravenous injection of tumor-bearing mice, the bio-distribution and in vivo photoacoustic images of ICG-encapsulated HA micelles accumulating in tumors were also investigated. Our study further encourages the application of this HA-ICG-based nano-platform as a tumor-specific contrast agent for PAI.

  11. Stability of complex coacervate core micelles containing metal coordination polymer.

    PubMed

    Yan, Yun; de Keizer, Arie; Cohen Stuart, Martien A; Drechsler, Markus; Besseling, Nicolaas A M

    2008-09-01

    We report on the stability of complex coacervate core micelles, i.e., C3Ms (or PIC, BIC micelles), containing metal coordination polymers. In aqueous solutions these micelles are formed between charged-neutral diblock copolymers and oppositely charged coordination polymers formed from metal ions and bisligand molecules. The influence of added salt, polymer concentration, and charge composition was investigated by using light scattering and cryo-TEM techniques. The scattering intensity decreases strongly with increasing salt concentration until a critical salt concentration beyond which no micelles exist. The critical micelle concentration increases almost exponentially with the salt concentration. From the scattering results it follows that the aggregation number decreases with the square root of the salt concentration, but the hydrodynamic radius remains constant or increases slightly. It was concluded that the density of the core decreases with increasing ionic strength. This is in agreement with theoretical predictions and is also confirmed by cryo-TEM measurements. A complete composition diagram was constructed based on the composition boundaries obtained from light scattering titrations.

  12. Nanoporous Electrospun Fibrous Meshes: Size-Controlled Reverse Micelles Strategy.

    PubMed

    Mao, Wei; Yoo, Hyuk Sang

    2016-05-01

    A simple and efficient method to fabricate size-controlled nanoporous-nanofibrous meshes has been demonstrated by introducing and removing novel size-controllable porogens, reverse micelles, on electrospun polymeric nanofibers. Poly(D,L-lactide) and reverse micelles composed of amphiphilic diblock copolymer, poly(ethylene glycol) methyl ether-block-poly(ε-caprolactone), were first dissolved in an acetone/chloroform (3:1, v/v) mixture and then electrospun into nanofibers, followed by 70% EtOH post-treatment. During the post-treatment, the reverse micelles were dissolved in 70% EtOH at room temperature thus separated from the poly(D,L-lactide) nanofibers backbone, resulting in a nanoporous nanofibrous structure. The pores on the nanofibers are size-controllable because the sizes of the reverse micelles can be adjusted by varying the water content inside them. The sizes of reverse micelles, which ranged from 100 nm to 700 nm, are investigated by dynamic light scattering. The pores of various sizes on the poly(D,L-lactide) nanofibers have areas ranging from 20 μm2 to 80 μm2 were observed by field-emission scanning electron microscopy. PMID:27483927

  13. Protein and water confined in nanometer-scale reverse micelles studied by near infrared, terahertz, and ultrafast visible spectroscopies.

    PubMed

    Murakami, Hiroshi

    2013-01-01

    Protein-containing reverse (PCR) micelles are suitable systems to study the properties of proteins and waters in a cell-like environment. A model for determining the structural parameters of PCR micelles, such as the aqueous cavity size and molecule number of water within the reverse micelle, is presented. The model is based on an important hypothesis that the structural parameters of the protein-unfilled reverse micelle do not change after solubilization of protein. I describe a procedure using near infrared spectroscopy of OH stretching vibration band of water to verify the hypothesis. Further, the terahertz (THz) absorption spectrum of myoglobin is derived from THz time-domain spectroscopy of the PCR micellar solution, and the states of waters in reverse micelles with and without protein are discussed on the basis of the structural parameters. The last topic is on internal dynamics of PCR micelles on timescales from femtoseconds to nanoseconds studied by femtosecond time-resolved fluorescence spectroscopy.

  14. Numerical Investigation of Laser Propulsion for Transport in Water Environment

    SciTech Connect

    Han Bing; Li Beibei; Zhang Hongchao; Chen Jun; Shen Zhonghua; Lu Jian; Ni Xiaowu

    2010-10-08

    Problems that cumber the development of the laser propulsion in atmosphere and vacuum are discussed. Based on the theory of interaction between high-intensity laser and materials, as air and water, it is proved that transport in water environment can be impulsed by laser. The process of laser propulsion in water is investigated theoretically and numerically. It shows that not only the laser induced plasma shock wave, but also the laser induced bubble oscillation shock waves and the pressure induced by the collapsing bubble can be used. Many experimental results show that the theory and the numerical results are valid. The numerical result of the contribution of every propulsion source is given in percentage. And the maximum momentum coupling coefficient Cm is given. Laser propulsion in water environment can be applied in many fields. For example, it can provide highly controllable forces of the order of micro-Newton ({mu}N) in microsystems, such as the MEMS (Micro-electromechanical Systems). It can be used as minimally invasive surgery tools of high temporal and spatial resolution. It can be used as the propulsion source in marine survey and exploitation.

  15. Archival Legacy Investigation of Circumstellar Environments (ALICE). Survey results

    NASA Astrophysics Data System (ADS)

    Soummer, Remi; Choquet, Elodie; Pueyo, Laurent; Brendan Hagan, J.; Gofas-Salas, Elena; Rajan, Abhijith; Chen, Christine; Perrin, Marshall D.; Debes, John H.; Golimowski, David A.; Hines, Dean C.; N'Diaye, Mamadou; Schneider, Glenn; Mawet, Dimitri; Marois, Christian

    2016-01-01

    We report on the status of the ALICE project (Archival Legacy Investigation of Circumstellar Environments. HST/AR-12652), which consists in a consistent reanalysis of the entire HST-NICMOS coronagraphic archive with advanced post-processing techniques. Over the last two years, we have developed a sophisticated pipeline able to handle the data of the 400 stars of the archive. We present the results of the overall reduction campaign and discuss the first statistical analysis of the candidate detections. As we will deliver high-level science products to the STScI MAST archive, we are defining a new standard format for high-contrast science products, which will be compatible with every new high-contrast imaging instrument and used by the JWST coronagraphs. We present here an update and overview of the specifications of this standard.

  16. Experimental Investigation of Organic Synthesis in Hydrothermal Environments

    NASA Technical Reports Server (NTRS)

    Shock, Everett L.

    1998-01-01

    The results of the investigation were presented at a Astrobiology Institute General Meeting. Seafloor hydrothermal systems may be the most likely locations on the early Earth for the emergence of life. Because of the disequilibrium inherent in such dynamic, mixing environments, abundant chemical energy would have been available for formation of the building blocks of life. In addition, theoretical studies suggest that organic compounds in these conditions would reach metastable states, due to kinetic barriers to the formation of stable equilibrium products (CO2 and methane). The speciation of organic carbon in metastable states is highly dependent on the oxidation state, pH, temperature, pressure and bulk composition of the system. The goal of our research is to investigate the effects of a number external variables on the formation, transformation, and stability of organic compounds at hydrothermal conditions. We have begun experimental work to attempt to control the oxidation state of simulated hydrothermal systems by using buffers composed of mineral powders and gas mixtures. We are also beginning to test the stability of organic compounds under these conditions.

  17. 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.

  18. Preparation of Two Types of Polymeric Micelles Based on Poly(β-L-Malic Acid) for Antitumor Drug Delivery.

    PubMed

    Yang, Tiehong; Li, Wei; Duan, Xiao; Zhu, Lin; Fan, Li; Qiao, Youbei; Wu, Hong

    2016-01-01

    Polymeric micelles represent an effective delivery system for poorly water-soluble anticancer drugs. In this work, two types of CPT-conjugated polymers were synthesized based on poly(β-L-malic acid) (PMLA) derivatives. Folic acid (FA) was introduced into the polymers as tumor targeting group. The micellization behaviors of these polymers and antitumor activity of different self-assembled micelles were investigated. Results indicate that poly(ethylene glycol)-poly(β-L-malic acid)-campotothecin-I (PEG-PMLA-CPT-I, P1) is a grafted copolymer, and could form star micelles in aqueous solution with a diameter of about 97 nm, also that PEG-PMLA-CPT-II (P2) is an amphiphilic block copolymer, and could form crew cut micelles with a diameter of about 76 nm. Both P1 and P2 micelles could improve the cellular uptake of CPT, especially the FA-modified micelles, while P2 micelles showed higher stability, higher drug loading efficiency, smaller size, and slower drug release rate than that of P1 micelles. These results suggested that the P2 (crew cut) micelles possess better stability than that of the P1 (star) micelles and might be a potential drug delivery system for cancer therapy.

  19. 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

  20. Preparation of Two Types of Polymeric Micelles Based on Poly(β-L-Malic Acid) for Antitumor Drug Delivery.

    PubMed

    Yang, Tiehong; Li, Wei; Duan, Xiao; Zhu, Lin; Fan, Li; Qiao, Youbei; Wu, Hong

    2016-01-01

    Polymeric micelles represent an effective delivery system for poorly water-soluble anticancer drugs. In this work, two types of CPT-conjugated polymers were synthesized based on poly(β-L-malic acid) (PMLA) derivatives. Folic acid (FA) was introduced into the polymers as tumor targeting group. The micellization behaviors of these polymers and antitumor activity of different self-assembled micelles were investigated. Results indicate that poly(ethylene glycol)-poly(β-L-malic acid)-campotothecin-I (PEG-PMLA-CPT-I, P1) is a grafted copolymer, and could form star micelles in aqueous solution with a diameter of about 97 nm, also that PEG-PMLA-CPT-II (P2) is an amphiphilic block copolymer, and could form crew cut micelles with a diameter of about 76 nm. Both P1 and P2 micelles could improve the cellular uptake of CPT, especially the FA-modified micelles, while P2 micelles showed higher stability, higher drug loading efficiency, smaller size, and slower drug release rate than that of P1 micelles. These results suggested that the P2 (crew cut) micelles possess better stability than that of the P1 (star) micelles and might be a potential drug delivery system for cancer therapy. PMID:27649562

  1. Preparation of Two Types of Polymeric Micelles Based on Poly(β-L-Malic Acid) for Antitumor Drug Delivery

    PubMed Central

    Duan, Xiao; Zhu, Lin; Fan, Li; Qiao, Youbei; Wu, Hong

    2016-01-01

    Polymeric micelles represent an effective delivery system for poorly water-soluble anticancer drugs. In this work, two types of CPT-conjugated polymers were synthesized based on poly(β-L-malic acid) (PMLA) derivatives. Folic acid (FA) was introduced into the polymers as tumor targeting group. The micellization behaviors of these polymers and antitumor activity of different self-assembled micelles were investigated. Results indicate that poly(ethylene glycol)-poly(β-L-malic acid)-campotothecin-I (PEG-PMLA-CPT-I, P1) is a grafted copolymer, and could form star micelles in aqueous solution with a diameter of about 97 nm, also that PEG-PMLA-CPT-II (P2) is an amphiphilic block copolymer, and could form crew cut micelles with a diameter of about 76 nm. Both P1 and P2 micelles could improve the cellular uptake of CPT, especially the FA-modified micelles, while P2 micelles showed higher stability, higher drug loading efficiency, smaller size, and slower drug release rate than that of P1 micelles. These results suggested that the P2 (crew cut) micelles possess better stability than that of the P1 (star) micelles and might be a potential drug delivery system for cancer therapy. PMID:27649562

  2. Interaction of cellulase with sodium dodecyl sulfate at critical micelle concentration level.

    PubMed

    Xiang, Jin; Fan, Jun-Bao; Chen, Nan; Chen, Jie; Liang, Yi

    2006-05-01

    The interactions between Trichoderma reesei cellulase and an anionic surfactant, sodium dodecyl sulfate (SDS), at critical micelle concentration level have been investigated using isothermal titration calorimetry, fluorescence spectroscopy, and circular dichroism. SDS micelles have dual interactions with cellulase: electrostatic at first and then hydrophobic interactions. When the concentration of SDS is smaller than 45.0mM, SDS micelles cause a partial loss in the hydrolytic activity together with a steep decrease in the alpha-helical content of cellulase. With further increasing the concentration of SDS, however, a re-formation of the alpha-helical structure and a partial recovery of the hydrolytic activity of cellulase induced by SDS micelles are observed. Taken together, these results indicate that SDS micelles exert dual effects on cellulase through binding as both a denaturant and a recovery reagent.

  3. 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.

  4. 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

  5. Doxorubicin-loaded alginate-g-poly(N-isopropylacrylamide) micelles for cancer imaging and therapy.

    PubMed

    Ahn, Dong-Gyun; Lee, Jangwook; Park, So-Young; Kwark, Young-Je; Lee, Kuen Yong

    2014-12-24

    Chemotherapy is a widely adopted method for the treatment of cancer. However, its use is often limited due to side effects produced by anti-cancer drugs. Therefore, various drug carriers, including polymeric micelles, have been investigated to find a method to overcome this limitation. In this study, alginate-based, self-assembled polymeric micelles were designed and prepared using alginate-g-poly(N-isopropylacrylamide) (PNIPAAm). Amino-PNIPAAm was chemically introduced to the alginate backbone via carbodiimide chemistry. The resulting polymer was dissolved in distilled water at room temperature and formed self-assembled micelles at 37 °C. Characteristics of alginate-g-PNIPAAm micelles were dependent on the molecular weight of PNIPAAm, the degree of substitution, and the polymer concentration. Doxorubicin (DOX), a model anti-cancer drug, was efficiently encapsulated in alginate-g-PNIPAAm micelles, and sustained release of DOX from the micelles was achieved at 37 °C in vitro. These micelles accumulated at the tumor site of a tumor-bearing mouse model as a result of the enhanced permeability and retention effect. Interestingly, DOX-loaded alginate-g-PNIPAAm micelles showed excellent anti-cancer therapeutic efficacy in a mouse model without any significant side effects. This approach to designing and tailoring natural polymer-based systems to fabricate nanoparticles at human body temperature may provide a useful means for cancer imaging and therapy. PMID:25487046

  6. 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

  7. 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.

  8. Synthesis of hybrid gold/iron oxide nanoparticles in block copolymer micelles for imaging, drug delivery and magnetic hyperthermia.

    SciTech Connect

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

    2009-10-01

    In our study, hybrid gold/iron oxide loaded thermoresponsive micelles were synthesized for combined hyperthermia and chemotherapy, and optical imaging. Polymeric micelles made of amphiphilic block copolymer of poly(N-isopropylacrylamide-co-acrylamide)-block-poly({var_epsilon}-caprolactone) were conjugated with gold/iron oxide particles which are self-assembled at the hydrophobic polymer core. Thermal sensitivity and magnetic and optical properties of the hybrid gold/iron oxide micelles were investigated for the combined therapy and optical imaging.

  9. Electrochemical Investigation of Corrosion in the Space Shuttle Launch Environment

    NASA Technical Reports Server (NTRS)

    Calle, L. M.

    2004-01-01

    Corrosion studies began at NASA/Kennedy Space Center in 1966 during the Gemini/Apollo Programs with the evaluation of long-term protective coatings for the atmospheric protection of carbon steel. An outdoor exposure facility on the beach near the launch pad was established for this purpose at that time. The site has provided over 35 years of technical information on the evaluation of the long-term corrosion performance of many materials and coatings as well as on maintenance procedures. Results from these evaluations have helped NASA find new materials and processes that increase the safety and reliability of our flight hardware, launch structures, and ground support equipment. The launch environment at the Kennedy Space Center (KSC) is extremely corrosive due to the combination of ocean salt spray, heat, humidity, and sunlight. With the introduction of the Space Shuttle in 1981, the already highly corrosive conditions at the launch pad were rendered even more severe by the acidic exhaust from the solid rocket boosters. It has been estimated that 70 tons of hydrochloric acid (HC1) are produced during a launch. The Corrosion Laboratory at NASA/KSC was established in 1985 to conduct electrochemical studies of corrosion on materials and coatings under conditions similar to those encountered at the launch pads. I will present highlights of some of these investigations.

  10. Archival legacy investigations of circumstellar environments: overview and first results

    NASA Astrophysics Data System (ADS)

    Choquet, Élodie; Pueyo, Laurent; Hagan, J. Brendan; Gofas-Salas, Elena; Rajan, Abhijith; Chen, Christine; Perrin, Marshall D.; Debes, John; Golimowski, David; Hines, Dean C.; N'Diaye, Mamadou; Schneider, Glenn; Mawet, Dimitri; Marois, Christian; Soummer, Rémi

    2014-08-01

    We are currently conducting a comprehensive and consistent re-processing of archival HST-NICMOS coronagraphic surveys using advanced PSF subtraction methods, entitled the Archival Legacy Investigations of Circumstellar Environments program (ALICE, HST/AR 12652). This virtual campaign of about 400 targets has already produced numerous new detections of previously unidentified point sources and circumstellar structures. We present five newly spatially resolved debris disks revealed in scattered light by our analysis of the archival data. These images provide new views of material around young solar-type stars at ages corresponding to the period of terrestrial planet formation in our solar system. We have also detected several new candidate substellar companions, for which there are ongoing followup campaigns (HST/WFC3 and VLT/SINFONI in ADI mode). Since the methods developed as part of ALICE are directly applicable to future missions (JWST, AFTA coronagraph) we emphasize the importance of devising optimal PSF subtraction methods for upcoming coronagraphic imaging missions. We describe efforts in defining direct imaging high-level science products (HLSP) standards that can be applicable to other coronagraphic campaigns, including ground-based (e.g., Gemini Planet Imager), and future space instruments (e.g., JWST). ALICE will deliver a first release of HLSPs to the community through the MAST archive at STScI in 2014.

  11. 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

  12. 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.

  13. 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

  14. Results of microbiological Investigations of Orbital Station MIR Environment

    NASA Astrophysics Data System (ADS)

    Novikova, N.

    15-year experience of orbital station MIR service demonstrated that specifically modified space vehicle environment allows to consider spaceship habitats as a certain ecological niche of microbial community development and functioning, which was formed from the organisms of different physiological and taxonomical groups. As a result of on-board experiments and revision of interior and equipment more than 234 microorganisms were identified. They were represented by technophylic specia, which cause material damage, as well as potential pathogens (bacteria, actinomyces spp, fungi), which capable to grow on artificial substrates. Resident colonization of interior and equipment of space habitat by bacterial and fungal associations, taking place during long-term microbiota exposure on cosmophysic, physic-chemical and biological factors, which is accompanied by appearance of technological and medical risks, capable to provide significant influence on safety of humans and reliability of space equipment. These risks are due to such processes: biodestruction of synthetic and organic polymeres, biocorrosion of metals, biofoulding of surfaces (biofilms), formation of obturation in vital activity support system, occurrence of biodisturbances resulting in devise and equipment failure, occurrence and development of supertolerants and other variants with unpredictable attributes, which are expressed as a result of phenotypical and genotypical modifications. Based on the information from results of in-flight and laboratory microbiological investigations, the following suppositions can be made to characterize evolution of the microbial community aboard long-operating space vehicle: - environment of a long-operating piloted space vehicle may be a peculiar kind of ecological niche for development and reproduction of bacilli and fungi belonging to particular species, - bacteriofungal associations primarily reside on decorative-finish and structural materials of space interior and

  15. Minimal motif peptide structure of metzincin clan zinc peptidases in micelles.

    PubMed

    Onoda, Akira; Suzuki, Takako; Ishizuka, Hiroaki; Sugiyama, Rumiko; Ariyasu, Shinya; Yamamura, Takeshi

    2009-12-01

    It is well known that the functions of metalloproteins generally originate from their metal-binding motifs. However, the intrinsic nature of individual motifs remains unknown, particularly the details about metal-binding effects on the folding of motifs; the converse is also unknown, although there is no doubt that the motif is the core of the reactivity for each metalloprotein. In this study, we focused our attention on the zinc-binding motif of the metzincin clan family, HEXXHXXGXXH; this family contains the general zinc-binding sequence His-Glu-Xaa-Xaa-His (HEXXH) and the extended GXXH region. We adopted the motif sequence of stromelysin-1 and investigated the folding properties of the Trp-labeled peptides WAHEIAHSLGLFHA (STR-W1), AWHEIAHSLGLFHA (STR-W2), AHEIAHSLGWFHA (STR-W11), and AHEIAHSLGLFHWA (STR-W14) in the presence and absence of zinc ions in hydrophobic micellar environments by circular dichroism (CD) measurements. We accessed successful incorporation of these zinc peptides into micelles using quenching of Trp fluorescence. Results of CD studies indicated that two of the Trp-incorporated peptides, STR-W1 and STR-W14, exhibited helical folding in the hydrophobic region of cetyltrimethylammonium chloride micelle. The NMR structural analysis of the apo STR-W14 revealed that the conformation in the C-terminus GXXH region significantly differred between the apo state in the micelle and the reported Zn-bound state of stromelysin-1 in crystal structures. The structural analyses of the qualitative Zn-binding properties of this motif peptide provide an interesting Zn-binding mechanism: the minimum consensus motif in the metzincin clan, a basic zinc-binding motif with an extended GXXH region, has the potential to serve as a preorganized Zn binding scaffold in a hydrophobic environment.

  16. 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

  17. 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.

  18. A micelle-like structure of poloxamer-methotrexate conjugates as nanocarrier for methotrexate delivery.

    PubMed

    Ren, Jin; Fang, Zhengjie; Yao, Li; Dahmani, Fatima Zohra; Yin, Lifang; Zhou, Jianping; Yao, Jing

    2015-06-20

    The purpose of this study was to develop a novel featured and flexible methotrexate (MTX) formulation, in which MTX was physically entrapped and chemically conjugated in the same drug delivery system. A series of poloxamer-MTX (p-MTX) conjugates was synthesized, wherein MTX was grafted to poloxamer through an ester bond. p-MTX conjugates could self-assemble into micelle-like structures in aqueous environment and the MTX end was in the inner-core of micelles. Moreover, free MTX could be physically entrapped into p-MTX micelles hydrophobic core region to increase the total drug loading. Importantly, the resulting MTX-loaded p-MTX micelles showed a biphasic release of MTX, with a relative fast release of the entrapped MTX (about 6-7h) followed by a sustained release of the conjugated MTX. The pharmacokinetics study showed that the mean residence time (MRT) was extended in the case of MTX-loaded p-MTX micelles, indicating a delayed MTX elimination from the bloodstream and prolonged in vivo residence time. Besides, the area under curve (AUC) of MTX-loaded p-MTX micelles was greater than free MTX, indicating a drug bioavailability improvement. Overall, MTX-loaded p-MTX micelles might be a promising nanosized drug delivery system for the cancer therapy.

  19. Investigating the Marine Environment and Its Resources, Part II.

    ERIC Educational Resources Information Center

    Lien, Violetta F.

    This is the second of two volumes comprising a resource unit designed to help students become more knowledgeable about the marine environment and its resources. Included in this volume are discussions of changes in the human and marine environment, human needs, marine resources, living marine resources, marine transportation, marine energy…

  20. Investigating the Marine Environment and Its Resources, Part I.

    ERIC Educational Resources Information Center

    Lien, Violetta F.

    This is the first of two volumes comprising a resource unit designed to help students become more knowledgeable about the marine environment and its resources. Included in this volume are discussions of geography of the Gulf of Mexico, geology, physical characteristics of the marine environment, marine ecology, and ocean/land interaction.…

  1. Teaching Materials for Environmental Education. Investigating Your Environment.

    ERIC Educational Resources Information Center

    Forest Service (USDA), Washington, DC.

    The environment lesson plans in this packet are designed to take an in-depth look at different components of the environment. The plans were developed with the assistance of specialists in educational processes and educators, students, and resource-agency people for whom they are designed. They have been field-tested in environmental education…

  2. Experimental Investigation of Organic Synthesis in Hydrothermal Environments

    NASA Technical Reports Server (NTRS)

    Shock, Everett L.

    1998-01-01

    Seafloor hydrothermal systems may be the most likely locations on the early Earth for the emergence of life. Because of the disequilibrium inherent in such dynamic, mixing environments, abundant chemical energy would have been available for formation of the building blocks of life. In addition, theoretical studies suggest that organic compounds in these conditions would reach metastable states, due to kinetic barriers to the formation of stable equilibrium products (CO2 and methane). The speciation of organic carbon in metastable states is highly dependent on the oxidation state, pH, temperature, pressure and bulk composition of the system. The goal of our research is to investigate the effects of a number external variables on the formation, transformation, and stability of organic compounds at hydrothermal conditions. We have begun experimental work to attempt to control the oxidation state of simulated hydrothermal systems by using buffers composed of mineral powders and gas mixtures. We are also beginning to test the stability of organic compounds under these conditions. The experiments are being performed using the hydrothermal bomb apparatus at the U.S. Geological Survey in Menlo Park, CA and the supercritical water oxidizer (SCWO) at NASA Ames Research Center in Moffet Field, CA. The amino acids decomposed rapidly. Even after the approximately 15 minutes between addition of the amino acids and the first sampling, no amino acids were detected in the PPM system by GC- MS, while in the FeFeO system the amino acids were present at a level of less than 50% of original. Carboxylic acids, ammonia, and CO2 were the main products, along with some unidentified compounds. The ratios of carboxylic acids and concentrations of other products seem to have remained stable during the experiments, consistent with observations of other metastable systems and theoretical predictions.

  3. Adverse environments: investigating local variation in child growth.

    PubMed

    Moffat, Tina; Galloway, Tracey

    2007-01-01

    Epigenetic and life history approaches to child growth are centered on the relationship between the organism and its environment. However, defining and operationalizing the concept of environment is challenging, in light of the multiple variables that influence growth. Moreover, the concept of adaptation as it applies to child growth is seldom considered in the developed country context. This paper presents a study of children living in three neighborhoods in the City of Hamilton, Ontario, Canada. Two of the communities are considered adverse environments on the basis of low socioeconomic status, and their inner city, industrial location. In contrast to children living in the higher socioeconomic status area, children in these adverse environments display negative growth indicators, i.e., somewhat constrained linear growth in one and risk for overweight and obesity in both. Although both these inner city neighborhoods constitute adverse environments, they differ in ways that have a significant impact on children's growth. We argue for a definition of "adverse environment" that is broadly based, incorporating a range of physical, social, and temporal factors that are highly localized and sensitive to community-level influences on growth and health. As well, we consider whether higher prevalence of overweight and obesity is adaptive in any way to these adverse environments and conclude that they are more likely to be deleterious than adaptive in either the long or short term.

  4. Polymeric Micelles for Delivery of Poorly Soluble Drugs: Preparation and Anticancer Activity In Vitro of Paclitaxel Incorporated into Mixed Micelles Based on Poly(ethylene Glycol)-Lipid Conjugate and Positively Charged Lipids

    PubMed Central

    WANG, JUNPING; MONGAYT, DIMITRY; TORCHILIN, VLADIMIR P.

    2006-01-01

    Paclitaxel-loaded mixed polymeric micelles consisting of poly(ethylene glycol)-distearoyl phosphoethanolamine conjugates (PEG-PE), solid triglycerides (ST), and cationic Lipofectin® lipids (LL) have been prepared. Micelles with the optimized composition (PEG-PE/ST/LL/paclitaxel = 12/12/2/1 by weight) had an average micelle size of about 100 nm, and zeta-potential of about 26 mV. Micelles were stable and did not release paclitaxel when stored at 4°C in the darkness (just 2.9% of paclitaxel have been lost after 4 months with the particle size remaining unchanged). The release of paclitaxel from such micelles at room temperature was also insignificant. However, at 37°C, approx. 16% of paclitaxel was released from PEG-PE/ST/LL/paclitaxel micelles in 72 h, probably, because of phase transition in the ST-containing micelle core. In vitro anticancer effects of PEG-PE/ST/LL/paclitaxel and control micelles were evaluated using human mammary adenocarcinoma (BT-20) and human ovarian carcinoma (A2780) cell lines. Paclitaxel in PEG-PE/ST/LL micelles demonstrated the maximum anti-cancer activity. Cellular uptake of fluorescently-labeled paclitaxel-containing micelles by BT-20 cells was investigated using a fluorescence microscopy. It seems that PEG-PE/ST/LL micelles, unlike micelles without the LL component, could escape from endosomes and enter the cytoplasm of BT-20 cancer cells thus increasing the anticancer efficiency of the micellar paclitaxel. PMID:15848957

  5. 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

  6. 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.

  7. Electrosorption of pectin onto casein micelles.

    PubMed

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

    2002-01-01

    Pectin, a polysaccharide derived from plant cells of fruit, is commonly used as stabilizer in acidified milk drinks. To gain a better understanding of the way that pectin stabilizes these drinks, we studied the adsorption and layer thickness of pectin on casein micelles in skim milk dispersions. Dynamic light scattering was used to measure the layer thickness of adsorbed pectin onto casein micelles in situ during acidification. The results indicate that the adsorption of pectin onto casein micelles is multilayered and takes place at and below pH 5.0. Renneting, i.e., cleaving-off kappa-casein from the casein micelles, did not alter the adsorption pH. It did, however, show that pectin arrests the rennet-induced flocculation of casein micelles below pH 5.0. From the findings we concluded the attachment of pectin onto casein micelles is driven by electrosorption. Adsorption measurements confirmed the multilayered nature of the adsorption of pectin onto casein micelles. Both the adsorbed amount and the layer thickness increased with decreasing pH in the relevant range 3.5-5.0. The phase behavior of a casein micelles/pectin mixture was determined and could be explained in terms of thermodynamic incompatibility being relevant above pH 5.0 and adsorption, leading to either stabilization and bridging, being relevant below pH 5.0. The results confirm that electrosorption is the driving force for the adsorption of pectin onto casein micelles.

  8. Novel pH-sensitive micelles generated by star-shape copolymers containing zwitterionic sulfobetaine for efficient cellular internalization.

    PubMed

    Cao, Jun; Zhai, Shuying; Li, Chenlong; He, Bin; Lai, Yusi; Chen, Yuanwei; Luo, Xianglin; Gu, Zhongwei

    2013-11-01

    pH-sensitive micelles are considered promising carriers for tumor targeted drug delivery. In this study, novel pH-sensitive star-shape copolymers of amphiphilic poly(epsilon-caprolactone)-b-poly(N, N-diethylaminoethyl methacrylate)-r-poly(N-(3-sulfopropyl)-N-methacryloxyethy-N, N-diethylammoniumbetaine) (4sPCLDEAS) are designed and synthesized with the combination of ring opening polymerization (ROP) and atom radical transferpolymerization (ATRP). The structure of the copolymers is characterized by proton nuclear magnetic resonance spectra (1HNMR). The poly(N-(3-sulfopropyl)-N-methacryloxyethy-N, N-diethylammoniumbetaine) segment is used instead of poly(ethylene glycol) (PEG) as hydrophilic block in the copolymers to form polymeric micelles. The micelles present spherical shape, narrow size distribution, and are reponsive to the acidity. The CMC of the micelles is as low as 1 x 10(-3) mg mL(-1). Doxorubin (DOX) is efficiently encapsulated in the micelles and the drug release is pH dependant. The cytotoxicity as well as the intracellular drug delivery of the micelles are investigated. The micelles are nontoxic to human cervical carcinoma (Hela) cells. The DOX-loaded micelles are internalized in Hela cells efficiently, which are better than that of hydrophilic doxorubicin hydrochloride (DOX x HCl). These pH-sensitive micelles are potential promising carriers for anti-cancer drug delivery. PMID:24059084

  9. Isothermal titration calorimetric analysis on solubilization of an octane oil-in-water emulsion in surfactant micelles and surfactant-anionic polymer complexes.

    PubMed

    Zhang, Hui; Zeeb, Benjamin; Salminen, Hanna; Weiss, Jochen

    2015-01-15

    Polymers may alter the ability of surfactant micelles to solubilize hydrophobic molecules depending on surfactant-polymer interactions. In this study, isothermal titration calorimetry (ITC) was used to investigate the solubilization thermodynamics of an octane oil-in-water emulsion in anionic sodium dodecylsulphate (SDS), nonionic polyoxyethylene sorbitan monooleate (Tween 80), cationic cetyltrimethylammonium bromide (CTAB) surfactant micelles and respective complexes formed by these micelles and an anionic polymer (carboxymethyl cellulose). Results indicated that the oil solubilization in single ionic micelles was endothermic, while in nonionic micelles or mixed ionic/nonionic micelles it was exothermic. The addition of carboxymethyl cellulose did not influence the solubilization behavior in these micelles, but affected the solubilization capacities of these systems. The solubilization capacity of cationic micelles or mixed cationic/nonionic micelles was enhanced while that of nonionic or anionic micelles was decreased. Based on the phase separation model, a molecular pathway mechanism driven by enthalpy was proposed for octane solubilization in surfactant micelles and surfactant-polymer complexes.

  10. Complex coacervate core micelles from iron-based coordination polymers.

    PubMed

    Wang, Junyou; de Keizer, Arie; Fokkink, Remco; Yan, Yun; Cohen Stuart, Martien A; van der Gucht, Jasper

    2010-07-01

    Complex coacervate core micelles (C3Ms) from cationic poly(N-methyl-2-vinyl-pyridinium iodide)-b-poly(ethylene oxide) (P2MVP(41)-b-PEO(205)) and anionic iron coordination polymers are investigated in the present work. Micelle formation is studied by light scattering for both Fe(II)- and Fe(III)-containing C3Ms. At the stoichiometric charge ratio, both Fe(II)-C3Ms and Fe(III)-C3Ms are stable for at least 1 week at room temperature. Excess of iron coordination polymers has almost no effect on the formed Fe(II)-C3Ms and Fe(III)-C3Ms, whereas excess of P2MVP(41)-b-PEO(205) copolymers in the solution can dissociate the formed micelles. Upon increasing salt concentration, the scattering intensity decreases. This decrease is due to both a decrease in the number of micelles (or an increase in CMC) and a decrease in aggregation number. The salt dependence of the CMC and the aggregation number is explained using a scaling argument for C3M formation. Compared with Fe(II)-C3Ms, Fe(III)-C3Ms have a lower CMC and a higher stability against dissociation by added salt.

  11. 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

  12. 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

  13. Micelle-templated composite quantum dots for super-resolution imaging

    NASA Astrophysics Data System (ADS)

    Xu, Jianquan; Fan, Qirui; Mahajan, Kalpesh D.; Ruan, Gang; Herrington, Andrew; Tehrani, Kayvan F.; Kner, Peter; Winter, Jessica O.

    2014-05-01

    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 Mn2+ 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.

  14. Effect of the lipid chain melting transition on the stability of DSPE-PEG(2000) micelles.

    PubMed

    Kastantin, Mark; Ananthanarayanan, Badriprasad; Karmali, Priya; Ruoslahti, Erkki; Tirrell, Matthew

    2009-07-01

    Micellar nanoparticles are showing promise as carriers of diagnostic and therapeutic biofunctionality, leading to increased interest in their properties and behavior, particularly their size, shape, and stability. This work investigates the physical chemistry of micelles formed from DSPE-PEG(2000) monomers as it pertains to these properties. A melting transition in the lipid core of spheroidal DSPE-PEG(2000) micelles is observed as an endothermic peak at 12.8 degrees C upon heating in differential scanning calorimetry thermograms. Bulky PEG(2000) head groups prevent regular crystalline packing of lipids in both the low-temperature glassy and high-temperature fluid phases, as evidenced by wide-angle X-ray scattering. Equilibrium micelle geometry is spheroidal above and below the transition temperature, indicating that the entropic penalty to force the PEG brush into flat geometry is greater than the enthalpic benefit to the glassy core to pack in an extended configuration. Increased micelle stability is seen in the glassy phase with monomer desorption rates significantly lower than in the fluid phase. Activation energies for monomer desorption are 156+/-6.7 and 79+/-5.0 kJ/mol for the glassy and fluid phases, respectively. The observation of a glass transition that increases micelle stability but does not perturb micelle geometry is useful for the design of more effective biofunctional micelles.

  15. 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

  16. Effect of the lipid chain melting transition on the stability of DSPE-PEG(2000) micelles.

    PubMed

    Kastantin, Mark; Ananthanarayanan, Badriprasad; Karmali, Priya; Ruoslahti, Erkki; Tirrell, Matthew

    2009-07-01

    Micellar nanoparticles are showing promise as carriers of diagnostic and therapeutic biofunctionality, leading to increased interest in their properties and behavior, particularly their size, shape, and stability. This work investigates the physical chemistry of micelles formed from DSPE-PEG(2000) monomers as it pertains to these properties. A melting transition in the lipid core of spheroidal DSPE-PEG(2000) micelles is observed as an endothermic peak at 12.8 degrees C upon heating in differential scanning calorimetry thermograms. Bulky PEG(2000) head groups prevent regular crystalline packing of lipids in both the low-temperature glassy and high-temperature fluid phases, as evidenced by wide-angle X-ray scattering. Equilibrium micelle geometry is spheroidal above and below the transition temperature, indicating that the entropic penalty to force the PEG brush into flat geometry is greater than the enthalpic benefit to the glassy core to pack in an extended configuration. Increased micelle stability is seen in the glassy phase with monomer desorption rates significantly lower than in the fluid phase. Activation energies for monomer desorption are 156+/-6.7 and 79+/-5.0 kJ/mol for the glassy and fluid phases, respectively. The observation of a glass transition that increases micelle stability but does not perturb micelle geometry is useful for the design of more effective biofunctional micelles. PMID:19358585

  17. Measurement and control of pH in the aqueous interior of reverse micelles.

    PubMed

    Marques, Bryan S; Nucci, Nathaniel V; Dodevski, Igor; Wang, Kristina W C; Athanasoula, Evangelia A; Jorge, Christine; Wand, A Joshua

    2014-02-27

    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 (1)H 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.

  18. 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

  19. Investigating Elementary School Students' Perceptions about Environment through Their Drawings

    ERIC Educational Resources Information Center

    Ozsoy, Sibel

    2012-01-01

    The purpose of this study is to determine elementary school students' perceptions about environment through their drawings. The study was carried out during the spring semester of 2010-2011 academic year. A total of 429 elementary school students, including 68 fourth grade, 78 fifth grade, 97 sixth grade, 85 seventh grade, 101 eighth grade,…

  20. A Molecular Investigation of Genotype by Environment Interactions

    PubMed Central

    Dean, A. M.

    1995-01-01

    The fitnesses conferred by seven lactose operons, which had been transduced into a common genetic background from natural isolates of Escherichia coli, were determined during competition for growth rate-limiting quantities of galactosyl-glycerol, a naturally occurring galactoside. The fitnesses of these same operons have been previously determined on lactose and three artificial galactosides, lactulose, methyl-galactoside and galactosyl-arabinose. Analysis suggests that although marked genotype by environment interactions occur, changes in the fitness rankings are rare. The relative activities of the β-galactosidases and the permeases were determined on galactosyl-glycerol, lactose, lactulose and methyl-galactoside. Both enzymes display considerable kinetic variation. The β-galactosidase alleles provide no evidence for genotype by environment interactions at the level of enzyme activity. The permease alleles display genotype by environment interactions with a few causing changes in activity rankings. The contributions to fitness made by the permeases and the β-galactosidases were partitioned using metabolic control analysis. Most of the genotype by environment interaction at the level of fitness is generated by changes in the distribution of control among steps in the pathway, particularly at the permease where large control coefficients ensure that its kinetic variation has marked fitness effects. Indeed, changes in activity rankings at the permease account for the few changes in fitness rankings. In contrast, the control coefficients of the β-galactosidase are sufficiently small that its kinetic variation is in, or close to, the neutral limit. The selection coefficients are larger on the artificial galactosides because the control coefficients of the permease and β-galactosidase are larger. The flux summation theorem requires that control coefficients associated with other steps in the pathway must be reduced, implying that the selection at these steps will

  1. Temperature Triggered Self-Assembly of Polypeptides into Multivalent Spherical Micelles

    PubMed Central

    Dreher, Matthew R.; Simnick, Andrew J.; Fischer, Karl; Smith, Richard J.; Patel, Anand; Schmidt, Manfred; Chilkoti, Ashutosh

    2010-01-01

    We report herein thermally responsive elastin-like polypeptides (ELPs) in a linear AB diblock architecture with an N-terminal peptide ligand that self-assemble into spherical micelles when heated slightly above body temperature. A series of 10 ELP block copolymers (ELPBCs) with different molecular weights and hydrophilic-to-hydrophobic block ratios were genetically synthesized by recursive directional ligation. The self-assembly of these polymers from unimers into micelles was investigated by light scattering, fluorescence spectroscopy and cryo-TEM. These ELPBCs undergo two phase transitions as a function of solution temperature: a unimer to spherical micelle transition at an intermediate temperature, and a micelle to bulk aggregate transition at a higher temperature when the hydrophilic-to-hydrophobic block ratio is between 1:2 and 2:1. The critical micelle temperature is controlled by the length of the hydrophobic block and the size of the micelle is controlled by both the total ELPBC length and hydrophilic-to-hydrophobic block ratio. These polypeptide micelles display a critical micelle concentration in the range of 4-8 μM demonstrating high stability of these structures. These studies have also identified a subset of ELPBCs bearing terminal peptide ligands that are capable of forming multivalent spherical micelles that present multiple copies of the ligand on their corona in the clinically relevant temperature range of 37-42 °C and target cancer cells. These ELPBCs may be useful for drug targeting by thermally triggered multivalency. More broadly, the design rules uncovered by this study should be applicable to the design of other thermally reversible nanoparticles for diverse applications in medicine and biology. PMID:18085778

  2. The interaction of Co 2+ ions and sodium deoxycholate micelles

    NASA Astrophysics Data System (ADS)

    Sun, Y.; Yang, Z.-L.; Zhang, L.; Zhou, N.-F.; Weng, S.-F.; Wu, J.-G.

    2003-07-01

    To mimic the interaction between divalent metal ions and bile slats in vivo, two groups of coordination complex compounds, crystalline and gel-like, were synthesized in vitro by mixing the aqueous solutions of CoCl 2 with sodium deoxycholate (NaDC) at various concentrations. Structures and compositions of the compounds were investigated using FT-IR, EXAFS, XRD as well as elemental and ICP analysis, respectively. Then the interaction of Co 2+ with deoxycholate in solution was observed by laser light scattering (LLS), Transmission electronic microscope techniques and ICP analysis. Conclusions are (1) the crystalline complexes, Co (DC) 2·3H 2O were obtained by reaction of Co 2+ with mono-molecules of NaDC, and the gel-like complexes, Na nCo m(DC) n+2 m formed by reaction of Co 2+ with NaDC micelles. The gel-like complexes exhibit the non-stoichiometric character; (2) the coordination structures of carboxyl groups with Co 2+ were different between the crystalline and gel-like complexes. In Co(DC) 2·3H 2O complex, the carboxyl groups of deoxycholate coordinated with Co 2+ in chelating and pseudo-chelating modes, but that in bridge mode in the case of Na nCo m(DC) n+2 m complexes. The non-stoichiometric complexes of Na nCo m(DC) n+2 m are formed with a macromolecular structure through the Co 2+ bridges; (3) NaDC can increase the solubility of Co(DC) 2·3H 2O in aqueous solution, and larger micelles (30-80 nm diameter) formed in the supernate. It is a mixed micelle formed by Co 2+ ions bridges connecting with NaDC simple micelles. So these micelles are a new kind of micelle containing two kinds of metal ions; (4) these results are in agreement with those formed under physiological conditions in that the different states such as gel, precipitate, micelles of various structures are present in bile of gallbladder. An ideal model of the interaction between Co 2+ and bile salts in vivo has been proposed.

  3. Investigation of human-robot interface performance in household environments

    NASA Astrophysics Data System (ADS)

    Cremer, Sven; Mirza, Fahad; Tuladhar, Yathartha; Alonzo, Rommel; Hingeley, Anthony; Popa, Dan O.

    2016-05-01

    Today, assistive robots are being introduced into human environments at an increasing rate. Human environments are highly cluttered and dynamic, making it difficult to foresee all necessary capabilities and pre-program all desirable future skills of the robot. One approach to increase robot performance is semi-autonomous operation, allowing users to intervene and guide the robot through difficult tasks. To this end, robots need intuitive Human-Machine Interfaces (HMIs) that support fine motion control without overwhelming the operator. In this study we evaluate the performance of several interfaces that balance autonomy and teleoperation of a mobile manipulator for accomplishing several household tasks. Our proposed HMI framework includes teleoperation devices such as a tablet, as well as physical interfaces in the form of piezoresistive pressure sensor arrays. Mobile manipulation experiments were performed with a sensorized KUKA youBot, an omnidirectional platform with a 5 degrees of freedom (DOF) arm. The pick and place tasks involved navigation and manipulation of objects in household environments. Performance metrics included time for task completion and position accuracy.

  4. Investigating Factors Affecting Group Processes in Virtual Learning Environments

    ERIC Educational Resources Information Center

    Hazari, Sunil; Thompson, Sandra

    2015-01-01

    With the widespread popularity of distance learning, there is a need to investigate elements of online courses that continue to pose significant challenges for educators. One of the challenges relates to creating and managing group projects. This study investigated business students' perceptions of group work in online classes. The constructs…

  5. 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)

  6. Study of the Formation and Solution Properties of Worm-Like Micelles Formed Using Both N-Hexadecyl-N-Methylpiperidinium Bromide-Based Cationic Surfactant and Anionic Surfactant

    PubMed Central

    Yan, Zhihu; Dai, Caili; Feng, Haishun; Liu, Yifei; Wang, Shilu

    2014-01-01

    The viscoelastic properties of worm-like micelles formed by mixing the cationic surfactant N-hexadecyl-N-methylpiperidinium bromide (C16MDB) with the anionic surfactant sodium laurate (SL) in aqueous solutions were investigated using rheological measurements. The effects of sodium laurate and temperature on the worm-like micelles and the mechanism of the observed shear thinning phenomenon and pseudoplastic behavior were systematically investigated. Additionally, cryogenic transmission electron microscopy images further ascertained existence of entangled worm-like micelles. PMID:25296131

  7. 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

  8. Shaping and patterning gold nanoparticles via micelle templated photochemistry.

    PubMed

    Kundrat, F; Baffou, G; Polleux, J

    2015-10-14

    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.

  9. 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

  10. SNF Interim Storage Canister Corrosion and Surface Environment Investigations

    SciTech Connect

    Bryan, Charles R.; Enos, David G.

    2015-09-01

    This progress report describes work being done at Sandia National Laboratories (SNL) to assess the localized corrosion performance of container/cask materials used in the interim storage of spent nuclear fuel (SNF). Of particular concern is stress corrosion cracking (SCC), by which a through-wall crack could potentially form in a canister outer wall over time intervals that are shorter than possible dry storage times. In order for SCC to occur, three criteria must be met. A corrosive environment must be present on the canister surface, the metal must susceptible to SCC, and sufficient tensile stress to support SCC must be present through the entire thickness of the canister wall. SNL is currently evaluating the potential for each of these criteria to be met.

  11. Reduction-Responsive Polymeric Micelles and Vesicles for Triggered Intracellular Drug Release

    PubMed Central

    Sun, Huanli; Cheng, Ru; Deng, Chao

    2014-01-01

    Abstract Significance: The therapeutic effects of current micellar and vesicular drug formulations are restricted by slow and inefficient drug release at the pathological site. The development of smart polymeric nanocarriers that release drugs upon arriving at the target site has received a tremendous amount of attention for cancer therapy. Recent Advances: Taking advantage of a high reducing potential in the tumor tissues and in particular inside the tumor cells, various reduction-sensitive polymeric micelles and vesicles have been designed and explored for triggered anticancer drug release. These reduction-responsive nanosystems have demonstrated several unique features, such as good stability under physiological conditions, fast response to intracellular reducing environment, triggering drug release right in the cytosol and cell nucleus, and significantly improved antitumor activity, compared to traditional reduction-insensitive counterparts. Critical Issues: Although reduction-sensitive micelles and polymersomes have accomplished rapid intracellular drug release and enhanced in vitro antitumor effect, their fate inside the cells including the mechanism, site, and rate of reduction reaction remains unclear. Moreover, the systemic fate and performance of reduction-sensitive polymeric drug formulations have to be investigated. Future Directions: Biophysical studies should be carried out to gain insight into the degradation and drug release behaviors of reduction-responsive nanocarriers inside the tumor cells. Furthermore, novel ligand-decorated reduction-sensitive nanoparticulate drug formulations should be designed and explored for targeted cancer therapy in vivo. Antioxid. Redox Signal. 21, 755–767. PMID:24279980

  12. 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

  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. 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.

  15. High intensity focused ultrasound responsive metallo-supramolecular block copolymer micelles.

    PubMed

    Liang, Bo; Tong, Rui; Wang, Zhenhua; Guo, Shengwei; Xia, Hesheng

    2014-08-12

    The metal-supramolecular diblock copolymer containing mechano-labile bis(terpyridine)-Cu(II) complex linkage in the junction point was synthesized. These metal-ligand containing amphiphilic copolymers are able to self-assemble in aqueous solution to form spherical micelles with poly(propylene glycol) block forming the hydrophobic core. It is found that high intensity focused ultrasound can open the copolymer micelles and trigger the release of the payload in the micelle. The micellar properties and release kinetics of encapsulated guest molecule in response to ultrasound stimuli were investigated. The weak Cu(II)-terpyridine dynamic bond in the copolymer chain can be cleaved under ultrasound and thus leads to the disruption of the copolymer micelle and the release of loaded cargo. This study will open up a new way for the molecular design of ultrasound modulated drug delivery systems. PMID:25072274

  16. 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

  17. UVES Investigates the Environment of a Very Remote Galaxy

    NASA Astrophysics Data System (ADS)

    2002-03-01

    Surplus of Intergalactic Material May Be Young Supercluster Summary Observations with ESO's Very Large Telescope (VLT) have enabled an international group of astronomers [1] to study in unprecedented detail the surroundings of a very remote galaxy, almost 12 billion light-years distant [2]. The corresponding light travel time means that it is seen at a moment only about 3 billion years after the Big Bang. This galaxy is designated MS 1512-cB58 and is the brightest known at such a large distance and such an early time. This is due to a lucky circumstance: a massive cluster of galaxies ( MS 1512+36 ) is located about halfway along the line-of-sight, at a distance of about 7 billion light-years, and acts as a gravitational "magnifying glass". Thanks to this lensing effect, the image of MS1512-cB58 appears 50 times brighter . Nevertheless, the apparent brightness is still as faint as magnitude 20.6 (i.e., nearly 1 million times fainter than what can be perceived with the unaided eye). Moreover, MS 1512-cB58 is located 36° north of the celestial equator and never rises more than 29° above the horizon at Paranal. It was therefore a great challenge to secure the present observational data with the UVES high-dispersion spectrograph on the 8.2-m VLT KUEYEN telescope . The extremely detailed UVES-spectrum of MS 1512-cB58 displays numerous signatures (absorption lines) of intergalactic gas clouds along the line-of-sight . Some of the clouds are quite close to the galaxy and the astronomers have therefore been able to investigate the distribution of matter in its immediate surroundings. They found an excess of material near MS 1512-cB58, possible evidence of a young supercluster of galaxies , already at this very early epoch. The new observations thus provide an invaluable contribution to current studies of the birth and evolution of structures in the early Universe. This is the first time this kind of observation has ever been done of a galaxy at such a large distance . All

  18. Fluid mechanics and solidification investigations in low-gravity environments

    NASA Technical Reports Server (NTRS)

    Fichtl, G. H.; Lundquist, C. A.; Naumann, R. J.

    1980-01-01

    Fluid mechanics of gases and liquids and solidification processes were investigated under microgravity conditions during Skylab and Apollo-Soyuz missions. Electromagnetic, acoustic, and aerodynamic levitation devices, drop tubes, aircraft parabolic flight trajectories, and vertical sounding rockets were developed for low-g simulation. The Spacelab 3 mission will be carried out in a gravity gradient flight attitude; analyses of sources of vehicle dynamic accelerations with associated g-levels and angular rates will produce results for future specific experiments.

  19. Laboratory investigations: Low Earth orbit environment chemistry with spacecraft surfaces

    NASA Astrophysics Data System (ADS)

    Cross, Jon B.

    1990-03-01

    Long-term space operations that require exposure of material to the low earth orbit (LEO) environment must take into account the effects of this highly oxidative atmosphere on material properties and the possible contamination of the spacecraft surroundings. Ground-based laboratory experiments at Los Alamos using a newly developed hyperthermal atomic oxygen (AO) source have shown that not only are hydrocarbon based materials effected but that inorganic materials such as MoS2 are also oxidized and that thin protective coatings such as Al2O3 can be breached, producing oxidation of the underlying substrate material. Gas-phase reaction products, such as SO2 from oxidation of MoS2 and CO and CO2 from hydrocarbon materials, have been detected and have consequences in terms of spacecraft contamination. Energy loss through gas-surface collisions causing spacecraft drag has been measured for a few select surfaces and has been found to be highly dependent on the surface reactivity.

  20. Laboratory investigations: Low Earth orbit environment chemistry with spacecraft surfaces

    NASA Technical Reports Server (NTRS)

    Cross, Jon B.

    1990-01-01

    Long-term space operations that require exposure of material to the low earth orbit (LEO) environment must take into account the effects of this highly oxidative atmosphere on material properties and the possible contamination of the spacecraft surroundings. Ground-based laboratory experiments at Los Alamos using a newly developed hyperthermal atomic oxygen (AO) source have shown that not only are hydrocarbon based materials effected but that inorganic materials such as MoS2 are also oxidized and that thin protective coatings such as Al2O3 can be breached, producing oxidation of the underlying substrate material. Gas-phase reaction products, such as SO2 from oxidation of MoS2 and CO and CO2 from hydrocarbon materials, have been detected and have consequences in terms of spacecraft contamination. Energy loss through gas-surface collisions causing spacecraft drag has been measured for a few select surfaces and has been found to be highly dependent on the surface reactivity.

  1. 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.

  2. Micelle Formation of n-Decyltrimethylammonium Perfluorocarboxylates

    PubMed

    Yoshida; Matsuoka; Moroi

    1997-03-15

    Critical micelle concentrations (CMCs) of three ionic surfactants that contain n-decyltrimethylammonium ion as a surfactant cation and bromide, perfluoroacetate, and perfluoropropionate anions as a counterion, respectively, were determined by electrical conductivity at several temperatures. The degrees of counterion binding to micelle were obtained at the same temperatures as the change in CMC with total counterion concentration. Molecular weights of micelles were determined by static light scattering. The change in monomeric surfactant ion concentration with total surfactant concentration was determined by membrane potential measurement. The mass-action model was applied to micelle formation to calculate the three micellization parameters: micellization constant, micelle aggregation number, and number of counterions per micelle. Thermodynamic parameters (DeltaG0, DeltaH0, DeltaS0) of the micelle formations were calculated from the temperature dependence of these parameters. At lower temperatures micellization has been found to be entropy driven, whereas it is enthalpy driven at higher temperatures. For n-decyltrimethylammonium perfluoropropionate, however, the tendency is quite different from those of other surfactants. The micellization parameters also made it possible to evaluate the concentration change of monomeric surfactant ion with total surfactant concentration. The evaluated concentration explains the results from the membrane potential measurement.

  3. Workshop on Radar Investigations of Planetary and Terrestrial Environments

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Contents include the following: Salt Kinematics and InSAR. SAR Interferometry as a Tool for Monitoring Coastal Changes in the Nile River Delta of Egypt. Modem Radar Techniques for Geophysical Applications: Two Examples. WISDOM Experiment on the EXOMARS ESA Mission. An Ice Thickness Study Utilizing Ground Penetrating Radar on the Lower Jamapa. Probing the Martian Subsurface with Synthetic Aperture Radar. Planetary Surface Properties from Radar Polarimetric Observations. Imaging the Sub-surface Reflectors : Results From the RANETA/NETLANDER Field Test on the Antarctic Ice Shelf. Strategy for Selection of Mars Geophysical Analogue Sites. Observations of Low Frequency Low Altitude Plasma Oscillations at Mars and Implications for Electromagnetic Sounding of the Subsurface. Ionospheric Transmission Losses Associated with Mars-orbiting Radar. A Polarimetric Scattering Model for the 2-Layer Problem. Radars for Imaging and Sounding of Polar Ice Sheets. Strata: Ground Penetrating Radar for Mars Rovers. Scattering Limits to Depth of Radar Investigation: Lessons from the Bishop Tuff.

  4. 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

  5. An Instrument for Investigating Chinese Language Learning Environments in Singapore Secondary Schools

    ERIC Educational Resources Information Center

    Chua, Siew Lian; Wong, Angela F. L.; Chen, Der-Thanq

    2009-01-01

    This paper describes how a new classroom environment instrument, the "Chinese Language Classroom Environment Inventory (CLCEI)", was developed to investigate the nature of Chinese language classroom learning environments in Singapore secondary schools. The CLCEI is a bilingual instrument (English and Chinese Language) with 48 items written in both…

  6. Solvation dynamics in aqueous anionic and cationic micelle solutions: sodium alkyl sulfate and alkyltrimethylammonium bromide.

    PubMed

    Tamoto, Yushi; Segawa, Hiroshi; Shirota, Hideaki

    2005-04-26

    Solvation dynamics of the fluorescence probe, coumarin 102, in anionic surfactant, sodium alkyl sulfate (C(n)H(2n+1)SO(4)Na; n = 8, 10, 12, and 14), and cationic surfactant, alkyltrimethylammonium bromide (C(n)H(2n+1)N(CH(3))(3)Br; n = 10, 12, 14, and 16), micelle solutions have been investigated by a picosecond streak camera system. The solvation dynamics in the time range of 10(-10)-10(-8) s is characterized by a biexponential function. The faster solvation time constants are about 110-160 ps for both anionic and cationic micelle solutions, and the slower solvation time constants for sodium alkyl sulfate and alkyltrimethylammonium bromide micelle solutions are about 1.2-2.6 ns and 450-740 ps, respectively. Both the faster and the slower solvation times become slower with longer alkyl chain surfactant micelles. The alkyl-chain-length dependence of the solvation dynamics in both sodium alkyl sulfate and alkyltrimethylammonium bromide micelles can be attributed to the variation of the micellar surface density of the polar headgroup by the change of the alkyl chain length. The slower solvation time constants of sodium alkyl sulfate micelle solutions are about 3.5 times slower than those of alkyltrimethylammonium bromide micelle solutions for the same alkyl-chain-length surfactants. The interaction energies of the geometry optimized mimic clusters (H(2)O-C(2)H(5)SO(4)(-) and H(2)O-C(2)H(5)N(CH(3))(3)(+)) have been estimated by the density functional theory calculations to understand the interaction strengths between water and alkyl sulfate and alkyltrimethylammonium headgroups. The difference of the slower solvation time constants between sodium alkyl sulfate and alkyltrimethylammonium bromide micelle solutions arises likely from their different specific interactions.

  7. Semi-crystalline polymethylene-b-poly(acrylic acid) diblock copolymers: aggregation behavior, confined crystallization and controlled growth of semicrystalline micelles from dilute DMF solution.

    PubMed

    Wang, Hongfang; Wu, Cong; Xia, Guangmei; Ma, Zhi; Mo, Guang; Song, Rui

    2015-03-01

    In this paper, we have systematically investigated the aggregation behavior, confined crystallization and controlled growth of a novel polyolefin analogue-containing block copolymers (BCPs), i.e., polymethylene-b-poly(acrylic acid) diblock copolymers (PM-b-PAA). On cooling from a homogenous DMF solution at 80 °C, PM-b-PAA was found to crystallize and aggregate with well-defined disk-like micelles. The aggregate behavior and in-plane morphology of PM-b-PAA could be easily controlled by modifying the block ratio, solution pH and solvent composition (DMF-water), by manipulating the crystallization of PM block and the stretching degree of solvated PAA corona. Further investigation of the crystalline feature of PM-b-PAA indicated that the crystallization of PM was retarded by tethered amorphous PAA segments. The crystalline micelle could construct a nano-confined environment with PM folding as the core into a thickness of the mono-layered polyethylene. Finally, when cultured in dilute DMF solution at 50 °C, the initial crystalline micelles, being as self-seeds, could follow a living growth mechanism and develop into single crystals, with well-defined lozenge-shaped morphology.

  8. Semi-crystalline polymethylene-b-poly(acrylic acid) diblock copolymers: aggregation behavior, confined crystallization and controlled growth of semicrystalline micelles from dilute DMF solution.

    PubMed

    Wang, Hongfang; Wu, Cong; Xia, Guangmei; Ma, Zhi; Mo, Guang; Song, Rui

    2015-03-01

    In this paper, we have systematically investigated the aggregation behavior, confined crystallization and controlled growth of a novel polyolefin analogue-containing block copolymers (BCPs), i.e., polymethylene-b-poly(acrylic acid) diblock copolymers (PM-b-PAA). On cooling from a homogenous DMF solution at 80 °C, PM-b-PAA was found to crystallize and aggregate with well-defined disk-like micelles. The aggregate behavior and in-plane morphology of PM-b-PAA could be easily controlled by modifying the block ratio, solution pH and solvent composition (DMF-water), by manipulating the crystallization of PM block and the stretching degree of solvated PAA corona. Further investigation of the crystalline feature of PM-b-PAA indicated that the crystallization of PM was retarded by tethered amorphous PAA segments. The crystalline micelle could construct a nano-confined environment with PM folding as the core into a thickness of the mono-layered polyethylene. Finally, when cultured in dilute DMF solution at 50 °C, the initial crystalline micelles, being as self-seeds, could follow a living growth mechanism and develop into single crystals, with well-defined lozenge-shaped morphology. PMID:25608942

  9. UVES Investigates the Environment of a Very Remote Galaxy

    NASA Astrophysics Data System (ADS)

    2002-03-01

    Surplus of Intergalactic Material May Be Young Supercluster Summary Observations with ESO's Very Large Telescope (VLT) have enabled an international group of astronomers [1] to study in unprecedented detail the surroundings of a very remote galaxy, almost 12 billion light-years distant [2]. The corresponding light travel time means that it is seen at a moment only about 3 billion years after the Big Bang. This galaxy is designated MS 1512-cB58 and is the brightest known at such a large distance and such an early time. This is due to a lucky circumstance: a massive cluster of galaxies ( MS 1512+36 ) is located about halfway along the line-of-sight, at a distance of about 7 billion light-years, and acts as a gravitational "magnifying glass". Thanks to this lensing effect, the image of MS1512-cB58 appears 50 times brighter . Nevertheless, the apparent brightness is still as faint as magnitude 20.6 (i.e., nearly 1 million times fainter than what can be perceived with the unaided eye). Moreover, MS 1512-cB58 is located 36° north of the celestial equator and never rises more than 29° above the horizon at Paranal. It was therefore a great challenge to secure the present observational data with the UVES high-dispersion spectrograph on the 8.2-m VLT KUEYEN telescope . The extremely detailed UVES-spectrum of MS 1512-cB58 displays numerous signatures (absorption lines) of intergalactic gas clouds along the line-of-sight . Some of the clouds are quite close to the galaxy and the astronomers have therefore been able to investigate the distribution of matter in its immediate surroundings. They found an excess of material near MS 1512-cB58, possible evidence of a young supercluster of galaxies , already at this very early epoch. The new observations thus provide an invaluable contribution to current studies of the birth and evolution of structures in the early Universe. This is the first time this kind of observation has ever been done of a galaxy at such a large distance . All

  10. Structural behaviour of mixed cationic surfactant micelles: a small-angle neutron scattering study.

    PubMed

    Bergström, L Magnus; Garamus, Vasil M

    2012-09-01

    Self-assembly in mixtures of two single-chain cationic surfactants, with different tail lengths (CTAB and DTAB) as well as of a single-chain (DTAB) and a double-chain (DDAB) cationic surfactant, with identical tail lengths, have been investigated with small-angle neutron scattering (SANS) and rationalised in terms of bending elasticity properties. The growth behaviour of micelles with respect to surfactant composition appears completely different in the two surfactant mixtures. DTAB form small oblate spheroidal micelles in presence of [NaBr]=0.1 M that transform into prolate spheroidal mixed CTAB/DTAB micelles upon adding moderate amounts of CTAB, so as to give a mole fraction y=0.20 in solution. Most unexpectedly, upon further addition of CTAB the mixed CTAB/DTAB micelles grow with an almost equal rate in both length and width directions to form tablets. In contrast to this behaviour, mixed DDAB/DTAB micelles grow virtually exclusively in the length direction, in presence of [NaBr]=0.1 M, to form elongated ellipsoidal (tablet-shaped) and subsequently long wormlike micelles as the fraction of DDAB in the micelles increases. Mixed DDAB/DTAB micelles grow to become as long as 2000Å before an abrupt transition to large bilayer structures occurs. This means that the micelles are much longer at the micelle-to-bilayer transition as compared to the same mixture in absence of added salt. It is found that the point of transition from micelles to bilayers is significantly shifted towards higher fractions of aggregated DTAB as an appreciable amount of salt is added to DDAB/DTAB mixtures, indicating a considerable reduction of the spontaneous curvature with an increasing [NaBr]. By means of deducing the various bending elasticity constants from our experimental results, according to a novel approach by ours, we are able to conclude that the different growth behaviours appear as a consequence of a considerably lower bending rigidity, as well as higher saddle-splay constant

  11. 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

  12. 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.

  13. 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

  14. A molecular dynamics study of the breathing and deforming modes of the spherical ionic SDS and nonionic C12E8 micelles

    NASA Astrophysics Data System (ADS)

    Wang, Lin; Fujimoto, Kazushi; Yoshii, Noriyuki; Okazaki, Susumu

    2016-01-01

    In order to investigate shape of the micelles and its thermal fluctuations, molecular dynamics calculations have been performed for spherical ionic sodium dodecyl sulfate (SDS) and nonionic octaethyleneglycol monododecyl ether (C12E8) micelles. New statistical functions suitable for extracting the fluctuations of the shape of the spherical micelles were defined using spherical harmonics and Legendre polynomials. The breathing and deforming modes of the SDS and C12E8 micelles were analyzed in detail based on these new functions. The elastic nature of the micelle core was also discussed. The present analysis gives a new molecular picture that the micelle shape is a superposition of the various kinds of breathing and deforming modes, and each mode has a specific relaxation time of the shape fluctuation.

  15. Photosensitizer cross-linked nano-micelle platform for multimodal imaging guided synergistic photothermal/photodynamic therapy.

    PubMed

    Liu, Xiaodong; Yang, Guangbao; Zhang, Lifen; Liu, Zhuang; Cheng, Zhenping; Zhu, Xiulin

    2016-08-18

    The multifunctional nano-micelle platform holds great promise to enhance the accuracy and efficiency of cancer diagnosis and therapy. In this work, an amphiphilic poly[(poly(ethylene glycol) methyl ether methacrylate)-co-(3-aminopropyl methacrylate)]-block-poly(methyl methacrylate) (P(PEGMA-co-APMA)-b-PMMA) block copolymer was synthesized by successive RAFT polymerizations and subsequent chemical modification. Then the multifunctional micelles with high solubility in physiological environments were developed by a self-assembly and crosslinking processes. The photosensitizer segment, 5,10,15,20-tetrakis (4-carboxyphenyl) porphyrin (TCPP), serves as a tetra-functional cross-linker, photodynamic agent, fluorescence indicator, as well as magnetic resonance (MR) contrast agent after labelling with manganese ions (Mn(2+)), while IR825 simultaneously locating in the interior of the fabricated micelles contributed to the photoacoustic (PA) imaging ability and the photothermal effect. The prepared nanoparticles show great stability in a physiological environment with uniform morphology and diameters of around 80 nm as disclosed by stability investigation, TEM and DLS analysis. IR825@P(PEGMA-co-APMA)-b-PMMA@TCPP/Mn nanoparticles displayed high in vivo tumor uptake with a long blood circulation half-life (∼3.64 h) by the EPR effect after intravenous (i.v.) injection, as revealed by fluorescence, MR and PA imaging models. In vivo anti-tumor effects were achieved via a combined photothermal and photodynamic therapy without noticeable dark toxicity, and this strategy was able to induce a remarkably improved synergistic therapeutic effect to both superficial and deep regions of tumors under mild conditions compared with either single photothermal or photodynamic mechanisms. PMID:27503666

  16. 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)

  17. Pluronic® P123/F127 mixed micelles delivering sorafenib and its combination with verteporfin in cancer cells

    PubMed Central

    Pellosi, Diogo Silva; Moret, Francesca; Fraix, Aurore; Marino, Nino; Maiolino, Sara; Gaio, Elisa; Hioka, Noboru; Reddi, Elena; Sortino, Salvatore; Quaglia, Fabiana

    2016-01-01

    Here, we developed Pluronic® P123/F127 (poloxamer) mixed micelles for the intravenous delivery of the anticancer drug sorafenib (SRB) or its combination with verteporfin (VP), a photosensitizer for photodynamic therapy that should complement well the cytotoxicity profile of the chemotherapeutic. SRB loading inside the core of micelles was governed by the drug:poloxamer weight ratio, while in the case of the SRB–VP combination, a mutual interference between the two drugs occurred and only specific ratios could ensure maximum loading efficiency. Coentrapment of SRB did not alter the photophysical properties of VP, confirming that SRB did not participate in any bimolecular process with the photosensitizer. Fluorescence resonance energy-transfer measurement of micelles in serum protein-containing cell-culture medium demonstrated the excellent stability of the system in physiologically relevant conditions. These results were in line with the results of the release study showing a release rate of both drugs in the presence of proteins slower than in phosphate buffer. SRB release was sustained, while VP remained substantially entrapped in the micelle core. Cytotoxicity studies in MDA-MB231 cells revealed that at 24 hours, SRB-loaded micelles were more active than free SRB only at very low SRB concentrations, while at 24+24 hours a prolonged cytotoxic effect of SRB-loaded micelles was observed, very likely mediated by the block in the S phase of the cell cycle. The combination of SRB with VP under light exposure was less cytotoxic than both the free combination and VP-loaded micelles + SRB-loaded micelles combination. This behavior was clearly explainable in terms of micelle uptake and intracellular localization. Besides the clear advantage of delivering SRB in poloxamer micelles, our results provide a clear example that each photochemotherapeutic combination needs detailed investigations on their particular interaction, and no generalization on enhanced cytotoxic

  18. Polymer micelles with hydrophobic core and ionic amphiphilic corona. 1. Statistical distribution of charged and nonpolar units in corona.

    PubMed

    Lysenko, Evgeny A; Kulebyakina, Alevtina I; Chelushkin, Pavel S; Rumyantsev, Artem M; Kramarenko, Elena Yu; Zezin, Alexander B

    2012-12-11

    Polymer micelles with hydrophobic polystyrene (PS) core and ionic amphiphilic corona from charged N-ethyl-4-vinylpyridinium bromide (EVP) and uncharged 4-vinylpyridine (4VP) units spontaneously self-assembled from PS-block-poly(4VP-stat-EVP) macromolecules in mixed dimethylformamide/methanol/water solvent. The fraction of statistically distributed EVP units in corona-forming block is β = [EVP]/([EVP]+[4VP]) = 0.3-1. Micelles were transferred into water via dialysis technique, and pH was adjusted to 9, where 4VP is insoluble. Structural characteristics of micelles were investigated both experimentally and theoretically as a function of corona composition β. Methods of dynamic and static light scattering, electrophoretic mobility measurements, sedimentation velocity, transmission electron microscopy, and UV spectrophotometry were applied. All micelles possessed spherical morphology. The aggregation number, structure, and electrophoretic mobility of micelles changed in a jumplike manner near β ~ 0.6-0.75. Below and above this region, micelle characteristics were constant or insignificantly changed upon β. Theoretical dependencies for micelle aggregation number, corona dimensions, and fraction of small counterions outside corona versus β were derived via minimization the micelle free energy, taking into account surface, volume, electrostatic, and elastic contributions of chain units and translational entropy of mobile counterions. Theoretical estimations also point onto a sharp structural transition at a certain corona composition. The abrupt reorganization of micelle structure at β ~ 0.6-0.75 entails dramatic changes in micelle dispersion stability in the presence of NaCl or in the presence of oppositely charged polymeric (sodium polymethacrylate) or amphiphilic (sodium dodecyl sulfate) complexing agents.

  19. Pluronic® P123/F127 mixed micelles delivering sorafenib and its combination with verteporfin in cancer cells

    PubMed Central

    Pellosi, Diogo Silva; Moret, Francesca; Fraix, Aurore; Marino, Nino; Maiolino, Sara; Gaio, Elisa; Hioka, Noboru; Reddi, Elena; Sortino, Salvatore; Quaglia, Fabiana

    2016-01-01

    Here, we developed Pluronic® P123/F127 (poloxamer) mixed micelles for the intravenous delivery of the anticancer drug sorafenib (SRB) or its combination with verteporfin (VP), a photosensitizer for photodynamic therapy that should complement well the cytotoxicity profile of the chemotherapeutic. SRB loading inside the core of micelles was governed by the drug:poloxamer weight ratio, while in the case of the SRB–VP combination, a mutual interference between the two drugs occurred and only specific ratios could ensure maximum loading efficiency. Coentrapment of SRB did not alter the photophysical properties of VP, confirming that SRB did not participate in any bimolecular process with the photosensitizer. Fluorescence resonance energy-transfer measurement of micelles in serum protein-containing cell-culture medium demonstrated the excellent stability of the system in physiologically relevant conditions. These results were in line with the results of the release study showing a release rate of both drugs in the presence of proteins slower than in phosphate buffer. SRB release was sustained, while VP remained substantially entrapped in the micelle core. Cytotoxicity studies in MDA-MB231 cells revealed that at 24 hours, SRB-loaded micelles were more active than free SRB only at very low SRB concentrations, while at 24+24 hours a prolonged cytotoxic effect of SRB-loaded micelles was observed, very likely mediated by the block in the S phase of the cell cycle. The combination of SRB with VP under light exposure was less cytotoxic than both the free combination and VP-loaded micelles + SRB-loaded micelles combination. This behavior was clearly explainable in terms of micelle uptake and intracellular localization. Besides the clear advantage of delivering SRB in poloxamer micelles, our results provide a clear example that each photochemotherapeutic combination needs detailed investigations on their particular interaction, and no generalization on enhanced cytotoxic

  20. Hemocompatible curcumin-dextran micelles as pH sensitive pro-drugs for enhanced therapeutic efficacy in cancer cells.

    PubMed

    Raveendran, Radhika; Bhuvaneshwar, G S; Sharma, Chandra P

    2016-02-10

    Curcumin, a component in spice turmeric, is renowned to possess anti-cancer therapeutic potential. However, low aqueous solubility and instability of curcumin which subsequently affects its bioavailability pose as major impediments in its translation to clinical application. In this regard, we focused on conjugating hydrophobic curcumin to the hydrophilic backbone of dextran via succinic acid spacer to design a pro-drug. The structural confirmation of the conjugates was carried out using FTIR and (1)H NMR spectroscopy. Critical micelle measurement affirmed the micelle formation of the pro-drug in aqueous media. The size distribution and zeta potential of the curcumin-dextran (Cur-Dex) micelles were determined using dynamic light scattering technique. The micellar architecture bestowed curcumin negligible susceptibility to degradation under physiological conditions along with enhanced aqueous solubility. Biocompatibility of the micelles was proved by the blood component aggregation and plasma protein interaction studies. In vitro release studies demonstrated the pH sensitivity release of curcumin which is conducive to the tumour micro environment. Profound cytotoxic effects of Cur-Dex micelles in C6 glioma cells were observed from MTT and Live/Dead assay experiments. Moreover, enhanced cellular internalization of the Cur-Dex micelles compared to free curcumin in the cancer cells was revealed by fluorescence microscopy. Our study focuses on the feasibility of Cur-Dex micelles to be extrapolated as promising candidates for safe and efficient cancer therapy.

  1. Hemocompatible curcumin-dextran micelles as pH sensitive pro-drugs for enhanced therapeutic efficacy in cancer cells.

    PubMed

    Raveendran, Radhika; Bhuvaneshwar, G S; Sharma, Chandra P

    2016-02-10

    Curcumin, a component in spice turmeric, is renowned to possess anti-cancer therapeutic potential. However, low aqueous solubility and instability of curcumin which subsequently affects its bioavailability pose as major impediments in its translation to clinical application. In this regard, we focused on conjugating hydrophobic curcumin to the hydrophilic backbone of dextran via succinic acid spacer to design a pro-drug. The structural confirmation of the conjugates was carried out using FTIR and (1)H NMR spectroscopy. Critical micelle measurement affirmed the micelle formation of the pro-drug in aqueous media. The size distribution and zeta potential of the curcumin-dextran (Cur-Dex) micelles were determined using dynamic light scattering technique. The micellar architecture bestowed curcumin negligible susceptibility to degradation under physiological conditions along with enhanced aqueous solubility. Biocompatibility of the micelles was proved by the blood component aggregation and plasma protein interaction studies. In vitro release studies demonstrated the pH sensitivity release of curcumin which is conducive to the tumour micro environment. Profound cytotoxic effects of Cur-Dex micelles in C6 glioma cells were observed from MTT and Live/Dead assay experiments. Moreover, enhanced cellular internalization of the Cur-Dex micelles compared to free curcumin in the cancer cells was revealed by fluorescence microscopy. Our study focuses on the feasibility of Cur-Dex micelles to be extrapolated as promising candidates for safe and efficient cancer therapy. PMID:26686156

  2. 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

  3. 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.

  4. Investigating the effectiveness of the surfactant dioctyl sodium sulfosuccinate to disperse oil in a changing marine environment

    NASA Astrophysics Data System (ADS)

    Steffy, David A.; Nichols, Alfred C.; Kiplagat, George

    2011-12-01

    We investigated the surfactant dioctyl sodium sulfosuccinate (DOSS) and its delivery system Corexit 9500A, used to disperse oil released during the Gulf of Mexico spill during the summer of 2010. DOSS is an organic sulfonic acid salt that acts as a synthetic detergent and disrupts the interfacial tension between the salt water and crude oil phases. The disruption reaches a maximum at or above the critical micelle concentration (CMC). The CMC for the surfactant was determined to be 0.17% solution in deionized water at a pH of 7.2 and a temperature of 21.1 °C (70°F). The CMC is lower in salt water, at 0.125% solution. This has been identified as a "salting out" effect (Somasundaran, 2006). The CMC of DOSS in both saline and deionized water occurred at lower-percent solutions at higher temperatures. The surface tension versus concentration plots can be modeled using a power equation, with correlation coefficients consistently over 0.94. Surface tension versus concentration plots are scalable to fit the desired temperature by the function f(x) = (1/1+Xα), where α =T1/T2. Tests measured the stability of the DOSS micelles when exposed to a continuous UVA radiation. This photodegradation is directly related to the duration of exposure.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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

  10. 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

  11. 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

  12. Molecular dynamics study of free energy of transfer of alcohol and amine from water phase to the micelle by thermodynamic integration method

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

    Free energy of transfer of methylamine, octylamine, methanol, and octanol from water phase to sodium dodecyl sulfate (SDS) micelle has been calculated using thermodynamic integration method combined with molecular dynamics calculations. Together with the results for alkanes obtained in our previous study [K. Fujimoto, N. Yoshii, and S. Okazaki, J. Chem. Phys. 133, 074511 (2010)], 10.1063/1.3469772, the effect of polar group on the partition of hydrophilic solutes between water phase and the micelle has been investigated in detail at a molecular level. The calculations showed that the molecules with octyl group are more stable in the SDS micelle than in the water phase due to their hydrophobicity of long alkyl chain. In contrast, methanol and methylamine are stable in the water phase as well as in the micelle because of their high hydrophilicity. The spatial distribution of methylamine, octylamine, methanol, and octanol has also been evaluated as a function of the distance, R, from the center of mass of SDS micelle to the solutes. The distribution shows that the methylamine molecule is adsorbed on the SDS micelle surface, while the methanol molecule is delocalized among the whole system, i.e., in the water phase, on the surface of the micelle, and in the hydrophobic core of the micelle. The octylamine and octanol molecules are solubilized in the SDS micelle with palisade layer structure and are not found in the water phase.

  13. Periodic behavior of lanthanide coordination within reverse micelles.

    PubMed

    Ellis, Ross J; Meridiano, Yannick; Chiarizia, Renato; Berthon, Laurence; Muller, Julie; Couston, Laurent; Antonio, Mark R

    2013-02-18

    Trends in lanthanide(III) (Ln(III)) coordination were investigated within nanoconfined solvation environments. Ln(III) ions were incorporated into the cores of reverse micelles (RMs) formed with malonamide amphiphiles in n-heptane by contact with aqueous phases containing nitrate and Ln(III); both insert into pre-organized RM units built up of DMDOHEMA (N,N'-dimethyl-N,N'-dioctylhexylethoxymalonamide) that are either relatively large and hydrated or small and dry, depending on whether the organic phase is acidic or neutral, respectively. Structural aspects of the Ln(III) complex formation and the RM morphology were obtained by use of XAS (X-ray absorption spectroscopy) and SAXS (small-angle X-ray scattering). The Ln(III) coordination environments were determined through use of L(3)-edge XANES (X-ray absorption near edge structure) and EXAFS (extended X-ray absorption fine structure), which provide metrical insights into the chemistry across the period. Hydration numbers for the Eu species were measured using TRLIFS (time-resolved laser-induced fluorescence spectroscopy). The picture that emerges from a system-wide perspective of the Ln-O interatomic distances and number of coordinating oxygen atoms for the extracted complexes of Ln(III) in the first half of the series (i.e., Nd, Eu) is that they are different from those in the second half of the series (i.e., Tb, Yb): the number of coordinating oxygen atoms decrease from 9O for early lanthanides to 8O for the late ones--a trend that is consistent with the effect of the lanthanide contraction. The environment within the RM, altered by either the presence or absence of acid, also had a pronounced influence on the nitrate coordination mode; for example, the larger, more hydrated, acidic RM core favors monodentate coordination, whereas the small, dry, neutral core favors bidentate coordination to Ln(III). These findings show that the coordination chemistry of lanthanides within nanoconfined environments is neither

  14. Uptake of organic pollutants by silica--polycation-Immobilized micelles for groundwater remediation.

    PubMed

    Mishael, Yael G; Dubin, Paul L

    2005-11-01

    Interest has grown in designing new materials for groundwater treatment via "permeable reactive barriers". In the present case, a model siliceous surface, controlled pore glass (CPG), was treated with a polycation (quaternized polyvinyl pyridine, QPVP) which immobilizes anionic/nonionic mixed micelles, in order to solubilize a variety of hydrophobic pollutants. Polymer adsorption on CPG showed atypically slow kinetics and linear adsorption isotherms, which may be a consequence of the substrate porosity. The highest toluene solubilization efficiency was achieved for the silica-polycation-immobilized micelles (SPIM) with the highest polymer loading and lowest micelle binding, a result discussed in terms of the configuration of the bound polymer and the corresponding state of the bound micelles. The ability of SPIM to treat simultaneously a wide range of pollutants and reduce their concentration in solution by 20-90% was demonstrated. Optimization of SPIM systems for remediation calls for a better understanding of both the local environment of the bound micelles and their intrinsic affinities for different hydrophobic pollutants.

  15. An Empirical Investigation of the Dimensionality of the Physical Literacy Environment in Early Childhood Classrooms

    ERIC Educational Resources Information Center

    Dynia, Jaclyn M.; Schachter, Rachel E.; Piasta, Shayne B.; Justice, Laura M.; O'Connell, Ann A.; Yeager Pelatti, Christina

    2016-01-01

    This study investigated the dimensionality of the physical literacy environment of early childhood education classrooms. Data on the classroom physical literacy environment were collected from 245 classrooms using the Classroom Literacy Observation Profile. A combination of confirmatory and exploratory factor analysis was used to identify five…

  16. Student-Centred Learning Environments: An Investigation into Student Teachers' Instructional Preferences and Approaches to Learning

    ERIC Educational Resources Information Center

    Baeten, Marlies; Dochy, Filip; Struyven, Katrien; Parmentier, Emmeline; Vanderbruggen, Anne

    2016-01-01

    The use of student-centred learning environments in education has increased. This study investigated student teachers' instructional preferences for these learning environments and how these preferences are related to their approaches to learning. Participants were professional Bachelor students in teacher education. Instructional preferences and…

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. Reverse micelle microstructural transformations induced by surfactant molecular structure, concentration, and temperature.

    PubMed

    Shrestha, Rekha Goswami; Shrestha, Lok Kumar; Ariga, Katsuhiko; Abe, Masahiko

    2011-09-01

    We have investigated the microstructural transformations of nonionic surfactant reverse micelles induced by surfactant molecular architecture, surfactant concentration, and temperature in nonaqueous media. The investigations were based on small-angle X-ray scattering (SAXS) and rheometry techniques. Polyglycerol polyoleic acid esters spontaneously self-assembled into reverse micelle in n-decane under ambient conditions, whose shape, size, and internal structure could be controlled by the surfactant molecular architecture, concentration, and temperature. The maximum size of the micelles was found to increase with an increase in the hydrophilic headgroup size of the surfactant. On the other hand, an opposite trend was observed with an increase in the number of oleate chain per surfactant molecules, which was well supported by rheology data; viscosity decreased with the number of oleate chain per surfactant molecule. The SAXS and rheology data have shown a clear evidence of one dimensional micellar growth with increase in the surfactant concentration. The relative viscosity, eta(r), of the reverse micelle exhibited steeper concentration dependence behavior than those predicted for a dispersion of spherical particles based on the Krieger-Dougherty relation which provided a clear evidence of the presence of elongated micelles at higher concentration. An ellipsoidal prolate-to-sphere type transition was observed upon heating.

  2. Tumor homing indocyanine green encapsulated micelles for near infrared and photoacoustic imaging of tumors.

    PubMed

    Uthaman, Saji; Bom, Joon-suk; Kim, Hyeon Sik; John, Johnson V; Bom, Hee-Seung; Kim, Seon-Jong; Min, Jung-Joon; Kim, Il; Park, In-Kyu

    2016-05-01

    Photoacoustic imaging (PAI) is an emerging analytical modality that is under intense preclinical development for the early diagnosis of various medical conditions, including cancer. However, the lack of specific tumor targeting by various contrast agents used in PAI obstructs its clinical applications. In this study, we developed indocyanine green (ICG)-encapsulated micelles specific for the CD 44 receptor and used in near infrared and photoacoustic imaging of tumors. ICG was hydrophobically modified prior to loading into hyaluronic acid (HA)-based micelles utilized for CD 44 based-targeting. We investigated the physicochemical characteristics of prepared HA only and ICG-encapsulated HA micelles (HA-ICG micelles). After intravenous injection of tumor-bearing mice, the bio-distribution and in vivo photoacoustic images of ICG-encapsulated HA micelles accumulating in tumors were also investigated. Our study further encourages the application of this HA-ICG-based nano-platform as a tumor-specific contrast agent for PAI. PMID:26743660

  3. Actively targeted delivery of anticancer drug to tumor cells by redox-responsive star-shaped micelles.

    PubMed

    Shi, Chunli; Guo, Xing; Qu, Qianqian; Tang, Zhaomin; Wang, Yi; Zhou, Shaobing

    2014-10-01

    In cancer therapy nanocargos based on star-shaped polymer exhibit unique features such as better stability, smaller size distribution and higher drug capacity in comparison to linear polymeric micelles. In this study, we developed a multifunctional star-shaped micellar system by combination of active targeting ability and redox-responsive behavior. The star-shaped micelles with good stability were self-assembled from four-arm poly(ε-caprolactone)-poly(ethylene glycol) copolymer. The redox-responsive behaviors of these micelles triggered by glutathione were evaluated from the changes of micellar size, morphology and molecular weight. In vitro drug release profiles exhibited that in a stimulated normal physiological environment, the redox-responsive star-shaped micelles could maintain good stability, whereas in a reducing and acid environment similar with that of tumor cells, the encapsulated agent was promptly released. In vitro cellular uptake and subcellular localization of these micelles were further studied with confocal laser scanning microscopy and flow cytometry against the human cervical cancer cell line HeLa. In vivo and ex vivo DOX fluorescence imaging displayed that these FA-functionalized star-shaped micelles possessed much better specificity to target solid tumor. Both the qualitative and quantitative results of the antitumor effect in 4T1 tumor-bearing BALB/c mice demonstrated that these redox-responsive star-shaped micelles have a high therapeutic efficiency to artificial solid tumor. Therefore, the multifunctional star-shaped micelles are a potential platform for targeted anticancer drug delivery.

  4. How do polymeric micelles cross epithelial barriers?

    PubMed

    Pepić, Ivan; Lovrić, Jasmina; Filipović-Grčić, Jelena

    2013-09-27

    Non-parenteral delivery of drugs using nanotechnology-based delivery systems is a promising non-invasive way to achieve effective local or systemic drug delivery. The efficacy of drugs administered non-parenterally is limited by their ability to cross biological barriers, and epithelial tissues particularly present challenges. Polymeric micelles can achieve transepithelial drug delivery because of their ability to be internalized into cells and/or cross epithelial barriers, thereby delivering drugs either locally or systematically following non-parenteral administration. This review discusses the particular characteristics of various epithelial barriers and assesses their potential as non-parenteral routes of delivery. The material characteristics of polymeric micelles (e.g., size, surface charge, and surface decoration) and of unimers dissociated from polymeric micelles determine their interactions (non-specific and/or specific) with mucus and epithelial cells as well as their intracellular fate. This paper outlines the mechanisms governing the major modes of internalization of polymeric micelles into epithelial cells, with an emphasis on specific recent examples of the transport of drug-loaded polymeric micelles across epithelial barriers.

  5. Structure and molecular dynamics of sodium dodecylsulfate micelles modified with hydrophilic short-chain imidazolium salts in aqueous solution.

    PubMed

    Lin, Jia-Hsien; Hou, Sheng-Shu

    2016-07-15

    This study uses pyrene solubilization and NMR experiments to investigate the effects of two hydrophilic short-chain ionic liquids (ILs), 1-ethyl-3-methylimidazolium tetrafluoroborate (EmimBF4) and 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF4) on the micellization of sodium dodecylsulfate (SDS) in the aqueous phase. The results of the pyrene solubilization experiments indicate that the added short-chain ILs not only promote the micellization of SDS but also modify micelle properties. For NMR studies, the present study focuses on (1) the compositions and spatial arrangements of component molecules and (2) the molecular dynamics of DS(-) in the Rmim-modified SDS micelle. Using pulsed field gradient (PFG) NMR measurements, the composition of the Rmim-modified SDS micelle was calculated by the diffusion data and was found to be correlated with the [SDS]. Two-dimensional nuclear Overhauser effect spectroscopy (2D NOESY) experiments confirm that the 1-alkyl-3-methylimidazolium cation (Rmim(+)) is located inside the Rmim-modified SDS micelle. Corresponding to the microstructure of the Rmim-modified SDS micelle, in terms of (1)H T1 relaxation, the fast motion of SDS α-CH2 and β-CH2 segments are markedly restricted by the attached Rmim(+) to the sulfate group of DS(-), whereas the central carbons and the terminal CH3 group of DS(-) are only slightly affected. The chemical shift analysis indicates that the surface of the Rmim-modified SDS micelle is dehydrated by the absorbed Rmim(+) and becomes more hydrophobic than that of the pure SDS micelle. Insertion of Rmim(+) into the Rmim-modified SDS micelle appears to be driven through the hydrophobic interaction, and it is shown to combine with SDS molecules to constitute the hydrophobic part of the Rmim-modified SDS micelle.

  6. Folate-conjugated polymer micelles for active targeting to cancer cells: preparation, in vitro evaluation of targeting ability and cytotoxicity

    NASA Astrophysics Data System (ADS)

    You, Jian; Li, Xin; de Cui, Fu; Du, Yong-Zhong; Yuan, Hong; Hu, Fu qiang

    2008-01-01

    To obtain an active-targeting carrier to cancer cells, folate-conjugated stearic acid grafted chitosan oligosaccharide (Fa-CSOSA) was synthesized by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)-mediated coupling reaction. The substitution degree is 22.1%. The critical micelle concentrations (CMCs) of Fa-CSOSA were 0.017 and 0.0074 mg ml-1 in distilled water and PBS (pH 7.4), respectively. The average volume size range of Fa-CSOSA micelles was 60-120 nm. The targeting ability of Fa-CSOSA micelles was investigated against two kinds of cell lines (A549 and Hela), which have different amounts of folate receptors in their surface. The results indicated that Fa-CSOSA micelles presented a targeting ability to the cells (Hela) with a higher expression of folate receptor during a short-time incubation (<6 h). As incubation proceeded, the special spatial structure of the micelles gradually plays a main role in cellular internalization of the micelles. Good internalization of the micelles into both Hela and A549 cells was shown. Then, paclitaxel (PTX) was encapsulated into the micelles, and the content of PTX in the micelles was about 4.8% (w/w). The average volume size range of PTX-loaded micelles was 150-340 nm. Furthermore, the anti-tumor efficacy in vitro was investigated by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) method. The IC50 of Taxol (a clinical formulation containing PTX) on A549 and Hela cells was 7.0 and 11.0 µg ml-1, respectively. The cytotoxicity of PTX-loaded micelles was improved sharply (IC50 on A549: 0.32 µg ml-1 IC50 on Hela: 0.268 µg ml-1). This is attributed to the increased intracellular delivery of the drug. The Fa-CSOSA micelles that are presented may be a promising active-targeting carrier candidate via folate mediation.

  7. 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

  8. Targeted anti-thrombotic protein micelles

    PubMed Central

    Kim, Wookhyun; Haller, Carolyn; Dai, Erbin; Wang, Xiowei; Hagemeyer, Christoph E.; Liu, David R.; Peter, Karlheinz; Chaikof, Elliot L.

    2015-01-01

    Activated platelets provide a promising target for imaging inflammatory and thrombotic events along with site-specific delivery of a variety of therapeutic agents. Herein, we report the efficient design of multifunctional protein micelles bearing targeting and therapeutic proteins by one-pot transpeptidation using an evolved sortase A. Conjugation to the corona of a single-chain antibody (scFv), which binds to the ligand induced binding site (LIBS) of activated GPIIb/IIIa receptors enabled efficient detection of thrombi. Inhibiting thrombus formation was subsequently accomplished by incorporating the catalytically active domain of thrombomodulin (TM) onto the micelle corona for local generation of activated protein C, which serves to inhibit thrombin formation. An effective strategy has been developed for preparation of protein micelles that can be targeted to sites of activated platelets with broad potential for treatment of acute thrombotic events. PMID:25504546

  9. Vibrational dynamics of ice in reverse micelles.

    PubMed

    Dokter, Adriaan M; Petersen, Christian; Woutersen, Sander; Bakker, Huib J

    2008-01-28

    The ultrafast vibrational dynamics of HDO:D(2)O ice at 180 K in anionic reverse micelles is studied by midinfrared femtosecond pump-probe spectroscopy. Solutions containing reverse micelles are cooled to low temperatures by a fast-freezing procedure. The heating dynamics of the micellar solutions is studied to characterize the micellar structure. Small reverse micelles with a water content up to approximately 150 water molecules contain an amorphous form of ice that shows remarkably different vibrational dynamics compared to bulk hexagonal ice. The micellar amorphous ice has a much longer vibrational lifetime than bulk hexagonal ice and micellar liquid water. The vibrational lifetime is observed to increase linearly from 0.7 to 4 ps with the resonance frequency ranging from 3100 to 3500 cm(-1). From the pump dependence of the vibrational relaxation the homogeneous linewidth of the amorphous ice is determined (55+/-5 cm(-1)).

  10. Entropic effects, shape, and size of mixed micelles formed by copolymers with complex architectures.

    PubMed

    Kalogirou, Andreas; Gergidis, Leonidas N; Moultos, Othonas; Vlahos, Costas

    2015-11-01

    The entropic effects in the comicellization behavior of amphiphilic AB copolymers differing in the chain size of solvophilic A parts were studied by means of molecular dynamics simulations. In particular, mixtures of miktoarm star copolymers differing in the molecular weight of solvophilic arms were investigated. We found that the critical micelle concentration values show a positive deviation from the analytical predictions of the molecular theory of comicellization for chemically identical copolymers. This can be attributed to the effective interactions between copolymers originated from the arm size asymmetry. The effective interactions induce a very small decrease in the aggregation number of preferential micelles triggering the nonrandom mixing between the solvophilic moieties in the corona. Additionally, in order to specify how the chain architecture affects the size distribution and the shape of mixed micelles we studied star-shaped, H-shaped, and homo-linked-rings-linear mixtures. In the first case the individual constituents form micelles with preferential and wide aggregation numbers and in the latter case the individual constituents form wormlike and spherical micelles. PMID:26651715

  11. NMR characterization of membrane protein–detergent micelle solutions using microcoil equipment

    PubMed Central

    Stanczak, Pawel; Horst, Reto; Serrano, Pedro; Wüthrich, Kurt

    2010-01-01

    Using microcoil NMR technology, the uniformly 2H,15N-labeled integral membrane protein OmpX and the phosphocholine derivative detergent Fos-10 (n-decylphosphocholine), we investigated solutions of mixed protein–detergent micelles to determine the influence of the detergent concentration on the NMR spectra of the protein. In a first step, we identified key parameters that influence the composition of the micelle solutions, which resulted in a new protocol for the preparation of well-defined concentrated protein solutions. This led to the observation that high-quality 2D [15N,1H]-TROSY spectra of OmpX reconstituted in mixed micelles with Fos-10 were obtained only in a limited range of detergent concentrations. Outside of this range from about 90 mM to 180 mM, we observed a significant decrease of the average peak intensity. Relaxation-optimized NMR measurements of the rotational and translational diffusion coefficients of the OmpX/Fos-10 mixed micelles, Dr and Dt, respectively, then showed that the stoichiometry and the effective hydrodynamic radius of the protein-containing micelles are not significantly affected by high Fos-10 concentrations, and that the deterioration of NMR spectra is due to the increased viscosity at high detergent concentrations. The paper thus provides a basis for refined guidelines on the preparation of integral membrane proteins for structural studies. PMID:19950959

  12. NMR characterization of membrane protein-detergent micelle solutions by use of microcoil equipment.

    PubMed

    Stanczak, Pawel; Horst, Reto; Serrano, Pedro; Wüthrich, Kurt

    2009-12-30

    Using microcoil NMR technology, the uniformly (2)H,(15)N-labeled integral membrane protein OmpX, and the phosphocholine derivative detergent Fos-10 (n-decylphosphocholine), we investigated solutions of mixed protein-detergent micelles to determine the influence of the detergent concentration on the NMR spectra of the protein. In a first step, we identified key parameters that influence the composition of the micelle solutions, which resulted in a new protocol for the preparation of well-defined concentrated protein solutions. This led to the observation that high-quality 2D [(15)N,(1)H]-transverse relaxation-optimized spectroscopy (TROSY) spectra of OmpX reconstituted in mixed micelles with Fos-10 were obtained only in a limited range of detergent concentrations. Outside of this range from about 90-180 mM, we observed a significant decrease of the average peak intensity. Relaxation-optimized NMR measurements of the rotational and translational diffusion coefficients of the OmpX/Fos-10 mixed micelles, D(r) and D(t), respectively, then showed that the stoichiometry and the effective hydrodynamic radius of the protein-containing micelles are not significantly affected by high Fos-10 concentrations and that the deterioration of NMR spectra is due to the increased viscosity at high detergent concentrations. The paper thus provides a basis for refined guidelines on the preparation of integral membrane proteins for structural studies.

  13. Structure and rheological behavior of casein micelle suspensions during ultrafiltration process

    NASA Astrophysics Data System (ADS)

    Pignon, F.; Belina, G.; Narayanan, T.; Paubel, X.; Magnin, A.; Gésan-Guiziou, G.

    2004-10-01

    The stability and mechanism underlying the formation of deposits of casein micelles during ultrafiltration process were investigated by small-angle and ultra small-angle x-ray scattering (SAXS and USAXS). The casein micelle dispersions consisted of phospho-caseinate model powders and the measurements probed length scales ranging from 1 to 2000 nm. Rheometric and frontal filtration measurements were combined with SAXS to establish the relationship between the rheological behavior of deposits (shear and/or compression) and the corresponding microstructure. The results revealed two characteristic length scales for the equilibrium structure with radius of gyrations Rg, about 100 and 5.6 nm pertaining to the globular micelles and their non-globular internal structure, respectively. The SAXS measurements further indicated that the increase of temperature from 20 to 70 °C or the decrease of pH from 6.6 to 6 lead to agglomeration of the globular micelles. In situ scattering measurements showed that the decrease of permeation flows is directly related to the deformation and compression of the micelles in the immediate vicinity of the membrane.

  14. Titration of fatty acids solubilized in cationic and anionic micelles. Calorimetry and thermodynamic modeling.

    PubMed

    Söderman, Olle; Jönsson, Bengt; Olofsson, Gerd

    2006-02-23

    The electrostatic properties of charged surfactant micelles are investigated through titrations of fatty acid probes solubilized in the micelles. The titration process is followed by means of calorimetric measurements and by determining the pH values as a function of added base. This approach yields a complete thermodynamic description of the titration process. In particular, we find that the process is endothermic at 298 K. This is contrary to the titration of carboxylic acids in water, where DeltaH is approximately 0. To identify the main effect underlying the difference in DeltaH between titration in a micelle and water, a thermodynamic model has been developed which focuses on the transfer properties of charged and uncharged species from bulk water to the surface of a micelle and which incorporates a dielectric discontinuity at the micellar surface. The model relies on the use of the Poisson-Boltzmann equation which is solved using a finite element method. Experimental results and the model calculations imply that the dielectric discontinuity at (or near) the micellar surface plays a major role and hence must be included when analyzing the titration behavior of an acid functionality at the surface of a charged micelle.

  15. Solubilization of n-alkylbenzenes into gemini surfactant micelles in aqueous medium.

    PubMed

    Nakahara, Hiromichi; Kojima, Yui; Moroi, Yoshikiyo; Shibata, Osamu

    2014-05-27

    Solubilization of benzene, toluene, ethylbenzene, n-propylbenzene, n-butylbenzene, and n-pentylbenzene into micelles of decanediyl-1-10-bis(dimethyltetradecylammonium bromide) (14-10-14,2Br(-)) has been investigated in the temperature range from 288.2 to 308.2 K. The equilibrium concentrations of all the solubilizates are determined spectrophotometrically. The concentration of the solubilizates remains constant below the critical micelle concentration (cmc) and increases linearly with an increase in 14-10-14,2Br(-) concentration above the cmc. Compared to the mother micelle, the solubilized micelles indicate much larger hydrodynamic diameters, which are determined by dynamic light scattering. Therefore, the Gibbs energy change for the solubilization of n-alkylbenzenes has been evaluated by the partitioning of the solubilizates between the aqueous and micellar phases. Furthermore, the enthalpy and entropy changes for the solubilization could be calculated from temperature dependence of the Gibbs energy change. From the thermodynamic parameters, it is found that the solubilization for the present system is entropy-driven and that the location of the solubilizates moves into the inner core of the micelle with an elongation of their alkyl chains. The movement on the location is also supported by the results of absorption spectra, Fourier transform infrared (FTIR) spectra, and two-dimensional nuclear Overhauser effect spectroscopy (2-D NOESY). PMID:24802668

  16. Direct Measurement of the Thermodynamics of Chiral Recognition in Bile Salt Micelles.

    PubMed

    Anderson, Shauna L; Rovnyak, David; Strein, Timothy G

    2016-04-01

    Isothermal titration calorimetry (ITC) is shown to be a sensitive reporter of bile salt micellization and chiral recognition. Detailed ITC characterization of bile micelle formation as well as the chiral recognition capabilities of sodium cholate (NaC), deoxycholate (NaDC), and taurodeoxycholate (NaTDC) micelle systems are reported. The ΔH(demic) of these bile salt micelle systems is directly observable and is strongly temperature-dependent, allowing also for the determination of ΔCp(demic). Using the pseudo-phase separation model, ΔG(demic) and TΔS(demic) were also calculated. Chirally selective guest-host binding of model racemic compounds 1,1'-bi-2-napthol (BN) and 1,1'-binaphthyl-2,2'-diylhydrogenphosphate (BNDHP) to bile salt micelles was then investigated. The S-isomer was shown to bind more tightly to the bile salt micelles in all cases. A model was developed that allows for the quantitative determination of the enthalpic difference in binding affinity that corresponds to chiral selectivity, which is on the order of 1 kJ mol(-1).

  17. 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.

  18. 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.

  19. Polymeric micelles as carriers of diagnostic agents.

    PubMed

    Trubetskoy

    1999-04-01

    This review deals with diagnostic applications of polymeric micelles composed of amphiphilic block-copolymers. In aqueous solutions these polymers spontaneously form particles with diameter 20-100 nm. A variety of diagnostic moieties can be incorporated covalently or non-covalently into the particulates with high loads. Resulting particles can be used as particulate agents for diagnostic imaging using three major imaging modalities: gamma-scintigraphy, magnetic resonance imaging and computed tomography. The use of polyethyleneoxide-diacyllipid micelles loaded with chelated (111)In/Gd(3+) as well as iodine-containing amphiphilic copolymer in percutaneous lymphography and blood pool/liver imaging are discussed as specific examples.

  20. "Non-equilibrium" block copolymer micelles with glassy cores: a predictive approach based on theory of equilibrium micelles.

    PubMed

    Nagarajan, Ramanathan

    2015-07-01

    Micelles generated in water from most amphiphilic block copolymers are widely recognized to be non-equilibrium structures. Typically, the micelles are prepared by a kinetic process, first allowing molecular scale dissolution of the block copolymer in a common solvent that likes both the blocks and then gradually replacing the common solvent by water to promote the hydrophobic blocks to aggregate and create the micelles. The non-equilibrium nature of the micelle originates from the fact that dynamic exchange between the block copolymer molecules in the micelle and the singly dispersed block copolymer molecules in water is suppressed, because of the glassy nature of the core forming polymer block and/or its very large hydrophobicity. Although most amphiphilic block copolymers generate such non-equilibrium micelles, no theoretical approach to a priori predict the micelle characteristics currently exists. In this work, we propose a predictive approach for non-equilibrium micelles with glassy cores by applying the equilibrium theory of micelles in two steps. In the first, we calculate the properties of micelles formed in the mixed solvent while true equilibrium prevails, until the micelle core becomes glassy. In the second step, we freeze the micelle aggregation number at this glassy state and calculate the corona dimension from the equilibrium theory of micelles. The condition when the micelle core becomes glassy is independently determined from a statistical thermodynamic treatment of diluent effect on polymer glass transition temperature. The predictions based on this "non-equilibrium" model compare reasonably well with experimental data for polystyrene-polyethylene oxide diblock copolymer, which is the most extensively studied system in the literature. In contrast, the application of the equilibrium model to describe such a system significantly overpredicts the micelle core and corona dimensions and the aggregation number. The non-equilibrium model suggests ways to

  1. Dynamics of acrylodan-labeled bovine and human serum albumin sequestered within aerosol-OT reverse micelles.

    PubMed

    Lundgren, J S; Heitz, M P; Bright, F V

    1995-10-15

    We investigate the effects of hydration on acrylodan-labeled bovine and human serum albumin (BSA-Ac and HSA-Ac) in aerosol-OT (AOT) reverse micelles solubilized in n-heptane. Time-resolved fluorescence intensity decay experiments reveal a dipolar relaxation process surrounding the acrylodan cybotactic region. This process is best described by a two-term rate law wherein the average relaxation increases with increased hydration. However, the actual rate constants describing the relaxation process either remain unchanged or actually decrease with increased hydration. The results illustrate that the fractional contribution associated with the individual relaxation pathways causes the observed changes in relaxation dynamics. The recovered rotational reorientation dynamics of the acrylodan residue are also affected by the extent of protein hydration. As hydration is increased, the semiangle through which the acrylodan residue precesses increases by 10 degrees for both protein systems. Interestingly, the recovered semiangles for the native proteins equal those recovered at lower hydration when the proteins are sequestered within the AOT reverse micelle. These results demonstrate the importance of hydration on protein behavior in environments where water is limited (e.g., biosensor interfaces and sol--gel-derived biocomposites).

  2. Synthesis, characterization, and evaluation of mPEG–SN38 and mPEG–PLA–SN38 micelles for cancer therapy

    PubMed Central

    Xie, Jing; Zhang, Xiaomin; Teng, Meiyu; Yu, Bo; Yang, Shuang; Lee, Robert J; Teng, Lesheng

    2016-01-01

    7-Ethyl-10-hydroxy camptothecin (SN38) is a potent topoisomerase inhibitor and a metabolite of irinotecan. Its clinical development has been hampered by its poor solubility. To address this problem, methoxy poly(ethylene glycol)-2000 (mPEG2K)–SN38 and mPEG2K–poly(lactide) (PLA1.5K)–SN38 conjugates were prepared and then dispersed into an aqueous medium to form micelles. Physicochemical characteristics of SN38–polymer conjugate micelles, for example, micelle diameter, zeta potential, morphology, and drug content, were then evaluated. The results showed that the mean diameters of mPEG2K–SN38 and mPEG2K–PLA1.5K–SN38 micelles were ~130 and 20 nm, respectively. These two micelles had similar drug contents. mPEG2K–PLA1.5K–SN38 micelles were more homogeneous than mPEG2K–SN38 micelles. Moreover, in vitro drug release behavior of the micelles was studied by high performance liquid chromatography. SN38 release from mPEG2K–SN38 micelles was much faster than from mPEG2K–PLA1.5K–SN38 micelles. In vitro cytotoxicity, cellular uptake, and apoptosis assays of the SN38–polymer conjugate micelles were carried out on BEL-7402 human liver cancer cells. In vivo biodistribution and antitumor tumor efficacy studies were carried out in a nude mouse xenograft model derived from BEL-7402 cells. The results showed that mPEG2K–PLA1.5K–SN38 micelles were significantly more effective than mPEG2K–SN38 micelles in tumor inhibition, and the inhibitory effect of mPEG2K–PLA1.5K–SN38 micelles on tumor growth was significantly greater than that of mPEG2K–SN38 micelles (1,042 vs 1,837 mm) at 30 days. In conclusion, mPEG–PLA–SN38 is a promising anticancer agent that warrants further investigation. PMID:27217746

  3. Synthesis, characterization, and evaluation of mPEG-SN38 and mPEG-PLA-SN38 micelles for cancer therapy.

    PubMed

    Xie, Jing; Zhang, Xiaomin; Teng, Meiyu; Yu, Bo; Yang, Shuang; Lee, Robert J; Teng, Lesheng

    2016-01-01

    7-Ethyl-10-hydroxy camptothecin (SN38) is a potent topoisomerase inhibitor and a metabolite of irinotecan. Its clinical development has been hampered by its poor solubility. To address this problem, methoxy poly(ethylene glycol)-2000 (mPEG2K)-SN38 and mPEG2K-poly(lactide) (PLA1.5K)-SN38 conjugates were prepared and then dispersed into an aqueous medium to form micelles. Physicochemical characteristics of SN38-polymer conjugate micelles, for example, micelle diameter, zeta potential, morphology, and drug content, were then evaluated. The results showed that the mean diameters of mPEG2K-SN38 and mPEG2K-PLA1.5K-SN38 micelles were ~130 and 20 nm, respectively. These two micelles had similar drug contents. mPEG2K-PLA1.5K-SN38 micelles were more homogeneous than mPEG2K-SN38 micelles. Moreover, in vitro drug release behavior of the micelles was studied by high performance liquid chromatography. SN38 release from mPEG2K-SN38 micelles was much faster than from mPEG2K-PLA1.5K-SN38 micelles. In vitro cytotoxicity, cellular uptake, and apoptosis assays of the SN38-polymer conjugate micelles were carried out on BEL-7402 human liver cancer cells. In vivo biodistribution and antitumor tumor efficacy studies were carried out in a nude mouse xenograft model derived from BEL-7402 cells. The results showed that mPEG2K-PLA1.5K-SN38 micelles were significantly more effective than mPEG2K-SN38 micelles in tumor inhibition, and the inhibitory effect of mPEG2K-PLA1.5K-SN38 micelles on tumor growth was significantly greater than that of mPEG2K-SN38 micelles (1,042 vs 1,837 mm) at 30 days. In conclusion, mPEG-PLA-SN38 is a promising anticancer agent that warrants further investigation. PMID:27217746

  4. Structure of polyglycerol oleic acid ester nonionic surfactant reverse micelles in decane: growth control by headgroup size.

    PubMed

    Shrestha, Lok Kumar; Dulle, Martin; Glatter, Otto; Aramaki, Kenji

    2010-05-18

    The structure of polyglycerol oleic acid ester nonionic surfactant micelles in n-decane has been investigated at room temperature by small-angle X-ray scattering (SAXS), dynamic light scattering (DLS), and densiometry techniques. The scattering data were evaluated by indirect Fourier transformation (IFT) or generalized indirect Fourier transformation (GIFT) methods depending on the volume fractions of the surfactants and also by model fit. A simple route to the growth control of reverse micelles by headgroup size of the surfactant was investigated. Additionally, the dependence of reverse micellar structure (shape and size) on temperature, composition, and added water was also investigated. The indirect Fourier transformation gives the real space pair-distance distribution function, p(r): a facile way for the quantitative estimation of structure parameters of the aggregates. It was found that the size of the reverse micelles increases with increasing the headgroup size of the surfactant. Globular type of micelles with maximum diameter ca. 6 nm observed in the monoglycerol oleic acid ester/decane system at 25 degrees C transferred into elongated prolate type micelles with maximum diameter ca. 19.5 nm in the hexaglycerol oleic acid ester/decane system. In a particular surfactant and oil system, increasing temperature decreased the micellar size. The size of the micelle was decreased by approximately 25% upon increasing temperature from 25 to 75 degrees C in the 5 wt % diglycerol oleic acid ester/decane system. Concentration could not modulate the structure of micelles despite a wide variation in the surfactant concentration (5-25 wt %). Nevertheless, increasing surfactant concentration reduces the intermicellar distance, and a strong repulsive interaction peak was observed in the scattering curves at higher surfactant concentrations. Besides, the results obtained from the dynamic light scattering have shown the signature of diffusion hindrance relative to hard sphere

  5. Modulation of fluorescence properties of MMeAQ in micelles and cyclodextrins

    NASA Astrophysics Data System (ADS)

    Burai, Tarak Nath; Bag, Nirmalya; Agarwal, Shipra; Siva Subramaniam Iyer, E.; Datta, Anindya

    2010-08-01

    The interactions of the N-methylquinoline-3-amine (MMeAQ) with three cyclodextrins and micelles have been investigated using fluorescence spectroscopic techniques. It is shown that cationic and neutral surfactants enhance the fluorescence quantum yield of the MMeAQ in water by breakup of aggregates of MMeAQ and incorporation into the micelles. However such enhancement is not observed in SDS micelle. The fluorescence enhancement of MMeAQ in β-cyclodextrin host is rationalized in the light of the stoichiometry of the inclusion complexes. There is no such interaction is observed for α-CD and γ-CD. Quantum chemical calculation has also been performed in order to support the experimental findings of cationic species.

  6. Activity and stability of yeast alcohol dehydrogenase (YADH) entrapped in aerosol OT reverse micelles.

    PubMed

    Sarcar, S; Jain, T K; Maitra, A

    1992-02-20

    The activity and stability of yeast alcohol dehydrogenase (YADH) entrapped in aerosol OT reverse micellar droplets have been investigated spectrophotometrically. Various physical parameters, e.g., water pool size, w(0), pH, and temperature, were optimized for YADH in water/AOT/isooctane reverse micelles. It was found that the enzyme exhibits maximum activity at w(0) = 28 and pH 8.1. It was more active in reverse micelles than in aqueous buffers at a particular temperature and was denatured at about 307 degrees C in both the systems. At a particular temperature YADH entrapped in reverse micelles was less stable than when it was dissolved in aqueous buffer.

  7. On-line micellar electrokinetic chromatography-electrospray ionization mass spectrometry using anodically migrating micelles

    SciTech Connect

    Yang, L.; Harrata, A.K.; Lee, C.S. |

    1997-05-15

    On-line micellar electrokinetic chromatography (MEKC)-electrospray ionization mass spectrometry (ESIMS) is demonstrated for the analysis of chlorotriazine herbicides and barbiturates. In this study, the micellar velocity is directly manipulated by the adjustment of electroosmosis rather than the electrophoretic velocity of the micelle. The electroosmotic flow is adjusted against the electrophoretic velocity of the micelle by changing the solution pH in MEKC. The elimination of MEKC surfactant introduction into ESIMS is achieved with an anodically migrating micelle, moving away from the electrospray interface. The effects of moving surfactant boundary in the MEKC capillary on separation efficiency and resolution of triazine herbicides and barbiturates are investigated. The mass detection of herbicides and barbiturates sequentially eluted from the MEKC capillary is acquired using the positive and negative electrospray modes, respectively. 30 refs., 8 figs., 3 tabs.

  8. 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.

  9. Thermodynamics of Micelle Formation: Prediction of Micelle Size and Size Distribution

    PubMed Central

    Tanford, Charles

    1974-01-01

    This paper presents a simple theory for the calculation of micelle size and other properties of micelleforming systems. The theory is based on the separate estimation of the components of the free energy arising from hydrophobic attraction and from head group repulsion, each as a function of micelle size. The difficult problem of an a priori calculation of the repulsive factor is circumvented by using experimental values of this parameter, derived from pressure-area curves of monolayers at an interface between an aqueous solution and liquid hydrocarbon. Though some parameters of the theory are still somewhat uncertain, self-consistent and physically realistic values can be assigned that lead to almost exact prediction of experimental micelle sizes and critical micelle concentrations for two distinctly different ionic detergents. PMID:4525294

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

    NASA Astrophysics Data System (ADS)

    Ray, D.; Aswal, V. K.

    2015-06-01

    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.

  11. Quantitating the association of charged molecules with ionic micelles

    NASA Astrophysics Data System (ADS)

    Stevenson, Sarah A.; Blanchard, G. J.

    2007-05-01

    We have studied micelles comprised of cationic (CTAB) and anionic (SDS) surfactants through the interactions of solution phase anionic disodium fluorescein (DSF) and cationic rhodamine 110 (R110) dyes with perylene sequestered within the micelles. Fluorescence lifetime measurements monitor energy transfer between the nonpolar optical donor within the micelle and ionic probes in the surrounding solution. The efficiency of this process is mediated by the extent to which the ionic dyes interact with the micelle palisade layer, and our fluorescence lifetime data allow us to determine the association constants for acceptor-micelle interactions.

  12. Encapsulating Subsite Analogues of the [FeFe]-Hydrogenases in Micelles Enables Direct Water Interactions.

    PubMed

    Fritzsch, Robby; Brady, Owen; Adair, Elaine; Wright, Joseph A; Pickett, Christopher J; Hunt, Neil T

    2016-07-21

    Encapsulation of subsite analogues of the [FeFe]-hydrogenase enzymes in supramolecular structures has been shown to dramatically increase their catalytic ability, but the molecular basis for this enhancement remains unclear. We report the results of experiments employing infrared absorption, ultrafast infrared pump-probe, and 2D-IR spectroscopy to investigate the molecular environment of Fe2(pdt)(CO)6 (pdt: propanedithiolate) [1] encapsulated in the dispersed alkane phase of a heptane-dodecyltrimethylammonium bromide-water microemulsion. It is demonstrated that 1 is partitioned between two molecular environments, one that closely resembles bulk heptane solution and a second that features direct hydrogen-bonding interactions with water molecules that penetrate the surfactant shell. Our results demonstrate that the extent of water access to the normally water-insoluble subsite analogue 1 can be tuned with micelle size, while IR spectroscopy provides a straightforward tool that can be used to measure and fine-tune the chemical environment of catalyst species in self-assembled structures. PMID:27396585

  13. Complex coacervate core micelles as diffusional nanoprobes.

    PubMed

    Bourouina, Nadia; Cohen Stuart, Martien A; Kleijn, J Mieke

    2014-01-14

    Because of their ease of preparation and versatile modification opportunities, complex coacervate core micelles (C3Ms) may be a good alternative for expensive diffusional probes, such as dendrimers. However, C3Ms are unstable at high salt concentrations and may fall apart in contact with other polymers or (solid) materials. Therefore, we designed and characterized small (15 nm radius), stable fluorescent C3Ms. These were formed by electrostatic interactions between poly(ethylene oxide-methacrylic acid) (PEO-PMAA) and fluorescently labelled poly(allylamine hydrochloride) (PAH) and irreversible cross-linking of the core through amide bonds. We compared the properties of the cross-linked and non-cross-linked micelles. The radii of the two types of micelles were quite similar and independent of the ionic strength. Surprisingly, both were found to be stable at salt concentrations as high as 1.5 M. However, unlike the non-cross-linked C3Ms, the stability of the cross-linked C3Ms is independent of the pH. As a first example of their application as diffusional nanoprobes, we present results on the diffusion of the fluorescent micelles measured in xanthan solutions using fluorescence recovery after photobleaching (FRAP).

  14. Chain exchange in block copolymer micelles

    NASA Astrophysics Data System (ADS)

    Lu, Jie; Bates, Frank; Lodge, Timothy

    2014-03-01

    Block copolymer micelles are aggregates formed by self-assembly of amphiphilic copolymers dispersed in a selective solvent, driven by unfavorable interactions between the solvent and the core-forming block. Due to the relatively long chains being subject to additional thermodynamic and dynamic constraints (e.g., entanglements, crystallinity, vitrification), block copolymer micelles exhibit significantly slower equilibration kinetics than small molecule surfactants. As a result, details of the mechanism(s) of equilibration in block copolymer micelles remain unclear. This present works focuses on the chain exchange kinetics of poly(styrene-b-ethylenepropylene) block copolymers in squalane (C30H62) using time-resolved small angle neutron scattering (TR-SANS). A mixture of h-squalane and d-squalane is chosen so that it contrast matches a mixed 50/50 h/d polystyrene micelle core. When the temperature is appropriate and isotopically labeled chains undergo mixing, the mean core contrast with respect to the solvent decreases, and the scattering intensity is therefore reduced. This strategy allows direct probing of chain exchange rate from the time dependent scattering intensity I(q, t).

  15. Molecular Exchange Dynamics in Block Copolymer Micelles

    NASA Astrophysics Data System (ADS)

    Bates, Frank; Lu, Jie; Choi, Soohyung; Lodge, Timothy

    2012-02-01

    Poly(styrene-b-ethylene propylene) (PS-PEP) diblock copolymers were mixed with squalane (C30H62) at 1% by weight resulting in the formation of spherical micelles. The structure and dynamics of molecular exchange were characterized by synchrotron small-angle x-ray scattering (SAXS) and time resolved small-angle neutron scattering (TR-SANS), respectively, between 100 C and 160 C. TR-SANS measurements were performed with solutions initially containing deuterium labeled micelle cores and normal cores dispersed in a contrast matched squalane. Monitoring the reduction in scattering intensity as a function of time at various temperatures revealed molecular exchange dynamics highly sensitive to the core molecular weight and molecular weight distribution. Time-temperature superposition of data acquired at different temperatures produced a single master curve for all the mixtures. Experiments conducted with isotopically labeled micelle cores, each formed from two different but relatively mondisperse PS blocks, confirmed a simple dynamical model based on first order kinetics and core Rouse single chain relaxation. These findings demonstrate a dramatic transition to nonergodicity with increasing micelle core molecular weight and confirm the origins of the logarithmic exchange kinetics in such systems.

  16. 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.

  17. Non-diffusing radiochromic micelle gel

    NASA Astrophysics Data System (ADS)

    Jordan, Kevin; Sekimoto, Masaya

    2010-11-01

    The addition of Laponite, a synthetic clay nanoparticle material to radiochromic leuco Malachite Green micelle hydrogel eliminates diffusion of the cationic dye by electrostatic binding. The clay nanoparticles also increased dose sensitivity ten-fold relative to the parent gel formulation. This material is a suitable 3D water equivalent dosimeter with optical CT readout.

  18. 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)

  19. Solubilization of flurbiprofen into aptamer-modified PEG-PLA micelles for targeted delivery to brain-derived endothelial cells in vitro.

    PubMed

    Mu, Chaofeng; Dave, Nimita; Hu, Jing; Desai, Pankaj; Pauletti, Giovanni; Bai, Shuhua; Hao, Jiukuan

    2013-01-01

    Novel aptamer-functionalized polyethylene glycol-polylactic acid (PEG-PLA) (APP) micelles were developed with the objective to target the transferrin receptor on brain endothelial cells. Flurbiprofen, a potential drug for therapeutic management of Alzheimer's disease (AD), was loaded into the APP micelles using the co-solvent evaporation method. Results indicated that 9.03% (w/w) of flurbiprofen was entrapped in APP with good retention capacity in vitro. Targeting potential of APPs was investigated using the transferring receptor-expressing murine brain endothelial bEND5 cell line. APPs significantly enhanced surface association of micelles to bEND5 cells as quantified by fluorescence spectroscopy. Most importantly, APPs significantly enhanced intracellular flurbiprofen delivery when compared to unmodified micelles. These results suggest that APP micelles may offer an effective strategy to deliver therapeutically effective flurbiprofen concentrations into the brain for AD patients.

  20. Charged Diblock Copolymers at Interfaces: Micelle Dissociation Upon Compression

    SciTech Connect

    Checco, A.; Theodoly, O.; Muller, P.

    2010-05-20

    We use grazing incidence X-ray scattering to study the surface micellization of charged amphiphilic diblock copolymers poly(styrene-block-acrylic acid) at the air-water interface. Scattering interference peaks are consistent with the formation of hexagonally packed micelles. The remarkable increase of inter-micelle distance upon compression is explained by a dissociation of micelles into a brush. Hence, surface micelles reorganize, whereas micelles of the same copolymers in solutions are 'frozen'. We show indeed that the energetic cost of unimer extraction from micelles is much lower for surface than for solution. Finally, a model combining electrostatic interactions and micelle/brush equilibrium explains surface pressure vs. area without free parameters. keywords - soft matter, liquids and polymers, biological physics, chemical physics and physical chemistry.

  1. Charged Diblock Copolymers at Interfaces: Micelle Dissociation Upon Compression

    SciTech Connect

    Theodoly, O.; Checco, A; Muller, P

    2010-01-01

    We use grazing incidence X-ray scattering to study the surface micellization of charged amphiphilic diblock copolymers poly(styrene-block-acrylic acid) at the air-water interface. Scattering interference peaks are consistent with the formation of hexagonally packed micelles. The remarkable increase of inter-micelle distance upon compression is explained by a dissociation of micelles into a brush. Hence, surface micelles reorganize, whereas micelles of the same copolymers in solutions are 'frozen'. We show indeed that the energetic cost of unimer extraction from micelles is much lower for surface than for solution. Finally, a model combining electrostatic interactions and micelle/brush equilibrium explains surface pressure vs. area without free parameters.

  2. 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

  3. 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

  4. Solubilization of polycyclic aromatic hydrocarbons by perfluorinated surfactant micelles.

    PubMed

    An, Youn-Joo; Carraway, Elizabeth R; Schlautman, Mark A

    2002-01-01

    Due to their chemical and thermal stability, perfluorinated surfactants (PFSs) are promising materials for the development of novel environmental remediation applications. This stability also leads to the persistence of PFS in the environment; therefore, their properties and behavior should be well understood. This study focused on polycyclic aromatic hydrocarbon (PAH) and PFS interactions, particularly the solubilization of PAHs by PFS micelles. Naphthalene. phenanthrene, and pyrene were selected as representative PAHs and an anionic PFS, ammonium perfluorooctanoate (APFO) was used. Critical micelle concentration (CMC) values of APFO measured by surface tension, fluorescence probe, and solubility enhancement methods fell in the range of 20-30 mM at 22 +/- 1 degrees C. Apparent solubilities of molecular oxygen and PAHs in APFO micellar solutions depended linearly on the APFO concentration. Molar solubilization ratio (MSR) values were determined to be 9.50 x 10(-4), 4.17 x 10(-3), 2.31 x 10(-4), and 4.09 x 10(-5) and mole fraction micellar partition coefficient (Kmic) values were found to be 1.89 x 10(2), 9.50 x 10(2), 2.12 x 10(3), and 3.79 x 10(3) for oxygen, naphthalene, phenanthrene, and pyrene, respectively at 22 +/- 1 degrees C. log Kmic values for three PAHs were shown to be linearly correlated with the log values of octanol-water partition coefficients (log Kow).

  5. 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

  6. Triggered-release polymeric conjugate micelles for on-demand intracellular drug delivery

    NASA Astrophysics Data System (ADS)

    Cao, Yanwu; Gao, Min; Chen, Chao; Fan, Aiping; Zhang, Ju; Kong, Deling; Wang, Zheng; Peer, Dan; Zhao, Yanjun

    2015-03-01

    Nanoscale drug delivery platforms have been developed over the past four decades that have shown promising clinical results in several types of cancer and inflammatory disorders. These nanocarriers carrying therapeutic payloads are maximizing the therapeutic outcomes while minimizing adverse effects. Yet one of the major challenges facing drug developers is the dilemma of premature versus on-demand drug release, which influences the therapeutic regiment, efficacy and potential toxicity. Herein, we report on redox-sensitive polymer-drug conjugate micelles for on-demand intracellular delivery of a model active agent, curcumin. Biodegradable methoxy poly(ethylene glycol)-poly(lactic acid) copolymer (mPEG-PLA) was conjugated with curcumin via a disulfide bond or ester bond (control), respectively. The self-assembled redox-sensitive micelles exhibited a hydrodynamic size of 115.6 ± 5.9 (nm) with a zeta potential of -10.6 ± 0.7 (mV). The critical micelle concentration was determined at 6.7 ± 0.4 (μg mL-1). Under sink conditions with a mimicked redox environment (10 mM dithiothreitol), the extent of curcumin release at 48 h from disulfide bond-linked micelles was nearly three times higher compared to the control micelles. Such rapid release led to a lower half maximal inhibitory concentration (IC50) in HeLa cells at 18.5 ± 1.4 (μg mL-1), whereas the IC50 of control micelles was 41.0 ± 2.4 (μg mL-1). The cellular uptake study also revealed higher fluorescence intensity for redox-sensitive micelles. In conclusion, the redox-sensitive polymeric conjugate micelles could enhance curcumin delivery while avoiding premature release, and achieving on-demand release under the high glutathione concentration in the cell cytoplasm. This strategy opens new avenues for on-demand drug release of nanoscale intracellular delivery platforms that ultimately might be translated into pre-clinical and future clinical practice.

  7. A systematic investigation of the rate laws valid in intracellular environments.

    PubMed

    Grima, R; Schnell, S

    2006-10-20

    Recently there has been significant interest in deducing the form of the rate laws for chemical reactions occurring in the intracellular environment. This environment is typically characterized by low-dimensionality and a high macromolecular content; this leads to a spatial heterogeneity not typical of the well stirred in vitro environments. For this reason, the classical law of mass action has been presumed to be invalid for modeling intracellular reactions. Using lattice-gas automata models, it has recently been postulated [H. Berry, Monte Carlo simulations of enzyme reactions in two dimensions: Fractal kinetics and spatial segregation, Biophys. J. 83 (2002) 1891-1901; S. Schnell, T.E. Turner, Reaction kinetics in intracellular environments with macromolecular crowding: simulations and rate laws, Prog. Biophys. Mol. Biol. 85 (2004) 235-260] that the reaction kinetics is fractal-like. In this article we systematically investigate for the first time how the rate laws describing intracellular reactions vary as a function of: the geometry and size of the intracellular surface on which the reactions occur, the mobility of the macromolecules responsible for the crowding effects, the initial reactant concentrations and the probability of reaction between two reactant molecules. We also compare the rate laws valid in heterogeneous environments in which there is an underlying spatial lattice, for example crystalline alloys, with the rate laws valid in heterogeneous environments where there is no such natural lattice, for example in intracellular environments. Our simulations indicate that: (i) in intracellular environments both fractal kinetics and mass action can be valid, the major determinant being the probability of reaction, (ii) the geometry and size of the intracellular surface on which reactions are occurring does not significantly affect the rate law, (iii) there are considerable differences between the rate laws valid in heterogeneous non-living structures such

  8. Doxorubicin-loaded micelles of reverse poly(butylene oxide)-poly(ethylene oxide)-poly(butylene oxide) block copolymers as efficient "active" chemotherapeutic agents.

    PubMed

    Cambón, A; Rey-Rico, A; Mistry, D; Brea, J; Loza, M I; Attwood, D; Barbosa, S; Alvarez-Lorenzo, C; Concheiro, A; Taboada, P; Mosquera, V

    2013-03-10

    Five reverse poly(butylene oxide)-poly(ethylene oxide)-poly(butylene oxide) block copolymers, BOnEOmBOn, with BO ranging from 8 to 21 units and EO from 90 to 411 were synthesized and evaluated as efficient chemotherapeutic drug delivery nanocarriers and inhibitors of the P-glycoprotein (P-gp) efflux pump in a multidrug resistant (MDR) cell line. The copolymers were obtained by reverse polymerization of poly(butylene oxide), which avoids transfer reaction and widening of the EO block distribution, commonly found in commercial poly(ethylene oxide)-poly(propylene oxide) block copolymers (poloxamers). BOnEOmBOn copolymers formed spherical micelles of 10-40 nm diameter at lower concentrations (one order of magnitude) than those of equivalent poloxamers. The influence of copolymer block lengths and BO/EO ratios on the solubilization capacity and protective environment for doxorubicin (DOXO) was investigated. Micelles showed drug loading capacity ranging from ca. 0.04% to 1.5%, more than 150 times the aqueous solubility of DOXO, and protected the cargo from hydrolysis for more than a month due to their greater colloidal stability in solution. Drug release profiles at various pHs, and the cytocompatibility and cytotoxicity of the DOXO-loaded micelles were assessed in vitro. DOXO loaded in the polymeric micelles accumulated more slowly inside the cells than free DOXO due to its sustained release. All copolymers were found to be cytocompatible, with viability extents larger than 95%. In addition, the cytotoxicity of DOXO-loaded micelles was higher than that observed for free drug solutions in a MDR ovarian NCI-ADR-RES cell line which overexpressed P-gp. The inhibition of the P-gp efflux pump by some BOnEOmBOn copolymers, similar to that measured for the common P-gp inhibitor verapamil, favored the retention of DOXO inside the cell increasing its cytotoxic activity. Therefore, poly(butylene oxide)-poly(ethylene oxide) block copolymers offer interesting features as cell

  9. Amphiphilic polymeric micelle as pseudostationary phase in electrokinetic chromatography for analysis of eight corticosteroids in cosmetics.

    PubMed

    Xu, Xiaojin; Ni, Xinjiong; Cao, Yuhua; Zhuo, Xiaolu; Yang, Xiaoxiao; Cao, Guangqun

    2014-03-01

    Amphiphilic polymeric micelle, as a novel pseudostationary phase in EKC was used to determine eight kinds of corticosteroids namely hydrocortisone, prednisolone, hydrocortisone acetate, prednisone, cortisone acetate, prednisolone acetate, dexamethasone, and triamcinolone acetonide in cosmetics. Amphiphilic random copolymer poly(methyl methacrylate-co-methacrylic acid) (P(MMA-co-MAA)) was micellizated via neutralization in alkaline aqueous solution. The influences of the molar ratio of monomer MMA to MAA, the concentration of polymer and pH on the polymeric micelle microstructure and EKC performances were investigated. As molar ratio of MMA to MAA in P(MMA-co-MAA) increased, both CMC and environmental polarity of the inner core in polymeric micelle decreased dramatically. With increasing monomer ratio, the size of polymeric micelles increased firstly, and then decreased, finally increased again. ζ potential of the micelle had a slight decline trend. As increment of polymer concentration, the size of the polymeric micelle increased steadily. By optimizing the monomer ratio, the polymer concentration, and pH of the running buffer, as well as operation conditions such as separation voltage and temperature, the eight analytes could be separated within 16.5 min using 7.5 mg/mL polymer with the monomer ratio of 7:3 dissolved in pH 9.2 borax buffer as the running buffer. The method has been used for analysis of corticosteroids in cosmetic samples with simple extraction; the recoveries for eight analytes were between 85.9 and 106%. This method was of accuracy, repeatability, pretreatment simplicity, and could be applied to the quality control of cosmetics.

  10. Growth Behavior, Geometrical Shape, and Second CMC of Micelles Formed by Cationic Gemini Esterquat Surfactants.

    PubMed

    Bergström, L Magnus; Tehrani-Bagha, Alireza; Nagy, Gergely

    2015-04-28

    Micelles formed by novel gemini esterquat surfactants have been investigated with small-angle neutron scattering (SANS). The growth behavior of the micelles is found to differ conspicuously depending on the length of the gemini surfactant spacer group. The gemini surfactant with a long spacer form rather small triaxial ellipsoidal tablet-shaped micelles that grow weakly with surfactant concentration in the entire range of measured concentrations. Geminis with a short spacer, on the other hand, form weakly growing oblates or tablets at low concentrations that start to grow much more strongly into polydisperse rodlike or wormlike micelles at higher concentrations. The latter behavior is consistent with the presence of a second CMC that marks the transition from the weakly to the strongly growing regime. It is found that the growth behavior in terms of aggregation number as a function of surfactant concentration always appear concave in weakly growing regimes, while switching to convex behavior in strongly growing regimes. As a result, we are able to determine the second CMC of the geminis with short spacer by means of suggesting a rather precise definition of it, located at the point of inflection of the growth curve that corresponds to the transition from concave to convex growth behavior. Our SANS results are rationalized by comparison with the recently developed general micelle model. In particular, this theory is able to explain and reproduce the characteristic appearances of the experimental growth curves, including the presence of a second CMC and the convex strongly growing regime beyond. By means of optimizing the agreement between predictions from the general micelle model and results from SANS experiments, we are able to determine the three bending elasticity constants spontaneous curvature, bending rigidity, and saddle-splay constant for each surfactant. PMID:25835031

  11. The interaction of Cu 2+ ions and NaDC micelles

    NASA Astrophysics Data System (ADS)

    Sun, Y.; Yang, Z.-L.; Zhang, L.; Hu, T.-D.; Soloway, R. D.; Weng, S.-F.; Wu, J.-G.

    2002-05-01

    By mixing an aqueous solution of CuCl 2 with an NaDC aqueous solution of various concentration and initial molar ratio, seven coordinated samples with distinct appearances and characters were obtained. Their structures and components were investigated by FT-IR spectroscopy, EXAFS (the extended X-ray absorption fine structure), thermal analysis, X-ray diffraction, laser light scattering, TEM (transmission electron micrograph), element analysis and ICP (inductively coupled plasma) analysis. The following conclusions were given: (1) The complexes of Cu 2+-NaDC with distinct appearances and properties were synthesized. (2) After Cu(DC) 2 dissolved in NaDC aqueous solution, larger micelles (30-90 nm diameter) formed in the supernate, it is a mixed micelle with Cu(DC) 2 and NaDC. So these micelles are a new kind of micelle containing two kinds of metal ions. This is a new result using metal ions as bridges to form micelle. (3) According to the different concentration of Cu 2+ to NaDC, the complexes formed as gel or poly-crystals. Both the composition of gel complexes and the coordination structure of carboxyl groups with metal ions varied with the initial molar ratio of Cu 2+ to Na +. The gel complexes exhibits the non-stoichiometric character. (4) These results are in agreement with physiological condition. All the different states such as gel, precipitate, micelles of various structures are present in bile of gallbladder. We can suggest an ideal model of the interaction between Cu 2+ and bile salts in vivo.

  12. Amphiphilic polymeric micelle as pseudostationary phase in electrokinetic chromatography for analysis of eight corticosteroids in cosmetics.

    PubMed

    Xu, Xiaojin; Ni, Xinjiong; Cao, Yuhua; Zhuo, Xiaolu; Yang, Xiaoxiao; Cao, Guangqun

    2014-03-01

    Amphiphilic polymeric micelle, as a novel pseudostationary phase in EKC was used to determine eight kinds of corticosteroids namely hydrocortisone, prednisolone, hydrocortisone acetate, prednisone, cortisone acetate, prednisolone acetate, dexamethasone, and triamcinolone acetonide in cosmetics. Amphiphilic random copolymer poly(methyl methacrylate-co-methacrylic acid) (P(MMA-co-MAA)) was micellizated via neutralization in alkaline aqueous solution. The influences of the molar ratio of monomer MMA to MAA, the concentration of polymer and pH on the polymeric micelle microstructure and EKC performances were investigated. As molar ratio of MMA to MAA in P(MMA-co-MAA) increased, both CMC and environmental polarity of the inner core in polymeric micelle decreased dramatically. With increasing monomer ratio, the size of polymeric micelles increased firstly, and then decreased, finally increased again. ζ potential of the micelle had a slight decline trend. As increment of polymer concentration, the size of the polymeric micelle increased steadily. By optimizing the monomer ratio, the polymer concentration, and pH of the running buffer, as well as operation conditions such as separation voltage and temperature, the eight analytes could be separated within 16.5 min using 7.5 mg/mL polymer with the monomer ratio of 7:3 dissolved in pH 9.2 borax buffer as the running buffer. The method has been used for analysis of corticosteroids in cosmetic samples with simple extraction; the recoveries for eight analytes were between 85.9 and 106%. This method was of accuracy, repeatability, pretreatment simplicity, and could be applied to the quality control of cosmetics. PMID:24338855

  13. Investigating Critical Thinking and Knowledge Construction in an Interactive Learning Environment

    ERIC Educational Resources Information Center

    Wang, Qiyun; Woo, Huay Lit; Zhao, Jianhua

    2009-01-01

    Critical thinking and knowledge construction have become essential competencies for people in the new information age. In this study, we designed an interactive learning environment involving three forms of interaction: individual reflections, group collaboration and, class discussions. The purpose of this study was to investigate the extent to…

  14. An Investigation of Mathematically Promising Students' Cognitive Abilities and Their Contributions to Learning Environment

    ERIC Educational Resources Information Center

    Budak, Ibrahim; Kaygin, Bulent

    2015-01-01

    In this study, through the observation of mathematically promising students in regular classrooms, relevant learning environments and the learning needs of promising students, teacher approaches and teaching methods, and the differences between the promising students and their normal ability peers in the same classroom were investigated.…

  15. Investigating the Development of Work-Oriented Groups in an e-Learning Environment

    ERIC Educational Resources Information Center

    Yu, Chia-Ping; Kuo, Feng-Yang

    2012-01-01

    In this study, we have investigated developmental patterns of virtual groups in the e-learning environment. Our findings suggest that for virtual groups formed for the purpose of e-learning, dependency and inclusion characterize the initial stage of group development, as such characteristics reinforce cooperative relationships and help to build a…

  16. An Investigation of an Open-Source Software Development Environment in a Software Engineering Graduate Course

    ERIC Educational Resources Information Center

    Ge, Xun; Huang, Kun; Dong, Yifei

    2010-01-01

    A semester-long ethnography study was carried out to investigate project-based learning in a graduate software engineering course through the implementation of an Open-Source Software Development (OSSD) learning environment, which featured authentic projects, learning community, cognitive apprenticeship, and technology affordances. The study…

  17. Stopped-flow kinetic studies of sphere-to-rod transitions of sodium alkyl sulfate micelles induced by hydrotropic salt.

    PubMed

    Zhang, Jingyan; Ge, Zhishen; Jiang, Xiaoze; Hassan, P A; Liu, Shiyong

    2007-12-15

    The kinetics and mechanism of sphere-to-rod transitions of sodium alkyl sulfate micelles induced by hydrotropic salt, p-toluidine hydrochloride (PTHC), were investigated by stopped-flow with light scattering detection. Spherical sodium dodecyl sulfate (SDS) micelles transform into short ellipsoidal shapes at low salt concentrations ([PTHC]/[SDS], chi(PTHC)=0.3 and 0.4). Upon stopped-flow mixing aqueous solutions of spherical SDS micelles with PTHC, the scattered light intensity gradually increases with time. Single exponential fitting of the dynamic traces leads to characteristic relaxation time, tau(g), for the growth process from spherical to ellipsoidal micelles, and it increases with increasing SDS concentrations. This suggests that ellipsoidal micelles might be produced by successive insertion of unimers into spherical micelles, similar to the case of formation of spherical micelles as suggested by Aniansson-Wall (A-W) theory. At chi(PTHC) > or = 0.5, rod-like micelles with much higher axial ratio form. The scattered light intensity exhibits an initially abrupt increase and then levels off. The dynamic curves can be well fitted with single exponential functions, and the obtained tau(g) decreases with increasing SDS concentration. Thus, the growth from spherical to rod-like micelles might proceed via fusion of spherical micelles, in agreement with mechanism proposed by Ikeda et al. At chi(PTHC)=0.3 and 0.6, the apparent activation energies obtained from temperature dependent kinetic studies for the micellar growth are 40.4 and 3.6 kJ/mol, respectively. The large differences between activation energies for the growth from spherical to ellipsoidal micelles at low chi(PTHC) and the sphere-to-rod transition at high chi(PTHC) further indicate that they should follow different mechanisms. Moreover, the sphere-to-rod transition kinetics of sodium alkyl sulfate with varying hydrophobic chain lengths (n=10, 12, 14, and 16) are also studied. The longer the carbon chain

  18. Stopped-flow kinetic studies of sphere-to-rod transitions of sodium alkyl sulfate micelles induced by hydrotropic salt.

    PubMed

    Zhang, Jingyan; Ge, Zhishen; Jiang, Xiaoze; Hassan, P A; Liu, Shiyong

    2007-12-15

    The kinetics and mechanism of sphere-to-rod transitions of sodium alkyl sulfate micelles induced by hydrotropic salt, p-toluidine hydrochloride (PTHC), were investigated by stopped-flow with light scattering detection. Spherical sodium dodecyl sulfate (SDS) micelles transform into short ellipsoidal shapes at low salt concentrations ([PTHC]/[SDS], chi(PTHC)=0.3 and 0.4). Upon stopped-flow mixing aqueous solutions of spherical SDS micelles with PTHC, the scattered light intensity gradually increases with time. Single exponential fitting of the dynamic traces leads to characteristic relaxation time, tau(g), for the growth process from spherical to ellipsoidal micelles, and it increases with increasing SDS concentrations. This suggests that ellipsoidal micelles might be produced by successive insertion of unimers into spherical micelles, similar to the case of formation of spherical micelles as suggested by Aniansson-Wall (A-W) theory. At chi(PTHC) > or = 0.5, rod-like micelles with much higher axial ratio form. The scattered light intensity exhibits an initially abrupt increase and then levels off. The dynamic curves can be well fitted with single exponential functions, and the obtained tau(g) decreases with increasing SDS concentration. Thus, the growth from spherical to rod-like micelles might proceed via fusion of spherical micelles, in agreement with mechanism proposed by Ikeda et al. At chi(PTHC)=0.3 and 0.6, the apparent activation energies obtained from temperature dependent kinetic studies for the micellar growth are 40.4 and 3.6 kJ/mol, respectively. The large differences between activation energies for the growth from spherical to ellipsoidal micelles at low chi(PTHC) and the sphere-to-rod transition at high chi(PTHC) further indicate that they should follow different mechanisms. Moreover, the sphere-to-rod transition kinetics of sodium alkyl sulfate with varying hydrophobic chain lengths (n=10, 12, 14, and 16) are also studied. The longer the carbon chain

  19. Preparation of core-shell nanofibers with selectively localized CNTs from Shish Kebab-like hierarchical composite micelles.

    PubMed

    Liu, Chang-Lei; Wang, Mei-Jia; Wu, Gang; You, Jiao; Chen, Si-Chong; Liu, Ya; Wang, Yu-Zhong

    2014-08-01

    A novel and facile bottom-up strategy for preparing core-shell nanofibers with selectively localized carbon nanotubes is developed using hierarchical composite micelles of crystalline-coil copolymer and carbon nanotubes as the building blocks. An amphiphilic di-block copolymer of poly (p-dioxanone) (PPDO) and PEG (polyethylene glycol) functionalized with pyrene moieties at the chain ends of PPDO blocks (Py-PPDO-b-PEG) is designed for constructing composite micelles with multiwalled carbon nanotubes (MWCNTs). The self-assembly of Py-PPDO-b-PEG and MWCNTs is co-induced by the crystallization of PPDO blocks and the π-π stacking interactions between pyrene moieties and MWCNTs, resulting in composite micelles with "shish kebab"-like nanostructure. A mixture of composite micelles and polyvinyl alcohol (PVA) water solution is then used as the spinning solution for preparing electrospun nanofibers. The morphologies of the nanofibers with different composition are investigated by SEM and TEM. The results suggest that the MWCNTs selectively localized in the core of the nanofibers of MWCNTs/Py-PPDO-b-PEG/PVA. The alignment and interfusion of composite micelles during the formation of nanofibers may confine the carbon nanotubes in the hydrophobic core region. In contrast, the copolymer without pyrene moieties cannot form composite micelles, thus these nanofibers show selective localization of MWCNTs in the PVA shell region. PMID:25048154

  20. The Formation of pH-Sensitive Wormlike Micelles in Ionic Liquids Driven by the Binding Ability of Anthranilic Acid.

    PubMed

    You, Qing; Zhang, Yan; Wang, Huan; Fan, Hongfu; Guo, Jianping; Li, Ming

    2015-01-01

    Wormlike micelles are typically formed by mixing cationic and anionic surfactants because of attractive interactions in oppositely charged head-groups. The structural transitions of wormlike micelles triggered by pH in ionic liquids composed of N-alkyl-N-methylpyrrolidinium bromide-based ILs (ionic liquids) and anthranilic acid were investigated. These structures were found responsible for the variations in flow properties identified by rheology and dynamic light scattering, and account for the structures observed with cryogenic transmission electron microscopy (Cryo-TEM). High-viscosity, shear-thinning behavior, and Maxwell-type dynamic rheology shown by the system at certain pH values suggested that spherical micelles grow into entangled wormlike micelles. Light scattering profiles also supported the notion of pH-sensitive microstructural transitions in the solution. Cryo-TEM images confirmed the presence of spherical micelles in the low-viscosity sample and entangled wormlike micelles in the peak viscosity sample. Nuclear magnetic resonance spectroscopy analysis revealed that the pH sensitivity of ionic liquid systems originated from the pH-dependent binding ability of anthranilic acid to the cationic headgroup of ionic liquids. PMID:26703567

  1. The Formation of pH-Sensitive Wormlike Micelles in Ionic Liquids Driven by the Binding Ability of Anthranilic Acid

    PubMed Central

    You, Qing; Zhang, Yan; Wang, Huan; Fan, Hongfu; Guo, Jianping; Li, Ming

    2015-01-01

    Wormlike micelles are typically formed by mixing cationic and anionic surfactants because of attractive interactions in oppositely charged head-groups. The structural transitions of wormlike micelles triggered by pH in ionic liquids composed of N-alkyl-N-methylpyrrolidinium bromide-based ILs (ionic liquids) and anthranilic acid were investigated. These structures were found responsible for the variations in flow properties identified by rheology and dynamic light scattering, and account for the structures observed with cryogenic transmission electron microscopy (Cryo-TEM). High-viscosity, shear-thinning behavior, and Maxwell-type dynamic rheology shown by the system at certain pH values suggested that spherical micelles grow into entangled wormlike micelles. Light scattering profiles also supported the notion of pH-sensitive microstructural transitions in the solution. Cryo-TEM images confirmed the presence of spherical micelles in the low-viscosity sample and entangled wormlike micelles in the peak viscosity sample. Nuclear magnetic resonance spectroscopy analysis revealed that the pH sensitivity of ionic liquid systems originated from the pH-dependent binding ability of anthranilic acid to the cationic headgroup of ionic liquids. PMID:26703567

  2. Decoration of pH-sensitive copolymer micelles with tumor-specific peptide for enhanced cellular uptake of doxorubicin

    PubMed Central

    Chen, Qing; Long, Miaomiao; Qiu, Lipeng; Zhu, Mengqin; Li, Zhen; Qiao, Mingxi; Hu, Haiyang; Zhao, Xiuli; Chen, Dawei

    2016-01-01

    To improve the targeting efficacy of hyaluronic acid (HA)-based micelles, pH-sensitive mixed micelles based on HA-g-poly(L-histidine) (PHis) and d-α-tocopheryl polyethylene glycol 2000 copolymers were prepared and decorated with human epidermal growth factor receptor 2 (Her2) peptide, a tumor cell-specific peptide ligand, on their surface. The doxorubicin-loaded micelles (HA-PHis/peptide–d-α-tocopheryl polyethylene glycol 2000 mixed micelles [PHTM]) were characterized to have a unimodal size distribution and pH-dependent drug release pattern. In vitro tumor targeting studies demonstrated that PHTM exhibited the pronounced cytotoxicity and efficient internalization in MDA-MB-231 cells overexpressing CD44 and Her2 receptors. In vivo investigation into micelles in MDA-MB-231 tumor-bearing mice confirmed that PTHM could reach the tumor site more effectively and exert excellent tumor killing activity. In general, Her2 peptide decoration can enhance the selective cytotoxicity and antitumor activity of HA-based micelles. PMID:27799766

  3. Spatial structure of zervamicin IIB bound to DPC micelles: implications for voltage-gating.

    PubMed Central

    Shenkarev, Z O; Balashova, T A; Efremov, R G; Yakimenko, Z A; Ovchinnikova, T V; Raap, J; Arseniev, A S

    2002-01-01

    Zervamicin IIB is a 16-amino acid peptaibol that forms voltage-dependent ion channels with multilevel conductance states in planar lipid bilayers and vesicular systems. The spatial structure of zervamicin IIB bound to dodecylphosphocholine micelles was studied by nuclear magnetic resonance spectroscopy. The set of 20 structures obtained has a bent helical conformation with a mean backbone root mean square deviation value of approximately 0.2 A and resembles the structure in isotropic solvents (Balashova et al., 2000. NMR structure of the channel-former zervamicin IIB in isotropic solvents. FEBS Lett 466:333-336). The N-terminus represents an alpha-helix, whereas the C-terminal part has a mixed 3(10)/alpha(R) hydrogen-bond pattern. In the anisotropic micelle environment, the bending angle on Hyp10 (23 degrees) is smaller than that (47 degrees) in isotropic solvents. In the NOESY (Nuclear Overhauser Effect Spectroscopy) spectra, the characteristic attenuation of the peptide signals by 5- and 16-doxylstearate relaxation probes indicates a peripheral mode of the peptaibol binding to the micelle with the N-terminus immersed slightly deeper into micelle interior. Analysis of the surface hydrophobicity reveals that the zervamicin IIB helix is amphiphilic and well suited to formation of a tetrameric transmembrane bundle, according to the barrel-stave mechanism. The results are discussed in a context of voltage-driven peptaibol insertion into membrane. PMID:11806918

  4. Hydrogen-bonding-induced complexation of polydimethylsiloxane-graft-poly(ethylene oxide) and poly(acrylic acid)-block-polyacrylonitrile micelles in water.

    PubMed

    Hu, Aijuan; Cui, Yushuang; Wei, Xiaoling; Lu, Zaijun; Ngai, To

    2010-09-21

    Polydimethylsiloxane-graft-poly(ethylene oxide) (PDMS-g-PEO) copolymers form micelles in water with PDMS as the core and PEO as the corona. The introduction of poly(acrylic acid)-block-polyacrylonitrile (PAA-b-PAN) block copolymers in water leads to the formation of micellar complexes due to the hydrogen bonding between carboxyl groups and ether oxygens among the PAA and PEO chains in the corona of the micelles. The effects of pH, molar ratios (r) of PAA/PEO, and the standing time on the directly mixing these two micelles in water have been investigated using laser light scattering (LLS) and transmission electron microscopy (TEM). Our results showed that the complexation between PAA and PEO in the corona was greatly enhanced at a pH below 3.5. For a fixed pH value, the interactions between these two micelles in water were governed by the value of r. At r < ∼0.6, mixing the two micelles in water resulted in a large floccule because the smaller PAA-b-PAN micelles act as physical cross-links, which are absorbed onto one PDMS-g-PEO micelle and simultaneously bonded to PEO chains on the other micelles, forming bridges and causing flocculation. At ∼0.6 < r < ∼1.2, the mixing led to stable micellar complexes with a layer of PAA-b-PAN micelles absorbed onto the initial PDMS-g-PEO micelles. At r > ∼1.2, the resultant micellar complexes first remained stable, but they precipitated from solution after a long time standing.

  5. In vitro anticancer activity of docetaxel-loaded micelles based on poly(ethylene oxide)-poly(epsilon-caprolactone) block copolymers: Do nanocarrier properties have a role?

    PubMed

    Ostacolo, Luisanna; Marra, Monica; Ungaro, Francesca; Zappavigna, Silvia; Maglio, Giovanni; Quaglia, Fabiana; Abbruzzese, Alberto; Caraglia, Michele

    2010-12-01

    In this paper we have investigated the behavior of core-shell poly(ethylene oxide)-poly(epsilon-caprolactone) (PEO-PCL) micelles derived from copolymers with linear triblock (TR) and 4-arm star-diblock (ST) architectures for the delivery of docetaxel (DTX). DTX was loaded inside micelles (DTX-TR(m) and DTX-ST(m)) with high efficiency and released slowly for more than two weeks. DTX-loaded micelles based on both copolymers had very similar properties in terms of mean size, zeta potential, loading ability and release rate in buffered saline. However, the stability of DTX-ST(m) was very poor in aqueous media with proteins resulting in a strong and progressive aggregation. We studied the effect of increasing concentrations of free DTX or DTX-loaded micelles on growth inhibition of human breast MCF-7 and MDA-MB468 and prostate PC3 and DU145 adenocarcinoma cell lines. DTX-loaded TR micelles induced cell growth inhibition similarly to free DTX whereas DTX-ST(m) showed lower cytotoxicity. On the other hand, by normalizing IC(50) values for the actual amount of DTX released from micelles in the medium, DTX-loaded ST micelles became more active than free DTX in all cell lines tested. Both free DTX and DTX-loaded TR micelles displayed a significantly lower cytotoxic activity in G(2)/M phase synchronized cells, whereas cytotoxicity of DTX-loaded ST micelles did not change. Cytotoxicity was related to micelle stability, uptake and release rate in cell culture media. Our results suggest that for a correct interpretation of cytotoxicity of nanocarriers, the evaluation of their behavior in biologically relevant conditions is of utmost importance to select proper systems for further in vivo testing.

  6. Interaction of chlorpromazine and trifluoperazine with ionic micelles: electronic absorption spectroscopy studies

    NASA Astrophysics Data System (ADS)

    Caetano, Wilker; Tabak, Marcel

    1999-10-01

    The characteristics of binding of two phenothiazine antipsychotic drugs, namely, chlorpromazine (CPZ) and trifluoperazine (TFP), to cationic cetyltrimethylammonium chloride (CTAC), zwitterionic N-hexadecyl- N, N-dimethyl-3-ammonio-1-propanesulfonate (HPS), neutral t-octylphenoxypolyethoxyethanol (TRITON X-100) and polyoxyethylene dodecyl ether (Brij-35) micelles were investigated using electronic absorption spectroscopy. Binding constants Kb and p Ka values of drugs in micelles were estimated using the red shifts of the maximum absorption upon alkalization or in the presence of detergents. The p Ka of TFP seems to be shifted by 2.5-4.1 units to lower values in the presence of different surfactants as compared to the experimental value of p Ka obtained in buffer which is around 7.0. Consideration of the second p Ka around 4.0 reported in the literature for TFP leads to a better rationalization of p Ka changes for this compound. The changes in p Ka contributed by electrostatic effects are all positive, small for CTAC (+0.2), and greater for HPS (+0.9). For CPZ the p Ka shift due to its interaction with micelles is in the 0.7-2.3 range, the direction of the shift depending on the charge of the polar head. The electrostatic contribution for the shift is great for CTAC (-0.8) and smaller for HPS (+0.2). This result suggests a more polar localization in the micelle of CPZ as compared to TFP. The values of binding constants Kb for TFP and CPZ in different protonation states show that electrostatic interactions are essential in the affinity of the drugs to micelles bearing different charges on their headgroups (CTAC, HPS). Data for Brij-35 demonstrate that the additional charge on the TFP ring at pH 2.0 leads to a decrease of binding constant probably due to the repulsion of the phenothiazine ring from the protons accumulated at the polar head of the micelle at acidic pH values. For this micelle at pH 5.0 TFP has a Kb 3-fold greater than that for CPZ while at pH 2.0 Kb for

  7. Encapsulation of GFP in Complex Coacervate Core Micelles.

    PubMed

    Nolles, Antsje; Westphal, Adrie H; de Hoop, Jacob A; Fokkink, Remco G; Kleijn, J Mieke; van Berkel, Willem J H; Borst, Jan Willem

    2015-05-11

    Protein encapsulation with polymers has a high potential for drug delivery, enzyme protection and stabilization. Formation of such structures can be achieved by the use of polyelectrolytes to generate so-called complex coacervate core micelles (C3Ms). Here, encapsulation of enhanced green fluorescent protein (EGFP) was investigated using a cationic-neutral diblock copolymer of two different sizes: poly(2-methyl-vinyl-pyridinium)41-b-poly(ethylene-oxide)205 and poly(2-methyl-vinyl-pyridinium)128-b-poly(ethylene-oxide)477. Dynamic light scattering and fluorescence correlation spectroscopy (FCS) revealed a preferred micellar composition (PMC) with a positive charge composition of 0.65 for both diblock copolymers and micellar hydrodynamic radii of approximately 34 nm. FCS data show that at the PMC, C3Ms are formed above 100 nM EGFP, independent of polymer length. Mixtures of EGFP and nonfluorescent GFP were used to quantify the amount of GFP molecules per C3M, resulting in approximately 450 GFPs encapsulated per micelle. This study shows that FCS can be successfully applied for the characterization of protein-containing C3Ms.

  8. Molecular exchange in block copolymer micelles: when corona chains overlap

    NASA Astrophysics Data System (ADS)

    Lu, Jie; Lodge, Timothy; Bates, Frank; Choi, Soohyung

    2013-03-01

    The chain exchange kinetics of poly(styrene-b-ethylenepropylene) (PS-PEP) diblock copolymer micelles in squalane (C30H62) was investigated using time-resolved small angle neutron scattering (TR-SANS). The solvent is a mixture of h-squalane and d-squalane that contrast-matches a mixed 50/50 h/d PS micelle core. As isotope labeled chains exchange, the core contrast decreases, leading to a reduction in scattering intensity. This strategy therefore allows direct probing of the chain exchange rate. Separate copolymer micellar solutions containing either deuterium labeled (dPS) or normal (hPS) poly(styrene) core blocks were prepared and mixed at room temperature, below the core glass transition temperature. The samples were heated to several temperatures (around 100 °C) and monitored by TR-SANS every 5 min. As polymer concentration was increased from 1% to 15% by volume, we observed a significant slowing down of chain exchange rate. Similar retarded kinetics was found when part of the solvent in the 1% solution was replaced by homopolymer PEP (comparable size as corona block). Furthermore, if all the solvent is replaced with PEP, no exchange was detected for up to 3hr at 200 °C. These results will be discussed in terms of a molecular model for chain exchange Infineum, Iprime, NIST, ORNL

  9. 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.

  10. Rheological study of the shape transition of block copolymer-nonionic surfactant mixed micelles.

    PubMed

    Löf, David; Schillén, Karin; Torres, Miguel F; Müller, Alejandro J

    2007-10-23

    A rheological study of mixed micelles formed by PEO-PPO-PEO triblock copolymer P123 and nonionic surfactant C12EO6 in aqueous solutions has been carried out with the purpose of investigating the time dependence of a shape transition of the mixed micelles and characterizing the shape before and after the transition. The rheology results presented in this report give clear evidence that the P123-C12EO6 mixed micelle grows and changes gradually in shape from spherical to elongated (rodlike) geometry with increasing temperature. These results are in accordance with the results found in the parallel dynamic and static light scattering and calorimetrical investigation.1,2 By using steady-state rheology, the time dependence of the sphere-to-rod transition of the mixed micelle system was carefully followed with time and temperature as simultaneously recorded variables in the experiments. This was performed by a designed novel experimental procedure. A temperature ramp was applied at a rate of 2.6 degrees C/min from a temperature below to a temperature above the shape transition at a constant shear rate while the viscosity of the solution was measured. The investigation was limited to two different compositions, surfactant-to-copolymer molar ratios (MR=nC12EO6/nP123) of 2.2 and 6.0 with varying total concentration from 1.5 to 21 wt % in comparison with the neat component. At low concentration, a slow transition was observed, which indicated that the mixed micelles are still growing into rods for several minutes after reaching the final temperature. At a total concentration of 4.0 wt % and above, the system reached equilibrium quickly. A concentration-dependent kinetic process is therefore anticipated, which was also found in the time-resolved static light scattering experiments previously performed (Löf, D.; Schillén, K.; Olofsson, G.; Niemiec, A.; Loh, W. J. Phys. Chem. B 2007, 111, 5911). At concentrations above 10 wt %, shear-thinning behavior was observed for the

  11. An investigation of model forensic bone in soil environments studied using infrared spectroscopy.

    PubMed

    Howes, Johanna M; Stuart, Barbara H; Thomas, Paul S; Raja, Sophil; O'Brien, Christopher

    2012-09-01

    Infrared spectroscopy has been used to examine changes to bone chemistry as a result of soil burial. Pig carcasses were buried as part of a controlled field study, and pig bone was used in soil environments established in the laboratory. The variables of species type, bone pretreatment, soil type and pH, moisture content, temperature, and burial time were investigated. The crystallinity index (CI) and the organic and carbonate contents of the bones were monitored. The data revealed decreasing trends in the organic and carbonate contents and an increase in the CI of the bone with burial time. An acidic soil environment and soil type are the factors that have the most influence on bone chemistry as a result of burial. The study demonstrates the potential of infrared spectroscopy as a straightforward method of monitoring the changes associated with aging of bones in a variety of soil environments.

  12. Biodegradable mixed MPEG-SS-2SA/TPGS micelles for triggered intracellular release of paclitaxel and reversing multidrug resistance

    PubMed Central

    Dong, Kai; Yan, Yan; Wang, Pengchong; Shi, Xianpeng; Zhang, Lu; Wang, Ke; Xing, Jianfeng; Dong, Yalin

    2016-01-01

    In this study, a type of multifunctional mixed micelles were prepared by a novel biodegradable amphiphilic polymer (MPEG-SS-2SA) and a multidrug resistance (MDR) reversal agent (d-α-tocopheryl polyethylene glycol succinate, TPGS). The mixed micelles could achieve rapid intracellular drug release and reversal of MDR. First, the amphiphilic polymer, MPEG-SS-2SA, was synthesized through disulfide bonds between poly (ethylene glycol) monomethyl ether (MPEG) and stearic acid (SA). The structure of the obtained polymer was similar to poly (ethylene glycol)-phosphatidylethanolamine (PEG-PE). Then the mixed micelles, MPEG-SS-2SA/TPGS, were prepared by MPEG-SS-2SA and TPGS through the thin film hydration method and loaded paclitaxel (PTX) as the model drug. The in vitro release study revealed that the mixed micelles could rapidly release PTX within 24 h under a reductive environment because of the breaking of disulfide bonds. In cell experiments, the mixed micelles significantly inhibited the activity of mitochondrial respiratory complex II, also reduced the mitochondrial membrane potential, and the content of adenosine triphosphate, thus effectively inhibiting the efflux of PTX from cells. Moreover, in the confocal laser scanning microscopy, cellular uptake and 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide assays, the MPEG-SS-2SA/TPGS micelles achieved faster release and more uptake of PTX in Michigan Cancer Foundation-7/PTX cells and showed better antitumor effects as compared with the insensitive control. In conclusion, the biodegradable mixed micelles, MPEG-SS-2SA/TPGS, could be potential vehicles for delivering hydrophobic chemotherapeutic drugs in MDR cancer therapy. PMID:27785018

  13. 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

  14. 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.

  15. 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.

  16. Toward Understanding Pore Formation and Mobility During Controlled Directional Solidification in a Microgravity Environment Investigation (PFMI)

    NASA Technical Reports Server (NTRS)

    Grugel, R. N.; Anilkumar, A. V.; Luz, P.; Jeter, L.; Volz, M. P.; Spievy, R.; Smith, G.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Porosity in the form of "bubbles and pipes" can occur during controlled directional solidification processing of metal alloys. It is detrimental to material properties and precludes obtaining meaningful scientific results. On Earth, density differences allow an initiated bubble can rise through the liquid and "pop" at the surface resulting in a sound casting. This is not likely to occur in a microgravity environment and, unfortunately, a number of experiments conducted in microgravity have suffered from porosity effects. The current investigation is a systematic effort towards understanding porosity formation and mobility during controlled directional solidification in a microgravity environment. This will be investigated by utilizing a transparent material, succinonitrile (SCN), in conjunction with a translating temperature gradient stage so that direct observation and recording of pore generation and mobility can be made. The talk will cover the porosity problem, the details of the proposed experiments and the experimental hardware, and the expectations from the microgravity experiments.

  17. An investigation into environment dependent nanomechanical properties of shallow water shrimp (Pandalus platyceros) exoskeleton.

    PubMed

    Verma, Devendra; Tomar, Vikas

    2014-11-01

    The present investigation focuses on understanding the influence of change from wet to dry environment on nanomechanical properties of shallow water shrimp exoskeleton. Scanning Electron Microscopy (SEM) based measurements suggest that the shrimp exoskeleton has Bouligand structure, a key characteristic of the crustaceans. As expected, wet samples are found to be softer than dry samples. Reduced modulus values of dry samples are found to be 24.90 ± 1.14 GPa as compared to the corresponding values of 3.79 ± 0.69 GPa in the case of wet samples. Hardness values are found to be 0.86 ± 0.06 GPa in the case of dry samples as compared to the corresponding values of 0.17 ± 0.02 GPa in the case of wet samples. In order to simulate the influence of underwater pressure on the exoskeleton strength, constant load creep experiments as a function of wet and dry environments are performed. The switch in deformation mechanism as a function of environment is explained based on the role played by water molecules in assisting interface slip and increased ductility of matrix material in wet environment in comparison to the dry environment.

  18. The alignment of a voltage-sensing peptide in dodecylphosphocholine micelles and in oriented lipid bilayers by nuclear magnetic resonance and molecular modeling.

    PubMed Central

    Mattila, K; Kinder, R; Bechinger, B

    1999-01-01

    The S4 segments of voltage-gated sodium channels are important parts of the voltage-sensing elements of these proteins. Furthermore, the addition of the isolated S4 polypeptide to planar lipid bilayers results in stepwise increases of ion conductivity. In order to gain insight into the mechanisms of pore formation by amphipathic peptides, the structure and orientation of the S4 segment of the first internal repeat of the rat brain II sodium channel was investigated in the presence of DPC micelles by multidimensional solution NMR spectroscopy and solid-state NMR spectroscopy on oriented phospholipid bilayers. Both the anisotropic chemical shift observed by proton-decoupled (15)N solid-state NMR spectroscopy and the attenuating effects of DOXYL-stearates on TOCSY crosspeak intensities of micelle-associated S4 indicate that the central alpha-helical portion of this peptide is oriented approximately parallel to the membrane surface. Simulated annealing and molecular dynamics calculations of the peptide in a biphasic tetrachloromethane-water environment indicate that the peptide alpha-helix extends over approximately 12 residues. A less regular structure further toward the C-terminus allows for the hydrophobic residues of this part of the peptide to be positioned in the tetrachloromethane environment. The implications for possible pore-forming mechanisms are discussed. PMID:10512830

  19. cRGD-functionalized reduction-sensitive shell-sheddable biodegradable micelles mediate enhanced doxorubicin delivery to human glioma xenografts in vivo.

    PubMed

    Zhu, Yaqin; Zhang, Jian; Meng, Fenghua; Deng, Chao; Cheng, Ru; Feijen, Jan; Zhong, Zhiyuan

    2016-07-10

    Biodegradable micelles are one of the most studied systems for the delivery of hydrophobic anticancer drugs. Their therapeutic efficacy in vivo is, however, suboptimal, partly due to poor tumor cell uptake as well as slow intracellular drug release. Here, we show that cRGD-functionalized intracellularly shell-sheddable biodegradable PEG-SS-PCL micelles mediate enhanced doxorubicin (DOX) delivery to U87MG glioma xenografts in vivo, resulting in significantly improved tumor growth inhibition as compared to reduction-insensitive cRGD/PEG-PCL controls. cRGD/PEG-SS-PCL micelles revealed a small size of ca. 61nm, a decent DOX loading of 14.9wt%, and triggered drug release in a reductive environment (10mM glutathione). Flow cytometry, confocal microscopy, and MTT assays demonstrated that cRGD/PEG-SS-PCL micelles with a cRGD ligand density of 20% efficiently delivered and released DOX into αvβ3 integrin overexpressing U87MG cells. The in vivo pharmacokinetics studies displayed that DOX-loaded cRGD20/PEG-SS-PCL micelles had a prolonged elimination half-life time of 3.51h, which was comparable to that of cRGD20/PEG-PCL counterparts, indicating that disulfide bonds in the PEG-SS-PCL micelles are stable in the circulation. Notably, in vivo imaging and biodistribution studies in U87MG glioma xenografts showed that cRGD20/PEG-SS-PCL micelles led to efficient accumulation as well as fast drug release in the tumor. The therapeutic outcomes demonstrated that DOX-loaded cRGD20/PEG-SS-PCL micelles exhibited little side effects and superior tumor growth inhibition as compared to non-targeting PEG-SS-PCL and reduction-insensitive cRGD20/PEG-PCL counterparts. The reduction-sensitive shell-sheddable biodegradable micelles have appeared as a fascinating platform for targeted tumor chemotherapy.

  20. Synergistic dual-pH responsive copolymer micelles for pH-dependent drug release

    NASA Astrophysics Data System (ADS)

    Deng, Hongzhang; Zhao, Xuefei; Liu, Jinjian; Zhang, Jianhua; Deng, Liandong; Liu, Jianfeng; Dong, Anjie

    2016-01-01

    The tuning of the structure of nanocarriers with fast acidic-degradation rate and high stability in physiological conditions or during storage is under intensive study. In this context, a kind of dual-pH responsive micelles with well-balanced stability, that is, fast hydrolysis in acidic environment and stability towards blood drug release at 7.4 were developed. This is achieved by the self-assembly of micelles of poly(ethylene glycol)-b-(poly ε-caprolactone-g-poly(2,2-dimethyl-1,3-dioxolane-4-yl)methylacrylate-co-2(dimethylamino)ethyl methacrylate) (mPEG-b-(PCL-g-P(DA-co-DMAEMA))) copolymers with two inert pH responsive moieties of DA and DMAEMA. The fast synergistic acid-triggered disassembly and high stability at physiological condition of the mPEG-b-(PCL-g-P(DA-co-DMAEMA)) micelles was verified by 1H NMR, particle size and optical stability measurements, which was induced and mediated by the synergistic pH responses of the hydrolysis of the ketal in DA moieties and the switch in solubility of tertiary amino moieties (DMAEMA) under mild acid conditions. It was observed that the hydrolysis rate of the ketal could be promoted by increasing the content of DMAEMA moieties. The fast intracellular disassembly of the micelles depending on the contents of DMAEMA moieties was also traced by fluorescence resonance energy transfer (FRET). The in vitro release studies showed that the release of DOX from mPEG-b-(PCL-g-P(DA-co-DMAEMA)) micelles at mild acid condition was significantly accelerated by increasing the content of DMAEMA moieties, while greatly impeding drug release in physiological conditions. The antitumor activity of DOX-loaded micelles was studied in MCF-7 and 4T1 cells in vitro and in 4T1 tumor-bearing Balb-c mice in vivo. The results indicated the DOX-loaded micelles with higher content of DMAEMA moieties exhibited enhanced anticancer activity. Collectively, the synergistic dual-pH responsive design of mPEG-b-(PCL-g-P(DA-co-DMAEMA)) micelles provided a new

  1. Stable polymer micelle systems as anti-cancer drug delivery carriers

    NASA Astrophysics Data System (ADS)

    Zeng, Yi

    2005-07-01

    Several temporarily stable polymer micelle systems that might be used as ultrasonic-activated drug delivery carriers were synthesized and investigated. These polymeric micelle systems were PlurogelRTM, Tetronic RTM, poly(ethylene oxide)-b-poly(N-isopropylacrylamide) and poly(ethylene oxide)-b-poly(N-isopropylacrylamide-co-2-hydroxyethyl methacrylate-lactate n). In previous work in our lab, Pruitt et al. developed a stabilized drug carrier named PlurogelRTM [5, 6]. Unfortunately, the rate of the successful PlurogelRTM synthesis was only about 30% by simply following Pruitt's process. In this work, this rate was improved to 60% by combining the process of adding 0.15 M NaCl and/or 10 mul/ml n-butanol and by preheating the solution before polymerization. TetronicsRTM were proved not to be good candidates to form temporarily stable polymeric micelle system by polymerizing interpenetrating networks inside their micelle cores. Tetronic micelle systems treated by this process still were not stable at concentrations below their critical micelle concentration (CMC). Poly(ethylene oxide)-b-poly(N-isopropylacrylamide)-N,N-bis(acryloyl)cystamine micelle-like nanoparticles were developed and characterized. When the N,N-bis(acryloyl)cystamine (BAC) was from 0.2 wt% to 0.75 wt% of the mass of poly(N-isopropylacrylamide), diameters of the nanoparticles at 40°C were less than 150 nm. The cores of the nanoparticles were hydrophobic enough to sequester 1,6-diphenylhexatriene (DPH) and the anti-cancer drug doxorubicin (DOX). Nanoparticles with 0.5 wt% BAC stored at room temperature in 0.002 mg/ml solutions were stable for up to two weeks. Poly(ethylene oxide)-b-poly(N-isopropylacrylamide-co-2-hydroxyethyl methacrylate-lactate n) micelle systems were synthesized and characterized. The degree of polymerization of lactate side group, n, was 3 or 5. The copolymers with N-isopropylacrylamide:2-hydroxyethyl methacrylate-lactate3: poly(ethylene oxide) (NIPAAm:HEMA-lactate 3:PEO) ratios of

  2. Radiochromic leuco dye micelle hydrogels: II. Low diffusion rate leuco crystal violet gel.

    PubMed

    Babic, Steven; Battista, Jerry; Jordan, Kevin

    2009-11-21

    Radiation-sensitive hydrogels offer the capability of verifying intricate dose distributions in three-dimensional (3D) space conveniently in a single measurement with sub-millimetre spatial resolution. In this study, a new radiochromic hydrogel called leuco crystal violet (LCV) micelle gel is introduced. Upon irradiation, LCV converts to crystal violet (CV(+)). Triton X-100 micelles are used to provide the required hybrid-interfacing environment to dissolve LCV. The diffusion coefficient of the LCV gel has been measured to be 0.036 +/- 0.001 mm(2) h(-1), which is a factor of 25 times less than the standard radiochromic ferrous xylenol-orange (FX) gel; LCV gels without Triton X-100 micelles have a diffusion coefficient of 0.33 +/- 0.02 mm(2) h(-1). The LCV gel formulation contains: 1 mM LCV, 25 mM trichloroacetic acid, 4 mM Triton X-100 and 4% w/w gelatin. The primary innovative feature of this 3D hydrogel is that the radiation-induced CV(+) dye is more soluble in the Triton X-100 micelles than in the surrounding water which consequently leads to more stable post-irradiation dose distributions. A dosimetric characterization revealed that the dose response is reproducible to within 1% over three separate batches, independent of energy, dose rate and dose fractionation but is affected by the temperature ( approximately 4% per degree C) during irradiation. LCV micelle gels scanned optically with a yellow light source are a promising system for 3D dose verification. They may prove to be, especially, useful for scanning large volume dosimeters (i.e. 20 cm) since they are easily manufactured, transparent and near colourless prior to irradiation.

  3. Radiochromic leuco dye micelle hydrogels: II. Low diffusion rate leuco crystal violet gel

    NASA Astrophysics Data System (ADS)

    Babic, Steven; Battista, Jerry; Jordan, Kevin

    2009-11-01

    Radiation-sensitive hydrogels offer the capability of verifying intricate dose distributions in three-dimensional (3D) space conveniently in a single measurement with sub-millimetre spatial resolution. In this study, a new radiochromic hydrogel called leuco crystal violet (LCV) micelle gel is introduced. Upon irradiation, LCV converts to crystal violet (CV+). Triton X-100 micelles are used to provide the required hybrid-interfacing environment to dissolve LCV. The diffusion coefficient of the LCV gel has been measured to be 0.036 ± 0.001 mm2 h-1, which is a factor of 25 times less than the standard radiochromic ferrous xylenol-orange (FX) gel; LCV gels without Triton X-100 micelles have a diffusion coefficient of 0.33 ± 0.02 mm2 h-1. The LCV gel formulation contains: 1 mM LCV, 25 mM trichloroacetic acid, 4 mM Triton X-100 and 4% w/w gelatin. The primary innovative feature of this 3D hydrogel is that the radiation-induced CV+ dye is more soluble in the Triton X-100 micelles than in the surrounding water which consequently leads to more stable post-irradiation dose distributions. A dosimetric characterization revealed that the dose response is reproducible to within 1% over three separate batches, independent of energy, dose rate and dose fractionation but is affected by the temperature (~4% per °C) during irradiation. LCV micelle gels scanned optically with a yellow light source are a promising system for 3D dose verification. They may prove to be, especially, useful for scanning large volume dosimeters (i.e. 20 cm) since they are easily manufactured, transparent and near colourless prior to irradiation.

  4. The critical micelle concentration of tetraethylammonium perfluorooctylsulfonate in water.

    PubMed

    López-Fontán, José L; González-Pérez, Alfredo; Costa, Julian; Ruso, Juan M; Prieto, Gerardo; Schulz, Pablo C; Sarmiento, Félix

    2006-02-15

    The aggregation characteristics of tetraethylammonium perfluorooctylsulfonate in water were studied by several techniques: conductivity, pH, ion-selective electrodes, and surface tension. It was concluded that the aggregation process is gradual and starts with the formation of oligomers such as ion pairs that grow to give spherical micelles, which become wormlike with increasing concentration. Because of the size and hydrophobicity of the counterion, micelles quickly increase in ionization degree up to about 0.5. Differences among different critical micelle concentration values in the literature are explained on the basis of the gradual formation of micelles.

  5. 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

  6. The pressure-induced, lactose-dependent changes in the composition and size of casein micelles.

    PubMed

    Wang, Pengjie; Jin, Shaoming; Guo, Huiyuan; Zhao, Liang; Ren, Fazheng

    2015-04-15

    The effects of lactose on the changes in the composition and size of casein micelles induced by high-pressure treatment and the related mechanism of action were investigated. Dispersions of ultracentrifuged casein micelle pellets with 0-10% (w/v) lactose were subjected to high pressure (400 MPa) at 20 °C for 40 min. The results indicated that the level of non-sedimentable caseins was positively related to the amount of lactose added prior to pressure treatment, and negatively correlated to the size. A mechanism for the pressure-induced, lactose-dependent changes in the casein micelles is proposed. Lactose inhibits the hydrophobic interactions between the micellar fragments during or after pressure release, through the hydrophilic layer formed by their hydrogen bonds around the micellar fragments. In addition, lactose does not favour the association between calcium and the casein aggregates after pressure release. Due to these two functions, lactose inhibited the formation of larger micelles after pressure treatment.

  7. Detergent properties influence the stability of the glycophorin A transmembrane helix dimer in lysophosphatidylcholine micelles.

    PubMed

    Stangl, Michael; Veerappan, Anbazhagan; Kroeger, Anja; Vogel, Peter; Schneider, Dirk

    2012-12-19

    Detergents might affect membrane protein structures by promoting intramolecular interactions that are different from those found in native membrane bilayers, and fine-tuning detergent properties can be crucial for obtaining structural information of intact and functional transmembrane proteins. To systematically investigate the influence of the detergent concentration and acyl-chain length on the stability of a transmembrane protein structure, the stability of the human glycophorin A transmembrane helix dimer has been analyzed in lyso-phosphatidylcholine micelles of different acyl-chain length. While our results indicate that the transmembrane protein is destabilized in detergents with increasing chain-length, the diameter of the hydrophobic micelle core was found to be less crucial. Thus, hydrophobic mismatch appears to be less important in detergent micelles than in lipid bilayers and individual detergent molecules appear to be able to stretch within a micelle to match the hydrophobic thickness of the peptide. However, the stability of the GpA TM helix dimer linearly depends on the aggregation number of the lyso-PC detergents, indicating that not only is the chemistry of the detergent headgroup and acyl-chain region central for classifying a detergent as harsh or mild, but the detergent aggregation number might also be important.

  8. Inulin based micelles loaded with curcumin or celecoxib with effective anti-angiogenic activity.

    PubMed

    Mandracchia, Delia; Tripodo, Giuseppe; Trapani, Adriana; Ruggieri, Simona; Annese, Tiziana; Chlapanidas, Theodora; Trapani, Giuseppe; Ribatti, Domenico

    2016-10-10

    Curcumin (CUR) and celecoxib (CLX) are two highly hydrophobic drugs which show bioavailability problems due to their poor aqueous solubility. The aim of this study was to encapsulate each of these drugs in micelles based on biodegradable and amphiphilic polymers to investigate their anti-angiogenesis activity. Here we use an amphiphilic polymer, based on two natural substances from renewable resources (Inulin and Vitamin E, INVITE), as a self-assembling system for the drug delivery of CUR and CLX. By the in vivo assay of chick embryo chorioallantoic membrane (CAM) it was assessed that both INVITE-CUR and INVITE-CLX micelles possess remarkable anti-angiogenic activity, while the INVITE micelles alone resulted intrinsically pro-angiogenic. Furthermore, it has been shown that encapsulation of CUR and CLX in INVITE micelles enhances of several magnitudes the water-solubility of CUR and CLX (14·10(5) and 3·10(2) times for CUR and CLX, respectively). These results may have interesting implications not only in anticancer or diabetic maculopathy therapy based on the anti-angiogenesis strategy but also for regenerative medicine where over-production of new vessels is required.

  9. Leuco-crystal-violet micelle gel dosimeters: I. Influence of recipe components and potential sensitizers.

    PubMed

    Nasr, A T; Alexander, K; Schreiner, L J; McAuley, K B

    2015-06-21

    Radiochromic leuco crystal violet (LCV) micelle gel dosimeters are promising three-dimensional radiation dosimeters because of their spatial stability and suitability for optical readout. The effects of surfactant type and surfactant concentration on dose sensitivity of LCV micelle gels are tested, demonstrating that dose sensitivity and initial colour of the gel increases with increasing Triton x-100 (Tx100) concentration. Using Cetyl Trimethyl Ammonium Bromide (CTAB) in place of Tx100 produces gels that are nearly colourless prior to irradiation, but reduces the dose sensitivity. The separate effects of Tri-chloro acetic acid concentration and pH are investigated, revealing that controlling the pH near 3.6 is crucial for achieving high dose sensitivity. The sensitizing effect of chlorinated species on dose sensitivity is tested using 2,2,2-trichloroethanol (TCE), chloroform, and 1,1,1-trichloro-2-methyl-2-propanol hemihydrate. TCE gives the largest improvement in dose sensitivity and is recommended for use in micelle gel dosimeters because it is less volatile and safer to use than chloroform. Preliminary experiments on a new gel containing CTAB as the surfactant and TCE show that this new gel gives a dose sensitivity that is 24% higher than that of previous LCV micelle gels and is nearly colourless prior to irradiation. PMID:26020840

  10. Ramping of pH Across the Water-Pool of a Reverse Micelle.

    PubMed

    Mukherjee, Puspal; Gupta, Shradhey; Rafiq, Shahnawaz; Yadav, Rajeev; Jain, Vipin Kumar; Raval, Jayraj; Sen, Pratik

    2016-02-23

    In this work, we have addressed the problem of "acidity" of the water-pool of a reverse micelle (RM) through the well-known inversion of sucrose reaction as a tool of investigation. This reaction has been performed inside positively and negatively charged RM and the rates are compared with that in bulk water. We propose that the buffer-like action in a water-pool is much stronger than expected earlier. The rate of sucrose hydrolysis slowed down in the negatively charged AOT reverse micelle while it sped up for the positively charged CTAB reverse micelle. However, temperature-dependent measurements showed that the activation energy remained the same for all the cases. It has been concluded that a proton gradient exists inside the water-pool of the reverse micelle and it determines the buffer-like action of the water-pool that persists until about 2 N of HCl in AOT RM of w(0) = 10.5.

  11. Leuco-crystal-violet micelle gel dosimeters: I. Influence of recipe components and potential sensitizers

    NASA Astrophysics Data System (ADS)

    Nasr, A. T.; Alexander, K.; Schreiner, L. J.; McAuley, K. B.

    2015-06-01

    Radiochromic leuco crystal violet (LCV) micelle gel dosimeters are promising three-dimensional radiation dosimeters because of their spatial stability and suitability for optical readout. The effects of surfactant type and surfactant concentration on dose sensitivity of LCV micelle gels are tested, demonstrating that dose sensitivity and initial colour of the gel increases with increasing Triton x-100 (Tx100) concentration. Using Cetyl Trimethyl Ammonium Bromide (CTAB) in place of Tx100 produces gels that are nearly colourless prior to irradiation, but reduces the dose sensitivity. The separate effects of Tri-chloro acetic acid concentration and pH are investigated, revealing that controlling the pH near 3.6 is crucial for achieving high dose sensitivity. The sensitizing effect of chlorinated species on dose sensitivity is tested using 2,2,2-trichloroethanol (TCE), chloroform, and 1,1,1-trichloro-2-methyl-2-propanol hemihydrate. TCE gives the largest improvement in dose sensitivity and is recommended for use in micelle gel dosimeters because it is less volatile and safer to use than chloroform. Preliminary experiments on a new gel containing CTAB as the surfactant and TCE show that this new gel gives a dose sensitivity that is 24% higher than that of previous LCV micelle gels and is nearly colourless prior to irradiation.

  12. Interaction with Mixed Micelles in the Intestine Attenuates the Permeation Enhancing Potential of Alkyl-Maltosides.

    PubMed

    Gradauer, Kerstin; Nishiumi, Ayano; Unrinin, Kota; Higashino, Haruki; Kataoka, Makoto; Pedersen, Betty L; Buckley, Stephen T; Yamashita, Shinji

    2015-07-01

    The purpose of the present study was to investigate the interaction of intestinal permeation enhancers with lipid and surfactant components present in the milieu of the small intestine. Maltosides of different chain lengths (decyl-, dodecyl-, and tetradecyl-maltoside; DM, DDM, TDM, respectively) were used as examples of nonionic, surfactant-like permeation enhancers, and their effect on the permeation of FD4 across Caco-2 monolayers was monitored. To mimic the environment of the small intestine, modified versions of fasted and fed state simulated intestinal fluid (FaSSIFmod, FeSSIFmod6.5, respectively) were used in addition to standard transport media (TM). Compared to the buffer control, 0.5 mM DDM led to a 200-fold permeation enhancement of FD4 in TM. However, this was dramatically decreased in FaSSIFmod, where a concentration of 5 mM DDM was necessary in order to elicit a moderate, 4-fold, permeation enhancement. Its capacity to promote permeation was diminished further when FeSSIFmod6.5 was employed. Even when cells were exposed to a concentration of 5 mM, no significant permeation enhancement of FD4 was observed. Analogous effects were observed in the case of DM and TDM, with slight deviations on account of differences in their critical micelle concentration (CMC). This observation was corroborated by calculating the amount of maltoside monomer versus micellar bound maltoside in FaSSIFmod and FeSSIFmod6.5, which demonstrated a reduced amount of free monomer in these fluids. To evaluate the in vivo significance of our findings, DDM solutions in TM, FaSSIFmod, and FeSSIFmod6.5 were used for closed intestinal loop studies in rats. Consistent with the results found in in vitro permeation studies, these investigations illustrated the overwhelming impact of sodium taurocholate/lecithin micelles on the permeation enhancing effect of DDM. While DDM led to a 20-fold increase in FD4 bioavailability when it was applied in TM, no significant permeation enhancement was

  13. Effect of Vesicle-to-Micelle Transition on the Interactions of Phospholipid/Sodium Cholate Mixed Systems with Curcumin in Aqueous Solution.

    PubMed

    Zhang, Sha; Wang, Xiaoyong

    2016-08-01

    The role of vesicle-to-micelle transition has been investigated in the interactions of phospholipid vesicles, phospholipid/sodium cholate (NaC) mixed vesicles, and phospholipid/NaC mixed micelles with curcumin in aqueous solution. The addition of NaC causes phospholipid vesicles to transit into phospholipid/NaC mixed vesicles and phospholipid/NaC mixed micelles. Turbidity measurement reveals that the presence of curcumin increases the NaC concentration for the solubilization of phospholipid vesicles, which indicates that the bound curcumin tends to suppress the vesicle-to-micelle transition. The pyrene polarity index and curcumin fluorescence anisotropy measurements suggest that phospholipid/NaC mixed micelles have a more compact structure than that of phospholipid vesicles and phospholipid/NaC mixed vesicles. Curcumin associated with phospholipid vesicles, phospholipid/NaC mixed vesicles, and phospholipid/NaC mixed micelles often results in higher intensities of absorption and fluorescence than those of free curcumin. However, phospholipid/NaC mixed vesicles lead to the highest values of absorption and fluorescence intensities, binding constant, and radical-scavenging capacity with curcumin. The different structures in the phospholipid bilayer of phospholipid/NaC mixed vesicles and the hydrophobic part of phospholipid/NaC mixed micelles where curcumin located are discussed to explain the interaction behaviors of phospholipid/NaC mixed systems with curcumin.

  14. Multi-targeted inhibition of tumor growth and lung metastasis by redox-sensitive shell crosslinked micelles loading disulfiram

    NASA Astrophysics Data System (ADS)

    Duan, Xiaopin; Xiao, Jisheng; Yin, Qi; Zhang, Zhiwen; Yu, Haijun; Mao, Shirui; Li, Yaping

    2014-03-01

    Metastasis, the main cause of cancer related deaths, remains the greatest challenge in cancer treatment. Disulfiram (DSF), which has multi-targeted anti-tumor activity, was encapsulated into redox-sensitive shell crosslinked micelles to achieve intracellular targeted delivery and finally inhibit tumor growth and metastasis. The crosslinked micelles demonstrated good stability in circulation and specifically released DSF under a reductive environment that mimicked the intracellular conditions of tumor cells. As a result, the DSF-loaded redox-sensitive shell crosslinked micelles (DCMs) dramatically inhibited cell proliferation, induced cell apoptosis and suppressed cell invasion, as well as impairing tube formation of HMEC-1 cells. In addition, the DCMs could accumulate in tumor tissue and stay there for a long time, thereby causing significant inhibition of 4T1 tumor growth and marked prevention in lung metastasis of 4T1 tumors. These results suggested that DCMs could be a promising delivery system in inhibiting the growth and metastasis of breast cancer.

  15. Investigation into suitability of geopolymers (illite & metakaolin) for the space environment

    NASA Astrophysics Data System (ADS)

    Cesul, Brandon T.

    The United States has utilized high resolution imaging platforms for national defense since the beginning of the space age. In order to improve the resolution and swath width of imaging satellites, the primary restriction in optical hardware is the mirror size, specifically mirror diameter and mirror mass. This research addresses one of these concerns, reducing the mass of a spacecraft mirror by the use of innovative materials. In contemporary imagery satellites, monolithic glass is the material of choice to produce large aperture mirrors that can survive the space environment. However, material performance requirements for future imaging mission mirrors necessitate a lower areal density than glass with similar if not superior mechanical strength. Additionally, any material chosen must also be able to deal with the unique environment of low earth orbit, namely the near-vacuum conditions, radiation environment and interaction with atomic oxygen. This research focuses on investigation of a class of inorganic polymers known as geopolymers for use in the space environment. Geopolymers are based on aluminosilicate chemistry and have advantages of high specific strength combined with low densities, tailorable coefficients of thermal expansion, and easier curing processes than traditional space qualified epoxies. Geopolymers have a long history for use in terrestrial applications, but empirical data is not available addressing their suitability for the space environment. This research focused on determining whether the geopolymer as a bulk material will respond favorably to environmental conditions as experienced during typical spaceflight operations. Two different formulations of geopolymer were investigated, one based on metakaolin chemistry, and the other based on illite chemistry. Three primary objectives were identified for assessing whether geopolymers could survive the space environment: could the materials be processed to minimize curing shrinkage, characterizing

  16. Experimental investigation on interstage thermal environment of launch vehicle with multijets in wind tunnel

    NASA Astrophysics Data System (ADS)

    Lin, J.; Cao, C.; Wu, Y.; Zhang, S.

    2013-06-01

    During the stage separation course of a launch vehicle, the environment of the stage is quite serious because of the high temperature and pressure. It is very important to investigate the pressure and heat flux distribution under the interstage thermal environment, as is good for the design of stage configuration. This paper presents the test technique of a thermal environment simulation with multi-jets of the launch vehicle stage separation in 1-meter-diameter hypersonic wind tunnel (HWT). The internal and external flows run simultaneously. A hot jet technique that makes use of five engine jets at the same time is adopted to simulate the internal flow. Pressure and heat flux measurements have also been developed. Pressure, temperature and heat flux characteristics of the first-stage fore-envelop head and the second-stage aft-envelop head which vary with different separation distances and different exhaust windows are introduced. The results indicate that the environment of a small stage separation distance is severe. The smaller separation distance is, the less is the uniformity of pressure, temperature, and heat flux distributions. A coaxial thermocouple is available to measure the heat flux between stages, whereas the accuracy of the heat flux measurement as well as the heat flux simulation rules need further exploring and studying.

  17. Correlation of insulin-enhancing properties of vanadium-dipicolinate complexes in model membrane systems: phospholipid langmuir monolayers and AOT reverse micelles.

    PubMed

    Sostarecz, Audra G; Gaidamauskas, Ernestas; Distin, Steve; Bonetti, Sandra J; Levinger, Nancy E; Crans, Debbie C

    2014-04-22

    We explore the interactions of V(III) -, V(IV) -, and V(V) -2,6-pyridinedicarboxylic acid (dipic) complexes with model membrane systems and whether these interactions correlate with the blood-glucose-lowering effects of these compounds on STZ-induced diabetic rats. Two model systems, dipalmitoylphosphatidylcholine (DPPC) Langmuir monolayers and AOT (sodium bis(2-ethylhexyl)sulfosuccinate) reverse micelles present controlled environments for the systematic study of these vanadium complexes interacting with self-assembled lipids. Results from the Langmuir monolayer studies show that vanadium complexes in all three oxidation states interact with the DPPC monolayer; the V(III) -phospholipid interactions result in a slight decrease in DPPC molecular area, whereas V(IV) and V(V) -phospholipid interactions appear to increase the DPPC molecular area, an observation consistent with penetration into the interface of this complex. Investigations also examined the interactions of V(III) - and V(IV) -dipic complexes with polar interfaces in AOT reverse micelles. Electron paramagnetic resonance spectroscopic studies of V(IV) complexes in reverse micelles indicate that the neutral and smaller 1:1 V(IV) -dipic complex penetrates the interface, whereas the larger 1:2 V(IV) complex does not. UV/Vis spectroscopy studies of the anionic V(III) -dipic complex show only minor interactions. These results are in contrast to behavior of the V(V) -dipic complex, [VO2 (dipic)](-) , which penetrates the AOT/isooctane reverse micellar interface. These model membrane studies indicate that V(III) -, V(IV) -, and V(V) -dipic complexes interact with and penetrate the lipid interfaces differently, an effect that agrees with the compounds' efficacy at lowering elevated blood glucose levels in diabetic rats.

  18. Molecular Simulations of Dodecyl-β-maltoside Micelles in Water: Influence of the Headgroup Conformation and Force field Parameters

    PubMed Central

    Abel, Stéphane; Dupradeau, François-Yves; Raman, E. Prabhu; MacKerell, Alexander D.; Marchi, Massimo

    2011-01-01

    This paper deals with the development and validation of new potential parameter sets, based on the CHARMM36 and GLYCAM06 force fields, to simulate micelles of the two anomeric forms (α and β) of N-Dodecyl-ß-maltoside (C12G2), a surfactant widely used in the extraction and purification of membrane proteins. In this context, properties such as size, shape, internal structure and hydration of the C12G2 anomer micelles were thoroughly investigated by molecular dynamics simulations and the results compared with experiments. Additional simulations were also performed with the older CHARMM22 force field for carbohydrates (Kuttel, M. et al. J. Comp. Chem. 2002, 23, 1236-1243). We find that our CHARMM and GLYCAM parameter sets yields similar results in case of properties related to the micelle structure, but differ for other properties such as the headgroup conformation or the micelle hydration. In agreement with experiments, our results show that for all model potentials the β-C12G2 micelles have a more pronounced ellipsoidal shape than those containing α anomers. The computed radius of gyration is 20.2 Å and 25.4 Å for the α- and β-anomer micelles, respectively. Finally, we show that depending on the potential the water translational diffusion of the interfacial water is 7 - 11.5 times slower than that of bulk water due to the entrapment of the water in the micelle crevices. This retardation is independent of the headgroup in α- or β- anomers. PMID:21192681

  19. Stability, interaction, size, and microenvironmental properties of mixed micelles of decanoyl-N-methylglucamide and sodium dodecyl sulfate.

    PubMed

    Hierrezuelo, J M; Aguiar, J; Ruiz, C Carnero

    2004-11-23

    The mixed micellization between the nonionic surfactant decanoyl-N-methylglucamide (MEGA-10) and the common sodium dodecyl sulfate (SDS) in aqueous solutions of 0.1 M NaCl was investigated by the fluorescence probe method. The critical micelle concentrations were determined by the pyrene 1:3 ratio method. The experimental data are discussed in light of two mixing thermodynamic models within the framework of the pseudophase separation model, including the conventional regular solution theory and a recent treatment proposed by Maeda (J. Phys. Chem. B 2004, 108, 6043). This last approach provides a more appropriate description of the mixed system, particularly in two aspects: the nature of the interactions responsible for the stability of the mixed micelle and the behavior of the excess free energy per monomer of the system. By using the static quenching method, the mean micellar aggregation numbers of mixed micelles in the whole range of compositions were obtained. It was found that the micellar aggregation number initially increases with the content of the ionic component, then remains roughly constant, and, finally, decreases slightly for high content of this component. This behavior was analyzed taking into account the effects produced by the presence of the charged headgroups of sodium dodecyl sulfate, as this component increases its participation in the mixed micelle. The micropolarity of the mixed micelles was studied by the pyrene 1:3 ratio index. It was observed that the increasing participation of the ionic component induces the formation of micelles with a more dehydrated structure. Data of micellar microviscosity were obtained by using different methods, including fluorescence intensity measurements of Auramine O and steady-state fluorescence anisotropy of rhodamine B and diphenylbutadiene. The results obtained from these experiments are in good agreement and suggest the formation of mixed micelles with a less ordered structure as the content of SDS

  20. Dual-Purpose Magnetic Micelles for MRI and Gene Delivery

    PubMed Central

    Wang, Chunyan; Ravi, Sowndharya; Martinez, Gary.V.; Chinnasamy, Vignesh; Raulji, Payal; Howell, Mark; Davis, Yvonne; Seehra, Mohindar S.; Mohapatra, Subhra

    2013-01-01

    Gene therapy is a promising therapeutic approach for treating disease, but the efficient delivery of genes to desired locations with minimal side effects remains a challenge. In addition to gene therapy, it is also highly desirable to provide sensitive imaging information in patients for disease diagnosis, screening and post-therapy monitoring. Here, we report on the development of dual-purpose chitosan and polyethyleneimine (PEI) coated magnetic micelles (CP-mag-micelles) that can deliver nucleic acid-based therapeutic agents and also provide magnetic resonance imaging (MRI). These ‘theranostic’ CP-mag-micelles are composed of monodisperse hydrophobic superparamagnetic iron oxide nanoparticles (SPIONs) loaded into the cores of micelles that are self-assembled from a block copolymer of poly (D, L-lactide) (PLA) and monomethoxy polyethylene glycol (mPEG). For efficient loading and protection of the nucleic acids the micelles were coated with cationic polymers, such as chitosan and PEI. The morphology and size distribution of the CP-mag-micelles were characterized and their potential for use as an MRI-probe was tested using an MRI scanner. The T2 relaxivity of micelles was similar to CP-mag-micelles confirming that coating with cationic polymers did not alter magnetism. Nanoparticles coated with chitosan:PEI at a weight ratio of 5:5 showed higher transfection efficiency in HEK293, 3T3 and PC3 cells than with weight ratios of 3:7 or 7:3. CP-mag-micelles are biocompatible, can be delivered to various organs and are safe. A single injection of CP-mag-micelles carrying reporter plasmids in vivo expressed genes for at least one week. Collectively, our results demonstrate that a structural reinforcement of SPIONs loaded in the core of an mPEG-PLA micelle coated with cationic polymers provides efficient DNA delivery and enhanced MRI potential, and affords a promising candidate for theranostics in the future. PMID:22561339

  1. Stability and morphology of cerium oxide surfaces in an oxidizing environment: A first-principles investigation

    NASA Astrophysics Data System (ADS)

    Fronzi, Marco; Soon, Aloysius; Delley, Bernard; Traversa, Enrico; Stampfl, Catherine

    2009-09-01

    We present density functional theory investigations of the bulk properties of cerium oxides (CeO2 and Ce2O3) and the three low index surfaces of CeO2, namely, (100), (110), and (111). For the surfaces, we consider various terminations including surface defects. Using the approach of "ab initio atomistic thermodynamics," we find that the most stable surface structure considered is the stoichiometric (111) surface under "oxygen-rich" conditions, while for a more reducing environment, the same (111) surface, but with subsurface oxygen vacancies, is found to be the most stable one, and for a highly reducing environment, the (111) Ce-terminated surface becomes energetically favored. Interestingly, this latter surface exhibits a significant reconstruction in that it becomes oxygen terminated and the upper layers resemble the Ce2O3(0001) surface. This structure could represent a precursor to the phase transition of CeO2 to Ce2O3.

  2. Investigations on potential bacteria for the bioremediation treatment of environments contaminated with hydrocarbons

    SciTech Connect

    Lazar, I.; Voicu, A.; Dobrota, S.; Stefanescu, M.

    1995-12-31

    In Romania after more than 135 years of oil production and processing, some severe environmental pollution problems have accumulated. In this context a joint research group from Institute of Biology Bucharest and S.C. Petrostar S.A. Ploiesti became involved in a research project on bioremediation of an environment contaminated with hydrocarbon waste. In the first stage of this project, investigations on microbial communities occurring in environments contaminated with oil were carried out. In the second stage, the hundreds of bacterial strains and populations isolated from soils, slops, and water sites contaminated with waste oil and water waste oil mix were submitted to a screening program, to select a naturally occurring mixed culture with a high ability to degrade hydrocarbons.

  3. Fluorescence probe studies of the interactions between poly(oxyethylene) and surfactant micelles and microemulsion droplets in aqueous solutions

    SciTech Connect

    Zana, R.; Lianos, P.; Lang, J.

    1985-01-03

    The interaction between poly(ethylene oxide) (POE) and the aggregates present in micellar solutions of sodium dodecyl sulfate (SDS), mixed micellar solutions of SDS + 1-pentanol, and oil in water microemulsions made of SDS + 1-pentanol + oil (dodecane or toluene) has been investigated by means of fluorescence probing methods. It is shown that the addition of POE results in a decrease of the aggregation number of SDS in the aggregates present in all the systems investigated. Most likely this decrease is due to the adsorption of the POE chain in the micelle palisade layer and the ensuing increase of micelle ionization. 22 references, 5 figures, 2 tables.

  4. Physicochemical properties of pH-controlled polyion complex (PIC) micelles of poly(acrylic acid)-based double hydrophilic block copolymers and various polyamines.

    PubMed

    Warnant, J; Marcotte, N; Reboul, J; Layrac, G; Aqil, A; Jerôme, C; Lerner, D A; Gérardin, C

    2012-05-01

    The physicochemical properties of polyion complex (PIC) micelles were investigated in order to characterize the cores constituted of electrostatic complexes of two oppositely charged polyelectrolytes. The pH-sensitive micelles were obtained with double hydrophilic block copolymers containing a poly(acrylic acid) block linked to a modified poly(ethylene oxide) block and various polyamines (polylysine, linear and branched polyethyleneimine, polyvinylpyridine, and polyallylamine). The pH range of micellization in which both components are ionized was determined for each polyamine. The resulting PIC micelles were characterized using dynamic light scattering and small-angle X-ray scattering experiments (SAXS). The PIC micelles presented a core-corona nanostructure with variable polymer density contrasts between the core and the corona, as revealed by the analysis of the SAXS curves. It was shown that PIC micelle cores constituted by polyacrylate chains and polyamines were more or less dense depending on the nature of the polyamine. It was also determined that the density of the cores of the PIC micelles depended strongly on the nature of the polyamine. These homogeneous cores were surrounded by a large hairy corona of hydrated polyethylene oxide block chains. Auramine O (AO) was successfully entrapped in the PIC micelles, and its fluorescence properties were used to get more insight on the core properties. Fluorescence data confirmed that the cores of such micelles are quite compact and that their microviscosity depended on the nature of the polyamine. The results obtained on these core-shell micelles allow contemplating a wide range of applications in which the AO probe would be replaced by various cationic drugs or other similarly charged species to form drug nanocarriers or new functional nanodevices.

  5. Determining heat loss into the environment based on comprehensive investigation of boiler performance characteristics

    NASA Astrophysics Data System (ADS)

    Lyubov, V. K.; Malygin, P. V.; Popov, A. N.; Popova, E. I.

    2015-08-01

    A refined procedure for determining heat loss into the environment from heat-generating installations is presented that takes into account the state of their lining and heat insulation quality. The fraction of radiative component in the total amount of heat loss through the outer surfaces is determined. The results from experimental investigations of the thermal engineering and environmental performance characteristics of a foreign hot-water boiler in firing wood pellets are presented. A conclusion is drawn about the possibility of using such hot-water boilers for supplying heat to low-rise buildings, especially for the conditions of the North-Arctic region. The results from a thermal engineering investigation of wood pellets and furnace residue carried out on installations of a thermal analysis laboratory are presented together with the grain-size composition of fuel and indicators characterizing the mechanical strength of wood pellets. The velocity fields, flue gas flow rates, and soot particle concentrations are determined using the external filtration methods, and the composition of combustion products is investigated using a gas analyzer. The graphs of variation with time of boiler external surface temperature from the moment of achieving the nominal mode of operation and heat loss into the environment for stationary boilers are presented.

  6. 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.

  7. 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

  8. Investigating the Contextual Interference Effect Using Combination Sports Skills in Open and Closed Skill Environments.

    PubMed

    Cheong, Jadeera P G; Lay, Brendan; Razman, Rizal

    2016-03-01

    This study attempted to present conditions that were closer to the real-world setting of team sports. The primary purpose was to examine the effects of blocked, random and game-based training practice schedules on the learning of the field hockey trap, close dribble and push pass that were practiced in combination. The secondary purpose was to investigate the effects of predictability of the environment on the learning of field hockey sport skills according to different practice schedules. A game-based training protocol represented a form of random practice in an unstable environment and was compared against a blocked and a traditional random practice schedule. In general, all groups improved dribble and push accuracy performance during the acquisition phase when assessed in a closed environment. In the retention phase, there were no differences between the three groups. When assessed in an open skills environment, all groups improved their percentage of successful executions for trapping and passing execution, and improved total number of attempts and total number of successful executions for both dribbling and shooting execution. Between-group differences were detected for dribbling execution with the game-based group scoring a higher number of dribbling successes. The CI effect did not emerge when practicing and assessing multiple sport skills in a closed skill environment, even when the skills were practiced in combination. However, when skill assessment was conducted in a real-world situation, there appeared to be some support for the CI effect. Key pointsThe contextual interference effect was not supported when practicing several skills in combination when the sports skills were assessed in a closed skill environment.There appeared to be some support for the contextual interference effect when sports skills were assessed in an open skill environment, which were similar to a real game situation.A game-based training schedule can be used as an alternative

  9. Investigating the Contextual Interference Effect Using Combination Sports Skills in Open and Closed Skill Environments

    PubMed Central

    Cheong, Jadeera P.G.; Lay, Brendan; Razman, Rizal

    2016-01-01

    This study attempted to present conditions that were closer to the real-world setting of team sports. The primary purpose was to examine the effects of blocked, random and game-based training practice schedules on the learning of the field hockey trap, close dribble and push pass that were practiced in combination. The secondary purpose was to investigate the effects of predictability of the environment on the learning of field hockey sport skills according to different practice schedules. A game-based training protocol represented a form of random practice in an unstable environment and was compared against a blocked and a traditional random practice schedule. In general, all groups improved dribble and push accuracy performance during the acquisition phase when assessed in a closed environment. In the retention phase, there were no differences between the three groups. When assessed in an open skills environment, all groups improved their percentage of successful executions for trapping and passing execution, and improved total number of attempts and total number of successful executions for both dribbling and shooting execution. Between-group differences were detected for dribbling execution with the game-based group scoring a higher number of dribbling successes. The CI effect did not emerge when practicing and assessing multiple sport skills in a closed skill environment, even when the skills were practiced in combination. However, when skill assessment was conducted in a real-world situation, there appeared to be some support for the CI effect. Key points The contextual interference effect was not supported when practicing several skills in combination when the sports skills were assessed in a closed skill environment. There appeared to be some support for the contextual interference effect when sports skills were assessed in an open skill environment, which were similar to a real game situation. A game-based training schedule can be used as an alternative

  10. Investigating attentional tunneling through a flexible experimentation environment and eye tracking

    NASA Astrophysics Data System (ADS)

    Moehlenbrink, Christoph; Peinecke, Niklas; Papenfuß, Anne; Manske, Peer; Wies, Matthias

    2011-06-01

    Although attentional tunneling as a phenomenon is at least known since the late 1970ies, it is still an area of high research interest, since it bears connections to current and future applications in head-up and head-down displays. For example, it is still not fully answered to what degree highly dynamic scenarios influence the pilot's ability to keep up with routine tasks, and vice versa, when and whether dynamic scene changes stay unnoticed under high workload. In order to further investigate attentional tunneling a generic experimentation environment was set up. The core of the environment is DLR's flexible sensor simulation suite (F3S). This simulation software can be installed on specialized simulation platforms, for example a Vision Station, as well as on standard workstations and can be tuned to a simple view simulation with different levels of realism. It allows for a full and dynamic control of experimental scenarios, for example possible changes in the environment. For larger scenarios several platforms can be coupled to enable the investigation of team situations. As one of its key features the set-up includes a full eye-tracking solution that is further capable of recording dynamic areas of interest. Within a first experiment with a student sample F3S was used as a simple view simulation combined with synthetic approach scenarios. Subjects were asked to detect changes whilst flying highway-in-the-sky approaches with a head-up display. At the same time eye gaze positions where tracked. This novel approach to the investigation of attentional tunneling can prove that an environmental change, even though visually perceived, is not necessarily cognitively processed at the same time.

  11. Complex Coacervate Core Micelles with Spectroscopic Labels for Diffusometric Probing of Biopolymer Networks.

    PubMed

    Bourouina, Nadia; de Kort, Daan W; Hoeben, Freek J M; Janssen, Henk M; Van As, Henk; Hohlbein, Johannes; van Duynhoven, John P M; Kleijn, J Mieke

    2015-11-24

    We present the design, preparation, and characterization of two types of complex coacervate core micelles (C3Ms) with cross-linked cores and spectroscopic labels and demonstrate their use as diffusional probes to investigate the microstructure of percolating biopolymer networks. The first type consists of poly(allylamine hydrochloride) (PAH) and poly(ethylene oxide)-poly(methacrylic acid) (PEO-b-PMAA), labeled with ATTO 488 fluorescent dyes. We show that the size of these probes can be tuned by choosing the length of the PEO-PMAA chains. ATTO 488-labeled PEO113-PMAA15 micelles are very bright with 18 dye molecules incorporated into their cores. The second type is a (19)F-labeled micelle, for which we used PAH and a (19)F-labeled diblock copolymer tailor-made from poly(ethylene oxide)-poly(acrylic acid) (mPEO79-b-PAA14). These micelles contain approximately 4 wt % of (19)F and can be detected by (19)F NMR. The (19)F labels are placed at the end of a small spacer to allow for the necessary rotational mobility. We used these ATTO- and (19)F-labeled micelles to probe the microstructures of a transient gel (xanthan gum) and a cross-linked, heterogeneous gel (κ-carrageenan). For the transient gel, sensitive optical diffusometry methods, including fluorescence correlation spectroscopy, fluorescence recovery after photobleaching, and super-resolution single nanoparticle tracking, allowed us to measure the diffusion coefficient in networks with increasing density. From these measurements, we determined the diameters of the constituent xanthan fibers. In the heterogeneous κ-carrageenan gels, bimodal nanoparticle diffusion was observed, which is a signpost of microstructural heterogeneity of the network.

  12. Novel chitosan-derived nanomaterials and their micelle-forming properties.

    PubMed

    Zhang, Can; Ding, Ya; Ping, Qineng; Yu, Liangli Lucy

    2006-11-01

    Six novel N-alkyl-N-dimethyl and N-alkyl-N-trimethyl chitosan derivatives were chemically synthesized and characterized using FT-IR, 1H NMR, 13C NMR, differential scanning calorimetry (DSC), and X-ray diffraction spectrometry (XRD). The alkyl groups included octyl (C8H17-), decanyl (C10H21-), and lauryl (C12H25-). These chitosan derivatives were also evaluated for their micelle-forming properties using dynamic light scattering (DLS) and transmission electron microscopy (TEM) techniques. All six chitosan derivatives were capable of forming polymeric micelles in water with an average particle diameter ranging from 36 to 218 nm. Both N-octyl-N-dimethyl and N-octyl-N-trimethyl chitosan derivatives formed nanomicelles under the experimental conditions, with an average particle diameter of 36.0 and 52.5, respectively. Both the length of alkyl group and the N-trimethylation degree of the chitosan derivatives altered the size of their polymeric micelles. To further understand the effect of N-alkyl substitution degree of chitosan derivatives on size of their micelles, additional five N-octyl-N-trimethyl chitosan derivatives with N-alkyl substitution degree ranging from 8 to 58% were prepared and their micelle sizes were determined. The results showed that the diameter of the nanomicelles was proportional to the degree of N-octyl substitution. These data suggest that novel N-alkyl-N-dimethyl and N-alkyl-N-trimethyl chitosan derivatives may form nanomicelles. Additional research is required to further investigate the potential value-added utilization of these chitosan derivatives in controlled release and targeted delivery of hydrophobic bioactive food factors.

  13. Protein unfolding in detergents: effect of micelle structure, ionic strength, pH, and temperature.

    PubMed Central

    Otzen, Daniel E

    2002-01-01

    The 101-residue monomeric protein S6 unfolds in the anionic detergent sodium dodecyl sulfate (SDS) above the critical micelle concentration, with unfolding rates varying according to two different modes. Our group has proposed that spherical micelles lead to saturation kinetics in unfolding (mode 1), while cylindrical micelles prevalent at higher SDS concentrations induce a power-law dependent increase in the unfolding rate (mode 2). Here I investigate in more detail how micellar properties affect protein unfolding. High NaCl concentrations, which induce cylindrical micelles, favor mode 2. This is consistent with our model, though other effects such as electrostatic screening cannot be discounted. Furthermore, unfolding does not occur in mode 2 in the cationic detergent LTAB, which is unable to form cylindrical micelles. A strong retardation of unfolding occurs at higher LTAB concentrations, possibly due to the formation of dead-end protein-detergent complexes. A similar, albeit much weaker, effect is seen in SDS in the absence of salt. Chymotrypsin inhibitor 2 exhibits the same modes of unfolding in SDS as S6, indicating that this type of protein unfolding is not specific for S6. The unfolding process in mode 1 has an activation barrier similar in magnitude to that in water, while the activation barrier in mode 2 is strongly concentration-dependent. The strong pH-dependence of unfolding in SDS and LTAB suggests that the rate of unfolding in anionic detergent is modulated by repulsion between detergent headgroups and anionic side chains, while cationic side chains modulate unfolding rates in cationic detergents. PMID:12324439

  14. Complex Coacervate Core Micelles with Spectroscopic Labels for Diffusometric Probing of Biopolymer Networks.

    PubMed

    Bourouina, Nadia; de Kort, Daan W; Hoeben, Freek J M; Janssen, Henk M; Van As, Henk; Hohlbein, Johannes; van Duynhoven, John P M; Kleijn, J Mieke

    2015-11-24

    We present the design, preparation, and characterization of two types of complex coacervate core micelles (C3Ms) with cross-linked cores and spectroscopic labels and demonstrate their use as diffusional probes to investigate the microstructure of percolating biopolymer networks. The first type consists of poly(allylamine hydrochloride) (PAH) and poly(ethylene oxide)-poly(methacrylic acid) (PEO-b-PMAA), labeled with ATTO 488 fluorescent dyes. We show that the size of these probes can be tuned by choosing the length of the PEO-PMAA chains. ATTO 488-labeled PEO113-PMAA15 micelles are very bright with 18 dye molecules incorporated into their cores. The second type is a (19)F-labeled micelle, for which we used PAH and a (19)F-labeled diblock copolymer tailor-made from poly(ethylene oxide)-poly(acrylic acid) (mPEO79-b-PAA14). These micelles contain approximately 4 wt % of (19)F and can be detected by (19)F NMR. The (19)F labels are placed at the end of a small spacer to allow for the necessary rotational mobility. We used these ATTO- and (19)F-labeled micelles to probe the microstructures of a transient gel (xanthan gum) and a cross-linked, heterogeneous gel (κ-carrageenan). For the transient gel, sensitive optical diffusometry methods, including fluorescence correlation spectroscopy, fluorescence recovery after photobleaching, and super-resolution single nanoparticle tracking, allowed us to measure the diffusion coefficient in networks with increasing density. From these measurements, we determined the diameters of the constituent xanthan fibers. In the heterogeneous κ-carrageenan gels, bimodal nanoparticle diffusion was observed, which is a signpost of microstructural heterogeneity of the network. PMID:26535962

  15. Genes and Environment in Multiple Sclerosis project: A platform to investigate multiple sclerosis risk.

    PubMed

    Xia, Zongqi; White, Charles C; Owen, Emily K; Von Korff, Alina; Clarkson, Sarah R; McCabe, Cristin A; Cimpean, Maria; Winn, Phoebe A; Hoesing, Ashley; Steele, Sonya U; Cortese, Irene C M; Chitnis, Tanuja; Weiner, Howard L; Reich, Daniel S; Chibnik, Lori B; De Jager, Philip L

    2016-02-01

    The Genes and Environment in Multiple Sclerosis project establishes a platform to investigate the events leading to multiple sclerosis (MS) in at-risk individuals. It has recruited 2,632 first-degree relatives from across the USA. Using an integrated genetic and environmental risk score, we identified subjects with twice the MS risk when compared to the average family member, and we report an initial incidence rate in these subjects that is 30 times greater than that of sporadic MS. We discuss the feasibility of large-scale studies of asymptomatic at-risk subjects that leverage modern tools of subject recruitment to execute collaborative projects.

  16. Archival Legacy Investigations of Circumstellar Environments (ALICE): Statistical assessment of point source detections

    NASA Astrophysics Data System (ADS)

    Choquet, Élodie; Pueyo, Laurent; Soummer, Rémi; Perrin, Marshall D.; Hagan, J. Brendan; Gofas-Salas, Elena; Rajan, Abhijith; Aguilar, Jonathan

    2015-09-01

    The ALICE program, for Archival Legacy Investigation of Circumstellar Environment, is currently conducting a virtual survey of about 400 stars, by re-analyzing the HST-NICMOS coronagraphic archive with advanced post-processing techniques. We present here the strategy that we adopted to identify detections and potential candidates for follow-up observations, and we give a preliminary overview of our detections. We present a statistical analysis conducted to evaluate the confidence level on these detection and the completeness of our candidate search.

  17. Vesicle-to-Micelle Oscillations and Spatial Patterns

    SciTech Connect

    Lagzi, Istvan; Wang, Dawei; Kowalczyk, Bartlomiej; Grzybowski, Bartosz A.

    2010-09-07

    A pH oscillator is coupled to and controls rhythmic interconversion of nanoscopic vesicles and micelles made of fatty acids. When changes in pH are combined with diffusion, self-assembly produces spatially extended patterns of vesicle/micelle “stripes” or concentric “shells”.

  18. 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

  19. 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…

  20. How Hydrogen Bonds Affect the Growth of Reverse Micelles around Coordinating Metal Ions.

    PubMed

    Qiao, Baofu; Demars, Thomas; Olvera de la Cruz, Monica; Ellis, Ross J

    2014-04-17

    Extensive research on hydrogen bonds (H-bonds) have illustrated their critical role in various biological, chemical and physical processes. Given that existing studies are predominantly performed in aqueous conditions, how H-bonds affect both the structure and function of aggregates in organic phase is poorly understood. Herein, we investigate the role of H-bonds on the hierarchical structure of an aggregating amphiphile-oil solution containing a coordinating metal complex by means of atomistic molecular dynamics simulations and X-ray techniques. For the first time, we show that H-bonds not only stabilize the metal complex in the hydrophobic environment by coordinating between the Eu(NO3)3 outer-sphere and aggregating amphiphiles, but also affect the growth of such reverse micellar aggregates. The formation of swollen, elongated reverse micelles elevates the extraction of metal ions with increased H-bonds under acidic condition. These new insights into H-bonds are of broad interest to nanosynthesis and biological applications, in addition to metal ion separations.

  1. 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.

  2. Periodic Arrays of Interfacial Cylindrical reverse Micelles

    SciTech Connect

    Nelson,M.; Cain, N.; Ocko, B.; Gin, D.; Hammond, S.; Schwartz, D.

    2005-01-01

    We report an approach for the fabrication of periodic molecular nanostructures on surfaces. The approach involves biomimetic self-organization of synthetic wedge-shaped amphiphilic molecules into multilayer arrays of cylindrical reverse micelles. The films were characterized by atomic force microscopy and X-ray reflectivity. These nanostructured films self-assemble in solution but remain stable upon removal and exposure to ambient conditions, making them potentially suitable for a variety of dry pattern transfer methods. We illustrate the generality of this approach by using two distinct molecular systems that vary in size by a factor of 2.

  3. Tryptophan octyl ester in detergent micelles of dodecylmaltoside: fluorescence properties and quenching by brominated detergent analogs.

    PubMed Central

    de Foresta, B; Gallay, J; Sopkova, J; Champeil, P; Vincent, M

    1999-01-01

    The fluorescence properties of tryptophan octyl ester (TOE), a hydrophobic model of Trp in proteins, were investigated in various mixed micelles of dodecylmaltoside (DM) and 7,8-dibromododecyl beta-maltoside (BrDM) or 10,11-dibromoundecanoyl beta-maltoside (BrUM). This study focuses on the mechanism via which these brominated detergents quench the fluorescence of TOE in a micellar system. The experiments were performed at a pH at which TOE is uncharged and almost completely bound to detergent micelles. TOE binding was monitored by its enhanced fluorescence in pure DM micelles or its quenched fluorescence in pure BrUM or BrDM micelles. In DM/BrUM and DM/BrDM mixed micelles, the fluorescence intensity of TOE decreased, as a nonlinear function of the molar fraction of brominated detergent, to almost zero in pure brominated detergent. The indole moiety of TOE is therefore highly accessible to the bromine atoms located on the detergent alkyl chain because quenching by bromines occurs by direct contact with the fluorophore. TOE is simultaneously poorly accessible to iodide (I(-)), a water-soluble collisional quencher. TOE time-resolved fluorescence intensity decay is heterogeneous in pure DM micelles, with four lifetimes (from 0.2 to 4.4 ns) at the maximum emission wavelength. Such heterogeneity may arise from dipolar relaxation processes in a motionally restricted medium, as suggested by the time-dependent (nanoseconds) red shift (11 nm) of the TOE emission spectrum, and from the existence of various TOE conformations. Time-resolved quenching experiments for TOE in mixed micelles showed that the excited-state lifetime values decreased only slightly with increases in the proportion of BrDM or BrUM. In contrast, the relative amplitude of the component with the longest lifetime decreased significantly relative to that of the short-lived species. This is consistent with a mainly static mechanism for the quenching of TOE by brominated detergents. Molecular modeling of TOE

  4. 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

  5. Investigation of Acoustic Fields for the Cassini Spacecraft: Reverberant Versus Launch Environments

    NASA Technical Reports Server (NTRS)

    Hughes, William O.; McNelis, Anne M.; Himelblau, Harry

    2000-01-01

    The characterization and understanding of the acoustic field within a launch vehicle's payload fairing (PLF) is critical to the qualification of a spacecraft and ultimately to the success of its mission. Acoustic measurements taken recently for the Cassini mission have allowed unique opportunities to advance the aerospace industry's knowledge in this field. Prior to its launch, the expected liftoff acoustic environment of the spacecraft was investigated in a full-scale acoustic test of a Titan IV PLF and Cassini simulator in a reverberant test chamber. A major goal of this acoustic ground test was to quantify and verify the noise reduction performance of special barrier blankets that were designed especially to reduce the Cassirii acoustic environment. This paper will describe both the ground test and flight measurements, and compare the Cassini acoustic environment measured during launch with that measured earlier in the ground test. Special emphasis will be given to the noise reduction performance of the barrier blankets and to the acoustic coherence measured within the PLF.

  6. Binary droplet collisions in a vacuum environment: an experimental investigation of the role of viscosity

    NASA Astrophysics Data System (ADS)

    Willis, Keeney; Orme, Melissa

    2001-11-01

    An experimental investigation of viscous binary droplet collisions in a vacuum environment is conducted. The fundamental ramifications of conducting such experiments in a vacuum environment are twofold. The first assures that the collision products are unimpeded by aerodynamic effects which tend to disrupt the collision process at a much earlier stage in the processes than if those aerodynamic effects were absent, and second, the phenomenon of encapsulation of the host medium between the colliding droplets is not present in this study; a fact that limits the scope of direct application of this study to a number of (but not all) applications. Use of an amplitude modulated forcing disturbance to the capillary stream insures that the collision products are able to deform unimpeded by interactions with neighboring collision products. Measurements over a broad range of Weber number, We, indicate that the value of the critical Weber number is more than 100 times greater for the 30cSt fluid than the corresponding value for similarly sized water drops in a standard ambient environment. Measurements of the oblate and prolate half-cycle oscillation periods resulting from the binary collision reveal a distinct behavior that is observed and documented here for the first time.

  7. Combined experimental and computational investigation of sterile air flows in surgical environments

    NASA Astrophysics Data System (ADS)

    McNeill, James; Hertzberg, Jean; Zhai, Zhiqiang

    2010-11-01

    Surgical environments in hospitals utilize downward, low-turbulence, sterile air flow across the patient to inhibit transmission of infectious diseases to the surgical site. Full-scale laboratory experiments using particle image velocimetry were conducted to investigate the air distribution above the patient area. Computational fluid dynamics models were developed to further investigate the air distribution within the operating room in order to determine the impact of ventilation design of airborne infectious disease pathways. Both Reynolds-averaged Navier-Stokes equations and large eddy simulation techniques are currently being used in the computational modeling to study the effect of turbulence modeling on the indoor air distribution. CFD models are being calibrated based on the experimental data and will be used to study the probability of infectious particles entering the sterile region of the room.

  8. Field investigation and analysis of buried pipelines under various seismic environments. Technical report

    SciTech Connect

    Wang, L.R.L.

    1982-08-01

    A research project is proposed in which the behavior of oil, water, sewer, and gas pipelines under various seismic environments, including seismic shaking and large ground deformation would be investigated. It is suggested that the investigation be conducted in the Beijing and Tangshan areas. Three major hazards to underground pipelines are identified: the effect of wave propagation; ground rupture and differential movement along fault lines; and soil liquefaction induced by ground shaking. Ruptures or severe distortions of the pipe are most often associated with fault movements, landslides, or ground squeeze associated with fault zones. A model is presented to evaluate the general longitudinal responses of buried pipelines, both segmented and continuous, subjected to ground shakings and vibrations. The results of these tests will be used to develop aseismic codes for buried pipelines.

  9. 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

  10. 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

  11. Thermal-sensitive viscosity transition of elongated micelles induced by breaking intermolecular hydrogen bonding of amide groups.

    PubMed

    Morita, Clara; Imura, Yoshiro; Ogawa, Tetsuya; Kurata, Hiroki; Kawai, Takeshi

    2013-05-01

    A heat-induced viscosity transition of novel worm-like micelles of a long alkyl-chain amidoamine derivative (C18AA) bearing intermolecular hydrogen-bonding group was investigated by cryo-TEM, FT-IR, and rheological measurements. At lower temperature, C18AA forms straight elongated micelles with a length on the order of micrometers due to strong intermolecular hydrogen-bonded packing of the amide groups, although the micelles rarely entangle and have low value of zero-shear viscosity. The straight elongated micelles likely became flexible and underwent a morphological transition from straight structure to worm-like structure at a certain temperature, which caused a drastic increase in viscosity due to entanglement of the micelles. This morphological transition was caused by a defect of intermolecular hydrogen bonding between the amide groups on heating. Furthermore, addition of LiCl, which acts as hydrogen-bond breaker, also promoted the viscosity transition, leading to a lowering of the transition temperature.

  12. Towards entropy-driven interstitial micelles at elevated temperatures from selective A1BA2 triblock solutions.

    PubMed

    Wołoszczuk, S; Jurga, S; Banaszak, M

    2016-08-01

    We simulate selective A1BA2-A and A1BA2-B triblock solutions (that is, mixtures of the A1BA2 triblock with a solvent of either type A or type B) using a lattice Monte Carlo method. Although the simulated triblock chains are compositionally symmetric in terms of the A to B volume ratio, the A1 block is significantly shorter than the A2 block. For the pure A1BA2 melt the phase behavior is relatively well known, including the existence and stability of the recently discovered interstitial micelles which were found at the very strong segregation limit. In this paper, we investigate the stability of the interstitial micelles as a function of triblock volume fraction in a selective solvent of either type A or type B. The main finding of this paper is that adding a selective solvent of type A shifts the stability of the interstitial micelles into significantly higher temperatures which may provide a pathway towards experimental studies of interstitial micelles in real triblock solutions. We also find that adding selective solvents to the A1BA2 melt gives rise to a variety of nonlamellar nanostructures for temperatures and compositions at which the interstitial micelles are stable. PMID:27627353

  13. Towards entropy-driven interstitial micelles at elevated temperatures from selective A 1 BA 2 triblock solutions

    NASA Astrophysics Data System (ADS)

    Wołoszczuk, S.; Jurga, S.; Banaszak, M.

    2016-08-01

    We simulate selective A 1 B A 2 -A and A 1 B A 2 -B triblock solutions (that is, mixtures of the A 1 B A 2 triblock with a solvent of either type A or type B ) using a lattice Monte Carlo method. Although the simulated triblock chains are compositionally symmetric in terms of the A to B volume ratio, the A 1 block is significantly shorter than the A 2 block. For the pure A 1 B A 2 melt the phase behavior is relatively well known, including the existence and stability of the recently discovered interstitial micelles which were found at the very strong segregation limit. In this paper, we investigate the stability of the interstitial micelles as a function of triblock volume fraction in a selective solvent of either type A or type B . The main finding of this paper is that adding a selective solvent of type A shifts the stability of the interstitial micelles into significantly higher temperatures which may provide a pathway towards experimental studies of interstitial micelles in real triblock solutions. We also find that adding selective solvents to the A 1 B A 2 melt gives rise to a variety of nonlamellar nanostructures for temperatures and compositions at which the interstitial micelles are stable.

  14. An investigation into the impact of cryogenic environment on mechanical stresses in FRP composites

    NASA Astrophysics Data System (ADS)

    Fifo, O.; Basu, B.

    2015-07-01

    Fibre reinforced polymer (FRP) composites are fast becoming a highly utilised engineering material for high performance applications due to their light weight and high strength. Carbon fibre and other high strength fibres are commonly used in design of aerospace structures, wind turbine blades, etc. and potentially for propellant tanks of launch vehicles. For the aforementioned fields of application, stability of the material is essential over a wide range of temperature particularly for structures in hostile environments. Many studies have been conducted, experimentally, over the last decade to investigate the mechanical behaviour of FRP materials at varying subzero temperature. Likewise, tests on aging and cycling effect (room to low temperature) on the mechanical response of FRP have been reported. However, a relatively lesser focused area has been the mechanical behaviour of FRP composites under cryogenic environment. This article reports a finite element method of investigating the changes in the mechanical characteristics of an FRP material when temperature based analysis falls below zero. The simulated tests are carried out using a finite element package with close material properties used in the cited literatures. Tensile test was conducted and the results indicate that the mechanical responses agree with those reported in the literature sited.

  15. Polymer Micelles Laden Hydrogel Contact Lenses for Ophthalmic Drug Delivery.

    PubMed

    Hu, Xiaohong; Tan, Huaping; Chen, Pin; Wang, Xin; Pang, Juan

    2016-06-01

    Hydrogel contact lens is an attractive drug carrier for the delivery of ophthalmic drugs. But limited drug loading capacity and burst release restricted its application in this field. Polymer micelle laden hydrogel contact lenses were designed for ophthalmic drug delivery in the work. β-CD/PAA/PEG ternary system was chosen to form polymer micelle. The micelle size could be adjusted by β-CD content and PAA/PEG concentration. The zeta potential of micelle was irrelevant to β-CD content, but influenced by PAA/PEG concentration. The absorbed drug concentration in micelle solution depended on both β-CD content and PAA/PEG concentration. Polymer micelle laden hydrogels were obtained by radical polymerization in situ. The transparency of polymer micelle laden hydrogel declined with PAA/PEG concentration increasing. The equilibrium water content and water loss showed that polymer micelle laden hydrogel with higher PAA/PEG concentration was in a higher swollen state. The dynamic viscoelastic properties howed that all polymer micelle laden hydrogels had some characteristics of crosslinked elastomers. The surface structure of freeze dried composite hydrogels was different from freeze dried pure hydrogel. The drug loading and releasing behaviors were detected to evaluate the drug loading and releasing capacity of hydrogels using orfloxacin and puerarin as model drugs. The results indicated the polymer micelle in hydrogel could hold or help to hold some ophthalmic drugs, and slow down orfloxacin release speed or keep puerarin stably stay for a time in hydrogels. In the end, it was found that the transparency of composite hydrogel became better after the hydrogel had been immersed in PBS for several weeks.

  16. Enhancing enzyme stability by construction of polymer-enzyme conjugate micelles for decontamination of organophosphate agents.

    PubMed

    Suthiwangcharoen, Nisaraporn; Nagarajan, Ramanathan

    2014-04-14

    Enhancing the stability of enzymes under different working environments is essential if the potential of enzyme-based applications is to be realized for nanomedicine, sensing and molecular diagnostics, and chemical and biological decontamination. In this study, we focus on the enzyme, organophosphorus hydrolase (OPH), which has shown great promise for the nontoxic and noncorrosive decontamination of organophosphate agents (OPs) as well as for therapeutics as a catalytic bioscavanger against nerve gas poisoning. We describe a facile approach to stabilize OPH using covalent conjugation with the amphiphilic block copolymer, Pluronic F127, leading to the formation of F127-OPH conjugate micelles, with the OPH on the micelle corona. SDS-PAGE and MALDI-TOF confirmed the successful conjugation, and transmission electron microscopy (TEM) and dynamic light scattering (DLS) revealed ∼100 nm size micelles. The conjugates showed significantly enhanced stability and higher activity compared to the unconjugated OPH when tested (i) in aqueous solutions at room temperature, (ii) in aqueous solutions at higher temperatures, (iii) after multiple freeze/thaw treatments, (iv) after lyophilization, and (v) in the presence of organic solvents. The F127-OPH conjugates also decontaminated paraoxon (introduced as a chemical agent simulant) on a polystyrene film surface and on a CARC (Chemical Agent Resistant Coating) test panel more rapidly and to a larger extent compared to free OPH. We speculate that, in the F127-OPH conjugates (both in the micellar form as well as in the unaggregated conjugate), the polypropylene oxide block of the copolymer interacts with the surface of the OPH and this confinement of the OPH reduces the potential for enzyme denaturation and provides robustness to OPH at different working environments. The use of such polymer-enzyme conjugate micelles with improved enzyme stability opens up new opportunities for numerous civilian and Warfighter applications.

  17. Cosolubilization of Coumarin30 and Warfarin in Cationic, Anionic, and Nonionic Micelles: A Micelle-Water Interfacial Charge Dependent FRET.

    PubMed

    Dar, Aijaz Ahmad; Chat, Oyais Ahmad

    2015-09-01

    Solubilization of structurally varied coumarins, viz., Warfarin (WF; a 4-hydroxy coumarin) and Coumarin30 (C30, a 7-amino coumarin) individually and in mixed states (cosolubilization) within the aqueous surfactant self-assemblies of varying architectures has been explored, exploiting steady-state, time-resolved fluorimetric, and spectrophotometric techniques. Cosolubilization studies within micelles, which have rarely been done in the literature, were specifically undertaken with the aim of understanding the effect of micelles on their photophysical phenomena when simultaneously present within these nanocarriers and assess their prospective use as an efficient FRET pair. WF solubilizes within CTAB micelles, whereas little or no solubilization is observed in Brij30 and SDS micelles. On the other hand, C30 solubilizes deep into the palisade layer of CTAB micelles, between negatively charged head groups in SDS micelles and between OE groups in Brij30 micelles. C30 and WF maintain their solubilization sites during cosolubilization. In SDS and Brij30 micelles, an increase in WF causes fluorescence quenching of C30 molecules, while in CTAB, an increase in WF causes an increase in fluorescence of C30 by excited WF molecules indicating FRET between the two molecules. PMID:26244283

  18. Three-dimensional structure of the water-insoluble protein crambin in dodecylphosphocholine micelles and its minimal solvent-exposed surface.

    PubMed

    Ahn, Hee-Chul; Juranić, Nenad; Macura, Slobodan; Markley, John L

    2006-04-01

    We chose crambin, a hydrophobic and water-insoluble protein originally isolated from the seeds of the plant Crambe abyssinica, as a model for NMR investigations of membrane-associated proteins. We produced isotopically labeled crambin(P22,L25) (variant of crambin containing Pro22 and Leu25) as a cleavable fusion with staphylococcal nuclease and refolded the protein by an approach that has proved successful for the production of proteins with multiple disulfide bonds. We used NMR spectroscopy to determine the three-dimensional structure of the protein in two membrane-mimetic environments: in a mixed aqueous-organic solvent (75%/25%, acetone/water) and in DPC micelles. With the sample in the mixed solvent, it was possible to determine (>NH...OC<) hydrogen bonds directly by the detection of (h3)J(NC)' couplings. H-bonds determined in this manner were utilized in the refinement of the NMR-derived protein structures. With the protein in DPC (dodecylphosphocholine) micelles, we used manganous ion as an aqueous paramagnetic probe to determine the surface of crambin that is shielded by the detergent. With the exception of the aqueous solvent exposed loop containing residues 20 and 21, the protein surface was protected by DPC. This suggests that the protein may be similarly embedded in physiological membranes. The strategy described here for the expression and structure determination of crambin should be applicable to structural and functional studies of membrane active toxins and small membrane proteins.

  19. Formation of wormlike micelle in a mixed amino-acid based anionic surfactant and cationic surfactant systems.

    PubMed

    Shrestha, Rekha Goswami; Shrestha, Lok Kumar; Aramaki, Kenji

    2007-07-01

    Formation of wormlike micelles in mixed anionic/cationic system without the addition of any salt has been studied. Amino-acid based anionic surfactant N-dodecylglutamic acid (LAD), which is practically immiscible with water at 25 degrees C upon neutralization by 2,2',2''-nitrilotriethanol (TEA) forms small micellar aggregates and the solution behaves like a Newtonian fluid. The rheological behavior of LAD/water/hexadecyltrimethylammonium bromide (CTAB) and LAD/water/dodecyltrimethylammonium bromide (DTAB) systems were investigated at different degrees of neutralization of the LAD depending on the concentration of the cationic surfactants and on temperature. Addition of CTAB to the dilute aqueous solution of the LAD-TEA-x (the neutralized product, where x represents the mole ratio of TEA) causes one dimensional micellar growth. After certain concentration the elongated micelles entangle forming a rigid network of viscoelastic wormlike micelles. Thus formed viscoelastic solutions follow Maxwellian behavior over a wide range of frequency and thus are considered to consist of transient network of wormlike micelles. By varying the degree of neutralization from 1:1 via 1:1.5 to 1:2 (molar ratio) phase and rheological behavior were modified in that the highly viscous region of viscoelastic wormlike micelles shifted to higher CTAB concentrations and no maxima in the zero-shear viscosity could be observed for the higher degree of neutralization of the LAD (1:1.5 and 1:2). However, the obtained rheological parameters showed scaling relationships that were consistent with the living polymer model. The zero-shear viscosity decays exponentially with temperature following Arrhenius behavior. The flow activation energy calculated from the Arrhenius plot is very close to the value reported for the typical wormlike micellar solution. In contrast to CTAB no formation of viscoelastic wormlike micelles could be observed with DTAB, although, the solution viscosity increases. The

  20. Novel polymer micelle mediated co-delivery of doxorubicin and P-glycoprotein siRNA for reversal of multidrug resistance and synergistic tumor therapy

    PubMed Central

    Zhang, Chun-ge; Zhu, Wen-jing; Liu, Yang; Yuan, Zhi-qiang; Yang, Shu-di; Chen, Wei-liang; Li, Ji-zhao; Zhou, Xiao-feng; Liu, Chun; Zhang, Xue-nong

    2016-01-01

    Co-delivery of chemotherapeutics and siRNA with different mechanisms in a single system is a promising strategy for effective cancer therapy with synergistic effects. In this study, a triblock copolymer micelle was prepared based on the polymer of N-succinyl chitosan–poly-L-lysine–palmitic acid (NSC–PLL–PA) to co-deliver doxorubicin (Dox) and siRNA–P-glycoprotein (P-gp) (Dox–siRNA-micelle). Dox–siRNA-micelle was unstable in pH 5.3 medium than in pH 7.4 medium, which corresponded with the in vitro rapid release of Dox and siRNA in acidic environments. The antitumor efficacy of Dox–siRNA-micelle in vitro significantly increased, especially in HepG2/ADM cells, which was due to the downregulation of P-gp. Moreover, almost all the Dox–siRNA-micelles accumulated in the tumor region beyond 24 h post-injection, and the co-delivery system significantly inhibited tumor growth with synergistic effects in vivo. This study demonstrated the effectiveness of Dox–siRNA-micelles in tumor-targeting and MDR reversal, and provided a promising strategy to develop a co-delivery system with synergistic effects for combined cancer therapy. PMID:27030638

  1. 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

  2. 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.

  3. Two-Step biocatalytic conversion of an ester to an aldehyde in reverse micelles.

    PubMed

    Yang, F; Russell, A J

    1994-02-01

    Lipases from Candida cyclindracea (L-1754) and wheat germ (L-3001) have been used to hydrolyze esters to their corresponding alcohols and acids in reverse micelles. Alcohol dehydrogenase from baker's yeast (YADH) was subsequently used to reduce the alcohol products to aldehydes. Cofactor recycling in the redox reaction was achieved using a sacrificial cosubstrate, as described previously. Four surfactants (sodium dioctylsulfosuccinate, Nonidet P-40 with Triton X-35, polyoxyethylene, 10-cetyl-ether, polyoxyethylene sorbitan trioleate) were employed to determine the effect of amphiphile on ester hydrolysis and redox reaction rates separately. The effect of type of organic solvent, W(0) [(water]/[surfactant)], and substrate concentration on separte enzyme activity were also investigated. A brief investigation of a single phase, two-step reaction catalyzed by the combination of lipase and YADH in reverse micelles is also reported. The activities of the enzymes are significantly different when used together instead of independently. (c) 1994 John Wiley & Sons, Inc.

  4. Photoinduced electron transfer from N,N-dimethylaniline to 7-amino Coumarins in protein-surfactant complex: Slowing down of electron transfer dynamics compared to micelles

    NASA Astrophysics Data System (ADS)

    Chakraborty, Anjan; Seth, Debabrata; Setua, Palash; Sarkar, Nilmoni

    2006-02-01

    Photoinduced electron transfer from N,N-dimethylaniline to different Coumarin dyes has been investigated in dodecyl trimethyl ammonium bromide (DTAB) micelles and in Bovine serum albumin (BSA)-DTAB protein-surfactant complex using steady-state and picosecond time-resolved fluorescence spectroscopy. We observed a slower fluorescence quenching rate in the DTAB micelles and in the protein-surfactant complex as compared to that in pure acetonitrile solution. Moreover, the observed fluorescence quenching in BSA-DTAB complex was found to be slower than that in DTAB micelles. In the correlation of free-energy change with the fluorescence quenching constant we observed a deviation in the fluorescence quenching electron transfer rate for Coumarin 151 (C-151) from the normal Marcus curve. This observation is ascribed to the stronger interaction of C-151 with the surfactant molecules present in the micelles. This is evident from the slower translation diffusion (DL) of Coumarin 151 compared to other probe molecules.

  5. Selective intracellular drug delivery from pH-responsive polyion complex micelle for enhanced malignancy suppression in vivo.

    PubMed

    Wang, Jixue; Xu, Weiguo; Guo, Hui; Ding, Jianxun; Chen, Jinjin; Guan, Jingjing; Wang, Chunxi

    2015-11-01

    The pH-triggered intracellular drug delivery platforms have attracted great interest in malignancy therapy. Herein, a pH-responsive polyion complex (PIC) micelle from anionic acid-sensitive methoxy poly(ethylene glycol)-block-poly(N(ϵ)-((1-carboxy-cis-cyclohexene)-2-carbonyl)-L-lysine) (mPEG-b-PCLL) and cationic doxorubicin (DOX), a model anthracycline antitumor drug, was constructed by electrostatic interaction for directional intracellular drug delivery in malignancy chemotherapy. The PIC micelle kept constant diameter at physiological condition (i.e., pH 7.4), while gradually swelled and finally disassembled at mimicking intratumoral pH (i.e., 6.8) and especially intracellular endo/lysosomal pH (i.e., 5.5). The DOX release from the PIC micelle at pH 7.4 was slow, whereas obviously accelerated at the intracellular acidic condition of pH 5.5. These results should be related to the rapid cleavage of the side amide bond of mPEG-b-PCLL in an acidic environment. The PIC micelle exhibited satisfactory tumor suppression toward the H22 hepatoma-bearing BALB/c mouse model compared with free DOX, which was demonstrated by the upregulated tumor inhibition rate, and the increased necrotic and apoptosis areas in tumor tissue. Furthermore, the enhanced security was also observed in the PIC micelle group in relation to that of free DOX. The above results strongly supported that the acid-sensitive PIC micelle was promising for selective intracellular drug delivery along with upregulated malignancy inhibition.

  6. Identifying gene-environment interactions in schizophrenia: contemporary challenges for integrated, large-scale investigations.

    PubMed

    van Os, Jim; Rutten, Bart P; Myin-Germeys, Inez; Delespaul, Philippe; Viechtbauer, Wolfgang; van Zelst, Catherine; Bruggeman, Richard; Reininghaus, Ulrich; Morgan, Craig; Murray, Robin M; Di Forti, Marta; McGuire, Philip; Valmaggia, Lucia R; Kempton, Matthew J; Gayer-Anderson, Charlotte; Hubbard, Kathryn; Beards, Stephanie; Stilo, Simona A; Onyejiaka, Adanna; Bourque, Francois; Modinos, Gemma; Tognin, Stefania; Calem, Maria; O'Donovan, Michael C; Owen, Michael J; Holmans, Peter; Williams, Nigel; Craddock, Nicholas; Richards, Alexander; Humphreys, Isla; Meyer-Lindenberg, Andreas; Leweke, F Markus; Tost, Heike; Akdeniz, Ceren; Rohleder, Cathrin; Bumb, J Malte; Schwarz, Emanuel; Alptekin, Köksal; Üçok, Alp; Saka, Meram Can; Atbaşoğlu, E Cem; Gülöksüz, Sinan; Gumus-Akay, Guvem; Cihan, Burçin; Karadağ, Hasan; Soygür, Haldan; Cankurtaran, Eylem Şahin; Ulusoy, Semra; Akdede, Berna; Binbay, Tolga; Ayer, Ahmet; Noyan, Handan; Karadayı, Gülşah; Akturan, Elçin; Ulaş, Halis; Arango, Celso; Parellada, Mara; Bernardo, Miguel; Sanjuán, Julio; Bobes, Julio; Arrojo, Manuel; Santos, Jose Luis; Cuadrado, Pedro; Rodríguez Solano, José Juan; Carracedo, Angel; García Bernardo, Enrique; Roldán, Laura; López, Gonzalo; Cabrera, Bibiana; Cruz, Sabrina; Díaz Mesa, Eva Ma; Pouso, María; Jiménez, Estela; Sánchez, Teresa; Rapado, Marta; González, Emiliano; Martínez, Covadonga; Sánchez, Emilio; Olmeda, Ma Soledad; de Haan, Lieuwe; Velthorst, Eva; van der Gaag, Mark; Selten, Jean-Paul; van Dam, Daniella; van der Ven, Elsje; van der Meer, Floor; Messchaert, Elles; Kraan, Tamar; Burger, Nadine; Leboyer, Marion; Szoke, Andrei; Schürhoff, Franck; Llorca, Pierre-Michel; Jamain, Stéphane; Tortelli, Andrea; Frijda, Flora; Vilain, Jeanne; Galliot, Anne-Marie; Baudin, Grégoire; Ferchiou, Aziz; Richard, Jean-Romain; Bulzacka, Ewa; Charpeaud, Thomas; Tronche, Anne-Marie; De Hert, Marc; van Winkel, Ruud; Decoster, Jeroen; Derom, Catherine; Thiery, Evert; Stefanis, Nikos C; Sachs, Gabriele; Aschauer, Harald; Lasser, Iris; Winklbaur, Bernadette; Schlögelhofer, Monika; Riecher-Rössler, Anita; Borgwardt, Stefan; Walter, Anna; Harrisberger, Fabienne; Smieskova, Renata; Rapp, Charlotte; Ittig, Sarah; Soguel-dit-Piquard, Fabienne; Studerus, Erich; Klosterkötter, Joachim; Ruhrmann, Stephan; Paruch, Julia; Julkowski, Dominika; Hilboll, Desiree; Sham, Pak C; Cherny, Stacey S; Chen, Eric Y H; Campbell, Desmond D; Li, Miaoxin; Romeo-Casabona, Carlos María; Emaldi Cirión, Aitziber; Urruela Mora, Asier; Jones, Peter; Kirkbride, James; Cannon, Mary; Rujescu, Dan; Tarricone, Ilaria; Berardi, Domenico; Bonora, Elena; Seri, Marco; Marcacci, Thomas; Chiri, Luigi; Chierzi, Federico; Storbini, Viviana; Braca, Mauro; Minenna, Maria Gabriella; Donegani, Ivonne; Fioritti, Angelo; La Barbera, Daniele; La Cascia, Caterina Erika; Mulè, Alice; Sideli, Lucia; Sartorio, Rachele; Ferraro, Laura; Tripoli, Giada; Seminerio, Fabio; Marinaro, Anna Maria; McGorry, Patrick; Nelson, Barnaby; Amminger, G Paul; Pantelis, Christos; Menezes, Paulo R; Del-Ben, Cristina M; Gallo Tenan, Silvia H; Shuhama, Rosana; Ruggeri, Mirella; Tosato, Sarah; Lasalvia, Antonio; Bonetto, Chiara; Ira, Elisa; Nordentoft, Merete; Krebs, Marie-Odile; Barrantes-Vidal, Neus; Cristóbal, Paula; Kwapil, Thomas R; Brietzke, Elisa; Bressan, Rodrigo A; Gadelha, Ary; Maric, Nadja P; Andric, Sanja; Mihaljevic, Marina; Mirjanic, Tijana

    2014-07-01

    Recent years have seen considerable progress in epidemiological and molecular genetic research into environmental and genetic factors in schizophrenia, but methodological uncertainties remain with regard to validating environmental exposures, and the population risk conferred by individual molecular genetic variants is small. There are now also a limited number of studies that have investigated molecular genetic candidate gene-environment interactions (G × E), however, so far, thorough replication of findings is rare and G × E research still faces several conceptual and methodological challenges. In this article, we aim to review these recent developments and illustrate how integrated, large-scale investigations may overcome contemporary challenges in G × E research, drawing on the example of a large, international, multi-center study into the identification and translational application of G × E in schizophrenia. While such investigations are now well underway, new challenges emerge for G × E research from late-breaking evidence that genetic variation and environmental exposures are, to a significant degree, shared across a range of psychiatric disorders, with potential overlap in phenotype. PMID:24860087

  7. Identifying Gene-Environment Interactions in Schizophrenia: Contemporary Challenges for Integrated, Large-scale Investigations

    PubMed Central

    2014-01-01

    Recent years have seen considerable progress in epidemiological and molecular genetic research into environmental and genetic factors in schizophrenia, but methodological uncertainties remain with regard to validating environmental exposures, and the population risk conferred by individual molecular genetic variants is small. There are now also a limited number of studies that have investigated molecular genetic candidate gene-environment interactions (G × E), however, so far, thorough replication of findings is rare and G × E research still faces several conceptual and methodological challenges. In this article, we aim to review these recent developments and illustrate how integrated, large-scale investigations may overcome contemporary challenges in G × E research, drawing on the example of a large, international, multi–center study into the identification and translational application of G × E in schizophrenia. While such investigations are now well underway, new challenges emerge for G × E research from late-breaking evidence that genetic variation and environmental exposures are, to a significant degree, shared across a range of psychiatric disorders, with potential overlap in phenotype. PMID:24860087

  8. Binary droplet collisions in a vacuum environment: an experimental investigation of the role of viscosity

    NASA Astrophysics Data System (ADS)

    Willis, K.; Orme, M.

    An experimental investigation of viscous binary droplet collisions in a vacuum environment is conducted. The fundamental ramifications of conducting such experiments in a vacuum environment are twofold. The first, which is the motivating factor of this work, assures that the collision products are unimpeded by aerodynamic effects which tend to disrupt the collision process at a much earlier stage in the processes than if they were absent, and second, the phenomenon of encapsulation of the host medium between the colliding droplets is not present in this study; a fact that limits the scope of direct application of this study to a number of (but not all) applications. Droplets are generated from capillary stream breakup with the imposition of an amplitude-modulated disturbance which results in the generation of highly uniform pre-collision drops at separations far extending those which are possible from a standard (monochromatic) sinusoidal disturbance. Hence, the collision products are able to deform unimpeded by interactions with neighboring collision products. Measurements over a broad range of Weber number, We, indicate that the value of the critical Weber number, Wec, is more than 100 times greater for the 30-cSt fluid than the corresponding value for similarly sized water drops in a standard ambient environment. Measurements of the oblate and prolate half-cycle oscillation periods resulting from the binary collision reveal a distinct behavior that is observed and documented here for the first time. Additionally, measurements of the radial extent of the deformed mass at the instant of maximum deformation have been conducted and allow quantification of the energy dissipation. These measurements show that the energy dissipation increases with increasing fluid viscosity, which contradicts the results published by others.

  9. Study of confined 5-aza[5]helicene in ytterbium(III) bis(2-ethylhexyl) sulfosuccinate reversed micelles.

    PubMed

    Abbate, Sergio; Caronna, Tullio; Longo, Alessandro; Ruggirello, Angela; Liveri, Vincenzo Turco

    2007-04-26

    Some relevant physicochemical properties of 5-aza[5]helicene (H5) in solutions of ytterbium bis(2-ethylhexyl) sulfosuccinate (Yb(DEHSS)3) reversed micelles have been investigated by UV-vis-NIR, photoluminescence, and FT-IR techniques with the aim of emphasizing the role played by specific Yb(III)/H5 interactions and confinement effects as driving forces of its binding to reversed micelles, preferential solubilization site, and local photophysical properties. It has been found that the binding strength of 5-aza[5]helicene to reversed micelles, triggered by steric and orientational constrains as well as the water content, is mainly regulated by its interaction with the Yb(III) counterion. Moreover, when H5 is entrapped in Yb(DEHSS)3 reversed micelles, the combined action of this interaction and of confinement effects leads to marked changes of its photophysical properties with respect to those of H5 molecularly dispersed in apolar medium. The influence of the entrapment of finite amounts of H5 on the reversed micelle structure was investigated by SAXS. The analysis of experimental results brings to the hypothesis that H5 is preferentially solubilized and opportunely oriented in the micellar palisade layer and that its insertion causes an unidimensional growth of reversed micelles. From an analysis of WAXS spectra of H5/Yb(DEHSS)3 composites, obtained by complete evaporation of the volatile components of the H5/water/Yb(DEHSS)3/n-heptane solutions, it was ascertained that also on these systems H5 is dispersed molecularly or in a quite amorphous state in the surfactant liquid crystals without forming a separate crystalline nanophase.

  10. Smart micelle@polydopamine core-shell nanoparticles for highly effective chemo-photothermal combination therapy

    NASA Astrophysics Data System (ADS)

    Zhang, Ruirui; Su, Shishuai; Hu, Kelei; Shao, Leihou; Deng, Xiongwei; Sheng, Wang; Wu, Yan

    2015-11-01

    In this investigation, we have designed and synthesized a novel core-shell polymer nanoparticle system for highly effective chemo-photothermal combination therapy. A nanoscale DSPE-PEG micelle encapsulating doxorubicin (Dox-M) was designed as a core, and then modified by a polydopamine (PDA) shell for photothermal therapy and bortezomib (Btz) administration (Dox-M@PDA-Btz). The facile conjugation of Btz to the catechol-containing PDA shell can form a reversible pH-sensitive boronic acid-catechol conjugate to create a stimuli-responsive drug carrier system. As expected, the micelle@PDA core-shell nanoparticles exhibited satisfactory photothermal efficiency, which has potential for thermal ablation of malignant tissues. In addition, on account of the PDA modification, both Dox and Btz release processes were pH-dependent and NIR-dependent. Both in vitro and in vivo studies illustrated that the Dox-M@PDA-Btz nanoparticles coupled with laser irradiation could enhance the cytotoxicity, and thus combinational therapy efficacy was achieved when integrating Dox, Btz, and PDA into a single nanoplatform. Altogether, our current study indicated that the micelle@polydopamine core-shell nanoparticles could be applied for NIR/pH-responsive sustained-release and synergized chemo-photothermal therapy for breast cancer.In this investigation, we have designed and synthesized a novel core-shell polymer nanoparticle system for highly effective chemo-photothermal combination therapy. A nanoscale DSPE-PEG micelle encapsulating doxorubicin (Dox-M) was designed as a core, and then modified by a polydopamine (PDA) shell for photothermal therapy and bortezomib (Btz) administration (Dox-M@PDA-Btz). The facile conjugation of Btz to the catechol-containing PDA shell can form a reversible pH-sensitive boronic acid-catechol conjugate to create a stimuli-responsive drug carrier system. As expected, the micelle@PDA core-shell nanoparticles exhibited satisfactory photothermal efficiency, which has

  11. Investigation of Loop Heat Pipe Survival and Restart After Extreme Cold Environment Exposure

    NASA Technical Reports Server (NTRS)

    Golliher, Eric; Ku, Jentung; Licari, Anthony; Sanzi, James

    2010-01-01

    NASA plans human exploration near the South Pole of the Moon, and other locations where the environment is extremely cold. This paper reports on the heat transfer performance of a loop heat pipe (LHP) exposed to extreme cold under the simulated reduced gravitational environment of the Moon. A common method of spacecraft thermal control is to use a LHP with ammonia working fluid. Typically, a small amount of heat is provided either by electrical heaters or by environmental design, such that the LHP condenser temperature never drops below the freezing point of ammonia. The concern is that a liquid-filled, frozen condenser would not restart, or that a thawing condenser would damage the tubing due to the expansion of ammonia upon thawing. This paper reports the results of an experimental investigation of a novel approach to avoid these problems. The LHP compensation chamber (CC) is conditioned such that all the ammonia liquid is removed from the condenser and the LHP is nonoperating. The condenser temperature is then reduced to below that of the ammonia freezing point. The LHP is then successfully restarted.

  12. Tempo and mode in fossil molluscs: Investigating organism-environment interactions, species, and speciation

    SciTech Connect

    Geary, D.H. )

    1992-01-01

    After 20 years of investigation into the tempo and mode of species-level change in the fossil record, it is clear that both punctuated equilibrium and phyletic gradualism occur, as do a variety of intermediate patterns. Important questions regarding the maintenance and diversification of species remain, however. The author documents a variety of evolutionary patterns from gastropods and bivalves, and uses these to discuss two basic issues: environment-organism interactions over time, and the importance of information on geographic variation. The tempo of morphological change is an expression of the interaction of organisms and their environment. The initial over which new species appear may be a geologic instant'' (Melanopsis gastropods), or may last 10[sup 4]--10[sup 5] years (Prunum gastropods), or 10[sup 6] years (Melanopsis). This wide range of intervals indicates a variety of tempos of environmental change, and/or different kinds of organismal responses. Analysis of geographic variation is of critical importance in understanding species and speciation, yet is lacking in many paleontological studies. An example of the utility of geographic information is a study of the muricid gastropod Acanthina, which demonstrates how a geographically localized form may spread through a species range. Another example involves a species of Pleuriocardia in stasis: geographic variation among roughly correlative samples greatly exceeds long-term temporal variation. Considerations of the mechanisms for stasis and change must take into account such intraspecific variation.

  13. Corrosion investigation of multilayered ceramics and experimental nickel alloys in SCWO process environments

    SciTech Connect

    Garcia, K.M.; Mizia, R.

    1995-02-01

    A corrosion investigation was done at MODAR, Inc., using a supercritical water oxidation (SCWO) vessel reactor. Several types of multilayered ceramic rings and experimental nickel alloy coupons were exposed to a chlorinated cutting oil TrimSol, in the SCWO process. A corrosion casing was designed and mounted in the vessel reactor with precautions to minimize chances of degrading the integrity of the pressure vessel. Fifteen of the ceramic coated rings were stacked vertically in the casing at one time for each test. There was a total of 36 rings. The rings were in groupings of three rings that formed five sections. Each section saw a different SCWO environment, ranging from 650 to 300{degrees}C. The metal coupons were mounted on horizontal threaded holders welded to a vertical rod attached to the casing cover in order to hang down the middle of the casing. The experimental nickel alloys performed better than the baseline nickel alloys. A titania multilayered ceramic system sprayed onto a titanium ring remained intact after 120-180 hours of exposure. This is the longest time any coating system has withstood such an environment without significant loss.

  14. Investigations on the interactions between vision and locomotion using a treadmill virtual environment

    NASA Astrophysics Data System (ADS)

    Thompson, William B.; Creem-Regehr, Sarah H.; Mohler, Betty J.; Willemsen, Peter

    2005-03-01

    Treadmill-based virtual environments have the potential to allow near natural locomotion through large-scale simulated spaces. To be effective, such devices need to provide users with visual and biomechanical sensations of walking that are sufficiently accurate to evoke perception-action couplings comparable to those occurring in the real world. We are exploring this problem using a custom built, computer controlled treadmill with a 6' by 10' walking surface, coupled to computer graphics presented on wide field-of-view back projection screens. The system has the added feature of being able to apply forces to the user to simulate walking on slopes and the effects of changes in walking speed. We have demonstrated the effectiveness of this system by showing that the perceptual-motor calibration of human locomotion in the real world can be altered by prior walking on the treadmill virtual environment when the visual flow associated with self-motion is mismatched relative to biomechanical walking speed. The perceptual-motor coupling that we have achieved is sufficient to allow investigation of a number of open questions, including the effect of walking on slopes on the visual estimation of slant and visual influences on gait and walking speed.

  15. Introducing and adapting a novel method for investigating learning experiences in clinical learning environments.

    PubMed

    Lachmann, Hanna; Ponzer, Sari; Johansson, Unn-Britt; Karlgren, Klas

    2012-09-01

    The Contextual Activity Sampling System (CASS) is a novel methodology designed for collecting data of on-going learning experiences through frequent sampling by using mobile phones. This paper describes how it for the first time has been introduced to clinical learning environments. The purposes of this study were to cross-culturally adapt the CASS tool and questionnaire for use in clinical learning environments, investigate whether the methodology is suitable for collecting data and how it is experienced by students. A study was carried out with 51 students who reported about their activities and experiences five times a day during a 2-week course on an interprofessional training ward. Interviews were conducted after the course. The study showed that CASS provided a range of detailed and interesting qualitative and quantitative data, which we would not have been able to collect using traditional methods such as post-course questionnaires or interviews. Moreover, the participants reported that CASS worked well, was easy to use, helped them structure their days and reflect on their learning activities. This methodology proved to be a fruitful way of collecting information about experiences, which could be useful for not only researchers but also students, teachers and course designers.

  16. An investigation of community noise in high-rise residential environments.

    PubMed

    Alam, Sheikh Mahbub; Eang, Lee Siew; Tan, Alan; Tiong, Tan Sze

    2010-06-01

    High-rise dwellers in Singapore are often subjected to several community noise sources in close proximity. These include food center, children playground, soccer playground, basketball playground, waste disposal truck, etc. A scientific and reliable approach is required for evaluation of the community noise and its impact on high-rise dwellers. A comprehensive noise survey by a cluster sampling technique, conducted among 522 households in five residential towns in Singapore, showed that community noise was one of the prime sources of noise in a high-rise residential environment. From a subjective noise survey, undertaken concurrent with objective noise measurements, a mean outdoor noise level of 59 dBA was established as an acceptable noise level in the indoor environment. To investigate the level of noise exposure from different community noise sources, software modeling and simulations were carried out. The predicted results were validated with field measured data at five 16 story residential buildings. Analysis of noise exposure data showed that except for waste disposal truck, noise exposure due to other community noise sources (building distance of 15 m) were within the established acceptable noise level. A factor analysis of the survey data identified the key factors related to the disturbance due to community noise sources.

  17. 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

  18. 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.

  19. An investigation of the role of the H II region environment on star formation

    NASA Astrophysics Data System (ADS)

    Healy, Kevin Robert

    Data from the Very Large Array, Hubble Space Telescope, and Two Micron All Sky Survey are used to investigate low-mass star formation in the vicinity of HII regions. The gas in H II regions is strongly affected by massive stars through their intense ultraviolet radiation and winds. The H II region environment is expected to affect the process of star formation, from triggering the collapse of cloud cores within the molecular cloud to truncating circumstellar disks in the interior of the H II region. Massive stars end their lives as supernovae, injecting freshly synthesized radionuclides and large amounts of radiant and kinetic energy into their surroundings. Most stars in the Galaxy form in such environments and recent measurements of meteorites demonstrate that the Solar System formed in this setting. The first part of this work describes a Very Large Array survey of water masers in portions of six H II regions. Previous observational studies demonstrate the link between star formation and water maser activity. This study uses high-resolution observations of water masers to pinpoint the sites of star formation in crowded or confused regions. The water maser survey identifies several sites of star formation that are very close to the ionization fronts being driven into the surrounding molecular cloud. The locations and numbers of these water masers indicate that the H II region environment may trigger the formation of protostars, but that the passage of the ionization front may play a role in prematurely terminating infall. Later evolutionary stages of star formation are characterized by infrared emission from circumstellar disks. Near-infrared photometry from the Two Micron All Sky Survey is used to show that stars with circumstellar disks in the star-forming region NGC 6357 cluster near ionization fronts, strongly suggesting exposure to the H II region environment rapidly (~10 4 years) evaporates circumstellar gas and dust. Hubble Space Telescope images in the

  20. Critical micelle concentration values for different surfactants measured with solid-phase microextraction fibers.

    PubMed

    Haftka, Joris J-H; Scherpenisse, Peter; Oetter, Günter; Hodges, Geoff; Eadsforth, Charles V; Kotthoff, Matthias; Hermens, Joop L M

    2016-09-01

    The amphiphilic nature of surfactants drives the formation of micelles at the critical micelle concentration (CMC). Solid-phase microextraction (SPME) fibers were used in the present study to measure CMC values of 12 nonionic, anionic, cationic, and zwitterionic surfactants. The SPME-derived CMC values were compared to values determined using a traditional surface tension method. At the CMC of a surfactant, a break in the relationship between the concentration in SPME fibers and the concentration in water is observed. The CMC values determined with SPME fibers deviated by less than a factor of 3 from values determined with a surface tension method for 7 out of 12 compounds. In addition, the fiber-water sorption isotherms gave information about the sorption mechanism to polyacrylate-coated SPME fibers. A limitation of the SPME method is that CMCs for very hydrophobic cationic surfactants cannot be determined when the cation exchange capacity of the SPME fibers is lower than the CMC value. The advantage of the SPME method over other methods is that CMC values of individual compounds in a mixture can be determined with this method. However, CMC values may be affected by the presence of compounds with other chain lengths in the mixture because of possible mixed micelle formation. Environ Toxicol Chem 2016;35:2173-2181. © 2016 SETAC. PMID:26873883

  1. EFFECT OF ULTRA-HIGH PRESSURE HOMOGENIZATION ON THE INTERACTION BETWEEN BOVINE CASEIN MICELLES AND RITONAVIR

    PubMed Central

    Corzo-Martínez, M.; Mohan, M.; Dunlap, J.; Harte, F.

    2014-01-01

    Purpose The aim of this work was to develop a milk-based powder formulation appropriate for pediatric delivery of ritonavir (RIT). Methods Ultra-high pressure homogenization (UHPH) at 0.1, 300 and 500 MPa was used to process a dispersion of pasteurized skim milk (SM) and ritonavir. Loading efficiency was determined by RP-HPLC-UV; characterization of RIT:SM systems was carried out by apparent average hydrodynamic diameter and rheological measurements as well as different analytical techniques including Trp fluorescence, UV spectroscopy, DSC, FTIR and SEM; and delivery capacity of casein micelles was determined by in vitro experiments promoting ritonavir release. Results Ritonavir interacted efficiently with milk proteins, especially, casein micelles, regardless of the processing pressure; however, results suggest that, at 0.1 MPa, ritonavir interacts with caseins at the micellar surface, whilst, at 300 and 500 MPa, ritonavir is integrated to the protein matrix during UHPH treatment. Likewise, in vitro experiments showed that ritonavir release from micellar casein systems is pH dependent; with a high retention of ritonavir during simulated gastric digestion and a rapid delivery under conditions simulating the small intestine environment. Conclusions Skim milk powder, especially, casein micelles are potentially suitable and efficient carrier systems to develop novel milk-based and low-ethanol powder formulations of ritonavir appropriate for pediatric applications. PMID:25270571

  2. Protease-Triggered, Integrin-Targeted Cellular Uptake of Recombinant Protein Micelles.

    PubMed

    Gao, Chen; Vargo, Kevin B; Hammer, Daniel A

    2016-09-01

    Targeting nanoparticles for drug delivery has great potential for improving efficacy and reducing side effects from systemic toxicity. New developments in the assembly of materials afford the opportunity to expose cryptic targeting domains in tissue-specific microenvironments in which certain proteases are expressed. Here, recombinant proteins are designed to combine the responsiveness to environmental proteases with specific targeting. Materials made recombinantly allow complete control over amino acid sequence, in which each molecule is identically functionalized. Previously, oleosin, a naturally occurring plant protein that acts as a surfactant, has been engineered to self-assemble into spherical micelles-a useful structure for drug delivery. To make oleosins that are locally activated to bind receptors, oleosin is genetically modified to incorporate the integrin-binding motif RGDS just behind a domain cleavable by thrombin. The resulting modified oleosin self-assembles into spherical micelles in aqueous environments, with the RGDS motif protected by the thrombin-cleavable domain. Upon the addition of thrombin, the RGDS is exposed and the binding of the spherical micelles to breast cancer cells is increased fourfold. PMID:27284959

  3. Anomalous phase separation kinetics observed in a micelle system

    SciTech Connect

    Wilcoxon, J.P.; Martin, J.E.

    1995-01-01

    The authors report a real-time, two-dimensional light scattering study of the evolution of structure of a two component nonionic micelle system undergoing phase separation. The micelles act like molecular slug-a-beds whose domain growth is lethargic (i.e. slower than the cube root of time prediction for simple binary fluids). In fact, the growth kinetics can be empirically described as a stretched exponential approach to a pinned domain size. Although the kinetics are not yet understood, the anomalous behavior may be due to the ability of the spherical micelles to reorganize into more complex structures.

  4. Biocleavable Polycationic Micelles as Highly Efficient Gene Delivery Vectors

    NASA Astrophysics Data System (ADS)

    Zhang, Min; Xue, Ya-Nan; Liu, Min; Zhuo, Ren-Xi; Huang, Shi-Wen

    2010-11-01

    An amphiphilic disulfide-containing polyamidoamine was synthesized by Michael-type polyaddition reaction of piperazine to equimolar N, N'-bis(acryloyl)cystamine with 90% yield. The polycationic micelles (198 nm, 32.5 mV), prepared from the amphiphilic polyamidoamine by dialysis method, can condense foreign plasmid DNA to form nanosized polycationic micelles/DNA polyelectrolyte complexes with positive charges, which transfected 293T cells with high efficiency. Under optimized conditions, the transfection efficiencies of polycationic micelles/DNA complexes are comparable to, or even higher than that of commercially available branched PEI (Mw 25 kDa).

  5. 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

  6. Role of Charge and Solvation in the Structure and Dynamics of Alanine-Rich Peptide AKA2 in AOT Reverse Micelles.

    PubMed

    Martinez, Anna Victoria; Małolepsza, Edyta; Domínguez, Laura; Lu, Qing; Straub, John E

    2015-07-23

    The propensity of peptides to form α-helices has been intensely studied using theory, computation, and experiment. Important model peptides for the study of the coil-to-helix transition have been alanine-lysine (AKA) peptides in which the lysine residues are placed on opposite sides of the helix avoiding charge repulsion while enhancing solubility. In this study, the effects of capped versus zwitterionic peptide termini on the secondary structure of alanine-rich peptides in reverse micelles are explored. The reverse micelles are found to undergo substantial shape fluctuations, a property observed in previous studies of AOT reverse micelles in the absence of solvated peptide. The peptides are observed to interact with water, as well as the AOT surfactant, including interactions between the nonpolar residues and the aliphatic surfactant tails. Computation of IR spectra for the amide I band of the peptide allows for direct comparison with experimental spectra. The results demonstrate that capped AKA2 peptides form more stable α helices than zwitterionic AKA2 peptides in reverse micelles. The rotational anisotropy decay of water is found to be distinctly different in the presence or absence of peptide within the reverse micelle, suggesting that the introduction of peptide significantly alters the number of free waters within the reverse micelle nanopool. However, neither the nature of the peptide termini (capped or charged) nor the degree of peptide helicity is found to significantly alter the balance of interactions between the peptides and the environment. Observed changes in the degree of helicity in AKA2 peptides in bulk solution and in reverse micelle environments result from changes in peptide confinement and hydration as well as direct nonpolar and polar interactions with the water-surfactant interface.

  7. Role of Charge and Solvation in the Structure and Dynamics of Alanine-Rich Peptide AKA2 in AOT Reverse Micelles

    PubMed Central

    2015-01-01

    The propensity of peptides to form α-helices has been intensely studied using theory, computation, and experiment. Important model peptides for the study of the coil-to-helix transition have been alanine–lysine (AKA) peptides in which the lysine residues are placed on opposite sides of the helix avoiding charge repulsion while enhancing solubility. In this study, the effects of capped versus zwitterionic peptide termini on the secondary structure of alanine-rich peptides in reverse micelles are explored. The reverse micelles are found to undergo substantial shape fluctuations, a property observed in previous studies of AOT reverse micelles in the absence of solvated peptide. The peptides are observed to interact with water, as well as the AOT surfactant, including interactions between the nonpolar residues and the aliphatic surfactant tails. Computation of IR spectra for the amide I band of the peptide allows for direct comparison with experimental spectra. The results demonstrate that capped AKA2 peptides form more stable α helices than zwitterionic AKA2 peptides in reverse micelles. The rotational anisotropy decay of water is found to be distinctly different in the presence or absence of peptide within the reverse micelle, suggesting that the introduction of peptide significantly alters the number of free waters within the reverse micelle nanopool. However, neither the nature of the peptide termini (capped or charged) nor the degree of peptide helicity is found to significantly alter the balance of interactions between the peptides and the environment. Observed changes in the degree of helicity in AKA2 peptides in bulk solution and in reverse micelle environments result from changes in peptide confinement and hydration as well as direct nonpolar and polar interactions with the water–surfactant interface. PMID:25337983

  8. Role of Charge and Solvation in the Structure and Dynamics of Alanine-Rich Peptide AKA2 in AOT Reverse Micelles.

    PubMed

    Martinez, Anna Victoria; Małolepsza, Edyta; Domínguez, Laura; Lu, Qing; Straub, John E

    2015-07-23

    The propensity of peptides to form α-helices has been intensely studied using theory, computation, and experiment. Important model peptides for the study of the coil-to-helix transition have been alanine-lysine (AKA) peptides in which the lysine residues are placed on opposite sides of the helix avoiding charge repulsion while enhancing solubility. In this study, the effects of capped versus zwitterionic peptide termini on the secondary structure of alanine-rich peptides in reverse micelles are explored. The reverse micelles are found to undergo substantial shape fluctuations, a property observed in previous studies of AOT reverse micelles in the absence of solvated peptide. The peptides are observed to interact with water, as well as the AOT surfactant, including interactions between the nonpolar residues and the aliphatic surfactant tails. Computation of IR spectra for the amide I band of the peptide allows for direct comparison with experimental spectra. The results demonstrate that capped AKA2 peptides form more stable α helices than zwitterionic AKA2 peptides in reverse micelles. The rotational anisotropy decay of water is found to be distinctly different in the presence or absence of peptide within the reverse micelle, suggesting that the introduction of peptide significantly alters the number of free waters within the reverse micelle nanopool. However, neither the nature of the peptide termini (capped or charged) nor the degree of peptide helicity is found to significantly alter the balance of interactions between the peptides and the environment. Observed changes in the degree of helicity in AKA2 peptides in bulk solution and in reverse micelle environments result from changes in peptide confinement and hydration as well as direct nonpolar and polar interactions with the water-surfactant interface. PMID:25337983

  9. Supramolecular Structural Forces in Stratifying Foam Films and Micelle Aggregation Number

    NASA Astrophysics Data System (ADS)

    Yilixiati, Subinuer; Zhang, Yiran; Wojcik, Ewelina; Rafiq, Rabees; Sharma, Vivek

    Understanding and controlling the drainage kinetics of thin films is an important problem that underlies the stability, lifetime and rheology of foams and emulsions. Foam films containing micelles, colloidal particles or polyelectrolyte-surfactant mixtures exhibit step-wise thinning or stratification, due to the influence of non-DLVO forces, including supramolecular oscillatory structural forces. In this study, we use experiments and theory to investigate the drainage and stratification in vertical and horizontal thin foam films (<100 nm) formed by aqueous sodium dodecyl sulfate (SDS) solutions. We determine how the concentration of surfactants and added salt influences the stepwise thinning process for micellar solutions, and how step size can be used for estimating micelle size and interactions. The concentration-dependent aggregation number extracted from our experiments match-up reasonably well with values obtained by other techniques including scattering and fluorescence.

  10. Hydrophobically Tailored Carbon Dots toward Modulating Microstructure of Reverse Micelle and Amplification of Lipase Catalytic Response.

    PubMed

    Sarkar, Saheli; Das, Krishnendu; Das, Prasanta Kumar

    2016-04-26

    This article delineates the modulation of microstructure of cationic reverse micelle utilizing hydrophobically modified carbon dots (CDs) with varying surface functionalizations. Citric acid was used as the source of the carbon core, and Na-salt of glycine, glycine, Na-salt of 11-aminoundecanoic acid, 11-aminoundecanoic acid, and n-hexadecylamine were used for the surface fabrication of CDs to produce CD 1s, CD 1a, CD 2s, CD 2a, and CD 3, respectively. All these CDs having dimension of 5-7 nm were characterized by spectroscopic and microscopic techniques. The hydrodynamic diameter of cetyltrimethylammonium bromide (CTAB) reverse micelle (CTAB/isooctane/n-hexanol/water) at z ([cosurfactant]/[surfactant]) = 6.4 and W0 ([water]/[surfactant]) = 44 is around 15-20 nm. Interestingly, the size of the water-in-oil (w/o) microemulsions dramatically increased up to 120-200 nm upon doping hydrophobic surface functionalized CD 2a and CD 3. This is possibly due to change in the micellar exchange dynamics and reorganization of the micellar aggregates via hydrophobic interaction between surfactant (CTAB) tail and hydrophobic surface modifier of the carbon dots. However, no alteration in the size of reverse micelles was noted in the presence of carbon dots CD 1s, CD 1a, and CD 2s. Spectroscopic and microscopic investigations confirmed that the hydrophobic CD 2a and CD 3 were localized at the interface of reverse micelles whereas CD 1s, CD 1a, and CD 2s were possibly located in the water pool (away from interface). The activity of Chromobacterium viscosum lipase encapsulated within CD 3 and CD 2a doped significantly large CTAB reverse micelles showed remarkable improvement (3.7-fold and 3.4-fold) in its catalytic response. However, hydrophilic carbon dots CD 1s and CD 2s as well as moderately hydrophobic CD 1a had no significant effect on the microstructure of reverse micelles as well as on the lipase activity. PMID:27035762

  11. A Design-Based Research Investigation of a Web-Based Learning Environment Designed to Support the Reading Process

    ERIC Educational Resources Information Center

    Kidwai, Khusro

    2009-01-01

    This research study had two purposes, (a) to design and develop a Web-based learning environment that supports the use of a set of reading strategies, and (b) to investigate the impact of this Web-based learning environment on readers' "memory" and "understanding" of an instructional unit on the human heart (Dwyer &…

  12. PEG-PE-based micelles co-loaded with paclitaxel and cyclosporine A or loaded with paclitaxel and targeted by anticancer antibody overcome drug resistance in cancer cells.

    PubMed

    Sarisozen, Can; Vural, Imran; Levchenko, Tatyana; Hincal, A Atilla; Torchilin, Vladimir P

    2012-05-01

    The over-expression of the P-glycoprotein (P-gp) in cancer cells is one of the main reasons of the acquired Multidrug Resistance (MDR). Combined treatment of MDR cancer cells with P-gp inhibitors and chemotherapeutic agents could result in reversal of resistance in P-gp-expressing cells. In this study, paclitaxel (PTX) was co-encapsulated in actively targeted (anticancer mAb 2C5-modified) polymeric lipid-core PEG-PE-based micelles with Cyclosporine A (CycA), which is one of the most effective first generation P-gp inhibitors. Cell culture studies performed using MDCKII (parental and MDR1) cell lines to investigate the potential MDR reversal effect of the formulations. The average size of both empty and loaded PEG₂₀₀₀-PE/Vitamin E mixed micelles was found between 10 and 25 nm. Zeta potentials of the formulations were found between -7 and -35 mV. The percentage of PTX in the micelles was found higher than 3% for both formulations and cumulative PTX release of about 70% was demonstrated. P-gp inhibition with CycA caused an increase in the cytotoxicity of PTX. Dual-loaded micelles demonstrated significantly higher cytotoxicity in the resistant MDCKII-MDR1 cells than micelles loaded with PTX alone. Micelle modification with mAb 2C5 results in the highest cytotoxicity against resistant cells, with or without P-gp modulator, probably because of better internalization bypassing the P-gp mechanism. Our results suggest that micelles delivering a combination of P-gp modulator and anticancer drug or micelles loaded with only PTX, but targeted with mAb 2C5 represent a promising approach to overcome drug resistance in cancer cells. PMID:22506922

  13. Self-assembled micelles of novel amphiphilic copolymer cholesterol-coupled F68 containing cabazitaxel as a drug delivery system.

    PubMed

    Song, Yanzhi; Tian, Qingjing; Huang, Zhenjun; Fan, Di; She, Zhennan; Liu, Xinrong; Cheng, Xiaobo; Yu, Bin; Deng, Yihui

    2014-01-01

    Despite being one of the most promising amphiphilic block copolymers, use of Pluronic F68 in drug delivery is limited due to its high critical micelle concentration (CMC). In this study, we developed a novel F68 derivative, cholesterol-coupled F68 (F68-CHMC). This new derivative has a CMC of 10 μg/mL, which is 400-fold lower than that of F68. The drug-loading capacity of F68-CHMC was investigated by encapsulating cabazitaxel, a novel antitumor drug. Drug-loaded micelles were fabricated by a self-assembly method with simple dilution. The optimum particle size of the micelles was 17.5±2.1 nm, with an entrapment efficiency of 98.1% and a drug loading efficiency of 3.16%. In vitro release studies demonstrated that cabazitaxel-loaded F68-CHMC micelles had delayed and sustained-release properties. A cytotoxicity assay of S180 cells showed that blank F68-CHMC was noncytotoxic with a cell viability of nearly 100%, even at a concentration of 1,000 μg/mL. The IC50 revealed that cabazitaxel-loaded F68-CHMC micelles were more cytotoxic than Tween 80-based cabazitaxel solution and free cabazitaxel. In vivo antitumor activity against S180 cells also indicated better tumor inhibition by the micelles (79.2%) than by Tween 80 solution (56.2%, P<0.05). Based on these results, we conclude that the F68-CHMC copolymer may be a potential nanocarrier to improve the solubility and biological activity of cabazitaxel and other hydrophobic drugs.

  14. Environment.

    ERIC Educational Resources Information Center

    White, Gilbert F.

    1980-01-01

    Presented are perspectives on the emergence of environmental problems. Six major trends in scientific thinking are identified including: holistic approaches to examining environments, life support systems, resource management, risk assessment, streamlined methods for monitoring environmental change, and emphasis on the global framework. (Author/SA)

  15. Novel pH-responsive polymeric micelles prepared through self-assembly of amphiphilic block copolymer with poly-4-vinylpyridine block synthesized by mechanochemical solid-state polymerization.

    PubMed

    Kondo, Shin-ichi; Asano, Yuna; Koizumi, Natsumi; Tatematsu, Kenjiro; Sawama, Yuka; Sasai, Yasushi; Yamauchi, Yukinori; Kuzuya, Masayuki; Kurosawa, Shigeru

    2015-01-01

    We fabricated polymeric micelles containing 5-fluorouracil (5-FU) or fluorescein using the amphiphilic block copolymer, poly-4-vinylpyridine-b-6-O-methacryloyl galactopyranose. Although the polymeric micelles were stable at pH 7.4, they readily decomposed at pH 5, resulting in near complete release of 5-FU. Uptake of polymeric micelles containing fluorescein by HepG2 and HCT116 cells was also investigated. With both cell types, strong fluorescence was observed after a 12-h incubation, but the fluorescence weakened after 24 h of incubation. The fluorescein incorporated into the polymeric micelles was released into acidic organelles (endosome and/or lysosome), from which it diffused throughout the cell. The cytotoxicity of polymeric micelles containing 5-FU was evaluated against HepG2 cells using a CCK-8 assay. The results suggest that polymeric micelles containing 5-FU are more cytotoxic to HepG2 cells than free 5-FU. PMID:26133065

  16. Dynamics of water at the interface in reverse micelles: measurements of spectral diffusion with two-dimensional infrared vibrational echoes.

    PubMed

    Fenn, Emily E; Wong, Daryl B; Giammanco, Chiara H; Fayer, M D

    2011-10-13

    Water dynamics inside of reverse micelles made from the surfactant Aerosol-OT (AOT) were investigated by observing spectral diffusion, orientational relaxation, and population relaxation using two-dimensional infrared (2D IR) vibrational echo spectroscopy and pump-probe experiments. The water pool sizes of the reverse micelles studied ranged in size from 5.8 to 1.7 nm in diameter. It is found that spectral diffusion, characterized by the frequency-frequency correlation function (FFCF), significantly changes as the water pool size decreases. For the larger reverse micelles (diameter 4.6 nm and larger), the 2D IR signal is composed of two spectral components: a signal from bulk-like core water, and a signal from water at the headgroup interface. Each of these signals (core water and interfacial water) is associated with a distinct FFCF. The FFCF of the interfacial water layer can be obtained using a modified center line slope (CLS) method that has been recently developed. The interfacial FFCFs for large reverse micelles have a single exponential decay (∼1.6 ps) to an offset plus a fast homogeneous component and are nearly identical for all large sizes. The observed ∼1.6 ps interfacial decay component is approximately the same as that found for bulk water and may reflect hydrogen bond rearrangement of bulk-like water molecules hydrogen bonded to the interfacial water molecules. The long time offset arises from dynamics that are too slow to be measured on the accessible experimental time scale. The influence of the chemical nature of the interface on spectral diffusion was explored by comparing data for water inside reverse micelles (5.8 nm water pool diameter) made from the surfactants AOT and Igepal CO-520. AOT has charged, sulfonate head groups, while Igepal CO-520 has neutral, hydroxyl head groups. It is found that spectral diffusion on the observable time scales is not overly sensitive to the chemical makeup of the interface. An intermediate-sized AOT reverse

  17. Dynamics of water at the interface in reverse micelles: measurements of spectral diffusion with two-dimensional infrared vibrational echoes.

    PubMed

    Fenn, Emily E; Wong, Daryl B; Giammanco, Chiara H; Fayer, M D

    2011-10-13

    Water dynamics inside of reverse micelles made from the surfactant Aerosol-OT (AOT) were investigated by observing spectral diffusion, orientational relaxation, and population relaxation using two-dimensional infrared (2D IR) vibrational echo spectroscopy and pump-probe experiments. The water pool sizes of the reverse micelles studied ranged in size from 5.8 to 1.7 nm in diameter. It is found that spectral diffusion, characterized by the frequency-frequency correlation function (FFCF), significantly changes as the water pool size decreases. For the larger reverse micelles (diameter 4.6 nm and larger), the 2D IR signal is composed of two spectral components: a signal from bulk-like core water, and a signal from water at the headgroup interface. Each of these signals (core water and interfacial water) is associated with a distinct FFCF. The FFCF of the interfacial water layer can be obtained using a modified center line slope (CLS) method that has been recently developed. The interfacial FFCFs for large reverse micelles have a single exponential decay (∼1.6 ps) to an offset plus a fast homogeneous component and are nearly identical for all large sizes. The observed ∼1.6 ps interfacial decay component is approximately the same as that found for bulk water and may reflect hydrogen bond rearrangement of bulk-like water molecules hydrogen bonded to the interfacial water molecules. The long time offset arises from dynamics that are too slow to be measured on the accessible experimental time scale. The influence of the chemical nature of the interface on spectral diffusion was explored by comparing data for water inside reverse micelles (5.8 nm water pool diameter) made from the surfactants AOT and Igepal CO-520. AOT has charged, sulfonate head groups, while Igepal CO-520 has neutral, hydroxyl head groups. It is found that spectral diffusion on the observable time scales is not overly sensitive to the chemical makeup of the interface. An intermediate-sized AOT reverse

  18. Schumann Resonances as a Means of Investigating the Electromagnetic Environment in the Solar System

    NASA Astrophysics Data System (ADS)

    Simões, F.; Rycroft, M.; Renno, N.; Yair, Y.; Aplin, K. L.; Takahashi, Y.

    2008-06-01

    The propagation of extremely low frequency (ELF, 3 Hz to 3 kHz) radio waves and resonant phenomena in the spherical Earth-ionosphere cavity has been studied for almost fifty years. When such a cavity is excited by naturally occurring broadband electromagnetic radiation, resonances can develop if the equatorial circumference is approximately equal to an integral number of wavelengths of the propagating electromagnetic waves; these are termed Schumann resonances. They provide information not only about thunderstorm and lightning activity on the Earth, and their relation to climate, but also on the properties of the low ionosphere. Similar investigations can be performed for any other planet or satellite, provided that it has an ionosphere. There are important differences between the Earth and other celestial bodies regarding, for example, the surface conductivity, the atmospheric conductivity profile, the geometry of the ionospheric cavity, and the sources of excitation. To a first approximation, the size of the cavity defines the fundamental resonant frequency, the atmospheric electron density profile controls the wave attenuation, the nature of the sources influences the electromagnetic field distribution in the cavity, and the body surface conductivity indicates to what extent the subsurface can be explored. The frequencies and attenuation rates of the principal eigenmodes depend upon the electrical properties of the cavity. Instruments that monitor the electromagnetic environment in the ELF range on the surface, on balloons, or on descent probes provide unique information on the cavity. In this paper, we present Schumann resonance models for selected inner planets, some gaseous giant planets and a few of their satellites. We review the crucial parameters of ELF electromagnetic waves in their atmospheric cavities, namely the electric and magnetic field spectra, their eigenfrequencies, and the associated Q-factors (damping factors). Then we present important

  19. Foton 11: ESA investigates further the space environment and its impact on organisms

    NASA Astrophysics Data System (ADS)

    1997-10-01

    Scientific research conducted under space conditions can provide new insight into how processes occur on Earth and organisms function. The unmanned Foton spacecraft has been used since 1988 to conduct such investigations. Now on its 11th mission and the fifth in which ESA has taken part, Foton is carrying some 80 kg of ESA payload: two ESA research facilities (an incubator and an experiment holder on the outside of the spacecraft) are on board along with 12 scientific experiments. The French space agency (CNES) and the German space agency (DARA) also have payload on the spacecraft. ESA's space-qualified incubator, called Biobox, keeps organisms at predefined conditions. During this mission, the three Biobox experiments are looking at the reaction of bone cells in microgravity. The second ESA facility, a pan-shaped container called Biopan attached to the outside of Foton, is used to expose experiment samples directly to the space environment in order to study the impact of space's extreme temperatures, ultraviolet and cosmic radiation, and near-perfect vacuum. On this mission, the six Biopan experiments are concentrating on exobiology, radiation biology and material science. Biopan has a motor-driven, hinged lid and is equipped with devices and sensors that measure the various aspects of the environment to which the experiments are subjected. Once Foton is in orbit, a telecommand is sent from ground and the lid opens to expose the samples to the environment. At the end of the mission, another command is sent and the lid closes. Since Biopan is on the outside of Foton, it also has its own ablative heat shield to protect the facility and samples during the spacecraft's re-entry and landing. Other ESA experiments on board Foton are looking into the effects of weightlessness on bacteria, the biological clocks of beetles and the aging of fruitflies. The scientific investigators responsible for the ESA experiments are from research institutes and universities in Belgium

  20. Investigating Factors That Influence Students' Management of Study Environment in Online Collaborative Groupwork

    ERIC Educational Resources Information Center

    Du, Jianxia; Xu, Jianzhong; Fan, Xitao

    2015-01-01

    The present study examines empirical models of students' management of the learning environment in the context of online collaborative groupwork. Such environment management is an important component of students' overall self-regulated learning strategy for effective learning. Student- and group-level predictors for study environment management in…

  1. Noncovalent interaction-assisted polymeric micelles for controlled drug delivery.

    PubMed

    Ding, Jianxun; Chen, Linghui; Xiao, Chunsheng; Chen, Li; Zhuang, Xiuli; Chen, Xuesi

    2014-10-01

    Polymeric micelles are one of the most promising nanovehicles for drug delivery. In addition to amphiphilicity, various individual or synergistic noncovalent interplays including strong hydrophobic, electrostatic, host-guest, hydrogen bonding, stereocomplex and coordination interactions have been recently employed to improve the physical stability of micelles, and even provide them with certain intelligences or bioactivities. Through the ingenious designs and precise preparations, many noncovalent-mediated micelles display great prospects in the realm of controlled drug delivery, and certain species have been promoted to clinical trials. The current review presents the diverse noncovalent interactions that are applied to enhance polymeric micelles as drug nanocarriers, and preliminarily discusses the future directions and perspectives of this field.

  2. 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

  3. Regulated pH-Responsive Polymeric Micelles for Doxorubicin Delivery to the Nucleus of Liver Cancer Cells.

    PubMed

    Li, Hao; Li, Xian; Zhang, Chao; Sun, Qiquan; Yi, Wei; Wang, Xuan; Cheng, Du; Chen, Shupeng; Liang, Biling; Shuai, Xintao

    2016-06-01

    A diblock copolymer of poly(ethylene glycol) (PEG) and poly(γ-benzyl L-glutamate) (PBLG), PEG-PBLG, was synthesized via the ring-opening polymerization of γ-benzyl L-glutamate N-carboxyanhydride (BLG-NCA) using allyl-PEG-NH2 as a macroinitiator. After deprotection of the benzyl groups, N,N-diisopropyl ethylenediamine (DIP) was conjugated to poly(L-glutamic acid) (PGA) blocks as side groups. The pendant DIP groups on the PGA blocks greatly enhance the pH-sensitivity of poly(ethylene glycol)-block-poly[N-(N',N'-diisopropylaminoethyl) glutamide] [PEG-PGA(DIP)] micelles, and a higher grafting percentage of DIP favors a faster acid-response. In neutral aqueous solution, the PEG-PGA(DIP) can self-assemble into stable micelles featuring an acid-responsive PGA(DIP) core with the encapsulated anticancer drug doxorubicin (DOX). In an acidic environment, the hydrophobic-hydrophilic transition of the PGA block leads to the gradual expansion and disassembly of these micelles and, consequently, an accelerated release of DOX. Thus, DOX transported by PEG-PGA(DIP) micelles can be entrapped more efficiently into the nuclei of hepatoma Bel 7402 cells.

  4. Effect of solvent and temperature on the size distribution of casein micelles measured by dynamic light scattering.

    PubMed

    Beliciu, C M; Moraru, C I

    2009-05-01

    The objectives of this study were to investigate the effect of the solvent on the accuracy of casein micelle particle size determination by dynamic light scattering (DLS) at different temperatures and to establish a clear protocol for these measurements. Dynamic light scattering analyses were performed at 6, 20, and 50 degrees C using a 90Plus Nanoparticle Size Analyzer (Brookhaven Instruments, Holtsville, NY). Raw and pasteurized skim milk were used as sources of casein micelles. Simulated milk ultrafiltrate, ultrafiltered water, and permeate obtained by ultrafiltration of skim milk using a 10-kDa cutoff membrane were used as solvents. The pH, ionic concentration, refractive index, and viscosity of all solvents were determined. The solvents were evaluated by DLS to ensure that they did not have a significant influence on the results of the particle size measurements. Experimental protocols were developed for accurate measurement of particle sizes in all solvents and experimental conditions. All measurements had good reproducibility, with coefficients of variation below 5%. Both the solvent and the temperature had a significant effect on the measured effective diameter of the casein micelles. When ultrafiltered permeate was used as a solvent, the particle size and polydispersity of casein micelles decreased as temperature increased. The effective diameter of casein micelles from raw skim milk diluted with ultrafiltered permeate was 176.4 +/- 5.3 nm at 6 degrees C, 177.4 +/- 1.9 nm at 20 degrees C, and 137.3 +/- 2.7 nm at 50 degrees C. This trend was justified by the increased strength of hydrophobic bonds with increasing temperature. Overall, the results of this study suggest that the most suitable solvent for the DLS analyses of casein micelles was casein-depleted ultrafiltered permeate. Dilution with water led to micelle dissociation, which significantly affected the DLS measurements, especially at 6 and 20 degrees C. Simulated milk ultrafiltrate seemed to give

  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. Setting the Time Frame - Investigating Culture-Environment Interactions in the Late Quaternary

    NASA Astrophysics Data System (ADS)

    Klasen, N.; Just, J.; Rethemeyer, J.

    2015-12-01

    We present a status update of luminescence age estimates of sediments from Ethiopia and the Iberian Peninsula that are related to human occupation and are currently being investigated in the interdisciplinary Collaborative Research Center "Our way to Europe - Culture-Environment Interaction and Human Mobility in the Late Quaternary" (CRC806). The aim of the project is to investigate the dispersal of anatomically modern humans from Africa to Europe, and a robust chronology is essential. In the CRC806, dating is provided by luminescence, palaeomagnetic and radiocarbon techniques. A key site of the CRC806 is Chew Bahir in Ethiopia. This lake basin is located in the source area of the emergence of anatomically modern humans. Radiocarbon, luminescence and palaeomagnetic dating have been used to develop an age-depth model for drill core sediments that date back to 115 ka over 42 m depth. The model is independent of palaeoclimatic proxy interpretation. On the Iberian Peninsula cave deposits have been dated with luminescence techniques and compared to radiocarbon ages wherever applicable. Recently, existing radiocarbon chronologies on the Iberian Peninsula have been revised in light of methodological developments. Robust luminescence dating is therefore especially important in this region, where the stratigraphy is difficult to constrain. We aim to improve the precision of luminescence age estimates by comparing different measurement techniques for equivalent dose and dose-rate determinations, and by using Bayesian statistics to develop age-depth models. Combining different chronological techniques has enabled the development of accurate and precise chronologies, which will allow a better understanding of the emergence of modern humans.

  7. Self-assembly of polymeric micelles into complex but regular superstructures based on highly controllable core-core fusion between the micelles.

    PubMed

    Wang, Liangyan; Wang, Yafen; Miao, Han; Chen, Daoyong

    2016-06-14

    Herein, we report a facile but highly controllable method to induce core-core fusion for not only spherical but also worm-like polymeric micelles, leading to various complex but regular superstructures including "random worm-like co-micelles", "block worm-like co-micelles" and octopus-like superparticles. PMID:27192018

  8. Investigation of Low Heat Accumulation Asphalt Mixture and Its Impact on Urban Heat Environment.

    PubMed

    Xie, Jianguang; Yang, Zhaoxu; Liang, Leilei

    2015-01-01

    This study is focused on investigating the effectiveness of low heat accumulation asphalt mixture and its impact on the urban heat environment. Infrared radiation experiments showed that the temperature of the asphalt mixture decreased with the increase in far-infrared radiant material. The results also revealed that, compared to asphalt with 0% far-infrared radiant content, the asphalt material with a certain ratio of far-infrared radiation material had higher stability at high and low temperatures as well as good water absorption capacity. The Marshall stability of the specimen mixed with 6% far-infrared radiant was higher by 12.2% and had a residual stability of up to 98.9%. Moreover, the low-temperature splitting tensile strength of the asphalt mixture with 6% far-infrared radiation material increased by 21.3%. The friction coefficient of the asphalt mixtures with 6% and 12% far-infrared radiation material increased by 17.7% and 26.9%, respectively. PMID:26222762

  9. Subjective estimation of thermal environment in recreational urban spaces—Part 1: investigations in Szeged, Hungary

    NASA Astrophysics Data System (ADS)

    Kántor, Noémi; Égerházi, Lilla; Unger, János

    2012-11-01

    During two investigation periods in transient seasons (14 weekdays in autumn 2009 and 15 weekdays in spring 2010) 967 visitors in two inner city squares of Szeged (Hungary) were asked about their estimation of their thermal environment. Interrelationships of subjective assessments—thermal sensation, perceptions and preferences for individual climate parameters—were analyzed, as well as their connections with the prevailing thermal conditions [air temperature, relative humidity, wind velocity, mean radiant temperature and physiologically equivalent temperature (PET)]. Thermal sensation showed strong positive relationships with air temperature and solar radiation perception, while wind velocity and air humidity perception had a negative (and weaker) impact. If a parameter was perceived to be low or weak, then it was usually desired to be higher or stronger. This negative correlation was weakest in the case of humidity. Of the basic meteorological parameters, Hungarians are most sensitive to variations in wind. Above PET = 29°C, people usually prefer lower air temperature and less solar radiation. The temperature values perceived by the interviewees correlated stronger with PET, but their means were more similar to air temperature. It was also found that the mean thermal sensation of Hungarians in transient seasons depends on PET according to a quadratic function ( R 2 = 0.912) and, consequently, the thermal comfort ranges of the locals differ from that usually adopted.

  10. Investigation on the high efficiency volume Bragg gratings performances for spectrometry in space environment: preliminary results

    NASA Astrophysics Data System (ADS)

    Loicq, Jérôme; Gaspar Venancio, Luis Miguel; Georges, Marc

    2012-09-01

    The special properties of Volume Bragg Gratings (VBGs) make them good candidates for spectrometry applications where high spectral resolution, low level of straylight and low polarisation sensitivity are required. Therefore it is of interest to assess the maturity and suitability of VBGs as enabling technology for future ESA missions with demanding requirements for spectrometry. The VBGs suitability for space application is being investigated in the frame of a project led by CSL and funded by the European Space Agency. The goal of this work is twofold: first the theoretical advantages and drawbacks of VBGs with respect to other technologies with identical functionalities are assessed, and second the performances of VBG samples in a representative space environment are experimentally evaluated. The performances of samples of two VBGs technologies, the Photo-Thermo-Refractive (PTR) glass and the DiChromated Gelatine (DCG), are assessed and compared in the Hα, O2-B and NIR bands. The tests are performed under vacuum condition combined with temperature cycling in the range of 200 K to 300K. A dedicated test bench experiment is designed to evaluate the impact of temperature on the spectral efficiency and to determine the optical wavefront error of the diffracted beam. Furthermore the diffraction efficiency degradation under gamma irradiation is assessed. Finally the straylight, the diffraction efficiency under conical incidence and the polarisation sensitivity is evaluated.

  11. A numerical investigation of a slow-moving convective line in a weakly sheared environment

    NASA Astrophysics Data System (ADS)

    Liu, Changhai

    2005-09-01

    A series of three-dimensional, cloud-resolving numerical simulations are performed to examine a slowpropagating, quasi-two-dimensional convective system in a weakly sheared environment during the Tropical Rainfall Measuring Mission Large-Scale Biosphere-Atmosphere (TRMM-LBA) field campaign. The focus is on the kinematics and thermodynamics, organization mechanisms, and dynamical effects of low-level shear, ice microphysics and tropospheric humidity. The control simulation, which is initialized with the observed sounding and includes full microphysics, successfully replicates many observed features of the convective system, such as the linear structure, spatial orientation, life cycle, and sluggish translation. The system at the mature stage displays a line-normal structure similar to that associated with squalltype convective systems, but the corresponding mesoscale circulation and thermodynamic modification are much weaker. Ice-phase microphysical processes are not necessary to the formation of the convective system, but they play a non-trivial role in the late evolution stage. In contrast, the low-level shear, albeit shallow and weak, is critical to the realistic realization of the convective line. The tropospheric moisture above the planetary boundary layer has an important impact on the behavior of convective organization. In particular, a dry layer in the lower troposphere significantly suppresses convective development and inhibits the generation of organized convection even though the convective available potential energy is substantial. The free-atmosphere humidity has received little attention in previous studies of organized convection and warrants further investigation.

  12. Investigation of Low Heat Accumulation Asphalt Mixture and Its Impact on Urban Heat Environment

    PubMed Central

    Xie, Jianguang; Yang, Zhaoxu; Liang, Leilei

    2015-01-01

    This study is focused on investigating the effectiveness of low heat accumulation asphalt mixture and its impact on the urban heat environment. Infrared radiation experiments showed that the temperature of the asphalt mixture decreased with the increase in far-infrared radiant material. The results also revealed that, compared to asphalt with 0% far-infrared radiant content, the asphalt material with a certain ratio of far-infrared radiation material had higher stability at high and low temperatures as well as good water absorption capacity. The Marshall stability of the specimen mixed with 6% far-infrared radiant was higher by 12.2% and had a residual stability of up to 98.9%. Moreover, the low-temperature splitting tensile strength of the asphalt mixture with 6% far-infrared radiation material increased by 21.3%. The friction coefficient of the asphalt mixtures with 6% and 12% far-infrared radiation material increased by 17.7% and 26.9%, respectively. PMID:26222762

  13. Investigating Hydrocarbon Seep Environments with High-Resolution, Three-Dimensional Geographic Visualizations.

    NASA Astrophysics Data System (ADS)

    Doolittle, D. F.; Gharib, J. J.; Mitchell, G. A.

    2015-12-01

    Detailed photographic imagery and bathymetric maps of the seafloor acquired by deep submergence vehicles such as Autonomous Underwater Vehicles (AUV) and Remotely Operated Vehicles (ROV) are expanding how scientists and the public view and ultimately understand the seafloor and the processes that modify it. Several recently acquired optical and acoustic datasets, collected during ECOGIG (Ecosystem Impacts of Oil and Gas Inputs to the Gulf) and other Gulf of Mexico expeditions using the National Institute for Undersea Science Technology (NIUST) Eagle Ray, and Mola Mola AUVs, have been fused with lower resolution data to create unique three-dimensional geovisualizations. Included in these data are multi-scale and multi-resolution visualizations over hydrocarbon seeps and seep related features. Resolution of the data range from 10s of mm to 10s of m. When multi-resolution data is integrated into a single three-dimensional visual environment, new insights into seafloor and seep processes can be obtained from the intuitive nature of three-dimensional data exploration. We provide examples and demonstrate how integration of multibeam bathymetry, seafloor backscatter data, sub-bottom profiler data, textured photomosaics, and hull-mounted multibeam acoustic midwater imagery are made into a series a three-dimensional geovisualizations of actively seeping sites and associated chemosynthetic communities. From these combined and merged datasets, insights on seep community structure, morphology, ecology, fluid migration dynamics, and process geomorphology can be investigated from new spatial perspectives. Such datasets also promote valuable inter-comparisons of sensor resolution and performance.

  14. Experimental investigations of the entrapment and persistence of organic liquid contaminants in the subsurface environment.

    PubMed Central

    Abriola, L M; Bradford, S A

    1998-01-01

    Organic liquids are common polluters of the subsurface environment. Once released, these nonaqueous phase liquids (NAPLs) tend to become entrapped within soils and geologic formations where they may serve as long-term contaminant reservoirs. The interphase mass transfer from such entrapped residuals will ultimately control environmental exposure levels as well as the persistence and/or remedial recovery of these contaminants in the subsurface. This paper summarizes National Institute of Environmental Health Sciences-sponsored research designed to investigate and quantify NAPL entrapment and interphase mass transfer in natural porous media. Results of soil column and batch experiments are presented that highlight research findings over the past several years. These experiments explore dissolution and volatilization of hydrocarbons and chlorinated solvents in sandy porous media. Initial concentration levels and long-term recovery rates are shown to depend on fluid flow rate, soil structure, NAPL composition, and soil wetting characteristics. These observations are explained in the context of conceptual models that describe entrapped NAPL morphology and boundary layer transport. The implications of these laboratory findings on the subsurface persistence and recovery of entrapped NAPLs are discussed. Images Figure 1 Figure 3 Figure 9 PMID:9703497

  15. Investigating GPS Water-Vapor Tomography in a Severe-Weather Environment

    NASA Astrophysics Data System (ADS)

    Elosegui, P.; Davis, J.; Normandeau, J.; Rancourt, K.; Flores, A.; Rius, A.

    2001-05-01

    Global Positioning System (GPS) networks have demonstrated the ability to accurately determine the horizontal structure of the time-varying atmospheric water vapor. GPS atmospheric applications have largely focused on the study of mesoscale weather systems and near real-time forecasting. The vertical structure of water vapor, however, has remained largely elusive, and no one has yet demonstrated the possibility of GPS water vapor profiling under rapidly varying conditions. The extreme and rapidly changing weather experienced at Mount Washington, New Hampshire, due in part to the vertical motions of the jet stream, makes this site unique for studying the critical role played by water vapor in atmospheric processes. We have conducted a GPS experiment at Mount Washington with the aim of investigating the use of tomography for determining the rapidly varying time-dependent three-dimensional water-vapor field on Mount Washington. In this presentation, we will describe the experiment, present our results, and discuss the prospect for the use of real-time GPS tomography in this environment.

  16. 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

  17. A thermodynamic analysis of charged mixed micelles in water.

    PubMed

    Maeda, Hiroshi

    2005-08-25

    A thermodynamic analysis is presented for electrically charged mixed micelles in water on the basis of the Gibbs-Duhem relation proposed by Hall in combination with the information on the degree of counterion binding. The proposed analyses are shown to work well for both ionic/nonionic mixed micelles and those consisting of ionic surfactants of like charges. Conclusions for ionic/nonionic mixed micelles are as follows. (1) The contribution from counterions is significant. (2) In media of low ionic strengths, the counterion concentration varies with the micellar mole fraction of the ionic species x. The dependency of the activity coefficients and the excess free energy on x is significantly influenced by this effect, but it can be corrected to a large extent in terms of the Corrin-Harkins relation. (3) The regular solution theory (RST) is not always valid even when the excess free energy is described well with the RST expression unless the observed range of the micelle composition is wide enough. (4) The RST overestimates x and underestimates the activity coefficient of the ionic species when applied to the mixed micelles to which it is inapplicable. For the ionic mixed micelles consisting of surfactants of like charges, the Lange-Shinoda approach is shown to be consistent with the present analysis in terms of the Gibbs-Duhem relation, but Motomura's approach is found to be not exact but approximate.

  18. Binding of vitamin A by casein micelles in commercial skim milk.

    PubMed

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

    2013-02-01

    Recent studies have shown that reassembled micelles formed by caseinates and purified casein fractions (α(s)- and β-casein) bind to hydrophobic compounds, including curcumin, docosahexaenoic acid, and vitamin D. However, limited research has been done on the binding of hydrophobic compounds by unmodified casein micelles in skim milk. In the present study, we investigated the ability of casein micelles in commercial skim milk to associate with vitamin A (retinyl palmitate), a fat-soluble vitamin commonly used to fortify milk. Milk protein fractions from different commercially available skim milk samples subjected to different processing treatments, including pasteurized, ultrapasteurized, organic pasteurized, and organic ultrapasteurized milks, were separated by fast protein liquid chromatography. The fractions within each peak were combined and freeze-dried. Sodium dodecyl sulfate-PAGE with silver staining was used to identify the proteins present in each of the fractions. The skim milk samples and fractions were extracted for retinyl palmitate and quantified against a standard using normal phase-HPLC. Retinyl palmitate was found to associate with the fraction of skim milk containing caseins, whereas the other proteins (BSA, β-lactoglobulin, α-lactalbumin) did not show any binding. The retinyl palmitate content in the various samples ranged from 1.59 to 2.48 µg of retinyl palmitate per mL of milk. The casein fractions contained between 14 and 40% of total retinyl palmitate in the various milks tested. The variation in the retention of vitamin A by caseins was probably explained by differences in the processing of different milk samples, including thermal treatment, the form of vitamin A emulsion used for fortification, and the point of fortification during processing. Unmodified casein micelles have a strong intrinsic affinity toward the binding of vitamin A used to fortify commercially available skim milks. PMID:23261375

  19. Cationic drug-based self-assembled polyelectrolyte complex micelles: Physicochemical, pharmacokinetic, and anticancer activity analysis.

    PubMed

    Ramasamy, Thiruganesh; Poudel, Bijay Kumar; Ruttala, Himabindu; Choi, Ju Yeon; Hieu, Truong Duy; Umadevi, Kandasamy; Youn, Yu Seok; Choi, Han-Gon; Yong, Chul Soon; Kim, Jong Oh

    2016-10-01

    Nanofabrication of polymeric micelles through self-assembly of an ionic block copolymer and oppositely charged small molecules has recently emerged as a promising method of formulating delivery systems. The present study therefore aimed to investigate the interaction of cationic drugs doxorubicin (DOX) and mitoxantrone (MTX) with the anionic block polymer poly(ethylene oxide)-block-poly(acrylic acid) (PEO-b-PAA) and to study the influence of these interactions on the pharmacokinetic stability and antitumor potential of the formulated micelles in clinically relevant animal models. To this end, individual DOX and MTX-loaded polyelectrolyte complex micelles (PCM) were prepared, and their physicochemical properties and pH-responsive release profiles were studied. MTX-PCM and DOX-PCM exhibited a different release profile under all pH conditions tested. MTX-PCM exhibited a monophasic release profile with no initial burst, while DOX-PCM exhibited a biphasic release. DOX-PCM showed a higher cellular uptake than that shown by MTX-PCM in A-549 cancer cells. Furthermore, DOX-PCM induced higher apoptosis of cancer cells than that induced by MTX-PCM. Importantly, both MTX-PCM and DOX-PCM showed prolonged blood circulation. MTX-PCM improved the AUCall of MTX 4-fold compared to a 3-fold increase by DOX-PCM for DOX. While a definite difference in blood circulation was observed between MTX-PCM and DOX-PCM in the pharmacokinetic study, both MTX-PCM and DOX-PCM suppressed tumor growth to the same level as the respective free drugs, indicating the potential of PEGylated polymeric micelles as effective delivery systems. Taken together, our results show that the nature of interactions of cationic drugs with the polyionic copolymer can have a tremendous influence on the biological performance of a delivery system. PMID:27318960

  20. Cationic drug-based self-assembled polyelectrolyte complex micelles: Physicochemical, pharmacokinetic, and anticancer activity analysis.

    PubMed

    Ramasamy, Thiruganesh; Poudel, Bijay Kumar; Ruttala, Himabindu; Choi, Ju Yeon; Hieu, Truong Duy; Umadevi, Kandasamy; Youn, Yu Seok; Choi, Han-Gon; Yong, Chul Soon; Kim, Jong Oh

    2016-10-01

    Nanofabrication of polymeric micelles through self-assembly of an ionic block copolymer and oppositely charged small molecules has recently emerged as a promising method of formulating delivery systems. The present study therefore aimed to investigate the interaction of cationic drugs doxorubicin (DOX) and mitoxantrone (MTX) with the anionic block polymer poly(ethylene oxide)-block-poly(acrylic acid) (PEO-b-PAA) and to study the influence of these interactions on the pharmacokinetic stability and antitumor potential of the formulated micelles in clinically relevant animal models. To this end, individual DOX and MTX-loaded polyelectrolyte complex micelles (PCM) were prepared, and their physicochemical properties and pH-responsive release profiles were studied. MTX-PCM and DOX-PCM exhibited a different release profile under all pH conditions tested. MTX-PCM exhibited a monophasic release profile with no initial burst, while DOX-PCM exhibited a biphasic release. DOX-PCM showed a higher cellular uptake than that shown by MTX-PCM in A-549 cancer cells. Furthermore, DOX-PCM induced higher apoptosis of cancer cells than that induced by MTX-PCM. Importantly, both MTX-PCM and DOX-PCM showed prolonged blood circulation. MTX-PCM improved the AUCall of MTX 4-fold compared to a 3-fold increase by DOX-PCM for DOX. While a definite difference in blood circulation was observed between MTX-PCM and DOX-PCM in the pharmacokinetic study, both MTX-PCM and DOX-PCM suppressed tumor growth to the same level as the respective free drugs, indicating the potential of PEGylated polymeric micelles as effective delivery systems. Taken together, our results show that the nature of interactions of cationic drugs with the polyionic copolymer can have a tremendous influence on the biological performance of a delivery system.

  1. Removal of diclofenac potassium from wastewater using clay-micelle complex.

    PubMed

    Karaman, Rafik; Khamis, Mustafa; Quried, Mohannad; Halabieh, Rawan; Makharzeh, Iman; Manassra, Adnan; Abbadi, Jehad; Qtait, Alaa; Bufo, Sabino Aurelio; Nasser, Ahmed; Nir, Shlomo

    2012-06-01

    The presence of an ionized carboxyl group in the widely used non-steroidal anti-inflammatory (NSAID) drug diclofenac potassium results in a high mobility of diclofenac and in its low sorption under conditions of slow sand filtration or subsoil passage. No diclofenac degradation was detected in pure water or sludge during one month. Tertiary treatments of wastewater indicated that the effective removal of diclofenac was by reverse osmosis, but the removal by activated carbon was less satisfactory. This study presents an efficient method for the removal of diclofenac from water by micelle-clay composites that are positively charged, have a large surface area and include large hydrophobic domains. Adsorption of diclofenac in dispersion by charcoal and a composite micelle (otadecyltrimethylammonium [ODTMA] and clay [montmorillonite]) was investigated. Analysis by the Langmuir isotherm revealed that charcoal had a somewhat larger number of adsorption sites than the composite, but the latter had a significantly larger binding affinity for diclofenac. Filtration experiments on a solution containing 300 ppm diclofenac demonstrated poor removal by activated carbon, in contrast to very efficient removal by micelle-clay filters. In the latter case the weight of removed diclofenac exceeded half that of ODTMA in the filter. Filtration of diclofenac solutions at concentrations of 8 and 80 ppb yielded almost complete removal at flow rates of 30 and 60 mL min(-1). One kilogram of ODTMA in the micelle-clay filter has been estimated to remove more than 99% of diclofenac from a solution of 100 ppb during passage of more than 100 m3.

  2. Smart micelle@polydopamine core-shell nanoparticles for highly effective chemo-photothermal combination therapy.

    PubMed

    Zhang, Ruirui; Su, Shishuai; Hu, Kelei; Shao, Leihou; Deng, Xiongwei; Sheng, Wang; Wu, Yan

    2015-12-14

    In this investigation, we have designed and synthesized a novel core-shell polymer nanoparticle system for highly effective chemo-photothermal combination therapy. A nanoscale DSPE-PEG micelle encapsulating doxorubicin (Dox-M) was designed as a core, and then modified by a polydopamine (PDA) shell for photothermal therapy and bortezomib (Btz) administration (Dox-M@PDA-Btz). The facile conjugation of Btz to the catechol-containing PDA shell can form a reversible pH-sensitive boronic acid-catechol conjugate to create a stimuli-responsive drug carrier system. As expected, the micelle@PDA core-shell nanoparticles exhibited satisfactory photothermal efficiency, which has potential for thermal ablation of malignant tissues. In addition, on account of the PDA modification, both Dox and Btz release processes were pH-dependent and NIR-dependent. Both in vitro and in vivo studies illustrated that the Dox-M@PDA-Btz nanoparticles coupled with laser irradiation could enhance the cytotoxicity, and thus combinational therapy efficacy was achieved when integrating Dox, Btz, and PDA into a single nanoplatform. Altogether, our current study indicated that the micelle@polydopamine core-shell nanoparticles could be applied for NIR/pH-responsive sustained-release and synergized chemo-photothermal therapy for breast cancer. PMID:26556382

  3. Temperature responsive complex coacervate core micelles with a PEO and PNIPAAm corona.

    PubMed

    Voets, Ilja K; Moll, Puck M; Aqil, Abdelhafid; Jérôme, Christine; Detrembleur, Christophe; Waard, Pieter de; Keizer, Arie de; Stuart, Martien A Cohen

    2008-09-01

    In aqueous solutions at room temperature, poly( N-methyl-2-vinyl pyridinium iodide)- block-poly(ethylene oxide), P2MVP 38- b-PEO 211 and poly(acrylic acid)- block-poly(isopropyl acrylamide), PAA 55- b-PNIPAAm 88 spontaneously coassemble into micelles, consisting of a mixed P2MVP/PAA polyelectrolyte core and a PEO/PNIPAAm corona. These so-called complex coacervate core micelles (C3Ms), also known as polyion complex (PIC) micelles, block ionomer complexes (BIC), and interpolyelectrolyte complexes (IPEC), respond to changes in solution pH and ionic strength as their micellization is electrostatically driven. Furthermore, the PNIPAAm segments ensure temperature responsiveness as they exhibit lower critical solution temperature (LCST) behavior. Light scattering, two-dimensional 1H NMR nuclear Overhauser effect spectrometry, and cryogenic transmission electron microscopy experiments were carried out to investigate micellar structure and solution behavior at 1 mM NaNO 3, T = 25, and 60 degrees C, that is, below and above the LCST of approximately 32 degrees C. At T = 25 degrees C, C3Ms were observed for 7 < pH < 12 and NaNO 3 concentrations below approximately 105 mM. The PEO and PNIPAAm chains appear to be (randomly) mixed within the micellar corona. At T = 60 degrees C, onion-like complexes are formed, consisting of a PNIPAAm inner core, a mixed P2MVP/PAA complex coacervate shell, and a PEO corona.

  4. Self-assembled 20-nm (64)Cu-micelles enhance accumulation in rat glioblastoma.

    PubMed

    Seo, Jai Woong; Ang, JooChuan; Mahakian, Lisa M; Tam, Sarah; Fite, Brett; Ingham, Elizabeth S; Beyer, Janine; Forsayeth, John; Bankiewicz, Krystof S; Xu, Ting; Ferrara, Katherine W

    2015-12-28

    There is an urgent need to develop nanocarriers for the treatment of glioblastoma multiforme (GBM). Using co-registered positron emission tomography (PET) and magnetic resonance (MR) images, here we performed systematic studies to investigate how a nanocarrier's size affects the pharmacokinetics and biodistribution in rodents with a GBM xenograft. In particular, highly stable, long-circulating three-helix micelles (3HM), based on a coiled-coil protein tertiary structure, were evaluated as an alternative to larger nanocarriers. While the circulation half-life of the 3HM was similar to 110-nm PEGylated liposomes (t1/2=15.5 and 16.5h, respectively), the 20-nm micelles greatly enhanced accumulation within a U87MG xenograft in nu/nu rats after intravenous injection. After accounting for tumor blood volume, the extravasated nanoparticles were quantified from the PET images, yielding ~0.77%ID/cm(3) for the micelles and 0.45%ID/cm(3) for the liposomes. For GBM lesions with a volume greater than 100mm(3), 3HM accumulation was enhanced both within the detectable tumor and in the surrounding brain parenchyma. Further, the nanoparticle accumulation was shown to extend to the margins of the GBM xenograft. In summary, 3HM provides an attractive nanovehicle for carrying treatment to GBM.

  5. Boronic acid shell-crosslinked dextran-b-PLA micelles for acid-responsive drug delivery.

    PubMed

    Zhao, Ziwei; Yao, Xuemei; Zhang, Zhe; Chen, Li; He, Chaoliang; Chen, Xuesi

    2014-11-01

    Herein, 3-carboxy-5-nitrophenylboronic acid (CNPBA) shell-crosslinked micelles based on amphiphilic dextran-block-polylactide (Dex-b-PLA) are prepared and used for efficient intracellular drug deliveries. Due to the reversible pH-dependent binding with diols to form boronate esters, CNPBA modified Dex-b-PLA shows excellent pH-sensitivity. In neutral aqueous conditions, CNPBA-Dex-b-PLA forms shell-crosslinked micelles to enable DOX loading, while in acid conditions, the boronate esters hydrolyze and the micelles de-crosslink to release loaded DOX. In vitro release studies indicate that the release of the DOX cargo is minimized at physiological conditions, while there is a burst release in response to low pHs. The cell viability of CNPBA-Dex-b-PLA investigated by MTT assay was more than 90%, indicating that, as a drug delivery system, CNPBA-Dex-b-PLA has good cytocompatibility. These features suggest that the pH-responsive biodegradable CNPBA-Dex-b-PLA can efficiently load and deliver DOX into tumor cells and enhance the inhibition of cellular proliferation in vitro, providing a favorable platform as a drug delivery system for cancer therapy.

  6. Heat-induced gelation of casein micelles in aqueous suspensions at different pH.

    PubMed

    Thomar, Peggy; Nicolai, Taco

    2016-10-01

    Heat-induced gelation of casein micelles in aqueous solution was investigated between pH 5.2 and pH 6.7 over a wide range of protein concentrations (C=25-160gL(-1)). For C≥40gL(-1) the casein micelles rapidly formed a self-supporting gel above a critical temperature (Tc). At C=160gL(-1), Tc decreased from 90°C at pH 6.5 to 30°C at pH 5.4 and increased with decreasing protein concentration. Oscillatory shear measurements during heating showed that the elastic modulus (Gel) of the gels increased strongly with increasing protein concentration, but was insensitive to the pH and the heating temperature except close to Tc where Gel decreased sharply with decreasing temperature. The microstructure of the gels was observed by confocal scanning laser microscopy. Heat-induced gelation of casein micelles was compared with that of sodium caseinate solutions free of calcium phosphate. PMID:27451368

  7. Overcoming tumor resistance to cisplatin through micelle-mediated combination chemotherapy.

    PubMed

    Zhou, Dongfang; Cong, Yuwei; Qi, Yanxin; He, Shasha; Xiong, Hejian; Wu, Yanjuan; Xie, Zhigang; Chen, Xuesi; Jing, Xiabin; Huang, Yubin

    2015-01-01

    The main obstacles to cancer therapy are the inability to target cancer cells and the acquired drug resistance after a period of chemotherapy. Reduced drug uptake and DNA repair are the two main mechanisms involved in cisplatin resistance. In the present investigation, canthaplatin, a Pt(iv) pro-drug of cisplatin and a protein phosphatase 2A (PP2A) inhibitor (4-(3-carboxy-7-oxa-bicyclo[2.2.1]heptane-2-carbonyl)piperazine-1-carboxylic acid tert-butyl ester), was designed and delivered using PEG-b-PLGA micelles for combination chemotherapy. Polymer/canthaplatin micelles facilitated the delivery of the drug into cancer cells through endocytosis and diminished DNA repair by PP2A inhibition, resulting in enhanced anti-tumor efficiency and excellent reversal ability of tumor resistance to cisplatin both in vitro and in vivo. Additionally, the polymer/canthaplatin micelles could prolong drug residence in the blood and decrease the side effects when compared to cisplatin.

  8. Goblet cell targeting nanoparticle containing drug-loaded micelle cores for oral delivery of insulin.

    PubMed

    Zhang, Peiwen; Xu, Yining; Zhu, Xi; Huang, Yuan

    2015-12-30

    Oral administration of insulin remains a challenge due to its poor enzymatic stability and inefficient permeation across epithelium. We herein developed a novel self-assembled polyelectrolyte complex nanoparticles by coating insulin-loaded dodecylamine-graft-γ-polyglutamic acid micelles with trimethyl chitosan (TMC). The TMC material was also conjugated with a goblet cell-targeting peptide to enhance the affinity of nanoparticles with epithelium. The developed nanoparticle possessed significantly enhanced colloid stability, drug protection ability and ameliorated drug release profile compared with graft copolymer micelles or ionic crosslinked TMC nanoparticles. For in vitro evaluation, Caco-2/HT29-MTX-E12 cell co-cultures, which composed of not only enterocyte-like cells but also mucus-secreting cells and secreted mucus layer, were applied to mimic the epithelium. Intracellular uptake and transcellular permeation of encapsulated drug were greatly enhanced for NPs as compared with free insulin or micelles. Goblet cell-targeting modification further increased the affinity of NPs with epithelium with changed cellular internalization mechanism. The influence of mucus on the cell uptake was also investigated. Ex vivo performed with rat mucosal tissue demonstrated that the nanoparticle could facilitate the permeation of encapsulated insulin across the intestinal epithelium. In vivo study preformed on diabetic rats showed that the orally administered nanoparticles elicited a prolonged hypoglycemic response with relative bioavailability of 7.05%.

  9. Toward Understanding Pore Formation and Mobility during Controlled Directional Solidification in a Microgravity Environment Investigation (PFMI)

    NASA Technical Reports Server (NTRS)

    Grugel, Richard N.; Anilkumar, A. V.; Luz, Paul; Jeter, Linda; Volz, Martin P.; Spivey, Reggie; Smith, G.

    2003-01-01

    The generation and inclusion of detrimental porosity, e.g., pipes and rattails can occur during controlled directional solidification processing. The origin of these defects is generally attributed to gas evolution and entrapment during solidification of the melt. On Earth, owing to buoyancy, an initiated bubble can rapidly rise through the liquid melt and pop at the surface; this is obviously not ensured in a low gravity or microgravity environment. Clearly, porosity generation and inclusion is detrimental to conducting any meaningful solidification-science studies in microgravity. Thus it is essential that model experiments be conducted in microgravity, to understand the details of the generation and mobility of porosity, so that methods can be found to eliminate it. In hindsight, this is particularly relevant given the results of the previous directional solidification experiments conducted in Space. The current International Space Station (ISS) Microgravity Science Glovebox (MSG) investigation addresses the central issue of porosity formation and mobility during controlled directional solidification processing in microgravity. The study will be done using a transparent metal-analogue material, succinonitrile (SCN) and succinonitrile-water 'alloys', so that direct observation and recording of pore generation and mobility can be made during the experiments. Succinonitrile is particularly well suited for the proposed investigation because it is transparent, it solidifies in a manner analogous to most metals, it has a convenient melting point, its material properties are well characterized and, it has been successfully used in previous microgravity experiments. The PFMI experiment will be launched on the UF-2, STS-111 flight. Highlighting the porosity development problem in metal alloys during microgravity processing, the poster will describe: (i) the intent of the proposed experiments, (ii) the theoretical rationale behind using SCN as the study material for

  10. Toward Understanding Pore Formation And Mobility During Controlled Directional Solidification In A Microgravity Environment Investigation (PFMI)

    NASA Technical Reports Server (NTRS)

    Grugel, R. N.; Anilkumar, A.; Luz, P.; Jeter, L.; Volz, M. P.; Spivey, R.; Smith, G. A.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    The generation and inclusion of detrimental porosity, e.g., "pipes" and "rattails" can occur during controlled directional solidification processing. The origin of these defects is generally attributed to gas evolution and entrapment during solidification of the melt. On Earth, owing to buoyancy, an initiated bubble can rapidly rise through the liquid melt and "pop" at the surface; this is obviously not ensured in a low gravity or microgravity environment. Clearly, porosity generation and inclusion is detrimental to conducting any meaningful solidification-science studies in microgravity. Thus it is essential that model experiments be conducted in microgravity, to understand the details of the generation and mobility of porosity, so that methods can be found to eliminate it. In hindsight, this is particularly relevant given the results of the previous directional solidification experiments conducted in Space. The current International Space Station (ISS) Microgravity Science Glovebox (MSG) investigation addresses the central issue of porosity formation and mobility during controlled directional solidification processing in microgravity. The study will be done using a transparent metal-analogue material, succinonitrile (SCN) and succinonitrile-water "alloys", so that direct observation and recording of pore generation and mobility can be made during the experiments. Succinonitrile is particularly well suited for the proposed investigation because it is transparent, it solidifies in a manner analogous to most metals, it has a convenient melting point, its material properties are well characterized and, it has been successfully used in previous microgravity experiments. The PFMI experiment will be launched on the UF-2, STS-111 flight. Highlighting the porosity development problem in metal alloys during microgravity processing, the poster will describe: (i) the intent of the proposed experiments, (ii) the theoretical rationale behind using SCN as the study material for

  11. Investigating hypoxia in aquatic environments: diverse approaches to addressing a complex phenomenon

    NASA Astrophysics Data System (ADS)

    Friedrich, J.; Janssen, F.; Aleynik, D.; Bange, H. W.; Boltacheva, N.; Çagatay, M. N.; Dale, A. W.; Etiope, G.; Erdem, Z.; Geraga, M.; Gilli, A.; Gomoiu, M. T.; Hall, P. O. J.; Hansson, D.; He, Y.; Holtappels, M.; Kirf, M. K.; Kononets, M.; Konovalov, S.; Lichtschlag, A.; Livingstone, D. M.; Marinaro, G.; Mazlumyan, S.; Naeher, S.; North, R. P.; Papatheodorou, G.; Pfannkuche, O.; Prien, R.; Rehder, G.; Schubert, C. J.; Soltwedel, T.; Sommer, S.; Stahl, H.; Stanev, E. V.; Teaca, A.; Tengberg, A.; Waldmann, C.; Wehrli, B.; Wenzhöfer, F.

    2014-02-01

    In this paper we provide an overview of new knowledge on oxygen depletion (hypoxia) and related phenomena in aquatic systems resulting from the EU-FP7 project HYPOX ("In situ monitoring of oxygen depletion in hypoxic ecosystems of coastal and open seas, and landlocked water bodies", http://www.hypox.net). In view of the anticipated oxygen loss in aquatic systems due to eutrophication and climate change, HYPOX was set up to improve capacities to monitor hypoxia as well as to understand its causes and consequences. Temporal dynamics and spatial patterns of hypoxia were analyzed in field studies in various aquatic environments, including the Baltic Sea, the Black Sea, Scottish and Scandinavian fjords, Ionian Sea lagoons and embayments, and Swiss lakes. Examples of episodic and rapid (hours) occurrences of hypoxia, as well as seasonal changes in bottom-water oxygenation in stratified systems, are discussed. Geologically driven hypoxia caused by gas seepage is demonstrated. Using novel technologies, temporal and spatial patterns of water-column oxygenation, from basin-scale seasonal patterns to meter-scale sub-micromolar oxygen distributions, were resolved. Existing multidecadal monitoring data were used to demonstrate the imprint of climate change and eutrophication on long-term oxygen distributions. Organic and inorganic proxies were used to extend investigations on past oxygen conditions to centennial and even longer timescales that cannot be resolved by monitoring. The effects of hypoxia on faunal communities and biogeochemical processes were also addressed in the project. An investigation of benthic fauna is presented as an example of hypoxia-devastated benthic communities that slowly recover upon a reduction in eutrophication in a system where naturally occurring hypoxia overlaps with anthropogenic hypoxia. Biogeochemical investigations reveal that oxygen intrusions have a strong effect on the microbially mediated

  12. An investigation of the close environment of β Cephei with the VEGA/CHARA interferometer

    NASA Astrophysics Data System (ADS)

    Nardetto, N.; Mourard, D.; Tallon-Bosc, I.; Tallon, M.; Berio, P.; Chapellier, E.; Bonneau, D.; Chesneau, O.; Mathias, P.; Perraut, K.; Stee, P.; Blazit, A.; Clausse, J. M.; Delaa, O.; Marcotto, A.; Millour, F.; Roussel, A.; Spang, A.; McAlister, H.; ten Brummelaar, T.; Sturmann, J.; Sturmann, L.; Turner, N.; Farrington, C.; Goldfinger, P. J.

    2011-01-01

    Context. High-precision interferometric measurements of pulsating stars help to characterize their close environment. In 1974, a close companion was discovered around the pulsating star β Cep using the speckle interferometry technique, and features at the limit of resolution (20 milli-arcsec or mas) of the instrument were mentioned that may be due to circumstellar material. β Cep has a magnetic field that might be responsible for a spherical shell or ring-like structure around the star as described by the MHD models. Aims: Using the visible recombiner VEGA installed on the CHARA long-baseline interferometer at Mt. Wilson, we aim to determine the angular diameter of β Cep and resolve its close environment with a spatial resolution up to 1 mas level. Methods: Medium spectral resolution (R = 6000) observations of β Cep were secured with the VEGA instrument over the years 2008 and 2009. These observations were performed with the S1S2 (30 m) and W1W2 (100 m) baselines of the array. Results: We investigated several models to reproduce our observations. A large-scale structure of a few mas is clearly detected around the star with a typical flux relative contribution of 0.23 ± 0.02. Our best model is a co-rotational geometrical thin ring around the star as predicted by magnetically-confined wind shock models. The ring inner diameter is 8.2 ± 0.8 mas and the width is 0.6 ± 0.7 mas. The orientation of the rotation axis on the plane of the sky is PA = 60 ± 1 deg, while the best fit of the mean angular diameter of β Cep gives ΦUD[ V] = 0.22 ± 0.05 mas. Our data are compatible with the predicted position of the close companion of β Cep. Conclusions: These results bring additional constraints on the fundamental parameters and on the future MHD and asteroseismological models of the star.

  13. Structuration in the Interface of Direct and Reversed Micelles of Sucrose Esters, Studied by Fluorescent Techniques

    PubMed Central

    Sandoval, Catalina; Ortega, Anakenna; Sanchez, Susana A.; Morales, Javier; Gunther, German

    2015-01-01

    Background Reactors found in nature can be described as micro-heterogeneous systems, where media involved in each micro-environment can behave in a markedly different way compared with the properties of the bulk solution. The presence of water molecules in micro-organized assemblies is of paramount importance for many chemical processes, ranging from biology to environmental science. Self-organized molecular assembled systems are frequently used to study dynamics of water molecules because are the simplest models mimicking biological membranes. The hydrogen bonds between sucrose and water molecules are described to be stronger (or more extensive) than the ones between water molecules themselves. In this work, we studied the capability of sucrose moiety, attached to alkyl chains of different length, as a surface blocking agent at the water-interface and we compared its properties with those of polyethylenglycol, a well-known agent used for this purposes. Published studies in this topic mainly refer to the micellization process and the stability of mixed surfactant systems using glycosides. We are interested in the effect induced by the presence of sucrose monoesters at the interface (direct and reverse micelles) and at the palisade (mixtures with Triton X-100). We believe that the different functional group (ester), the position of alkyl chain (6-O) and the huge capability of sucrose to interact with water will dramatically change the water structuration at the interface and at the palisade, generating new possibilities for technological applications of these systems. Results Our time resolved and steady state fluorescence experiments in pure SEs micelles show that sucrose moieties are able to interact with a high number of water molecules promoting water structuration and increased viscosity. These results also indicate that the barrier formed by sucrose moieties on the surface of pure micelles is more effective than the polyoxyethylene palisade of Triton X-100

  14. Colloidal micelles of block copolymers as nanoreactors, templates for gold nanoparticles, and vehicles for biomedical applications.

    PubMed

    Bakshi, Mandeep Singh

    2014-11-01

    Target drug delivery methodology is becoming increasingly important to overcome the shortcomings of conventional drug delivery absorption method. It improves the action time with uniform distribution and poses minimum side effects, but is usually difficult to design to achieve the desire results. Economically favorable, environment friendly, multifunctional, and easy to design, hybrid nanomaterials have demonstrated their enormous potential as target drug delivery vehicles. A combination of both micelles and nanoparticles makes them fine target delivery vehicles in a variety of biological applications where precision is primarily required to achieve the desired results as in the case of cytotoxicity of cancer cells, chemotherapy, and computed tomography guided radiation therapy.

  15. Choline Derivate-Modified Doxorubicin Loaded Micelle for Glioma Therapy.

    PubMed

    Li, Jianfeng; Yang, Huiying; Zhang, Yujie; Jiang, Xutao; Guo, Yubo; An, Sai; Ma, Haojun; He, Xi; Jiang, Chen

    2015-09-30

    Ligand-mediated polymeric micelles have enormous potential for improving the efficacy of glioma therapy. Linear-dendritic drug-polymer conjugates composed of doxorubicin (DOX) and polyethylene glycol (PEG) were synthesized with or without modification of choline derivate (CD). The resulting MeO-PEG-DOX8 and CD-PEG-DOX8 could self-assemble into polymeric micelles with a nanosized diameter around 30 nm and a high drug loading content up to 40.6 and 32.3%, respectively. The optimized formulation 20% CD-PEG-DOX8 micelles had superior cellular uptake and antitumor activity against MeO-PEG-DOX8 micelles. The subcellular distribution using confocal study revealed that 20% CD-PEG-DOX8 micelles preferentially accumulated in the mitochondria. Pharmacokinetic study showed area under the plasma concentration-time curve (AUC0-t) and Cmax for 20% CD-PEG-DOX8 micelles and DOX solution were 1336.58 ± 179.43 mg/L·h, 96.35 ± 3.32 mg/L and 1.40 ± 0.19 mg/L·h, 1.15 ± 0.25 mg/L, respectively. Biodistribution study showed the DOX concentration of 20% CD-PEG-DOX8 micelles treated group at 48 h was 2.37-fold higher than that of MeO-PEG-DOX8 micelles treated group at 48 h and was 24 fold-higher than that of DOX solution treated group at 24 h. CD-PEG-DOX8 micelles (20%) were well tolerated with reduced cardiotoxicity, as evaluated in the body weight change and HE staining studies, while they induced most significant antitumor activity with longest media survival time in an orthotopic mouse model of U87-luci glioblastoma model as displayed in the bioluminescence imaging and survival curve studies. Our findings consequently indicated that 20% CD-PEG-DOX8 micelles are promising drug delivery system for glioma chemotherapy. PMID:26356793

  16. Investigating Learners' Attitudes toward Virtual Reality Learning Environments: Based on a Constructivist Approach

    ERIC Educational Resources Information Center

    Huang, Hsiu-Mei; Rauch, Ulrich; Liaw, Shu-Sheng

    2010-01-01

    The use of animation and multimedia for learning is now further extended by the provision of entire Virtual Reality Learning Environments (VRLE). This highlights a shift in Web-based learning from a conventional multimedia to a more immersive, interactive, intuitive and exciting VR learning environment. VRLEs simulate the real world through the…

  17. Self-Regulated Learning in Technology Enhanced Learning Environments: An Investigation with University Students

    ERIC Educational Resources Information Center

    Lenne, Dominique; Abel, Marie-Helene; Trigano, Philippe; Leblanc, Adeline

    2008-01-01

    In Technology Enhanced Learning Environments, self-regulated learning (SRL) partly relies on the features of the technological tools. The authors present two environments they designed in order to facilitate SRL: the first one (e-Dalgo) is a website dedicated to the learning of algorithms and computer programming. It is structured as a classical…

  18. A Prospective Study Investigating the Links among Classroom Environment, School Connectedness, and Depressive Symptoms in Adolescents

    ERIC Educational Resources Information Center

    Shochet, Ian M.; Smith, Coral L.

    2014-01-01

    School connectedness and classroom environment have both been strongly linked to depressive symptoms, but their interrelation is unclear. We tested whether school connectedness mediated the link between classroom environment and depressive symptoms. A sample of 504 Australian seventh-and eighth-grade students completed the Classroom Environment…

  19. Investigating Effects of Problem-Based versus Lecture-Based Learning Environments on Student Motivation

    ERIC Educational Resources Information Center

    Wijnia, Lisette; Loyens, Sofie M. M.; Derous, Eva

    2011-01-01

    This study examines the effects of two learning environments (i.e., problem-based learning [PBL] versus lecture-based [LB] environments) on undergraduates' study motivation. Survey results demonstrated that PBL students scored higher on competence but did not differ from LB students on autonomous motivation. Analyses of focus groups further…

  20. Agent-Based Learning Environments as a Research Tool for Investigating Teaching and Learning.

    ERIC Educational Resources Information Center

    Baylor, Amy L.

    2002-01-01

    Discusses intelligent learning environments for computer-based learning, such as agent-based learning environments, and their advantages over human-based instruction. Considers the effects of multiple agents; agents and research design; the use of Multiple Intelligent Mentors Instructing Collaboratively (MIMIC) for instructional design for…

  1. Investigation of Primary Dew-Point Saturator Efficiency in Two Different Thermal Environments

    NASA Astrophysics Data System (ADS)

    Zvizdic, D.; Heinonen, M.; Sestan, D.

    2015-08-01

    The aim of this paper is to describe the evaluation process of the performance of the low-range saturator (LRS), when exposed to two different thermal environments. The examined saturator was designed, built, and tested at MIKES (Centre for Metrology and Accreditation, Finland), and then transported to the Laboratory for Process Measurement (LPM) in Croatia, where it was implemented in a new dew-point calibration system. The saturator works on a single-pressure-single-pass generation principle in the dew/frost-point temperature range between and . The purpose of the various tests performed at MIKES was to examine the efficiency and non-ideality of the saturator. As a test bath facility in Croatia differs from the one used in Finland, the same tests were repeated at LPM, and the effects of different thermal conditions on saturator performance were examined. Thermometers, pressure gauges, an air preparation system, and water for filling the saturator at LPM were also different than those used at MIKES. Results obtained by both laboratories indicate that the efficiency of the examined saturator was not affected either by the thermal conditions under which it was tested or by equipment used for the tests. Both laboratories concluded that LRS is efficient enough for a primary realization of the dew/frost-point temperature scale in the range from to , with flow rates between and . It is also shown that a considerable difference of the pre-saturator efficiency, indicated by two laboratories, did not have influence to the overall performance of the saturator. The results of the research are presented in graphical and tabular forms. This paper also gives a brief description of the design and operation principle of the investigated low-range saturator.

  2. SHERLOC: Scanning Habitable Environments With Raman & Luminescence for Organics & Chemicals, an Investigation for 2020

    NASA Astrophysics Data System (ADS)

    Beegle, L. W.; Bhartia, R.; DeFlores, L. P.; Asher, S. A.; Burton, A. S.; Clegg, S. M.; Conrad, P. G.; Edgett, K. S.; Ehlmann, B. L.; Langenhorst, F.; Fries, M.; Nealson, K. H.; Popp, J.; Sobron, P.; Steele, A.; Wiens, R. C.; Williford, K. H.

    2014-12-01

    The Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals SHERLOC investigation was recently selected for the Mars 2020 integrated payload. SHERLOC enables non-contact, spatially resolved, and highly sensitivity detection and characterization of organics and minerals in the Martian surface and near subsurface. SHERLOC is an arm-mounted, Deep UV (DUV) resonance Raman and fluorescence spectrometer utilizing a 248.6-nm DUV laser and 50 micron spot size. The laser is integrated to an autofocusing/scanning optical system, and co-boresighted to a context imager with a spatial resolution of 30 μm. SHERLOC operates over a 7 × 7 mm area through use of an internal scanning mirror. The 500 micron depth of view in conjunction with the MAHLI heritage autofocus mechanisms enables arm placements from 48 ±12.5 mm above natural or abraded surfaces without the need for rover arm repositioning/movement. Additionally, borehole interiors to a depth of ~25 mm, at angles from normal incidence to ±20 degrees, can be analyzed. Deep UV induced native fluorescence is very sensitive to condensed carbon and aromatic organics, enabling detection at or below 10-6 w/w (1 ppm) at <100 µm spatial scales. SHERLOC's deep UV resonance Raman enables detection and classification of aromatic and aliphatic organics with sensitivities of 10-2 to below 10-4 w/w at <50 µm spatial scales. In addition to organics, the deep UV Raman enables detection and classification of minerals relevant to aqueous chemistry with grain sizes below 20 µm grains. The instrument goals are to assess past aqueous history, detect the presence and preservation of potential biosignatures, and to support selection of return samples. To do this, SHERLOC will measure CHNOPS-containing mineralogy, measure the distribution and type of organics preserved at the surface, and correlate them to textural features.

  3. Archival Legacy Investigation of Circumstellar Environments (ALICE): Overview and first results

    NASA Astrophysics Data System (ADS)

    Choquet, E.; Soummer, R.; Pueyo, L.; Perrin, M.; Chen, C.; Debes, J.; Golimowski, D. A.; Hagan, J. B.; Hines, D. C.; Marois, C.; Mawet, D.; Mittal, T.; Moerchen, M.; N'Diaye, M.; Rajan, A.; Reid, N.; Wolff, S.; Schneider, G.

    2014-03-01

    We are currently conducting a comprehensive and consistent reprocessing of archival HST-NICMOS coronagraphic surveys using advanced PSF subtraction methods, entitled the Archival Legacy Investigation of Circumstellar Environments program (ALICE, HST/AR 12652). This virtual campaign of about 400 HST orbits has already produced numerous new detections of previously unidentified point sources and circumstellar structures. We present five newly spatially resolved debris disks revealed in scattered light by our analysis of the archival data. Three of these disks (HD 30447, HD 35841, and HD 141943) appear to be edge-on, the fourth (HD 191089) appears to be an asymmetric inclined ring, and the fifth, HD 202917 confirms a dramatic asymmetric arc that had previously been detected in ACS GTO observations. These images provide new views of material around young solar-type stars at ages corresponding to the period of terrestrial planet formation in our solar system. We have also detected several new candidate substellar companions, for which there is an ongoing followup campaign, and discuss preliminary statistical constraints ALICE places on the occurrence of brown dwarf and exo-planet companions around nearby stars. Since the methods developed as part of ALICE are directly applicable to future missions (JWST, AFTA coronagraph) we emphasize the importance of devising optimal PSF subtraction methods for upcoming coronagraphic imaging missions. We describe efforts in defining direct imaging highlevel science products (HLSP) standards that can be applicable to other coronagraphic campaigns, including ground-based (e.g., Gemini Planet Imager), and future space instruments (e.g., JWST). ALICE will deliver a first release of HLSPs to the community through the MAST archive at STScI in 2014.

  4. Investigating playa surface textures: The impact of chemistry and environment on surface morphology and dust

    NASA Astrophysics Data System (ADS)

    Tollerud, H. J.; Fantle, M. S.

    2010-12-01

    Mineral dust is an important component of geochemical cycles, but its impact on those cycles is not thoroughly understood. For instance, dust inputs to the ocean have been suggested to affect the iron cycle by stimulating natural iron fertilization, which then could modify climate. The influence of dust on geochemical cycles is determined by the chemical and mineralogical composition of dust inputs, which is governed in turn by the composition of dust source regions. A loose, unconsolidated surface texture is more easily ablated by wind, and so a location where composition and environmental characteristics encourage this type of surface is more likely to produce dust and influence geochemical cycles. Also, if evaporation concentrates evaporites such as calcite at the surface of a dust producing region, dust Ca concentrations are likely to be higher. Playas can be regionally significant dust source regions, and they are amenable to study as their surface textures often vary significantly across small areas. This study investigates surface processes experimentally, and compares the results to observations of surface texture in a natural playa system (the Black Rock Desert, Nevada). We dry surfaces with 25% to 75% clay and quartz at 40°C for approximately a day, wet the surface to simulate rain, and then repeat the cycle multiple times. We estimate surface roughness, measure surface strength with a penetrometer, and investigate thermal characteristics with an IR camera (wavelength range 8-12μm). We find that textures similar to those in playas can be reproduced with cycles of wetting and drying, such as might occur in an arid environment with intermittent rain. We investigate the addition of calcite and halite, since their precipitation potentially can disrupt the clay surfaces through the formation and expansion of crystals, thereby linking the chemical composition with the disruption of a strong surface texture and an increased chance of dust production. In the

  5. Non-ionic micelles and encapsulation.

    NASA Astrophysics Data System (ADS)

    Alexandridis, Paschalis

    2007-03-01

    The development of self-assembly as a useful approach to the synthesis and manufacturing of complex systems and materials is a central theme in our research. Amphiphilic block copolymers of the poly(ethylene oxide)-poly(propylene oxide) (PEO-PPO) family (commercially available as Poloxamers) are well-known for self-assembling into (core-shell spherical) micelles and (cubic, hexagonal, and lamellar) lyotropic liquid crystals in water. We are interested on how the aqueous phase behavior and structure of these non-ionic polymeric amphiphiles can be modulated by the addition of organic solvents or solutes. Our studies (i) probe the amphiphile organization in both micellar solutions and lyotropic liquid crystals, (ii) combine macroscopic observations (e.g., concentration-temperature micellization phase boundaries, ternary isothermal amphiphile-water-cosolvent phase diagrams) with microscopic measurements (from small-angle neutron and X-ray scattering), and (iii) aim to relate the type of structure formed and its properties to the relative swelling of the polymer blocks and to the location of the solvent/solute in the amphiphile assembly. These studies address the following practical questions: What are the ``right'' components and conditions for self-assembly? What if the conditions are no longer ``right''? How can we ``help'' self-assembly? Modulation of structure-property relationships in amphiphile-containing media is central to formulation of pharmaceutics and personal care products.

  6. 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

  7. Investigation of Pressurized Entrained-Flow Kraft Black Liquor Gasification in an Industrially Relevant Environment

    SciTech Connect

    Kevin Whitty

    2008-06-30

    The University of Utah's project 'Investigation of Pressurized Entrained-Flow Kraft Black Liquor Gasification in an Industrially Relevant Environment' (U.S. DOE Cooperative Agreement DE-FC26-04NT42261) was a response to U.S. DOE/NETL solicitation DE-PS36-04GO94002, 'Biomass Research and Development Initiative' Topical Area 4-Kraft Black Liquor Gasification. The project began September 30, 2004. The objective of the project was to improve the understanding of black liquor conversion in high pressure, high temperature reactors that gasify liquor through partial oxidation with either air or oxygen. The physical and chemical characteristics of both the gas and condensed phase were to be studied over the entire range of liquor conversion, and the rates and mechanisms of processes responsible for converting the liquor to its final smelt and syngas products were to be investigated. This would be accomplished by combining fundamental, lab-scale experiments with measurements taken using a new semi-pilot scale pressurized entrained-flow gasifier. As a result of insufficient availability of funds and changes in priority within the Office of Biomass Programs of the U.S. Department of Energy, the research program was terminated in its second year. In total, only half of the budgeted funding was made available for the program, and most of this was used during the first year for construction of the experimental systems to be used in the program. This had a severe impact on the program. As a consequence, most of the planned research was unable to be performed. Only studies that relied on computational modeling or existing experimental facilities started early enough to deliver useful results by the time to program was terminated Over the course of the program, small scale (approx. 1 ton/day) entrained-flow gasifier was designed and installed at the University of Utah's off-campus Industrial Combustion and Gasification Research Facility. The system is designed to operate at

  8. Sodium bromide induced micelle to vesicle transitions of newly synthesized anionic surface active ionic liquids based on dodecylbenzenesulfonate.

    PubMed

    Rao, K Srinivasa; Gehlot, Praveen Singh; Gupta, Hariom; Drechsler, Markus; Kumar, Arvind

    2015-03-19

    Dodecylbenezenesulfonate-based anionic surface active ionic liquids (DBS-ILs) paired with onium cations, n-butyltrimethylammonium ([N1114]), 1-butyl-3-methylimidazolium ([C4mim]), and N-butylpyridinium ([C4Py]) have been synthesized. DBS-ILs were found to be highly surface active having critical micelle concentration (CMC) lower than that of their conventional analogue sodium dodecylbenezenesulfonate ([Na][DBS]). The CMC values of DBS-ILs were determined from surface tension (ST) and isothermal titration calorimetry (ITC). DBS-ILs formed micelles predominantly in the aqueous medium, and unlike [Na]DBS, the micelles of DBS-ILs could be transformed into vesicles with the addition of sodium bromide (NaBr). Micelle to vesicle transitions (MVTs) were evidenced from dynamic light scattering (DLS), turbidity, proton nuclear magnetic resonance ((1)H NMR), and cryo-TEM techniques. Thermodynamics of aggregation was investigated from ITC which indicated that the aggregation process is primarily driven by the entropy factor. The formation of a vesicle upon addition of NaBr has been accounted to the increased electrostatic interactions between the less hydrated sulfonate headgroup and the more populated bigger sized counterions along with the favored cation-π or π-π interactions between them as evidenced from 2D-NOESY NMR experiments. The stimuli-responsive morphological transitions in the self-assembly of the reported anionic surface active ionic liquids (SAILs) will be useful for encapsulation and delivery of active (bio)molecules in the targeted biomedical applications.

  9. Competitive solubilization of phenol by cationic surfactant micelles in the range of low additive and surfactant concentrations.

    PubMed

    Chaghi, Radhouane; de Ménorval, Louis-Charles; Charnay, Clarence; Derrien, Gaëlle; Zajac, Jerzy

    2009-05-01

    Competitive interactions of phenol (PhOH) with micellar aggregates of hexadecyltrimethylammonium bromide (HTAB) against 1-butanol (BuOH) in aqueous solutions at surfactant concentrations close to the critical micelle concentration (CMC), BuOH concentration of 0.5 mmol kg(-1), and phenol contents of 1, 5, or 10 mmol kg(-1) have been investigated at 303 K by means of (1)H NMR spectroscopy, titration calorimetry, and solution conductimetry. The solubilization loci for phenol were deduced from the composition-dependence of the (1)H chemical shifts assigned to various protons in the surfactant and additive units. Since in pure HTAB solutions phenol is already in competition with Br(-), addition of 1 mmol kg(-1) NaBr to the system weakens the phenol competitiveness. The presence of butanol in the HTAB micelles causes phenol to penetrate deeper toward the hydrophobic micelle core. For higher phenol contents, the butanol molecules are constrained to remain in the bulk solution and are progressively replaced within the HTAB micelles by the aromatic units. The competitive character of phenol solubilization against butanol is well supported by changes in the thermodynamic parameters of HTAB micellization in the presence of both of the additives.

  10. Thermodynamically stable vesicle formation and vesicle-to-micelle transition of single-tailed anionic surfactant in water.

    PubMed

    Sakai, Takaya; Ikoshi, Risa; Toshida, Natsuko; Kagaya, Mariko

    2013-05-01

    The aggregation behavior of sodium 3,6,9,12,15-pentaoxa-heptacosanoate (AEC4-Na) in aqueous solution with increase of the concentration at 25 °C was investigated using differential scanning calorimetry, equilibrium surface tension, solubilization of an oil-soluble dye, steady-state fluorescence, dynamic light scattering, and freeze-fractured transmission electron microscopy. Vesicle formation of AEC4-Na preceded micelle formation below the critical micelle concentration (cmc). The vesicle-to-micelle transition was observed through a narrow concentration region above the cmc. The mean diameters of the vesicles and micelles were not affected by the concentration. All solutions over a wide range of concentrations were homogeneously transparent with a low Krafft point below 0 °C. These results indicate that the AEC4-Na vesicles have a thermodynamically stable structure. Vesicle formation may be caused by a pseudobinary mixed surfactant system composed of monomeric AEC4-Na and an acid soap that consists of a dimer complex formed between AEC4-Na and unneutralized AEC4-Na. The thermodynamic stability would then result from the inhibition of close intermolecular aggregation and flexibility of the molecular shape in the vesicles due to the oxyethylene units in AEC4-Na.

  11. The therapeutic effect of methotrexate-conjugated Pluronic-based polymeric micelles on the folate receptor-rich tumors treatment

    PubMed Central

    Chen, Yanzuo; Zhang, Wei; Huang, YuKun; Gao, Feng; Sha, Xianyi; Lou, Kaiyan; Fang, Xiaoling

    2015-01-01

    The therapeutic effect of methotrexate (MTX)-conjugated Pluronic-based polymeric mixed micelles (F127/P105-MTX) on the folate receptor-overexpressing tumors treatment was investigated in this study. Due to its high structural similarity to folic acid and the high expression of folate receptor in most solid tumors, MTX serves as not only a cytotoxic agent but also a homing ligand. Cellular uptake and the endocytic mechanism studies of MTX-conjugated mixed micelles were performed in folate receptor-rich KBv and folate receptor-deficient A-549 cancer cells. Additionally, the efficacy and safety studies of F127/P105-MTX in KBv tumor-bearing mice were evaluated. Results indicate that F127/P105-MTX significantly enhanced the cellular uptake in KBv cells as compared to that of conventional non-MTX-conjugated mixed micelles. Moreover, the results showed that F127/P105-MTX can be internalized by both caveolae- and clathrin-mediated endocytosis in energy-dependent and folate receptor-dependent manners. The in vitro and in vivo antitumor efficacies of F127/P105-MTX were significantly enhanced in comparison with MTX-entrapped mixed micelles. Furthermore, no acute toxicities to hematological system and major organs have been observed after intravenous administration during the regimen. Therefore, our results suggest that F127/P105-MTX could be an effective and safe nano-drug delivery system for cancer therapy, especially for the folate receptor-rich cancer treatment. PMID:26150715

  12. Rapid analysis of water- and fat-soluble vitamins by electrokinetic chromatography with polymeric micelle as pseudostationary phase.

    PubMed

    Ni, Xinjiong; Xing, Xiaoping; Cao, Yuhua; Cao, Guangqun

    2014-11-28

    A novel polymeric micelle, formed by random copolymer poly (stearyl methacrylate-co-methacrylic acid) (P(SMA-co-MAA)) has been used as pseudostationary phase (PSP) in electrokinetic chromatography (EKC) for simultaneous and rapid determination of 11 kinds of water- and fat-soluble vitamins in this work. The running buffer consisting of 1% (w/v) P(SMA-co-MAA), 10% (v/v) 1-butanol, 20% (v/v) acetonitrile, and 30 mM Palitzsch buffer solution (pH 9.2) was applied to improve the selectivity and efficiency, as well as to shorten analysis time. 1-Butanol and acetonitrile as the organic solvent modifiers played the most important roles for rapid separation of these vitamins. The effects of organic solvents on microstructure of the polymeric micelle were investigated. The organic solvents swell the polymeric micelle by three folds, lower down the surface charge density and enhance the microenviromental polarity of the polymeric micelle. The 11 kinds of water- and fat-soluble vitamins could be baseline separated within 13 min. The method was applied to determine water- and fat-soluble vitamins in commercial vitamin sample; the recoveries were between 93% and 111% with the relative standard derivations (RSDs) less than 5%. The determination results matched the label claim.

  13. Structure of epidermal growth factor bound to perdeuterated dodecylphosphocholine micelles determined by two-dimensional NMR and simulated annealing calculations.

    PubMed

    Kohda, D; Inagaki, F

    1992-01-28

    The interaction of mouse epidermal growth factor (mEGF) with micelles of a phospholipid analogue, perdeuterated dodecylphosphocholine (DPC), was investigated by two-dimensional 1H NMR. Sequence-specific resonance assignments of the micelle-bound mEGF have been made, and the chemical shifts were compared with those in the absence of DPC. DPC induced large chemical shift changes of the resonances from the residues in the C-terminal tail (residues 46-53) but little perturbation on the residues in the main core (residues 1-45). Starting from the three-dimensional structure in the absence of DPC, micelle-bound structures were calculated using the program XPLOR with interproton distance data obtained from NOESY spectra recorded in the presence of DPC. The C-terminal tail of mEGF was found to change conformation to form an amphiphilic structure when bound to the micelles. It is possible that induced fit in the C-terminal tail of mEGF occurs upon binding to a putative hydrophobic pocket of the EGF receptor.

  14. Determination of thermodynamic potentials and the aggregation number for micelles with the mass-action model by isothermal titration calorimetry: A case study on bile salts.

    PubMed

    Olesen, Niels Erik; Westh, Peter; Holm, René

    2015-09-01

    The aggregation number (n), thermodynamic potentials (ΔG, ΔH, ΔS) and critical micelle concentration (CMC) for 6 natural bile salts were determined on the basis of both original and previously published isothermal titration calorimetry (ITC) data. Different procedures to estimate parameters of micelles with ITC were compared to a mass-action model (MAM) of reaction type: n⋅S⇌Mn. This analysis can provide guidelines for future ITC studies of systems behaving in accordance with this model such as micelles and proteins that undergo self-association to oligomers. Micelles with small aggregation numbers, as those of bile salts, are interesting because such small aggregates cannot be characterized as a separate macroscopic phase and the widely applied pseudo-phase model (PPM) is inaccurate. In the present work it was demonstrated that the aggregation number of micelles was constant at low concentrations enabling determination of the thermodynamic potentials by the MAM. A correlation between the aggregation number and the heat capacity was found, which implies that the dehydrated surface area of bile salts increases with the aggregation number. This is in accordance with Tanford's principles of opposing forces where neighbouring molecules in the aggregate are better able to shield from the surrounding hydrophilic environment when the aggregation number increases.

  15. Advanced Logging Investigations of Aquifers In Coastal Environments: The Aliance Project

    NASA Astrophysics Data System (ADS)

    Pezard, P. A.; Gouze, P.; Pinettes, P.; Riley, M.; Löw, S.; Montoto, M.; Sessarego, J.-P.; Deltombe, J.-P.; Broun, P.

    The goal of ALIANCE is to improve the investigation, characterisation and monitor- ing of coastal aquifers for vulnerability assessment. For this, ALIANCE proposes to develop a set of geophysical approaches for the quantitative evaluation of brine intru- sion and test them in two end-member sites in terms of hydrogeological behaviour. This includes state-of-the-art geological, geochemical, petrophysical, logging and hy- drological methods, and the design of 5 new geophysical and hydrodynamical log- ging/testing sensors yielding new data for model validation. The new measurement methods include 2 new sources for hydrological testing experi- ments: 1) Harmonic Hydraulic Endoscopy tool (H2E) for scanning the hydraulic con- ductivity and fracture network connectivity of low permeability aquifers such as frac- tured granite, using the harmonic pressure perturbation method, 2) Controlled Fluid Injection System (CoFIS) for controlled fluid injection in terms of pressure and salin- ity for the more permeable aquifers, and 3 new receivers with geophysical logging sen- sors: 3) Doppler TeleViewer (DopTV) for the identification of flowing fractures from Doppler analysis during testing experiments, and for the determination of the fluid flow velocity in the direction orthogonal to the borehole surface., 4) Slim Hydraulic Formation Tester (SHyFT) for the measurement of the in situ fluid pressure between packers or from a sealed path, fluid sampling from discrete horizons in the aquifer, and evaluation of dm-scale permeability during testing and sampling. 5) MUlti Sensor Electrical Tool " (MuSET) for the measurement of the downhole electrical sponta- neous potential (SP) in conjunction with fluid pressure, temperature and electrical conductivity. The two end-member sites will be set up with 50 to 100 meters deep boreholes for long-term experimentation, testing of the new tools, and validation of site-specific ex- 1 perimental and modelling protocols from µm- to 100 m-scale. The

  16. Experimental investigations of the lunar photoelectron environment and related dust dynamics

    NASA Astrophysics Data System (ADS)

    Dove, Adrienne Rathert

    Airless bodies in space are exposed to a variety of charging environments in which a balance of currents due to plasma processes determines the surface charge. In the inner solar system, photoelectron emission is the dominant charging process on sunlit surfaces due to the intense solar UV radiation. This results in a positive surface potential with a photoelectron sheath above the surface. Conversely, the unlit side of the body will charge negatively due the collection of the fast-moving solar wind electrons. The interaction of charged dust grains with these positively and negatively charged surfaces, and with the photoelectron and plasma sheaths, may explain the occurrence of dust lofting, levitation and transport above the lunar surface and on other airless bodies. This dust has been recognized as a potentially great hazard to future exploration of dusty planetary surfaces, due to its abrasive and adhesive nature. An initial investigation explores the mechanisms that control adhesion of dust grains to insulating and conducting surfaces. Unfortunately, there is little known about the mechanisms of adhesion on widely varying surface types, but van der Waals and electrostatic forces are the dominant forces that are taken into consideration in this study, which measures the adhesive forces between ≤ 25 μm JSC-1 lunar simulant grains and various surfaces vacuum using a centrifugal force detachment method. UV irradiation effects on surface adhesion were also examined. In order to better understand the plasma processes at work on sunlit surfaces, we have performed laboratory experiments to study the physics of photoelectron sheaths above both conducting and insulating surfaces in vacuum. The first set of experiments determines the characteristics of photoelectron sheaths generated over a conducting Zr surface that is large in comparison to the Debye length of the sheath. These characteristics are derived from cylindrical Langmuir probe measurements, and are compared

  17. The effect of co-delivery of paclitaxel and curcumin by transferrin-targeted PEG-PE-based mixed micelles on resistant ovarian cancer in 3-D spheroids and in vivo tumors.

    PubMed

    Sarisozen, Can; Abouzeid, Abraham H; Torchilin, Vladimir P

    2014-10-01

    Multicellular 3D cancer cell culture (spheroids) resemble to in vivo tumors in terms of shape, cell morphology, growth kinetics, gene expression and drug response. However, these characteristics cause very limited drug penetration into deeper parts of the spheroids. In this study, we used multi drug resistant (MDR) ovarian cancer cell spheroid and in vivo tumor models to evaluate the co-delivery of paclitaxel (PCL) and a potent NF-κB inhibitor curcumin (CUR). PCL and CUR were co-loaded into the polyethylene glycol-phosphatidyl ethanolamine (PEG-PE) based polymeric micelles modified with transferrin (TF) as the targeting ligand. Cytotoxicity, cellular association and accumulation into the deeper layers were investigated in the spheroids and compared with the monolayer cell culture. Comparing to non-targeted micelles, flow cytometry and confocal imaging proved significantly deeper and higher micelle penetration into the spheroids with TF-targeting. Both in monolayers and in spheroids, PCL cytotoxicity was significantly increased when co-delivered with CUR in non-targeted micelles or as single agent in TF-targeted micelles, whereas TF-modification of co-loaded micelles did not further enhance the cytotoxicity. In vivo tumor inhibition studies showed good correlation with the 3D cell culture experiments, which suggests the current spheroid model can be used as an intermediate model for the evaluation of co-delivery of anticancer compounds in targeted micelles. PMID:25016976

  18. The effect of co-delivery of paclitaxel and curcumin by transferrin-targeted PEG-PE-based mixed micelles on resistant ovarian cancer in 3-D spheroids and in vivo tumors

    PubMed Central

    Sarisozen, Can; Abouzeid, Abraham H.; Torchilin, Vladimir P.

    2014-01-01

    Multicellular 3D cancer cell culture (spheroids) resemble to in vivo tumors in terms of shape, cell morphology, growth kinetics, gene expression and drug response. However, these characteristics cause very limited drug penetration into deeper parts of the spheroids. In this study, we used multi drug resistant (MDR) ovarian cancer cell spheroid and in vivo tumor models to evaluate the co-delivery of paclitaxel (PCL) and a potent NF-κB inhibitor curcumin (CUR). PCL and CUR were co-loaded into the polyethylene glycol-phosphatidyl ethanolamine (PEG-PE) based polymeric micelles modified with Transferrin (TF) as the targeting ligand. Cytotoxicity, cellular association and accumulation into the deeper layers were investigated in the spheroids and compared with the monolayer cell culture. Comparing to non-targeted micelles, flow cytometry and confocal imaging proved significantly deeper and higher micelle penetration into the spheroids with TF-targeting. Both in monolayers and spheroids, PCL cytotoxicity was significantly increased when co-delivered with CUR in non-targeted micelles or as single agent in TF-targeted micelles, whereas TF-modification of co-loaded micelles did not further enhance the cytotoxicity. In vivo tumor inhibition studies showed good correlation with the 3D cell culture experiments, which suggests the current spheroid model can be used as an intermediate model for evaluation of co-delivery of anticancer compounds in targeted micelles. PMID:25016976

  19. 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.

  20. 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

  1. Optimization of archaeogeophysical investigations in complex environments on example of advanced magnetic data analysis

    NASA Astrophysics Data System (ADS)

    Eppelbaum, L. V.

    2012-04-01

    How an archaeological-geophysical investigation could be optimised? Obviously, researchers a priori suggest to receiving maximum of archaeogeophysical information by minimal monetary and time expenditures. However, this solution of this task is not trivial one. Let us consider this problem on example of one of the most frequently applied archaeogeophysical methods - archaeomagnetic survey. The archaeomagnetic research optimisation can be solved on the basis of following criterions: (1) Necessary expenditures for realization of the integration (cost criterion C), (2) Necessary time for realization of the integration (time criterion T ), (3) Informativeness of archaeomagnetic examination (informational criterion Π). Criterions C and T can be easily determined by a direct calculation whereas evaluation of the criterion Π is a complex research problem. Besides this, it should be taken into account that criterions C and T , from one side, and criterion Π from other side, contradict with each other. A principal logical-heuristic model of the archaeomagnetic information can be described in the following form (after Eppelbaum et al. (2003)): II = Q U R U V, where Q is the quantitative estimation of archaeogeophysical information, R is the estimation of informational reliability corresponding to the semantic criterion, V is the estimation of informational value according to the pragmatic criterion, and U is the symbol of unification. Parameter Q Significance of the parameter Q will increase when we will apply the most effective processing and interpreting schemes. From the geophysical point of view, parameter Q is the most essential one. The developed advanced interpreting system for complex environments (oblique magnetization, rugged terrain relief and unknown level of the normal magnetic field) (Khesin et al., 1988, 1996; Eppelbaum et al., 2000, 2001; Eppelbaum et al., 2004, 2006, 2007; Finkelstein and Eppelbaum, 2007; Eppelbaum, 2010a, 2011a, 2011b; Eppelbaum and

  2. Investigation of Benthic Foraminiferal Non-Traditional Stable Isotopes to Reconstruct Methane Fluxes in Sedimentary Environments

    NASA Technical Reports Server (NTRS)

    Borrelli, C.; Gabitov, R. I.; Messenger, S. R.; Nguyen, A. N.; Torres, M. E.; Kessler, J. D.

    2015-01-01

    Methane (CH4) is an important greenhouse gas, with a global warming potential much higher than carbon dioxide (CO2) on a short time scale. Even if the residence time of CH4 in the atmosphere is relatively short (tens of years), one of the products of CH4 oxidation is CO2, a greenhouse gas with a much longer residence time in the atmosphere (tens to hundreds of years). CH4 has been proposed as one of the trigger mechanisms for rapid global climate change today and in the geological past. With regards to the geological past, numerous studies proposed the benthic foraminiferal carbon isotope ratio (Delta13C) as a tool to reconstruct the impact of marine CH4 on rapid climate changes; however, the investigation of modern benthic foraminiferal Delta13C have produced inconclusive results. CH4 has a distinctive hydrogen isotope (Delta(D)) and Delta13C signature compared to seawater, and sulfate reduction, often coupled to CH4 anaerobic oxidation in sediments, changes the sulfur isotope signature (Delta34S) of the remaining sulfate in porewater. Therefore, we hypothesize that the Delta(D) and Delta34S signature of infaunal benthic foraminiferal species can provide a complementary approach to Delta13C to study CH4 dynamics in sedimentary environments. Here, we present the preliminary results obtained analyzing Uvigerina peregrina Delta(D) and Delta34S from three different locations at Hydrate Ridge, offshore Oregon. Unfortunately, the lack of chemical data related to the moment of foraminiferal calcification makes difficult to build a robust relationship among the U. peregrina stable isotopes and the CH4 fluxes at the sampling sites. However, our results look very promising, as each site is characterized by a different Delta(D) and Delta34S signature. We emphasize that this study represents the first step in the development of new proxies (Delta(D)) and Delta34S), which may complement the more traditional benthic foraminiferal Delta13C values, to reconstruct marine CH4

  3. 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.

  4. 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

  5. pH-responsive biodegradable micelles based on acid-labile polycarbonate hydrophobe: synthesis and triggered drug release.

    PubMed

    Chen, Wei; Meng, Fenghua; Li, Feng; Ji, Shun-Jun; Zhong, Zhiyuan

    2009-07-13

    pH-responsive biodegradable micelles were prepared from block copolymers comprising of a novel acid-labile polycarbonate hydrophobe and poly(ethylene glycol) (PEG). Two new cyclic aliphatic carbonate monomers, mono-2,4,6-trimethoxybenzylidene-pentaerythritol carbonate (TMBPEC, 2a) and mono-4-methoxybenzylidene-pentaerythritol carbonate (MBPEC, 2b) were designed and successfully synthesized via a two-step procedure. The ring-opening polymerization of 2a or 2b in the presence of methoxy PEG in dichloromethane at 50 °C using zinc bis[bis(trimethylsilyl)amide] as a catalyst yielded the corresponding block copolymers PEG-PTMBPEC (3a) or PEG-PMBPEC (3b) with low polydispersities (PDI 1.03-1.04). The copolymerization of D,L-lactide (DLLA) and 2a under otherwise the same conditions could also proceed smoothly to afford PEG-P(TMBPEC-co-DLLA) (3c) block copolymer. These block copolymers readily formed micelles in water with sizes of about 120 nm as determined by dynamic light scattering (DLS). The hydrolysis of the acetals of the polycarbonate was investigated using UV/vis spectroscopy. The results showed that the acetals of micelles 3a, while stable at pH 7.4 are prone to rapid hydrolysis at mildly acidic pH of 4.0 and 5.0, with a half-life of 1 and 6.5 h, respectively. The acetal hydrolysis resulted in significant swelling of micelles, as a result of change of hydrophobic polycarbonate to hydrophilic polycarbonate. In comparison, the acetals of PMBPEC of micelles 3b displayed obviously slower hydrolysis at the same pH. Both paclitaxel and doxorubicin could be efficiently encapsulated into micelles 3a achieving high drug loading content (13.0 and 11.7 wt %, respectively). The in vitro release studies showed clearly a pH dependent release behavior, that is, significantly faster drug release at mildly acidic pH of 4.0 and 5.0 compared to physiological pH. These pH-responsive biodegradable micelles are promising as smart nanovehicles for targeted delivery of anticancer drugs.

  6. Formation and Fluorimetric Characterization of Micelles in a Micro-flow Through System with Static Micro Mixer

    PubMed Central

    Schuch, Michael; Gross, G. Alexander; Köhler, J. Michael

    2007-01-01

    The formation and behaviour of micelles of sodium dodecylsulfate in water by use of a static micro mixer were studied. Trisbipyridylruthenium(II) was applied as indicator dye, 9-methylanthracene was used for fluorescence quenching. All experiments were carried out by a micro fluid arrangement with three syringe pumps, a 2+1 two-step static micro mixer (IPHT Jena) and a on-line micro fluorimetry including a luminescence diode for excitation, a blue glass filter (BG 7, Linos), two edge filters (RG 630, Linos) and a photo counting module (MP 900, Perkin Elmer). It was possible to measure the fluorescence inside the PTFE tube (inner diameter 0.5 mm) directly. A linear dependence of fluorescence intensity from dye concentration was observed in absence of quencher and surfactant as expected. An aggregation number of about 62 was found in the flow rate range between 300 and 800 μL/min. The fluorescence intensity increases slightly, but significant with increasing flow rate, if no quencher is present. In the presence of quencher, the fluorescence intensity decreases with decreasing surfactant concentration and with enhanced flow rate. The strength of the flow rate effect on the fluorescence increases with decreasing surfactant concentration. The size of micelles was determined in micro channels by the micro fluorimetric method in analogy to the conventional system. The micelles extract the quencher from the solution and lower, this way, the quenching effect. The size of micelles was estimated and it could be shown, that the flow rate has only low effect on the aggregation number at the investigated flow rates. The effect of flow rate and surfactant concentration on the fluorescence in the presence of quencher was interpreted as a shift in the micelle concentration due to the shear forces. It is expected, that the fluorescence intensity is lowered, if more quencher molecules are molecular disperse distributed inside the solution. Obviously, the lowered fluorescence

  7. Quantification of Cholesterol Solubilized in Dietary Micelles: Dependence on Human Bile Salt Variability and the Presence of Dietary Food Ingredients.

    PubMed

    Coreta-Gomes, Filipe M; Vaz, Winchil L C; Wasielewski, Emeric; Geraldes, Carlos F G; Moreno, Maria João

    2016-05-10

    The solubility of cholesterol in bile salt (BS) micelles is important to understand the availability of cholesterol for absorption in the intestinal epithelium and to develop strategies to decrease cholesterol intake from the intestinal lumen. This has been the subject of intense investigation, due to the established relation between the development of diseases such as atherosclerosis and high levels of cholesterol in the blood. In this work we quantify the effect of BS variability on the amount of cholesterol solubilized. The effect of some known hypocholesterolemic agents usually found in the diet is also evaluated, as well as some insight regarding the mechanisms involved. The results show that, depending on the bile salt composition, the average value of sterol per micelle is equal to or lower than 1. The amount of cholesterol solubilized in the BS micelles is essentially equal to its total concentration until the solubility limit is reached. Altogether, this indicates that the maximum cholesterol solubility in the BS micellar solution is the result of saturation of the aqueous phase and depends on the partition coefficient of cholesterol between the aqueous phase and the micellar pseudophase. The effect on cholesterol maximum solubility for several food ingredients usually encountered in the diet was characterized using methodology developed recently by us. This method allows the simultaneous quantification of both cholesterol and food ingredient solubilized in the BS micelles even in the presence of larger aggregates, therefore avoiding their physical separation with possible impacts on the overall equilibrium. The phytosterols stigmasterol and stigmastanol significantly decreased cholesterol solubility with a concomitant reduction in the total amount of sterol solubilized, most pronounced for stigmasterol. Those results point toward coprecipitation being the major cause for the decrease in cholesterol solubilization by the BS micelles. The presence of

  8. Experimental investigation of initial system-environment correlations via trace-distance evolution

    SciTech Connect

    Smirne, Andrea; Cialdi, Simone; Vacchini, Bassano; Brivio, Davide; Paris, Matteo G. A.

    2011-09-15

    The trace distance between two states of an open quantum system quantifies their distinguishability and, for a fixed environmental state, can increase above its initial value only in the presence of initial system-environment correlations. We provide experimental evidence of such a behavior. In our all-optical apparatus, we exploit spontaneous parametric down conversion as a source of polarization entangled states and a spatial light modulator to introduce in a general fashion correlations between the polarization and the momentum degrees of freedom, which act as environment.

  9. 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

  10. Micelle bound structure and DNA interaction of brevinin-2-related peptide, an antimicrobial peptide derived from frog skin.

    PubMed

    Bandyopadhyay, Susmita; Ng, Boon Yee; Chong, Charmaine; Lim, Ming Zhen; Gill, Sonia Kiran; Lee, Ke Hui; Sivaraman, J; Chatterjee, Chiradip

    2014-10-01

    Brevinin-2-related peptide (BR-II), a novel antimicrobial peptide isolated from the skin of frog, Rana septentrionalis, shows a broad spectrum of antimicrobial activity with low haemolytic activity. It has also been shown to have antiviral activity, specifically to protect cells from infection by HIV-1. To understand the active conformation of the BR-II peptide in membranes, we have investigated the interaction of BR-II with the prokaryotic and eukaryotic membrane-mimetic micelles such as sodium dodecylsulfate (SDS) and dodecylphosphocholine (DPC), respectively. The interactions were studied using fluorescence and circular dichroism (CD) spectroscopy. Fluorescence experiments revealed that the N-terminus tryptophan residue of BR-II interacts with the hydrophobic core of the membrane mimicking micelles. The CD results suggest that interactions with membrane-mimetic micelles induce an α-helix conformation in BR-II. We have also determined the solution structures of BR-II in DPC and SDS micelles using NMR spectroscopy. The structural comparison of BR-II in the presence of SDS and DPC micelles showed significant conformational changes in the residues connecting the N-terminus and C-terminus helices. The ability of BR-II to bind DNA was elucidated by agarose gel retardation and fluorescence experiments. The structural differences of BR-II in zwitterionic versus anionic membrane mimics and the DNA binding ability of BR-II collectively contribute to the general understanding of the pharmacological specificity of this peptide towards prokaryotic and eukaryotic membranes and provide insights into its overall antimicrobial mechanism.

  11. Micelle bound structure and DNA interaction of brevinin-2-related peptide, an antimicrobial peptide derived from frog skin.

    PubMed

    Bandyopadhyay, Susmita; Ng, Boon Yee; Chong, Charmaine; Lim, Ming Zhen; Gill, Sonia Kiran; Lee, Ke Hui; Sivaraman, J; Chatterjee, Chiradip

    2014-10-01

    Brevinin-2-related peptide (BR-II), a novel antimicrobial peptide isolated from the skin of frog, Rana septentrionalis, shows a broad spectrum of antimicrobial activity with low haemolytic activity. It has also been shown to have antiviral activity, specifically to protect cells from infection by HIV-1. To understand the active conformation of the BR-II peptide in membranes, we have investigated the interaction of BR-II with the prokaryotic and eukaryotic membrane-mimetic micelles such as sodium dodecylsulfate (SDS) and dodecylphosphocholine (DPC), respectively. The interactions were studied using fluorescence and circular dichroism (CD) spectroscopy. Fluorescence experiments revealed that the N-terminus tryptophan residue of BR-II interacts with the hydrophobic core of the membrane mimicking micelles. The CD results suggest that interactions with membrane-mimetic micelles induce an α-helix conformation in BR-II. We have also determined the solution structures of BR-II in DPC and SDS micelles using NMR spectroscopy. The structural comparison of BR-II in the presence of SDS and DPC micelles showed significant conformational changes in the residues connecting the N-terminus and C-terminus helices. The ability of BR-II to bind DNA was elucidated by agarose gel retardation and fluorescence experiments. The structural differences of BR-II in zwitterionic versus anionic membrane mimics and the DNA binding ability of BR-II collectively contribute to the general understanding of the pharmacological specificity of this peptide towards prokaryotic and eukaryotic membranes and provide insights into its overall antimicrobial mechanism. PMID:25044683

  12. Novel in situ gel systems based on P123/TPGS mixed micelles and gellan gum for ophthalmic delivery of curcumin.

    PubMed

    Duan, Yuwei; Cai, Xiaoqing; Du, Hongliang; Zhai, Guangxi

    2015-04-01

    Curcumin, a natural polyphenol compound, has been widely reported for diverse pharmacological effects and already been investigated for eye diseases. However, the water-insolubility of curcumin and the inherent penetration barriers in cornea make it difficult for curcumin to enter eye. This work aimed to develop ion-sensitive curcumin-loaded Pluronic P123 (P123)/D-a-tocopheryl polyethylene glycolsuccinate (TPGS) mixed micelle in situ gels (CUR-MM-ISGs) to prolong ocular retention time and improve cornea permeability. Central composite design-response surface methodology was applied for the optimization of curcumin-loaded P123/TPGS mixed micelles (CUR-MMs). Characterization tests showed that CUR-MMs were in spherical shape with small size and low critical micelle concentration. After dispersing the micelles in gellan gum solution (0.2%, w/w) at the ratio of 3:1 and 1:1 (v/v), respectively, CUR-MM-ISGs were formed and presented transparent appearance. Sustained release profile was obtained in vitro for both CUR-MM-ISGs (3:1 or 1:1, v/v). The irritation test proved that CUR-MM-ISGs as ophthalmic formulations were gentle and biocompatible towards ocular tissues. In addition, the ex vivo corneal penetration study indicated that the cumulative drug permeation amount of CUR-MM-ISGs (3:1, v/v) was respectively 1.16-fold and 1.32-fold higher than CUR-MM-ISGs (1:1, v/v) and curcumin solution. It can be concluded from these results that the developed ion-sensitive mixed micelle in situ gel system is a potential ophthalmic delivery carrier for curcumin as a poorly soluble drug.

  13. NMR structure of the Arctic mutation of the Alzheimer's Aβ(1-40) peptide docked to SDS micelles

    NASA Astrophysics Data System (ADS)

    Usachev, K. S.; Filippov, A. V.; Khairutdinov, B. I.; Antzutkin, O. N.; Klochkov, V. V.

    2014-11-01

    The “Arctic” point mutation of the Alzheimer's amyloid β-peptide is a rare mutation leading to an early onset of Alzheimer's disease. The peptide may interact with neuronal membranes, where it can provide its toxic effects. We used 2D NMR spectroscopy to investigate the conformation of the “Arctic” mutant of Aβ1-40 Alzheimer's amyloid peptide in sodium dodecyl sulfate micelle solutions, which are the type of amphiphilic structures mimicking some properties of biomembranes. The study showed that the Arctic mutant of Aβ1-40 interacts with the surface of SDS micelles mainly through the Leu17-Asn27 310-helical region, while the Ile31-Val40 region is buried in the hydrophobic interior of the micelle. In contrast, wild-type Aβ1-40 interacts with SDS micelles through the Lys16-Asp23 α-helical region and Gly29-Met35. Both the Arctic mutant and the wild-type Aβ1-40 peptides interactions with SDS micelles are hydrophobic in nature. Aβ peptides are thought to be capable of forming pores in biomembranes that can cause changes in neuronal and endothelial cell membrane permeability. It has also been shown that Aβ peptides containing the “Arctic” mutation are more neurotoxic and aggregate more readily than the wild-type Aβ peptides at physiological conditions. Here, we propose that the extension of the helical structure of Leu17-Asn27 and a high aliphaticity (neutrality) of the C-terminal region in the Arctic Aβ peptides are consistent with the idea that formation of ion-permeable pores by Aβ oligomers may be one of prevailing mechanisms of a larger neuronal toxicity of the Arctic Aβ compared to the wild-type Aβ peptides, independent of oxidative damage and lipid peroxidation.

  14. Enhanced oral bioavailability of morin administered in mixed micelle formulation with PluronicF127 and Tween80 in rats.

    PubMed

    Choi, Yeon Ah; Yoon, You Hyun; Choi, Kwangik; Kwon, Mihwa; Goo, Soo Hyeon; Cha, Jin-Sun; Choi, Min-Koo; Lee, Hye Suk; Song, Im-Sook

    2015-01-01

    To overcome the low oral bioavailability of morin, a mixed micelle formulation with pharmaceutical excipients that facilitate solubilization and modulate P-glycoprotein (P-gp) was developed and evaluated in vitro and in vivo rats. Morin-loaded mixed micelle formulation with a morin-PluronicF127-Tween80 ratio of 1 : 10 : 0.02 (w/w/w) was prepared by a thin-film hydration method. The solubility, size distribution, drug encapsulation efficiency, and percent drug loading of the formulation were characterized. Subsequently, in vivo pharmacokinetic parameters of morin loaded in a PluronicF127 and Tween80 mixed-micelle formulation were investigated in rats. Absolute bioavailability of morin was dramatically increased by the oral administration of morin-loaded PluronicF127 and Tween80 mixed micelle from 0.4% to 11.2% without changing the systemic clearance and half-life. In Caco-2 cells, absorption permeability of morin from the novel formulation was increased 3.6-fold compared with that of morin alone. P-gp inhibition by cyclosporine A (CsA) increased absorptive permeability of morin 2.4-fold but decreased the efflux of morin by 52%, which was consistent with increased plasma concentration of morin in the pretreatment of CsA in rats. The morin formulation inhibited P-gp transport activity by 83.1% at 100 µM as morin concentration. Moreover, morin formulation increased paracellular permeability of Lucifer yellow by 1.6-1.8 fold. In conclusion, enhanced oral bioavailability of morin from morin-loaded PluronicF127 and Tween80 mixed micelle formulation can be attributed to increased intestinal permeation of morin, which was mediated at least by P-gp inhibition and enhanced paracellular route.

  15. 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 behavio