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

    PubMed

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

    2009-09-24

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

  3. 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.

  4. 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.

  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. PMID:24954150

  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. [Investigation on the spectral characteristics and existing state of a substituted 3H-indole molecular probe in triton X-100 reverse micelle].

    PubMed

    Luo, Jun-jian; Li, Jian; Shen, Xing-hai; Gao, Hong-cheng

    2005-02-01

    The interactions between a fluorescent molecular probe, i. e., [2-(p-hexylamino) phenyl-3, 3-dimethyl-5-ethoxycarbonyl-3H-indole] methyldioctadecylammonium iodide (A) and Triton X-100/heptane/hexanol/water reverse micelle have been investigated by spectroscopy. Micropolarity of the environment, fluorescence anisotropy parameter and the pH effect of A in Triton X-100 reverse micelle were determined. Furthermore, the state of water in reverse micellar systems was studied by FTIR. According to the above experimental results, some information on the structure of Triton X-100 reverse micelle was obtained and the probable site of A in this system was discussed. PMID:15852849

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

    SciTech Connect

    Keh, E.; Valeur, B.

    1981-02-01

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

  10. Physicochemical investigation of acrylamide solubilization in sodium bis(2-ethylhexyl)sulfosuccinate and lecithin reversed micelles.

    PubMed

    Calandra, P; Giordano, C; Ruggirello, A; Turco Liveri, V

    2004-09-01

    The state of acrylamide confined within dry sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and lecithin reversed micelles dispersed in CCl(4) has been investigated by FTIR and (1)H NMR spectroscopy. Measurements have been performed at 25 degrees C as a function of the acrylamide-to-surfactant molar ratio (R) at a fixed surfactant concentration (0.1 mol kg(-1)). The analysis of experimental data, corroborated by the results of SAXS measurements, is consistent with the hypothesis that acrylamide is quite uniformly distributed among reversed micelles mainly located in proximity to the surfactant head-group region and that its presence induces significant unidimensional growth of micellar aggregates. Moreover, the confinement of acrylamide within reversed micelles involves some changes of the typical H-bonded structure of pure solid acrylamide attributable to the establishment of system-specific acrylamide/surfactant head group interactions. Preliminary experiments showed that, by exposure to X-rays, the polymerization of acrylamide can be induced in the confined space of dry AOT and lecithin reversed micelles. PMID:15276058

  11. 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…

  12. 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

  13. Spectroscopic investigation of interactions of new potential anticancer drugs with DNA and non-ionic micelles.

    PubMed

    Mazzoli, Alessandra; Spalletti, Anna; Carlotti, Benedetta; Emiliani, Carla; Fortuna, Cosimo G; Urbanelli, Lorena; Tarpani, Luigi; Germani, Raimondo

    2015-01-29

    Photophysical properties of some azinium iodides in aqueous solution of nanostructured systems as DNA and nonionic micelles were investigated using steady-state and ultrafast time-resolved spectroscopy. Spectrophotometric and fluorimetric titrations of the investigated compounds with salmon testes DNA supplied evidence of a good interaction between the salts and DNA with binding constants of 10(4)-10(6) M(-1), making them interesting for pharmaceutical applications. The interaction with DNA also changes the photobehavior of the compounds, increasing the radiative deactivation pathway to the detriment of internal conversion and slowing down the excited state dynamics. The interaction of the azinium salts with the nonionic surfactant Triton X-100 from premicellar to postmicellar concentration was studied by spectrophotometric and fluorimetric titrations evidencing the ability of the micelles to associate the studied salts in their hydrophobic portion and to release them in the presence of DNA, acting as promising drug carriers. Also transient absorption spectroscopy with femtosecond resolution demonstrated the insertion of the investigated compounds into micellar aggregates. Preliminary measurements by confocal fluorescence microscopy on MCF-7 cells in the presence of the studied azinium salts showed that they are able to cross the cellular membrane and that their cytotoxicity can be expressed through interaction with DNA (RNA). In fact, they showed a significant fluorescence signal in all cell compartments, particularly (for 2 and 3) into punctuate structures within the nuclei compatible with a localization into the nucleoli. PMID:25545705

  14. Dodecylphosphocholine micelles as a membrane-like environment: new results from NMR relaxation and paramagnetic relaxation enhancement analysis.

    PubMed

    Beswick, V; Guerois, R; Cordier-Ochsenbein, F; Coïc, Y M; Tam, H D; Tostain, J; Noël, J P; Sanson, A; Neumann, J M

    1999-01-01

    To further examine to what extent a dodecyl-phosphocholine (DPC) micelle mimics a phosphatidylcholine bilayer environment, we performed 13C, 2H, and 31P NMR relaxation measurements. Our data show that the dynamic behavior of DPC phosphocholine groups at low temperature (12 degrees C) corresponds to that of a phosphatidylcholine interface at high temperature (51 degrees C). In the presence of helical peptides, a PMP1 fragment, or an annexin fragment, the DPC local dynamics are not affected whereas the DPC aggregation number is increased to match an appropriate area/volume ratio for accommodating the bound peptides. We also show that quantitative measurements of paramagnetic relaxation enhancements induced by small amounts of spin-labeled phospholipids on peptide proton signals provide a meaningful insight on the location of both PMP1 and annexin fragments in DPC micelles. The paramagnetic contributions to the relaxation were extracted from intra-residue cross-peaks of NOESY spectra for both peptides. The location of each peptide in the micelles was found consistent with the corresponding relaxation data. As illustrated by the study of the PMP1 fragment, paramagnetic relaxation data also allow us to supply the missing medium-range NOEs and therefore to complete a standard conformational analysis of peptides in micelles. PMID:9933923

  15. 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.

  16. Investigating the interaction of crystal violet probe molecules on sodium dodecyl sulfate micelles with hyper-Rayleigh scattering.

    PubMed

    Revillod, Guillaume; Russier-Antoine, Isabelle; Benichou, Emmanuel; Jonin, Christian; Brevet, Pierre-François

    2005-03-24

    We report the use of the nonlinear optical technique of hyper-Rayleigh scattering to investigate the interaction of the cationic probe molecule crystal violet with micelles of sodium dodecyl sulfate. An absolute value of (847 +/- 80) x 10(-30) esu is measured at the fundamental wavelength of 870 nm for the molecular hyperpolarizability of crystal violet free in pure aqueous solutions. In aqueous solutions of sodium dodecyl sulfate, above and below the critical micelle concentration, the measured hyperpolarizability of crystal violet is weaker than in the solution free of sodium dodecyl sulfate. From the comparison with linear optical photoabsorption spectroscopy data, this difference is attributed to electrostatic interactions between the cationic crystal violet molecules and the negatively charged sodium dodecyl sulfate surfactant molecules present in excess. Polarization resolved hyper-Rayleigh scattering measurements are then performed to show that, below and above the critical micelle concentration, crystal violet molecules also undergo symmetry changes upon interaction with sodium dodecyl sulfate. Above the critical micelle concentration, the minimum fraction of micelles interacting with at least one CV molecule is estimated. For instance, for a crystal violet aqueous concentration of 150 microM, this fraction is larger than 7%. PMID:16863205

  17. Effect of the constrained environment on the interactions between the surfactant and different polar solvents encapsulated within AOT reverse micelles.

    PubMed

    Durantini, Andrés M; Falcone, R Dario; Silber, Juana J; Correa, N Mariano

    2009-08-24

    Herein, we report a study of the interactions between different nonaqueous polar solvents, namely, ethylene glycol (EG), propylene glycol (PG), glycerol (GY), dimethylformamide (DMF), and dimethylacetamide (DMA), and the polar heads of sodium 1,4-bis-2-ethylhexylsulfosuccinate (AOT) in nonaqueous AOT/n-heptane reverse micelles. The goal of our study is to gain insights into the unique reverse-micelle microenvironment created upon encapsulation of these polar solvents. For the first time, the study is focused on determining which regions of the AOT molecular structure are involved in the interactions with the polar solvents. We use FTIR spectroscopy--a noninvasive technique--to follow the changes in the AOT C=O band and the symmetric and asymmetric SO(3)(-) vibration modes upon increasing the content of polar solvents in the micelles. The results show that GY interacts through H bonds with the SO(3)(-) group, thereby removing the Na(+) counterions from the interface remaining in the polar core of the micelles. PG and EG interact through H bonds, mainly with the C=O group of AOT, penetrating into the oil side of the interface. Thus, they interact weakly with the Na(+) counterion, which seems to be close to the AOT sulfonate group. Finally, DMF and DMA, encapsulated inside the reverse micelles, interact neither with the C=O nor with the SO(3)(-) groups, but their weakly bulk-associated structure is broken because of the interactions with Na(+). We suggest that DMF and DMA can complex the Na(+) ions through their carbonyl and nitrogen groups. Hence, our results do not only give insights into how the constrained environment affects the bulk properties of polar solvents encapsulated within reverse micelles but--more importantly--they also help us to answer the tricky question about which regions of the AOT moiety are involved in the interactions with the polar solvents. We believe that our results show a clear picture of the interactions present at the nonaqueous reverse-micelle

  18. Geokinetic environment investigations

    NASA Astrophysics Data System (ADS)

    Hartnett, E. B.; Carleen, E. D.; Blaney, J. I.

    1981-03-01

    This report covers the development and implementation of special concepts, techniques and instrumentation for the collection, analysis and application of geokinetic data. The Geokinetic Data Acquisition System (GDAS) was modified, maintained and operationally deployed to various sites designated by AFGL. Tests were conducted at the Defense Nuclear Agency (DNA) CASINO Facility in Maryland; Central Inertial Guidance Test Facility (CIGTF), Holloman AFB, N.M.; Space Transportation System (STS) Launch Complex, Vandenberg AFB, Ca. and the SAC Wing V Minuteman Complex at Cheyenne, Wy. The CASINO data contributed to SAMSO's MX/TGG Advanced Development Bridge II Program for radiation hardening of third generation hardware. The CIGTF investigation supported USAF requirements for highly precise azimuth reference. The Hill AFB the performance of a minuteman III missile guidance system in an engineering silo. The STS program at Vandenberg AFB was to assist in determining the nature of a Titan III-D pressure load. The SAC Wing V deployment was to investigate plateau/valley basin geologic characteristics in respect to motion response.

  19. 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

  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. PMID:26539742

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

    PubMed

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

    2014-09-01

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

  2. 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. PMID:22145934

  3. 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.

  4. Spectrophotometric investigation of the binding of vitamin E to water-containing reversed micelles.

    PubMed

    Avellone, G; Bongiorno, D; Ceraulo, L; Ferrugia, M; Turco Liveri, V

    2002-03-01

    The distribution constants of vitamin E partitioned between apolar organic phase and water-containing reversed micelles of sodium bis (2-ethylhexyl) sulfosuccinate (AOT), didodecyldimethylammonium bromide (DDAB), soybean phosphatidylcholine (lecithin) and tetraethylene glycol monododecyl ether (C12E4) have been evaluated by a spectrophotometric method. The results suggest that in the presence of domains from apolar organic solvent to surfactant and to water, vitamin E is partitioned between the micellar palisade layer and the organic solvent and also that its binding strength to reversed micelles depends mainly by specific interactions between the head group of vitamin E and that of the surfactant. Moreover, in addition to the advantageous interactions between vitamin E and water, the dependence of the distribution constants upon the molar ratio R (R=[water]/[surfactant]) indicates a competition between water and vitamin E for the binding sites at the water/surfactant interface. The biological implications of the preferential location and confinement of vitamin E in water-containing reversed micelles are discussed. PMID:11839455

  5. Investigation of interaction parameters in mixed micelle using pulsed field gradient NMR spectroscopy.

    PubMed

    Gharibi, H; Javadian, S; Sohrabi, B; Behjatmanesh, R

    2005-05-01

    Pulsed field gradient NMR spectroscopy was used to determine the partitioning of surfactant between monomeric and micellar forms in a mixed CTAB (hexadecyltetramethylammonium bromide) and Triton X-100 [p-(1,1,3-tetramethylbutyl)polyoxyethylene] system. In addition, potentiometric and surface tension measurements were used to determine the free concentration of ionic surfactant and the critical micelle concentration (CMC) of mixtures of n-alkyltrimethylammonium bromide (C(n)TAB, n=12, 14, 16, 18) and Triton X-100. Regular solution theory cannot describe the behavior of the activity coefficient and the excess Gibbs free energy of mixtures of ionic and nonionic surfactants. To overcome these shortcomings, we developed a new model that combines Van Laar expressions and the theory of nonrandom mixing in mixed micelles. The Van Laar expressions contain an additional parameter, rho, which reflects differences in the size of the components of the mixture. Nonrandom mixing theory was introduced to describe nonrandom mixing in mixed micelles. This effect was modeled by a packing parameter, P*. The proposed model provided a good description of the behavior of binary surfactant mixtures. The results indicated that head group size and packing constraints are important contributors to nonideal surfactant behavior. In addition, the results showed that as the chain length of the C(n)TAB molecule in C(n)TAB/Triton X-100 mixtures was increased, the head group size parameter remained constant, but the interaction and packing parameters increased. Increase of the temperature caused an increase in the interaction parameter beta and a decrease in the packing parameter (P*). PMID:15797433

  6. Mixed Micelles of Sodium Cholate and Sodium Dodecylsulphate 1:1 Binary Mixture at Different Temperatures – Experimental and Theoretical Investigations

    PubMed Central

    Jójárt, Balázs; Poša, Mihalj; Fiser, Béla; Szőri, Milán; Farkaš, Zita; Viskolcz, Béla

    2014-01-01

    Micellisation process for sodium dodecyl sulphate and sodium cholate in 1∶1 molar ratio was investigated in a combined approach, including several experimental methods and coarse grained molecular dynamics simulation. The critical micelle concentration (cmc) of mixed micelle was determined by spectrofluorimetric and surface tension measurements in the temperature range of 0–50°C and the values obtained agreed with each other within the statistical error of the measurements. In range of 0–25°C the cmc values obtained are temperature independent while cmc values were increased at higher temperature, which can be explained by the intensive motion of the monomers due to increased temperature. The evidence of existing synergistic effect among different constituent units of the micelle is indicated clearly by the interaction parameter (β1,2) calculated from cmc values according to Rubingh. As the results of the conductivity measurements showed the negative surface charges of the SDS-NaCA micelle are not neutralized by counterions. Applying a 10 µs long coarse-grained molecular dynamics simulation for system including 30-30 SDS and CA (with appropriate number of Na+ cations and water molecules) we obtained semi-quantitative agreement with the experimental results. Spontaneous aggregation of the surfactant molecules was obtained and the key steps of the micelle formation are identified: First a stable SDS core was formed and thereafter due to the entering CA molecules the size of the micelle increased and the SDS content decreased. In addition the size distribution and composition as well as the shape and structure of micelles are also discussed. PMID:25004142

  7. Mixed micelles of sodium cholate and sodium dodecylsulphate 1:1 binary mixture at different temperatures--experimental and theoretical investigations.

    PubMed

    Jójárt, Balázs; Poša, Mihalj; Fiser, Béla; Szőri, Milán; Farkaš, Zita; Viskolcz, Béla

    2014-01-01

    Micellisation process for sodium dodecyl sulphate and sodium cholate in 1∶1 molar ratio was investigated in a combined approach, including several experimental methods and coarse grained molecular dynamics simulation. The critical micelle concentration (cmc) of mixed micelle was determined by spectrofluorimetric and surface tension measurements in the temperature range of 0-50°C and the values obtained agreed with each other within the statistical error of the measurements. In range of 0-25°C the cmc values obtained are temperature independent while cmc values were increased at higher temperature, which can be explained by the intensive motion of the monomers due to increased temperature. The evidence of existing synergistic effect among different constituent units of the micelle is indicated clearly by the interaction parameter (β1,2) calculated from cmc values according to Rubingh. As the results of the conductivity measurements showed the negative surface charges of the SDS-NaCA micelle are not neutralized by counterions. Applying a 10 µs long coarse-grained molecular dynamics simulation for system including 30-30 SDS and CA (with appropriate number of Na+ cations and water molecules) we obtained semi-quantitative agreement with the experimental results. Spontaneous aggregation of the surfactant molecules was obtained and the key steps of the micelle formation are identified: First a stable SDS core was formed and thereafter due to the entering CA molecules the size of the micelle increased and the SDS content decreased. In addition the size distribution and composition as well as the shape and structure of micelles are also discussed. PMID:25004142

  8. How does bile salt penetration affect the self-assembled architecture of pluronic P123 micelles?--light scattering and spectroscopic investigations.

    PubMed

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

    2015-08-14

    The triblock copolymer of the type (PEO)20-(PPO)70-(PEO)20 (P123) forms a mixed supramolecular aggregate with different bile salts, sodium deoxycholate (NaDC) and sodium taurocholate (NaTC), having different hydrophobicity. These mixed micellar systems have been investigated through dynamic light scattering (DLS) and other various spectroscopic techniques. DLS measurements reveal that the bile salts penetrate into the core-corona region of the P123 micelle and further addition of bile salts causes formation of a new supramolecular aggregate. Further CONTIN analysis confirms existence of two types of complexes at higher molar ratios of bile salt-P123 (>1 : 3). Due to the bile salt penetration, the polarity of the core-corona region of bile salt-P123 mixed micelle increases which results in red shift in the absorption and emission spectra of coumarin 153 (C153) and coumarin 480 (C480). The rotational diffusion of the hydrophobic probe C153 and a hydrophilic probe C480 has been investigated in these bile salt-P123 mixed systems and for both the probes a decrease in the average reorientation time has been observed. The reason behind this decrease in the average reorientation time is the increase in both polarity and hydration of the core-corona region in these mixed micelles. Moreover, these bile salt-P123 mixed micelles are characterized by fluorescence correlation spectroscopy (FCS) techniques. As hydrophobic solute 4-(dicyanomethylene)-2-methyl-6-(p-dimethylamino-styryl)-4H-pyran (DCM) resides in the core region of the bile salt-P123 mixed micelles, the translational diffusion of DCM becomes faster in these mixed micelles compared to that in pure P123 micelle. However, for cationic probe rhodamine 6G perchlorate (R6G), a totally opposite trend in the translational diffusion coefficients has been observed. Both anisotropy and FCS measurements confirm that bile salts affect the core region of the P123 micelle more than the corona region. Besides, all these

  9. 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.

  10. The crowded environment of a reverse micelle induces the formation of β-strand seed structures for nucleating amyloid fibril formation.

    PubMed

    Yeung, Priscilla S-W; Axelsen, Paul H

    2012-04-11

    A hallmark of Alzheimer's disease is the accumulation of insoluble fibrils in the brain composed of amyloid beta (Aβ) proteins with parallel in-register cross-β-sheet structure. It has been suggested that the aggregation of monomeric Aβ proteins into fibrils is promoted by "seeds" that form within compartments of the brain that have limited solvent due to macromolecular crowding. To characterize these seeds, a crowded macromolecular environment was mimicked by encapsulating Aβ40 monomers into reverse micelles. Fourier-transform infrared spectroscopy revealed that monomeric Aβ proteins form extended β-strands in reverse micelles, while an analogue with a scrambled sequence does not. This is a remarkable finding, because the formation of extended β-strands by monomeric Aβ proteins suggests a plausible mechanism whereby the formation of amyloid fibrils may be nucleated in the human brain. PMID:22448820

  11. Energy degradation pathways and binding sites environment of micelle bound ruthenium(II) photosensitizers

    SciTech Connect

    Dressick, W.J.; Cline, J. III; Demas, J.N.; DeGraff, B.A.

    1986-11-26

    A series of ..cap alpha..-diimine Ru(II) sensitizers were studied in aqueous, alcohol, and sodium lauryl sulfate (NaLS) micellar solutions. The emission efficiency, lifetime, and spectra change dramatically on micellization. From the temperature dependence of the excited-state lifetime and luminescence quantum efficiencies, coupled with spectral fitting, they interpret these changes and elucidate the environment of the micellized sensitizer. The increased efficiencies and lifetimes on micellization arise from decreased rates of deactivation via the photoactive d-d state and by a decrease in other intramolecular nonradiative paths. Radiationless decay theory permits semiquantitative calculation of nonradiative rate constants. A model describing the binding site and local solvent environment for the sensitizers is proposed. Implications of the results for solar energy conversion schemes are described.

  12. Mixed micelles of Triton X-100, sodium dodecyl dioxyethylene sulfate, and synperonic l61 investigated by NOESY and diffusion ordered NMR spectroscopy.

    PubMed

    Denkova, Pavletta S; Van Lokeren, Luk; Willem, Rudolph

    2009-05-14

    Mixed micelles formed from nonionic surfactant Triton X-100 (TX100), anionic surfactant sodium dodecyl dioxyethylene sulfate (SDP2S), and triblock copolymer Synperonic L61 (SL61) were investigated by 1H NMR spectroscopy. The size and shape of the aggregates were determined by diffusion ordered NMR spectroscopy (DOSY), while 2D nuclear Overhauser enhanced spectroscopy (NOESY) NMR was used to study the mutual spatial arrangement of the surfactant molecules in the aggregated state. An average micellar hydrodynamic radius of 3.6 nm, slightly increasing upon increasing TX100 molar fraction, was found for the mixed systems without additives. Addition of SL61 to the mixed micellar systems results in a slight increase of micellar radii. In the presence of AlCl3, an increase of TX100/SDP2S micellar sizes from 4 to 10 nm was found when increasing the SDP2S molar fraction. The mixed TX100/SDP2S micelles in the presence of both AlCl3 and polymer SL61 are almost spherical, with a radius of 4.5 nm. 2D NOESY data reveal that, as the individual TX100 micelles, mixed TX100/SDP2S and TX100/SDP2S/SL61/AlCl3 micelles also have a multilayer structure, with partially overlapping internal and external layers of TX100 molecules. In these mixed micelles, the SDP2S molecules are located at the level of the external layer of TX100 molecules, whereas the SL61 polymer is partially incorporated inside of the micellar core. PMID:19385612

  13. Ultrafast dynamics of water in cationic micelles

    NASA Astrophysics Data System (ADS)

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

    2007-03-01

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

  14. Enhanced solubilization and desorption of organochlorine pesticides (OCPs) from soil by oil-swollen micelles formed with a nonionic surfactant.

    PubMed

    Zheng, Guanyu; Selvam, Ammaiyappan; Wong, Jonathan W C

    2012-11-01

    The effect of oil-swollen micelles formed with nonionic surfactant polyoxyethylene sorbitan monooleate (Tween 80), cosurfactant 1-pentanol, and linseed oil on the solubilization and desorption of organochlorine pesticides (OCPs) including DDT and γ-HCH from both loam soil and clay soil were investigated. Results showed that the solubilizing capacities of oil-swollen micelles were dependent on the critical micelle concentration (CMC) of Tween 80. Once the concentrations of oil-swollen micelles exceeded the CMC of Tween 80, the oil-swollen micelles exhibited much higher solubilizing capacity than empty Tween 80 micelles for the two OCPs. Desorption tests revealed that oil-swollen micelles could successfully enhance desorption of OCPs from both loam soil and clay soil. However, compared with the efficiencies achieved by empty Tween 80 micelles, oil-swollen micelles exhibited their superiority to desorb OCPs only in loam soil-water system while was less effective in clay soil-water system. Distribution of Tween 80, 1-pentanol and linseed oil in soil-water system revealed that the difference in the sorption behavior of linseed oil onto the two soils is responsible for the different effects of oil-swollen micelles on the desorption of OCPs in loam soil and clay soil systems. Therefore, oil-swollen micelles formed with nonionic surfactant Tween 80 are better candidates over empty micelle counterparts to desorb OCPs from soil with relatively lower sorption capacity for oil fraction, which may consequently enhance the availability of OCPs in soil environment during remediation processes of contaminated soil. PMID:22998366

  15. 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.

  16. 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)…

  17. 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…

  18. The Effect of Hydrophilic and Hydrophobic Structure of Amphiphilic Polymeric Micelles on Their Transportation in Rats.

    PubMed

    Deng, Feiyang; Yu, Chao; Zhang, Hua; Dai, Wenbing; He, Bing; Zheng, Ying; Wang, Xueqing; Zhang, Qiang

    2016-01-01

    In the previous study, we have clarified how the hydrophilic and hydrophobic structures of amphiphilic polymers impact the transport of their micelles (PEEP-PCL, PEG-PCL and PEG-DSPE micelles) in epithelial MDCK cells (Biomaterials 2013, 34: 6284-6298). In this study, we attempt to clarify the behavior of the three micelles in rats. Coumarin-6 loaded micelles were injected into different sections of intestine of rats and observed by confocal laser scanning microscope (CLSM) or orally administrated and conducted pharmacokinetic study. All of the three kinds of micelles were able to cross the intestinal epithelial cells and enter blood circulation. The PEEP-PCL micelles demonstrated the fastest distribution mainly in duodenum, while the PEGDSPE micelles showed the longest distribution with the highest proportion in ileum of the three. No significant difference was observed among the pharmacokinetic parameters of the three micelles. The results were consistent in the two analysis methods mentioned above, yet there were some differences between in vivo and in vitro results reported previously. It might be the distinction between the environments in MDCK model and intestine that led to the discrepancy. The hydrophobicity of nanoparticles could both enhance uptake and hinder the transport across the mucus. However, there was no intact mucus in MDCK model, which preferred hydrophobic nanoparticles. PEEP was the most hydrophilic material constructing the micelles in the study and its uptake would be increased in rats compared to that in MDCK model, while DSPE was more hydrophobic than the others and MDCK model would be more ideal for its uptake. Considering the inconsistency of the results in the two models, whether the methods researchers were generally using at present were reasonable needs further investigation. PMID:26201346

  19. Kinetics of thermo-induced micelle-to-vesicle transitions in a catanionic surfactant system investigated by stopped-flow temperature jump.

    PubMed

    Zhang, Jingyan; Liu, Shiyong

    2011-07-21

    The kinetics of thermo-induced micelle-to-vesicle transitions in a catanionic surfactant system consisting of sodium dodecyl sulfate (SDS) and dodecyltriethylammonium bromide (DEAB) were investigated by the stopped-flow temperature jump technique, which can achieve T-jumps within ∼2-3 ms. SDS/DEAB aqueous mixtures ([SDS]/[DEAB] = 2/1, 10 mM) undergo microstructural transitions from cylindrical micelles to vesicles when heated above 33 °C. Upon T-jumps from 20 °C to final temperatures in the range of 25-31 °C, relaxation processes associated with negative amplitudes can be ascribed to the dilution-induced structural rearrangement of cylindrical micelles and to the dissolution of non-equilibrium mixed aggregates. In the final temperature range of 33-43 °C the obtained dynamic traces can be fitted by single exponential functions, revealing one relaxation time (τ) in the range of 82-440 s, which decreases with increasing temperature. This may be ascribed to the transformation of floppy bilayer structures into precursor vesicles followed by further growth into final equilibrium vesicles via the exchange and insertion/expulsion of surfactant monomers. In the final temperature range of 45-55 °C, vesicles are predominant. Here T-jump relaxations revealed a distinctly different kinetic behavior. All dynamic traces can only be fitted with double exponential functions, yielding two relaxation times (τ(1) and τ(2)), exhibiting a considerable decrease with increasing final temperatures. The fast process (τ(1)∼ 5.2-28.5 s) should be assigned to the formation of non-equilibrium precursor vesicles, and the slow process (τ(2)∼ 188-694 s) should be ascribed to their further growth into final equilibrium vesicles via the fusion/fission of precursor vesicles. In contrast, the reverse vesicle-to-micelle transition process induced by a negative T-jump from elevated temperatures to 20 °C occurs quite fast and almost completes within the stopped-flow dead time (∼2-3 ms

  20. Proton transfer in ionic and neutral reverse micelles.

    PubMed

    Lawler, Christian; Fayer, Michael D

    2015-05-14

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

  1. Bactericidal block copolymer micelles.

    PubMed

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

    2011-05-12

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

  2. Association of chlorophyll with inverted micelles of dodecylpyridinium iodide in toluene

    SciTech Connect

    Seely, G.R.; Ma, X.C.; Nieman, R.A.; Gust, D. )

    1990-02-22

    Dodecylpyridinium iodide forms inverted micelles in water-containing toluene at concentrations higher than 10{sup {minus}4} M, as it reportedly does in other nonpolar solvents. Micelle formation is characterized by changes in the charge-transfer absorption band, and in the chemical shifts of protons, especially those on or near the pyridinium group. The micelles associate with chlorophyll a, also dissolved in the toluene, as evidenced by large changes in the chemical shift of some of the surfactant and the chlorophyll resonances. The fluorescence quantum yield of chlorophyll is little reduced by the presence of 10{sup {minus}3} M 2,2{prime}-dithiobis(5-nitropyridine), a quencher which is soluble in toluene and probably associates weakly with the micelles, but is strongly reduced by the presence of the bis(tetramethylammonium) salt of 5,5{prime}-dithiobis(2-nitrobenzoic acid), which is solubilized only in the presence of the inverted micelles, and furthermore forms a complex with chlorophyll. These cationic inverted micelles constitute a new environment for the pursuit of chlorophyll model system investigations.

  3. 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

  4. Micelle Structure and Hydrophobic Hydration.

    PubMed

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

    2015-08-26

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

  5. 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.

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

    PubMed

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

    2009-03-01

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

  7. 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.

  8. 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.

  9. 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…

  10. 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

  11. Mars Scout: Micromissions to Investigate Martian Environments

    NASA Technical Reports Server (NTRS)

    Cabrol, N. A.; Ori, G. G.; Grin, E. A.; Sims, M. H.; Marinangeli, L.; McKay, C.; Marshall, J.; Thomas, H.; Rabbette, M.; Landheim, R.

    2000-01-01

    Environments can be local, regional, or global. They can include one or more geological, morphological, climatological, and biological types. An environment also represents all the interactions that take place in the identified boundaries. Current planned missions to Mars in the Surveyor Program assume a good knowledge of the Martian environment that we do not have because it cannot be obtained only from orbit. There is a missing step between orbital data and the complex Surveyor missions to be landed that needs to be filled. The Ames/IRSPS Scout Mission Concept originally proposed in February 1999 filled this gap by landing a series of small (less than 10 kgs. each) scout missions. The Mars Environment Scout Mission Concept is being developed to explore the possibility of sending a series of small, simple, and inexpensive stations to the surface of Mars. The objective(s) would be to document either: (a) the environmental diversity of Mars, (b) a specific Martian environment, and/or (c) a region of interest. This type of mission will provide critical information about environments that is currently not available, and could also be used as precursors helping the design, preparation, and planning of more complex future missions to come.

  12. 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

  13. Tailor-made dimensions of diblock copolymer truncated micelles on a solid by UV irradiation.

    PubMed

    Liou, Jiun-You; Sun, Ya-Sen

    2015-09-28

    We investigated the structural evolution of truncated micelles in ultrathin films of polystyrene-block-poly(2-vinylpyridine), PS-b-P2VP, of monolayer thickness on bare silicon substrates (SiOx/Si) upon UV irradiation in air- (UVIA) and nitrogen-rich (UVIN) environments. The structural evolution of micelles upon UV irradiation was monitored using GISAXS measurements in situ, while the surface morphology was probed using atomic force microscopy ex situ and the chemical composition using X-ray photoelectron spectroscopy (XPS). This work provides clear evidence for the interpretation of the relationship between the structural evolution and photochemical reactions in PS-b-P2VP truncated micelles upon UVIA and UVIN. Under UVIA treatment, photolysis and cross-linking reactions coexisted within the micelles; photolysis occurred mainly at the top of the micelles, whereas cross-linking occurred preferentially at the bottom. The shape and size of UVIA-treated truncated micelles were controlled predominantly by oxidative photolysis reactions, which depended on the concentration gradient of free radicals and oxygen along the micelle height. Because of an interplay between photolysis and photo-crosslinking, the scattering length densities (SLD) of PS and P2VP remained constant. In contrast, UVIN treatments enhanced the contrast in SLD between the PS shell and the P2VP core as cross-linking dominated over photolysis in the presence of nitrogen. The enhancement of the SLD contrast was due to the various degrees of cross-linking under UVIN for the PS and P2VP blocks. PMID:26251976

  14. 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.

  15. Interaction of lactoferrin and lysozyme with casein micelles.

    PubMed

    Anema, Skelte G; de Kruif, C G Kees

    2011-11-14

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

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

    PubMed Central

    2012-01-01

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

  17. 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

  18. Redox-responsive micelles self-assembled from dynamic covalent block copolymers for intracellular drug delivery.

    PubMed

    Yang, Qinglai; Tan, Lianjiang; He, Changyu; Liu, Bingya; Xu, Yuhong; Zhu, Zhenggang; Shao, Zhifeng; Gong, Bing; Shen, Yu-Mei

    2015-04-01

    Redox-responsive micelles self-assembled from dynamic covalent block copolymers with double disulfide linkage in the backbone have been developed successfully. The amphiphilic block copolymers PEG-PLA associated with complementary H-bonding sequences can self-assemble into spherical micelles in aqueous media with sizes from 34 nm to 107 nm with different molar mass of PEG and PLA. Moreover, in vitro drug release analyses indicate that reductive environment can result in triggered drug release profiles. The glutathione (GSH) mediated intracellular drug delivery was investigated against HeLa human cervical carcinoma cell line. Flow cytometry and fluorescence microscopy measurements demonstrated that the micelles exhibited faster drug release in glutathione monoester (GSH-OEt) pretreated HeLa cells than that in the nonpretreated cells. Cytotoxicity assay of DOX-loaded micelles indicated the higher cellular proliferation inhibition against 10 mM of GSH-OEt pretreated HeLa cells than that of the nonpretreated ones. These reduction-responsive, biodegradable and biocompatibility micelles could provide a favorable platform to construct excellent drug delivery systems for cancer therapy. PMID:25662913

  19. 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

  20. 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

  1. Polymeric Micelles for Acyclovir Drug Delivery

    PubMed Central

    Sawdon, Alicia J.; Peng, Ching-An

    2014-01-01

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

  2. 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

  3. Complex coacervate core micelles.

    PubMed

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

    2009-01-01

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

  4. Investigation of the micropolarity in reverse micelles of nonionic poly(ethylene oxide) surfactants using 4-nitropyridine-N-oxide as absorption probe.

    PubMed

    Bandula, Rodica; Vasilescu, Marilena; Lemmetyinen, Helge

    2005-07-15

    The micropolarities of the reverse micelle (RM) interior of nonionic poly(ethylene oxide) surfactants of the alkyl ether type (poly(ethylene oxide)[4] lauryl ether (C12E4, Brij 30)), alkyl-aryl ethers (poly(ethylene oxide)[4] nonylphenyl ether (C9PhiE4), poly(ethylene oxide)[5] nonylphenyl ether (C9PhiE5), and poly(ethylene oxide)[5] octylphenyl ether (C8PhiE5)), and poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymers (Pluronics P123, F127) were investigated as a function of the water content by applying the absorption probe technique, using 4-nitropyridine-N-oxide (NP) as a probe. The change in the micellar aggregate micropolarity in different solvents (cyclohexane, decane, n-butanol, and n-butyl acetate) at various water contents has been investigated. The research was focused on the determination of the effects of surfactant structure and solvent type on the hydration degrees of the PEO chains in the region at the core limit, where the NP probe was located. All results regarding the polarities in RM and PEO/water calibration mixtures have been expressed in terms of Kosower's Z values, using the linear dependence of E(NP) on Kosower's Z. The PPO/butanol mixtures have also been used for RM in butanol as a reference system. The data revealed that local polarity in RM is dependent on the surfactant type, block copolymer composition, solvent nature, and water content. At the same water content, the results clearly indicate a lower hydration degree of triblock copolymers, as compared to the surfactants of the alkyl ether and alkyl-aryl ether type, but for P123 and F127 Pluronics in n-butanol the hydration is higher owing to the behavior of butanol as cosurfactant and to its hydration. PMID:15925636

  5. Giant rodlike reversed micelles

    SciTech Connect

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

    1994-05-04

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

  6. 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…

  7. 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…

  8. Diclofenac/biodegradable polymer micelles for ocular applications

    NASA Astrophysics Data System (ADS)

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

    2012-07-01

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

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

    PubMed

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

    2000-08-01

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

  10. Decision investigation and support environment (DISE)

    NASA Astrophysics Data System (ADS)

    VonPlinsky, Michael J.; Johnson, Pete; Crowder, Ed

    2001-09-01

    The "Decision Integration and Support Environment" (DISE) is a Bayesian network (BN) based modeling and simulation of the target nomination and aircraft tasking decision process. FTI has developed two BNs to model these processes, incorporating aircraft, target, and overall mission priorities from the Air Operations Center (OAC) and the mission planners/command staff. DISE operates in event driven interactions with FTI's AOC model, being triggered from within the Time Critical Target (TCT) Operations cell. As new target detections are received by the AOC from off-board ISR Sources and processed by the Automatic Target Recognition (ATR) module in the AOC, DISE is called to determine if the target should be prosectued, and if so, which of the available aircraft should be tasked to attack it. A range of decision criteria, with priorities established off-line and input into the tool, are associated with this process, including factors such as: * Fuel Level - amount of fuel in aircraft * Type of Weapon - available weapons on board aircraft * Probability of Survival - depends on the type of TST, time criticality and other factors * Potential Collateral Damage - amount of damage incurred on TST surroundings * Time Criticality of TST - how "critical" it is to attack the target depending on its launch status * Time to Target - aircraft's distance (in minutes) from the TST * Current Mission Priority - priority of the mission to which the aircraft is currently assigned * TST Mission Priority - determined when the target is originally nominated * Possible Reassignment - represents whether it is even possible to reassign the aircraft * Aircraft Re-tasking Availability - represents any factor not taken into account by the model, including commander override.

  11. Investigation on the structure of water/AOT/IPM/alcohols reverse micelles by conductivity, dynamic light scattering, and small angle X-ray scattering.

    PubMed

    Zhang, Xiaoguang; Chen, Yingjun; Liu, Jiexiang; Zhao, Chuanzhuang; Zhang, Haijiao

    2012-03-29

    We have systematically investigated the effect of alcohols (ethanol, propanol, butanol, and pentanol) on the structure of the water/AOT/IPM system using conductivity, dynamic light scattering (DLS), and small-angle X-ray scattering (SAXS) techniques. The results show that no percolation phenomenon is observed in the water/AOT/IPM system, whereas the addition of ethanol (propanol and butanol) induces apparently percolation. The threshold water content (W(p)) depends closely on the alcohol type and concentration. The effect of alcohols on the conductance behavior is discussed from the physical properties of alcohols, the interfacial flexibility, and the attractive interactions between droplets. The hydrodynamic diameter of droplets (d(H)) obtained from DLS increases markedly with the increase in water content (W(0)); however, it decreases gradually with increasing alcohol chain length and concentration. SAXS measurements display distinctly the shoulder, the low hump peaks, and the heavy tail phenomenon in the pair distance distribution function p(r) profile, which rely strongly on the alcohol species and its concentration. The gyration radius (R(g)) increases with increasing W(0), and decreases with the increase of alcohol chain length and concentration. Schematic diagram of the conductance mechanism of water/AOT/IPM/alcohol systems is primarily depicted. Three different phases of the discrete droplets, the oligomers, and the isolated ellipsoidal droplets existed in the different W(0) ranges correspond to three different stages in the conductivity-W(0) curve. Coupling the structure characteristics of reverse micelles obtained from DLS and SAXS techniques with conductivity could be greatly helpful to deeply understand the percolation mechanism of water/AOT/IPM/alcohols systems. PMID:22380931

  12. 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. PMID:23472857

  13. 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.

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

    PubMed

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

    2015-01-01

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

  15. Electron solvation in aqueous reverse micelles: Equilibrium properties

    NASA Astrophysics Data System (ADS)

    Laria, Daniel; Kapral, Raymond

    2002-10-01

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

  16. pH-induced vesicle-to-micelle transition in amphiphilic diblock copolymer: investigation by energy transfer between in situ formed polymer embedded gold nanoparticles and fluorescent dye.

    PubMed

    Maiti, Chiranjit; Banerjee, Rakesh; Maiti, Saikat; Dhara, Dibakar

    2015-01-01

    The ability to regulate the formation of nanostructures through self-assembly of amphiphilic block copolymers is of immense significance in the field of biology and medicine. In this work, a new block copolymer synthesized by using reversible addition-fragmentation chain transfer (RAFT) polymerization technique from poly(ethylene glycol) monomethyl ether acrylate (PEGMA) and Boc-l-tryptophan acryloyloxyethyl ester (Boc-l-trp-HEA) was found to spontaneously form pH-responsive water-soluble nanostructures after removal of the Boc group. While polymer vesicles or polymerosomes were formed at physiological pH, the micelles were formed at acidic pH (< 5.2), and this facilitated a pH-induced reversible vesicle-to-micelle transition. Formation of these nanostructures was confirmed by different characterization techniques, viz. transmission electron microscopy, dynamic light scattering, and steady-state fluorescence measurements. Further, these vesicles were successfully utilized to reduce HAuCl4 and stabilize the resulting gold nanoparticles (AuNPs). These AuNPs, confined within the hydrophobic shell of the vesicles, could participate in energy transfer process with fluorescent dye molecules encapsulated in the core of the vesicles, thus forming a nanometal surface energy transfer (NSET) pair. Subsequently, following the efficiency of energy transfer between this pair, it was possible to monitor the process of transition from vesicles to micelles. Thus, in this work, we have successfully demonstrated that NSET can be used to follow the transition between nanostructures formed by amphiphilic block copolymers. PMID:25494810

  17. Reverse micelles in supercritical fluids. (2) Fluorescence and absorption spectral probes of adjustable aggregation in the two-phase region

    SciTech Connect

    Yazdi, P.; McFann, G.J.; Fox, M.A.; Johnston, K.P. )

    1990-09-06

    The properties of bis(2-ethylhexyl) sodium sulfosuccinate (AOT) reverse micelles and microemulsions in supercritical fluid (SCF) ethane, liquid propane, and other alkanes are reported. The microscopic environment inside the reverse micelles was investigated with the absorption probe pyridine N-oxide and the fluorescence probe 8-anilino-1-naphthalenesulfonic acid (ANS). The microscopic behavior is related directly to a macroscopic property, the water-to-surfactant ratio W{sub o}. In the one-phase region, a reverse micelle in a SCF is much like that in a liquid solvent. However, in the two-phase region, both the microscopic and macroscopic properties may be adjusted with pressure in ethane and propane, because of changes in the partitioning of the components between the phases.

  18. 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

  19. Effect of confinement on excited-state proton transfer of firefly's chromophore D-luciferin in AOT reverse micelles.

    PubMed

    Kuchlyan, Jagannath; Banik, Debasis; Kundu, Niloy; Ghosh, Surajit; Banerjee, Chiranjib; Sarkar, Nilmoni

    2014-03-27

    Excited-state intermolecular proton transfer of D-luciferin in reverse micelles has been investigated using steady-state and time-resolved fluorescence spectroscopy measurement. The different polar cores have been chosen for the study of proton transfer dynamics in aerosol-OT (AOT) reverse micelles. It is shown that aqueous reverse micelle is the suitable environment for the photoprotolytic reaction of D-luciferin. The neutral form of the chromophore is present both in ground and excited state at W0 = 0. The proton transfer in nanometer size water pool of water/AOT/n-heptane begins at W0 = 8 and increases with increasing W0 values. However, the intermolecular excited-state proton transfer (ESPT) of D-luciferin is inhibited in nonaquous reverse micelles with DMF and DMSO as a polar core. Thus, the requirement of ESPT of D-luciferin to take place in reverse micelles consists of polar protic solvent like water as a polar core. PMID:24624892

  20. 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

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

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

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

  2. 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.

  3. Integrated site investigation procedure for environment protection toward sustainable development

    NASA Astrophysics Data System (ADS)

    Omar, R. C.; Roslan, R.; Baharuddin, I. N. Z.

    2013-06-01

    The spatial configuration of cities and their relationship to the urban environment has recently been the subject of empirical, theoretical and policy research. An awareness of environmental issues can assist policy makers, planners, developers and others to recognize the constraints imposed upon development due the physical environment especially in areas, which are susceptible to erosion, flooding and landslide. This paper highlights the key requirements for considering an assessment to protect our urban environment by incorporating three main factor i.e. policy practice, planning process and engineering investigation. Base on this three main factor the framework of the assessment is carried out. The assessment can be divided into three different categories, namely as investigation for planning, investigation for urban development and specialized investigation and mitigation. The minimum requirements for the planning and urban development investigation are listed. These guidelines suggest the level at which the various types of investigation should be carried out as well as the range of application, the scope and methodology to be used for different investigation. It is hoped that this procedure will provide guidance in the establishment and protection of urban ecosystem toward sustainable development.

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

    PubMed

    Yusof, Nor Saadah Mohd; Ashokkumar, Muthupandian

    2015-05-01

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

  5. [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

  6. 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

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

    PubMed Central

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

    2013-01-01

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

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

    PubMed

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

    2016-03-01

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

  9. 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.

  10. Investigation of expert system design approaches for electronic design environments

    NASA Astrophysics Data System (ADS)

    Poppens, Susan A.

    1987-12-01

    Various schemes were investigated that are available for the design effort of electronic systems. The information is to be incorporated into a knowledge base to determine approaches for a particular design. Various design methodologies are to be investigated for their appropriateness and application in the aforesaid design environment. The second phase is to focus on the knowledge base gathered in the design effort for electronic design. This knowledge base is to be incorporated into a rule based expert system which can be utilized by the design engineer in the design/development of functional specifications.

  11. 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.

  12. Toward rational design of protein detergent complexes: determinants of mixed micelles that are critical for the in vitro stabilization of a G-protein coupled receptor.

    PubMed

    O'Malley, Michelle A; Helgeson, Matthew E; Wagner, Norman J; Robinson, Anne S

    2011-10-19

    Although reconstitution of membrane proteins within protein detergent complexes is often used to enable their structural or biophysical characterization, it is unclear how one should rationally choose the appropriate micellar environment to preserve native protein folding. Here, we investigated model mixed micelles consisting of a nonionic glucosylated alkane surfactant from the maltoside and thiomaltoside families, bile salt surfactant, and the steryl derivative cholesteryl hemisuccinate. We correlated several key attributes of these micelles with the in vitro ligand-binding activity of hA(2)aR in these systems. Through small-angle neutron scattering and radioligand-binding analysis, we found several key aspects of mixed micellar systems that preserve the activity of hA(2)aR, including a critical amount of cholesteryl hemisuccinate per micelle, and an optimal hydrophobic thickness of the micelle that is analogous to the thickness of native mammalian bilayers. These features are closely linked to the headgroup chemistry of the surfactant and the hydrocarbon chain length, which influence both the morphology and composition of resulting micelles. This study should serve as a general guide for selecting the appropriate mixed surfactant systems to stabilize membrane proteins for biophysical analysis. PMID:22004748

  13. 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. PMID:25996409

  14. 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. PMID:25173042

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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

  20. 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.

  1. Preparation and characterization of magnetic thermosensitive fluorouracil micelles.

    PubMed

    Zhang, Min; Jin, Xueqin; Gou, Guojing

    2016-06-01

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

  2. 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.

  3. 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.

  4. Experimental investigation of turbulent mixing in post-explosion environment

    NASA Astrophysics Data System (ADS)

    Smith, Josh; Hargather, Michael

    2015-11-01

    Experiments are performed to investigate the turbulent mixing of product gases and the ambient environment in a post-explosion environment. The experiments are performed in a specially constructed shock tunnel where thermite-enhanced explosions are set off. The explosives are detonated at one end of the tunnel, producing a one-dimensional shock wave and product gas expansion which moves toward the open end of the tunnel. Optical diagnostics are applied to study the shock wave motion and the turbulent mixing of the gases after the detonation. Results are presented for schlieren, shadowgraph, and interferometry imaging of the expanding gases with simultaneous pressure measurements. An imaging spectrometer is used to identify the motion of product gas species. Results show varying shock speed with thermite mass and the identification of turbulent mixing regions.

  5. Formation of catalysts in inverse micelles

    SciTech Connect

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

    1990-01-01

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

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

    PubMed

    Strubbe, Filip; Prasad, Manoj; Beunis, Filip

    2015-02-01

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

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

    PubMed

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

    2004-11-20

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

  8. 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.

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

    NASA Astrophysics Data System (ADS)

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

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

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

    PubMed

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

    2013-06-01

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

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

    PubMed Central

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

    2009-01-01

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

  12. Investigation of crystal growth from solutions. [in zero gravity environments

    NASA Technical Reports Server (NTRS)

    Miyagawa, I.

    1974-01-01

    The quality was investigated of a crystal of Rochelle salt grown from a solution placed in the zero-gravity environment of Skylab 4. The crystal has the following unique features: (1) the typical cavity is a long tube extending along the c-axis, the average length being 4mm, compared to 0.1mm that is the average size for earth-grown crystals; and (2) the crystal consists of several single crystals, the axes of which are parallel to each other. A preliminary measurement was made on the ferroelectric hysteresis curve of this Rochelle salt crystal.

  13. Interaction of 6-methoxyquinoline with anionic sodium dodecylsulfate micelles: Photophysics and rotational relaxation dynamics at different pH.

    PubMed

    Varma, Y Tej; Pant, Debi D

    2016-04-01

    Interactions of different species of 6-methoxyquinoline (6MQ) with anionic micelles have been studied at different pre-micellar, micellar and post-micellar concentrations using steady state, time resolved fluorescence and fluorescence anisotropy techniques. The sensitivity of fluorescence of 6MQ to change in its local environment was used to probe sodium dodecylsulfate (SDS) micelles. At post-micellar concentrations of SDS, the observed blue shift in the fluorescence spectrum and increase in quantum yield are attributed to the incorporation of solute molecule to micelles. 6MQ has been found to bind to the surface of the anionic micelles instead of penetrating inside the core of micelles. The binding constant (Kb) calculated for 6MQ revealed that the electrostatic forces mediate charged probe-micelle association, whereas, hydrophobic interaction allowed neutral 6MQ to associate with SDS micelles. The charged 6MQ gets inserted deeper into the micelle surface than its neutral form. The fluorescence anisotropy decay of 6MQ in SDS micelles studied at different pH allowed determination of restriction of motion of the fluorophore. The location of the probe molecule in micellar systems is justified by a variety of spectral parameters such as refractive index, dielectric constant, ET(30), average fluorescence decay time, radiative and non-radiative rate constants, and rotational relaxation time. The micro-environment around the fluorophore reveals that the photophysics of 6MQ is very sensitive to the microenvironment of SDS and probe molecules reside at the water-micelle interface. PMID:26775098

  14. 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.

  15. Glycation Reactions of Casein Micelles.

    PubMed

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

    2016-04-13

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

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. Synthesis and characterization of pH-sensitive poly(itaconic acid)-poly(ethylene glycol)-folate-poly(l-histidine) micelles for enhancing tumor therapy and tunable drug release.

    PubMed

    Sun, Yuan; Li, Yapeng; Nan, Shuli; Zhang, Liangzi; Huang, Hailong; Wang, Jingyuan

    2015-11-15

    pH responsive intracellular tumor targeting is increasingly investigated as a pathway to trigger the release of anti-tumor drugs once the drug carrier reached the unique acidic environment of the solid tumors or after the drug carrier has been taken up by cells, resulting in the localization of the micelles in the acidic endosomes and lysosomes. Poly(itaconic acid)-poly(ethylene glycol)-folate-poly(l-histidine) (PIA-PEG-FA-PHIS) was synthesized as a carrier for tumor-targeted drug delivery. The micelles were internalized by receptor-mediated endocytosis, and the combination of active targeting and triggered release resulted in apparent cytotoxicity and antitumor activity. The MTT assay showed DOX-loaded micelles had higher and obvious cytotoxicity against Hela cells at pH 5.0 than that at pH 7.4. Cellular uptake experiments revealed that these pH-responsive PIA-PEG-FA-PHIS micelles were taken up in great amounts by receptor-mediated endocytosis and delivered to lysosomes, triggering release of DOX into the cytoplasm. These indicated that the PIA-PEG-FA-PHIS micelles could be a promising drug delivery system with preeminent stability for targeting the hydrophobic drugs to cancer cells and releasing DOX in to the cells by sensing the acidic environment of the endosomes for cancer therapy. PMID:26210102

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

    PubMed

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

    2008-06-01

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

  2. 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.

  3. 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.

  4. Investigations on 4x4 polymer couplers for airborne environment

    NASA Astrophysics Data System (ADS)

    Klotzbuecher, Thomas; Sprzagala, M.; Koch, Anne; Teubner, Ulrich

    2004-09-01

    Due to the potential of high data rates up to several Gb/s, low electromagnetic interference sensitivity and weight reduction capabilities, in future, optical data transmission will become standard in airplanes. The requirements on the necessary optical components that have to be operated in airborne environment in general are extremely high. In addition, airframe manufacturers are interested in low cost components. An example for such an optical component is a star coupler for data distribution, in particular, a device made on base of polymers. The applicability of such 4x4 polymer star couplers under extreme environmental conditions was investigated. The investigations were made at temperatures from -40 to +80 °C and up to 98 % humidity. Different types of housings were tested (polymer, metal, ceramic). It was found that housing of the polymer couplers is required necessarily, since non-housed components exhibit a large insertion loss increase of up to 0.5 dB during temperature variation. Best results were achieved with metal or ceramic housings exhibiting a maximum insertion loss increase of approximately 0.1 dB. However, due to a large difference of thermal expansion coefficients of filling and housing material, respectively, ceramic housings mechanically failed (crack formation) and thus metal housings are first choice. The results were also compared to those achieved for commercial 4x4 multimode couplers made of glass and based on fused bi-conical taper technology.

  5. 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

  6. Branching mechanisms in surfactant micelles

    NASA Astrophysics Data System (ADS)

    Dhakal, Subas; Sureshkumar, Radhakrishna

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

  7. 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

  8. In vitro degradation behavior of poly(lactide)-poly(ethylene glycol) block copolymer micelles in aqueous solution.

    PubMed

    Yang, Liu; El Ghzaoui, Abdeslam; Li, Suming

    2010-11-15

    Self-assembling micelles were prepared from polylactide-poly(ethylene glycol) (PLA-PEG) block copolymer by using two different methods: direct dissolution and dialysis. The in vitro degradation properties of the micelles were investigated at 37°C and monitored by using various techniques. During the investigated degradation time, the size of micelles by dialysis remains stable, while that of micelles by direct dissolution first increases, followed by a collapse of micellar structure. The composition of PLA-PEG copolymers greatly affects the degradation of micelles. Micelles with longer hydrophobic PLA blocks exhibit less size changes due to more compact structure. On the other hand, the structural integrity of L/D mixed micelles is preserved for longer time than that of single micelles, in agreement with the stereocomplexation effect between L-PLA and D-PLA blocks. As degradation proceeds, the average molar mass of copolymer decreases and the distribution becomes wider, especially for micelles by dialysis and L/D mixed micelles with a more compact structure. Additionally, the PEG content in the copolymer chains increases during degradation, leading to a decrease of glass transition and crystallization temperature of the copolymers. However, the residual LA fragments produced by degradation disfavors the crystallization of PEG blocks, thus resulting in the decrease of melting temperature and melting enthalpy. PMID:20816736

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

    PubMed

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

    2000-09-15

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

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

    PubMed Central

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

    2011-01-01

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

  11. 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.

  12. 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.

  13. Investigation of building energy autonomy in the sahelian environment

    NASA Astrophysics Data System (ADS)

    Coulibaly, O.; Ouedraogo, A.; Kuznik, F.; Baillis, D.; Koulidiati, J.

    2012-02-01

    In this study, the energy generation of a set of photovoltaic panels is compared with the energy load of a building in order to analyse its autonomy in the sahelian environment when taking into account, the orientation, the insulation and the energy transfer optimisation of its windows. The Type 56 TRNSYS multizone building model is utilized for the energy load simulation and the Type 94 model of the same code enables the coupling of photovoltaic (PV) panels with the building. Without insulation, the PV energy generation represents 73.52 and 111.79% of the building electric energy load, respectively for poly-crystalline and mono-crystalline panels. For the same PV characteristics and when we insulate the roof and the floor, the energy generation increases to represent successively 121.09 and 184.13%. In the meantime, for building without insulation and with insulate the roof, the floor and 2 cm insulated walls, the energy consumption ratios decrease respectively from 201.13 to 105.20 kWh/m2/year. The investigations finally show that it is even possible to generate excess energy (positive energy building) and reduce the number and incident surface area of the PV panels if we conjugate the previous model with building passive architectural design mode (orientation, solar protection ...).

  14. Experimental investigation of magnetic mineral formation in hydrocarbon environments

    NASA Astrophysics Data System (ADS)

    Abubakar, Rabiu; Muxworthy, Adrian; Sephton, Mark; Fraser, Alastair

    2013-04-01

    Experimental investigation of magnetic mineral formation in hydrocarbon environments Rabiu Abubakar, Adrian Muxworthy, Mark Septhon and Alastair Fraser Dept. of Earth Science and Engineering, Imperial College London Magnetic anomalies have been observed over oil fields from aeromagnetic surveys. These anomalies have been linked with the presence of hydrocarbons and that has generated a lot of interest over possible application of magnetism in the exploration of oil and gas but there has also been debate over the origin of the magnetic minerals causing the magnetic anomaly. Our approach was to generate crude oil in the lab using three source rocks from the Wessex Basin, England, which is a hydrocarbon province. The source rocks were the Kimmeridge Clay, Oxford Clay and the Blue Lias. The source rocks were powered and pyrolysed in a high pressure vessel. The crude oil was then extracted and the magnetic signal of the remaining pyrolysate measured. We discovered a significant contrast in the magnetic hysteresis and thermomagnetic properties between the pyrolysate and the unpyrolysed (immature) source rocks. We will present the preliminary results, which indicate that magnetic minerals were generated as a result of heat and therefore related linked to maturation of the source rocks

  15. 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

  16. 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.

  17. 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

  18. 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…

  19. 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…

  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. 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.

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

    PubMed

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

    2009-04-01

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

  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. 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

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

    PubMed

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

    2013-07-01

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

  6. 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

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

    PubMed

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Kim, Hyun Chang; Won, You-Yeon

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

  9. 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.

  10. Mars Scout: An Astrobiology Micromission to Investigate Martian Environments

    NASA Technical Reports Server (NTRS)

    Cabrol, N. A.; Ori, G. G.; Grin, E. A.; Marinangeli, L.; McKay, C. P.; Marshall, J.; Thomas, H. J.; Rabette, M.; Sims, M.; Landheim, R.

    2000-01-01

    The Mars Scout Mission Concept explores the possibility of sending a series of small, simple, and cheap stations at the surface of Mars which will provide the critical information about environments that are missing today.

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

    PubMed

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

    2016-02-01

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

  12. 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

  13. 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.

  14. Modulation of excited-state proton-transfer reactions of 7-hydroxy-4-methylcoumarin in ionic and nonionic reverse micelles.

    PubMed

    Choudhury, Sharmistha Dutta; Pal, Haridas

    2009-05-14

    The prototropic behavior of the dye, 7-hydroxy-4-methylcoumarin (7H4MC), has been studied in cationic benzyldimethylhexadecylammonium chloride (BDHC) and nonionic poly(oxyethylene)(tetramethylbutyl)phenyl ether (TritonX-100, TX-100) reverse micelles using ground-state absorption and steady-state and time-resolved fluorescence measurements. The results have been compared with the previous results in the anionic sodium 1,4-bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles. Although the probe dye, 7H4MC, is indicated to reside in the interfacial region in all of the reverse micelles studied, significant differences have been observed in the evolution of the different prototropic species. In BDHC reverse micelles, the anionic form is favored over the tautomeric form at the higher w0 values, which is contrary to the observation in AOT reverse micelles where both of these forms are almost equally produced. The higher propensity for the formation of the anionic form in BDHC reverse micelles has been explained on the basis of the additional electrostatic stabilization of the anionic species in the cationic BDHC reverse micelles compared to that in the anionic AOT reverse micelles. On the other hand, in TX-100 reverse micelles, the anionic form is not very evident, but interestingly, the tautomer form begins to appear beyond w0=2. The appearance of the tautomeric species apparently coincides with the formation of the water pool in the TX-100 reverse micelles. However, due to the more restricted nature of the water molecules within this reverse micelle (mostly dispersed around the oxyethylene chains), deprotonation of the 7H4MC dye and the consequential stabilization of the anionic form are considerably reduced. The results clearly reveal that the aqueous environment in the vicinity of the probe is quite different for the reverse micelles considered, and these differences largely modulate the prototropic processes of the excited dye. PMID:19374362

  15. 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

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

    PubMed Central

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

    2012-01-01

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

  17. Micelle hydrogels for three-dimensional dose verification

    NASA Astrophysics Data System (ADS)

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

    2009-05-01

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

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

    PubMed Central

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

    2014-01-01

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

  19. 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

  20. Some Speculation about the Investigation of Person-Environment Transactions.

    ERIC Educational Resources Information Center

    Holland, John L.

    1987-01-01

    Speculates about the outcomes of person-environment research and suggests how more successful research might be planned. Focuses on congruence effects and the value of meta-analysis. Suggests careful use of theory; attention to both environmental and personal assessment; identification of potent personal, environmental, and theoretical variables;…

  1. 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,…

  2. Micelles Protect and Concentrate Activated Acetic Acid

    NASA Astrophysics Data System (ADS)

    Todd, Zoe; House, C.

    2014-01-01

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

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

    PubMed

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

    2010-01-01

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

  4. 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.

  5. 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…

  6. 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

  7. 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

  8. Ultrasound-Mediated Polymeric Micelle Drug Delivery.

    PubMed

    Xia, Hesheng; Zhao, Yue; Tong, Rui

    2016-01-01

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

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

    PubMed

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

    2011-09-01

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

  10. Formation of micelles in homopolymer-copolymer mixtures

    NASA Astrophysics Data System (ADS)

    Müller, Marcus; Cavallo, Anna; Binder, Kurt

    2007-03-01

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

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

    NASA Astrophysics Data System (ADS)

    Pang, Yoonsoo; Deak, John; Dlott, Dana

    2005-03-01

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

  12. Investigating Your Environment: Teaching Materials for Environmental Education. October 1978 Edition.

    ERIC Educational Resources Information Center

    Forest Service (USDA), Washington, DC.

    Included are seven lesson plans for secondary school students: (1) soil investigations; (2) water investigations; (3) forest investigations; (4) investigating some animals and their environment; (5) a land use simulation; (6) investigating the human community; and (7) developing environmental investigations. Each lesson plan has seven components:…

  13. 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.

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

    PubMed

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

    2011-04-15

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

  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. 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

  17. 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

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

    PubMed

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

    2015-07-15

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

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2016-02-23

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

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

    PubMed

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

    2015-07-01

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

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

    PubMed

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

    2014-05-16

    Quantum dots (QDs) have tremendous potential for biomedical imaging, including super-resolution techniques that permit imaging below the diffraction limit. However, most QDs are produced via organic methods, and hence require surface treatment to render them water-soluble for biological applications. Previously, we reported a micelle-templating method that yields nanocomposites containing multiple core/shell ZnS-CdSe QDs within the same nanocarrier, increasing overall particle brightness and virtually eliminating QD blinking. Here, this technique is extended to the encapsulation of Mn-doped ZnSe QDs (Mn-ZnSe QDs), which have potential applications in super-resolution imaging as a result of the introduction of Mn(2+) dopant energy levels. The size, shape and fluorescence characteristics of these doped QD-micelles were compared to those of micelles created using core/shell ZnS-CdSe QDs (ZnS-CdSe QD-micelles). Additionally, the stability of both types of particles to photo-oxidation was investigated. Compared to commercial QDs, micelle-templated QDs demonstrated superior fluorescence intensity, higher signal-to-noise ratios, and greater stability against photo-oxidization,while reducing blinking. Additionally, the fluorescence of doped QD-micelles could be modulated from a bright 'on' state to a dark 'off' state, with a modulation depth of up to 76%, suggesting the potential of doped QD-micelles for applications in super-resolution imaging. PMID:24762566

  3. 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

  4. Charge-conversional and pH-sensitive PEGylated polymeric micelles as efficient nanocarriers for drug delivery.

    PubMed

    Liu, Gong-Yan; Li, Min; Zhu, Cong-Shan; Jin, Qiao; Zhang, Zong-Cai; Ji, Jian

    2014-09-01

    A novel amphiphilic copolymer, poly (ethylene glycol)-graft-polyethyleneimine/amide (PEG-g-PEI/amide), is synthesized by grafting PEG and1,2-cis-Cyclohexanedicarboxylic anhydride onto the PEI. PEGylated polymeric micelles can be assembled from the amphiphilic copolymers with well-defined nano-sizes, and anti-cancer drugs are successfully loaded into micelle core formed by the amide. The amides with neighboring carboxylic acid groups exhibit pH-dependent hydrolysis and can reversibly shield the cationic charge of amine groups on the PEI, giving the micelles a charge-conversion property from negative to positive in acidic tumor tissue environment. Meanwhile, the cleavage of amide bonds at acidic pH also results in the disassembly of the micelle and pH-responsive drug release. These micelles are promising drug delivery systems due to their smart properties: PEGylation, suitable size, charge-conversion, and simultaneous pH-sensitive drug release. PMID:24866398

  5. 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.

  6. 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.

  7. Formulation of Acid-Sensitive Micelles for Delivery of Cabazitaxel into Prostate Cancer Cells.

    PubMed

    Aydin, Omer; Youssef, Ibrahim; Yuksel Durmaz, Yasemin; Tiruchinapally, Gopinath; ElSayed, Mohamed E H

    2016-04-01

    We report the synthesis of an amphiphilic triblock copolymer composed of a hydrophilic poly(ethylene glycol) (PEG) block, a central poly(acrylic acid) (PAA) block, and a hydrophobic poly(methyl methacrylate) (PMMA) block using atom transfer radical polymerization technique. We examined the self-assembly of PEG-b-PAA-b-PMMA copolymers in aqueous solutions forming nanosized micelles and their ability to encapsulate hydrophobic guest molecules such as Nile Red (NR) dye and cabazitaxel (CTX, an anticancer drug). We used 2,2β'-(propane-2,2-diylbis(oxy))-diethanamine to react with the carboxylic acid groups of the central PAA block forming acid-labile, shell cross-linked micelles (SCLM). We investigated the loading efficiency and release of different guest molecules from non-cross-linked micelles (NSCLM) and shell cross-linked micelles (SCLM) prepared by reacting 50% (SCLM-50) and 100% (SCLM-100) of the carboxylic acid groups in the PAA in physiologic (pH 7.4) and acidic (pH 5.0) buffer solutions as a function of time. We examined the uptake of NR-loaded NSCLM, SCLM-50, and SCLM-100 micelles into PC-3 and C4-2B prostate cancer cells and the effect of different micelle compositions on membrane fluidity of both cell lines. We also investigated the effect of CTX-loaded NSCLM, SCLM-50, and SCLM-100 micelles on the viability of PC-3 and C4-2B cancer cells compared to free CTX as a function of drug concentration. Results show that PEG-b-PAA-b-PMMA polymers form micelles at concentrations ≥11 μg/mL with an average size of 40-50 nm. CTX was encapsulated in PEG-b-PAA-b-PMMA micelles with 55% loading efficiency in NSCLM. In vitro release studies showed that 30% and 85% of the loaded CTX was released from SCLM-50 micelles in physiologic (pH 7.4) and acidic (pH 5.0) buffer solutions over 30 h, confirming micelles' sensitivity to solution pH. Results show uptake of NSCLM and SCLM into prostate cancer cells delivering their chemotherapeutic cargo, which triggered efficient cancer

  8. A study of the thermodynamic properties of surfactant mixtures: Mixed micelle formation and mixed surfactant adsorption

    SciTech Connect

    Lopata, J.J.

    1992-12-31

    The volumetric mixing in anionic/nonionic, cationic/nonionic, and anionic/cationic mixed micelles was determined by examining the total surfactant apparent molar volumes at total surfactant concentrations much greater than the mixture critical micelle concentration. The mixed surfactant systems investigated were: sodium dodecyl sulfate and a polyethoxylated nonylphenol, at 0.15 M NaCl and with no added NaCl; cetyl pyridinium chloride and polyethoxylated nonylphenol, at 0.03 M NaCl; and sodium dodecyl sulfate and dodecyl pyridinium chloride, at 0.15 M NaCl. The results of this study suggest that the electrostatic interactions in the mixed micelles do no significantly effect the molar volume of the mixed micelle. Therefore, the micelle hydrophobic core dominates the volumetric mixing in mixed micelles. The adsorption of sodium dodecyl sulfate and a polyethoxylated nonylphenol and well defined mixtures thereof was measured on gamma alumina. A pseudo-phase separation model to describe mixed anionic/nonionic admicelle (adsorbed surfactant aggregate) formation was developed. In this model, regular solution theory was used to describe the anionic/nonionic surfactant interactions in the mixed admicelle and a patch-wise adsorption model was used to describe surfactant adsorption on a heterogeneous surface. Regular solution theory was tested on specific homogeneous surface patches by examining constant total surfactant adsorption levels. For the adsorption of binary surfactant mixtures adsorbing at total equilibrium concentrations above the mixture critical micelle concentration, simultaneous solution of the pseudo-phase separation models for mixed admicelle and mixed micelle formation predicts that the surfactant compositions in the monomer, micelle, and admicelle pseudo-phases are constant at a constant total adsorption level.

  9. A biophysical characterization of the interaction of a hepatitis C virus membranotropic peptide with micelles.

    PubMed

    Alves, N S; Mendes, Y S; Souza, T L F; Bianconi, M L; Silva, J L; Gomes, A M O; Oliveira, A C

    2016-04-01

    Membrane fusion is a highly regulated process that allows enveloped viruses to enter cells and replicate. Viral glycoproteins trigger membrane fusion by means of internal sequences known as fusion peptides. The hepatitis C virus (HCV) genome encodes the envelope glycoproteins E1 and E2, but their specific roles in the fusion step and the localization of the fusion peptide remain uncharacterized. Here, we studied the biophysics of the interactions between the glycoprotein E2 peptide HCV421-445 and four different micellar systems providing ionic, non-ionic and zwitterionic surfaces to investigate the importance of electrostatic interactions for peptide-membrane binding. Circular dichroism, fluorescence spectroscopy and calorimetry were used to characterize peptide-micelle interactions and structural changes. Fluorescence quenching showed that HCV421-445 interacts with SDS or CTAB ionic, n-OGP non-ionic and DPC zwitterionic micelles. The indole ring of Trp seems to anchor the peptide in micelles. Trp residues seem to be more deeply inserted in ionic and non-ionic micelles where peptide interactions are more stable than with DPC zwitterionic micelles. The interaction with zwitterionic micelles appears to occur at the surface. Both interaction types are exothermic because of peptide-micelle interactions and a gain of secondary structure in the helical conformation. HCV421-445 interacts with detergent monomers and micelles. Peptide-micelle interaction is pH-independent. HCV421-445 interacts with membranes, promoting aggregation and coalescence of vesicles with content leakage, suggesting that HCV421-445 may participate in membrane fusion. This structural characterization contributes to our understanding of the molecular process that promotes fusion, which is important in the further development of new antiviral therapies. PMID:26773352

  10. 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

  11. 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.

  12. 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

  13. 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)

  14. Investigation of mechanisms of gas hydrates accumulation in permafrost environments

    NASA Astrophysics Data System (ADS)

    Chuvilin, E. M.

    2012-12-01

    The feature of permafrost sediments is capability to accumulate a quantity of natural gases foremost methane with low admixture of carbon dioxide. In consequence of natural and climatic changes, formation of favorable thermobaric conditions for transformation of intra-permafrost gas accumulations from free state into gas hydrate is possible. In consideration of high gas-saturation of frozen sediments, the active processes of hydrate formation in permafrost during the transgression of arctic seas or under continental glaciations can be expected. A special experimental technique was elaborated to perform physical modeling of hydrate formation conditions in cryogenic ice-containing sediments. The experiments were carried out under constant negative temperatures in interval from -2 oC to -9 oC. Methane (99.98%) was used as hydrate-former gas. During the experiments the kinetics of gas consumption in porous media was investigated and also part of porous water turned into hydrate and hydrate- saturation of sediment samples were estimated. Experiments show that hydrate formation in gas saturated sediments occurs actively not only in freezing sediments (above 0 oC) but also in frozen sediments (below 0 oC). Intensity of hydrate formation in frozen sediments depends on such factors as ice-saturation, thermobaric conditions and gas composition. Experimental data shows that after attenuation of hydrate formation in frozen sediments the considerable activization of hydrate accumulation processes during the increasing of temperature above 0 oC can occur. That leads to the thawing of porous ice, which does not turn into hydrate, and attendant this process structural-textural changes result in appearance of new gas-water contacts. As a result there is second hydrate formation on background of thawing of ice. Based on analysis of geological data and experimental researches possible geological models of gas hydrates formation in shallow permafrost under the sea transgression and

  15. 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

  16. 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

  17. Role of membrane lipids in peptide hormone function: binding of enkephalins to micelles.

    PubMed Central

    Deber, C M; Behnam, B A

    1984-01-01

    In the course of their biological function, peptide hormones must be transferred from an aqueous phase to the lipid-rich environment of their membrane-bound receptor proteins. We have investigated the possible influence of phospholipids in this process, using 360-MHz 1H and 90-MHz 13C NMR spectroscopy to examine the association of the opioid peptides [Met]- and [Leu]enkephalins (Tyr-Gly-Gly-Phe-Met/Leu) with phospholipid micelles. Binding of peptides to lipid was monitored in NMR spectra by selective chemical shift movements (e.g., the Phe aromatic ring protons) and residue-specific line broadening (e.g., of Met/Leu carbonyl- and alpha-carbon resonances). Results established that the zwitterionic hormones associate hydrophobically both with a neutral lipid (lysophosphatidylcholine) and (also electrostatically) with a negative lipid (lysophosphatidylglycerol). An association constant of Ka = 3.7 X 10(1) M-1 was calculated for the hydrophobic binding of enkephalin to lysophosphatidylcholine. NMR data suggested that enkephalin binds to the lipid with Met/Leu, Phe, and likely Tyr side-chain substituents associated with nonpolar interior regions of the micelle, whereas the COOH-terminal carboxylate moiety of the peptide is located in the surface of the lipid particle. An "attraction-interaction" model is proposed for hormone-lipid association wherein negative lipids attract the hormone electrostatically, while site-specific hydrophobic contacts facilitate its entry, concentration, and orientation into the lipid phase. PMID:6320173

  18. 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

  19. 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

  20. 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

  1. 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.

  2. Stimulus-responsive polymeric micelles for the light-triggered release of drugs.

    PubMed

    Wang, Bin; Chen, Kefu; Yang, Rendang; Yang, Fei; Liu, Jin

    2014-03-15

    Ethyl cellulose macroinitiator was firstly synthesized by direct acylation of ethyl cellulose with 2-bromopropionyl bromide in a room temperature. And a light-responsive triblock copolymer of ethyl cellulose-g-poly(2-hydroxyethyl methacrylate)-g-poly(spiropyran ether methacrylate) (EC-g-PHEMA-g-PSPMA) was prepared by atom transfer radial polymerization. The amphiphilic structure of the copolymer enabled it to aggregate into spherical micelles in aqueous solution with an average diameter of 100 nm. The micelles exhibited light-responsive performance because of the SPMA monomer. The hydrophobic side chain of PSPMA became hydrophilic under UV light, which decreased the average size of the micelles. Additionally, the diameters of the micelles can be recovered when subsequently irradiated with visible light. The loading and light-triggered release profiles of model drugs were also investigated, and results showed that the release behavior can be controlled by changing the light wavelength. PMID:24528761

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

    PubMed

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

    2013-08-01

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

  4. Simple model for the growth behaviour of mixed lecithin-bile salt micelles.

    PubMed

    Madenci, Dilek; Salonen, Anniina; Schurtenberger, Peter; Pedersen, Jan Skov; Egelhaaf, Stefan U

    2011-02-28

    Mixed lecithin-bile salt micelles are known to have a cylindrical or worm-like structure. We investigated their shape, length, flexibility and cross-sectional structure using small-angle neutron scattering (SANS). A broad range of sample compositions was studied varying both the total amphiphile concentration and the molar ratio of bile salt (sodium taurochenodeoxycholate, NaTCDC) to lecithin (egg yolk phosphatidylcholine, EYL). The length of the micelles was quantitatively linked to the micellar composition by introducing a simple model. The model takes into account the partitioning of lecithin and bile salt between the bulk, cylindrical parts and the end caps of the micelles. The model also sheds light on the organization of the micelles, both in their cylindrical regions and end caps. PMID:21135948

  5. 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

  6. Structure, dynamics, and insertion of a chloroplast targeting peptide in mixed micelles.

    PubMed

    Wienk, H L; Wechselberger, R W; Czisch, M; de Kruijff, B

    2000-07-18

    Nuclear-encoded, chloroplast-destined proteins are synthesized with transit sequences that contain all information to get them inside the organelle. Different proteins are imported via a general protein import machinery, but their transit sequences do not share amino acid homology. It has been suggested that interactions between transit sequence and chloroplast envelope membrane lipids give rise to recognizable, structural motifs. In this study a detailed investigation of the structural, dynamical, and topological features of an isolated transit peptide associated with mixed micelles is described. The structure of the preferredoxin transit peptide in these micelles was studied by circular dichroism (CD) and multidimensional NMR techniques. CD experiments indicated that the peptide, which is unstructured in aqueous solution, obtained helical structure in the presence of the micelles. By NMR it is shown that the micelles introduced ill-defined helical structures in the transit peptide. Heteronuclear relaxation experiments showed that the whole peptide backbone is very flexible. The least dynamic segments are two N- and C-terminal helical regions flanking an unstructured proline-rich amino acid stretch. Finally, the insertion of the peptide backbone in the hydrophobic interior of the micelle was investigated by use of hydrophobic spin-labels. The combined data result in a model of the transit peptide structure, backbone dynamics, and insertion upon its interaction with mixed micelles. PMID:10889029

  7. Disruption of reverse micelles and release of trapped ribonuclease A photochemically induced by Malachite Green leuconitrile derivative.

    PubMed

    Uda, Ryoko M; Nishikawa, Tsuyoshi; Morita, Yoshitsugu

    2011-03-15

    Photoinduced disruption of a sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelle is triggered by a Malachite Green leuconitrile derivative (MGL). UV irradiation of MGL solubilized in an AOT-water-chloroform mixture creates a cationic surfactant that interacts electrostatically with the anionic AOT. We investigated the disruption of the reverse micelle by using proton nuclear magnetic resonance spectroscopy and found that UV irradiation of MGL decreases the number of water molecules solubilized in the interior of the AOT reverse micelles. Furthermore, the photoinduced disruption of the reverse micelle is shown to release ribonuclease A, which is trapped in the water in the interior of the AOT reverse micelle. This photoinduced release may offer a desirable transport system of biopolymers. PMID:21237464

  8. pH-Responsive Hyaluronic Acid-Based Mixed Micelles for the Hepatoma-Targeting Delivery of Doxorubicin

    PubMed Central

    Wu, Jing-Liang; Tian, Gui-Xiang; Yu, Wen-Jing; Jia, Guang-Tao; Sun, Tong-Yi; Gao, Zhi-Qin

    2016-01-01

    The tumor targetability and stimulus responsivity of drug delivery systems are crucial in cancer diagnosis and treatment. In this study, hepatoma-targeting mixed micelles composed of a hyaluronic acid–glycyrrhetinic acid conjugate and a hyaluronic acid-l-histidine conjugate (HA–GA/HA–His) were prepared through ultrasonic dispersion. The formation and characterization of the mixed micelles were confirmed via 1H-NMR, particle size, and ζ potential measurements. The in vitro cellular uptake of the micelles was evaluated using human liver carcinoma (HepG2) cells. The antitumor effect of doxorubicin (DOX)-loaded micelles was investigated in vitro and in vivo. Results indicated that the DOX-loaded HA–GA/HA–His micelles showed a pH-dependent controlled release and were remarkably absorbed by HepG2 cells. Compared with free DOX, the DOX-loaded HA–GA/HA–His micelles showed a higher cytotoxicity to HepG2 cells. Moreover, the micelles effectively inhibited tumor growth in H22 cell-bearing mice. These results suggest that the HA–GA/HA–His mixed micelles are a good candidate for drug delivery in the prevention and treatment of hepatocarcinoma. PMID:27043540

  9. Reduction-Sensitive Polymeric Micelles Based on Docetaxel-Polymer Conjugates Via Disulfide Linker for Efficient Cancer Therapy.

    PubMed

    Guo, Yuanyuan; Zhang, Pei; Zhao, Qingyun; Wang, Kaiming; Luan, Yuxia

    2016-03-01

    In this article, the low-molecular weight biodegradable methoxy poly (ethylene glycol)-poly (d,l-lactide-co-glycolide) (PP) is chosen as polymeric skeleton to be conjugated with docetaxel (DTX) by disulfide bond (PP-SS-DTX) to construct the reduction-sensitive drug delivery system. The conjugates are synthesized via three steps and are further employed to physically load free DTX to develop the PP-SS-DTX/DTX micelles which exhibit many merits including high drug loading content, good stability, and stimuli-sensitive release of drugs. The hydrodynamic diameter of PP-SS-DTX/DTX micelles determined by DLS is 112.3 nm. The hemolysis assay reveals the good blood compatibility of PP-SS-DTX/DTX micelles. In order to investigate the reductive sensitivity of PP-SS-DTX/DTX micelles, dithiothreitol (DTT) is added into the release medium and a programmed drug release mode is observed in the conjugated micelles. In vitro cytotoxity assay shows that the PP-SS-DTX/DTX micelles are more cytotoxic than that of free DTX solution for both MCF-7 and B16F10 cancer cells. In addition, the PP-SS-DTX/DTX micelles also show a higher cellular uptake rate than that of free DTX. Hence, the prepared reduction-sensitive PP-SS-DTX/DTX micelles are effective on inhibiting cancer cells compared with the free DTX which would be a promising carrier in cancer therapy. PMID:26647779

  10. 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.

  11. 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

  12. Casein Micelle Dispersions under Osmotic Stress

    PubMed Central

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

    2009-01-01

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

  13. 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.

  14. Dynamic Processes in Diblock Copolymer Micelles

    NASA Astrophysics Data System (ADS)

    Robertson, Megan; Singh, Avantika

    2013-03-01

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

  15. 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

  16. Spatial structure of fibrinopeptide B in water solution with DPC micelles by NMR spectroscopy

    NASA Astrophysics Data System (ADS)

    Blokhin, Dmitriy S.; Fayzullina, Adeliya R.; Filippov, Andrei V.; Karataeva, Farida Kh.; Klochkov, Vladimir V.

    2015-12-01

    Fibrinopeptide B (GluFib) is one of the factors of thrombosis. Normal blood protein soluble, fibrinogen (fibrinopeptide A and fibrinopeptide B), is transformed into the insoluble, fibrin, which in the form of filaments adheres to the vessel wall at the site of injury, forming a grid. However, the spatial structure of this peptide has not been established till now. In this article, GluFib peptide is investigated together with dodecylphosphocholine (DPC) micelles which were used for mimicking the environment of peptide in blood vessels. The spatial structure was obtained by applying 1D and 2D 1H-1H NMR spectroscopy (TOCSY, NOESY). It was shown that the fibrinopeptide B does not have a secondary structure but we can distinguish the fragment Gly 9 - Arg 14 with a good convergence (the backbone RMSD for the Gly9 - Arg14 is 0.18 ± 0.08 Å).

  17. [Construction of biotin-modified polymeric micelles for pancreatic cancer targeted photodynamic therapy].

    PubMed

    Deng, Chun-yue; Long, Ying-ying; Liu, Sha; Chen, Zhang-bao; Li, Chong

    2015-08-01

    In this study, we explored the feasibility of biotin-mediated modified polymeric micelles for pancreatic cancer targeted photodynamic therapy. Poly (ethylene glycol)-distearoyl phosphatidyl ethanolamine (mPEG2000-DSPE) served as the drug-loaded material, biotin-poly(ethylene glycol)-distearoyl phosphatidyl ethanolamine (Biotin-PEG3400-DSPE) as the functional material and the polymeric micelles were prepared by a thin-film hydration method. The targeting capability of micelles was investigated by cell uptake assay in vitro and fluorescence imaging in vivo and the amounts of Biotin-PEG-DSPE were optimized accordingly. Hypocrellin B (HB), a novel photosensitizer was then encapsulated in biotinylated polymeric micelles and the anti-tumor efficacy was evaluated systemically in vitro and in vivo. The results showed that micelles with 5 mol % Biotin-PEG-DSPE demonstrated the best targeting capability than those with 20 mol % or 0.5 mol % of corresponding materials. This formulation has a small particle size [mean diameter of (36.74 ± 2.16) nm] with a homogeneous distribution and high encapsulation efficiency (80.06 ± 0.19) %. The following pharmacodynamics assays showed that the biotinylated micelles significantly enhanced the cytotoxicity of HB against tumor cells in vitro and inhibited tumor growth in vivo, suggesting a promising potential of this formulation for treatment of pancreatic cancer, especially those poorly permeable, or insensitive to radiotherapy and chemotherapy. PMID:26669006

  18. 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

  19. Influence of surfactant structure on reverse micelle size and charge for nonpolar electrophoretic inks.

    PubMed

    Parent, Mary E; Yang, Jun; Jeon, Yoocharn; Toney, Michael F; Zhou, Zhang-Lin; Henze, Dick

    2011-10-01

    Electrophoretic inks, which are suspensions of colorant particles that are controllably concentrated and dispersed by applied electric fields, are the leading commercial technology for high-quality reflective displays. Extending the state of the art for high-fidelity color in these displays requires improved understanding and control of the colloidal systems. In these inks, reverse micelles in nonpolar media play key roles in media and particle charging. Here we investigate the effect of surfactant structure on reverse micelle size and charging properties by synthesizing different surfactants with variations in polyamine polar head groups. Small-angle X-ray scattering (SAXS) and dynamic light scattering (DLS) were used to determine the micelle core plus shell size and micelle hydrodynamic radius, respectively. The results from SAXS agreed with DLS and showed that increasing polyamines in the surfactant head increased the micelle size. The hydrodynamic radius was also calculated on the basis of transient current measurements and agreed well with the DLS results. The transient current technique further determined that increasing polyamines increased the charge stabilization capability of the micelles and that an analogous commercial surfactant OLOA 11000 made for a lower concentration of charge-generating ions in solution. Formulating magenta inks with the various surfactants showed that the absence of amine in the surfactant head was detrimental to particle stabilization and device performance. PMID:21863832

  20. Worm-like micelles of CTAB and sodium salicylate under turbulent flow.

    PubMed

    Rodrigues, Roberta K; da Silva, Marcelo A; Sabadini, Edvaldo

    2008-12-16

    Polymers with high molecular weight and worm-like micelles are drag-reducing agents under turbulent flow. However, in contrast to the polymeric systems, the worm-like micelles do not undergo mechanical degradation due to the turbulence, because their macromolecular structure can be spontaneously restored. This very favorable property, together with their drag-reduction capability, offer the possibility to use such worm-like micelles in heating and cooling systems to recirculate water while expending less energy. The formation, growth, and stability of worm-like micelles formed by cetyltrimethylammonium bromide (CTAB) and sodium salicylate (NaSal) were investigated using the self-fluorescence of salicylate ions and the ability of the giant micelles to promote hydrodynamic drag reduction under turbulent flow. The turbulence in solutions of CTAB-Sal was produced within the double-gap cell of a rotational rheometer. Detailed diagrams were obtained for different ratios of Sal and CTAB, which revealed transitions associated with the thermal stability of giant micelles under turbulent flow. PMID:19053646

  1. Recent advances in polymeric micelles for anti-cancer drug delivery.

    PubMed

    Biswas, Swati; Kumari, Preeti; Lakhani, Prit Manish; Ghosh, Balaram

    2016-02-15

    Block co-polymeric micelles receive increased attention due to their ability to load therapeutics, deliver the cargo to the site of action, improve the pharmacokinetic of the loaded drug and reduce off-target cytotoxicity. While polymeric micelles can be developed with improved drug loading capabilities by modulating hydrophobicity and hydrophilicity of the micelle forming block co-polymers, they can also be successfully cancer targeted by surface modifying with tumor-homing ligands. However, maintenance of the integrity of the self-assembled system in the circulation and disassembly for drug release at the site of drug action remain a challenge. Therefore, stimuli-responsive polymeric micelles for on demand drug delivery with minimal off-target effect has been developed and extensively investigated to assess their sensitivity. This review focuses on discussing various polymeric micelles currently utilized for the delivery of chemotherapeutic drugs. Designs of various stimuli-sensitive micelles that are able to control drug release in response to specific stimuli, either endogenous or exogenous have been delineated. PMID:26747018

  2. 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.

  3. Structure of block copolymer micelles in the presence of co-solvents

    NASA Astrophysics Data System (ADS)

    Robertson, Megan; Wang, Shu; Le, Kim Mai; Piemonte, Rachele; Madsen, Louis

    2015-03-01

    Amphiphilic block copolymer micelles in water are under broad exploration for drug delivery applications due to their high loading capacity and targeted drug delivery. We aim to understand the kinetic and thermodynamic processes that underlie the self-assembly of diblock copolymer micelle systems. The present work focuses on diblock copolymers containing poly(ethylene oxide) (a hydrophilic polymer) and polycaprolactone (a hydrophobic polymer), which spontaneously self-assemble into spherical micelles in water. Addition of a common good solvent (a co-solvent) for both of the constituting blocks, such as tetrahydrofuran (THF), reduces the interfacial tension at the core-corona interface. We are currently investigating the effect of this phenomenon on the micelle structural properties, using scattering experiments and nuclear magnetic resonance. We have characterized the hydrodynamic radius, core radius, corona thickness, aggregation number, degree of swelling of the micelle core with the co-solvent, and unimer (free chain) concentration, as a function of the co-solvent concentration. Fundamental knowledge from these studies will inform design of drug delivery systems by allowing us to tailor micelle properties for optimal cargo loading.

  4. 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.

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

    PubMed

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

    2016-01-21

    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. PMID:26801043

  6. 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

  7. 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…

  8. 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…

  9. An Investigation of Some Features of the Psychosocial Learning Environment in Some Nigerian Secondary Schools.

    ERIC Educational Resources Information Center

    Akindehin, Folajimi

    1993-01-01

    Investigated features of the classroom- and school-level psychological learning environments in some secondary schools in Ondo State, Nigeria. It was found that age of a school has no effect on classroom- and school-level psychosocial learning environments. The presumed superiority of old schools over new schools in the provision of favorable…

  10. Shell-cross-linked micelles containing cationic polymers synthesized via the RAFT process: toward a more biocompatible gene delivery system.

    PubMed

    Zhang, Ling; Nguyen, T L Uyen; Bernard, Julien; Davis, Thomas P; Barner-Kowollik, Christopher; Stenzel, Martina H

    2007-09-01

    Block copolymers poly(2-(dimethylamino) ethyl methacrylate)-b-poly(polyethylene glycol methacrylate) (PDMAEMA-b-P(PEGMA)) were prepared via reversible addition fragmentation chain transfer polymerization (RAFT). The polymerization was found to proceed with the expected living behavior resulting in block copolymers with varying block sizes of low polydispersity (PDI <1.3). The resulting block copolymer was self-assembled in an aqueous environment, leading to the formation of pH-responsive micelles. Further stabilization of the micellar system was performed in water using ethylene glycol dimethacrylate and the RAFT process to cross-link the shell. The cross-linked micelle was found to have properties significantly different from those of the uncross-linked block copolymer micelle. While a distinct critical micelle concentration (CMC) was observed using block copolymers, the CMC was absent in the cross-linked system. In addition, a better stability against disintegration was observed when altering the ionic strength such as the absence of changes of the hydrodynamic diameter with increasing NaCl concentration. Both cross-linked and uncross-linked micelles displayed good binding ability for genes. However, the cross-linked system exhibited a slightly superior tendency to bind oligonucleotides. Cytotoxicity tests confirmed a significant improvement of the biocompatibility of the synthesized cross-linked micelle compared to that of the highly toxic PDMAEMA. The cross-linked micelles were taken up by cells without causing any signs of cell damage, while the PDMAEMA homopolymer clearly led to cell death. PMID:17691844

  11. 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)

  12. 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

  13. Solute partitioning in aqueous surfactant assemblies: comparison of hydrophobic-hydrophilic interactions in micelles, alcohol-swollen micelles, microemulsions, and synthetic vesicles

    SciTech Connect

    Russell, J.C.; Whitten, D.G.

    1982-11-03

    The structures of anionic assemblies including sodium lauryl sulfate (SLS) micelles, alcohol-swollen SLS micelles, microemulsions, and vesicles of a mixture of dipalmitoyllecithin and dicetyl phosphate are investigated by using the ground-state complexation of a hydrophilic quencher (methyl viologen) with several hydrophobic fluorescent probes, including surfactant stilbenes and 1,4-diphenylbutadiene. In SLS micelles this complexation can be decreased nearly an order of magnitude by addition of 1-heptanol, indicating that the structure of the micelle can be adjusted from the highly open structure of the pure micelle to a much more closed structure in which hydrophobic solubilizates can be sequestered from hydrophilic reagents bound to the surface. The fluorescence quenching process in anionic vesicles is strongly dependent on temperature; at low temperatures quenching occurs, while at higher temperatures addition of methyl viologen appears to increase the stilbene fluorescence, indicating that the dicationic quencher binds to the vesicle surface, increasing the order of the system. These results indicate that the degree of organization of surfactant systems can be adjusted by simple changes in composition. 33 references.

  14. 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.

  15. 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

  16. Negative adsorption due to electrostatic exclusion of micelles.

    PubMed

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

    2005-10-15

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

  17. 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.

  18. Correlating proton transfer dynamics to probe location in confined environments.

    PubMed

    Sedgwick, Myles; Cole, Richard L; Rithner, Christopher D; Crans, Debbie C; Levinger, Nancy E

    2012-07-25

    The dramatic impact of differing environments on proton transfer dynamics of the photoacid HPTS prompted us to investigate these systems with two highly complementary methods: ultrafast time-resolved transient absorption and two-dimensional NMR spectroscopies. Both ultrafast time-resolved transient absorption spectroscopy and time-resolved anisotropy decays demonstrate the proton transfer dynamics depend intimately on the specific reverse micellar system. For w(0) = 10 reverse micelles formed with anionic AOT surfactant, the HPTS proton transfer dynamics are similar to dynamics in bulk aqueous solution, and the corresponding (1)H 2D NOESY NMR spectra display no cross peaks between HPTS and AOT consistent with the HPTS residing well hydrated by water in the interior of the reverse micelle water pool. In contrast, ultrafast transient absorption experiments show no evidence for HPTS photoinduced proton transfer reaction in reverse micelles formed with the cationic CTAB surfactant. In CTAB reverse micelles, clear cross peaks between HPTS and CTAB in the 2D NMR spectra show that HPTS embeds in the interface. These results indicate that the environment strongly impacts the proton transfer reaction and that complementary experimental techniques develop understanding of how location critically affects molecular responses. PMID:22765228

  19. 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

  20. 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

  1. A study of the synergistic effect of folate-decorated polymeric micelles incorporating Hydroxycamptothecin with radiotherapy on xenografted human cervical carcinoma.

    PubMed

    You, Hong; Fu, ShaoZhi; Qin, XingHu; Yu, YanXin; Yang, Bo; Zhang, GuangPeng; Sun, XiaoYang; Feng, Yue; Chen, Yue; Wu, JingBo

    2016-04-01

    In this study, Hydroxycamptothecin (HCPT)-loaded micelles were formed in water by the self-assembly of folate (FA)-decorated amphiphilic block copolymer, methoxy poly(ethylene glycol)-poly(ε-caprolactone) (MPEG-PCL), and achieved a hydrodynamic diameter about of 132 nm. HCPT release from the micelles exhibited no initial burst but showed a sustained release profile. The cytotoxicity and targeting ability of FA conjugated polymeric micelles was investigated by using methylthiazoletetrazolium (MTT) and fluorescence microscopy. We found that FA-conjugated micelles had superior cytotoxicity against HeLa cells compared to non-conjugated micelles, and that they exerted this effect by folate receptor (FR)-mediated endocytosis. In addition, HeLa cells were xenografted into nude mice and subjected to radiotherapy (RT) and/or HCPT-loaded micelle treatment. The antitumor efficacy was detected by analysis of tumor growth delay (TGD) and median survival time. Micro fluorine-18-deoxyglucose PET/computed tomography ((18)F-FDG PET/CT) was performed to assess early tumor response to HCPT-loaded micelles in combination with RT. Analysis of cell cycle redistribution, apoptosis and expression of histone H2AX phosphorylation (λ-H2AX) was used to evaluate the mechanism by which HCPT loaded micelles led to radiosensitization. Taken together, the results showed that HCPT-loaded FA decorated micelles efficiently sensitized xenografts in mice to RT, and induced G2/M phase arrest, apoptosis and expression of λ-H2AX. PMID:26752212

  2. FTIR study of horseradish peroxidase in reverse micelles.

    PubMed

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

    2001-04-20

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

  3. Water-induced micelle formation of block copoly(oxyethylene-oxypropylene-oxyethylene) in o-xylene

    SciTech Connect

    Wu, Guangwei; Zhou, Zukang; Chu, B. )

    1993-04-12

    Static and dynamic light scattering, viscometry, NMR, and vapor pressure osmometry techniques have been employed to study the water-induced micellization behavior of poly(oxyethylene-oxypropylene-oxyethylene) block copolymer, Pluronic L64, in o-xylene solution. Results show that Pluronic L64 does not form polymolecular micelles in the absence of water or in the presence of a small amount of water (molar ratio water/EO < 0.15). Micelles, consisting of a PPO shell and a PEO and H[sub 2]O core, are formed when the water to EO molar ratio (Z) in the micelle is greater than 0.2. For Z < 1.3, spherical micelles with an average hydrodynamic radius R[sub h] of ca. 9.2 nm are formed, with R[sub h] almost independent of Z. For Z > 1.3, both the aggregation number and the hydrodynamic radius become dependent on the Z value, then the micelle shape could be nonspherical. As experimentally evidenced by NMR spectra, the solubilized water can be classified into bound water and free water. Most likely, water is not evenly distributed in the core, as the environments of EO units at different positions in the block copolymer are not identical.

  4. 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. PMID:25002267

  5. 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. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 825-834, 2016. PMID:26743660

  6. Modulation of partition and localization of perfume molecules in sodium dodecyl sulfate micelles.

    PubMed

    Fan, Yaxun; Tang, Haiqiu; Strand, Ross; Wang, Yilin

    2016-01-01

    The influence of perfume molecules on the self-assembly of the anionic surfactant sodium dodecyl sulfate (SDS) and their localization in SDS micelles have been investigated by ζ potential, small angle X-ray scattering (SAXS), one- and two-dimensional NMR and isothermal titration microcalorimetry (ITC). A broad range of perfume molecules varying in octanol/water partition coefficients P are employed. The results indicate that the surface charge, size and aggregation number of the SDS micelles strongly depend on the hydrophobicity/hydrophilicity degree of perfume molecules. Three distinct regions along the log P values are identified. Hydrophilic perfumes (log P < 2.0) partially incorporate into the SDS micelles and do not lead to micelle swelling, whereas hydrophobic perfumes (log P > 3.5) are solubilized close to the end of the hydrophobic chains in the SDS micelles and enlarge the micelles with higher ζ potential and a larger aggregation number. The incorporated fraction and micelle properties show increasing tendency for the perfumes in the intermediate log P region (2.0 < log P < 3.5). Besides, the molecular conformation of perfume molecules also affects these properties. The perfumes with a linear chain structure or an aromatic group can penetrate into the palisade layer and closely pack with the SDS molecules. Furthermore, the thermodynamic parameters obtained from ITC show that the binding of the perfumes in the intermediate log P region is more spontaneous than those in the other two log P regions, and the micellization of SDS with the perfumes is driven by entropy. PMID:26458054

  7. Intrinsic parameters for the structure control of nonionic reverse micelles in styrene: SAXS and rheometry studies.

    PubMed

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

    2011-05-17

    Shape, size, and internal structure of nonionic reverse micelle in styrene depending on surfactant chain length, concentration, temperature, and water addition have been investigated using a small-angle X-ray scattering (SAXS) technique. The generalized indirect Fourier transformation (GIFT) method has been employed to deduce real-space structural information. The consistency of the GIFT method has been tested by the geometrical model fittings, and the micellar aggregation number (N(agg)) has been determined. It was found that diglycerol monocaprate (C(10)G(2)), diglycerol monolaurate (C(12)G(2)), and diglycerol monomyristate (C(14)G(2)), spontaneously self-assemble into reverse micelles in organic solvent styrene under ambient conditions. The micellar size and the N(agg) decrease with an increase in surfactant chain length, a scenario that could be understood from the modification of the critical packing parameter (cpp). A clear picture of one-dimensional (1-D) micellar growth was observed with an increase in surfactant weight fraction (W(s)) in the C(10)G(2) system, which eventually formed rodlike micelles at W(s) ≥ 15%. On the other hand, micelles shrunk favoring a rod-to-sphere type transition upon heating. Reverse micelles swelled with water, forming a water pool at the micellar core; the size of water-incorporated reverse micelles was much bigger than that of the empty micelles. Model fittings showed that water addition not only increase the micellar size but also increase the N(agg). Zero-shear viscosity was found to decrease with surfactant chain but increase with W(s), supporting the results derived from SAXS. PMID:21488609

  8. 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

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

    PubMed

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

    2004-11-15

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

  10. 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.

  11. 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. PMID:27107206

  12. Steady-state and time-resolved fluorescence studies of reverse micelles in liquids and supercritical solvents

    SciTech Connect

    Zhang, Jing.

    1992-01-01

    The authors investigate the effects of temperature, salt concentration, and water loading on the internal dynamics of AOT Aerosol-OT, sodium bis (2-ethylhexyl sulfosuccinate) micelles in liquid heptane, using ANS-like (anilino-naphthalene sulfate) fluorescent probes. The important results from these experiments are that: (1) the molecular geometry of the probe is the predominant factor controlling partitioning even at high water loadings; (2) the photophysics of ANS is strongly dependent on the water content and temperature and corresponds to changes in local polarity and viscosity; (3) addition of electrolytes changes the dynamic fluorescence which is in turn related to the changes in internal microenvironments; and (4) a nanosecond solvent relaxation process occurs within reverse micelles. It was wondered if the continuous phase (alkane) density could be used to control the internal dynamics within a reverse micelle. To answer this question, research focused on: (1) the effects of water loading, temperature, and fluid density on solute partitioning and determination of the density effects on micellar aggregates; (2) the effects of solute structure on the distribution of probe molecules within reverse micelles; and (3) the effects of fluid density, water concentration, and temperature on the reorganizational dynamics within AOT reverse micelles. Simple thermodynamic measurements and nanosecond solvent relaxation experiments are used to account for this partitioning and water reorganization in AOT reverse micelles, respectively. Results on excited-state deprotonation reactions in AOT reverse micelles maintained in sub-critical propane, provides a useful model for density-controlled deprotonation reactions within reverse micelles. Preliminary work shows that the continuous phase density can be used to control reactions within reverse micelles formed in near- and supercritical alkanes.

  13. 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

  14. Synergistic effect of pH-responsive wormlike micelles based on a simple amphiphile.

    PubMed

    Wu, Xuepeng; Wu, Yining; Yang, Shuai; Zhao, Mingwei; Gao, Mingwei; Li, Hao; Dai, Caili

    2016-05-18

    Imagine a novel solution that can be switched reversibly from low viscosity to high viscosity with only one additive, upon different commands. To this end, we have developed a simple and effective route to form smart, multi-response wormlike micelles based on a synthesized surfactant, N-cetyl-N,N-diisopropanolammonium bromide (CDIAB). Moreover, we provide new insight into the effects of synergy on this smart wormlike micelle. Rheological measurements were used to study the morphology of the wormlike micelles; (1)H NMR spectroscopy and density functional theory (DFT) calculations were employed to investigate the molecular arrangements and mechanism of the synergy involved in the reversible reactions of pH-response and CO2-response of the micelles in solution. Based on the abovementioned results, it is encouraging to discover that binding energy and electrostatic interaction are the basic driving forces in the formation of wormlike micelles. Moreover, stable viscoelastic behavior was observed in the CDIAB system, with strong binding energy and electrostatic interactions. It is highly anticipated that the synergy observed in this surfactant will be of particular interest due to its novel mechanism and unique properties. PMID:27094804

  15. 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.

  16. Multifunctional Mixed Micelles Cross-Assembled from Various Polyurethanes for Tumor Therapy.

    PubMed

    Pan, Zhicheng; Ren, Yanji; Song, Nijia; Song, Yuanqing; Li, Jiehua; He, Xueling; Luo, Feng; Tan, Hong; Fu, Qiang

    2016-06-13

    A challenge in the development of multifunctional drug delivery systems is to establish a reasonable and effective synthetic route for multifunctional polymer preparation. Herein, we propose a unique protocol to prepare multifunctional micelles by a cross-assembly process using three different functional polyurethanes incorporating acidic sensitive hydrazone, folic acid for active targeting, and gemini quaternary ammonium (GQA) as efficient cell uptake ligands, respectively. These multifunctional mixed micelles (GFHPMs) have been endowed tunable particle sizes and zeta potential and a unique three-order-layer cross-assemble structure. Their drug-loading contents have been significantly improved, and drug release profiles displayed controlled release of their payloads under acid condition. The folate and GQA ligands showed a synergistic effect to enhance the cell uptake. Biodistribution and antitumor effect of these micelles were systematically investigated in vivo, the mixed micelles could penetrate into the depths of tumors, and drug concentrations in tumors reached the maximum of 6.5% ID/g at 24 h, resulting in an excellent therapeutic effect that the volumes of tumors treated with GFHPM are five times smaller than those treated with blank micelles. Our present work provides an effective approach to the design of multifunctional nanocarriers for tumor-targeted and programmed intracellular drug delivery. PMID:27133950

  17. N-isopropylacrylamide copolymers for the preparation of pH-sensitive liposomes and polymeric micelles.

    PubMed

    Leroux, J; Roux, E; Le Garrec, D; Hong, K; Drummond, D C

    2001-05-14

    Hydrophobically-modified copolymers of N-isopropylacrylamide bearing a pH-sensitive moiety were investigated for the preparation of pH-responsive liposomes and polymeric micelles. The copolymers having the hydrophobic anchor randomly distributed within the polymeric chain were found to more efficiently destabilize egg phosphatidylcholine (EPC)/cholesterol liposomes than the alkyl terminated polymers. Release of both a highly-water soluble fluorescent contents marker, pyranine, and an amphipathic cytotoxic anti-cancer drug, doxorubicin, from copolymer-modified liposomes was shown to be dependent on pH, the concentration of copolymer, the presence of other polymers such as polyethylene glycol, and the method of preparation. Both polymers were able to partially stabilize EPC liposomes in human serum. These polymers were found to self-assemble to form micelles. The critical association concentration was low (9--34 mg/l) and influenced by the position of the alkyl chains. In phosphate buffered saline, the micelles had a bimodal size distribution with the predominant population having a mean diameter of 35 nm. The polymeric micelles were studied as a delivery system for the photosensitizer aluminum chloride phthalocyanine, (AlClPc), currently evaluated in photodynamic therapy. pH-Responsive polymeric micelles loaded with AlClPc were found to exhibit increased cytotoxicity against EMT-6 mouse mammary cells in vitro than the control Cremophor EL formulation. PMID:11389986

  18. Micelle and microemulsion properties of cesium di-dodecyl-dimethylsulfosuccinate, Cs-AOT

    SciTech Connect

    Sheu, E.Y.; Nostro, P.L.; Capuzzi, G.; Baglioni, P.

    1999-09-28

    Cesium di-2-ethylsulfosuccinate (Cs-AOT) micelles in aqueous solutions and Cs-AOT/water/n-decane microemulsions were investigated, at 22 {plus{underscore}minus} 0.1 C, by small angle neutron scattering (SANS). The critical micelle concentration of Cs-AOT is {approximately}2mM, comparable to that of Na-AOT. However, their solution properties and micellar structures were found to be very different. The solubility of Na-AOT in water is approximately 1 wt %, and the micelles grow from spherical (at a concentration of about 0.1 wt %) to oblate objects with eccentricity equal to about 0.8 (at a concentration of 1 wt %), whereas Cs-AOT is largely soluble in water, over 30 wt %, and its micelles are disklike at 1 wt %. As the surfactant concentration increases, micelles may go through an L{sub 3} region, and enter the lamellar phase. Cs-AOT/water/n-decane microemulsions, with a [water]/[Cs-AOT] = 29.1, form isotropic L{sub 2} phases only at very low Cs-AOT + ater volume fractions (below 0.0165), whereas Na-AOT has a large L{sub 2} region. These differences are probably due to the degree of charge condensation near the AOT polar headgroups. A theoretical description is needed to better understand this behavior.

  19. 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

  20. Hierarchical assembly of block copolymer micelles into reversible networks: MC simulations

    NASA Astrophysics Data System (ADS)

    Wang, Zilu; Dormidontova, Elena

    2015-03-01

    The rapid development of nanoscience has considerably expanded the range of building blocks for complex self-assembled nanostructure formation, which show great potential for numerous advanced applications. We apply Monte Carlo simulations to gain understanding of molecular mechanism of self-assembly of nanostructures formed by diblock copolymer micelles interconnected by means of metal-ligand complexation. These systems exhibit interesting chemical and mechanical stimuli-responsive behavior and possess two levels of self-assembly: 1) self-assembly of diblock copolymers into micelles and 2) reversible inter-micelle bridging by coordination bonding between metal ions and ligands attached to the corona of nanoparticles, which is responsible for the network viscoelastic properties. Using MC simulations we investigate the effect of metal-ligand complexation on diblock-copolymer micelle formation and vice versa. We analyze the extent of intra- and inter-micelle loops and bridges formed by metal-ligand complexation in relation to the degree of crosslinking and elastic properties of the network. The effect of polymer concentration, hydrophilic block length, metal to oligomer ratio and type of complexation (2:1 or 3:1) on equilibrium properties of reversible networks will be discussed.

  1. 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

  2. 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.…

  3. Investigation of Junior Secondary Students' Perceptions of Mathematics Classroom Learning Environments in China

    ERIC Educational Resources Information Center

    Yang, Xinrong

    2013-01-01

    This paper reports the findings of a study investigating junior secondary school students' perceptions of mathematics classroom learning environments in China. An adapted 'What Is Happening In this Classroom?' questionnaire was administered to a sample of 2324 junior secondary school students from 72 classrooms in six provinces.…

  4. Investigation of DBMS for Use in a Research Environment. Rand Paper Series 7002.

    ERIC Educational Resources Information Center

    Rosenfeld, Pilar N.

    This investigation of the use of database management systems (DBMS) in a research environment used the Rand Corporation as a case study. After a general introduction in section 1, eight sections present the major components of the study. Section 2 contains an overview of DBMS terminology and concepts, followed in section 3 by a general dsecription…

  5. Investigating Design and Technology Students' Participation and Learning in a Technology Mediated Learning Environment

    ERIC Educational Resources Information Center

    Yeo, Tiong Meng; Quek, Choon Lang

    2008-01-01

    This study investigates how 15 Design & Technology (D&T) students (aged 15 years) participated in three stages of the design process in a technology mediated environment. The three stages are named "Situation," "Ideation" and "Development." The learning process is mediated by "Knowledge Forum" (KF), an asynchronous online discussion tool. The…

  6. 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…

  7. 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…

  8. Spectroscopic study of the melting and reconstruction of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles from their frozen states.

    PubMed

    Suzuki, Akira; Yui, Hiroharu

    2015-04-01

    The confinement of water in organic self-assemblies with nanometer-sized pores is ubiquitous in nature. Water pools in sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles have been intensively studied as a representative model of such confined water. However, the freezing and melting behavior of such water pools is poorly understood owing to their poor structural stability under phase transition. In the present work, the melting of iced water pools accompanied by a reconstruction of AOT reverse micelles was studied with infrared spectroscopy. For all AOT reverse micelles tested (Rw: 1.2-4.4 nm), a characteristic ice-water coexistence phase was observed during melting. The results provide experimental evidence of the previously proposed core-shell structure of the water pool. For larger frozen reverse micelles (Rw>2.3 nm), shifts of the υ(OH) bands were observed. The spectra of the shifted υ(OH) bands were similar to those for the melted water pools in the smaller micelles. The mechanism of the reconstruction of AOT reverse micelles from their frozen states and the corresponding transient changes in the local environments were also discussed. PMID:25569193

  9. 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

  10. 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

  11. 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.

  12. 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.

  13. Nanotoxicity comparison of four amphiphilic polymeric micelles with similar hydrophilic or hydrophobic structure

    PubMed Central

    2013-01-01

    Background Nanocarriers represent an attractive means of drug delivery, but their biosafety must be established before their use in clinical research. Objectives Four kinds of amphiphilic polymeric (PEG-PG-PCL, PEEP-PCL, PEG-PCL and PEG-DSPE) micelles with similar hydrophilic or hydrophobic structure were prepared and their in vitro and in vivo safety were evaluated and compared. Methods In vitro nanotoxicity evaluations included assessments of cell morphology, cell volume, inflammatory effects, cytotoxicity, apoptosis and membrane fluidity. An umbilical vein cell line (Eahy.926) and a kind of macrophages (J774.A1) were used as cell models considering that intravenous route is dominant for micelle delivery systems. In vivo analyses included complete blood count, lymphocyte subset analysis, detection of plasma inflammatory factors and histological observations of major organs after intravenous administration to KM mice. Results All the micelles enhanced inflammatory molecules in J774.A1 cells, likely resulting from the increased ROS levels. PEG-PG-PCL and PEEP-PCL micelles were found to increase the J774.A1 cell volume. This likely correlated with the size of PEG-PG-PCL micelles and the polyphosphoester structure in PEEP-PCL. PEG-DSPE micelles inhibited the growth of Eahy.926 cells via inducing apoptosis. This might relate to the structure of DSPE, which is a type of phospholipid and has good affinity with cell membrane. No evidence was found for cell membrane changes after treatment with these micelles for 24 h. In the in vivo study, during 8 days of 4 time injection, each of the four nanocarriers altered the hematic phase differently without changes in inflammatory factors or pathological changes in target organs. Conclusions These results demonstrate that the micelles investigated exhibit diverse nanotoxicity correlated with their structures, their biosafety is different in different cell model, and there is no in vitro and in vivo correlation found. We believe

  14. 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

  15. 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.

  16. Dynamics of solvent and rotational relaxation of glycerol in the nanocavity of reverse micelles.

    PubMed

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

    2006-03-23

    The dynamics of solvent and rotational relaxation of Coumarin 480 and Coumarin 490 in glycerol containing bis-2-ethyl hexyl sulfosuccinate sodium salt (AOT) reverse micelles have been investigated with steady-state and time-resolved fluorescence spectroscopy. We observed slower solvent relaxation of glycerol confined in the nanocavity of AOT reverse micelles compared to that in pure glycerol. However, the slowing down in the solvation time on going from neat glycerol to glycerol confined reverse micelles is not comparable to that on going from pure water or acetonitrile to water or acetonitrile confined AOT reverse micellar aggregates. While solvent relaxation times were found to decrease with increasing glycerol content in the reverse micellar pool, rotational relaxation times were found to increase with increase in glycerol content. PMID:16539469

  17. Micelle-derived catalysts for extended Schulz-Flory

    SciTech Connect

    Not Available

    1985-01-01

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

  18. 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

  19. Peptide-micelle hybrids containing fasudil for targeted delivery to the pulmonary arteries and arterioles to treat pulmonary arterial hypertension.

    PubMed

    Gupta, Nilesh; Ibrahim, Hany M; Ahsan, Fakhrul

    2014-11-01

    This study investigates the respirability and efficacy of peptide-micelle hybrid nanoparticles as carriers for inhalational therapy of pulmonary arterial hypertension (PAH). CARSKNKDC (CAR), a cell-penetrating and lung-homing peptide, conjugated polyethylene glycol-distearoyl-phosphoethanolamine micelles containing fasudil, an investigational anti-PAH drug, were prepared by solvent evaporation method and characterized for various physicochemical properties. The pharmacokinetics and pharmacological efficacy of hybrid particles containing fasudil were evaluated in healthy rats and monocrotaline-induced PAH rats. CAR micelles containing fasudil had an entrapment efficiency of approximately 58%, showed controlled release of the drug, and were monodispersed with an average size of approximately 14 nm. Nuclear magnetic resonance scan confirmed the drug's presence in the core of peptide-micelle hybrid particles. Compared with plain micelles, CAR peptide increased the cellular uptake by approximately 1.7-fold and extended the drug half-life by approximately fivefold. The formulations were more prone to accumulate in the pulmonary vasculature than in the peripheral blood, which is evident from the ratio of the extent of reduction of pulmonary and systemic arterial pressures. On the whole, this study demonstrates that peptide-polymer hybrid micelles can serve as inhalational carriers for PAH therapy. PMID:25266507

  20. 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.

  1. 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

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

    PubMed

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

    2013-07-17

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

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

    PubMed

    Yokoyama, Masayuki

    2014-08-01

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

  4. 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

  5. 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.

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

    PubMed

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

    2015-03-20

    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. PMID:25708980

  7. Antibacterial polyelectrolyte micelles for coating stainless steel.

    PubMed

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

    2012-05-01

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

  8. On the composition fluctuations of reverse micelles.

    PubMed

    Tovstun, Sergey A; Razumov, Vladimir F

    2010-11-15

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

  9. 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.

  10. 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)

  11. MACROSTRUCTURE AND VISCOSITY OF AGGREGATING COLLOIDAL CASEIN MICELLES UNDER STRONG SHEARING FORCE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Casein particle gels are the main constituents in many classes of soft food colloids. In this study, we examined the stability of casein micelles under strong hydrodynamic forces, and investigated the effect of continuous applied shear on the coagulation properties of rennet-induced milk. At the a...

  12. 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

  13. 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.

  14. 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

  15. Preparation of HIFU-triggered tumor-targeted hyaluronic acid micelles for controlled drug release and enhanced cellular uptake.

    PubMed

    Zheng, Shaohui; Jin, Zhen; Han, Jiwon; Cho, Sunghoon; Nguyen, Van Du; Ko, Seong Young; Park, Jong-Oh; Park, Sukho

    2016-07-01

    In this study, a novel type of high intensity focused ultrasound (HIFU)-triggered active tumor-targeting polymeric micelle was prepared and investigated for controlled drug release and enhanced cellular uptake. Amphiphilic hyaluronic acid (HA) conjugates were synthesized to form docetaxel loaded micelles in aqueous conditions with high encapsulation efficiencies of over 80%. The micelle sizes were limited to less than 150nm, and they varied slightly according to the encapsulated drug amount. Modifying the micellar surface modification with polyethylene glycol diamine successfully inhibited premature drug leakage at a certain level, and it can be expected to prolong the circulation time of the particles in blood. In addition, high-intensity focused ultrasound was introduced to control the release of docetaxel from micelles, to which the release behavior of a drug can be tuned. The in-vitro cell cytotoxicity of docetaxel-loaded micelles was verified against CT-26 and MDA-MB-231 cells. The IC50 values of drug-loaded micelles to CT-26 and MDA-MB-231 cells were 1230.2 and 870.9ng/mL, respectively. However, when exposed to HIFU, the values decreased significantly, to 181.9 and 114.3ng/mL, suggesting that HIFU can enhance cell cytotoxicity by triggering the release of a drug from the micelles. Furthermore, cellular uptake tests were conducted via the quantitative analysis of intracellular drug concentration within CT-26 (CD44 negative), MDA-MB-231 (CD44 positive), and MDA-MB-231 (CD44 blocked), and then imaged with coumarin-6 loaded micelles. The results verified that intracellular drug delivery can be enhanced efficiently via the CD44 receptor-mediated endocytosis of HA micelles. Moreover, HIFU enhanced the cellular uptake behavior by altering the permeability of the cell membrane. It was also able to aid with the extravasation of micelles into the interior of tumors, which will be explained in further research. Therefore, the present study demonstrates that the micelles

  16. Dynamic multicompartment-core micelles in aqueous media.

    PubMed

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

    2009-09-15

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

  17. 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

  18. 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

  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. Zero order delivery of itraconazole via polymeric micelles incorporated in situ ocular gel for the management of fungal keratitis.

    PubMed

    Jaiswal, Munmun; Kumar, Manish; Pathak, Kamla

    2015-06-01

    The aim of this article is to investigate the role of amphiphilic block copolymer-based polymeric micelles of itraconazole for the management of fungal keratitis to overcome the limitations of the conventional dosage form. The polymeric micelles were made using pluronics above critical micelle concentration. Itraconazole-loaded polymeric micelles prepared by rotary evaporation method were characterized and the optimized micellar formulation (M5) was selected on the basis of least micelle size (79.99 nm), maximum entrapment efficiency (91.32%±1.73%) and in vitro permeation (90.28%±0.31%) in 8h, that best fitted zero-order kinetics. M5 was developed as pH sensitive in situ gel and characterized for various parameters. The optimized in situ gel (F5) proved to be superior in its ex vivo transcorneal permeation when compared with Itral(®) eye drop and pure drug suspension, exhibiting 41.45%±0.87% permeation with zero-order kinetics (r(2)=0.994) across goat cornea. Transmission electron microscopy revealed spherical polymeric micelles entrapped in the gel matrix. A spectrum of tests revealed hydration capability, non-irritancy, and histologically safe gel formulation that had appropriate handling characteristics. Conclusively, a controlled release pH-sensitive ocular formulation capable of carrying drug to the anterior segment of the eye via topical delivery was successfully developed for the treatment of fungal keratitis. PMID:25889081

  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. Structure of diglycerol monomyristate reverse micelles in styrene: a small-angle X-ray scattering (SAXS) study.

    PubMed

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

    2011-08-01

    Structure of diglycerol monomyristate (designated as C14G2) nonionic surfactant reverse micelles in aromatic solvent styrene has been investigated as a function of surfactant concentration, temperature, and water addition by using small-angle X-ray scattering (SAXS) technique. Structure of micelles in real-space so called pair-distance distribution function, p(r), was obtained by the generalized indirect fourier transformation (GIFT) evaluation of SAXS data. It was found that C14G2 spontaneously self-assembles into spheroid reverse micelles with maximum diameter approximately 3.0 nm when added into styrene under ambient condition. The micellar shape and size remained essentially the same despite a wide variation in surfactant concentration (5 to 30%) but an opposite trend was observed with the rise of temperature; size decreased by approximately 25% with increase in temperature from 25 to 75 degrees C. Addition of traces water favored micellar growth and eventually ellipsoid prolate type micelles were formed, whose scenario is understood in terms of decrease in the critical packing parameter (cpp); water hydrates the surfactant's headgroup and decreases cpp. At a particular concentration of water, increasing temperature decreased the micellar size due to dehydration of headgroup. It is interesting to note that size of 1.57% water incorporated micelle is approximately 2.5 times bigger than the empty micelles. PMID:22103110

  3. Development of Long-Circulating Zwitterionic Cross-Linked Micelles for Active-Targeted Drug Delivery.

    PubMed

    Lin, Weifeng; Ma, Guanglong; Kampf, Nir; Yuan, Zhefan; Chen, Shengfu

    2016-06-13

    Blood stability, active targeting, and controlled drug release are the most important features to design desirable drug carriers. Here, we demonstrate a zwitterionic biodegradable cross-linked micelle based on a penta-block copolymer, which utilizes poly(carboxybetaine methacrylate) as hydrophilic segment, poly(ε-caprolactone) as biodegradable hydrophobic segment, poly(S-2-hydroxyethyl-O-ethyl dithiocarbonate methacrylate) (PSODMA) block as thiol protecting segment for cross-linking, and cyclic Arg-Gly-Asp-d-Tyr-Lys [c(RGDyK)] as targeting ligand. As a result, this micelle possessed excellent colloidal stability at high dilution and in 50% fetal bovine serum. In vitro drug release experiment showed no burst release under physiological conditions but accelerated drug release in mimicking tumor tissue environment. In vivo tests showed that the drug-loaded micelles had prolonged half-life in bloodstream, enhanced therapeutic efficiency, and reduced cardiac toxicity and biotoxicity compared with free drug formulation. Taken together, the reported c(RGDyK)-modified zwitterionic interfacially cross-linked micelle has emerged as an appealing platform for cancer therapy. PMID:27050797

  4. Reconstitutable Charged Polymeric (PLGA)2-b-PEI Micelles for Gene Therapeutics Delivery

    PubMed Central

    Mishra, Deepa; Kang, Han Chang; Bae, You Han

    2011-01-01

    This study investigated the potential of creating a charged polymeric micelle-based nucleic acid delivery system that could easily be reconstituted by the addition of water. (PLGA36kDa)2-b-bPEI25kDa (PLGA MW 36kDa, bPEI Mw 25kDa, PLGA:bPEI block ratio = 2) was synthesized and used to prepare cationic micelles. The copolymer retained proton-buffering capability from the bPEI block within the endosomal pH range. Micelle/pDNA complexes retained their particle size (100–150 nm) and surface charge (30–40 mV) following reconstitution. It was found that adding a small amount of low molecular weight bPEI (1.8 kDa) completely shielded pDNA in the micelle/pDNA complexes and enhanced transfection efficiency 50–100 fold for both fresh and reconstituted complexes without affecting complex size. Transfection efficiency for “reconstituted” micelle/pDNA/bPEI1.8kDa (WR 1) complexes was 16-fold higher than its “fresh” counterpart. Although transfection levels achieved using “reconstituted” micelle/pDNA/bPEI1.8kDa complexes were 3.6-fold lower than control “fresh” bPEI25kDa/pDNA (N/P 5) complexes, transfection levels were 39-fold higher than “reconstituted” bPEI25kDa/pDNA (N/P 5) complexes. The micelle/pDNA/bPEI1.8kDa system showed very low cytotoxicity in MCF7 cells even with pDNA doses up to 20 μg, and transfection levels increased linearly with increasing pDNA dose. These results indicate that this PLGA-b-bPEI polymeric micelle-based system is well suited as a reconstitutable gene delivery system, and has high potential for use as a delivery system for gene therapy applications. PMID:21354616

  5. 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

  6. Naproxen conjugated mPEG-PCL micelles for dual triggered drug delivery.

    PubMed

    Karami, Zahra; Sadighian, Somayeh; Rostamizadeh, Kobra; Parsa, Maliheh; Rezaee, Saeed

    2016-04-01

    A conjugate of the NSAIDs drug, naproxen, with diblock methoxy poly(ethylene glycol)-poly(ε-caprolactone) (mPEG-PCL) copolymer was synthesized by the reaction of copolymer with naproxen in the presence of dicyclohexylcarbodiimide and dimethylaminopyridine. The naproxen conjugated copolymers were characterized with different techniques including (1)HNMR, FTIR, and DSC. The naproxen conjugated mPEG-PCL copolymers were self-assembled into micelles in aqueous solution. The TEM analysis revealed that the micelles had the average size of about 80 nm. The release behavior of conjugated copolymer was investigated in two different media with the pH values of 7.4 and 5.2. In vitro release study showed that the drug release rate was dependant on pH as it was higher at lower pH compared to neutral pH. Another feature of the conjugated micelles was a more sustained release profile compared to the conjugated copolymer. The kinetic of the drug release from naproxen conjugated micelles under different values of pH was also investigated by different kinetic models such as first-order, Makoid-Banakar, Weibull, Logistic, and Gompertz. PMID:26838895

  7. 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.

  8. 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.

  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. 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

  11. 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

  12. Micelle Morphology and Mechanical Response of Triblock Gels

    SciTech Connect

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

    2010-01-12

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

  13. 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.

  14. Implicit solvent simulations of DPC micelle formation.

    PubMed

    Lazaridis, Themis; Mallik, Buddhadeb; Chen, Yong

    2005-08-11

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

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. Preparatiion of metal colloids in inverse micelles

    SciTech Connect

    Wilcoxon, J.P.

    1990-11-23

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

  20. Structured Hydrogels using Micelles as Templates

    NASA Astrophysics Data System (ADS)

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

    2008-03-01

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

  1. 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

  2. Reverse micelles for the removal of dyes from aqueous solutions.

    PubMed

    Majhi, S; Sharma, Y C; Upadhyay, S N

    2009-08-01

    The ability of reverse micelles to solvate organic dyes in the aqueous core was investigated with methyl orange (MO) and methylene blue (MB) using hexadecyl trimethyl ammonium bromide (HTAB) and sodium dodecyl benzene sulphonate (SDBS) surfactants in a polar amyl alcohol medium. The removal trend of the dyes from water was studied with different concentrations of the dyes. The effects of NaCl and CaCl2 salts on removal efficiency of the surfactants were investigated and results were compared. It was observed that the separation of dyes from the aqueous phase to the organic phase depends on the electrostatic interaction between the dye molecule and surfactant head groups. In the case of NaCl, with increasing salt concentration, the removal (%) of dye decreases. For CaCl2, removal of methyl orange shows a gradual increase with increasing dye concentration, whereas, for methylene blue, its removal decreases with increasing dye concentration. PMID:19803326

  3. An investigation of pointing postures in a 3D stereoscopic environment.

    PubMed

    Lin, Chiuhsiang Joe; Ho, Sui-Hua; Chen, Yan-Jyun

    2015-05-01

    Many object pointing and selecting techniques for large screens have been proposed in the literature. There is a lack of quantitative evidence suggesting proper pointing postures for interacting with stereoscopic targets in immersive virtual environments. The objective of this study was to explore users' performances and experiences of using different postures while interacting with 3D targets remotely in an immersive stereoscopic environment. Two postures, hand-directed and gaze-directed pointing methods, were compared in order to investigate the postural influences. Two stereo parallaxes, negative and positive parallaxes, were compared for exploring how target depth variances would impact users' performances and experiences. Fifteen participants were recruited to perform two interactive tasks, tapping and tracking tasks, to simulate interaction behaviors in the stereoscopic environment. Hand-directed pointing is suggested for both tapping and tracking tasks due to its significantly better overall performance, less muscle fatigue, and better usability. However, a gaze-directed posture is probably a better alternative than hand-directed pointing for tasks with high accuracy requirements in home-in phases. Additionally, it is easier for users to interact with targets with negative parallax than with targets with positive parallax. Based on the findings of this research, future applications involving different pointing techniques should consider both pointing performances and postural effects as a result of pointing task precision requirements and potential postural fatigue. PMID:25683543

  4. 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.

  5. 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.

  6. Modeling the Self-Assembly and Stability of DHPC Micelles Using Atomic Resolution and Coarse Grained MD Simulations.

    PubMed

    Kraft, Johan F; Vestergaard, Mikkel; Schiøtt, Birgit; Thøgersen, Lea

    2012-05-01

    Membrane mimics such as micelles and bicelles are widely used in experiments involving membrane proteins. With the aim of being able to carry out molecular dynamics simulations in environments comparable to experimental conditions, we set out to test the ability of both coarse grained and atomistic resolution force fields to model the experimentally observed behavior of the lipid 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC), which is a widely used lipid for biophysical characterization of membrane proteins. It becomes clear from our results that a satisfactory modeling of DHPC aggregates in solution poses different demands to the force field than do the modeling of bilayers. First, the representation of the short tailed lipid DHPC in the coarse grained force field MARTINI is assessed with the intend of successfully self-assemble micelles with structural characteristics comparable to experimental data. Then, the use of the recently presented polarizable water model in MARTINI is shown to be essential for producing micelles that are structurally in accordance with experiments. For the atomistic representations of DHPC micelles in solution the GROMOS96 force field with lipid parameters by A. Kukol fails to maintain stable micelles, whereas the most recent CHARMM36 lipid parameters and GROMOS96 with the so-called Berger lipid parameters both succeed in this regard. PMID:26593649

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

    NASA Astrophysics Data System (ADS)

    Thachepan, Surachai; Li, Mei; Mann, Stephen

    2010-11-01

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

  8. 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

  9. Enhanced gene expression promoted by hybrid magnetic/cationic block copolymer micelles.

    PubMed

    Haladjova, E; Rangelov, S; Tsvetanov, Ch B; Posheva, V; Peycheva, E; Maximova, V; Momekova, D; Mountrichas, G; Pispas, S; Bakandritsos, A

    2014-07-15

    We report on novel gene delivery vector systems based on hybrid polymer-magnetic micelles. The hybrid micelles were prepared by codissolution of hydrophobically surface modified iron oxide and amphiphilic polystyrene-b-poly(quaternized 2-vinylpyridine) block copolymer (PS-b-P2QVP) in organic solvent. After extensive dialysis against water, micelles with positively charged hydrophilic corona of PQVP and hydrophobic PS core were prepared, in which magnetic nanoparticles were randomly distributed. The hybrid micelles were used to form complexes with linear (salmon sperm, 2000 bp, corresponding to M(w) of 1.32 × 10(6) Da) and plasmid (pEGFP-N1, 4730 bp, corresponding to M(w) of 3.12 × 10(6) Da) DNA. The resulting magnetopolyplexes of phosphate:amine (P/N) ratios in the 0.05-20 range were characterized by light scattering, ζ-potential measurements, and transmission electron microscopy as well as cytotoxicity and gel retardation assays. The investigated systems displayed a narrow size distribution, particle dimensions below 360 nm, whereas their ζ-potential values varied from positive to negative depending of the P/N ratio. The resulting vector nanosystems exhibited low toxicity. They were able to introduce pEGFP-N1 molecules into the cells. The application of a magnetic field markedly boosted the transgene expression efficiency of the magnetopolyplexes, which was even superior to those of commercial transfectants such as Lipofectamine and dendritic polyethylenimine. PMID:24945823

  10. 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.

  11. Electron-transfer reactions and functionalization of cytochrome P450cam monooxygenase system in reverse micelles.

    PubMed

    Ichinose, Hirofumi; Michizoe, Junji; Maruyama, Tatsuo; Kamiya, Noriho; Goto, Masahiro

    2004-06-22

    Enzyme-based electron-transfer reactions involved in the cytochrome P450 monooxygenase system were investigated in nanostructural reverse micelles. A bacterial flavoprotein, putidaredoxin reductase (PdR), was activated and shown to be capable of catalyzing the electron transport from NADH to electron-carrier proteins such as cytochrome b5 (tCyt-b5) and putidaredoxin (Pdx) in reverse micelles. Ferric tCyt-b5 in reverse micelles was effectively converted to its ferrous form by the exogenous addition of separately prepared reverse micellar solution harboring PdR and NADH. The fact that direct interactions of macromolecular proteins should be possible in the reverse micellar system encouraged us to functionalize a multicomponent monooxygenase system composed of the bacterial cytochrome P450cam (P450cam), putidaredoxin (Pdx), and PdR in reverse micelles. The successful camphor hydroxylation reaction catalyzed by P450cam was significantly dependent on the coexistence of Pdx, PdR, and NADH but not H2O2, suggesting that the oxygen-transfer reactions proceeded via a "monooxygenation" mechanism. This is the first report of a multicomponent cytochrome P450 system exhibiting enzymatic activity in organic media. PMID:15986701

  12. Detergent Properties Influence the Stability of the Glycophorin A Transmembrane Helix Dimer in Lysophosphatidylcholine Micelles

    PubMed Central

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

    2012-01-01

    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. PMID:23260047

  13. Giant rodlike reversed micelles formed by sodium bis(2-ethylhexyl) phosphate in n-heptane

    SciTech Connect

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

    1994-08-01

    The solution behaviors of sodium bis(2-ethylhexyl) phosphate (NaDEHP) in n-heptane were investigated by light-scattering and viscosity measurements. NaDEHP forms giant rodlike reversed micelles, with a radius of gyration as large as 53 nm, which violently contrasts with the literature view that the average micellar aggregation numbers in nonaqueous or apolar media are much smaller (seldom exceeding 20) than those in aqueous media. Significantly, a small amount of water plays the role of an antimicellar growth agent; i.e., the reversed micellar size decreases remarkably when [open quotes]dry[close quotes] solutions are exposed to humid air from which water vapor is absorbed or when bulk water is directly added - a behavior which is distinctly opposite to that for sodium bis(2-ethylhexyl) sulfosuccinate/apolar medium systems. Thus, the literature views that large micelles can only be found in aqueous media and that the surfactant headgroups in reversed micelles are linked together by hydrogen bonds are misleading. It is suggested that the primary contribution to the driving force for the growth of rodlike NaDEHP reversed micelles is long-range electrostatic interactions among the headgroups of the surfactant molecules and their counterions, and a possible mechanism for the effect of water is also discussed. 27 refs., 7 figs., 1 tab.

  14. 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

  15. Ground-based simulation of LEO environment: Investigations of a select LDEF material: FEP Teflon (trademark)

    NASA Technical Reports Server (NTRS)

    Cross, Jon B.; Koontz, Steven L.

    1993-01-01

    The Long Duration Exposure Facility (LDEF) has produced a wealth of data on materials degradation in the low earth orbit (LEO) space environment and has conclusively shown that surface chemistry (as opposed to surface physics-sputtering) is the key to understanding and predicting the degradation of materials in the LEO environment. It is also clear that materials degradation and spacecraft contamination are closely linked and that the fundamental mechanisms responsible for this linking are in general not well understood especially in the area of synergistic effects. The study of the fundamental mechanisms underlying materials degradation in LEO is hampered by the fact that the degradation process itself is not observed during the actual exposure to the environment. Rather the aftermath of the degradation process is studied, i.e., the material that remains after exposure is observed and mechanisms are proposed to explain the observed results. The EOIM-3 flight experiment is an attempt to bring sophisticated diagnostic equipment into the space environment and monitor the degradation process in real time through the use of mass spectrometry. More experiments of this nature which would include surface sensitive diagnostics (Auger and photoelectron spectroscopes) are needed to truly unravel the basic chemical mechanisms involved in the materials degradation process. Since these in-space capabilities will most likely not be available in the near future, ground-based LEO simulation facilities employing sophisticated diagnostics are needed to further advance the basic understanding of the materials degradation mechanisms. The LEO simulation facility developed at Los Alamos National Laboratory has been used to investigate the atomic oxygen/vacuum ultraviolet (AO/VUV) enhanced degradation of FEP Teflon. The results show that photo-ejection of polymer fragments occur at elevated temperature (200 C), that VUV synergistic rare gas sputtering of polymer fragments occur even at

  16. Encapsulation of paclitaxel into lauric acid-O-carboxymethyl chitosan-transferrin micelles for hydrophobic drug delivery and site-specific targeted delivery.

    PubMed

    Nam, Joung-Pyo; Park, Seong-Cheol; Kim, Tae-Hun; Jang, Jae-Yeang; Choi, Changyong; Jang, Mi-Kyeong; Nah, Jae-Woon

    2013-11-30

    Transferrin/PEG/O-carboxymethyl chitosan/fatty acid/paclitaxel (TPOCFP) micelles were tested for suitability as a drug carrier characterized by low cytotoxicity, sustained release, high cellular uptake, and site-specific targeted delivery of hydrophobic drugs. Characterization, drug content, encapsulation efficiency, and in vitro drug release were investigated. When the feeding amount of paclitaxel (PTX) was increased, the drug content increased, but loading efficiency decreased. TPOCFP micelles had a spherical shape, with a particle size of approximately 140-649 nm. In vitro cell cytotoxicity and hemolysis assays were conducted to confirm the safety of the micelles. Anticancer activity and confocal laser scanning microscopy (CLSM) were used to confirm the targeting efficiency of target ligand-modified TPOCFP micelles. Anticancer activity and CLSM results clearly demonstrated that transferrin-modified TPOCFP micelles were quickly taken up by the cell. The endocytic pathway of TPOCFP micelles was analyzed by flow cytometry, revealing transfection via receptor-mediated endocytosis. These results suggest that PTX-encapsulated TPOCFP micelles may be used as an effective cancer-targeting drug delivery system for chemotherapy. PMID:24076228

  17. Complexation of AB+, AB+C, ACB+, and A(B+-stat-C) block copolymer micelles with poly(styrene sulfonate) as models for tunable gene delivery vectors

    NASA Astrophysics Data System (ADS)

    Laaser, Jennifer; Jiang, Yaming; Lohmann, Elise; Reineke, Theresa; Lodge, Timothy

    We investigate the complexation of poly(styrene sulfonate) with micelles with mixed cationic/hydrophilic coronas as models for tunable gene delivery vectors. The micelles are self-assembled from AB+, AB+C, ACB+, and A(B+-stat-C) block polymer architectures, where the hydrophobic A blocks (poly(styrene)) form the micelle cores, and the cationic B blocks (poly(dimethylamino ethyl methacrylate)) and hydrophilic, nonionic C blocks (poly(poly(ethylene glycol) methyl ether methacrylate)) form the coronas. We find that hydrophilic units do not change the colloidal stability of the complexes, and complexes based on all four micelle architectures form broad, multimodal size distributions. While complexes based on the AB+, AB+C, and ACB+polymer architectures are kinetically trapped at low ionic strength, however, those based on the A(B+-stat-C) architecture rapidly rearrange into single-micelle complexes when the linear polyanion is in excess. This suggests that the randomly-placed hydrophilic units break up the ion pairing between the cationic and anionic chains and promote formation of over-charged complexes. Design of the micelle architecture may thus provide a powerful way control the structure and stability of micelle-polyelectrolyte complexes for gene delivery applications.

  18. The effects of organic modifier on physicochemical and chromatographic characteristics of self-assembled micelle from poly (stearyl methacrylate-co-methacrylic acid) in electrokinetic chromatography.

    PubMed

    Zhang, Min; Ni, Xinjiong; Cao, Yuhua; Xin, Xiaoping; Cao, Guangqun

    2016-08-01

    In our previous work, organic solvents, especially 1-butanol, play a key role to separate highly hydrophobic analytes in EKC using the polymeric micelle self-assembled from amphiphilic random copolymer poly (stearyl methacrylate-co-methyl acrylic acid) (P(SMA-co-MAA)) as a novel pseudostationary phase. Herein, the influences of organic solvents on polymeric micelle physicochemical properties including environmental micropolarity and dimension, as well as chromatographic characteristics containing elution window, hydrophobic selectivity and polar group selectivity were investigated in detail. P(SMA-co-MAA) has extremely low CMC of 1.26 × 10(-6) g/mL, and the self-assembled micelles with selective solvent method had regular spherical structure with diameter about 50 nm. The experimental results showed that methanol, isopropanol or acetonitrile molecules could not penetrate into the interior of the polymeric micelles, and mainly affected the properties of surrounding running buffer. Too much these organic solvents led to elution window narrowed down, methylene selectivity and group selectivity weaken, even the micelles collasped. Whereas, addition of 2% 1-butanol did not influence the elution window, instead, improved the hydrophobic selectivity. Furthermore, both better group selectivity and faster migration for relatively hydrophobic analytes could be achieved simultaneously. It indicated that 1-butanol could insert into the polymeric micelle and 2% 1-butanol was enough to modify the structure of the micelles. PMID:27334427

  19. 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. PMID:27403579

  20. Synergistic effect of folate-mediated targeting and verapamil-mediated P-gp inhibition with paclitaxel -polymer micelles to overcome multi-drug resistance.

    PubMed

    Wang, Feihu; Zhang, Dianrui; Zhang, Qiang; Chen, Yuxuan; Zheng, Dandan; Hao, Leilei; Duan, Cunxian; Jia, Lejiao; Liu, Guangpu; Liu, Yue

    2011-12-01

    Multidrug resistance (MDR) in tumor cells is a significant obstacle for successful cancer chemotherapy. Overexpression of drug efflux transporters such as P-glycoprotein (P-gp) is a key factor contributing to the development of tumor drug resistance. Verapamil (VRP), a P-gp inhibitor, has been reported to be able to reverse completely the resistance caused by P-gp. For optimal synergy, the drug and inhibitor combination may need to be temporally colocalized in the tumor cells. Herein, we investigated the effectiveness of simultaneous and targeted delivery of anticancer drug, paclitaxel (PTX), along with VRP, using DOMC-FA micelles to overcome tumor drug resistance. The floate-functionalized dual agent loaded micelles resulted in the similar cytotoxicity to PTX-loaded micelles/free VRP combination and co-administration of two single-agent loaded micelles, which was higher than that of PTX-loaded micelles. Enhanced therapeutic efficacy of dual agent micelles could be ascribe to increased accumulation of PTX in drug-resistant tumor cells. We suggest that the synergistic effect of folate receptor-mediated internalization and VRP-mediated overcoming MDR could be beneficial in treatment of MDR solid tumors by targeting delivery of micellar PTX into tumor cells. As a result, the difunctional micelle systems is a very promising approach to overcome tumor drug resistance. PMID:21903258

  1. 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.

  2. Experimental investigation of microbiologically influenced corrosion of selected steels in sugarcane juice environment.

    PubMed

    Wesley, Sunil Bala; Maurya, Devendra Prasad; Goyal, Hari Sharan; Negi, Sangeeta

    2013-12-01

    In the current study, ferritic stainless grades AISI 439 and AISI 444 were investigated as possible construction materials for machinery and equipment in the cane-sugar industry. Their performance in corrosive cane-sugar juice environment was compared with the presently used low carbon steel AISI 1010 and austenitic stainless steel AISI 304. The Tafel plot electrochemical technique was used to evaluate general corrosion performance. Microbiologically influenced corrosion (MIC) behaviour in sugarcane juice environment was studied. Four microbial colonies were isolated from the biofilms on the metal coupon surfaces on the basis of their different morphology. These were characterized as Brevibacillus parabrevis, Bacillus azotoformans, Paenibacillus lautus and Micrococcus sp. The results of SEM micrographs showed that AISI 439 and AISI 304 grades had suffered maximum localized corrosion. MIC investigations revealed that AISI 444 steel had the best corrosion resistance among the tested materials. However from the Tafel plots it was evident that AISI 1010 had the least corrosion resistance and AISI 439 the best corrosion resistance. PMID:23764955

  3. 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.

  4. Structural changes of α-chymotrypsin in reverse micelles of AOT studied by steady state and transient state fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Andrade, Suzana M.; Costa, Silvia M. B.

    2001-05-01

    Time-resolved fluorescence of α-chymotrypsin (α-chym) solubilised in sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles was studied as a function of the amount of encapsulated water and initial pH. In reverse micelles the anionic interface leads to some conformational rearrangements at "pH ext" =10 due to electrostatic interactions with the ionised groups of α-chym. The data point to the protein's location in a bulk water environment, which accounts for its high stability in these reverse micelles and allows the distinction of three emitting classes of tryptophan residues within the protein's matrix. Fluorescence quenching results show that these residues are differently accessed to the quencher molecules used (acrylamide, succinimide and iodide) and are consistent with a mechanism of penetration for the interaction with the protein.

  5. 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. PMID:24615733

  6. Effect of compressed CO2 on the size and stability of reverse micelles: Small-angle x-ray scattering and phase behavior study

    NASA Astrophysics Data System (ADS)

    Zhang, Jianling; Han, Buxing; Liu, Juncheng; Zhang, Xiaogang; Yang, Guanying; He, Jun; Liu, Zhimin; Jiang, Tao; Wang, Jun; Dong, Baozhong

    2003-02-01

    Synchrotron radiation small-angle x-ray scattering (SAXS) and phase behavior investigations were combined to study the effect of compressed CO2 on the stability and structure of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles in isooctane at different temperatures, CO2 pressures, AOT concentrations, and the molar ratios of water to surfactant w ([H2O]/[AOT]). SAXS measurements indicate that the size of the reverse micelles depends markedly on the pressure of CO2 and w. Increasing pressure of CO2 results in reduction of the micellar size. The effect of CO2 pressure on the size and structure of the reverse micelles is nearly independent of the concentration of the surfactant. The results of SAXS also give the information about the stability of the reverse micelles, which agrees with that obtained from the phase behavior investigation.

  7. 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. PMID:22453608

  8. Redox and pH-responsive degradable micelles for dually activated intracellular anticancer drug release.

    PubMed

    Chen, Wei; Zhong, Ping; Meng, Fenghua; Cheng, Ru; Deng, Chao; Feijen, Jan; Zhong, Zhiyuan

    2013-08-10

    Redox and pH dual-responsive biodegradable micelles were developed based on poly(ethylene glycol)-SS-poly(2,4,6-trimethoxybenzylidene-pentaerythritol carbonate) (PEG-SS-PTMBPEC) copolymer and investigated for intracellular doxorubicin (DOX) release. PEG-SS-PTMBPEC copolymer with an Mn of 5.0-4.1kg/mol formed micellar particles with an average diameter of 140nm and a low polydispersity of 0.12. DOX was loaded into PEG-SS-PTMBPEC micelles with a decent drug loading content of 11.3wt.%. The in vitro release studies showed that under physiological conditions only ca. 24.5% DOX was released from DOX-loaded micelles in 21h. The release of DOX was significantly accelerated at pH5.0 or in the presence of 10mM glutathione (GSH) at pH7.4, in which 62.8% and 74.3% of DOX was released, respectively, in 21h. The drug release was further boosted under 10mM GSH and pH 5.0 conditions, with 94.2% of DOX released in 10h. Notably, DOX release was also facilitated by 2 or 4h incubation at pH 5.0 and then at pH 7.4 with 10mM GSH, which mimics the intracellular pathways of endocytosed micellar drugs. Confocal microscopy observation indicated that DOX was delivered and released into the nuclei of HeLa cells following 8h incubation with DOX-loaded PEG-SS-PTMBPEC micelles, while DOX was mainly located in the cytoplasm for reduction-insensitive PEG-PTMBPEC controls. MTT assays revealed that DOX-loaded PEG-SS-PTMBPEC micelles had higher anti-tumor activity than reduction-insensitive controls, with low IC50 of 0.75 and 0.60μg/mL for HeLa and RAW 264.7 cells, respectively, following 48h incubation. PEG-SS-PTMBPEC micelles displayed low cytotoxicity up to a concentration of 1.0mg/mL. These redox and pH dual-bioresponsive degradable micelles have appeared as a promising platform for targeted intracellular anticancer drug release. PMID:23306022

  9. 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

  10. 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

  11. Investigating performance and lung function in a hot, humid and ozone-polluted environment.

    PubMed

    Gomes, Elisa Couto; Stone, Vicki; Florida-James, Geraint

    2010-09-01

    Large urbanized areas, where sports events take place, have a polluted environment and can also reach high temperatures and humidity levels. The aim of this study was to investigate the impact of a hot, humid and ozone-polluted (O(3)) environment on (1) performance of an 8 km time trial run, (2) pulmonary function, and (3) subjective respiratory symptoms in endurance-trained runners. Using crossover randomized design, 10 male participants (mean V(O)₂(max)= 64.4 mlO(2) kg(-1) min(-1), SD = 4.4) took part in a time trial run under four different conditions: 20 degrees C + 50% relative humidity (rh) (Control), 20 degrees C + 50% rh + 0.10 ppm O(3) (Control + O(3)), 31 degrees C + 70% rh (Heat), 31 degrees C + 70% rh + 0.10 ppm O(3) (Heat + O(3)). Heart rate, ratings of perceived exertion and minute ventilation were collected during the run. Lung function was measured pre and post-exercise. The runners completed a respiratory symptoms questionnaire after each trial. The completion time of both the Heat (32 min 35 s) and Heat + O(3) (33 min 09 s) trials were significantly higher (P < 0.0001) when compared to the Control + O(3) (30 min 27 s) and Control (30 min 15 s) trials. There were no significant changes between pre/post lung function measures or between trials. The effective dose of ozone simulated in the present study did not affect the performance and therefore, ozone-pollution, at an environmentally relevant concentration, did not compound the impairment in performance beyond that induced by a hot, humid environment. PMID:20449752

  12. 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

  13. Water induced microstructure transformation of diglycerol monolaurate reverse micelles in ethylbenzene.

    PubMed

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

    2012-01-01

    Water induced microstructure transitions of diglycerol monolaurate (C(12)G(2)) reverse micelles in aromatic liquid ethylbenzene have been investigated using small-angle X-ray scattering (SAXS) and rheometry. The SAXS data have been evaluated by generalized indirect Fourier transformation (GIFT) and geometrical model fittings. We found that the C(12)G(2) spontaneously self-assembles into ellipsoidal prolate micelles in ethylbenzene under ambient conditions. The maximum diameter of the micellar core is ca. 5.0 nm. We noted that 5% C(12)G(2)/ethylbenzene solubilize 0.8% water and the water causes micellar growth; micellar size is ~ 3 times bigger than the empty micelles. Rheology data showed that viscosity of 5% C(12)G(2)/ethylbenzene increases with increase in the water concentration sustaining the SAXS results that the viscosity increase is caused due to micellar growth. We found that increase in temperature of the water incorporated system decreases micellar size, which is equivalent to a rod-to-sphere type transition. The water induced microstructure transformations can be explained in terms of critical packing parameter, cpp. Water hydrates hydrophilic headgroup of surfactant so that effective cross-sectional area of surfactant increases. As a result the cpp decreases and micelles grow. On the other hand, increasing temperature promotes interpenetration of solvent and surfactant chain as a result cpp increases due to decrease in the effective cross-sectional area of surfactant. Moreover dehydration may occur and micelles with more curved interface are formed due to increases in the cpp. PMID:23018854

  14. 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

  15. 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.

  16. 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.

  17. 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. PMID:20550251

  18. 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.

  19. Archival Legacy Investigation of Circumstellar Environments (ALICE). Candidates point sources and high-level science products

    NASA Astrophysics Data System (ADS)

    Choquet, Elodie; Chen, C.; Debes, J. H.; Golimowski, D. A.; Hagan, J.; Hines, D. C.; Lonsdale, S.; Marois, C.; Mawet, D.; Mittal, T.; Moerchen, M.; N'Diaye, M.; Perrin, M. D.; Pueyo, L.; Rajan, A.; Reid, I. N.; Schneider, G.; Wolff, S.; Soummer, R.

    2014-01-01

    The Archival Legacy Investigation of Circumstellar Environments (ALICE) project (HST/AR program 12652; PI Soummer) is currently conducting a comprehensive and consistent reprocessing of HST-NICMOS coronagraphic survey data to search for point sources and disks using advanced PSF subtraction. The Karhunen-Loeve Image Projection (KLIP) algorithm based on principal component analysis was developed for this project. We present the main concept for the pipeline, reduction strategy, and PSF subtraction implementation and performance. The ALICE pipeline was designed to process automatically approximately 400 targets in the NICMOS coronagraphic archive, and to deliver High-Level Science Products (HLSPs) back to the MAST archive at STScI. The HLSPs are defined in collaboration with other similar projects to define a standard format for high-contrast imaging. We present and discuss the ALICE point source candidates detected in the NICMOS archive together with a statistical analysis of the population of background objects.

  20. Investigating factor structure of an instrument to measure social work students' preparedness for managed care environments.

    PubMed

    Kane, Michael N; Houston-Vega, Mary Kay; Tan, Philip P; Hawkins, Wesley E

    2002-01-01

    This study investigated the factor structure of an instrument to measure social work students' perceptions of preparedness to enter managed care environments. Exploratory statistical procedures to reduce data through principle component analysis identified nine factors with eigenvalues greater than 1.0. These factors include: perceived understanding of agency financial agendas, managing personal risk and liability, perceived understanding of agency documentation requirements, awareness of ethical and value conflicts in documentation, classroom preparation for documentation, understanding the fit between client advocacy and managed care agendas, worrying about law suits in employment settings, perceived understanding of managed care gatekeeping and service authorization, and perceptions of field preparation for documentation. Recommendations are made for utilizing this brief self-report instrument in training students for managed care settings. PMID:12425449

  1. QuakeSim: a Web Service Environment for Productive Investigations with Earth Surface Sensor Data

    NASA Astrophysics Data System (ADS)

    Parker, J. W.; Donnellan, A.; Granat, R. A.; Lyzenga, G. A.; Glasscoe, M. T.; McLeod, D.; Al-Ghanmi, R.; Pierce, M.; Fox, G.; Grant Ludwig, L.; Rundle, J. B.

    2011-12-01

    The QuakeSim science gateway environment includes a visually rich portal interface, web service access to data and data processing operations, and the QuakeTables ontology-based database of fault models and sensor data. The integrated tools and services are designed to assist investigators by covering the entire earthquake cycle of strain accumulation and release. The Web interface now includes Drupal-based access to diverse and changing content, with new ability to access data and data processing directly from the public page, as well as the traditional project management areas that require password access. The system is designed to make initial browsing of fault models and deformation data particularly engaging for new users. Popular data and data processing include GPS time series with data mining techniques to find anomalies in time and space, experimental forecasting methods based on catalogue seismicity, faulted deformation models (both half-space and finite element), and model-based inversion of sensor data. The fault models include the CGS and UCERF 2.0 faults of California and are easily augmented with self-consistent fault models from other regions. The QuakeTables deformation data include the comprehensive set of UAVSAR interferograms as well as a growing collection of satellite InSAR data.. Fault interaction simulations are also being incorporated in the web environment based on Virtual California. A sample usage scenario is presented which follows an investigation of UAVSAR data from viewing as an overlay in Google Maps, to selection of an area of interest via a polygon tool, to fast extraction of the relevant correlation and phase information from large data files, to a model inversion of fault slip followed by calculation and display of a synthetic model interferogram.

  2. Solvation and Deprotonation Dynamics in Reverse Micelles via Broadband Femtoseond Transient Absorption (BFTA) Spectroscopy

    NASA Astrophysics Data System (ADS)

    Cole, Richard

    2009-10-01

    Broadband femtosecond transient absorption (BFTA) spectroscopy is a useful tool in characterizing femtosecond and picosecond physical and chemical dynamics such as solvation, electron transfer, and deprotonation dynamics. This presentation will focus on our most recent results, which utilize BFTA spectroscopy in the ultraviolet-visible (UV-vis) spectral range to probe deprotonation and solvation dynamics in the nanoscopic confinement of reverse micelles. In these studies, pyranine, a `photo-acid', probes both solvation and deprotonation dynamics in reverse micelles formed from cationic (cetyl trimethylammonium bromide, CTAB), anionic (sodium dioctyl sulfosuccinate, AOT), and neutral (polyoxyethylene nonylphenylether, Igepal) surfactants. Dynamic behavior will be discussed in terms of the degree of nanoscopic confinement (micellar size) and the impact of varying interfacial environments.

  3. 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

  4. 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

  5. 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…

  6. 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)

  7. 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

  8. 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

  9. 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.

  10. 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. PMID

  11. 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

  12. Effects of depletion interactions on block copolymer micelles

    NASA Astrophysics Data System (ADS)

    Abbas, Sayeed; Lodge, Timothy P.

    2008-03-01

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

  13. 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

  14. 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 &…

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

    PubMed

    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

  16. 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

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

    SciTech Connect

    Miyagishi, S.; Nishida, M.

    1980-11-01

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

  18. A theoretical investigation of electric properties of L-arginine phosphate monohydrate including environment polarization effects

    NASA Astrophysics Data System (ADS)

    Fonseca, T. L.; Sabino, J. R.; Castro, M. A.; Georg, H. C.

    2010-10-01

    The dipole moment (μ), linear polarizability (α¯), and first hyperpolarizability (βtot) of the asymmetric unit of L-arginine phosphate (LAP) monohydrate crystal are investigated using the supermolecule approach in combination with an iterative electrostatic polarization scheme. Environment polarization effects are attained by assuring the convergence of the dipole moment of LAP embedded in the polarization field of the surrounding molecules whose atomic sites are treated as point charges. The results obtained show that in the presence of the embedding charges, the value of μ is increased by 9% but the static values of α¯ and βtot are decreased, respectively, by 3% and 13%, as compared with the isolated situation. The MP2/6-311+G(d) model predicts for the in-crystal dipole moment the converged value of 33 D, in good concordance with the available experimental result of 32 D. Our estimates for the converged results of α¯ and βtot are, respectively, 22.51×10-24 and 5.01×10-30 esu. Dispersion effects are found to have a small impact on the nonlinear optical responses of LAP in the visible region. In addition, MP2/6-311G results obtained for βtot by using isolated and embedded LAP dimers show that crystal packing effects have a significant contribution of the electrostatic interactions. Our results suggest that the role of the crystal environment is to minimize the effects of the intermolecular interactions in the electric properties. That is, μ and βtot gain a more additive character in the presence of the field of the embedding charges. This is specially marked for βtot.

  19. 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

  20. Principal role of the stepwise aggregation mechanism in ionic surfactant solutions near the critical micelle concentration. Molecular dynamics study.

    PubMed

    Burov, Stanislav V; Vanin, Alexandr A; Brodskaya, Elena N

    2009-08-01

    The validity of the assumption on the predominant contribution of the stepwise processes to the ionic micelle formation/destruction in the vicinity of critical micelle concentration was investigated by molecular dynamics simulation. A coarse-grained model was used to describe the surfactant/water mixture. The cluster size distribution was estimated directly from molecular dynamics simulations or obtained from a reduced set of kinetic equations. The good agreement between two approaches shows that the neglect of the terms responsible for cluster fusion/fission is fully justified and that such processes are less important than stepwise aggregation. PMID:19591445

  1. Mechanism of YF3 nanoparticle formation in reverse micelles.

    PubMed

    Lemyre, Jean-Luc; Lamarre, Sébastien; Beaupré, Ariane; Ritcey, Anna M

    2011-10-01

    This article reports an investigation of the mechanism of YF(3) nanoparticle formation in two variants of the reverse microemulsion precipitation method. These two variants involve the addition of F(-), either as a microemulsion or directly as an aqueous solution, to Y(3+) dispersed in nonionic reverse micelles. The two methods yield amorphous and single-crystal nanoparticles, respectively. The kinetics of reagent mixing are studied by (19)F NMR and colorimetric model reactions, and the particle growth is monitored by TEM. Mixing and nucleation are shown to occur within seconds to minutes whereas particle growth continues for 4 to 48 h, depending on the particle type. Moreover, the growth rate remains constant during most of the growth period, indicating that Ostwald ripening is the most probable growth mechanism. The single-emulsion method also produces a minority amorphous population that exhibits significantly different growth kinetics, attributed to a coagulation mechanism. Secondary growth experiments, involving the addition of precursor ions to mature particles, have been conducted to evaluate the relative importance of nucleation and the competitive growth of existing particle populations. The key differences between the two methods reside in the nucleation step. In the case of the classical method, nucleation occurs upon intermicellar collisions and under conditions of comparable concentrations of Y(3+) and F(-). This method generates more numerous stable nuclei and smaller particles. In the single-microemulsion method, nucleation occurs in the presence of excess F(-) through the interaction of Y(3+)-containing micelles with microdroplets of aqueous F(-). These conditions lead to the formation of crystalline particles and a wider size distribution of unstable nuclei. PMID:21842856

  2. Examination of Gossypol-Pluronic Micelles as Potential Radiosensitizers.

    PubMed

    Tomoda, Keishiro; Chiang, Carol; Kozak, Kevin R; Kwon, Glen S

    2015-11-01

    Chemoradiotherapy, the combination of chemotherapy and radiotherapy to treat cancer, has the potential to enhance local therapeutic effects and simultaneously treat systemic disease. However, chemoradiotherapy may also enhance normal tissue effects leading to both acute and late toxicities. Furthermore, subtherapeutic chemoradiotherapy may result in aggressive tumor repopulation. Tumor-specific radiosensitizing chemotherapy may yield a synergistic therapeutic effect and avoid augmentation of normal tissue toxicity. In this study, the radiosensitizing effects of gossypol were investigated. Also, Pluronics were studied for gossypol solubilization and co-radiosensitization effects. Gossypol inhibits Bcl-2 and Bcl-XL, antiapoptotic proteins that are overexpressed in various cancer cells. Pluronic micelles (P85, F88, L35, and P123) effectively encapsulated gossypol, raising its water solubility by more than 1000-fold. Cytotoxic, anticlonogenic, and radiosensitizing effects were evaluated to characterize gossypol and Pluronic combinations. Gossypol and P85 had the strongest antiproliferative effect on A549 human lung adenocarcinoma cells in a cell viability assay. The IC50 value was seven times lower than gossypol only treatment (330 ± 70 nM vs 2400 ± 400 nM, (mean ± SE)). Gossypol and P85 showed significant inhibition of clonogenic survival, approximately 30% inhibition, compared to treatment with gossypol alone. An experimental sequencing study demonstrated greater inhibition of clonogenic survival when drug treatment followed radiation compared to a sequence of drug treatment followed by radiation. These results suggest that Pluronic micelles readily solubilize gossypol and that the combination of gossypol and P85 may augment the therapeutic effects of ionizing radiation. PMID:26246329

  3. 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…

  4. 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.

  5. 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

  6. Therapeutic surfactant-stripped frozen micelles.

    PubMed

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

    2016-01-01

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

  7. Cellular Uptake and Movement in 2D and 3D Multicellular Breast Cancer Models of Fructose-Based Cylindrical Micelles That Is Dependent on the Rod Length.

    PubMed

    Zhao, Jiacheng; Lu, Hongxu; Xiao, Pu; Stenzel, Martina H

    2016-07-01

    While the shape effect of nanoparticles on cellular uptake has been frequently studied, no consistent conclusions are available currently. The controversy mainly focuses on the cellular uptake of elongated (i.e., filaments or rod-like micelles) as compared to spherical (i.e., micelles and vesicles) nanoparticles. So far, there is no clear trend that proposes the superiority of spherical or nonspherical nanoparticles with conflicting reports available in the literature. One of the reasons is that these few reports available deal with nanoparticles of different shapes, surface chemistries, stabilities, and aspects ratios. Here, we investigated the effect of the aspect ratio of cylindrical micelles on the cellular uptake by breast cancer cell lines MCF-7 and MDA-MB-231. Cylindrical micelles, also coined rod-like micelles, of various length were prepared using fructose-based block copolymers poly(1-O-methacryloyl-β-d-fructopyranose)-b-poly(methyl methacrylate). The critical water content, temperature, and stirring rate that trigger the morphological transition from spheres to rods of various aspect ratios were identified, allowing the generation of different kinetically trapping morphologies. High shear force as they are found with high stirring rates was observed to inhibit the formation of long rods. Rod-like micelles with length of 500-2000 nm were subsequently investigated toward their ability to translocate in breast cancer cells and penetrate into MCF-7 multicellular spheroid models. It was found that shorter rods were taken up at a higher rate than longer rods. PMID:27286273

  8. 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

  9. 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.

  10. Archival Legacy Investigation of Circumstellar Environments (ALICE): Overview and First Results

    NASA Astrophysics Data System (ADS)

    Soummer, Remi; Barman, T. S.; Chen, C.; Choquet, E.; Comeau, T.; Debes, J. H.; Golimowski, D. A.; Hagan, J.; Hines, D. C.; Lonsdale, S.; Marois, C.; Mawet, D.; Mittal, T.; Moerchen, M.; N'Diaye, M.; Perrin, M. D.; Pueyo, L.; Rajan, A.; Reid, I. N.; Schneider, G.; Wolff, S.

    2014-01-01

    The Archival Legacy Investigation of Circumstellar Environments (ALICE) project ((HST/AR program 12652) is currently conducting a comprehensive and consistent reprocessing of HST-NICMOS coronagraphic survey data to search for point sources and disks using advanced PSF subtraction. This project has already been very successful with numerous detections of previously unseen point sources and several debris disks that we are currently following up by multiple avenues. We give an overview of the project including preliminary scientific results with companion candidates, improved images of known disks, and first scattered light image of several disks. ALICE will deliver high-level science products (HLSPs) to the community through the MAST archive at STScI. The goal is to define a HLSP standard that can be applicable to other projects including ground-based (e.g., Gemini Planet Imager), and future space instruments (e.g., JWST). The ALICE pipeline takes full advantage of the LAPLACE PSF library (Schneider et al. 2012) for coronagraphic data, which provides enhanced calibration of NICMOS coronagraphic data and is available from the MAST archive.

  11. 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.

  12. 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

  13. 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

  14. 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

  15. Laboratory investigation on the different activation mechanisms for aluminum and zinc anodes in sea water environment

    NASA Astrophysics Data System (ADS)

    basir, Ali. EL.; Elazhari, Omar A.; Shartel, K.; Esmal, M.

    2013-12-01

    Cathodic protection (CP) is one practical and economical corrosion control option used to protect steel structures. The common sacrificial anodes used for CP system are aluminum (AL), and zinc (Zn) and their alloys. These three metals and their alloys can provide the starting basis for steel protection in sea water environment. actually many sacrificial anodes (SA) activation processes are widely used to improve the performance protection of steel . Based on the finding and the analysis of the results the aluminum and its alloys should be activated by the activation element rather than by cold working. However, activating the zinc and its alloys provides some improvement in the anode performance and could be considered as a reliable activation mechanism similar to the activation by alloying addition to zinc of similar purity. Finally, this paper discusses the use of cold working as a new activation mechanism, by using extensive laboratory investigation under simulated environmental conditions, and anode current capacity, polarization corrosion rates and protection ability were determined and discussed for this study.

  16. 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.

  17. 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.

  18. Disulfide-Linked Amphiphilic Polymer-Docetaxel Conjugates Assembled Redox-Sensitive Micelles for Efficient Antitumor Drug Delivery.

    PubMed

    Zhang, Pei; Zhang, Huiyuan; He, Wenxiu; Zhao, Dujuan; Song, Aixin; Luan, Yuxia

    2016-05-01

    Here, we prepared novel redox-sensitive drug delivery system based on copolymer-drug conjugates methoxy poly(ethylene glycol)-poly(γ-benzyl l-glutamate)-disulfide-docetaxel (mPEG-PBLG-SS-DTX) to realize the desirable cancer therapy. First, copolymers of methoxy poly(ethylene glycol)-poly(γ-benzyl l-glutamate) (mPEG-PBLGs) with different molecular weight (mPEG2000-PBLG1750 and mPEG5000-PBLG1750) were synthesized via the ring open polymerization (ROP) of 5-benzyl-l-glutamate-N-carboxyanhydride (γ-Bzl-l-Glu-NCA) initiated by monoamino-terminated mPEG (mPEG-NH2). Then, the docetaxel (DTX) was conjugated to the block polymers through a linkage containing disulfide bond to obtain mPEG-PBLG-SS-DTXs, including mPEG2000-PBLG1750-SS-DTX and mPEG5000-PBLG1750-SS-DTX. The obtained copolymer-drug conjugates mPEG2000-PBLG1750-SS-DTX and mPEG5000-PBLG1750-SS-DTX could self-assemble into nanosized micelles in aqueous environment via dialysis method with a low critical micelle concentration (CMC, 3.98 and 6.94 μg/mL, respectively). The size of the micelles was approximately 101.3 and 148.9 nm, respectively, with a narrow size distribution. They released approximately 40% DTX in a sustained way in the presence of 50 mM DTT after 120 h in comparison with only approximately 10% DTX released from micelles in the absence of DTT. The high cytotoxicity was identified for mPEG-PBLG-SS-DTXs micelles against MCF-7/ADR and A549 cells, and the IC50 of mPEG-PBLG-SS-DTXs micelles against MCF-7/ADR for 24 h was roughly a 15th of the value of free DTX. Moreover, the mPEG-PBLG-SS-DTXs micelles could be efficiently uptaken by MCF-7/ADR and A549 cells. Thus, the present constructed mPEG-PBLG-SS-DTXs micelles were very promising for effective cancer therapy. PMID:27018501

  19. Tunable parameters for the structural control of reverse micelles in glycerol monoisostearate/oil systems: a SAXS study.

    PubMed

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

    2009-04-21

    Formation of reverse micelles in surfactant/oil binary systems without water addition and the tunable parameters for the structure control of such micelles are presented. The small-angle X-ray scattering (SAXS) technique has been used for the structural characterization of micelles. It has been found that the nonionic surfactant glycerol monoisostearate (abbreviated as iso-C18G1) forms reverse micelles in different organic solvents such as cyclohexane, n-decane, and n-hexadecane without the addition of water. The structure (shape and size) of the reverse micelles has been found to depend on the solvent nature (alkyl chain length of oil), composition, temperature, and added water. Phase behavior study has shown that iso-C18G1 forms isotropic single-phase solutions in the aforementioned oils at 25 degrees C. At lower temperatures (<20 degrees C) II phases (dispersion of solid or liquid crystal phase) has been observed. SAXS data were evaluated by the generalized indirect Fourier transformation (GIFT) method, which has drawn a clear picture on the structural variations of the reverse micellar aggregates. Small globular types of micelles are found in the iso-C18G1/cyclohexane system. On the other hand, elongated ellipsoidal prolatelike or rodlike micelles are found in iso-C18G1/decane or iso-C18G1/hexadecane systems. The underlying mechanism of this structural evolution may be explained in terms of the transfer free energy of hydrophilic glycerol moiety from hydrophilic to hydrophobic environment of oils with different chain lengths. Besides, the penetration of oils to the lipophilic chain of the surfactant in reverse micellar systems differs depending on the chain length of oils. Lowering temperature and increasing surfactant concentration similarly lead to micellar growth while the cross-section structure remains essentially unchanged. Addition of trace water induced micellar growth, which is accompanied by the rapid swelling of the micellar core. The results

  20. 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

  1. A Simple Dual-pH Responsive Prodrug-Based Polymeric Micelles for Drug Delivery.

    PubMed

    Mao, Jie; Li, Yang; Wu, Tong; Yuan, Conghui; Zeng, Birong; Xu, Yiting; Dai, Lizong

    2016-07-13

    To precisely deliver drug molecules at a targeted site and in a controllable manner, there has been great interest in designing a synergistical drug delivery system that can achieve both surface charge-conversion and controlled release of a drug in response to different stimuli. Here we outline a simple method to construct an intelligent drug carrier, which can respond to two different pH values, therefore achieving charge conversion and chemical-bond-cleavage-induced drug release in a stepwise fashion. This drug carrier comes from the self-assembly of a block copolymer-DOX conjugate synthesized through a Schiff base reaction between poly(2-(diisopropylamino)ethyl methacrylate-b-poly(4-formylphenyl methacrylate-co-polyethylene glycol monomethyl ether methacrylate) (PDPA-b-P(FPMA-co-OEGMA)) and DOX. The surface charge of the BCP-DOX micelles reversed from negative to positive when encountering a weakly acidic environment due to the protonation of PDPA segments. In vitro cellular uptake measurement shows that the cellular uptake and internalization of the BCP-DOX micelles can be significantly enhanced at pH ∼ 6.5. Moreover, this drug carrier exhibits a pH-dependent drug release owing to the cleavage of the imine bond at pH < 5.5. With this dual-pH responsive feature, these micelles may have the ability to precisely deliver DOX to the cancer cells. PMID:27280955

  2. Heat stability of aggregated particles of casein micelles and kappa-carrageenan.

    PubMed

    Flett, Kelly L; Corredig, Milena; Goff, H Douglas

    2010-06-01

    Aggregated particles of casein micelles and kappa-carrageenan were produced as a dried milk ingredient, then reconstituted and subjected to a heat treatment of 70 degrees C for 10 min. The reconstituted aggregates were found to be unstable when heated. Light scattering results showed that the aggregates dissociated partially into casein micelles. It was hypothesized that the removal of ions during ultrafiltration before spray-drying to produce the powdered ingredient significantly decreased stability upon reconstitution and heat treatment. When ions, either from whey permeate or calcium addition, were added to reconstituted aggregates, stability was greatly enhanced and the aggregates remained intact when subjected to heat. The effect of heat treatment on aggregates freshly produced with skim milk powder and kappa-carrageenan was also studied. These aggregates were found to be stable during heating due to the unchanged ionic environment. Therefore, incorporation of powdered aggregates of casein micelles and kappa-carrageenan into products would require the addition of whey permeate or calcium after reconstitution for stability during subsequent heating. PMID:20629864

  3. Sorption of nonionic organic compounds in soil-water systems containing a micelle-forming surfactant

    SciTech Connect

    Sun, S.; Inskeep, W.P.; Boyd, S.A. |

    1994-12-31

    The solubility enhancement of nonionic organic compounds (NOCs) by surfactants may represent an important tool in chemical and biological remediation of contaminated soils. In aqueous systems, the presence of dissolved surfactant emulsions or micelles may enhance the solubility of NOCs by acting as a hydrophobic partitioning phase for the NOCs. However, most environmental remediation efforts involve soil-water or sediment-water systems, where surfactant molecules may also interact with the solid phase. An understanding of the effect of surfactants on the sorption and distribution of NOCs in soil or sediment environments will provide an essential basis for utilizing surfactants in environmental remediation. In this study, the authors examined the effect of a micelle-forming surfactant (Triton X-100) on the sorption of 2,2{prime},4,4{prime},5,5{prime}-PCB, 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (p,p{prime}-DDT) and 1,2,4-trichlorobenzene (1,2,4-TCB). A conceptual model, which accurately describes the functional dependence of K* on Triton X-100 concentration, was developed based on the partition coefficients of these NOCs by soil, soil-surfactant, surfactant monomer and surfactant micelle phases. This model can be further modified to provide quantitative prediction of K* of a given NOC at different surfactant concentrations.

  4. 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

  5. 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

  6. Free-energy analysis of solubilization in micelle

    NASA Astrophysics Data System (ADS)

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

    2006-04-01

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

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

    PubMed

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

    2016-06-01

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

  8. 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.; Çağatay, 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.

    2013-08-01

    In this paper we synthesize the new knowledge on oxygen and oxygen-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 land-locked water bodies", 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 analysed in field studies in various aquatic environments, including the Baltic Sea, the Black Sea, Scottish and Scandinavian fjords, Ionian Sea lagoons and embayments, and in 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 submicromolar oxygen distributions were resolved. Existing multi-decadal 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 not 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 natural and anthropogenic hypoxia overlap. Biogeochemical investigations reveal that oxygen intrusions have a strong effect on microbially-mediated redox cycling of elements. Observations and modeling studies of

  9. 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

  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. 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

  12. 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

  13. 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

  14. 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.

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

    PubMed

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

    2015-12-01

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

  16. 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

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

    PubMed

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

    2007-10-01

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

  18. Microencapsulation of superoxide dismutase into poly(epsilon-caprolactone) microparticles by reverse micelle solvent evaporation.

    PubMed

    Youan, Bi-Botti Célestin

    2003-01-01

    The aim of this work was to encapsulate superoxide dismutase (SOD) in poly(epsilon-caprolactone) (PCL) microparticles by reverse micelle solvent evaporation. The concentration of PCL, the hydrophile-lipophile balance (HLB), and concentration of the sucrose ester used as surfactant in the organic phase were investigated as formulation variables. Relatively higher encapsulation efficiency (approximately 48%) and retained enzymatic activity (>90%) were obtained with microparticle formulation made from the 20% (w/v) PCL and 0.05% (w/v) sucrose ester of HLB = 6. This formulation allowed the in vitro release of SOD for at least 72 hr. These results showed that reverse micelle solvent evaporation can be used to efficiently encapsulate SOD in PCL microparticles. Such formulations may improve the bioavailability of SOD. PMID:14612345

  19. The use of ultrasound to release chemotherapeutic drugs from micelles and liposomes.

    PubMed

    Ahmed, Salma E; Martins, Ana M; Husseini, Ghaleb A

    2015-01-01

    Several drug delivery systems have been investigated to reduce the side effects of chemotherapy by encapsulating the therapeutic agent in a nanosized carrier until it reaches the tumor site. Many of these particles are designed to be responsive to the mechanical and thermal perturbations delivered by ultrasound. Once the nanoparticle reaches the desired location, ultrasound is applied to release the chemotherapy drug only in the vicinity of the targeted (cancer) site, thus avoiding any detrimental interaction with healthy cells in the body. Studies using liposomes and micelles have shown promising results in this area, as these nanoparticles with simple, yet effective structures, showed high efficiency as drug delivery vehicles both in vitro and in vivo. This article reviews the design and application of two novel nanosized chemotherapeutic carriers (i.e. micelles and liposomes) intended to be actuated by ultrasound. PMID:25203857

  20. Bioconjugation of biotin to the interfaces of polymeric micelles via in situ click chemistry.

    PubMed

    Wang, Xiaojuan; Liu, Li; Luo, Yan; Zhao, Hanying

    2009-01-20

    Azido-containing amphiphilic triblock copolymer poly(ethylene glycol)-b-poly(azidoethyl methacrylate)-b-poly(methyl methacrylate) (PEG-b-PAzEMA-b-PMMA) was prepared by postpolymerization functionalization of poly(ethylene glycol)-b-poly(hydroxyethyl methacrylate)-b-poly(methyl methacrylate) (PEG-b-PHEMA-b-PMMA). In aqueous media, PEG-b-PAzEMA-b-PMMA self-assembled into spherical micelles with the azide groups at the hydrophobic/hydrophilic interface due to the molecular architecture. Biotin was conjugated to the micelles by in situ click chemistry between azide groups and alkynated biotin, resulting in the formation of a functional interface between the hydrophilic shell and the hydrophobic core. The bioavailability of biotin to avidin was demonstrated by an avidin/4'-hydroxyazobenzene-2-carboxylic acid (avidin/HABA) assay, transmission electron microscopy, and dynamic light scattering investigations. PMID:19105785

  1. Improvement in electric and dielectric properties of nanoferrite synthesized via reverse micelle technique

    NASA Astrophysics Data System (ADS)

    Thakur, Sangeeta; Katyal, S. C.; Singh, M.

    2007-12-01

    Nano nickel zinc ferrite (Ni0.58Zn0.42Fe2O4) with fascinating dielectric properties which reveal a direction for application was synthesized by reverse micelle technique. Dielectric constant and dielectric losses are controlled up to a measurement temperature of around 473K at higher frequency range of 9-19MHz. The dielectric loss of the sample investigated at room temperature is only 0.003 at 19MHz. The presently studied nanoferrite also exhibits a high value of dc resistivity, 108Ωcm. High resistivity and low dielectric constant and loss can be corelated to small grain size and better compositional stoichiometry obtained as a result of processing via reverse micelle technique at low sintering temperature (773K).

  2. Hydrophobically Modified Halloysite Nanotubes as Reverse Micelles for Water-in-Oil Emulsion.

    PubMed

    Cavallaro, Giuseppe; Lazzara, Giuseppe; Milioto, Stefana; Parisi, Filippo

    2015-07-14

    An easy strategy to obtain inorganic reverse micelles based on halloysite nanotubes (HNTs) and alkyltrimethylammonium bromides has been developed. The selective modification of the HNTs external surface with cationic surfactants endows to generate tubular nanostructures with a hydrophobic shell and a hydrophilic cavity. The influence of the surfactants alkyl chain on the HNTs functionalization degree has been investigated. The dynamic behavior of the surfactant/HNT hybrids in solvents with variable polarity has been correlated to their affinity toward hydrophobic media explored through partition experiments. The water-in-oil emulsion is able to solubilize copper sulfate, proving the incorporation and the loading of hydrophilic compounds into the HNTs lumen. Here we have fabricated ecocompatible reverse micelles with tunable hydrophobic/hydrophilic interface that might be suitable for industrial and biological applications as well as for selective organic synthesis. PMID:26119491

  3. 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.

  4. 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

  5. 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

  6. pH-responsive diblock copolymer micelles at the silica/aqueous solution interface: Adsorption kinetics and equilibrium studies.

    PubMed

    Sakai, Kenichi; Smith, Emelyn G; Webber, Grant B; Schatz, Christophe; Wanless, Erica J; Bütün, Vural; Armes, Steven P; Biggs, Simon

    2006-08-01

    The adsorption behavior of two examples of a weakly basic diblock copolymer, poly(2-(dimethylamino)ethyl methacrylate)-block-poly(2-(diethylamino)ethyl methacrylate) (PDMA-PDEA), at the silica/aqueous solution interface has been investigated using a quartz crystal microbalance with dissipation monitoring and an optical reflectometer. Dynamic and static light scattering measurements have also been carried out to assess aqueous solution properties of such pH-responsive copolymers. In alkaline solution, core-shell micelles are formed above the critical micelle concentration (cmc) by both copolymers, whereas the chains are molecularly dissolved (as unimers) at all concentrations in acidic solution. As a result, the adsorption behavior of PDMA-PDEA diblock copolymers on silica is strongly dependent on both the copolymer concentration and the solution pH. Below the cmc at pH 9, the cationic PDMA-PDEA copolymers adsorb as unimers and the conformation of the adsorbed polymer is essentially flat. At concentrations just above the cmc, the initial adsorption of copolymer onto the silica is dominated by the unimers due to their faster diffusion compared to the much larger micelles. Rearrangement of the adsorbed unimers and/or their subsequent displacement by micelles from solution is then observed during an equilibration period, and the final adsorbed mass is greater than that observed below the cmc. At concentrations well above the cmc, the much higher proportion of micelles in solution facilitates more effective competition for the surface at all stages of the adsorption process and no replacement of initially adsorbed unimers by micelles is evident. However, the adsorbed layer undergoes gradual rearrangement after initial adsorption. This relaxation is believed to result from a combination of further copolymer adsorption and swelling of the adsorbed layer. PMID:16869582

  7. 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

  8. Structural Properties of Water Nano-pockets Encapsulated in Polymerized Reverse Micelles

    NASA Astrophysics Data System (ADS)

    Urquidi, Jacob; Banuelos, Jose L.; Levinger, Nancy

    2009-03-01

    Reverse micelles, that is, small surfactant coated droplets of polar solvent, can form in a range of systems of varying surfactant and polar solvent. SANS has been used to characterize the shape, size and polydispersity of these reverse micelle systems which are macroscopically clear but nanoscopically heterogeneous. Particular sensor applications have been developed using a reverse micellar starting material to create a sample that is macroscopically a robust solid with encapsulated nanoscopic pockets of fluid. This poster will discuss the nanopockets of the fluid phase (water in this case) within the matrix as investigated by small angle X-ray scattering (SAXS) and neutron scattering techniques. The SAXS technique was used to investigate the polydispersity, shape, and distribution of the nanopockets of fluid. Neutron scattering was used to lend insight into the nature of the water encapsulated within these micelles by looking at the position, width, and height of the First Sharp Diffraction Peak (FSDP) to probe the physical perturbations that the water is subject to.

  9. Spectroscopic Analysis of 10MAG/LDAO Reverse Micelles to Determine Characteristic Properties and Behavioral Extrema

    NASA Astrophysics Data System (ADS)

    Berg, Joshua; Mawson, Cara; Norris, Zach; Nucci, Nathaniel

    Reverse micelles are spontaneously organizing complexes of surfactant that encapsulate a nanoscale pool of water in a bulk non-polar solvent. Reverse micelle (RM) mixtures have a wide range of applications, including biophysical investigation of protein systems. A new RM mixture composed of decyl-1-monoglycerol (10MAG) and lauryldimethylammonium-N-oxide (LDAO) was recently described. This mixture has the potential to prove more widely applicable for use of RMs in applications that involve encapsulation of macromolecules, yet little is known about the phase behavior or size of reverse micelles created by this mixture. Data describing such behaviors for this mixture are presented here. We have used dynamic light scattering (DLS) and fluorescence spectroscopy to investigate the size and partitioning behavior of RMs in varying mixtures of 10MAG, LDAO, water, pentane, and hexanol. These data demonstrate that the 10MAG/LDAO RM mixture exhibits markedly different phase and RM size behavior than that of commonly used RM surfactant mixtures. The implications of these findings for use of the 10MAG/LDAO mix for RM applications will also be addressed. Funding provided by Rowan University.

  10. An investigation of nucleation events in a coastal urban environment in the Southern Hemisphere

    NASA Astrophysics Data System (ADS)

    Mejía, J. F.; Morawska, L.

    2009-10-01

    Ambient aerosols play an important role in atmospheric processes affecting the human and natural environments. They affect air quality, reduce visibility, and induce climate change by directly scattering and/or absorbing the incoming solar radiation (Charlson et al., 1992; Kim et al., 2006), or indirectly by acting as cloud condensation nuclei (Hobbs, 1993). Aerosol particles are emitted from a variety of anthropogenic and natural sources either directly into the atmosphere or as secondary particles by gas-to-particle formation process. There is growing interest in studying and analysing the mechanisms of formation of secondary particles. The development of new instruments during the 1990s to measure the particle size distribution of nanoparticles (<50 nm) has enabled scientists to observe the formation and growth of new particles (see Kulmala et al. (2004) for review). Nucleation events, that is, the appearance of a mode below 25-30 nm in the particle number size distribution, known as "nucleation mode" (e.g. Dal Maso et al., 2007; Tunved et al., 2003), usually in very large numbers, have been observed around the world. For example, they have been reported in remote (e.g. Tunved et al., 2003), urban (e.g. Jeong et al., 2004; Zhang et al., 2004) and coastal areas (e.g. Vaattovaara et al., 2006) and at various latitudes in the upper troposphere and the lower stratosphere (Lee et al., 2003). It has been shown that the probability of nucleation was increased by elevated sulphur dioxide (SO2) concentrations (Stanier et al., 2004). This gas is mainly emitted from anthropogenic sources such as the combustion of sulphur-containing fossil fuel (Stern, 2005). Therefore, aerosol nucleation in the atmosphere would be expected to be enhanced by human activities (see also Curtius (2006) for discussion). In urban air, morning nucleation events have been found to be consistent with peaks in traffic (Jeong et al., 2004). In contrast, in coastal environments, higher concentrations

  11. Investigations in Ecology: Looking Into Earth's Life Systems and Man's Impact on Environment.

    ERIC Educational Resources Information Center

    Schultz, Beth; Marcuccio, Phyllis

    An exploration of earth's life systems and man's impact on his environment are provided in this boxed set of 70 skill cards for upper elementary and high school students. The core idea of the subject matter is that nothing exists in isolation, with both the man-dominated environment and natural habitats used to illustrate the importance of…

  12. 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…

  13. 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…

  14. 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…

  15. 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…

  16. 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…

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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

  2. Solar energy storage using surfactant micelles

    NASA Astrophysics Data System (ADS)

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

    1982-09-01

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

  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. PMID:27319219

  4. Facile construction of dual-bioresponsive biodegradable micelles with superior extracellular stability and activated intracellular drug release.

    PubMed

    Chen, Wei; Meng, Fenghua; Cheng, Ru; Deng, Chao; Feijen, Jan; Zhong, Zhiyuan

    2015-07-28

    It is still a major challenge for targeted cancer chemotherapy to design stable biodegradable micellar drug delivery systems which show a rapid and complete intracellular drug release. Here, reversibly core-crosslinked pH-responsive biodegradable micelles were developed based on poly(ethylene glycol)-poly(2,4,6-trimethoxybenzylidene-pentaerythritol carbonate-co-pyridyl disulfide carbonate) [PEG-P(TMBPEC-co-PDSC)] copolymers and investigated for intracellular doxorubicin (DOX) release. PEG-P(TMBPEC-co-PDSC) copolymers formed micelles with a small size of 58.6nm were readily crosslinked by the addition of dithiothreitol (DTT). Notably, in vitro release studies showed that under physiological conditions only ca. 19.9% of DOX was released from the reversibly crosslinked micelles in 24h at a low micelle concentration of 40μg/mL. The release of DOX was accelerated at pH5.0 or in the presence of 10mM glutathione (GSH) at pH7.4, in which 64.2% and 44.1% of DOX was released, respectively, in 24h. The drug release was further boosted at pH5.0 and 10mM GSH, with 98.8% of DOX released in 12h. Moreover, DOX release was also facilitated by a 4h incubation at pH5.0 followed by incubation at pH7.4 with 10mM GSH. Confocal microscopy indicated that DOX was delivered and released into the nuclei of RAW 264.7 cells following a 12h incubation with DOX-loaded reversibly crosslinked micelles. MTT assays revealed that DOX-loaded reversibly crosslinked micelles had much higher antitumor activity than irreversibly crosslinked controls, with low IC50 values of 1.65 and 1.14μg/mL for HeLa and RAW 264.7 cells, respectively, following a 48h incubation. The blank crosslinked micelles had a low cytotoxicity of up to a concentration of 0.8mg/mL. These reversibly crosslinked pH-sensitive biodegradable micelles with superior extracellular stability but activated intracellular drug release provide a novel platform for tumor-targeting drug delivery. PMID:25987525

  5. 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

  6. 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

  7. Furoxan-Bearing Micelles for Nitric Oxide Delivery.

    PubMed

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

    2016-07-01

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

  8. 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

  9. 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

  10. 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

  11. Spectroscopic Investigation of the Effects of Environment on Newly-Developed Near Infrared Emitting Dyes

    NASA Astrophysics Data System (ADS)

    McNamara, Louis E.; Liyanage, Nalaka; Delcamp, Jared; Hammer, Nathan I.

    2015-06-01

    The effects of environment on the photophysical properties of a series of newly-developed near infrared emitting dyes was studied spectroscopically. Properties of interest include fluorescence emission, fluorescence lifetime, and quantum yield. Tracking how the photophysics of these compounds are affected in the solid phase, in thin films, in solution, and at the single molecule level with changing environment will provide a deeper insight into how dye structure affects their function.

  12. 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

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

    PubMed

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

    2014-03-01

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

  14. 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

  15. Microviscosity in Pluronic and Tetronic poly(ethylene oxide)-poly(propylene oxide) block copolymer micelles

    SciTech Connect

    Nivaggioli, T.; Tsao, B.; Alexandridis, P.; Hatton, T.A. )

    1995-01-01

    The micellar microviscosity afforded by Pluronic and Tetronic poly(ethylene oxide)-poly(propylene oxide) block copolymer aqueous solutions has been investigated by fluorescence and NMR spectroscopy. Comparison is made with bulk poly(propylene oxide) (PPO) samples of different molecular weights. The microviscosity in Pluronic PEO-PPO-PEO copolymer micelles is much larger than that observed in conventional surfactant micelles and depends strongly on the size of the hydrophobic PPO block: the larger this block, the higher the viscosity. Above the critical micellar temperature (CMT), as temperature increases, the microviscosity decreases. However, this decrease is not as important as that observed in bulk PPO. Hence, the relative microviscosity, defined as the ratio of the two observed phenomena, increases. This suggests structural transformation of the micelles resulting in a core becoming more and more compact as temperature increases. Such results have been confirmed by NMR studies that showed broadening of the PPO peak and relatively constant spin-lattice relaxation time, T[sub i], with increasing temperature while the PEO signal remained relatively sharp with an exponential increase in T[sub 1]. 30 refs., 9 figs., 1 tab.

  16. 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. PMID:26437259

  17. Synergetic binding and lateral segregation in polymer decorated micelles and nanoparticles

    NASA Astrophysics Data System (ADS)

    Szleifer, Igal; Nap, Rikkert

    2009-03-01

    Nanocarriers show great potential as drug delivery devices or as imaging agents. Experimental relevant examples of nanocarriers involve micelles made of low molecular weight polyethylene glycol and phospholipids. An important feature of these 'nano' micelles is that the polymers are mobile. A fundamental question is how different polymeric coatings result in optimal nanoparticle-surface interactions. We used a molecular theory to investigate the effect of the conformational entropy, specific interactions and lateral mobility on the structure of the polymer coatings and the binding of the nanocarrier to a cell surface. In micelles that contain chains of different molecular weights, the long and short polymer chains segregate upon approaching the surface, as a result of competing entropic forces. Nanocarriers made of mixtures of weak polyelectrolytes with ligands at their free ends and neutral polymers can bind to charged surfaces or through specific ligand-receptor interactions. We show that under appropriate conditions there is a dramatic synergetic effect between electrostatic and ligand-receptor binding. The synergetic effect is due to the optimal compensation between charge regulation, specific binding and counterion release. The potential use of these carriers for cancer drug delivery will be discussed.

  18. Lack of a unique kinetic pathway in the growth and decay of Pluronic micelles.

    PubMed

    Arranja, Alexandra; Waton, Gilles; Schosseler, François; Mendes, Eduardo

    2016-01-21

    We report kinetic experiments on dilute brine solutions of P84, P94 and P104 Pluronic copolymer micelles. The growth and the decay of micelles after temperature steps are measured by non-standard time resolved multi-angle photon correlation spectroscopy. Several concurrent mechanisms are at work during the very slow equilibration of solutions, namely insertion/expulsion of unimers, aggregation/dissociation of micellar aggregates, and fusion/budding of micellar aggregates. Their relative rates determine both the kinetic pathways and the morphologies of the micellar assemblies, which depend markedly on modest changes in the copolymer molecular weight. For the typical Pluronic copolymers investigated here, none of these elementary processes can be neglected if the resulting morphology is to be explained. This feature imposes multiple kinetic behaviours where growth and decay of Pluronic micelles become strongly dependent on the thermal history. We point out to some possible shortcomings in the studies of micellar growth kinetics by light scattering techniques. Extensive time-resolved multiangle measurements are a prerequisite for avoiding these pitfalls. PMID:26523415

  19. 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

  20. 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

  1. 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. PMID:26214201

  2. Mechanism of formation of composite CdS-ZnS ultrafine particles in reverse micelles

    SciTech Connect

    Sato, Hiroshi; Hirai, Takayuki; Komasawa, Isao

    1995-07-01

    The mechanism of formation of composite cadmium sulfide and zinc sulfide ultrafine particles (Cd{sub 1{minus}x}Zn{sub x}S) by simultaneous precipitation of cadmium sulfide and zinc sulfide in sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane reverse micelles has been studied. The particle formation process was followed by the change in UV-visible absorption spectra. The effects of the reactant concentration, the molar ratio of cadmium to zinc ions, and the water content on the particle formation process were investigated. The resultant particles were richer in CdS than the feed composition of the cadmium to zinc ions in the reaction solution. The particle composition was found to be controlled by the solubility of the CdS and ZnS ultrafine particles. The particle coagulation process was analyzed on the basis of a statistical distribution of particles among the reverse micelles. The coagulation rate constant was controlled by the composition and the size of the particles and by the size of the reverse micelles.

  3. 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

  4. Toughening of epoxies based on self-assembly of nano-sized amphiphilic block copolymer micelles

    NASA Astrophysics Data System (ADS)

    Liu, Jia

    As a part of a larger effort towards the fundamental understanding of mechanical behaviors of polymers toughened by nanoparticles, this dissertation focuses on the structure-property relationship of epoxies modified with nano-sized poly(ethylene-alt-propylene)-b-poly(ethylene oxide) (PEP-PEO) block copolymer (BCP) micelle particles. The amphiphilic BCP toughener was incorporated into a liquid epoxy resin and self-assembled into well-dispersed 15 nm spherical micelle particles. The nano-sized BCP, at 5 wt% loading, can significantly improve the fracture toughness of epoxy (ca. 180% improvement) without reducing modulus at room temperature and exhibits only a slight drop (ca. 5°C) in glass transition temperature (Tg). The toughening mechanisms were found to be BCP micelle nanoparticle cavitation, followed by matrix shear banding, which mainly accounted for the observed remarkable toughening effect. The unexpected "nano-cavitation" phenomenon cannot be predicted by existing physical models. The plausible causes for the observed nano-scale cavitation and other mechanical behaviors may include the unique structural characteristics of BCP micelles and the influence from the surrounding epoxy network, which is significantly modified by the epoxy-miscible PEO block. Other mechanisms, such as crack tip blunting, may also play a role in the toughening. Structure-property relationships of this nano-domain modified polymer are discussed. In addition, other important factors, such as strain rate dependence and matrix crosslink density effect on toughening, have been investigated. This BCP toughening approach and conventional rubber toughening techniques are compared. Insights on the decoupling of modulus, toughness, and Tg for designing high performance thermosetting materials with desirable physical and mechanical properties are discussed.

  5. 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

  6. 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. PMID:22856300

  7. Crystallization of confined water pools with radii greater than 1 nm in AOT reverse micelles.

    PubMed

    Suzuki, Akira; Yui, Hiroharu

    2014-07-01

    Freezing of water pools inside aerosol sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles has been investigated. Previous freezing experiments suffer from collision and fusion of AOT micelles and resultant loss of water from the water pool by shedding out during the cooling process. These phenomena have restricted the formation of ice to only when the radius of the water pool (Rw) is below 1 nm, and only amorphous ice has been observed. To overcome the size limitation, a combination of rapid cooling and a custom-made cell allowing thin sample loading is applied for instantaneous and homogeneous freezing. The freezing process is monitored with attenuated total reflection infrared spectroscopy (ATR-IR) measurements. A cooling rate of ca. -100 K/min and a sample thickness of ca. 50 μm overcomes the limitations mentioned above and allows the crystallization of water pools with larger radii (Rw > 1 nm). The corresponding ATR-IR spectra of the frozen water pools with Rw < 2.0 nm show similar features to the spectrum of metastable cubic ice (Ic). Further increase of the radius of the water pool (Rw > 2.0 nm), unfortunately, drastically decreased the integrated area of the ν(OH) band observed just after freezing, indicating the breakup of the micellar structure and shedding out of the water pool. In addition, it was revealed that Ic ice can also be formed in flexible organic self-assembled AOT reverse micelles for at least Rw ≤ ca. 2 nm, as well as in inorganic and solid materials with a pore radius of ca. 2 nm. The dependence of the phase transition temperature on the curvature of the reverse micelles is discussed from the viewpoint of the Gibbs-Thomson effect. PMID:24885023

  8. New amphiphilic diblock copolymers: surfactant properties and solubilization in their micelles.

    PubMed

    Garnier, Sébastien; Laschewsky, André

    2006-04-25

    Several series of amphiphilic diblock copolymers are investigated as macrosurfactants in comparison to reference low-molar-mass and polymeric surfactants. The various copolymers share poly(butyl acrylate) as a common hydrophobic block but are distinguished by six different hydrophilic blocks (one anionic, one cationic, and four nonionic hydrophilic blocks) with various compositions. Dynamic light scattering experiments indicate the presence of micelles over the whole concentration range from 10(-4) to 10 g x L(-1). Accordingly, the critical micellization concentrations are very low. Still, the surface tension of aqueous solutions of block copolymers decreases slowly but continuously with increasing concentration, without exhibiting a plateau. The longer the hydrophobic block, the shorter the hydrophilic block, and the less hydrophilic the monomer of the hydrophilic block is, the lower the surface tension is. However, the effects are small, and the copolymers reduce the surface tension much less than standard low-molar-mass surfactants. Also, the copolymers foam much less and even act as anti-foaming agents in classical foaming systems composed of standard surfactants. The copolymers stabilize O/W emulsions made of methyl palmitate as equally well as standard surfactants but are less efficient for O/W emulsions made of tributyrine. However, the copolymer micelles exhibit a high solubilization power for hydrophobic dyes, probably at their core-corona interface, in dependence on the initial geometry of the micelles and the composition of the block copolymers. Whereas micelles of copolymers with strongly hydrophilic blocks are stable upon solubilization, solubilization-induced micellar growth is observed for copolymers with moderately hydrophilic blocks. PMID:16618143

  9. Simvastatin Prodrug Micelles Target Fracture and Improve Healing

    PubMed Central

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

    2014-01-01

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

  10. Superlattice Formation in Binary Mixtures of Block Copolymer Micelles

    SciTech Connect

    Abbas, Sayeed; Lodge, Timothy P.

    2008-08-26

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

  11. Polymer Micelles with Crystalline Cores for Thermally Triggered Release

    PubMed Central

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

    2012-01-01

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

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

    PubMed

    Mittal, Anupama; Chitkara, Deepak

    2016-01-01

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

  13. Structure and dynamics of melittin in lysomyristoyl phosphatidylcholine micelles determined by nuclear magnetic resonance.

    PubMed Central

    Yuan, P; Fisher, P J; Prendergast, F G; Kemple, M D

    1996-01-01

    Mixed micelles of the 26-residue, lytic peptide melittin (MLT) and 1-myristoyl-2-hydroxyl-sn-glycero-3-phosphocholine (MMPC) in aqueous solution at 25 degrees C were investigated by (13)C- and (31)P-NMR spectroscopy. (13)C alpha chemical shifts of isotopically labeled synthetic MLT revealed that MLT in the micelle is predominantly alpha-helical and that the peptide secondary structure is stable from pH 4 to pH 11. Although the helical transformation of MLT as determined from NMR is evident at lipid:peptide molar ratios as low as 1:2, tryptophan fluorescence measurements demonstrate that well-defined micellar complexes do not predominate until lipid:peptide ratios exceed 30:1. (31)P linewidth measurements indicate that the interaction between phosphate ions in solution and cationic groups on MLT is pH dependent, and that the phosphoryl group of MMPC senses a constant charge, most likely +2, on MLT from pH 4 to pH 10. (13)C-NMR relaxation data, analyzed using the model-free formalism, show that the peptide backbone of MLT is partially, but not completely, immobilized in the mixed micelles. Specifically, order parameters (S(2)) of C alpha-H vectors averaged 0.7 and were somewhat larger for residues in the N-terminal half of the molecule. The amino terminal glycine had essentially the same range of motion as the backbone carbons. Likewise, order parameters for the trp side chain were similar to those found for the peptide C alpha moieties, as was verified by trp fluorescence anisotropy decay data. In contrast, the motion of the lysine side chains was less restricted, the average S(2) values for the C epsilon-H vectors being 0.19, 0.30, and 0.44 for lys-7, 21, and 23, respectively, for MLT in the mixed micelles. Values of the effective correlation time of the local motion tau e were in the motional narrowing limit and usually longer for side-chain atoms than for those in the backbone. The dynamics were independent of pH from pH 4 to pH 9, but at pH 11 the correlation

  14. Investigating Information Technologies in Disasters: Three Essays on Micro-Blogging and Free and Open Source Software (FOSS) Environment

    ERIC Educational Resources Information Center

    Li, Pu

    2012-01-01

    This dissertation aims to investigate how advanced information technologies cope with the various demands of disaster response. It consists of three essays on the exploration of micro-blogging and FOSS environments. The first essay looks at the usage of micro-blogging in the aftermath of the massive 2008 China earthquake and explores the…

  15. The Development of Route Learning in Down Syndrome, Williams Syndrome and Typical Development: Investigations with Virtual Environments

    ERIC Educational Resources Information Center

    Purser, Harry R. M.; Farran, Emily K.; Courbois, Yannick; Lemahieu, Axelle; Sockeel, Pascal; Mellier, Daniel; Blades, Mark

    2015-01-01

    The ability to navigate new environments has a significant impact on the daily life and independence of people with learning difficulties. The aims of this study were to investigate the development of route learning in Down syndrome (N = 50), Williams syndrome (N = 19), and typically developing children between 5 and 11 years old (N = 108); to…

  16. Investigation of the "Convince Me" Computer Environment as a Tool for Critical Argumentation about Public Policy Issues

    ERIC Educational Resources Information Center

    Adams, Stephen T.

    2003-01-01

    The "Convince Me" computer environment supports critical thinking by allowing users to create and evaluate computer-based representations of arguments. This study investigates theoretical and design considerations pertinent to using "Convince Me" as an educational tool to support reasoning about public policy issues. Among computer environments…

  17. Investigating Plane Geometry Problem-Solving Strategies of Prospective Mathematics Teachers in Technology and Paper-and-Pencil Environments

    ERIC Educational Resources Information Center

    Koyuncu, Ilhan; Akyuz, Didem; Cakiroglu, Erdinc

    2015-01-01

    This study aims to investigate plane geometry problem-solving strategies of prospective mathematics teachers using dynamic geometry software (DGS) and paper-and-pencil (PPB) environments after receiving an instruction with GeoGebra (GGB). Four plane geometry problems were used in a multiple case study design to understand the solution strategies…

  18. Investigating Design and Technology Students' Peer Interactions in a Technology-Mediated Learning Environment: A Case study

    ERIC Educational Resources Information Center

    Yeo, Tiong Meng; Quek, Choon Lang

    2011-01-01

    This research investigates students' peer interactions in the Design and Technology (D&T) environment supported by "Knowledge Forum". The sample comprised of 15 students who had no prior experience in using "Knowledge Forum" to mediate their D&T learning. Their interaction with peers occurred in three stages: design situation, ideation and…

  19. Socio-Technical Dimensions of an Outdoor Mobile Learning Environment: A Three-Phase Design-Based Research Investigation

    ERIC Educational Resources Information Center

    Land, Susan M.; Zimmerman, Heather Toomey

    2015-01-01

    This design-based research project examines three iterations of Tree Investigators, a learning environment designed to support science learning outdoors at an arboretum and nature center using mobile devices (iPads). Researchers coded videorecords and artifacts created by children and parents (n = 53) to understand how both social and…

  20. Transformational and Passive Leadership: An Initial Investigation of University Instructors as Leaders in a Virtual Learning Environment

    ERIC Educational Resources Information Center

    Bogler, Ronit; Caspi, Avner; Roccas, Sonia

    2013-01-01

    The study investigated whether students perceive their university instructors in a virtual learning environment as leaders. Referring to the full range leadership theory (FRLT), we examined the effects of transformational and passive leadership styles of university instructors on students' satisfaction and learning outcomes. Completed web-based…

  1. Tungsten in the environment: A geochemical and mineralogical investigation of an emerging contaminant

    NASA Astrophysics Data System (ADS)

    Datta, S.; Hobson, C.; Mohajerin, T. J.; Johannesson, K. H.; Tappero, R.; Telfeyan, K.; Witten, M. L.; Sheppard, P. R.

    2012-12-01

    Interest in tungsten (W) research has increased in the past several years, as it may have previously unrecognized human toxicological and environmentally degrading effects [1][2]. In 2002, the Center for Disease Control (CDC) investigated several clusters of acute lymphatic leukemia in both Nevada and in Arizona. The study found residents had urinary W levels above the 95th percentile for the US [1][3]. After this, the EPA classified W as an emerging contaminant. Field studies have shown that W is mobile in the environment [1][4], but there is still a paucity of knowledge about the actual behavior of W in groundwater flow systems and the processes that control W concentration and transport. Here the hypothesis being tested is that physical and chemical changes from chemical weathering, mineral dissolution and precipitation, and redox reactions catalyzed by microbial activity control W transport and sequestration. Sediment samples have been collected from three different localities with elevated W. Fallon, NV is the first site being analyzed, along with Sierra Vista, AZ and Cheyenne Bottoms refuge near Hoisington, KS. The first few centimeters of the sediment profile are scraped aside and then sediment core samples are collected at incremental depths of approximately two feet, starting with a near surface sample. The sediment cores are being studied for total extractability of W from the sediments and then the mineral associations within the sediments are studied by petrographic observations and FESEM assisted single grain mapping (also to understand the association of W to Fe, Mn and S in these sediments). Various extraction techniques of the sediment samples including sequential extractions (assisted by microwave digestion) are done along with solid state synchrotron analyses (by acquiring μXRF maps and having specific hotspots analyzed for μXRD and μXANES). This elucidates valuable information about W's oxidation state, concentration, and where it is bound in

  2. Experimental investigation of local environment effects on the quantum teleportation fidelity

    NASA Astrophysics Data System (ADS)

    Knoll, Laura T.; Schmiegelow, Christian T.; Larotonda, Miguel A.

    2015-09-01

    Quantum teleportation relies on entanglement as the quantum resource to be able to communicate with fidelities beyond the classical limit. Nevertheless, the entangled resource may be afflicted by local noise, affecting its ability to serve as the entangled resource for quantum teleportation. We obtain experimental data on the influence of different local environments on the ability of an initially entangled pair of qubits to act as a teleportation resource, after it has been disturbed by noise. We generate selected conditions on the noise parameter space, both theoretically and experimentally, and we find that an already noisy protocol can be made practically insensitive to a further addition of noise. The experimental results are based on a photonic implementation of the quantum teleportation algorithm, with a polarization-entangled pair acting as the quantum resource. The state to be teleported is an additional qubit encoded in the path internal degree of freedom of Alice's photon. Interactions with different local environments on both sides of the system are either implemented with an extra qubit as the environment, or simulated as a weighed average of pure states. We compare our experimental results with the theoretical predictions, and by performing quantum process tomography we can calculate the fidelity of the quantum teleportation scheme and evaluate the effect of local environments.

  3. The Investigation of the Attitudes of Geography Teachers towards Environment in Turkey

    ERIC Educational Resources Information Center

    Karakus, Ufuk

    2013-01-01

    This study was carried out to reveal whether the attitudes of the geography teachers in Turkey towards the environment change according to different variables, using ''Attitude Scale" for 404 geography teachers working in various high schools throughout the country. The data were analysed by SPSS statistical software. The result…

  4. Developing Information Technology Fluency in College Students: An Investigation of Learning Environments and Learner Characteristics

    ERIC Educational Resources Information Center

    Sardone, Nancy B.

    2011-01-01

    The confluence of powerful technologies of computers and network connectivity has brought explosive growth to the field of Information Technology (IT). The problem presented in this study is whether the type of learning environment where IT concepts are taught to undergraduates has a relationship to the development of IT fluency and course…