The Experts below are selected from a list of 6933 Experts worldwide ranked by ideXlab platform

Hideki Sakai - One of the best experts on this subject based on the ideXlab platform.

  • one step preparation of chitosan coated cationic liposomes by an improved supercritical reverse phase evaporation method
    Langmuir, 2006
    Co-Authors: Katsuto Otake, Hideki Sakai, Takeshi Shimomura, Toshihiro Goto, Tomohiro Imura, Takeshi Furuya, Satoshi Yoda, Yoshihiro Takebayashi, Masahiko Abe
    Abstract:

    High-pressure carbon dioxide in contact with water dissolves to form carbonic acid, causing a decrease in pH. By use of these characteristics of a CO2/H2O biphasic system, chitosan-coated cationic liposomes of l-α-Dipalmitoylphosphatidylcholine were successfully prepared by an improved supercritical reverse-phase evaporation (ISCRPE) method. Liposome−chitosan complexes carrying a positive charge were prepared in a single-step procedure without the use of acid or organic solvent, including ethanol. The maximum trapping efficiency of liposomes prepared by the ISCRPE method was 17%, with or without the addition of chitosan, compared to only 2% for liposomes prepared by the Bangham method. Furthermore, the liposomal dispersion was stable at room temperature in a sealed tube for over 30 days.

  • membrane properties of binary and ternary systems of ganglioside gm1 Dipalmitoylphosphatidylcholine dioleoylphosphatidylcholine
    Colloids and Surfaces B: Biointerfaces, 2004
    Co-Authors: Yumiko Ohta, Shoko Yokoyama, Hideki Sakai
    Abstract:

    Abstract The membrane properties of the ganglioside GM1 (GM1)/dioleoylphosphatidylcholine (DOPC) binary system and GM1/Dipalmitoylphosphatidylcholine (DPPC)/DOPC ternary system were investigated using surface pressure measurements and atomic force microscopy (AFM), and the effect of surface pressure on the properties of the membranes was examined. Mixed GM1/DPPC/DOPC monolayers were deposited on mica using the Langmuir–Blodgett technique for AFM. GM1 and DOPC were immiscible and phase-separated. The AFM image of the GM1/DOPC (1:1) monolayer showed island-like GM1 domains embedded in the DOPC matrix. There was no morphological change on varying surface pressure. The surface pressure–area isotherm of the GM1/DPPC/DOPC (2:9:9) monolayer showed a two-step collapse as in the DPPC/DOPC (1:1) monolayer. The AFM image for the GM1/DPPC/DOPC monolayer showed DPPC and GM1 domains in the DOPC matrix, and the DPPC-rich phase containing GM1 showed a percolation pattern the same as the GM1/DPPC (1:9) monolayer. The percolation pattern in the GM1/DPPC/DOPC monolayer changed as the surface pressure was varied. The surface pressure-responsive change in morphology of GM1 was affected by the surrounding environment, suggesting that the GM1 localized in each organ has a specific role.

  • effect of membrane composition on surface states of ganglioside gm1 Dipalmitoylphosphatidylcholine dioleoylphosphatidylcholine monolayers
    Colloids and Surfaces B: Biointerfaces, 2004
    Co-Authors: Shoko Yokoyama, Yumiko Ohta, Hideki Sakai
    Abstract:

    Abstract The surface states of ganglioside GM1 (GM1)/Dipalmitoylphosphatidylcholine (DPPC)/dioleoylphosphatidylcholine (DOPC) monolayers having various compositions were investigated using atomic force microscopy (AFM), and the effect of the composition on the surface states of the membrane was examined. The AFM images for the ternary system showed a DPPC-rich phase containing GM1 in the DOPC matrix, which indicated that the morphology varied as the composition of the monolayers changed. The AFM images for the GM1/DPPC/DOPC monolayers having (2:9:9) and (4:18:9) molar ratios showed a percolation pattern similar to that observed for the GM1/DPPC (1:9) monolayer. The AFM image for the GM1/DPPC/DOPC (2:18:9) monolayer showed a dotted pattern with a high topography. Monolayers having a higher content of DOPC than DPPC and/or having a higher content of GM1 showed dot-like domains in the DPPC-rich phase containing GM1. In conclusion, the surface states of GM1/DPPC/DOPC monolayers changed depending on the composition. These results may be related to a diversity of GM1 in various organs.

Peter J Wilde - One of the best experts on this subject based on the ideXlab platform.

  • adsorption of bile salts and pancreatic colipase and lipase onto digalactosyldiacylglycerol and Dipalmitoylphosphatidylcholine monolayers
    Langmuir, 2010
    Co-Authors: B S Chu, Patrick A Gunning, Gillian T Rich, M J Ridout, Richard M Faulks, Martin S J Wickham, Victor J Morris, Peter J Wilde
    Abstract:

    It is increasingly recognized that changes in the composition of the oil-water interface can markedly affect pancreatic lipase adsorption and function. To understand interfacial mechanisms determining lipase activity, we investigated the adsorption behavior of bile salts and pancreatic colipase and lipase onto digalactosyldiacylglycerol (DGDG) and Dipalmitoylphosphatidylcholine (DPPC) monolayers at the air-water interface. The results from Langmuir trough and pendant drop experiments showed that a DGDG interface was more resistant to the adsorption of bile salts, colipase, and lipase compared to that of DPPC. Atomic force microscopy (AFM) images showed that the adsorption of bile salts into a DPPC monolayer decreased the size of the liquid condensed (LC) domains while there was no visible topographical change for DGDG systems. The results also showed that colipase and lipase adsorbed exclusively onto the mixed DPPC-bile salt regions and not the DPPC condensed phase. When the colipase and lipase were in excess, they fully covered the mixed DPPC-bile salt regions. However, the colipase and lipase coverage on the mixed DGDG-bile salt monolayer was incomplete and discontinuous. It was postulated that bile salts adsorbed into the DPPC monolayers filling the gaps between the lipid headgroups and spacing out the lipid molecules, making the lipid hydrocarbon tails more exposed to the surface. This created hydrophobic patches suitable for the binding of colipase and lipase. In contrast, bile salts adsorbed less easily into the DGDG monolayer because DGDG has a larger headgroup, which has strong intermolecular interactions and the ability to adopt different orientations at the interface. Thus, there are fewer hydrophobic patches that are of sufficient size to accommodate the colipase on the mixed DGDG-bile salt monolayer compared to the mixed DPPC-bile salt regions. The results from this work have reinforced the hypothesis that the interfacial molecular packing of lipids at the oil-water interface influences the adsorption of bile salts, colipase, and lipase, which in turn impacts the rate of lipolysis.

  • adsorption of bile salts and pancreatic colipase and lipase onto digalactosyldiacylglycerol and Dipalmitoylphosphatidylcholine monolayers
    Langmuir, 2010
    Co-Authors: B S Chu, Patrick A Gunning, Gillian T Rich, M J Ridout, Richard M Faulks, Martin S J Wickham, Victor J Morris, Peter J Wilde
    Abstract:

    It is increasingly recognized that changes in the composition of the oil−water interface can markedly affect pancreatic lipase adsorption and function. To understand interfacial mechanisms determining lipase activity, we investigated the adsorption behavior of bile salts and pancreatic colipase and lipase onto digalactosyldiacylglycerol (DGDG) and Dipalmitoylphosphatidylcholine (DPPC) monolayers at the air−water interface. The results from Langmuir trough and pendant drop experiments showed that a DGDG interface was more resistant to the adsorption of bile salts, colipase, and lipase compared to that of DPPC. Atomic force microscopy (AFM) images showed that the adsorption of bile salts into a DPPC monolayer decreased the size of the liquid condensed (LC) domains while there was no visible topographical change for DGDG systems. The results also showed that colipase and lipase adsorbed exclusively onto the mixed DPPC−bile salt regions and not the DPPC condensed phase. When the colipase and lipase were in ex...

Giovanni Puglisi - One of the best experts on this subject based on the ideXlab platform.

  • new amphiphilic conjugates of amino poly ethylene glycols with lipoamino acids as surface modifiers of colloidal drug carriers
    Macromolecular Chemistry and Physics, 2013
    Co-Authors: Rosario Pignatello, Valentina Panto, Giuseppe Impallomeni, Giovanni Marco Carnemolla, Claudia Carbone, Giovanni Puglisi
    Abstract:

    Poly(ethylene glycol) (PEG2000) polymers containing one or two amine residues are linked to α-lipoamino acids (LAA) to produce mono- and homo-disubstituted PEG–LAA conjugates as new materials for the surface coating of colloidal drug carriers. Conjugates are characterized by FT-IR, 1H-NMR, and MALDI–TOF mass spectrometry. Differential scanning calorimetry studies are performed to assess the interaction of PEG2000–LAAs with a biomembrane model (Dipalmitoylphosphatidylcholine multilamellar liposomes). Whereas the parent PEGs affect only the superficial structure of the bilayers, the amphiphilic PEG–LAA conjugates exert a modulated perturbing effect on the thermotropic profile of liposomes. A molar concentration between 5% and 10% is individuated as the more suitable to produce stable vesicles.

  • Phospholipid vesicles as a drug delivery system: Part I. Interaction of cytidine-5'-diphosphate choline with charged and zwitterionic phospholipids
    Thermochimica Acta, 1992
    Co-Authors: C Rosa, D Grasso, C. A. Ventura, Massimo Fresta, Giovanni Puglisi
    Abstract:

    Abstract Charged (dipalmitoylphosphatidylserine (DPPS) and dipalmitoylphosphatidic acid (DPPA) and zwitterionic (dipalmitoylphosphatidylethanolamine (DPPE) and Dipalmitoylphosphatidylcholine (DPPC) phospholipid vesicles were used as a drug delivery device containing cytidine-5'-diphosphate choline (CDP-choline). To evaluate the interaction between the membrane surface and CDP-choline, the thermodynamic behaviour, linked with gel-liquid crystal phase transition was analyzed by differential scanning calorimetry (DSC) and scanning dilatometry (SD). Analysis of thermodynamic parameters shows that the interaction between CDP-choline and phospholipid heads is very weak for DPPC, but is strong for DPPE and DPPA systems; DPPS interacts very strongly with CDP-choline so is not able to form liposomes.

B S Chu - One of the best experts on this subject based on the ideXlab platform.

  • adsorption of bile salts and pancreatic colipase and lipase onto digalactosyldiacylglycerol and Dipalmitoylphosphatidylcholine monolayers
    Langmuir, 2010
    Co-Authors: B S Chu, Patrick A Gunning, Gillian T Rich, M J Ridout, Richard M Faulks, Martin S J Wickham, Victor J Morris, Peter J Wilde
    Abstract:

    It is increasingly recognized that changes in the composition of the oil-water interface can markedly affect pancreatic lipase adsorption and function. To understand interfacial mechanisms determining lipase activity, we investigated the adsorption behavior of bile salts and pancreatic colipase and lipase onto digalactosyldiacylglycerol (DGDG) and Dipalmitoylphosphatidylcholine (DPPC) monolayers at the air-water interface. The results from Langmuir trough and pendant drop experiments showed that a DGDG interface was more resistant to the adsorption of bile salts, colipase, and lipase compared to that of DPPC. Atomic force microscopy (AFM) images showed that the adsorption of bile salts into a DPPC monolayer decreased the size of the liquid condensed (LC) domains while there was no visible topographical change for DGDG systems. The results also showed that colipase and lipase adsorbed exclusively onto the mixed DPPC-bile salt regions and not the DPPC condensed phase. When the colipase and lipase were in excess, they fully covered the mixed DPPC-bile salt regions. However, the colipase and lipase coverage on the mixed DGDG-bile salt monolayer was incomplete and discontinuous. It was postulated that bile salts adsorbed into the DPPC monolayers filling the gaps between the lipid headgroups and spacing out the lipid molecules, making the lipid hydrocarbon tails more exposed to the surface. This created hydrophobic patches suitable for the binding of colipase and lipase. In contrast, bile salts adsorbed less easily into the DGDG monolayer because DGDG has a larger headgroup, which has strong intermolecular interactions and the ability to adopt different orientations at the interface. Thus, there are fewer hydrophobic patches that are of sufficient size to accommodate the colipase on the mixed DGDG-bile salt monolayer compared to the mixed DPPC-bile salt regions. The results from this work have reinforced the hypothesis that the interfacial molecular packing of lipids at the oil-water interface influences the adsorption of bile salts, colipase, and lipase, which in turn impacts the rate of lipolysis.

  • adsorption of bile salts and pancreatic colipase and lipase onto digalactosyldiacylglycerol and Dipalmitoylphosphatidylcholine monolayers
    Langmuir, 2010
    Co-Authors: B S Chu, Patrick A Gunning, Gillian T Rich, M J Ridout, Richard M Faulks, Martin S J Wickham, Victor J Morris, Peter J Wilde
    Abstract:

    It is increasingly recognized that changes in the composition of the oil−water interface can markedly affect pancreatic lipase adsorption and function. To understand interfacial mechanisms determining lipase activity, we investigated the adsorption behavior of bile salts and pancreatic colipase and lipase onto digalactosyldiacylglycerol (DGDG) and Dipalmitoylphosphatidylcholine (DPPC) monolayers at the air−water interface. The results from Langmuir trough and pendant drop experiments showed that a DGDG interface was more resistant to the adsorption of bile salts, colipase, and lipase compared to that of DPPC. Atomic force microscopy (AFM) images showed that the adsorption of bile salts into a DPPC monolayer decreased the size of the liquid condensed (LC) domains while there was no visible topographical change for DGDG systems. The results also showed that colipase and lipase adsorbed exclusively onto the mixed DPPC−bile salt regions and not the DPPC condensed phase. When the colipase and lipase were in ex...

Shoko Yokoyama - One of the best experts on this subject based on the ideXlab platform.

  • membrane properties of binary and ternary systems of ganglioside gm1 Dipalmitoylphosphatidylcholine dioleoylphosphatidylcholine
    Colloids and Surfaces B: Biointerfaces, 2004
    Co-Authors: Yumiko Ohta, Shoko Yokoyama, Hideki Sakai
    Abstract:

    Abstract The membrane properties of the ganglioside GM1 (GM1)/dioleoylphosphatidylcholine (DOPC) binary system and GM1/Dipalmitoylphosphatidylcholine (DPPC)/DOPC ternary system were investigated using surface pressure measurements and atomic force microscopy (AFM), and the effect of surface pressure on the properties of the membranes was examined. Mixed GM1/DPPC/DOPC monolayers were deposited on mica using the Langmuir–Blodgett technique for AFM. GM1 and DOPC were immiscible and phase-separated. The AFM image of the GM1/DOPC (1:1) monolayer showed island-like GM1 domains embedded in the DOPC matrix. There was no morphological change on varying surface pressure. The surface pressure–area isotherm of the GM1/DPPC/DOPC (2:9:9) monolayer showed a two-step collapse as in the DPPC/DOPC (1:1) monolayer. The AFM image for the GM1/DPPC/DOPC monolayer showed DPPC and GM1 domains in the DOPC matrix, and the DPPC-rich phase containing GM1 showed a percolation pattern the same as the GM1/DPPC (1:9) monolayer. The percolation pattern in the GM1/DPPC/DOPC monolayer changed as the surface pressure was varied. The surface pressure-responsive change in morphology of GM1 was affected by the surrounding environment, suggesting that the GM1 localized in each organ has a specific role.

  • effect of membrane composition on surface states of ganglioside gm1 Dipalmitoylphosphatidylcholine dioleoylphosphatidylcholine monolayers
    Colloids and Surfaces B: Biointerfaces, 2004
    Co-Authors: Shoko Yokoyama, Yumiko Ohta, Hideki Sakai
    Abstract:

    Abstract The surface states of ganglioside GM1 (GM1)/Dipalmitoylphosphatidylcholine (DPPC)/dioleoylphosphatidylcholine (DOPC) monolayers having various compositions were investigated using atomic force microscopy (AFM), and the effect of the composition on the surface states of the membrane was examined. The AFM images for the ternary system showed a DPPC-rich phase containing GM1 in the DOPC matrix, which indicated that the morphology varied as the composition of the monolayers changed. The AFM images for the GM1/DPPC/DOPC monolayers having (2:9:9) and (4:18:9) molar ratios showed a percolation pattern similar to that observed for the GM1/DPPC (1:9) monolayer. The AFM image for the GM1/DPPC/DOPC (2:18:9) monolayer showed a dotted pattern with a high topography. Monolayers having a higher content of DOPC than DPPC and/or having a higher content of GM1 showed dot-like domains in the DPPC-rich phase containing GM1. In conclusion, the surface states of GM1/DPPC/DOPC monolayers changed depending on the composition. These results may be related to a diversity of GM1 in various organs.