The Experts below are selected from a list of 260013 Experts worldwide ranked by ideXlab platform
Andreas Seidelmorgenstern - One of the best experts on this subject based on the ideXlab platform.
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transport of butane in a porous vycor glass membrane in the region of condensation pressure
Journal of Membrane Science, 2007Co-Authors: Petr Uchytil, R Petrickovic, Andreas SeidelmorgensternAbstract:Abstract The transport and the separation efficiency in porous membranes can be strongly influenced by the condensation of Permeating gases. An accurate experimental monitoring of Permeating vapors and condensates in small pores of membranes is very desirable. The dynamic permeation method is one of the methods which can be used to perform a corresponding study. The following experimental arrangement was applied: a constant higher pressure P 1 was set on an open side of the membrane; on the opposite closed side the change of a lower pressure P 2 was measured. The dynamic permeation set-up was used at first in transport measurements of a noncondensable gas through a Vycor glass membrane (mean pore radius around 2 nm). The obtained data were compared with the results of alternatively performed steady state permeation measurements. Subsequently, the permeability was studied for the condensable gas butane through the Vycor glass membrane, particularly for elevator pressure conditions near the saturated vapor pressure. Also for this purpose the dynamic permeation experiment was found to be very convenient. It enables to measure the mass transport for very small pressure gradients across the membrane. The permeation results obtained correspond well with the liquid butane permeability of Vycor membrane quantified previously in independent pervaporation experiments. This agreement confirms the presence of liquid butane in small pores of Vycor glass during the transient gas transport at relatively high pressures.
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Transport of butane in a porous Vycor glass membrane in the region of condensation pressure
Journal of Membrane Science, 2007Co-Authors: Petr Uchytil, R Petrickovic, Andreas SeidelmorgensternAbstract:The transport and the separation efficiency in porous membranes can be strongly influenced by the condensation of Permeating gases. An accurate experimental monitoring of Permeating vapors and condensates in small pores of membranes is very desirable. The dynamic permeation method is one of the methods which can be used to perform a corresponding study. The following experimental arrangement was applied: a constant higher pressure P1 was set on an open side of the membrane; on the opposite closed side the change of a lower pressure P2 was measured. The dynamic permeation set-up was used at first in transport measurements of a noncondensable gas through a Vycor glass membrane (mean pore radius around 2 nm). The obtained data were compared with the results of alternatively performed steady state permeation measurements. Subsequently, the permeability was studied for the condensable gas butane through the Vycor glass membrane, particularly for elevator pressure conditions near the saturated vapor pressure. Also for this purpose the dynamic permeation experiment was found to be very convenient. It enables to measure the mass transport for very small pressure gradients across the membrane. The permeation results obtained correspond well with the liquid butane permeability of Vycor membrane quantified previously in independent pervaporation experiments. This agreement confirms the presence of liquid butane in small pores of Vycor glass during the transient gas transport at relatively high pressures. Copyright © 2007 Elsevier B.V. All rights reserved. [accessed 2013 November 26th
Petr Uchytil - One of the best experts on this subject based on the ideXlab platform.
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transport of butane in a porous vycor glass membrane in the region of condensation pressure
Journal of Membrane Science, 2007Co-Authors: Petr Uchytil, R Petrickovic, Andreas SeidelmorgensternAbstract:Abstract The transport and the separation efficiency in porous membranes can be strongly influenced by the condensation of Permeating gases. An accurate experimental monitoring of Permeating vapors and condensates in small pores of membranes is very desirable. The dynamic permeation method is one of the methods which can be used to perform a corresponding study. The following experimental arrangement was applied: a constant higher pressure P 1 was set on an open side of the membrane; on the opposite closed side the change of a lower pressure P 2 was measured. The dynamic permeation set-up was used at first in transport measurements of a noncondensable gas through a Vycor glass membrane (mean pore radius around 2 nm). The obtained data were compared with the results of alternatively performed steady state permeation measurements. Subsequently, the permeability was studied for the condensable gas butane through the Vycor glass membrane, particularly for elevator pressure conditions near the saturated vapor pressure. Also for this purpose the dynamic permeation experiment was found to be very convenient. It enables to measure the mass transport for very small pressure gradients across the membrane. The permeation results obtained correspond well with the liquid butane permeability of Vycor membrane quantified previously in independent pervaporation experiments. This agreement confirms the presence of liquid butane in small pores of Vycor glass during the transient gas transport at relatively high pressures.
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Transport of butane in a porous Vycor glass membrane in the region of condensation pressure
Journal of Membrane Science, 2007Co-Authors: Petr Uchytil, R Petrickovic, Andreas SeidelmorgensternAbstract:The transport and the separation efficiency in porous membranes can be strongly influenced by the condensation of Permeating gases. An accurate experimental monitoring of Permeating vapors and condensates in small pores of membranes is very desirable. The dynamic permeation method is one of the methods which can be used to perform a corresponding study. The following experimental arrangement was applied: a constant higher pressure P1 was set on an open side of the membrane; on the opposite closed side the change of a lower pressure P2 was measured. The dynamic permeation set-up was used at first in transport measurements of a noncondensable gas through a Vycor glass membrane (mean pore radius around 2 nm). The obtained data were compared with the results of alternatively performed steady state permeation measurements. Subsequently, the permeability was studied for the condensable gas butane through the Vycor glass membrane, particularly for elevator pressure conditions near the saturated vapor pressure. Also for this purpose the dynamic permeation experiment was found to be very convenient. It enables to measure the mass transport for very small pressure gradients across the membrane. The permeation results obtained correspond well with the liquid butane permeability of Vycor membrane quantified previously in independent pervaporation experiments. This agreement confirms the presence of liquid butane in small pores of Vycor glass during the transient gas transport at relatively high pressures. Copyright © 2007 Elsevier B.V. All rights reserved. [accessed 2013 November 26th
R Petrickovic - One of the best experts on this subject based on the ideXlab platform.
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transport of butane in a porous vycor glass membrane in the region of condensation pressure
Journal of Membrane Science, 2007Co-Authors: Petr Uchytil, R Petrickovic, Andreas SeidelmorgensternAbstract:Abstract The transport and the separation efficiency in porous membranes can be strongly influenced by the condensation of Permeating gases. An accurate experimental monitoring of Permeating vapors and condensates in small pores of membranes is very desirable. The dynamic permeation method is one of the methods which can be used to perform a corresponding study. The following experimental arrangement was applied: a constant higher pressure P 1 was set on an open side of the membrane; on the opposite closed side the change of a lower pressure P 2 was measured. The dynamic permeation set-up was used at first in transport measurements of a noncondensable gas through a Vycor glass membrane (mean pore radius around 2 nm). The obtained data were compared with the results of alternatively performed steady state permeation measurements. Subsequently, the permeability was studied for the condensable gas butane through the Vycor glass membrane, particularly for elevator pressure conditions near the saturated vapor pressure. Also for this purpose the dynamic permeation experiment was found to be very convenient. It enables to measure the mass transport for very small pressure gradients across the membrane. The permeation results obtained correspond well with the liquid butane permeability of Vycor membrane quantified previously in independent pervaporation experiments. This agreement confirms the presence of liquid butane in small pores of Vycor glass during the transient gas transport at relatively high pressures.
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Transport of butane in a porous Vycor glass membrane in the region of condensation pressure
Journal of Membrane Science, 2007Co-Authors: Petr Uchytil, R Petrickovic, Andreas SeidelmorgensternAbstract:The transport and the separation efficiency in porous membranes can be strongly influenced by the condensation of Permeating gases. An accurate experimental monitoring of Permeating vapors and condensates in small pores of membranes is very desirable. The dynamic permeation method is one of the methods which can be used to perform a corresponding study. The following experimental arrangement was applied: a constant higher pressure P1 was set on an open side of the membrane; on the opposite closed side the change of a lower pressure P2 was measured. The dynamic permeation set-up was used at first in transport measurements of a noncondensable gas through a Vycor glass membrane (mean pore radius around 2 nm). The obtained data were compared with the results of alternatively performed steady state permeation measurements. Subsequently, the permeability was studied for the condensable gas butane through the Vycor glass membrane, particularly for elevator pressure conditions near the saturated vapor pressure. Also for this purpose the dynamic permeation experiment was found to be very convenient. It enables to measure the mass transport for very small pressure gradients across the membrane. The permeation results obtained correspond well with the liquid butane permeability of Vycor membrane quantified previously in independent pervaporation experiments. This agreement confirms the presence of liquid butane in small pores of Vycor glass during the transient gas transport at relatively high pressures. Copyright © 2007 Elsevier B.V. All rights reserved. [accessed 2013 November 26th
Shiroh Futaki - One of the best experts on this subject based on the ideXlab platform.
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acid wash in determining cellular uptake of fab cell Permeating peptide conjugates
Biopolymers, 2007Co-Authors: Shouju Kameyama, Mayo Horie, Takeo Kikuchi, Takao Omura, Akiko Tadokoro, Toshihide Takeuchi, Ikuhiko Nakase, Yukio Sugiura, Shiroh FutakiAbstract:Successful intracellular delivery of various bioactive molecules has been reported using cell-Permeating peptides (CPPs) as delivery vectors. To determine the effects of CPPs on the cellular uptake of immunoglobulin Fab fragment, conjugates of a radio-iodinated Fab fragment with CPPs (CPP-(125)I-Fab) derived from HIV-1 TAT, HIV-1 REV, and Antennapedia (ANP) were prepared. These vectors are rich in basic amino acids, and their strong adsorption on cell surfaces often results in overestimation of internalized peptides. Cell wash with an acidic buffer (0.2M glycine-0.15M NaCl, pH 3.0) was thus employed in this study to remove cell-surface adsorbed CPP-(125)I-Fab conjugates. This procedure enabled clearer understanding of the methods of internalization of CPP-(125)I-Fab conjugates. The kinetics of internalization of REV-(125)I-Fab conjugate was rapid, and a considerable fraction of REV-(125)I-Fab was taken up by HeLa cells as early as 5 min after administration. It was also shown that cellular uptake of these conjugates was significantly inhibited in the presence of endocytosis/ macropinocytosis inhibitors, in the order REV-(125)I-Fab > or = TAT-(125)I-Fab > or = ANP-(125)I-Fab; this order was the same as for effectiveness of intracellular delivery. Simultaneous cell washing with phosphate-buffered saline (PBS) and this acidic buffer effectively separated the internalized conjugates from the cell-surface-adsorbed ones, and considerable differences were observed in these amounts dependent on the employed CPPs.
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Acid wash in determining cellular uptake of Fab/cell-Permeating peptide conjugates.
Biopolymers, 2007Co-Authors: Shouju Kameyama, Mayo Horie, Takeo Kikuchi, Takao Omura, Akiko Tadokoro, Toshihide Takeuchi, Ikuhiko Nakase, Yukio Sugiura, Shiroh FutakiAbstract:Successful intracellular delivery of various bioactive molecules has been reported using cell-Permeating peptides (CPPs) as delivery vectors. To determine the effects of CPPs on the cellular uptake of immunoglobulin Fab fragment, conjugates of a radio-iodinated Fab fragment with CPPs (CPP-(125)I-Fab) derived from HIV-1 TAT, HIV-1 REV, and Antennapedia (ANP) were prepared. These vectors are rich in basic amino acids, and their strong adsorption on cell surfaces often results in overestimation of internalized peptides. Cell wash with an acidic buffer (0.2M glycine-0.15M NaCl, pH 3.0) was thus employed in this study to remove cell-surface adsorbed CPP-(125)I-Fab conjugates. This procedure enabled clearer understanding of the methods of internalization of CPP-(125)I-Fab conjugates. The kinetics of internalization of REV-(125)I-Fab conjugate was rapid, and a considerable fraction of REV-(125)I-Fab was taken up by HeLa cells as early as 5 min after administration. It was also shown that cellular uptake of these conjugates was significantly inhibited in the presence of endocytosis/ macropinocytosis inhibitors, in the order REV-(125)I-Fab > or = TAT-(125)I-Fab > or = ANP-(125)I-Fab; this order was the same as for effectiveness of intracellular delivery. Simultaneous cell washing with phosphate-buffered saline (PBS) and this acidic buffer effectively separated the internalized conjugates from the cell-surface-adsorbed ones, and considerable differences were observed in these amounts dependent on the employed CPPs.
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effects of cell Permeating peptide binding on the distribution of 125i labeled fab fragment in rats
Bioconjugate Chemistry, 2006Co-Authors: Shouju Kameyama, Mayo Horie, Takeo Kikuchi, Takao Omura, Toshihide Takeuchi, Ikuhiko Nakase, Yukio Sugiura, Shiroh FutakiAbstract:The peptides comprising the sequence of HIV-1 Tat protein (positions 48-60), Antennapedia (positions 43-58), and HIV-1 Rev protein (positions 34-50) are known to be cell-Permeating. In this study, we examined how the distribution of Fab fragments in rats is affected by conjugation with these peptides. Fab fragment was iodinated by a chloramine-T method and then chemically conjugated with cell-Permeating peptide. The complex of 125I-Fab and cell-Permeating peptide was administered to male rats intravenously at a dose of 1 mg/kg, and whole-body autoradiography was performed at 4 and 24 h after administration. The patterns of distribution of 125I-Fab exhibited remarkable variation depending on the cell-Permeating peptide used. In particular, at 4 h, high concentrations of radioactivity were observed in the spleen, adrenal gland, renal medulla, and liver with Rev peptide-Fab complex, in the liver and spleen with Tat peptide-Fab complex, and in the spleen, adrenal gland, and liver with Antennapedia peptide-Fab complex. Even at 24 h, high concentrations of radioactivity were still observed in the spleen and renal medulla of rat with Rev peptide-Fab complex, and in the spleen and renal cortex of rat with Antennapedia peptide-Fab complex. These findings demonstrate that the patterns of distribution of peptide-125I-Fab complexes can be modulated by selection of cell-penetrating peptides. Moreover, the patterns of retention of peptide-125I-Fab complexes in internal organs also differed at 24 h after administration. These findings provide valuable information for the development of novel antibody pharmaceuticals and therapeutic systems.
Andreas Bernkopschnurch - One of the best experts on this subject based on the ideXlab platform.
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self emulsifying peptide drug delivery systems how to make them highly mucus Permeating
International Journal of Pharmaceutics, 2018Co-Authors: Janine Griesser, Gergely Hetenyi, Hatice Kadas, Frederic Demarne, Vincent Jannin, Andreas BernkopschnurchAbstract:Abstract Aim It was the aim of this study to evaluate the mucus Permeating properties of self-emulsifying drug delivery systems (SEDDS) exhibiting different size and zeta potential. Methods Various SEDDS were prepared and characterized regarding droplet size, zeta potential and stability. Desmopressin was incorporated as model peptide drug and log P (SEDDS/water) was determined. Thereafter, mucus permeation studies with freshly isolated porcine mucus via Transwell method were performed. Moreover, the impact of water movement on mucus permeation of SEDDS was investigated. Different types of nanocarriers including nanoparticles and liposomes served as references. Results SEDDS exhibited an initial droplet size of 25.0 ± 2.2, 49.5 ± 4.6, 123.5 ± 12.1, 226.2 ± 93.4 and 502.9 ± 93.7 nm and a zeta potential of +24.4 ± 4.6, +10.6 ± 2.0, 0.2 ± 3.8, −8.2 ± 3.4 and −35.1 ± 2.7 mV. Log P was in the range of 1.29–2.09 and mucus permeation studies with these SEDDS revealed a clear correlation between droplet size and permeation rate. The smaller SEDDS were, the higher their mucus Permeating properties were. Negatively charged SEDDS demonstrated a higher permeation rate than positively charged SEDDS. In comparison to liposomes and solid nanocarriers SEDDS exhibited up to 5-fold higher mucus Permeating properties. Conclusion Small droplet size and negative zeta potential of SEDDS could be identified as key parameters for their mucus Permeating properties.
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insulin loaded mucus Permeating nanoparticles addressing the surface characteristics as feature to improve mucus permeation
International Journal of Pharmaceutics, 2016Co-Authors: Irene Pereira De Sousa, Thomas Moser, Corinna Steiner, Barbara Fichtl, Andreas BernkopschnurchAbstract:Abstract Aim It was the aim of this study to combine two strategies – namely the virus-mimicking strategy and the surface PEGylation strategy – in order to generate highly mucus Permeating nanocarriers for oral insulin delivery. Methods Chondroitin sulphate was covalently conjugated with poly(ethylene glycol) 5 kDa at different degree of modification and with the functionalized polymers NPs were formulated via complexation with chitosan. NPs were characterized by particle size, zeta potential, surface hydrophilicity and permeation ability in porcine mucus and on excised mucosa. Results The NPs presented a size between 510 and 670 nm and a zeta potential between −1 and −5 mV when dispersed in simulated intestinal fluid. The mucus permeation test revealed a correlation between the NPs hydrophilicity and their ability to move through mucus. A 5-fold higher amount of NPs with the higher degree of PEGylation could permeate through fresh mucus compared to non-PEGylated NPs. Moreover, highly PEGylated NPs showed a 3.7-fold greater ability to be retained in intestinal mucosa against buffer flow compared to unmodified NPs. Finally, insulin was incorporated with a payload of 2.18% and the release profile showed a 65% release within 4 h. Conclusions Results of this study provide strong evidence for the potential of combining different surface modification strategies in order to improve the mucus Permeating properties of NPs for oral peptide delivery.
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mucus Permeating thiolated self emulsifying drug delivery systems
European Journal of Pharmaceutics and Biopharmaceutics, 2016Co-Authors: Julia Rohrer, Sabine Hauptstein, Alexandra Partenhauser, Caroline Marie Gallati, Barbara Matuszczak, Muthanna Abdulkarim, Mark Gumbleton, Andreas BernkopschnurchAbstract:Abstract Context Mucus represents a critical obstacle for self-emulsifying drug delivery systems (SEDDS) targeting the epithelial membrane site. Objective The aim of the study was the development of a novel SEDDS to overcome the mucus barrier. Materials and methods Two novel conjugates N -dodecyl-4-mercaptobutanimidamide (thiobutylamidine-dodecylamine, TBA-D) and 2-mercapto- N -octylacetamide (thioglycolicacid-octylamine, TGA-O) were synthesized, incorporated into SEDDS and analyzed for stability, cytotoxicity and physico-chemical characteristics using dynamic light scattering. Mucus interaction studies were performed using in vitro assays based on multiple particle tracking, rotational silicone tubes and rheology. Results and discussion TBA-D was synthesized using dodecylamine and iminothiolane as thiol precursor (yield = 55 ± 5%). TGA-O was obtained via crosslinking of octylamine with SATA ((2,5-dioxopyrrolidin-1-yl) 2-acetylsulfanylacetate) (yield = 70 ± 6%). The chemical structure of target compounds was confirmed via NMR analysis. The thiol-conjugates were incorporated in an amount of 3% (m/m) into SEDDS (Cremophor EL 30%, Capmul MCM 30%, Captex 355 30% and propylene glycol 10%), namely thiolated SEDDS leading to a droplet size around 50 nm and zeta potential close to 0 mV. Thiolated SEDDS with an effective diffusion coefficient 〈Deff〉 of up to 0.871 ± 0.122 cm 2 s −1 × 10 −9 were obtained. Rotational silicone studies show increased permeation of the thiolated SEDDS A in comparison with unthiolated control. Rheological studies confirmed the mucolytic activity of the thiol-conjugates which differed only by 3% from DTT (dithiothreitol) serving as positive control. Conclusion Low molecular weight thiol-conjugates were identified to improve the mucus permeation, leading to highly efficient mucus Permeating SEDDS, which were superior to conventional SEDDS and might thus be a new carrier for lipophilic drug delivery.
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mucus Permeating thiomer nanoparticles
European Journal of Pharmaceutics and Biopharmaceutics, 2015Co-Authors: Saskia Kollner, Sarah Dunnhaupt, Claudia Waldner, Sabine Hauptstein, Pereira I De Sousa, Andreas BernkopschnurchAbstract:The aim of this study was to develop and evaluate a novel mucoadhesive drug delivery system based on thiolated poly(acrylic acid) nanoparticles exhibiting mucolytic properties to enhance particle diffusion into deeper mucus regions before adhesion. Mediated by a carbodiimide, cysteine and the mucolytic enzyme papain were covalently attached to poly(acrylic acid) via amide bond formation. The conjugates were co-precipitated with calcium chloride in order to obtain papain modified (PAA-pap) and thiolated nanoparticles (PAA-cys) as well as particles containing both conjugates (PAA-cys-pap). The nanoparticulate systems were characterized regarding particle size distribution and zeta potential. Particle transport was investigated by diffusion studies across intestinal mucus using two different techniques. Furthermore, mucoadhesive properties of all particles were evaluated via rheological measurements. Results demonstrated that all nanoparticles were in a size range of 158-214 nm and showed negative zeta potentials. Due to the presence of papain, the PAA-cys-pap particles were capable of cleaving mucoglycoprotein substructures and consequently exhibited a 2.0-fold higher penetration into the mucus layer in comparison with PAA-cys particles. Within the rheological studies, an 1.9-fold increase in mucoadhesion could be achieved for the nanoparticulate system based on thiolated PAA compared to papain modified particles (PAA-pap). Therefore, the newly developed particulate system (PAA-cys-pap) is characterized by mucoadhesive as well as mucolytic properties. The combination of both effects - mucus-Permeating and mucoadhesive properties - might be a promising strategy for the development of oral drug delivery systems to overcome the mucus barrier and providing a prolonged residence time close to the absorption membrane.
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mucus Permeating carriers formulation and characterization of highly densely charged nanoparticles
European Journal of Pharmaceutics and Biopharmaceutics, 2015Co-Authors: Irene Pereira De Sousa, Corinna Steiner, Matthias Schmutzler, Matthew D Wilcox, Gert J Veldhuis, Jeffrey P Pearson, Christian W Huck, Willi Salvenmoser, Andreas BernkopschnurchAbstract:Abstract The GI mucus layer represents a significant block to drug carriers absorption. Taking an example from nature, virus-mimicking nanoparticles (NPs) with highly densely charged surface were designed with the aim to improve their mucus permeation ability. NPs were formulated by combining chitosan with chondroitin sulfate and were characterized by particle size, ζ-potential and hydrophobicity. The interaction occurring between NPs and diluted porcine intestinal mucus was investigated by a new method. Furthermore, the rotating tube technique was exploited to evaluate the NPs permeation ability in fresh undiluted porcine intestinal mucus. NPs (400–500 nm) presenting a slightly positive (4.02 mV) and slightly negative (−3.55 mV) ζ-potential resulted to be hydrophobic and hydrophilic, respectively. On the one hand the hydrophobic NPs undergo physico-chemical changes when incubated with mucus, namely the size increased and the ζ-potential decreased. On the other hand, the hydrophilic NPs did not significantly change size and net charge during incubation with mucus. Both types of NPs showed a 3-fold higher diffusion ability compared to the reference 50/50 dl -lactide/glycolide copolymer NPs (136 nm, −23 mV, hydrophilic). Based on these results, this work gives valuable information for the further design of mucus-penetrating NPs.
