The Experts below are selected from a list of 222 Experts worldwide ranked by ideXlab platform
Mohammad R. Kasaai - One of the best experts on this subject based on the ideXlab platform.
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Dilute solution properties and degree of chain branching for dextran
Carbohydrate Polymers, 2012Co-Authors: Mohammad R. KasaaiAbstract:Abstract Hydrodynamic Volume, radius of gyration, and viscometric constants, K and a , for dextran, with a wide molecular weight range were calculated using experimental reported average-molecular weights ( M n , M w ), and intrinsic viscosity, [ η ], data in water and 0.05 M Na 2 SO 4 . Degree of chain branching for dextran was also determined using different procedures. This study demonstrated that Hydrodynamic Volume and radius of gyration of a dextran sample with M w M w are almost identical, whereas the latter parameters for a dextran sample with M w > 20 kDa was smaller than that of its linear counterpart. Values of 0.506 in water and 0.512, 0.425 and 0.273 in 0.05 M Na 2 SO 4 for the exponent a were obtained. A smaller value for a was obtained for a larger M w range. Molecular weights of desirable nano-particles for various branches of nanotechnology can be estimated from a derived radius of gyration–molecular weight relationship.
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Calculation of viscometric constants, Hydrodynamic Volume, polymer-solvent interaction parameter, and expansion factor for three polysaccharides with different chain conformations.
Carbohydrate research, 2008Co-Authors: Mohammad R. KasaaiAbstract:The viscometric constants, K and a, for three polysaccharides: hydroxyethylcellulose (HEC); hydroxypropylcellulose (HPC); and chitosan, were calculated at 30 degrees C using intrinsic viscosity, [eta] and molecular weight (M(n), M(w), M(z)) data. The polydispersity correction factor, q(MHS), and Hydrodynamic Volume for each polymer sample were also calculated. The value of q(MHS) for the polymer samples was taken into account in the calculation of the viscometric constants. The polymer-solvent interaction parameters for the three polysaccharides were estimated by both semiempirical and numerical methods using intrinsic viscosity and molecular weight data. Hydrodynamic expansion factors were also estimated using the latter data. The quality of the solvents for the three polymers was compared using exponent a, polymer-solvent interaction parameter, and expansion factor data. This study resulted in the following constants for: The values of 0.60, 1.08, and 0.885 for exponents a indicate that HEC, HPC, and chitosan behave as a flexible random coil, linear and extended conformations, respectively. The values of exponents a for the three polysaccharides appear to be inversely related to their K values. The results of the expansion factor were consistent with the results of exponent a and polymer-solvent interaction parameters.
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Intrinsic viscosity–molecular weight relationship and Hydrodynamic Volume for pullulan
Journal of Applied Polymer Science, 2006Co-Authors: Mohammad R. KasaaiAbstract:A numerical method for determination of Mark-Houwink-Sakurada (MHS) equation constants, a and K, was tested with success for two series of pullulan standard samples having narrow and broad molecular weight distributions (MWD) and taken into account their polydispersity. Different solvents, which were used to determine the intrinsic viscosities and the viscometric constants, a and K (published in the literature for pullulan), were compared. The various parameters affecting the constants are discussed. The procedure to determine the correct value of the Hydrodynamic Volume for pullulan was also described. This study resulted in the following MHS equations for narrow and broad MWD series of pullulan samples with M w in the range of 5-1000 kDa: [η]=1.990×10 -4 M v 0.667 =1.990×10 -4 q MHS M w 0.667 =1.956×10 -4 M w 0.667 (Narrow MWD) [η] = 2.263×10 -4 M v 0.657 =2.263×10 -4 q MHS M w 0.657 =2.056×10 -4 M w 0.657 (Broad MWD) where q MHS is the polydispersity correction factor and [if] is the intrinsic viscosity in dL g -1 . The plot of log K versus exponent a was linear and inversely related. This curve was used to estimate the constant K for pullulan with a known exponent a. Among various reported solvents, the diluted aqueous salt solutions have more advantages than other solvents.
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intrinsic viscosity molecular weight relationship and Hydrodynamic Volume for pullulan
Journal of Applied Polymer Science, 2006Co-Authors: Mohammad R. KasaaiAbstract:A numerical method for determination of Mark-Houwink-Sakurada (MHS) equation constants, a and K, was tested with success for two series of pullulan standard samples having narrow and broad molecular weight distributions (MWD) and taken into account their polydispersity. Different solvents, which were used to determine the intrinsic viscosities and the viscometric constants, a and K (published in the literature for pullulan), were compared. The various parameters affecting the constants are discussed. The procedure to determine the correct value of the Hydrodynamic Volume for pullulan was also described. This study resulted in the following MHS equations for narrow and broad MWD series of pullulan samples with M w in the range of 5-1000 kDa: [η]=1.990×10 -4 M v 0.667 =1.990×10 -4 q MHS M w 0.667 =1.956×10 -4 M w 0.667 (Narrow MWD) [η] = 2.263×10 -4 M v 0.657 =2.263×10 -4 q MHS M w 0.657 =2.056×10 -4 M w 0.657 (Broad MWD) where q MHS is the polydispersity correction factor and [if] is the intrinsic viscosity in dL g -1 . The plot of log K versus exponent a was linear and inversely related. This curve was used to estimate the constant K for pullulan with a known exponent a. Among various reported solvents, the diluted aqueous salt solutions have more advantages than other solvents.
Jorge M Seminario - One of the best experts on this subject based on the ideXlab platform.
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calculating the Hydrodynamic Volume of poly ethylene oxylated single walled carbon nanotubes and hydrophilic carbon clusters
Journal of Physical Chemistry B, 2013Co-Authors: Alfredo D Bobadilla, Errol L G Samuel, James M Tour, Jorge M SeminarioAbstract:Poly(ethylene glycol) (PEG) functionalization of carbon nanotubes (CNTs) is widely used to render CNTs suitable as vectors for targeted drug delivery. One recently described PEGylated version uses an oxidized single-walled carbon nanotube called a hydrophilic carbon cluster (HCC). The resulting geometric dimension of the hybrid PEG–CNT or PEG–HCC is an important factor determining its ability to permeate the cellular membrane and to maintain its blood circulation. Molecular dynamics (MD) simulations were performed to estimate the maximum length and width dimensions for a PEGylated single-walled carbon nanotube in water solution as a model for the PEG–HCC. We ensured maximum PEGylation by functionalizing each carbon atom in a CNT ring with an elongated PEG molecule, avoiding overlapping between PEGs attached to different CNT rings. We suggest that maximum PEGylation is important to achieve an optimal drug delivery platform.
Thomas P Davis - One of the best experts on this subject based on the ideXlab platform.
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molecular weight Hydrodynamic Volume dictates the systemic pharmacokinetics and tumour disposition of polypeg star polymers
Nanomedicine: Nanotechnology Biology and Medicine, 2015Co-Authors: Song Yang Khor, Victoria M Mcleod, Jinming Hu, Lisa M Kaminskas, Michael R Whittaker, Christopher J H Porter, John F. Quinn, Mark Williamson, Thomas P DavisAbstract:Abstract Herein we report for the first time the biological fate of poly[(oligoethylene glycol) acrylate] (POEGA) star polymers synthesised via a versatile arm-first reversible addition-fragmentation chain transfer (RAFT) polymerisation approach. The biopharmaceutical behaviour of three different molecular weight (49, 64 and 94kDa) POEGA stars was evaluated in rats and nude mice bearing human MDA MB-231 tumours after intravenous administration. The 94kDa star polymer exhibited a longer plasma exposure time than the 49kDa or 64kDa star polymer; an observation attributable to differences in the rates of both polymer biodegradation and urinary excretion. Tumour biodistribution also correlated with molecular weight and was greatest for the longest circulating 94kDa star. Different patterns of liver and spleen biodistribution were observed between mice and rats for the different sized polymers. The polymers were also well-tolerated in vivo and in vitro at therapeutic concentrations. From the Clinical Editor Advances in nanotechnology has enabled scientists to produce nanoparticle as drug carriers in cancer therapeutics. In this article, the authors studied the biological fate of poly[(oligoethylene glycol) acrylate] (POEGA) star polymers of different size, after intravenous injections. This would allow the subsequent comparison to other drug delivery systems for better drug delivery.
Barry J Bauer - One of the best experts on this subject based on the ideXlab platform.
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size separation of single wall carbon nanotubes by flow field flow fractionation
Analytical Chemistry, 2008Co-Authors: Jaehun Chun, Jeffrey A Fagan, Erik K. Hobbie, Barry J BauerAbstract:Flow-field flow fractionation (flow-FFF) is used to separate single wall carbon nanotubes (SWNTs) dispersed in aqueous medium by the use of DNA. Online measurements are made of SWNT concentration, molar mass, and size by using UV−vis absorption and multiangle light scattering (MALS). Separations are made of both unfractionated SWNTs and SWNT fractions made by use of size exclusion chromatography (SEC). The SEC fractions are well resolved by flow-FFF. SWNT Hydrodynamic Volume from calibrations with polymer latex particles in flow-FFF are compared to calibrations of Hydrodynamic Volume from the SEC fractions derived from dissolved polymers. Rod lengths of the SWNTs are calculated from online measurements of MALS and those are compared to rod lengths from Hydrodynamic models based on latex sphere calibrations. Samples with varied sizes were prepared by fracturing SWNTs through extended sonication. Flow-FFF of these fractured samples shows very broad size distributions compared to the original SEC and flow-FF...
Alfredo D Bobadilla - One of the best experts on this subject based on the ideXlab platform.
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calculating the Hydrodynamic Volume of poly ethylene oxylated single walled carbon nanotubes and hydrophilic carbon clusters
Journal of Physical Chemistry B, 2013Co-Authors: Alfredo D Bobadilla, Errol L G Samuel, James M Tour, Jorge M SeminarioAbstract:Poly(ethylene glycol) (PEG) functionalization of carbon nanotubes (CNTs) is widely used to render CNTs suitable as vectors for targeted drug delivery. One recently described PEGylated version uses an oxidized single-walled carbon nanotube called a hydrophilic carbon cluster (HCC). The resulting geometric dimension of the hybrid PEG–CNT or PEG–HCC is an important factor determining its ability to permeate the cellular membrane and to maintain its blood circulation. Molecular dynamics (MD) simulations were performed to estimate the maximum length and width dimensions for a PEGylated single-walled carbon nanotube in water solution as a model for the PEG–HCC. We ensured maximum PEGylation by functionalizing each carbon atom in a CNT ring with an elongated PEG molecule, avoiding overlapping between PEGs attached to different CNT rings. We suggest that maximum PEGylation is important to achieve an optimal drug delivery platform.
