Solute diffusion in hydrated polymer networks. Part 1.—Cellulose gels

Brown, Wyn; Chitumbo, K.

doi:10.1039/f19757100001

Cited by 28 publications

(7 citation statements)

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“…Increased hydrodynamic friction has been said to have a dominant role in the hindered diffusion of solutes in gels 86,88 . Finally, interactions between the solvent and polymer matrix increase the local viscosity of the solvent; this is also known as “solvent structuring.” 89 Tanigushi and Horigome state that the water in the vicinity of the polymer (bound water) can be structured around the polymer and therefore be unable to contribute to the transport of solutes, while the bulk water is highly mobile and can solvate the solutes 90 . But investigating the causes of hindered diffusion in gels is difficult using macroscopic diffusion measurements since the various factors which affect diffusion cannot be directly isolated.…”

Section: Diffusion In Gelsmentioning

confidence: 99%

“…For instance, Kou and Amidon attribute a low phenylpropanolamine diffusivity in swollen poly(HEMA‐co‐MA) gels to an interaction between the solute and the network 107 . Similarly, Brown and Chitumbo claim the low diffusivity of ethylene glycol and crown [15–5] ether in cellulose gels is due to weak interactive forces between the solute and the gel matrix 89 . Leloup and Colonna attribute the same behavior for bovine serum albumin in amylose gels to hydrodynamic friction between the solute and matrix 108 .…”

Section: Diffusion In Gelsmentioning

confidence: 99%

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Factors Determining Hydrogel Permeability

Gehrke

Fisher

Palasis

et al. 1997

Annals of the New York Academy of Sciences

112

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HYDROGELSHydrogels are water-swollen networks of biological, synthetic, or semi-synthetic polymers.I2 In contrast to polymer solutions, the polymer chains in hydrogels are crosslinked, either chemically or physically. Since the polymer chains are held together by crosslinks, hydrogels behave like solids rather than liquids, despite containing at least 20 and often over 90% water by weight. Thus hydrogels exhibit elastic responses to stress rather than the viscoelastic responses of uncrosslinked polymer solutions of equivalent composition.The most significant property of a gel is its equilibrium degree of swelling (Q), the amount of water absorbed by the gel, expressed as the ratio of swollen gel volume (or mass) to dry gel volume (or mass). The high water content of gels makes them soft, rubbery, hydrophilic materials, which enhances biocompatibility owing to reduced mechanical irritation and minimized interfacial tension. Their permeability to water and solutes can be readily adjusted by varying the crosslinker concentration at synthesis or copolymerizing with more hydrophilic or more hydrophobic monomers.'Hydrogels have many technological uses, both medical and n~n-medical.'-~ Owing to their often good biocompatibility and easily adjustable permeability, they have been used in a range of biomedical applications including contact lenses, diapers, soft and hard tissue prostheses, bioartificial organs, and other^.^".^ The most intensively studied biomedical application for hydrogels is as vehicles for the delivery of pharmaceuticals. Hydrogels can be used to release drugs slowly over time, protect drugs from degrading environments, or to trigger release in response to a wide variety of chemical and physical ~timu1i.l~"~~ In these gel applications, it is often the transport of solutes through the gel which determines the performance of the resulting product.

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Section: Diffusion In Gelsmentioning

confidence: 99%

Section: Diffusion In Gelsmentioning

confidence: 99%

Factors Determining Hydrogel Permeability

Gehrke

Fisher

Palasis

et al. 1997

Annals of the New York Academy of Sciences

112

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“…For molecules of similar size and excluded volume, one would expect an identical decrease in diffusion coefficient. Thus, in vitro, in a hydrated neutral cellulose gel, Brown and Chitumbo (1975a) found that, for both small molecules and microions, the network perturbation of the diffusion process could be represented by a single common factor, reducing diffusion coefficients in common fashion for both uncharged and charged species; for larger molecules, the excluded volume effect was, of course, larger. In the absence of charge on the gel, no differential effect on small neutral and small charged molecules was found.…”

Section: Bulk Polyelectrolyte Effectsmentioning

confidence: 99%

Passage of ions and dextran molecules across the rete mirabile of the eel. The effects of charge.

Rasio¹,

Goresky²

1985

Circulation Research

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SUMMARY. The countercurrent-perfused rete mirabile of the eel is a preparation in which capillary permeability values can be determined accurately in broadscale fashion. To provide insight into charge effects on transendothelial passage, the permeability values of small inorganic cations (labeled sodium and rubidium, and stable potassium) and anions (labeled chloride, iodide, sulfate, and ferrocyanide) were compared to those expected for neutral solutes with approximately matched diffusion coefficients, and that of a neutral dextran fraction was compared to that of a negatively charged dextran sulfate with a similar diffusion coefficient. In the small ion experiments, the labeled iodide values were unexpectedly high, apparently due to the contamination of the labeled iodide solution with IJ~. The permeabilities of the rest of the ions clustered at a level about 0.5 of the values which would have been expected for neutral solutes with similar diffusion coefficients. The decrement was interpreted to reflect the presence, of both positive and negative charges along the transendothelial pathway, which effectively decrease the dimensions of the limiting part of the pathway for the charged microions relative to that accessible to comparable nonelectrolytes. The larger negatively charged dextran sulfate was also reduced in its passage, in comparison with its matching neutral dextran; this was taken to indicate the presence of a larger1 scale average net negative charge along its pathway. The data indicate the presence of a staggering of positive and negative charges along the transendothelial pathway accessible to the microions, and a net negative charge in the more restricted part of the pathway available to the dextrans. (CircRes 56: 74-83, 1985) BLOOD capillary permeability to small ions has long been known to be a minute fraction of that for water, irrespective of the methods used and tissues investigated. The data have been interpreted as indicating the presence of differing paths for the passage of ions and water across the endothelial wall, the mechanism for the transfer of each usually being thought to be passive [except in certain special areas, such as the tight capillaries of the central nervous system and the eye, where evidence for some active transport of sodium and potassium ions has been presented (Bradbury and Stulcova, 1970;Eisenberg and Suddith, 1979;Betz and Goldstein, 1980)]. It has been expected that appropriately designed studies with ions and charged molecules would provide information concerning the effects of local fixed charges, if these are present in the regions where inorganic ions and other charged materials traverse the capillary wall.Few capillary beds have been thoroughly examined from this point of view. The glomerular apparatus of the kidney constitutes the one exception. Studies of glomerular filtration of moderately large molecules with different charges and comparable molecular size have provided evidence for a charge effect in this structure. These studies indicate that, altho...

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“…We propose the range t recirculationloop .t equilibriium , where t equilibrium is the time necessary to reach equilibrium and t recirculationloop defined as the ratio of the volume of the recirculation loop V loop to the recirculation flow rate Q recirculationloop . It should be stressed that the peak obtained for short times has been already reported (Brown and Chitumbo, 1975), but it has never been quantitatively taken into account. 4.…”

Section: Tablementioning

confidence: 90%

“…This work intends to explore and analyze the influence of a surprisingly rarely reported effect in the batch diffusion cell method, linked to the use of a small volume recirculation loop. In fact, this type of device is often implemented in order to ensure solute concentration analysis, based on continuous analytical methods such as the detectors classically used in liquid chromatography for instance (Harland and Peppas, 1993;Brown and Chitumbo, 1975;Brown and Johnsen, 1981;Grassi et al, 2001;Wiedemann et al, 1998). Apart from the interest of getting a continuous, automated and monitored signal, a major advantage of this strategy is to prevent volume sampling which is time consuming, may be tricky (particularly for gas phase applications) and complicates data treatment if significant volume changes are operated on the system.…”

Section: Introduction: Fundamentals Of Diffusion Kineticsmentioning

confidence: 99%