Mesh Size of Charged Polyacrylamide Hydrogels from Partitioning Measurements

Abstract

The equilibrium partition coefficient of fluorescently labeled dextrans with molecular masses from 10 to 70 kDa and of two fluorescently labeled proteins was measured for anionic and cationic polyacrylamide gels with 5% bisacrylamide cross-linking. The gels were synthesized using 2-acrylamido-2-methylpropanesulfonic acid and (3-(methacryloylamino)propyl)trimethylammonium chloride monomers within fused silica capillaries with a square section. Partition coefficients were obtained by measuring the fluorescence intensity in the gel-filled capillaries equilibrated with dilute solutions of each probe. The partition coefficients show an exponential decay with gel concentration in agreement with the Ogston model for partitioning in fibrous gels. Comparison of the data for 10 kDa dextran with this model yields fiber radii of 0.79 and 0.99 nm for the anionic and the cationic gels, respectively, which are similar in magnitude to values reported in the literature for neutral polyacrylamide gels. Mesh sizes calculated on the basis of a single-pore-radius model vary between about 11 and about 6 nm for gels with gel concentrations between 0.1 and 0.26 g/cm3. Predictions of the dependence of the partition coefficient on the size of the solute based on the Ogston model are, however, only approximate. Better predictions are obtained with an empirical fit based on a model that considers the flexibility of the polymer chains.

Radiotracer measurements of protein mass transfer: Kinetics in ion exchange media

“…It can be seen that the apparent pore size is considerably smaller for SP-Sepharose-XL than for SP-Sepharose-FF, presumably because the dextran grafts occupy a portion of the pore space. The results for S-HyperD conform to previous results by Farnan et al [21], and to more recent measurements by Russell and Carta [22] for gels similar to the S-HyperD gel but supported in quartz capillaries. The very small apparent pore size suggests that S-HyperD contains a charged homogeneous polymer gel that excludes neutral macromolecules but strongly adsorbs oppositely charged proteins.…”

Multiphysics modeling of responsive characteristics of ionic-strength-sensitive hydrogel

“…As such, the MECis model is able to efficiently predict the swelling/ shrinking behavior of ionic-strength-sensitive hydrogel quantitatively and qualitatively. (Hooper et al 1990) 10 −4 ∼1 Initial diameter of hydrogel (mm) (Hooper et al 1990) 10 Initial fixed charge density(mM) 335H343, 457, 572 Initial mesh size r 0 (nm) (Kizilay and Okay 2003;Russell and Carta 2005) 25 Intrinsic binding constant K d (M −1 ) (Miura et al 1999) 10 3.8 Temperature T(K) (Hooper et al 1990) 298…”

“…Initial diameter of hydrogel (mm) (Hooper et al 1990) 10 Initial fixed charge density(mM) 335H343, 343, 343, 340, 325 Initial mesh size r 0 (nm) (Kizilay and Okay 2003;Russell and Carta 2005) 25 Intrinsic binding constant K d (M −1 ) (Miura et al 1999) 10 3.8…”

Decoupling Polymer Properties to Elucidate Mechanisms Governing Cell Behavior

“…81 However, varying acrylamide and bis-acrylamide concentrations may expose different amounts of chemical moieties to cells, leading to unexpected cell responses (e.g., the cytotoxicity of acrylamide in vivo 82 ). In addition, as the cross-linking degree increases, the pore size decreases within the gel network, 83,84 indicating the coupling of cross-linking and structural parameters. 85 In parallel, the intrinsic properties of PEGcontaining hydrogels are coupled, as mesh size, 85 modulus, 86,87 and degradation rates 88,89 change with PEG content.…”