Multicomponent diffusion of sodium alginate solutions with added salt. II. Charged vs. Uncharged system

Abstract

Diffusion coefficients are reported for dilute aqueous solutions of sodium alginate, and for three compositions of the ternary system comprising of sodium alginate/sodium chloride/water at 20°C applying the conductimetric method. From binary transport data the ternary diffusion coefficients for alginate of added salt (NaCl) can be qualitatively calculated. Due to electrostatic interactions between the ions the diffusive flow of the alginate polyelectrolyte and added salt reveal strong coupling. At pH>5.0 (20°C) and ionic strength of 0.015 M NaCl each mole of diffusing alginate cotransports approximately 210 moles of NaCl. Coupled flow of NaCl ceased if the solution pH is approaching pH 5.5, close to the isoelectric point of alginate (pH 5.4). Between pH 4.5–5.0 the coupled transport of NaCl is governed by the diffusion of the protonated alginate concentration gradient due to the diffusion induced electric field along the neutral alginate. At acidic pH (3.5–4.0) diffusing alginate generates a counter flow of NaCl due to additional bound protons, yielding a net positive charge hence the D21‐value is large and positive.

The Effect of Layer-by-Layer Assembly Coating on the Proliferation and Differentiation of Neural Stem Cells

“…Studies into the biological effects of LbL encapsulation on mammalian cells are rarely reported. Here, we used the gelatin (type A) and alginate as polycation and polyanion for encapsulation because they both are biodegradable and displayed opposite charge under neutral pH as the isoelectric point (IEP) of gelatin is 7–9 (according to the manufacturer), while the IEP of alginate is 5.4 . Both gelatin and alginate are widely used in tissue engineering of NSCs, and they have been found to promote functions of NSCs, such as proliferation or differentiation. − The LbL sheets and microspheres, which consist of gelatin or alginate, are based on their positive or negative charges under certain conditions of pH. − In this research, we included insulin-like growth factor-1 (IGF-1) in the nanomembrane that functioned as a regulator reservoir.…”

Development of a Hybrid Nanoink for 3D Bioprinting of Heterogeneous Tumor Models

“…47 Carboxyl groups available on the alginate have a negative charge at a pH of approximately 7.2−7.4 due to the isoelectric point of these functional groups at pH 5.4. 48 When the alginate molecules interact with CNCs, the carboxyl groups of alginate face away from the CNCs and increased the possibilities of cross-linking via the divalent ions. 46 But with dual UV + Ca 2+ -cross-linking, the AGC246 and AG210 gels possessed about the same compression modulus, indicating that CNC incorporation and ionic cross-linking can be used as an alternative strategy in place of UV cross-linking, which requires a higher density of reactive functional groups and photoinitiators.…”

“…With only Ca 2+ -cross-linking, the AGC246 hydrogel was observed to be much stronger than the AG210 hydrogel, which can be explained by the electrostatic interactions and the rigidity of the CNCs . Carboxyl groups available on the alginate have a negative charge at a pH of approximately 7.2–7.4 due to the isoelectric point of these functional groups at pH 5.4 . When the alginate molecules interact with CNCs, the carboxyl groups of alginate face away from the CNCs and increased the possibilities of cross-linking via the divalent ions .…”

Transport properties of aqueous solutions of sodium alginate at 298.15K

“…2) and its derivatives in alginate gels are used in anti cellulite cosmetics, due to their lipolytic activity on fatty cells. In addition, their gelation properties play an important role in the stability of extracellular polymer substances (Straatmann & Borchard, 2003) and they have been widely used to encapsulate cells for artificial organ applications (Rebecca, Li, & Altreuter, 1996), as well as, drug delivery systems for realising proteins, anti-inflammatory compounds, or gentle preparation of nanoparticles (Paradies, Wagner, & Fischer, 1996).…”

“…A few diffusion coefficients for the binary aqueous systems containing sodium alginate (Paradies et al, 1996;Straatmann & Borchard, 2003), have been reported, but as far as the authors know, after careful literature search, no data are available in the literature for systems involving sodium alginate with caffeine for the same concentrations at 298.15 K. We have been particularly interested in the characterization of diffusion and viscosity of sodium alginate in aqueous dilute solutions, beneath 0.5%, alone and in combination with caffeine at 298.15 K. In the present work, the interdiffusion coefficients were measured using an open-ended conductimetric capillary cell in aqueous solutions (Ribeiro, Lobo, Azevedo, Miguel, & Burrows, 2001;Ribeiro, Lobo, & Natividade, 2002;Ribeiro et al, 2005;Ribeiro et al, 2006;Ribeiro et al, 2007) and in aqueous solutions in presence of caffeine, at 0.005 mol dm À3 , 0.010 mol dm À3 , 0.025 mol dm À3 and 0.050 mol dm À3 concentrations. Densities and viscosities were also measured.…”