Alginate as immobilization material: III. Diffusional properties

Abstract

The rate of diffusion of serum albumin (MW 6.9 x 10(4) D) out of beads of calcium alginate gels depends upon the concentration and uronic acid composition of the alginate (ManA/GulA ratio), the conditions under which the beads are produced, the pH, and the temperature. The diffusion coefficient decreases with increasing alginate concentration, and (ManA/GulA) ratio and with decreasing pH. Diffusion out of the beads, in which the alginate is uniformly distributed (homogeneous gel), is faster than out of the beads in which the alginate is concentrated at the surface (inhomogeneous gel). The temperature dependence of the diffusion coefficient follows the Arrhenius law, with an activation energy of approximately 23 kJ x mol(-1).

Model-based experimental analysis of enzyme kinetics in aqueous–organic biphasic systems

“…The quadratic equation 4-14 was used to fit the alginate density profile, where w alg is the alginate mass fraction, lg a w the average alginate mass fraction, d a model parameter to be fitted, and R the bead radius. The quadratic dependence is in accordance with previous observations (Martinsen et al, 1992;Skjak-Braek et al, 1989). (4-16)…”

Diluted Acid Pretreatment of Pinus Radiata for Bioethanol Production Using Immobilized Saccharomyces Cerevisiae Ir2-9 in a Simultaneous Saccharification and Fermentation Process

“…[10][11][12] There are several studies on the composition of alginate and their suitability for cell immobilization. [13][14][15][16][17] Yamagiwa et al 18 tried the two-step preparation procedure by recoating the calcium alginate cell beads by plain alginate as a double layer to enhance the gel stability. 19,20 Ruggeri et al 21 have attempted polyacrylamide coating over the alginate cell beads to enhance the structural stability.…”

Alginate Composition Effects on a Neural Stem Cell–Seeded Scaffold

“…17,21 Beads composed of high G alginate are also known to be more porous than high M alginate, thus enhancing diffusion of molecules into and out of the matrix. 26 Poly-L-lysine (PLL) coating is commonly employed as a means of strengthening the alginate bead and providing a barrier to immune system components such as IgG. 27,28 However, the PLL coating layer may itself cause an unfavorable foreign body response and slight toxicity to encapsulated cells, and its use remains controversial.…”

“…Additionally, the increased gel porosity of high G alginate (which could be further enhanced by swelling) and the potential for stabilization of trophic factors by interaction with the alginate matrix are possible explanations. 26,47 Since neurotrophic factors are larger than insulin (approximately 20-30 kDa vs. 5 kDa), the increased porosity of high G alginate may be necessary to allow for adequate release. The release timing of individual neurotrophic factors may be explained by cellular events and their relationship to evolving environmental cues, and the quantities and timing of neurotrophic factor release is likely to vary with culture conditions.…”