The relative extension of alginates having different chemical composition

Swelling and Mechanical Properties of Alginate Hydrogels with Respect to Promotion of Neural Growth

“…6 Subsequently, our in vitro neurite outgrowth assay revealed a sharp and noncontinuous transition from adhesive to nonadhesive states for Ca-alginate NaCl hydrogels that was observed between 4 and 6 mM of CaCl 2 ; these qualitative changes were pH independent and were detected in hydrogels derived from both G-enriched and M-enriched alginates with viscosities ranging from 21 to 145 mPa.…”

“…Indeed, the affinity to bind Ca 2 + increases with a greater number of G-blocks present in the polymer. 6 On the other hand, alginate viscosity is proportional to polysaccharide chain length, and high-viscosity alginates can form larger hydrogels because of the higher probability of crosslinking of the polysaccharide chains and physical entanglement. 7 The dissociation constants for mannuronic and guluronic acid monomers are 3.38 and 3.65, respectively.…”

“…M and G are distributed within the polymer chain in varying proportions to produce heterogeneous alternating (MG) and homogeneous (MM or GG) sequences in the primary structure. [5][6][7][8][9] In aqueous solutions (sols), alginate exists as a negatively charged polyanion that forms a hydrogel by the physical association of polysaccharide chains through ionic crosslinking of G residues by multivalent cations (e.g., Ca 2 + , Sr 2 + , Ba 2 + , Zn 2 + , Cu 2 + , Ni 2 + , or Fe 3 + ). This process has been described by the egg-box model in which divalent ions interact with two adjacent G residues and with two G residues of an opposing chain.…”

“…10,11 The density of the alginate fiber network within a hydrogel and its gel strength are regulated by the number of connected gelling sites; as a result, these properties are elevated with an increasing level of crosslinking ion saturation in the alginate and reduced with an increasing number of free G blocks. 6,[12][13][14] The behavior of charged polyelectrolytes, which includes alginates, is strongly regulated by the pH and ionic strength of the surrounding solution; pH controls the degree of dissociation of the guluronic and mannuronic acid groups, while ionic strength triggers the interaction of the resulting negative charges along the polymer chains. 15,16 Most polyelectrolyte-based gels disintegrate upon immersion in solutions of high ionic strength.…”

Drug Targeting in IBD Treatment – Existing and New Approaches

“…Having in mind bio/mucoadhesive properties of natural biopolymers, cationic chitosan and anionic alginate were selected for formulation of the budesonide loaded microparticulated DDS with a potential for IBD targeting. Sodium alginate LF 10/60 which consists of 65-75% of guluronic acid (G) and 25-35% of manuronic acid (M) was used for particle preparation because MG types compared with MM and GG types of sodium alginate have better flexibility (Smidsrød, 1973), and polymer gels formed from alginate with high percentage of guluronic acid (>70%) have highest mechanical strength and stability towards monovalent ions (Martinsen, 1991). Chitosan with low viscosity, highly deacetylated was chosen for polyelectrolyte complexation with sodium alginate.…”