Gelation Behavior by the Lanthanoid Adsorption of the Cyanobacterial Extracellular Polysaccharide

Abstract

The self-organization behavior of an extracellular polysaccharide (sacran) extracted from the cyanobacterium Aphanothece sacrum in response to lanthanoid ion adsorption was investigated. Consequently, cryogenic TEM images revealed that sacran could be cross-linked by Nd(3+) trivalent ions and formed a fibrous nanostructural network containing water. Furthermore, sacran adsorbed trivalent metal ions at a 3:1 ratio, which was the theoretical ionic adsorption and showed more efficient adsorption than alginate based on electric conductivity titration. The critical gelation concentrations, Cg, where sacran formed tough gels upon metal ion binding were estimated. The Cg for trivalent metal ions was lower than that for divalent ions, and the Cg for lanthanoid ions was particularly low at 10(-3) to 10(-4) M, changing every four elemental numbers. The extracellular matrix of Aphanothece sacrum, sacran, may adsorb metal ions to create fibrous nanostructures that reinforce the jelly matrix.

Potential Use of a Megamolecular Polysaccharide Sacran as a Hydrogel-Based Sustained Release System

“…The p-values for significance were set at 0.05. . [11][12][13]15) In our preliminary study, we confirmed that the incubation with sacran solution at 4°C for 5 h after the addition of AlCl 3 was necessary to obtain the homogenous sacran-hydrogel. Therefore, to examine whether sacran-hydrogels can be formed in the presence of various drugs, sacran-hydrogels were prepared by the addition of AlCl 3 as a cross-linker, in BPAA, PD and CPM systems as model compounds of acidic, neutral and basic drugs, respectively (Fig.…”

“…1) was extracted from the Japanese indigenous cyanobacterium Aphanothece sacrum, which is mass-aquacultured in rivers with a high ionic concentration, and which possesses an abundance of a jelly-like extracellular matrix (ECM) with a high water content (97.5%). [11][12][13][14] Sacran is a heteropolysaccharide containing various sugar residues such as glucose, galactose, mannose, xylose, rhamnose, fucose, galacturonic acid and glucuronic acid, and traces of alanine, galactosamine and muramic acid; 11% of the monosaccharides contain a sulfate group and 22% of them contain a carboxyl group. Sacran also has an extremely high molecular weight (approximately 20 MDa) and is surprisingly long (more than 8 µm).…”

“…Recently, Okajima et al revealed that sacran can form a hydrogel through an electrostatic interaction with cationic heavy metal ions and that it can be applied for the recovery of rare metals. [11][12][13]15) However, until now there has been no report on the application of sacran-hydrogel for a transdermal drug carrier.…”

Anti-inflammatory Effects of Novel Polysaccharide Sacran Extracted from Cyanobacterium <i>Aphanothece sacrum</i> in Various Inflammatory Animal Models

“…It is extracted from the Japanese indigenous cyanobacterium Aphanothece sacrum, which possesses a jelly-like extracellular matrix (ECM) with high water content (97.5-98.3%). [8][9][10][11][12] Sacran is a heteropolysaccharide composed of various sugar residues such as glucose, galactose, mannose, xylose, rhamnose, fucose, galacturonic acid and glucuronic acid, and contains traces of alanine, galactosamine and muramic acid; 11% of monosaccharides contain a sulfate group and 22% of them contain a carboxyl group. In addition, sacran was reported to be a supergiant molecule with extremely high molecular weight ranging over 10 7 g/mol and micrometer-scaled (more than 8 µm).…”

Wide-Bore Capillary Hydrodynamic Chromatography with ICP-MS Detection for Evaluation of Lanthanide Uptake by Molecular Aggregates

“…A polysaccharide, which forms gels in the presence of the Ln ions, is recently reported as an adsorbent of potential use for their recovery. 15,16 Living cells (e.g. Gram-positive bacteria) have also been proposed as candidates for selective recovery of Lns.…”