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Abstract: Cyanobacteria are regarded as very eco‐friendly microreactors for the production of various biomolecules such as polysaccharides by fixing not only carbon but also nitrogen in water. Cyanobacterial polysaccharides having various functional groups such as hydroxyls, carboxyls, sulfates, etc. have the ability to interact with metals or inorganics, to create bionanocomposites. Sacran, a supergiant cyanobacterial anionic polysaccharide extracted from the extracellular matrix of Aphanothece sacrum which is mass‐cultivated in freshwater, is mainly used to create functional bionanocomposites. Gel‐type bionanocomposites of sacran with various metal cations are formed and showed photoresponsive functions. Metal recovery is performed from the sacran bionanocomposite gels. Sacran chains are complexed with multi‐wall carbon nanotubes (MWCNT) to give viscose dispersion from which MWCNT bionanocomposites can be collected by electrophoresis. The MWCNT/sacran dispersion retains the capability of adsorbing various metal ions to form hardened hydrogel beads. Finally, natural inorganic sepiolite can be used for sacran bionanocomposites which show an efficient neodymium ion adsorption ability. Thus, cyanobacterial polysaccharides are useful for preparing eco‐friendly and functional bionanocomposites with various hard materials. [ABSTRACT FROM AUTHOR]

The evaporative interface on polysaccharides has evolved to form hierarchical structures with moisture sensitivity to enable organisms to live in drying environments. Here, the discovery of the morphological instability of polysaccharides, especially the reversible self‐assembly/disassembly between micron‐fibers and microparticles in response to changes in aquatic environments, is reported. This is similar but different to the dynamic instability observed in cytoskeletal proteins, in terms of an accompanying the polymeric deformation. The formation of the polymeric fibers containing crystalline structures can be flexibly controlled by controlling the polymer concentration and salt concentration in aqueous mixtures. Moreover, the microparticles having crosslinking points in the interior acquire the ability to retain a larger number of water molecules in drying environments and behave as super‐moisturizing materials. [ABSTRACT FROM AUTHOR]

In this study, the solution structure of sacran, cyanobacterial polysaccharide, was estimated by synchrotron X-ray scattering. The chain conformation of sacran in solvent significantly differs depending on the concentration even though it has extraordinary stiffness (109 nm of persistent length). The sacran assemblies under concentrated conditions exhibited hierarchical structure ( i.e ., macroscopic liquid crystalline domain consisting of helices of sacran chains). The findings enable us to design sacran-based functional materials for various applications and to understand the molecular behavior of anionic biopolymers such as glycosaminoglycan and deoxyribonucleic acid. [ABSTRACT FROM AUTHOR]

The thin hydrogel films consisting of water-swollen polymer networks can potentially be applied for biomedical fields. Recently, natural polysaccharides have great attentions to be developed as wound healing and protection. In the present study, we newly prepared and characterized a physically crosslinked-hydrogel film composed of a novel megamolecular polysaccharide sacran for wound dressing application. We successfully fabricated a physically crosslinked-sacran hydrogel film by a solvent-casting method. The thickness of a sacran hydrogel film was lower than that of a sodium alginate (Na-alginate) film. Importantly, the swollen ratio of a sacran hydrogel film in water at 24 h was 19-fold, compared to initial weight. Meanwhile, a Na-alginate hydrogel film was completely broken apart after rehydration. Moreover, a sacran hydrogel film did not show any cytotoxicity on NIH3T3 cells, a murine fibroblast cell line. The in vivo skin hydration study revealed that a sacran hydrogel film significantly increased the moisture content on hairless mice skin and considerably improved wound healing ability, compared to control (non-treated), probably due to not only the moisturing effect but also the anti-inflammatory effect of sacran. These results suggest that sacran has the potential properties as a basic biomaterial in a hydrogel film for wound dressing application. [ABSTRACT FROM AUTHOR]

Moreover, the microparticles having crosslinking points in the interior behave as super-moisturizing materials. Super-Moisturizing Materials from Morphological Deformation of Suprapolysaccharides B Front Cover b : In article number 2200163, Kosuke Okeyoshi, Tatsuo Kaneko, and co-workers discover the morphological instability of polysaccharides, especially the reversible self-assembly/disassembly between micron-fibers and microparticles in response to changes in aquatic environments. [Extracted from the article]

We have investigated the electric conductivity, dielectric relaxation behavior, and viscosity for the aqueous solution of cyanobacterial megamolecules, molecular weight = 1.6 x 107 g/mol, named sacran. Sacran is an anionic polyelectrolyte which has carboxylate and sulfate groups on the saccharide chain. The electric conductivity and the zero shear viscosity demonstrated three crossover concentrations at 0.004,0.02, and 0.1 wt%. The viscosity was found to be scaled as ~c1.5, ~c0.5, ~c1.5, and ~c3.0 with increasing the sacran concentration. At 0.1 wt%, the sacran chain formed a weak gel which exhibits macroscopic liquid crystal domains including Schlieren texture. Therefore, these crossover concentrations are considered to be the overlap concentration, entanglement concentration, and gelation concentration (or critical polyelectrolyte concentration), respectively. Dielectric relaxation analysis exhibited the fact that sacran has two types of counterions with different counterion-polyion interaction, i.e., strongly bound and loosely bound counterions. The dielectric parameters such as relaxation time or relaxation strength are sensitive to both the entanglement concentration and the gelation concentration, but not the overlap concentration. The number density of bound counterions calculated from the relaxation strength revealed that the counterion is condensed on the sacran chain with raising the sacran concentrations. The decrease in the charge density of the sacran chain reduces the repulsive force between the chains and this would cause the helix transformation or gelation behavior. The chain conformation of sacran in pure water and the gelation mechanism are discussed in relation with the behavior of polyelectrolytes and liquid crystals. [ABSTRACT FROM AUTHOR]

The giant anionic polysaccharide “sacran”,whichis composed of 6-deoxyhexoses, pentoses, uronic acids as well as hexoses,showed hydrophobization and insolubilization phenomena in responseto ultraviolet light irradiation. The sacran solution became turbid,and microparticles were formed by photoirradiation. To visualize theresults of this photoreaction, anionic polysaccharide gels cross-linkedby metal cations were used. As a result, we observed that sacran-gelswith trivalent metal ions gradually contracted depending on the photoirradiationenergy. In contrast, alginate gels used as a comparison degraded insteadof contracting. This photoshrinkage of the sacran gels may be attributedto the hydrophobization of uronic acid based on photodecarboxylation.We propose that sacran-metal ion gels can function as effective, photoresponsivegels. [ABSTRACT FROM AUTHOR]

Anionic polysaccharide (PS) was extracted from Aphanothece stagnina biomaterials where trivalent metal ions were remarkably condensed from environmental water. Structural analyses indicated that the PS was considered to be a kind of sulfated rhamnoglucan-containing uronic acid at a composition of 23 mol% and that the total composition of anionic groups such as sulfate and carboxylate was 31 mol% to the monosaccharide residues. Since the PS was found to be a huge macromolecule with an ultra-high molecular weight (3.14 × 10 g/mol), the simple calculation indicated that about 9.5 × 10 anions exist on one chain of the PS. The electric conductivity of the highly anionic PS solutions indicated that the metal ions such as Ga, La, and Ca complexed ionically with PS chains. The PS formed the gels as a result of trivalent metal complexation, but the gelation behavior of the PS was different from that of the representative metal-complexable polysaccharide, alginate, in terms of the minimum gel formation concentration and the average molecular weight between cross-linking points. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]