Cyanobacterial supra-polysaccharide: Self-similar hierarchy, diverse morphology, and application prospects of sacran fibers.

The biological functions of polysaccharides are influenced by their chemistry and chain conformation, which have resulted in various functional applications and new uses for polysaccharides in recent years. Sacran is an intriguing ampholytic polysaccharide with several key properties such as metal adsorption, anti-inflammatory nature, and transdermal drug-carrying capacity. It has an extremely high molecular weight over 107 g/mol, which is much higher than those of the previously reported microbial polysaccharides. In particular, it has a remarkable self-orienting characteristic over a large length scale, which could produce a bundle with twisted morphologies from the nanoscale to the microscale with diameters of ~1 µm and lengths of >800 µm. In this review, morphological variations, as well as novel self-organization and hierarchical self-assembly are comprehensively discussed. Sacran fibers deform into various forms, such as two- and three-dimensional flexible fibers and micro-nano fragments, during their evaporation. The self-assembly and disassembly of the sacran are explained in terms of the preparation process and factors that influence the morphology. This review will pave the way for the development of novel modules such as humidity-sensitive actuators, micro-patterned cell scaffolds, and uniaxially oriented membranes.

Super-Moisturizing Materials from Morphological Deformation of Suprapolysaccharides.

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.

Vapor-Sensitive Materials from Polysaccharide Fibers with Self-Assembling Twisted Microstructures.

Polysaccharides play a variety of roles in nature, including molecular recognition and water retention. The microscale structures of polysaccharides are seldom utilized in vitro because of the difficulties in regulating self-assembled structures. Herein, it is demonstrated that a cyanobacterial polysaccharide, sacran, can hierarchically self-assemble as twisted fibers from nanoscale to microscale with diameters of ≈1 µm and lengths >800 µm that are remarkably larger than polysaccharides previously reported. Unlike other rigid fibrillar polysaccharides, the sacran fiber is capable of flexibly transforming into two-dimensional (2D) snaking and three-dimensional (3D) twisted structures at an evaporative air-water interface. Furthermore, a vapor-sensitive film with a millisecond-scale response time is developed from the crosslinked polymer due to the spring-like behavior of twisted structures. This study increases understanding of the functions of fibers in nature and establishes a novel approach to the design of environmentally adaptive materials for soft sensors and actuators.

Cationic Polymer Brush/Giant Polysaccharide Sacran Assembly: Structure and Lubricity.

A highly effective aqueous lubrication strategy employing electrostatic assembly of a negatively charged ultrahigh molecular weight natural polysaccharide named "sacran" and a positively charged poly[2-(methacryloyloxy)ethyltrimethylammonium chloride] (PMTAC) brush was investigated. The PMTAC brush was compressed through the adsorption of sacran to produce the layered structure of a PMTAC brush/sacran hybrid bottom layer and a poorly hydrated sacran top layer. The dynamic friction coefficients of the PMTAC brush were drastically reduced in salt-free sacran aqueous solutions, and the lubrication mode transition from the brush-lubrication regime to hydrodynamic lubrication was promoted. The electrostatic assembly was inhibited by the addition of NaCl into the lubricant solutions, leading to the loss of the lubrication effect. The hydrodynamic lubrication would be encouraged by the local viscosity enhancement at the friction boundary due to the poorly hydrated and highly viscous PMTAC brush/sacran hybrid film produced by the spontaneous electrostatic assembly.

Micelle-Mediated Self-Assembly of Microfibers Bridging Millimeter-Scale Gap To Form Three-Dimensional-Ordered Polysaccharide Membranes.

Micelle-mediated three-dimensional-ordered polysaccharide membranes are constructed by introducing cationic/anionic surfactant into a liquid crystalline polysaccharide solution. Upon drying mixtures of the polysaccharide solution with the surfactant such as cetyltrimethylammonium bromide or sodium dodecyl sulfate (SDS), the polymeric microfibers deposit as a nucleus to form a membrane, bridging millimeter-scale gap with high probability. In particular, in a solution with SDS micellar structures, the microscale fibers with diameter ∼1 µm disassemble into nanoscale fibers with diameter ∼50 nm. This transformation allows the polymeric network to become finer in nanoscale, and the vertical membrane is formed much more easily than that from a pure polysaccharide solution. Furthermore, it is clarified that the vertical membrane has been successfully formed with three-dimensionally ordered microstructures with a linearly oriented and layered structure. This method will shed light on the preparation of hybrid materials with biocompatibility and responsivity to stimuli such as magnetics, electrics, and optics via hybridization with nanomaterials dispersed by surfactants.

Development of Functional Bionanocomposites Using Cyanobacterial Polysaccharides.

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.

Drying-Induced Self-Similar Assembly of Megamolecular Polysaccharides through Nano and Submicron Layering.

We propose a self-similar assembly to generate planar orientation of megamolecular polysaccharides on the nanometer scale and submicron scale. Evaporating the aqueous liquid crystalline (LC) solution on a planar air-LC interface induces polymer layering by self-assembly and rational action of macroscopic capillary forces between the layers. To clarify the mechanisms of nanometer- and submicron-scale layering, the polymer films are investigated by electron microscopy.

Milliscale Self-Integration of Megamolecule Biopolymers on a Drying Gas-Aqueous Liquid Crystalline Interface.

A drying environment is always a proposition faced by dynamic living organisms using water, which are driven by biopolymer-based micro- and macrostructures. Here, we introduce a drying process for aqueous liquid crystalline (LC) solutions composed of biopolymer with extremely high molecular weight components such as polysaccharides, cytoskeletal proteins, and DNA. On controlling the mobility of the LC microdomain, the solutions showed milliscale self-integration starting from the unstable gas-LC interface during drying. In particular, we first identified giant rod-like microdomains (∼1 µm diameter and more than 20 µm length) of the mega-molecular polysaccharide, sacran, which is remarkably larger than other polysaccharides. These microdomains led to the formation of a single milliscale macrodomain on the interface. In addition, the dried polymer films on a solid substrate also revealed that such integration depends on the size of the microdomain. We envision that this simple drying method will be useful not only for understanding the biopolymer hierarchization at the macroscale level but also for preparation of surfaces with direction controllability, as seen in living organisms, for use in various fields such as diffusion, mechanics, and photonics.

Anionic complexes of MWCNT with supergiant cyanobacterial polyanions.

Multi-walled carbon nanotubes (MWCNTs) were well dispersed in an aqueous solution of the cyanobacterial polysaccharide, sacran, with an ultra-high molecular weight >10 million g/mol. MWCNTs powder was put into aqueous solutions of various polysaccharides including sacran and was dispersed under sonication. As a result of the turbidity measurement of the supernatant, it was found that sacran showed the highest MWCNT-dispersion efficiency of all the polysaccharides used here. Cryogenic transmission electron microscopic (Cryo-TEM) studies directly demonstrated the existence of MWCNTs in the supernatant, and high-resolution TEM observation revealed that MWCNTs covered by sacran chains made their efficient dispersion in water. Raman spectroscopy demonstrated the existence of MWCNT in dried sample from supernatant and the interaction between MWCNT and sacran. The ζ-potential measurement of the dispersion indicated the negative surface charges of the sacran/MWCNT complexes. Then the MWCNT complexes were able to fabricate by ionic interaction; electrophoresis of the anionic complex formed the sacran/MWCNT gels on the anode while the droplet of sacran/MWCNT dispersion formed gel beads in the presence of the lanthanoid cations.

Dataset of Sac/CNF-Ag nanocomposites for antibacterial properties.

The data in this article includes a variety of analysis, including swelling, viscosity and FT-IR to better understand the thermal-mechanical, viscoelastic and swelling properties of sacran, CNF, and Ag nanoparticles individually and collectively. The fabrication method of Sacran, CNF, and Sac/CNF-Ag composite films is also demonstrated in this data item and are related to the research article "Facile design of antibacterial sheets of sacran and nanocellulose". This data article summarizes all the information so that it is evident how silver nanoparticle-polysaccharide hydrogels might be employed as an on-demand dressings due to their proven ability to reduce bacterial viability.

Photoshrinkage in polysaccharide gels with trivalent metal ions.

The giant anionic polysaccharide "sacran", which is composed of 6-deoxyhexoses, pentoses, uronic acids as well as hexoses, showed hydrophobization and insolubilization phenomena in response to ultraviolet light irradiation. The sacran solution became turbid, and microparticles were formed by photoirradiation. To visualize the results of this photoreaction, anionic polysaccharide gels cross-linked by metal cations were used. As a result, we observed that sacran-gels with trivalent metal ions gradually contracted depending on the photoirradiation energy. In contrast, alginate gels used as a comparison degraded instead of contracting. This photoshrinkage of the sacran gels may be attributed to the hydrophobization of uronic acid based on photodecarboxylation. We propose that sacran-metal ion gels can function as effective, photoresponsive gels.

Anti-inflammatory effects of sacran, a novel polysaccharide from Aphanothece sacrum, on 2,4,6-trinitrochlorobenzene-induced allergic dermatitis in vivo.

BACKGROUND: Sacran is a newly discovered sulfated polysaccharide extracted from an algae, Aphanothece sacrum, grown in a river of the Kyushu region in Japan. OBJECTIVE: To evaluate sacran's inhibitory effect in 2,4,6-trinitrochlorobenzene (TNCB)-induced allergic dermatitis in NC/Nga mice. METHODS: Sacran was extracted by acid and alkaline treatment of A sacrum cyanobacterial biomaterials. To sensitize mice, 150 µL of 5% TNCB was applied epicutaneously on the abdomen of each mouse on day 1 and challenged with 15 µL of 1% TNCB applied on the ear skin of mice on day 8 and then every other day to induce skin lesions. Serum levels of inflammatory markers were measured and histopathologic examination of ear skin specimens performed. On the other hand, sacran's transepidermal water loss was evaluated in 11 volunteer women with dry skin. RESULTS: Epicutaneous application of sacran in mice has significantly inhibited the development of allergic dermatitis skin lesions and reduced the number of scratching behavior episodes (P < .01). In addition, sacran efficiently inhibited IgE (P < .001), tumor necrosis factor α (P = .02), interleukin 4, interleukin 5, and interferon γ (P < .01; vs buffer in the TNCB group) production and eosinophilic infiltration in the chemical allergen-exposed ear skin. In addition, sacran-treated body regions of human volunteers with dry skin significantly reduced transepidermal water loss levels compared with exogenous hyaluronic acid (P < .01), which is known to improve skin moisture and exert skin barrier repair activity. CONCLUSIONS: This study suggests that sacran exerts anti-inflammatory effects by improving skin barrier function and reducing T(H)2 cytokine production.

Anti-allergic effects of Vernonia amygdalina leaf extracts in hapten-induced atopic dermatitis-like disease in mice.

BACKGROUND: Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by pruritic and eczematous skin lesions. In this study, AD-like disease was induced in NC/Nga mice so as to evaluate the anti-allergic effects of Vernonia amygdalina leaf extracts (VAM). METHODS: Forty NC/Nga mice were purchased for each of the two protocols (prophylactic and curative) of the study. Mice were randomly divided in groups of five or six after sensitization with 5% trinitrochlorobenzene (TNCB): aqueous extracts (VAM1), methanolic extracts (VAM2), hydrocortisone (HCT), buffer for the control (TNCB) and the normal mice (NORM) groups. RESULTS: As for HCT, VAM1 and VAM2-pretreated mice showed significantly lower number of scratching behavior episodes (p < 0.01; vs. TNCB) following TNCB challenge. In addition, VAM1, VAM2 exerted a significant inhibitory effect on the development of AD skin symptoms (vs. TNCB group; p < 0.001), the production of IgE, TNF-alpha (p < 0.05), IL-5 and IFN-gamma (p < 0.01) (vs. TNCB group) and on the increase in ear thickness (p < 0.05) in prophylactic protocol. In the AD curative protocol, topical VAM1, VAM2 markedly improved skin lesions such as erythema/hemorrhage (p < 0.05), scaling/dryness, erosion/excoriation (p < 0.01) (vs. TNCB mice). Furthermore, a significant decrease in ear thickness was noted in VAM1, VAM2, HCT groups (vs. TNCB group; p < 0.05) as well as the serum total IgE, MCP-1 (p < 0.01) and eotaxin (p < 0.05). VAM2 also improved chronic eczema dermatitis skin symptoms in a patient. CONCLUSIONS: Results from this report suggest that VAM extracts, known as ERK pathway inhibitor, prevent and improve atopic/eczema dermatitis syndrome.

Interfacial self-assembly of polysaccharide rods and platelets bridging over capillary lengths.

HYPOTHESIS: Generation of long-range ordering of colloidal particles through anisotropic interactions is of growing interest in material designing. At submicron-scale, routine works use synthetic spheres or rods but the knowledge pertaining to assembly of binary combination of particles is severely restricted. Improved understanding of the fundamental aspects that drive self-assembly, can lead to robust strategies for fabrication of topographically oriented films. EXPERIMENT: The fluidical geometry of a liquid crystalline (LC) solution of polysaccharide consisting of micron-sized rod and platelet units was explored. The solutions, characterized for their rheological behavior, were evaporated from a rectangular cavity. The assembly and orientation of the units was monitored by polarizing microscopy and the interparticle capillary forces approximated mathematically. FINDINGS: The units deposited into an uninterrupted membrane upon interfacial evaporation, forming a bridge along the 8 mm gap, linking the substrates. The membrane, composed of a lamellar structure, was uniaxially oriented along the direction of the gap. The rheological estimations corroborated an extremely high value of viscosity with the presence of crosslinking junctions in this solution when compared to a solution with only rod units, capable of bridging a maximum of 1 mm. It has been demonstrated for the very first time that the presence of platelet-units contributes lateral capillary interactions and assist rod-units towards a wider, self-assembled structure.

Cyanobacterial polysaccharide gels with efficient rare-earth-metal sorption.

The cyanobacterial polysaccharide sacran, which contains carboxylate and sulfate groups, was extracted from Aphanothece sacrum , and the metal sorption behavior of sacran was investigated. Heterogels, where the sacran chains were trapped by polyvinyl alcohol networks, were prepared and immersed in NdCl3 solutions to shrink and cloud due to Nd binding. These heterogels had the ability to sorb excessive amounts of Nd ions, more than the stoichiometric ratio of 1:3 (sacran anion/Nd). Furthermore, the sacran-containing gels sorbed Nd ions under highly acidic conditions below pH 2 more efficiently than alginate-containing gels. We speculated that the strong Nd condensation effect of the sulfate groups in sacran under the acidic conditions may enhance the Nd sorption to the carboxylate groups.

Gelation behavior by the lanthanoid adsorption of the cyanobacterial extracellular polysaccharide.

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.

Rheopectic Behavior for Aqueous Solutions of Megamolecular Polysaccharide Sacran.

The rheopectic behavior of sacran aqueous solutions, a natural giant molecular polysaccharide with a molecular weight of 1.6 × 107 g/mol, was investigated. When a low shear was applied to 1.0 wt.% sacran solution, the shear viscosity increased from 7.2 to 34 Pas. The increment in the viscosity was enhanced as the shear rate decreased. The shear viscosity was independent of the time at a shear rate of 0.8 s-1; simultaneously, thixotropic behavior was observed at shear rates higher than 1.0 s-1. A crossover was observed at 0.15 wt.% for the concentration dependence of both the viscosity increase and zeta potential, which was the vicinity of the helix transition concentration or gelation concentration. It was clear that the molecular mechanism for the rheopexy was different at lower and higher regions of the crossover concentration.

Cyanobacterial megamolecule sacran efficiently forms LC gels with very heavy metal ions.

We extracted the megamolecular polysaccharide sacran, which contains carboxylate and sulfate groups, from the jellylike extracellular matrix (ECM) of the cyanobacterium Aphanothece sacrum, which has mineral adsorption bioactivity. We investigated the gelation properties of sacran binding with various heavy metal ions. The sacran chain adsorbed heavier metal ions such as indium, rare earth metals, and lead ions more efficiently to form gel beads. In addition, trivalent metal ions adsorbed onto the sacran chains more efficiently than did divalent ions. The investigation of the metal ion binding ratio on sacran chains demonstrated that sacran adsorbed gadolinium trivalent ions more efficiently than indium trivalent ions. Gel bead formation may be closely correlated to the liquid-crystalline organization of sacran.

[Super Liquid Crystalline Polysaccharides Produced by Ultimately-ecological Microreactors].

　Cyanobacteria fix carbon dioxide and nitrogen from the atmosphere using solar energy to produce various biomolecules, and thus are regarded as ultimately ecological microreactors. Sacran is a cyanobacterial polysaccharide with a very high molecular weight of 29 Mg/mol, which is extracted from Aphanothece sacrum cyanobacterium mass-cultivated in freshwater environments such as river or spring. Sacran is a water-soluble heteropolysaccharide comprising more than 6 kinds of sugar residues and contains 12% sulfate anionic groups and 27% carboxyls. Sacran has a super-absorbent function of water, which can retain 6000 mL for 1 g specimen, due to very long hydrating chains. The value is much higher than hyaluronic acid or conventional super-absorbent polymers. Sacran exhibits self-orienting behavior in dilute solution at a concentration range over 0.25 wt%, which is quite low when compared with conventional liquid crystalline polysaccharides. Mesogenic helical chains of sacrans have extremely high aspect ratios of 1600 for highly persistent lengths of 32 micrometer. Through the liquid crystallinity, sacran solution shows a shear-thinning behavior and the solution spread over a substrate such as biological skin very efficiently to create a thin layer. Applied on atopic dermatitis skin sacran solution exerts excellent moisturizing effect and anti-itching action.

[Unidirectionally-oriented Membrane Formation of Supra-polysaccharides Sacran and Application to Drug Delivery System].

　The geometric structures of soft materials can be controlled on the macro-scale using interfacial or mechanical instability, e.g., fingering patterns of viscous liquid and buckling patterns of gels during swelling/deswelling. These patterns can be used as smart materials for capturing/releasing and mass-transportation applications. Here we introduce the emergence of a uniaxially oriented membrane by drying an aqueous liquid-crystalline solution, composed of megamolecular supra-polysaccharides "sacran", from a limited space. By controlling the geometries of the evaporation front, multiple nuclei emerge that grow into upright membranes with uniaxial orientation. Notably, the uniaxially orientated membrane composed of rod-like microdomains is rationally formed along the dynamic three-phase contact line. Besides, the membrane macroscopically partitions the three-dimensional cuboid cell for evaporating the aqueous solution. We envision that such a uniaxially oriented membrane can be used as soft biomaterials such as dialysis membranes with directional controllability in medical and pharmaceutical fields.