Comparison of curdlan and its carboxymethylated derivative by means of Rheology, DSC, and AFM

Unlocking the potential of beta-glucans: a comprehensive review from synthesis to drug delivery carrier potency

Modernization and lifestyle changes have resulted in a number of diseases, including cancer, that require complicated and thorough treatments. One of the most important therapies is the administration of antibiotics and medicines. This is known as chemotherapy for cancer, and it is a regularly utilised treatment plan in which the medications used have negative side effects. This has resulted in extensive research on materials capable of delivering pharmaceuticals to particular targets over an extended period of time. Biopolymers have often been preferred as effective drug delivery carriers. Of these, β-glucan, a natural polysaccharide, has not been extensively studied as a drug delivery carrier, despite its unique properties. This review discusses the sources, extraction techniques, structures, and characteristics of β-glucan to provide an overview. Furthermore, the different methods employed to encapsulate drugs into β-glucan and its role as an efficient drug, SiRNA and Plasmid DNA carrier have been elaborated in this article. The capacity of β-glucan-based to specifically target and alter tumour-associated macrophages, inducing an immune response ultimately resulting in tumour suppression has been elaborated. Finally, this study aims to stimulate further research on β-glucan by thoroughly describing its many characteristics and demonstrating its effectiveness as a drug delivery vehicle.

Combined experiments and molecular simulations for understanding the thermo-responsive behavior and gelation of methylated glucans with different glycosidic linkages

HYPOTHESIS

Elucidation of the micro-mechanisms of sol-gel transition of gelling glucans with different glycosidic linkages is crucial for understanding their structure-property relationship and for various applications. Glucans with distinct molecular chain structures exhibit unique gelation behaviors. The disparate gelation phenomena observed in two methylated glucans, methylated (1,3)-β-d-glucan of curdlan (MECD) and methylated (1,4)-β-d-glucan of cellulose (MC), notwithstanding their equivalent degrees of substitution, are intricately linked to their unique molecular architectures and interactions between glucan and water.

EXPERIMENTS

Density functional theory and molecular dynamics simulations focused on the electronic property distinctions between MECD and MC, alongside conformational variations during thermal gelation. Inline attenuated total reflection Fourier transform infrared spectroscopy tracked secondary structure alterations in MECD and MC. To corroborate the simulation results, additional analyses including circular dichroism, rheology, and micro-differential scanning calorimetry were performed.

FINDINGS

Despite having similar thermally induced gel networks, MECD and MC display distinct physical gelation patterns and molecular-level conformational changes during gelation. The network of MC gel was formed via a "coil-to-ring" transition, followed by ring stacking. In contrast, the MECD gel comprised compact irregular helices accompanied by notable volume shrinkage. These variations in gelation behavior are ascribed to heightened hydrophobic interactions and diminished hydrogen bonding in both systems upon heating, resulting in gelation. These findings provide valuable insights into the microstructural changes during gelation and the thermo-gelation mechanisms of structurally similar polysaccharides.

Rheology and gelation of aqueous carboxymethylated curdlan solution: Impact of the degree of substitution

Curdlan is a unique (1,3)-β-D-glucan with bioactivity and exceptional gelling properties. By chemical functionalization such as carboxymethylation, the physicochemical properties of curdlan can be significantly tailored. However, how the carboxymethylation extent of curdlan affects its rheology and gelation characteristics has yet to be fully understood. Herein, we investigated the impact of the degree of substitution (DS, ranging from 0.04 to 0.97) on the rheological and gelation behavior of carboxymethylated curdlan (CMCD). It was found that CMCD with DS below 0.20, resembling native curdlan, still retained its gelling capability. As the DS increased beyond 0.36, there was a significant increase in its water solubility instead of gelation, resulting in transparent solutions with steady/complex viscosities adhering to the Cox-Merz rule. Moreover, CMCD with high DS demonstrated the ability to undergo in-situ gelation in the presence of metal ions, attributed to the nonspecific electrostatic binding. Additionally, in vitro cytocompatibility testing showed positive compatibility across varying DS in CMCD. This research offers a holistic understanding of the viscosifying and gelling behaviors of CMCD with varying DS, thereby fostering their practical application as thickeners and gelling agents in fields ranging from food and biomedicine to cosmetics and beyond.

Curdlan-polyphenol complexes prepared by pH-driven effectively enhanced their physicochemical stability, antioxidant and prebiotic activities

In this study, the curdlan-polyphenol complexes were constructed by a pH-driven method. The interaction between curdlan and various hydrophobic polyphenols (curcumin, quercetin, and chlorogenic acid) was investigated. Curdlan could self-assemble into particles for loading polyphenols through hydrogen bonding and hydrophobic interactions. The three polyphenols were embedded in curdlan in an amorphous state. The curdlan-curcumin complex showed the lowest viscoelasticity but exhibited the highest curcumin loading ability (34.04 ± 1.73 mg/g). However, the curdlan-chlorogenic acid complex emerged the opposite trend, indicating that the loading capacity was associated with the hydrophobicity of polyphenols. The antioxidant activity of curdlan significantly increased after combining with polyphenols, which could be maintained during in vitro simulated gastrointestinal digestion. In particular, the curdlan-quercetin complex exhibited the highest antioxidant activity and short-chain fatty acid concentration, which could influence gut microbiota composition by promoting the proliferation of Prevotella and inhibiting the growth of Escherichia_Shigella. In conclusion, the curdlan-polyphenol complexes prepared by an alcohol-free pH-driven method could effectively enhance the gastrointestinal stability of polyphenols as well as increase the antioxidant and prebiotic activities of curdlan, which could be applied as a functional ingredient to improve gut health.

Comparative study on chain conformations, physicochemical and rheological properties of three acidic polysaccharides from Opuntia dillenii Haw. fruits

In this study, three acidic polysaccharides (OFPP-1, OFPP-2 and OFPP-3) were isolated from the pulps of Opuntia dillenii Haw. fruits, and their chain conformations, physicochemical and rheological properties were investigated. The molecular weight and conformational parameters (Mw, Mn, Mz, Rg and Rh) of OFPPs in 0.1 M NaNO3 solution were detected by HPSEC-MALLS-RI. In addition, based on the parameters ρ and v, it was concluded that these three polysaccharide chains exhibited sphere-like conformation in 0.1 M NaNO3 solution, which was consistent with AFM and TEM observations. Furthermore, the Congo Red experiment showed that OFPP-2 had a triple-helix structure, which may be conducive to its biological activity. This study also found that OFPPs were semi-crystalline structures with high thermal and pH stability. The rheological analyses indicated that the apparent viscosity of OFPPs solutions exhibited concentration-, temperature-, and pH-dependence, and the viscoelasticity of them was affected by molecular characteristics and concentration. The results of this study are helpful to elucidate the structure-activity relationship of OFPPs. Moreover, this study can provide theoretical reference for the application of OFPPs as bioactive ingredients or functional materials in the food, pharmaceutical and cosmetic industries and the development and utilization of the O. dillenii Haw. fruits resource.

A novel curdlan/methyl cellulose/walnut green husk polyphenol edible composite film for walnut packaging

In this study, polyphenols were extracted from walnut green husk, an agricultural waste, and were incorporated into curdlan (CD) and methyl cellulose (MC) to create a novel edible composite film. For structural character, the film matrix was tightly bound primarily by non-covalent bonds and the addition of walnut green husk polyphenols (WGHP) significantly reduced the surface roughness of the composite film. For mechanical properties, the addition of WGHP improve the flexibility of films, and it significantly improved the barrier ability of ultraviolet rays and water-vapor. Furthermore, the incorporation of WGHP to the CD-MC film resulted in enhanced antioxidant and antibacterial effects, which effectively retards lipid oxidation in fried walnuts. Consequently, the fabricated CD-MC-WGHP composite film bears immense potential for use in food preservation applications, particularly in extending the shelf life of fried walnuts.

High-moisture extrusion of curdlan: Texture and structure

High-moisture extrusion is a promising thermomechanical technology extensively employed in manufacturing fibrous meat analogues from plant-based proteins, garnering considerable research attention. However, polysaccharide-based extrusion has been rarely explored. The present study investigates the effects of varying extruder barrel temperatures (130 °C-200 °C) on the texture and structure of curdlan extrudates, and highlights the formation mechanism. Results showed that the single chain of curdlan aggregates to form triple-helix chains upon extrusion, consequently enhancing the crystallinity, particularly at 170 °C. The hardness, chewiness, and mechanical properties improved with increasing barrel temperature. Moreover, barrel temperatures affected the macrostructure, the extrudates maintained intact morphologies except at 160 °C due to the melting of curdlan gel as confirmed by the differential scanning calorimetry thermogram. Microstructural analysis revealed that curdlan extrudates transited through three phases: original gel (130 °C, 140 °C, and 150 °C), transition state (160 °C), and regenerated gel (170 °C, 180 °C, 190 °C, and 200 °C). The steady state of regenerated gel (170 °C) exhibited higher crystallinity and smaller fractal dimension, resulting in a more compact and crosslinked gel network. This study elucidates the structure transition of curdlan gel at extremely high temperatures, offering valuable technical insights for developing theories and methods with respect to polysaccharide-based extrusion that may find applications in food-related fields.

Do Curdlan Hydrogels Improved with Bioactive Compounds from Hop Exhibit Beneficial Properties for Skin Wound Healing?

Chronic wounds, among others, are mainly characterized by prolonged inflammation associated with the overproduction of reactive oxygen species and pro-inflammatory cytokines by immune cells. As a consequence, this phenomenon hinders or even precludes the regeneration process. It is known that biomaterials composed of biopolymers can significantly promote the process of wound healing and regeneration. The aim of this study was to establish whether curdlan-based biomaterials modified with hop compounds can be considered as promising candidates for the promotion of skin wound healing. The resultant biomaterials were subjected to an evaluation of their structural, physicochemical, and biological in vitro and in vivo properties. The conducted physicochemical analyses confirmed the incorporation of bioactive compounds (crude extract or xanthohumol) into the curdlan matrix. It was found that the curdlan-based biomaterials improved with low concentrations of hop compounds possessing satisfactory hydrophilicity, wettability, porosity, and absorption capacities. In vitro, tests showed that these biomaterials were non-cytotoxic, did not inhibit the proliferation of skin fibroblasts, and had the ability to inhibit the production of pro-inflammatory interleukin-6 by human macrophages stimulated with lipopolysaccharide. Moreover, in vivo studies showed that these biomaterials were biocompatible and could promote the regeneration process after injury (study on Danio rerio larvae model). Thus, it is worth emphasizing that this is the first paper demonstrating that a biomaterial based on a natural biopolymer (curdlan) improved with hop compounds may have biomedical potential, especially in the context of skin wound healing and regeneration.

Emulsifying properties and bioavailability of clove essential oil Pickering emulsions stabilized by octadecylaminated carboxymethyl curdlan

In the present study, clove essential oil (CEO) Pickering emulsions were stabilized by octadecylamine-modified carboxymethyl curdlan (CMCD-ODA) at different pH values. The droplet size and negatively charged zeta potential of the CMCD-ODA emulsions decreased as the pH increased from 3.0 to 11.0. Rheology results indicated that the CMCD-ODA polymer/emulsion prepared at pH 5.0 showed higher apparent viscosity and viscoelasticity than other pH conditions, which might prevent droplets from flocculating. The Pickering emulsions obtained at pH 5.0 were spherical droplets with a uniform size distribution and a mean diameter of 9.54 μm, and they exhibited excellent stability during 28 days of storage. The morphological structures of the emulsions investigated by confocal laser scanning microscopy and scanning electron microscopy indicated that the CMCD-ODA Pickering emulsion obtained at pH 5.0 was stabilized by loading amphiphilic CMCD-ODA polymer around the spherical oil droplets and forming a weak gel network structure. The CEO-loaded CMCD-ODA emulsions had higher antioxidant capacity than free CEO after 28 days of storage at pH 5.0. Given the good emulsion stability, antioxidant activity, and great antibacterial effect, the CEO-loaded carboxymethyl curdlan Pickering emulsion has promising applications in food, cosmetic, and biomedicine industries.

Isolation, purification, structural characterization, and hypoglycemic activity assessment of polysaccharides from Hovenia dulcis (Guai Zao)

Hovenia dulcis polysaccharides (HDPs) have a variety of important biological activities associated with potential applications in food engineering, pharmacy science, and health care. Herein, we isolated and purified polysaccharides from H. dulcis. Chemical composition analysis revealed that the purified polysaccharides (HDPs-2A) were composed of different molar ratios of mannose, Rha, GalA, GlcA, Glc, Gal, and Ara and had a molecular weight of 372.91 kDa. The structure of HDPs-2A was assessed by FT-IR, periodate oxidation, Smith degradation, methylation analysis, and NMR, allowing us to determine that the backbone of HDPs-2A is composed primarily of →5)-α-L-Araf-(1→, →5)-α-L-Araf-(1→, →3,5)-α-L-Araf-(1→, →6)-β-D-Galp-(1→, →3,6)-β-D-Galp-(1→, T-β-D-Galp, →3)-β-D-Galp-(1→, and T-α-D-Glcp. The results of atomic force microscopy (AFM) showed that HDPs-2A present an irregular polymer particle morphology in water. X-ray diffraction (XRD) results showed that HDPs-2A have a single crystal structure. Finally, we demonstrated that HDPs-2A have a good therapeutic effect on a rat model of type 2 diabetes.

Curdlan production from cassava starch hydrolysates by Agrobacterium sp. DH-2

Curdlan is an edible microbial polysaccharide and can be used in food, biomedical and biomaterial fields. To reduce the cost of curdlan production, this study investigated the suitability of cassava starch hydrolysates as carbon source for curdlan production. Cassava starch was hydrolyzed into maltose syrup using β-amylase and pullulanase at various enzyme dosages, temperature, time and addition order of two enzymes. The maltose yield of 53.17% was achieved at starch loading 30% by simultaneous addition β-amylase 210 U/g starch and pullulanase 3 U/g starch at 60 °C for 9 h. Cassava starch hydrolysates were used as carbon source for curdlan production by Agrobacterium sp. DH-2. The curdlan production reached 28.4 g/L with the yield of 0.79 g/g consumed sugar and molecular weight of 1.26 × 10⁶ Da at 96 h with cassava starch hydrolysate at 90 g/L initial sugar concentration. Curdlan produced from cassava starch hydrolysates was characterized using FT-IR spectra and thermo gravimetric analysis. This work indicated that cassava starch was a potential renewable feedstock for curdlan production.

Freeze-thaw and solvent-exchange strategy to generate physically cross-linked organogels and hydrogels of curdlan with tunable mechanical properties

Physical gels from natural polysaccharides present the advantage of no toxic cross-linking agents and no chemical modification during preparation. Herein, novel physical gels, transparent organogels and opaque hydrogels from the microorganism-derived (1,3)-β-D-glucan of curdlan were prepared in dimethyl sulfoxide (DMSO) using the freeze-thaw technique, followed by a solvent-exchange strategy with water. The mechanical and structural properties of these gels were investigated by rheology, scanning electron microscopy, attenuated total reflection infrared spectroscopy, wide-angle X-ray diffraction and small-angle X-ray scattering. Gelation mechanisms and intermolecular interaction models have also been proposed. The good solvent DMSO serves as both a crosslinker and a pore-foaming agent in organogels. The reversible macromolecular conformation changes and phase separation of curdlan endow the gels with reversible transparency, volume change and tunable mechanical strength. The new design strategy of facile preparation and performance tuning provides a platform for developing new organogels and sterile hydrogels of curdlan.

Polyvinyl alcohol inclusion can optimize the sol-gel, mechanical and hydrophobic features of agar/konjac glucomannan system

The practical features (e.g., sol-gel, mechanical and hydrophobic) of biopolymer systems are crucial for their materials applications. This work reveals how polyvinyl alcohol (PVA) inclusion affects the practical features of agar/konjac glucomannan (KGM) system. From rheological analysis, incorporating PVA (especially 6%) enhanced the chain entanglements of resulted ternary solution (A₇₀K₂₄P₆) with stabilized sol-gel transition point. Such effect not only increased the zero-shear viscosity (ca. 1.5 times that of agar/KGM counterpart) and structural recovery degree of A₇₀K₂₄P₆ solution, but also caused reduced crystallites and simultaneously increased tensile strength, elongation at break and hydrophobicity for A₇₀K₂₄P₆ film from solution dehydration. This ternary film exhibited a tensile strength of ca. 105 MPa, an elongation at break of ca. 20%, and a water contact angle of ca. 97.6°. Additionally, incorporating PVA almost unaffected the morphology of film fracture surface. These results are valuable for the design of agar/KGM systems with improved practical features.

Deacetylation enhances the properties of konjac glucomannan/agar composites

From a microstructural point of view, this work concerns how deacetylation improves the practical characteristics of deacetylated-konjac glucomannan/agar (DK/A) composite films. As disclosed by infrared spectroscopy and X-ray diffraction, the deacetylation of konjac glucomannan (KGM) enhanced the chain interactions in DK/A composites and suppressed the realignment of agar molecules into crystallites. The enhanced associations between acetyl-free regions of KGM and agar reduced the exposure of OH groups and thus increased the hydrophobicity of the composites. Besides, the partial removal of acetyl groups allowed shortened distances between chains; consequently, denser composite matrices emerged with lower water vapor permeability and higher tensile strength. Also, the KGM deacetylation increased the matrix flexibility and elongation at break for DK/A composites, associated with the hindered rearrangement of agar chains. Thus, altering the deacetylation degree of KGM may be an effective way to design KGM-based composites with improved hydrophobicity and mechanical performance.

The effect of carboxymethylation on the macromolecular conformation of the (1 → 3)-β -D-glucan of curdlan in water

The chain conformational change in curdlan during carboxymethylation was investigated using nuclear magnetic resonance (NMR), circular dichroism (CD) spectroscopy, and atomic force microscopy (AFM). The distributions of carboxymethyl substituents within anhydroglucose unit (AGU) of CMCD were found to follow the order of OH (6) > OH (4) > OH (2) for CMCD with a low DS and OH (6) > OH (2) > OH (4) for CMCD with relatively high DS. The increased carboxymethylation level induced the chain conformation transition of curdlan from triple helix to random coil in water. The DS of 0.25 was the critical value of chain conformation transition, below which CMCD chains were triple helices. For DS larger than 0.25, CMCD existed in the state of random coils. The intermolecular hydrogen bonding between C2 hydroxyls in AGU sustained the triple helical conformation and stiffness of the polymer chain, which weakened with the increase in DS.

Understanding the Effect of Conformational Rigidity on Rheological Behavior and Formation of Polysaccharide-Based Hybrid Hydrogels

The importance of conformational rigidity on macroscopic rheological properties was revealed using two model polysaccharides, namely, xanthan gum and hyaluronic acid. Xanthan gum has a rigid tertiary conformation due to its ordered double-helical structure, and the interactions between the tertiary structures result in the formation of a network/quaternary structure. In comparison, hyaluronic acid possesses a relatively flexible tertiary conformation due to its secondary random coil structure. Xanthan gum exhibits a much stronger shear thinning and more solidlike behavior compared to hyaluronic acid, owing to its network/quaternary structure. The rigid tertiary structure and the presence of a network/quaternary structure also endow xanthan gum with better resistance against environmental changes (e.g., salt and/or urea addition, temperature change) compared to hyaluronic acid. The network/quaternary structure allows xanthan gum to form gels with chitosan via electrostatic interactions when using the vapor-induced gelation technique, which is not possible for hyaluronic acid due to its flexible tertiary conformation under similar conditions.

Molecular dynamic simulation: Structural insights of multi-stranded curdlan in aqueous solution

In this work, by using molecular dynamic simulation we provide microscale structure information which helps to reveal the molecular mechanisms concerning the multi-chain conformational behavior of short curdlan. Through simulations starting with different conformations of curldan dodecasaccharides, it is found that the right-handed triple helix is thermodynamically the most stable conformation in aqueous solutions, which is well maintained and stabilized by an inter-strand hydrogen bonding network of the C₂ hydroxyls. Unlike any predicted forms, the inter-strand hydrogen bonds exhibit a left-handed double helix pattern with preferred global orientations. Temperature REMD results suggest that the formation of triple helix is temperature sensitive, but the already formed triple helix is not. Investigation of curdlan with numbers of repeating units from 3 to 12 captures a critical value of 6, which in a way elucidates the relationship between the formation of triple helix and the chain length.

Recent advances in the production of biomedical systems based on polyhydroxyalkanoates and exopolysaccharides

In recent years, growing attention has been devoted to naturally occurring biological macromolecules and their ensuing application in agriculture, cosmetics, food and pharmaceutical industries. They inherently have antigenicity, low immunogenicity, excellent biocompatibility and cytocompatibility, which are ideal properties for the design of biomedical devices, especially for the controlled delivery of active ingredients in the most diverse contexts. Furthermore, these properties can be modulated by chemical modification via the incorporation of other (macro)molecules in a random or controlled way, aiming at improving their functionality for each specific application. Among the wide variety of natural polymers, microbial polyhydroxyalkanoates (PHAs) and exopolysaccharides (EPS) are often considered for the development of original biomaterials due to their unique physicochemical and biological features. Here, we aim to fullfil a gap on the present associated literature, bringing an up-to-date overview of ongoing research strategies that make use of PHAs (poly (3-hydroxybutyrate), poly (3-hydroxybutyrate-co-3-hydroxyvalerate), poly (3-hydroxyoctanoate), poly(3-hydroxypropionate), poly (3-hydroxyhexanoate-co-3-hydroxyoctanoate), and poly (3-hydroxybutyrate-co-3-hydroxyhexanoate)) and EPS (bacterial cellulose, alginates, curdlan, pullulan, xanthan gum, dextran, hyaluronan, and schizophyllan) as sources of interesting and versatile biomaterials. For the first time, a monograph addressing the properties, pros and cons, status, challenges, and recent progresses regarding the application of these two important classes of biopolymers in biomedicine is presented.

Effect of alkali-neutralization treatment on triple-helical aggregates and independent triple helices of curdlan

Triple-helical aggregates (THAs) have been proven to affect the biological activities and functional properties of triple-helix polysaccharides. Thus, it's urgent to seek a method to reduce the size of THAs while preserving independent triple helices (ITHs). In this study, the effects of alkali-neutralization (AN) treatment on THAs and ITHs of curdlan were studied. The positive values of the Congo red test data (R²>0.99) fitted using a Logistic model indicated that AN treatment (C_NaOH/HCl>0.28 mol/L) facilitated the disaggregation of THAs. Congo red test, sedimentation test, and turbidity test showed that AN treatment (C_NaOH/HCl = 1.0 mol/L) significantly reduced the size of THAs to approximately 1 μm while effectively increasing the relative amount of ITHs to approximately 199 %. Fourier transform infrared spectroscopy and X-ray diffraction analysis showed that AN treatment basically unchanged the primary structure of curdlan chains, but affected the crystalline structure and the intermolecular and intramolecular hydrogen bonding of curdlan.

Quality characteristics of fortified silver carp surimi with soluble dietary fiber: Effect of apple pectin and konjac glucomannan

The study focused on assessing quality parameters of the surimi incorporated with soluble dietary fibers apple pectin and konjac glucomannan at different levels. The results showed that apple pectin at 0.025% and konjac glucomannan at a 2% level exhibited improved gel-forming ability significantly (p < 0.05). SDS- PAGE revealed high molecular weight protein crosslinks in apple pectin treated surimi gels and disappearance of myosin bands in konjac glucomannan treated surimi gels. The water holding capacity of surimi was the highest when 0.075 g/100 g of apple pectin was added. Konjac glucomannan treated gels exhibited superior whiteness values. The analysis of soluble protein revealed that hydrophobic bonds increased in both the treatments. The hardness values of pectin gels enhanced as the level increased. Other TPA parameters are shown an inconsistent trend. It can be demonstrated that the incorporation of apple pectin and konjac glucomannan at a level of 0.025 and 2.0% may be a novel strategy to improve the gel strength of the surimi.

A freeze-thawing method applied to the fabrication of 3-d curdlan/polyvinyl alcohol hydrogels as scaffolds for cell culture

In this work, an innovative composite hydrogel composed of curdlan (CD)/polyvinyl alcohol (PVA) hydrogels with a 3-d network structure was successfully prepared by freeze-thaw processing. The presence of interactions, changes in crystallinity, and thermal behaviour were investigated by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and thermogravimetry (TGA and DTG), respectively. The morphology of the hydrogels was investigated by scanning electron microscopy (SEM). With the increase of PVA concentration, the composite hydrogel had a greater mechanical strength while remaining remarkably ductile as evinced by tensile test results. PVA content affects the swelling and water retention of CD/PVA hydrogels. The results of CCK-8 assay showed that CD/PVA hydrogels have no cytotoxic effect on the mouse fibroblast L929 cells. The AO/EB double-staining experiment further proved that the cells in the composite hydrogels had good cytocompatibility. The porous biohydrogels developed in the present work can provide an ideal cell growth environment as a scaffold. CD/PVA hydrogels highlight the value of this system for cell adhesion and proliferation, and further soft tissue engineering application.

DSC and TMA Studies of Polysaccharide Physical Hydrogels

Various kinds of polysaccharides found in a wide variety of plants, bacteria, crustaceans and insects form hydrogels via physical aggregation in aqueous media. The major mass of hydrogels is water filled, ca. 95 - 99.5%, in a network structure, although the solid shape of the gel is maintained. In this paper, firstly the wide range of gelation mechanisms are briefly described, and then the thermal analysis of representative gel-forming polysaccharides, such as carrageenan, alginate, galactomannan, and pectin, is introduced. By differential scanning calorimetry (DSC), gel-sol and the sol-gel transition temperature of thermoreversible hydrogels are measured and phase diagram is established. It is suggested that binary systems showing sinusoidal gel-sol-gel transition are capable of being assembled. By thermomechanical analysis (TMA), the dynamic modulus (E') at around 1 × 104 Pa of thermo-irreversible hydrogels was obtained using a sample holder designed to measure the viscoelastic properties in water. Reliable coordination is shown between the results obtained by DSC and TMA. In this review, the current research and several topics on concerning the thermal properties of polysaccharide physical hydrogels are introduced.

Impact of heating and drying temperatures on the properties of konjac glucomannan/curdlan blend films

The impact of preparation conditions including heating temperature (from 60 °C to 90 °C) and drying temperatures (from 25 °C to 90 °C) on the properties of pure curdlan film and konjac glucomannan (KGM) and curdlan blend films were analyzed. Microstructure analysis indicated the KGM addition could significantly improve the relatively poor film-forming property of curdlan. FTIR and X-ray analysis showed that at high heating temperature 90 °C, molecular interaction might be enhanced in the films due to the stretched structure of curdlan and dissociation of curdlan bundles or triple-helix structure. This was supported by the changes in the mechanical property, surface hydrophobicity, moisture barrier, and moisture tolerance property. The impacts of drying temperature were some different for the curdlan film and KGM/curdlan blend film, and were explained from the molecular hydrophilicity-hydrophobicity, compactness of the films, curdlan conformation, and molecular interaction. This work guided biodegradable film production especially with curdlan added.

Beta-d-glucan-based drug delivery system and its potential application in targeting tumor associated macrophages

Use of polysaccharides as carriers in drug delivery system is a hot topic, especially those with specific recognition of immune cells, enabling them to be applied in targeting delivery system. β-d-glucans are naturally occurring non-digestible polysaccharides with immunomodulatory activities that have attracted increasing attention to serve as therapeutic agents or immune-adjuvants. Being able to be specifically recognized by immune cells like macrophages, β-d-glucans can be developed as promising carriers for targeting delivery with stability, biocompatibility and specificity when applied in immunotherapy. Targeting tumor associated macrophages (TAMs) is an emerging strategy for cancer immunotherapy since it exerts anti-cancer effects based on modulating body immunity in tumor microenvironment (TME). This new strategy does not require high concentration of drugs to kill cancer cells directly and lessen tumor recurrence by creating unique immune memory for malignant cells. In this review, construction strategies of polysaccharide-based drug delivery system of three types of β-d-glucan including non-yeast and yeast β-d-glucans as well as hyper-branched β-d-glucan are discussed with reference to their branching characteristics and conformation. The applications of these β-d-glucans as nano-carrier for drug delivery targeting TAMs are also discussed.

Sulfoethylation of polysaccharides-A comparative study

The heterogeneous sulfoethylation of cellulose, xylan, α-1,3-glucan, glucomannan, pullulan, curdlan, galactoglucomannan, and agarose was studied using sodium vinylsulfonate (NaVS) as reagent in presence of sodium hydroxide and iso-propanol (i-PrOH) as slurry medium. The influence of the concentration of polymer, water, and NaOH (solid or aqueous solution) on the degree of substitution (DS) was investigated. The sulfoethylation rendered the polysaccharides studied water-soluble. Sulfoethylation of heteropolysaccharides yielded products with higher DS compared to the conversion of homopolysaccharides. Structure characterization was carried out by means of ¹³C-NMR spectroscopy.

Molecular dynamic simulation: Conformational properties of single-stranded curdlan in aqueous solution

Recently, molecular dynamic simulation technique has been proved to be a powerful tool providing structural insights for better understanding the functionality of carbohydrates. Here, by using molecular dynamic simulation method we investigated the detailed conformational properties of the single-stranded curdlan with 12 glucose units. The results showed that the right-handed 6/1 helix structure was thermodynamically the most stable conformation in solution. The formation of the helix conformation was determined by many factors such as the glycosidic linkage, explicit water solvation and hydrogen bonds. When temperature was increased, the representative helix conformation was found becoming unstable giving rise to metastable conformations because when water mobility was accelerated with temperature, the hydrogen bonding strength between the curdlan chain and water went down, breaking the continuity of the hydrogen bonding network of water and hydroxyl groups. When the number of repeating glucose units varied from 6 to 24, the major helix conformation remained, but the conformational properties of longer chains were more apparently aff ;ected by chain flexibility.

Effects of carbon sources on production and properties of curdlan using Agrobaterium sp. DH-2

Curdlan has wide potential application in the food and biomedical fields due to its unique thermal gel and biological activity. This study investigated the effect of six sugars including glucose, fructose, lactose, maltose, sucrose and xylose as carbon sources on production and properties of curdlan using Agrobacterium sp. DH-2. The maximum production (38.1 g/L and 37.4 g/L, respectively) and yield (0.58 g curdlan/g sucrose and 0.53 g curdlan/g maltose, respectively) of curdlan were achieved by sucrose and maltose, followed by glucose, fructose, lactose and xylose. Scanning electron micrographs showed that the surface of cells was smooth in strain growth phase, while cells were covered by curdlan matrix acted as a net in the curdlan synthesis phase. The highest glucosyltransferase activity (19.9 U/g biomass) corresponded to the maximum curdlan production using the sucrose medium. The molecular weight and gel strength of curdlan were influenced by the carbon sources. The curdlan from xylose medium resulted in a maximum molecular weight of 1.59 × 10⁶ Da and the highest gel strength of 989.2 g/cm², while the curdlan from sucrose medium resulted in a lowest molecular weight of 1.10 × 10⁶ Da and gel strength of 672.8 g/cm². The high molecular weight of curdlan had high gel strength.

Curdlan enhances the structure of myosin gel model

The aim of this work was to investigate the gelation mechanism of curdlan on surimi using a myosin gel model. Experimental results showed that with increased levels of curdlan, the water-holding capacity, gel strength, and storage modulus of a myosin gel first increased and then decreased. The optimum level of curdlan was found to be 1%. Moreover, myosin-curdlan mixed gel showed decreased water liquidity based on the results of low-field nuclear magnetic resonance. The enhanced physicochemical properties of myosin-curdlan mixed gel were attributed to the strengthened hydrogen bonding and to the uniform and compact network structure shown by Fourier-transform infrared spectroscopy and scanning electron microscopy. The results of this study suggest that curdlan has the potential to be used in surimi-based seafood products to enhance the gel structure.