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.

Fructose/glycerol/water as a biosourced LTTM solvent to design a variety of sodium alginate-based soft materials with enhanced rheological properties

Sodium alginate was associated to a ternary solvent composed of fructose, glycerol, and water in a 1:1:5 M ratio (FGW), classified as a natural Low Transition Temperature Mixture (LTTM), to generate various soft materials. The rheological properties of mixtures composed of sodium alginate and FGW were thoroughly analyzed and compared to their aqueous analogues. FGW-based solutions present a pronounced shear-thinning character combined to high viscosity, up to 8000 Pa.s. The overlap concentrations and intrinsic viscosities values evidence a good solvent character of FGW for alginate polymer chains. The increase of alginate concentration in FGW leads to materials with enhanced elasticity (up to 6000 Pa) and high energy of activation (55 kJ/mol). Interestingly, the addition of divalent calcium cations in FGW according to two optimized experimental protocols, allows for the generation of never described ionotropic gels in FGW under various shapes as bulk gels or beads of gels able to encapsulate extracted vegetal actives that are used in the cosmetic industry. Thus, FGW appears as a well-suited solvent of alginate to design a broad range of new biobased soft materials.

Effect of subcritical water temperature on the chain conformation and immune activity of ginger polysaccharides

In this study, the ginger polysaccharides extracted from hot water (HW-G) were modified with subcritical water (SW-G) to effectively regulate their immune activity, and the relationship between polysaccharide chain conformation and immune activity at different subcritical water temperatures was investigated. The results indicated that, compared with HW-G, the xylose and mannose were degraded at high temperatures. The molecular weight of ginger polysaccharide decreased from 1.083 × 106 g/mol to 3.113 × 105 g/mol after subcritical water modification (100-160 °C). The chain conformation transitioned from rigid rod chain to semi-rigid chain and eventually to random coil. The degree of relaxation of the polysaccharide chains showed a continuous increase trend. Additionally, ginger polysaccharide modified by subcritical water at 130 °C was found to promote the proliferation and phagocytosis of 264.7 cells more obviously and signally increase the secretion levels of NO, IL-6, TNF-α and IL-1β. When the subcritical water temperature exceeds 130 °C, the activity of ginger polysaccharide begins to decline rapidly. These findings demonstrate a close correlation between polysaccharide chain conformation and immunomodulatory activity, confirming the feasibility of the subcritical water temperature effect as a means of immune activity regulation, which opens up a new approach to obtaining highly active polysaccharides.

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.

Chain conformation, mucoadhesive properties of fucoidan in the gastrointestinal tract and its effects on the gut microbiota

Fucoidans are valuable marine polysaccharides with various bioactivities and physicochemical properties. However, its digestive properties, mucoadhesive properties, and bioactivity in the gastrointestinal tract are still unclear. In this study, simulated digestion, fecal fermentation in vitro, and rheology models were utilized to investigate the chain conformation, influence on gut microbiota, and mucin adhesive properties of fucoidan from the sea cucumber Thelenota ananas (Ta-FUC). The results showed that Ta-FUC was nondigestible with a temporary decrease in molecular weight in gastric conditions, accompanied by the chain conformation becoming more flexible. Moreover, Ta-FUC exhibited strong mucin adhesive function in the simulated intestinal environment, with supramolecular disulfide, hydrogen, and hydrophobic interactions in order of intensity. During fermentation, Ta-FUC was degraded by the intestinal flora to produce various short-chain fatty acids and promoted the relative abundance of Bacteroidota and Firmicutes, reducing the proportion of Proteobacteria. Therefore, these results indicate that Ta-FUC could be a potential prebiotic and ingredient for developing targeted delivery systems in the functional food and pharmaceutical industries.

Influence of ultrasound assisted metal-free Fenton reaction on the structural characteristic and immunostimulatory activity of a β-D-glucan isolated from Dictyophora indusiata

The present study aimed to evaluate the influence of ultrasound assisted H₂O₂/ascorbic acid reaction on the structural characteristic and immunostimulatory activity of a β-D-glucan isolated from D. indusiata, so as to reveal its potential structure-immunostimulatory activity relationship. A purified β-D-glucan, named as DP, was quickly isolated from D. indusiata, and further identified as a 1,3-β-D-glucan with 1,6-β-D-Glcp as branched chains, which exhibited a rigid rod chain conformation in 0.9 % (w/v) of NaCl solution. Furthermore, results showed that the primary structure of DP was overall stable after the degradation by ultrasound assisted H₂O₂/ascorbic acid reaction. However, the molar mass and chain conformation of DP obviously changed. In addition, DP and its degraded products exerted remarkable immunostimulatory activity in vitro and in vivo, which could activate the nuclear factor-κB (NF-κB) signaling pathway through toll-like receptor 4 (TLR4). Indeed, the immunostimulatory activity of DP was closely-correlated to its molar mass and chain conformation. An appropriate degradation of molar mass could promote its immunostimulatory activity. While the transformation of chain conformation from rigid rod to random coil could cause the significant decrease of its immunostimulatory activity. These findings are beneficial to better understanding the structure-immunostimulatory activity relationship of β-D-glucans from edible mushrooms.

Extraction, purification, structural characterization, and gut microbiota relationship of polysaccharides: A review

Intestinal dysbiosis is one of the major causes of the occurrence of metabolic syndromes, such as obesity, diabetes, nonalcoholic fatty liver disease, and cardiovascular diseases. Polysaccharide-based microbial therapeutic strategies have excellent potential in the treatment of metabolic syndromes, but the underlying regulatory mechanisms remain elusive. Identification of the internal regulatory mechanism of the gut microbiome and the interaction mechanisms involving bacteria and the host are essential to achieve precise control of the gut microbiome and obtain valuable clinical data. Polysaccharides cannot be directly digested; the behavior in the intestinal tract is considered a "bridge" between microbiota and host communication. To provide a relatively comprehensive reference for researchers in the field, we will discuss the polysaccharide extraction and purification processes and chemical and structural characteristics, focusing on the polysaccharides in gut microbiota through the immune system, gut-liver axis, gut-brain axis, energy axis interactions, and potential applications.

Conformation and anticancer activity of a novel mannogalactan from the fruiting bodies of Sanghuangporus sanghuang on HepG2 cells

A novel water-soluble mannogalactan (SSPS1) with an average molecular weight of 2.04 × 10⁴ Da was obtained from the fruiting bodies of the Sanghuangporus sanghuang. It revealed that SSPS1 was composed of d-galactose, d-mannose, l-fucose, 3-O-methylgalactose and d-glucose in a ratio of 6.2:3.9:3.1:2.1:1.0. The structural elucidation of SSPS1 consisted of 1, 6-linked α-D-Galp, 1, 6-linked α-D-Manp and 1, 6-linked 3-O-methyl-α-D-Galp backbone with branching at O-2 of 1, 6-α-D-mannosyl residues by α-L-Fucp and α-D-Glcp units. The conformational parameters suggested that a flexible chain conformation of SSPS1 in solution based on light scattering and atomic force microscopy imaging. Intriguingly, it presented potent anticancer activity on HepG2 cell with Rq and Ra values increased dramatically up to 73.93 nm and 53.92 nm compared with the control. The analysis of flow cytometry indicated SSPS1 could induce the apoptosis of HepG2 cells and arrest them via S phase. Western blot assay further uncovered that apoptosis process was triggered by SSPS1 via a mitochondria-mediated signaling pathway, which was evidenced by an increased ratio of Bax/Bcl-2, the release of cytochrome c and the strong activation of caspase-3 and 9. Taken together, these results suggested that SSPS1 might be applied in functional food as an anticancer agent.

Different molecular sizes and chain conformations of water-soluble yeast β-glucan fractions and their interactions with receptor Dectin-1

Although β-glucan could bind to Dectin-1 to exert bioactivity, the influence of molecular size and chain conformation of β-glucan on its interaction with Dectin-1 is still unclear. This work investigated the molecular sizes and chain conformations of five water-soluble yeast β-glucan (WYG1-5) fractions as well as their interactions with Dectin-1 by fluorescence spectroscopy and microscale thermophoresis. Results revealed a spherical conformation for higher molecular weight WYG and a stiff chain conformation for smaller molecular weight WYG. The WYG and Dectin-1 interactions were in the order of WYG-2 > WYG-1 > WYG-3 > WYG-4 > WYG-5. The spherical WYG-2 exhibited the largest binding constant of 7.91 × 10⁵ M¹ and the lowest dissociation constant of 22.1 nM to Dectin-1. Additionally, the underlying interaction mechanism showed that it may be easier for spherical WYG with longer side chains to interact with receptor Dectin-1.

Molecular dynamics investigation of structural and mechanical properties of silica nanorod reinforced dental resin composites

In this work, molecular dynamics simulations are conducted to investigate the structural and mechanical properties of dental materials, i.e., the silica nanorod reinforced Bis-GMA/TEGDMA resin composite. The effects of loading content and size of the silica nanorods on the composite stiffness were performed by examining resin chain conformation, hydrogen bonds and matrix/filler binding energy. It is revealed that the presence of the silica nanorod causes polymer chain expansion, endowing the resins with higher stiffness. Moreover, the volumetric hydrogen bonds and binding energy increase considerably with the loading content, but decrease gradually with the diameter or show almost independence of the length. Furthermore, the composite moduli were quantified by the micromechanics models and the transverse moduli were well predicted by the Counto model, signifying a perfect bonding between the matrix and nanorod. The chain expansion and energetic matrix/filler interactions are believed to contribute to the significant mechanical reinforcement of the composites with the loading content. However, the length of the nanorod has a little effect on the composite moduli due to the unaltered interfacial interaction. In contrast, a smaller diameter is supposed to give a larger modulus, and this is not observed in this work due to the synergic effects of improved matrix/filler interaction and actual reduced filler volume fraction. The mechanical enhancement by the rod-like structures is more influenced by the loading content, but less so by the size of the nanorod, and it also exhibits superior mechanical performance as compared to nanoparticles. The findings thus extend the current understanding of the nanostructure and mechanical properties of silica nanorod reinforced dental resin composites from an atomic/molecular perspective.

Conformational and rheological properties of bacterial cellulose sulfate

In this study, a water-soluble bacterial cellulose sulfate (BCS) was prepared with sulfur trioxide pyridine complex (SO3· Py) in a lithium chloride (LiCl)/dimethylacetamide (DMAc) homogeneous solution system using bacterial cellulose (BC). The structural study showed that the value for the degrees of substitution of BCS was 1.23. After modification, the C-6 hydroxyl group of BC was completely substituted and the C-2 and C-3 hydroxyl groups were partially substituted. In an aqueous solution, the BCS existed as a linear polymer with irregular coil conformation, which was consistent with the findings observed using atomic force microscopy. The steady-state shear flow and dynamic viscoelasticity were systematically determined over a range of BCS concentrations (1 %-4 %, w/v) and temperature (5 °C-50 °C). Steady-state flow experiments revealed that BCS exhibited shear thinning behavior, which increased with an increase in concentration and a decrease in temperature. These observations were quantitatively demonstrated using the cross model. Moreover, based on the dynamical viscoelastic properties, we confirmed that BCS was a temperature-sensitive and weak elastic gel, which was somewhere between a dilute solution and an elastic gel. Therefore, considering the special synthetic strategy and rheological behavior, BCS might be used as a renewable material in the field of biological tissue engineering, especially in the manufacture of injectable hydrogels, cell scaffolds, and as a drug carrier.

Structure characterization and in vitro immunomodulatory activities of carboxymethyl pachymaran

Carboxymethyl pachymaran (CMP) was prepared from Poria cocos polysaccharide by carboxymethylation. Two types of CMP (CMP-1 and CMP-2) were further purified by DEAE-52 anion-exchange chromatography. The structure characteristics and immunomodulatory activities of CMP-1 and CMP-2 were investigated. CMP-1 was determined as β-(1 → 3)-d-glucan. A β-(1 → 3)-d-glucan backbone structure was also found in CMP-2, which was mainly consistent of mannose and glucose, with the mole ratio of 0.03:1. The molecular weight of CMP-1 was 126.1 kDa with a 30.4 nm irregular sphere in distilled water. However, the molecular weight of CMP-2 was 172.6 kDa in a 19.9 nm spherical structure in water solution. Both CMP-1 and CMP-2 had triple helical structure, which can promote the proliferation and the phagocytosis of macrophages. Moreover, CMP-1 and CMP-2 both could improve the secretions of NO, TNF-α and IL-6 by increasing the expression of iNOS, TNF-α and IL-6 mRNA, but CMP-1 exhibited a stronger immunomodulatory ability than that of CMP-2. Our results indicated that CMP-1 and CMP-2 can act as potential immunomodulatory agents.

Ultrasound irradiation alters the spatial structure and improves the antioxidant activity of the yellow tea polysaccharide

In this study, the impact of ultrasound irradiation on the structural characteristics and antioxidant properties of yellow tea polysaccharides with different molecular weights (Mw) were investigated. Native yellow tea polysaccharide containing YTPS-3N, YTPS-5N and YTPS-7N were prepared through precipitation with ethanol at various concentrations of 30%, 50%, and 70%, respectively, and irradiated with high intensity ultrasound (20 kHz) for 55 min to yield yellow tea polysaccharide including YTPS-3U, YTPS-5U and YTPS-7U. The molecular weight (Mw) of YTPS-3N (from 37.7 to 15.1 kDa) and YTPS-5N (from 14.6 to 5.2 kDa) sharply decreased upon ultrasound irradiation, coincidentally particle size (Zavg) was also significantly reduced for YTPS-3N (40%), YTPS-5N (48%) and YTPS-7N (54%). The high-performance liquid chromatography and Fourier transform-infrared spectroscopy analysis revealed a partial degradation of native yellow tea polysaccharide treated with ultrasound, though the monosaccharide composition was not altered. Furthermore, changes in morphology and the breakdown of native yellow tea polysaccharide upon irradiation was confirmed with the circular dichroism spectrum, atomic force and scanning electron microscopy. As a consequence, irradiation of yellow tea polysaccharide increased free radical scavenging activity with YTPS-7U exhibiting the highest levels of 2, 2-diphenyl-1-picrylhydrazyl free radical, superoxide and hydroxyl radicals scavenging activity. These results suggest that the alteration of the spatial structure of yellow tea polysaccharide can enhance its antioxidant activity which is an important property for functional foods or medicines.

Mechanistic investigation of enzymatic degradation of polyethylene terephthalate by nuclear magnetic resonance

The biocatalytic degradation of polyethylene terephthalate (PET) by thermophilic microbial enzymes has recently emerged as an option for a future eco-friendly recycling process for plastic waste, as it occurs under mild conditions and requires no harmful additives. In this chapter, we present a brief overview of solution and solid-state nuclear magnetic resonance (NMR) spectroscopic methods for the characterization of composition and chemical microstructure of PET and also associated chain dynamics over multiple time scales. Such detailed information provides an understanding of the enzymatic PET degradation mechanism by polyester hydrolases at the molecular level.

Structure and chain conformation characterization of arabinoglucan from by-product of peanut oil processing

A neutral polysaccharide (NPP) from peanut sediment of aqueous extraction process was purified via anion-exchange and gel-filtration chromatography. The weight-average molecular weight and polydispersity index were 3.36 × 10⁴ Da and 1.06. Composition of glucose (82.66 %, molar percentage) and arabinose (17.34 %) suggested an arabinoglucan structure. Multiple medium-length chains consisting of many 1,4-linked α-Glcp and a few 1,5-linked α-Araf maintained the main chain structure. The backbone was substituted at O-6 and O-3 positions, attached by side chains consisting of two to six α-Glcp and terminated with Araf and Glcp. Degree of branching was 42.50 %. Aggregates formed in NPP aqueous solution. They were eliminated by DMSO combining with sonication. Consequently, the average radius of gyration (R_g), hydrodynamic radius (R_h), and R_g/R_h ratio were 17.0 nm, 5.8 nm and 2.93, respectively, indicating extended rigid chain conformation. The backbone substituted at O-3 and short branching chains probably together induced this conformation.

Effects of structural and conformational characteristics of citrus pectin on its functional properties

Ultrasonic degradation has become a fascinating strategy for preparing modified pectin, contributing to the improvement of pectin's functional characteristics. In this study, the impacts of structural and conformational characteristics of original and ultrasound-treated citrus pectins on their functional properties were examined. The results showed that compared with ultrasound-treated pectins, untreated pectin presented higher rheological and gelling properties primarily attributed to its larger weight-average molecular weight (M_w), degree of methoxylation, amount of neutral sugar side chains, and z-average radius of gyration, as well as the more extended flexible-chain conformation. However, the ultrasound-treated pectins had better emulsifying properties than untreated pectin in an oil-in-water emulsion system. These properties, visually suggested by morphology analysis, including enhanced emulsifying capacity, emulsifying stability, reduced mean droplet size and negatively charged zeta potential. Moreover, the M_w and chain conformation of untreated and ultrasound-treated pectins played more decisive roles in their functional properties than the others.

Chain conformation of an acidic polysaccharide from green tea and related mechanism of α-amylase inhibitory activity

An acidic tea polysaccharide (TPSA) isolated from green tea was fractionated using a precipitation-fractionation method into seven fractions with different molecular weights. TPSA was characterized as a hyperbranched polysaccharide with a globular homogeneous conformation by analysis of solution parameters of each fraction using static light scattering and viscosity analyses. Observation by transmission electron microscopy confirmed that TPSA occurred as globular homogeneous particles with size in the range of 20-40 nm. To simulate the branched chain segments of TPSA, four model molecules were designed based on chemical structure of TPSA. Molecular docking analysis indicated that the branched chain segments of TPSA similar to the TPSA-4 model molecule showed preferential binding to α-amylase to form the TPSA/α-amylase complex through hydrogen bonding interactions. Circular dichroism spectroscopy showed that the structure of α-amylase was not significantly affected by TPSA. The mechanism of α-amylase inhibitory activity of TPSA was simulated by molecular docking analysis. The branched chain segments of TPSA similar to the TPSA-4 model molecule likely act as a potential competitor to the starch substrate to inhibit the activity of α-amylase.

Purification, structural characterization, and immunomodulatory activity of the polysaccharides from Ganoderma lucidum

A preliminary relationship was illustrated between the structural characteristics and corresponding immunomodulatory activities of G. lucidum polysaccharides. Two polysaccharides (GLP-1 and GLP-2) were purified from Ganoderma lucidum extracts by gradient ethanol precipitation and a Q-Sepharose Fast Flow (QFF) strong anion-exchange column. The monosaccharide composition, high-performance gel permeation chromatography-multi-angle laser light scattering-refractive index (HPGPC-MALLS-RI), Fourier-transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM), methylation analysis, and nuclear magnetic resonance (NMR) were used to characterize these polysaccharides. The GLP-1 polysaccharide was elucidated as d-galactoglucan with a flexible random linear conformation that mainly composed of →6)-β-d-Glcp-(1→, →6)-α-d-Galp-(1→, and →3)-β-d-Glcp-(1→ residues. GLP-2 was found to be a relatively homogeneous β-d-glucan that possessing →6)-β-d-Glcp-(1→ and →3)-β-d-Glcp-(1→ residues packaged into a spherical conformation. Immunomodulatory activities in vivo demonstrated that GLP-1 produced better protection of the spleen and thymus and was more effective for promoting hematopoiesis and improving IgA levels in serum. Our results suggest that the immunomodulatory activities of G. lucidum polysaccharides are highly corresponded to their structural characteristics such as carbohydrate composition, molecular weight and advanced conformation. This study provides a preliminary basis for studying the relationship between polysaccharide structure characterization and pharmacological activities.

Chain conformation and rheological properties of an acid-extracted polysaccharide from peanut sediment of aqueous extraction process

A polysaccharide (PPS) in peanut sediment of aqueous extraction process was obtained at pH4.0, purified via anion-exchange chromatography. The composition, chain conformation and rheological properties were investigated. PPS mainly consisted of arabinose, galacturonic acid, xylose, and rhamnose. The intrinsic viscosity [η] was 0.71 dL/g in 0.1 M NaNO₃ solution. The weight-average molar mass Mw and polydispersity index were 3.77 × 10⁵ g/mol and 1.25, suggesting high homogeneity. The average radius of gyration (R_g), hydrodynamic radius (R_h), R_g/R_h ratio and conformation parameter v were 25.5, 18.2, 1.40 and 0.21, respectively, indicating compact coil chain conformation with branched structure. Molecular morphology revealed that PPS displayed chain shape comprised of spheres with a diameter range of 15-50 nm and apparent length of chains mainly ranged from 100 to 300 nm. The aggregation caused by molecular self-association enhanced with concentration increasing. Additionally, Newtonian behavior was observed at various concentrations. Increase in temperature effectively broke this behavior. 10.0 wt.% PPS possessed activation energy of 21.7 KJ/mol, was structured liquid and almost fitted Cox-Merz rule. These closely related with its conformation and molecular self-association behavior.

Effect of ultrasonic intensity on the conformational changes in citrus pectin under ultrasonic processing

In this study, the effects of ultrasonic intensity on conformational changes in aqueous citrus pectin solution under ultrasonic processing and its possible transition mechanism were investigated. The results demonstrated that higher ultrasonic intensity (104.7 W/cm²) caused larger alterations in the molecular and conformational parameters of the semiflexible pectin (Mark-Houwink relation exponent a: 0.820, conformational parameter α: 0.607, structural parameter ρ: 2.22) in aqueous solution. Meanwhile, the semiflexible chain of pectin became more flexible (a: 0.804, α: 0.601, ρ: 1.75) at higher ultrasonic intensity in aqueous solution, as was verified by atomic force microscopy. Moreover, conformational changes in pectin from semiflexible chains to flexible chains or even flexible coils (a: 0.791, α: 0.597, ρ: 1.70) could be attributed to the decreased degree of methoxylation and neutral sugars in side chains and the destruction of inter- and intramolecular hydrogen bonds under ultrasonic processing. Therefore, these results have important implications for understanding the ultrasonic modification of pectin.

Anhydrous thiomers: Strategy for enhanced mucoadhesion

AIM

The aim of this study was to evaluate the impact of the absence of water during the synthesis of thiolated poly(acrylic acid) (PAA) on its mucoadhesive properties. Previously, thiolation of hydrophilic polymers was performed in aqueous media, where (poly)acrylates undergo a conformational transition to form an entangled network of polymer chains stabilized by neutralization. The impact of chain entanglement, porosity and degree of functionalization of anhydrous precipitated polymers on their mucoadhesive characteristics were therefore evaluated in comparison to the equivalent products synthesized in water and dried by lyophilization.

METHODS

Anhydrous synthesis and purification procedures were designed for the thiolation and entire preactivation of PAA by means of immobilization of l-cysteine (PAA-Cys) and 2-mercaptonicotinic acid (PAA-Cys-MNA), respectively. The obtained conjugates were characterized chemically and for their particle size. Differences in mucoadhesive properties were determined by means of the residence time as well as tensile strength of polymer test disks on porcine small intestinal mucosa.

RESULTS

Anhydrous products revealed a 4.2-fold higher amount of immobilized free thiol moieties for PAA-Cys and a 3.1-fold higher quantity of 2-mercaptonicotinic acid for PAA-Cys-MNA. The impact of particle size of anhydrous products on their mucoadhesive properties was negligible. In comparison to the corresponding aqueous products a 2.5-fold increase in residence time for PAA-Cys and 21.2-fold increase for PAA-Cys-MNA was achieved and in agreement with these results, the improvement in the total work of adhesion was 2.9-fold for PAA-Cys and 5.1-fold for PAA-Cys-MNA.

CONCLUSION

According to these findings, anhydrous synthesis conditions seem to be a promising tool for improved modification rates and moreover enhanced mucoadhesive properties of hydrophilic polymers.

One-dimensional poly(L-lysine)-block-poly(L-threonine) assemblies exhibit potent anticancer activity by enhancing membranolysis

Herein, we report the oncolytic activity of cationic, one-dimensional (1D) fibril assemblies formed from coil-sheet poly(L-lysine)-block-poly(L-threonine) (PLL-b-PLT) block copolypeptides for cancer therapy. The 1D fibril assemblies can efficiently interact with negatively charged cellular and mitochondrial membranes via electrostatic interactions, leading to necrosis via membrane lysis and apoptosis via the mitochondria-lytic effect. The concept is analogous to that of 1D drug carriers that exhibit enhanced cell penetration. In comparison to free PLL chains, PLL-b-PLT fibril assemblies exhibit selective cytotoxicity toward cancer cells, low hemolysis activity, enhanced membranolytic activity, and a different apoptosis pathway, which may be due to differences in the peptide-membrane interactions. Antitumor studies using a metastatic LL2 lung carcinoma model indicate that the fibril assemblies significantly inhibited tumor growth, improved survival in tumor-bearing mice and suppressed lung metastasis without obvious body weight loss. An additive efficacy was also observed for treatment with both PLL-b-PLT and cisplatin. These results support the feasibility of using 1D fibril assemblies as potential apoptotic anticancer therapeutics.

STATEMENT OF SIGNIFICANCE

We report that cationic, one-dimensional (1D) fibril assemblies formed by coil-sheet poly(L-lysine)-block-poly(L-threonine) (PLL-b-PLT) block copolypeptides exhibited potent anticancer activity by enhancing membranolysis. The 1D fibril assemblies can efficiently interact with negatively charged cellular and mitochondrial membranes via electrostatic interactions, leading to necrosis via membrane lysis and apoptosis via mitochondria-lytic effect. Moreover, the fibril assemblies exhibited low hemolytic activity and selective cytotoxicity toward cancer cell, which is advantageous as compared to PLL and most antimicrobial/anticancerous peptides. This study provides a new concept of using cationic, 1D fibril assemblies for cancer therapy.

Macromolecular properties and hypolipidemic effects of four sulfated polysaccharides from sea cucumbers

The present study investigates the relationship between the high-order structure and hypolipidemic activity of four well-defined sulfated fucans from sea cucumber. The chain conformation, determined by a combination of AFM and SEC-MALLS-RI, indicate that fucosylated chondroitin sulfate (fCS) from Pearsonothuria graeffei (fCS-Pg) and Isostichopus badionotus (fCS-Ib), and fucoidan from P.graeffei (fuc-Pg) were assigned as a random coil conformation with polysaccharide chain outstretched, while I. badionotus (fuc-Ib) was assigned as a spherical conformation and exhibited high viscosity. Fuc-Pg and fuc-Ib with higher molecular weights had a greater impact in inhibiting pancreatic lipase activity in vitro. However, fCS-Pg, fCS-Ib and fuc-Pg with random linear conformation exhibited excellent hypolipidemic activity in Sprague-Dawley rats (SD rats) fed on high-fat diet (HFD), whereas fuc-Ib showed only a modest effect. Our results indicate that structural characteristics, including side branch and sulfation pattern can affect the chain conformation of polysaccharides, which determine their physicochemical properties and hypolipidemic activity.

Structural elucidation and antioxidant activity a novel Se-polysaccharide from Se-enriched Grifola frondosa

Se-GFP-22, a heteropolysaccharide, with a weight-average M_w of 4.13×10⁶Da, was purified from the crude Se-polysaccharide (Se-GFP) isolated from fruit bodies of Se-enriched Grifola frondosa. Selenium was accumulated efficiently in Grifola frondosa during cultivation with Na₂SeO₃. The structure was investigated through FT-IR, GC, GC-MS, NMR, HPSEC-MALL-RI, particle size, Conge-red test, CD, AFM and SEM. Se-GFP-22 was deduced as a backbone chain of 1,4-α-d-Glcp units with a branched point at C6 of both 1,3,6-β-d-Manp and 1,4,6-α-d-Galp units. A typical absorption for selenium ester was existed in Se-GFP-22. Se-GFP-22 adopted as a spherical conformation with random coils. A novel Se-polysaccharide of different monosaccharide constituents, molecular weight, linkage types and high content of selenium has been isolated from G. frondosa. The antioxidant effect of Se-GFP-22 was more potent than that of G. frondosa polysaccharide (GFP-22), which may be influenced by the co-effect of polysaccharide and Se, molecular weight, degree of branching and configuration.

Structure, chain conformation, and immunomodulatory activity of the polysaccharide purified from Bacillus Calmette Guerin formulation

A polysaccharide, coded as BDP, purified from the injection powder of Bacillus Calmette Guerin (BCG) polysaccharide and nucleic acid, was composed mainly of α-D-(1→4)-linked glucan with (1→6)-linked branches and trace amounts of fucose and mannose from the results of FT-IR, HPAEC-PAD and NMR spectrum. The Mw, Mn, Mz, and [Formula: see text] were determined to be 1.320×10(5)g/mol, 1.012×10(5)g/mol, 2.139×10(5)g/mol, and 21.8±3.2%nm by using HPSEC-MALLS, respectively. The ν value from [Formula: see text] was calculated to be 0.52±0.01, which firstly clarified that BDP existed as random coils in 0.9% NaCl aqueous solution. AFM and SEM combined with Congo-red test also revealed that the polysaccharide was irregular globular like or curly structure. Furthermore, in vitro tests on RAW264.7 murine macrophages cells revealed that BDP exhibited significant immunomodulatory activity.