Conformation dependent depolymerisation kinetics of polysaccharides studied by viscosity measurements

Polysaccharide-based formulations as potential carriers for pulmonary delivery - A review of their properties and fates

Polysaccharides can be elite carriers for therapeutic molecules due to their versatility and low probability to trigger toxicity and immunogenic responses. Local and systemic therapies can be achieved through particle pulmonary delivery, a promising non-invasive alternative. Successful pulmonary delivery requires particles with appropriate flowability to reach alveoli and avoid premature clearance mechanisms. Polysaccharides can form micro-, nano-in-micro-, and large porous particles, aerogels, and hydrogels. Herein, the characteristics of polysaccharides used in drug formulations for pulmonary delivery are reviewed, providing insights into structure-function relationships. Charged polysaccharides can confer mucoadhesion, whereas the ability for specific sugar recognition may confer targeting capacity for alveolar macrophages. The method of particle preparation must be chosen considering the properties of the components and the delivery device to be utilized. The fate of polysaccharide-based carriers is dependent on enzyme-triggered hydrolytic and/or oxidative mechanisms, allowing their complete degradation and elimination through urine or reutilization of released monosaccharides.

Modified citrus pectins by UV/H2O2 oxidation at acidic and basic conditions: Structures and in vitro anti-inflammatory, anti-proliferative activities

Two modified citrus pectins, MCP4 and MCP10, were prepared by UV/H₂O₂ treatment at pH 4 and pH 10, respectively, and their structures were characterized. MCP10 had a rhamnogalacturonan-I (RG-I) enriched backbone with a high degree of branching (DB ∼61 %) and a low methoxylation degree (24 %). MCP4 had a homogalacturonan enriched backbone with a high degree (46 %) of methoxylation and a low DB (∼41 %) of RG-I branches. MCP10 exhibited a higher anti-inflammatory activity than MCP4 in suppressing the NF-κB expression and the production of pro-inflammatory factors TNF-α and IL-1β of THP-1 cells stimulated by lipopolysaccharide. MCP10 also showed a stronger inhibitory effect on Caco-2 cell proliferation. The stronger bioactivities of MCP10 may be attributable to the abundant branches and the proper length of terminal galactan residues attached to the RG-I domain.

Mechanical strength, structural and hydration properties of ethanol-treated starch tablets and their impact on the release of active ingredients

Ethanol-treated starch (ETS) shows potentiality to be used for binder of pharmaceutical tablets. This study was aimed to evaluate the mechanical strength, structural and hydration properties of ETS tablets and ETS tablets containing lauric acid and ascorbic acid and their release behavior. ETS was prepared from cassava starch at the temperatures of 80, 90, and 100 °C. The active compounds were entrapped within the ETS tablets by two methods, including dry mixing and ethanol solubilisation. The results indicated that ETS tablets from temperatures of 80 °C showed granular shapes, had high friability and low crushing strength indexes, and dispersed and released active ingredients rapidly upon contact with water. Meanwhile, ETS tablets from temperatures of 90 and 100 °C exhibited non-granular particles, had low friability and high crushing strength indexes. Upon hydration, the tablets of non-granular ETS containing lauric acid eroded gradually and released active ingredients during tablet's erosion, meanwhile ascorbic acid diffused out gradually from the swelled tablets.

Gluten-Degrading Proteases in Wheat Infected by Fusarium graminearum-Protease Identification and Effects on Gluten and Dough Properties

Recently, we have observed a relationship between poor breadmaking quality and protease activities related to fungal infection. This study aims to identify potential gluten-degrading proteases secreted by fungi and to analyze effects of these proteases on rheological properties of dough and gluten. Fusarium graminearum-infected grain was used as a model system. Zymography showed that serine-type proteases secreted by F. graminearum degrade gluten proteins. Zymography followed by liquid chromatography-mass spectrometry (MS)/MS analysis predicted one serine carboxypeptidase and seven serine endo-peptidases to be candidate fungal proteases involved in gluten degradation. Effects of fungal proteases on the time-dependent rheological properties of dough and gluten were analyzed by small amplitude oscillatory shear rheology and large deformation extensional rheology. Our results indicate that fungal proteases degrade gluten proteins not only in the grain itself, but also during dough preparation and resting. Our study gives new insights into fungal proteases and their potential role in weakening of gluten.

Applications of Algal Polysaccharides and Derivatives in Therapeutic and Agricultural Fields

BACKGROUND

Recently, researchers have given more and more consideration to natural polysaccharides thanks to their huge properties such as stability, biodegradability and biocompatibility for food and therapeutics applications.

METHODS

a number of enzymatic and chemical processes were performed to generate bioactive molecules, such as low molecular weight fractions and oligosaccharides derivatives from algal polysaccharides.

RESULTS

These considerable characteristics allow algal polysaccharides and their derivatives such as low molecular weight polymers and oligosaccharides structures to have great potential to be used in lots of domains, such as pharmaceutics and agriculture etc. Conclusion: The present review describes the mains polysaccharides structures from Algae and focuses on the currents agricultural (fertilizer, bio-elicitor, stimulators, signaling molecules and activators) and pharmaceutical (wound dressing, tissues engineering and drugs delivery) applications by using polysaccharides and/or their oligosaccharides derivatives obtained by chemical, physical and enzymatic processes.

Application of xanthan gum as polysaccharide in tissue engineering: A review

Xanthan gum is a microbial high molecular weight exo-polysaccharide produced by Xanthomonas bacteria (a Gram-negative bacteria genus that exhibits several different species) and it has widely been used as an additive in various industrial and biomedical applications such as food and food packaging, cosmetics, water-based paints, toiletries, petroleum, oil-recovery, construction and building materials, and drug delivery. Recently, it has shown great potential in issue engineering applications and a variety of modification methods have been employed to modify xanthan gum as polysaccharide for this purpose. However, xanthan gum-based biomaterials need further modification for several targeted applications due to some disadvantages (e.g., processing and mechanical performance of xanthan gum), where modified xanthan gum will be well suited for tissue engineering products. In this review, the current scenario of the use of xanthan gum for various tissue engineering applications, including its origin, structure, properties, modification, and processing for the preparation of the hydrogels and/or the scaffolds is precisely reviewed.

Fucosylated chondroitin sulfate oligosaccharides exert anticoagulant activity by targeting at intrinsic tenase complex with low FXII activation: Importance of sulfation pattern and molecular size

Fucosylated chondroitin sulfates (fCSs) are structurally unusual glycosaminoglycans isolated from sea cucumbers that exhibit potent anticoagulant activity. These fCSs were isolated from sea cucumber, Isostichopus badionotus and Pearsonothuria graeffei. Fenton reaction followed by gel filtration chromatography afforded fCS oligosaccharides, with different sulfation patterns identified by mass and NMR spectroscopy, and these were used to clarify the relationship between the structures and the anticoagulant activities of fCSs. In vitro activities were measured by activated partial thromboplastin time (APTT), thrombin time (TT), thrombin and factor Xa inhibition, and activation of FXII. The results showed that free radicals preferentially acted on GlcA residues affording oligosaccharides that were purified from both fCSs. The inhibition of thrombin and factor X activities, mediated through antithrombin III and heparin cofactor II of fCSs oligosaccharides were affected by their molecular weight and fucose branches. Oligosaccharides with different sulfation patterns of the fucose branching had a similar ability to inhibit the FXa by the intrinsic factor Xase (factor IXa-VIIIa complex). Oligosaccharides with 2,4-O-sulfo fucose branches from fCS-Ib showed higher activities than ones with 3,4-O-disulfo branches obtained from fCS-Pg. Furthermore, a heptasaccharide is the minimum size oligosaccharide required for anticoagulation and FXII activation. This activity was absent for fCS oligosaccharides smaller than nonasaccharides. Molecular size and fucose branch sulfation are important for anticoagulant activity and reduction of size can reverse the activation of FXII caused by native fCSs.

Ionically gelled alginate foams: physical properties controlled by operational and macromolecular parameters

Alginates in the format of scaffolds provide important functions as materials for cell encapsulation, drug delivery, tissue engineering and wound healing among others. The method for preparation of alginate-based foams presented here is based on homogeneous, ionotropic gelation of aerated alginate solutions, followed by air drying. The method allows higher flexibility and better control of the pore structure, hydration properties and mechanical integrity compared to foams prepared by other techniques. The main variables for tailoring hydrogel properties include operational parameters such as degree of aeration and mixing times and concentration of alginate, as well as macromolecular properties such as the type of alginate (chemical composition and molecular weight distribution). Exposure of foams to γ-irradiation resulted in a dose-dependent (0-30 kGy) reduction in molecular weight of the alginate and a corresponding reduction in tensile strength of the foams.

Exploring the (1 --> 3)-beta-D-glucan conformational phase diagrams to optimize the linear to macrocycle conversion of the triple-helical polysaccharide scleroglucan

The immunologically important (1 --> 6) comb-like branched (1 --> 3)-beta-D-glucans scleroglucan, schizophyllan, lentinan, and others, exist mainly as linear triple-helical structures in aqueous solution. Partial interconversion from linear to circular topology has been reported to take place following conformational transition of the triple-helical structure and subsequent regeneration of the triplex conformation. We here report on experimental data indicating that complete strand separation of the triple-helical structure is required for this interconversion. NaOH or dimethylsulfoxide was used to induce dissociation of the triplex at combinations of concentrations and temperatures shown by calorimetry to yield a conformational transition of the triplex structures. For the alkaline treatment at 55 degrees C, it is found that up to about 30% of the material readily can be converted to the cyclic topology. This fraction increased to about 60% when the subsequent annealing of the scleroglucan in aqueous solution at pH 7 was carried out at 100 degrees C. Further increase of the annealing temperature yielded a smaller relative amount of cyclic species. The data indicate that the lower molecular weight fraction of the molecular weight distributions can be converted selectively to the macrocyclic topology by conditions that do not yield complete strand separation of the whole sample. These findings add to previous reports by providing more details about how the conditions required for the linear triplex to macrocycle interconversion relate to the conformational properties of the triple-helical structure. Copyright 1999 John Wiley & Sons, Inc.

Conformations and flexibility of native and re-natured xanthan in aqueous solutions

The conformation and flexibility of sonicated 'native' and 're-natured' xanthan have been investigated by size exclusion chromatography (SEC) with coupled multi-angle light scattering and viscosity detectors. 'Native' xanthan (NX) refers to xanthan dissolved in moderate ionic strength aqueous solution, which has not been exposed either to high temperature or very low ionic strength, and 're-natured' xanthan (RX) here refers to xanthan which has been heated above the conformational melting temperature and then recooled. The mass distributions of the NX and RX are virtually identical, implying that the RX does not involve aggregates of, or disassociated fragments of, NX. The flexibilities and conformations between NX and RX, however, are strikingly different; RX is far stiffer than NX, the persistence lengths being roughly 1000 A and 300 A, respectively, and the mass per unit length M/L of the RX is roughly double that of NX. With estimated M/L of 200 Da/A and 98 Da/A, respectively, the results strengthen the notion that RX is double stranded, whereas as NX appears single stranded. The nature and mechanism of formation of the double-stranded form is still unclear, and a few speculative scenarios are suggested. Finally, preliminary results on the kinetics of xanthan self-association in HCI are presented which illustrate the complexity of such processes in xanthan.

Dependence of the content of unsubstituted (cellulosic) regions in prehydrolysed xanthans on the rate of hydrolysis by Trichoderma reesei endoglucanase

Removal of side chains from the bacterial polysaccharides xanthan and xylinan (acetan) results in the formation of unsubstituted cellulosic regions that are susceptible to hydrolysis by cellulases (beta-1,4-endoglucanases). In contrast to cellulose derivatives, low degrees of substitution (DS) may be obtained in xanthan without affecting the solubility in water, and longer unsubstituted regions are obtained for the same DS due to the regular distribution of side chains. By varying the fraction of cellobiosic residues carrying a side chain from 1.0 to 0.54, the viscosimetrically detected rate of hydrolysis by cellulase of conformationally disordered xanthan, increased by 4 orders of magnitude. An increase was also obtained by removing side chains from xylinan. An analysis of the kinetic data suggests that very long unsubstituted regions (more than 10 glucose residues) are required for maximum rate of hydrolysis by cellulase.

Degradation of double-stranded xanthan by hydrogen peroxide in the presence of ferrous ions: comparison to acid hydrolysis

Conformationally ordered, double-stranded xanthan, degraded in the presence of H2O2 and Fe2+ (at 20 degrees C) or in dilute acid (0.1 M HCl at 80 degrees C), produced xanthan variants with weight-average molecular weights (Mw) ranging from 2 x 10(6) to 5.4 x 10(4). In both cases the fraction of cleaved linkages in the glucan backbone (alpha), measured as reducing ends, increased to very high values (0.05 for Mw = 2-3 x 10(4)), demonstrating that a large number of linkages in the backbone could be cleaved without a correspondingly large reduction in Mw, in accordance with the double-stranded nature of xanthan. Extensive degradation (more than 10-fold reduction in Mw) in both cases released single-stranded, conformationally disordered oligomers; this release was accompanied by an increase in the rate of acid hydrolysis of the glucan backbone and a pronounced increase in the rate of release of glucose monomer. In contrast, there was no significant change in the rate of reducing end-group formation associated with the release of oligomers upon degradation with H2O2/Fe2+. Both types of degradation were accompanied by changes in the composition of the side chains. However, in contrast to acid hydrolysis, where the terminal beta-D-mannose is preferentially hydrolyzed, the reaction with H2O2/Fe2+ resulted in removal of both mannose and glucuronic acid at approximately equal rates. This observation can be explained by a preferential attack on the inner alpha-D-mannose, with concomitant removal of the entire side chain. Removal of side chains and the release of single-stranded oligomers by H2O2/Fe2+ strongly influenced the optical rotation and also broadened the chiroptically detected conformational transition, whereas no change in the transition temperature was observed.