Effects of Chitooligosaccharides on Human Red Blood Cell Morphology and Membrane Protein Structure

Nano cellulose-laden alginate/chitosan sponge with enhanced biological and hemostatic behavior

Present study describes about hybrid hemostat developed with alginate (Alg), chitosan (Chito) and TEMPO-oxidized nanofibrillar cellulose (TOCNF) via lyophilization. All samples were analyzed under scanning electron microscopy (SEM) to determine their microstructure, size, and distribution of pores. Cell viability and proliferation of the scaffolds tested using fibroblast type L929 cells, showed it to be an excellent medium for cell generation. Blood coagulation started in ∼7.5 min, and most of the fibrin network formation took place in the Alg-Chito-TOCNF sponge, making it a suitable hemostatic material.

Chitosan oligosaccharide combined with running benefited the immune status of rats

Chitosan oligosaccharide (COS) degraded by chitosan, is an easily accessible and biocompatible natural molecule, which can facilitate the immune system. Running is one of the most effective forms of exercise. Persistence in running can effectively improve the body's resistance against pathogens. However, whether the combination of COS and running could benefit immune status still remains to be elucidated. We used Sprague-Dawley (SD) rats to explore the combinatory effect of COS and running. The organs and blood of the rats were collected after four weeks and the organ body mass index, biochemical and blood routine examination, cytokines, and T cells in the spleen and blood were detected and analyzed. In the group intragastric administration of COS only, the level of blood lactate dehydrogenase was increased, while the blood creatinine, red blood cells, lymphocytes, and serum TNF were decreased. Furthermore, COS combined with running promoted the development of spleen and lung, the level of lymphocytes, T cell and CD8⁺ T cell ratio in the blood, and serum TNF level. At the same time, the level of lactate dehydrogenase, serum IL-2, and T cell ratio in spleen were decreased. Therefore, our study indicated that COS combined with running could improve the immune status of rats.

Development of Blood-Cell-Selective Fluorescent Biodots for Lysis-Free Leukocyte Imaging and Differential Counting in Whole Blood

Complete blood count with leukocyte (white blood cell, WBC) differential is one of the most frequently ordered clinical test for disease diagnosis. Herein, multifunctional fluorescent carbon dots derived from biomolecules (biodots) for rapid lysis-free whole blood analysis are developed. Specifically, two types of biodots are molecularly engineered through hydrothermal synthesis for differential blood cells labeling. Type I biodots synthesized from amino acid (serine/threonine) precursors and passivated with polyethylenimine can label both red blood cells (RBCs) and WBCs with excellent contrast in fluorescence intensity, enabling direct counting of leukocytes in whole blood samples without a tedious RBC lysis step. It also allows three-part leukocyte differential counting by flow cytometry without using expensive fluorophore-conjugated antibodies. On the other hand, Type II biodots synthesized from the same amino acid precursors but passivated with a biopolymer (chitosan) are able to selectively lyse RBCs with greater than 98% efficiency to allow simultaneous fluorescent labeling of leukocytes for WBC counting in whole blood. It is envisioned that these novel nanoreagents, which eliminate the cumbersome lysis and antibody conjugation steps for selective labeling of different blood cells, would revolutionize disease diagnostics toward achieving faster, cheaper, and more accurate whole blood analyses in one test.

Effects of Chitosan Oligosaccharides on Human Blood Components

Chitosan oligosaccharide (COS) is known for its unique biological activities such as anti-tumor, anti-inflammatory, anti-oxidant, anti-bacterial activity, biological recognition, and immune enhancing effects, and thus continuous attracting many research interests in drug, food, cosmetics, biomaterials and tissue engineering fields. In comparison to its corresponding polymer, COS has much higher absorption profiles at the intestinal level, which results in permitting its quick access to the blood flow and potential contacting with blood components. However, the effects of COS on blood components remain unclear to date. Herein, two COS with different molecular weight (MW) were characterized by FTIR and ¹H NMR, and then their effects on human blood components, including red blood cells (RBCs) (hemolysis, deformability, and aggregation), coagulation system [activated partial thromboplastin time (APTT), prothrombin time (PT), thrombin time (TT), and the concentration of fibrinogen (Fib)], complement (C3a and C5a activation), and platelet (activation and aggregation), were comprehensively studied. In the case of RBCs, COS exhibited a low risk of hemolysis in a dose and molecular weight dependent manner and the irreversible aggregation was observed in their high concentration. For coagulation system, COS has a mild anticoagulation activity through blocking the intrinsic coagulation pathway. In addition, COS showed no effect on complement activation in C3a and C5a and on platelet activation while inhibition of platelet aggregation was evident. Finally, the mechanism that effects of COS on blood components was discussed and proposed.

Assessment of toxicity and oxidative DNA damage of sodium hypochlorite, chitosan and propolis on fibroblast cells

The objective of this study was to evaluate and compare the cytotoxicity and genotoxicity on human fibroblast cell lines of sodium hypochlorite (NaOCl), chitosan and propolis as root canal irrigating solutions. Human fibroblast cells were exposed to chitosan, propolis and NaOCl for 4 and 24 h. Cell viability was assessed by 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide, and oxidative DNA damage was assessed by determination of 8-hydroxydeoxyguanosine (8-OHdG) level with an ELISA kit. The data of cell cytotoxicity were analysed statistically using a test of one-way analysis of variance at a significance level of p < 0.05. In the NaOCI group, the 8-OHdG level was higher than in the chitosan group, but there was no statistical difference when compared with the other groups (p < 0.05). It was determined that the irrigation solutions were cytotoxic, depending on the dose and time. NaOCl was the most toxic solution after both 4 and 24 h of exposure (p < 0.05). Chitosan and propolis may be alternatives to NaOCl for irrigation solutions, because they are both less toxic and produce less oxidative DNA damage.

Interactions of oligochitosan with blood components

Oligochitosan (OCHI) is known to have some specific biological activities. However, its interactions with blood components and related correlation with molecular structures remains to be clarified due to its growing use in biomedical areas. Herein, a series of OCHI were prepared by hydrogen peroxide induced degradation combined fractionation in ethanol solutions and their molecular structures were characterized by GPC, FTIR, ¹H and ¹³C NMR, and then the interactions of the prepared OCHI with blood components, including red blood cells (hemolysis, deformability, and aggregation), coagulation system, complement (C3a, and C5a activation), and platelet (activation, and aggregation), were investigated. For red blood cells, OCHI has a quite low risk of hemolysis in a dose- and MW-dependent manner and the deformability and aggregation were observed in its high MW fraction. The coagulation tests revealed that OCHI is capable of a mild anticoagulation through blocking the intrinsic pathway and the anticoagulation corresponding MW was identified. In terms of complement, OCHI could inhibit C3a in a dose-dependent manner and activate C5a with its high MW fraction. In addition, there is no significant effect of OCHI on platelet activation and aggregation. Based on above results, the interactions related mechanism was discussed and proposed.

Biocompatibility studies of intravenously administered ionic-crosslinked chitosan-BSA nanoparticles as vehicles for antitumour drugs

In this study, a new alternative of ionic crosslinked nanoparticles (NPs) based on chitosan (C) and bovine serum albumin (A; BSA) was evaluated as drug delivery system for antitumour compounds (doxorubicin hydrochloride as a model). The different responses to the pH of the medium were determined by the electrostatic interactions induced by each polymeric combination (C50/A50; C80/A20; C20/A80). NPs revealed a nanoscale size (167-392 nm) and a positive net charge (12-26 mV), modulated by doxorubicin (DOX) loading. Drug loading capacity was higher than 5.2 ± 1.8 μgDOX/mgNP (Encapsulation efficiency = 34%), and an initial burst release was followed by a sustained delivery. Cellular uptake assays confirmed the entry of NPs in three human tumor cells (MCF7, T47D and Hela), triggering antioxidant responses (superoxide dismutase, catalase, glutathione reductase and total glutathione content) in those cells. This was also consistent with the decreased in IC50 values observed after the incubation of these cells with C20/A80-DOX and C50/A50-DOX NPs (1.90-3.48 μg/mL) compared with free DOX (2.36-6.025 μg/mL). In vivo results suggested that the selected proportions of chitosan-BSA created nonhemolytic and biocompatible stable NPs at the selected dose of 20 mg/kg. Despite the different formulations, this study demonstrated that these NPs could serve as safe drug carriers in further in vivo investigations.

Influence of chitosan oligosaccharide on the gelling and wound healing properties of injectable hydrogels based on carboxymethyl chitosan/alginate polyelectrolyte complexes

In situ injectable hydrogels for wound healing based on carboxymethyl chitosan (CMCS) and alginate were developed in this work. The liquid mixture of CMCS and alginate solutions formed a gel by polyelectrolyte complexation after addition of d-glucono-δ-lactone (GDL), which slowly hydrolyzed and donated protons. When chitosan oligosaccharide (COS) was added into the mixture, a two-stage gelling process occurred. The primary gelling process was similar to that of the hydrogel without COS, while the secondary gelling process appeared about 20 min later, and much stronger hydrogels with storage modulus G' about 1 MPa, 10⁴ times higher, were obtained. COS also significantly influenced the microstructure of hydrogels as well as their biological activities. The hydrogels with 0.5% of COS significantly promoted proliferation of human umbilical cord mesenchymal stem cells (HUMSCs). These injectable hydrogels, especially when COS was added, remarkably accelerated the wound healing process in a mouse skin defect model. Microscopic wound analysis showed an increase of the thickness and integrity of epidermal tissue, increased formation of collagen fibers, and enhanced expression of vascular endothelial growth factor as compared to the control group.

Cocoa Pod Husk Pectin Intended as a Pharmaceutical Excipient Has No Adverse Effects on Haematological Parameters in Sprague Dawley Rats

Natural polymer research has recently become the focus of intensive research in the quest for new enabling excipients for novel drugs in pharmaceutical formulation for optimal treatment outcomes. Evaluations of some excipients have shown deleterious haematological effects of varying extents on the safety profile of these excipients. A 90-day subchronic toxicity study was conducted to evaluate the influence of cocoa pod husk (CPH) pectin on indicators for haematotoxicity. Male and female Sprague Dawley rats (SDRs) were fed with CPH pectin in doses up to 71.4 mg/kg. The effects of CPH pectin on the haematological indices, direct and total bilirubin, and the spleen were determined. The results indicated that CPH pectin did not induce any untoward toxic effects on the haematological indices, bilirubin levels, and the spleen. There were, however, elevations in MCV at day 30, which was not sustained after the 90 days. The data obtained from this study did not reveal any remarkable findings of toxicological relevance to the haematopoietic system.

Comprehensive analysis of the in vitro and ex ovo hemocompatibility of surface engineered iron oxide nanoparticles for biomedical applications

A set of biomedically relevant iron oxide nanoparticles with systematically modified polymer surfaces was investigated regarding their interaction with the first contact partners after systemic administration such as blood cells, blood proteins, and the endothelial blood vessels, to establish structure-activity relationships. All nanoparticles were intensively characterized regarding their physicochemical parameters. Cyto- and hemocompatibility tests showed that (1) the properties of the core material itself were not relevant in short-term incubation studies, and (2) toxicities increased with higher polymer mass, neutral = anionic < cationic surface charge and charge density, as well as agglomeration. Based on this, it was possible to classify the nanoparticles in three groups, to establish structure-activity relationships and to predict nanosafety. While the results between cyto- and hemotoxicity tests correlated well for the polymers, data were not fully transferable for the nanoparticles, especially in case of cationic low molar mass polymer coatings. To evaluate the prediction efficacy of the static in vitro models, the results were compared to those obtained in an ex ovo shell-less hen's egg test after microinjection under dynamic flow conditions. While the polymers demonstrated hemotoxicity profiles comparable to the in vitro tests, the size-dependent risks of nanoparticles could be more efficiently simulated in the more complex ex ovo environment, making the shell-less egg model an efficient alternative to animal studies according to the 3R concept.

The mechanism of formation, structure and physiological relevance of covalent hemoglobin attachment to the erythrocyte membrane

Covalent hemoglobin binding to membranes leads to band 3 (AE1) clustering and the removal of erythrocytes from the circulation; it is also implicated in blood storage lesions. Damaged hemoglobin, with the heme being in a redox and oxygen-binding inactive hemichrome form, has been implicated as the binding species. However, previous studies used strong non-physiological oxidants. In vivo hemoglobin is constantly being oxidised to methemoglobin (ferric), with around 1% of hemoglobin being in this form at any one time. In this study we tested the ability of the natural oxidised form of hemoglobin (methemoglobin) in the presence or absence of the physiological oxidant hydrogen peroxide to initiate membrane binding. The higher the oxidation state of hemoglobin (from Fe(III) to Fe(V)) the more binding was observed, with approximately 50% of this binding requiring reactive sulphydryl groups. The hemoglobin bound was in a high molecular weight complex containing spectrin, ankyrin and band 4.2, which are common to one of the cytoskeletal nodes. Unusually, we showed that hemoglobin bound in this way was redox active and capable of ligand binding. It can initiate lipid peroxidation showing the potential to cause cell damage. In vivo oxidative stress studies using extreme endurance exercise challenges showed an increase in hemoglobin membrane binding, especially in older cells with lower levels of antioxidant enzymes. These are then targeted for destruction. We propose a model where mild oxidative stress initiates the binding of redox active hemoglobin to the membrane. The maximum lifetime of the erythrocyte is thus governed by the redox activity of the cell; from the moment of its release into the circulation the timer is set.

Surface charge-bias impact of amine-contained pseudozwitterionic biointerfaces on the human blood compatibility

This work discusses the impact of the charge bias and the hydrophilicity on the human blood compatibility of pseudozwitterionic biomaterial gels. Four series of hydrogels were prepared, all containing negatively-charged 3-sulfopropyl methacrylate (SA), and either acrylamide, N-isopropylacrylamide, 2-dimethylaminoethyl methacrylate (DMAEMA) or [2-(methacryloyloxy)ethyl]trimethylammonium (TMA), to form S_nA_m, S_nN_m, S_nD_m or S_nT_m hydrogels, respectively. An XPS analysis proved that the polymerization was well controlled from the initial monomer ratios. All gels present high surface hydrophilicity, but varying bulk hydration, depending on the nature/content of the comonomer, and on the immersion medium. The most negative interfaces (pure SA, S7A3, S5A5) showed significant fibrinogen adsorption, ascribed to the interactions of the αC domains of the protein with the gels, then correlated to considerable platelet adhesion; but low leukocyte/erythrocyte attachments were measured. Positive gels (excess of DMAEMA or TMA) are not hemocompatible. They mediate protein adsorption and the adhesion of human blood cells, through electrostatic attractive interactions. The neutral interfaces (zeta potential between -10mV and +10mV) are blood-inert only if they present a high surface and bulk hydrophilicity. Overall, this study presents a map of the hemocompatible behavior of hydrogels as a function of their surface charge-bias, essential to the design of blood-contacting devices.

Chitosan treatment abrogates hypercholesterolemia-induced erythrocyte's arginase activation

This study aimed to evaluate the protective effect of chitosan (CS) against hypercholesterolemia (HC) induced arginase activation and disruption of nitric oxide (NO) biosynthesis using erythrocytes as cellular model. Human erythrocytes were isolated and classified into eight groups. Next, cells were treated with l-arginine (l-ARG), N^ω-nitro-l-arginine methyl ester (l-NAME), CS or CS + l-ARG in the presence of normal plasma or cholesterol enriches plasma. Then, erythrocytes were incubated at 37 °C for 24 h. The present results revealed that, HC induced significant increase of cholesterol inclusion into erythrocytes membrane compared to control. Moreover, HC caused significant decrease in nitric oxide synthase (NOS) activity similar to l-NAME; however, arginase activity and arginase/NOS ratio significantly increased compared to control. On contrast, treatment of HC with, l-arginine, CS or CS plus l-arginine prevents HC induced cholesterol loading into erythrocytes membrane, NOS inhibition and arginase activation. This study suggested that CS could be protective agent against HC induced disruption of erythrocyte’s oxidative status and arginase activation.

Nanoscale Surface Characterization of Human Erythrocytes by Atomic Force Microscopy: A Critical Review

Erythrocytes (red blood cells, RBCs), the most common type of blood cells in humans are well known for their ability in transporting oxygen to the whole body through hemoglobin. Alterations in their membrane skeletal proteins modify shape and mechanical properties resulting in several diseases. Atomic force microscopy (AFM), a new emerging technique allows non-invasive imaging of cell, its membrane and characterization of surface roughness at micrometer/nanometer resolution with minimal sample preparation. AFM imaging provides direct measurement of single cell morphology, its alteration and quantitative data on surface properties. Hence, AFM studies of human RBCs have picked up pace in the last decade. The aim of this paper is to review the various applications of AFM for characterization of human RBCs topology. AFM has been used for studying surface characteristics like nanostructure of membranes, cytoskeleton, microstructure, fluidity, vascular endothelium, etc., of human RBCs. Various modes of AFM imaging has been used to measure surface properties like stiffness, roughness, and elasticity. Topological alterations of erythrocytes in response to different pathological conditions have also been investigated by AFM. Thus, AFM-based studies and application of image processing techniques can effectively provide detailed insights about the morphology and membrane properties of human erythrocytes at nanoscale.

Effects of chito-oligosaccharides supplementation on growth performance, intestinal cytokine expression, autochthonous gut bacteria and disease resistance in hybrid tilapia Oreochromis niloticus ♀ × Oreochromis aureus ♂

We investigated the effects of incorporating chitinase (ChiB565)-hydrolyzed shrimp shell chitin into the diet of hybrid tilapia (Oreochromis niloticus ♀ × Oreochromis aureus ♂) with regard to production, intestinal immune status and autochthonous gut bacteria, and protection against bacterial pathogen Aeromonas hydrophila. Five experimental diets were formulated by supplementing the basal diet with the hydrolyzed shrimp shell chitin (0.0%, T1 control; 0.8%, T3; 1.6%, T4; or 2.4%, T5) or 0.1% commercial chitosan-oligosaccharides as commercial recommendation dose (T2, positive control). After a 35-day feeding trial, we found no significant difference in weight gain, feed conversion ratio or survival rate in tilapia among all treatment groups. However, the levels of mRNAs encoding the pro-inflammatory protein tumor necrosis factor-α and the stress-response protein heat shock protein 70 were much lower in groups T2, T3, T4 and T5 (p < 0.001). The levels of transforming growth factor-β were higher in groups T2 and T4 (p < 0.001 and p < 0.0001, respectively). In addition, group T3 and T4 with 0.8% and 1.6% hydrolyzed shrimp shell chitin supplementation respectively changed marginally their autochthonous gut bacteria (0.60 < Cs < 0.80). When challenged with A. hydrophila, the mortality of groups fed chito-oligosaccharides was lower than the control, especially in groups T4 and T5 (p < 0.05). These results indicate that dietary intake of chito-oligosaccharides can improve intestinal health, changed autochthonous gut bacteria, and improve resistance to infection by A. hydrophila, even with higher efficiency than receiving the manufacturer recommended dose of the commercial chitosan-oligosaccharides.

Biocompatibility and hemocompatibility of polyvinyl alcohol hydrogel used for vascular grafting--In vitro and in vivo studies

Polyvinyl alcohol hydrogel (PVA) is a synthetic polymer with an increasing application in the biomedical field that can potentially be used for vascular grafting. However, the tissue and blood-material interactions of such gels and membranes are unknown in detail. The objectives of this study were to: (a) assess the biocompatibility and (b) hemocompatibility of PVA-based membranes in order to get some insight into its potential use as a vascular graft. PVA was evaluated isolated or in copolymerization with dextran (DX), a biopolymer with known effects in blood coagulation homeostasis. The effects of the mesenchymal stem cells (MSCs) isolated from the umbilical cord Wharton's jelly in the improvement of PVA biocompatibility and in the vascular regeneration were also assessed. The biocompatibility of PVA was evaluated by the implantation of membranes in subcutaneous tissue using an animal model (sheep). Histological samples were assessed and the biological response parameters such as polymorphonuclear neutrophilic leucocytes and macrophage scoring evaluated in the implant/tissue interface by International Standards Office (ISO) Standard 10993-6 (annex E). According to the scoring system based on those parameters, a total value was obtained for each animal and for each experimental group. The in vitro hemocompatibility studies included the classic hemolysis assay and both human and sheep bloods were used. Relatively to biocompatibility results, PVA was slightly irritant to the surrounding tissues; PVA-DX or PVA plus MSCs groups presented the lowest score according to ISO Standard 10993-6. Also, PVA was considered a nonhemolytic biomaterial, presenting the lowest values for hemolysis when associated to DX.

Evaluation of chitooligosaccharide application on mineral accumulation and plant growth in Phaseolus vulgaris

Chitooligosaccharides (COS) - water soluble derivatives from chitin, are an interesting group of molecules for several biological applications, for they can enter plant cells and bind negatively charged molecules. Several studies reported an enhanced plant growth and higher crop yield due to chitosan application in soil grown plants, but no studies have looked on the effect of COS application on plant mineral nutrient dynamics in hydroponically grown plants. In this study, Phaseolus vulgaris was grown in hydroponic culture and the effect of three different concentrations of COS on plant growth and mineral accumulation was assessed. There were significant changes in mineral allocations for Mo, B, Zn, P, Pb, Cd, Mn, Fe, Mg, Ca, Cu, Na, Al and K among treatments. Plant morphology was severely affected in high doses of COS, as well as lignin concentration in the stem and the leaves, but not in the roots. Chlorophyll A, B and carotenoid concentrations did not change significantly among treatments, suggesting that even at higher concentrations, COS application did not affect photosynthetic pigment accumulation. Plants grown at high COS levels had shorter shoots and roots, suggesting that COS can be phytotoxic to the plant. The present study is the first detailed report on the effect of COS application on mineral nutrition in plants, and opens the door for future studies that aim at utilizing COS in biofortification or phytoremediation programs.

In vitro antioxidant and antiproliferative activities of 5-hydroxymethylfurfural

5-HMF is widely presented in foods and produced through the degradation of hexoses and Maillard reaction during heat treatment of foods containing reducing sugars and amino acids in an acid environment. However, controversial conclusions on the biological effects of 5-HMF have been drawn in previous studies. Therefore, the main aim of this study was to investigate the antioxidant and antiproliferative activities of 5-HMF. The 2,2'-azinobis-3-ethylbenzothiazolin-6-sulfonic acid (ABTS) assay, the 1,1-diphenyl-2-picryhydrazyl (DPPH) assay, and the hemolysis assay induced by 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) were performed to evaluate the antioxidant capacity of 5-HMF. The results showed that 5-HMF exhibited novel antioxidant activity by scavenging the ABTS and DPPH free radicals and inhibited the AAPH-induced hemolysis in a dose-dependent manner. In the hemolysis assay, the reduction of ROS and MDA contents and the increase in enzyme activities of SOD, CAT, and GPx were found in erythrocytes pretreated with 5-HMF, which demonstrated that 5-HMF could prevent the peroxidation from the source to protect the erythrocytes. The morphological changes of erythrocytes was also verified by observation using atomic force microscopy. The inhibitory effect of 5-HMF on human cancer cell proliferation was investigated by MTT assay, flow cytometric analysis, and the TUNEL and DAPI costaining assay. The results showed that 5-HMF displayed higher antiproliferative activity on human melanoma A375 cells than other cell lines. Further investigation on the action mechanisms revealed that 5-HMF could induce A375 cell apoptosis and G0/G1 cell cycle arrest. The A375 cell apoptosis that 5-HMF induced was characterized by a TUNEL and DAPI costaining assay. These findings suggest that 5-HMF could be developed as a novel natural antioxidant with potential applications in cancer chemoprevention.

Interaction mechanism of cortisol and catecholamines with structural components of erythrocyte membranes

Nonspecific mechanisms of the stress hormones interaction with erythrocyte membranes were studied by means of atomic force microscopy, fluorescence analysis, and IR spectroscopy. It was shown that stress hormones (cortisol, adrenaline, noradrenaline) can bind to erythrocyte membranes with high affinity (K(b) approximately 10(6) M(-1)). The binding mechanism involves hydrogen bonds and hydrophobic and electrostatic interactions. Active groups of the hormones (NH(2), NHCH(3), keto, and hydroxy groups) interact simultaneously with CO and NH groups both of proteins and phospholipids. This leads to the formation of complex protein-lipid domains that distort the surface of the erythrocyte membrane. Water dipoles are displaced from the domains to adjacent regions and facilitate membrane loosening. The interaction of hormones with the membrane is accompanied by structural transitions of disorder --> order (tangle --> alpha-helix, tangle --> beta-structure) in membrane proteins and structural transitions of order --> order in phospholipids. Formation of large domains (clusters) of the lipid-protein and lipid nature leads to distortion of membranes and deteriorates their elasticity and rheological properties.

Anti-inflammatory activity of chitooligosaccharides in vivo

All the reports to date on the anti-inflammatory activity of chitooligosaccharides (COS) are mostly based on in vitro methods. In this work, the anti-inflammatory activity of two COS mixtures is characterized in vivo (using balb/c mice), following the carrageenan-induced paw edema method. This is a widely accepted animal model of acute inflammation to evaluate the anti-inflammatory effect of drugs. Our data suggest that COS possess anti-inflammatory activity, which is dependent on dose and, at higher doses, also on the molecular weight. A single dose of 500 mg/kg b.w. weight may be suitable to treat acute inflammation cases; however, further studies are needed to ascertain the effect upon longer inflammation periods as well as studies upon the bioavailability of these compounds.

Degradation of chitosans with chitinase G from Streptomyces coelicolor A3(2): production of chito-oligosaccharides and insight into subsite specificities

We have studied the degradation of soluble heteropolymeric chitosans with a bacterial family 19 chitinase, ChiG from Streptomyces coelicolor A3(2), to obtain insight into the mode of action of ChiG, to determine subsite preferences for acetylated and deacetylated sugar units, and to evaluate the potential of ChiG for production of chito-oligosaccharides. Degradation of chitosans with varying degrees of acetylation was followed using NMR for the identity (acetylated/deacetylated) of new reducing and nonreducing ends as well as their nearest neighbors and using gel filtration to analyze the size distribution of the oligomeric products. Degradation of a 64% acetylated chitosan yielded a continuum of oligomers, showing that ChiG operates according to a nonprocessive, endo mode of action. The kinetics of the degradation showed an initial rapid phase dominated by cleavage of three consecutive acetylated units (A; occupying subsites -2, -1, and +1), and a slower kinetic phase reflecting the cleavage of the glycosidic linkage between a deacetylated unit (D, occupying subsite -1) and an A (occupying subsite +1). Characterization of isolated oligomer fractions obtained at the end of the initial rapid phase and at the end of the slower kinetic phase confirmed the preference for A binding in subsites -2, -1, and +1 and showed that oligomers with a deacetylated reducing end appeared only during the second kinetic phase. After maximum conversion of the chitosan, the dimers AD/AA and the trimer AAD were the dominating products. Degradation of chitosans with varying degrees of acetylation to maximum degree of scission produced a wide variety of oligomer mixtures, differing in chain length and composition of acetylated/deacetylated units. These results provide insight into the properties of bacterial family 19 chitinases and show how these enzymes may be used to convert chitosans to several types of chito-oligosaccharide mixtures.