Teses / dissertações sobre o tema "Polysaccharide"

This investigation looks at the hydrodynamic characterisation of both covalent and non-covalent protein polysaccharide complexes in the context of novel treatments and healthcare. New techniques were employed and evaluated, such as the MUTLTISIG and SEDFIT-MSTAR algorithms for sedimentation equilibrium analysis, as well as the Extended Fujita Approach for sedimentation velocity. Other characterisation techniques were used such as viscometry, density measurement, Dynamic Light Scattering and Size Exclusion Chromatography coupled to Multi Angle Light Scattering. Therapeutics for the treatment of Diabetes Mellitus and Coeliac Disease were considered. There is evidence to suggest that a protein polysaccharide complex extracted from the pulp of pumpkins has a hypoglycaemic effect in human physiology. This extract was assessed in terms of molecular integrity as a precursor to human trial studies. Equally, a novel treatment for Coeliac Disease, gliadin intolerance found in approximately 1% of the population, was assessed in terms of protecting the immune system from gliadin. Well-established methods, along with newly developed methods, were also used to characterise two glycoproteins relevant to the healthcare and food industries: Human gastric mucin, a natural lubricant found in the human stomach, and gum arabic, a plant extract from the Acacia tree. Findings from these investigations were able to add to our current understanding of these two macromolecules.

L'établissement de relations structure-propriétés peut conduire à l'amélioration des propriétés des réseaux et des gels et à l'élaboration de systèmes plus performants en vue d'une application définie. Aussi, au cours de ce travail, nous nous somme proposes de mettre en évidence la structure qui intervient pour les mélanges kappa carraghenane-caroube et agarose-caroube. Différentes techniques expérimentales d'étude nous ont permis d'aborder la gélification ainsi que les réseaux et les gels à l'état final : la résonance magnétique nucléaire du carbone 13 (RMN 13C); la diffusion aux petits angles des rayons X (DPAX); la rhéologie; la modélisation moléculaire. Les études par RMN 13C et DPAX. Nous ont permis de couvrir les domaines moléculaire et macromoléculaire. La rhéologie nous a amené à une investigation du domaine supramoléculaire. Enfin, la modélisation moléculaire a constitué une approche théorique du phénomène. Nous avons essaye d'établir des corrélations entre les informations fournies par les différentes méthodes de façon à aboutir à un modèle pour ces gels à deux composants macromoléculaires

Polysaccharides are one of the most abundant and diverse families of natural polymers, and have an incredibly wide range of natural functions including structural reinforcement, energy storage, aqueous rheology modification, and communication and identity. Application of native polysaccharides like cellulose as sustainable materials is limited by some inherent drawbacks such as insolubility in common solvents including water, and poor dimensional stability. To increase their functionality and utility, researchers have sought to tailor the chemical and physical properties of cellulose and other polysaccharides using a variety of chemical modification techniques, resulting in a number of important, useful commercial derivatives. Because of their greater biocompatibility and biodegradability, and low immunogenicity, naturally derived cationic polymers including cationic polysaccharide derivatives are very attractive candidates for biomedical applications, due to the fact that they are capable of binding with anionic biomolecules, such as nucleic acids and certain proteins, via electrostatic interactions. However, there are relatively few practical synthetic methods reported for their preparation. We demonstrated a useful and efficient strategy for cationic polysaccharide salt preparation by reaction of 6-bromo-6-deoxypolysaccharides such as 6-bromo-6-deoxycellulose esters with pyridine or 1-methylimidazole exclusively at the C-6 position, resulting in high degrees of substitution (DSs). These permanently cationic polysaccharide derivatives have been demonstrated to dissolve readily in water, and bind strongly with a hydrophilic and anionic surface. Availability of these cationic polysaccharides will facilitate structure-property relationship studies for biomedical uses including drug delivery and bioelectronics applications. We also extended the chemistry, reacting 6-imidazolo-6-deoxycellulose with propane sultone, leading to a new synthetic pathway to zwitterionic cellulose derivatives. In addition to cationic and zwitterionic derivatives, we found a simple, efficient route to carboxyl-containing polysaccharide derivatives from curdlan esters via regioselective ring-opening reactions catalyzed by triphenylphosphine (Ph3P) under mild conditions. Curdlan, a polysaccharide used by the food industry and in biomedical applications, was employed as starting material for preparing these carboxyl-containing derivatives by a reaction sequence of bromination, azide displacement and ring-opening reaction with cyclic anhydrides, affording high conversions. These modification techniques have been demonstrated to display essentially complete regio- and chemo-selectivity at C-6. These novel polysaccharide-based materials starting from abundant and inexpensive curdlan are promising for some applications such as amorphous solid dispersion (ASD) oral drug delivery.
Ph. D.

Astragalus gombo Bunge (Fabaceae) est une plante bien représentée dans le Sahara Septentrional Est Algérien (région de Ouargla, Algérie) et couramment utilisée comme fourrage pour les animaux ou en médecine traditionnelle. Malgré de nombreuses publications sur la richesse en polysaccharides d’autres espèces appartenant au genre Astragalus et la description de leurs propriétés biologiques putatives ou avérées, aucune étude ne s’est intéressée à l’espèce gombo. L’objectif de ce travail de thèse a donc été de réaliser des investigations sur plusieurs parties de cette plante en vue d’extraire, identifier et caractériser son contenu en polysaccharides. Dans un second temps les propriétés biologiques et rhéologiques de ces polymères ont été étudiées afin d’identifier d’éventuelles voies de valorisation. Les résultats obtenus ont permis de détecter la présence de composés pectiques et hémicellulosiques dans la tige d’Astragalus gombo et celle d’un galactomannane dans les graines. Le galactomannane est de haute masse moléculaire (1,1x106 Da) et est constitué d’une chaine principale de β-(1→4)-D-mannane ramifiée en α-(1→6) par des résidus Dgalactopyranoses avec un rapport M/G de 1,7. La caractérisation de ses propriétés rhéologiques a révélé un comportement typique rhéofluidifiant et des propriétés viscoélastiques. L’étude des activités biologiques associées à ce biopolymère a révélé son potentiel comme prébiotique et antioxydant
Astragalus gombo Bunge (Fabaceae) is a terrestrial plant occuring in the East Septentrional Sahara (Ouargla, Algeria). It is commonly used as fodder or in traditional medicine by local populations. Despite numerous publications focusing on polysaccharidic contents of Astragalus species and the designation of their putative or proved biological activities, no study has examined those of A. gombo. The objective of this thesis was firstly to investigate several organs of this plant for their polysaccharide contents. In a second step, the biological and rheological properties of these biopolymers have been studied to identify ways of adding value. Results led to the identification of pectic compounds and hemicelluloses in the rods of Astragalus gombo whereas a galactomannan was detected in its seeds. This galactomannan was a high molecular weight macromolecule composed of a β-(1→4)-D-mannan skeleton ramified by residues of D-galactopyranoses. The M/G ratio was of 1.7. The characterization of its rheological behavior was typic of that of a rheofluidifiant fluid with viscoelastic properties. The study of its biological properties showed its potential as prebiotic and antioxidant agent

Thesis submitted in fulfilment of the requirements for the degree Master of Technology: Food Technology in the Faculty of Applied Sciences at the Cape Peninsula University of Technology
The aim of this study was to evaluate bambara groundnut [BGN] non-starch polysaccharides [NSP] subject to the incorporation into model and food systems with a view to establish their functional and physicochemical properties. BGN insoluble dietary fibre [BGNIF] and soluble dietary fibre [BGNSF] were successfully extracted from four varieties (black-eye: BLE, red: RED, brown: BRN and brown-eye: BRE). Physicochemical properties evaluated revealed the high bulk density of all BGNIF and BGNSF varieties, which could contribute to cost-effective packaging. The microstructures of BGNIFs were irregular in shape with different sizes. The colour parameters (lightness, redness, yellowness, chroma and hue angle) differed significantly [p ≤ 0.05] across all BGNIF and BGNSF varieties; and indicated a yellowish-red colour for BGNIFs and a light yellow colour for BGNSFs. Negligible amounts of condensed tannins [CT] were found in BGNIFs (0.014 – 0.160 mg.g-1). Higher amounts polyphenols [PP] were present in BGNSFs (45.42 – 55.90 mg.g-1 gallic acid equivalents [GAE]) compared to the amount PP in BGNIFs (6.14 – 15.56 mg.g-1 GAE). Major sugars identified were arabinose/galactose, xylose and mannose in BGNIFs, and xylose and mannose in BGNSFs. The functional properties evaluated revealed high swelling capacity of BGNIFs (6.37 – 7.72 ml.g-1) and no significant [p > 0.05] difference in water retention capacity. Fat absorption capacity ranged from 1.38 – 1.52 g oil.g-1 dry weight for BGNIFs and 4.04 – 4.55 g oil.g-1 dry weight for BGNSFs. Variability in BGNIF (91.2%) and BGNSF (79.4%) physicochemical and functional properties could both be explained by two principal components (BGNIF component 1: PP, redness, yield; and component 2: xylose, yellowness and chroma; BGNSF component 1: yellowness, chroma, mannose content; and component 2: redness, fat absorption and fructose content). Following an IV optimal mixture design, an optimum white bread formulation was obtained using 59.5% water, 4.3% yeast and 8.5% BGNIF. Bread enriched with the four BGNIF varieties (BLE, RED, BRN and BRE) were tested for several physicochemical properties. Significant [p ≤ 0.05] differences existed between the control and BGNIF enriched loaves for crumb grain characteristics (including pore area distribution, feret angle, circularity, roundness and aspect ratio). Specific loaf volume of BGNIF enriched loaves ranged from 3.33 – 3.85 ml.g-1 and were significantly [p ≤ 0.05] lower compared to the control bread (4.16 ml.g-1). Favourable texture characteristics obtained with the BGNIF enriched breads were lower hardness, chewiness and gumminess compared to the control loaf. Crust and crumb colour parameters (lightness, redness, yellowness, chroma and hue angle) were significantly [p ≤ 0.05] different across all loaves. BRE BGNIF bread (3.43 ± 0.20) had the significantly [p ≤ 0.05] lowest crumb colour difference compared to the control bread; whilst BRN (1.72 ± 0.42) and BRE (2.44 ± 0.78) loaves had the lowest significant [p ≤ 0.05] crust colour difference compared to the control. Favourable chemical properties were the high total dietary fibre [TDF] (7.14 – 8.33%) content of all BGNIF enriched loaves compared to the control loaf (4.96%). Significant [p ≤ 0.05] differences were also observed for some loaves for moisture content, condensed tannins and polyphenol content. Variability in bread physicochemical properties was differentiated by three components (component 1: bread textural properties; component 2: specific loaf volume and bread lightness; component 3: crumb colour parameters) which accounted for a cumulative variation of 92.8%. All bread loaves were also sensorially acceptable as rated moderately like to like very much (>3 rating on a 5-point hedonic scale) by consumers for all parameters (appearance, crust and crumb colour, aroma, taste, texture and overall acceptability) evaluated. Furthermore, brown BGNSF was tested for stabilising effects in an orange beverage emulsion. BGNSF and orange oil were varied at two levels each based on a 22 augmented factorial design and the effects determined on the equilibrium backscattering [BS] flux as emulsion stability indicator. The BS profiles which resulted from the Turbiscan stability analysis revealed flocculation at low rates as the major destabilisation mechanism. The optimal formulation producing a stable emulsion was identified as low oil (6%) and high BGNSF (30%) concentrations. The objective of this study was therefore achieved and showed that positive physicochemical and functional properties are associated with BGNIF and BGNSF from black-eye, red, brown and brown-eye varieties. Furthermore, the incorporation of BGN fibres in white bread and a beverage emulsion was shown to contribute positive technological properties in these systems.

Thesis (Doctor of Philosophy)--Case Western Reserve University, 2010
Department of Chemical Engineering Title from PDF (viewed on 2010-05-25) Includes abstract Includes bibliographical references and appendices Available online via the OhioLINK ETD Center

The role of hydrophobic substituents on the gelation mechanism of highly esterified pectin and the cellulose derivatives methylcellulose and hydroxypropylmethylcellulose (HPMC) has been explored by monitoring the behaviour of the amphiphilic polysaccharides in varying combinations of an ethylene glycoVwater solvent. The gelling ability (mechanical spectroscopy, visual observation) of very highly esterified (- 100%) pectin in high concentrations of ethylene glycol (>60%) is greatly reduced, however, the polymer still undergoes conformational ordering (CD, OR). A model for gel formation involving a two stage process has been proposed, comprising adoption of the ordered structure stabilised by hydrogen bonding between OH groups of contiguous polysaccharide chains, followed by (or coincident with) aggregation of the ordered sequences by 'hydrophobic' clustering of the fundamental structural subunits to form the three dimensional gel network. It has been found that ethylene glycol promotes the fIrst stage (ordering) but is antagonistic to the second (aggregation). The reversibility (mechanical spectroscopy) of the thermo-gelling cellulose derivatives can be largely abolished in the presence of ethylene glycol (40% for methylcellulose, 10% for HPMC), attributed to solubilisation of the proposed ordered 'bundle' structure at low temperatures removing the enthalpic advantage (DSC) of gel melting. The increased sensitivity of HPMC to modification of the solvent environment is due to the presence of the polar hydroxypropyl substituent causing an inceptive destabilisation of the 'bundle' structure. It is suggested that gelation is driven by the entropic advantage of melting-out 'cages' of structured water surrounding the hydrophobic groups giving rise to intermolecular 'hydrophobic' aggregation.

Thesis (MSc)--Stellenbosch University, 2015.
ENGLISH ABSTRACT: Lignocellulosic material is composed of three major macromolecule components i.e., cellulose, hemicelluloses and lignin. These components are chemically associated and directly linked to each other through covalent bonding which is scientifically denoted as lignin-carbohydrate complexes (LCCs) and their interaction is fundamentally important as to understand wood formation and reactivity during chemical and biological processing e.g. pulping and enzymatic hydrolysis. The association of lignin with polysaccharides (covalent linkages) has been surrounded by contradictions and controversy in several wood chemistry studies. These linkages exist in lignocellulosic materials from wood to herbaceous plants. In woody plants, they consist of ester and ether linkages through sugar hydroxyl to α-carbonyl of phenyl-propane unit on lignin. However, in herbaceous plants ferulic and p-coumaric acids are esterified to hemicelluloses and lignin respectively. In recent studies, the existence of the bonds has been shown by applying indirect analysis strategies which resulted to low yields and contaminations. The general aim of the current study was to isolate and fractionate LCCs from raw lignocellulosic materials (E. grandis and sugarcane bagasse) and corresponding processed materials (chemical pulps and water-insoluble residues (WIS)) in order to determine the chemical structure of the residual lignin associated with polysaccharides and how they affected industrial processing. The objective of the study is to compile a document that when the development of pulping and bio-ethanol bio-refinery will greatly depends on the detailed wood chemistry on how the components interact with each before and after hemicelluloses pre-extraction prior to pulping and steam explosion pre-treatment prior to enzymatic hydrolysis. The current study was focusing on understanding the effect LCCs isolated from two different industrial processing methods, i.e. pulping and enzymatic hydrolysis (EH). There were two lignocelluloses feedstocks used for pulping, i.e. Eucalyptus grandis and sugarcane bagasse whereas sugarcane bagasse was the only feedstock used for enzymatic hydrolysis. Hemicelluloses pre-extracted (mild alkali or dilute acid and autohydrolysis for sugarcane bagasse) pulps of Kraft or soda AQ from E. grandis and sugarcane bagasse were used to understand the effect of xylan pre-extraction prior to pulping on lignin-carbohydrate complexes has not been reported to the best knowledge of the primary author. Also prior to EH the material was subjected to two different treatment methods, i.e. steam explosion and ionic liquid fractionation in varying conditions. The study illustrated the types of extracted and fractionated LCCs from hemicelluloses pre-extracted pulps and WIS in comparison to the non-extracted pulps and reports from the literature. Lignin-carbohydrate complexes (LCCs) were isolated and fractionated by an inorganic method which yielded reasonable quantification quantities and no contamination and low yields for the hardwood compared to reports of using an enzymatic method. To the best knowledge of the authors, no work has been done on WIS material. The lignocelluloses were subjected to ball milling which was followed by a sequence of inorganic solvents swelling and dissolution into 2 fractions i.e. glucan-lignin and xylan-lignin-glucan. Characterisation of the isolated LCCs was made using a variety of analytical tools such as FTIR-PCA, HPLC, GPC and GC-MS. LCCs were evident when FTIR and HPLC studies were conducted. Residual lignin isolated from the lignocelluloses was assumed to be chemically bonded to carbohydrates and mostly to xylan. Approximately 60% and 30% of the lignin was linked to xylan while for the second and first fractions respectively. It is reported that lignin associated with xylan is more resistant and reduce the delignification process than when linked to glucan that is easily hydrolysable. With the FTIR and GPC analyses of LCC fractions, it was evident that the ester bonds of LCCs were destroyed through pre-extraction and pre-treatment, where this resulted to more cellulose being more accessible to alkaline pulping and enzymatic hydrolysis respectively. The linkages were either partially broken down or completely destroyed leading to significant changes of chemical structures. The polydispersity of the LCCs assisted in determining the structure of lignin, either existing as monolignols on the surfaces of fibres or a as complex two or three-dimensional structure that is linked to carbohydrates as the Mw increased or decreased. In general, these findings may have an important implication for the overall efficiency on bio-refinery. The molecular weights (Mw) of the extracted LCCs were measured by gel permeation chromatography. From the chromatograms, it was observed that the materials that were subjected to pre-processing prior to further processing, the Mw shifted to lower Mws regions. It was found that LCCs isolated from mild alkali pre-extracted pulps had high lignin syringyl to guaiacyl lignin contents than LCCs isolated from dilute acid pre-extracted pulps. High syringyl/guaiacyl ratio (S/G ratio) was an indication of low lignin content as a result of processing which will result to high product yields after downstream processing. The 5 average S/G ratio for the pulps from E. grandis and sugarcane bagasse was ranging between 1.1 to 19.01 and 1.4 to 18.16 respectively, while for the WIS-material generated from ionic liquid fractionated and steam exploded materials ranged from 3.29 to 9.27 and 3.5 to 13.3 respectively. The S/G ratios of the LCCs extracted from E. grandis and sugarcane bagasse pulps ranged from 0.42 to 2.39 and 0.041 to 0.31 was respectively while for the LCCs extracted from water-insoluble-solids (WIS) material generated from steam exploded material was from 4.87 to 10.40. The determination of S/G ratio is recommended for the LCC extraction and characterisation study as an evaluation of residual lignin in processed materials such as pulps and WIS. The obtained saccharifications were low, possibly due to the severity of the steam explosion pre-treatment and ionic liquid fractionation conditions which resulted on high accumulation of acetic acid and increased in cellulose crystallinity respectively. From quantitative analysis of the LCCs perspective it could be concluded that free lignin was present in mild alkali pre-extracted pulps than for the dilute acid pre-extracted pulps.
AFRIKAANSE OPSOMMING: Cellulose materiaal is saamgestel uit drie groot makromolekule komponente naamlik, sellulose, hemisellulose en lignien. Hierdie komponente is chemies verwante en direk met mekaar verbind deur kovalente binding wat wetenskaplik aangedui as lignien-koolhidraat komplekse (LCCs) en hul interaksie is fundamenteel belangrik as hout vorming en reaktiwiteit tydens chemiese en biologiese verwerking bv om te verstaan verpulping en ensiematiese hidrolise. Die vereniging van lignien met polisakkariede (kovalente verbindings) is omring deur teenstrydighede en omstredenheid in verskeie hout chemie studies. Hierdie skakeling bestaan in cellulose materiaal uit hout te kruidagtige plante. In houtagtige plante, hulle bestaan uit ester en eter bindings deur suiker hidroksiel te α-karboniel van feniel-propaan eenheid op lignien. Maar in kruidagtige plante ferulic en p-coumaric sure veresterd te hemisellulose en lignien onderskeidelik. In onlangse studies, het die bestaan van die bande is getoon deur die toepassing van indirekte analise strategieë wat gelei tot lae opbrengste en kontaminasie. Die algemene doel van die huidige studie was om te isoleer en fraksioneer LCCs van rou cellulose materiaal (E. grandis en suikerriet bagasse) en die ooreenstemmende verwerkte materiaal (chemiese pulp en water-oplosbare residue (WIS)) ten einde die chemiese struktuur van die te bepaal oorblywende lignien wat verband hou met polisakkariede en hoe hulle geaffekteerde industriële verwerking. Die doel van die studie is 'n dokument op te stel dat wanneer die ontwikkeling van verpulping en bio-etanol bio-raffinadery sal grootliks afhang van die gedetailleerde hout chemie oor hoe om die komponente met mekaar voor en na hemisellulose pre-onttrekking voor verpulping en stoom ontploffing pre-behandeling voor ensiematiese hidrolise. Die huidige studie was die fokus op die begrip van die effek LCCs geïsoleerd van twee verskillende industriële verwerking, maw verpulping en ensiematiese hidrolise (EH). Daar was twee lignocelluloses voerstowwe gebruik vir verpulping, dws Eucalyptus grandis en suikerriet bagasse terwyl suikerriet bagasse was die enigste grondstof gebruik vir ensiematiese hidrolise. Hemisellulose pre-onttrek (ligte alkali of verdunde suur en autohydrolysis vir suikerriet bagasse) pulp van Kraft of soda AQ van E. grandis en suikerriet bagasse is gebruik om die effek van Xylan pre-onttrekking te voor verstaan verpulping op lignien-koolhidraat komplekse het nie aan die berig is beste kennis van die primêre outeur. Ook voor EH die materiaal is onderworpe aan twee verskillende behandeling metodes, naamlik stoom ontploffing en ioniese vloeistof fraksionering in wisselende toestande. Die studie geïllustreer die tipes onttrek en gefractioneerd LCCs van hemisellulose pre-onttrek pulp en WIS in vergelyking met die nie-onttrek pulp en verslae van die literatuur. Lignien-koolhidraat komplekse (LCCs) is geïsoleer en gefraksioneer deur 'n anorganiese metode wat redelike kwantifisering hoeveelhede en geen besoedeling en lae opbrengste opgelewer vir die hardehout vergelyking met verslae van die gebruik van 'n ensiematiese metode. Na die beste kennis van die skrywers, het geen werk op WIS materiaal gedoen. Die lignocelluloses is onderworpe aan die bal maal wat gevolg is deur 'n reeks van anorganiese oplosmiddels swelling en ontbinding in 2 breuke dws glucan-lignien en Xylan-lignien-glucan. Karakterisering van die geïsoleerde LCCs is gemaak met behulp van 'n verskeidenheid van analitiese gereedskap soos FTIR-PCA, HPLC, GPC en GC-MS. LCCs was duidelik wanneer FTIR en HPLC studies is uitgevoer. Residuele lignien geïsoleerd van die lignocelluloses is aanvaar moet word chemies gebind aan koolhidrate en meestal te xylan. Ongeveer 60% en 30% van die lignien is gekoppel aan xylan terwyl dit vir die tweede en eerste breuke onderskeidelik. Dit is gerapporteer dat lignien wat verband hou met Xylan is meer bestand en die delignification proses as wanneer gekoppel aan glucane wat maklik hidroliseerbare verminder. Met die FTIR en GPC ontledings van LCC breuke, was dit duidelik dat die ester bande van LCCs is deur pre-ontginning en pre-behandeling, waar dit gelei tot meer sellulose om meer toeganklik te alkaliese verpulping en ensiematiese hidrolise onderskeidelik vernietig. Die skakeling is óf gedeeltelik afgebreek of heeltemal vernietig lei tot beduidende veranderinge van chemiese strukture. Die polydispersity van die LCCs bygestaan in die bepaling van die struktuur van lignien, hetsy bestaande as monolignols op die oppervlak van die vesel of 'n as komplekse twee of drie-dimensionele struktuur wat gekoppel is aan koolhidrate as die Mw vermeerder of verminder. In die algemeen, kan hierdie bevindinge het 'n belangrike implikasie vir die algehele doeltreffendheid op bio-raffinadery. Die molekulêre gewigte (Mw) die onttrek LCCs gemeet deur gelpermeasie- chromatografie. Van die chromatograms, was dit opgemerk dat die materiaal wat blootgestel is aan die pre-verwerking voor verdere verwerking, die Mw verskuif MWS streke te verlaag. Daar is gevind dat LCCs geïsoleerd van ligte alkali pre-onttrek pulp het hoë lignien syringyl lignien inhoud as LCCs geïsoleerd van verdunde suur vooraf onttrek pulp te guaiacyl. Hoë syringyl / guaiacyl verhouding (S/G-verhouding) was 'n aanduiding van 'n lae lignien inhoud as 'n resultaat van verwerking wat sal lei tot 'n hoë produk opbrengste ná stroomaf verwerking. Die gemiddelde S/G-verhouding vir die pulp van E. grandis en suikerriet bagasse was wat wissel tussen 1,1-19,01 en 1,4-18,16 onderskeidelik, terwyl dit vir die WIS-materiaal gegenereer uit ioniese vloeistof gefraksioneer en stoom ontplof materiaal het gewissel 3,29-9,27 en 3.5 13,3 onderskeidelik. Die S/G verhoudings van die LCCs onttrek uit E. grandis en suikerriet bagasse pulp gewissel 0,42-2,39 en ,041-,31 was onderskeidelik terwyl dit vir die LCCs onttrek uit water-oplosbare-vastestowwe (WIS) materiaal gegenereer uit stoom ontplof materiaal was van 4,87-10,40. Die bepaling van S/G-verhouding word aanbeveel vir die LCC ontginning en karakterisering studie as 'n evaluering van die oorblywende lignien in verwerkte materiaal soos pulp en WIS. Die verkry saccharifications was laag, moontlik as gevolg van die erns van die stoom ontploffing pre-behandeling en ioniese vloeistof fraksionering voorwaardes wat gelei op 'n hoë opeenhoping van asynsuur en vermeerder in sellulose kristalliniteit.

La prise en charge du diabète de type I se fait à l’heure actuelle par des injections pluriquotidiennes d’insuline ou par l’utilisation d’une pompe à insuline qui va mimer l’activité pancréatique. Dans ce contexte, les nanogels sensibles au glucose représentent des candidats à fort potentiel pour une délivrance contrôlée de l’insuline.La majorité des matériaux développés à ce jour ne présentent pas d’études en vue d’application in vivo et ce, pour diverses raisons telles que la non validation du caractère biocompatible et biorésorbable de la matrice polymère. Afin de répondre à ces deux critères, nous avons choisi de développer des nanogels à base de polysaccharides biocompatibles et biodégradables.Des travaux antérieurs au sein du laboratoire ont porté sur la conception d’hydrogels à base d’acide hyaluronique. Le polysaccharide a été fonctionnalisé avec des dérivés de l’acide phénylboronique (PBA) et du maltose. Ces modifications permettent dans des conditions physiologiques de générer des réticulations boronate-ester. Ces liaisons permettent d’induire une modification de la structure des hydrogels en réponse à divers stimuli tel que le pH ou l’addition de composés saccharidiques.Afin de faciliter l’administration de tels matériaux, nous avons étendu ce concept à la formation de nanogels. Des nanogels sensibles au pH et/ou à l’addition de saccharides ont pu être obtenus en conditions physiologiques grâce au choix judicieux des polysaccharides partenaires modifiés par le PBA et des molécules portant des fonctions diol. Ces nanogels sont capables de piéger l’insuline lors de leur formation avec une efficacité d’encapsulation allant de 45% à 80% et une capacité d’encapsulation de 10% à 60%. Les premiers tests ont montré un faible relargage de l’insulin par nos nanogels.Finalement, au vue de la sensibilité au pH de nos nanogels et l’environnement acide présent autour des tumeurs, leur utilisation pour le traitement du cancer a été étudié. Des analyses in vitro ont démontré une faible toxicité de nos gels sur les cellules cancéreuses. Les premières expériences in vivo ont montré la capacité des nanogels à circuler dans le sang
Type 1 diabetes management is currently done by multiple insulin injections or by the use of an insulin pump that will mimic pancreatic activity. In this context, glucose-sensitive nanogels represent high potential candidates for controlled delivery of insulin.The majority of materials developed so far are limited to biological in vitro studies, which is partly due to the non-biocompatibility and limited biodegradability of polymers used for the preparation of such materials. To fulfill these criteria, we proposed to develop nanogels based on biocompatible and biodegradable polysaccharides.Previous work in our laboratory focused on the design of boronate-crosslinked hydrogels based on hyaluronic acid. This polysaccharide was functionalized with derivatives of phenylboronic acid (PBA) and of maltose. The dynamic covalent boronate ester crosslinks between the polysaccharide chains enabled to induce a structural change of the hydrogel in response to various stimuli such as pH or addition of carbohydrate molecules.In order to facilitate administration of such materials, we extended the concept to the formation of nanogels. Sugar- and pH-sensitive nanogels could be successfully obtained in physiological conditions thanks to the judicious choice of the polysaccharide partners, bearing PBA moieties and diol-containing molecules.These nanogels can entrap insulin during their formation with an entrapment efficiency of 45% to 80% and a loading capacity ranging from 10% to 60%. Preliminary experiments indicated a low release of insulin from the nanogels.Finally, in view of the pH-sensitivity of these nanogels and the slight acidic pH of the tumor environment, we investigated their potential application for the treatment of cancer. In vitro experiment demonstrated a low toxicity of our nanogels on cancer cells. Preliminary in vivo experiments indicated that the nanogels can circulate in the bloodstream

Les gamétophytes de Schizymenia dubyi (Gigartinales, Gymnophlacées) collectés en Sicile, possèdent un hétéropolysaccharide sulfaté inhabituel, contenant de l'acide glucuronique. Pauvre en anhydro-3,6-galactose, ses propriétés rhéologiques sont celles d'un épaississant. Le polymère d'une masse moléculaire de 290. 000, est constitué d'une structure principale rappelant le omicron -carraghénane sulfatée en C-2 et C-4, et de substitutions secondaires en 1,3,6 ; 1,4,6 ; 1,3,4 et 1,6. Le polysaccharide présente, in vitro, une activité antiherpétique (HSV-1 DE50 : 30 µg/ml), sans montrer de toxicité sur la lignée de cellules Vero au dessous de 200 µg/ml. Le mécanisme d'action a été attribué à l'inhibition de l'attachement du virus sur les cellules-hôtes par interférence avec les processus d'adsorption. L'évaluation de l'activité anti-VIH-1 du polymère montre l'inhibition de la formation des syncitia et de l'activité de la transcriptase inverse à partir de 5 µg/ml, sans montrer de toxicité sur la lignée lymphocytaire MT4. L'efficacité maximale est observée lorsque les cellules sont traitées avant et au moment de l'infection. Le polysaccharide présente un large spectre d'action puisqu'il agit sur plusieurs virus enveloppés (HSV-1, HSV-2, VSV, VIH-1)et non enveloppé (Polio 2). Il possède, par ailleurs, une activité antiprolifératrice sur la lignée de cellules bien différenciées telles que le carcinome bronchopulmonaire non-à-petites cellules (NSCLC), par différenciation terminale
Schizymenia dubyi (Gigartinales, Gymnophlaeaceae) collected from Sicily contains an unusual sulfated heteropolysaccharide with glucuronic acid. The viscous polysaccharide is composed of galactose, uronic acid and sulfate in a molar ratio of 1/0. 75/1. 3, having a molecular weight of 290. 000. No anhydro-3. 6-galactose was detected. The structural characteristics of this sulfated galactan is close to that omicron-carrageenan with sulfatation in C-2 and C-4, but with secondary ramifications in 1,3,6 ; 1,4,6 ; 1,3,4 and 1,6. The polysaccharide marked in vitro specific activity against HSV-1DE50 : 30 µg/ml) presents no toxicity to Vero cell growth concentrations up to 200 µg/ml. The anti-HSV-1 mechanism action of the polymer can be attributed to the inhibition of virus attachment to the cell surface by interfering with the virus adsorption process. Evaluation of the anti-HIV-1 effect of the polysaccharide indicated that syncitial formation and HIV-associated reverse transcriptase was completely suppressed at 5 µg/ml. No toxicity was found at this concentrations on MT4 cells. To achieve their optimal effect on virus replication, the polysaccharide shoud be present before or during the initial virus adsorption period. The polymer have been found to inhibit the replication of wide variety of enveloped viruses, including as well as herpesviruses (HSV-1 and HSV-2), Rhabdoviruses (Vesicular stomatite virus VSV), Retroviruses (HIV-1) and nonenveloped viruses (Polio-2). The polysaccharide have proved to inhibit in vitro the proliferation of well-differentiated pathologic cells such as human non-small-cell bronchopulmonary carcinoma (NSCLC-N6) by terminal differentiation

Lignocellulosic biomass is believed to serve a prominent role in tomorrow’s sustainable energy and material development. Among the polysaccharide fractions of lignocellulosic biomass, the potential of hemicelluloses as a valuable material resource is increasingly recognized. Thanks to their hydrophilic structure, hemicelluloses are suitable substrates for hydrogel design. The work summarized in this thesis aims to develop feasible strategies for the conversion of O-acetyl galactoglucomannan (AcGGM), an ample hemicellulose in softwood, into hydrogels. Within this framework, four synthetic pathways targeting the formation of crosslinked hydrogel networks from pure or unrefined AcGGM fractions were developed.   Aqueous AcGGM-rich and lignin-containing side-stream process liquors of forest industry, known as softwood hydrolysates (SWHs) were formulated into highly swellable hydrogels by: i) allyl-functionalization of AcGGM chains of crude SWH to obtain a viable precursor for hydrogel synthesis via free-radical crosslinking, ii) directly incorporating unmodified SWH fractions into semi-interpenetrating polymer networks (semi-IPNs). SWH hydrogels and semi-IPNs were characterized with appreciable maximum swelling ratios of Qeq = 170 and Qeq = 225, respectively.   Rapid crosslinking of AcGGM through thiol-click chemistry was addressed by first imparting thiol functionality onto pure AcGGM chains in a one-pot procedure. The thiolated AcGGM proved to be a suitable substrate for the synthesis of hemicellulose hydrogels via thiol-ene and thiol Michael addition reactions. Finally, sequential full IPNs were developed by subjecting single network hydrogels of pure AcGGM to a second network formation. IPNs obtained through either free radical crosslinking or thiol-ene crosslinking exhibited higher shear storage moduli than their single network counterparts.

QC 20161102

The work describes in this these is divided in two parts. 1 - The polysaccharides mixture obtained by hot water extraction of Aloe Vahombe leaves is composed of at least four different partially acetylated beta ( 1-4) glucomanns, which differ in molecular weight glucose to mannose ratios and acetyl contents. Futhermore, on fraction contains a small but significant amount of protein. 2- The structure of the Micromonospora cell wall polysaccharide has been investigated by using methylation. Smith degradation, partial hydrolyses and NMR spectroscopy. Its components are N-acetylglucosamine, D-mannose. D-xylose, and phosphoric acid. In the molar ratios of 4:4:2:2. They are linked together in a repeating unit as indicated page 119. During the methylation, the major part of the N-acetylglucosamine is degraded into 3-acetamido-furan
Les recherches exposées dans cette thèse se divisent en deux parties. La première a pour objet l'étude structurale des polysaccharides végétaux isolés à partir d’Aloe Vahombe (Liliaceae). Il s'agit d'un mélange de ß-(1-4)-glucomannanes linéaires partiellement acétylés qui diffèrent par leur poids moléculaire, la teneur en mannose et glucose et leur degré d'acétylation. L'un des polysaccharides étudiés contient une petite mais significative fraction protéinique qui semble liée par une liaison covalente au niveau de la sérine. Dans la seconde partie sont exposés les résultats concernant la structure d'un polysaccharide des parois de Micromonospora, microorganisme appartenant à l'ordre des Actinomycétales. Le poids moléculaire de cette fraction, chromatographiquement homogène, se situe entre 5000 et 10000 daltons. Elle est composée de N-acétyl-D- glucosamine, D- mannose, D-xylose et acide phosphorique en proportions approximatives 4:4:2:2. Les résultats des réactions classiques dans la chimie des sucres (méthylation, dégradation de Smith, hyvdrolyses partielles) ainsi que les renseignements apportés par les analyses spectrales (RMN 1 H et 13 C, masse) suggèrent pour ce polysaccharide la structure indiquée page 119. Au cours de sa méthylation une importante dégradation de la N-acétyl-D-glucosamine pu être mise en évidence, conduisant à un produit qui a pu être identifié comme étant le 3-acétamido-furanne

Des hydrogels hybrides ont été développés comme alternative aux hydrogels d’agar utilisés en microbiologie. Notre stratégie repose sur la fonctionnalisation de polymères avec des groupements triéthoxysilanes, puis leurs mises en jeu dans le procédé sol-gel afin de fabriquer un hydrogel hybride organique-inorganique. Ce procédé est bio-orthogonal et biocompatible. Il se déroule en milieu aqueux, à pH physiologique et température ambiante. Dans une première partie, nous avons développé des hydrogels à base de PEG bisilylé. Nous avons montré que l’incorporation de PEG monosilylé permettait un relâchement du réseau de l’hydrogel. Dans une seconde partie, nous avons développé des hydrogels à base d’hydroxypropyl méthyl cellulose (HPMC). L’optimisation de la silylation de ce composé a été réalisée. L’étude de la composition de l’hydrogel (masse molaire de l’HPMC, concentration, taux de silylation) a été étudiée et a permis la préparation d’hydrogels aux propriétés similaires aux références commerciales d’agar. Nous avons ensuite étendu notre étude aux hydrogels hybrides à base d’autres polysaccharides. Le chitosan, la dextrine, la pectine et l’acide hyaluronique ont ainsi été silylés et des hydrogels hybrides ont été préparés à partir de ces précurseurs. Les hydrogels de dextrine silylée se sont révélés les plus prometteurs pour une application à la microbiologie. La composition a été optimisée et les tests microbiologiques ont validé ce composé comme une alternative à l’agar.Nous avons montré que les hydrogels synthétiques obtenus par le procédé sol-gel constituaient une alternative solide aux hydrogels d’agar. La maitrise des différents paramètres (ex : silylation, mise en forme, composition) permet d’adapter leurs propriétés
Hybrid hydrogels have been developed as an alternative to agar hydrogels used in microbiology. Our strategy is based on the functionalization of polymers with triethoxysilane groups, and then their use in the sol-gel process to produce an organic-inorganic hybrid hydrogels. This process is bio-orthogonal and biocompatible. It takes place in aqueous medium, at physiological pH and ambient temperature. In a first part, we developed hydrogels based on bisilylated PEG. We have shown that the incorporation of monosilylated PEG allowed a loosening of the hydrogel network. In a second part, we developed hydrogels based on hydroxypropyl methyl cellulose (HPMC). Silylation of HPMC silylation has been optimised. The study of hydrogel composition (HPMC molecular weight, concentration, silylation rate) allowed the production of hydrogels with properties similar to the agar commercial references. We then extended our study to hybrid hydrogels made from others polysaccharides. Chitosan, dextrin, pectin and hyaluronic acid were thus silylated and hybrid hydrogels were prepared from these precursors. Silylated dextrin hydrogels proved to be highly suitable for microbiology applicationWe showed that synthetics hydrogels obtained by sol-gel process constituted a solid alternative to agar hydrogels. The control of the various parameters (e.g. silylation, shaping, composition) makes it possible to prepare hydrogels with tunable properties

L'acide hyaluronique est un polysaccharide fortement hydraté. Grâce à sa présence naturelle dans le corps humain et aux nombreuses possibilités de modifications chimiques de ce polysaccharide, l'acide hyaluronique est un bon candidat pour la conception de transporteurs de principes actifs. Dans cette thèse, nous avons synthétisé différents types de dérivés du HA en milieu aqueux. Ceux-ci comprennent les dérivés alkylés du HA, HA-cyclodextrine conjugués et des copolymères «hybrides» composés de HA et d'un copolymère thermosensible de l'éthylène glycol.Basé sur la capacité d'accueillir des molécules hydrophobes paclitaxel dans leurs hydrophobes "nanocavités", nous avons ensuite montré la formation de multicouches de polyélectrolytes de capsules à partir de ces dérivés du HA. L'insertion des molécules paclitaxel dans la paroi des capsules a été réalisée par pré-complexation avec les dérivés du HA en solution, et ensuite déposition ces PTX-polyélectrolytes avec le poly(L-lysine) selon la technique de couche par couche.Dans les deux cas, les capsules chargées de PTX ont été trouvés qu'elles permettent de réduire la viabilité et la prolifération des cellules cancéreuses. Ces multicouches ouvrent de nouvelles voies vers des applications en nanomédecine, comme systèmes transporteurs de médicaments hydrophobes. L'acide hyaluronique modifié par maleimide a été réagit avec poly(diethyleneglycolmethacrylate - oligoethyleneglycolmethacrylate (poly(DEGMA-co-OEGMA)) modifié par thiol afin d'obtenir le copolymère «hybrides» thermosensible. La valeur de la LCST de ce copolymère de HA est autour de 35 °C en déterminant par les mesures du point de trouble des solutions. Au-dessus de cette température, le HA-poly(DEGMA-co-OEGMA) conduit à la formation des nanogels avec la capacité d'encapsuler des molécules hydrophobes dans leur domaine hydrophobe.Les nanogels chargés en PTX ont montré une cytotoxicité plus élevée avec des cellules du cancer surexprimant le récepteur CD44. Ces résultats suggèrent que ces nanogels thermosensible pourraient s'avérer être des candidats intéressants pour la libration thérapeutique dans le traitement de cancer
Hyaluronic acid is a highly hydrated polysaccharide of great biological interest. It can be easily chemically modified, resulting in many kinds of functional polysaccharide derivatives. In this thesis, we have synthesized different types of HA derivatives in aqueous media. These comprise alkylated HA derivatives, HA-cyclodextrin conjugates, and hybrid copolymers made of HA and of a thermosensitive ethylene glycol copolymer. Based on the ability of alkylated HA and cyclodextrin grafted HA to accomodate hydrophobic molecules paclitaxel into their hydrophobic “nanocavities”, we then demonstrated the formation of polyelectrolyte multilayer capsules based on these HA derivatives. The loading of PTX in the nanoshell was achieved by first complexing PTX with HA derivatives in solution and then, depositing these PTX-containing polyelectrolytes alternately with poly(L-lysine) according to the layer-by-layer technique. In the two cases, the PTX loaded capsules were found to decrease the viability and proliferation of MDA MB 231 breast cancer cells, while unloaded capsules did not impact cell viability. Due to these promising results, these hydrophobic polysaccharide nanoshells open new avenues for applications of hydrophobic drug-carrier systems in nanomedicine.Thiol modified poly(diethyleneglycolmethacrylate - oligoethyleneglycolmethacrylate (poly(DEGMA-co-OEGMA)) was reacted with a HA-maleimide conjugate to obtain HA- poly(DEGMA-co-OEGMA). The LCST value of this HA-copolymer was determined to be around 35°C via turbidity measurements. At the body temperature, HA-copolymer was thus shown to self-assemble into nanogels with the ability to encapsulate hydrophobic molecules into their hydrophobic domain. . In vitro cell culture studies showed that with incorporating the hydrophobic anti-cancer drug paclitaxel, the nanogels exhibited high efficiency and selectivity in the eradication of CD44 positive human ovarian cancer cells. These results suggest that these temperature-triggered nanogels hold great potential for the delivery of chemotherapeutics in anti-cancer therapy

Today, the majority of materials used for single-use packaging are petroleum-based synthetic polymers. With increased concern about the environmental protection, efforts have been made to develop alternative biodegradable materials from renewable resources. Starch offers an attractive alternative since it is of low cost and abundant. However, the starch material is brittle without plasticizer and the mechanical properties of starch materials are highly sensitive to moisture.

In nature, the plant cell walls combine mechanical stiffness, strength and toughness despite a highly hydrated state. This interesting combination of properties is attributed to a network based on cellulose microfibrils. Inspired by this, microfibrillated cellulose (MFC) reinforced starch-based nanocomposites films and foams were prepared. Films with a viscous matrix and MFC contents from 10 to 70wt% were successfully obtained by solvent casting. The films were characterized by DSC, DMA, FE-SEM, XRD, mercury density measurements, and dynamic water vapor sorption (DVS). At 70wt% MFC content a high tensile strength together with high modulus and high work of fracture was observed. This was due to the nanofiber and matrix properties, favourable nanofiber-matrix interaction, a good dispersion of nanofibers and the MFC network.

Novel nanocomposite foams were obtained by freeze-drying aquagels prepared from 8wt% solutions of amylopectin starch and MFC. The MFC content was varied from 10 to 70wt%. For composite foam with MFC contents up to 40wt%, improved mechanical properties were observed in compression. The mechanical properties depended both on the cell wall properties and the cell-structure of the foam. The effect of moisture (20-80% RH) on the dynamical properties of composite foam with 40wt% MFC was also investigated and compared to those of neat starch foam. Improved storage modulus was noted with MFC content, which was a result of the nanofiber network in the cell-wall. In addition, the moisture content decreased with MFC content, due to the less hydrophilic nature of MFC.

Cellulose tris(3,5-dimethylphenylcarbamate) (CDMPC) is among the most common stationary phases used in chiral separation column. Nevertheless, there is no crystal structure of CDMPC reported yet for reference. Modelling studies of CDMPC so far have been based on the basis of the parameterized structure of the dry crystalline structure of cellulose tris(phenylcarbamate) (CTPC) predicted in late 80s. Solvent effect was not considered explicitly in those studies. In 2016, Okada et al. reported that the number of monomeric units of CDMPC would influence the structure of the chiral stationary phase (CSP), and hence the chiral recognition ability. However, most of the previous modelling studies ignored the chain-length effect and considered CDMPC with at most twelve residues. In this study, the effects of explicit solvent and number of residues on CDMPC are investigated specifically. Modelling of two chain lengths (9-mer and 18-mer) of CDMPC using molecular simulation in both implicit and explicit solvent environments were performed. Predicted elution order of selected enantiomers on 18-mer CDMPC agrees better with experiments. Design principles of polysaccharides-CSPs were discussed based on this study.

Plant cell wall polysaccharides are abundant natural polymers making them potential sources for sustainable and biodegradable materials. Interfacial behavior, including adsorption and enzymatic degradation, of several plant cell wall polysaccharides and their derivatives were studied with a quartz crystal microbalance with dissipation monitoring (QCM-D), surface plasmon resonance (SPR) and atomic force microscopy (AFM). Xyloglucan adsorption isotherms were obtained to probe how cellulose-hemicellulose interactions were affected by the type of cellulose substrate and molar mass of xyloglucan. Xyloglucan as small as a heptasaccharide still adsorbed irreversibly onto cellulose. Carboxymethyl cellulose (CMC) adsorption onto cellulose and viscoelastic properties and water contents of the adsorbed CMC layers were obtained from a combination of QCM-D and SPR data. The CMC samples formed hydrated and viscoelastic layers compared to the relatively rigid xyloglucan layer. Pectin model surfaces were prepared by pectin adsorption from citric phosphate buffer onto gold substrates. These pectin model surfaces were used for subsequent interaction studies with xyloglucan and enzymatic degradation behavior. There is a strong correlation between the degree of esterification (DE) and film resistance to degradation with the high DE being the most susceptible to degradation. The adsorption of two mixed linkage glucans (MLG), barley and lichen MLG, onto regenerated cellulose (RC) surfaces in the absence and presence of other matrix polysaccharides was studied. Viscoelastic properties of the resulting layer were compared as a function of the proprotion of '-(1''3) linkages with lichen MLG forming softer gel-like layers on RC. The lichen MLG layers were further used for enzymatic degradation studies with respect to enzyme concentration, temperature, pH and ionic strength. These studies show that polymer adsorption is a promising strategy to modify material surfaces and provides fundamental understanding of interactions and biodegradation of cell wall polysaccharides at solid/liquid interfaces.
Ph. D.

Myasthenia gravis (MG) is an autoimmune disorder in which auto-antibodies directed at the acetylcholine receptors (AChR) of the neuromuscular junction (NMJ) block, alter or destroy their targets. The anti-AChR antibodies cause activation of the classical complement pathway leading to inflammatory injury at the NMJ. Decay Accelerating Factor (DAF), a member of complement regulatory proteins, prevents activation of autologous components of complement pathways. The absence of DAF, in knock-out mouse models, has been shown to significantly increase the susceptibility to experimental autoimmune MG. A previous study showed that a high proportion of South African MG patients of African genetic ancestry develop immunosuppressive therapy-resistant extraocular muscle (EOM) dysfunction. We hypothesized that these patients have deficient DAF expression in their EOMs resulting in less protection from complement injury. Sequence analysis of relevant regions of the DAF gene revealed a single nucleotide polymorphism (SNP), c.-198C>G, in the promoter region in MG patients of African genetic ancestry with severe EOM MG involvement (MG n=101; Control n= 132; Odds ratio= 6.6; p=0.009). DAF-luciferase reporter assays, using 3 different cell lines (COS-7, HT1080 and C2C12) revealed that the c.-198C>G SNP (Mut-DAF) led to an increase in DAF promoter activity (

Cereus triangularis est un cactus non endémique de la sous-famille des Cactoïdées très présent dans le nord de Madagascar. Ses cladodes sont utilisées sous la forme de décoctions dans la pharmacopée Malgache. Bien que riche en hydrocolloides comme la plupart des cactus appartenant à cette sous famille il n’est pas exploité pour la production de polysaccharide. Notre travail a donc consisté à définir les conditions d’extraction des polysaccharides hydrosolubles des cladodes de cette plante, à en identifier la structure, à en caractériser les propriétés physico-chimiques et à explorer des voies enzymatiques pour leur dégradation en oligomères et/ou en polymères de faibles masses molaires. Nos travaux ont conduit à l’identification d’un arabinogalactane de type I de haute masse molaire. Ce polysaccharide est constitué d’une chaîne principale de galactane de type β-(1,4)-D-GalP substituée en position 3 par des groupements T-α-L-Araƒ-(1, ou des chaînes latérales d’arabinanes. Le comportement rhéologique de ce galactane est typique des polymères rheofluidifiants ayant des propriétés de gel faible. La mise en œuvre de dégradations enzymatique à l’aide d’une galactanase fongique a conduit à l’obtention de fractions de plus faibles masses molaires que celles des polymères natifs qui ont pu être testées avec succès pour leurs propriétés prébiotiques
Cereus triangularis is a non endemic cactus belonging to the sub-family of Cactoideae, well represented in the north of Madagascar. Its cladodes are used in food decoction as a traditional medicine in Madagascar. Even if the hydrocolloid content of this cactus is high as observed with other ones from the same sub-family, it is not exploited for the production of polysaccharides. In this study we have defined an extraction procedure to collect the soluble polysaccharide from the cladodes of this cactus and characterized the structure of it before to investigate its physico-chemical properties and to degrade it into oligosaccharides using enzymes. Structural analyses have revealed that this polysaccharide is a type I arabinogalactan with a high molecular weight. It is mainly composed of a galactan backbone of β-(1,4)-D-GalP substituted at position 3 by T-α-L-Araƒ-(1, or arabinan chains. The rheological properties of this galactan are characteristic of a pseudoplastic fluid with a weak gel behavior. Its enzymatic degradation using a fungal galactanase led to the production of oligomers and low molecular weight polysaccharides which have been successfully tested as prebiotics

Glycosaminoglycans (GAGs), a large family of complex, unbranched polysaccharides, display a variety of essential physiological functions. The structural complexity of GAGs greatly impedes their availability, thus making it difficult to understand the biological roles of GAGs and structure-property relationships. A method that can access GAGs and their analogs with defined structure at relatively large scales will facilitate our understandings of GAG biological roles and biosynthesis modulation. Cellulose is an abundant and renewable natural polymer. Applications of cellulose and cellulose derivatives have drawn increasing attention in recent decades. Chemical modification is an efficient method to append new functionalities to the cellulose backbones. This dissertation describes chemical modification of cellulose and cellulose derivatives to prepare unsulfated and sulfated GAG analogs. Through these studies, we have also discovered novel chemical reactions to modify cellulose. Systematic study of these novel chemistries is also included in this dissertation. We first demonstrated our preparation of two unsulfated GAG analogs by chemical modification of a commercially available cellulose ester. Cellulose acetate was first brominated, followed by azide displacement to introduce azides as the GAG amine precursors. The resulting 6-N3 cellulose acetate was then saponified to liberate 6-OH groups, followed by subsequent (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) oxidation of the liberated primary hydroxyl groups to carboxyl groups. Finally, the azides were reduced to amines using a novel reducing reagent, dithiothreitol (DTT). Alternatively, another process utilized thioacetic acid to reduce azides to a mixture of amine and acetamido groups. Through pursuing these GAG analogs, we applied novel azide reductions by DTT and thioacetic acid that are new to polysaccharide chemistry. We systematically investigated the scope of DTT and thioacetic acid azide reduction chemistry under different conditions, substrates, and functional group tolerance. Selective chlorination is another interesting reaction we discovered in functionalization of cellulose esters. We applied this chlorination reaction to hydroxyethyl cellulose (HEC). We then utilized the chlorinated HEC as a substrate for displacement reactions with different types of model nucleophiles to demonstrate the scope of its utility. Overall, we have designed a novel synthetic route to two unsulfated GAG analogs by chemical modification of cellulose acetate. Through exploration of GAG analogs synthesis, we discovered novel methods to modify polysaccharide and polysaccharide derivatives, including azide reduction chemistry and selective chlorination reactions. Successful synthesis of various types of GAG analogs will have great potential biomedical applications and facilitate structure-activity relationship studies.
Doctor of Philosophy
Polysaccharides are long chains of natural sugars. Glycosaminoglycans (GAGs) are an important class of polysaccharides which have complicated chemical structures and play critical roles in many biological processes, including regulation of cell growth, promotion of cell adhesion, anticoagulation, and wound repair. Current methods to obtain these GAGs and GAG analogs are expensive, lengthy, and limited in capability. Novel methods to access these GAGs and their analogs would be promising and would facilitate understanding of biological activities of GAGs. Cellulose is an abundant polymer on earth and provides structural reinforcement in plant cell walls. Cellulose can be further chemically modified to tailor its physiochemical properties. Cellulose and cellulose derivatives have been widely used in many industries for various applications, such as textiles, plastic films, automotive coatings, and drug formulation. This dissertation focuses on modifying inexpensive, abundant cellulose and its derivatives to GAGs and GAG analogs. We start from the simple plant polysaccharide cellulose and obtain structurally complicated analogs of animal-sourced GAGs and GAG analogs. We reached our goal by designing a carefully crafted synthetic route, finally successfully obtaining two types of novel GAG analogs. During this process, we discovered two useful chemical reactions. We systematically investigated these chemical reactions and demonstrated their utility for polysaccharide chemical modification. These successful chemical syntheses of GAGs and their analogs will accelerate our understanding of their natural functions and have potential biomedical applications. The novel chemical methods we discovered will be helpful in chemical modification of polysaccharides.

La faible stabilité thermique et les problèmes d’agrégations irréversibles limitent l’utilisation de nanocomposites polymères à renfort cellulosique. Dans ce contexte, des CNC thermiquement stable et fortement dispersés ont été préparés par des procédés verts, basés sur des méthodes en milieu aqueux, telle que l'adsorption physique et la modification de surface. Ces deux types de CNC extrudables ont été utilisés comme renfort dans des polymères réputés hydrophobes. Les composites biosourcés à matrice polymère ainsi réalisés sont caractérisés par une amélioration du module visqueux, de la résistance à la traction et du module d’Young. On constate également sur les images de microscopie électronique à balayage, qu’à la différence des observations réalisées avec les CNC non traités, qu’aucun micro-agrégat cellulosique n’est observé dans la matrice polymère. Ces deux méthodes, développées en milieu aqueux, apparaissent ainsi comme des solutions industriellement viables
The low thermal stability and irreversible agglomeration issues are limiting to process the polymer nanocomposites using CNC as the reinforcing phase. In this context, thermally stable and highly dispersed CNC were prepared by green process (Aqueous based methods) like physical adsorption and surface modification. These two different Extrudable CNC was reinforced in to hydrophobic polymers. Ensuing polymer nanocomposites had a positive impact on the storage modulus, tensile strength, Young’s modulus. Importantly, no evidence of micro aggregates in the matrix was observed in the scanning electron microscopy images contrary to non-treated CNC. Both the surface modification and adsorption are the water based methods and is an industrially viable solution. Also, it can be applicable at industrial level

Les virus influenza provoquent chaque année la grippe saisonnière qui peut toucher 5 à 15 % de la population. Les médicaments antiviraux sont un moyen important complémentaire à la vaccination pour le traitement et la prévention de la grippe. Actuellement, deux classes d'antiviraux ont été approuvées, l'une pour inhiber l'étape de décapsidation (l'inhibiteur du canal ionique M2), et l'autre pour empêcher la libération de néo-virions (l'inhibiteur de la neuraminidase). Cependant, de plus en plus de virus sont nativement résistants aux inhibiteurs de la protéine M2. Des virus résistants aux inhibiteurs de la neuraminidase ont également circulé durant les hivers 2008 - 2009. Le développement de nouveaux médicaments afin de substituer ou de compléter ces inhibiteurs est donc crucial dans la lutte contre les virus de la grippe. L'accent mis ces dernières années sur l'activité biologique des sucres (oligosaccharides/polysaccharides) montre une voie pour l'étude de l'activité antivirale d'une des plus importantes biosources. Dans le but d'évaluer le potentiel antigrippal des molécules dérivées de sucres, nous avons effectué un criblage à partir d'une bibliothèque de 245 composés de polysaccharides et d'oligosaccharides, dont la plupart proviennent d'algues et de végétaux supérieurs. Plusieurs molécules actives réparties dans différentes familles de sucres ont été mises en évidence. Parmi les candidats d'intérêt, l'oligosaccharide sulfaté 152, appartenant à la famille des arabinogalactanes de l'espèce Codium fragile, a présenté une activité inhibitrice vis-à-vis des deux virus influenza de type A et de type B in vitro. Le mécanisme d'action de cet oligosaccharide a été caractérisé. Il montre que les deux glycoprotéines de surface, l'hémagglutinine et la neuraminidase, sont les cibles virales de cette molécule

Le biofilm est défini comme une communauté microbienne adhérant à une surface biotique ou abiotique, et engluée dans une matrice extracellulaire auto-produite. Les biofilms naturels sont composés de plusieurs espèces microbiennes et leurs interactions, qu'elles soient synergiques ou antagonistes, jouent un rôle important dans le développement, la composition et le fonctionnement des consortia impliqués. De plus, ces relations impliquent souvent la production de molécules antagonistes limitant la croissance ou l'adhésion bactérienne. Enfin la composition de la matrice extracellulaire joue un rôle important dans la robustesse du biofilm. Au cours de ce travail, l'étude des interactions au sein de biofilms mixtes constitués par K. pneumoniae et S. epidermidis a permis d'isoler un polysaccharide produit par K. pneumoniae, capable d'inhiber l'adhésion aux surfaces abiotiques de plusieurs autres espèces bactériennes à Gram-négatif et à Gram-positif. La caractérisation physico-chimique de cette molécules de haut poids moléculaire a permis de mettre en évidence qu'elle était composée de galactose, glucose, rhamnose et d'acide glucuronique. Par ailleurs, l'analyse d'extraits de mutants déficients pour la production de capsule a montré que ce polysaccharide correspondait à la capsule de K. pneumoniae. Son mode d'action consisterait à inhiber les interactions initiales entre bactéries et surface. Le suivi dans le temps de la formation de biofilm monospecies par K. pneumoniae avec la technique Biofilm Ring Test® a également permis de mettre en évidence un phénotype original. En effet, la détection initiale d'agrégats bactériens est suivie par une modification apparente de leur structure, qui serait liée à des changements de leur robustesse face aux forces d'aimantation magnétique. La présence d'ADN extracellulaire au sein de la matrice du biofilm pourrait jouer un rôle dans la survenue de ce phénotype comme l'indique les mesures effectuées en présence de l'enzyme DNAse I. En parallèle, l'observation de biofilm formés par K. pneumoniae dans des modèles expérimentaux cinétiques a mis en évidence des décrochements massifs de biomasse au cours de la maturation du biofilm, qui pourraient être corrélées aux modifications internes de robustesse de la matrice. L'ensemble de ces données permet de mieux caractériser les interactions intimes survenant à l'intérieur de biofilms constitués par K. pneumoniae et à terme de mieux caractériser et donc prévenir leur formation et dissémination
Biofilms are defined as microbial communities adhering to biotic or abiotic surfaces and embedded in a self-produced extracellular matrix. Natural biofilms are composed of several microbial species and their interactions, synergistic or antagonistic, play important roles in development, composition and functioning of the consortia. Furthermore, the relationships often involve the production of antagonist molecules that impair competitors' growth or adhesion. The composition and evolution of the extracellular matrix plays also an important role in the biofilms' robustness. In this work, study of the interactions within biofilms formed by K. pneumoniae and S. epidermidis led to the isolation of a polysaccharide produced by K. pneumoniae able to inhibit the adherence to abiotic surfaces of several Gram-negative and Gram-positive bacterial species. The physico-chemical characterization of this high molecular weight molecule showed it was composed of galactose, glucose, rhamnose and glucuronic acid. This data, together with the analysis of extracts from capsule-deficient mutants, indicated that the capsule of K. pneumoniae was responsible for the biofilm inhibition phenotype, probably by inhibiting the initial interactions between bacteria and surface. By monitoring the formation of monospecies biofilm by K. pneumoniae with the Biofilm Ring Test® technique, we were able to detect an original phenotype. Indeed, detection of bacterial aggregates still occurred after a few hours of incubation but in a different way, probably related to changes of the biofilm robustness towards magnetic forces. The presence of extracellular DNA in the matrix of the biofilm is likely to play a role in the occurrence of this phenotype, as indicated by the assays performed in presence of the enzyme DNase I. At the same time, observations of biofilm formed by K. pneumoniae in kinetic experimental models showed massive detachment events during biofilm maturation, which could be correlated to changes in internal strength of the matrix. All these dtat contribute to a better characterization of the intimate interactions occuring within biofilms formed by K. pneumoniae and will ultimately lead to the development of efficient anti-biofilm strategies

Les biofilms ont longtemps été décrits comme des organisations évolutives de microorganismes, attachés à une surface et englués dans une matrice contenant, entre autre, des polysaccharides. En partant de ce constat BioFilm Control a souhaité cribler des microorganismes pour la production d’exopolysaccharides, en utilisant le BioFilm Ring Test® (BRT). Le principe repose sur la coincubation de microorganismes avec des particules magnétiques en microplaque. Les particules sont plus ou moins attirées par un aimant en fonction du stade d’organisation du biofilm. En se formant, il piège, dans sa matrice visqueuse, les particules qui perdent leur mobilité. Celle-ci est révélée par une aimantation qui provoque l’apparition d’un spot (pas de biofilm) ou non (biofilm). Une analyse d’images quantifie ce processus et permet de le standardiser. La démarche a consisté dans un premier temps à vérifier le comportement de microorganismes modèles producteurs de polysaccharides (bactéries et microalgues) avec le BRT. L’étude a été étendue au criblage d’une banque de lactobacilles. Les résultats inattendus ont orienté l’étude vers l’analyse du rôle exact des polysaccharides et plus généralement de l’implication des macromolécules dans la structuration du biofilm. Pour cela, la dégradation séquentielle de chaque famille macromoléculaire a été réalisée via des enzymes dépolymérisantes sur les biofilms de Leuconostoc mesenteroides et Bacillus sp. Au regard des résultats obtenus, l’utilisation du BRT a été étendue à la caractérisation qualitative et quantitative d’enzymes de dégradation de polysaccharides
Biofilms were described for a long time as evolutionary structures elaborated by microorganisms, fixed on a surface and maintained in a polysaccharidic matrix. From this assessment, BioFilm Control chose to screen microorganisms for their capacity to produce exopolysaccharides (EPS), using theBioFilm Ring Test® (BRT). The principle is the co-incubation of magnetic particles with microbial culture on microplates. The mobility of particles depends on the stage of biofilm formation. During this formation, particles are trapped in the matrix and loose their mobility. Revelation is induced by magnet which causes a spot in the absence of biofilm. The pictures analysis quantifies this phenomenon and standardizes different results. This approach was realised, at first step, by the test of EPS-producing bacteria or microalgae with the BRT. The study was extended to the screening of a lactobacilli collection. Unexpected results guided the research toward the understanding of the role of macromolecules in biofilm structuring. To study their implication, sequential enzymatic degradation has been achieved for each macromolecular family of Leuconostoc mesenteroïdes and Bacillus sp. biofilms. Using the results, BRT was then appreciated as a suitable method to detect and quantify polysaccharide degrading enzymes

Thesis (M.S.) -- University of Maryland, College Park, 2003.
Thesis research directed by: Dept. of Chemical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

The work described in this thesis addresses two classes of mixed biopolymer systems: (a) starches and sodium caseinate ; (b) gelling seaweed polysaccharides (x-carrageenan - both with and without locust bean gum - agar and alginate) and proteins (gelatin and blood plasma proteins). The viscosity and swelling volume of a 1% potato starch paste in distilled, deionised water is markedly reduced in the presence of caseinate. Similar effects were seen with simple electrolytes suggesting that this occurs as a consequence of a non-specific ionic strength effect. In contrast a 4% maize starch paste in distilled, deionized water undergoes a viscosity and swelling volume increase in the presence of caseinate. However, when pasted in a 0.1M, pH 7.0 phosphate buffer caseinate addition has little effect on the viscosity of the fresh paste and at high concentrations appears to prevent retrogradation on ageing. It is suggested that in buffer caseinate prevents the leaching of starch polysaccharides from the swollen granule and therefore maintains amylose in the granular phase. This is attributable to the high ionic strength of the solvent, allowing caseinate and the starch polysaccharides to phase separate. In water the unfavourable entropy, change due to the uneven distribution of the counter-ions, prevents phase separation and results in an interpenetrating network. Studies on the large deformation stress relaxation behaviour and melting points of 2% carrageenan, 0.5% carrageenan/0.5% locust bean gum (LBG) and 2% agar gels in a variety of solvent media indicate that the inclusions of 0-20% gelatin and 0-5% bovine serum albumin (BSA) give different results depending on both protein and polysaccharide. The main points of this study show that agar/gelatin mixed gel undergoes a distinct phase inversion at 4-7% gelatin levels, which is not seen with the carrageenan gels containing gelatin. Even when 20% gelatin is incorporated into a 2% carrageenan gel the melting point of the gel is unaltered from that of carrageenan alone. In the presence of high levels of BSA the carrageenan/LBG gel undergoes a marked increase in melting point. Investigations using locust bean gums of variable protein content suggests a possible (LBG)protein-BSA interaction since the melting point increases with the LBG protein content. It is shown that carrageenan/LBG gels have clear regions when formed by autoclaving in the presence of blood plasma. This supports the idea of an association between the protein in the insoluble husk and the blood plasma proteins. The interaction mixtures of BSA with sodium alginate at the interface and in bulk solution have been studied through the techniques of microelectrophoresis and ultracentrifugation respectively, to further elucidate the association between denatured proteins above their isoelectric point and anionic polysaccharides. Both techniques clearly show that the macromolecules can associate electrostatically at pH's above the pI of the protein.

The effects of ionizing radiation on solutions of (1) sodium alginate, (2) alginate gels (wet and dry), (3) xanthan gum, (4), locust bean gum (LBG) and (5) carboxymethyl cellulose (CMC), have been investigated. Problems arise in the radiation sterilization of these gums (either as a solution or gel) due to reduction in their viscosity and the gel strength, caused by the high doses (25kGy) commonly used for the purpose of sterilization. The alginates used here were manugel DMB, manugel DPB and manucol DMF. The irradiations were carried out using 'Co-ry-source and the gels and solutions were analysed by measurement of their apparent viscosities using a Brookfield viscometer L.V.T. The data shows that 2% solutions of the sodium salt of the three alginates used here are all pseudoplastic. There is a rapid decrease in viscosity of solutions irradiated up to a dose of 0.5kGy, and the initial rate of viscosity decrease is unaffected by the presence or absence of air. Inclusion of mannitol at high concentration (15%) could, at least partially, protect the alginate solutions degradation by scavenging -OH radicals. The possibility of using 60Co-7-radiation to sterilize alginate gels (wet gels) was also studied. Gels of this type have potential use of wound care. Those prepared here could bend easily. Irradiated to 25 kGy, the gels readily crack by becoming more brittle, are easily squashed and lose water. Inclusion of mannitol improved the quality of the gels and again indicates its protective role in these systems. When alginate solutions containing mannitol and the gelling agents 5-gluconolactone and calcium orthophosphate were irradiated separately and then mixed, gels were formed, indicating that pre-sterilization of the components by irradiation is a feasible method of preparation of sterile gels. Gels that were concentrated (dry) by water evaporation were more stable to radiation (25 kGy). The gels that had the greatest capability to take up saline and to be manipulated most easily (both before and after irradiation) were those that contained initially 2% alginate and 5% mannitol, and dried to a quarter of the original weight (ie. the gel now contained 8% alginate and 20% mannitol). These gels were clear and pliable and after irradiation to 30 kGy remain stable in saline for up to 24 hours. The effect of ionizing radiation on xanthan and LBG solutions are also studied. The initial studies indicated that these solutions were also pseudoplastic. Irradiation of xanthan gum solutions caused a rapid initial decrease in apparent viscosity. t-Butanol had some protective effect on xanthan-LBG and xanthan-NaC1 solutions. Addition of mannitol (20%) to xanthan gum solutions again only partially protects the solutions. The solutions with highest apparent viscosity were those prepared by mixing equal volumes of solutions of LBG 1%, mannitol (20%) and ascorbic acid (10" mol dm') and solutions of xanthan gum (1%), mannitol (20%) and ascorbic acid (10' mol dm'). The viscosity of this solution falls from 300,000 cps to 250,000 (shear rate 0.07s4), after irradiation to 25 kGy. Therefore, whereas xanthan gum solutions containing readily depolymerized by irradiation, very high viscosity irradiated xanthan solutions containing thickening agents (LBG) and radiation protectors (mannitol - ascorbic acid) can be prepared. Solutions of CMC are also pseudoplastic. Irradiation to 25 kGy resulted in a decrease in the apparent viscosity of solutions of CMC/mannitol/ascorbic acid from — 180,000cps to 8,000cps, whereas for solutions of CMC alone and for CMC/mannitol solutions the viscosity was less than 500cps. This further illustrates the protective effect of ascorbic acid as was observed for xanthan solutions and also suggests that mannitol radicals cause depolymerization of CMC.

Thesis (PhD (Process Engineering))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: The ongoing trend in papermaking industries is to lower production costs by increasing the low cost filler content in the sheets. However, the disruption of inter-fibre bonding is accompanied by a deterioration of paper stiffness and mechanical properties if filler content exceeds 18 wt%. Polysaccharide solutions, such as starch, are often used as a low cost biodegradable additive to improve internal sheet strength when added to the wet-end of production. The amount of starch that can be added is however limited as only a small percentage will be retained in the paper web. A dual additive multifunctional polysaccharide system was developed to allow higher filler loading levels without detrimental deterioration in paper properties. In order to achieve a larger surface area for fibre/filler interaction and to reduce drainage losses, at least one of these additives was in particulate form. Anionic, cationic, and unsaturated derivatives were prepared using sodium monochloroacetate, 3-chloro-2-hydroxypropyltrimethylammonium chloride, and allyl bromide, respectively. The degree of substitution was determined by 1H-NMR spectroscopy and back titration methods and the interaction of the ionic modified derivatives with paper components was determined using fluorescence microscopy. Anionic modified polysaccharide particles were prepared using techniques such as macrogel ultrasonification, water-in-water emulsification, and in-situ cross-linking and carboxymethylation of granular starch. A process of adding sequential layers of oppositely charged polyelectrolyte layers onto the filler particles was also investigated. A novel approach of preparing modified particles with tailored size and distribution using microfluidics was studied and modelled using response surface methodology. Hand sheets were prepared using the dual additive system and improvements in stiffness, tear resistance, breaking length, and folding endurance were observed. The modified granular maize starch particles had a pre-eminent effect on improving stiffness at higher filler loadings (14% improvement at 30 wt% filler loading), while bulky particles prepared using microfluidics showed a more consistent improvement (between 6% and 10%) across the loading range. Overall improvements gained by the introduction of multi-layered soluble polymers onto fillers suggest that the introduction of nanotechnology to the papermaking process should be of potential benefit to the industry. Furthermore, the dual additive system developed during the course of this study should also be tested on a continuous pilot plant papermaking process.
AFRIKAANSE OPSOMMING: Die papierindustrie neig voortdurend daarna om produksiekostes te verlaag deur die persentasie lae koste vulstof wat gebruik word te verhoog. Aangesien die vulstof vesel kontak belemmer, gaan hoër vlakke (> 18 wt%) egter gepaard met ’n verlaging in papier styfheid en meganiese eienskappe. Polisakkaried oplossings, soos byvoorbeeld stysel, word dikwels gebruik as lae koste vergaanbare bymiddel om papier intern te versterk wanneer dit voor die vormingsproses bygevoeg word. Slegs ’n beperkte hoeveelheid stysel word egter behou in die papier matriks en oormatige oplossings ontsnap tydens dreinering in die afvalwater. ’n Dubbele multi-funksionele polisakkaried bymiddelsisteem was ontwikkel wat ongewensde verwakking in papiereienskappe verminder tydens vulstof verhogings. Ten minste een van die bymiddels was in partikelvorm om sodoende ’n groter oppervlak te bied vir vesel/vulstof interaksie en om dreineringsverliese te verminder. Anioniese, kationiese, sowel as onversadigde derivate was berei deur onderskeidelik gebruik te maak van natrium monochloroasetaat, 3-chloro-2-hidroksiepropieltrimetielammonium chloried, en alliel bromied. Die graad van substitutiese was bepaal met behulp van 1H-KMR spektroskopie sowel as titrasie tegnieke terwyl die ioniese interaksie van die gemodifiseerde stysels met die papierkomponente ondersoek was met behulp van fluoressensie mikroskopie. Anioniese polisakkaried partikels was berei met tegnieke soos makro-jel ultrasonifikasie, water-in-water emulsifikasie, en in-situ kruisbinding en karboksiemetielasie van stysel granulate. ’n Proses was ook ondersoek waar vulstof partikels omhul was in verskeie lae poliëlektroliet oplossings. ’n Nuwe benadering was toegepas waar gemodifiseerde partikels met voorafbepaalde grootte en verspreiding berei is deur gebruik te maak van mikrofluïdika en gemodelleer met behulp van oppervlakte ontwerp metodeleer. Papier toetse was uitgevoer met die bymiddelsisteem en algehele verbetering in styfheid, skeurweerstand, breeklengte, en voulydsaamheid is waargeneem. Die gemodifiseerde stysel granulate het die grootste verbetering in styfheid by hoë vulstofladings getoon (14% verbetering by 30 wt% vulstoflading) terwyl die groter mikrofluïdika-bereide partikels algehele verbetering (tussen 6% en 10%) getoon het oor die hele vulstoflading reeks. Die verbeteringe in styfheid sowel as meganiese eienskappe van papier voorberei met poliëlektroliet omhulde vulstof toon dat aanwending van nanotegnologie in hierdie bedryf potensieel voordelig kan wees. Opskalering van die polisakkaried bymiddels ontwikkel gedurende hierdie studie behoort uitgevoer te word vir verdere toetse op ’n kontinue papier loodsaanleg.

As a continuation of the research on the pigment formation from catecholamines, we studied the polysaccharide-mediated oxidation of serotonin and other 5-hydroxy indoles into pigmented substances. As for catecholamines, we observed that many polysaccharides promote the oxidation of such compounds, particularly in the presence of Cu (II). The same polysaccharides, e.g., carrageenan or fucoidan, which strongly promoted the oxidation of catecholamines, strongly promoted the oxidation of serotonin, leading to the formation of darkly colored pigments. The reactions were evaluated using RP-HPLC and size exclusion chromatography (SEC) as the main analytical techniques. SEC proved particularly informative as these analyses allowed us to monitor (1) the decline in the substrate, (2) the formation of low-molecular mass oxidation products, (3) the formation of polysaccharide-associated pigments, and (4) the formation of potential pigment-based nanoparticles. We observed that increased amounts of polysaccharide or Cu (II) increased the amount of pigment generated. However, other cations like Co(II), Ni(II), Mn(II), or Fe(II) had no or very little effect on the reactivity. Apart from serotonin, 5-hydroxy indole could serve as a substrate to generate polysaccharide-associated pigments. However, reactions with the related substrate, 5-hydroxy indole-3-acetic acid yielded a low molecular mass chromophore, but not any polysaccharide-associated pigments. Large-scale reactions were set up in an attempt to isolate and characterize any pigments that were generated. The reaction mixtures could readily be dialyzed and lyophilized to obtain polysaccharide-associated pigments. Pigments were evaluated using UV-Vis spectroscopy, SEC analysis, FT_IR spectroscopy, and atomic absorption spectroscopy to evaluate the amount of Cu remaining in the materials.

In this study, surface plasmon resonance (SPR) and quartz crystal microbalance with dissipation monitoring (QCM-D) were combined to investigate the adsorption behavior of two platelet adhesion-related blood proteins, human serum albumin (HSA) and human serum fibrinogen (HSF), on two polysaccharide materials used for hemodialysis membrane applications: regenerated cellulose and cellulose acetate. The study aims to provide insight into the design of novel hemocompatible polysaccharide materials. Information such as real-time adsorption curves, adsorbed amounts, and water contents of the protein layers were obtained and analyzed. The results suggested 1) monolayer adsorption of HSA on both cellulose and cellulose acetate, possibly with different HSA conformations; 2) a multilayer of HSF or some degree of end-on adsorption on both surfaces. The study of HSA adsorption onto cellulose acetate surfaces with different degrees of substitution indicated that the change in content of acetyl groups may not be the main factor governing the adsorbed HSA amount but may affect the conformation of adsorbed HSA molecules.
Master of Science

Grewia gum is obtained from the inner stem bark of the edible plant Grewia mollis Juss (Fam. Tiliaceae) which grows widely in the middle belt region of Nigeria, and is also cultivated. The dried and pulverised inner stem bark is used as a thickening agent in some food delicacies in that region of the country. This ability of the material to increase solution viscosity has generated a lot of interest and is the catalysing momentum for this research. Such materials have been used as stabilizers or suspending agents in cosmetics, foods and liquid medications, and as mucoadhesives and controlled release polymeric matrices in solid dosage forms. The physicochemical characterization of candidate excipients forms an essential step towards establishing suitability for pharmaceutical application. For natural gums, this usually requires isolation of the gum from the storage site by extraction processes. Grewia polysaccharide gum was extracted and dried using techniques such as air-drying, freeze-drying or spray-drying. Component analysis of the gum showed that it contains five neutral sugars: glucose, galactose, rhamnose, arabinose and xylose. The gum contains traces of elements such as zinc, magnesium, calcium and phosphorus. At low substance weight, the gum hydrates in aqueous medium swelling and dispersing to give a highly viscous dispersion with pseudoplasmic flow behaviour. The method by which drying is achieved can have significant effect on some physicochemical properties of the gum. Consequently, the intrinsic viscosity and molecular weight, and parameters of powder flow were shown to differ with the method of drying. The gum has good thermal stability. In comparison with established excipients, grewia gum may be preferable to gum Arabic or sodium carboxymethylcellulose as a suspending agent in ibuprofen suspension formulations. The release retardant property of the gum was superior to guar and Metolose® in ibuprofen matrices. Similarly, carboxy methylcellulose, Methocel®, gum Arabic or Metolose® may not be preferable to grewia gum when controlled release of a soluble drug like cimetidine is indicated. The mucoadhesive performance of the gum compared favourably with excellent mucoadhesives such as hydroxypropyl methylcellulose, carboxymethylcellulose, guar and carbopol 971 P.

L’association de polysaccharides naturels et de polypeptides recombinants de type élastine (ELP) dans des structures de copolymères à blocs doit permettre d’accéder à des matériaux possédant des propriétés d’auto-assemblage sous l’action de stimuli et potentiellement bioactifs. Nous avons réalisé et présentons ici la synthèse d'une série de bioconjugués polysaccharide-b-ELP, dans lesquels 4 polysaccharides hydrophiles différents ont été couplés à l'extrémité N-terminale de l’ELP par "chimie click".Ces bioconjugués ont été caractérisés par RMN 1D et 2D, SEC et FTIR. Leur thermo-sensibilité et leur auto-assemblage induit par la température ont été étudiés par spectroscopie UV-Visible, DLS, SLS, SANS et AFM liquide à température contrôlée. Cette étude a démontré que les bioconjugués polysaccharide-b-ELP peuvent s'auto-assembler en milieu aqueux en nanoparticules bien définies au-dessus d'une température de transition spécifique et modulable (Tt) et se désassembler de façon réversible sous la Tt, ce qui les rend particulièrement prometteurs pour la conception de vecteurs de principes actifs à libération contrôlée. La fonctionnalisation chimiosélective des résidus méthionine du segment ELP par chimie de l'oxaziridine a également été exploitée pour moduler les propriétés des bioconjugués
The combination of natural polysaccharides and recombinant elastin-like polypeptides (ELPs) into block copolymers is expected to lead to materials with precise stimuli-responsive self-assembly properties and bioactivities. Herein, we report the synthesis of a series of polysaccharide-b-ELP bioconjugates, in which 4 different hydrophilic polysaccharides were coupled to the N-terminal end of an ELP via “click chemistry”. The resulting bioconjugates were characterized by 1D and 2D NMR, SEC and FTIR. Their thermal sensitivity and temperature-triggered self-assembly in aqueous solution were investigated by UV-Vis spectrometry, DLS, SLS, SANS and temperature-controlled liquid AFM. This study demonstrated that polysaccharide-b-ELP bioconjugates can self-assemble into well-defined nanoparticles in aqueous condition above a specific and tunable transition temperature (Tt) and reversibly disassemble below the Tt, which make them particularly promising candidates for the design of controlled drug delivery nanocarriers. Chemoselective functionalizations of the ELP segment at methionine residues using oxaziridine chemistry were additionally applied for further tuning of bioconjugates’ properties