Synthesis and Characterization of Cellulose fiber-silica nanocomposites

Cellulose fiber-silica nanocomposites with novel mechanical, chemical and thermal properties have potential to be widely applied in different area. Monodispered silica nanoparticles play an important role in enhancing hybrids properties of hardness, strength, thermal stability etc. On the other hand, cellulose is one of the world’s most abundant and renewable polymers and possesses several unique properties required in many areas and biomedicine. The aim of this master thesis is to study if silica particles from reaction of sodium silicate and sulphuric acid can be adsorbed onto cellulose fiber surfaces via in situ growth. First, nanosilica particles were synthesized. Effect of pH and silica contents were tested. In theoretical part, introduction of silica, methods of preparation of nanosilica from sodium silicate, effect factors and additives were discussed. Then, cellulose fiber-silica nanocomposites were synthesis via route from sodium silicate and route silicic acid. In the experiment of route from sodium silicate, the effects of types of sodium silicate, pH and target ratio of silica to fiber were investigated. From another aspect, the effects of types of sodium silicate, fiber concentration in mixture solution and target ratio of silica to fiber were tested in the experiment of route from silicic acid. Samples were investigated via zeta potential measurement, particle size distribution, ash content measurement and Scanning Electron Microscopy (SEM). The Results of the experiment of preparing silica sol were that the particle size of silica sol was smaller prepared in pH 11.7 than that prepared in pH 9.3. Then in the experiment of synthesis of cellulose fiber-silica nanocomposites, it was concluded that the zeta potential of all the samples were around -16 mV and the highest ash content of all the samples was only 1.4%. The results of SEM images showed only a few of silica particles could be observed on the fiber surface, which corresponded to the value of ash content measurement.

Dietary cellulose has no effect on the regeneration of hemoglobin in growing rats with iron deficiency anemia

The objective of the present study was to determine the effect of cellulose on intestinal iron absorption in rats during recovery from iron deficiency anemia. Twenty-one-day-old male Wistar-EPM rats were fed an iron-free ration for two weeks to induce anemia. At 5 weeks of age, the rats were divided into two groups (both groups receiving 35 mg of elemental iron per kg diet): cellulose group (N = 12), receiving a diet containing 100 g of cellulose/kg and control (N = 12), receiving a diet containing no cellulose. The fresh weight of the feces collected over a 3-day period between the 15th and 18th day of dietary treatment was 10.7 ± 3.5 g in the group receiving cellulose and 1.9 ± 1.2 g in the control group (P<0.001). Total food intake was higher in the cellulose group (343.4 ± 22.0 g) than in the control (322.1 ± 13.1 g, P = 0.009) during the 3 weeks of dietary treatment. No significant difference was observed in weight gain (cellulose group = 132.8 ± 19.2, control = 128.0 ± 16.3 g), hemoglobin increment (cellulose group = 8.0 ± 0.8, control = 8.0 ± 1.0 g/dl), hemoglobin level (cellulose group = 12.3 ± 1.2, control = 12.1 ± 1.3 g/dl) or in hepatic iron levels (cellulose group = 333.6 ± 112.4, control = 398.4 ± 168.0 µg/g dry tissue). We conclude that cellulose does not adversely affect the regeneration of hemoglobin, hepatic iron level or the growth of rats during recovery from iron deficiency anemia.

Functional cellulose microspheres for pharmaceutical applications

Dissolving cellulose is the first main step in preparing novel cellulosicmaterials. Since cellulosic fibres cannot be easily dissolved in water-based solvents, fibres were pretreated with ethanol-acid solution prior to the dissolution. Solubility and changes on the surface of the fibres were studied with microscopy and capillary viscometry. After the treatment, the cellulose fibres were soluble in alkaline urea-water solvent. The nature of this viscous solution was studied rheologically. Cellulose microspheres were prepared by extruding the alkaline cellulose solution through the needle into an acidic medium. By altering the temperature and acidity of the mediumit was possible to adjust the specific surface area and pore sizes of themicrospheres. A typical skin-core structure was found in all samples. Microspheres were oxidised in order to introduce anionic carboxylic acid groups (AGs). Anionic microspheres are more hydrophilic; their water-uptake increased 25 times after oxidation and they could swell almost to their original state (88%) after drying and shrinking. Swelling was studied in simulated physiological environments, corresponding to stomach acid and intestines (pH 1.2-7.4). Oxidised microspheres were used as a drug carriers. They demonstrated a highmass uniformity, which would enable their use for personalised dosing among different patients, including children. The drug was solidified in microspheres in amorphous form. This enhanced solubility and could be used for more challenging drugs with poor solubility. The pores of themicrospheres also remained open after the drug was loaded and they were dried. Regardless of the swelling, the drug was released at a constant rate in all environments.

Stability and properties of cellulose-sodium hydroxide solution systems

Since cellulose is a linear macromolecule it can be used as a material for regenerated cellulose fiber products e.g. in textile fibers or film manufacturing. Cellulose is not thermoformable, thus the manufacturing of these regenerated fibers is mainly possible through dissolution processes preceding the regeneration process. However, the dissolution of cellulose in common solvents is hindered due to inter- and intra-molecular hydrogen bonds in the cellulose chains, and relatively high crystallinity. Interestingly at subzero temperatures relatively dilute sodium hydroxide solutions can be used to dissolve cellulose to a certain extent. The objective of this work was to investigate the possible factors that govern the solubility of cellulose in aqueous NaOH and the solution stability. Cellulose-NaOH solutions have the tendency to form a gel over time and at elevated temperature, which creates challenges for further processing. The main target of this work was to achieve high solubility of cellulose in aqueous NaOH without excessively compromising the solution stability. In the literature survey an overview of the cellulose dissolution is given and possible factors contributing to the solubility and solution properties of cellulose in aqueous NaOH are reviewed. Furthermore, the concept of solution rheology is discussed. In the experimental part the focus was on the characterization of the used materials and properties of the prepared solutions mainly concentrating on cellulose solubility and solution stability.

Dexamethasone and sodium carboxymethyl cellulose prevent postoperative intraperitoneal adhesions in rats

We aimed to evaluate the effects of the barrier agent sodium carboxymethyl cellulose (SCMC) with and without dexamethasone for the prevention of postoperative adhesion formation in a rat model of postoperative peritoneal adhesion. A total of 160 three-month old male and female Wistar rats underwent a laparotomy, and adhesions were induced by ileocecal abrasion. Rats were randomly assigned to 4 groups (n=40 each): group A, untreated; group B, treated with SCMC only; group C1, treated with SCMC + 3 mg dexamethasone, and group C2, treated with SCMC + 8 mg dexamethasone. After 12 days, adhesion formation and histopathological changes were compared. In groups A, B, C1, and C2, the mortality rates were 10, 5, 5, and 5%, respectively. In groups C1 and C2, the adhesions were filmy and easy to dissect and were milder compared with those in groups A and B. The total adhesion score in group C1 (3.38±0.49) was significantly lower than that of group B (6.01±0.57; P<0.01) or group A (8.01±0.67; P<0.05). There was no significant difference in adhesion formation between groups C1 and C2. Compared with groups A and B, groups C1 and C2 exhibited milder histopathological changes. SCMC in combination with dexamethasone can prevent adhesion formation and is a better barrier agent than SCMC alone. The safety and feasibility of SCMC in combination with dexamethasone to prevent adhesion formation after abdominal surgery warrants further clinical study.

Fatty acid ethyl esters production using a non-commercial lipase in pressurized propane medium

The objective of this work is to investigate the production of fatty acid ethyl esters from soybean oil in compressed propane using a non-commercial lipase from Yarrowia lipolytica and two commercial ones as catalysts, Amano PS and Amano AY30. The experiments were performed in the temperature range of 35-65 °C. at 50 bar, enzyme concentration of 5 wt%, oil to ethanol molar ratio of 1:6 and 1:9, and solvent to substrates mass ratio of 2:1 and 4:1. The results indicated that low reaction conversions were generally obtained with the use of commercial and non-commercial lipases in pressurized propane medium. On the other hand, the aspects of low solvent to substrates mass ratio and mild temperature and pressure operating conditions used to produce ethyl esters justify further investigations to improve reaction yields.

Ultrafiltration performance of PVDF, PES, and cellulose membranes for the treatment of coconut water (Cocos nucifera L.)

Ultrafiltration (UF) inhibits the enzymatic activity which is responsible for color changes of coconut water without the need for heat treatment. In the present study, UF performance in terms of the permeate flux and enzymatic retention of the coconut water was evaluated at laboratory unit (LU) and pilot unit (PU). The membranes studied were polyethersulfone 150 kDa (UP150), polyvinylidene fluoride 150 kDa (UV150) and cellulose 30 kDa (UC030). The UP150 membrane showed the best permeate flux. The UC030 membrane showed the lowest flux, but it resulted in 100% enzymatic retention, while the other membranes showed enzymatic retentions between 71 and 85%. The application of the UC030 in the pilot unit (PU) resulted in a flux value higher than that obtained in the LU due to the tangential velocity effect. The UC030 membrane has proved adequate for industrial applications.

Functionalisation of spruce O-acetyl-galactoglucomannans for barrier and composite applications

The increasing use of energy, food, and materials by the growing population in the world is leading to the situation where alternative solutions from renewable carbon resources are sought after. The growing use of plastics depends on the raw-oil production while oil refining are politically governed and required for the polymer manufacturing is not sustainable in terms of carbon footprint. The amount of packaging is also increasing. Packaging is not only utilising cardboard and paper, but also plastics. The synthetic petroleum-derived plastics and inner-coatings in food packaging can be substituted with polymeric material from the renewable resources. The trees in Finnish forests constitute a huge resource, which ought to be utilised more effectively than it is today. One underutilised component of the forests is the wood-derived hemicelluloses, although Spruce Oacetyl-galactoglucomannans (GGMs) have previously shown high potential for material applications and can be recovered in large scale. Hemicelluloses are hydrophilic in their native state, which restrains the use of them for food packaging as non-dry item. To cope with this challenge, we intended to make GGMs more hydrophobic or amphiphilic by chemical grafting and consequently with the focus of using them for barrier applications. Methods of esterification with anhydrides and cationic etherification with a trimethyl ammonium moiety were established. A method of controlled synthesis to obtain the desired properties by the means of altering temperature, reaction time, the quantity of the reagent, and even the solvent for purification of the products was developed. Numerous analytical tools, such as NMR, FTIR, SEC-MALLS/RI, MALDI-TOF-MS, RP-HPLC and polyelectrolyte titration were used to evaluate the products from different perspectives and to acquire parallel proofs of their chemical structure. Modified GGMs with different degree of substitution and the correlating level of hydrophobicity was applied as coatings on cartonboard and on nanofibrillated cellulose-GGM films to exhibit barrier functionality. The water dispersibility in processing was maintained with GGM esters with low DS. The use of chemically functionalised GGM was evaluated for the use as barriers against water, oxygen and grease for the food packaging purposes. The results show undoubtedly that GGM derivatives exhibit high potential to function as a barrier material in food packaging.

Adsorption capacity of phenolic compounds onto cellulose and xylan

The interaction between three phenolic compounds (catechin, caffeic acid and ferulic acid) onto two dietary fibres (cellulose and xylan) has been evaluated to inquire possible interferences on the biodisponibility of phenolic compounds. The adsorption kinetics were performed using solutions containing 100 mg/L of phenolic compounds during a contact time ranging between 10 and 120 minutes at pH 2.0, 4.5, and 7.0. After the kinetics, isotherms were obtained using phenolic compounds concentration ranging between 10 and 80 mg/L during 60 minutes, at pH 2.0 and 7.0 and temperature of 36 °C. Results indicate that adsorbed quantities mainly changed in function of pH, however the maximum adsorption was only of 0.978 mg of caffeic acid/g of xylan at pH 2 and after 60 min. Redlich-Peterson model were able to predict the adsorption isotherms of all phenolic compounds onto cellulose, except for caffeic acid at pH 7.0. The low adsorption capacities observed suggest that both dietary fibres are unable to compromise the biodisponibility of phenolic compounds, especially in the small intestine, where they are partially absorbed.

Développement de méthodes analytiques de séparation des produits de digestion enzymatique des dérivés de cellulose

La cellulose et ses dérivés sont utilisés dans un vaste nombre d’applications incluant le domaine pharmaceutique pour la fabrication de médicaments en tant qu’excipient. Différents dérivés cellulosiques tels que le carboxyméthylcellulose (CMC) et l’hydroxyéthylcellulose (HEC) sont disponibles sur le commerce. Le degré de polymérisation et de modification diffèrent énormément d’un fournisseur à l’autre tout dépendamment de l’origine de la cellulose et de leur procédé de dérivation, leur conférant ainsi différentes propriétés physico-chimiques qui leurs sont propres, telles que la viscosité et la solubilité. Notre intérêt est de développer une méthode analytique permettant de distinguer la différence entre deux sources d’un produit CMC ou HEC. L’objectif spécifique de cette étude de maitrise était l’obtention d’un profil cartographique de ces biopolymères complexes et ce, par le développement d’une méthode de digestion enzymatique donnant les oligosaccharides de plus petites tailles et par la séparation de ces oligosaccharides par les méthodes chromatographiques simples. La digestion fut étudiée avec différents paramètres, tel que le milieu de l’hydrolyse, le pH, la température, le temps de digestion et le ratio substrat/enzyme. Une cellulase de Trichoderma reesei ATCC 26921 fut utilisée pour la digestion partielle de nos échantillons de cellulose. Les oligosaccharides ne possédant pas de groupements chromophores ou fluorophores, ils ne peuvent donc être détectés ni par absorbance UV-Vis, ni par fluorescence. Il a donc été question d’élaborer une méthode de marquage des oligosaccharides avec différents agents, tels que l’acide 8-aminopyrène-1,3,6-trisulfonique (APTS), le 3-acétylamino-6-aminoacridine (AA-Ac) et la phénylhydrazine (PHN). Enfin, l’utilisation de l’électrophorèse capillaire et la chromatographie liquide à haute performance a permis la séparation des produits de digestion enzymatique des dérivés de cellulose. Pour chacune de ces méthodes analytiques, plusieurs paramètres de séparation ont été étudiés.

Les esters cyclopropane-1,1-dicarboxyliques et les dérivés cyclopropaniques 1,2,3-substitués : synthèses et applications

Les cyclopropanes sont des motifs d’une grande importance puisqu’ils sont présents dans plusieurs molécules biologiquement actives en plus d’être de puissants intermédiaires dans la synthèse de molécules complexes. Au cours de cet ouvrage, nous avons développé une nouvelle méthode générale pour la synthèse d’ylures d’iodonium de malonates, soit d’importants précurseurs d’esters cyclopropane-1,1-dicarboxyliques. Ainsi, à l’aide de ces ylures, une méthode très efficace pour la synthèse d’esters cyclopropane-1,1-dicarboxyliques racémiques a été développée. Des travaux ont aussi été entrepris pour la synthèse énantiosélective de ces composés. Par ailleurs, les esters cyclopropane-1,1-dicarboxyliques ont été utilisés dans le développement de deux nouvelles méthodologies, soit dans une réaction de cycloaddition (3+3) avec des imines d’azométhines et dans la formation d’allènes par l’addition-1,7 de cuprates. Nous avons aussi poursuivi l’étude synthétique du cylindrocyclophane F impliquant l’utilisation de cyclopropanes pour le contrôle des centres chiraux. Ainsi l’addition-1,5 d’un cuprate sur un ester cyclopropane-1,1-dicarboxylique a été utilisée comme l’une des étapes clés de notre synthèse. L’autre centre chiral a pu être contrôlé par l’hydrogénolyse sélective d’un cyclopropylméthanol. Ces études ont, par ailleurs, mené au développement d’une nouvelle réaction d’arylcyclopropanation énantiosélective utilisant des carbénoïdes de zinc générés in situ à partir de réactifs diazoïques. Cette méthode permet d’accéder très efficacement aux cyclopropanes 1,2,3-substitués. De plus, nous avons développé la première réaction de Simmons-Smith catalytique en zinc menant à un produit énantioenrichi.

Les propriétés mécaniques du réseau cellulose/xyloglucanes dans la croissance apicale du tube pollinique

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

Les effets du dalcetrapib, un inhibiteur de la protéine de transfert des esters de cholestérol (CETP), sur la structure et la fonction des lipoprotéines de haute densité (HDL) dans l’étude dal-PLAQUE2

Introduction : Le dalcetrapib, inhibiteur de la glycoprotéine hydrophobe de transfert des esters de cholestérol (CETP), a été étudié dans le cadre de l’essai clinique de phase II dal-PLAQUE2 (DP2). L’objectif principal est d’étudier l’effet du dalcetrapib après 1 an de traitement sur la structure et la fonction des HDL dans une sous-population de la cohorte DP2. Méthode : Les sujets de la cohorte DP2 ayant une série de mesures de cIMT et des échantillons de plasma et sérum au baseline et à 1 an de traitement furent sélectionnés (379 sujets: 193 du groupe placebo (PCB) et 186 du groupe dalcetrapib (DAL)). Des données biochimiques prédéterminées, le profil des concentrations et tailles des sous-classes de HDL et LDL en résonance magnétique nucléaire (RMN) et 2 mesures de capacité d’efflux de cholestérol (CEC) du sérum ont été explorées. Les données statistiques furent obtenues en comparant les changements à un an à partir du « baseline » avec un ANOVA ou ANCOVA. La procédure normalisée de fonctionnement d’essai d’efflux de cholestérol permet de calculer l’efflux fractionnel (en %) de 3H-cholestérol des lignées cellulaires BHK-ABCA1 (fibroblastes) et J774 (macrophages, voie ABCA1) et HepG2 (hépatocytes, voie SR-BI), vers les échantillons sériques de la cohorte DP2. Résultats : Pour la biochimie plasmatique, un effet combiné des changements d’activité de CETP dans les 2 groupes a causé une réduction de 30% dans le groupe DAL. Après 1 an de traitement dans le groupe DAL, la valeur de HDL-C a augmenté de 35,5% (p < 0,001) et l’apoA-I a augmenté de 14,0% (p < 0,001). Au profil RMN, dans le groupe DAL après 1 an de traitement, il y a augmentation de la taille des HDL-P (5,2%; p < 0,001), des grosses particules HDL (68,7%; p < 0,001) et des grosses particules LDL (37,5%; p < 0,01). Les petites particules HDL sont diminuées (-9,1%; p < 0,001). Il n’y a aucune différence significative de mesure de cIMT entre les deux groupes après 1 an de traitement. Pour la CEC, il y a augmentation significative par la voie du SR-BI et une augmentation via la voie ABCA1 dans le groupe DAL après 1 an de traitement. Conclusion : Après un an de traitement au dalcetrapib, on note une hausse de HDL-C, des résultats plutôt neutres au niveau du profil lipidique par RMN et une CEC augmentée mais trop faible pour affecter la valeur de cIMT chez les échantillons testés.

Modification of Polypropylene/Polystyrene blend using Nanoclay and Sisal Cellulose nano fiber

Cochin University of Science and Technology