Les " gels attractifs " constituent une catégorie particulière de fluides complexes. Ces gels sont formés à partir d'une suspension de particules attractives en faible concentration volumique. La microstructure du gel est très facilement modifiée par l'application d'une contrainte. Ainsi, il est possible de structurer ces gels par un cisaillement dans une géométrie suffisamment confinée. Nous avons étudié en détail ce phénomène dans des gels de noirs de carbone ainsi que dans des suspensions de billes de verre dans de l'huile rendues attractives par la présence d'une faible quantité d'eau. Nous avons reproduit ce phénomène dans des simulations numériques de dynamique moléculaire, ce qui permet d'étudier les conditions nécessaires à l'apparition de telles structures. Enfin, en géométrie peu confinée, le mécanisme de rupture et d'écoulement de ces gels en volume est complexe puisque leur rupture est en perpétuelle compétition avec leurcinétique de reformation. Nous avons étudié la rupture des gels de noir de carbone en couplant des techniques classiques de rhéologie avec une technique de mesure locale de déplacement par ultrasons. Ces expériences nous ont permis d'établir un lien entre le comportement global du matériau (sa rhéologie macroscopique) et la dynamique locale de fluidification.

<p>Even though women make up over half the population in the United States, medical advancements in areas of women's health have typically lagged behind the rest of the medical field. Specifically, two major threats to women's reproductive health include human immunodeficiency virus (HIV), and cervical cancer with accompanying human papillomavirus (HPV) infection. This dissertation presents the development and application of two novel optical imaging technologies aimed at improving these aspects of women's reproductive health.</p><p>The presented work details the instrumentation development of a probe-based, dual-modality optical imaging instrument, which uses simultaneous imaging of fluorimetry and multiplexed low coherence interferometry (mLCI) to measure in vivo microbicide gel thickness distributions. The study explores the optical performance of the device and provides proof of concept measurements on a calibration socket, tissue phantom, and in vivo human data. Once the instrument is fully characterized, it is applied in a clinical trial in which in vivo human vaginal gel thickness distributions. The gel distribution data obtained by the modalities are compared in order to assess the ability of mLCI making accurate in vivo measurements. Differences between the fluorimetry and mLCI modalities are then exploited in order to show a methodology for calculating the extent of microbicide gel dilution with the dual-modality instrument data.</p><p>Limitations in cervical cancer screening are then addressed as angle-resolved low coherence interferometry (a/LCI) is used in an ex vivo pilot study to assess the feasibility of a/LCI in identifying dysplasia in cervical tissues. The study found that the average nuclear diameter found by a/LCI in the basal layer of ectocervical epithelium showed a statistically significant increase in size in dysplastic tissue. These results indicate that a/LCI is capable of identifying cervical dysplasia in ectocervical epithelium. The results of the work presented in this dissertation show that dual-modality optical imaging with fluorimetry and mLCI, and the a/LCI technique show promise in advancing technologies that are used in the field of women's reproductive health.</p> / Dissertation

In this thesis, the macroscopic phase separation of milk proteins and high molecular weight oat beta-glucan was investigated. A better knowledge of this model system will improve our ability to control structure in dairy gels containing nutritionally significant concentrations of dietary fiber. A phase behaviour diagram was obtained experimentally, and the results were then modelled using theoretical models based on thermodynamic incompatibility between casein micelles and beta-glucan and demonstrated that casein micelles are the main contributors to the instability of these mixtures. Water in water emulsion systems formed at high concentrations of protein and beta-glucan upon mixing, and were visualized using confocal scanning laser microscopy. For the first time, the dynamics of phase separation of these mixtures were followed using diffusing wave and ultrasonic spectroscopy, as well as with rheological methods. The work explored the formation of different bi-continuous networks by controlling the gelation of the protein phase using chymosin. This enzymatic reaction specifically destabilizes the casein micelles, allowing for a kinetic control of protein gelation within or between phase separated domains. The addition of -carrageenan and the effect of shear on the mixtures were evaluated as possible strategies for controlling the growth of the phase separated domains in dairy gels containing concentrations of beta-glucan high enough to be nutritionally significant. Results indicated that different structures could be obtained depending on the processing conditions, for example, the mode of addition of the polysaccharides or the pre-shearing conditions. This work represents a novel approach for incorporating nutritionally significant concentrations of beta-glucan in dairy foods, and serves as proof of concept for further development of an important application area linked to the development of reduced fat dairy products with additional health benefits. / Canadian Dairy Commission (CDC) and Natural Sciences and Engineering Research Council (NSERC)

Homogeneous single C-S-H gels have been prepared for the investigation of alkali binding potential and crystallisation. A distribution coefficient, R_d, was introduced to express the partition of alkali between solid and aqueous phases at 25°C. R_d is independent of alkali hydroxide concentration and depends only on Ca:Si ratio over wide ranges of alkali concentration. The trend of numerical values of R_d indicates that alkali bonding into the solid improves as its Ca:Si ratio decreases. Reversibility is demonstrated, indicating a possibility of constant R_d value of the material. Al has been introduced to form C-A-S-H gels and their alkali sorption properties also determined. Al substituted into C-S-H markedly increases R_d, indicating enhancement of alkali binding. However, the dependence of R_d on alkali concentration is non-ideal with composition. A two-site model for bonding is presented. Crystallisation both under saturated steam and 1 bar vapour pressure has been investigated. It has been shown that heat treatment by saturated steam causes crystallisation of gels. The principal minerals obtained were (i) C-S-H gel and Ca(OH)₂ at ~55°C, (ii) 1.1 nm tobermorite, jennite and afwillite at 85-130°C, and (iii) xonotlite, foshagite and hillebrandite at 150-180°C. Properties of crystalline C-S-H were also reported for reversible phase transformation, pH conditioning ability, seeding effect and solubility. At 1 bar pressure, crystallisation is slower than in saturated steam due to lower water activity. Tobermorite-like nanodomains develop during reaction at low Ca/Si ratios. In some Ca-rich compositions, Ca(OH)₂ is exsolved and occurs as nano-sized crystallites.

Tyrimo tikslas. Sumodeliuoti puskiečius burnos gleivinės preparatus su skystuoju jonažolių ekstraktu ir pagrįsti jų tinkamumą biofarmaciniais tyrimais. Uždaviniai. 1. Parinkti veikliosios medžiagos (jonažolių ištraukų) sudėtį ir įvertinti jų kokybę 2. Parinkti tinkamas pagalbines medžiagas hidrofilinių puskiečių preparatų formulavimui 3. Sumodeliuoti hidrofilinius puskiečius preparatus su skystuoju jonažolių ekstraktu 4. Pagrįsti hidrofilinių puskiečių preparatų su skystuoju jonažolių ekstraktu kokybę, atliekant veikliųjų junginių atpalaidavimo tyrimą in vitro. Metodai. Suminis flavonoidų kiekis (pagal rutiną) nustatytas spektrofotometriniu metodu. pH reikšmė nustatyta potenciometriniu metodu. Atlikta dinaminės klampos matavimo metodas, biofarmacinis veikliųjų junginių atpalaidavimo iš gelių tyrimas in vitro. Veikliosios medžiagos antimikrobinis aktyvumas nustatytas pagal Ph Eur. 01/2002, 2.6.12 metodą. Tyrimo objektas. Hidrofiliniai puskiečiai preparatai su skystuoju jonažolių ekstraktu (1:1). Tyrimo rezultatai. Pagaminti skystieji jonažolių ekstraktai (1:1) tamsiai rudos spalvos, kuriuose nustatytas suminis flavonoidų kiekis 6,03013 – 6,48663 mg/ml. Jonažolių geliai rudos spalvos, kurių klampa ≥ 0,80 Pa•s, pH reikšmė 4,78-6,63, suminis flavonoidų kiekis ≥ 0,08 mg/ml. Veikliųjų junginių atpalaidavimo tyrimas in vitro parodė, kad po 6 val iš jonažolių karbomero ir poloksamero gelių atpalaiduota apie 16 proc. flavonoidų. Išvados. 1. Remiantis nustatytu suminiu flavonoidų... [toliau žr. visą tekstą] / Purpose of work. To make models of the semi liquid mouth products, containing St. John's Wort extract and validate their suitability for biopharmaceutical research. Tasks. 1. Select the active material substance (St. John's Wort extracts) and assess their quality. 2. Select suitable excipients for the formulation of hydrophilic semi-hard products. 3. To make models of hydrophilic group of semi products with St. John's Wort extract. 4. Substantiate the quality of hydrophilic, semi-hard products with St. John's Wort extract, performing release study in vitro of the active compounds. Methods. The total flavinoid content (by routine) was determined by spectrophotometry. The value of pH is set by potentiometric method. Dynamic viscosity measurement and the study in vitro of the biopharmaceutical active compound release from gels were carried out. The antimicrobial activity of the active substance was determined in accordance with Ph. Eur set. 01/2002 2.6.12 method. The object of study. The effect of hydrophilic semi-hard products containing St. John's Wort extracts (1:1). Results. St. John's Wort extracts liquid (1:1) has been produced in dark brown color with a prescribed amount of total flavinoids from 6.03013 to 6.48663 mg/ml. The gels of St. John's Wort are also in brown colour with a viscosity of ≥ 0.80 Pa•s, a pH value of 4.78 to 6.63, total flavinoid content of ≥ 0.03 mg/ml. The active compounds release study in vitro showed that about 16 pct. flavonoids from St. John's... [to full text]

[Truncated abstract] The synthetic hydrogel poly(2-hydroxyethyl methacrylate) (PHEMA) has been used as a biocompatible biomaterial in ocular devices, such as soft contact lenses, intraocular lenses and an artificial cornea. Due to its favourable properties as an already established (but non-biodegradable) biomaterial, PHEMA is an interesting candidate for use as a material for scaffolds in tissue engineering. A tenant of tissue engineering scaffolds is obtaining the appropriate porous morphology to allow for successful cellular attachment and support. PHEMA hydrogels exhibit varied morphological features, which range from non-porous (homogeneous) to macroporous (heterogeneous) and can be readily obtained by fine-tuning the polymerisation conditions. A desirable feature for matrices that are to be used as tissue supports is the ability to biodegrade in a biological environment. This thesis describes the preparation and enzymatic biodegradation behaviour of novel porous PHEMA hydrogels that have been crosslinked with biodegradable peptide-based crosslinking agents. Peptide-based crosslinking agents were designed to contain two terminal polymerisable groups flanking an internal biodegradable backbone. This backbone was specifically designed to be targeted by the proteolytic enzyme papain. The general design template allowed for the development of a synthetic methodology that was readily implemented for the production of a range of olefin-peptide conjugates. A suite of olefin-peptide conjugates of general structure I were synthesised, characterised and further tested with papain to determine their biodegradation properties. ... The second strategy for producing bioresorbable degradation fragments involved the incorporation of the highly hydrophilic comonomer, poly(ethylene glycol) PEG into the PHEMA backbone. The addition of PEG to PHEMA resulted in the formation of homogeneous hydrogels that had an improved hydrophilicity compared to their heterogeneous PHEMA counterparts. The synthetic conditions for the preparation of PHEMA and PHEMA-co-PEG hydrogels by photoinitiated polymerisation were thoroughly investigated. It was found that the pore morphology and general properties (non-porous to macroporous) of these hydrogels could be controlled by the appropriate choice of polymerisation conditions. The hydrogels were characterised by scanning electron microscopy, thermal gravimetric analysis and differential scanning calorimetry. The peptide-based crosslinking agents were successfully co-polymerised with the HEMA and PEGMA via photoinitiated polymerisation to provide a range of PHEMA and PHEMA-co-PEG hydrogels that displayed both homogeneous and heterogeneous hydrogel properties. The final crosslinked hydrogels were characterised by scanning electron microscopy and were subjected to enzymatic hydrolysis. The PHEMA-peptide conjugate hydrogels proved to be biodegradable, with degradation behaviour dependent on the hydrogel formulation and the length of the peptide-based crosslinking agent.

Thesis (M.Sc. (Pharmacy)) - Rhodes University, 2008

Στην παρούσα εργασία μελετήθηκαν φυσικά πηκτώματα κατά συστάδων συμπολυμερών σε ιοντικό υγρό. Τα συμπολυμερή που μελετήθηκαν ήταν το τρισυσταδικό συμπολυμερές πολυ(αιθυλενοξείδιο)-πολυ(στυρόλιο)-πολυ(αιθυλενοξείδιο) (PEO-PS-PEO) και το αστεροειδές συμπολυμερές πολυ(στυρόλιο)-πολυ(αιθυλενοξείδιο) (PS10PEO10) στο ιοντικό υγρό εξαφθοροφωσφορούχο 1-βουτυλο-3-μεθυλιμιδαζόλιο [BMIM][PF6], το οποίο είναι "καλός" διαλύτης για το PEO και "κακός" διαλύτης για το PS. Αρχικά πραγματοποιήθηκε μοριακός χαρακτηρισμός των συμπολυμερών PEO-PS-PEO και PS10PEO10 μέσω των τεχνικών χρωματογραφίας αποκλεισμού μεγεθών (SEC) και της φασματοσκοπίας πυρηνικού μαγνητικού συντονισμού (1H-NMR). Στη συνέχεια πραγματοποιήθηκε η μελέτη των συμπολυμερών σε αραιά διαλύματα μέσω των τεχνικών της δυναμικής σκέδασης φωτός (DLS) και της ιξωδομετρίας. Παρατηρήθηκε πως τα συμπολυμερή PEO-PS-PEO και PS10PEO10 δημιουργούν πολυμοριακά και μονομοριακά "μαλακά" νανοσωματίδια μικκυλιακού τύπου, αντίστοιχα. Από τη DLS προσδιορίστηκε η υδροδυναμική ακτίνα, Rh, των σωματιδίων. Μέσω της τεχνικής της ιξωδομετρίας AMVn υπολογίστηκε η κρίσιμη συγκέντρωση επικάλυψης, c*, στην οποία τα σωματίδια αρχίζουν να εφάπτονται μεταξύ τους. Σε υψηλές συγκεντρώσεις των πολυμερών παρατηρείται η δημιουργία φυσικών πηκτωμάτων λόγω της πλήρωσης του όγκου του διαλύματος από τα σωματίδια. Μέσω ρεολογικών μελετών προσδιορίστηκε η κρίσιμη συγκέντρωση σχηματισμού πηκτώματος, cgel. Παρατηρήθηκε μεγάλη εξάρτηση του σχετικού ιξώδους από τη συγκέντρωση του συμπολυμερούς καθώς και η αύξηση της ισχύος (μέτρου αποθήκευσης) και του χρόνου χαλάρωσης των φυσικών πηκτωμάτων με την αύξηση της συγκέντρωσης. Τέλος, πραγματοποιήθηκε σύγκριση μεταξύ των συστημάτων PEO-PS-PEO/[BMIM][PF6] και PS10PEO10/[BMIM][PF6]. Διαπιστώθηκε πως το PS10PEO10 παρουσιάζει μεγαλύτερη cgel από το PEO-PS-PEO λόγω της μικρότερης πυκνότητας των αλυσίδων στην κορώνα του αστεροειδούς από αυτή του τρισυσταδικού με αποτέλεσμα τα σωματίδια του αστεροειδούς να διεισδύουν πολύ περισσότερο μεταξύ τους για να επιτευχθεί το φαινόμενο του συνωστισμού. / In the present study the properties of physical gels formed by block copolymers in an ionic liquid were studied. The triblock poly(ethylene oxide)-poly(styrene)-poly(ethylene oxide) (PEO-PS-PEO) and the star polystyrene-polyethylene (PS10PEO10) copolymers were studied in 1-butyl-3-methylimadazolium hexafluapophoshate, [BMIM][PF6], which is a good solvent for the PEO blocks and bad solvent for the PS blocks. Initially, the copolymers were characterized by size exclusion chromatography (SEC) and neutron magnetic resonance (1H-NMR). At a next step the study of the polymers in dilute solutions was followed by dynamic light scattering (DLS) and AMVn viscometry. It was found that PEO-PS-PEO and PS10PEO10 self assemble into multimolecular and monomolecular, micellar type soft nanoparticles, respectively. The size of the particles was calculated by DLS. From the AMVn viscometry, the critical overlap concentration at which the formed nanoparticles start adhering to each other, c*, was calculated. At high polymer concentrations, the formation of gels was observed which was due to the jamming of the particles in the total volume of the solution. Through rheological studies, the critical gelation concentration, cgel, was determined. Above cgel a dramatic viscosity rise was observed. At the same time, the storage modulus Go and the relaxation time τR of the system increased also with increasing concentration. Finally, the comparison between the PEO-PS-PEO/[BMIM][PF6] and PS10PEO10/[BMIM][PF6] systems was discussed. It was concluded that the PS10PEO10 copolymer exhibits a higher value of cgel than that of PEO-PS-PEO copolymer due to the lower density of the chains in the corona of the star nanoparticles.

Made available in DSpace on 2014-10-09T12:43:17Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:18Z (GMT). No. of bitstreams: 1 06443.pdf: 4052789 bytes, checksum: ad0a002c9a73bb765e639e0bde37d570 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Ce travail de thèse porte sur la synthèse et l'étude physico-chimique de polymères associatifs hydrosolubles à associations complémentaires. Utilisant la chimie covalente réversible, ce système met en jeu l'association d'un poly(diol) et d'un poly(acrylamide) partiellement hydrolysé portant des fonctions d'acide boronique. Ces dernières sont introduites par une technique de greffage qui a été optimisée et finement caractérisée. Le mélange des deux polymères permet d'obtenir des solutions visqueuses et des gels dynamiques et ceci pour de faibles concentrations. La possibilité de viscosifier des formulations en-dessous de la concentration de gélification constitue un résultat marquant qui distingue ce système de nombreux polymères à association hydrophobe. Dans le régime de gel, les propriétés rhéologiques linéaires sont analysées en relation avec l'étude de la force des interactions moléculaires qui ont été mesurées par la RMN du bore et une technique de fluorescence. La rhéologie non-linéaire apporte des informations essentielles sur la relation entre le cisaillement et la structure du réseau réversible formé. L'utilisation d'un système de visualisation de l'échantillon sous écoulement permet l'observation d'effets locaux fortement non-linéaires. L'influence des différents paramètres, comme le pH et la température, sur les propriétés dynamiques des solutions peut être rationalisée et modélisée en termes de lois d'échelles. L'originalité de ce concept de système associatif par associations complémentaires est mise en perspective au travers d'une revue de la littérature rationalisant le lien entre architecture et rhéologie des polymères associatifs hydrosolubles. / This thesis deals with the synthesis and the physical chemistry study of water-soluble complementary associative polymers. Based on reversible covalent chemistry, this system brings into play the association of a poly(diol) and of a partially hydrolyzed poly(acrylamide) bearing boronic acid moieties. The latter are introduced by a grafting technique which has been optimized and finely characterized. The mixing of these two polymers allows obtaining viscous solutions and visco-elastic gels at relatively low polymer concentrations. The possibility to make formulations viscous below the gel point represents a remarkable result, which differentiates this system to numerous associative polymers based on hydrophobic interactions. In the gel regime, the linear rheological properties are analyzed with regard to the strength of molecular interactions which have been measured by boron NMR and a fluorescence technique. Non-linear rheology brings essential information about the relationship between shearing and the structure of the formed reversible network. The use of a visualization setup of samples under flow enables the observation of very non-linear local effects such as wall slip and shear-banding. The influence of various parameters, as pH and temperature, on the dynamical properties of solutions and gels can be rationalized and modeled in terms of scaling laws. The originality of this concept of associative system with complementary associations is put into perspective through a literature review on the relationship between architecture and molecular interactions on one hand, and rheological properties of associative polymers on the other hand.