Carbohydrate-protein interactions are responsible for several biological functions. While these interactions maintain high levels of specificities, the binding strength of individual carbohydrate-protein recognitions are weak, with dissociation constants (Kd) ~10-3-10-6 M. In order to increase the binding strengths meaningful to physiological functions, multivalent, clustered patches of carbohydrate ligands are required. Synthetic glycoclusters contribute in a significant manner to understand the fine details of the weak carbohydrate-protein interactions. The extent of clustering of the ligands, spatial, topological orientations and the nature of the scaffolds are prominent issues to address the carbohydrate-protein interactions in general. Chapter 1 of the Thesis presents a summary of the synthetic cluster glycosides, mechanisms and energetics of their interactions with lectins. The presence of several ligands within the molecular scaffold is not sufficient, rather there exists a critical demand on the spatial disposition of the individual ligands in the multivalent ligand system to achieve enhanced binding affinities. In order to assess the multivalent effects, influence of linkers and the spatial disposition of the ligands, a systematic study was undertaken, involving a series of the most minimal of the multivalent sugar ligand system, namely, the bivalent sugar ligands. In a programme, it was desired to study the bivalent and monovalent sugar ligand-lectin interactions in a two-dimensional membrane model system. An appropriate model system was the Langmuir monolayer formations of the sugar ligands and their recognitions of the lectins at the interface. A series of bivalent and monovalent glycolipids were thus designed and synthesized. Molecular structure of the ligands utilized to study the lectins binding behavior at the air-water interface are presented in Figure 1. The sugar density dependent lectin binding at the air-water interface caused by the glycolipids was studied in detail. Prior to lectin binding studies, the monolayer behavior of the glycolipids (GL), non-sugars (NS) and their mixtures were assessed. It was observed that the apparent molecular areas of the mixed monolayers increased with increasing percentage of the glycolipid in the mixed monolayer. Interactions of the glycolipid mixed monolayers with lectin were assessed at a constant surface pressure of 10 mN/m. The adsorption kinetics of the lectin concanavalin A (Con A) with the mixed monolayers was monitored by the surface area variation (ΔA) as a function of time. The detailed studies showed a maximum increase in ΔA of 10% of the bivalent glycolipids in the mixed monolayer and a ΔA of 20% of the monovalent glycolipids (Figure 2). With both bivalent and monovalent glycolipids, change in the area per molecule had decreased progressively with higher percentage of the glycolipids in the monolayers. On the other hand, with ethylene glycol spacers, the relative responses and the amount of bound lectin increased. Figure 2. Ligand-lectin interactions at the air-water interface as a function of the percentage of (a) bivalent glycolipids and (b) monovalent glycolipids in the mixed monolayers. To verify the specificity of these interactions, the mannopyranoside non-specific lectin, namely, wheat germ agglutinin (WGA) was tested and there were no deviations in the ΔA for various ratios of the sugar–non-sugar mixed monolayers. The study established that (i) maximal binding of the lectin to the bivalent glycolipids occurred at lower sugar densities at the interface than that for the monovalent glycolipids and (ii) the surface presenting sparsely populated sugar residues are efficient for a lectin binding. Chapter 2 presents the details of synthesis and ligand-lectin interactions at the air-water interface, relevant in the two-dimensional membrane model system. A study of the multivalent effects originating through glycolipid micelles and their lectin interactions was undertaken in another programme. The kinetic studies of the glycolipid micelles-lectin interactions were conducted with the aid of surface plasmon resonance (SPR) technique. Prior to the SPR studies, the critical micellar concentration (CMC), aggregation number and the hydrodynamic diameter of each glycolipid (GL-1 to GL-6, Figure 1) micelles were determined. The glycolipid micelles were used as the analytes on a Con A immobilized surface. The sensorgrams obtained for the interaction of the various glycolipid micelles with Con A are presented in Figure 3. Figure 3. Sensorgrams obtained for the binding of various glycolipids micelles to a Con A immobilized surface, at a constant glycolipid concentration of 250 µM. The kinetic studies of the interactions were performed and the analysis showed that the bivalent analyte model provided a better fitting for the interaction sensorgrams. The analysis revealed that the ka1/kd1 values remained largely uniform for all the glycolipids, whereas the ka2/kd2 values were about two orders of magnitude larger for the bivalent glycolipid (GL-4 to GL-6) micelle-lectin interactions than for the monovalent series (GL-1 to GL-3) (Table 1). From the SPR studies, it emerged that the additional sugar unit in the bivalent glycolipid micelles provided a favorable complexation between the sugar ligand and the lectin. Further, the glycolipid micelles mediated layer-by-layer Con A multilayer formation was also studied by SPR and atomic force microscopy (AFM) methods. Chapter 3 provides the SPR studies of glycolipid micelles-lectin interactions. A study of the monomolecular recognitions of the mono- and bivalent sugar ligands 1-8 (Figure 4) to a lectin was undertaken subsequently. The kinetic studies of the bivalent vs monovalent ligands during lectin binding were conducted by employing the SPR technique, for which the sugar ligands 1-6 were used as the analytes on a lectin coated sensor surface. Figure 4. Structures of the mono- and bivalent sugar ligands 1-8 and the NS derivative. The following observations were made from the SPR analysis. (i) Within the mono- and bivalent series, the response units increased in the series 1–3 and 4–6; (ii) the equilibrium responses were attained within 105 seconds in the monovalent ligands and (iii) the association response gradually increased for the bivalent ligands 5 and 6 and reached an equilibrium after ~3 min. An important outcome of the kinetic studies was the identification of ka and kd for the monomolecular interactions, that were distinctly different for the bivalent ligands. Specifically, the ka was significantly faster and kd was slower for bivalent sugar ligands, in comparison to the monovalent sugar ligands (Table 2). Table 2. SPR derived kinetic parameters for the interactions of sugar ligand to a Con A immobilized surface at 25 oC. Isothermal titration calorimetry (ITC) studies were also conducted, in order to correlate the functional valencies and the thermodynamic parameters. The studies were conducted at ligand concentrations much below their CMCs. The general observations from the ITC studies were that the binding site saturations were slower for the monovalent sugar ligands, in comparison to the bivalent sugar ligands. It was observed that the binding affinities of bivalent ligands 5 and 6 enhanced ~5 times higher than the monovalent ligands 2 and 3 (Table 3). The effective linker length, which allowed the sugar ligands to be functionally active, was determined to be ~15 Å and this separation was necessary for the intermolecular cross-linking formation. The dynamic light scattering (DLS) study of the bivalent ligands 5 or 6-lectin complexes showed the presence of intermolecular cross-linked complexes that existed in solution from the initial stages of the binding process. Upon realizing the nanometric diameters of the sugar ligand-lectin complex, an attempt was undertaken to visualize the complexes by transmission electron micoscopy (TEM). In TEM, 4-Con A complex exhibited particle sizes in the range of 5-10 nm, matching nearly the size of the lectin alone. On the other hand, 5–Con A and 6–Con A complexes provided sizes varying between 20¬150 nm. These particle sizes corresponded to similar aggregate sizes derived from the DLS studies. Chaper 4 describes the kinetic, thermodynamic, DLS and TEM studies of sugar ligand-lectin intearctions. Table 3. Binding stoichiometries and thermodynamic parameters of the sugar ligand-Con A interactions at 25 oC.a Ligand n Ka (x 10 -4) ΔG ΔH TΔS 1 0.91 9.14 ( ± 0.75) -6.76 -3.39 3.37 2 1.01 5.76 (± 0.80) -6.49 -3.98 2.51 3 1.09 7.06 (± 1.23) -6.61 - 3.01 3.60 4 1.10 5.75 (± 0.27) -6.49 - 6.39 0.10 5 0.50 20.6 (± 1.7) -7.59 - 12.80 -5.21 6 0.47 37. 4 (± 2. 4) -7.61 -11.54 -3.93 7 1.03 0.86 (± 0.06) -5.36 -7.9 -2.62 8 1.05 2.48 (± 0.12) -5.99 -6.3 -0.32 MeαMan 1.04 0.79 (± 0.04) -5.27 -7.83 -2.56 Ka is in the unit of M-1; ΔG, ΔH and TΔS are in the units of kcal mol-1. Errors in ΔG are ~1-4%. Errors in ΔH are in the range of 1-8%. Errors in TΔS are in the range of 1-6 %. A study was undertaken further to assess the kinetic interactions of the tumor-associated T-antigen with a lectin. Synthesis of amine-tethered T-antigen and lactose derivatives (Figure 5) were accomplished and an assessment of their kinetic interactions with lectin peanut agglutinin (PNA) was conducted. Figure 5. Structures of the amine-tethered T-antigen, lactose and mannose derivatives. The lectin PNA was used as the analyte onto the sugar ligand immobilized surfaces. It was found that the interaction with T-antigen showed higher response units than the lactose derivative (Figure 6). The kinetic studies of PNA with immobilized T-antigen and the lactose derivatives demonstrated that the binding followed a bivalent analyte model of the interaction. The T-antigen derivative interacted with the lectin and relatively faster association (ka) and a slower dissociation (kd) were observed, in comparison to the lactose derivative. The ratio of second binding kinetic constants (ka2/kd2) was observed higher than the first binding kinetic constants (ka1/kd1). Further, the ITC studies were conducted, in order to provide the thermodynamic parameters governing the lectin-T-antigen interactions. The combined approach of SPR and ITC studies showed that the T-antigen derivative exhibited a higher binding affinity to PNA than the lactose derivative. Chapter 5 presents synthesis of the T-antigen and lactose derivatives and studies of their lectin interactions. In summary, the thesis provides a detailed insight into the kinetic and thermodynamic parameters of the bivalent sugar ligand-lectin interactions, in comparison to the monovalent sugar ligands. Langmuir monolayer formation of the sugar ligands and the assessment of their lectin binding at the air-water interface demonstrated that the surface presenting sparsely populated sugar residues are efficient for a lectin binding. The kinetic studies of various glycolipid micelles-lectin interactions showed that the additional sugar unit in the bivalent glycolipid micelles provided a favorable complexation between the sugar ligand and the lectin. The detailed monomolecular kinetic studies showed that the bivalent sugar ligands underwent a faster association (kon) and a slower dissociation (koff) of the ligand-lectin complexes. The ITC studies on sugar ligand-lectin interactions led to identify not only the thermodynamic parameters, but also the influence of the hydrophobic alkyl units and the linker moieties. The DLS and TEM characterizations of sugar ligand-lectin complexes showed the status of the complexation, sizes and the morphologies. The studies were extended further to tumor associated T-antigen-lectin interactions. Overall, the Thesis establishes the most minimal multivalent sugar ligands, namely, the bivalent sugar ligand-letin interactions. The studies presented in the Thesis should be useful to design multivalent sugar ligands for highly avid lectin interactions and also to raise possibilities for the construction of defined lectin oligomers, facilitated through the multivalent sugar ligand-lectin cross-linking interactions.

Even in times of renewable energy revolution fossil fuels will play a major role in energy supply, transportation, and chemical industry. Therefore, increasing demand for crude oil will still have to be met in the next decades by developing new oil re-serves. To cope with this challenge, companies and researchers are constantly seeking for new methods to increase the recovery factor of oil fields. For that reason, many enhanced oil recovery (EOR) methods have been developed and applied in the field. EOR methods alter the physico-chemical conditions inside the reservoir. One possibility to achieve this is to inject an aqueous solution containing special chemicals into the oil-bearing zone. Polymers, for example, increase the viscosity of the injected water and hence improve the displacement of the oil to the production well. The injection of surfactant solutions results in reduced capillary forces, which retain the oil in the pores of the reservoir. Some surfactants form viscoelastic solutions under certain conditions. The possibil-ity to apply those solutions for enhanced oil recovery has been investigated by some authors in the last years in low salinity brines. Reservoir brines, however, often contain high salt concentrations, which have detrimental effects on the properties of many chemical solutions applied for EOR operations. The Triphenoxymethane derivatives, which were the subject of study in this thesis, form viscoelastic solutions even in highly saline brines. The aim of this thesis was to investigate the efficiency and the mode-of-action of this new class of chemical EOR molecules with respect to oil mobilization in porous media.

Mixed association of calix[4]resorcinarene with ethyl sulfonate groups on the lower rim and dimethylaminomethyl groups on the upper rim (CR) and cationic surfactant 4-aza-1-hexadecyl-azoniabicyclo[2.2.2]octane bromide (DABCO-16) is studied by methods of tensiometry, conductometry, potentiometry and NMR spectroscopy at fixed CR concentration and varied surfactant concentration. Beyond ca. 0.4 mM of DABCO-16, mixed aggregates enriched by CR are proved to be formed due to electrostatic forces, while beyond ca. 5 mM, aggregates enriched by surfactant occur due to the hydrophobic effect. Spectrophotometry monitoring of the solubilization of a hydrophobic dye, Orange OT, demonstrated that only the second type of mixed aggregate enriched by DABCO-16 is capable of binding the organic probe, while the mixed system where the surfactant is a minor component shows no binding capacity towards Orange OT. This finding can be used for the design of nanocontainers with controllable binding/release properties. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Even in times of renewable energy revolution fossil fuels will play a major role in energy supply, transportation, and chemical industry. Therefore, increasing demand for crude oil will still have to be met in the next decades by developing new oil re-serves. To cope with this challenge, companies and researchers are constantly seeking for new methods to increase the recovery factor of oil fields. For that reason, many enhanced oil recovery (EOR) methods have been developed and applied in the field. EOR methods alter the physico-chemical conditions inside the reservoir. One possibility to achieve this is to inject an aqueous solution containing special chemicals into the oil-bearing zone. Polymers, for example, increase the viscosity of the injected water and hence improve the displacement of the oil to the production well. The injection of surfactant solutions results in reduced capillary forces, which retain the oil in the pores of the reservoir. Some surfactants form viscoelastic solutions under certain conditions. The possibil-ity to apply those solutions for enhanced oil recovery has been investigated by some authors in the last years in low salinity brines. Reservoir brines, however, often contain high salt concentrations, which have detrimental effects on the properties of many chemical solutions applied for EOR operations. The Triphenoxymethane derivatives, which were the subject of study in this thesis, form viscoelastic solutions even in highly saline brines. The aim of this thesis was to investigate the efficiency and the mode-of-action of this new class of chemical EOR molecules with respect to oil mobilization in porous media.

No description available.

Specific interactions of ligands with receptors is one of the approaches for active targeting of anticancer drugs to cancer cells. Over expression of integrin receptors is a physiological manifestation in several cancers and is associated with cancer progression and metastasis, which makes it an attractive target for cancer chemotherapy. The peptide sequence for this integrin recognition is the Arg-Gly-Asp (RGD). Self-assembly offers a unique way of presenting ligands to target receptors for recognition and binding. This study focuses on development of integrin specific peptide amphiphile self-assemblies as carriers for targeted delivery of paclitaxel to α v β 3 integrin overexpressing cancers. Amphiphiles composed of conjugates of different analogs of RGD (linear, cyclic or glycosylated) and aliphatic fatty acid with or without 8-amino-3,6-dioxaoctanoic acid (ADA) as linker were synthesized and characterized. The amphiphiles exhibited Critical Micellar Concentration in the range of 7-30 μM. Transmission electron microscopy images revealed the formation of spherical micelles in the size range of 10-40 nm. Forster Resonance Energy Transfer studies revealed entrapment of hydrophobic dyes within a tight micellar core and provided information regarding the cargo exchange within micelles. The RGD micelles exhibited competitive binding with 55% displacement of a bound fluorescent probe by the cyclic RGD micelles. The internalization of fluorescein isothiocynate (FITC) loaded RGD micelles was significantly higher in A2058 melanoma cells compared to free FITC within 20 minutes of incubation at 37°C. The same micelles showed significantly lower internalization at 4°C and on pretreatment with 0.45M sucrose confirming endocytotic uptake of the RGD micellar carriers. The IC50 of paclitaxel in A2058 melanoma cells was lower when treated within RGD micelles as compared to treatment of free drug. On the other hand, IC50 values increased by 2 to 9 fold for micellar treatment in comparison to free drug in Detroit 551 cells. In A2058 melanoma xenograft mice model, the Paclitaxel-RGD micelles exhibited a significant inhibition of tumor growth in comparison to control treatment for both alternate day and twice weekly treatments. The studies showed the feasibility of using the non covalent peptide based self-assemblies as vehicles for targeted delivery in cancer.

No description available.

<p></p><p>This doctoral dissertation takes the reader through a journey where applied shear rheology and flow-velocimetry are used to understand the mesoscopic factors that control the flow behavior of three microstructured fluids. Three individual protocols that measure relative physical and mechanical properties of the flow are developed. Each protocol aims to advance the particular transformation of novel soft materials into a commercial product converging in the demonstration of the real the chemical, physical and thermodynamical factors that could potentially drive their successful transformation. </p> <p> </p> <p>First, this dissertation introduces the use of rotational and oscillatory shear rheometry to quantify the solvent evaporation effect on the flow behavior of polymer solutions used to fabricate isoporous asymmetric membranes. Three different A-B-C triblock copolymer were evaluated: polyisoprene-<i>b</i>-polystyrene-<i>b</i>-poly(4-vinylpyridine) (ISV); polyisoprene-<i>b</i>-polystyrene-<i>b</i>-poly(<i>N</i>,<i>N</i>-dimethylacrylamide) (ISD); and polyisoprene-<i>b</i>-polystyrene-<i>b</i>-poly(<i>tert</i>-butyl methacrylate) (ISB). The resulting evaporation-induced microstructure showed a solution viscosity and film viscoelasticity strongly dependent on the chemical structure of the triblock copolymer molecules. </p> <p> </p> <p>Furthermore, basic shear rheometry, flow birefringence, and advanced flow-velocimetry are used to deconvolute the flow-microstructure relationships of concentrated surfactant solutions. Sodium laureth sulfate in water (SLE₁S) was used to replicate spherical, worm-like, and hexagonally packed micelles and lamellar structures. Interesting findings demonstrated that regular features of flow curves, such as power-law shear thinning behavior, resulted from a wide variety of experimental artifacts that appeared when measuring microstructured fluids with shear rheometry.</p> <p> </p> <p>Finally, the successful integration of shear rheometry to calculate essential parameters to be used in a cost-effective visualization technique (still in development) used to calculate the dissolution time of polymers is addressed. The use of oscillatory rheometry successfully quantify the viscoelastic response of polyvinyl alcohol (PVA) solutions and identify formulations changes such as additive addition. The flow behavior of PVA solutions was correlated to dissolution behavior proving that the developed protocol has a high potential as a first screening tool.</p><br><p></p>

The thesis outlines possible medical applications of soft matter assemblies as nanotechnology based systems as well as their potential in the emerging field of nanomedicine. Nanomedicine can be defined as the investigation area encompassing the design of diagnostics and therapeutics at the nanoscale, including nanobots, nanobiosensors, nanoparticles and other nanodevices, for the remediation, prevention and diagnosis of a variety of illnesses. The ultimate goal of nanomedicine is to improve patient quality-of-life. Because nanomedicine includes the rational design of an enormous number of nanotechnology-based products focused on miscellaneous diseases, a variety of nanomaterials can be employed. Therefore, the thesis is driven by a focus on recent advances in the manufacture of soft matter-based nanomedicines specifically designed to improve cancer diagnostics and chemotherapy efficacy. It will in particular highlight liposomes, polymer-drug conjugates, drug- loaded block copolymer micelles and biodegradable polymeric nanoparticles, emphasizing the current investigations and potential novel approaches towards overcoming the remaining challenges in the field as well as a brief overview of formulations that are in clinical trials and marketed products. Based on vehicle-related and...

Made available in DSpace on 2014-12-17T15:42:26Z (GMT). No. of bitstreams: 1 ZilvamMS_TESE_reduzido.pdf: 9108618 bytes, checksum: 613dad3fd1a359dce84e2af73b067934 (MD5) Previous issue date: 2013-02-22 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Surfactant-polymer interactions are widely used when required rheological properties for specific applications, such as the production of fluids for oil exploration. Studies of the interactions of chitosan with cationic surfactants has attracted attention by being able to cause changes in rheological parameters of the systems making room for new applications. The commercial chitosan represents an interesting alternative to these systems, since it is obtained from partial deacetylation of chitin: the residues sites acetylated can then be used for the polymer-surfactant interactions. Alkyl ethoxylated surfactants can be used in this system, since these non-ionic surfactants can interact with hydrophobic sites of chitosan, modifying the rheology of solutions or emulsions resultants, which depends on the relaxation phenomenon occurring in these systems. In this work, first, inverse emulsions were prepared from chitosan solution as the dispersed phase and cyclohexane as the continuous phase were, using CTAB as a surfactant. The rheological analysis of these emulsions showed pronounced pseudoplastic behavior. This behavior was attributed to interaction of "loops" of chitosan chains. Creep tests were also performed and gave further support to these discussions. Subsequently, in order to obtain more information about the interaction of chitosan with non-ionic surfactants, solutions of chitosan were mixed with C12E8 and and carried out rheological analysis and dynamic light scattering. The systems showed marked pseudoplastic behavior, which became less evident when the concentration of surfactant was increased. Arrhenius and KWW equations were used to obtain parameters of the apparent activation energy and relaxation rate distribution, respectively, to which were connected to the content of surfactant and temperature used in this work / As intera??es tensoativo-pol?mero s?o amplamente usadas quando s?o necess?rias propriedades reol?gicas para aplica??es espec?ficas, como a produ??o de fluidos para explora??o do petr?leo. Estudos das intera??es de quitosana com tensoativos cati?nicos tem chamado aten??o por serem capazes de causar mudan?as nos par?metros reol?gicos dos sistemas abrindo espa?o para novas aplica??es. A quitosana comercial representa uma alternativa interessante para estes sistemas, uma vez que ela ? obtida a partir da desacetila??o parcial da quitina: os s?tos acetilados residuais podem, ent?o, ser usados para as intera??es pol?mero-tensoativo. Tensoativos alquil etoxilados podem ser utilizados neste sistema, pois estes tensoativos n?o i?nicos podem interagir com s?tios hidrof?bicos da quitosana, modificando a reologia de solu??es ou emuls?es resultantes, os quais dependem do fen?meno de relaxa??o ocorrendo nestes sistemas. Neste trabalho, primeiramente, foram preparadas emuls?es inversas de solu??o de quitosana como fase dispersa e cicloexano como fase cont?nua usando CTAB como tensoativo. A an?lise reol?gica destas emuls?es mostrou pronunciado comportamento pseudopl?stico. Esta pseudoplasticidade foi atribu?da ? intera??o por la?os loops de cadeias de quitosana. Ensaios de flu?ncia tamb?m foram executados e deram maior suporte a estas discuss?es. Em seguida, a fim de se obter maiores informa??es sobre as intera??es da quitosana com tensoativos n?o i?nicos, solu??es de quitosana foram misturadas com C12E8 e levadas ?s an?lises reol?gica e de espalhamento din?mico de luz. Os sistemas tiveram elevado comportamento pseudopl?stico, o qual se tornava menos evidente, quando o teor de tensoativo foi aumentado. Equa??es de Arrhenius e de KWW foram usadas para obter par?metros de energia de ativa??o aparente e de distribui??o da taxa de relaxa??o, respectivamente, aos quais foram relacionados em fun??o do teor de tensoativo e da temperatura, usados neste trabalho