This master thesis is focused on the evaluation of the influence of particle surface properties on the results of microrheological measurements with biopolymer solutions. Hyaluronan has been chosen as negatively charged polymer, chitosan as positively charged polymer and glycerol and its solutions of various concentrations were used as homogenous model systems. Dynamic light scattering and single particle tracking microrheology were chosen from passive microrheological techniques. Particles with various surface modifications (neutral, positive surface charge and negative surface charge) were used for the experiments. The results of microrheological techniques were then compared with classic rheology and moreover the glycerol results were compared with tabulated values.

Diploma thesis main goal is to obtain new pieces of knowledge about relationship between hydrogel structures and its flow and transport properties. Thesis is mainly focusing on combining pertinent biopolymers into model hydrogels based on agarose. Then perform correlation of results obtained by diffusion methods, and by rheologic measurements on macroscopic and microscopic level. Properties of hydrogels were measured by selected rheologic measurements, dynamic light scattering method, and correlative fluorescence spectroscopy. From these methods various parameters (MSD modules, values of complex viscosity) were obtained. Afterwards transport properties of prepared hydrogels were studied by observing Rhodamine 6G diffusion. Here two different approaches were used. From macroscopic perspective, simple principles of mass diffusion from dye solution to cuvettes filled with hydrogels containing individual biopolymers were used. From microscopic perspective, dye was added during the sample preparation and then the mass diffusion was investigated using FCS. Based on evaluated results it was discovered that added biopolymers don’t influence properties of carrier medium, in this case agarose hydrogels. During the study of prepared hydrogels’ reactivity and barrier properties some differences were observed. Charge of biopolymer and its charge density were discovered as main factors influencing transport of charged solutes into prepared hydrogels.

In the production of biodiesel via the transesterification of vegetable oils, purification to international standards is challenging. A key measure of biodiesel quality is the level of free glycerol in the biodiesel. In order to remove glycerol from fatty acid methyl ester (FAME or biodiesel), a membrane separation setup was tested. The main objective of this thesis was to develop a membrane process for the separation of free glycerol dispersed in FAME after completion of the transesterification reaction and to investigate the effect of different factors on glycerol removal. These factors included membrane pore size, pressure, temperature, and methanol, soap and water content. First, a study of the effect of different materials present in the transesterification reaction, such as water, soap, and methanol, on the final free glycerol separation was performed using a modified polyacrylonitrile (PAN) membrane, with 100 kD (ultrafiltration) molecular weight cut off for all runs at 25°C. Results showed low concentrations of water had a considerable effect in removing glycerol from the FAME. The mechanism of separation of free glycerol from FAME was due to the removal of an ultrafine dispersed glycerol-rich phase present in the untreated (or raw) FAME. The size of the droplets and the free glycerol separation both increased with increasing water content of the FAME. Next, three types of polymeric membranes in the ultrafiltration range with different molecular weight cut off, were tested at three fixed operating pressures and three operating temperatures (0, 5 and 25oC) to remove the free glycerol from a biodiesel reactor effluent. The ASTM standard for free glycerol concentration was met for the experiments performed at 25°C. The results of this study indicate that glycerol could be separated from raw FAME to meet ASTM and EN standards at methanol feed concentrations of up to 3 mass%. The process was demonstrated to rely on the formation of a dynamic polar layer on the membrane surface. Ceramic membranes of different pore sizes (0.05 µm (ultrafiltration (UF) range) and 0.2 µm (microfiltration (MF) range)) were used to treat raw FAME directly using the membrane separation set up at temperatures of 0, 5 and 25°C. The results were encouraging for the 0.05 µm pore size membrane at the highest temperature (25°C). The effect of temperature on glycerol removal was evident from its relation with the concentration factor (CF). Higher temperatures promoted the achievement of the appropriate CF value sooner for faster separation. Membrane pore size was also found to affect separation performance. A subsequent study revealed the effect of different variables on the size of the glycerol droplets using dynamic light scattering (DLS). A key parameter in the use of membrane separation technology is the size of the glycerol droplets and the influence of other components such as water, methanol and soaps on that droplet size. The effect of water, methanol, soap and glycerol on the size of suspended glycerol droplets in FAME was studied using a 3-level Box-Behnken experimental design technique. Standard statistical analysis techniques revealed the significant effect of water and glycerol on increasing droplet size while methanol and soap served to reduce the droplet size. Finally, a study on the effect of trans-membrane pressure (TMP) at different water concentrations in the FAME phase on glycerol removal using UF (0.03 µm pore size, polyethersulfone (PES)) and MF (0.1 and 0.22 µm pore sizes, PES) membranes at 25, 40 and 60°C was performed. Results showed that running at 25°C for the two membrane types produced the best results for glycerol removal and exceeded the ASTM and EN standards. An enhancement of glycerol removal was found by adding small amounts of water up to the maximum solubility limit in biodiesel. An increase in temperature resulted in an increase in the solubility of water in the FAME and less effective glycerol removal. Application of cake filtration theory and a gel layer model showed that the gel layer on the membrane surface is not compressible and the specific cake resistance and gel layer concentration decrease with increasing temperature. An approximate value for the limiting (steady-state) flux was reported and it was found that the highest fluxes were obtained at the lowest initial water concentrations at fixed temperatures. In conclusion, dispersed glycerol can be successfully removed from raw FAME (untreated FAME) using a membrane separation system to meet the ASTM biodiesel fuel standards. The addition of water close to the solubility limit to the FAME mixture enables the formation of larger glycerol droplets and makes the separation of these droplets straightforward.

No description available.

No description available.

No / Biosimilar pharmaceuticals are complex biological molecules that have similar physicochemical properties to the originator therapeutic protein. They are produced by complex multi-stage processes and are not truly equivalent. Therefore, for a biosimilar to be approved for market it is important to demonstrate that the biological product is highly similar to a reference product. This includes its primary and higher order structures and its aggregation behaviour. Representative lots of both the proposed biosimilar and the reference product are analysed to understand the lot-to-lot variability of both drug substances in the manufacturing processes. Whilst it is not easy to characterise every variation of a protein structure at present additional analytical technologies need to be utilised to ensure the safety and efficacy of any potential biosimilar product. We have explored the use of Taylor dispersion analysis (TDA) to analyse such batch to batch variations in the model protein, bovine serum albumin (BSA) and compared the results to that obtained by conventional dynamic light scattering analysis (DLS). Inter and intra batch differences were evident in all grades of BSA analysed. However, the reproducibility of the TDA measurements, enabled the stability and reversibility of BSA aggregates to be more readily monitored. This demonstrates that Taylor dispersion analysis is a very sensitive technique to study higher order protein states and aggregation. The results, here, also indicate a correlation between protein purity and the physical behaviour of the samples after heat shocking. Here, the protein with the highest quoted purity resulted in a reduced increase in the measured hydrodynamic radius after heat stressing, indicating that less unfolding/aggregation had occurred. Whilst DLS was also able to observe the presence of aggregates, its bias towards larger aggregates indicated a much larger increase in hydrodynamic radii and is less sensitive to small changes in hydrodynamic radii. TDA was also able to identify low levels of larger aggregates that were not observed by DLS. Therefore, given the potential for immunogenicity effects that may result from such aggregates it is suggested that TDA may be suitable in the evaluating detailed batch to batch variability and process induced physical changes of biopharmaceuticals and biosimilars.

A range of microgels with two different functionalities were synthesized, and their utility in novel bioapplications was examined. Cationic microgels with varying properties were developed by tuning synthesis conditions. Their size and primary amine content was analyzed, and one microgel system was selected as a model construct. Its primary amine groups were conjugated to two dyes with properties favorable for utilization as contrast agents in photoacoustic imaging. The concentration of contrast agent in single particles was determined. The implications of a high local dye concentration in the generation of high intensity photoacoustic signals, are discussed. The second bioapplication involved the targeted delivery of fibrinolytics to fibrin clots, in order to bring about dissolution of abnormal thrombi. For this purpose, core/shell microgels with carboxylic acid groups in their shells were synthesized in three size ranges. Following this, their dimension based differential localization in and around porous fibrin clots was examined. Fibrin-specific peptides were then conjugated onto the shells of these particles and the conjugates were shown to demonstrate strong interactions with the fibrin clots. The microgels conjugated to the peptide with the highest binding affinity to fibrin, were observed to bring about disruption of fibrin clots, merely through interference in the dynamic interactions among clot fibers, due to the equilibrium nature of the fibrin polymer. The implications of these novel results and future studies required to facilitate a better understanding of the phenomena involved, are discussed.

Cerebral blood flow (CBF) measures are central to the investigation of ischemic strokes, spreading depressions, functional and neuronal activation. Laser Speckle Contrast Imaging (LSCI) is an optical imaging technique that has been used to obtain CBF measures in vivo at high spatial and temporal resolutions, by quantifying the localized spatial blurring of backscattered coherent light induced by blood flow. Despite being widely used for biomedical applications, LSCI's critical limitations such as its tendency to underestimate large flow changes and its inability to accurately estimate CBF through a thinned skull have not been overcome. This dissertation presents a new Multi Exposure Speckle Imaging (MESI) technique that combines a new instrument and mathematical model to overcome these limitations. Additionally, in a pilot clinical study, an adapted neurosurgical microscope was used to obtain intra-operative LSCI images of CBF in humans. The MESI instrument accurately estimates experimental constants by imaging backscattered speckles over a wide range of the camera's exposure durations. The MESI mathematical model helps account for light that has scattered from both static and moving particles. In controlled flow experiments using tissue simulating phantoms, the MESI technique was found to estimate large changes in flow accurately and the estimates of flow changes were found to be unaffected by the presence of static particles in these phantoms. In an in vivo experiment in which the middle cerebral artery in mice was occluded to induce ~100% reduction in CBF, not only was the reduction in CBF accurately estimated by the MESI technique but these estimates of CBF changes were found to be unaffected by the presence of a thinned skull. The validity of statistical models used to derive the MESI mathematical model was confirmed using in vivo dynamic light scattering (DLS) measurements of CBF in mice. The MESI technique's potential to estimate absolute values of CBF in vivo was demonstrated by comparing CBF estimates obtained using the MESI technique to DLS measurements. The MESI technique's ability to measure CBF changes quantitatively through a thinned skull makes it particularly useful in chronic and long term studies leading to the development of better, more accurate stroke models. / text

A proteína P21 do Trypanosoma cruzi participa no processo de infecção da célula hospedeira, desse modo é de grande importância: elucidar as vias de sinalização induzidas pela proteína, bem como caracterizar a nível molecular e estrutural a P21. O que vai auxiliar no entendimento da função biológica da P21 e sua participação no processo de infecção. A P21 recombinante é expressa Escherichia coli em sua maioria na fração insolúvel. Visando aumento de proteína na fração solúvel, foi realizada a clonagem do gene da P21 em vetor pSMT3, bem como testes de expressão subsequentes em diferentes cepas de expressão de E. coli, em vetor pET-28 e pSMT3 e variadas condições de expressão e lise celular. Desse modo obtiveram-se as condições que permitissem uma maior concentração da P21 na fração solúvel. A expressão foi realizada no vetor pET-28, cepa BL21, a 37°C com meio 2xYT a 0.5 mM de IPTG, utilizando a técnica de sonicação como lise. A P21 foi purificada em cromatografia de afinidade e posteriormente em coluna de exclusão molecular. Foram realizados estudos de modelagem por homologia levaram a elaborar a hipótese de que a P21 tem a função de inibidor de serinoprotease do tipo kunitz. Posteriormente essa hipótese foi confirmada com ensaios de avaliação da atividade inibitória da P21 frente à tripsina, quimiotripsina e elastase neutrofílica, o qual a P21 mostrou capaz de inibir a elastase neutrofílica. Estudos com espalhamento dinâmico da luz (DLS) revelaram que as amostras testadas de P21 contém diferentes concentrações de agregados de alto peso molecular em todos os pHs avaliados. Outras medidas foram realizadas para avaliar o estado de agregação da P21 de acordo com a temperatura e verificou-se que entre 32-52 °C, a proteína apresenta menor raio hidrodinâmico, indicando menor agregação nesse intervalo. Estudos de dicroísmo circular revelaram que a P21 apresenta por volta de 20% de α hélice, 32% de folha-β, 22% de volta e 23 % estrutura randômica. De acordo com a curva de desnaturação referente ao espectro de CD obtido, a P21 se mostra desnaturada a partir de 64°C. / The Trypanosoma cruzi protein P21 participates in the host cell infection process, but its specific function is poorly described. Thus it is important to elucidate the signaling pathways induced by the protein and characterize the P21 at the structural and molecular levels, as a contribution towards the understanding of the P21 biological function and its role in the infection process. The Escherichia coli recombinant P21 is expressed mostly in the insoluble fraction. Aiming to increase protein in the soluble fraction, we performed the cloning of the P21 gene in pSMT3 vector and subsequent expression tests in different expression strains of E. coli in pET-28 and pSMT3 vectors and varied expression conditions and cell lysis. Thus we obtained conditions that allow a greater concentration of the P21 in the soluble fraction. The expression vector was performed using vector pET-28, in Bl21 strain at 37°C in 2xYT culture medium with 0.5 mM IPTG, using the sonication technique in cell lysis. The recombinant P21 was purified by Ni affinity chromatography and subsequently a molecular exclusion column. We performed homology modeling studies which led to assume that P21 can be a serinprotease inhibitor of Kunitz type. Furthermore, this hypothesis was confirmed in the experiments testing the P21 inhibitory activity against the trypsin, chymotrypsin and elastase. We found the P21 exclusively inhibit neutrophil elastase. Studies using dynamic light scattering (DLS) revealed that the samples containing P21 contained large molecular weigth aggregates in different concentrations at all evaluated pHs. Others measurements were performed to assess the P21 aggregation state according to the temperature and we found that between 32-52 °C the protein had a smaller hydrodynamic radius, indicating less aggregation in this range. Circular dichroism (CD) studies revealed that P21 has about 20% α-helix, 32% β, -sheet, 22% turn and 23% of random structure. According to the denaturation curve for the CD spectrum obtained, the P21 was denatured from 64°C.

A β2GPI é uma glicoproteína que circula livre ou em lipoproteínas. Adsorve em superfícies negativas, tem efeitos anticoagulantes e moduladores da inflamação. Neste trabalho caracterizou-se a interação de moléculas da proteína entre si e com superfícies lipídicas. O SDS-PAGE e o imunoblot da β2GPI identificaram monômeros, dímeros e oligômeros. Técnicas de espalhamento de luz (estático, dinâmico, Raios-X) revelaram que β2GPI forma soluções aquosas de macroagregados anisométricos. Seca sobre mica, a β2GPI forma elipsóides prolatos, observáveis por microscopia de força atômica. A forma e o tamanho das partículas dependeram de pH e concentração de proteína. A interação entre a β2GPI e superfícies lipídicas foi estudada por microgravimetria. Superfícies de fosfatidilcolina pura adsorveram β2GPI mais fracamente do que ouro ou misturas com fosfatidilserina. A adsorção de lipoproteínas artificiais à β2GPI foi dependente de pH. Sugere-se que os efeitos biológicos da β2GPI sejam mediados por interações proteína-proteína e proteína-lipídio, e dependentes de pH. / β2GPI is a blood glycoprotein circulating free or bound to lipoproteins. β2GPI adsorbs to negatively charged surfaces, acting as anticoagulant and modulator of inflammation. This work was designed to characterize the interaction between protein molecules and among protein molecules and lipid surfaces. The β2GPI SDS-PAGE and immunoblot revealed monomer, dimer and oligomers. Light scattering methods (static, dynamic and X-ray) showed that β2GPI generates aqueous solutions of anisometric macroaggregates. Atomic force microscopy showed that β2GPI dried on muscovite surfaces assembles itself in prolate ellipsoids. The particle shape and size depended both on the pH and protein concentration. The interaction among β2GPI and lipid surfaces was studied by microgravimetry. β2GPI adsorption to pure phosphatidylcholine was weaker than to gold or phosphatidylcholine/phosphatidylserine surfaces. Artificial lipoproteins adsorbed to β2GPI in a pH dependent manner. Results suggest that β2GPI biological effects could be mediated by protein-protein interactions and lipid surface binding, and pH dependent.