Orientador: Ana Liz Garcia Alves / Resumo: As terapias regenerativas com a utilização de células tronco mesenquimais (CTMs) têm sido amplamente empregadas com a finalidade de modificar a progressão de enfermidades locomotoras em animais de grande porte. Estudos sobre o comportamento das células tronco, portanto, mostram-se de extrema importância para que, cada vez mais, elucidar sua ação, efeito e eficácia nos tratamentos propostos. A inserção das CTMs derivadas do tecido adiposo de muares em microcápsulas de hidrogel gera expectativas promissoras para a proteção da célula contra anticorpos do receptor, bem como processos inflamatórios exacerbados, distribuição de agentes terapêuticos e supressão de processos inflamatórios. O presente trabalho teve por objetivo verificar o comportamento das CTMs após o encapsulamento em hidrogel, quanto a sua viabilidade, migração, além da avaliação morfológica e imuno-histoquímica. Avaliação da morfologia da cápsula, dos poros, a rugosidade por microscopia eletrônica de varredura (MEV) e observação das células encapsuladas pela microscopia confocal de varredura a laser. A porcentagem de células viáveis manteve-se ao longo dos momentos em uma média de 93%, então o biomaterial permitiu a difusão de nutrientes e oxigênio adequadamente. A diminuição da quantidade de células no interior das cápsulas é justificada pela possível migração das mesmas através dos microporos das microcápsulas permitindo a aderência à placa de cultivo. Na avaliação morfológica foi possível identificar as células... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Regenerative therapies using mesenchymal stem cells (MSCs) have been widely widespread to treat locomotor diseases in large animals. Studies on the behavior of stem cells are extremely important to increase our knowledge regarding their action, effect and effectiveness in the proposed treatments. The insertion of muar adipose-derived MSCs into hydrogel microcapsules yields promising expectations for cell protection against immune response, as well as exacerbated inflammatory processes, delivery of therapeutic agents, and suppression of inflammatory processes. The present research aimed to verify the behavior of MSCs after hydrogel encapsulation, including cell viability, migration, morphological and immunohistochemical pattern. Evaluation of capsule morphology, pore size, roughness by scanning electron microscopy (SEM) and observation of encapsulated cells by confocal laser scanning microscopy. The percentage of viable cells remained throughout the moments at an average of 93%, so the biomaterial allowed the diffusion of nutrients and oxygen properly. A decreased amount of cells number inside the capsules is justified by the possible migration of them through the microcapsule micropores allowing adherence to the culture plate. The cells showed positive CD44 staining, absence in MHC II. The capsules were evaluated with SEM for their morphology, the area of circular and irregular pores and the size of the cells. It was possible to confirm the presence of stem cells in the micro... (Complete abstract click electronic access below) / Doutor

Aujourd'hui, la transplantation est le seul traitement efficace proposé aux patients souffrant d'une insuffisance hépatique aiguë ou fulminante. La pénurie actuelle de greffons se traduit par un taux de mortalité élevé chez les patients en attente urgente d'un organe. La nécessité de disposer d'un système de suppléance hépatique transitoire apparaît donc primordiale. Un organe bioartificiel exploitant les performances potentielles de cellules (hépatocytes dans le cas d'un foie bioartificiel) permettrait de suppléer le large éventail de ses fonctions métaboliques. Notre équipe propose le concept d'un bioréacteur à lit fluidisé contenant des hépatocytes, issus de la lignée cellulaire humaine C3a, immobilisés dans des billes d'alginate. Dans ce travail l'objectif a été d'analyser le fonctionnement du système de suppléance hépatique extracorporel par la mise en place d'un modèle in vitro se rapprochant au mieux de la situation in vivo. La présence de cellules au sein des billes d'alginate n'a pas d'influence sur le comportement global du lit fluidisé alors que l'emploi de plasma, de masse volumique proche des billes, peut engendrer une instabilité. Ensuite, l'organisation, la viabilité et les fonctionnalités (synthèse d'albumine, production d'urée et capacité d'élimination de l'ammoniac) des hépatocytes à l'intérieur des billes d'alginate ont été étudiés en conditions statiques et dynamiques. Dans le bioréacteur, les hépatocytes gardent leurs pleines potentialités. Pour l'urée, l'encapsulation semble améliorer le métabolisme. Il apparaît que la sortie de l'albumine des billes est améliorée par la fluidisation. Enfin, nous avons montré que les contraintes dans le bioréacteur ne provoque qu'une faible altération des propriétés mécaniques des billes après 6 heures d'utilisation. Au vu des fonctions métaboliques assumées par les hépatocytes C3a encapsulés dans des billes d'alginate, l'emploi de ce dispositif en vue d'une suppléance hépatique pourra être envisagé.

<p>Transplantation of islets of Langerhans is a potential treatment of type 1 diabetes that aims to restore normal glucose homeostasis. Microencapsulation of islets could enable transplantation in the absence of immunosuppression, which would be beneficial as the side effects associated with immunosuppression outweigh the potential benefits of islet transplantation. Alginate is a polysaccharide that can be harvested from brown algae and is often used for microencapsulation of cells.</p><p>The aim of this study was to evaluate alginate/poly-L-lysine/alginate capsules with regard to their biocompatibility and permeability to cytokines. Moreover, the function of microencapsulated islets was studied <i>in vitro</i> as well as their ability to reverse hyperglycaemia in diabetic mice.</p><p>Microencapsulated rodent islets functioned well <i>in vitro</i>, with similar insulin release rates and glucose oxidation rates as naked islets. However, when cultured with interleukin-1β and tumour necrosis factor-α, microencapsulated islets were functionally suppressed, showing that the capsules are permeable to these cytokines. The biocompatibility of capsules varied depending on their composition. The presence of poly-L-lysine in the capsule decreased the biocompatibility. However, the biocompatibility of the capsules was improved when the coating alginate had been epimerised, i.e. enyzmatically tailored. Transplantation of microencapsulated allogeneic islets to immune competent mice lowered blood glucose concentrations up to 1 month after implantation. The success of the microencapsulated islet graft depended on the composition of the alginate/poly-L-lysine/alginate capsule used, as capsules that had poor biocompatibility failed to reverse hyperglycaemia more than transiently in athymic nude mice.</p><p>In conclusion, alginate/poly-L-lysine/alginate capsules can protect islets of Langerhans from allogeneic rejection in mice. However, the composition of the capsule is of critical importance in the success of transplantation. Epimerised alginates may provide a novel capsule with ideal properties for microencapsulation of islets of Langerhans.</p>

Transplantation of islets of Langerhans is a potential treatment of type 1 diabetes that aims to restore normal glucose homeostasis. Microencapsulation of islets could enable transplantation in the absence of immunosuppression, which would be beneficial as the side effects associated with immunosuppression outweigh the potential benefits of islet transplantation. Alginate is a polysaccharide that can be harvested from brown algae and is often used for microencapsulation of cells. The aim of this study was to evaluate alginate/poly-L-lysine/alginate capsules with regard to their biocompatibility and permeability to cytokines. Moreover, the function of microencapsulated islets was studied in vitro as well as their ability to reverse hyperglycaemia in diabetic mice. Microencapsulated rodent islets functioned well in vitro, with similar insulin release rates and glucose oxidation rates as naked islets. However, when cultured with interleukin-1β and tumour necrosis factor-α, microencapsulated islets were functionally suppressed, showing that the capsules are permeable to these cytokines. The biocompatibility of capsules varied depending on their composition. The presence of poly-L-lysine in the capsule decreased the biocompatibility. However, the biocompatibility of the capsules was improved when the coating alginate had been epimerised, i.e. enyzmatically tailored. Transplantation of microencapsulated allogeneic islets to immune competent mice lowered blood glucose concentrations up to 1 month after implantation. The success of the microencapsulated islet graft depended on the composition of the alginate/poly-L-lysine/alginate capsule used, as capsules that had poor biocompatibility failed to reverse hyperglycaemia more than transiently in athymic nude mice. In conclusion, alginate/poly-L-lysine/alginate capsules can protect islets of Langerhans from allogeneic rejection in mice. However, the composition of the capsule is of critical importance in the success of transplantation. Epimerised alginates may provide a novel capsule with ideal properties for microencapsulation of islets of Langerhans.

Probiotics and prebiotic are becoming increasingly important to consumers to alleviate issues surrounding gut health, despite the lack of definitive efficacy studies to support health claims. The addition of both probiotics and prebiotics to foods is challenging due to the harsh environmental conditions within the food itself and during transit through the gastrointestinal (GI) tract. To circumvent these challenges encapsulation technology is being explored to protect sensitive ingredients and to control their release within the lower intestines thereby maximizing the health benefiting effects. The overall goal of this research was to design a protein delivery capsule using phase separated pea protein isolate (PPI)-alginate (AL) mixtures for the entrapment of the synbiot which includes the probiotics, Bifidobacterium adolescentis, and the prebiotic, fructooligosaccharides (FOS), such that the capsule design provides highly effective protection and release within the GI tract. Research was carried out in three studies.<p> In study 1, PPIn (native isolate) and AL interactions were studied in dilute aqueous solutions as a function of pH and biopolymer mixing ratio. Turbidimetric analysis and electrophoretic mobility during an acid titration was used to determine conditions where phase separation occurred. Critical structure forming events associated with the formation of soluble and insoluble complexes in a 1:1 PPIn-AL mixture were found to occur at pH 5.00 and 2.98, respectively, with optimal interactions occurring at pH 2.10. As the PPIn-AL ratio increased, critical pH values shifted towards higher pH until a mixing ratio between 4:1 and 8:1was reached, above which structure formation became independent of the ratios through to ratios of 20:1. Electrophoretic mobility measurements showed a similar trend, where the isoelectric point (pI) shifted from pH 4.00 (homogeneous PPIn) to pH 1.55 (1:1 PPIn-AL). As the ratio increased towards 8:1 PPIn-AL, net neutrality values shifted to higher pHs (~3.80) before becoming constant at higher ratios. Maximum coacervate formation occurred at a mixing ratio of 4:1. Based on these findings, capsule design by segregative phase separation was only used in future studies, due to the acidic nature associated with associative phase separation.<p> In study 2, capsule formation using a native and commercial PPI was studied, and showed no difference between the two formulations during challenge experiments in simulated gastric juice (SGJ). As a result study 3 focused on optimization and characterization of capsules prepared using the commercial PPI. Capsule designs were investigated as a function of protein concentration, prebiotic level, and extrusion conditions (20 vs. 27 G needle) in order to determine protective ability for B. adolescentis within SGJ. Capsule designs were also measured in terms of protein and prebiotic retention during the encapsulation process, geometric mean diameter and size distribution, swelling behaviour and release characteristics within simulated intestinal fluids (SIF). All capsules provided adequate protection over the 2 h duration within SGJ. Capsule breakdown and release was similar for all designs within SIF, with a release mechanism believed to be tied to enzymatic degradation of the PPI material within the wall matrix and/or the amount of excessive Na+ present in the SIF. Capsule size was found to be dependent only on the needle gauge used in the extrusion process. Swelling behaviour of the capsules with SGJ was also found to be dependent only on the protein concentration, where capsules shrank once immersed in SGJ.<p> A 2.0% PPI-0.5% AL capsule without FOS and extruded through a 20 G needle represents the best and most cost effective design for entrapping, protecting and delivering probiotic bacteria. Future work to establish the role FOS could play post-release as the entrapping probiotics colonize the GI tract, and the protective effect of the capsules wall on FOS structure during transit is recommended.

Probiotics and prebiotic are becoming increasingly important to consumers to alleviate issues surrounding gut health, despite the lack of definitive efficacy studies to support health claims. The addition of both probiotics and prebiotics to foods is challenging due to the harsh environmental conditions within the food itself and during transit through the gastrointestinal (GI) tract. To circumvent these challenges encapsulation technology is being explored to protect sensitive ingredients and to control their release within the lower intestines thereby maximizing the health benefiting effects. The overall goal of this research was to design a protein delivery capsule using phase separated pea protein isolate (PPI)-alginate (AL) mixtures for the entrapment of the synbiot which includes the probiotics, Bifidobacterium adolescentis, and the prebiotic, fructooligosaccharides (FOS), such that the capsule design provides highly effective protection and release within the GI tract. Research was carried out in three studies.<p> In study 1, PPIn (native isolate) and AL interactions were studied in dilute aqueous solutions as a function of pH and biopolymer mixing ratio. Turbidimetric analysis and electrophoretic mobility during an acid titration was used to determine conditions where phase separation occurred. Critical structure forming events associated with the formation of soluble and insoluble complexes in a 1:1 PPIn-AL mixture were found to occur at pH 5.00 and 2.98, respectively, with optimal interactions occurring at pH 2.10. As the PPIn-AL ratio increased, critical pH values shifted towards higher pH until a mixing ratio between 4:1 and 8:1was reached, above which structure formation became independent of the ratios through to ratios of 20:1. Electrophoretic mobility measurements showed a similar trend, where the isoelectric point (pI) shifted from pH 4.00 (homogeneous PPIn) to pH 1.55 (1:1 PPIn-AL). As the ratio increased towards 8:1 PPIn-AL, net neutrality values shifted to higher pHs (~3.80) before becoming constant at higher ratios. Maximum coacervate formation occurred at a mixing ratio of 4:1. Based on these findings, capsule design by segregative phase separation was only used in future studies, due to the acidic nature associated with associative phase separation.<p> In study 2, capsule formation using a native and commercial PPI was studied, and showed no difference between the two formulations during challenge experiments in simulated gastric juice (SGJ). As a result study 3 focused on optimization and characterization of capsules prepared using the commercial PPI. Capsule designs were investigated as a function of protein concentration, prebiotic level, and extrusion conditions (20 vs. 27 G needle) in order to determine protective ability for B. adolescentis within SGJ. Capsule designs were also measured in terms of protein and prebiotic retention during the encapsulation process, geometric mean diameter and size distribution, swelling behaviour and release characteristics within simulated intestinal fluids (SIF). All capsules provided adequate protection over the 2 h duration within SGJ. Capsule breakdown and release was similar for all designs within SIF, with a release mechanism believed to be tied to enzymatic degradation of the PPI material within the wall matrix and/or the amount of excessive Na+ present in the SIF. Capsule size was found to be dependent only on the needle gauge used in the extrusion process. Swelling behaviour of the capsules with SGJ was also found to be dependent only on the protein concentration, where capsules shrank once immersed in SGJ.<p> A 2.0% PPI-0.5% AL capsule without FOS and extruded through a 20 G needle represents the best and most cost effective design for entrapping, protecting and delivering probiotic bacteria. Future work to establish the role FOS could play post-release as the entrapping probiotics colonize the GI tract, and the protective effect of the capsules wall on FOS structure during transit is recommended.

Articular cartilage functions to maintain joint mobility. The loss of healthy, functional articular cartilage due to osteoarthritis or injury can severely compromise quality of life. To address this issue, cartilage tissue engineering approaches are currently in development. Bone marrow-derived mesenchymal progenitor cells (MPCs) hold much promise as an alternative cell source for cartilage tissue engineering. While previous studies have established that MPCs from humans and multiple other species undergo in vitro chondrogenic differentiation, additional research is needed to define conditions that will enhance MPC differentiation, increase matrix production by differentiating cultures, and support development of functional tissue-engineered cartilage constructs. Mechanical loading may be an important factor regulating chondrogenic differentiation of MPCs and cartilage matrix formation by chondrogenic MPCs. This thesis work evaluated the influence of oscillatory unconfined compressive mechanical loading on in vitro MPC chondrogenic activity and biosynthesis within hydrogel suspension. Loading was conducted using MPCs cultured in media supplements supporting chondrogenic differentiation. Possible interactions between the number of days in chondrogenic media preceding loading initiation and the ability of the MPC culture to respond to mechanical stimulation were explored in two different loading studies. The first loading study investigated the effects of 3 hour periods of daily oscillatory mechanical stimulation on subsequent chondrogenic activity, where chondrogenic activity represented an assessment of cartilage matrix production by differentiating MPCs. This study found that oscillatory compression of MPCs initiated during the first seven days of culture did not enhance chondrogenic activity above the level supported by media supplements alone. The second loading study evaluated changes in biosynthesis during a single 20 hour period of oscillatory mechanical stimulation to assess mechanoresponsiveness of the MPC cultures. This study found that MPCs modulated proteoglycan and protein synthesis in a culture time-dependent and frequency-dependent manner upon application of oscillatory compression. Together the two loading studies provide an assessment of dynamic compressive mechanical loading influences on MPC cultures undergoing chondrogenic differentiation. The information gained through in vitro studies of differentiating MPC cultures will increase basic knowledge about progenitor cells and may also prove valuable in guiding the future development of cartilage tissue engineering approaches.

Hydrogels are three dimensional, insoluble, porous and crosslinked polymer networks. Due to their high water content, they have great resemblance to natural tissues, and therefore, demonstrate high biocompatibility. The porous structure provides an aqueous environment for the cells and also allows influx of nutrients needed for cellular viability. In this study, a natural biodegradable material, agarose (Aga), was used and semi-interpenetrating networks (semi-IPN) were prepared with polymers having different charges, such as positively charged chitosan (Ch) and negatively charged alginate (Alg). Hydrogels were obtained by the thermal activation of agarose with the entrapment of Ch or Alg in the Aga hydrogel structures. Chemical composition of hydrogels were determined by ATR-FTIR examinations, mechanical properties of hydrogels were examined through compression tests, morphologies were confirmed by scanning electron microscopy (SEM) and confocal microscopy, thermal properties were evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Moreover, swelling ratios, water contact angles and surface free energies (SFE) were determined. Cell proliferation and cell migration within these hydrogels were examined by using L929 fibroblast cell line. MTS assays were carried out to observe the cell proliferation on hydrogels. Confocal microscopy was used in order to examine the cell behavior such as cell attachment and cell migration towards the hydrogels. It was observed that addition of positively charged Ch into agarose increased the ultimate compressive strength (UCS), decreased elastic modulus (E), increased the thermal stability and hydrophobicity of the semi-IPN hydrogels. On the other hand, addition of negatively charged Alg into agarose decreased UCS, E, thermal stability and hydrophilicity. Cell-material interaction results showed that Aga hydrogels in tissue engineering applications was improved by adding different charged polyelectrolytes. Cell migration within Aga hydrogels was enhanced by adding Ch, and hindered by addition of Alg. Maximum cell proliferation and maximum penetration of the cells were obtained with the Ch/Aga hydrogels most probably due to attraction between the negatively charged cell surface and the positively charged Ch/Aga hydrogel surface. It was shown that cell interaction of agarose hydrogel scaffolds could be enhanced by introducing chitosan within the agarose hydrogels and obtained structures could be candidates for tissue engineering applications.

Alginates are copolymers of &beta / -D-mannuronic (M) and &alpha / -L-guluronic acids (G). In this study, Azotobacter vinelandii ATCC&reg / 9046 was used to produce alginate in a fermentor. The effect of parameters such as dissolved oxygen tension (DOT), agitation speed, initial concentrations of sucrose and calcium on the properties of alginate were examined. Changes of DOT in the range of 1 and 10 % affected alginate production. The optimum DOT giving high alginate yield (4.51 g/L) and maximum viscosity was observed as 5 % yielding moderate GG-blocks of 55 %. Both high and low agitation levels reduced alginate production, but these conditions increased GG-block alginates as 76 and 87 % at 200 and 700 rpm, respectively. Moderate sucrose and calcium concentrations, 20 g/L and 50 mg/L, respectively were found better since further increase in their concentrations did not lead to a considerable improvement in alginate production and quality. Sodium alginates produced in this work were investigated for maximum heavy metal uptake with a special focus on copper ion and the highest copper uptake was around 1.9 mM Cu2+/g alginate. Findings showed that the block distribution of alginate was not as important as expected for copper removal. Alginate together with calcium ions was used for the removal of turbidity. The amount of GG-block was found to be important in turbidity removal. Alginate having 55 % GG block and 8.9 cP viscosity resulted in a final turbidity lower than 1 NTU at 2 mg/L of alginate with 60 mg/L of calcium ion.

Motivated by the need to design minimally-invasive treatments for wide-necked cerebral aneurysms, we used computational modeling to assess aneurysm hemodynamics, examined in vitro cellular responses arising from mechanical and chemical stresses, and designed novel materials that cooperatively adhere to the endothelium. We first hypothesized that because aneurysm geometry plays an important role in hemodynamics, changes in flow patterns may affect the shear stress experienced on the aneurysm wall. We defined flow regimes based on aneurysm hemodynamic and geometric parameters, which may correlate with aneurysm rupture. Because of the direct contact between endothelial cells (ECs) and blood flow, we then evaluated how changes in hemodynamics and inflammatory cytokines affect the expression of cell adhesion molecules (CAMs) and matrix remodeling factors on ECs. We subsequently designed biomaterials that complement the dynamic EC surface and have the ability to conform to any geometry through in situ crosslinking. Antibody-conjugated hydrogels facilitated synergistic EC adhesion using cooperativity as an adhesion strategy. We optimized the presentation of antibodies to inflammatory CAMs on polyvinyl alcohol (PVA) and alginate hydrogels to achieve strong adhesion to inflamed ECs. We synthesized photocrosslinkable, aminated PVA hydrogels and determined the effect of substrate stiffness on cell adhesion. We also evaluated the effects of antibody presentation on cell adhesion strength and dynamics using alginate hydrogels. Taken together, the results of this work may be used to design hydrogels for vascular remodeling applications under shear stress, including embolic agents for cerebral aneurysms. / Engineering and Applied Sciences