Every year, accidents, falls, sport injuries and other incidents cause thousands of people to suffer spinal cord injury (SCI). In the United States alone, it is estimated that the number of Americans that live with SCI is around 259,000, with 12,000 new cases that happen annually (1). These injuries lead to spinal cord damages expressed by massive nerve tract degeneration followed by neurological loss, paralysis and disabilities. Therapy of SCI patients with non-steroidal anti-inflammatory drugs (NSAIDs) help in diminishing secondary injury and lessen pain and swelling. However these drugs do not promote tissue repair. Therefore there is an unmet clinical need to develop technologies and therapeutic strategies that compensate loss of neuronal tissue, support and facilitate reestablishment of nerve tracks connectivity in the injured spinal cord. Recent progress in nerve regeneration indicates that a tissue engineering approach using soft tissue scaffolds, stem cells and neurotrophins, can lead to a partial therapy in animal models of SCI. Bioengineered scaffolds prepared by freeze casting technology provide an experimental tool for guidance of regenerating neuronal tracts and/or axons and therefore are useful for regeneration of injured spinal cord. In this engineering approach for scaffold preparation, temperature controlled directional solidification of an aqueous polymer(s) solution creates channels of different diameters that can direct axonal outgrowth of neurons populating the scaffold. In a previous study from our laboratory, such scaffolds promoted differentiation of neurons, a process facilitated by co-population of the scaffold’s channels with endothelial cells. “Green” plant proteins, such as soybean proteins, are becoming an attractive alternative source of natural polymers for a variety of biomedical applications including scaffold fabrication for neuronal tissue regeneration. In the present study, we developed a second generation of improved, microchanneled composite scaffolds from gelatin and soy protein isolate cross-linked with genipin (2 w/v %, 0.5 w/v %, 1 w/v %, respectively). The fabrication of these scaffolds by a controlled freeze drying technique, their mechanical properties (stiffness, ~3-4 kPa) as well as their uniform longitudinal channels of a diameter of ~30-55 µm is described. Preliminary biocompatibility experiments in 2D and 3D using the above mentioned scaffolds populated with either undifferentiated PC12 cells or nerve growth factor differentiated PC12 cells indicated partial biocompatibility of the scaffolds for neuronal growth. Improving the biocompatibility of these composite scaffolds is under investigation in our laboratory. / Bioengineering

Iron-sulfur clusters are simple inorganic cofactors that are ubiquitous in living systems. The assembly of iron sulfur clusters is an essential process and must be carefully controlled in order to limit the release of toxic free iron or sulfide. Thus far there are three known protein systems for iron sulfur cluster assembly including the <i>nif, suf,</i> and <i>isc</i> systems. The <i>nif</i> system makes iron-sulfur clusters for nitrogenase production, while both the <i>suf</i> and <i>isc</i> systems provide iron-sulfur clusters for general cellular use. In <i>Azotobacter vinelandii</i> the isc operon contains eight genes which are transcribed together as a single operon: <i>iscR iscS iscU iscA hscB hscA fdx iscX</i>. The two central <i>isc</i> players include IscS, a cysteine desulfurase, and IscU the proposed site of iron-sulfur cluster assembly. Using <i>A. vinelandii</i> as a model organism, we have sought to better understand the mechanism of <i>in vivo isc</i> cluster assembly. In order test the scaffold hypothesis, we constructed strains that allowed for quick and rapid isolation of IscU. The purification of IscU with a bound [2Fe-2S] cluster strongly supports the model that IscU serves as the site of cluster synthesis <i>in vivo</i>. Additionally, using this same genetic system we isolated an IscU39DA variant with an oxygen stable bound [2Fe-2S] cluster. The IscU39^DA scaffold came in tight α₂β₂ complex with IscS and was not separated by high salt, size exclusion, or reducing conditions. On the other hand, wild-type IscU also associated with IscS in a α₂β₂ complex, but readily dissociated upon increased salt concentration. The tight association of IscU39^DA and IscS was found to occur regardless of the presence of a bound [Fe-S] cluster. We conclude that the IscU Asp-39 residue is essential for mediating the dissociation of IscU and IscS. In addition to studying IscS and IscU, we were interested to further understand how the isc system is regulated in response to external factors. Previous work has demonstrated that IscR controls expression of the isc operon in <i>Escherichia coli</i>. When IscR is holo this protein represses <i>isc</i> expression, while in its apo-form it allows <i>isc</i> expression. In <i>A. vinelandii</i> we found that ∆<i>iscR</i> strains exhibit in a 5 – 7 fold elevation of isc expression. Additionally, ∆<i>iscR</> strains reveal a small growth phenotype on plates, and a tendency to form spontaneous suppressor mutations allowing reversion to wild-type growth. Loss of apo-IscR function was found to cause a more severe effect on growth than the loss of holo-IscR function, suggesting IscR has cellular roles in addition to the regulation of the <i>isc</i> operon. / Ph. D.

Osteoarthritis is the most prevalent musculoskeletal disease in humans, severely reducing the standard of living of millions of people. Osteoarthritis is characterized by degeneration and loss of articular cartilage which leads to pain, and loss of joint motility and function. Individuals suffering from severe osteoarthritis are commonly treated with full knee replacements. The procedure does eliminate the problem of degrading cartilage tissue; however, it does not fully restore function and its lifetime can be limited. To overcome the disadvantages of current treatments, tissue engineering has become a focus of research to regenerate cartilage. Tissue engineering attempts to repair or replace damaged tissue with cells, biomaterials, and/or molecular signals. Biodegradable scaffolds serve as a temporary replacement for the tissue until it has regenerated. Two types of scaffolds that have been used in tissue engineering are electrospun scaffolds and hydrogels. We have proposed and fabricated a scaffold for cartilage tissue engineering that incorporates an electrospun cylinder and a thermosetting hydrogel in order to provide improved properties compared to either individual material. Electrospun cylinders were created by sintering electrospun mats that include salt pores. The addition of salt pores decreased the mechanical properties of the electrospun materials while also improving the capability of cells to infiltrate into the scaffold. The sintering process involved the connecting of one electrospun mat to an adjacent one. Specifically, poly(d,l-lactide) was capable of sintering to an adjacent electrospun mat when exposed to either heat (near the glass transition temperature) or tetrahydrofuran vapor. The sintering process did not deteriorate the structure or function of the electrospun material. Sintering allowed the creation of unique structures of electrospun material that previously could not be produced. A thermosetting hydrogel was added to the scaffold to replicate the function of proteoglycans present in articular cartilage. A composite scaffold of electrospun polymer and hydrogel showed improved mechanical properties and better integration of the scaffold in vivo compared to an electrospun scaffold with no hydrogel. In conclusion, the composite electrospun and hydrogel scaffold could become an excellent tissue engineering scaffold to treat patients suffering from osteoarthritis. / Ph. D.

This thesis presents the preparation of hyaluronan-based biomaterials with imaging capability and their application as scaffolds in tissue engineering. First, we have synthesized HA derivatives functionalized with different chemoselective groups. Then, functional ligands with capacities for hydrophobic drug loading, imaging, and metal ion coordination were chemically conjugated to HA by chemoselective reactions with these groups. An injectable in situ forming HA hydrogel was prepared by hydrazone cross-linking between hybrid iron-oxide nanogel and HA-aldehyde (paper-I). The degradation of this hydrogel could be monitored by MRI and UV-vis spectroscopy since it contained iron oxide as a contrast agent and pyrene as a fluorescent probe. Additionally, this hydrogel has a potential for a delivery of hydrophobic drugs due to its pyrene hydrophobic domains. The degradation study showed that degradability of the hydrogel was correlated with its structure. Based on the obtained results, disulfide cross-linked and fluorescently labeled hydrogels with different HA concentration were established as a model to study the relationship between the structure of the hydrogel and its degradability (paper-II). We demonstrated that disulfide cross-linked HA hydrogel could be tracked non-invasively by fluorescence imaging. It was proved that the in vivo degradation behavior of the hydrogel is predictable basing on its in vitro degradation study. In paper-III, we developed a disulfide cross-linked HA hydrogel for three-dimensional (3D) cell culture. In order to improve cell viability and adhesion to the matrix, HA derivatives were cross-linked in the presence of fibrinogen undergoing polymerization upon the action of thrombin. It led to the formation of an interpenetrating double network (IPN) of HA and fibrin. The results of 3D cell culture experiments revealed that the IPN hydrogel provides the cells with a more stable environment for proliferation. The results of the cellular studies were also supported by in vitro degradation of IPN monitored by fluorescence measurements of the degraded products. In paper-IV, the effect of biomineralization on hydrogel degradation was evaluated in a non-invasive manner in vitro. For this purpose, two types of fluorescently labeled hydrogels with the different ability for biomineralization were prepared. Fluorescence spectroscopy was applied to monitor degradation of the hydrogels in vitro under two different conditions in longitudinal studies. Under the supply of Ca2+ ions, the BP-modified hydrogel showed the tendency to bio-mineralization and reduction of the rate of degradation. Altogether, the performed studies showed the importance of imaging of hydrogel biomaterials in the design of optimized scaffolds for tissue engineering.

As fraturas em equinos são responsáveis por grande prejuízo financeiro devido às dificuldades encontradas para instituir seu tratamento nessa espécie, principalmente em animais adultos. Entre as dificuldades técnicas no tratamento de fraturas em equinos estão a alta resistência óssea, que acarreta fraturas com grande transmissão de energia, e a escassez de materiais e técnicas de osteossíntese específicos para a espécie, gerando mau prognóstico em muitos casos. Estas fraturas, quando cominutivas acarretam em falhas ósseas, criando um espaço entre os fragmentos de maior tamanho e ainda extensa lesão de tecidos adjacentes, o que dificulta e prolonga o tempo de consolidação óssea. Atualmente a terapia com células tronco vem sendo bastante estudada em ortopedia, contudo o ambiente onde essas células são depositadas determina o caminho para onde elas vão se diferenciar. Para a utilização de células tronco em ortopedia, estas devem sem implantadas junto a um suporte tridimensional, por exemplo os biopolímeros, que além de fornecer um meio para a multiplicação e diferenciação dessas células, também deve apresentar características biomecânicas semelhantes ao tecido a ser reparado, que no caso da ortopedia é o tecido ósseo. O objetivo desse estudo foi avaliar as propriedades biomecânicas de dois biopolímeros a poliuretana de mamona com carbonato de cálcio e uma formulação de quitosana com fosfato de cálcio. Foram preparadas duas formulações diferentes de cada biopolímero, em corpos de prova cilíndricos de 12 mm de comprimento e 6 mm de diâmetro, sendo: poliuretana de mamona porosa e compacta, e quitosana com secagem a 38 e 60 graus Celsius. Essas formulações foram submetidas a ensaios compressivos nos momentos 3, 24, 48 e 72 horas após o preparo e avaliadas quanto sua resistência à compressão, deformação relativa e módulo de elasticidade. A poliuretana de mamona compacta apresentou o maior valor de resistência à compressão (45,805 N/mm2) após 48 horas. A fórmula de quitosana com secagem a 38oC apresentou a menor deformação relativa (3,952 %) após 72 horas de preparo e o maior valor de módulo de elasticidade encontrado foi na poliuretana de mamona compacta após 72 horas (1354,284 N/mm2). Sendo assim a poliuretana de mamona compacta apresenta maior resistência à compressão do que o osso esponjoso de terceiro metacarpiano equino e semelhante aos substitutos ósseos comerciais mais resistentes. A fórmula de quitosana 38oC apresentou valores similares aos observados no osso esponjoso equino. Podemos concluir com esses dados que a poliuretana de mamona compacta e a fórmula de quitosana 38oC apresentam características biomecânicas desejáveis nos materiais para enxerto ósseo. / Equine fractures are responsible for great economic losses due to difficulties in establishing their treatment, mainly regarding adult animals. Among technical difficulties faced in the equine fractures treatment, there are high bone strenght, which results in high energy fractures and the lack of materials and specific osteosynthesis techniques for the specimen, resulting bad prognostic in many cases. When cominutives, these fractures result in bone gaps, creating spaces between bigger fragments and still extensive surrounding tissue damages, which difficults and extends time for bone consolidation. Nowadays, therapy with steam cells is focused in orthopedy, but environment where these cells are established determines the path they will take. For the use of steam cells in orthopedy, they must be implanted together with a tridimensional support such as biopolymers which, besides offering conditions for replication and differentiation of these cells, they must present biomechanic characteristics similar to the tissue to be healed, which is the bone. The target of this study was to evaluate biomechanic properties of two biopolymers, a castor oil polyurethane with calcium carbonate and a formulation of chitosan with calcium phosphate. Two different formulations of each biopolymer were prepared, in cilindric parts of 12mm lenght and 6mm diameter: porous and compact castor oil polyurethane, and chitosan drying at 38oC and 60oC. These formulations were submitted to compressed tests at 3, 24 and 72 hours after preparation and evaluated for compressive strenght, relative deformation and modulus of elasticity. The compact castor oil polyurethane presented greater compressive value (45,805 N/mm2) after 48 hours. Chitosan formulation drying at 38oC presented lower relative deformation (3,952%) 72 hours after prepared, and the highest value for modulus of elasticity found was compact castor oil polyurethane after 72 hours (1354,284 N/mm2). Thus, compact castor oil polyurethane presents higher compressive strenght than trabecular bone of the third equine metacarpal and similar to strenghter comercial bone grafts. The formulation chitosan 38oC presented similar values to those observed in equine trabecular bone. With these data, we can conclude that the compact castor oil polyurethane and the formulation of chitosan 38oC present desirable biomechanic characteristics in materials for bone grafts.

A busca por técnicas alternativas para suprir a escassez de tecidos e órgãos danificados levou ao surgimento da engenharia de tecidos. Scaffolds biológicos criados a partir da matriz extracelular (MEC) de órgãos e tecidos tem sido uma promissora ferramenta aplicada para suprir esta necessidade. A matriz extracelular placentária descelularizada surge como uma potencial ferramenta para a produção de scaffolds biológicos para recelularização e implantação em áreas lesionadas. Para ser classificado como um scaffolds biológico ideal, a matriz extracelular deve ser acelular e ter preservada suas proteínas e características físicas para viabilizar a adesão celular. Neste contexto, desenvolvemos o scaffolds biológico descelularizado a partir de placentas caninas com 35 e 40 dias de gestação. A eficiência da descelularização foi confirmada pela ausência de conteúdo celular e quantidade de DNA remanescente. A arquitetura vascular e as proteínas da matriz extracelular, tais como, colágenos tipo I, III e IV, laminina e fibronectina, foram preservadas. Para o processo de recelularização, utilizamos células-tronco progenitoras endoteliais derivadas do saco vitelino canino (SVC) e células tronco mesenquimais (CTMs) derivadas de medula óssea canina (CMOC) e de polpa de dente canina (CPDC). O processo de recelularização em placas não aderentes por 7 e 14 dias, na presença do scaffolds placentário secos em ponto crítico auxiliou na eficiência da recelularização, comprovada por imunofluorescência e microscopia eletrônica de varredura, evidenciando a adesão das células no scaffolds e comprovando ser um promissor biomaterial para utilização na medicina regenerativa tecidual. / The search for alternative techniques to address the scarcity of damaged tissues and organs has led to the emergence of tissue engineering. Biological scaffolds created from the extracellular matrix (ECM) of organs and tissues have been a promising applied tool to meet this need. The decellularized placental extracellular matrix appears as a potential tool for the production of biological scaffolds for recellularization and implantation in injured areas. To be classified as an ideal biological scaffold, the extracellular matrix must be acellular and have preserved its proteins and physical characteristics to enable cell adhesion. In this context, we developed the biological scaffold decellularized from canine placentas with 35 and 40 days of gestation. The efficiency of the decellularization was confirmed by the absence of cellular content and amount of DNA remaining. Vascular architecture and extracellular matrix proteins, such as collagens type I, III and IV, laminin and fibronectin, have been preserved. For the process of recellularization, we used stem cells derived from the canine yolk sac (CYSC) and mesenchymal stem cells (MSCs) derived from canine bone marrow (CBMC) and canine dental pulp (CDPC). The process of recellularization in non-adherent plaques for 7 and 14 days in the presence of placental scaffold dried at a critical point assisted in the efficiency of the recellularization, evidenced by immunocytochemistry and scanning electron microscopy, evidencing the adhesion of the cells in the scaffold and proving to be a promising biomaterial for use in tissue regenerative medicine.

A limitation to engineering viable thick tissues (greater than a few hundred microns in thickness) has been the lack of vascularisation and a vascular supply. A key element in engineering such tissues is the generation of a supporting scaffold with a defined and wellcharacterized architecture. To date relatively little attention has been paid to characterization. The objective of this research was to develop well-characterized structures which will inform the rational design of the next generation of engineered thick tissues. Specifically, this research aimed to test combinations of various culturing environments, cell mono- and co-cultures, and scaffold architectures; develop improved imaging techniques and structural/spatial analytical methods to characterise porous polymer scaffolds; and use various spatial and morphological measures to quantify the relationships between scaffold geometric structure and cell distribution. Isotropic and anisotropic pore scaffolds were manufactured and then processed with nondestructive and destructive imaging methods, and characterised using image analysis methods to measure geometric parameters such as the degree of anisotropy/isotropy, porosity, and fractal parameters of pore and strut networks. Cells were introduced into scaffolds using a range of seeding methods and cultured in static and hydrodynamic environments. Quantification of the spatial cell distribution in cell-seeded scaffolds was done with first-order spatial statistics and fractal analysis. Findings comparing various destructive and non-destructive imaging methods found that cryotape cryohistology was the most accurate method for processing bare polymer scaffolds and eliminated histological artefacts common to other techniques. It was found with the various image analysis methods, surface and internal scaffold geometric architectures were strongly isotropic for porogen-fused porogen-leached scaffolds and anisotropic for TIPS scaffolds. For both isotropic and anisotropic pore scaffolds, collagen hydrogel infusion and droplet methods gave the highest cell seeding efficiencies (at 100% efficiency). The key finding in this study was that first-order spatial statistics and fractal analysis of cell distribution revealed that the geometric structure of the scaffolds had the strongest effect on spatial cell infiltration and distribution compared to the influence of culture environment or mono- and co-culture. Isotropic pore scaffolds had a higher level of cell distribution. Further work with optimizing the growth environment parameters, and utilizing collagen-infused cell-seeded scaffolds, may assist in achieving better cell growth. The work presented therefore provides the analytical basis for the rational design of tissue engineering scaffolds.

A limitation to engineering viable thick tissues (greater than a few hundred microns in thickness) has been the lack of vascularisation and a vascular supply. A key element in engineering such tissues is the generation of a supporting scaffold with a defined and wellcharacterized architecture. To date relatively little attention has been paid to characterization. The objective of this research was to develop well-characterized structures which will inform the rational design of the next generation of engineered thick tissues. Specifically, this research aimed to test combinations of various culturing environments, cell mono- and co-cultures, and scaffold architectures; develop improved imaging techniques and structural/spatial analytical methods to characterise porous polymer scaffolds; and use various spatial and morphological measures to quantify the relationships between scaffold geometric structure and cell distribution. Isotropic and anisotropic pore scaffolds were manufactured and then processed with nondestructive and destructive imaging methods, and characterised using image analysis methods to measure geometric parameters such as the degree of anisotropy/isotropy, porosity, and fractal parameters of pore and strut networks. Cells were introduced into scaffolds using a range of seeding methods and cultured in static and hydrodynamic environments. Quantification of the spatial cell distribution in cell-seeded scaffolds was done with first-order spatial statistics and fractal analysis. Findings comparing various destructive and non-destructive imaging methods found that cryotape cryohistology was the most accurate method for processing bare polymer scaffolds and eliminated histological artefacts common to other techniques. It was found with the various image analysis methods, surface and internal scaffold geometric architectures were strongly isotropic for porogen-fused porogen-leached scaffolds and anisotropic for TIPS scaffolds. For both isotropic and anisotropic pore scaffolds, collagen hydrogel infusion and droplet methods gave the highest cell seeding efficiencies (at 100% efficiency). The key finding in this study was that first-order spatial statistics and fractal analysis of cell distribution revealed that the geometric structure of the scaffolds had the strongest effect on spatial cell infiltration and distribution compared to the influence of culture environment or mono- and co-culture. Isotropic pore scaffolds had a higher level of cell distribution. Further work with optimizing the growth environment parameters, and utilizing collagen-infused cell-seeded scaffolds, may assist in achieving better cell growth. The work presented therefore provides the analytical basis for the rational design of tissue engineering scaffolds.

As fraturas em equinos são responsáveis por grande prejuízo financeiro devido às dificuldades encontradas para instituir seu tratamento nessa espécie, principalmente em animais adultos. Entre as dificuldades técnicas no tratamento de fraturas em equinos estão a alta resistência óssea, que acarreta fraturas com grande transmissão de energia, e a escassez de materiais e técnicas de osteossíntese específicos para a espécie, gerando mau prognóstico em muitos casos. Estas fraturas, quando cominutivas acarretam em falhas ósseas, criando um espaço entre os fragmentos de maior tamanho e ainda extensa lesão de tecidos adjacentes, o que dificulta e prolonga o tempo de consolidação óssea. Atualmente a terapia com células tronco vem sendo bastante estudada em ortopedia, contudo o ambiente onde essas células são depositadas determina o caminho para onde elas vão se diferenciar. Para a utilização de células tronco em ortopedia, estas devem sem implantadas junto a um suporte tridimensional, por exemplo os biopolímeros, que além de fornecer um meio para a multiplicação e diferenciação dessas células, também deve apresentar características biomecânicas semelhantes ao tecido a ser reparado, que no caso da ortopedia é o tecido ósseo. O objetivo desse estudo foi avaliar as propriedades biomecânicas de dois biopolímeros a poliuretana de mamona com carbonato de cálcio e uma formulação de quitosana com fosfato de cálcio. Foram preparadas duas formulações diferentes de cada biopolímero, em corpos de prova cilíndricos de 12 mm de comprimento e 6 mm de diâmetro, sendo: poliuretana de mamona porosa e compacta, e quitosana com secagem a 38 e 60 graus Celsius. Essas formulações foram submetidas a ensaios compressivos nos momentos 3, 24, 48 e 72 horas após o preparo e avaliadas quanto sua resistência à compressão, deformação relativa e módulo de elasticidade. A poliuretana de mamona compacta apresentou o maior valor de resistência à compressão (45,805 N/mm2) após 48 horas. A fórmula de quitosana com secagem a 38oC apresentou a menor deformação relativa (3,952 %) após 72 horas de preparo e o maior valor de módulo de elasticidade encontrado foi na poliuretana de mamona compacta após 72 horas (1354,284 N/mm2). Sendo assim a poliuretana de mamona compacta apresenta maior resistência à compressão do que o osso esponjoso de terceiro metacarpiano equino e semelhante aos substitutos ósseos comerciais mais resistentes. A fórmula de quitosana 38oC apresentou valores similares aos observados no osso esponjoso equino. Podemos concluir com esses dados que a poliuretana de mamona compacta e a fórmula de quitosana 38oC apresentam características biomecânicas desejáveis nos materiais para enxerto ósseo. / Equine fractures are responsible for great economic losses due to difficulties in establishing their treatment, mainly regarding adult animals. Among technical difficulties faced in the equine fractures treatment, there are high bone strenght, which results in high energy fractures and the lack of materials and specific osteosynthesis techniques for the specimen, resulting bad prognostic in many cases. When cominutives, these fractures result in bone gaps, creating spaces between bigger fragments and still extensive surrounding tissue damages, which difficults and extends time for bone consolidation. Nowadays, therapy with steam cells is focused in orthopedy, but environment where these cells are established determines the path they will take. For the use of steam cells in orthopedy, they must be implanted together with a tridimensional support such as biopolymers which, besides offering conditions for replication and differentiation of these cells, they must present biomechanic characteristics similar to the tissue to be healed, which is the bone. The target of this study was to evaluate biomechanic properties of two biopolymers, a castor oil polyurethane with calcium carbonate and a formulation of chitosan with calcium phosphate. Two different formulations of each biopolymer were prepared, in cilindric parts of 12mm lenght and 6mm diameter: porous and compact castor oil polyurethane, and chitosan drying at 38oC and 60oC. These formulations were submitted to compressed tests at 3, 24 and 72 hours after preparation and evaluated for compressive strenght, relative deformation and modulus of elasticity. The compact castor oil polyurethane presented greater compressive value (45,805 N/mm2) after 48 hours. Chitosan formulation drying at 38oC presented lower relative deformation (3,952%) 72 hours after prepared, and the highest value for modulus of elasticity found was compact castor oil polyurethane after 72 hours (1354,284 N/mm2). Thus, compact castor oil polyurethane presents higher compressive strenght than trabecular bone of the third equine metacarpal and similar to strenghter comercial bone grafts. The formulation chitosan 38oC presented similar values to those observed in equine trabecular bone. With these data, we can conclude that the compact castor oil polyurethane and the formulation of chitosan 38oC present desirable biomechanic characteristics in materials for bone grafts.

Les polymères conducteurs organiques présentent des propriétés électriques qui offrent de nombreuses possibilités de materiaux, tels que les batteries, les diodes électroluminescentes, les dispositifs microélectroniques, les cellules photovoltaïques, les inhibiteurs de corrosion, les capteurs, etc. Parmi eux, la PANI et le PPS ont été largement étudiés en raison de leur stabilité ou propriétés électriques de protonation réglable ainsi que leur faible coût de production. Néanmoins, ces structures sont généralement représentées comme des structures linéaires et donc il y a un intérêt à obtenir des structures hémicyclique ou des analogues cycliques pour augmenter leur potentiel d'utilisation comme agents de séquestration de métaux et/ou de gaz, matériaux de détection ainsi que des nouveaux semi-conducteurs organiques cycliques qui présentent des propriétés différentes de leurs homologues linéaires. Avec la croissance démographique et l'industrialisation, la consommation d'énergie est en nette progression ce qui entraîne la libération de grandes quantités de CO2 dans l'atmosphère et perturbe l'équilibre en carbone de notre planète. Une option pour réduire la concentration de CO2 est l'utilisation de la capture du CO2 et de la technologie de stockage. Dans ce contexte, nous démontrons ici une stratégie basée sur une réaction de substitution nucléophile aromatique, pour la synthèse de hétéracalixarenes qui sont des précurseurs de calixarènes avec un hétéroatome sur le pont, leurs intermédiaires et les structures oligomèriques sont dérivés de ces hétéracalixarenes avec un sélectivité, des propriétés de capture et optoéletroniques optimisées pour un utilisation en capture de CO2. / Optoelectronic properties of π-conjugated chromophores have been widely used since the discovery in the late 70’s of the conducting properties of synthetic organic polymers. Indeed, due to their chemical structures organic conducting polymers exhibit electrical properties that provide useful materials such as batteries, light-emitting diodes, microelectronic devices, photovoltaic cells, corrosion inhibitors, sensors etc. Among them, polyaniline and polysulfide have been extensively studied for this purpose due to their environmental stability, oxidation or protonation-adjustable electrical properties and low cost production. Nevertheless, these structures are generally depicted as linear structures and there is an interest in achieving hemicyclic or cyclic analogues structures to extend their potential of use as metal-gas sequestering agents and/or sensing materials as well as new organic cyclic semiconductors exhibiting different properties from their linear counterparts. With population growth and increased industrialization in the world, energy consumption is increasing significantly resulting in the release of large amounts of carbon dioxide (CO2) into the atmosphere and disturbing the carbon balance of our planet. One way to reduce the CO2 concentration is the use of carbon capture and storage technology. In this context, we report here a very simple strategy, based on a nucleophilic aromatic substitution reaction, for the synthesis of heteracalixarenes, their intermediates and oligomeric structures derived from these heteracalixarenes with optimized optoelectronic properties, selectivity and capture properties for use in carbon capture.