Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / VÃrias estratÃgias tÃm sido utilizadas para que materiais, quando em contato com sangue, possam reduzir a adsorÃÃo de proteÃnas do plasma e, consequentemente, a probabilidade de formaÃÃo de trombos. AlÃm disso, outro problema associado à a calcificaÃÃo, descrita como um processo de formaÃÃo de fosfato de cÃlcio, que à a causa primÃria de falhas em tecidos moles e implantes devido à deposiÃÃo destes sais. A quitosana e a carragenana sÃo dois polÃmeros que apresentam propriedades que os tornam promissores para utilizaÃÃo como biomateriais. A quitosana, em funÃÃo dos grupos amino em sua estrutura, pode promover a adesÃo plaquetÃria, sendo necessÃria uma modificaÃÃo quÃmica, como reaÃÃes de sulfonataÃÃo, que visam diminuir a adsorÃÃo de proteÃnas plasmÃticas. A presenÃa de grupos sulfato na carragenana pode contribuir para a obtenÃÃo de superfÃcies com propriedades antitrombogÃnicas sem a necessidade de modificaÃÃo quÃmica da estrutura. A formaÃÃo de complexos polieletrolÃticos (PECs) alia a biocompatibilidade superior da quitosana com a densidade de carga da carragenana, gerada pela presenÃa dos grupos sulfato. Esse trabalho teve por objetivo estudar os efeitos da calcificaÃÃo e da trombogenicidade de filmes de quitosana e carragenana caracterizando-os atravÃs de tÃcnicas de microscopia e espectroscopia, assim como realizar estudo de revestimento de superfÃcie metÃlica utilizando estes polÃmeros. Observou-se uma diminuiÃÃo nos efeitos de calcificaÃÃo para as blendas de quitosana e carragenana e nos filmes sulfonatados (Ca/P 0,11 ou ausÃncia de fÃsforo), reduzindo a formaÃÃo e deposiÃÃo de sais de cÃlcio quando comparados com a quitosana natural (Ca/P 2,78). Ensaios de adesÃo plaquetÃria mostraram melhoria das superfÃcies de quitosana quando modificadas pela sulfonataÃÃo, ou quando misturadas com carragenana, apresentando adesÃo, em mÃdia, de 1 a 2 plaquetas/0,01 mmÂ, contra a formaÃÃo de trombos em filme de quitosana. No ensaio de revestimento, a modificaÃÃo da superfÃcie metÃlica foi evidenciada pela alteraÃÃo da quantidade percentual de carbono e oxigÃnio na composiÃÃo quÃmica da superfÃcie quando comparado o aÃo eletropolido bruto e apÃs a inserÃÃo da quitosana. As sucessivas mudanÃas sofridas pelo Ãngulo de contato reforÃam o sucesso do grafting dos polÃmeros, atravÃs da formaÃÃo de uma camada hidrofÃlica tanto para quitosana natural quanto para a sulfonatada. Pelos resultados obtidos, pode-se inferir que a quitosana sulfonatada e as blendas de quitosana/carragenana mostram-se promissoras para serem utilizadas como biomateriais em contato com sangue. / Various strategies have been proposed to reduce the plasma proteins adsorption and consequently the probability of thrombus formation on materials when contacted with blood. Furthermore, another problem associated with biomaterials is the calcification process, which is described as calcium phosphate formation, which is the primary cause of failures in soft tissues and implants. Chitosan and carrageenan are two polymers that show properties that make them promising for use as biomaterials. Chitosan, due to amino groups in its structure, may promote platelet adhesion, being necessary to perform a chemical modification on it, such as sulfonation reactions, in order to reduce plasma protein adsorption. The presence of sulfate groups in carrageenan structure may contribute to obtain surfaces with antithrombogenic properties without the need of chemical modification on its structure. The formation of polyelectrolyte complexes (PECs) combines the high biocompatibility of chitosan with the charge density of carrageenan, generated by the presence of sulfate groups. This work aimed to study the effects of calcification and thrombogenicity of chitosan and carrageenan films, characterizing them by microscopy and spectroscopy techniques. We also conducted the study of metal surfaces coating using these polymers. A reduction in the effects of calcification for chitosan and carrageenan blends and for sulfonated chitosan films (Ca/P 0.11 or phosphate absence) was observed, reducing the formation and deposition of calcium salts when compared with pristine chitosan (Ca/P 2.78). Assays of platelet adhesion for chitosan surfaces when modified by sulfonation reaction or when blended with carrageenan, showed adhesion on average of 1 to 2 platelets/0.01mm2 against thrombus formation on chitosan film. For the coating essays, the modification on metal surface was characterized by the changing of carbon and oxygen percentage amount on the chemical composition surface, comparing the raw electropolished steel and grafted chitosan. The successive changes observed in the contact angle reinforce the success of the grafting of polymers, forming a hydrophilic layer both for pristine and sulfonated chitosan. From the results obtained, it can be inferred that the sulfonated chitosan and chitosan/carrageenan blends are promising for use as biomaterials in blood contact.

M. Tech. (Department of Chemical Engineering, Faculty of Engineering and Technology), Vaal University of Technology. / Fuel cell technology is a promising clean energy source compared to internal combustion engines and electricity generating plants which are associated with high emissions of greenhouse gases. The aim of this study was to modify chitosan into polymer electrolyte membranes suitable for use in PEMFC and DMFC fuel cells. Chitosan modification was done with 2-aminoethanesulfonic acid (2-AESA), dimethylformamide (DMF) and silica nanoparticles. The effect of the modification on the properties of the developed chitosan membranes was studied using FTIR, XRD, SEM-EDS and TGA. The performance of the membrane electrode assemblies was investigated. The formation of electrostatic interactions in the developed sulfonated chitosan membranes was confirmed via the Fourier transform infrared (FTIR) analysis, indicating a shift in the wavenumber of the N-H bonds from 1581 cm-1 on the chitosan spectrum to a lower wavenumber of 1532 cm-1 in the FTIR spectra of the membranes and by the new peak at the wavenumber of ~1260 cm-1 attributed to the asymmetric O=S=O stretching vibrations of the sulphate groups and sulfonic acid groups from the cross-linking sulphuric acid solution and 2-aminoethanesulfonic acid incorporated on the chitosan polymer chain during the modification. Notably, the FTIR spectra of the developed sulfonated chitosan membranes lacked the peak at the wavenumber of ~1153 cm-1 attributed to the stretching of C-O-C bonds of the polysaccharide ring of chitosan. A reaction mechanism was proposed in this study illustrating the possible conversion of the polysaccharide rings of chitosan into a poly (cyclohexene-oxide) thermoplastic rings in the developed membranes. The TGA/DTGA results of the developed sulfonated chitosan membranes showed three degradation stages. The initial weight loss occurred at temperatures ˂100 °C due to the evaporation of volatile components and water molecules inside the membranes. The second degradation phase of the membranes occurred at 208 ℃ with a loss in weight of >30% resulting from the decomposition of cross-linking networks. The third degradation stage was associated with the decomposition of the main polymer backbone of the membranes and occurred at 263°C for the chitosan membranes modified with 2-aminoethanesulfonic acid and at 266 °C for the chitosan membrane modified with silica nanofiller. The TGA/DTGA curves of Nafion 117 showed a small loss in weight of ~ 5% before a sharp decomposition that occurred between 346–505 °C. The XRD diffractograms of the developed sulfonated chitosan membranes showed amorphous phases, the crystal peaks of chitosan at 2theta of 10° and 20° were flattened on the membranes. The SEM images showed a homogenous surface morphology for the sulfonated chitosan membrane with a higher weight percentage of 2-aminoethanesulfonic acid (13,6 wt.%). The SEM images performed on the surface of the sulfonated chitosan membrane modified silica nanoparticles showed a slight agglomeration associated with the migration of the unbonded silica to the surface. The methanol permeability coefficient of the developed sulfonated chitosan membrane modified with 2-aminoethanesulfonic acid was calculated to be 2.29x10-6 cm2/s. This value was close to the methanol permeability coefficient of 2.33x10-6 cm2/s associated with unfavourable depolarisation at the cathode in direct methanol fuel cells when using Nafion 117. The proton diffusion coefficient of Nafion 117 was calculated to be 1.64x10-5 cm2/s and that of the developed sulfonated chitosan membrane modified with 2-aminoethanesulfonic acid was found to be 6.56x10-6 cm2/s, respectively. The fuel cell performance of the developed sulfonated chitosan membrane modified with 2AESA was investigated in a hydrogen fuel cell (PEMFC) supplied with H2 and O2 directly from the electrolyser. The sulfonated chitosan membrane modified with 2-aminoethanesulfonic acid (13.6 wt.%) achieved an open-circuit voltage of ~0.9 V and a maximum power output of 64.7 mW/cm2 at a maximum current of 70 mA. The current produced by the developed chitosan membrane was applied into the load and was able to turn (power) the electric fan. The sulfonated chitosan membrane modified with silica nanoparticles (2 wt.%) yielded an open-circuit voltage of ~0.9 V and attained a maximum power output of 58 mW/cm2 at a maximum current output of 60 mA/cm2. The current generated by the membrane was also able to turn the electric fan. The Nafion 117 membrane was also investigated under similar conditions and obtained an open-circuit voltage of 0.6 V and a maximum power output of 130 mW/cm2 at the maximum current output of 308 mA. The current produced by Nafion 117 was supplied into the load and was able to turn the electric fan.