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Advisor(s)
Abstract(s)
O osso é um tecido conjuntivo muito complexo, e é um dos mais resistentes do
organismo. É fundamental na capacidade de carga do esqueleto, e apresenta funções
mecânicas, metabólicas, de suporte e de protecção. As lesões ósseas ocorrem devido à
idade, mas também devido a traumatismos e doenças.
O processo de reparação óssea é muito dinâmico e envolve uma série de
fenómenos: migração, diferenciação, proliferação celular e síntese da matriz
extracelular óssea. Quando um biomaterial é inserido num defeito ósseo, o organismo
reconhece o biomaterial como um corpo estranho, desencadeando um conjunto de
respostas que visam a reparação óssea, mas podendo também rejeitar o biomaterial e
desencadear uma resposta inflamatória.
Neste trabalho, um novo scaffold de alumina foi produzido, através de um
processo inovador, para que futuramente possa ser usado na regeneração. O material foi
caracterizado mecanicamente, através de ensaio de dureza, resistência, porosidade e
absorção de água. Biologicamente, o material foi caracterizado através de ensaios in
vitro com osteoblastos humanos: ensaio do brometo de [3-(4,5-dimetiltiazol-2-il) -2,5-
difeniltetrazolio], para avaliar a citotoxicidade do mesmo, e Microscopia Electrónica de
Varrimento, para observar a adesão ou não das células ao material. Foram também
realizados ensaios in vivo, inserindo o material em defeitos ósseos induzidos em ratos
Wistar, de modo a caracterizar o material quanto à sua biocompatibilidade e capacidade
de osteointegração.
Os ensaios mecânicos revelaram que o material possui uma elevada resistência
mecânica, assim como uma densidade semelhante à do osso, e uma porosidade que
permite os osteoblastos aderirem ao material. Os ensaios in vitro, revelaram que o
material não é citotóxico e que permite a adesão celular na sua superfície. No entanto,
os resultados in vivo, não confirmaram os dados obtidos in vitro, uma vez que a análise
histológica revelou que o material induz inflamação a curto e a longo prazo no local de
implantação. Tal resultado, permite afirmar, que este material desencadeia uma resposta
inflamatória local, tendo estes resultados relevância clínica, uma vez que a alumina é
muito usada no revestimento de próteses dentárias e femorais, e desse modo, este
trabalho levanta algumas questões quanto à fiabilidade de se usarem dispositivos
produzidos com este material, e em que o mesmo contacta directamente com os tecidos.
Bone is a very complex connective tissue, and one of the hardest in the body. It’s essential in the skeleton load-bearing capacity due to its mechanical, support and protective properties. Bone damages occur not only due to age, but also as a result of traumas and illnesses. The bone regeneration process is a very dynamic process and involves different stages: migration, differentiation, cellular proliferation and extracellular matrix synthesis. When a biomaterial is implanted in a bone injury, the body identifies it as a foreign body, and this triggers not only a set of responses aiming to repair the bone damage, but can also reject the biomaterial and trigger inflammatory answer. In this work, a new alumina scaffold was produced, through an innovative process to be used in a near future for bone regeneration. The scaffold was characterized mechanically, by harness, resistance, porosity and water absorption assays. Moreover, it was also characterized in a biological environment. The in vitro studies were done with human osteoblasts: [3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium] bromide was used to evaluate the biomaterial’s cytotoxicity, and Scanning Electron Microscopy was used to characterize the cell adhesion to the scaffold to determine the biomaterial’s biocompatibility and osteointegration capacity. In vivo studies were also performed. The scaffold was inserted in Wistar rats. The mechanical assays revealed that the scaffold has a very high mechanical resistance, a density similar to the bones’, and a porosity that allows the osteoblast cells to adhere. In vitro studies revealed the biomaterial’s lack of cytotoxicity, and also cell adhesion to the scaffold. However, the in vivo results didn’t confirm the in vitro ones. The histological analysis showed that the biomaterial induces inflammation at short and long term in the bone injuries. Such results suggest that this scaffold triggers a local inflammatory response, and it can be claimed that this findings are clinically relevant because alumina is usually used as coating of dental and femoral prosthesis and so this work raises some questions about the applicability of devices made with alumina to be used directly in living tissues.
Bone is a very complex connective tissue, and one of the hardest in the body. It’s essential in the skeleton load-bearing capacity due to its mechanical, support and protective properties. Bone damages occur not only due to age, but also as a result of traumas and illnesses. The bone regeneration process is a very dynamic process and involves different stages: migration, differentiation, cellular proliferation and extracellular matrix synthesis. When a biomaterial is implanted in a bone injury, the body identifies it as a foreign body, and this triggers not only a set of responses aiming to repair the bone damage, but can also reject the biomaterial and trigger inflammatory answer. In this work, a new alumina scaffold was produced, through an innovative process to be used in a near future for bone regeneration. The scaffold was characterized mechanically, by harness, resistance, porosity and water absorption assays. Moreover, it was also characterized in a biological environment. The in vitro studies were done with human osteoblasts: [3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium] bromide was used to evaluate the biomaterial’s cytotoxicity, and Scanning Electron Microscopy was used to characterize the cell adhesion to the scaffold to determine the biomaterial’s biocompatibility and osteointegration capacity. In vivo studies were also performed. The scaffold was inserted in Wistar rats. The mechanical assays revealed that the scaffold has a very high mechanical resistance, a density similar to the bones’, and a porosity that allows the osteoblast cells to adhere. In vitro studies revealed the biomaterial’s lack of cytotoxicity, and also cell adhesion to the scaffold. However, the in vivo results didn’t confirm the in vitro ones. The histological analysis showed that the biomaterial induces inflammation at short and long term in the bone injuries. Such results suggest that this scaffold triggers a local inflammatory response, and it can be claimed that this findings are clinically relevant because alumina is usually used as coating of dental and femoral prosthesis and so this work raises some questions about the applicability of devices made with alumina to be used directly in living tissues.
Description
Keywords
Tecido ósseo Doenças ósseas Biomateriais Biomateriais - Aplicação clínica Scaffold - Alumina Regeneração óssea - Biomaterial de alumina