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Preparação e caraterização de scaffolds de colagénio-nanohidroxiapatite modificados com o-phospho-L-serine para a regeneração tecidular óssea
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O tecido ósseo é constantemente submetido a processos dinâmicos e fisiológicos inerentes à reabsorção e à formação óssea, de modo a garantir a integridade do esqueleto. Na maioria dos casos, o processo de reparação óssea é desencadeado pela fragilidade ou fratura do osso, como por exemplo em caso defeitos de grandes dimensões. Porém, o processo de reparação nem sempre ocorre de forma ideal. Neste sentido, novas estratégias terapêuticas coadjuvantes ao processo de reparação óssea tem vindo a ser exaustivamente estudas pela Engenharia de Tecidos. Atualmente, alguns biomateriais ou materiais biomiméticos tem vindo a ser utilizados na prática clínica em substituição dos enxertos autólogos reconhecidos como gold standard. A variedade destes materiais tem vindo a propiciar, progressivamente, o sucesso de tratamento. Contudo, o material ideal para a regeneração óssea requer ainda mais investigação. Este material deve ter propriedades similares ao osso natural como osteointegração, osteoindução e osteogénese. O objetivo desta dissertação consiste em reportar as propriedades físico-químicas e mecânicas dos scaffolds biocompósitos de colagénio/nano-hidroxiapatite modificados com O-phospho-L-serine (fosfoserina), obtidos através do método de criogelação, como potenciais substitutos ósseos. A análise da morfologia e da superfície dos biocompósitos foi realizada utilizando a Microscopia Eletrónica de Varrimento (SEM) e os resultados mostraram que os criogéis produzidos apresentam uma estrutura altamente porosa com a presença de cristais nanométricos de hidroxiapatite. De acordo com a análise química resultante da Espetroscopia de Infravermelho por Transformada de Fourier (FT-IR), os picos de colagénio e hidroxiapatite nos scaffolds biocompósitos coincidem com os valores reportados na literatura e a fosfoserina não interfere com a ligação formada pelas moléculas de colagénio e os agregados de hidroxiapatite. O resultado do teste de absorção de solventes revela que diferentes concentrações do aminoácido em estudo têm influência da captação de água, isto é, os scaffolds biocompósitos de colagénio/nano-hidroxiapatite com maior concentração de fosfoserina apresentam maior captação de água comparativamente às amostras com menor concentração de aminoácido. Por outro lado, quando as amostras são emergidas em PBS (tampão salino), os scaffolds com fosfoserina mostram menor coeficiente de absorção. Por fim, segundo a análise dinâmico-mecânica, as amostras com fosfoserina apresentam uma redução das propriedades mecânicas, mas não significativamente, enquanto as propriedades viscoelásticas apresentam alteração, revelando deformação da amostra. Os resultados deste estudo permitem concluir que os scaffolds biocompósitos de colagénio/nano-hidroxiapatite com fosfoserina apresentam propriedades físico-químicas e mecânicas propícias a estudos in vitro com culturas celulares.
In order to mantain a healthy skeleton, bone tissue is constantly subjected to dynamic and physiological processes of reabsorption and new bone formation. Usually, the process of bone healing is triggered in some cases of tissue fragility or tissue damaged like e.g. large defects. In other way, sometimes the healing process does not respond approprieately. Fortunately, bone tissue engineering offers new therapeutic strategies to aid in the muscoskeletal healing. The development and use of biomaterials or biomimetic materials that can replace autologous grafts, recognized as gold standard, are often used today in daily clinical practice. Besides increased the range of choice, these biomaterials also have improved the clinical treatment. Nonetheless, the ideal material for bone regeneration requires further investigation. This material must have the same characteristics that we find in the native bone such osteointegration, osteoinduction and osteogenisis properties. This dissertation try to investigate and expose the physicochemical and mechanical properties of collagen/nano-hydroxyapatite biocomposites scaffolds modified with O-phospho-L-serine (phosphoserine), obtained by cryogelation method, as potential bone substitutes. Morphology and surface analysis was performed using Scanning Eletron Microscope (SEM) and revealed that all cryogel scaffolds had highly porous structure with interconnective porosity with the presence of nanometric crystals of hydroxyapatite. According to the chemical analysis through Fourier Transform Infrared Spectroscopy (FT-IR), the peaks of collagen and hydroxyapatite in the biocomposite scaffolds are coincident with the values reported in the literature and the phosphoserine do not interfer with the link between collagen molecules and hydroxyapatite aggregates. The swelling tests has been shown that different concentrations of the aminoacid in study, have influence in water uptake, i.e., collagen/nano-hydroxyapatite biocomposites scaffolds with high content of phosphoserine display higher water uptake than low phosphoserine content. On the other hand, when the samples are in PBS (phosphate buffer), the samples with phosphoserine show lower degree of swelling behavior. Finally, in agreement with Dynamic Mechanical Analysis (DMA), the samples with phosphoserine show lower mechanical properties, but no significantly, even as visco-elastic properties have changed and reveals samples deformation. The results of this investigation allow to assert that collagen/nano-hydroxyapatite biocomposite scaffolds modified with phosphoserine exhibit advantgeous physicochemical and mechanical properties for in vitro studies.
In order to mantain a healthy skeleton, bone tissue is constantly subjected to dynamic and physiological processes of reabsorption and new bone formation. Usually, the process of bone healing is triggered in some cases of tissue fragility or tissue damaged like e.g. large defects. In other way, sometimes the healing process does not respond approprieately. Fortunately, bone tissue engineering offers new therapeutic strategies to aid in the muscoskeletal healing. The development and use of biomaterials or biomimetic materials that can replace autologous grafts, recognized as gold standard, are often used today in daily clinical practice. Besides increased the range of choice, these biomaterials also have improved the clinical treatment. Nonetheless, the ideal material for bone regeneration requires further investigation. This material must have the same characteristics that we find in the native bone such osteointegration, osteoinduction and osteogenisis properties. This dissertation try to investigate and expose the physicochemical and mechanical properties of collagen/nano-hydroxyapatite biocomposites scaffolds modified with O-phospho-L-serine (phosphoserine), obtained by cryogelation method, as potential bone substitutes. Morphology and surface analysis was performed using Scanning Eletron Microscope (SEM) and revealed that all cryogel scaffolds had highly porous structure with interconnective porosity with the presence of nanometric crystals of hydroxyapatite. According to the chemical analysis through Fourier Transform Infrared Spectroscopy (FT-IR), the peaks of collagen and hydroxyapatite in the biocomposite scaffolds are coincident with the values reported in the literature and the phosphoserine do not interfer with the link between collagen molecules and hydroxyapatite aggregates. The swelling tests has been shown that different concentrations of the aminoacid in study, have influence in water uptake, i.e., collagen/nano-hydroxyapatite biocomposites scaffolds with high content of phosphoserine display higher water uptake than low phosphoserine content. On the other hand, when the samples are in PBS (phosphate buffer), the samples with phosphoserine show lower degree of swelling behavior. Finally, in agreement with Dynamic Mechanical Analysis (DMA), the samples with phosphoserine show lower mechanical properties, but no significantly, even as visco-elastic properties have changed and reveals samples deformation. The results of this investigation allow to assert that collagen/nano-hydroxyapatite biocomposite scaffolds modified with phosphoserine exhibit advantgeous physicochemical and mechanical properties for in vitro studies.
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Keywords
Scaffolds Colagénio Criogelação Regeneração óssea Fosfoserina Collagen Phosphoserine Bone regeneration Cryogelation