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Fabrico de scaffolds para substituição óssea utilizando pós de titânio e agentes poragéneos
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Abstract(s)
O desenvolvimento de soluções alternativas ao enxerto ósseo é fundamental para o sucesso da engenharia de tecido ósseos, baseada na utilização de scaffolds como alternativa para a substituição e regeneração óssea. Um scaffold é fabricado utilizando materiais biocompatíveis de origem metálica, cerâmica ou polimérica. Os materiais poliméricos possuem propriedades mecânicas adequadas, mas baixa bioatividade; os cerâmicos embora estruturalmente semelhantes ao osso, resultam habitualmente em scaffolds com baixa resistência mecânica. As espumas metálicas surgiram na literatura como uma alternativa viável. Neste contexto, neste trabalho testa-se o fabrico de corpos porosos a partir de pós metálicos de titânio e de diferentes agentes poragéneos. O objetivo é obter uma boa relação entre comportamento mecânico, propriedades físico-químicas e bioatividade do scaffold, o mais semelhantes possível às do osso trabecular humano. O procedimento de fabrico consistiu na mistura e homogeneização de titânio na forma pó com um agente poragéneo. Para este fim testou-se cloreto de sódio (NaCl) e amido de batata, com diferentes relações mássicas metal/poragéneo - 30/70, 50/50, 70/30. As foram compactadas, seguindo-se a eliminação do agente poragéneo por dissolução em água destilada para o sal ou por calcinação, respetivamente no caso do cloreto de sódio e do amido. A última etapa de processamento foi a sinterização dos corpos verdes, testando-se as temperaturas de 800ºC, 900ºC e 1000ºC. Para a compactação das amostras foi necessário projetar e fabricar um molde metálico. Após o fabrico dos scaffolds, caracterizaram-se as respetivas propriedades físicas, químicas, mecânicas e de biocompatibilidade de microscopia eletrónica de varrimento, ensaio mecânico de compressão, testes de citotoxicidade. Os melhores resultados foram obtidos para scaffolds com 30 % em massa de amido de batata, que apresentaram propriedades mecânicas semelhantes às do osso trabecular, nomeadamente módulo de Young de 0.82 GPa e tensão de carga máxima de 115.18 MPa. Estes scaffolds apontam para um efeito de crescimento de células animais. No entanto, a partir de 50 % de amido de batata as amostras perderam integridade estrutural o que inviabilizou o seu fabrico. A utilização de 30 %, 50 % e 70 % em massa de cloreto de sódio como agente poragéneo resultou em scaffolds com integridade estrutural. Os melhores resultados obtiveram-se para 70 % de cloreto de sódio, resultando em poros de grande dimensão, com diâmetro até 3 mm. Os scaffolds com 30 % de cloreto de sódio apresentaram módulo de 0.56 GPa e tensão de carga máxima de 18.86 MPa. Todos scaffolds sinterizados apresentaram uma camada exterior de óxido de titânio e porosidade.
Abstract The development of alternative solutions to bone grafting is fundamental for the success of bone tissue engineering, based on the use of scaffolds as an alternative for bone replacement and regeneration. A scaffold is manufactured using biocompatible materials of metallic, ceramic or polymeric origin. Polymeric materials have adequate mechanical properties but low bioactivity; Ceramics, although structurally similar to bone, usually result in scaffolds with low mechanical strength. Metallic foams have emerged in the literature as a viable alternative. In this context, this work tests the manufacture of porous bodies from titanium metal powders and different poragen agents. The objective is to obtain a good relationship between mechanical behavior, physicochemical properties and bioactivity of the scaffold, as similar as possible to those of human trabecular bone. The manufacturing procedure consisted of mixing and homogenizing titanium in powder form with a poragen agent. For this purpose, sodium chloride (NaCl) and potato starch were tested, with different metal/poragen mass ratios - 30/70, 50/50, 70/30. The substances were compacted, followed by the elimination of the poragen agent by dissolution in distilled water for salt or by calcination, respectively in the case of sodium chloride and starch. The last processing step was the sintering of the green bodies, testing the temperatures of 800ºC, 900ºC and 1000ºC. For the compaction of the samples, it was necessary to design and manufacture a metal mold. After the manufacture of the scaffolds, the respective physical, chemical, mechanical and biocompatibility properties of scanning electron microscopy, mechanical compression test, and cytotoxicity tests were characterized. The best results were obtained for scaffolds with 30 % by weight of potato starch, which showed mechanical properties similar to those of trabecular bone, namely Young's modulus of 0.82 GPa and maximum load stress of 115.18 MPa. These scaffolds point to an animal cell growth effect. However, from 50 % potato starch onwards, the samples lost structural integrity, which made their manufacture unfeasible. The use of 30 %, 50 % and 70 % by mass of sodium chloride as a poragen agent resulted in scaffolds with structural integrity. The best results were obtained for 70 % sodium chloride, resulting in large pores, with a diameter of up to 3 mm. The scaffolds with 30 % sodium chloride had a modulus of 0.56 GPa and a maximum load stress of 18.86 MPa. All sintered scaffolds had an outer layer of titanium oxide and porosity.
Abstract The development of alternative solutions to bone grafting is fundamental for the success of bone tissue engineering, based on the use of scaffolds as an alternative for bone replacement and regeneration. A scaffold is manufactured using biocompatible materials of metallic, ceramic or polymeric origin. Polymeric materials have adequate mechanical properties but low bioactivity; Ceramics, although structurally similar to bone, usually result in scaffolds with low mechanical strength. Metallic foams have emerged in the literature as a viable alternative. In this context, this work tests the manufacture of porous bodies from titanium metal powders and different poragen agents. The objective is to obtain a good relationship between mechanical behavior, physicochemical properties and bioactivity of the scaffold, as similar as possible to those of human trabecular bone. The manufacturing procedure consisted of mixing and homogenizing titanium in powder form with a poragen agent. For this purpose, sodium chloride (NaCl) and potato starch were tested, with different metal/poragen mass ratios - 30/70, 50/50, 70/30. The substances were compacted, followed by the elimination of the poragen agent by dissolution in distilled water for salt or by calcination, respectively in the case of sodium chloride and starch. The last processing step was the sintering of the green bodies, testing the temperatures of 800ºC, 900ºC and 1000ºC. For the compaction of the samples, it was necessary to design and manufacture a metal mold. After the manufacture of the scaffolds, the respective physical, chemical, mechanical and biocompatibility properties of scanning electron microscopy, mechanical compression test, and cytotoxicity tests were characterized. The best results were obtained for scaffolds with 30 % by weight of potato starch, which showed mechanical properties similar to those of trabecular bone, namely Young's modulus of 0.82 GPa and maximum load stress of 115.18 MPa. These scaffolds point to an animal cell growth effect. However, from 50 % potato starch onwards, the samples lost structural integrity, which made their manufacture unfeasible. The use of 30 %, 50 % and 70 % by mass of sodium chloride as a poragen agent resulted in scaffolds with structural integrity. The best results were obtained for 70 % sodium chloride, resulting in large pores, with a diameter of up to 3 mm. The scaffolds with 30 % sodium chloride had a modulus of 0.56 GPa and a maximum load stress of 18.86 MPa. All sintered scaffolds had an outer layer of titanium oxide and porosity.
Description
Keywords
Scaffolds metal/cerâmico Substituição óssea Pós metálicos Titânio Agentes poragéneos Porosidade Metal/ceramic scaffolds Bone substitution Metal powders Titanium Space-holders Porosity