Publicação
Strategies for the stabilization and preservation of prosthetic heart valves
| Resumo: | Every year around 60000 heart valve replacements are performed in the USA alone and more than 250000 worldwide. Valve replacement involves two major types: the mechanical valves (MHVs) and biological valves (BHVs), while MHVs are more durable they require long term anti coagulation treatment. Biological valves possess the inherent capacity to be much more compat ible with the human physiology, using crosslinking agents like glutaraldehyde (GLUT), it is possi ble to increase durability of the tissue by making it stiffer. This process involves the use of tissues like pericardium from animals like cows and pigs or even the autologous from the patient, after crosslinking these tissues are then mounted on stents which are inserted into the heart to replace the old valve. The problem is that through calcification processes these valves can only last at most 15 years average. In this work, the development of an easy and fast method to crosslink pericardium using other agents besides glutaraldehyde such as sodium periodate or a carbodiimide system (EDC/NHS) is proposed. In order to optimize the process, the reactions were studied in a range of times and concentrations. Mechanical behavior was studied using a tensile tests and it is im portant to emphasize that was possible to obtain better samples than when using GLUT cross linking. Chemical studies of the tissue involved FTIR-ATR, NMR and HPIC of hydrolyzed tissue to determine which amino acids reacted with the crosslinking agents. Morphological analysis in volved the use of SEM in order to see the arrangement of the collagen fibres present in the peri cardium tissue. Assays mimicking in vivo calcification were performed by immersing samples in SBF solution for 7 days. On a second phase the addition of hyaluronic acid to the tissue is studied while periodate or EDC crosslinking is taking place. Generally, it is possible to conclude a much greater resistance to calcification processes maintaining good biomechanical properties or in some cases improving. |
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| Autores principais: | Landum, Daniel Leiria Mendes |
| Assunto: | Pericardium Glutaraldehyde Glycosaminoglycans Sodium Metaperiodate EDC/NHS |
| Ano: | 2019 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade Nova de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório Institucional da UNL |
| Resumo: | Every year around 60000 heart valve replacements are performed in the USA alone and more than 250000 worldwide. Valve replacement involves two major types: the mechanical valves (MHVs) and biological valves (BHVs), while MHVs are more durable they require long term anti coagulation treatment. Biological valves possess the inherent capacity to be much more compat ible with the human physiology, using crosslinking agents like glutaraldehyde (GLUT), it is possi ble to increase durability of the tissue by making it stiffer. This process involves the use of tissues like pericardium from animals like cows and pigs or even the autologous from the patient, after crosslinking these tissues are then mounted on stents which are inserted into the heart to replace the old valve. The problem is that through calcification processes these valves can only last at most 15 years average. In this work, the development of an easy and fast method to crosslink pericardium using other agents besides glutaraldehyde such as sodium periodate or a carbodiimide system (EDC/NHS) is proposed. In order to optimize the process, the reactions were studied in a range of times and concentrations. Mechanical behavior was studied using a tensile tests and it is im portant to emphasize that was possible to obtain better samples than when using GLUT cross linking. Chemical studies of the tissue involved FTIR-ATR, NMR and HPIC of hydrolyzed tissue to determine which amino acids reacted with the crosslinking agents. Morphological analysis in volved the use of SEM in order to see the arrangement of the collagen fibres present in the peri cardium tissue. Assays mimicking in vivo calcification were performed by immersing samples in SBF solution for 7 days. On a second phase the addition of hyaluronic acid to the tissue is studied while periodate or EDC crosslinking is taking place. Generally, it is possible to conclude a much greater resistance to calcification processes maintaining good biomechanical properties or in some cases improving. |
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