Desarrollo y caracterización de biomateriales de titanio funcionalizados con respuesta biológica modulable
- Autores: Parsa Rezvanian
- Directores de la Tesis: José Pérez Rigueiro (dir. tes.)
- Lectura: En la Universidad Politécnica de Madrid ( España ) en 2018
- Idioma: español
- Tribunal Calificador de la Tesis: Gustavo Víctor Guinea Tortuero (presid.), Milagros Ramos Gómez (secret.), María Arroyo Hernández (voc.), Diego Velasco Bayón (voc.), Miguel Ángel Garrido Maneiro (voc.)
- Programa de doctorado: Programa de Doctorado en Ingeniería de Estructuras, Cimentaciones y Materiales por la Universidad Politécnica de Madrid
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- Enlaces
- Tesis en acceso abierto en: Archivo Digital UPM
- Resumen
Titanium and its alloys are among the most-frequently used biomaterials for the replacement of hard tissue. This choice is due to their good corrosion resistance, superior mechanical properties and excellent biocompatibility. The feature that separates titanium and titanium alloys from the rest of the metallic biomaterials, is their elastic modulus which is lower than that of the rest of the metallic biomaterials and closer to the elastic modulus of bone. These properties make titanium alloys the ultimate choice for fabrication of biomaterials for hard tissue replacement, particularly for load-bearing applications. However, a drawback in using titanium as bone implant is that it lacks the ability to establish a direct contact with the adjacent bone. More often, the implant is surrounded by a capsule of fibrous tissue. The specialized tissue is able to form on top of the fibrous tissue layer, but the fibrous tissue acts as a mechanically weak link between the implant and the newly formed bone. The presence of this fibrous tissue layer might cause infections or loosening of the implant and lead to the need for revision surgery. In this regard, development of biomaterials capable of establishing a close integration with bone tissue is of outmost importance. One strategy to address this problem is to modify the surface of the material by covalently binding proper biomolecules capable of promoting the activity of specialized bone cells on the surface, while preserving the excellent bulk properties of the material.
To do so, it is necessary to consider three distinct but complementing steps. Firstly, the proper functional groups have to be generated on the surface of the substrate material. Secondly, a proper cross-linking chemistry must be employed in order to link the surface functional groups to the target biomolecule and thirdly, a biomolecule has to be chosen which should be able to induce the desired effect in the cells, while being compatible with the cross-linking chemistry.
Thus, the objective of this work is to develop a robust method for the covalent immobilization of various biomolecules on the surface of Ti-6Al-4V alloy. In this regard, a novel technique for the deposition of amine functional groups on the Ti-6Al-4V substrates known as Activated Vapor Silanization (AVS) was used and studied. By varying the deposition parameters of AVS, different layers of amine functional groups were deposited on Ti-6Al-4V substrates and characterized in terms of roughness and surface amine concentration. Based on the findings, two optimal functionalization conditions were selected and further characterized in terms of layer thickness, contact angle, cell response and stability under physiological conditions.
Four different target biomolecules were addressed in this work: Collagen type I, albumin, fibrinogen and fibronectin. Initially, each protein was physically adsorbed on the surface of the bare Ti-6Al-4V alloys and the response of mouse pre-osteoblasts (MC3T3-E1) and bone marrow mesenchymal stem cells (BM-MSC) to the adsorption of these proteins was determined. It was concluded that collagen type I and fibronectin were able to positively influence the adhesion of BM-MSCs on the Ti-6Al-4V samples.
On the other hand, all mentioned proteins were covalently immobilized on the surface of AVS-functionalized Ti-6Al-4V samples using EDC/NHS as cross-linker. The immobilized proteins were characterized by atomic force microscopy (AFM) and fluorescence microscopy. Additionally, the stability of the immobilized proteins was assessed by exposure to detergents and, as expected, it was found that the covalently immobilized proteins were more stable than the physically adsorbed ones.
Finally, the reaction of BM-MSCs to the covalently immobilized collagen type I and fibronectin was investigated by performing cell cultures. In this regard, a cleaning protocol for removal of excess EDC/NHS as a possible cause of toxicity was also developed. Ultimately, it was concluded that the covalent immobilization of either collagen type I or fibronectin leads to an enhanced BM-MSC adhesion on Ti-6Al-4V. This finding may be employed for the development of bone-contacting biomaterials with enhanced biological properties.
