Hybrid organic-inorganic borosilicate materials by sol-gel for bone tissue engineering

• Autor(a) principal: Coelho, Soraia Alexandra Ramos
• Data de Publicação: 2018
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/25818
• topic: Hybrid materials; Polydimetilsiloxane; Borosilicate; Sol-gel; Bioactivity; Cytocompatibility; Angiogenesis

Polydimethylsiloxane (PDMS) - SiO2 - CaO based hybrid materials, prepared by sol-gel, have proven to be very promising materials in tissue engineering applications and drug delivery systems. These hybrid materials present biocompatible, osteogenic and bioactive properties, that will support osteoblast attachment and bone growth. The incorporation of therapeutic ions, such as boron (B), is known to stimulate bone regeneration and angiogenesis, which makes it an alternative to the use of vascular growth factors, due to its low cost, high stability and potentially greater safety. The combination of such ions in hybrid materials prepared by the sol-gel method is a novelty. The main purpose of this work was to produce, by sol-gel method, bioactive and biocompatible hybrid materials within the system PDMS-SiO2-B2O3-CaO capable of releasing calcium and boron to stimulate angiogenesis. Another purpose was to achieve a better understanding of the effect of boron in the structure and microstructure of this material. For that, five different compositions with different amounts of boron were prepared using the same precursors and sol-gel route, resulting in different monolithic materials, with distinct structures and microstructures. The material’s structure was analysed by Fourier Transform Infrared Spectrometry (FT-IR) and solid state Nuclear Magnetic Resonance (NMR) techniques, that expose the presence of hybrid bonds (Si-O-Si) between organic (PDMS) and inorganic phase (TEOS), as well as borosiloxane bonds (B-O-Si). From the results of nuclear magnetic resonance of 11B it was found that the presence of the modifier ion (calcium) in the compositions changes the boron coordination, from trigonal (BO3) to tetrahedral (BO4). These groups are attached to silicon. Thus, it was verified that the increase of boron amount in the system led to a decrease in the specific surface area (SSA), obtained by BET method, as well as the mesoporosity of the material. On the other hand, SEM micrography’s showed an increase in macroporosity with the boron concentration. The bioactivity tests performed in vitro by immersion of the materials in Kokukos’s simulated body fluid (SBF), demonstrated that the material was able to form a layer of calcium phosphate on its surface, and to release therapeutic ions in the supernatant liquid. Thus, this suggests the potential of these materials to be used in the field of tissue regeneration. The relationship among structure, microstructure and ion release were discussed aiming the identification of the formulations that will continue for further studies with specific angiogenesis-related cell lines