Design of new photocrosslinkable highly bioactive composite materials for bone tissue repair

• Autor(a) principal: Middleton, Herbert Daniel
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/36244
• topic: Biomaterials; Tissue engineering; Platelet lysates; Composite hydrogels; Photocrosslinking

As the population ages, average bone mass decreases, resulting in ever more bonerelated injuries and pathologies. This requires a reassessment of the current treatment methods, and a collective effort to revolutionise the medical and biomaterial fields. The following thesis sets out a detailed explanation of how the skeletal system functions at a molecular, material, and cellular level, drawing comparisons to the functionality of a computer. After critically reviewing the state of the art of bone tissue engineering through the use of biomaterials, and the numerous up-and-coming technologies used to produce and deliver these, an objective to develop a near-next generation composite photocrosslinkable viscoelastic hydrogel precursor is set out. The first practical part of this project was the synthesis of the mineral component of bone tissue, hydroxyapatite, via chemical precipitation. After this, chemical modifications were conducted on the surface of the synthesised powder and a commercial, medical-grade nanosized hydroxyapatite, used for comparative purposes, in order to provide these with photosensitive methacrylic groups and evaluated by different material characterisation methods. The second part of this project revolved around incorporating these modified powders within photocrosslinkable protein solutions and analysing the rheological properties of the hydrogel precursor and then, upon light exposure, mechanical properties of the resulting hydrogel. The two protein solutions were gelatin methacryloyl, synthesised using an established protocol to methacrylate gelatin, provided bovine serum albumin methacryloyl, and commercial platelet lysates methacryloyl. Finally, the resulting composite hydrogels were then tested in vitro in order to ascertain the biological performance to the produced materials. The synthesised and commercial powders were proven to be pure hydroxyapatite by X-ray diffraction and FTIR spectroscopy and the surface modifications using polyethylenimine and methacrylic groups was verified by using ζ-potential measurements and solid-state nuclear magnetic resonance. The rheological and viscometric performance were measured using a rheometer and hydrogel cylinders were mechanically tested using a uniaxial compression machine, with the aforementioned assays all indicating that particle methacrylation was possible for the commercial hydroxyapatite, and that the presence of methacrylic groups improved mechanical and rheological performance.