3D-printed biomimetic bone
(English) Over 2 million bone grafting procedures are performed each year. In the last years, synthetic calcium phosphates have drawn the attention of the researchers for their close similarity to the mineral phase of bone by offering exceptional bioactivity, osteoconductivity, and biocompatibility....
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2021 |
| País: | España |
| Institución: | CBUC, CESCA |
| Repositorio: | TDR. Tesis Doctorales en Red |
| OAI Identifier: | oai:www.tdx.cat:10803/692635 |
| Acceso en línea: | http://hdl.handle.net/10803/692635 https://dx.doi.org/10.5821/dissertation-2117-420264 |
| Access Level: | acceso abierto |
| Palabra clave: | Àrees temàtiques de la UPC::Enginyeria biomèdica 616.7 |
| Sumario: | (English) Over 2 million bone grafting procedures are performed each year. In the last years, synthetic calcium phosphates have drawn the attention of the researchers for their close similarity to the mineral phase of bone by offering exceptional bioactivity, osteoconductivity, and biocompatibility. Especially promising showed to be biomimetic calcium deficient hydroxyapatite (CDHA), which can be obtained through hydrolysis of a-tricalcium phosphate (a-TCP) at physiological temperature in a self-setting reaction. This has been exploited in calcium phosphate cements. Furthermore, this material can be fabricated by robocasting which offers great opportunities for patient-specific bone graft production by allowing control of external geometry and internal macroporosity of such obtained CDHA scaffolds. The present thesis is divided into two parts: (i) investigation of CDHA physicochemical changes after incubation in culture medium over long time periods, (ii) design and fabrication of 3D robocasted CDHA bone grafts to enhance their biological properties by two strategies, (a) the incorporation of ions and (b) the introduction of concave porosity in the printed filaments. Chapter 1 presents an overview of bone composition and biology, bone grafting strategies with their advantages and disadvantages, as well as puts forward strategies to enhance their biological performance. Chapter 2 investigates the physicochemical changes that undergoes CDHA after incubation in culture medium over extended time periods depending on the morphology of crystals (needle-like versus plate-like) and specific surface area (SSA). The study focuses on the structural changes such as crystallinity evolution, as well as the chemical ones in terms of local gradient of carbonation (confocal Raman microscopy mapping) and global ionic incorporation. Last but not least, differences in protein adsorption content and protein patterns (LC- MS/MS proteomics analysis) are put forward depending on the sample type. Overall, higher carbonation, ionic incorporation and protein adsorption capability and selectivity was observed for fine specimens of needle-like crystal morphology than coarse specimens of plate-like one. Chapter 3 and Chapter 4 explore two independent strategies to enhance biological properties of 3D printed CDHA. Chapter 3 explores incorporation of different ions (Sr, Mg, and Si) by soaking 3D CDHA in ionic solutions during the biomimetic setting at physiological temperatures. This easy strategy of chemical modification of scaffolds is evaluated by X-ray diffraction (XRD), scanning electron microscopy (SEM), inductively coupled plasma (ICP-OES), and fourier-transform infrared spectroscopy (FTIR). Furthermore, an ionic release study was performed and evaluated by ICP-OES. A comparison between scaffolds, before and after the release, was carried out by FTIR to obtain information about crystallinity and the evolution of the hydrated layer. Chapter 4 proposes the use of gelatin microspheres to introduce concave macropores into the robocasted filaments of 3D CDHA scaffolds. Neither the phase transformation responsible for the hardening of the scaffold nor the formation of characteristic network of needle-like hydroxyapatite crystals was affected by the addition of gelatin microspheres. The partial dissolution of the gelatin resulted in the creation of spherical pores throughout the filaments and exposed on the surface, increasing filament porosity from 0.2% to 67.9%. Moreover, the presence of retained gelatin proved to have a very significant effect on the mechanical properties, reducing the strength but simultaneously giving the scaffolds an elastic behavior, despite the high content of ceramic as a continuous phase. Notwithstanding the inherent difficulty of in vitro cultures with this highly reactive material, the presence of retained gelatin in the scaffolds was shown to favor the proliferation of MG-63 cells, as well as the spreading of hMSCs. |
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