Magnesium-based bioresorbable cellular metal as bone substitute

The design and development of an osteoinductive environment to reconstruct and treat large bone defects is still a challenge. Biodegradable porous metals have been proposed to bridge healthy parts of the tissue when the lesion overcomes the bone self-healing capacity. Mg-based scaffolds promise to a...

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Autores:: Posada Pérez, Viviana Marcela

Tipo de recurso:: Doctoral thesis

Fecha de publicación:: 2021

Institución:: Universidad Nacional de Colombia

Repositorio:: Universidad Nacional de Colombia

Idioma:: eng

Description
Summary:	The design and development of an osteoinductive environment to reconstruct and treat large bone defects is still a challenge. Biodegradable porous metals have been proposed to bridge healthy parts of the tissue when the lesion overcomes the bone self-healing capacity. Mg-based scaffolds promise to assist in this bridging process, providing the mechanical properties and adapting to the new requirements such as weight and geometry as the healing time advances. Moreover, the porous condition guides the tissue and blood vessels' growth, and the release of Mg2+ accelerates the healing process. However, the Mg support is limited by its rapid degradation, which hinders the appropriate integration with the tissue. Additionally, the degradation is again accelerated in the porous condition, and the complex geometry limits the application of current protection methods. The present thesis aims to create an open-porous Mg-based scaffold for bone tissue engineering, focused on enhanced corrosion resistance and biocompatibility. Porous Mg materials were then fabricated in various geometrical configurations: random pores, truncated octahedron, and diamond unit cells. The control over the degradation of the material was achieved by modifying the first nanometers of the surface, avoiding changes in the architecture of the structures, and preserving the bulk properties of the material such as open porosity and lightweight. The nanometric modification was created via low-energy Ar+ irradiation, which developed well-ordered nanostructures on the surface, followed by Al-rich nanoclusters' accumulation. The creation of the Al-rich nanoclusters accelerated the passivation kinetics of the porous Mg, enhancing the apatite nucleation ability when immersing the materials in physiological fluids. Moreover, the apatite formation ability was conditioned to the concentration of Al on the near-surface, which offered surfaces for different biological purposes by tailoring the CaP ratio. Superior properties regarding in vitro biodegradation and biocompatibility were obtained on hydroxylapatite tailored surfaces, such as decreased weight loss, conservation of the strut size during the immersion time, and decreased H2 and Mg2+ release. Furthermore, higher cell density was adhered to and proliferated on the DPNS surfaces indicating outstanding biocompatibility. The increase in biocompatibility was also supported by the formation of focal adhesion points and increased osteogenic potential, and the immune response modulation of the cells seeded on the modified surfaces. Finally, the material was tested in vivo, demonstrating steady corrosion and improved porous structure stability after 8 weeks of implantation in Wistar rats.

Magnesium-based bioresorbable cellular metal as bone substitute

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