3D bioprinting in liquid medium for the bioengineering of hybrid structures for regeneration of human tissues

• Autor(a) principal: Sousa, Liliana Raquel Coelho
• 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/10773/25645
• topic: Tissue engineering; 3D printing; Hydrogels; Xanthan gum

Regenerative medicine and tissue engineering have emerged as alternative methodologies for the replacement of injured tissues or organs. This new approach combines the use of natural or synthetic materials with cells in order to produce a fabric that has the same structure and functionality as the original. Different bioprinting techniques have been used to produce hydrogel structures containing cells. However, such approaches have been limited to simple 2D or three-dimensional structures (3D), since the manufacture of more complex hydrogel structures, such as branched-out blood vessels, requires a support bath in order to prevent collapse of the during the printing process. This work is based on the development of a bath with rheological properties suitable for the processing of complex hydrogel structures by 3D layer-by-layer printing. On the other hand, it is also intended that this the same bath can be photo-cross-linked after printing of the structures so that hydrogels, cross-linked by reversible processes, can be easily removed from the hydrogel bath to form perforated constructions equally attractive for the regeneration of tissues and organs since they ensure controlled transport of nutrients and oxygen. Xanthan gum has excellent rheological properties, is biocompatible and easily chemically modified by the diversity of functional groups that it presents. Thus, 3D printing of complex asymmetric structures based on alginate hydrogels in viscous solution of xanthan gum was carried out. The alginate crosslinked rapidly in the xanthan gum bath by the presence of calcium chloride, getting deposited layer to layer without causing entrainment of the lower layers, collapsing or dispersing in the bath. After printing, we were able to remove an artery with asymmetric branches and inject colored solution in each of the branches, demonstrating the successful manufacture of a complex and perforated branched network. It was also evaluated the biocompatibility of the bath by printing alginate filaments with L929 cells, after which, after 7 days in culture, high cell viability with formation of cell aggregates was observed. For the formation of a hydrogel bath, I proceeded to the chemical modification of xanthan gum incorporating in the secondary polymer chain methacrylic groups, photopolymerizable by the action of UV light. 3D printing of a tortuous alginate filament in a methacrylated xanthan gum bath followed by the bath photoreticulation process proved the possibility of combining 2 hydrogels in a single device. In addition, removal of the alginate hydrogel by EDTA lavage demonstrated the high chemical and structural stability of the xanthan gum hydrogel for the formation of perforated devices. In short, a biocompatible and easy-to-process bath has been developed successfully for 3D printing processes aimed at a variability of biomedical applications.