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[EN] Fifty years after the first human landed on the Moon mankind has started to plan the next steps for manned space exploration missions. When the time required to return to Earth exceeds 400-500 days (as in travels to Mars), the level of independence that the crew must possess is highly increased. To ensure the survival and good living conditions of this future explorers, new developments regarding medical infrastructure and resources must be carried out. In this work, the topic of this study was to investigate how 3D printing and bioprinting can be of use to improve the autonomy of the crew when facing the most probable clinical scenarios that can occur in long-term space exploratory missions. The printing parameters of thermoplastics, such as polycaprolactone (PCL), that can be used as a possible support material along bioprinting were studied, including the use or not of alternate layers or the printing starting point. For bioprinting, and taking bone constructs as the tissue of study, a new bioink based on human plasma (which potentially could be derived from the injured astronaut who needs the treatment), alginate, and methylcellulose (that can be grow and used in isolated areas) was designed. An inverted bioprinter was designed and built to be able to test the work capacity of this biomaterial in altered gravity conditions. As result, it was observed that the use of alternated layers involves the generation of more anisotropic structures, as the z-axis pore is limited to the layer height, while the x and y-pore size can be tailored to specific needs. The defects created because of the alignment, or the lack of it, at the new layer starting point, significantly affects the mechanical behavior of the scaffolds. ix The cooling down rate, or even printing speed, can be modified to obtain more chaotic micropatterns including nanofibers without the need of using further technologies. A plasma-based bioink was successfully designed and combined with hydroxyapatite-forming CPC which resembles the native mineral phase of bone. The results have shown that the plasma-based bioink and CPC form a synergistic system supporting adhesion, proliferation, and osteogenic differentiation of bone cells. Thanks to the inverted bioprinter, it has been demonstrated that the developed bioinks and support materials, like CPC, are suitable for extrusion (bio)printing. They are so adhesive that they can even be printed upside-down and therefore, against Earth’s gravity. Therefore, they could be used at altered gravity conditions on space exploration missions., [ES] Cincuenta años después de que el primer ser humano aterrizara en la Luna, la humanidad ha comenzado a planificar los próximos pasos para las misiones de exploración espacial tripuladas. Cuando el tiempo necesario para regresar a la Tierra supera los 400 - 500 días (como en los viajes a Marte), el nivel de independencia que debe poseer la tripulación aumenta considerablemente. Para garantizar la supervivencia y las buenas condiciones de vida de estos futuros exploradores, se deben realizar nuevos desarrollos en cuanto a infraestructuras y recursos médicos. En este trabajo, se estudió cómo la impresión 3D y la bioimpresión pueden ser de utilidad para mejorar la autonomía de la tripulación ante los escenarios clínicos más probables que pueden ocurrir en misiones de larga duración. Para ello se estudiaron algunos parámetros de impresión de termoplásticos, como la policaprolactona (PCL), que pueden utilizarse x como posible material de soporte a lo largo de la bioimpresión (ejemplo de parámetros: uso o no de capas alternas o la alineación del punto de partida de la impresión en cada capa). Para la bioimpresión, y tomando las construcciones óseas como tejido de estudio, se diseñó un nuevo material compuesto a base de plasma humano (que puede ser obtenido de los astronautas), alginato y metilcelulosa (que se puede obtener y utilizar en áreas aisladas). Se diseñó y construyó una bioimpresora invertida para poder probar la capacidad de trabajo de este biomaterial en condiciones de gravedad alterada. Como resultado se obtuvo que el uso de capas alternas implica la generación de más estructuras anisotrópicas, ya que normalmente el poro del eje z está limitado a la altura de la capa, mientras que el tamaño de los poros x e y se pueden adaptar a necesidades especıificas. Los defectos creados por la alineación, o la falta de ella, en el punto de inicio de la nueva capa, afectan significativamente al comportamiento mecánico de los andamios. La velocidad de enfriamiento, o incluso la velocidad de impresión, se puede modificar para obtener micropatrones más caóticos, incluso nanofibras, sin necesidad de utilizar tecnologías adicionales. Se diseñó con éxito una biotinta a base de plasma y se combinó con un cemento de fosfato cálcico formador de hidroxiapatita, que se asemeja al mineral nativo del hueso. Nuestros resultados mostraron que la deposición combinada de la biotinta basada en plasma y la pasta de CPC para dar lugar a constructos celularizados, forman un sistema sinérgico que apoya la adhesión, la proliferación y la diferenciación osteogénica de las células óseas. Gracias a la bioimpresora invertida desarrollada, se ha podido demostrar que la biotinta desarrollada y los materiales de soporte, como el cemento óseo de fosfato cálcico autoajustable, son aptos para la (bio)impresión extrusión. Son tan adhesivos que incluso se pueden imprimir al revés y, por lo tanto, contra la gravedad de la Tierra, pudiendo usarse en condiciones de gravedad alterada., DAAD Research Grant. Program: Short-Term Grants, 2018 (57378443). – Project "3D Printing of Living Tissue for Space Exploration" funded from the European Space Agency (ESA). Funds came them partially by the University of Dresden via a contract (No. 4000123640/17/NL/BJ/gp/TUD) of OHB System AG, Bremen and by OHB System AG itself, under a contract of the European Space Agency ESA (contract No. 4000123640/18/NL/BJ/gp). – "Low intensity ultrasounds for early detection and modulation of tumour and stroma". Convocatoria Proyecto Retos I+D+i 2017. AEI/FEDER: DPI2017-90147-R. Entidad financiadora: Agencia Estatal de Investigación, Ministerio de Economía, Industria y Competitividad, Gobierno de España.

The search of suitable combinations of stem cells, biomaterials and scaffolds manufacturing methods have become a major focus of research for bone engineering. The aim of this study was to test the potential of dental pulp stem cells to attach, proliferate, mineralize and differentiate on 3D printed polycaprolactone (PCL) scaffolds. A 100% pure Mw: 84,500 +- 1000 PCL was selected. 5 x 10 x 5 mm3 parallelepiped scaffolds were designed as a wood-pilled structure composed of 20 layers of 250 microm in height, in a non-alternate order ([0,0,0,90,90,90º]). 3D printing was made at 170 ºC. Swine dental pulp stem cells (DPSCs) were extracted from lower lateral incisors of swine and cultivated until the cells reached 80% confluence. The third passage was used for seeding on the scaffolds. Phenotype of cells was determined by flow Cytometry. Live and dead, Alamar blue™, von Kossa and alizarin red staining assays were performed. Scaffolds with 290 + 30 micron strand diameter, 938 x 80 micron pores in the axial direction and 689 x 13 micron pores in the lateral direction were manufactured. Together, cell viability tests, von Kossa and Alizarin red staining indicate the ability of the printed scaffolds to support DPSCs attachment, proliferation and enable differentiation followed by mineralization. The selected material-processing technique-cell line (PCL-3D printing-DPSCs) triplet can be though to be used for further modelling and preclinical experiments in bone engineering studies., Grant PAPIIT IA207420, UNAM, México and AEI/FEDER, UE (DPI2017-90147-R) Spain.