Development of 3D bioprinting techniques based on supportive media
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The production of anatomically complex tissues and organs with high biological function requires bioinks to have contradictory material properties. Properties that enable bioinks to be mechanically self-sufficient and accurate in terms of geometric fidelity may not be inherently compatible for cell viability and vice versa. Such is the practical dilemma of bioprinting, leading to the development of bioinks with balanced mechanical and biological properties that do not excel in either respect. In this thesis, the development of a customised, modular, extrusion-based 3D bioprinter and two novel supportive bath strategies is described. This custom bioprinter is able to extrude low-concentration, low-viscosity bioinks deep into the developed support baths and suspend the extruded bioink in 3D space. Printing structures in this manner reduces the demand for mechanically strong bioinks during the fabrication process as the structure’s weight is supported by the bath in all dimensions. These supportive strategies enable the production of larger and geometrically more complex anatomical structures whilst using a low-concentration, low-viscosity alginate hydrogel bioink. Therefore the material’s mechanical needs for bioprinting are addressed in such a way that encourages the use of bioinks with qualities that can be biologically more favourable. The support baths detailed in this thesis includes a quiescently gelled gelatine-based approach and a fluidised-agar fluid gel approach. The gelatine baths are prepared in a very simple, reliable, and repeatable two-step manner, and printed structures embedded within the gel are removed gently and easily by utilising gelatine’s physiologically relevant melting temperature to liquefy the support. Blood vessel-like structures and noses were fabricated in this manner. Agar fluid gel support baths are also simple to produce and only require a gelled puck of agar be blended prior to its application as a supportive material. Agar fluid gel baths have been used successfully to support the fabrication of geometrically challenging structures such as bucky balls and Eiffel towers as well as replicate anatomical models such as ears, noses, brains, and hearts, which are easily separated from their supports by washing away the residual fluid gel.