Bio-inspired 3D micro structuring of a liver lobule via direct laser writing: A comparative study with SU-8 and SUEX

Abstract

Real biological tissues show a great variety of different geometric morphologies with special features on different geometric scales. An interesting example is the liver lobule that is the basic subunit of a liver. The lobule is a quasihexagonal macroscopic structure with periodic like so-called sinusoidal elements with structural features on the micro- and macroscale made of proteins, cells, and fluids. Various tools from micromachining and nanotechnology have demonstrated their capabilities to construct micromorphologies precisely, but even the reconstruction of such a system in technical polymers is challenging. In this work, the rapidly evolving technique of multiphoton polymerization has been explored for the construction of a scaffold that mimics the micromorphology of the liver with high resolution and detail up to the millimeter scale. At the end, a highly complex fluidically perfusable structure was achieved and simulations showed that the occurring shear stress, fluid velocity, and stream lines are comparable to the native liver lobule. Hereby, the photoresists SU-8 and SUEX TDFS were compared in terms of their processability, achievable resolution, and suitability for the intended application. Our results have shown that SUEX needs lower writing velocities but is easier to process and achieves a considerable higher resolution than SU-8. The scaffold could provide a base frame with a geometrically defined morphology for hepatic cells to adhere to, which could act as a starting point for cells to build new liver tissue for further integration in more complex systems.