Biomimetic Structuring of Silicones for Cell Control and Strain-Stiffening

In the first part of this thesis research, an artificial extra-cellular matrix formed the basis for experiments with a pathogenic species of amoeba, Acanthamoeba castellanii. In order to find new therapeutic approaches to fighting diseases caused by this species, the migratory behavior of Acanthamoeba castellanii in micro-pillar structures made of silicone, which were used to mimic the confined environment of an extra-cellular matrix, was explored. For the experiments, amoebae ingested microparticles of varying shapes. While it was found that sphere-shaped particles with a diameter smaller than the distance between the micro-pillars did not impact migration behavior, absorption of larger particles by Acanthamoeba castellanii caused migration to be strongly reduced. However, in some instances, it appeared that Acanthamoeba castellanii was nonetheless able to successfully navigate the pillar structures. These observations could serve as a basis for developing methods aimed at capturing amoebae before they can enter the human body. In the second part of this thesis, the focus was on developing a material with specific mechanical properties geared at mimicking an intra-cellular effect, namely the cross-linking of fibers within the cytoskeleton as a reaction to deformation of the cell and thereby increasing its stiffness. Emulating this effect, a strain-stiffening material was developed using a flexible, slat-structured silicone. When the material is elongated, these slats touch, thereby leading to a stiffening of the material. Employing finite element analysis, the degree to which various geometrical factors of the structure and friction between the slats affect the material’s stiffening behavior was examined, and the results were verified using tensile tests. The structure that resulted from my efforts yields a stiffening behavior that is material-independent, speed-independent and reversible, and that occurs also when the material is elongated.