Microengineered conductive scaffolds for cell-based actuation

A functional 3D-engineered scaffold where cells are able to grow in vitro mimics the microstructural, mechanical, electrical and biochemical features of the cell's natural extracellular matrix (ECM) that is crucial for supporting numerous cell functions such as proliferation and growth. The scaffolds electrical conductivity and deformability are particularly essential for assorted cell types that rely on electrical signals to perform various cellular mechanical functions as in skeletal muscle cells contraction that transpire upon electrical stimulation. My thesis presents successful procedures for developing electrically-conductive, deformable 3D artificial cellular scaffolds that provide the deformability to accommodate muscle cell contraction and the electrical conductivity to enable cell-to-cell signalling, both of which are vital aspects in 3D cell tissue scaffolds and biohybrid robotics. I employed a novel microengineering approach based on a sacrificial template made from interconnected tetrapod-shaped zinc oxide micro particles with two state of the art methods that are based on (1) a hydrogel permeated with a filler material that renders it conductive and (2) a conductive polymer. The hydrogel system is based on polyacrylamide where the interconnected zinc oxide microchannels network is coated with an exfoliated graphene flakes dispersion that eventually creates a graphene framework structure and promotes an outstanding electrical conductivity using an extremely low filler concentration. This method imposes no significant impact on the hydrogel mechanical integrity and maintains the original matrix toughness and physicochemical properties, thus achieves versatile, conductive, microchannel-containing 3D scaffolds. Composites of polyacrylamide and a semi-synthetic gelatin methacryloyl hydrogel were also developed as a facile way of generating a biofunctional conductive scaffold that enhances and promotes skeletal muscle cells spreading and proliferation. Additionally, the suitability of non-contractile fibroblast cells for biohybrid actuators is analyzed and presented in a pioneering study. In the second microengineered system, I analyzed a 3D fibrous conductive scaffold based on a conductive poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) polymer that proved suitable for culturing contractile cells. The scaffolds exhibit four orders of magnitude greater specific conductivity than previously reported 3D PEDOT:PSS structures even after two weeks of storage in water in addition to demonstrating a substantial mechanical stability in an aqueous environment. Biofunctional studies with fibroblasts, skeletal muscle cells and cardiomyocytes derived from induced pluripotent stem cells cultured on biofunctionalized scaffolds were carried out in terms of cell adhesion, distribution, beating behavior and their scaffold deformation ability