Cells Embedded in Cytoskeleton Composites for Living Materials*

The cytoskeleton is a network of interconnected polymers that underlies many mechanical processes of cells including cell division, motility, signaling, and growth. The cytoskeleton's adaptability stems from the mechanical properties of its biopolymers, including rigid microtubules and semiflexible actin filaments. However, how the presence of organelles and vesicles in the cytoskeleton impacts its structure and mechanics has so far been largely overlooked. Moreover, understanding how cells embedded in fibrous scaffolds are spatially distributed, and how they modify the scaffold structure and mechanics is critical to engineering tissue and living materials. Here, we examine the spatial distribution of embedded cells in networks of actin and microtubules; and, in turn, the impact of the embedded cells on the network structure. Using multi-spectral confocal microscopy and spatial image autocorrelation we quantify the characteristic structural correlation length-scales of both the cells and the filamentous network and map the relationship between cell concentration, filament rigidity, and network mesh size. Our preliminary results suggest that both rigidity and mesh size play important roles in the spatial distribution of cells; and that a non-monotonic dependence of network connectivity on cell density emerges at intermediate cell densities. Our future work will investigate how the presence of the network influences cell growth, which is critical to tissue regeneration technologies, and relevant to cell growth in the extracellular matrix.