Supervisor: Francesca Serra
Project description
Many types of living cells are not round but have a spindle-like shape. When they are grown at high density, they align with the neighboring cells. In this, their behavior is similar to that of liquid crystals, complex fluids commonly found in displays. It is hypothesized that cell alignment affects the patterns of cell migration and the cell-cell communication. In well-aligned cell layers (or in liquid crystals) one can define an average direction, described as a vector called the nematic director. However, there can be many situations where a uniform alignment of cells everywhere is impossible. In these scenarios the cells form “topological defects”, small regions where the order is disrupted and the cells’ orientation is not uniform. Topological defects are ubiquitous in physics, from superconductors to cosmic strings. There is increasing evidence that these defects play a key role also in the organization of cell layers and of tissues, for example in tumors, and for tissue morphogenesis.
In my lab, we can impose distortions or defects by changing the shape of the substrates, for example by patterning small ridges that help guide the cells. We want to ask the questions: what type of alignments do cells achieve when they walk on a substrate that has many curves and bumps? How are defects connected to the curvature of the substrate? How does surface treatment affect the behavior? These questions are fundamental both for physics and biology. In physics, because we study topological defects in dynamic out-of-equilibrium systems, and in biology because we use liquid crystals for a better understanding of cells' organization in tissues.
The projects will involve fabricating the patterned substrates starting from a template (PDMS soft lithography) or with 3D printing, observing cells with optical microscopy and fluorescence microscopy and analyzing the data with available programs in ImageJ and Matlab. Examples of specific projects are: 1) Fabricating samples with "inflatable" bumps and analyzing the topological defects formed by cells on them; 2) Analyzing datasets of cells grown under different condition and extracting their liquid crystal order and topological defect arrangement; 3) Setting up a system for liquid crystal photo-alignment using polarized light.