Abstract

While most current biological research focuses on molecular aspects of cells, we are interested in their global physical – mechanical and optical – properties. The mechanical properties of cells are largely determined by the cytoskeleton, an internal hybrid polymer network. This cytoskeleton evolves during the normal differentiation of cells, is involved in many cellular functions, and is characteristically altered in many diseases, including cancer. We can exploit the deformability of the cytoskeleton as a link between molecular structure and biological function to distinguish between different cells using a microfluidic optical stretcher. We find that optical deformability is sensitive enough to monitor the subtle changes during the progression of cells from normal to cancerous and even metastatic state. We can also distinguish stem cells from more differentiated cells. In both cases, their mechanical properties are tuned to the specific requirements imposed on the cells by physical constraints. Further research focuses on the interplay between cell and tissue mechanics for an improved understanding of axonal pathfinding during development and novel therapeutic approaches in traumatic injuries to the CNS and neurodegenerative diseases. Another example for the importance of physics are the optical properties of cells, specifically in the retina. We have recently shown that there are glial cells in the retina that act as optical fibers and that photoreceptor cells even invert their usual nuclear chromatin arrangement to turn them into microlenses. In both cases cells utilize physics in order to improve the light transmission through the retina and help to mitigate the disadvantage of its inverted structure.