Friday 28 January; Leiden, Holger Kress "Optical control of the mechanical and chemical microenvironment of living cells"



Joan van der Waals Colloquium
Time: 16.00 - 17.00 hrs

Location: Sitterzaal, Oortgebouw

Living cells routinely exert mechanical forces to fulfill their tasks. Immune cells for example migrate through tissue and internalize extracellular objects. Over the last decades, molecular and cellular biology were successful in identifying a large number of molecules that are involved in cell migration and phagocytosis, which is the internalization and degradation of extracellular objects. However the mechanical properties of these important processes and their interplay with biochemical cell signaling are just beginning to be unraveled. To investigate the interplay of mechanics
and signaling on a single cell level, tools are required to control the mechanical and chemical microenvironment of cells. We are using optical trapping techniques to study cell mechanics on a sub-cellular level. Optical tweezers allow us to apply well defined forces locally to selected cell locations while simultaneous live cell imaging enables us to monitor the subsequent cellular responses. As an example for this approach, I will
present a study on the cell mechanics of phagocytosis. We found that thin membrane protrusions of immune cells act as tentacles which catch extracellular objects and we characterized the mechanical properties of this behavior. In addition, I will present a recently developed method to create flexible molecular concentration patterns around single cells. Our strategy uses optically manipulated microsources, which steadily release molecules. This technique enables the control of molecular concentrations over length
scales down to onemicrometer and timescales from fractions of a second to an hour. We demonstrate this technique by manipulating the migration of single human immune cells. We expect that the large spatial, temporal and chemical flexibility of this method makes it applicable to a broad range of interdisciplinary research areas, where it is of interest to stimulate single cells or developing organisms locally with specific molecules.