Projects

The binding of particles such as bacteria, viruses or debris to living cells and the possible uptake into the cell interior – phagocytosis – represent central processes in cell biology and immunology. The observation of such binding and uptake processes, which usually occur stepwise, is usually limited by the spatial and temporal resolution of light microscopes. Despite modern fluorescence techniques, fluctuation based processes, such as the (re-)organization of molecular bonds can hardly be observed or analyzed. The measurement of e.g. binding strength is not possible at all. Therefore, many partial processes like binding, particle transport or active engulfment into the cell body are not sufficiently understood, especially not regarding the cell mechanics. The smaller the particle or the cellular structure, the faster are their movements. Many processes occur on scales of nanometers and milliseconds, which are not addressable by most optical methods especially for living cells. Using the established technique of Photonic Force Microscopy, various interaction processes between particle and living cells shall be induced and then controlled variably in space and time. Binding, particle transport at the surface and the actual uptake consist of many, multi-scale processes (10^-9 to 10^-5 meters and 10^-5 to 10^2 seconds) and can be better understood, if measuring and analyzing these processes is possible on a large temporal and spatial bandwidth. This shall be accomplished by using fast, coherent, i.e. label-free methods such as interferometric 3D particle tracking (at 1 MHz sampling rate) or the recently developed live-cell super-resolution microscopy method, based on rotating coherent scattered (ROCS) light enabling a sampling rate of more than 100 Hz. On the other side, also fluorescence-based methods shall be used, such as confocal spinning disc scanning, which we want to extend by an electro-optical tunable lens to enable fast acquisition of 3D image stacks.