Project Details
Projekt
Energetic investigations of induced particle uptake in functionalized, synthetic membrane systems.
Subject Area
Biophysics
Term
from 2015 to 2019
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 280366404
Living cells take up bacteria into their interior typically by phagocytosis, if both mechano-chemical signals and the required energy can be summoned up. In particular, macrophages, as part of our immune system, take up bacteria, but also uncoated particles, which is only possible by the interplay of different biophysical forces. For a better analysis of the relevant forces and to better assess the role of known factors during phagocytosis, a possible approach is to use biomimetic systems, which show a significantly reduced complexity relative to a cell. The simplest biomimetic variant of the cell is a giant unilamellar vesicle (GUV), where the chemical and mechanical properties of the spherical lipid bilayer can be manipulated in many different ways. In order to engulf and uptake a particle, the membrane of the GUV has to be deformed significantly. In a recent study it could be shown that the adhesion energy released during particle binding and wrapping can compensate the energy costs for membrane deformation and that cytoskeleton forces were dispensable. The goal of the collaborative proposal of the working groups Rohrbach and Römer is to better understand the physical mechanisms of particle uptake, in particular the role of the membrane deformation. In this context, we want to establish two complementary measurement techniques allowing to determine the energetics during particle uptake into an artificial cell (GUV). By using a photonic force microscope for small and medium uptake forces and an atomic force microscope for medium and larger forces, a particle will be approached in a controlled manner to the membrane, while the particle displacements are measured precisely to determine the changes in force and energy. In a bottom-up approach we will add stepwise more complexity to the biomimetic system, such that the force and energy profiles during particle uptake are measured always with exactly the same experimental scheme. On the one hand the complexity of the system can be increased by adding different lipids and receptors into the GUV membrane, on the other hand the size, the shape / orientation and the surface functionalization of the particle will be changed in a well-controlled manner. Mathematical modelling will help to improve the mechanistic understanding during particle uptake and to better interpret the experimental data.
DFG Programme
Research Grants
