Scanning force microscope and force spectroscope

• Subject Area: Statistical Physics, Nonlinear Dynamics, Complex Systems, Soft and Fluid Matter, Biological Physics
• Term: Funded in 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 449375068

A comprehensive understanding of the initial processes of microbial biofilm formation is the major goal of our research. Specifically, we aim to understand cell adhesion in combination with protein adsorption in many different situations. We are particularly interested in the oral cavity or specific sites of infection in the body. The expertise of the participating research groups, (bio-) physics, medical microbiology and dentistry, allows us to study the phenomenon literally "from bench to bedside and back": For example, force spectroscopy with a single, living bacterium can be used to determine its adhesion to different materials and in different environments (e.g. in contact with saliva or blood). The material spectrum ranges from precisely characterized model surfaces to clinical implants, some of which have already been implanted in the human body. Different types of bacteria/yeasts can be investigated from the pathogen side. For individual species we have access to wild types as well as genetically specifically modified bacteria. However, we do not only want to determine the adhesive force, but also record detailed force-distance curves using individual bacterial probes, as these curves allow deeper insights into the nature of the interactions, the number of interacting molecules, their length and stiffness, and the size of the area with which the bacterium comes into contact with the surface.The atomic force microscope setup applied for here is also intended to answer new questions that could not be dealt with with the existing devices so far, e.g. because the signal/noise ratio is an order of magnitude higher than with current devices, the movement in the Z-axis is too restricted, or because no suitable optical control is available. For example, we would like to elucidate why individual bacteria of the identical cell population sometimes exhibit very large differences in their adhesion behavior. The hypothesis is that the newly synthesized areas after cell division differ from older cell wall areas in terms of adhesion. Since it is possible to differentiate age by fluorescent labelling, a fluorescence microscope has also been applied for. The extended working range of the proposed setup in the Z-axis also enables us to record force-distance curves by single cell force spectroscopy even on rougher surfaces such as cell culture monolayers, tissue samples or authentic biofilms generated on implants in the host or animal model.Since the device applied for can also scan faster than the devices available to us (at very low contact forces), it will also enable us to investigate protein aggregation, material transport using vesicles of proteins or the diffusivity of molecules through or in membranes. For the latter, a microfluidics platform is to be developed that can be built into the atomic force microscope, so that membranes and vesicles can be formed and immediately characterized there.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Rasterkraftmikroskop und -spektroskop
• Instrumentation Group: 5091 Rasterkraft-Mikroskope
• Applicant Institution: Universität des Saarlandes
• Leader: Professorin Dr. Karin Jacobs