Biophysical methods to quantify mechanics, shapes and forces

• Applicant: Professor Dr. Jochen Guck (†)
• Subject Area: Statistical Physics, Nonlinear Dynamics, Complex Systems, Soft and Fluid Matter, Biological Physics ; Biophysics
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 492010287

Biophysical properties are becoming increasingly important in many biology branches: from cells to tissues up to the organism level, the mechanical properties of the physical environment are perceived and translated into biochemical responses eventually leading to a change in the phenotype of biological systems. During their life cycle, parasites face the most challenging environmental conditions and they evolve a wide range of mechanisms to adapt to them: changes in the body shape, surface properties like adhesion, mechanical properties, motility modes and metabolism. Developing tools to quantify these properties is essential to elucidate the complex mechanisms underlying the physics of parasitism. The present Z-project provides a toolset of advanced biophysical methods for the other experimental projects within this SPP. During this first period, the “Biophysical Methods Workshop” in Erlangen was organized to inform the collaborators about the physical methods available at our institute and to show the working principles through theoretical and practical sessions. This step was essential to increase the collaboration network between the different projects. From this event, many collaborative projects were established and first rounds of measurements were performed. The methods available, and the respective results obtained, include: (1) Atomic force microscopy-enabled nanoindentation was used to characterize the surface mechanical properties (adhesion and stiffness) of Nematodes and Platyhelminthes. The surface features of these parasites and their mechanical properties are crucial for their locomotion and attachment mechanisms. (2) Brillouin microscopy was used to investigate the differences in the mechanics of the ventral disc of Giardia duodenalis showing different values of viscoelastic properties for knock-out mutants of different disc proteins compared to the wild type. The same technique was used for the analysis of the viscoelastic properties of a Toxoplasma gondii-infected dendritic cell and a nematode, Heligmosomoides polygirus. (3) Optical diffraction tomography allowed to obtain 3D maps of the sample mass density and to detect changes in the volume and the dry mass of different Giardia mutants and genotypes. This technique was also used for the study of Trypanosoma and Toxoplasma infected dendritic cells. (4) Hydrogel beads with well-defined mechanical properties (elastic modulus 0.5 – 15 kPa) and size (diameter 8 – 25 µm) were used for different purposes by many collaborators. In the coming funding period, these projects will be continued and elaborated, and new collaborative projects started. We will also establish several new techniques in response to specific needs, such as line-scanning Brillouin microscopy, Raman microscopy, and Optical Coherence Elastography. Together we are providing the first quantification of parasite mechanical properties and shapes, based on now established protocols and experimental procedures.

• DFG Programme: Priority Programmes
• Subproject of: SPP 2332: Physics of Parasitism