Atomic force microscopy

Atomic force microscopy (AFM) is a process for the mechanical scanning of surfaces.

Single molecules (proteins, DNA), membranes, cells and tissues can be examined. Living cells are measured in physiological buffers at 37 ° C. Fixed samples can also be measured.

IMAGING Here a fine needle with a precisely defined vertical force is guided over the surface in a grid pattern. The resulting x-y-z data is merged into a 3D image. Depending on the sample and the measuring tip, the lateral and vertical resolution extends into the sub-nanometer range (nm = 10^-9 meters).

FORCE SPECTROSCOPY In addition to the image, atomic force microscopy is used to apply and measure forces in the piconewton range (pN; 10^-12 Newton). In this way, atomic force microscopy enables the biomechanical characterization of the matrix, cells and tissue.

SINGLE CELL FORCE SPECTROSCOPY (SCFS) The SCFS is a special form of force spectroscopy in which the adhesive forces between two cells, or between cell and matrix, are quantified.

QUANTITATIVE NANOMECHANICAL IMAGING Quantitative nanomechanical imaging represents a combination of imaging and force spectroscopy. As with imaging, a measuring probe is scanned over the surface in a grid-like manner, but here the surface is calculated from the data by the force spectroscopy carried out in defined positions. In addition, biomechanical parameters (elasticity, adhesion, deformation, dissipation) are also recorded. In addition to the surface image, up to 7 different data records are created from a scan.

DYNAMIC MEASUREMENTS The dynamics of cellular systems are recorded and quantified by repeated measurements (imaging, force spectroscopy, SCFS). Paired experiments can be carried out, since the addition of agents or solution exchange during the measurement is possible.

CORRELATIVE MEASUREMENTS Three AFMs from the technology platform are combined with fluorescence microscopes so that specifically marked cells and areas can be examined (e.g. cytoskeletal structures in cells during the application of force).

The following devices are used:

>Bioscope Catalyst (Bruker), coupled with inverted fluorescence microscope (Leica)

>Nanowizard III (JPK), coupled with light microscope (Zeiss) or confocal microscope (Leica)

> Three Multimodes (Bruker)

>CellHesion 200 (JPK), coupled with fluorescence microscope (Zeiss)