Mechanobiology

Cells are dynamic systems packed with force-generating machines. From adhesion, migration and cell division to molecular processes, everything is linked to force generation and binding between molecules. AFMs can quantify these at the cellular and molecular level with micro to nanoscale spatial resolution, providing a deeper understanding of how living systems utilize forces.

AFM force measurements encompass a wide range of complexities depending on the imaging conditions (dry vs. liquid), mode (non-vibrating or vibrating), and the forces to be measured. Stiffness measurements combine accurate force measurements with scanning in liquids. Measurements of interaction forces such as antibody-antigen require one binding partner to be attached to the tip typically using biochemical crosslinking strategies.¹ Other applications extend from force measurements of bacterial cell adhesion² to the stretching of individual collagen fibrils.³

Mechanobiology experiments use the direct interaction of the AFM tip with the sample surface and the spring constant of the cantilever to measure forces. pressing the tip onto the sample surface bends the cantilever and causes a deflection of the laser spot on the photodetector. This signal difference can be converted to a force-distance curve (force applied per distance approached) using the spring constant k [N/m] (how much force is required to bend the cantilever a certain distance). The recording of a force-distance curve is straightforward using the included software.⁴ The interpretation of the data on the other hand can be more complex, as it needs to take into account several parameters of the probe and sample.⁵

AFMWorkshop AFMs have been used for force-distance measurements of yeast cell clusters⁶, cardiomyocytes⁷, tumor cells⁸, and aorta tissue⁹.

There are almost unlimited variations of AFM experiments for which supply two AFM setups depending on the application.

The HR-AFM is a sample scanning AFM, where the sample moves on XYZ piezoelectric elements. This system differentiates itself by a very low noise floor of <35 pm and is ideal for imaging very small features such as molecules, either dry or in liquid at room temperature. The HR-AFM uses a video tube microscope and light reflected from the sample surface to identify areas of interest and can be equipped with a dunk and scan probe holder for measurements in liquids under ambient conditions.

The LS-AFM is a tip scanning AFM, where the tip moves on XYZ piezoelectric elements. This system is typically mounted on an inverted light microscope (bright field and fluorescence correlation) and is ideal for imaging live systems such cells in liquid using a heated stage. The LS-AFM can also be purchased separately and integrated with other laboratory instruments.