Introduction to Turku BioImaging key technologies (see the Turku BioImaging Black Book for more information).

Atomic Force Microscopy

Atomic Force Microscopy (AFM) is a mechanical microscopy technique, where images from biological samples can be obtained at atomic resolution, and forces between individual molecules or cells can be quantitatively measured.

The principle of AFM is similar to an old-fashioned record turntable: a sharp tip attached to a flexible spring-like cantilever mechanically senses the force between the tip and the sample. Such forces cause the cantilever to bend, and the deflection is measured using a laser beam reflected from the cantilever. The tip is atomically sharp, so, in principle, a force between two single atoms can be measured. In biological AFM, an optical microscope is often additionally employed to adjust the system and to choose the sample area to be studied. The AFM can be operated in liquid and under physiological conditions, making it possible to study living biological specimens such as cells. The technique is label-free, making sample preparation straightforward. In addition to high-resolution images (AFM imaging) quantitative force measurements (AFM force spectroscopy) are possible using the same device.

AFM imaging is suitable when the resolution of optical microscopy is not sufficient, when a sample needs to be imaged under native physiological conditions, or when the type of sample preparation required for electron microscopy is not possible. AFM is primarily used to obtain surface topography images. AFM force spectroscopy is a good choice when binding forces and dynamics between molecules such as receptors and ligands, or between cells and a substrate, need to be determined. AFM can also be used to manipulate objects with high precision, for example to study the effects of specific mechanical stimuli on cells. Turku BioImaging offers several atomic force microscopes, which can be used simultaneously with advanced light microscopic techniques, such as confocal microscopy and STED superresolution microscopy.