Atomic Force Microscopy of the Cell

Abstract

An atomic force microscope (AFM) enables to describe the surface structure by tracing the sample surface with a probe (needle) even in water. Its resolution is almost equivalent to that of an electron microscope. Therefore, it is expected that the motility of cell surfaces can be viewed at living state in culture medium. However, in practice, we had to wait for the development of today’s high-speed AFM, because the probe had to scan several micron squares faster than the movement of the cell surface for detecting the surface structure in detail. The AFM used (Olympus BIXAM) captures an area of 6 μm × 4 μm at a rate of 1 frame/10 seconds. Although it is not necessarily fast, the movements of lamellipodia extending from the cell surface and actin filaments beneath the cell membrane were clearly detected. On the other hand, application of unroofing method and cryo-sectioning method to AFM sample preparation made it possible for the first time to observe the intracellular structure in water by AFM.