Park AFM's True Non-Contact Mode Images Inner Side of Cell Membranes

Park Systems XE-Bio, the leading atomic force microscopy (AFM) system for cell biology imaging, was featured in the Journal of Electron Microscopy (October, 2012) in an article entitled “Use of the unroofing technique for atomic force microscopic imaging of the intra-cellular cytoskeleton under aqueous conditions.”  The article was the Editor’s Choice for the bimonthly journal and an image from the article taken by the Park XE-Bio (the cytoplasmic surface of the ventral cell membrane) was the journal’s cover image.

The article describes the research of Professor Jiro Usukura and his team at Nagoya University EcoTopia Science Institute (Japan). Using ultrasonication, the researchers unroofed a cell membrane (removed the top layer) to expose the inner side or cytoplasmic membrane. Once exposed, the Park XE-Bio atomic force microscope was able to image the very soft and high-resolution details of the underlying intracellular cytoskeleton and the cytoplasmic surface of the cell membrane. The XE-Bio can do this very delicate imaging, even in an aqueous environment, thanks to its True Non-Contact ModeTM where the tip of the AFM probe can collect extremely accurate imagery data without making contact with the surface of the sample. This mode preserves the physical integrity of the sample while extending the life of the AFM probe tip.

According to Usukura, “The measurement capabilities of Park XE-Bio and True Non-Contact ModeTM imaging in a more biologically relevant condition demonstrate that it is an important tool for imaging intracellular structures and cell surfaces in the native, aqueous state.”

With the XE-Bio images, the researchers were able to see the details of actin filaments that form a complex meshwork on the cytoplasmic surface of the membrane. Examining the filaments at higher magnification, they noted characteristic periodic striations of about 5 nm formed by the assembly of G-actin. They also detected microtubules, often tethered to the membrane surface by fine filaments. For the first time in a water environment, they were even able to see clathrin coats on the membrane. While electron micrographs of freeze-etched samples can yield somewhat higher resolution, the Park XE-Bio provides nanoscale images in the more biologically relevant – wet – state. This makes the atomic force microscopy of the XE-Bio an important tool for imaging intracellular structures and cell surfaces.

As Dr. Sang-joon Cho, Chief Scientist at Park Systems put it, “AFM has not yet been used for the intracellular measurement of membrane cytoskeletons in vivo. Professor Usukura and his team successfully imaged various types of intracellular actin filaments directly at higher resolution by using Park XE-Bio with unroofing techniques.  They enabled a new and important application of AFM in biology.” He noted that True Non-Contact ModeTM is ideal for imaging soft biological samples because it provides a method for measuring sample topography with minimal or no contact between the tip and the sample surface.

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