APPLICATION OF ATOMIC-FORCE MICROSCOPY TO ULTRASTRUCTURAL AND HISTOCHEMICAL-STUDIES OF FIXED AND EMBEDDED CELLS

Various methods of sample preparation were used to study the cellular ultrastructure with an atomic force microscope (AFM), A rather satisfa ctory fine structure of cellular cross section, that was comparable to low to medium magnification electron micrographs, was obtained when u ltrathin sections of epoxy embedded materials cut with a diamond knife were examined by use of a non-contact mode. No surface treatment was necessary to image the surface contour of ultrathin sections, Accordin g to this method, cellular membranes appeared as an elevation in contr ast to depression of the intercellular space and cytoplasm, The chroma tin and nucleolus showed an elevated image against the depression of n ucleoplasm, resulting in the formation of images comparable to those o btained by conventional transmission electron microscopy, In the secti on treated for; post-embedding immunohistochemical reaction, colloidal gold particles larger than 10-15 nm in diameter could be detected as elevations, By means of Kelvin force probe microscopy (KFM), enhanceme nt of the surface potential was detected at exactly the same location as topographically detected gold particles, Application of KFM is expe cted to become a valuable tool for novel histochemistry with the use o f AFM.