Scanning Near-field Optical Microscope: a Method for Investigating Chromosomes

Karyotypes of human metaphase chromosomes are used to detect genetic defects like deletions or translocations. For these investigations the chromosomes are treated by the trypsin‐Giemsa protocol, resulting in a typical banding pattern. These patterns are investigated using conventional light microscopy. Because of the diffraction limit, even the smallest visible band contains 1 million base pairs. We want to improve resolution by using bright‐field scanning near‐field optical microscopy (SNOM). Images of trypsin‐Giemsa‐treated chromosomes are presented and compared with conventional light microscopic, scanning force and scanning fluorescence near‐field optical microscopic data. For fluorescence investigations, the chromosomes were stained using propidium iodide. To our knowledge, it is the first attempt to investigate G‐banded chromosomes by SNOM.© 1997 John Wiley & Sons, Ltd.