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 similar to 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. (C) 1997 by John Wiley & Sons, Ltd.