Soft X-ray imaging of living cells in water: flash contact soft X-ray microscope

摘要

Flash contact soft X-ray microscopy (FCSXRM) is an imaging technology for observing living cells in aqueous conditions with a spatial resolution of several tens of nm. The principle of soft X-ray imaging for living cells is carbon imaging, which provides us with a carbon-density-distribution map of the specimens. Carbon and oxygen have absorption edges in the soft X-ray wavelength range at 4.4 and 2.3 nm, respectively. Between these edges, the photoabsorption crosssection of carbon is about 10 times greater than that of oxygen. Thus, one can obtain soft X-ray images of living cells in water using this wavelength range.Laser-produced plasma is used as a flash X-ray source. A table-top FCSXRM, named FCSXRM ETL Mark 3, was developed in 1996 for convenient laboratory use of SXRM. The X-ray image of a specimen is recorded on a photoresist polymethyl methacrylate (PMMA) membrane supported on a silicon wafer. The X-ray image is then enlarged by an atomic force microscope (AFM). The practical resolution achieved by the system is about 40 nm, including the tip effect of the AFM. In this article, I discuss the possible roles of the FCSXRM for nanometer-scale imaging of living cells under physiological conditions. (C) 2004 Published by Elsevier B.V.