ToF-SIMS imaging and depth profiling of HeLa cells treated with bromodeoxyuridine

Time-of-flight (ToF) SIMS 2D images and molecular depth profiles of human HeLa cells treated with bromodeoxyuridine (BrdU) were acquired in the dual beammode (Bi-3(+) analysis beam, C-60(+) etching beam). Several preparation protocols were investigated and were compared to a simple wash-and-dry method. The feasibility of using C-60 to clean the samples prior to imaging with Bi was also investigated quantitatively by calibrating full depth profiles of the cells using atomic force microscopy. BrdU was used as a marker for the cell nucleus, facilitating identification and localization of subcellular features during depth profiling. Results show that C-60 can be used to remove the surface contamination and to access different layers within the cells for 2D imaging. For a 1 nA, 10 keV C-60(+) beam incident at 45 degrees. and rastered over a 500 x 500 mu m(2) area, similar to 1 nm of biological material was sputtered every second. Our results show that HeLa cells were completely removed after etching with 1.3 x 10(15) C-60(+) ions per cm(2), giving an average etching rate of 3.9 nm for every 10(13) C-60 per cm(2) at 10 keV and 45 degrees. incidence. Copyright (C) 2010 John Wiley & Sons, Ltd.