TOF-SIMS 3D imaging of native and non-native species within HeLa cells.

In this study, a non-native chemical species, bromodeoxyuridine (BrdU), was imaged within single HeLa cells using time-of-flight secondary ion mass spectrometry (TOF-SIMS). z-corrected 3D images were reconstructed that accurately portray the distribution of intracellular BrdU as well as other intracellular structures. The BrdU was localized to the nucleus of cells, whereas structures composed of CxHyOz(-) species were located in bundles on the periphery of cells. The CxHyOz(-) subcellular features had a spatial resolution at or slightly below a micrometer (900 nm), as defined by the distance between the 16% and 84% intensities in a line scan across the edge of the features. Additionally, important parameters influencing the quality of the HeLa cell 3D images were investigated. Atomic force microscopy measurements revealed that the HeLa cells were sputtered at a rate of approximately 4 nm per 10(13) C60(+) ions/cm(2) at 10 keV and a 45° incident angle. Optimal 3D images were acquired using a Bi3(+) liquid metal ion gun operating in the simultaneous high mass and spatial resolution mode.