Multimodal Imaging of Chemically Fixed Cells in Preparation for NanoSIMS.

In this work, we have employed time-of-flight secondary ion mass spectrometry (ToF-SIMS) to image chemically fixed adrenal cells prepared for transmission electron microscopy (TEM) and subsequent high-spatial-resolution NanoSIMS imaging. The sample fixation methodology preserves cell morphology, allows analysis in the ultrahigh vacuum environment, and reduces topographic artifacts, thus making these samples particularly favorable for ToF-SIMS analysis. ToF-SIMS imaging enables us to determine the chemistry and preservation capabilities of the chemical fixation as well as to locate specific ion species from OsO4. The OsO4 species have been localized in lysosomes of cortical cells, a type of adrenal cell present in the culture. NanoSIMS imaging of the (190)Os(16)O(-) ion species in cortical cells reveals the same localization as a wide range of OsO4 ions shown with ToF-SIMS. Even though we did not use during NanoSIMS imaging the exact OsxOy(-) ion species discovered with ToF-SIMS, ToF-SIMS allowed us to define the specific subcellular features in a high spatial resolution imaging mode. This study demonstrates the possibility for application of ToF-SIMS as a screening tool to optimize high-resolution imaging with NanoSIMS, which could replace TEM for localization in ultrahigh resolution imaging analyses.