AVS 65th International Symposium & Exhibition
    Applied Surface Science Division Tuesday Sessions
       Session AS+BI-TuM

Paper AS+BI-TuM6
Small Molecule Imaging in Single Frozen-Hydrated Cells using High-Resolution Gas Cluster Ion Beam Secondary Ion Mass Spectrometry (GCIB-SIMS)

Tuesday, October 23, 2018, 9:40 am, Room 204

Session: Applied Surface Science: From Electrochemistry to Cell Imaging, a Celebration of the Career of Nicholas Winograd
Presenter: Hua Tian, Pennsylvania State Univeristy
Authors: H. Tian, Pennsylvania State Univeristy
N. Winograd, Pennsylvania State Univeristy
Correspondent: Click to Email
Cell heterogeneity leads to the development of antibacterial resistance and tumor relapses in response to drug treatment. Cell-to-cell differences have been extensively investigated at the DNA level. The study of rapid and dynamic small molecule fluctuations in single cells has lagged. However, the complete spectrum of biomolecules can be a direct indicator of cell phenotype and a reflection of immediate response to environment and chemical stress. There is currently no method to directly detect small molecules in their original state because of the rapid and dynamic nature of these molecules and impossibility of amplifying the metabolites. Previously, the characterization of drug and small molecules in cells are conducted using ensembles of cells, with which the spatial distribution, a vital piece for understanding biological processes is lost. The development of high resolution CCIB-SIMS in our lab has positioned us to directly image small molecule fluctuation in single cells under cryopreservation. The approach takes advantage of three aspects of GCIB-SIMS - low chemical damage, high yield of intact biomolecules, and the possibility of sub-micron lateral resolution. In this work, we utilize a DC beam buncher-ToF SIMS instrument to achieve high lateral resolution. Moreover, this configuration simplifies depth profiling since erosion and spectral acquisition are performed with a single beam. In addition, the flexibility of gas candidates for GCIB allows us to explore tailored beam for ionization enhancement, such as HCl, CH4, CO2 or H2O (1~100%) doped Ar cluster beams. To illustrate this instrumental protocol, chemically resolved 3D images of single cells, HeLa cells and drug treated A549 (Carcinoma) and A673 (Ewing tumor) cells are imaged using a novel 70 keV (CO2)14000+ beam with a spot size of 1 µm. The stable intermediates from various biochemical pathways are visualized in single HeLa cells, demonstrating the sufficiency of the chemical sensitivity using GCIB. The drug propranolol is localized within the cellular structure of A673 and A549 cells, while no sign of fexofenadine is observed. This indicates that propranolol has high passive permeability in contrast to low passive permeability expressed by fexofenadine. Surprisingly, a lipid composition change is shown in A673 cells, particularly the depletion of phosphatidylinositol species after treatment. The approach provides a complete chemical picture of single cells at near original physiological and morphological state, opening the opportunities for single cell metabolomics and heterogeneity studies using SIMS.