Quantitative SIMS Imaging of Cholesterol in the Membranes of Individual Cells from Differentially Treated Populations

摘要

Time of flight secondary ion mass spectrometry (ToF-SIMS) is a well-established bioanalytical method for directly imaging the chemical distribution across single-cells. Here we report a protocol for the use of SIMS imaging to comparatively quantify the relative difference in lipid composition between the plasma membranes of two cells. This development enables direct comparison of the chemical effects of different drug treatments and incubation conditions in the plasma membrane at the single-cell level. Relative, quantitative ToF-SIMS imaging has been used here to compare macrophage cells treated to contain elevated levels of cholesterol with respect to control cells. In-situ fluorescence microscopy with two different membrane dyes was used to discriminate morphologically similar but differentially treated cells prior to SIMS analysis. SIMS images of fluorescently identified cells reveal that the two populations of cells have distinct outer leaflet membrane compositions with the membranes of the cholesterol-treated macrophages containing more than twice the amount of cholesterol of control macrophages. Relative quantification with SIMS to compare the chemical composition of single-cells can provide valuable information about normal biological functions, causative agents of diseases, and possible therapies for diseases.