Fig. 2. Confocal microscopy of cell lines. (a) Fluorescence imaging of PNT2 cells with localization of SiaNAz-modified glycans. Cells without ManNAz treatment (control) and with ManNAz treatment were stained with Hoechst 33342 (blue), CellMask™ Deep Red (green), and DBCO–Cy3 (red). (b) Detection of produced hydroxyl radicals in PNT2 cells through live cell imaging. After treating the cells with ManNAz and attaching the FeBABE probe to the sialylated glycans, cells were stained with Hoechst 33342 (blue) and CellMask™ Deep Red (green). Pro-fluorescent rhodamine was then added along with hydrogen peroxide and DMSO. The produced hydroxyl radicals (rhodamine, red) at different time points including t = 0 min (starting point), t = 15 min (middle point), and t = 30 min (endpoint) are shown in the middle panel. The combined photos are shown in the lower right panel. The intensities of the stains varying over time are shown in Fig. S4.† .