Fig. 5. (a) STED image of Ru-Arg₈ in a single HeLa cell. (b) Confocal and STED images of Ru-ER in a single HeLa cell demonstrating the tubular structure of the ER. The corresponding plot profile compares confocal () with STED (). The fluorescence-intensity was fit to a Gaussian distribution (OriginPro) to obtain the separated distributions for the STED profile fitting, indicated by grey dashed lines. Both complexes were introduced to HeLa cells separately, for 4 h, at 70 μM in cell culture media. Samples were fixed with 3.8% paraformaldehyde for 15 minutes, and then mounted with Prolong Gold for 24 h before imaging. Both complexes were excited at 488 nm white light laser, and the emission collected between 590 and 700 nm. The 660 nm STED depletion laser was used for both complexes. Data is raw with no post-processing performed.