Uptake of fluorescent fructose derivatives in MDA-MB-435 (a,d), MDA-MB-231 (b,e), and MCF-7 cells (c,f). MDA-MB-435 cells incubated with 2-NBDG (g) showed comparable fluorescence intensities to cells incubated with 1-NBDF. Fluorescence of MDA-MB-435 cells incubated with Cy5.5-DG (h) was similar to the fluorescence of cells incubated with 1-Cy5.5-F. Incubation of MDA-MB-231 and MCF7 cells with Cy5.5-DG and NBDG resulted in similar fluorescence intensities as the ones observed after uptake of fluorescent fructose derivatives (data not shown). 1-Cy5.5-DF showed cytoplasmic rather than nuclear accumulation in MDA-MB-435 cells (i). Incubation with Cy5.5-NHS ester results in the staining of MDA-MB-435 cells (j). Incubation of MDA-MB-435 cells with C-1 fructose derivatives at low temperature results in minimal uptake of the probes (k,l).