Fig. 3
In vivo measurement of growth in tumors labeled with PEG–CF3–Gd2O3–TRITC–MSN. a IVIS imaging of GFP and TRITC fluorescence in a mouse injected with labeled MB49-GFP+ cells. The top row indicates GFP signal arising from the cells. The day 1 signal is low because the number of implanted cells is small; when the tumor reaches a significant size, a large signal is detected. The second row shows the signal from PEG–CF3–Gd2O3–TRITC–MSN. The signal is detectable immediately, despite a small number of tumor cells implanted. MB49 cells engulf the particles where they remain in the cytoplasm. Following each mitotic event, the cytoplasm is split between the daughter cells, thus dividing the signal in half with each cellular division. In b, we confirm a relative and progressive attenuation of the TRITC signal. Taken together, the increase in GFP fluorescence as the tumor grows coincides with the diffusion of TRITC fluorescence. Thus, the labeling provides an additional level of early detection not found in unlabeled MB49 tumors