Fluorescence microscopy of glioma cell uptake of rhodamine B labeled Gd-dendrimer generations in vivo versus ex vivo. A) Synthetic scheme for production of rhodamine B (RB) labeled Gd-polyamidoamine dendrimers. The naked polyamidoamine dendrimer is first reacted with rhodamine B and then with Gd-DTPA. B) As shown by fluorescence microscopy in vitro, rhodamine B Gd-G2, rhodamine B Gd-G5, and rhodamine B Gd-G8 accumulate in glioma cells. Rhodamine B Gd-G2 dendrimers enter RG-2 glioma cells, and in some cases, the nucleus (left). Rhodamine B Gd-G5 dendrimers enter the cytoplasm of RG-2 glioma cells, but do not localize within the nucleus (middle). Rhodamine B Gd-G8 dendrimers enter RG-2 glioma cells in vitro (right). Shown are merged confocal images of blue fluorescence from DAPI-Vectashield nuclear (DNA) stain and red fluorescence from rhodamine B labeled Gd-dendrimers. Scale bars = 20 µm. C) At 2 hours dynamic contrast-enhanced MRI shows substantial extravasation of rhodamine B Gd-G5 dendrimers and some extravasation of rhodamine B Gd-G8 dendrimers. Rhodamine B Gd-G5 n=6, rhodamine B Gd-G8 n=2. D) Low power fluorescence microscopy ex vivo of brain tumor and normal brain surrounding tumor shows that there is substantial accumulation of rhodamine B Gd-G5 dendrimers within tumor tissue (left, T = tumor, N = normal, scale bar = 100 µm). High power shows subcellular localization within malignant glioma cells (upper right, scale bar = 20 µm). Hemotoxylin and Eosin stain of tumor and surrounding brain (lower right, scale bar = 100 µm). Tumor volume is 31 mm3. E) Also shown by low power fluorescence microscopy ex vivo is some accumulation of rhodamine B Gd-G8 dendrimers within brain tumor tissue (left, T = tumor, N = normal, scale bar = 100 µm). High power confirms minimal subcellular localization within glioma cells (upper right, scale bar = 20 µm). Hematoxylin and Eosin stain of tumor and surrounding brain (lower right, scale bar = 100 µm). Tumor volume is 30 mm3.