Fluorescent Labeling of Amine Dendrimers

For instance, a dendrimer easily can be coupled with a large number of fluorescent dyes and still provide additional coupling sites for biotinylation. The only limitation to the number of fluorescent modifications is if fluorescence quenching starts to take place, in which case no further modifications will result in increased signal. A series of such conjugates using different levels of fluorophore modification should be done to determine the optimal level of dye-to-dendrimer before quenching occurs. 

Dendrimers bearing certain fluorescent molecules attached on their periphery have been shown to be environmentally sensitive probes for the presence of certain metal ions or to changes in pH (Balzani et al., 2000 Paola et al., 2005). In addition, PAMAM dendrimers modified with the relatively hydrophobic dye Oregon Green 488 were shown to be a more effective transfection agent for anti-sense oligonucleotides than the dendrimer alone-plus the complex could be tracked within the cell due to the fluorescence of the dye (Yoo and Juliano, 2000). 

In a fume hood, dissolve the DyLight 649 NHS ester at a concentration of lOmg/ml in dry DMF. 

Dissolve the amine-dendrimer to be modified in DMF or buffer (50mM sodium borate, pH 8.5) at a concentration of at least lOmg/ml. Avoid the use of amine-containing buffers for an aqueous reaction, such as Tris or imidazole, as these will react with the 

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