Dendrimer SynthesisGeneration 4 EDA core PAMAM dendrimer was purchased from Dendritech (Midland, MI) as methanol solution (26 wt%). Acetic anhydride, pyridine, succinic anhydride, glycidol and all the remaining chemicals/solvents were purchased from Aldrich. Milli-Q deionized water (with resistivity >18 MΩcm) was used in all of the experiments. Regenerated cellulose dialysis membranes were purchased from Fisher Scientific. 4.1 mL of pyridine was added to 11.56 g of a solution of EDA core G4-NH 2 PAMAM dendrimer (3.0056 g) in methanol. The resulting solution was diluted to 40 mL by addition of methanol in a 250-ml round-bottom flask. A solution of 2.6 g acetic anhydride in methanol was then added drop wise to the dendrimer/pyridine mixture under continuous stirring. The resulting solution was equlibrated for 24 hours. The methanol was then removed from the reaction mixture on a rotary evaporator. The oily crude product was diluted and dialyzed with deionized water (6 X 4 liters) for three days to remove the excess reactants and byproducts. The final product was removed from the aqueous retentate, dissolved in deionized water and lyophilized. The yield (3.15g) was estimated at 88.2%. G4 EDA core PAMAM Dendrimer with Acetamide (NHCOCH 3 ) Terminal Groups (G4-Ac)