Fluorometric assay for detection and quantitation of polyamidoamine dendrimers

Polyamidoamine dendrimers are protein-like nanomaterials that have many potential biological applications. Research studies using dendrimers often require their detection and quantitation. This article describes a simple, inexpensive, and rapid fluorometric assay based on the ability of dendrimers to bind the fluorescent probe, 8-anilino-1-naphthalene-sulfonic acid. This interaction leads to an enhanced fluorescence intensity of the dye that shows a linear relationship with dendrimer concentration. The procedure is applicable to dendrimers that have various surface functional groups and internal cores. Amine- and hydroxyl-terminated dendrimers gave the best calibration curves under alkaline conditions (pH 7.4). Carboxyl-terminated dendrimers required acidic conditions for their measurement. The assay for dendrimers with an amine surface and an ethylene diamine core was accurate between 0 and 100 μM and produced a within-run coefficient of less than 5%. Under the assay conditions used, the fluorescence signal strength was dependent on type of surface group and core length of the dendrimer.