Best practices for purification and characterization of PAMAM dendrimer

Poly(amidoamine) (PAMAM) dendrimer are branched polymers with low degrees of heterogeneity. Current synthesis methods, however, result in substantial batch variability. We present our optimized procedure for post-synthesis (and post-market) purification of a generation 5 PAMAM dendrimer by membrane dialysis and demonstrate its effectiveness and limitations using a representative lot of biomedical grade dendrimer. This method successfully removes trailing generation defect structures, thereby reducing the heterogeneity of the material (PDI reduced from 1.04 to 1.02). Optimized analytical techniques to characterize the unpurified and purified dendrimer are also detailed. The efficiency of the purification method is successfully monitored by these analytics and dendrimer parameters that are critical for subsequent modification reactions and biological evaluation (M(n), M(w), PDI, average number of end groups) obtained. To provide better definition of the variability that should be expected between lots of synthesized material, HPLC traces for three additional commercial lots of dendrimer are also presented.