Isolation and Characterization of Dendrimers with Precise Numbers of Functional Groups

Substantial attention has been devoted to nanoparticles conjugated with functional ligands. Application of these materials has included building blocks for nano-scale structures,[1] materials for sensing and detection,[2] platforms for targeted delivery,[3] imaging and diagnostic systems,[4] and probes of biological structure.[5] One of the challenging features of these systems is the heterogeneous distribution of ligands per particle. For the vast majority of systems reported, these distributions are not characterized nor are they incorporated in design parameters. The implications of this heterogeneity are two-fold: First, mixtures containing many ligand/particle ratios make studies that investigate composition–activity relationships complex; second, production of materials with a consistent distribution of ligand/particle ratios is problematic because of inconsistencies in the nanoparticle preparations and reaction kinetics. New methods that exhibit precise control over the number of ligands per particle have the potential for dramatically improved functional efficacy, batch reproducibility, and an enhanced ability to probe the relationship between activity and the number of ligands conjugated to a particle.