Doubly dendronized poly(norbornene)s as siRNA delivery systems

Abstract

The synthesis of a new class of dendronized polymers that possesses two different dendrons, polyglycerol dendrons (PGDs) along the polymer backbone and polylysine dendrons (PLDs) on the side-chains, is reported. Norbornene monomers containing PLDs prepared using standard peptide coupling are polymerized via ring-opening metathesis polymerization (ROMP). The resulting polylysine-dendronized poly(norbornene)s (PLD-PNBs) are further reacted to build the additional PG dendrons on the main-chains using iterative dihydroxylation and allylation, thus affording doubly dendronized polymers. The surfaces of the PLD and PGD (third-generation for both dendrons) on each repeat unit are decorated with 8 amine and 8 hydroxyl groups, respectively. These multiple peripheral groups are useful handles for incorporating additional functionalities such as targeting moieties and fluorophores as well as for making the final structure water-soluble. The doubly dendronized polymers can also be modified to generate multiple amine-based positively charged groups desired for gene delivery applications.