dendrimer

A dendrimer is a polymer grown like a tree, branch upon branch, from a single central core. Starting from the centre, each chemical step adds another ring of branches, and each ring is called a generation. The result is a globe-shaped molecule with a roomy interior and a crowded surface bristling with many identical chemical end-groups — a structure so regular that, unlike most polymers, every molecule is essentially the same size.

This precise architecture gives two ways to carry a drug. Small molecules can be held in the pockets inside the branched interior, or they can be chemically attached to the many reactive groups on the surface. Those surface groups also make dendrimers easy to decorate with targeting molecules, imaging dyes or solubilising chains, all on one well-defined scaffold.

The honest caveat is toxicity. Dendrimers with many positively charged surface groups, such as full-generation PAMAM dendrimers, can disrupt cell membranes and cause harm, so their surfaces are often capped or neutralised to make them safer. They are also expensive and laborious to synthesise generation by generation, which has slowed their move from the laboratory into approved products.