Scientists at the University of Michigan have been working with branched polymers just nanometers long called dendrimers, which can carry many different types of molecules attached to their ends. Armed with contrast agents and drugs, a dendrimer can then locate and signal the presence of diseased tissue. But building a multifaceted dendrimer complex is labor intensive and requires separate, lengthy reaction steps for each additional molecule. In the current issue of the journal Chemistry and Biology, Youngseon Choi and his colleagues describe a different technique, which exploits the natural tendencies of DNA to speed up the process. The team first made separate batches of dendrimers, each carrying a single type of molecule as well as a small swatch of noncoding DNA. When solutions of these dendrimers were combined, the lengths of DNA formed complementary pairs, knitting the two dendrimer complexes together.
Using this approach, assembling a therapeutic dendrimer that could deliver five drugs to five different types of cells would require 10 steps. The traditional approach would require 25, each taking between two and three months. "With this approach, you can target a wide variety of molecules, drugs [and] contrast agents to almost any cell," comments study co-author James Baker of the University of Michigan. The results have proved the concept is feasible, the authors note, and could usher in a new age of self-assembling disease-fighters.