Dendrimers - the quick guide

For many, polymers equal plastics. But polymers come in lots of varieties. Even nature makes them. Dendrimers are the young upstarts of the polymer family – but they have promise. Building blocks for nanotechnology, and Trojan horses for drugs delivery are just a couple of ideas that are knocking around.

What are they? | The technology | Any money in this? | Market intelligence | Where’s the buzz?

What are they?

Dendrimers are molecules with lots of branches that spin out of a central core. The name harks back to the ancient Greek – dendron means trees and meros means part. Dendrimers are polymers, but very different from the linear arrays of monomers, the building blocks of polymers, that gave us all those plastics. To get polyethylene and similar stuff you join up monomers by creating “cross links” to link long runs of molecules. In the 1980s, Donald Tomalia, a researcher at the Dow Chemical Company, got the ball polymer rolling. His group made the first dendrimers.

The technology

Dendrimers may look simple and elegant, but they are large and complex and take some making. You have to build them up, a step at a time, starting with suitable monomers and adding more bits. A dendrimer has three basic ingredients – a core sits in the middle, with branches spreading out from it, and ending with end groups. The skills is in tailoring the ingredients, especially the end groups, to create polymers with clever physical and chemical properties.

Even if you aren’t into elegant “balls” of stuff, the underlying science of dendrimers applies to what they call “hyperbranched polymers”. One way of thinking of these is as long Christmas trees with the top chopped off. There are several layers branches on the branches.

Any money in this?

When the pharmaceuticals industry is on to something, then why ask the question? James R. Baker, director of the Center for Biologic Nanotechnology at University of Michigan, runs a research group that sticks molecules on the end groups that can latch on to cancer cells – and only cancer cells. Inject the dendrimers into the blood and they will home in on the cancer cells, delivering a killer drug dose without damaging anything else. Baker’s group has $13 million from the National Cancer Institute and $3 million from NASA for his work.

Cambridge Display Technology, the company that makes polymer light-emitting devices (PLEDs), likes the idea of dendrimers so much that it bought Opsys, a company in the business. “CDT believes that dendrimers have excellent potential for future materials formulations for PLED displays, especially where high efficiencies are required, for example in battery-operated applications.”

Even traditional polymer makers are looking at the possibilities. The techniques mean that they can tweak their materials to alter their properties in subtle ways. For example, paints are polymers and ICI Paints has patented dendrimer-like polymers for toughening paints.

Market intelligence

Dow Chemical has transferred its IPR, 196 patents, to Dendritic NanoTechnologies in exchange for an ownership stake in the firm.

In January 2004, Starpharma began human clinical testing of VivaGel, a dendrimer-based topical microbiocide for preventing HIV transmission.

Where’s the buzz?

Start ups are branching out. The Australian company Starpharma, for example, a 1996 spin-out from Melbourne’s Biomolecular Research Institute, is “creating value from dendrimer-based nanotechnology”. Starpharma has its eyes on dendrimer nanodrugs and non-pharma applications. The company floated in 2000

Donald Tomalia has also spun himself out of Dow and into Dendritic NanoTechnologies Inc. (DNT) of Mount Pleasant, Michigan. The company, set up in 2003, modestly describes itself as “the world’s leading developer and provider of advanced dendritic polymers”. DNT sums up the buzz with its proclamation that: “These new types of nanostructures (particles so small they allow us to build new structures, literally, atom-by-atom) hold great promise for real-world applications, such as biotechnology and pharmaceuticals.”