SciTechStory: Janus dendrimers and dendrimersomes

One of the groovy things about science is that obscure discoveries can suddenly become world-changing.

As an example; examine the organic material called a Janus dendrimer. Janus was the dual-faced Roman god. Dendron is the Greek word for ‘tree’ or many branches. A dendrimer is a molecular sphere with many branches forming the shape. (Picture the elaborate crystalline structure of a snowflake as a three-dimensional ball.)

The Janus dendrimer has two ‘sides’ – it’s said to be amphiphilic; polar on one side, non-polar on the other.  Thus attracted to fat compounds on one side, and water on the other. This bipolar configuration is useful to molecular chemists because they can make different reactions happen on different sides of the same molecule.

One of the things that can be done with a dendrimer is use its bipolar nature to ‘self-assemble’ into a variety of shapes, that is, using the contrasting polarities to attract certain things to one area, repel in other areas, and generally cause the molecules to move about dynamically into new configurations. This is what Virgil Percec and his team at the University of Pennsylvania (USA) have done to make Janus dendrimers create a new family of tubes, disks, vesicles (bubbles), and other shapes. This is in itself interesting, but the important part for the future is that these Janus dendrimer shapes are more useful and easier to make than those created by other types of nanotechnology.

As reported in Science, the Percec team developed techniques to make Janus dendrimers form what they call dendrimersomes “dendrimer bodies” that could have wide application in the encapsulation and delivery of drugs, cosmetics, imaging compounds, diagnostic materials and many other substances. In this it has well established competition: liposomes and polymersomes. Both of these are vesicle (bubble) shaped molecular substances that are already used for encapsulating drugs and other materials. However, they have drawbacks. Liposomes tend to be unstable and have short lifetimes. Polymersomes tend to be thick, relatively inflexible, and don’t accommodate the shapes necessary to be a good biological receptor. Also, both liposomes and polymersomes create many different shapes when they form that are difficult to control and standardize.

By comparison, dendrimersomes are quite stable, tend to be uniform in size, are the right dimensions for many biological surfaces (especially cell membranes), and are relatively easy to make into useful shapes. It’s the ability to control the shape and uniformity of dendrimersomes that makes them such an outstanding candidate for real-world applications.

“This is truly groundbreaking work,” says Donald A. Tomalia of Central Michigan University, who discovered dendrimers in 1979. “It’s the first step toward a huge family of dendrimersome structures. I can see an endless number of libraries that one can construct by varying the structures of Janus dendrimers, so this paper is just the tip of the iceberg.”

[Source: American Chemical Society, Chemical and Engineering News]

What the University of Pennsylvania team has done makes dendrimersomes a more (commercially) viable technology, but it will still take years for the techniques to be refined and scaled so that significant quantities can be manufactured. In the meantime, it will remain in competition with research work on liposomes and polymersomes. If, a few years down the road, one of these emerges as the commercial champion, it will be because it’s overcome a number of hurdles – including toxicity, safety, and manageability. Nevertheless, dendrimersomes appear to be emerging as a favorite.

See also: Researchers Create Janus Dendrimer Assemblies for Drug Delivery:

An international collaboration led by chemists and engineers from the University of Pennsylvania has prepared a library of synthetic biomaterials that mimic cellular membranes and that show promise in targeted delivery of cancer drugs, gene therapy, proteins, imaging and diagnostic agents and cosmetics safely to the body in the emerging field called nanomedicine.