Scientists have come up with an elegant method for the synthesis of dendrimers, branched polymer-like molecules with applications in many fields from nanotechnology to biomedicine.

Dendrimers have been known about for almost 30 years, but the difficulty in synthesising such complex molecules has limited their application. Michael Malkoch at the Royal Institute of Technology, Stockholm and colleagues in Sweden and the US have now devised a method of assembling dendrimers with half the number of steps of existing methods. 

Up until now, the two main methods for making dendrimers have involved using just one sort of branched monomer, which is converted to the dendrimer by repetitive growth and activation steps. Malkoch's method uses two different monomers alternately, eliminating the need for activation. Not only does this mean that fewer steps are needed to make a dendrimer of a given size, but because both the reactions used are highly efficient, purification is much easier.

Malkoch says that this is a significant advance, because reliable reactions are essential to make such large molecules. The slightest glitches in a sequence of reactions can result in accumulated defects in the final product, he says. A further benefit is that the dendrimers are always ready to react, making the synthesis of derivatives much easier. 

Barry Sharpless, W. M. Keck Professor of Chemistry at the Scripps Research Institute in La Jolla, California, says that 'Malkoch and colleagues have provided a beautiful new dendrimer synthesis. It is simple and efficient, and to the best of my knowledge, represents the state of the art.' 

Malkoch concludes that their method will allow 'the synthesis of a wide variety of architectures and hybrid materials.' Furthermore, the ease of their method should help to increase the commercial availability of dendrimers and thus prospects for their widespread application, he says.  

David J Barden