Friday, January 21, 2005

Dendrimers could have cancer in their clutches

A dendrimer docks on cellular folate receptors, which are over-expressed on the surface of cancer cells.
Image courtesy of the Michigan Center for Biologic Nanotechnology

My old Detroit News colleague, science writer Karl Leif Bates, is doing PR for the University of Michigan now, and he sends me this piece of breaking news from the Michigan Center for Biologic Nanotechnology and its star secretary of nanostate, James Baker.

I love this item because it involves my two favorite molecules -- nature's own DNA, and the manmade, tendriled dendrimer. Plus, while a quarter of my brain is dreaming of molecular assemblers, another quarter is wowed by the shorter-term prospects for nano in diagnosing and treating diseases. The other two-quarters is none of your business.

Here's an excerpt from the release

DNA molecules used to assemble nanoparticles

    University of Michigan researchers have developed a faster, more efficient way to produce a wide variety of nanoparticle drug delivery systems, using DNA molecules to bind the particles together. Nanometer-scaled dendrimers can be assembled in many configurations by using attached lengths of single-stranded DNA molecules, which naturally bind to other DNA strands in a highly specific fashion.

    "With this approach, you can target a wide variety of molecules---drugs, contrast agents -- to almost any cell," said Dr. James R. Baker Jr., the Ruth Dow Doan Professor of Nanotechnology and director of the Center for Biologic Nanotechnology at U-M. Nanoparticle complexes can be specifically targeted to cancer cells and are small enough to enter a diseased cell, either killing it from within or sending out a signal to identify it. But making the particles is notoriously difficult and time-consuming.

    The nanoparticle system used by Baker's lab is based on dendrimers, star-like synthetic polymers that can carry a vast array of molecules on the ends of their arms. It is possible to build a single dendrimer carrying many different kinds of molecules such as contrast agents and drugs, but the synthesis process is long and difficult, requiring months for each new molecule added to the dendrimer in sequential steps. And the yield of useful particles drops with each successive step of synthesis.

    For a paper published Jan. 21 in the journal Chemistry and Biology, U-M Biomedical Engineering graduate student Youngseon Choi built nanoparticle clusters of two different functional dendrimers, one designed for imaging and the other for targeting cancer cells. Each of the dendrimers also carried a single-stranded, non-coding DNA synthesized by Choi.

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