Wei Qu, Northwestern University, cartoons; Xuan Jiang, Johns Hopkins University, microscopic images
Practically every week, scientists announce a new breakthrough in the ability of nanoparticles to deliver genes, drugs or chemical messengers inside cells. Nanoparticles of different shapes and chemical makeup can track down and target specific cells of a chemist's choosing, and perform a variety of tasks.
This image depicts DNA molecules (light green), packaged into nanoparticles by using a polymer with two different segments. One segment is positively charged, which binds the polymer to the DNA. This is shown in teal. The brown portion shows a protective coating on the nanoparticle's surface. By adjusting the solvent surrounding these molecules, researchers at Johns Hopkins and Northwestern universities were able to control the shape of the nanoparticles. The team's animal tests showed that a nanoparticle's shape can dramatically affect how well it delivers gene therapy.
This is possible because DNA behaves strangely among nanoscale particles, explained Chad Mirkin of Northwestern. Spherical nucleic acids, one of his lab's inventions
and an up-and-coming therapeutic technology, allow DNA to do something it otherwise can't: Enter cells. To insert gene fragments into cells, researchers have to trick the cell, which is designed to block invasion. This is frequently done using viruses, but those can have a wide range of side effects.
Instead, spherical nucleic acids attach short strands of DNA or RNA to a gold or silver nanoparticle's surface, and the DNA molecules will organize into a spherical shape, Mirkin said. "You arrange a simple molecule in a spherical form, and it naturally enters cells better than anything known to man," he said. "That is a paradigm shifter for how we think about creating new therapeutics--in this case, involving the world's most important molecule, and learning how to arrange it in new forms on the nanoscale."