Wednesday, March 29, 2006

Rapid Nano Molding

Continued from page 1

By Kevin Bullis

The researchers have used nanotubes and virus particles as masters, for example, and made copies of them with a resolution down to half a nanometer. For the drug-delivery particles, they made the master out of silicon, using lithography techniques, making a series of disc shapes on a wafer. They then poured PFPE over the disks and cured them to form a mold. To make replicas of the discs, they pressed the mold into another liquid poured onto a flat surface. This liquid filled the mold, then was cured to form solid replicas of the original disks. Using lithography brings control over the size and shape, says DeSimone, with the "precision and uniformity of the electronics industry."

Larken Euliss, a chemist at UNC who works with DeSimone, says recent research shows that differences in size and shape matter when it comes to effectively delivering drugs to cells. Their methods could lead to more effective drug-delivery structures, which tend now to be spherical. A cigar-shaped particle, for example, could be thin enough to escape through the wall of a blood vessel, and so reach a tumor, and it's long shape would let researcher load more drug cargo.

Drug delivery particles are just one application. Zhilian Zhou, a researcher working with DeSimone, has developed a fuel cell with significantly higher performance than current ones, in part, using the molding method to pattern a key membrane.

Ultimately, DeSimone would like to take advantage of the synthesis method's ability to form copies of viruses to make emergency "vaccines." He's already been able to make copies of viruses, but these copies do not have the same chemical composition as viruses, and so won't link to cells like viruses do. DeSimone says it should be possible to incorporate active molecules into the molding process, though, and thereby create "artificial viruses" that can bind to cells and block real viruses from doing so. And since the virus copies have no DNA, they would not be dangerous, he says.