Nature's Nano-beakers

Materials scientists are becoming increasingly intrigued by the prospects of making compounds on a nanometer (one-billionth of a meter) scale. But finding reaction vessels small enough to hold those materials is tough. It turns out that nature may provide excellent nano-beakers. Even more remarkable: They’re everywhere.

A team of scientists from Montana State University (MSU) in Bozeman and Temple University in Philadelphia, Pa., has emptied a virus of its infectious genetic matter and found that the harmless shell makes an excellent container for tiny amounts of materials. Virologist Mark Young of MSU and Temple chemist Trevor Douglas took a virus that infects black-eyed peas, spilled out its RNA, and filled the 18-nanometer-diameter cavity with tungstate ions that formed a crystal. “If you think of viruses as containers of incredibly well-defined sizes, you can pick the size you want,” says Douglas. Viruses run 15 to 200 nanometers in diameter and generally come in the form of spheres or rods. What’s more, the supply is limitless. Viruses reproduce themselves with remarkable size consistency, and are easily renewable.

The next step in this unusual virus hunt calls for Young and Douglas to synthesize magnetic oxides for use as contrast agents in magnetic resonance imaging. The properties of the materials vary greatly with size-even 100 atoms makes a difference. Precisely-sized magnetic oxides formed within viral shells could replace variably-sized synthetic crystals that are made in bulk solutions.

The scientists also hope to take advantage of a virus’s natural instinct for honing in on particular cells. Viral shells are ideal for targeting specific human cells-after all, that’s what viruses do when they infect an individual. Young and Douglas believe it could be possible to deploy viral cavities loaded with magnetic imaging agents to detect the very early stages of cancer. Similarly, it could be possible to load up viral shells with a cancer drug and use them to seek out and destroy tumor cells. So it turns out that viruses-a grave human pest-may be an extremely valuable tool in some unexpected areas.