There's no doubt that space travel is a risky business. Even in low Earth orbit, today's astronauts face potential mechanical failure and the mental strain of isolation. However, the future of space exploration lies beyond Earth's protective magnetosphere, where an even bigger threat lurks in the form of heavy ion radiation.

In just one day of interstellar space travel, for example, an astronaut will face radiation levels equal to a year's worth of incidental radiation on Earth. This radiation can cause DNA to mutate and cells to die.

To battle this invisible threat, NASA and the National Cancer Institute (NCI) awarded $11 million to seven United States' universities this winter for the development of nano-scale biomedical technologies that detect, diagnose, and battle radiation exposure, cancer, and other diseases at the cellular level.

Baker is building a device so small that it fits inside white blood cells and reports cellular damage caused by radiation. The technology will be applied to cancer patients and astronauts.

A spacecraft and the astronauts inside it make for little more than a speed bump to heavy ion radiation in interstellar space. In fact, heavy ion radiation passes through the body like tiny bullets and leaves a microscopic trail of destruction behind them.

The destruction often takes the form as distinct breaks in the DNA of white blood cells. The damage is so bad that the cells hit by the radiation often carry out what is called apoptosis, or programmed cell death. A variety of enzymes are quickly made and released during this cellular suicide, one of the first is Caspase 3.

"Caspase 3 chews up cells from the inside," Baker said. It also chews through a loose bond on Baker's nano device that allows it to give off a detectable fluorescent glow.

Like all good design, Baker's synthetic spherical macromolecule does a lot with very little. Called a dendrimer, it is made from just two types of molecules often found in plastics, which means it doesn't disintegrate easily.

The core is a simple diamine molecule, usually ammonia, bound on all sides with acrylic acid, a simple building block of plastic. Then ammonia is layered on top of the acids, and so on. Thus, the dendrimer is built, layer by layer, like a microscopic jawbreaker.

The use of a diamine and an acid layer allows for a variety of possibilities, Baker said. Depending whether the last layer is a diamine or an acid, different kinds of chemical components can be bound to the outside, and the dendrimer's function is easily changed.

To make a Caspase-detecting dendrimer, Baker adds two components. One fools the white blood cells into identifying the dendrimer as a blood sugar. Thus the cell absorbs it readily.

The other addition is a two-pronged molecular system that uses a technique called fluorescence resonance energy transfer, or FRET. The system is made of two closely bound molecules; one gives off fluorescent energy and the other absorbs it.

Before the cell undergoes apoptosis, (whether induced by radiation or by the cell's own biological clock) the FRET system stays bound together, the fluorescence stays absorbed within the dendrimer, and the white blood cell is dark inside. But once apoptosis begins and Caspase-3 is released, the FRET bond is quickly broken. Suddenly, the white blood cell is awash in fluorescent light.

Baker's team is concurrently devising a retinal scanning device that measures the amount of fluorescence inside an astronaut's body. If the level is above baseline, then counteracting drugs could be taken, such as those being developed by Marcelo Vazquez and his space medicine team at Brookhaven National Lab on Long Island.

"This system will allow us to measure how much radiation your cells receive because white blood cells are the most sensitive in the body," Vazquez said. "If they achieve this, it will be a good step forward in long term space exploration."