Developing nanosensors for astronauts

Along with space suits, freeze-dried food and barf bags, tomorrow's astronauts may travel with nanomolecular devices inside their white blood cells to detect early signs of damage from dangerous radiation or infection.

NASA is investing US$2 million to develop this "Star Trek" technology at the University of Michigan Medical School's Center for Biologic Nanotechnology. The three-year research grant is to be directed by James R. Baker, Jr., M.D.

"Our goal is to develop a non-invasive system that, when placed inside the blood cells of astronauts, will monitor continuously for radiation exposure or infectious agents," says Baker.

"Radiation-induced illness is a serious concern in space travel," says Baker. "Radiation changes the flow of calcium ions within white blood cells and eventually triggers irreversible cell death. Even if individual incidences of exposure are within acceptable limits, the cumulative effect of radiation can be toxic to cells. So, it's important to monitor continuously for early signs of damage."

In this project, U-M researchers are developing intra-cellular devices to sense pre-malignant and cancerous changes inside living cells. Created from synthetic polymers called dendrimers, the devices are fabricated layer-by-layer into spheres with a diameter of less than five nanometers.

Because the nanosensors are so small, they pass easily through membranes into white blood cells called lymphocytes, where they are in a perfect position to detect the first signs of biochemical changes from radiation.

Nanosensors will avoid problems associated with current much-larger implantable sensors, which can cause inflammation; and eliminate the need to draw and test blood samples. U-M scientists hope the devices can be administered transdermally - or through the skin - every few weeks, avoiding the need for injections or IVs during space missions.

"We can attach fluorescent tags to dendrimers, which glow in the presence of proteins associated with cell death," Baker explains. "Our plan is to develop a retinal-scanning device with a laser capable of detecting fluorescence from lymphocytes as they pass one-by-one through narrow capillaries in the back of the eye. If we can incorporate the tagged sensors into enough lymphocytes, a 15-second scan should be sufficient to detect radiation-induced cell damage."