In the 1966 science-fiction movie Fantastic Voyage, scientists are shrunk down to near-nano size and injected into an ailing patient to conduct repairs on his body from the inside.

Bio-engineers at the Massachusetts Institute of Technology have not (yet) miniaturized a submarine and scientists played by Raquel Welch and Donald Pleasance. They have, however, created particles far smaller than a period on this page that are designed to travel inside your cells and deliver chemotherapy drugs or other payloads—on command.

Soon after the nano-age dawned a mere three or four years ago, engineers began experimenting with nano-particles designed to passively deliver time-released meds such as cisplatin, a common chemotherapy drug. Recently, nano-researchers have tried zapping hollowed-out particles with lasers that melt and release drugs imbedded inside them. Neither method has worked satisfactorily.

Now a team led by Sangeeta Bhatia of M.I.T.'s Division of Health Sciences and Technology has created all-purpose iron-oxide nano-spheres that are deployed to seek out tumors or other target cells. Once in place, they wait to be activated by radio waves from outside the body.

"The idea sounds fantastical, but the technologies are there to do it," Bhatia told the Boston Globe.

Drugs are delivered by binding them to these iron-oxide spheres, creating a package that is attached to strands of DNA and peptides that are designed to target, say, the cells of a cancerous tumor.

Chemical codes in the DNA and peptides work like little boats that are engineered to fit into only into a specific cellular structure, or "dock." Once they've found their dock, they summon other nanospheres, which collect like clotting blood platelets.

The package then waits until someone outside turns on a clicker set to a precise frequency. This causes the iron-oxide particle to heat up and the double-helix strand of the package's DNA to separate, or "melt," releasing the drug. The frequency used to trigger the release depends on the length of the DNA.

Combinations of drugs can be activated in sequence using different frequencies at different times. Such targeted treatment aimed only at tumors or other specific cells might reduce the sometimes debilitating side-effects of cancer-fighting chemotherapy drugs. Those drugs are now delivered systemically through out the body, where they sometimes attack not only tumors, but also healthy cells.