The results of the human trials are startling. Even at a lower-than-usual dose, multiple lung metastases shrank or even disappeared after one patient received only two-hour-long intravenous infusions of an experimental cancer drug. Another patient saw her cervical tumor reduce by nearly 60 percent after six months of treatment. Though the drug trial—by Bind Biosciences in Cambridge, Massachusetts—of an experimental nanotechnology-based technique was designed simply to show whether the technology is safe, the encouraging results revive hopes that nanomedicine could realize its elusive promise.

For more than a decade, researchers have been trying to develop nanoparticles that would deliver drugs more effectively and safely. The idea is that a nanoparticle containing a drug compound could selectively target tumor cells or otherwise diseased cells, and avoid healthy ones. Antibodies or other molecules can be attached to the nanoparticle and used to precisely identify target cells. "One of the largest advantages of nanotechnology is you can engineer things in particle form so that chemotherapeutics can be targeted to tumor cells, protecting the healthy cells of the body and protecting patients from side effects," says Sara Hook, nanotechnology development projects manager with the National Cancer Institute.