Biomedical Engineering: Drug Deliveryman

Imagine writing a letter of life-and-death importance and trying to mail it only to discover that you have the wrong address, the wrong envelope and no way to buy a stamp. Robert Langer of the Massachusetts Institute of Technology has been wrestling with a problem very much like that for 25 years. In his case the letters are life-saving drugs, and the goal is to deliver them to the right place at the right dose and at the right time.

Langer's career as pharmaceutical postman began in 1974 when he graduated from M.I.T. with a doctorate in chemical engineering. He had 20 job offers from oil companies but opted instead for a postdoctorate position at Children's Hospital in Boston with Judah Folkman, one of the world's leading cancer researchers. It may have seemed an odd choice for an engineer with a bankable resume, but it gave Langer a unique perspective on a fast-growing field. He has since become the leading pioneer of modern biomedical engineering, earning scores of awards and distinctions and nearly 400 patents.

His assignment in Folkman's lab was to find a way to release gradually a stream of large organic molecules into the tissue of a laboratory animal. Researchers had already tried encasing large molecules like the one Langer was testing in polymers (long-chain molecules, such as silicone, that are semipermeable to certain types of molecules). Unfortunately, this particular molecule--like most of the new drugs being created in biotech labs--was much too large to fit through the tiny holes in any of the available polymers. The problem, polymer experts told Langer, was unsolvable.

But he solved the problem simply by turning it upside down. Rather than try to sift marbles through a screen too fine to let them through, Langer in effect wrapped the screen around the marbles, creating a three-dimensional matrix honeycombed with marble-size chutes and ladders that would allow his molecules to slowly work their way out. It was a breakthrough that ushered in a new generation of drug-delivery systems.

Langer also changed forever the way the materials used in these systems are designed. Researchers in the past had relied on off-the-shelf materials for medical applications. (The fabric in the first artificial heart, for example, was the same polyether urethane used in women's girdles.) Langer reversed the search process; in his lab, researchers first determine the exact physiological requirements of a system and then design a polymer to meet those specs.

In 1986, for example, Langer and neurosurgeon Henry Brem devised the first dime-size chemotherapy wafers to treat brain cancer. These wafers release powerful cancer-fighting drugs slowly in the site where a tumor has been removed in order to kill any cancer cells the surgeon has missed. By confining the drugs to the site of the tumor, the effects on other organs are minimized--always a major consideration in chemotherapy. The same concept has since been applied to prostate, spinal and ovarian cancers.