MIT Scientist And Engineer Describes A New Field In An NSF Lecture
How can doctors deliver drugs in ways less invasive and more controlled than an injection? Robert S. Langer views the question as an engineering design problem. Langer, Germeshausen Professor of Chemical and Biomedical Engineering at MIT, described how researchers are using biomaterials to create engineering solutions to medical problems in a lecture at the National Science Foundation's (NSF) headquarters on June 17.
Langer's lecture, "Biomaterials: From Basic Science and Engineering to Clinical Practice," focused on advances in biomaterials, a field that Langer pioneered. "Historically, materials have found their way into medicine by clinicians," he said. For the first artificial heart, doctors' search for a strong substance with flexibility led them to use polyether urethane, found in girdles. "I thought we could do better," said Langer. After all, "something designed as a lady's girdle might not be the best thing to put in a human body."
Since Langer began his work in 1974, genetic engineering has made possible larger and larger "macromolecule" drugs, such as growth hormones. With the help of NSF grants, Langer found that certain hydrophobic polymers made it possible to deliver macromolecular drugs like albumin into the body and at a controlled rate over a period of time.
Since then, biomaterials have enabled the slow release of ever-larger bioengineered proteins into the body, with release times ranging from one day to more than three years. Products like Lupron Depot permit controlled release of medicines that would normally deteriorate in minutes to be released slowly over four months.
"I'd like to think these are the tip of the iceberg," said Langer. Researchers are also working on ways to deliver growth hormones and methods to provide a constant release of insulin for diabetics. Fortune magazine cited estimates that these new technologies will cause sales in the drug-delivery sector to almost triple, reaching $25 billion by 2006.
For medicines like insulin, research is also exploring methods for administering doses in preprogrammed "pulses," or on demand. Using an oscillating magnetic field, a wristwatch-like device could, for example, release a dose of insulin just before a diabetic's meal. The magnetic field would release the drug by squeezing drug-containing pores at a microscopic level. Trials using such a device on mice are underway.
With Dr. Henry Brem, an oncologist at Johns Hopkins University, Langer explored more focused drug delivery for types of brain cancer. Treatment usually involves chemotherapy, which can have terrible side effects for the liver and other organs. For a more targeted release of the drug BCNU, doctors inserted a dime-sized polymer wafer containing BCNU in the surgical cavity at the tumor. As the polymer eroded, it released the drug over time directly to the tumor without the impediment of the blood-brain barrier. In this study, physicians have used the polymer wafers to treat thousands of brain cancer victims, with significant improvements.
In tissue engineering, cells from a patient can be cultivated on a polymer mesh or "scaffold", allowing regeneration of the cartilage for an ear, for example. Physicians could also apply these techniques to regenerate damaged tendons, sciatic nerve endings and skin tissue.
"We've raised more questions than we've answered," Langer concluded, but biomaterials have already contributed products "that can relieve suffering and prolong life for many people."