Fourth in a series of reports on biomedical engineering innovations.
Bob might be your next-door neighbor. He's an affable, 60-something retired engineer who took a buyout before the Internet bubble burst. He golfs, enjoys his grandchildren, and likes to travel with his wife of 35 years. The only problem is that he's getting old—and he knows it. He's bald on top, his skin is starting to sag in places, his eyesight isn't what it used to be, and he sometimes can't hear what his dinner companions are saying. Even worse, the diabetes that he was diagnosed with in his 40s is getting more difficult to control: his blood sugar seems like it is up one minute, down the next. And it seems as though all his friends have had at least one heart attack.
Bob is worried about getting old.
As an engineer, Bob knows that the body is just one big system that runs by chemical gradients and electrical impulses. So why is it so difficult to come up with replacement parts when bodies like his start to break down?
Luckily for Bob—and especially for those of us who are younger and can wait a few more years—engineers and doctors, mostly in the United States, have stepped up their search for ways to build replacement parts.
The current effort is focused on so-called biohybrid or bioartificial organs, which combine living cells with materials such as silicon and polymers. The hybrid organs get their structure from the inorganic material while relying on living tissue, grown from cadavers, animals, or, one day, from the patient's own body, to do the complex tasks they do best, such as processing biochemicals and filtering blood. Although biohybrids are being tested outside the body and are at least five years away from reaching the market, ultimately they are being designed as implants—seamless replacement parts.
Construction of replacement organs got off to a rocky start, when the first two companies to come out with a product, living skin, went bankrupt nearly two years ago [see "Synthetic Skin," IEEE Spectrum, December 2002]. But tissue engineers have gone back to the lab. And nowadays it's a semiconductor lab.
A good portion of the newest innovations involve growing cells in specifically ordered arrays on chips made of semiconductor material. Electrical impulses pattern the cells as they would be in a natural organ and stimulate them appropriately so they develop into the needed tissues. Researchers have taken a page from the books of microelectromechanical systems (MEMS) developers and have built tiny systems using semiconductor fabrication techniques to address diseases that are now either marginally treatable or untreatable.
Many, if not most, of the new biohybrid research projects target some of the primary disorders of aging: kidney failure, emphysema, and heart disease—all among the top 10 killers of Americans older than 65. In 2001, heart disease alone killed one-third of everyone older than 65 who died in the United States. Kidney disease also takes a significant toll: more than 72 000 people in the United States die each year from end-stage renal disease. And current, stopgap therapies are costly: the 350 000 Americans who need kidney dialysis require a total annual expenditure of US $25 billion.
If I'd known I was going to live this long, I'd have taken better care of myself. —Ragtime musician James Herbert ("Eubie") Blake, at age 100, in 1983