"We'd like to put a little sensor in the blood near the heart to receive early indicators of heart attack, the Troponin-T, then actually be able to interface it with a micro-fabricated pump that could release thrombolytic agents," Grant says. "If you could dissolve that blood clot, you could save a lot more myocardium, and maybe save a life."

Helping heart patients is just one of the areas in which biosensors could one day revolutionize health care.

Another area, one of particular interest to Grant and patients such as Aimee Leonhard, is diabetes. Already diabetics have access to implantable insulin pumps, small machines that work by means of a partially implanted tube placed in the hip or abdominal region. This tube is attached to a credit card-sized external pump that gives patients a ready supply of insulin.

Grant foresees a better way: a fully implanted biosensor that will read an individual's glucose level and then automatically instruct the pump as to when the body needs insulin and how much to release.

For Leonhard, this would be life-changing. "To have a technology where you don't have to pierce yourself six or more times a day? My fingertips are sore when I go to pick things up," she says. Even more important, the on-demand glucose reading and insulin injection would eliminate any inconsistencies in treatment. "It would be like having a normal pancreas again, because this is what the pancreas is supposed to be doing," she says.

Building such a device won't be easy. Perhaps the greatest challenge? Building an implantable sensor that the body won't reject. "This area of biocompatibility, getting the body to accept these devices, is one of the big hurdles," she says. That's because, unlike an artificial joint or pacemaker, an implanted sensor has to communicate with the tissue surrounding it. Thick fibrous tissue or calcified tissue -- conditions these other devices tolerate -- slows down the transport of the analyte and impedes the sensor from doing its work. Because of biocompatibility problems, there are no sensors on the market now that can be left in the body for more than three or four days.

"Of course you want a body to reject viruses, harmful bacteria and have a strong defense system, so it's a challenge to design a sensor the body won't reject. A human body will do everything it can to reject a foreign object. If you could get one to work for even a month, that would be groundbreaking."

Grant and others in her field suspect the answer to making a biosensor compatible may lie in some type of engineered tissue, a membrane that would be grown specifically to coat the device and "fool" the body into accepting it. This membrane would likely be grown using human stem cells.

Unfortunately, tissue compatibility isn't the only problem: the need to improve sensor sensitivity is also an issue. Attaching and immobilizing antibodies on the tip of a tiny fiber is hard on them. Because antibodies are much more at home in aqueous environments, Grant and her colleague Shubhra Gangopadhyay, Lapierre Chair Professor in electrical and computer engineering, are looking to develop sensors designed with something called a "liquid core wave guide system."