The team envisions eventually placing the detection chip and reader in doctors' offices and health-care facilities. McDevitt is a scientific advisor to LabNow, a company that hopes to commercially developing the chip. It plan to get the disposable chip down to less than $20 each, while the analyzers that would be in ambulances and physicians' offices are "basically souped-up digital cameras" and cost in the thousands. McDevitt says that the next trial, in ambulances, should begin this summer.

A heart-attack detection that analyzes saliva has some key advantages, according to James Januzzi, an associate professor of medicine at Harvard Medicine School and chief of the Coronary Care Unit at Massachusetts General Hospital. "The test can potentially be done much earlier, with much more rapid results than if they were done off of blood," he says. He adds that, in heart-attack treatment, "delays in diagnosis and delays in presentation are the two biggest problems right now. We have excellent therapies, but the problem is . . . the diagnosis is delayed. Time is of the essence in treatment."

Others, however, are unsure if the nano biochip will be useful in clinical practice, because there is a time lag for the proteins to show up in saliva, as is the case in blood. "The biomarkers take time to go up," says Thomas Wang, a physician at Massachusetts General Hospital and assistant professor at Harvard Medical School who has studied cardiovascular biomarkers. Many proteins, he points out, take hours to become elevated, so having a faster test may not necessarily be beneficial. "The concept is interesting," he says, but the researchers "would have to demonstrate that being able to make the diagnosis in the ambulance translates to any clinical benefit."

Some biomarkers do take several hours to show up, acknowledges McDevitt, but he says that the proteins are detectable at lower levels at earlier times than blood biomarkers are. He speculates that because saliva is constantly replenished, it may show a quicker response than blood. One protein that the group tested for, myoglobin (which elevates in other injuries as well), is one of the faster biomarkers, taking four hours for its maximum levels to appear in saliva, according to McDevitt.