Imagine placing an adhesive bandage on a cut and having the bandage tell you immediately that dangerous bacteria have gotten into the wound and that you need to seek a doctor's help. Researchers at the University of Rochester have taken the first major step toward a bandage that will change color depending on what kind of bacteria may be present in a wound. It can give an instant diagnosis as to whether the wound may require special care or what kind of antibiotics may work best in treating it. The bandage is part of the Center for Future Health's "smart medical home"-a series of devices working in conjunction in the home to monitor a family's health.
Benjamin Miller, assistant professor of chemistry at the University, and Philippe Fauchet, professor and chair of electrical and computer engineering, have devised a sand-grain sized wafer that can differentiate between two classes of bacteria, called Gram-positive and Gram-negative. The sensor, the first substantial improvement in identifying Gram-positive and negative bacteria since Hans Christian Joachim Gram developed the original staining technique in 1884, is reported in the upcoming issue of the Journal of the American Chemical Society. The accomplishment is evidence that it's indeed possible to accurately identify bacteria with a silicon sensor, spurring Miller's team to expand the research to several other types of bacteria, including salmonella, listeria and enteropathogenic E. coli, all of which can cause serious disease in humans.
Today, if a doctor needs to identify whether a bacterial infection is of the Gram positive or negative variety, the bacteria need to be stained and examined under a microscope. "The Gram stain has been an important tool in analyzing bacteria for more than a century, but it's amazing to me that we're still using a procedure that's effectively out of the Stone Age," says Miller. "We can now get the same information immediately, at home or in the doctor's office, and we're working on similar ways to detect dozens of other potentially harmful bacteria."
The technique currently used by doctors uses a stain that interacts with the cell walls of bacteria, changing the color of the bacteria depending on their Gram type. The drawbacks to this method are that it is prone to human error, since a person has to make the judgment of whether or not the bacteria have changed color under the microscope. The "smart bandage," as it's been nicknamed, zeroes in on a type of molecule called lipid A on the surface of Gram-negative bacteria. In an earlier publication, Miller showed how he was able to create a complementary molecule that binds to lipid A, while his newest research shows that it's possible to link that molecule to a silicon sensor that will change when the detector molecule binds to the lipid. Currently, the color change is subtle and could be missed by a human eye, but the bandage is part of a "smart medical home"-a home designed by several researchers at the University to monitor health at home-so a simple device could read the bandage, confer with other instruments throughout the house to determine if the kind of bacteria in the wound is something of particular danger to you, and make a recommendation.
"This is an important step in changing the way preventive medicine is perceived and practiced," says Alice Pentland, chair of the department of dermatology at the University of Rochester. "This kind of research can put a very simple and accurate tool into the hands of anyone, giving them more control over their own health than ever before."
The team has lined up a dozen more types of pathogenic bacteria and already mapped out all the targets for which they will need to devise a binding molecule. Among those in the team's sights are antibiotic-resistant strains.
"We're working on a way to detect whether or not a certain strain of bacteria is antibiotic resistant, and which antibiotic that may be," says Miller. "That will be extremely challenging, but we think we can do it."
Miller plans to create an array of dozens of different bacterial sensors that can be mounted into a flexible bandage and will change color dramatically enough so a glance will tell you whether you have a serious infection. Then you could grab your bandage-reader from the medicine cabinet, scan it over your cut and know in seconds what kind of infection you have. But Miller is working toward something much more sophisticated than that.
Miller's work is part of the Center for Future Health, a University of Rochester team of researchers working to create a "smart medical home" that will help people keep far better tabs on their personal health with the help of advanced electronics like Miller's bandage, computers and the Internet. Ultimately, once you scan your bandage, the reader will connect to a home PC responsible for monitoring residents' health, reporting what kind of bacteria is present. The house will check a medical database via the web to determine what kind of treatment is necessary, confer with other sensors that have been monitoring your gait for signs of stroke, your skin for signs of melanoma, and your medicine cabinet to make sure you haven't been taking anything that may conflict with any new medication, and suggest to you in spoken English what steps you need to take to treat your infection. The idea of the bandage and the medical home is to give people more control of their own health, so that they and their doctors are better prepared to deal with health issues.
The technology Miller is pursuing may go well beyond the home as well. The food packaging industry has shown interest, since a wrapping, say around a pound of ground beef, may be able to change to a cautioning yellow if the meat is contaminated. Or, in Third World countries where pollution of drinking water is a constant threat, plastic cups or water jugs could be designed to turn a bright red if there are dangerous pollutants present. "We may even see this technology being used as an early warning in the case of biowarfare," he says.
The biggest hurdle to the development of the smart bandage is now cleared. "We've shown that we can detect and identify a single, distinct kind of bacteria," says Miller. "Now that we have that out of the way, we know it can be done. Finding the molecules to detect other bacteria will be much easier."
The research was funded by the Wm. Keck Foundation.