Clemson scientist Jeffrey Anker and four colleagues have been awarded a five-year, $1.57 million grant from the National Institutes of Health to develop an imaging technique and dye-based sensor to detect and monitor bacterial infections on implanted medical devices.
Approximately one in 25 patients admitted to a hospital in the U.S. will acquire an infection, leading to a reported 99,000 deaths per year. The majority of these hospital-acquired infections involve bacteria growing on implanted medical devices. These devices include metal plates and rods for bone fracture repairs; artificial knees, ankles and hips; prosthetic heart valves, pacemakers and artificial hearts; and urinary and intravascular catheters. Though infections are rare in most implant surgeries, implant-associated infections are difficult and expensive to cure.
“Bacterial colonization of medical implants is a major cause of device failure and often requires device removal coupled with long-term antibiotic treatment,” said Anker, associate professor of chemistry in Clemson University’s College of Science, with a joint appointment in bioengineering. “However, detection is challenging at early stages when the bacteria are localized to inaccessible regions of the implant. Our research will focus on developing sensors that will coat the implant. Then we’ll use X-ray beams to scan the sensors, enabling us to detect and monitor the infection.”
With current technologies, there is no effective way to monitor these kinds of infections, either at early stages or during antibiotic treatment when bacteria are not found in the blood. Doctors need a method to monitor the resistant bacteria localized at the implant surface to treat implant infections at early stages and to determine if infections are eradicated.
“If the patient has an infection, the antibiotics will treat the symptoms. But some bacteria often remain on the surface of the implant in the form of a biofilm, which is similar to plaque on your teeth, and the biofilm is resistant to treatment,” Anker said. “But the bacteria that lie dormant within the biofilm’s protective environment will periodically sprout and start another infection. At this point, the implant typically needs to be tediously cleansed during a surgical procedure called debridement. If the biofilm isn’t fully mature, this is sometimes effective. But if the biofilm has been long established, then debridement usually isn’t good enough. The implant will then need to be removed and the remaining infection treated with antibiotics before a new implant is inserted.”
Anker’s research is designed to find ways to detect implant infections early when they are much easier to cure. With funding from the NIH grant, the team will aspire to develop and improve a dye-based film that will coat implants and serve as an acid sensor.
In the human body, most bacteria generate local acidic environments, similar to the process that causes tooth decay. Anker’s system will use focused X-ray beams to see through human tissue and strike the coating of the implant in a precise series of layers that will combine to create a computerized image. If an infection is present, the colors revealed in the image will indicate its location and severity.
“What we’re attempting to do is quite challenging,” Anker said. “We’re trying to put a sensor on a plate that will be able to reside in a human body for a reasonable period of time in order to monitor changes in local acidity that will detect infection. Bacteria produce a lot of acids. A human’s immune system also produces acids. So if low pH is detected on the surface of an implant, it will be reasonable to assume that the implant is infected. But our research will also delve more into these aspects to determine their validity.”
