United States.
Scientists at Johns Hopkins University have shown that a new layer made with nanofibers that release antibiotics has the potential to better prevent some serious bacterial infections linked to total joint replacement surgery.
The researchers say the technology would have "wide applicability" in the use of orthopedic prostheses, such as hip and knee joint prostheses, as well as pacemakers, stents and other implantable medical devices. In contrast to other coatings in development, the researchers report that the new material can release multiple antibiotics in a strategically timed manner for optimal effect.
"We can coat any metal implant we put in patients, from prosthetic joints, rods, screws and plates to pacemakers, implantable defibrillators and dental hardware," says Lloyd S. Miller, M.D., Ph.D., Associate Professor of Dermatology and Orthopedic Surgery at the Johns Hopkins University School of Medicine.
For years, surgeons and biomedical engineers have looked for better ways — including antibiotic coatings — to reduce the risk of infections that are a known complication of implanting artificial hip, knee and shoulder joints.
For three years, the team focused on designing a thin, biodegradable plastic coating that could release multiple antibiotics at the desired rates. This coating is composed of a nanofiber mesh embedded in a thin film; both components are made of polymers used for degradable sutures.
To test the technology's ability to prevent infection, the researchers loaded the nanofiber coating with the antibiotic rifampicin in combination with one of the other three antibiotics: vancomycin, daptomycin or linezolid. "Rifampicin has excellent anti-biofilm activity but cannot be used alone because bacteria rapidly develop resistance," Miller says. The coatings released vancomycin, daptomycin or linezolid for seven to 14 days and rifampicin for three to five days. "We were able to deploy two antibiotics against the potential infection, ensuring that rifampin was never present as a single agent," Miller says.
Coating load of nanofibers with antibiotics
The team then used each combination to coat titanium Kirschner wires — a type of bolt used in orthopedic surgery to fix the bone in place after wrist fractures — inserted it into the knee joints of anesthetized mice and introduced a strain of Staphylococcus aureus, a bacterium that commonly causes biofilm-associated infections in orthopedic surgeries. The bacteria were designed to emit light, allowing researchers to non-invasively track the infection over time.
After the two-week test, each of the rodents' joints and adjacent bones were removed for further study. Miller and Mao found that not only had the infection been prevented, but also the bone loss often seen near infected joints had been completely avoided, creating the patients' prosthetic loosening, they had also been completely avoided in animals that received pins with the antibiotic-impregnated coating.
Source: Johns Hopkins Medicine.
