DURHAM, NC — Biomedical engineers and surgeons at Duke University and UCLA have demonstrated an antibiotic coating that can be applied to orthopedic implants minutes before surgery that eliminates the chances of an infection around the implant. In early trials in mice, the coating prevented all subsequent infections, even without infusions of antibiotics into the bloodstream, which is the current standard of care. After 20 days, the coating did not reduce the bone’s ability to fuse with the implant and was completely absorbed by the body.

“We’ve shown that a point-of-care, antibiotic-releasing coating protects implants from bacterial challenge, and can be quickly and safely applied in the operating room without the need to modify existing implants,” said Christopher Hart, a resident physician in UCLA Orthopaedic Surgery who helped conduct the experiments.

The new antimicrobial coating is made of two polymers, one that repels water and one that mixes well with water. Both are combined in a solution with an antibiotic of the physician’s choosing and then applied directly to the orthopedic implant by dipping, painting or spraying. When exposed to a bright ultraviolet light, the two polymers couple together and self-assemble into a grid-like structure that traps the antibiotics.

The reaction is an example of “click chemistry,” which is a general way of describing reactions that happen quickly at room temperature, produce only a single reaction product, have an extremely high yield and occur within a single container.

"This study is a great example of the power of click chemistry in biomedical applications,” said Weixian Xi, now a senior scientist at Illumina who was a postdoctoral researcher at UCLA during the study. “This ‘smart’ and ‘clickable’ polymeric coating enables protections of implants from bacterial infection and makes a personalized approach possible."

The click chemistry polymer grid also has an affinity for metal. Tests involving various types of implants showed that the coating was very difficult to rub off during surgical procedures. Once inside the body, however, the conditions cause the polymer to degrade, slowly releasing the antibiotics over the course of two to three weeks.

The researchers have not yet tested their coating on larger animals. Since larger animals—such as humans—have larger bones and need larger implants, there is much more surface area to protect against bacterial infections. But the researchers are confident that their invention is up to the task and plan to pursue the steps needed to commercialize the product.

“We believe this transdisciplinary work represents the future of surgical implants, providing a point of application coating that transforms the implant from a hotspot for infection into a ‘smart’ antimicrobial therapeutic,” Bernthal said. “You only need to treat a single patient with an infected implant to realize how transformational this could be for patient care—saving both life and limbs for many.”

The results appeared online September 16 in the journal Nature Communications.