Newly developed “smart” coatings for surgical orthopedic implants can monitor strain on the devices, providing early warning of implant failures while killing infection-causing bacteria, according to researchers at the University of Illinois Urbana-Champaign. The coatings combine flexible sensors with a nanostructured antibacterial surface inspired by the wings of dragonflies and cicadas.
In a recent study, a multidisciplinary team of researchers demonstrated that the coatings effectively prevented infection in live mice and mapped strain in commercial implants applied to sheep spines, allowing for the detection of various implant or healing failures.
“This innovative approach combines bio-inspired nanomaterial design with flexible electronics to address a complex, long-term biomedical issue,” explained study leader Qing Cao, a professor of materials science and engineering at the University of Illinois.
Orthopedic implant-related infections and device failures are significant problems, impacting up to 10% of patients, Cao noted. Previous approaches to combating infection have had limitations, such as the formation of biofilms on water-repellent surfaces and the short-term effectiveness and potential toxicity of antibiotic-laden coatings against drug-resistant bacterial strains.
Drawing inspiration from the naturally antibacterial wings of cicadas and dragonflies, the research team created a thin foil patterned with nanoscale pillars resembling those on the insects’ wings. When a bacterial cell attempts to bind to the foil, the pillars puncture its cell wall, leading to its demise.
“Employing a mechanical approach to kill bacteria enabled us to overcome many challenges associated with chemical methods, while also providing the necessary flexibility to apply the coating to implant surfaces,” stated Gee Lau, a coauthor of the study and a professor of pathobiology.
On the opposite side of the nanostructured foil, where it comes into contact with the implant device, the researchers incorporated arrays of highly sensitive and flexible electronic sensors to monitor strain. This monitoring capability could enable physicians to track the healing progress of individual patients, guide their rehabilitation to shorten recovery time and minimize risks, as well as repair or replace devices before they reach the point of failure.
To test their prototype devices, the engineering group collaborated with Annette McCoy, a professor of veterinary clinical medicine. They implanted the foils in live mice and monitored them for signs of infection, even when bacteria were introduced. They also applied the coatings to commercially available spinal implants and monitored the strain on the implants in sheep spines under normal load to diagnose device failures. The coatings performed effectively in both functions.
While the prototype electronics require wires, the researchers are now aiming to develop wireless power and data communication interfaces for their coatings, which is a crucial step for clinical application. They are also working on large-scale production of the nanopillar-textured bacteria-killing foil.
“These antibacterial coatings have numerous potential applications, and since our approach utilizes a mechanical mechanism, it holds promise for situations where chemicals or heavy metal ions, as used in current commercial antimicrobial coatings, could be harmful,” Cao emphasized.
Support for this work was provided by the National Science Foundation and the U.S. Congressionally Directed Medical Research Programs.
For more information: ScienceAdvances
Image: In this computer illustration of the coating, the purple area represents the bacteria-popping pillars, while the circuits represent the stress-sensing components.
