Researchers at the University of Illinois developed “smart” coatings for orthopedic implants that can monitor strain on the devices.
These coatings monitor strain to provide early warnings of implant failures while killing infection-causing bacteria. They integrate flexible sensors with a nanostructured antibacterial surface. Researchers say they received inspiration for the surface from the wings of dragonflies and cicadas.
In a study published in the journal Science Advances, the team found the coatings prevented infections in live mice. The coatings also mapped strain in commercial implants applied to sheep spines, warning of various implant or healing failures.
“This is a combination of bio-inspired nanomaterial design with flexible electronics to battle a complicated, long-term biomedical problem,” said study leader Qing Cao, a U. of I. professor of materials science and engineering.
How the team developed its “smart” coatings
The team undertook this effort because infection and device failure represent major issues with orthopedic implants, Cao said. A number of approaches have severe limitations. Biofilms can still form on water-repelling surfaces and coatings laden with antibiotic chemicals or drugs run out in a span of months and have toxic effects on the surrounding tissue, the researchers say. Meanwhile, they provide little efficacy against drug-resistant strains of bacterial pathogens.
So, the researchers created a thin foil patterned with nanoscale pillars like those found on the wings of cicadas and dragonflies. When a bacterial cell attempts to bind to the foil, the pillars puncture the cell wall, killing it.
“Using a mechanical approach to killing bacteria allowed us to bypass a lot of the problems with chemical approaches, while still giving us the flexibility needed to apply the coating to implant surfaces,” said pathobiology professor Gee Lau, a coauthor of the study.
The backside of the foil, which contacts the implant, features integrated arrays of highly sensitive, flexible electronic sensors. These monitor strain, potentially helping physicians watch the healing progress of individual patients. With the sensors, physicians can guide rehabilitation, shorten recovery time and minimize risks. Plus, the researchers say they can repair or replace devices before they hit the point of failure, thanks to the monitoring.
In order to test the prototypes, the researchers implanted foils in live mice and monitored for sign of infection. They also applied the coatings to commercially available spinal implants. The team also monitored strain to the implants in sheep spines under the normal load for device failure. In both functions, the coatings performed well, the researchers said.
Their prototype required wires, but the team plans to develop wireless power and data communication interfaces for the coatings. They also want to develop large-scale production of the nanopillar-textured, bacteria-killing foil.
“These types of antibacterial coatings have a lot of potential applications, and since ours uses a mechanical mechanism, it has potential for places where chemicals or heavy metal ions – as are used in commercial antimicrobial coatings now – would be detrimental,” Cao said.