United States. Researchers at the University of Illinois Urbana-Champaign developed a "smart" coating for surgical orthopedic implants.
It can monitor strain on devices to provide early warning of implant failures while killing infection-causing bacteria.
Such coatings integrate flexible sensors with a nanostructured antibacterial surface, inspired by the wings of dragonflies and cicadas.
A multidisciplinary team of researchers found that the coatings prevented infection in live mice and mapped stress on commercial implants applied to sheep spines to warn of various implants or failures in healing.
"This is a combination of bioinspired nanomaterial design with flexible electronics to combat a complicated long-term biomedical problem," said study leader Qing Cao, a professor of materials science and engineering at the University of I.
"Both infection and device failure are major problems with orthopedic implants, each affecting up to 10 percent of patients," Cao continued. Several approaches to fighting the infection have been tried, but all have serious limitations.
Cao explained, "Biofilms can still form on water-repellent surfaces, and coatings loaded with chemical antibiotics or drugs are depleted within months and have toxic effects on surrounding tissue with little efficacy against drug-resistant bacterial pathogen strains."
Taking inspiration from the naturally antibacterial wings of cicadas and dragonflies, the Illinois team created a thin sheet stamped with nanoscale pillars like those found on insect wings. When a bacterial cell tries to attach to the lamina, the abutments pierce the cell wall and kill it.
"Using a mechanical approach to kill bacteria allowed us to avoid many of the problems with chemical approaches, while also giving us the flexibility needed to apply the coating to implant surfaces," said Professor of Pathobiology Gee Lau, a co-author of the study.
At the back of the nanostructured foil, where it comes into contact with the implant device, the researchers integrated flexible and highly sensitive electronic sensor arrays to monitor the strain.
This could help doctors observe the healing progress of individual patients, guide their rehabilitation to shorten recovery time and minimize risks, and repair or replace devices before they reach the point of failure.
The engineering group then teamed up with professor of veterinary clinical medicine Annette McCoy to test their prototype devices. They implanted the slides into live mice and monitored them for any signs of infection, even when bacteria were introduced.
They also applied the coatings to commercially available spinal implants and monitored the tension of the implants in sheep spines under normal load for the diagnosis of device failures. The coatings performed both functions well.
"The prototype electronics required wires, but the researchers plan to develop wireless data and power communication interfaces for their coatings, a crucial step for clinical application," Cao said. They are also working to develop large-scale production of the sheet that kills bacteria with nanopillar texture.
"These types of antibacterial coatings have many potential applications and, since ours uses a mechanical mechanism, it has potential for places where chemicals or heavy metal ions, as now used in commercial antimicrobial coatings, would be harmful," Cao added.
