Smart surgical implant coating provides early warning of failure while preventing infection

May 05, 2023

(Nanowerk News) Newly developed “smart” coatings for surgical orthopedic implants can monitor tension in the device to provide early warning of implant failure while killing infection-causing bacteria, University of Illinois Urbana-Champaign researchers report. The coating integrates a flexible sensor with a nano-structured antibacterial surface inspired by dragonfly and cicada wings.

In a new study in the journal Science Advances (“Smart coatings with integrated physico-antimicrobial and strain mapping functions for orthopedic implants”), a multidisciplinary research team discovered a coating preventing infection in live mice and the strain mapped to a commercial implant applied to sheep spines to warn of multiple implants or healing failure.

“It is a combination of bio-inspired nanomaterial design with flexible electronics to combat complex long-term biomedical problems,” said study leader Qing Cao, U. of I professor of materials science and engineering. Smart coatings on orthopedic implants, developed at the University of Illinois Urbana-Champaign, have bacteria-killing nanopillars on one side and flexible strain-mapping electronics on the other. This can help doctors guide patient rehabilitation and repair or replace devices before they fail. (Image: Beckman ITG, University of Illinois)

Device infection and failure are major problems with orthopedic implants, each affecting up to 10% of patients, said Cao. Several approaches to fighting infection have been tried, but all have severe limitations, he says: Biofilms can still form on water-repellent surfaces, and coatings laden with antibiotic or medicinal chemicals wear out over months and have toxic effects on the surroundings. . tissues with little efficacy against drug-resistant strains of pathogenic bacteria.

Taking inspiration from the naturally antibacterial wings of crickets and dragonflies, the Illinois team created thin foils patterned with nanoscale pillars similar to those found in insect wings. When the bacterial cell tries to bind to the foil, the pillars puncture the cell wall, killing it.

“Using a mechanical approach to kill bacteria allows us to bypass many of the problems with chemical approaches, while still giving us the flexibility needed to apply coatings to implant surfaces,” said pathobiology professor Gee Lau, a co-author of the study.

On the back side of the nanostructured foil, where it contacts the implanted device, the researchers integrated an array of highly sensitive and flexible electronic sensors to monitor tension. This can help doctors see each patient’s healing progress, guide their rehabilitation to shorten recovery time and minimize risks, and repair or replace devices before they reach a point of failure, the researchers said.

The engineering group then teamed up with clinical veterinary professor Annette McCoy to test their prototype device. They implanted foil in live mice and monitored them for signs of infection, even when bacteria entered. They also applied coatings to commercially available spinal implants and monitored the pressure on the implants in lamb quills under normal loads for the diagnosis of device failure. Coatings perform both functions well.

The electronic prototypes require cables, but the researchers next plan to develop wireless power and data communication interfaces for their coatings, an important step for clinical applications, Cao said. They are also working to develop large-scale production of nanopillar-textured bacteria-killing foils.

“This type of antibacterial coating has many potential applications, and because we employ a mechanical mechanism, it has the potential for places where chemicals or heavy metal ions – such as those used in commercial antimicrobial coatings now – would be detrimental,” said Cao.

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