Orthopedic implants are growing more popular due to demographic changes. However, they still offer dangers to patients. Periprosthetic infections are the most common cause of early orthopedic failure. Effective treatment requires implant removal and surgical debridement of diseased tissues. Early diagnosis of implant infections is difficult.
New “smart” coatings for surgical orthopedic implants can monitor device strain and provide early warning of implant failures while destroying infection-causing microorganisms. The coatings combine flexible sensors with a nanostructured antibacterial surface inspired by dragonfly and cicadas’ wings.
A multidisciplinary team of researchers discovered that the coatings prevented infection in live mice and mapped strain in commercial implants placed on sheep spines to warn of potential implant or healing failures.
Study leader Qing Cao, a U. of I. professor of materials science and engineering, said, “This is a combination of bio-inspired nanomaterial design with flexible electronics to battle a complicated, long-term biomedical problem.”
According to Cao, orthopedic implants have significant concerns with infection and device failure, which each impact up to 10% of patients. There have been numerous attempts to fight the disease. However, each has serious drawbacks.
He said, Water-repellent surfaces still allow for the formation of biofilms, and coatings containing antibiotic chemicals or medications quickly lose their effectiveness against drug-resistant bacterial pathogen strains and have hazardous side effects on the tissue around them.
The Illinois team developed a thin foil with nanoscale pillar patterns like those on the wings of cicadas and dragonflies, which are naturally antibacterial. The pillars puncture the cell wall of any bacteria that tries to bind to the foil, destroying it.
Pathobiology professor Gee Lau, a co-author of the study, said, “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.”
The study combines insect-inspired nanostructured foils with highly sensitive flexible electronics. The device prototypes were used with already-existing spinal implants for display purposes. In order to measure strain, the researchers combined arrays of sensitive, flexible electronic sensors, which could help doctors monitor the recovery of specific patients, direct their rehabilitation, and replace or repair equipment before it reaches the point of failure.
The engineering team then worked with veterinary clinical care professor Annette McCoy to put their prototype devices to the test. They implanted the foils in live mice and watched them for any signs of illness, even after introducing bacteria. They also put the coatings on commercially available spinal implants and measured implant strain in sheep spines under normal load to diagnose device failure. The coatings efficiently served both purposes.
The prototype electronics required wires, but the researchers plan to develop wireless power and data communications interfaces for their coatings, which Cao describes as a critical step toward clinical applicability. They are also trying to scale up production of the nanopillar-textured bacteria-killing foil.
The researcher said, “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.”
The study was funded by the National Science Foundation and the Congressionally Directed Medical Research Programmes in the United States.
- Zhang, Y., Cui, J., Chen, et al. A smart coating with integrated physical antimicrobial and strain-mapping functionalities for orthopedic implants. Science Advances. DOI: 10.1126/sciadv.adg7397