Coating Opens Door to More Safety

When patients have hip, knee or dental replacement surgery, they run the risk of having their bodies reject the implant. But the smart coating developed mitigates that risk by fostering bone growth into the implant. The coating creates a crystalline layer next to the implant, and a mostly amorphous outer layer that touches the surrounding bone. The amorphous layer dissolves over time, releasing calcium and phosphate, which encourages bone growth.

Cross-sectional transmission electron microscope image of the functionally graded smart coating with nano-silver particles distributed throughout the entire thickness of the coating. “The bone grows into the coating as the amorphous layer dissolves, resulting in improved bonding, or osseointegration,” says Afsaneh Rabiei, co-author of a paper describing the research. This bonding also makes the implant more functional, because the bonding helps ensure that the bone and the implant do a better job of sharing the load.

“We call it a smart coating because we can tailor the rate at which the amorphous layer dissolves to match the bone growth rate of each patient,” Rabiei says. This is important because people have very different rates of bone growth. For example, young people’s bones tend to grow far faster than the bones of older adults.

The researchers have also incorporated silver nanoparticles throughout the coating to ward off infections. By incorporating silver into the coating, the silver particles will act as antimicrobial agents as the amorphous layer dissolves, Rabiei says. This will not only limit the amount of antibiotics patients will need following surgery, but will provide protection from infection at the implant site for the life of the implant. Moreover, according to the researchers, the silver is released more quickly right after surgery, when there is more risk of infection, due to the faster dissolution of the amorphous layer of the coating. Silver release will slow down while the patient is healing.; Source: North Carolina State University