Researchers at
North Carolina State University
have developed a "smart coating" that helps surgical implants bond
more closely with bone and ward off infection.
|
| 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 crystalline nano-grains can be seen near the interface
with the titanium implant and mostly amorphous layer on the top
portion of the coating. Credit: Dr. Afsaneh Rabiei, North Carolina
State University. |
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 at NC State 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.
"The bone grows into the coating as the amorphous layer
dissolves, resulting in improved bonding, or osseointegration,"
says Dr. Afsaneh Rabiei, an NC State associate professor of
mechanical and aerospace engineering, associate faculty member of
biomedical engineering and 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. Currently, implant
patients are subjected to an intense regimen of antibiotics to
prevent infection immediately following surgery. However, the site
of the implant will always remain vulnerable to infection. But 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, 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. "That is another reason why we
call it smart coating," Rabiei says.
The research was funded by the National Science Foundation, and
was accomplished with assistance from the Center for Nanophase
Materials Sciences and Shared Research Equipment User Facilities at
Oak Ridge National Laboratory.
The research, "Functionally graded hydroxyapatite coatings doped
with antibacterial components," was co-authored by Rabiei, former
NC State Ph.D. student Xiao Bai, and Oak Ridge National Laboratory
researchers Karren More and Christopher Rouleau. The research is
published online by Acta BioMaterialia.
SOURCE
