A team of researchers at the University of Connecticut have developed a biomaterial scaffold that generates small amounts of electricity when compressed. The piezoelectric material is intended to facilitate cartilage regeneration in joints. Normal movement of a joint in which the scaffold is implanted will create repeated small bursts of electricity. The researchers hypothesize that this electrical charge is a key component of cartilage healing, and helps to attract cells that will colonize and grow within the scaffold.
Cartilage regeneration is a highly active research area in regenerative medicine and tissue engineering. This is because it tends to wear out relatively easily (particularly the cartilage that lines our joints), doesn’t heal itself very well, and is difficult to regenerate. Therefore, cartilage is a prime candidate for new and disruptive regenerative medical technologies.
To date, researchers have tried all sorts of approaches to regrow cartilage, including growth factors and cells delivered within biomaterial scaffolds. However, the newly regenerated tissue doesn’t always behave as desired. “The regrown cartilage doesn’t behave like native cartilage. It breaks, under the normal stresses of the joint,” said Thanh Nguyen, one of the UConn researchers involved in the study.
Nguyen and colleagues have identified electricity as a previously underexplored factor in cartilage regeneration that may assist in the regeneration process. They decided to explore piezoelectric materials that can produce electricity in response to mechanical deformation, a process they say already occurs within the body. “Piezoelectricity is a phenomenon that also exists in the human body,” said Yang Liu, another developer of the new technology. “Bone, cartilage, collagen, DNA and various proteins have a piezoelectric response. Our approach to healing cartilage is highly clinically translational, and we will look into the related healing mechanism.”
Creating an implantable scaffold made from poly-L lactic acid (PLLA) nanofibers, the researchers implanted it into rabbits with injured knee cartilage. The PLLA material is typically used to stitch surgical incisions and it is also biodegradable, and so will eventually break down, allowing the new cartilage to replace it. It is also piezoelectric, and so requires movement to generate electricity.
The researchers allowed the rabbits to use a treadmill to encourage movement, and generate electricity within the injured cartilage. They observed that the treated rabbit knees demonstrated robust cartilage regeneration, and the new cartilage appeared to be mechanically strong and resistant to breaking down under normal movement.
See a video of one of the rabbits hopping on a treadmill post implantation (because why not?)
Study in Science Translational Medicine: Exercise-induced piezoelectric stimulation for cartilage regeneration in rabbits