Scientists at Georgia Tech have developed a nanocluster protein coating to be used on titanium implants that creates a substantially stronger bond with the human body than bare metal. The clusters seem to promote bone growth around the implants by manipulating the biological signals that trigger stem cells to differentiate into bone tissue.
In this study, Georgia Tech School of Chemistry and Biochemistry professor David Collard and his students coated clinical-grade titanium with a high density of polymer strands — akin to the bristles on a toothbrush. Then, García and Tim Petrie — formerly a graduate student at Georgia Tech and currently a postdoctoral fellow at the University of Washington — modified the polymer to create three or five self-assembled tethered clusters of the engineered fibronectin, which contained the arginine-glycine-aspartic acid (RGD) sequence to which integrins binds.
To evaluate the in vivo performance of the coated titanium in bone healing, the researchers drilled two-millimeter circular holes into a rat’s tibia bone and pressed tiny clinical-grade titanium cylinders into the holes. The research team tested coatings that included individual strands, pairs, three-strand clusters and five-strand clusters of the engineered fibronectin protein.
Analysis of the bone-implant interface four weeks later revealed a 50 percent enhancement in the amount of contact between the bone and implants coated with three- or five-strand tethered clusters compared to implants coated with single strands. The experiments also revealed a 75 percent increase in the contact of the three- and five-strand clusters compared to the current clinical standard for replacement-joint implants, which is uncoated titanium.
The researchers also tested the fixation of the implants by measuring the amount of force required to pull the implants out of the bone. Implants coated with three- and five-strand tethered clusters of the engineered fibronectin fragment displayed 250 percent higher mechanical fixation over the individual strand and pairs coatings and a 400 percent improvement compared to the unmodified polymer coating. The three- and five-cluster coatings also exhibited a twofold enhancement in pullout strength compared to uncoated titanium.
Press release: Nanocluster Protein Coating on Titanium Strengthens Implant Attachment…
Abstract in Science Translational Medicine: Multivalent Integrin-Specific Ligands Enhance Tissue Healing and Biomaterial Integration