The research involved coating implants with clusters of a protein that copies the body’s own cell-adhesion material fibronectin, revealing that 50% more contact can be made with the surrounding bone than for implants coated with protein pairs or individual strands.
The implants can be fixed in place more securely than plugs made from the bare titanium that is currently used. It is thought that the biologically inspired material improves the growth of bone around the implant and helps strengthen the attachment and integration of the implant to the bone. This innovative research provides an insight into how the nanoscale engineering of materials to present biological motifs with precise nanoscale spacing can enhance biological responses.
To develop the connection, the scientists from Georgia Institute of Technology coated clinical-grade titanium with engineered fibronectin, helping to create an amplified signal for attracting integrins, receptors that attach to the fibronectin and direct and enhance bone formation around the implant.
The research involved drilling circular holes into the tibia bone of a rat and pressing small clinical-grade titanium cylinders into the holes. The coatings were then tested using individual strands, pairs, three-strand clusters and five-strand clusters of the engineered fibronectin protein. The function of these surfaces were then analysed in terms of the promotion of bone growth, the growth of bone surrounding the implant and how strongly attached the implant was to the bone.
When the bone-implant interface was checked a month later, there was a 50% 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. There was also a 75% increase in the contact of the three- and five-strand clusters compared to uncoated titanium.
Team member, Andrés García, commented “Our results demonstrate that engineering coatings that present clustered bioadhesive motifs significantly enhance biomaterial integration and function in animal models and these strategy outperforms non-clustered ligands and the current clinical standard.”
It is hoped that the research, published in the journal Science Translational Medicine [Petriel et al, Sci Transl Med (2010) doi: 10.1126/scitranslmed.3001002], could bring about longer-lasting implants, especially as hip and knee replacements usually only last about 15 years before the components start to deteriorate. With existing medical devices not able to fully integrate with host tissues, there seems more promise in using techniques where biological components are combined with synthetic materials. The team now hope to add to their research by examining other applications with larger animal models, including those in which the implant is already loaded.