Invention: Tissue Integration with Metallic and Polymer Implants
What It Is: A technique for coating implants with materials to improve the interface between medical devices and the human body.How It Works: Implants – whether in the hip, knee, or elsewhere in the body – can drastically improve patient quality of life. However, these implants sometimes loosen from their attachment points in the body, causing pain and requiring surgical removal. The reason for this loosening is that human cells do not attach to and grow well on implants made of inert materials such as titanium, other metals, or polymers. Improving the integration of implants with bone or other tissue could help the more than half a million Americans who receive implants each year. Professors Jeffrey Schwartz (Chemistry) and Jean Schwarzbauer (Molecular Biology) collaborated on the development of a method for coating implants with surfaces that can promote the growth of bone and other cells and the attachment of implants to human tissues in the body.
Together they have demonstrated that they can coat metal or polymer surfaces with self-assembling monolayers of phosphonates, a class of stable and easily available substances. The phosphonate forms a one-molecule thick layer that can permeate and coat all surfaces of the implant evenly. The phosphonate permanently binds to the implant and does not degrade in the body. The team has shown that the phosphonate binds to titanium, stainless steel, nylon, polyurethane, and poly (aryl-ether-ether-ketone) or PEEK, a polymer that is used in implants.
The phosphonate layer acts as a substrate for the growth of bone forming cells, or osteoblasts, and other types of cells. For example, bone cells will not grow well on inert surfaces of titanium or polymers but they will grow on the phosphonate-coated implants. The bone cells can then integrate with host bone in the patient receiving the implant. “We discovered a phosphorous-based coating that self-assembles and worked almost as well as the biologic approach,” said Schwartz.
Jean Schwarzbauer’s team in Molecular Biology performed the experiments that helped move Schwartz’s coating from idea to reality. “Figuring out ways to get cells to stick when and where you want them to stick was really a challenge,” said Schwarzbauer.
Applications: Prior to surgically placing the implant in the body, the implant can be coated with the phosphonate coating. When the implant is placed in the body, bone cells will grow on its surface and connect with the bone of the implant recipient.
Inspiration: A chance conversation between Professor Schwartz and a physician friend led Schwartz to apply his background in surface organic chemistry to exploring potential coatings that could improve implants. To explore whether the new coating could work in living systems, Schwartz turned to the laboratory of molecular biologist Jean Schwarzbauer for studies of the coatings on cells.
Collaborators: Schwartz and Schwarzbauer worked with Ellen Gawalt, Michael Avaltroni, Michael Carolus, Michael Danahy, Brett Silverman, Kim Midwood, Joseph Dennes, Casey Jones, Patrick Donnelly, Stephen Bandini and others.
Commercial Status: Self-Assembled Monolayer of Phosphonate (SAMP) has been licensed by Orthobond, a privately held company based in North Brunswick, NJ. Contact Marc Burel.