Augmenting the articular cartilage-implant interface: functionalizing with a collagen adhesion protein

The lack of integration between implants and articular cartilage is an unsolved problem that negatively impacts the development of treatments for focal cartilage defects. Many approaches attempt to increase the number of matrix-producing cells that can migrate to the interface, which may help to reinforce the boundary over time but does not address the problems associated with an initially unstable interface. The objective of this study was to develop a bio-adhesive implant to create an immediate bond with the extracellular matrix components of articular cartilage. We hypothesized that implant-bound CollageN Adhesion protein, CNA, would increase the interfacial strength between a poly(vinly alcohol), PVA, implant and articular cartilage immediately after implantation, without preventing cell migration into the implant. By way of a series of in vitro immunohistochemical and mechanical experiments, we demonstrated that: free CNA can bind to articular cartilage, implant-bound CNA can bind to collagen type II and that implants functionalized with CNA result in a four-fold increase in interfacial strength with cartilage relative to un-treated implants at day zero. Of note, the interfacial strength significantly decreased after 21 days in culture which may be an indication that the protein itself has lost its effectiveness. Our data suggests that functionalizing scaffolds with CNA may be a viable approach towards creating an initially stable interface between scaffolds and articular cartilage. Further efforts are required to ensure long-term interface stability.