Synergistic Interactions of a Synthetic Lubricin-Mimetic with Fibronectin for Enhanced Wear Protection

Lubricin, a major mucinous glycoprotein of mammalian synovial fluids, is believed to provide excellent lubrication to cartilage surfaces. Consequently, when joint disease or replacement leads to increased friction and surface damage in the joint, robust synthetic lubricin alternatives that could be used therapeutically to improve lubrication and surface protection are needed. Here, we report the characterization of a lubricating multiblock bottle-brush polymer whose architecture was inspired by lubricin, and we investigate the role of fibronectin (FN), a glycoprotein found in the superficial zone of cartilage, in mediating the tribological properties of the polymer upon shear between mica surfaces. Our surface force apparatus (SFA) normal force measurements indicate that the lubricin mimetic could be kept anchored between mica surfaces, even under high contact pressures, when an intermediate layer of FN was present. Additional SFA friction measurements shows that FN would also extend the wearless friction regime of the polymer up to pressures of 3.4 MPa while ensuring stable friction coefficients (µ ≈ 0.28). These results demonstrate synergistic interactions between our lubricin mimetic and FN in assisting the lubrication and wear protection of ideal (mica) substrates upon shear. Collectively, these findings suggest that our proposed lubricin mimetic might be a promising alternative to lubricin, as similar mechanisms could also potentially facilitate the interaction between the polymer and cartilage surfaces in articular joints and prosthetic implants in vivo.