Arthritis is a significant debilitating disease that affects millions of people in the US alone. When the cartilage, a cushion that helps reduce friction between bones, gets damaged, it leads to diseases such as arthritis, causing pain. This Faculty Early Career Development (CAREER) award aims to understand how the surface of articular cartilage direct and control friction. In addition to the cartilage covering the ends of bones, synovial fluid also serves as the natural lubricant of joints that reduces friction. Combined cartilage and synovial fluid maintain healthy joints, thanks to the lubricating molecules that stick to the surface of the cartilage. This study focuses on examining the biomechanical behaviors of lubricating molecules sticking to the cartilages. Results from this research will help identify molecular strategies to treat arthritis. This research is highly interdisciplinary involving biophysics, polymer physics, surface chemistry, biology, and tribology. This project also supports several educational and outreach activities involving the inclusion and training of underrepresented groups in biomaterials and mechanobiology-relevant research.

Lubricant film formation is critical during locomotion to lubricate and wear-protect the surface of articulated joints. The molecular components of the cartilage extracellular matrix surface provide anchoring sites for lubricating molecules, thus serving as a platform for the assembly of the load/energy-dissipative films. The role of the collagens family in mediating the adsorption of lubricating and wear-protecting molecules has been studied in depth. However, the role of fibronectin, another important cartilage extracellular matrix component, and its various conformations in regulating synovial fluid component adsorption and wear-protecting properties has been overlooked. This award fills this knowledge gap by determining the role of cartilage surface fibronectin in mediating the adsorption and retention of synovial fluid components to regulate joint boundary lubrication and wear protection. To test this hypothesis, this project will: i) develop articular cartilage surface models to control molecular compositions and conformations, ii) quantify synovial fluid component adsorption, and iii) perform nanomechanical and nanotribological characterizations to establish relationships between fibronectin-mediated synovial fluid film formation and tribological performance.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.