(387f) Nanomechanics of Macromolecular Assembly of Synovial Fluid Components on Articular Cartilage Extracellular Matrix

Articular cartilage extracellular matrix (AC-ECM) is a complex macromolecular network that regulates the proper function of synovial joint locomotion, together with the lubricating and wear protective synovial fluid. Changes in the composition and physical properties of the AC-ECM lead to the development of debilitating diseases, such as osteoarthritis, with over 30 million adults living with it in the United States alone. Among several AC-ECM components that have been identified at the cartilage surface are collagen type I (Col-I), collagen type II (Col-II), and fibronectin (Fn). Their roles in mediating synovial fluid component adsorption, assembly and retention has yet to be investigated. In this study, we present an articular cartilage surface model to elucidate how cartilage surface molecular composition mediates adsorption and supramolecular assembly of protecting synovial fluid nanofilms. First, Col-I, Col-II, or Fn were deposited on self-assembled monolayers to model the AC-ECM surface, controlling protein grafting density and conformation at physiological temperatures (37°C). Next, synovial fluid component amounts and nanomechanical properties adsorbed onto Col-I, Col-II, or Fn were quantified and characterized using a combination of quartz crystal microbalance with dissipation (QCM-D) and surface forces apparatus (SFA). Our findings indicate that more synovial fluid components bind to Fn precursor films and that the viscoelasticity of nanofilms under confinement depends on the precursor protein film. In summary, our proposed AC-ECM surface model allows for a quantitative comparison of how the major components of cartilage contribute to synovial fluid nanomechanics and are thus more prone to dysfunction in the altered synovial joint environment.