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Orthopedic and Rehabilitation Engineering

Orthopedic and Rehabilitation Engineering - Poster Session B

Poster K15 - Elucidating the role of fibronectin conformation on synovial fluid film formation using a simple model of articular cartilage surface

Thursday, October 24, 2024
2:45 PM - 3:45 PM EST
Location: Exhibit Hall E, F & G

Introduction:  Synovial fluid (SF) is a lubricant found between articulated joints that reduces friction and surface damage during movement. The molecular mechanisms through which articular cartilage surface extracellular matrix (ECM) proteins regulate the adsorption of SF components remain largely unclear. Pathologies, like arthritis, can impact the concentration and conformation of such proteins, fibronectin (Fn) among others. This research investigates the hypothesis that unfolded Fn protein conformation facilitates the adsorption of SF components for the formation of a lubricating and protecting film.

Materials and

Methods:  The adsorption of SF components is quantified using the Quartz Crystal Microbalance with Dissipation (QCM-D) technique, which records time-resolved frequency and dissipation changes in a resonating quartz crystal. The QCM-D crystal surface is functionalized in this model with Fn, to mimic the Fn at the articular cartilage surface. The precursor film of Fn is formed from 35-50 ug/ml of bulk concentration in pH 4 to induce conformational changes, or in pH 7 to maintain the conformation. Then, SF at 25% dilution is flowed over the crystal surface in the QCM-D fluidic chamber. The adsorbed mass of these films is quantified using the Sauerbrey equation, which communicates the linear relationship between the frequency changes of an oscillating quartz crystal and its mass changes.

Results, Conclusions, and Discussions: Preliminary results show important differences in the amount of adsorption of SF on Fn films formed at pH 4 (unfolded) vs. pH 7 (compact) and the amount of Fn precursor film adsorption between the two concentrations tested, 35 ug/ml and 50 ug/ml. These results indicate more Fn precursor film adsorption in pH 4 at 50 ug/ml and more SF adsorption at 35 ug/ml in pH 4 and 7. Future studies will characterize unfolded and folded fractions of Fn due to changes in pH and ionic strength. We predict the Fn conformational changes impact the adsorption of SF components and therefore the lubricating and surface damage protecting performance function.

Acknowledgements (Optional):