Because one of the principal functions of articular cartilage in joints is to provide support in diarthrodial joints, transmitting loads with minimum friction and wear, it is likely that understanding the lubrication mechanism in articular cartilage will lead to therapeutic strategies to relieve mild symptomatic osteoarthritis, and possibly to improve the efficacy and expected lifetime of prosthetic implants. For this reason, we used a pin-on-disc tribometer to measure the friction coefficient of both pristine and mechanically damaged cartilage samples in the presence of different lubricant solutions. We find that the experimental set-up allows us to assess different lubrication mechanisms active in cartilage. Among the lubricants considered, 100mg/ml of 100,000 Da polyethylene oxide (PEO) in phosphate buffered saline (PBS) appears to be as effective as synovial fluid (SF), especially on the mechanically-damaged cartilage. It is possible that the viscosity of the lubricant enhances cartilage lubrication via the interstitial fluid pressurization mechanism, maximized by the experimental set up adopted in our friction tests.

We also conducted experiments to investigate how single walled carbon nanotubes (SWNTs) interact with phospholipid membranes. The work will both contribute to prevent adverse health effects due to SWNTs, and enable the applicability of SWNTs in advanced scientific areas such as controlled drug delivery, tissue (i.e., cartilage) culture and regeneration, and/or cancer therapy. Our primary results suggest that the presence of liposomes can keep SWNTs dispersed in water at low surfactant concentration. It is likely that individual or slightly bundled SWNTs interact with phospholipid membranes without significant disruption of the structure of phospholipid bilayer.