Liposome Coated Silk Microspheres Are Effective Lubricants

We present results of our work to develop a liposome based coating on silk microspheres to couple the lubrication properties of highly hydrated phospholipid head groups with the cushioning effects and wear resistance of silk. We show that this liposome coated silk microsphere suspension is an effective lubricant, capable of providing a low coefficient of friction on the order of 0.02, minimizing surface wear and avoiding degradation even over relatively prolonged cycling conditions. We propose that the lubricating properties of the liposome coated silk microspheres are a result of an efficient rolling mechanism. Details of the nanostructure of liposome coated silk microspheres were characterized by confocal laser scanning microscopy and scanning electron microscopy, the lubrication properties and nano-scaled surface wear were characterized using a tribometer and an atomic force microscope. With current therapeutic options for improving joint comfort being limited, liposome coated silk microspheres, which are biocompatible and slowly degradable, plus the appropriate tribological properties, offer an intriguing opportunity. This work was supported by the National Science Foundation.