Poly-phosphocholinated Liposomes Form Stable Superlubrication Vectors

We have prepared phosphatidylcholine (PC) vesicles (liposomes) incorporating a novel lipid/poly-phosphocholine conjugate. This both stabilizes the liposomes against aggregation (for example during storage or when being delivered) and at the same time allows them to act as very efficient lubricating elements readily attaining superlubric performance (defined as coefficient of friction  < 10-2) via hydration lubrication, at physiological salt concentrations and pressures. In contrast, vesicles sterically-protected by poly(ethylene glycol) chains (PEGylation), which is the general method-of-choice, while equally stable to aggregation, are much poorer lubricants under these conditions, attributed to relatively poor hydration of the PEG. Our approach enables the use of PC liposomes as stable superlubrication vectors in potential biomedical applications.