Lipid vesicles – liposomes - in aqueous dispersion are frequently protected against aggregation by functionalizing with poly(ethylene glycol) (PEG) moieties, which form a sterically-stabilizing, brush-like corona about the vesicles. Such PEGylation of lipid vesicles nonetheless has drawbacks when liposomes are used as lubrication vectors via the hydration lubrication mechanism, as has been proposed, <i>inter alia</i>, for lubricating articular cartilage in osteoarthritic (OA) joints via intra-articular (IA) injection. We have functionalized liposomes with a brush-like corona using a lipid-polymer moiety whose monomers have a phosphorylcholine structure, essentially identical to the headgroups of phosphatidylcholines, the most common lipids in our bodies: poly[2-(methacryloyloxy)ethyl phosphorylcholine], pMPC. Such moieties are much more hydrated than PEG moieties, and lead to excellent colloidal stabilization of the liposome dispersions, and in addition to correspondingly improved properties of the protected vesicles. Thus they not only result in far better lubrication – by an order of magnitude – than otherwise-identical but PEGylated liposomes, but, remarkably, in far longer retention times following IA injection, and, even more remarkably, in strong down-regulation of cartilage-degrading chondrocyte genes following surgical induction of OA in a murine model.

Functionalizing lipid vesicles by polyphosphocholinated brushes: from superlubrication to gene regulation

ACS Spring 2022

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