Phosphoinositide-containing polymerized liposomes: Stable membrane-mimetic vesicles for protein-lipid binding analysis

Stable phosphoinositide (PIPn)-containing liposomes were prepared using polydiacetylene photochemistry. Tethered pentacosadiynyl inositol polyphosphate (InsP(n)) analogues of Ins(1,3,4)P-3, Ins(1,4,5)P-3, and Ins(1,3,4,5)P-4 were synthesized, incorporated into vesicles made up of diyne-phosphatidylcholine and -phosphatidylethanolamine, and polymerized by UV irradiation. The polymerized liposome nanoparticles showed markedly increased stability over conventional PIPn-containing vesicles as a result of the covalent conjugated ene-yne network in the acyl chains. The polymerized liposomes were specifically recognized by PIPn binding PH domains in liposome overlay assays and amplified luminescent proximity homogeneous assays. Moreover, the biotin moiety allowed attachment of the nanoparticles to a streptavidin-coated sensor chips in surface plasmon resonance (SPR) sensor. The PIPn headgroups displayed on SPR sensors showed higher affinities for PH domains and PIPn monoclonal antibodies than did monomeric PIPn-analogues with biotinylated acyl chains.