Nanometre-sized molecular oxygen sensors prepared from polymer stabilized phospholipid vesicles

Abstract

Nanometre-sized, chemically-stabilized phospholipid vesicle sensors have been developed for detection of dissolved molecular oxygen. Sensors were prepared by forming 150 nm phospholipid vesicles from 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) or DOPC doped with small (<1%) mole percentages of 1,2-dioleoyl-sn-glycero-3-phosphoethanol amine-N-(7-nitro-2-1,3-benzoxadiazol-4-yl) (NBD-PE). Sensors were stabilized via cross-linking polymerization of hydrophobic methacrylate monomers partitioned into the hydrophobic interior of the DOPC bilayer. The resultant unilamellar, nanometre-sized, polymer–lipid vesicles are spherical, biocompatible and protect sensing components that are loaded into the aqueous interior of the vesicle from interfering species in the exterior environment. For O₂ detection, the oxygen-sensitive fluorescent dye, tris(1,10-phenanthroline)ruthenium(II) chloride (Ru(phen)₃) was encapsulated into the aqueous interior of the polymerized phospholipid vesicle. NBD-PE was introduced into the phospholipid bilayer of the sensor as a reference dye, allowing ratiometric sensors to be constructed. The resultant sensors show high sensitivity, excellent reversibility and excellent linearity over a physiological range of dissolved oxygen concentrations. These results suggest that polymerized phospholipid vesicle sensors can be used for monitoring intracellular O₂ dynamics.