Preparation of luminescent chemosensors by post-functionalization of vesicle surfaces

Surface-reactive luminescent vesicles were prepared by self-assembly of phospholipids, amphiphilic maleimides and fluorophors in aqueous solution. Those preformed liposomes were functionalized with various thiolated receptor units using a thiol-click reaction. As recognition elements, a bis-Zn(2+)-cyclen derivative for the detection of phosphate moieties or a DNA aptamer for the specific binding of the antibiotic ampicillin were utilized. A FRET-based assay revealed the close spatial proximity of the membrane-embedded dansyl molecules with the subsequently immobilized thiols, which is the origin for the signaling mechanism of the obtained vesicular sensors. Those receptor-functionalized liposomes indicate the binding of the targets to their surface by changes of the fluorescence emission properties of the membrane co-embedded carboxyfluorescein dyes. The post-functionalization concept can also be used for molecular imprinting on vesicle surfaces. The template-guided patterning of receptors based on bis-Zn(2+)-cyclen resulted in fluorescent sensors suitable for the specific recognition of a bivalent peptide.