Enhancement of heterogeneous assays using fluorescent magnetic liposomes.

Interactions between solution phase analytes and surface immobilized biorecognition elements in heterogeneous binding assay formats, such as enzyme-linked immunosorbent assays (ELISAs), are often hindered by mass transfer limitations. In order to improve detection limits and decrease assay times, an applied magnetic field can be used to promote target binding events if the species used for signal generation is rendered magnetic. Here, a ferromagnetic metal oxide-oleic acid complex was incorporated into the lipid bilayer of fluorescent dye-encapsulating liposomes, allowing for their influence under a magnetic field while maintaining their high interior encapsulation volume for signaling molecules. In a high-throughput sandwich-hybridization assay, these DNA-tagged liposomes yielded enhanced sensitivity, in addition to reduced assay times and reagent concentrations, when used with an underlying magnet. These magnetic signaling reagents offer superior performance and adaptability to standard assay formats.