Nanoparticles, such as liposomes etc., containing multiple reporter molecules, e.g. dyes, fluorophores, FRET pairs, semiconductor nanocrystals, fluorescent chelates, chelate complexes, coordination complexes, mass tags, Raman tags, lanthanides, enzymes, enzymatic substrates, etc., through a combination of multiple physical and/or chemical interactions are disclosed. The reporter molecules are associated with the nanoparticle in at least two different ways, i.e. through different mechanisms. The nanoparticle is targeted through a targeting agent such as an antibody, an antibody fragment, a nucleotide, a peptide, an aptamer, biotin, avidin, or a ligand. The nanoparticles are useful in bioassays or imaging where an analyte is to be detected by binding of the nanoparticle to the analyte and detection of a signal from the reporter molecules.
