Polyanionic Polydentate Europium Complexes as Ultrabright One- or Two-photon Bioprobes.

A family of europium (III) complexes based on a polydentate ligand functionalized by charge-transfer antennae presents remarkable one- and two-photon photophysical proper-ties in water or buffer. A detailed analysis of their emission properties suggests that the wrapping of the ligand around the central rare-earth ion results in an overall Cs symmetry in agreement with the theoretical simulation and that about 65-70 % of the emission intensity is concentrated in the hypersensitive D → F transition at 615 nm. Their brightness is excellent, in the range of the best lanthanide bioprobes making them very attractive for bio-imaging experiments.

Design of Novel, Water Soluble and Highly Luminescent Europium Labels with Potential to Enhance Immunoassay Sensitivities.

To meet the continual demands of more-sensitive immunoassays, the synthesis of novel luminescent Eu(III) chelate labels having similar substituted 4-(phenylethynyl)pyridine chromophores in three different chelate structure classes are reported. Significantly enhanced luminescence intensities were obtained, evidently caused by the intra-ligand charge transfer (ILCT) mediated sensitization, but the alternative ligands triplet state process cannot be ruled out. Based on the present study, even quite small changes on the chelate structure, and, especially, on the substituents' donor/acceptor strength on both ends of 4-(phenylethynyl)pyridine subunits have an unpredictable effect on the luminescence.

Homogeneous duplex polymerase chain reaction assay using switchable lanthanide fluorescence probes.

We have developed a duplex polymerase chain reaction (PCR) assay based on switchable lanthanide chelate complementation probes. In the complementation probe technology, two nonfluorescent oligonucleotide probes, one labeled with a lanthanide ion carrier chelate and another with a light absorbing antenna ligand, form a fluorescent complex by self-assembly of the reporter molecules when the two probes are hybridized in adjacent positions to the target DNA. Here we report the synthesis of a new terbium(III) (Tb(III)) ion carrier chelate and a new light-absorbing antenna ligand for Tb(III) and the development of a duplex Chlamydia trachomatis (Ct) PCR assay.

Ligand enabling visible wavelength excitation of europium(III) for fluoroimmunoassays in aqueous micellar solutions.

Fluorescent reporters based on lanthanide ions, such as europium chelates, enable highly sensitive detection in immunoassays and other ligand binding assays. Unfortunately they normally require UV-excitation produced by a xenon flash or nitrogen laser light source. In order to use modern solid state excitation sources such as light emitting diodes (LEDs), these reporters need to be excited at wavelengths longer than 365 nm, where high-powered ultraviolet LEDs are available.

Improved surface stability and biotin binding properties of streptavidin coating on polystyrene.

The ultimate nature of streptavidin to bind biotin tightly is widely utilized in many solid-phase based applications to provide a universal binding surface for biotinylated molecules. However, the preparation of the streptavidin coatings by passive adsorption may heavily alter the binding properties of native streptavidin and may not result in the best possible capture surface for demanding solid-phase assays. By introducing sulphydryl groups through primary amines in the protein, we have activated and conjugated native streptavidin into larger protein polymers resulting in high local binding density when coated on polystyrene.