A novel homogeneous assay for DNA using europium as the signalling agent.

A review of lanthanides and their luminescent properties, concentrating in particular on sensitized emission and the use of lanthanide chelates as reporter groups in assays, will be presented. Assays of the format where a target (analyte) uniquely and selectively complexes with a labelled probe (reagent) is discussed. The labelling of probes with efficient luminescent reporter groups or radioisotopes is also highlighted, this allows for the accurate determination of the concentration of target - probe conjugate. These types of assay systems can be categorized into two classes, homogeneous and heterogeneous assays. The specific application of both formats in nucleic acid assays are discussed. Most assay systems are of the heterogeneous type which tend to be complicated and error prone, thus the need for homogeneous methods will be stressed. The development of these systems, their current application to DNA assays and, more specifically, in the detection of nucleotide base sequences using lanthanide chelates as reporter groups is reviewed. The synthesis of two novel intercalator probes, their derivatives based on the known sensitizer ligand PDCA (1,10-phenanthroline-2,9-dicarboxylic acid) and their luminescent complexes are presented. A novel homogeneous assay for the detection of the point mutation which occurs in the DNA of Cystic Fibrosis sufferers is also presented. The assay utilizes two reagents to detect a specific DNA sequence in a longer nucleic strand, One, an oligonucleotide with a non-luminescent europium/EDTA chelate and the other, a duplex DNA intercalator linked via a short chain to a ligand capable of efficiently sensitizing europium luminescence upon complexation, A strongly luminescent ternary complex is formed when a matched single stranded DNA target is mixed with probe and sensitizer reagents. Assay results and trials will also be presented