Lanthanide-based time-resolved luminescence immunoassays

Abstract

The sensitive and specific detection of analytes such as proteins in biological samples is critical for a variety of applications, for example disease diagnosis. In immunoassays a signal in response to the concentration of analyte present is generated by use of antibodies labeled with radioisotopes, luminophores, or enzymes. All immunoassays suffer to some extent from the problem of the background signal observed in the absence of analyte, which limits the sensitivity and dynamic range that can be achieved. This is especially the case for homogeneous immunoassays and surface measurements on tissue sections and membranes, which typically have a high background because of sample autofluorescence. One way of minimizing background in immunoassays involves the use of lanthanide chelate labels. Luminescent lanthanide complexes have exceedingly long-lived luminescence in comparison with conventional fluorophores, enabling the short-lived background interferences to be removed via time-gated acquisition and delivering greater assay sensitivity and a broader dynamic range. This review highlights the potential of using lanthanide luminescence to design sensitive and specific immunoassays. Techniques for labeling biomolecules with lanthanide chelate tags are discussed, with aspects of chelate design. Microtitre plate-based heterogeneous and homogeneous assays are reviewed and compared in terms of sensitivity, dynamic range, and convenience. The great potential of surface-based time-resolved imaging techniques for biomolecules on gels, membranes, and tissue sections using lanthanide tracers in proteomics applications is also emphasized.

Interpretation of europium(III) spectra

“…Time-gated spectroscopy is also useful to measure europium(III) spectra in biological samples, because the technique allows exclusion of the background fluorescence of the biological material [776][777][778][779][780][781][782]. Time-resolved detection of europium(III) forms the basis of several biomedical analyses and bioanalytical assays [33,93,[783][784][785][786]. In section 3.8, it is described how time- complexes [790].…”

Magnetic Bead‐Based Immunoassay Coupled with Tyramide Signal Amplification for Detection of Salmonella in Foods

“…In the dose-response curves obtained from the developed assay, we observed a dynamic range of three orders of magnitude between 10 2 and 10 5 CFU/mL and between 10 3 and 10 6 CFU/mL with and without enrichment, respectively. This is in agreement with a previous report that well-performing sandwich assays using a multiwell plate format or other array formats should exhibit a dynamic range of 2-3 orders of magnitude (Nielsen et al, 2004;Hagan et al, 2011;Aydin et al, 2014). Linear regression equations were obtained as Y 5 1959.1x 2 4610 (R 2 5 0.959) for enriched samples, and as Y 5 1799.5x 2 6745 (R 2 5 0.976) for nonenriched samples.…”

Lighting up cells with lanthanide self-assembled helicates

“…3 ]@SiO 2 /NH 2 , display a larger quantum yield (28%) than the parent helicate and can be conjugated with streptavidin or with monoclonal antibodies (mAbs) [66]. Immunoassays with the nanoparticles derivatized with the goat anti-mouse immunoglobulin G (IgG) mAb (figure 11) were able to detect 15 ng ml 21 of the biotinylated 5D10 antibody on a streptavidin-coated plate with a SNR of 100. However, non-specific binding of the derivatized nanoparticles limits the sensitivity of the analysis.…”