Selected strategies for improving sensitivity and reliability of immunoassays

Selected recent advances in immunoassay are reviewed. Development has continued on new labels (beta-lactamase, pyrophosphatase, luciferases, photoproteins, pyridopyridazines, europium cryptates, metal carbonyl complexes, porphines, phosphors) and label-detection methods (e.g., chemiluminescence assays, thermometric assays, NADP(+)- and FADP-based coupled assays). Various methods have been explored to increase assay sensitivity, including label amplification via catalyzed reporter deposition (peroxidase label) and immuno-polymerase chain reaction (DNA label). The focus of new immunoassay strategies has been on improved reliability (bispecific antibodies), assay simplification (piezoelectric and surface plasmon resonance immunosensors, phase-modulation fluorescence spectroscopy, polymerized bilayer assemblies), and simultaneous multianalyte testing (e.g., quadruple labeling with lanthanides, one-step test devices for drugs of abuse).