Abstract
Förster resonance energy transfer (FRET) is a phenomenon widely utilized in biomedical research of macromolecular interactions. In FRET energy is transferred between two fluorophores, the donor and the acceptor. Herein we describe a novel approach utilizing time-resolved FRET (TR-FRET) for the detection of antibodies not only in a solution-phase homogenous assay but also in single- and two-step solid-phase assays. Our method is based on the principle that the Y-shaped immunoglobulin G molecule is able to simultaneously bind two identical antigen molecules. Hence, if a specific IgG is mixed with donor- and acceptor-labeled antigens, the binding of antigens can be measured by TR-FRET. Using donor- and acceptor-labeled streptavidins (SAs) in conjunction with a polyclonal and a monoclonal anti-SA antibody we demonstrate that this approach is fully functional. In addition we characterize the immune complexes responsible for the TR-FRET signal using density gradient ultracentrifugation and solid-phase immunoassays. The homogenous TR-FRET assay described provides a rapid and robust tool for antibody detection, with a wide potential in medical diagnostics.