Development of immunoassays with improved sensitivity, specificity and reliability are of major interest in modern
bioanalytical research. We describe the development of a new immunomagnetic fluorescence detection (IM-FD)
assay based on specific antigen/antibody interactions and on accumulation of the fluorescence signal on
superparamagnetic PE beads in combination with the use of extrinsic fluorescent labels. IM-FD can be easily
modified by varying the order of coatings and assay conditions. Depending on the target molecule, antibodies
(ABs), entire proteins, or small protein epitopes can be used as capture molecules. The presence of target molecules
is detected by fluorescence microscopy using fluorescently labeled secondary or detection antibodies. Here, we
demonstrate the potential of the new assay detecting the two tumor markers IGF-I and p53 antibodies in the
clinically relevant concentration range. Our data show that the fluorescence-based bead assay exhibits a large
dynamic range and a high sensitivity down to the subpicomolar level.
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