Optimization of the Coupling of Target Recognition and Signal Generation - Advanced Fluorescence Reporters in Chemistry and Biology - page 81

Fig. 31 (A) Principle of a sandwich immunoassay using FDA particulate labels. The analyte is
first immobilized by the capture antibody preadsorbed on the solid phase (a) and then exposed to
antibody-coated microparticle labels (b). Every microparticle contains

10 8 FDA molecules. High
signal amplification is achieved after solubilisation, release, and conversion of the precursor FDA
into fluorescein molecules by the addition of DMSO and NaOH (c). (B) Calibration curves of
IgG-FDA microcrystal labels with increasing surface coverage of detector antibody (a-d) com-
pared with direct FITC-labeled detector antibody (e). The fluorescence signals increase with
increasing IgG concentration. FDA microcrystals with a high IgG surface coverage (c,d) perform
better than those with lower surface coverage (a,b). (Reprinted with permission from [ 189 ].
Copyright 2002 American Chemical Society)

PCR product [ 192 ]. The dye-doped polymer nanoparticles [ 13 ], silica nanoparticles
[ 14 ] and nano-size all-dye aggregates [ 15 ] are overviewed in other chapters of this
topic.

4.4 Involving Fluorophore Communication

In addition to increasing the number of fluorophores per binding site, there are
several other intriguing phenomena that can be utilized for fluorescence signal
amplification. For instance, when a high local concentration of fluorophores is
reached in a nanoscopic system, inter-fluorophore communication can occur.