We present a versatile and facile route for highly sensitive detection of
analytes through coupling the enlargement of gold nanoparticles (Au NPs)
with fluorescence decrease. The fluorescence intensity of dye molecules
(e.g., fluorescein or rhodamine B) significantly decreased with the
increasing concentration of reducing agents, such as hydrogen peroxide and
hydroquinone. The sensitivity for the detection of reducing agents was much
higher than other detection methods based on the absorbance measurement of
enlarged gold nanoparticles or quantum dot-enzyme hybridization. We could
successfully detect acetylthiocholine with the detection limit of several nM
orders, using an enzymatic reaction by acetylcholinesterase, a key route for
the detection of toxic organophosphate compounds. The fluorescence
decreasing approach described in this work requires only a simple addition
of fluorescence dye to the reaction solution without any chemical
modification. The strategy of fluorescence decrease coupled with
nanoparticle growth will be applied on the fluorescent substrate to develop
detection templates for highly sensitive optical biosensor.