1 research outputs found
Aspartic Acid-Promoted Highly Selective and Sensitive Colorimetric Sensing of Cysteine in Rat Brain
Direct selective determination of cysteine in the cerebral
system
is of great importance because of the crucial roles of cysteine in
physiological and pathological processes. In this study, we report
a sensitive and selective colorimetric assay for cysteine in the rat
brain with gold nanoparticles (Au-NPs) as the signal readout. Initially,
Au-NPs synthesized with citrate as the stabilizer are red in color
and exhibit absorption at 520 nm. The addition of an aqueous solution
(20 μL) of cysteine or aspartic acid alone to a 200 μL
Au-NP dispersion causes no aggregation, while the addition of an aqueous
solution of cysteine into a Au-NP dispersion containing aspartic acid
(1.8 mM) causes the aggregation of Au-NPs and thus results in the
color change of the colloid from wine red to blue. These changes are
ascribed to the ion pair interaction between aspartic acid and cysteine
on the interface between Au-NPs and solution. The concentration of
cysteine can be visualized with the naked eye and determined by UV–vis
spectroscopy. The signal output shows a linear relationship for cysteine
within the concentration range from 0.166 to 1.67 μM with a
detection limit of 100 nM. The assay demonstrated here is highly selective
and is free from the interference of other natural amino acids and
other thiol-containing species as well as the species commonly existing
in the brain such as lactate, ascorbic acid, and glucose. The basal
dialysate level of cysteine in the microdialysate from the striatum
of adult male Sprague–Dawley rats is determined to be around
9.6 ± 2.1 μM. The method demonstrated here is facile but
reliable and durable and is envisaged to be applicable to understanding
the chemical essence involved in physiological and pathological events
associated with cysteine