We present a novel colorimetric method inspired by nature’s
complex mechanisms, capable of selectively determining serotonin with
high sensitivity. This method exploits the inherent binding affinity
of serotonin with sialic acid (SA) molecules anchored to gold nanoparticles
(SA-AuNPs). Upon serotonin binding, SA-AuNPs aggregate, and a characteristic
red shift in the absorbance of SA-AuNPs accompanied by a dramatic
color change (red to blue) occurs, readily observable even without
instrumentation. The proposed method effectively eliminates interventions
from potential interfering species such as dopamine, epinephrine, l-tyrosine, glucosamine, galactose, mannose, and oxalic acid.
The absence of a color change with l-tryptophan, a structurally
related precursor of serotonin, further confirms the high selectivity
of this approach for serotonin detection. The colorimetric method
has a wide linear dynamic range (0.05–1.0 μM), low limit
of detection (0.02 μM), and fast response time (5 min). The
limit of detection of the method is lower than other colorimetric
serotonin sensors reported so far. The possible use of the proposed
method in biological sample analysis was evaluated by employing a
serotonin recovery assay in processed human plasma. The recoveries
ranged from 90.5 to 104.2%, showing promising potential for clinical
applications.