Discrimination and Identification of Catecholamines Using Unmodified Gold Nanoparticles-Based Sensor Array

Catecholamines (CAs) play various pivotal roles in the mammalian central and peripheral nervous systems both as neurotransmitters and hormones [1]. Therefore, detection of their abnormalities in the biological fluid, in terms of their concentrations and by products, is of quite importance. Inspired by the superb performance of biological olfactory systems, “chemical nose” strategies have been developed for detection and differentiation of diverse families of analytes [2]. Unlike the traditional “lock-and-key” design, this alternative sensor architecture involves utilizing non-selective sensing elements to generate a fingerprint response pattern which is unique for each analyte [3]. Herein, a colorimetric sensor array based on unmodified gold nanoparticles was developed to sensitively detect and identify multiple structurally similar CAs including dopamine, epinephrine, norepinephrine, and L-dopa in aqueous media. Size dependency of assembly process encouraged us to employ AuNPs with four distinct particle sizes as sensing elements and visual differentiation tools to construct a colorimetric nanoarray. The target CAs seem to act as “molecular bridges”, shortening the interparticle distance and inducing the aggregation of AuNPs. This aggregation produces changes in both the color and UV-vis spectra of AuNPs generating a visual molecular fingerprint of each analyte. The cumulative array responses were differentiated by principal component analysis (PCA) and hierarchical cluster analysis (HCA) with 100% classification accuracy demonstrating the versatility of this simple nanoarray platform. Furthermore, color difference maps were created to provide a visual tool for classifications and semi-quantitative analysis without exploiting any statistical techniques. The obtained results suggest that the proposed colorimetric nanoarray has promising perspective in clinical diagnostics.