A Triple-Channel Colorimetric Sensor Array for Identification of Biothiols Based on Color RGB (Red/Green/Blue) as Signal Readout

The detection and discrimination of biothiols is of cardinal significance because of their key roles in biological systems and numerous diseases. The present work has developed a simple but effective colorimetric sensor array for identification of biothiols. The sensor array is based on utilization of triple-channel properties (the red (R), green (G), and blue (B) alterations) of polydopamine (PDA)-functionalized gold nanoparticles (AuNPs). Five metal ions (Fe3+, Mg2+, Ca2+, Ag+, and Hg2+) as sensing elements are anchored on the surface of PDA–AuNPs through chelating reaction between metal ions and PDA. Different thiols show distinct binding affinities toward these metal ions, generating diverse colorimetric response patterns (i.e., RGB variations) as “fingerprints” related to each specific biothiol, which can be quantitatively differentiated by linear discriminant analysis (LDA) and hierarchical clustering analysis (HCA). The sensor array can well discriminate six biothiols (dithiothreitol, l-cysteine, glutathione, mercaptoethanol, mercaptosuccinic acid, and mercaptoacetic acid) with 100% accuracy and high sensitivity at the 30 nM level. The sensing strategy, with simple preparation, fast response, excellent sensitivity, and especially stable and high-throughput signal output, is promising for practical applications in artificial olfactory systems.