Toward Food Freshness Monitoring: Coordination Binding–Based Colorimetric Sensor Array for Sulfur-Containing Amino Acids

Abstract

Herein, a self-assembled colorimetric chemosensor array composed of off-the-shelf catechol dyes and a metal ion (i.e., Zn2+) has been used for the sulfur-containing amino acids (SCAAs; i.e., glutathione, glutathione disulfide, L–cysteine, DL–homocysteine, and L–cystine). The coordination binding–based chemosensor array (CBSA) fabricated by a competitive assay among SCAAs, Zn2+ ions, and catechol dyes [i.e., pyrocatechol violet (PV), bromopyrogallol red (BPR), pyrogallol red (PR), and alizarin red S (ARS)] yielded fingerprint-like colorimetric changes. We succeeded in the qualification of SCAAs based on pattern recognition [i.e., a linear discrimination analysis (LDA)] with 100% correct classification accuracy. The semiquantification of reduced/oxidized forms of SCAAs was also performed based on LDA. Furthermore, we carried out a spike test of glutathione in food samples using the proposed chemosensor array with regression analysis. It is worth mentioning that we achieved a 91–110% recovery rate in real sample tests, which confirmed the accuracy of the constructed model. Thus, this study represents a step forward in assessing food freshness based on supramolecular analytical methods.

Printed 384‐Well Microtiter Plate on Paper for Fluorescent Chemosensor Arrays in Food Analysis

“…Chromatographic data were acquired and processed using Shimadzu LabSolutions (Shimadzu, Japan). HPLC equipped with a Waters XBridge BEH Phenyl column, 130 Å, 3.5 μm, 4.6 mm×150 mm for GSH in tomato was conducted according to previous reports [13c,28] . The labeling reagent, 1,4‐benzoquinone was employed to perform pre‐column derivatization for the examination of the target GSH in the freshly made tomato juice by HPLC, which formed N 5 ‐(1‐((carboxymethyl)amino)‐3‐((2,5‐dihydroxyphenyl)thio)‐1‐oxopropan‐2‐yl)glutamine (GSH‐HQ).…”

Optical sensor arrays for the detection and discrimination of natural products

“…Some colorimetric sensor arrays for identifying thiols were developed using indictor-metal ion complexes based on IDAs. 54,94 In these arrays, metal ions act as receptors, and catechol-containing indicators act as signal labels. Different from IDAs, Lei et al presented a new strategy to construct a colorimetric sensor array for thiols using a series of urease-metal ion pairs.…”

Methodologies for Spontaneous Preparation of Chemosensors and Their Arrays Using Off‐the‐Shelf Reagents

“…[104] Furthermore, the concept of CBSAs has been expanded to clinical applications and food analysis. [82,105] In this assay, two esculetin derivatives, namely 37 and 54, and Zn 2 + ions were used as off-the-shelf building blocks for fluorescent CBSA to discriminate sulfur-containing amino acids (SCAAs) as essential biomarkers. [106] The fluorescence detection mechanism relies on a competitive assay involving the catechol fluorophores, Zn 2 + ions, and the target SCAAs (namely cysteine (Cys), glutathione (GSH), homocysteine (HCy), cystine (CySS), and GSH disulfide (GSSG)).…”

“…The concept of CBSAs was further applied to solid‐state chemical sensing using a PCSAD, which successfully detected GlyP in a commercially available herbicide using a combination of imaging analysis and pattern recognition techniques [104] . Furthermore, the concept of CBSAs has been expanded to clinical applications and food analysis [82,105] . In this assay, two esculetin derivatives, namely 37 and 54 , and Zn 2+ ions were used as off‐the‐shelf building blocks for fluorescent CBSA to discriminate sulfur‐containing amino acids (SCAAs) as essential biomarkers [106] .…”