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To simplify the sensing procedures, chemosensors have become a promising option, which can exhibit optical property changes based on molecular recognition ( Hyman and Franz, 2012 Lee et al., 2015 Wu et al., 2015 Yan et al., 2017 Khorasani et al., 2019 Roy, 2021). However, the requirement of expensive instruments, complex sensing procedures, and trained personnel limits their application for rapid and straightforward analysis.
SCAAs are currently quantified by instrumental methods (i.e., high-performance liquid chromatography (HPLC) ( Zhu et al., 2020) and mass spectrometry (MS) ( Kuster et al., 2008), or enzyme-linked immunosorbent assay (ELISA) ( Kurose et al., 1997) because of their high reliability and accuracy. Thus, by quantifying the reduced form and the oxidized form of SCAAs, the freshness of food samples can be assessed. The reduced form of SCAAs acts as antioxidants in food ( Nikolantonaki et al., 2018), which is oxidized by air over time.
Among the common biochemical components, sulfur-containing amino acids (SCAAs) including L–cysteine (Cys) ( Cebi et al., 2017 Garcia et al., 2015), L–cystine (CySS) ( Chen and Li, 2019), DL–homocysteine (HCys) ( Hoey et al., 2007), glutathione reduced form (GSH) ( Xu et al., 2015), and glutathione oxidized form (GSSG) ( Moreira et al., 2011) have been used as analyte markers in food samples, including wine ( Valero et al., 2003), wheat flour ( Reinbold et al., 2008), and fruit juice ( Fracassetti et al., 2011), to evaluate food quality. Freshness is the main standard for food quality assessment, including the physical form ( Luo et al., 2021), the number of microorganisms ( Jacxsens et al., 2003), and biochemical components ( Lonchamp et al., 2009). To date, there is an increasing demand from consumers to evaluate the safety of food products. Thus, this study represents a step forward in assessing food freshness based on supramolecular analytical methods. It is worth mentioning that we achieved a 91–110% recovery rate in real sample tests, which confirmed the accuracy of the constructed model. Furthermore, we carried out a spike test of glutathione in food samples using the proposed chemosensor array with regression analysis. The semiquantification of reduced/oxidized forms of SCAAs was also performed based on LDA. We succeeded in the qualification of SCAAs based on pattern recognition with 100% correct classification accuracy. The coordination binding–based chemosensor array (CBSA) fabricated by a competitive assay among SCAAs, Zn 2+ ions, and catechol dyes yielded fingerprint-like colorimetric changes. Herein, a self-assembled colorimetric chemosensor array composed of off-the-shelf catechol dyes and a metal ion (i.e., Zn 2+) has been used for the sulfur-containing amino acids (SCAAs i.e., glutathione, glutathione disulfide, L–cysteine, DL–homocysteine, and L–cystine). 2Key Laboratory of Green Chemistry and Chemical Processes, Department of Chemistry, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, China.1Institute of Industrial Science, The University of Tokyo, Tokyo, Japan.Other features include NFC, memory card slot, 3.5mm audio jack, and a fingerprint reader.Xiaojun Lyu 1, Wei Tang 1, Yui Sasaki 1, Jie Zhao 2, Tingting Zheng 2, Yang Tian 2 and Tsuyoshi Minami 1* Its large metal body has unique styling and hides a huge battery. It also has 3D cameras on both the front and back, and a system for adding modules to the back. This unique phone has a display that shows glasses-free 3D content in both landscape and portrait, and has quad-HD resolution in 2D mode.