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Abstract Polythiophenes (PTs) with flexible backbones possess inherent polymer behaviors, including molecular wire effects and dynamic structural changes in π‐conjugated systems. The chemical sensing at the functionalized side chains can manipulate such polymer characteristics, resulting in various optical patterns depending on the analyte structures and their concentrations. The unique optical patterns derived from polymer properties contribute to group categorization over a wide concentration range for pattern recognition. This review aims to provide a concise overview of the potential of PT chemosensor arrays using actual sensing examples in environmental monitoring, medical diagnostics, and food analysis. Furthermore, this review summarizes the methodologies that use polymer gels to realize practical chemosensor array chips for onsite analysis.

Here, we propose a printed 96-well microtiter paper-based chemosensor array device (PCSAD) to simultaneously detect metal ions for river water assessment. Colorimetric chemosensors for metal ions have been designed based on molecular self-assembly using off-the-shelf catechol dyes and a phenylboronic acid (PBA) derivative. The colorimetric self-assembled chemosensors consisting of catechol dyes and a PBA derivative on a 96-well microtiter paper substrate demonstrated various color changes according to the disassembly of the ensembles by the addition of nine types of metal ions. An in-house-made algorithm was used to automate imaging analysis and extract color intensities at seven types of color channels from a captured digital image, allowing for rapid data processing. The obtained information-rich inset data showed fingerprint-like colorimetric responses and was applied to the qualitative and quantitative pattern recognition of metal ions using chemometric techniques. The feasibility of the 96-well microtiter PCSAD for environmental assessment has been revealed by the demonstration of a spike-and-recovery test against metal ions in a river water sample.

Determination of oxyanions is of paramount importance because of the essential role they play in metabolic processes involved in various aquatic environmental problems. In this investigation, a novel chemical sensor array has been developed by using gold nanoparticles modified with different chain lengths of aminothiols (AET-AuNPs) as sensing elements. The proposed sensor array provides a fingerprint-like response pattern originating from cross-reactive binding events and capable of targeting various anions, including the herbicide glyphosate. In addition, chemometric techniques, linear discrimination analysis (LDA) and the support vector machine (SVM) algorithm were employed for analyte classification and regression/prediction. The obtained sensor array demonstrates a remarkable ability to determine multiple oxyanions in both qualitative and quantitative analysis. The described methodology could be used as a simple, sensitive and fast routine analysis for oxyanions in both laboratory and field settings. [ABSTRACT FROM AUTHOR]

The simultaneous identification of multiple metal ions in water has attracted enormous research interest in the past few decades. We herein describe a novel method for multiple metal ion detection using a carbon quantum dots (CQDs)-based chemosensor array and the CQDs are functionalized with different amino acids (glutamine, histidine, arginine, lysine and proline), which act as sensing elements in the sensor array. Eleven metal ions are successfully identified by the designed chemosensor array, with 100% classification accuracy. Importantly, the proposed method allowed the quantitative prediction of the concentration of individual metal ions in the mixture with the aid of a support vector machine (SVM). The sensor array also enables the qualitative detection of unknown metal ions under the interference of tap water and local river water. Thus, the strategy provides a novel high-throughput approach for the identification of various analytes in complex systems. [ABSTRACT FROM AUTHOR]

Chemosensor arrays have a great potential for on-site applications in real-world scenarios. However, to fabricate on chemosensor array a number of chemosensors are required to obtain various optical patterns for multi-analyte detection. Herein, we propose a minimized chemosensor array composed of only two types of carboxylate-functionalized polythiophene derivatives for the detection of eight types of metal ions. Upon recognition of the metal ions, the polythiophenes exhibited changes in their fluorescence intensity and various spectral shifts. Although both chemosensors have the same polymer backbone and recognition moiety, only the difference in the number of methylene groups contributed to the difference in the fluorescence response patterns. Consequently, the metal ions in aqueous media were successfully discriminated qualitatively and quantitatively by the chemosensor microarray on the glass chip. This study offers an approach for achieving a minimized chemosensor array just by changing the alkyl chain lengths without the necessity for many receptors and reporters. [ABSTRACT FROM AUTHOR]

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.

The simultaneous identification of multiple metal ions in water has attracted enormous research interest in the past few decades. We herein describe a novel method for multiple metal ion detection using a carbon quantum dots (CQDs)-based chemosensor array and the CQDs are functionalized with different amino acids (glutamine, histidine, arginine, lysine and proline), which act as sensing elements in the sensor array. Eleven metal ions are successfully identified by the designed chemosensor array, with 100% classification accuracy. Importantly, the proposed method allowed the quantitative prediction of the concentration of individual metal ions in the mixture with the aid of a support vector machine (SVM). The sensor array also enables the qualitative detection of unknown metal ions under the interference of tap water and local river water. Thus, the strategy provides a novel high-throughput approach for the identification of various analytes in complex systems.

A novel fluorescence chemosensor array composed of pyrenylboronic acid-based probes for multi- anion detection has been developed. The pyrenylboronic acid derivatives showed fluorescence quenching or enhancement due to photoinduced electron transfer originating from anion binding. The recognition ability was assessed by fluorescence titrations and electrospray ionization mass spectrometry. Because the array is constructed with cross-reactive probes, the combination of differential binding affinities for anions (i.e., fluoride, acetate, oxalate, malonate, citrate, dihydrogen phosphate, and pyrophosphate) and pattern recognitions, such as linear discriminant analysis, offered a successful simultaneous anion detection with a classification rate of 100%. Furthermore, the chemosensor array allowed for quantitative prediction of oxalate, malonate, and citrate in mixtures using a support vector machine. Importantly, the array system employs low-cost and commercially available reagents as probes. Thus, this study could lead to the development of user-friendly and high-throughput methods to detect a variety of analytes in complicated systems.

Herein, a very simple colorimetric chemosensor array is reported for saccharides (D-glucose, D-fructose, D-xylose, D-galactose, D-mannose, L-rhamnose, and N-acetyl-D-gluosamine). While various types of chemosensors for saccharides have been investigated extensively to-this-date, tremendous additional efforts are still required on a regular basis for the syntheses of new chemosensors. Complicated syntheses would be a bottleneck, given that artificial receptor-based chemosensing systems are not so popular in comparison to biomaterial-based (e.g., enzyme-based) sensing systems. Toward this end, chemosensor array systems using molecular self-assembled materials can avoid the abovementioned synthetic efforts and achieve simultaneous qualitative and quantitative detection of a number of guest saccharides. Using a practical approach, we focus on an indicator displacement assay (IDA) to fabricate a chemosensor array for colorimetric saccharide sensing. On this basis, 3-nitrophenylboronic acid (3-NPBA) spontaneously reacts with catechol dyes such as alizarin red S (ARS), bromopyrogallol red (BPR), pyrogallol red (PR), and pyrocatechol violet (PV), and yields boronate ester derivatives with color changes. The addition of saccharides into the aqueous solution of the boronate esters induces color recovery owing to the higher binding affinity of 3-NPBA for saccharides, thus resulting in the release of dyes. By employing this system, we have succeeded in discriminating saccharides qualitatively and quantitatively with a classification success rate of 100%. Most importantly, our chemosensor array has been fabricated by only mixing low cost commercially available reagents in situ, which means that complicated synthetic processes are avoided for saccharide sensing. We believe this simple colorimetric assay that uses only commercially available reagents can create new, user-friendly supramolecular sensing pathways for saccharides.

Here, we propose a printed 96-well microtiter paper-based chemosensor array device (PCSAD) to simultaneously detect metal ions for river water assessment. Colorimetric chemosensors for metal ions have been designed based on molecular self-assembly using off-the-shelf catechol dyes and a phenylboronic acid (PBA) derivative. The colorimetric self-assembled chemosensors consisting of catechol dyes and a PBA derivative on a 96-well microtiter paper substrate demonstrated various color changes according to the disassembly of the ensembles by the addition of nine types of metal ions. An in-house-made algorithm was used to automate imaging analysis and extract color intensities at seven types of color channels from a captured digital image, allowing for rapid data processing. The obtained information-rich inset data showed fingerprint-like colorimetric responses and was applied to the qualitative and quantitative pattern recognition of metal ions using chemometric techniques. The feasibility of the 96-well microtiter PCSAD for environmental assessment has been revealed by the demonstration of a spike-and-recovery test against metal ions in a river water sample., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Sasaki, Lyu and Minami.)

[Display omitted] • Chemosensor arrays combined with powerful data processing for multi-dimensional chemical information. • Portable digital apparatuses to record optical response patterns without using spectrophotometers. • Solid support materials such as polymer gels and paper for the realization of solid-state chemosensor arrays. Supramolecular optical chemosensors are useful tools in analytical chemistry for the visualization of molecular recognition information. One advantage is that they can be utilized for array systems to detect multiple analytes. However, chemosensor arrays have been evaluated mainly in the solution phase, which limits a wide range of practical applications. Thus, appropriate solid support materials such as polymer gels and papers are required to broaden the scope of the application of chemosensors as on-site analytical tools. In this review, we summarize the actual approaches for the fabrication of solid-state chemosensor arrays combined with powerful data processing techniques and portable digital recorders for real-world applications. [ABSTRACT FROM AUTHOR]

Abstract: Nowadays there is an increasing consumer demand for high quality, minimally processed, additive-free and microbiologically safe foods. The future implication of non-thermal food processing techniques, such as ultra-high hydrostatic pressure and gamma irradiation develop rapidly in the food industrial area. Being non-thermal treatments, components involved in the sensory and nutritional quality remain unaffected. In order to gain experience on feasibility of non-thermal pasteurisation of egg, the effects of ultra-high hydrostatic pressure (UHP) treatment and gamma irradiation levels were investigated. In the present study fresh liquid egg white samples were subjected to ultra-high hydrostatic pressure of 400 MPa for 15 min at 4 °C and gamma irradiation of 3 kGy doses. Near infrared spectroscopy and chemosensor array measurements (electronic nose) were performed in order to monitor the quality changes caused by the applied treatments compared to untreated control samples. The recorded near infrared spectra and the sensor signal responses of the chemosensor array were classified by our self-developed qualitative evaluation method the polar qualification system (PQS) and the spectra recognition tool (SRT). The results of PQS were compared to traditional qualitative mathematical statistical methods such us principal component analysis (PCA), linear discriminant analysis (LDA) and to their combination using the first few principal components in calculation of the discriminant functions (PCA+CDA). [Copyright &y& Elsevier]

• The design strategy for chemosensor arrays with rational combinations of reporter/receptor components. • Self-assembled chemosensors utilizing inter- and intramolecular interactions for minimized but information-rich pattern recognition. • A single chemosensor for simultaneous multi-analyte detection. Supramolecular chemosensor arrays are powerful analytical methods to classify and quantify analytes using pattern recognition. This Review summarizes approaches based on molecular self-assemblies to realize chemosensor arrays comprising a small number of supramolecular chemosensors. After discussing the conventional design strategy for chemosensor arrays, an overview of simple minimized but multifunctional chemosensor arrays for multi-analyte detection is provided. In this context, self-assembled chemosensor arrays utilizing inter- or intramolecular interactions have been highly useful for obtaining information-rich patterns from a smaller number of chemosensors in environmental and biochemical applications. Finally, self-assembly for pattern recognition "without" a chemosensor array is shown to be the simplest example for chirality sensing. The knowledge related to self-assembled chemosensor arrays gathered in this Review will be useful for developing "sophisticated chemosensor arrays" for real-world scenarios. [ABSTRACT FROM AUTHOR]

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). The coordination binding-based chemosensor array (CBSA) fabricated by a competitive assay among SCAAs, Zn 2+ 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., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Lyu, Tang, Sasaki, Zhao, Zheng, Tian and Minami.)

We herein propose an easy-to-prepare mini-chemosensor array constructed by two-types of off-the-shelf coumarin dyes for simultaneous classification and quantification of sulfur-containing amino acids (SCAAs) (i.e., l-cysteine, l-cystine, l-homocysteine, glutathione, and glutathione disulfide). The detection mechanism of SCAAs relied on a coordination-based sensor array (CBSA) utilizing the competitive binding among the coumarin dye, a Zn 2+ ion and SCAAs. The reversible feature of the coordination bond of the coumarin-Zn 2+ resulted in UV/vis spectral shifts and fluorescence enhancement in response to the analytes, offering the multianalyte detection in high accuracy. Furthermore, a mixture of glutathione and l-cysteine was successfully quantified in a sample containing human blood serum. This study would be an important example of the optical chemosensor array toward the rapid and accurate detection of biomarkers.

A novel fluorescence chemosensor array composed of pyrenylboronic acid-based probes for multi- anion detection has been developed. The pyrenylboronic acid derivatives showed fluorescence quenching or enhancement due to photoinduced electron transfer originating from anion binding. The recognition ability was assessed by fluorescence titrations and electrospray ionization mass spectrometry. Because the array is constructed with cross-reactive probes, the combination of differential binding affinities for anions (i.e., fluoride, acetate, oxalate, malonate, citrate, dihydrogen phosphate, and pyrophosphate) and pattern recognitions, such as linear discriminant analysis, offered a successful simultaneous anion detection with a classification rate of 100%. Furthermore, the chemosensor array allowed for quantitative prediction of oxalate, malonate, and citrate in mixtures using a support vector machine. Importantly, the array system employs low-cost and commercially available reagents as probes. Thus, this study could lead to the development of user-friendly and high-throughput methods to detect a variety of analytes in complicated systems., (Copyright © 2020 Cao, Cao, Kubota, Sasaki, Asano, Lyu, Zhang, Zhou, Zhao, Xu, Wu, Minami and Liu.)

[This corrects the article DOI: 10.3389/fchem.2019.00049.].

Herein, a very simple colorimetric chemosensor array is reported for saccharides ( D -glucose, D -fructose, D -xylose, D -galactose, D -mannose, L -rhamnose, and N -acetyl- D -gluosamine). While various types of chemosensors for saccharides have been investigated extensively to-this-date, tremendous additional efforts are still required on a regular basis for the syntheses of new chemosensors. Complicated syntheses would be a bottleneck, given that artificial receptor-based chemosensing systems are not so popular in comparison to biomaterial-based (e.g., enzyme-based) sensing systems. Toward this end, chemosensor array systems using molecular self-assembled materials can avoid the abovementioned synthetic efforts and achieve simultaneous qualitative and quantitative detection of a number of guest saccharides. Using a practical approach, we focus on an indicator displacement assay (IDA) to fabricate a chemosensor array for colorimetric saccharide sensing. On this basis, 3-nitrophenylboronic acid (3-NPBA) spontaneously reacts with catechol dyes such as alizarin red S (ARS), bromopyrogallol red (BPR), pyrogallol red (PR), and pyrocatechol violet (PV), and yields boronate ester derivatives with color changes. The addition of saccharides into the aqueous solution of the boronate esters induces color recovery owing to the higher binding affinity of 3-NPBA for saccharides, thus resulting in the release of dyes. By employing this system, we have succeeded in discriminating saccharides qualitatively and quantitatively with a classification success rate of 100%. Most importantly, our chemosensor array has been fabricated by only mixing low cost commercially available reagents in situ , which means that complicated synthetic processes are avoided for saccharide sensing. We believe this simple colorimetric assay that uses only commercially available reagents can create new, user-friendly supramolecular sensing pathways for saccharides.