Chemosensors

15 pages, 3546 KiB

Open AccessArticle

Urea Biosensing through Integration of Urease to the PEDOT-Polyamine Conducting Channels of Organic Electrochemical Transistors: pH-Change-Based Mechanism and Urine Sensing

by Jael R. Neyra Recky, Marjorie Montero-Jimenez, Juliana Scotto, Omar Azzaroni and Waldemar A. Marmisollé

Chemosensors 2024, 12(7), 124; https://doi.org/10.3390/chemosensors12070124 (registering DOI) - 3 Jul 2024

Abstract

We present the construction of an organic electrochemical transistor (OECT) based on poly(3,4-ethylendioxythiophene, PEDOT) and polyallylamine (PAH) and its evaluation as a bioelectronic platform for urease integration and urea sensing. The OECT channel was fabricated in a one-step procedure using chemical polymerization. Then, [...] Read more.

We present the construction of an organic electrochemical transistor (OECT) based on poly(3,4-ethylendioxythiophene, PEDOT) and polyallylamine (PAH) and its evaluation as a bioelectronic platform for urease integration and urea sensing. The OECT channel was fabricated in a one-step procedure using chemical polymerization. Then, urease was immobilized on the surface by electrostatic interaction of the negatively charged enzyme at neutral pH with the positively charged surface of PEDOH-PAH channels. The real-time monitoring of the urease adsorption process was achieved by registering the changes on the drain–source current of the OECT upon continuous scan of the gate potential during enzyme deposition with high sensitivity. On the other hand, integrating urease enabled urea sensing through the transistor response changes resulting from local pH variation as a consequence of enzymatic catalysis. The response of direct enzyme adsorption is compared with layer-by-layer integration using polyethylenimine. Integrating a polyelectrolyte over the adsorbed enzyme resulted in a more stable response, allowing for the sensing of urine even from diluted urine samples. These results demonstrate the potential of integrating enzymes into the active channels of OECTs for the development of biosensors based on local pH changes. Full article

(This article belongs to the Special Issue Electrochemical Biosensors: Advances and Prospects)

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14 pages, 1793 KiB

Open AccessArticle

Environmental Pollution Monitoring via Capillary Zone Electrophoresis and UHPLC Simultaneous Quantification of Some Antipsychotic Drug Residues in Industrial Wastewater Effluents

by Alhumaidi B. Alabbas, Rachid Slimani, Imane El Ouahabi, Abdelkader Zarrouk, Said Lazar, Rachid Azzallou, Noha F. Shalaby and Sherif A. Abdel-Gawad

Chemosensors 2024, 12(7), 123; https://doi.org/10.3390/chemosensors12070123 - 2 Jul 2024

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Abstract

Monitoring and measuring pharmaceutical pollutants in environmental samples is a vital and complex task due to their potential detrimental effects on human health, even at low levels. Using capillary zone electrophoresis (CZE) and ultra-high-performance liquid chromatography (UHPLC), it was possible to separate and [...] Read more.

Monitoring and measuring pharmaceutical pollutants in environmental samples is a vital and complex task due to their potential detrimental effects on human health, even at low levels. Using capillary zone electrophoresis (CZE) and ultra-high-performance liquid chromatography (UHPLC), it was possible to separate and measure three commonly used antipsychotic drugs, chlorpromazine (CPZ), haloperidol (HAL), and risperidone (RIS), in wastewater of the pharmaceutical industry. The technique of solid-phase extraction (SPE) was developed and implemented as a very effective method for preparing samples prior to analysis. The settings of the capillary electrophoretic and chromatographic techniques were adjusted to obtain the most efficient separation profile for the medications being studied. The concentration of all the medicines being investigated ranged from 0.5 to 50 µg/mL. SPE was used to treat real wastewater samples after a thorough validation process that followed the rules set by ICH-Q2B. The developed assays were then effectively employed to identify the tested antipsychotic substances in the real wastewater samples. The provided methodologies may be efficiently utilized to monitor the extent of environmental contamination caused by the investigated pharmaceuticals. Full article

(This article belongs to the Special Issue Chemical Sensors and Analytical Methods for Environmental Monitoring)

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17 pages, 2830 KiB

Open AccessArticle

Electrochemical Detection of Acetaminophen in Pharmaceuticals Using Rod-Shaped α-Bi₂O₃ Prepared via Reverse Co-Precipitation

by Ljubica Andjelković, Slađana Đurđić, Dalibor Stanković, Aleksandar Kremenović, Vladimir B. Pavlović, Dejan A. Jeremić and Marija Šuljagić

Chemosensors 2024, 12(7), 122; https://doi.org/10.3390/chemosensors12070122 - 2 Jul 2024

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Abstract

This study employed a novel synthetic approach involving a modified reverse co-precipitation method utilizing glacial acetic acid to synthesize α-Bi₂O₃. X-ray powder diffraction and scanning and transmission electron microscopy analyses revealed the formation of a rod-like α-Bi₂O [...] Read more.

This study employed a novel synthetic approach involving a modified reverse co-precipitation method utilizing glacial acetic acid to synthesize α-Bi₂O₃. X-ray powder diffraction and scanning and transmission electron microscopy analyses revealed the formation of a rod-like α-Bi₂O₃ microstructure. The prepared material was utilized to modify a glassy carbon paste (GCP) electrode for the development of an electrochemical sensor for acetaminophen (APAP) detection using differential pulse voltammetry (DPV). Cyclic voltammetry studies revealed that the GCP@Bi₂O₃ electrode exhibited enhanced electrochemical properties compared to the bare GCP. The designed GCP@Bi₂O₃ sensor detected APAP in the linear concentration range from 0.05 to 12.00 µM, with LOQ and LOD of 36 nM and 10 nM, respectively. Additionally, the developed sensor demonstrated sufficient precision, repeatability, and selectivity toward APAP detection. The recovery values between the declared and found APAP content in a pharmaceutical formulation (Caffetin^®) displayed the advantageous accuracy, precision, and applicability of the GCP@Bi₂O₃ sensor and the developed DPV method for real-time APAP detection in pharmaceuticals, with minimal interference from the matrix effect. Full article

(This article belongs to the Section Electrochemical Devices and Sensors)

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17 pages, 8490 KiB

Open AccessArticle

Selective Determination of 4,4′-Oxydianiline (4,4′-ODA) in Plastic Packaging Using Molecularly Imprinted Polymer Sensor Integrated with Pyrolyzed Copper/Carbon Composite

by Xuejun Zhou, Pengcheng Ye, Zhiding Huang, Chun Yang, Jiefang Ren, ** Wang and Shali Tang

Chemosensors 2024, 12(7), 121; https://doi.org/10.3390/chemosensors12070121 - 1 Jul 2024

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Abstract

This study focuses on the synthesis, fabrication, and characterization of a molecularly imprinted polymer (MIP) sensor tailored for the selective determination of 4,4′-oxydianiline (4,4′-ODA) in plastic products. Notably, by integrating the sensor matrix with pyrolyzed copper/carbon material derived from Cu-BTC MOF, a remarkable [...] Read more.

This study focuses on the synthesis, fabrication, and characterization of a molecularly imprinted polymer (MIP) sensor tailored for the selective determination of 4,4′-oxydianiline (4,4′-ODA) in plastic products. Notably, by integrating the sensor matrix with pyrolyzed copper/carbon material derived from Cu-BTC MOF, a remarkable enhancement in electrochemical performance is achieved. The Cu-BTC material is grown successfully on the surface of carbon nanotubes (CNTs) and subjected to calcination at 800 °C, yielding a CNT/Cu/C composite. This composite exhibits an increased surface area and enhanced electron transfer capability, resulting in an improved current response. To augment the selective detection capability of the modified electrodes for 4,4′-ODA, molecularly imprinted polymers (MIPs) were incorporated onto the composite surface. The modified electrode (CNT-2/Cu/C/MIP/GCE) was synthesized using acrylamide (AM) and methacrylic acid (MAA) as dual-functional monomers with 4,4′-ODA as a template molecule via precipitation polymerization. The differential pulse voltammetric (DPV) current response to 4,4′-ODA showed a favorable linear relationship within the concentration range of (0.15–10 μM,10–100 μM), with a detection limit of 0.05 μM. Moreover, the CNT-2/Cu/C/MIP/GCE sensor demonstrates exceptional sensitivity, specificity, consistency, and durability. Furthermore, this approach has proven effective in detecting 4,4′-ODA in spiked nylon spatula samples, with recovery rates ranging from 86.3% to 103.5%. Full article

(This article belongs to the Section Materials for Chemical Sensing)

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15 pages, 2372 KiB

Open AccessArticle

Study on the Characterization and Degradation Pattern of Circular RNA Vaccines Using an HPLC Method

by Feiran Cheng, Ji Li, Chaoying Hu, Yu Bai, Jianyang Liu, Dong Liu, Qian He, Qiuheng **, Qunying Mao, Zhenglun Liang and Miao Xu

Chemosensors 2024, 12(7), 120; https://doi.org/10.3390/chemosensors12070120 - 1 Jul 2024

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Abstract

Circular RNA (circRNA) vaccines have attracted increasing attention due to their stable closed-loop structures and persistent protein expression ability. During the synthesis process, nicked circRNAs with similar molecular weights to those of circRNAs are generated. Analytical techniques based on differences in molecular weight, [...] Read more.

Circular RNA (circRNA) vaccines have attracted increasing attention due to their stable closed-loop structures and persistent protein expression ability. During the synthesis process, nicked circRNAs with similar molecular weights to those of circRNAs are generated. Analytical techniques based on differences in molecular weight, such as capillary electrophoresis, struggle to distinguish between circRNAs and nicked circRNAs. The characteristic degradation products of circRNAs and their biological activities remain unclear. Therefore, develo** methods to identify target circRNAs and non-target components and investigating degradation patterns will be beneficial to gaining an in-depth understanding of the properties and quality control of circRNAs vaccines. The reversed-phase HPLC (RP-HPLC) method was established for identification of target circRNAs, product-related substances, and impurities. Subsequently, we investigated the degradation patterns of circRNAs under thermal acceleration conditions and performed biological analysis of degradation products and linear precursors. Here, RP-HPLC method effectively identified circRNAs and nicked circRNAs. With thermal acceleration, circRNAs exhibited a “circular→nicked circRNAs→degradation products” degradation pattern. Biological analysis revealed that the immunogenicity of degradation products significantly decreased, whereas linear precursors did not possess immunogenicity. Thus, our established RP-HPLC method can be used for purity analysis of circRNA vaccines, which contributes to the quality control of circRNA vaccines and promoting the development of circRNA technology. Full article

(This article belongs to the Section Analytical Methods, Instrumentation and Miniaturization)

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15 pages, 1876 KiB

Open AccessArticle

Microflow Injection System for Efficient Cu(II) Detection across a Broad Range

by David Ricart, Antonio David Dorado, Conxita Lao-Luque and Mireia Baeza

Chemosensors 2024, 12(7), 119; https://doi.org/10.3390/chemosensors12070119 - 29 Jun 2024

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Abstract

In this study, a modular, multi-step, photometric microflow injection analysis (micro-FIA) system for the automatic determination of Cu(II) in a bioreactor was developed. The system incorporates diverse 3D-printed modules, including a platform formed by a mixer module to mix Cu(II) with hydroxylamine, which [...] Read more.

In this study, a modular, multi-step, photometric microflow injection analysis (micro-FIA) system for the automatic determination of Cu(II) in a bioreactor was developed. The system incorporates diverse 3D-printed modules, including a platform formed by a mixer module to mix Cu(II) with hydroxylamine, which reduces Cu(II) to Cu(I) linked to a diluter module via a Tesla valve, a chelation mixer module, a disperser module, and a detector module provided by an LED light source at λ = 455 nm and a light dependence resistor (LDR) as a light intensity detector. The system measures the color intensity resulting from the chelation between Cu(I) and neocuproine. The micro-FIA system demonstrated good capability for automatic and continuous Cu(II) determination, in a wide range of Cu concentrations, from 34 to 2000 mg L⁻¹. The device exhibits a good repeatability (coefficient of variation below 2% across the measured concentration range), good reproducibility, and has an accuracy of around 100% between 600 and 1900 mg L⁻¹. Real samples were analyzed using both the micro-FIA system and an atomic absorption spectroscopy method, revealing no statistically significant differences. Additionally, a Tesla valve located before the detector substituted a 3-way solenoid valve, eliminating the need for moving parts. Full article

(This article belongs to the Special Issue Microfluidic Device Based Chemical and Biochemical Sensors)

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14 pages, 1293 KiB

Open AccessArticle

Shungite Paste Electrodes: Basic Characterization and Initial Examples of Applicability in Electroanalysis

by Michaela Bártová, Martin Bartoš, Ivan Švancara and Milan Sýs

Chemosensors 2024, 12(7), 118; https://doi.org/10.3390/chemosensors12070118 - 28 Jun 2024

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Abstract

This article introduces a new type of carbon paste electrode prepared from black raw shungite. In powdered form, this carbonaceous material was mixed with several nonpolar binders. The resulting shungite pastes were microscopically and electrochemically characterized. Mixtures of several pasting liquids with different [...] Read more.

This article introduces a new type of carbon paste electrode prepared from black raw shungite. In powdered form, this carbonaceous material was mixed with several nonpolar binders. The resulting shungite pastes were microscopically and electrochemically characterized. Mixtures of several pasting liquids with different contents of shungite powder were tested to select the optimal composition and compared with other types of carbon paste-based electrodes made of graphite and glassy carbon powder. In terms of physical and mechanical properties, shungite paste electrodes (ShPEs) formed a composite mass being like dense pastes from glassy carbon microspheres, having harder consistency than that of traditional graphitic carbon pastes. The respective electrochemical measurements with ShPEs were based on cyclic voltammetry of ferri-/ferro-cyanide redox pairs, allowing us to evaluate some typical parameters such as electrochemically active surface area, double-layer capacitance, potential range in the working media given, heterogeneous rate constant, charge-transfer coefficient, exchange current density, and open-circuit potential. The whole study with ShPEs was then completed with three different examples of possible electroanalytical applications, confirming that the carbon paste-like configuration with powdered shungite represents an environmentally friendly (green) and low-cost electrode material with good stability in mixed aqueous-organic mixtures, and hence with interesting prospects in electroanalysis of biologically active organic compounds. It seems that similar analytical parameters of the already established variants of carbon paste electrodes can also be expected for their shungite analogues. Full article

(This article belongs to the Special Issue Recent Advances in Electrode Materials for Electrochemical Sensing)

17 pages, 4876 KiB

Open AccessArticle

Electronic Nose and GC-MS Analysis to Detect Mango Twig Tip Dieback in Mango (Mangifera indica) and Panama Disease (TR4) in Banana (Musa acuminata)

by Wathsala Ratnayake, Stanley E. Bellgard, Hao Wang and Vinuthaa Murthy

Chemosensors 2024, 12(7), 117; https://doi.org/10.3390/chemosensors12070117 - 24 Jun 2024

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Abstract

Volatile organic compounds (VOCs), as a biological element released from plants, have been correlated with disease status. Although analysis of VOCs using GC-MS is a routine procedure, it has limitations, including being time-consuming, laboratory-based, and requiring specialist training. Electronic nose devices (E-nose) provide [...] Read more.

Volatile organic compounds (VOCs), as a biological element released from plants, have been correlated with disease status. Although analysis of VOCs using GC-MS is a routine procedure, it has limitations, including being time-consuming, laboratory-based, and requiring specialist training. Electronic nose devices (E-nose) provide a portable and rapid alternative. This is the first pilot study exploring three types of commercially available E-nose to assess how accurately they could detect mango twig tip dieback and Panama disease in bananas. The devices were initially trained and validated on known volatiles, then pure cultures of Pantoea sp., Staphylococcus sp., and Fusarium odoratissimum, and finally, on infected and healthy mango leaves and field-collected, infected banana pseudo-stems. The experiments were repeated three times with six replicates for each host-pathogen pair. The variation between healthy and infected host materials was evaluated using inbuilt data analysis methods, mainly by principal component analysis (PCA) and cross-validation. GC-MS analysis was conducted contemporaneously and identified an 80% similarity between healthy and infected plant material. The portable C 320 was 100% successful in discriminating known volatiles but had a low capability in differentiating healthy and infected plant substrates. The advanced devices (PEN 3/MSEM 160) successfully detected healthy and diseased samples with a high variance. The results suggest that E-noses are more sensitive and accurate in detecting changes of VOCs between healthy and infected plants compared to headspace GC-MS. The study was conducted in controlled laboratory conditions, as E-noses are highly sensitive to surrounding volatiles. Full article

(This article belongs to the Special Issue The Second Edition of GC, MS and GC-MS Analytical Methods: Opportunities and Challenges)

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20 pages, 3236 KiB

Open AccessArticle

First Direct Gravimetric Detection of Perfluorooctane Sulfonic Acid (PFOS) Water Contaminants, Combination with Electrical Measurements on the Same Device—Proof of Concepts

by George R. Ivanov, Tony Venelinov, Yordan G. Marinov, Georgi B. Hadjichristov, Andreas Terfort, Melinda David, Monica Florescu and Selcan Karakuş

Chemosensors 2024, 12(7), 116; https://doi.org/10.3390/chemosensors12070116 - 22 Jun 2024

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Abstract

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are pollutants of concern due to their long-term persistence in the environment and human health effects. Among them, perfluorooctane sulfonic acid (PFOS) is very ubiquitous and dangerous for health. Currently, the detection levels required by the legislation can [...] Read more.

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are pollutants of concern due to their long-term persistence in the environment and human health effects. Among them, perfluorooctane sulfonic acid (PFOS) is very ubiquitous and dangerous for health. Currently, the detection levels required by the legislation can be achieved only with expensive laboratory equipment. Hence, there is a need for portable, in-field, and possibly real-time detection. Optical and electrochemical transduction mechanisms are mainly used for the chemical sensors. Here, we report the first gravimetric detection of small-sized molecules like PFOS (MW 500) dissolved in water. A 100 MHz quartz crystal microbalance (QCM) measured at the third harmonic and an even more sensitive 434 MHz two-port surface acoustic wave (SAW) resonator with gold electrodes were used as transducers. The PFOS selective sensing layer was prepared from the metal organic framework (MOF) MIL-101(Cr). Its nano-sized thickness and structure were optimized using the discreet Langmuir–Blodgett (LB) film deposition method. This is the first time that LB multilayers from bulk MOFs have been prepared. The measured frequency downshifts of around 220 kHz per 1 µmol/L of PFOS, a SAW resonator-loaded Q_L-factor above 2000, and reaction times in the minutes' range are highly promising for an in-field sensor reaching the water safety directives. Additionally, we use the micrometer-sized interdigitated electrodes of the SAW resonator to strongly enhance the electrochemical impedance spectroscopy (EIS) of the PFOS contamination. Thus, for the first time, we combine the ultra-sensitive gravimetry of small molecules in a water environment with electrical measurements on a single device. This combination provides additional sensor selectivity. Control tests against a bare resonator and two similar compounds prove the concept’s viability. All measurements were performed with pocket-sized tablet-powered devices, thus making the system highly portable and field-deployable. While here we focus on one of the emerging water contaminants, this concept with a different selective coating can be used for other new contaminants. Full article

(This article belongs to the Special Issue Chemical Sensors and Analytical Methods for Environmental Monitoring)

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