Editor’s Choice Articles

Editor’s Choice articles are based on recommendations by the scientific editors of MDPI journals from around the world. Editors select a small number of articles recently published in the journal that they believe will be particularly interesting to readers, or important in the respective research area. The aim is to provide a snapshot of some of the most exciting work published in the various research areas of the journal.

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17 pages, 7400 KiB  
Article
Au-Decorated Polyaniline-ZnO Electrospun Composite Nanofiber Gas Sensors with Enhanced Response to NO2 Gas
by Maryam Bonyani, Seyed Mojtaba Zebarjad, Kamal Janghorban, Jin-Young Kim, Hyoun Woo Kim and Sang Sub Kim
Chemosensors 2022, 10(10), 388; https://doi.org/10.3390/chemosensors10100388 - 24 Sep 2022
Cited by 13 | Viewed by 2004
Abstract
Ternary systems are less studied for sensing applications due to complex synthesis procedures. However, they have more sources of resistance modulation, leading to an enhanced gas response. In this study, a ternary system, namely Au-decorated ZnO-polyaniline (PANI) composite nanofibers with different amounts of [...] Read more.
Ternary systems are less studied for sensing applications due to complex synthesis procedures. However, they have more sources of resistance modulation, leading to an enhanced gas response. In this study, a ternary system, namely Au-decorated ZnO-polyaniline (PANI) composite nanofibers with different amounts of PANI (10, 25, and 50 wt.%) were synthesized for NO2 gas sensing studies. First, ZnO nanofibers were synthesized by electrospinning, and then an Au layer (9 nm) was coated on the ZnO nanofibers. Finally, PANI was coated onto the prepared Au-decorated ZnO nanofibers. NO2 gas sensing investigations indicated that the sensor with 25 wt.% PANI had the best response to NO2 gas at 300 °C. In addition, the optimized sensor exhibited high selectivity to NO2 gas. The improved performance of the optimal gas sensor was attributed to the role of Au, the formation of ZnO-PANI heterojunctions, and the optimal amount of PANI. The promising effect of this ternary system for NO2 sensing was demonstrated, and it can be extended to other similar systems. Full article
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21 pages, 6013 KiB  
Article
Development of a Novel Electrochemical Biosensor Based on Organized Mesoporous Carbon and Laccase for the Detection of Serotonin in Food Supplements
by Dorin Dăscălescu and Constantin Apetrei
Chemosensors 2022, 10(9), 365; https://doi.org/10.3390/chemosensors10090365 - 11 Sep 2022
Cited by 9 | Viewed by 2026
Abstract
Serotonin is a biogenic amine that has multiple roles in the human body and is mainly known as the happiness hormone. A new laccase (Lac)-based biosensor has been developed for the qualitative and quantitative determination of serotonin in three dietary supplements from three [...] Read more.
Serotonin is a biogenic amine that has multiple roles in the human body and is mainly known as the happiness hormone. A new laccase (Lac)-based biosensor has been developed for the qualitative and quantitative determination of serotonin in three dietary supplements from three different manufacturers. The enzyme was immobilized on an organized mesoporous carbon-modified carbon screen-printed electrode (OMC-SPE) by the drop-and-dry method, the active surface being pretreated with glutaraldehyde. With the new biosensor, serotonin was selectively detected from different solutions. Square-wave voltammetry was the technique used for the quantitative determination of serotonin, obtaining a detection limit value of 316 nM and a quantification limit value of 948 nM in the linearity range of 0.1–1.2 µM. The pH for the determinations was 5.2; at this value, the biocatalytic activity of the laccase was optimal. At the same time, the electrochemical performance of the OMC-SPE/Lac biosensor was compared with that of the unmodified sensor, a performance that highlighted the superiority of the biosensor and the very important role of the enzyme in electrodetection. The results obtained from the quantitative determination of serotonin by square-wave voltammetry were compared with those from the FTIR method, revealing a very good correlation between the results obtained by the two quantitative determination methods. Full article
(This article belongs to the Special Issue Voltammperometric Sensors)
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22 pages, 2092 KiB  
Review
Electrochemical Sensors and Their Applications: A Review
by Jaya Baranwal, Brajesh Barse, Gianluca Gatto, Gabriela Broncova and Amit Kumar
Chemosensors 2022, 10(9), 363; https://doi.org/10.3390/chemosensors10090363 - 09 Sep 2022
Cited by 128 | Viewed by 33491
Abstract
The world of sensors is diverse and is advancing at a rapid pace due to the fact of its high demand and constant technological improvements. Electrochemical sensors provide a low-cost and convenient solution for the detection of variable analytes and are widely utilized [...] Read more.
The world of sensors is diverse and is advancing at a rapid pace due to the fact of its high demand and constant technological improvements. Electrochemical sensors provide a low-cost and convenient solution for the detection of variable analytes and are widely utilized in agriculture, food, and oil industries as well as in environmental and biomedical applications. The popularity of electrochemical sensing stems from two main advantages: the variability of the reporting signals, such as the voltage, current, overall power output, or electrochemical impedance, and the low theoretical detection limits that originate from the differences in the Faradaic and nonFaradaic currents. This review article attempts to cover the latest advances and applications of electrochemical sensors in different industries. The role of nanomaterials in electrochemical sensor research and advancements is also examined. We believe the information presented here will encourage further efforts on the understanding and progress of electrochemical sensors. Full article
(This article belongs to the Special Issue Electrochemical Detection: Analytical and Biological Challenges)
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12 pages, 2513 KiB  
Article
Polyethylenimine-Based Electrochemical Sensor for the Determination of Caffeic Acid in Aromatic Herbs
by Felipe Zamarchi, Tânia Regina Silva, João Paulo Winiarski, Edson Roberto Santana and Iolanda Cruz Vieira
Chemosensors 2022, 10(9), 357; https://doi.org/10.3390/chemosensors10090357 - 02 Sep 2022
Cited by 17 | Viewed by 2152
Abstract
An electrochemical sensor based on carbon paste modified with polyethyleneimine was developed and employed for the determination of caffeic acid in aromatic herbs. The sensor was prepared by mixing polyethylenimine (1.5% v/v), graphite powder, and mineral oil. The polyethylenimine-based electrode [...] Read more.
An electrochemical sensor based on carbon paste modified with polyethyleneimine was developed and employed for the determination of caffeic acid in aromatic herbs. The sensor was prepared by mixing polyethylenimine (1.5% v/v), graphite powder, and mineral oil. The polyethylenimine-based electrode showed an enhancement of charge transfer at the electrode–solution interface and a higher current intensity for the electrochemical reaction of caffeic acid, in comparison to the unmodified electrode. The calibration plot of caffeic acid constructed in 0.1 mol L−1 acetate buffer (pH 5.0) by square wave voltammetry was linear in the range of 1.25 to 19.9 μmol L−1 with a limit of detection of 0.13 μmol L−1, respectively. Finally, the proposed sensor was employed to monitor the caffeic acid with accuracy in dried Thymus vulgaris and Salvia officinalis samples, with recovery results from 93 to 105%. Full article
(This article belongs to the Special Issue Voltammperometric Sensors)
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34 pages, 4970 KiB  
Review
Cellulose-Based Functional Materials for Sensing
by Valeria Gabrielli and Marco Frasconi
Chemosensors 2022, 10(9), 352; https://doi.org/10.3390/chemosensors10090352 - 26 Aug 2022
Cited by 15 | Viewed by 4976
Abstract
The growing bioeconomic demand for lightweight materials with combined sustainability, large-scale production, ease in functionalization and competitive mechanical properties has seen the revival of cellulose as a scaffold for several applications. In particular, due to its multifunctional features, cellulose has found application in [...] Read more.
The growing bioeconomic demand for lightweight materials with combined sustainability, large-scale production, ease in functionalization and competitive mechanical properties has seen the revival of cellulose as a scaffold for several applications. In particular, due to its multifunctional features, cellulose has found application in sensor and biosensor fabrication. Nonetheless, the great variety of cellulose properties and formulations makes the choice of the best suited cellulose-based material for a specific sensing strategy a difficult task. This review offers a critical discussion and guide for the reader towards the understanding of which of the multiple cellulose derivatives and properties can be exploited for the optimal performance of the desired sensing device. We introduce the unique molecular structure, nanoarchitecture and main properties of cellulose and its derivatives. The different functionalization approaches for anchoring receptors on cellulose derivatives and the processing methodologies for fabricating cellulose-based sensors are explored. As far as the use and performance of cellulose-based functional materials in sensors is concerned, we discuss the recent advances of optical and electrochemical sensors and biosensors for biomedical and environmental monitoring. Full article
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41 pages, 2036 KiB  
Review
Liquid Chromatography on the Different Methods for the Determination of Lipophilicity: An Essential Analytical Tool in Medicinal Chemistry
by José X. Soares, Álvaro Santos, Carla Fernandes and Madalena M. M. Pinto
Chemosensors 2022, 10(8), 340; https://doi.org/10.3390/chemosensors10080340 - 18 Aug 2022
Cited by 19 | Viewed by 5784
Abstract
Lipophilicity is one of many parameters involved in the biological activity of drugs, as it affects their pharmacokinetic and pharmacodynamic behavior. Generally, lipophilicity is assessed by the partition coefficient of a compound between a nonpolar phase (n-octanol) and an aqueous phase [...] Read more.
Lipophilicity is one of many parameters involved in the biological activity of drugs, as it affects their pharmacokinetic and pharmacodynamic behavior. Generally, lipophilicity is assessed by the partition coefficient of a compound between a nonpolar phase (n-octanol) and an aqueous phase (water), expressed as P (partition coefficient) or as its decimal logarithm (Log P). The gold standard method for the experimental determination of Log P is the shake-flask method. In this context, chromatographic methods enable the direct and simple quantification of the partitioned compound between the two phases. This review discusses the use of liquid chromatography (LC) for direct and indirect determination of lipophilicity. Beyond the classical isotropic log P determination, methods for assessing anisotropic lipophilicity are also reviewed. Several examples are discussed that highlight the versatility of LC technique and current trends. The last section of this review focuses on a case study describing an experience of our group and emphasizing the dual role of LC in determining Log P. Full article
(This article belongs to the Collection Women Special Issue in Chemosensors and Analytical Chemistry)
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15 pages, 4902 KiB  
Article
Synthesis of ZIF-8 Coating on ZnO Nanorods for Enhanced Gas-Sensing Performance
by Bo Huang, Wen Zeng and Yanqiong Li
Chemosensors 2022, 10(8), 297; https://doi.org/10.3390/chemosensors10080297 - 30 Jul 2022
Cited by 8 | Viewed by 1860
Abstract
Firstly, ZnO nanorods were prepared by a relatively simple method, and then self-sacrificed by a water bath heating method to generate a commonly used porous ZIF-8 and firmly attached to the ZnO surface. The successful synthesis of synthetic composites was demonstrated with various [...] Read more.
Firstly, ZnO nanorods were prepared by a relatively simple method, and then self-sacrificed by a water bath heating method to generate a commonly used porous ZIF-8 and firmly attached to the ZnO surface. The successful synthesis of synthetic composites was demonstrated with various detection methods. The gas-sensing results show that the ZIF-8-coated ZnO with a core-shell structure exhibits better response than the raw ZnO because of the increased specific surface area and active sites. Full article
(This article belongs to the Special Issue Application and Advance of Gas Sensors)
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24 pages, 18053 KiB  
Review
A Critical Review on the Use of Molecular Imprinting for Trace Heavy Metal and Micropollutant Detection
by Patrick Marcel Seumo Tchekwagep, Robert D. Crapnell, Craig E. Banks, Kai Betlem, Uwe Rinner, Francesco Canfarotta, Joseph W. Lowdon, Kasper Eersels, Bart van Grinsven, Marloes Peeters and Jake McClements
Chemosensors 2022, 10(8), 296; https://doi.org/10.3390/chemosensors10080296 - 27 Jul 2022
Cited by 11 | Viewed by 3099
Abstract
Molecular recognition has been described as the “ultimate” form of sensing and plays a fundamental role in biological processes. There is a move towards biomimetic recognition elements to overcome inherent problems of natural receptors such as limited stability, high-cost, and variation in response. [...] Read more.
Molecular recognition has been described as the “ultimate” form of sensing and plays a fundamental role in biological processes. There is a move towards biomimetic recognition elements to overcome inherent problems of natural receptors such as limited stability, high-cost, and variation in response. In recent years, several alternatives have emerged which have found their first commercial applications. In this review, we focus on molecularly imprinted polymers (MIPs) since they present an attractive alternative due to recent breakthroughs in polymer science and nanotechnology. For example, innovative solid-phase synthesis methods can produce MIPs with sometimes greater affinities than natural receptors. Although industry and environmental agencies require sensors for continuous monitoring, the regulatory barrier for employing MIP-based sensors is still low for environmental applications. Despite this, there are currently no sensors in this area, which is likely due to low profitability and the need for new legislation to promote the development of MIP-based sensors for pollutant and heavy metal monitoring. The increased demand for point-of-use devices and home testing kits is driving an exponential growth in biosensor production, leading to an expected market value of over GPB 25 billion by 2023. A key requirement of point-of-use devices is portability, since the test must be conducted at “the time and place” to pinpoint sources of contamination in food and/or water samples. Therefore, this review will focus on MIP-based sensors for monitoring pollutants and heavy metals by critically evaluating relevant literature sources from 1993 to 2022. Full article
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24 pages, 2300 KiB  
Review
Progress in Electrochemical Biosensing of SARS-CoV-2 Virus for COVID-19 Management
by Md. Mahbubur Rahman
Chemosensors 2022, 10(7), 287; https://doi.org/10.3390/chemosensors10070287 - 20 Jul 2022
Cited by 23 | Viewed by 2886
Abstract
Rapid and early diagnosis of lethal coronavirus disease-19 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an important issue considering global human health, economy, education, and other activities. The advancement of understanding of the chemistry/biochemistry and the structure of [...] Read more.
Rapid and early diagnosis of lethal coronavirus disease-19 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an important issue considering global human health, economy, education, and other activities. The advancement of understanding of the chemistry/biochemistry and the structure of the SARS-CoV-2 virus has led to the development of low-cost, efficient, and reliable methods for COVID-19 diagnosis over “gold standard” real-time reverse transcription-polymerase chain reaction (RT-PCR) due to its several limitations. This led to the development of electrochemical sensors/biosensors for rapid, fast, and low-cost detection of the SARS-CoV-2 virus from the patient’s biological fluids by detecting the components of the virus, including structural proteins (antigens), nucleic acid, and antibodies created after COVID-19 infection. This review comprehensively summarizes the state-of-the-art research progress of electrochemical biosensors for COVID-19 diagnosis. They include the detection of spike protein, nucleocapsid protein, whole virus, nucleic acid, and antibodies. The review also outlines the structure of the SARS-CoV-2 virus, different detection methods, and design strategies of electrochemical SARS-CoV-2 biosensors by highlighting the current challenges and future perspectives. Full article
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16 pages, 3695 KiB  
Article
Development and Optimization of Electrochemical Method for Determination of Vitamin C
by Ivana Škugor Rončević, Danijela Skroza, Ivana Vrca, Ana Marija Kondža and Nives Vladislavić
Chemosensors 2022, 10(7), 283; https://doi.org/10.3390/chemosensors10070283 - 15 Jul 2022
Cited by 13 | Viewed by 2203
Abstract
The focus of this work was to develop a simple electrochemical method for the determination of vitamin C (VitC) by using a specially constructed microelectrode made from pyrolytic graphite sheet (PGS). A procedure for quantifying VitC in a real sample was established. VitC [...] Read more.
The focus of this work was to develop a simple electrochemical method for the determination of vitamin C (VitC) by using a specially constructed microelectrode made from pyrolytic graphite sheet (PGS). A procedure for quantifying VitC in a real sample was established. VitC shows a single quasi-reversible reaction. The method was optimized, and analytical determination was performed by using cyclic voltammetry and square wave voltammetry for electroanalytical purposes. The obtained results show a linear response of the PGS electrode in a wide concentrations range. For the lower concentration range, 0.18–7.04 µg L−1, the sensitivity is 11.7 µAcm−2/mgL−1, while for the higher concentration range, 10.6–70.4 µg L−1, the sensitivity is 134 µAcm−2/mgL−1, preserving the linearity of 0.998 and 0.999. The second objective was to determine the effect of the addition of five different types of “green” biowaste on plant growth, VitC content, and antioxidant activity in arugula (Eruca sativa L.) using the developed method. After three weeks of cultivation, small differences in growth and large differences in certain nutritional characteristics were observed. The addition of black coffee makes the soil slightly alkaline and causes a significant increase in VitC content and antioxidant activity. Full article
(This article belongs to the Special Issue Chemosensors and Biosensors for Food Quality and Safety)
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47 pages, 3612 KiB  
Review
A Review on Potential Electrochemical Point-of-Care Tests Targeting Pandemic Infectious Disease Detection: COVID-19 as a Reference
by Gokul Chandra Biswas, Swapnila Choudhury, Mohammad Mahbub Rabbani and Jagotamoy Das
Chemosensors 2022, 10(7), 269; https://doi.org/10.3390/chemosensors10070269 - 11 Jul 2022
Cited by 26 | Viewed by 3940
Abstract
Fast and accurate point-of-care testing (POCT) of infectious diseases is crucial for diminishing the pandemic miseries. To fight the pandemic coronavirus disease 2019 (COVID-19), numerous interesting electrochemical point-of-care (POC) tests have been evolved to rapidly identify the causal organism SARS-CoV-2 virus, its nucleic [...] Read more.
Fast and accurate point-of-care testing (POCT) of infectious diseases is crucial for diminishing the pandemic miseries. To fight the pandemic coronavirus disease 2019 (COVID-19), numerous interesting electrochemical point-of-care (POC) tests have been evolved to rapidly identify the causal organism SARS-CoV-2 virus, its nucleic acid and antigens, and antibodies of the patients. Many of those electrochemical biosensors are impressive in terms of miniaturization, mass production, ease of use, and speed of test, and they could be recommended for future applications in pandemic-like circumstances. On the other hand, self-diagnosis, sensitivity, specificity, surface chemistry, electrochemical components, device configuration, portability, small analyzers, and other features of the tests can yet be improved. Therefore, this report reviews the developmental trend of electrochemical POC tests (i.e., test platforms and features) reported for the rapid diagnosis of COVID-19 and correlates any significant advancements with relevant references. POCTs incorporating microfluidic/plastic chips, paper devices, nanomaterial-aided platforms, smartphone integration, self-diagnosis, and epidemiological reporting attributes are also surfed to help with future pandemic preparedness. This review especially screens the low-cost and easily affordable setups so that management of pandemic disease becomes faster and easier. Overall, the review is a wide-ranging package for finding appropriate strategies of electrochemical POCT targeting pandemic infectious disease detection. Full article
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13 pages, 1810 KiB  
Article
UV-Excited Fluorescence as a Basis for the In-Situ Identification of Natural Binders in Historical Painting: A Critical Study on Model Samples
by Margherita Longoni, Ester Sara Cacciola and Silvia Bruni
Chemosensors 2022, 10(7), 256; https://doi.org/10.3390/chemosensors10070256 - 01 Jul 2022
Cited by 4 | Viewed by 2495
Abstract
The fluorescence emission by aged organic binders used in painting is a well-known phenomenon. Several literature studies were devoted to its investigation, both on pure binders and on their mixtures with some pigments. Nevertheless, a systematic study about the real possibility of exploiting [...] Read more.
The fluorescence emission by aged organic binders used in painting is a well-known phenomenon. Several literature studies were devoted to its investigation, both on pure binders and on their mixtures with some pigments. Nevertheless, a systematic study about the real possibility of exploiting such a phenomenon for the non-invasive identification of binders in ancient paintings is still lacking. In the present work, a prototype portable fluorimeter was used to analyze a significant number of model painting samples containing different binders (drying oils, egg yolk, milk, animal glue, and gum Arabic) mixed with various pigments having different hues. The model samples were naturally aged in a period ranging from fifteen to one year. The effects on the spectral pattern due to the different binders, the recipes used to prepare them, and the pigments mixed with them were examined. The fluorescence spectra were corrected for the absorption of the emitted radiation due to the pigments. Finally, the corrected spectra were treated by principal component analysis to determine if the possibility of distinguishing at least the most fluorescent and common binders, i.e., drying oils and egg, existed. It was shown that, even if the technique cannot be effectively applied in the case of mixed or superimposed binders, it allows to put forward at least a preliminary hypothesis when pure binders are used. Full article
(This article belongs to the Special Issue Advances in Fluorescence Sensing)
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22 pages, 5042 KiB  
Review
Advances in Electrochemical Techniques for the Detection and Analysis of Genetically Modified Organisms: An Analysis Based on Bibliometrics
by Yuhong Zheng, Hassan Karimi-Maleh and Li Fu
Chemosensors 2022, 10(5), 194; https://doi.org/10.3390/chemosensors10050194 - 21 May 2022
Cited by 17 | Viewed by 3296
Abstract
Since the first successful transgenic plants obtained in 1983, dozens of plants have been tested. On the one hand, genetically modified plants solve the problems of agricultural production. However, due to exogenous genes of transgenic plants, such as its seeds or pollen drift, [...] Read more.
Since the first successful transgenic plants obtained in 1983, dozens of plants have been tested. On the one hand, genetically modified plants solve the problems of agricultural production. However, due to exogenous genes of transgenic plants, such as its seeds or pollen drift, diffusion between populations will likely lead to superweeds or affect the original traits. The detection technology of transgenic plants and their products have received considerable attention. Electrochemical sensing technology is a fast, low-cost, and portable analysis technology. This review interprets the application of electrochemical technology in the analysis and detection of transgenic products through bibliometrics. A total of 83 research articles were analyzed, spanning 2001 to 2021. We described the different stages in the development history of the subject and the contributions of countries and institutions to the topic. Although there were more annual publications in some years, there was no explosive growth in any period. The lack of breakthroughs in this technology is a significant factor in the lack of experts from other fields cross-examining the subject. Through keyword co-occurrence analysis, different research directions on this topic were discussed. The use of nanomaterials with excellent electrical conductivity allows for more sensitive detection of GM crops by electrochemical sensors. Furthermore, co-citation analysis was used to interpret the most popular reports on the topic. In the end, we predict the future development of this topic according to the analysis results. Full article
(This article belongs to the Collection Electrochemical Biosensors for Medical Diagnosis)
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13 pages, 5328 KiB  
Article
Digital Detection of Olive Oil Rancidity Levels and Aroma Profiles Using Near-Infrared Spectroscopy, a Low-Cost Electronic Nose and Machine Learning Modelling
by Claudia Gonzalez Viejo and Sigfredo Fuentes
Chemosensors 2022, 10(5), 159; https://doi.org/10.3390/chemosensors10050159 - 26 Apr 2022
Cited by 8 | Viewed by 2891
Abstract
The success of the olive oil industry depends on provenance and quality-trait consistency affecting the consumers' acceptability/preference and purchase intention. Companies rely on laboratories to analyze samples to assess consistency within the production chain, which may be time-consuming, cost-restrictive, and untimely obtaining results, [...] Read more.
The success of the olive oil industry depends on provenance and quality-trait consistency affecting the consumers' acceptability/preference and purchase intention. Companies rely on laboratories to analyze samples to assess consistency within the production chain, which may be time-consuming, cost-restrictive, and untimely obtaining results, making the process more reactive than predictive. This study proposed implementing digital technologies using near-infrared spectroscopy (NIR) and a novel low-cost e-nose to assess the level of rancidity and aromas in commercial extra-virgin olive oil. Four different olive oils were spiked with three rancidity levels (N = 17). These samples were evaluated using gas-chromatography-mass-spectroscopy, NIR, and an e-nose. Four machine learning models were developed to classify olive oil types and rancidity (Model 1: NIR inputs; Model 2: e-nose inputs) and predict the peak area of 16 aromas (Model 3: NIR; Model 4: e-nose inputs). The results showed high accuracies (Models 1–2: 97% and 87%; Models 3–4: R = 0.96 and 0.93). These digital technologies may change companies from a reactive to a more predictive production of food/beverages to secure product quality and acceptability. Full article
(This article belongs to the Special Issue Chemometrics for Multisensor Systems and Artificial Senses)
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17 pages, 1505 KiB  
Review
Advances in Nucleic Acid Amplification-Based Microfluidic Devices for Clinical Microbial Detection
by Thi Ngoc Diep Trinh and Nae Yoon Lee
Chemosensors 2022, 10(4), 123; https://doi.org/10.3390/chemosensors10040123 - 25 Mar 2022
Cited by 11 | Viewed by 3667
Abstract
Accurate and timely detection of infectious pathogens is urgently needed for disease treatment and control of possible outbreaks worldwide. Conventional methods for pathogen detection are usually time-consuming and labor-intensive. Novel strategies for the identification of pathogenic nucleic acids are necessary for practical application. [...] Read more.
Accurate and timely detection of infectious pathogens is urgently needed for disease treatment and control of possible outbreaks worldwide. Conventional methods for pathogen detection are usually time-consuming and labor-intensive. Novel strategies for the identification of pathogenic nucleic acids are necessary for practical application. The advent of microfluidic technology and microfluidic devices has offered advanced and miniaturized tools to rapidly screen microorganisms, improving many drawbacks of conventional nucleic acid amplification-based methods. In this review, we summarize advances in the microfluidic approach to detect pathogens based on nucleic acid amplification. We survey microfluidic platforms performing two major types of nucleic acid amplification strategies, namely, polymerase chain reaction (PCR) and isothermal nucleic acid amplification. We also provide an overview of nucleic acid amplification-based platforms including studies and commercialized products for SARS-CoV-2 detection. Technologically, we focus on the design of the microfluidic devices, the selected methods for sample preparation, nucleic acid amplification techniques, and endpoint analysis. We also compare features such as analysis time, sensitivity, and specificity of different platforms. The first section of the review discusses methods used in microfluidic devices for upstream clinical sample preparation. The second section covers the design, operation, and applications of PCR-based microfluidic devices. The third section reviews two common types of isothermal nucleic acid amplification methods (loop-mediated isothermal amplification and recombinase polymerase amplification) performed in microfluidic systems. The fourth section introduces microfluidic applications for nucleic acid amplification-based detection of SARS-CoV-2. Finally, the review concludes with the importance of full integration and quantitative analysis for clinical microbial identification. Full article
(This article belongs to the Special Issue Microfluidic Biosensing Platform)
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19 pages, 2579 KiB  
Review
A Review on the Use of Biochar Derived Carbon Quantum Dots Production for Sensing Applications
by Giovanni Lo Bello, Mattia Bartoli, Mauro Giorcelli, Massimo Rovere and Alberto Tagliaferro
Chemosensors 2022, 10(3), 117; https://doi.org/10.3390/chemosensors10030117 - 19 Mar 2022
Cited by 18 | Viewed by 4817
Abstract
Since their discovery, carbon dots have attracted a great deal of interest for their perspective biological applications. Nevertheless, the quenching of carbon dots photoluminescence represents an interesting feature for quantitative analysis in very low concentration of many species. A particular approach for the [...] Read more.
Since their discovery, carbon dots have attracted a great deal of interest for their perspective biological applications. Nevertheless, the quenching of carbon dots photoluminescence represents an interesting feature for quantitative analysis in very low concentration of many species. A particular approach for the production of carbon dots is the use of biochar, a carbonized biomass, as a precursor. In this work, we overview the main achievements accomplished by using biochar-derived carbon dots for detecting and quantifying inorganic and organic species. We also provide background knowledge of the main properties, production and purification routes of carbon dots. Full article
(This article belongs to the Special Issue Biochar Based Sustainable Sensing Platforms)
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16 pages, 9877 KiB  
Article
Rapid On-Site Detection of Illicit Drugs in Smuggled Samples with a Portable Electrochemical Device
by Marc Parrilla, Amorn Slosse, Robin Van Echelpoel, Noelia Felipe Montiel, Amelia R. Langley, Filip Van Durme and Karolien De Wael
Chemosensors 2022, 10(3), 108; https://doi.org/10.3390/chemosensors10030108 - 11 Mar 2022
Cited by 15 | Viewed by 4625
Abstract
The smuggling of illicit drugs urges the development of new tools for rapid on-site identification in cargos. Current methods rely on presumptive color tests and portable spectroscopic techniques. However, these methods sometimes exhibit inaccurate results due to commonly used cutting agents, the colorful [...] Read more.
The smuggling of illicit drugs urges the development of new tools for rapid on-site identification in cargos. Current methods rely on presumptive color tests and portable spectroscopic techniques. However, these methods sometimes exhibit inaccurate results due to commonly used cutting agents, the colorful nature of the sample or because the drugs are smuggled in common goods. Interestingly, electrochemical sensors can deal with these specific problems. Herein, an electrochemical device is presented that uses affordable screen-printed electrodes for the electrochemical profiling of several illicit drugs by square-wave voltammetry (SWV). The identification of the illicit compound is based on the oxidation potential of the analyte. Hence, a library of electrochemical profiles is built upon the analysis of illicit drugs and common cutting agents. This library allows the design of a tailor-made script that enables the identification of each drug through a user-friendly interface (laptop or mobile phone). Importantly, the electrochemical test is compared by analyzing 48 confiscated samples with other portable devices based on Raman and FTIR spectroscopy as well as a laboratory standard method (i.e., gas chromatography–mass spectrometry). Overall, the electrochemical results, obtained through the analysis of different samples from confiscated cargos at an end-user site, present a promising alternative to current methods, offering low-cost and rapid testing in the field. Full article
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27 pages, 3968 KiB  
Review
Inkjet Printing: A Viable Technology for Biosensor Fabrication
by Arif Hussain, Naseem Abbas and Ahsan Ali
Chemosensors 2022, 10(3), 103; https://doi.org/10.3390/chemosensors10030103 - 09 Mar 2022
Cited by 23 | Viewed by 5975
Abstract
Printing technology promises a viable solution for the low-cost, rapid, flexible, and mass fabrication of biosensors. Among the vast number of printing techniques, screen printing and inkjet printing have been widely adopted for the fabrication of biosensors. Screen printing provides ease of operation [...] Read more.
Printing technology promises a viable solution for the low-cost, rapid, flexible, and mass fabrication of biosensors. Among the vast number of printing techniques, screen printing and inkjet printing have been widely adopted for the fabrication of biosensors. Screen printing provides ease of operation and rapid processing; however, it is bound by the effects of viscous inks, high material waste, and the requirement for masks, to name a few. Inkjet printing, on the other hand, is well suited for mass fabrication that takes advantage of computer-aided design software for pattern modifications. Furthermore, being drop-on-demand, it prevents precious material waste and offers high-resolution patterning. To exploit the features of inkjet printing technology, scientists have been keen to use it for the development of biosensors since 1988. A vast number of fully and partially inkjet-printed biosensors have been developed ever since. This study presents a short introduction on the printing technology used for biosensor fabrication in general, and a brief review of the recent reports related to virus, enzymatic, and non-enzymatic biosensor fabrication, via inkjet printing technology in particular. Full article
(This article belongs to the Special Issue Feature Papers on Optical Chemical Sensors and Biosensors)
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26 pages, 2738 KiB  
Review
Flexible Sensors Based on Conductive Polymers
by Ileana-Alexandra Pavel, Sophie Lakard and Boris Lakard
Chemosensors 2022, 10(3), 97; https://doi.org/10.3390/chemosensors10030097 - 01 Mar 2022
Cited by 44 | Viewed by 8396
Abstract
Conductive polymers have attracted wide attention since their discovery due to their unique properties such as good electrical conductivity, thermal and chemical stability, and low cost. With different possibilities of preparation and deposition on surfaces, they present unique and tunable structures. Because of [...] Read more.
Conductive polymers have attracted wide attention since their discovery due to their unique properties such as good electrical conductivity, thermal and chemical stability, and low cost. With different possibilities of preparation and deposition on surfaces, they present unique and tunable structures. Because of the ease of incorporating different elements to form composite materials, conductive polymers have been widely used in a plethora of applications. Their inherent mechanical tolerance limit makes them ideal for flexible devices, such as electrodes for batteries, artificial muscles, organic electronics, and sensors. As the demand for the next generation of (wearable) personal and flexible sensing devices is increasing, this review aims to discuss and summarize the recent manufacturing advances made on flexible electrochemical sensors. Full article
(This article belongs to the Special Issue Smart Polymer-Based Chemical and Biological Sensors)
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12 pages, 1674 KiB  
Article
An Electrochemical and Raman Scattering Dual Detection Biosensor for Rapid Screening and Biomolecular Profiling of Cancer Biomarkers
by Shuvashis Dey, Emtiaz Ahmed, Pranjal Satishchandra Somvanshi, Abu Ali Ibn Sina, Alain Wuethrich and Matt Trau
Chemosensors 2022, 10(3), 93; https://doi.org/10.3390/chemosensors10030093 - 28 Feb 2022
Cited by 5 | Viewed by 2829
Abstract
Detecting circulating biomarkers sensitively and quantitatively is paramount for cancer screening, diagnosis, and treatment selection. Particularly, screening of a panel of circulating protein biomarkers followed by mapping of individual biomarkers could assist better diagnosis and understanding of the cancer progression mechanisms. Herein, we [...] Read more.
Detecting circulating biomarkers sensitively and quantitatively is paramount for cancer screening, diagnosis, and treatment selection. Particularly, screening of a panel of circulating protein biomarkers followed by mapping of individual biomarkers could assist better diagnosis and understanding of the cancer progression mechanisms. Herein, we present a miniaturized biosensing platform with dual readout schemes (electrochemical and Surface enhanced Raman scattering (SERS)) for rapid cancer screening and specific biomarker expressional profiling to support cancer management. Our approach utilizes a controlled nanomixing phenomena under alternative current electrohydrodynamic condition to improve the isolation of cancer-associated circulating proteins (i.e., Epidermal growth factor receptor (EGFR), BRAF, Programmed death-ligand 1 (PD-L1)) with antibody functionalized sensor surface for rapid and efficient isolation of the targets and subsequent labelling with SERS nanotags. The method employs Differential Pulse Voltammetry (DPV) for rapidly screening for the presence of the circulating proteins on biosensor surface irrespective of their type. Upon positive DPV detection, SERS is applied for sensitive read-out of individual biomarkers biomarker levels. In a proof-of-concept study, we demonstrate the dual detection biosensor for analysing circulating BRAF, EGFR and PDL-1 proteins and successfully screened both ensemble and individual biomarker expressional levels as low as 10 pg (1 ng/mL). Our findings clearly indicate the potential of the proposed method for cancer biomarker analysis which may drive the translation of this dual sensing concept in clinical settings. Full article
(This article belongs to the Special Issue Quantitative Sensing in the Microspace)
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33 pages, 4028 KiB  
Review
3D Printing Technologies in Biosensors Production: Recent Developments
by Giulia Remaggi, Alessandro Zaccarelli and Lisa Elviri
Chemosensors 2022, 10(2), 65; https://doi.org/10.3390/chemosensors10020065 - 07 Feb 2022
Cited by 26 | Viewed by 6172
Abstract
Recent advances in 3D printing technologies and materials have enabled rapid development of innovative sensors for applications in different aspects of human life. Various 3D printing technologies have been adopted to fabricate biosensors or some of their components thanks to the advantages of [...] Read more.
Recent advances in 3D printing technologies and materials have enabled rapid development of innovative sensors for applications in different aspects of human life. Various 3D printing technologies have been adopted to fabricate biosensors or some of their components thanks to the advantages of these methodologies over the traditional ones, such as end-user customization and rapid prototyping. In this review, the works published in the last two years on 3D-printed biosensors are considered and grouped on the basis of the 3D printing technologies applied in different fields of application, highlighting the main analytical parameters. In the first part, 3D methods are discussed, after which the principal achievements and promising aspects obtained with the 3D-printed sensors are reported. An overview of the recent developments on this current topic is provided, as established by the considered works in this multidisciplinary field. Finally, future challenges on the improvement and innovation of the 3D printing technologies utilized for biosensors production are discussed. Full article
(This article belongs to the Section (Bio)chemical Sensing)
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26 pages, 29132 KiB  
Review
Nanostructured Metal Oxide Semiconductors towards Greenhouse Gas Detection
by Mehran Dadkhah and Jean-Marc Tulliani
Chemosensors 2022, 10(2), 57; https://doi.org/10.3390/chemosensors10020057 - 30 Jan 2022
Cited by 15 | Viewed by 3343
Abstract
Climate change and global warming are two huge current threats due to continuous anthropogenic emissions of greenhouse gases (GHGs) in the Earth’s atmosphere. Accurate measurements and reliable quantifications of GHG emissions in air are thus of primary importance to the study of climate [...] Read more.
Climate change and global warming are two huge current threats due to continuous anthropogenic emissions of greenhouse gases (GHGs) in the Earth’s atmosphere. Accurate measurements and reliable quantifications of GHG emissions in air are thus of primary importance to the study of climate change and for taking mitigation actions. Therefore, the detection of GHGs should be the first step when trying to reduce their concentration in the environment. Throughout recent decades, nanostructured metal oxide semiconductors have been found to be reliable and accurate for the detection of many different toxic gases in air. Thus, the aim of this article is to present a comprehensive review of the development of various metal oxide semiconductors, as well as to discuss their strong and weak points for GHG detection. Full article
(This article belongs to the Special Issue Functional Nanomaterials for the Detection of Greenhouse Gases)
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20 pages, 5898 KiB  
Article
Introducing Graphene–Indium Oxide Electrochemical Sensor for Detecting Ethanol in Aqueous Samples with CCD-RSM Optimization
by Ramin Boroujerdi and Richard Paul
Chemosensors 2022, 10(2), 42; https://doi.org/10.3390/chemosensors10020042 - 24 Jan 2022
Cited by 11 | Viewed by 3275
Abstract
There is significant demand for portable sensors that can deliver selective and sensitive measurement of ethanol on-site. Such sensors have application across many industries, including clinical and forensic work as well as agricultural and environmental analysis. Here, we report a new graphene–indium oxide [...] Read more.
There is significant demand for portable sensors that can deliver selective and sensitive measurement of ethanol on-site. Such sensors have application across many industries, including clinical and forensic work as well as agricultural and environmental analysis. Here, we report a new graphene–indium oxide electrochemical sensor for the determination of ethanol in aqueous samples. Graphene layers were functionalised by anchoring In2O3 to its surface and the developed composite was used as a selective electrochemical sensor for sensing ethanol through cyclic voltammetry. The detection limit of the sensor was 0.068 mol/L and it showed a linear response to increasing ethanol in the environment up to 1.2 mol/L. The most significant parameters involved and their interactions in the response of the sensor and optimization procedures were studied using a four-factor central composite design (CCD) combined with response surface modelling (RSM). The sensor was applied in the detection of ethanol in authentic samples. Full article
(This article belongs to the Special Issue Recent Advances in Biosensors for Healthcare Applications)
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13 pages, 2071 KiB  
Article
In Situ Detection of Hydrogen Sulfide in 3D-Cultured, Live Prostate Cancer Cells Using a Paper-Integrated Analytical Device
by Jae-Hyung Kim, Young-Ju Lee, Yong-Jin Ahn, Minyoung Kim and Gi-Ja Lee
Chemosensors 2022, 10(1), 27; https://doi.org/10.3390/chemosensors10010027 - 10 Jan 2022
Cited by 8 | Viewed by 2382
Abstract
In this study, a paper-integrated analytical device that combined a paper-based colorimetric assay with a paper-based cell culture platform was developed for the in situ detection of hydrogen sulfide (H2S) in three-dimensional (3D)-cultured, live prostate cancer cells. Two kinds of paper [...] Read more.
In this study, a paper-integrated analytical device that combined a paper-based colorimetric assay with a paper-based cell culture platform was developed for the in situ detection of hydrogen sulfide (H2S) in three-dimensional (3D)-cultured, live prostate cancer cells. Two kinds of paper substrates were fabricated using a simple wax-printing methodology to form the cell culture and detection zones, respectively. LNCaP cells were seeded directly on the paper substrate and grown in the paper-integrated analytical device. The cell viability and H2S production of LNCaP cells were assessed using a simple water-soluble tetrazolium salt colorimetric assay and H2S-sensing paper, respectively. The H2S-sensing paper showed good sensitivity (sensitivity: 6.12 blue channel intensity/μM H2S, R2 = 0.994) and a limit of quantification of 1.08 μM. As a result, we successfully measured changes in endogenous H2S production in 3D-cultured, live LNCaP cells within the paper-integrated analytical device while varying the duration of incubation and substrate concentration (L-cysteine). This paper-integrated analytical device can provide a simple and effective method to investigate H2S signaling pathways and drug screening in a 3D culture model. Full article
(This article belongs to the Section Analytical Methods, Instrumentation and Miniaturization)
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20 pages, 9733 KiB  
Review
Recent Development of Optofluidics for Imaging and Sensing Applications
by Jiukai Tang, Guangyu Qiu and Jing Wang
Chemosensors 2022, 10(1), 15; https://doi.org/10.3390/chemosensors10010015 - 01 Jan 2022
Cited by 16 | Viewed by 3389
Abstract
Optofluidics represents the interaction of light and fluids on a chip that integrates microfluidics and optics, which provides a promising optical platform for manipulating and analyzing fluid samples. Recent years have witnessed a substantial growth in optofluidic devices, including the integration of optical [...] Read more.
Optofluidics represents the interaction of light and fluids on a chip that integrates microfluidics and optics, which provides a promising optical platform for manipulating and analyzing fluid samples. Recent years have witnessed a substantial growth in optofluidic devices, including the integration of optical and fluidic control units, the incorporation of diverse photonic nanostructures, and new applications. All these advancements have enabled the implementation of optofluidics with improved performance. In this review, the recent advances of fabrication techniques and cutting-edge applications of optofluidic devices are presented, with a special focus on the developments of imaging and sensing. Specifically, the optofluidic based imaging techniques and applications are summarized, including the high-throughput cytometry, biochemical analysis, and optofluidic nanoparticle manipulation. The optofluidic sensing section is categorized according to the modulation approaches and the transduction mechanisms, represented by absorption, reflection/refraction, scattering, and plasmonics. Perspectives on future developments and promising avenues in the fields of optofluidics are also provided. Full article
(This article belongs to the Special Issue Nanophotonic Biosensors: Challenges and Development)
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19 pages, 2042 KiB  
Review
Molecularly Imprinted Polymers for Chemical Sensing: A Tutorial Review
by Nadja Leibl, Karsten Haupt, Carlo Gonzato and Luminita Duma
Chemosensors 2021, 9(6), 123; https://doi.org/10.3390/chemosensors9060123 - 26 May 2021
Cited by 88 | Viewed by 8016
Abstract
The field of molecularly imprinted polymer (MIP)-based chemosensors has been experiencing constant growth for several decades. Since the beginning, their continuous development has been driven by the need for simple devices with optimum selectivity for the detection of various compounds in fields such [...] Read more.
The field of molecularly imprinted polymer (MIP)-based chemosensors has been experiencing constant growth for several decades. Since the beginning, their continuous development has been driven by the need for simple devices with optimum selectivity for the detection of various compounds in fields such as medical diagnosis, environmental and industrial monitoring, food and toxicological analysis, and, more recently, the detection of traces of explosives or their precursors. This review presents an overview of the main research efforts made so far for the development of MIP-based chemosensors, critically discusses the pros and cons, and gives perspectives for further developments in this field. Full article
(This article belongs to the Section Materials for Chemical Sensing)
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26 pages, 8544 KiB  
Review
Current Trends in Polymer Based Sensors
by Giancarla Alberti, Camilla Zanoni, Vittorio Losi, Lisa Rita Magnaghi and Raffaela Biesuz
Chemosensors 2021, 9(5), 108; https://doi.org/10.3390/chemosensors9050108 - 13 May 2021
Cited by 40 | Viewed by 5483
Abstract
This review illustrates various types of polymer and nanocomposite polymeric based sensors used in a wide variety of devices. Moreover, it provides an overview of the trends and challenges in sensor research. As fundamental components of new devices, polymers play an important role [...] Read more.
This review illustrates various types of polymer and nanocomposite polymeric based sensors used in a wide variety of devices. Moreover, it provides an overview of the trends and challenges in sensor research. As fundamental components of new devices, polymers play an important role in sensing applications. Indeed, polymers offer many advantages for sensor technologies: their manufacturing methods are pretty simple, they are relatively low-cost materials, and they can be functionalized and placed on different substrates. Polymers can participate in sensing mechanisms or act as supports for the sensing units. Another good quality of polymer-based materials is that their chemical structure can be modified to enhance their reactivity, biocompatibility, resistance to degradation, and flexibility. Full article
(This article belongs to the Section Materials for Chemical Sensing)
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19 pages, 5198 KiB  
Review
Recent Development in Nanomaterial-Based Electrochemical Sensors for Cholesterol Detection
by Hemraj Mahipati Yadav, Jong-Deok Park, Hyeong-Cheol Kang and Jae-Joon Lee
Chemosensors 2021, 9(5), 98; https://doi.org/10.3390/chemosensors9050098 - 29 Apr 2021
Cited by 25 | Viewed by 4672
Abstract
Functional nanomaterials have attracted significant attention in a variety of research fields (in particular, in the healthcare system) because of the easily controllable morphology, their high chemical and environmental stability, biocompatibility, and unique optoelectronic and sensing properties. The sensing properties of nanomaterials can [...] Read more.
Functional nanomaterials have attracted significant attention in a variety of research fields (in particular, in the healthcare system) because of the easily controllable morphology, their high chemical and environmental stability, biocompatibility, and unique optoelectronic and sensing properties. The sensing properties of nanomaterials can be used to detect biomolecules such as cholesterol. Over the past few decades, remarkable progress has been made in the production of cholesterol biosensors that contain nanomaterials as the key component. In this article, various nanomaterials for the electrochemical sensing of cholesterol were reviewed. Cholesterol biosensors are recognized tools in the clinical diagnosis of cardiovascular diseases (CVDs). The function of nanomaterials in cholesterol biosensors were thoroughly discussed. In this study, different pathways for the sensing of cholesterol with functional nanomaterials were investigated. Full article
(This article belongs to the Special Issue Microfluidic Biosensing Platform)
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22 pages, 2707 KiB  
Review
Metal Nanoparticle and Quantum Dot Tags for Signal Amplification in Electrochemical Immunosensors for Biomarker Detection
by Anton Popov, Benediktas Brasiunas, Asta Kausaite-Minkstimiene and Almira Ramanaviciene
Chemosensors 2021, 9(4), 85; https://doi.org/10.3390/chemosensors9040085 - 18 Apr 2021
Cited by 25 | Viewed by 4384
Abstract
With the increasing importance of healthcare and clinical diagnosis, as well as the growing demand for highly sensitive analytical instruments, immunosensors have received considerable attention. In this review, electrochemical immunosensor signal amplification strategies using metal nanoparticles (MNPs) and quantum dots (Qdots) as tags [...] Read more.
With the increasing importance of healthcare and clinical diagnosis, as well as the growing demand for highly sensitive analytical instruments, immunosensors have received considerable attention. In this review, electrochemical immunosensor signal amplification strategies using metal nanoparticles (MNPs) and quantum dots (Qdots) as tags are overviewed, focusing on recent developments in the ultrasensitive detection of biomarkers. MNPs and Qdots can be used separately or in combination with other nanostructures, while performing the function of nanocarriers, electroactive labels, or catalysts. Thus, different functions of MNPs and Qdots as well as recent advances in electrochemical signal amplification are discussed. Additionally, the methods most often used for antibody immobilization on nanoparticles, immunoassay formats, and electrochemical methods for indirect biomarker detection are overviewed. Full article
(This article belongs to the Special Issue Electrochemical Immunosensor)
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39 pages, 3803 KiB  
Review
Microneedle Arrays for Sampling and Sensing Skin Interstitial Fluid
by Navid Kashaninejad, Ahmed Munaz, Hajar Moghadas, Sharda Yadav, Muhammad Umer and Nam-Trung Nguyen
Chemosensors 2021, 9(4), 83; https://doi.org/10.3390/chemosensors9040083 - 16 Apr 2021
Cited by 51 | Viewed by 9621
Abstract
Dermal interstitial fluid (ISF) is a novel source of biomarkers that can be considered as an alternative to blood sampling for disease diagnosis and treatment. Nevertheless, in vivo extraction and analysis of ISF are challenging. On the other hand, microneedle (MN) technology can [...] Read more.
Dermal interstitial fluid (ISF) is a novel source of biomarkers that can be considered as an alternative to blood sampling for disease diagnosis and treatment. Nevertheless, in vivo extraction and analysis of ISF are challenging. On the other hand, microneedle (MN) technology can address most of the challenges associated with dermal ISF extraction and is well suited for long-term, continuous ISF monitoring as well as in situ detection. In this review, we first briefly summarise the different dermal ISF collection methods and compare them with MN methods. Next, we elaborate on the design considerations and biocompatibility of MNs. Subsequently, the fabrication technologies of various MNs used for dermal ISF extraction, including solid MNs, hollow MNs, porous MNs, and hydrogel MNs, are thoroughly explained. In addition, different sensing mechanisms of ISF detection are discussed in detail. Subsequently, we identify the challenges and propose the possible solutions associated with ISF extraction. A detailed investigation is provided for the transport and sampling mechanism of ISF in vivo. Also, the current in vitro skin model integrated with the MN arrays is discussed. Finally, future directions to develop a point-of-care (POC) device to sample ISF are proposed. Full article
(This article belongs to the Section Analytical Methods, Instrumentation and Miniaturization)
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26 pages, 5315 KiB  
Review
Application of PEDOT:PSS and Its Composites in Electrochemical and Electronic Chemosensors
by Nan Gao, Jiarui Yu, Qingyun Tian, Jiangfan Shi, Miao Zhang, Shuai Chen and Ling Zang
Chemosensors 2021, 9(4), 79; https://doi.org/10.3390/chemosensors9040079 - 13 Apr 2021
Cited by 68 | Viewed by 9424
Abstract
Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is a highly important and attractive conducting polymer as well as commercially available in organic electronics, including electrochemical and electronic chemosensors, due to its unique features such as excellent solution-fabrication capability and miscibility, high and controllable conductivity, excellent chemical and [...] Read more.
Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is a highly important and attractive conducting polymer as well as commercially available in organic electronics, including electrochemical and electronic chemosensors, due to its unique features such as excellent solution-fabrication capability and miscibility, high and controllable conductivity, excellent chemical and electrochemical stability, good optical transparency and biocompatibility. In this review, we present a comprehensive overview of the recent research progress of PEDOT:PSS and its composites, and the application in electrochemical and electronic sensors for detecting liquid-phase or gaseous chemical analytes, including inorganic or organic ions, pH, humidity, hydrogen peroxide (H2O2), ammonia (NH3), CO, CO2, NO2, and organic solvent vapors like methanol, acetone, etc. We will discuss in detail the structural, architectural and morphological optimization of PEDOT:PSS and its composites with other additives, as well as the fabrication technology of diverse sensor systems in response to a wide range of analytes in varying environments. At the end of the review will be given a perspective summary covering both the key challenges and potential solutions in the future research of PEDOT:PSS-based chemosensors, especially those in a flexible or wearable format. Full article
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26 pages, 1908 KiB  
Review
A Review of Microfluidic Detection Strategies for Heavy Metals in Water
by Annija Lace and John Cleary
Chemosensors 2021, 9(4), 60; https://doi.org/10.3390/chemosensors9040060 - 24 Mar 2021
Cited by 34 | Viewed by 7194
Abstract
Heavy metal pollution of water has become a global issue and is especially problematic in some developing countries. Heavy metals are toxic to living organisms, even at very low concentrations. Therefore, effective and reliable heavy metal detection in environmental water is very important. [...] Read more.
Heavy metal pollution of water has become a global issue and is especially problematic in some developing countries. Heavy metals are toxic to living organisms, even at very low concentrations. Therefore, effective and reliable heavy metal detection in environmental water is very important. Current laboratory-based methods used for analysis of heavy metals in water require sophisticated instrumentation and highly trained technicians, making them unsuitable for routine heavy metal monitoring in the environment. Consequently, there is a growing demand for autonomous detection systems that could perform in situ or point-of-use measurements. Microfluidic detection systems, which are defined by their small size, have many characteristics that make them suitable for environmental analysis. Some of these advantages include portability, high sample throughput, reduced reagent consumption and waste generation, and reduced production cost. This review focusses on developments in the application of microfluidic detection systems to heavy metal detection in water. Microfluidic detection strategies based on optical techniques, electrochemical techniques, and quartz crystal microbalance are discussed. Full article
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11 pages, 2129 KiB  
Article
Electrochemical Detection of Prostate Cancer Biomarker PCA3 Using Specific RNA-Based Aptamer Labelled with Ferrocene
by Alexei Nabok, Hisham Abu-Ali, Sarra Takita and David P. Smith
Chemosensors 2021, 9(4), 59; https://doi.org/10.3390/chemosensors9040059 - 24 Mar 2021
Cited by 24 | Viewed by 4549
Abstract
This paper reports on a feasibility study of electrochemical in-vitro detection of prostate cancer biomarker PCA3 (prostate cancer antigen 3) in direct assay with specific RNA aptamer labelled with a redox group (ferrocene) and immobilized on a screen-printed gold electrode surface. The cyclic [...] Read more.
This paper reports on a feasibility study of electrochemical in-vitro detection of prostate cancer biomarker PCA3 (prostate cancer antigen 3) in direct assay with specific RNA aptamer labelled with a redox group (ferrocene) and immobilized on a screen-printed gold electrode surface. The cyclic voltammograms and electrochemical impedance spectroscopy methods yield encouraging results on the detection of PCA3 in a range of concentrations from 1 μg/mL down to 0.1 ng/mL in buffer solutions. Both anodic and cathodic current values in cyclic voltammograms measurements and charge transfer resistance values in electrochemical impedance spectroscopy experiments correlate with the PCA3 concentration in the sample. Kinetics studies of the binding of the PCA3 to our aptamer demonstrated high specificity of the reaction with a characteristic affinity constant of approximately 4·1010 molar. The results of this work provide a background for the future development of novel, highly sensitive and cost-effective diagnostic methodologies for prostate cancer detection. Full article
(This article belongs to the Special Issue Electrochemical Immunosensor)
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20 pages, 658 KiB  
Review
Gas Sensors Based on Copper Oxide Nanomaterials: A Review
by Stephan Steinhauer
Chemosensors 2021, 9(3), 51; https://doi.org/10.3390/chemosensors9030051 - 05 Mar 2021
Cited by 105 | Viewed by 9088
Abstract
Metal oxide semiconductors have found widespread applications in chemical sensors based on electrical transduction principles, in particular for the detection of a large variety of gaseous analytes, including environmental pollutants and hazardous gases. This review recapitulates the progress in copper oxide nanomaterial-based devices, [...] Read more.
Metal oxide semiconductors have found widespread applications in chemical sensors based on electrical transduction principles, in particular for the detection of a large variety of gaseous analytes, including environmental pollutants and hazardous gases. This review recapitulates the progress in copper oxide nanomaterial-based devices, while discussing decisive factors influencing gas sensing properties and performance. Literature reports on the highly sensitive detection of several target molecules, including volatile organic compounds, hydrogen sulfide, carbon monoxide, carbon dioxide, hydrogen and nitrogen oxide from parts-per-million down to parts-per-billion concentrations are compared. Physico-chemical mechanisms for sensing and transduction are summarized and prospects for future developments are outlined. Full article
(This article belongs to the Section Nanostructures for Chemical Sensing)
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41 pages, 15347 KiB  
Review
Metal–Oxide Nanowire Molecular Sensors and Their Promises
by Hao Zeng, Guozhu Zhang, Kazuki Nagashima, Tsunaki Takahashi, Takuro Hosomi and Takeshi Yanagida
Chemosensors 2021, 9(2), 41; https://doi.org/10.3390/chemosensors9020041 - 22 Feb 2021
Cited by 27 | Viewed by 5585
Abstract
During the past two decades, one–dimensional (1D) metal–oxide nanowire (NW)-based molecular sensors have been witnessed as promising candidates to electrically detect volatile organic compounds (VOCs) due to their high surface to volume ratio, single crystallinity, and well-defined crystal orientations. Furthermore, these unique physical/chemical [...] Read more.
During the past two decades, one–dimensional (1D) metal–oxide nanowire (NW)-based molecular sensors have been witnessed as promising candidates to electrically detect volatile organic compounds (VOCs) due to their high surface to volume ratio, single crystallinity, and well-defined crystal orientations. Furthermore, these unique physical/chemical features allow the integrated sensor electronics to work with a long-term stability, ultra-low power consumption, and miniature device size, which promote the fast development of “trillion sensor electronics” for Internet of things (IoT) applications. This review gives a comprehensive overview of the recent studies and achievements in 1D metal–oxide nanowire synthesis, sensor device fabrication, sensing material functionalization, and sensing mechanisms. In addition, some critical issues that impede the practical application of the 1D metal–oxide nanowire-based sensor electronics, including selectivity, long-term stability, and low power consumption, will be highlighted. Finally, we give a prospective account of the remaining issues toward the laboratory-to-market transformation of the 1D nanostructure-based sensor electronics. Full article
(This article belongs to the Special Issue Nanomaterials-Based Sensors)
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17 pages, 1161 KiB  
Review
Recent Advances in Optical, Electrochemical and Field Effect pH Sensors
by Federico Vivaldi, Pietro Salvo, Noemi Poma, Andrea Bonini, Denise Biagini, Lorenzo Del Noce, Bernardo Melai, Fabio Lisi and Fabio Di Francesco
Chemosensors 2021, 9(2), 33; https://doi.org/10.3390/chemosensors9020033 - 05 Feb 2021
Cited by 35 | Viewed by 5952
Abstract
Although its first definition dates back to more than a century ago, pH and its measurement are still studied for improving the performance of current sensors in everyday analysis. The gold standard is the glass electrode, but its intrinsic fragility and need of [...] Read more.
Although its first definition dates back to more than a century ago, pH and its measurement are still studied for improving the performance of current sensors in everyday analysis. The gold standard is the glass electrode, but its intrinsic fragility and need of frequent calibration are pushing the research field towards alternative sensitive devices and materials. In this review, we describe the most recent optical, electrochemical, and transistor-based sensors to provide an overview on the status of the scientific efforts towards pH sensing. Full article
(This article belongs to the Collection pH Sensors, Biosensors and Systems)
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12 pages, 4168 KiB  
Article
Development of an ImmunoFET for Analysis of Tumour Necrosis Factor-α in Artificial Saliva: Application for Heart Failure Monitoring
by Daiva Vozgirdaite, Hamdi Ben Halima, Francesca G. Bellagambi, Albert Alcacer, Francisio Palacio, Nicole Jaffrezic-Renault, Nadia Zine, Joan Bausells, Abdelhamid Elaissari and Abdelhamid Errachid
Chemosensors 2021, 9(2), 26; https://doi.org/10.3390/chemosensors9020026 - 29 Jan 2021
Cited by 22 | Viewed by 4617
Abstract
Assessing tumour necrosis factor-α (TNF-α) levels in the human body has become an essential tool to recognize heart failure (HF). In this work, label-free, rapid, easy to use ImmunoFET based on an ion-sensitive field effect transistor (ISFET) was developed for the detection of [...] Read more.
Assessing tumour necrosis factor-α (TNF-α) levels in the human body has become an essential tool to recognize heart failure (HF). In this work, label-free, rapid, easy to use ImmunoFET based on an ion-sensitive field effect transistor (ISFET) was developed for the detection of TNF-α protein. Monoclonal anti-TNF-α antibodies (anti-TNF-α mAb) were immobilized on an ISFET gate made of silicon nitride (Si3N4) after salinization with 11-(triethoxysilyl) undecanal (TESUD). The obtained ISFET functionalized with the mAbs (ImmunoFET) was used to detect TNF-α protein in both phosphate buffer saline (PBS) and artificial saliva (AS). The change in the threshold voltage of the gate (∆VT) showed approximately linear dependency on the concentration of the antigens in the range 5–20 pg/mL for both matrixes. The cross-selectivity study showed that the developed ImmunoFET demonstrated to be selective towards TNF-α, when compared to other HF biomarkers such as N-terminal pro-brain natriuretic peptide (NT-proBNP), interleukin-10 (IL-10), and cortisol, even if further experiments have to be carried out for decreasing possible unspecific absorption phenomena. To the best of our knowledge, this is the first ImmunoFET that has been developed based on Si3N4 for TNF-α detection in AS by electrical measurement. Full article
(This article belongs to the Section Applied Chemical Sensors)
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13 pages, 3027 KiB  
Article
Carbon Dots Fluorescence-Based Colorimetric Sensor for Sensitive Detection of Aluminum Ions with a Smartphone
by Wei Wei, Juan Huang, Wenli Gao, Xiangyang Lu and Xingbo Shi
Chemosensors 2021, 9(2), 25; https://doi.org/10.3390/chemosensors9020025 - 29 Jan 2021
Cited by 28 | Viewed by 3955
Abstract
In this work, blue emission carbon dots (CDs) are synthesized in the one-pot solvothermal method using naringin as precursor. The CDs are used to develop a ratiometric fluorescence sensor for the sensitive analysis of Al3+ with a detection limit of 113.8 nM. [...] Read more.
In this work, blue emission carbon dots (CDs) are synthesized in the one-pot solvothermal method using naringin as precursor. The CDs are used to develop a ratiometric fluorescence sensor for the sensitive analysis of Al3+ with a detection limit of 113.8 nM. A fluorescence emission peak at 500 nm gradually appears, whereas the original fluorescence peak at 420 nm gradually decreases upon the increase in the Al3+ concentration. More importantly, the obvious color change of the CDs probe from blue to green under a 360 nm UV lamp can be identified by a smartphone and combined with the RGB (red/green/blue) analysis. This results in a visual and sensitive analysis of Al3+ with a detection limit of 5.55 μM. Moreover, the high recovery is in the 92.46–104.10% range, which demonstrates the high accuracy of this method for actual samples’ analysis. The use of a smartphone and the RGB analysis greatly simplifies the operation process, saves equipment cost, shortens the detection time, and provides a novel method for the instant, on-site, visual detection of Al3+ in actual samples. Full article
(This article belongs to the Special Issue Near-Infrared Fluorophores for Biomedical Research)
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21 pages, 5499 KiB  
Review
Electrochemical Impedance Spectroscopy on 2D Nanomaterial MXene Modified Interfaces: Application as a Characterization and Transducing Tool
by Juvissan Aguedo, Lenka Lorencova, Marek Barath, Pavol Farkas and Jan Tkac
Chemosensors 2020, 8(4), 127; https://doi.org/10.3390/chemosensors8040127 - 07 Dec 2020
Cited by 32 | Viewed by 7181
Abstract
This review presents the basic characteristics of MXene, a novel 2D nanomaterial with many outstanding properties applicable to electrochemical sensing and biosensing. The second part deals with electrochemical impedance spectroscopy (EIS) and its beneficial features applicable to ultrasensitive electrochemical sensing and label-free biosensing. [...] Read more.
This review presents the basic characteristics of MXene, a novel 2D nanomaterial with many outstanding properties applicable to electrochemical sensing and biosensing. The second part deals with electrochemical impedance spectroscopy (EIS) and its beneficial features applicable to ultrasensitive electrochemical sensing and label-free biosensing. The main part of the review presents recent advances in the integration of MXene to design electrochemical interfaces. EIS was used to evaluate the effect of anodic potential on MXene and the effect of the MXene preparation route and for characterization of MXene grafted with polymers. It also included the application of EIS as the main transducing tool for antibody- and aptamer-based biosensors or biosensors integrating molecularly imprinted polymers. Full article
(This article belongs to the Special Issue Analytical (Chem and Bio)sensors Based on EIS Measurements)
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17 pages, 4881 KiB  
Article
Graphene Oxide as a Sensing Material for Gas Detection Based on Nanomechanical Sensors in the Static Mode
by Gaku Imamura, Kosuke Minami, Kota Shiba, Kissan Mistry, Kevin P. Musselman, Mustafa Yavuz, Genki Yoshikawa, Koichiro Saiki and Seiji Obata
Chemosensors 2020, 8(3), 82; https://doi.org/10.3390/chemosensors8030082 - 02 Sep 2020
Cited by 17 | Viewed by 5758
Abstract
Graphene is a key material for gas sensing applications owing to its high specific surface area and vast chemical modification potential. To fully utilize the potential of graphene, a sensing platform independent of conductive properties is required. In this study, we employed membrane-type [...] Read more.
Graphene is a key material for gas sensing applications owing to its high specific surface area and vast chemical modification potential. To fully utilize the potential of graphene, a sensing platform independent of conductive properties is required. In this study, we employed membrane-type surface stress sensors (MSS)—A kind of nanomechanical sensor operated in the static mode—As a sensing platform and utilized graphene oxide (GO) as a gas sensing material. MSS detect surface stress caused by gas sorption; therefore, chemically modified graphene with low conductivity can be utilized as a gas sensing material. We evaluated the sensing performance of a GO-coated MSS by measuring its responses to five gases. We demonstrated with the GO-coated MSS the feasibility of GO as a gas sensing material for static mode nanomechanical sensors and revealed its high selectivity to water vapor. Moreover, we investigated the sensing mechanism of the GO-coated MSS by comparing it with the sensing performance of MSS coated with reduced graphene oxide and graphite powder and deduced key factors for sensitivity and selectivity. Considering the high sensitivity of the GO-coated MSS and the compact measurement system that MSS can realize, the present study provides a new perspective on the sensing applications of graphene. Full article
(This article belongs to the Section Materials for Chemical Sensing)
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11 pages, 2388 KiB  
Article
Molecular Imprinted Based Quartz Crystal Microbalance Sensors for Bacteria and Spores
by Usman Latif, Serpil Can, Hermann F. Sussitz and Franz L. Dickert
Chemosensors 2020, 8(3), 64; https://doi.org/10.3390/chemosensors8030064 - 04 Aug 2020
Cited by 14 | Viewed by 3228
Abstract
A molecular imprinting strategy was combined with mass-sensitive transducers to generate robust and reliable biomimetic sensor systems for the detection of bioparticles. The patterning of polymers with bioanalytes enabled us to detect Escherichia coli (E. coli) bacteria with quartz crystal microbalance [...] Read more.
A molecular imprinting strategy was combined with mass-sensitive transducers to generate robust and reliable biomimetic sensor systems for the detection of bioparticles. The patterning of polymers with bioanalytes enabled us to detect Escherichia coli (E. coli) bacteria with quartz crystal microbalance (QCM). The QCM sensor results were compared with direct Atomic Force Microscopy (AFM) measurements—bacteria cells adhering to the sensor coatings were counted. The recognition sites generated by Bacillus subtilis (B. subtilis) spores could successfully and reversibly recognize the template analyte and ensured rapid sensing. Cross sensitive measurements clearly showed the advantage of the molecular imprinting strategy, by which spores of Bacillus species (subtilis and thuringiensis) could easily be differentiated and selectively detected. The growth of B. subtilis from its spores was observed at 42 °C in appropriate nutrient solution of glucose and ammonium sulfate over a period of 15 h. Moreover, the growth of B. subtilis bacteria from its respective spores was studied by increasing the glucose concentration until saturation effect of the sensor. The polymeric sensor coatings were patterned to fix the B. subtilis in order to investigate osmotic effects according to a frequency response of 400 Hz by altering the ionic strength of 0.1 M. Full article
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23 pages, 9902 KiB  
Review
Macrocyclic Arenes Functionalized with BODIPY: Rising Stars among Chemosensors and Smart Materials
by Jianjun Huang, Yuyu Fang and Wim Dehaen
Chemosensors 2020, 8(3), 51; https://doi.org/10.3390/chemosensors8030051 - 06 Jul 2020
Cited by 13 | Viewed by 5498
Abstract
Macrocycles play a crucial role in supramolecular chemistry and the family of macrocyclic arenes represents one of the most important types of hosts. Among them, calixarenes, resorcinarenes and pillararenes are the most commonly encountered macrocyclic arenes, and they have received considerable attention. Boron-dipyrromethene [...] Read more.
Macrocycles play a crucial role in supramolecular chemistry and the family of macrocyclic arenes represents one of the most important types of hosts. Among them, calixarenes, resorcinarenes and pillararenes are the most commonly encountered macrocyclic arenes, and they have received considerable attention. Boron-dipyrromethene (BODIPY) dyes are fascinating compounds with multiple functionalization sites and outstanding luminescence properties including high fluorescence quantum yields, large molar absorption coefficients and remarkable photo- and chemical stability. The combination of macrocyclic arenes and BODIPY dyes has been demonstrated to be an effective strategy to construct chemosensors for various guests and smart materials with tailored properties. Herein, we firstly summarize the recent advances made so far in macrocyclic arenes substituted with BODIPY. This review only focuses on the three macrocyclic arenes of calixarenes, resorcinarenes and pillararenes, as there are no other macrocyclic arenes substituted BODIPY units at the present time. Hopefully, this review will not only afford a guide and useful information for those who are interested in developing novel chemosensors and smart materials, but also inspire new opportunities in this field. Full article
(This article belongs to the Special Issue Organic Fluorescent Materials as Chemical Sensors)
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18 pages, 3230 KiB  
Article
Chemical and Temperature Sensors Based on Functionalized Reduced Graphene Oxide
by Esteban Araya-Hermosilla, Matteo Minichino, Virgilio Mattoli and Andrea Pucci
Chemosensors 2020, 8(2), 43; https://doi.org/10.3390/chemosensors8020043 - 21 Jun 2020
Cited by 6 | Viewed by 3929
Abstract
In this work, we investigated the functionalization of reduced graphene oxide (rGO) with 2-(dodecen-1-yl) succinic anhydride (TPSA) to increase the rGO effective interactions with organic solvents both in liquid and vapor phases. Thermogravimetric analysis, STEM, XPS, FTIR-ATR, and Raman spectroscopy confirmed the effective [...] Read more.
In this work, we investigated the functionalization of reduced graphene oxide (rGO) with 2-(dodecen-1-yl) succinic anhydride (TPSA) to increase the rGO effective interactions with organic solvents both in liquid and vapor phases. Thermogravimetric analysis, STEM, XPS, FTIR-ATR, and Raman spectroscopy confirmed the effective functionalization of rGO with about the 30 wt% of grafted TPSA without affecting the structural characteristics of graphene but successfully enhancing its dispersibility in the selected solvent except for the apolar hexane. Solid TPSA-rGO dispersions displayed a reproducible semiconducting (activated) electrical transport with decreased resistance when heated from 20 °C to 60 °C and with a negative temperature coefficient of 10−3 K−1, i.e., comparable in absolute value with temperature coefficient in metals. It is worth noting that the same solid dispersions showed electrical resistance variation upon exposure to vapors with a detection limit in the order of 10 ppm and sensitivity α of about 10−4 ppm−1. Full article
(This article belongs to the Section Materials for Chemical Sensing)
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11 pages, 1811 KiB  
Article
Electrochemical Aptasensor for Detection of Dopamine
by Hisham Abu-Ali, Cansu Ozkaya, Frank Davis, Nik Walch and Alexei Nabok
Chemosensors 2020, 8(2), 28; https://doi.org/10.3390/chemosensors8020028 - 15 Apr 2020
Cited by 19 | Viewed by 5726
Abstract
This work presents a proof of concept of a novel, simple, and sensitive method of detection of dopamine, a neurotransmitter within the human brain. We propose a simple electrochemical method for the detection of dopamine using a dopamine-specific aptamer labeled with an electrochemically [...] Read more.
This work presents a proof of concept of a novel, simple, and sensitive method of detection of dopamine, a neurotransmitter within the human brain. We propose a simple electrochemical method for the detection of dopamine using a dopamine-specific aptamer labeled with an electrochemically active ferrocene tag. Aptamers immobilized on the surface of gold screen-printed gold electrodes via thiol groups can change their secondary structure by wrapping around the target molecule. As a result, the ferrocene labels move closer to the electrode surface and subsequently increase the electron transfer. The cyclic voltammograms and impedance spectra recorded on electrodes in buffer solutions containing different concentration of dopamine showed, respectively, the increase in both the anodic and cathodic currents and decrease in the double layer resistance upon increasing the concentration of dopamine from 0.1 to 10 nM L−1. The high affinity of aptamer-dopamine binding (KD ≈ 5 nM) was found by the analysis of the binding kinetics. The occurrence of aptamer-dopamine binding was directly confirmed with spectroscopic ellipsometry measurements. Full article
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29 pages, 5419 KiB  
Review
Silver Nanoparticles as Colorimetric Sensors for Water Pollutants
by Paolo Prosposito, Luca Burratti and Iole Venditti
Chemosensors 2020, 8(2), 26; https://doi.org/10.3390/chemosensors8020026 - 31 Mar 2020
Cited by 126 | Viewed by 14350
Abstract
This review provides an up-to-date overview on silver nanoparticles-based materials suitable as optical sensors for water pollutants. The topic is really hot considering the implications for human health and environment due to water pollutants. In fact, the pollutants present in the water disturb [...] Read more.
This review provides an up-to-date overview on silver nanoparticles-based materials suitable as optical sensors for water pollutants. The topic is really hot considering the implications for human health and environment due to water pollutants. In fact, the pollutants present in the water disturb the spontaneity of life-related mechanisms, such as the synthesis of cellular constituents and the transport of nutrients into cells, and this causes long / short-term diseases. For this reason, research continuously tends to develop always innovative, selective and efficient processes / technologies to remove pollutants from water. In this paper we will report on the silver nanoparticles synthesis, paying attention to the stabilizers and mostly used ligands, to the characterizations, to the properties and applications as colorimetric sensors for water pollutants. As water pollutants our attention will be focused on several heavy metals ions, such as Hg(II), Ni(II),Cu(II), Fe(III), Mn(II), Cr(III/V) Co(II) Cd(II), Pb(II), due to their dangerous effects on human health. In addition, several systems based on silver nanoparticles employed as pesticides colorimetric sensors in water will be also discussed. All of this with the aim to provide to readers a guide about recent advanced silver nanomaterials, used as colorimetric sensors in water. Full article
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19 pages, 2174 KiB  
Review
Heavy Metal/Toxins Detection Using Electronic Tongues
by Flavio M. Shimizu, Maria L. Braunger and Antonio Riul
Chemosensors 2019, 7(3), 36; https://doi.org/10.3390/chemosensors7030036 - 02 Aug 2019
Cited by 39 | Viewed by 4957
Abstract
The growing concern for sustainability and environmental preservation has increased the demand for reliable, fast response, and low-cost devices to monitor the existence of heavy metals and toxins in water resources. An electronic tongue (e-tongue) is a multisensory array mostly based on electroanalytical [...] Read more.
The growing concern for sustainability and environmental preservation has increased the demand for reliable, fast response, and low-cost devices to monitor the existence of heavy metals and toxins in water resources. An electronic tongue (e-tongue) is a multisensory array mostly based on electroanalytical methods and multivariate statistical techniques to facilitate information visualization in a qualitative and/or quantitative way. E-tongues are promising analytical devices having simple operation, fast response, low cost, easy integration with other systems (microfluidic, optical, etc) to enable miniaturization and provide a high sensitivity for measurements in complex liquid media, providing an interesting alternative to address many of the existing environmental monitoring challenges, specifically relevant emerging pollutants such as heavy metals and toxins. Full article
(This article belongs to the Special Issue Chemical Sensors for Heavy Metals/Toxin Detection)
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14 pages, 2239 KiB  
Article
Development of Novel and Highly Specific ssDNA-Aptamer-Based Electrochemical Biosensor for Rapid Detection of Mercury (II) and Lead (II) Ions in Water
by Hisham Abu-Ali, Alexei Nabok and Thomas J. Smith
Chemosensors 2019, 7(2), 27; https://doi.org/10.3390/chemosensors7020027 - 04 Jun 2019
Cited by 45 | Viewed by 7864
Abstract
In this work, we report on the development of an electrochemical biosensor for high selectivity and rapid detection of Hg2+ and Pb2+ ions using DNA-based specific aptamer probes labeled with ferrocene (or methylene blue) and thiol groups at their 5′ and [...] Read more.
In this work, we report on the development of an electrochemical biosensor for high selectivity and rapid detection of Hg2+ and Pb2+ ions using DNA-based specific aptamer probes labeled with ferrocene (or methylene blue) and thiol groups at their 5′ and 3′ termini, respectively. Aptamers were immobilized onto the surface of screen-printed gold electrodes via the SH (thiol) groups, and then cyclic voltammetry and impedance spectra measurements were performed in buffer solutions with the addition of HgCl2 and PbCl2 salts at different concentrations. Changes in 3D conformation of aptamers, caused by binding their respective targets, e.g., Hg2+ and Pb2+ ions, were accompanied by an increase in the electron transfer between the redox label and the electrode. Accordingly, the presence of the above ions can be detected electrochemically. The detection of Hg2+ and Pb2+ ions in a wide range of concentrations as low as 0.1 ng/mL (or 0.1 ppb) was achieved. The study of the kinetics of aptamer/heavy metal ions binding gave the values of the affinity constants of approximately 9.10−7 mol, which proved the high specificity of the aptamers used. Full article
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23 pages, 1386 KiB  
Review
Thin Films Sensor Devices for Mycotoxins Detection in Foods: Applications and Challenges
by Andréia O. Santos, Andreia Vaz, Paula Rodrigues, Ana C. A. Veloso, Armando Venâncio and António M. Peres
Chemosensors 2019, 7(1), 3; https://doi.org/10.3390/chemosensors7010003 - 04 Jan 2019
Cited by 20 | Viewed by 5945
Abstract
Mycotoxins are a group of secondary metabolites produced by different species of filamentous fungi and pose serious threats to food safety due to their serious human and animal health impacts such as carcinogenic, teratogenic and hepatotoxic effects. Conventional methods for the detection of [...] Read more.
Mycotoxins are a group of secondary metabolites produced by different species of filamentous fungi and pose serious threats to food safety due to their serious human and animal health impacts such as carcinogenic, teratogenic and hepatotoxic effects. Conventional methods for the detection of mycotoxins include gas chromatography and high-performance liquid chromatography coupled with mass spectrometry or other detectors (fluorescence or UV detection), thin layer chromatography and enzyme-linked immunosorbent assay. These techniques are generally straightforward and yield reliable results; however, they are time-consuming, require extensive preparation steps, use large-scale instruments, and consume large amounts of hazardous chemical reagents. Rapid detection of mycotoxins is becoming an increasingly important challenge for the food industry in order to effectively enforce regulations and ensure the safety of food and feed. In this sense, several studies have been done with the aim of developing strategies to detect mycotoxins using sensing devices that have high sensitivity and specificity, fast analysis, low cost and portability. The latter include the use of microarray chips, multiplex lateral flow, Surface Plasmon Resonance, Surface Enhanced Raman Scattering and biosensors using nanoparticles. In this perspective, thin film sensors have recently emerged as a good candidate technique to meet such requirements. This review summarizes the application and challenges of thin film sensor devices for detection of mycotoxins in food matrices. Full article
(This article belongs to the Special Issue Thin Film Based Sensors)
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14 pages, 5514 KiB  
Article
Real-Time Frequency Tracking of an Electro-Thermal Piezoresistive Cantilever Resonator with ZnO Nanorods for Chemical Sensing
by Andi Setiono, Jiushuai Xu, Michael Fahrbach, Maik Bertke, Wilson Ombati Nyang’au, Hutomo Suryo Wasisto and Erwin Peiner
Chemosensors 2019, 7(1), 2; https://doi.org/10.3390/chemosensors7010002 - 03 Jan 2019
Cited by 19 | Viewed by 5961
Abstract
The asymmetric resonance response in electro-thermal piezoresistive cantilever resonators causes a need of an optimization treatment for taking parasitic actuation-sensing effects into account. An electronic reference circuit for signal subtraction, integrated with the cantilever resonator has the capability to reduce the effect of [...] Read more.
The asymmetric resonance response in electro-thermal piezoresistive cantilever resonators causes a need of an optimization treatment for taking parasitic actuation-sensing effects into account. An electronic reference circuit for signal subtraction, integrated with the cantilever resonator has the capability to reduce the effect of parasitic coupling. Measurement results demonstrated that a symmetric amplitude shape (Lorentzian) and an optimized phase characteristic (i.e., monotonically decreasing) were successfully extracted from an asymmetric resonance response. With the monotonic phase response, real-time frequency tracking can be easier to implement using a phase-locked loop (PLL) system. In this work, an electro-thermal piezoresistive cantilever resonator functionalized with self-assembled monolayers of chitosan-covered ZnO nanorod arrays as sensitive layers has been investigated under different relative humidity (rH) levels. Enhancement of resonance phase response has been demonstrated by implementing the reference signal subtraction. Subsequently, a lock-in amplifier integrated with PLL system (MFLI, Zurich Instruments, Zurich, Switzerland) was then employed for continuously tracking the resonant frequency. As a result, we find a good correlation of frequency shift (∆f0) with change in rH monitored using a commercial reference sensor. Full article
(This article belongs to the Special Issue Nanotechnology Efforts for Chemical Sensors)
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