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Chemosensors, Volume 10, Issue 7 (July 2022) – 56 articles

Cover Story (view full-size image): The development of rapid and affordable diagnostic tools for molecular detection has been pushed forward by technical advancements. In this work, an inkjet printer was used to realize the droplet digital loop-mediated isothermal amplification, and a microfluidic chip was used as a droplet reservoir to perform droplet digital LAMP assays. This method successfully quantified HPV16 from CaSki cells, which has the potential for rapid molecular detection and can be extended to on-site analysis. View this paper
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23 pages, 4577 KiB  
Review
Metal Oxide Semiconductor Nanostructure Gas Sensors with Different Morphologies
by Ali Mirzaei, Hamid Reza Ansari, Mehrdad Shahbaz, Jin-Young Kim, Hyoun Woo Kim and Sang Sub Kim
Chemosensors 2022, 10(7), 289; https://doi.org/10.3390/chemosensors10070289 - 21 Jul 2022
Cited by 38 | Viewed by 3244
Abstract
There is an increasing need for the development of low-cost and highly sensitive gas sensors for environmental, commercial, and industrial applications in various areas, such as hazardous gas monitoring, safety, and emission control in combustion processes. Considering this, resistive-based gas sensors using metal [...] Read more.
There is an increasing need for the development of low-cost and highly sensitive gas sensors for environmental, commercial, and industrial applications in various areas, such as hazardous gas monitoring, safety, and emission control in combustion processes. Considering this, resistive-based gas sensors using metal oxide semiconductors (MOSs) have gained special attention owing to their high sensing performance, high stability, and low cost of synthesis and fabrication. The relatively low final costs of these gas sensors allow their commercialization; consequently, they are widely used and available at low prices. This review focuses on the important MOSs with different morphologies, including quantum dots, nanowires, nanofibers, nanotubes, hierarchical nanostructures, and other structures for the fabrication of resistive gas sensors. Full article
(This article belongs to the Special Issue Low-Cost Chemo/Bio-Sensors Based on Nanomaterials)
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13 pages, 2349 KiB  
Article
Optical Multisensor System Based on Lanthanide(III) Complexes as Near-Infrared Light Sources for Analysis of Milk
by Anastasiia Surkova, Andrey Bogomolov, Aleksandra Paderina, Viktoria Khistiaeva, Ekaterina Boichenko, Elena Grachova and Dmitry Kirsanov
Chemosensors 2022, 10(7), 288; https://doi.org/10.3390/chemosensors10070288 - 20 Jul 2022
Cited by 2 | Viewed by 1480
Abstract
Optical multisensor systems are easy-to-use and inexpensive analytical devices. In this work, we propose an optical multisensor system based on the luminescence of Nd(III) and Yb(III) complexes in the near-infrared (NIR) spectral region. The observed emission bands play the role of secondary light [...] Read more.
Optical multisensor systems are easy-to-use and inexpensive analytical devices. In this work, we propose an optical multisensor system based on the luminescence of Nd(III) and Yb(III) complexes in the near-infrared (NIR) spectral region. The observed emission bands play the role of secondary light sources for further analysis of milk—for the determination of fat content and for the recognition of adulteration. The samples for analysis were prepared by putting a drop of milk upon a thin glass covering the powdered mixture of lanthanide complexes, which were excited by a light-emitting diode (LED) in the ultraviolet region (the maximum intensity at 365 nm). The diffuse-reflectance spectra of samples were acquired in the short-wave NIR range 750–1100 nm using a portable NIR spectrometer. The developed optical system was tested using two sets of milk samples with varying concentration levels of fat and added urea. The obtained spectral data were analyzed using a number of multivariate prediction and classification methods of chemometrics and the results were statistically compared. The regression and classification model performances achieved in this proof-of-concept study illustrate the feasibility of the optical multisensor analysis based on luminescent light sources in the short-wave NIR range, in particular, for their application in the dairy. Full article
(This article belongs to the Special Issue Chemometrics for Multisensor Systems and Artificial Senses)
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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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12 pages, 3028 KiB  
Article
Self-Powered Photoelectrochemical Assay for Hg2+ Detection Based on g-C3N4-CdS-CuO Composites and Redox Cycle Signal Amplification Strategy
by Yonghuan Su, Lixia Su, Bingqian Liu, Youxiu Lin and Dianping Tang
Chemosensors 2022, 10(7), 286; https://doi.org/10.3390/chemosensors10070286 - 18 Jul 2022
Cited by 7 | Viewed by 1745
Abstract
A highly sensitive self-powered photoelectrochemical (spPEC) sensing platform was constructed for Hg2+ determination based on the g-C3N4-CdS-CuO co-sensitized photoelectrode and a visible light-induced redox cycle for signal amplification. Through successively coating the single-layer g-C3N4, [...] Read more.
A highly sensitive self-powered photoelectrochemical (spPEC) sensing platform was constructed for Hg2+ determination based on the g-C3N4-CdS-CuO co-sensitized photoelectrode and a visible light-induced redox cycle for signal amplification. Through successively coating the single-layer g-C3N4, CdS, and CuO onto the surface of an electrode, the modified electrode exhibited significantly enhanced PEC activity. The microstructure of the material was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). However, the boost in photocurrent could be noticeably suppressed due to the consumption of hole-scavenging agents (reduced glutathione) by the added Hg2+. Under optimal conditions, we discovered that the photocurrent was linearly related to the Hg2+ concentration in the range of 5 pM–100 nM. The detection limit for Hg2+ was 0.84 pM. Moreover, the spPEC sensor demonstrated good performance for the detection of mercury ions in human urine and artificial saliva. Full article
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13 pages, 4813 KiB  
Article
Effect of the Microstructure of ZnO Thin Films Prepared by PLD on Their Performance as Toxic Gas Sensors
by Didier Fasquelle, Stéphanie Députier, Valérie Bouquet and Maryline Guilloux-Viry
Chemosensors 2022, 10(7), 285; https://doi.org/10.3390/chemosensors10070285 - 16 Jul 2022
Cited by 6 | Viewed by 1650
Abstract
In 2008, the modified European Restriction of Hazardous Substances (RoHS) directive prohibited the use of hazardous substances such as lead, cadmium, and mercury. As such, an urgent need for lead-free components emerged in Europe. In this frame, we have decided to study the [...] Read more.
In 2008, the modified European Restriction of Hazardous Substances (RoHS) directive prohibited the use of hazardous substances such as lead, cadmium, and mercury. As such, an urgent need for lead-free components emerged in Europe. In this frame, we have decided to study the microstructure influence of zinc oxide thin films on the detection of hydrogen sulfide (H2S). Zinc oxide thin films were deposited by PLD on silicon substrates under different conditions to modify the microstructure. In order to compare our demonstrators to current commercial semiconductor gas sensors, measurements under H2S were also performed with sensors from Figaro and Winsen corporations. Gas sensors were therefore implemented by using commercial cases in view to test them with Simtronics gas detector DG477. The good sensitivity values measured at T = 400 °C under 100 ppm H2S, and response times as low as 30 s, definitely confirm that ZnO thin films could be developed for commercial sensors. Full article
(This article belongs to the Special Issue The State-of-the-Art Gas Sensor)
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10 pages, 2118 KiB  
Article
Visualization of Antimicrobial-Induced Bacterial Membrane Disruption with a Bicolor AIEgen
by Chengcheng Zhou, Zeyu Ding, Qiaoni Guo and Meijuan Jiang
Chemosensors 2022, 10(7), 284; https://doi.org/10.3390/chemosensors10070284 - 16 Jul 2022
Cited by 3 | Viewed by 1410
Abstract
Gram-negative bacteria are difficult to kill due to their complex cell envelope, including the outer membrane (OM) and cytoplasmic membrane (CM). To monitor the membranolytic action of antimicrobials on Gram-negative bacteria would facilitate the development of effective antimicrobials. In this paper, an aggregation-induced [...] Read more.
Gram-negative bacteria are difficult to kill due to their complex cell envelope, including the outer membrane (OM) and cytoplasmic membrane (CM). To monitor the membranolytic action of antimicrobials on Gram-negative bacteria would facilitate the development of effective antimicrobials. In this paper, an aggregation-induced emission luminogen (AIEgen) with microenvironment-sensitive properties was employed to indicate the interaction of antimicrobials with the OM and CM of Gram-negative bacteria. The damaged extent of OM and CM caused by antimicrobials with the change of dosage and incubation time can be visually captured based on the variation of two emission colors of IQ-Cm responding to OM-defective (green) and CM-disruptive bacteria (orange). Meanwhile, the activity assessment of antimicrobials can be easily realized within 1~2 h based on the distinct response of IQ-Cm to live and dead E. coli, which is much faster than the agar plate culture. This probe may shed light on the understanding of the interaction between the membrane-active antimicrobials and cell envelope of Gram-negative bacteria and contribute to the future development of antimicrobials. 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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18 pages, 4384 KiB  
Article
A Design of Real-Time Data Acquisition and Processing System for Nanosecond Ultraviolet-Visible Absorption Spectrum Detection
by Meng Xia, Nanjing Zhao, Gaofang Yin, Ruifang Yang, Xiaowei Chen, Chun Feng and Ming Dong
Chemosensors 2022, 10(7), 282; https://doi.org/10.3390/chemosensors10070282 - 15 Jul 2022
Cited by 2 | Viewed by 1781
Abstract
Ultraviolet-visible absorption spectroscopy is widely used to monitor water quality, and rapid optical signal detection is a key technology in the process of spectrum measurement. In this paper, an ultrafast spectrophotometer system that can achieve spectrum data acquisition in a single flash of [...] Read more.
Ultraviolet-visible absorption spectroscopy is widely used to monitor water quality, and rapid optical signal detection is a key technology in the process of spectrum measurement. In this paper, an ultrafast spectrophotometer system that can achieve spectrum data acquisition in a single flash of the xenon lamp (within 200 ns) is introduced, and a real-time denoising method for the spectrum is implemented on a field programmable gate array (FPGA) to work cooperatively with the nanosecond spectrum acquisition system, in order to guarantee the quality of the spectrum signals without losing running speed. The hardware of the data acquisition and processing system are constructed on a Xilinx Spartan 6 FPGA chip and its peripheral circuit, including an analog to digital converter and a complementary metal-oxide-semiconductor transistor (CMOS) sensor’s diver circuit. An oversampling method that is suitable for the CMOS sensor’s output is proposed, which works on the CMOS sensor’s dark current noise and readout noise. Another moving-average filter method is designed adaptively, which works on the low-frequency component to filter out the residual spectrum noise of the spectrum signal. The implementation of the filter on the FPGA has been optimized by using a pipelined structure and dual high-speed random-access memory (RAM). As a result, the CMOS linear image sensor successfully captured the spectrum of xenon flash light at the readout clock frequency of 500 kHz and the processing manipulation to the full UV-Vis spectrum data was accomplished at a sub-microsecond speed performance. After the digital filter and oversampling technology were implemented, the coefficient of variation of the measurements reduced from 9.57% to 1.74%, while the signal noise ratio (SNR) of the absorption spectrum increased nine times, compared to the raw data of the CMOS sensor’s output. The tests towards different analyte samples were conducted, and the system shows good performance on distinguishing different concentrations of different analyte solutions on both ultra-violet and visible spectrum bands. The present work showcases the potential of the CMOS sensor’s technique for the fast detection of contaminated water containing nitrate and organic compounds. Full article
(This article belongs to the Section Optical Chemical Sensors)
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16 pages, 4008 KiB  
Article
Fluorescent Calixarene-Schiff as a Nanovehicle with Biomedical Purposes
by José Antonio Lebrón, Manuel López-López, María Luisa Moyá, Mary Deasy, Ana Muñoz-Wic, Clara Beatriz García-Calderón, Iván Valle Rosado, Pilar López-Cornejo, Eva Bernal and Francisco José Ostos
Chemosensors 2022, 10(7), 281; https://doi.org/10.3390/chemosensors10070281 - 14 Jul 2022
Cited by 4 | Viewed by 2044
Abstract
Gene therapy is a technique that is currently under expansion and development. Recent advances in genetic medicine have paved the way for a broader range of therapies and laid the groundwork for next-generation technologies. A terminally substituted difluorene-diester Schiff Base calix[4]arene has been [...] Read more.
Gene therapy is a technique that is currently under expansion and development. Recent advances in genetic medicine have paved the way for a broader range of therapies and laid the groundwork for next-generation technologies. A terminally substituted difluorene-diester Schiff Base calix[4]arene has been studied in this work as possible nanovector to be used in gene therapy. Changes to luminescent behavior of the calixarene macrocycle are reported in the presence of ct-DNA. The calixarene macrocycle interacts with calf thymus DNA (ct-DNA), generating changes in its conformation. Partial double-strand denaturation is induced at low concentrations of the calixarene, resulting in compaction of the ct-DNA. However, interaction between calixarene molecules themselves takes place at high calixarene concentrations, favoring the decompaction of the polynucleotide. Based on cytotoxicity studies, the calixarene macrocycle investigated has the potential to be used as a nanovehicle and improve the therapeutic efficacy of pharmacological agents against tumors. Full article
(This article belongs to the Collection Women Special Issue in Chemosensors and Analytical Chemistry)
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30 pages, 11619 KiB  
Review
Recent Progress in Fluorescent Probes for Diabetes Visualization and Drug Therapy
by Tong-Tong Jia, Yashan Li and Huawei Niu
Chemosensors 2022, 10(7), 280; https://doi.org/10.3390/chemosensors10070280 - 14 Jul 2022
Cited by 9 | Viewed by 2279
Abstract
Diabetes has become one of the most prevalent endocrine and metabolic diseases that threaten human health, and it is accompanied by serious complications. Therefore, it is vital and pressing to develop novel strategies or tools for prewarning and therapy of diabetes and its [...] Read more.
Diabetes has become one of the most prevalent endocrine and metabolic diseases that threaten human health, and it is accompanied by serious complications. Therefore, it is vital and pressing to develop novel strategies or tools for prewarning and therapy of diabetes and its complications. Fluorescent probes have been widely applied in the detection of diabetes due to the fact of their attractive advantages. In this report, we comprehensively summarize the recent progress and development of fluorescent probes in detecting the changes in the various biomolecules in diabetes and its complications. We also discuss the design of fluorescent probes for monitoring diabetes in detail. We expect this review will provide new ideas for the development of fluorescent probes suitable for the prewarning and therapy of diabetes in future clinical transformation and application. Full article
(This article belongs to the Special Issue Fluorescent Sensors for Disease Diagnosis and Therapy)
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14 pages, 6596 KiB  
Article
Adsorption Mechanism of SO2 on Transition Metal (Pd, Pt, Au, Fe, Co and Mo)-Modified InP3 Monolayer
by Tianyu Hou, Wen Zeng and Qu Zhou
Chemosensors 2022, 10(7), 279; https://doi.org/10.3390/chemosensors10070279 - 14 Jul 2022
Cited by 2 | Viewed by 1425
Abstract
Using the first-principles theory, this study explored the electronic behavior and adsorption effect of SO2 on an InP3 monolayer doped with transition metal atoms (Pd, Pt, Au, Fe, Co and Mo). Through calculation and analysis, the optimum doping sites of TM [...] Read more.
Using the first-principles theory, this study explored the electronic behavior and adsorption effect of SO2 on an InP3 monolayer doped with transition metal atoms (Pd, Pt, Au, Fe, Co and Mo). Through calculation and analysis, the optimum doping sites of TM dopants on the InP3 monolayer were determined, and the adsorption processes of SO2 by TM-InP3 monolayers were simulated. In the adsorption process, all TM-InP3 monolayers and SO2 molecules were deformed to some extent. All adsorption was characterized as chemical adsorption, and SO2 acted as an electron acceptor. Comparing Ead and Qt, the order of the SO2 adsorption effect was Mo-InP3 > Fe-InP3 > Co-InP3 > Pt-InP3 > Pd-InP3 > Au-InP3. Except for the Au atom, the other five TM atoms as dopants all enhanced the adsorption effect of InP3 monolayers for SO2. Furthermore, the analysis of DCD and DOS further confirmed the above conclusions. Based on frontier orbital theory analysis, it is revealed that the adsorption of SO2 reduces the conductivity of TM-InP3 monolayers to different degrees, and it is concluded that Pd-InP3, Pt-InP3, Fe-InP3 and Mo-InP3 monolayers have great potential in the application of SO2 resistive gas sensors. This study provides a theoretical basis for further research on TM-InP3 as a SO2 sensor. Full article
(This article belongs to the Special Issue Gas Sensors for Monitoring Environmental Changes, 2nd Edition)
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19 pages, 4803 KiB  
Review
Chip-Based and Wearable Tools for Isothermal Amplification and Electrochemical Analysis of Nucleic Acids
by Claudia Patiti, Patrick Severin Sfragano, Serena Laschi, Serena Pillozzi, Anna Boddi, Olivia Crociani, Andrea Bernini and Ilaria Palchetti
Chemosensors 2022, 10(7), 278; https://doi.org/10.3390/chemosensors10070278 - 14 Jul 2022
Cited by 6 | Viewed by 1970
Abstract
The determination of nucleic acids has become an analytical diagnostic method with many applications in fields such as biomedical sciences, environmental monitoring, forensic identification, and food safety. Among the different methods for nucleic acid analysis, those based on the polymerase chain reaction (PCR) [...] Read more.
The determination of nucleic acids has become an analytical diagnostic method with many applications in fields such as biomedical sciences, environmental monitoring, forensic identification, and food safety. Among the different methods for nucleic acid analysis, those based on the polymerase chain reaction (PCR) are nowadays considered the gold standards. Isothermal amplification methods are an interesting alternative, especially in the design of chip-based architectures. Biosensing platforms hold great promise for the simple and rapid detection of nucleic acids since they can be embedded in lab-on-a-chip tools to perform nucleic acid extraction, amplification, and detection steps. Electrochemical transduction schemes are particularly interesting in the design of small and portable devices due to miniaturization, low-energy consumption, and multianalyte detection capability. The aim of this review is to summarize the different applications of isothermal amplification methods combined with electrochemical biosensing techniques in the development of lab-on-a-chip tools and wearable sensors. Different isothermal amplification methods are revised, and examples of different applications are discussed. Finally, a discussion on patented devices is also included. Full article
(This article belongs to the Section Analytical Methods, Instrumentation and Miniaturization)
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12 pages, 3024 KiB  
Article
Polypyrrole Film Deposited-TiO2 Nanorod Arrays for High Performance Ultraviolet Photodetectors
by Huan Wang, Pei Qin, Yun-Hui Feng, Hui-Liang Sun, Hui-Xiang Wu, Bo-Kai Liao, Yue-Bin Xi and Wei Wang
Chemosensors 2022, 10(7), 277; https://doi.org/10.3390/chemosensors10070277 - 13 Jul 2022
Cited by 3 | Viewed by 1374
Abstract
TiO2-based ultraviolet photodetectors have drawn great attention and are intensively explored. However, the construction of TiO2-based nanocomposites with excellent ultraviolet responses remains challenging. Herein, a TiO2 nanorod array was successfully prepared on fluorine-doped tin oxide (FTO) conductive glass [...] Read more.
TiO2-based ultraviolet photodetectors have drawn great attention and are intensively explored. However, the construction of TiO2-based nanocomposites with excellent ultraviolet responses remains challenging. Herein, a TiO2 nanorod array was successfully prepared on fluorine-doped tin oxide (FTO) conductive glass by a one-step hydrothermal method. Then, polypyrrole (PPy)-TiO2 nanorod array composites were designed via subsequent in situ oxidative polymerization. The morphologies, structures, and photocurrent responses of the nanocomposites were systematically investigated. The results demonstrated that polypyrrole-TiO2 exhibited a stronger photocurrent response than pure TiO2 due to the p-n junction formed between n-type TiO2 nanorod arrays and p-type polypyrrole. The PPy-TiO2 composite obtained by deposition three times had the best photoelectric properties, exhibiting good performance with a sensitivity of 41.7 and responsivity of 3.5 × 10−3 A/W. Finally, the mechanism of the photoelectrical response of PPy-TiO2 composites was discussed, guiding the design of high-performance TiO2-based ultraviolet photodetectors. Full article
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13 pages, 2457 KiB  
Article
Programmable, Universal DNAzyme Amplifier Supporting Pancreatic Cancer-Related miRNAs Detection
by Kunhan Nie, Yongjian Jiang, Na Wang, Yajun Wang, Di Li, Lei Zhan, Chengzhi Huang and Chunmei Li
Chemosensors 2022, 10(7), 276; https://doi.org/10.3390/chemosensors10070276 - 13 Jul 2022
Cited by 1 | Viewed by 1399
Abstract
The abnormal expression of miRNA is closely related to the occurrence of pancreatic cancer. Herein, a programmable DNAzyme amplifier for the universal detection of pancreatic cancer-related miRNAs was proposed based on its programmability through the rational design of sequences. The fluorescence signal recovery [...] Read more.
The abnormal expression of miRNA is closely related to the occurrence of pancreatic cancer. Herein, a programmable DNAzyme amplifier for the universal detection of pancreatic cancer-related miRNAs was proposed based on its programmability through the rational design of sequences. The fluorescence signal recovery of the DNAzyme amplifier showed a good linear relationship with the concentration of miR-10b in the range of 10–60 nM, with a detection limit of 893 pM. At the same time, this method displayed a high selectivity for miR-10b, with a remarkable discrimination of a single nucleotide difference. Furthermore, this method was also successfully used to detect miR-21 in the range of 10–60 nM based on the programmability of the DNA amplifier, exhibiting the universal application feasibility of this design. Overall, the proposed programmable DNAzyme cycle amplifier strategy shows promising potential for the simple, rapid, and universal detection of pancreatic cancer-related miRNAs, which is significant for improving the accuracy of pancreatic cancer diagnosis. Full article
(This article belongs to the Special Issue Feature Papers on Luminescent Sensing)
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32 pages, 4578 KiB  
Article
Substance Detection and Identification Using Frequency Doubling of the THz Broadband Pulse
by Vyacheslav A. Trofimov, Svetlana A. Varentsova, Yongqiang Yang and Zihao Cai
Chemosensors 2022, 10(7), 275; https://doi.org/10.3390/chemosensors10070275 - 13 Jul 2022
Cited by 1 | Viewed by 1372
Abstract
We propose and discuss an effective tool for substance detection and identification using a broadband THz pulse that is based on frequency conversion near the substance absorption frequencies. With this aim, we analyze the evolution of spectral intensities at the doubled absorption frequencies [...] Read more.
We propose and discuss an effective tool for substance detection and identification using a broadband THz pulse that is based on frequency conversion near the substance absorption frequencies. With this aim, we analyze the evolution of spectral intensities at the doubled absorption frequencies in order to prove their similarity to those at which the absorption of THz pulse energy occurs. This analysis is provided for both artificial THz signals and the real signals reflected from the substances under consideration. We demonstrate the feasibility of the proposed approach in the detection and identification of substances with an inhomogeneous surface, which is the most difficult case for practice, by using the method of spectral dynamic analysis and integral correlation criteria. Full article
(This article belongs to the Special Issue Machine Learning and Spectral Analysis for Smart Sensing)
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13 pages, 3418 KiB  
Communication
Investigation of the Atomic Layer Deposition of the Titanium Dioxide (TiO2) Film as pH Sensor Using a Switched Capacitor Amplifier
by Mozhdeh Nematzadeh, Ola Nilsen, Philipp Dominik Häfliger and Veronica Anne-Line Kathrine Killi
Chemosensors 2022, 10(7), 274; https://doi.org/10.3390/chemosensors10070274 - 12 Jul 2022
Viewed by 1352
Abstract
The electrical and chemical properties of the titanium dioxide (TiO2) coated spirals grown by the atomic layer deposition (ALD) technique in two different temperatures of 150 °C and 300 °C are studied. The thickness of the TiO2 layers studied are [...] Read more.
The electrical and chemical properties of the titanium dioxide (TiO2) coated spirals grown by the atomic layer deposition (ALD) technique in two different temperatures of 150 °C and 300 °C are studied. The thickness of the TiO2 layers studied are 20, 40, and 80 nm. A switched capacitor amplifier is used to investigate the pH response and the capacitance of the samples. It is found that the performance of the TiO2 samples depends on either the thickness or the deposition temperature due to the differences in the physical properties of the oxide layer such as surface roughness and film density. The high temperature samples are more crystalline, whereas the low temperature samples are more amorphous. Since there is a low pass filter effect in the electrolyte–sample interface, the TiO2 coated samples show the better response to the pH change for the high temperature samples as the sensor surface area for binding the hydrogen ions is larger and the charge transfer resistance is smaller. Furthermore, more roughness on the surface can be obtained by increasing the thickness, which reduces the charge transfer resistance. In this study, the 80 nm sample deposited at 300 °C gives the best pH response of 40 mV/pH. Full article
(This article belongs to the Section Materials for Chemical Sensing)
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53 pages, 1152 KiB  
Review
Wearable Sensor for Continuous Sweat Biomarker Monitoring
by Yuting Qiao, Lijuan Qiao, Zhiming Chen, Bingxin Liu, Li Gao and Lei Zhang
Chemosensors 2022, 10(7), 273; https://doi.org/10.3390/chemosensors10070273 - 12 Jul 2022
Cited by 30 | Viewed by 8386
Abstract
In recent years, wearable sensors have enabled the unique mode of real-time and noninvasive monitoring to develop rapidly in medical care, sports, and other fields. Sweat contains a wide range of biomarkers such as metabolites, electrolytes, and various hormones. Combined with wearable technology, [...] Read more.
In recent years, wearable sensors have enabled the unique mode of real-time and noninvasive monitoring to develop rapidly in medical care, sports, and other fields. Sweat contains a wide range of biomarkers such as metabolites, electrolytes, and various hormones. Combined with wearable technology, sweat can reflect human fatigue, disease, mental stress, dehydration, and so on. This paper comprehensively describes the analysis of sweat components such as glucose, lactic acid, electrolytes, pH, cortisol, vitamins, ethanol, and drugs by wearable sensing technology, and the application of sweat wearable devices in glasses, patches, fabrics, tattoos, and paper. The development trend of sweat wearable devices is prospected. It is believed that if the sweat collection, air permeability, biocompatibility, sensing array construction, continuous monitoring, self-healing technology, power consumption, real-time data transmission, specific recognition, and other problems of the wearable sweat sensor are solved, we can provide the wearer with important information about their health level in the true sense. Full article
(This article belongs to the Section (Bio)chemical Sensing)
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12 pages, 1992 KiB  
Communication
Electrochemical Immunosensor Modified with Nitrogen-Doped Reduced Graphene Oxide@Carboxylated Multi-Walled Carbon Nanotubes/Chitosan@Gold Nanoparticles for CA125 Detection
by Yingying Gu, Guoao Gong, Yuting Jiang, Jiangyang Qin, Yong Mei and Jun Han
Chemosensors 2022, 10(7), 272; https://doi.org/10.3390/chemosensors10070272 - 12 Jul 2022
Cited by 10 | Viewed by 1815
Abstract
Lung cancer is one of the malignant tumors with the highest mortality rate, and the detection of its tumor marker carcinoma antigen 125 (CA125) is significant. Here, an electrochemical immunoassay for CA125 was described. Nitrogen-doped reduced graphene oxide (N-rGO), carboxylated multi-walled carbon nanotubes [...] Read more.
Lung cancer is one of the malignant tumors with the highest mortality rate, and the detection of its tumor marker carcinoma antigen 125 (CA125) is significant. Here, an electrochemical immunoassay for CA125 was described. Nitrogen-doped reduced graphene oxide (N-rGO), carboxylated multi-walled carbon nanotubes (CMWCNTs) and gold nanoparticles (AuNPs) were applied to co-modify glassy carbon electrode (GCE), after incubation with Anti-CA125, the modified electrode was employed for the specific detection of CA125. The N-rGO@CMWCNTs (Nitrogen-doped reduced graphene oxide@carboxylated multi-walled carbon nanotubes) were used as a matrix, while CS@AuNPs (Chitosan@gold nanoparticles) with high conductivity and biocompatibility was immobilized on it through the reaction between carboxyl groups from CMWCNTs and amino groups, hydroxyl groups from chitosan (CS), resulting in the effect of double signal amplification. The immunosensor demonstrated excellent electrochemical performance with a linear detection range of 0.1 pg mL−1–100 ng mL−1, and the detection limit was as low as 0.04 pg mL−1 (S/N = 3). It had been verified that this method had good precision and high accuracy, and the immunosensor could remain stable for 10 days. This research provided a new method for the detection of CA125 in serum. Full article
(This article belongs to the Section (Bio)chemical Sensing)
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16 pages, 2937 KiB  
Article
An Integrated, Real-Time Convective PCR System for Isolation, Amplification, and Detection of Nucleic Acids
by Guijun Miao, Meng Guo, Ke Li, Xiangzhong Ye, Michael G. Mauk, Shengxiang Ge, Ningshao Xia, Duli Yu and Xianbo Qiu
Chemosensors 2022, 10(7), 271; https://doi.org/10.3390/chemosensors10070271 - 11 Jul 2022
Cited by 4 | Viewed by 1956
Abstract
Convective PCR (CPCR) can perform rapid nucleic acid amplification by inducing thermal convection to continuously, cyclically driving reagent between different zones of the reactor for spatially separate melting, annealing, and extending in a capillary tube with constant heating temperatures at different locations. CPCR [...] Read more.
Convective PCR (CPCR) can perform rapid nucleic acid amplification by inducing thermal convection to continuously, cyclically driving reagent between different zones of the reactor for spatially separate melting, annealing, and extending in a capillary tube with constant heating temperatures at different locations. CPCR is promoted by incorporating an FTA membrane filter into the capillary tube, which constructs a single convective PCR reactor for both sample preparation and amplification. To simplify fluid control in sample preparation, lysed sample or wash buffer is driven through the membrane filter through centrifugation. A movable resistance heater is used to heat the capillary tube for amplification, and meanwhile, a smartphone camera is adopted to monitor in situ fluorescence signal from the reaction. Different from other existing CPCR systems with the described simple, easy-to-use, integrated, real-time microfluidic CPCR system, rapid nucleic acid analysis can be performed from sample to answer. A couple of critical issues, including wash scheme and reaction temperature, are analyzed for optimized system performance. It is demonstrated that influenza A virus with the reasonable concentration down to 1.0 TCID50/mL can be successfully detected by the integrated microfluidic system within 45 min. Full article
(This article belongs to the Special Issue State of the Art in Nucleic Acid Detection)
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14 pages, 10551 KiB  
Article
One-Step Hydrothermal Synthesis of 3D Interconnected rGO/In2O3 Heterojunction Structures for Enhanced Acetone Detection
by Xiaoguang San, Yue Zhang, Lei Zhang, Guosheng Wang, Dan Meng, Jia Cui and Quan Jin
Chemosensors 2022, 10(7), 270; https://doi.org/10.3390/chemosensors10070270 - 11 Jul 2022
Cited by 4 | Viewed by 1611
Abstract
Acetone detection is of great significance for environmental monitoring or diagnosis of diabetes. Nevertheless, fast and sensitive detection of acetone at low temperatures remains challenging. Herein, a series of rGO-functionalized three-dimensional (3D) In2O3 flower-like structures were designed and synthesized via [...] Read more.
Acetone detection is of great significance for environmental monitoring or diagnosis of diabetes. Nevertheless, fast and sensitive detection of acetone at low temperatures remains challenging. Herein, a series of rGO-functionalized three-dimensional (3D) In2O3 flower-like structures were designed and synthesized via a facile hydrothermal method, and their acetone-sensing properties were systematically investigated. Compared to the pure 3D In2O3 flower-like structures, the rGO-functionalized 3D In2O3 flower-like structures demonstrated greatly improved acetone-sensing performance at relatively low temperatures. In particular, the 5-rGO/In2O3 sensor with an optimized decoration exhibited the highest response value (5.6) to 10 ppm acetone at 150 °C, which was about 2.3 times higher than that of the In2O3 sensor (2.4 at 200 °C). Furthermore, the 5-rGO/In2O3 sensor also showed good reproducibility, a sub-ppm-level detection limit (1.3 to 0.5 ppm), fast response and recovery rates (3 s and 18 s, respectively), and good long-term stability. The extraordinary acetone-sensing performance of rGO/In2O3 composites can be attributed to the synergistic effect of the formation of p-n heterojunctions between rGO and In2O3, the large specific surface area, the unique flower-like structures, and the high conductivity of rGO. This work provides a novel sensing material design strategy for effective detection of acetone. Full article
(This article belongs to the Special Issue Chemical Sensors for Volatile Organic Compound Detection)
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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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14 pages, 3066 KiB  
Article
An Enzyme-Free Photoelectrochemical Sensor Platform for Ascorbic Acid Detection in Human Urine
by Zhengzheng Zhao, Dongfang Han, Ren Xiao, Tianqi Wang, Zhishan Liang, Zhifang Wu, Fangjie Han, Dongxue Han, Yingming Ma and Li Niu
Chemosensors 2022, 10(7), 268; https://doi.org/10.3390/chemosensors10070268 - 11 Jul 2022
Cited by 5 | Viewed by 1995
Abstract
A novel enzyme-free photoelectrochemical (PEC) potential measurement system based on Dy-OSCN was designed for ascorbic acid (AA) detection. The separation and transmission of internal carriers were accelerated and the chemical properties became more stable under light excitation due to the regular microstructure of [...] Read more.
A novel enzyme-free photoelectrochemical (PEC) potential measurement system based on Dy-OSCN was designed for ascorbic acid (AA) detection. The separation and transmission of internal carriers were accelerated and the chemical properties became more stable under light excitation due to the regular microstructure of the prepared Dy-OSCN monocrystal. More importantly, the PEC potential method (OCPT, open circuit potential-time) used in this work was conducive to the reduction of photoelectric corrosion and less interference introduced during the detection process, which effectively ensured the repeatability and stability of the electrode. Under optimal conditions, the monocrystal successfully served as a matrix for the detection of AA, and the prepared PEC sensor exhibited a wide linear range from 7.94 × 10−6 mol/L to 1.113 × 10−2 mol/L and a sensitive detection limit of 3.35 μM. Practical human urine sample analysis further revealed the accuracy and feasibility of the Dy-OSCN-based PEC platform. It is expected that such a PEC sensor would provide a new way for rapid and non-invasive AA level assessment in human body constitution monitoring and lays a foundation for the further development of practical products. Full article
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18 pages, 9181 KiB  
Article
Semiconductor-Type Gas Sensors Based on γ-Fe2O3 Nanoparticles and Its Derivatives in Conjunction with SnO2 and Graphene
by Qi Qin, Diyor Olimov and Li Yin
Chemosensors 2022, 10(7), 267; https://doi.org/10.3390/chemosensors10070267 - 08 Jul 2022
Cited by 5 | Viewed by 1784
Abstract
The gas sensitivity of semiconductor metal oxides, such as γ-Fe2O3 and SnO2, is investigated together with the synergistic effects in conjunction with grapheme. Nanoparticles of γ-Fe2O3, γ-Fe2O3/SnO2, and [...] Read more.
The gas sensitivity of semiconductor metal oxides, such as γ-Fe2O3 and SnO2, is investigated together with the synergistic effects in conjunction with grapheme. Nanoparticles of γ-Fe2O3, γ-Fe2O3/SnO2, and γ-Fe2O3/SnO2/RGO, prepared by two-step fabrication, were assembled in gas-sensing devices to assess their sensitivities; response and recovery times for the detection of ethanol, methanol, isopropanol, formaldehyde, H2S, CO, and NO gases at different temperatures but constant concentrations of 100 particles per million (ppm); and H2S, which underwent the dynamic gas sensitivity test in different concentrations. Each sample’s crystallinity and microscopic morphology was investigated with X-ray diffraction and a scanning electron microscope. In comparative gas sensitivity measurements, the ternary composite of γ-Fe2O3/SnO2/RGO was identified as an ideal candidate, as it responds to all four tested liquids in the gas phase as well as H2S with a response value equal to 162.6. Further, only the ternary composite γ-Fe2O3/SnO2/RGO hybrid nanoparticles responded to NO gas with a sensor response value equal to 4.09 in 12 s. However, only the binary composite γ-Fe2O3/SnO2 responded to CO with a corresponding sensitivity of 1.59 units in 7 s. Full article
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16 pages, 20697 KiB  
Article
Design and Evaluation of Low-Power Co3O4 Gas Sensing Element as a Part of Cyber Physical Systems
by Marilena Moschogiannaki, George Vardakis, Emmanouil Gagaoudakis, Stefanos Papadakis and Vassilios Binas
Chemosensors 2022, 10(7), 266; https://doi.org/10.3390/chemosensors10070266 - 08 Jul 2022
Viewed by 1252
Abstract
Physical processes working in parallel with digital ones have transformed the way we view systems and have led to the creation of applications that boost the quality of people’s lives, increase security as well as decrease production costs of goods. Critical to this [...] Read more.
Physical processes working in parallel with digital ones have transformed the way we view systems and have led to the creation of applications that boost the quality of people’s lives, increase security as well as decrease production costs of goods. Critical to this evolution is the cost decrease in the components of such systems, among which are gas sensors. In this work, a custom-made Co3O4 gas sensing element is presented, which can potentially be used as part of a cyber-physical system (CPS) for O3 monitoring. To investigate its performance, a CPS is developed using low-cost, low-power micro-controller units (MCUs) and comparisons both with the laboratory equipment and commercial off-the-shelf (COTS) ozone sensors are provided. The experiments show that the Co3O4 sensor works at room temperature with low input voltage and low power consumption when used with the proposed MCUs. Moreover, an enhanced gas sensing performance against ozone is observed under low-pressure conditions due to the detection of low ozone concentrations (85.90 ppb) and good sensor response (113.1%) towards 1100 ppb O3. However, the drawbacks that need improvement relate to the kinetics of the charge carriers, which affect the response time and recovery behavior. The effect of humidity needs to be clarified in further works. Full article
(This article belongs to the Special Issue Nanomaterials Based on Bio/Chemical Sensors)
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11 pages, 1681 KiB  
Article
Development of a Paper-Based Analytical Method for the Selective Colorimetric Determination of Bismuth in Water Samples
by Panagiotis A. Bizirtsakis, Maria Tarara, Apostolia Tsiasioti, Paraskevas D. Tzanavaras and George Z. Tsogas
Chemosensors 2022, 10(7), 265; https://doi.org/10.3390/chemosensors10070265 - 08 Jul 2022
Cited by 6 | Viewed by 1726
Abstract
A novel, direct and simple colorimetric method employing μicroanalytical paper-based devices (μ-PADs) for the selective determination of bismuth is described. The suggested method exploits the colorimetric variation of bismuth after its rapid reaction with methyl thymol blue (MTB) in an acidic medium (pH [...] Read more.
A novel, direct and simple colorimetric method employing μicroanalytical paper-based devices (μ-PADs) for the selective determination of bismuth is described. The suggested method exploits the colorimetric variation of bismuth after its rapid reaction with methyl thymol blue (MTB) in an acidic medium (pH ranging between 0.7 and 3.0), modified with nitric acid, on the surface of a paper device at room temperature. The devices are low cost, composed of chromatographic paper and wax barriers and the analytical protocol is easily applicable with minimal technical expertise and without the need for experimental apparatus. The user must add a test sample and read the color intensity of the colored Bi(III)–MTB complex formed at the sensing area using a simple imaging device such as a flatbed scanner. Various chemical variables, such as HNO3 and MTB concentration, reaction time, ionic strength, detection zone size and photo-capture detector are optimized. A study of interfering ions such as K+, Na+, Ca2+, Mg2+, Cl, SO42− and HCO3− was also conducted. The stability of the paper devices is also studied in different maintenance conditions with particularly satisfactory results, rendering the method suitable for field analysis. The detection limits are as low as 3.0 mg L−1 with very satisfactory precision, ranging from 4.0% (intra-day) to 5.5% (inter-day). Natural water samples are successfully analyzed, and bismuth percentage recoveries were calculated in the range of 82.8 to 115.4%. Full article
(This article belongs to the Section Analytical Methods, Instrumentation and Miniaturization)
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14 pages, 4048 KiB  
Article
Gas Sensitive Characteristics of Polyaniline Decorated with Molybdenum Ditelluride Nanosheets
by Xinpeng Chen, Xiangdong Chen, Xing Ding and Xiang Yu
Chemosensors 2022, 10(7), 264; https://doi.org/10.3390/chemosensors10070264 - 06 Jul 2022
Cited by 4 | Viewed by 1449
Abstract
In this work, hydrochloric acid (HCl)-doped molybdenum ditelluride (MoTe2) nanosheets/polyaniline (PANI) nanofiber composites are prepared by in situ chemical oxidation polymerization, and then the composites are deposited on interdigital electrodes (IDEs) to fabricate a NH3 gas sensor. Morphological analysis of [...] Read more.
In this work, hydrochloric acid (HCl)-doped molybdenum ditelluride (MoTe2) nanosheets/polyaniline (PANI) nanofiber composites are prepared by in situ chemical oxidation polymerization, and then the composites are deposited on interdigital electrodes (IDEs) to fabricate a NH3 gas sensor. Morphological analysis of the composites reveals that the PANI fibers are deposited on 2D MoTe2 sheets, showing a porous mesh microstructure structure with a more continuous distribution of PANI layer. FTIR spectrum analysis indicates the interaction between the MoTe2 nanosheets and the PANI in the MoTe2/PANI composites. The results demonstrate that the as-prepared MoTe2/PANI composites exhibit higher response than the pure PANI, in particular, the 8 wt.% MoTe2/PANI composites display about 4.23 times enhancement in response value toward 1000 ppm NH3 gas compared with the pure PANI. The enhanced NH3 gas-sensitive properties may be due to the increasing surface area of MoTe2/PANI composite films and the possible interaction of the P-N heterojunctions formed between PANI and the 2H-MoTe2 nanosheets. Full article
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15 pages, 2432 KiB  
Article
Portable, Disposable, Biomimetic Electrochemical Sensors for Analyte Detection in a Single Drop of Whole Blood
by Sayantan Pradhan, Shane Albin, Rebecca L. Heise and Vamsi K. Yadavalli
Chemosensors 2022, 10(7), 263; https://doi.org/10.3390/chemosensors10070263 - 06 Jul 2022
Cited by 4 | Viewed by 2144
Abstract
Current diagnostics call for rapid, sensitive, and selective screening of physiologically important biomarkers. Point-of-care (POC) devices for the rapid, reliable, and easy acquisition of bioinformation at, or near the patient, offer opportunities for better healthcare management. Electrochemical biosensors with high sensitivity and ease [...] Read more.
Current diagnostics call for rapid, sensitive, and selective screening of physiologically important biomarkers. Point-of-care (POC) devices for the rapid, reliable, and easy acquisition of bioinformation at, or near the patient, offer opportunities for better healthcare management. Electrochemical biosensors with high sensitivity and ease of miniaturization are advantageous for such applications. We report a photolithographically micropatterned PEDOT:PSS and silk protein-based fully organic 3-electrode sensor (O3ES) for ultralow volume (single drop—10 µL) detection of analytes in whole blood. The O3ES produces reliable electrochemical signals in whole blood from a mouse model with minimal biofouling interference. The O3ES is demonstrated as a portable device for the simultaneous detection of dopamine, ascorbic acid and uric acid using voltammetry techniques. The O3ES displays excellent sensitivity towards each analyte in whole blood, and in the presence of each other. The water-based, ambient processing of the sensors allows the immobilization of enzymes in the organic working electrode. Amperometric detection of uric acid via uricase with high sensitivity in whole blood is demonstrated. Finally, the performance of the O3ES under enzymatic degradation is studied by monitoring sensitivity over an operating lifetime of ~14 days. This work demonstrates the realization of low-cost, disposable POC sensors capable of detecting blood metabolites using ultralow sample volumes. Full article
(This article belongs to the Section Electrochemical Devices and Sensors)
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13 pages, 2720 KiB  
Article
A Study on Regenerative Quartz Crystal Microbalance
by Ioan Burda
Chemosensors 2022, 10(7), 262; https://doi.org/10.3390/chemosensors10070262 - 05 Jul 2022
Cited by 4 | Viewed by 1598
Abstract
The quartz crystal microbalance with dissipation (QCM-D) represented a substantial breakthrough in the use of the QCM sensor in diverse applications ranging from environmental monitoring to biomedical diagnostics. To obtain the required selectivity and sensitivity of a volatile organic compounds (VOC) sensor, it [...] Read more.
The quartz crystal microbalance with dissipation (QCM-D) represented a substantial breakthrough in the use of the QCM sensor in diverse applications ranging from environmental monitoring to biomedical diagnostics. To obtain the required selectivity and sensitivity of a volatile organic compounds (VOC) sensor, it is necessary to coat the QCM sensor with a sensing film. As the QCM sensor is coated with the sensing film, an increase in the dissipation factor occurs, resulting in a shorter and shorter ring-down time. This decrease in ring-down time makes it difficult to implement the QCM-D method in an economical and portable configuration from the perspective of large-scale applications. To compensate for this effect, a regenerative method is proposed by which the damping effect produced by the sensing film is eliminated. In this sense, a regenerative circuit as an extension to a virtual instrument is proposed to validate the experimental method. The simulation of the ring-down time for the QCM sensor in the air considering the effect of the added sensing film, followed by the basic theoretical concepts of the regenerative method and the experimental results obtained, are analyzed in detail in this paper. Full article
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15 pages, 1772 KiB  
Article
Enose Lab Made with Vacuum Sampling: Quantitative Applications
by Guilherme G. Teixeira, António M. Peres, Letícia Estevinho, Pedro Geraldes, Cristina Garcia-Cabezon, Fernando Martin-Pedrosa, Maria Luz Rodriguez-Mendez and Luís G. Dias
Chemosensors 2022, 10(7), 261; https://doi.org/10.3390/chemosensors10070261 - 05 Jul 2022
Cited by 6 | Viewed by 1574
Abstract
A lab-made electronic nose (Enose) with vacuum sampling and a sensor array, comprising nine metal oxide semiconductor Figaro gas sensors, was tested for the quantitative analysis of vapor–liquid equilibrium, described by Henry’s law, of aqueous solutions of organic compounds: three alcohols (i.e., methanol, [...] Read more.
A lab-made electronic nose (Enose) with vacuum sampling and a sensor array, comprising nine metal oxide semiconductor Figaro gas sensors, was tested for the quantitative analysis of vapor–liquid equilibrium, described by Henry’s law, of aqueous solutions of organic compounds: three alcohols (i.e., methanol, ethanol, and propanol) or three chemical compounds with different functional groups (i.e., acetaldehyde, ethanol, and ethyl acetate). These solutions followed a fractional factorial design to guarantee orthogonal concentrations. Acceptable predictive ridge regression models were obtained for training, with RSEs lower than 7.9, R2 values greater than 0.95, slopes varying between 0.84 and 1.00, and intercept values close to the theoretical value of zero. Similar results were obtained for the test data set: RSEs lower than 8.0, R2 values greater than 0.96, slopes varying between 0.72 and 1.10, and some intercepts equal to the theoretical value of zero. In addition, the total mass of the organic compounds of each aqueous solution could be predicted, pointing out that the sensors measured mainly the global contents of the vapor phases. The satisfactory quantitative results allowed to conclude that the Enose could be a useful tool for the analysis of volatiles from aqueous solutions containing organic compounds for which Henry’s law is applicable. Full article
(This article belongs to the Special Issue Advances in Analytical Systems for Gaseous Mixture)
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12 pages, 4336 KiB  
Article
Pt/Au Nanoparticles@Co3O4 Cataluminescence Sensor for Rapid Analysis of Methyl Sec-Butyl Ether Impurity in Methyl Tert-Butyl Ether Gasoline Additive
by Zhaoxia Shi, Ling Xia, Gongke Li and Yufei Hu
Chemosensors 2022, 10(7), 260; https://doi.org/10.3390/chemosensors10070260 - 04 Jul 2022
Cited by 2 | Viewed by 1803
Abstract
High purity methyl tert-butyl ether (MTBE) can be used to adjust gasoline octane values. However, an isomer, methyl sec-butyl ether (MSBE), is the main by-product of its industrial production, and this affects the purity of MTBE. Pt/Au NPs@Co3O4 composites with [...] Read more.
High purity methyl tert-butyl ether (MTBE) can be used to adjust gasoline octane values. However, an isomer, methyl sec-butyl ether (MSBE), is the main by-product of its industrial production, and this affects the purity of MTBE. Pt/Au NPs@Co3O4 composites with a hollow dodecahedron three-dimensional structure were synthesized using ZIF-67 as a template, with Pt and Au nanoparticles (NPs) evenly distributed on the shell of the hollow structure. A CTL sensor was established for the determination of MSBE based on the specificity of Pt/Au NPs@Co3O4. The experimental results showed that Pt/Au NPs@Co3O4 had a strong specific cataluminescence (CTL) response to MSBE, with no interference from MTBE. The linear range was 0.10–90 mg/L, the limit of detection was 0.031 mg/L (S/N = 3), the RSD was 2.5% (n = 9), and a complete sample test could be completed in five minutes. The sensor was used to detect MSBE in MTBE of different purity grades, with recoveries ranging from 92.0% to 109.2%, and the analytical results were consistent with those determined by gas chromatography. These results indicate that the established method was accurate and reliable, and could be used for rapid analysis of MTBE gasoline additive. Full article
(This article belongs to the Special Issue Feature Papers on Luminescent Sensing)
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