Chemosensors

24 pages, 2488 KiB

Open AccessReview

Progress on Electrochemical Sensing of Pharmaceutical Drugs in Complex Biofluids

by Elain Fu, Khadijeh Khederlou, Noël Lefevre, Stephen A. Ramsey, Matthew L. Johnston and Lael Wentland

Chemosensors 2023, 11(8), 467; https://doi.org/10.3390/chemosensors11080467 - 21 Aug 2023

Cited by 5 | Viewed by 2939

Abstract

Electrochemical detection, with its advantages of being rapid, multi-time point, compatible with cost-effective fabrication methods, and having the potential for miniaturization and portability, has great promise for point-of-care drug monitoring. However, a continuing challenge concerns the robust and sensitive electrochemical detection of pharmaceutical [...] Read more.

Electrochemical detection, with its advantages of being rapid, multi-time point, compatible with cost-effective fabrication methods, and having the potential for miniaturization and portability, has great promise for point-of-care drug monitoring. However, a continuing challenge concerns the robust and sensitive electrochemical detection of pharmaceutical analytes from biological fluids. These complex matrices, such as saliva, sweat, interstitial fluid, urine, and blood/serum, contain multiple components that can contribute to an increased background or reduced analyte signal. In this mini-review, we discuss progress on electrochemical sensing in complex biofluids. We first introduce the challenge of drug titration in the management of various health conditions and provide an overview of the motivation for improved therapeutic drug monitoring, including current limitations. We then review progress on pharmaceutical drug detection from these biofluids with a focus on sample preprocessing, electrode modification for signal amplification, and/or electrode passivation to minimize fouling. Finally, we highlight promising strategies that have enabled robust drug quantification for clinical relevance and that may be useful for field-use systems. Full article

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

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17 pages, 3444 KiB

Open AccessArticle

Anodic Stripping Voltammetric Determination of Copper Ions in Cell Culture Media: From Transwell^® to Organ-on-Chip Systems

by Carmela Tania Prontera, Elisa Sciurti, Chiara De Pascali, Lucia Giampetruzzi, Francesco Biscaglia, Laura Blasi, Vanessa Esposito, Flavio Casino, Pietro Aleardo Siciliano and Luca Nunzio Francioso

Chemosensors 2023, 11(8), 466; https://doi.org/10.3390/chemosensors11080466 - 21 Aug 2023

Cited by 3 | Viewed by 1834

Abstract

The integration of sensing devices into cell culture systems is a topic of great interest in the study of pathologies and complex biological mechanisms in real-time. In particular, the fit-for-purpose microfluidic devices called organ-on-chip (OoC), which host living engineered organs that mimic in [...] Read more.

The integration of sensing devices into cell culture systems is a topic of great interest in the study of pathologies and complex biological mechanisms in real-time. In particular, the fit-for-purpose microfluidic devices called organ-on-chip (OoC), which host living engineered organs that mimic in vivo conditions, benefit greatly from the integration of sensors, enabling the monitoring of specific chemical-physical parameters that can be correlated with biological processes. In this context, copper is an essential trace element whose total concentration may be associated with specific pathologies, and it is therefore important to develop reliable analytical techniques in cell systems. Copper can be determined by using the anodic stripping voltammetry (ASV) technique, but its applicability in cell culture media presents several challenges. Therefore, in this work, the performance of ASV in cell culture media was evaluated, and an acidification protocol was tested to improve the voltammetric signal intensity. A Transwell^® culture model with Caco-2 cells was used to test the applicability of the developed acidification protocol by performing an off-line measurement. Finally, a microfluidic device was designed in order to perform the acidification of the cell culture medium in an automated manner and then integrated with a silicon microelectrode to perform in situ measurements. The resulting sensor-integrated microfluidic chip could be used to monitor the concentration of copper or other ions concentration in an organ-on-chip model; these functionalities represent a great opportunity for the non-destructive strategic experiments required on biological systems under conditions close to those in vivo. Full article

(This article belongs to the Special Issue Electrochemical Sensors for Food Control, Environmental Analysis, and Diagnosis in Medicine)

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25 pages, 3886 KiB

Open AccessReview

Aptamer–Molecularly Imprinted Polymer Multiple-Recognition System: Construction and Application

by Kangping Ning, Yingzhuo Shen, Yao Yao, Wenzheng Xie, Cheng Ma and Qin Xu

Chemosensors 2023, 11(8), 465; https://doi.org/10.3390/chemosensors11080465 - 18 Aug 2023

Cited by 3 | Viewed by 1517

Abstract

Molecularly imprinted polymers (MIPs) and aptamers (Apts) are widely used in substance detection due to their specific recognition abilities. However, both of them have limitations in terms of stability or sensitivity. Therefore, an increasingly employed strategy is to combine MIPs and aptamers to [...] Read more.

Molecularly imprinted polymers (MIPs) and aptamers (Apts) are widely used in substance detection due to their specific recognition abilities. However, both of them have limitations in terms of stability or sensitivity. Therefore, an increasingly employed strategy is to combine MIPs and aptamers to form mixed components for detecting various substances, such as viruses, bacteria, proteins, heavy-metal ions, and hormones. The aim of this review is to provide a comprehensive summary of the scientific research conducted on the construction and application of aptamer–MIP multiple-recognition components in the past five years. It also aims to analyze their research and development strategies, construction mechanisms, advantages, and potential applications, as well as limitations and current challenges that need to be addressed. Full article

(This article belongs to the Special Issue Bionic Recognition and Biosensors: A Theme Issue in Honor of Professor Hong-Yuan Chen)

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14 pages, 2921 KiB

Open AccessArticle

Quantitative Detection of the Influenza a Virus by an EGOFET-Based Portable Device

by Elena Y. Poimanova, Elena G. Zavyalova, Elena A. Kretova, Anton A. Abramov, Askold A. Trul, Oleg V. Borshchev, Anna K. Keshek, Sergey A. Ponomarenko and Elena V. Agina

Chemosensors 2023, 11(8), 464; https://doi.org/10.3390/chemosensors11080464 - 17 Aug 2023

Cited by 3 | Viewed by 1579

Abstract

Elaboration of biosensors on the base of organic transistors with embedded biomolecules which can operate in an aqueous environment is of paramount importance. Electrolyte-gated organic field-effect transistors demonstrate high sensitivity in detection of various analytes. In this paper, we demonstrated the possibility of [...] Read more.

Elaboration of biosensors on the base of organic transistors with embedded biomolecules which can operate in an aqueous environment is of paramount importance. Electrolyte-gated organic field-effect transistors demonstrate high sensitivity in detection of various analytes. In this paper, we demonstrated the possibility of quantitative fast specific determination of virus particles by an aptasensor based on EGOFET. The sensitivity and selectivity of the devices were examined with the influenza A virus as well as with control bioliquids like influenza B, Newcastle disease viruses or allantoic fluid with different dilutions. The influence of the semiconducting layer thickness on EGOFETs sensory properties is discussed. The fabrication of a multi-flow cell that simultaneously registers the responses from several devices on the same substrate and the creation of a multi-sensor flow device are reported. The responses of the elaborated bioelectronic platform to the influenza A virus obtained with application of the portable multi-flow mode are well correlated with the responses obtained in the laboratory stationary mode. Full article

(This article belongs to the Special Issue Chemosensors in Biological Challenges)

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14 pages, 2902 KiB

Open AccessArticle

Remote Measurements of Tear Electrolyte Concentrations on Both Sides of an Inserted Contact Lens

by Joseph R. Lakowicz, Ramachandram Badugu, Kundan Sivashanmugan and Albert Reece

Chemosensors 2023, 11(8), 463; https://doi.org/10.3390/chemosensors11080463 - 17 Aug 2023

Viewed by 2065

Abstract

In this paper, a method is described to perform ion concentration measurements on both sides of an inserted contact lens, without physical contact with the eye or the contact lens. The outer surface of an eye is covered with a tear film that [...] Read more.

In this paper, a method is described to perform ion concentration measurements on both sides of an inserted contact lens, without physical contact with the eye or the contact lens. The outer surface of an eye is covered with a tear film that has multiple layers. The central aqueous layer contains electrolytes and proteins. When a contact lens is inserted, it becomes localized in the central layer, which creates two layers known as the pre-lens tear film (PLTF) and the post-lens tear film (PoLTF). The PoLTF is in direct contact with the sensitive corneal epithelial cells which control electrolyte concentrations in tears. It is difficult to measure the overall electrolyte concentration in tears because of the small 7 μL volume of bulk tears. No methods are known, and no method has been proposed, to selectively measure the concentrations of electrolytes in the smaller volumes of the PLTF and the PoLTF. In this paper, we demonstrate the ability to localize fluorophores on each side of a contact lens without probe mixing or diffusion across the lens. We measured the concentration of sodium in the region of the PoLTF using a sodium-sensitive fluorophore positioned on the inner surface of a contact lens. The fluorescence measurements do not require physical contact and are mostly independent of eye motion and fluorophore concentration. The method is generic and can be combined with ion-sensitive fluorophores for the other electrolytes in tears. Instrumentation for non-contact measurements is likely to be inexpensive with modern opto-electronic devices. We expect these lenses to be used for measurements of other ions in the PLTF and the PoLTF, and thus become useful for both research and in the diagnosis of infections, keratitis and biomarkers for diseases. Full article

(This article belongs to the Special Issue Fluorescence and Raman Spectroscopy and Nanosensors in Analytical Chemistry)

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Graphical abstract

12 pages, 3721 KiB

Open AccessArticle

Highly Polarized SERS Based on Random Working Domains Composed of Nanorod Arrays for Self-Referenced Detection

by Xiaoyu Zhao, Deyuan Mao, Shuangshuang Zhao, Yuxia Wang, Xiaojie Guo, Yaxin Wang, Renxian Gao and Yongjun Zhang

Chemosensors 2023, 11(8), 462; https://doi.org/10.3390/chemosensors11080462 - 16 Aug 2023

Viewed by 1250

Abstract

When Ag film is sputtered onto polystyrene (PS) spheres, the curved Ag nanocaps form with scattered Ag nanoparticles along the brim of the Ag nanocap. Ion etching results in parallel PS nanorods due to the masking effects of the scattered Ag nanoparticles when [...] Read more.

When Ag film is sputtered onto polystyrene (PS) spheres, the curved Ag nanocaps form with scattered Ag nanoparticles along the brim of the Ag nanocap. Ion etching results in parallel PS nanorods due to the masking effects of the scattered Ag nanoparticles when the Ag cap array is transferred to another substrate with the top down. The highly polarized SERS substrate of random working domains composed of parallel nanorods is prepared when another 5 nm film is deposited. The nanorod diameters range from 10 nm to 20 nm, depending on the sizes of the masking Ag nanoparticles prepared by the magnetron control system and the ion etching process. Compared with other techniques, our nanorods have the advantages of highly ordered patterns in each domain, which show the excellent behavior of the polarized SERS for all PS spheres. This polarized SERS substrate is used to detect thiram with a concentration as low as 10⁻⁹ M when the background noise is successfully removed by a self-reference technique. Full article

(This article belongs to the Special Issue SERS Sensing Technology: Research, Progress and Applications)

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25 pages, 8049 KiB

Open AccessReview

Recent Advances in Rational Design and Engineering of Signal-Amplifying Substrates for Surface-Enhanced Raman Scattering-Based Bioassays

by Song Gao, Zhanchen Guo and Zhen Liu

Chemosensors 2023, 11(8), 461; https://doi.org/10.3390/chemosensors11080461 - 16 Aug 2023

Cited by 1 | Viewed by 2082

Abstract

In recent decades, surface-enhanced Raman spectroscopy (SERS) has become a powerful detection scheme for many applications, particularly bioassays, due to its unique strengths, such as its ultrasensitive performance. Due to the development of various SERS substrates, more SERS-based bioassays with improved sensitivity and [...] Read more.

In recent decades, surface-enhanced Raman spectroscopy (SERS) has become a powerful detection scheme for many applications, particularly bioassays, due to its unique strengths, such as its ultrasensitive performance. Due to the development of various SERS substrates, more SERS-based bioassays with improved sensitivity and reproducibility have been designed and manufactured. SERS is able to provide the intrinsic vibration information of molecules through the unique Raman fingerprint to enable direct detection and quantitation. Meanwhile, with the assistance of Raman-active labels, biomolecules, like proteins and nucleic acids, can be detected by the immunosandwich assay. In this review, we focus on the rational design and engineering of signal-enhancing substrates for SERS-based bioassays. Those substrates are classified into two categories, i.e., nanoparticles in colloidal suspension and nanostructures on a solid support. Each category is discussed in detail with stress on their biomedical application potential. Afterward, we summarize the SERS-based assays of proteins, nucleic acids, and viruses, for which both label-free and labeled approaches play important roles. Finally, we present the remaining challenges in the field of SERS-based bioassays and sketch out promising directions for future development. Full article

(This article belongs to the Special Issue Bionic Recognition and Biosensors: A Theme Issue in Honor of Professor Hong-Yuan Chen)

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19 pages, 3502 KiB

Open AccessArticle

Gas-Sensing Properties of Graphene Functionalized with Ternary Cu-Mn Oxides for E-Nose Applications

by Margus Kodu, Rainer Pärna, Tea Avarmaa, Indrek Renge, Jekaterina Kozlova, Tauno Kahro and Raivo Jaaniso

Chemosensors 2023, 11(8), 460; https://doi.org/10.3390/chemosensors11080460 - 15 Aug 2023

Cited by 1 | Viewed by 1386

Abstract

Chemiresistive gas sensors were produced by functionalizing graphene with a ~3 nm layer of mixed oxide xCu₂O⸱yMnO using pulsed laser deposition (PLD) from a hopcalite CuMn₂O₄ target. Sensor response time traces were recorded for strongly [...] Read more.

Chemiresistive gas sensors were produced by functionalizing graphene with a ~3 nm layer of mixed oxide xCu₂O⸱yMnO using pulsed laser deposition (PLD) from a hopcalite CuMn₂O₄ target. Sensor response time traces were recorded for strongly oxidizing (NO₂, O₃) and reducing (NH₃, H₂S) poisonous gases at ppb and ppm levels, respectively. The morphology of the MOX layer was modified by growth temperature during PLD, resulting in the optimization of the sensor response. Differences in decomposition or oxidation rates on catalytically active metal oxide (MOX) were utilized to achieve partial selectivity for pairs of gases that have similar adsorption and redox properties. The predominant selectivity towards ozone in most samples at different measuring conditions remained difficult to suppress. A distinct selectivity for H₂S emerged at higher measurement temperatures (100–150 °C), which was assigned to catalytic oxidation with O₂. Several gas–MOX interaction mechanisms were advanced to tentatively explain the sensor behavior, including reversible electron transfer in the simplest case of NO₂, decomposition via ionic transients for O₃, and complex catalytic oxidative transformations for NH₃ and H₂S. Full article

(This article belongs to the Special Issue Nanomaterials in Chemosensors and Biosensors: Development and Application)

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34 pages, 7042 KiB

Open AccessReview

Wearable Chemosensors in Physiological Monitoring

by Zeyi Tang, Tianrui Cui, Houfang Liu, Jinming Jian, Ding Li, Yi Yang and Tianling Ren

Chemosensors 2023, 11(8), 459; https://doi.org/10.3390/chemosensors11080459 - 15 Aug 2023

Viewed by 2174

Abstract

The development of flexible electronic technology has led to significant advancements in wearable sensors. In the past decades, wearable chemosensors have received much attention from researchers worldwide due to their high portability, flexibility, lightweight, and adaptability. It allows real-time access to the user’s [...] Read more.

The development of flexible electronic technology has led to significant advancements in wearable sensors. In the past decades, wearable chemosensors have received much attention from researchers worldwide due to their high portability, flexibility, lightweight, and adaptability. It allows real-time access to the user’s physiological status at the molecular level to analyze their health status. Therefore, it can be widely used in the field of precision medicine. This review introduces the sensing mechanisms of wearable chemosensors and recent progress in wearable sweat and interstitial fluid-based chemosensors. The complexities of wearable chemosensors are not to be underestimated, as there are considerable challenges in this field. This review aims to shed light on the difficulties associated with designing wearable sweat and interstitial fluid-based chemosensors and their potential development directions. Full article

(This article belongs to the Special Issue Chemosensors in Biological Challenges, Volume II)

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13 pages, 2901 KiB

Open AccessArticle

Development and Application of an Electrochemical Sensor with 1,10-Phenanthroline-5,6-dione-Modified Electrode for the Detection of Escherichia coli in Water

by Yining Fan, Yanran Liu, Guanyue Gao, Hanxin Zhang and Jinfang Zhi

Chemosensors 2023, 11(8), 458; https://doi.org/10.3390/chemosensors11080458 - 15 Aug 2023

Viewed by 1519

Abstract

The routine monitoring of bacterial populations is crucial for ensuring water quality and safeguarding public health. Thus, an electrochemical sensor based on a 1,10-phenanthroline-5,6-dione-modified electrode was developed and explored for the detection of E. coli. The modified electrode exhibited enhanced NADH oxidation [...] Read more.

The routine monitoring of bacterial populations is crucial for ensuring water quality and safeguarding public health. Thus, an electrochemical sensor based on a 1,10-phenanthroline-5,6-dione-modified electrode was developed and explored for the detection of E. coli. The modified electrode exhibited enhanced NADH oxidation ability at a low potential of 0.1 V, which effectively eliminated the interference from other redox compounds in bacteria. The sensitivity for NADH was 0.222 μA/μM, and the limit of detection was 0.0357 μM. Upon cell lysis, the intracellular NADH was released, and the concentration of E. coli was determined through establishing the relationship between the oxidation current signal and NADH concentration. The performance of the electrochemical sensor in the detection of NADH and E. coli suspensions was validated using the WST-8 colorimetric method. The blank recovery experiment in real water samples exhibited good accuracy, with recovery rates ranging from 89.12% to 93.26% and relative standard deviations of less than 10%. The proposed electrochemical sensor realized the detection of E. coli without the usage of biomarkers, which provides a promising approach for the broad-spectrum detection of microbial contents in complex water environments. Full article

(This article belongs to the Special Issue Bionic Recognition and Biosensors: A Theme Issue in Honor of Professor Hong-Yuan Chen)

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15 pages, 2657 KiB

Open AccessEditor’s ChoiceArticle

Eco-Friendly, High-Performance Humidity Sensor Using Purple Sweet-Potato Peel for Multipurpose Applications

by Sheik Abdur Rahman, Shenawar Ali Khan, Shahzad Iqbal, Muhammad Muqeet Rehman and Woo Young Kim

Chemosensors 2023, 11(8), 457; https://doi.org/10.3390/chemosensors11080457 - 15 Aug 2023

Cited by 6 | Viewed by 2268

Abstract

Biomaterials offer great potential for enhancing the performance of humidity sensors, which play a critical role in controlling moisture levels across different applications. By utilizing environmentally friendly, sustainable, and cost-effective biomaterials, we can improve the manufacturing process of these sensors while reducing our [...] Read more.

Biomaterials offer great potential for enhancing the performance of humidity sensors, which play a critical role in controlling moisture levels across different applications. By utilizing environmentally friendly, sustainable, and cost-effective biomaterials, we can improve the manufacturing process of these sensors while reducing our environmental impact. In this study, we present a high-performance humidity sensor that utilizes purple sweet potato peel (PSPP) as both the substrate and sensing layer. The PSPP is chosen for its polar hydrophilic functional groups, as well as its environmentally friendly nature, sustainability, and cost-effectiveness. Remarkably, this humidity sensor does not require an external substrate. It exhibits a wide detection range of 0 to 85% relative humidity at various operating frequencies (100 Hz, 1 kHz, and 10 kHz) in ambient temperature, demonstrating its effectiveness in responding to different humidity levels. The sensor achieves a high sensitivity value of 183.23 pF/%RH and minimal hysteresis of only 5% at 10 kHz under ambient conditions. It also boasts rapid response and recovery times of 1 and 2 s, respectively, making it suitable for use in high-end electronic devices. Moreover, the sensor’s applications extend beyond environmental monitoring. It has proven effective in monitoring mouth and nasal breathing, indicating its potential for respiratory monitoring and noncontact proximity response. These findings suggest that sweet potato peel material holds great promise as a highly stable, non-toxic, biodegradable, cost-effective, and environmentally friendly option for various domains, including healthcare monitoring. Full article

(This article belongs to the Section Applied Chemical Sensors)

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8 pages, 1951 KiB

Open AccessCommunication

Methods for Calibrating the Electrochemical Quartz Crystal Microbalance: Frequency to Mass and Compensation for Viscous Load

by Claes-Olof A. Olsson, Anna Neus Igual-Muñoz and Stefano Mischler

Chemosensors 2023, 11(8), 456; https://doi.org/10.3390/chemosensors11080456 - 14 Aug 2023

Viewed by 1694

Abstract

The main output from an Electrochemical Quartz Crystal Microbalance is a frequency shift. This note describes how to separate the mass- and viscous load contributions to this shift by a calibration procedure. The mass calibration is made by electroplating from a copper sulfate [...] Read more.

The main output from an Electrochemical Quartz Crystal Microbalance is a frequency shift. This note describes how to separate the mass- and viscous load contributions to this shift by a calibration procedure. The mass calibration is made by electroplating from a copper sulfate solution in ethanol/water with 100% current efficiency. An estimate of viscous load is obtained by measuring the energy dissipation and is related to frequency change using the Kanazawa–Gordon equation. Two approaches are discussed: either by performing calibration experiments in a series of water–glycerol mixtures or by following oscillations in frequency and dissipation by collecting data during the stabilization phase of the experiment. Full article

(This article belongs to the Special Issue Recent Advances in Quartz Crystal Microbalance-Based Sensor Applications: Part II)

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13 pages, 1224 KiB

Open AccessArticle

One-Step Chemiluminescent Assay for Hydrogen Peroxide Analysis in Water

by Ahlem Teniou, Ibrahim A. Madi, Riane Mouhoub, Jean Louis Marty and Amina Rhouati

Chemosensors 2023, 11(8), 455; https://doi.org/10.3390/chemosensors11080455 - 14 Aug 2023

Cited by 6 | Viewed by 2210

Abstract

The detection of hydrogen peroxide is of great importance in the environmental field. For this, a homogeneous technique has been developed here for sensitive and rapid quantification of hydrogen peroxide. In this technique, hemoglobin was used as a bioreceptor, where heme groups acted [...] Read more.

The detection of hydrogen peroxide is of great importance in the environmental field. For this, a homogeneous technique has been developed here for sensitive and rapid quantification of hydrogen peroxide. In this technique, hemoglobin was used as a bioreceptor, where heme groups acted as electroactive centers to catalyze hydrogen peroxide reduction. The chemiluminescence reagent luminol is also a peroxidase substrate and can be oxidized by hemoglobin—thus generating a CL signal. The principle of the designed biosensor was based on the competition between hydrogen peroxide and luminol towards hemoglobin. Under optimized conditions, the chemiluminescent signal decreased with increasing hemoglobin concentrations within the linear range of 0.5 to 12 mM, with a correlation coefficient R² of 0.99762. The limit of detection was calculated to be as low as 0.308 mM. The selectivity of the biosensor was successfully demonstrated against different interferents. The developed strategy provides a one step, simple, and low-cost bioanalytical method which can be applied for the monitoring of other peroxidase substrates. Full article

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

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15 pages, 5588 KiB

Open AccessArticle

Optical Dual Gas Sensor for Simultaneous Detection of Nitric Oxide and Oxygen

by Rispandi Mesin and Cheng-Shane Chu

Chemosensors 2023, 11(8), 454; https://doi.org/10.3390/chemosensors11080454 - 14 Aug 2023

Cited by 6 | Viewed by 1781

Abstract

This work presents a new optical dual sensor based on PtTFPP-containing electrospun fibers and CsPbBr₃ perovskite quantum dots (PQDs) for simultaneous detection of oxygen (O₂) and nitric oxide (NO) gases, wherein PtTFPP-containing electrospun fibers for O₂ sensing was based [...] Read more.

This work presents a new optical dual sensor based on PtTFPP-containing electrospun fibers and CsPbBr₃ perovskite quantum dots (PQDs) for simultaneous detection of oxygen (O₂) and nitric oxide (NO) gases, wherein PtTFPP-containing electrospun fibers for O₂ sensing was based on electrospinning process fabricated by platinum(II) meso-tetrakis (pentafluorophenyl) porphyrin (PtTFPP) complex immobilized in cellulose acetate (CA) matrix. CsPbBr₃ PQDs were used as NO-sensitive material and coated on the surface of PtTFPP-containing electrospun fibers. Both materials were excited by a UV LED with a central wavelength of 380 nm, and the fluorescence intensities of sensing materials were recorded and analyzed with a spectrometer. The experiment results show that the optical NO and O₂ sensors have linear Stern–Volmer plots, and the sensitivities are around 2.7 and 10.7, respectively. The response and recovery times of the optical NO sensor are 71 and 109 s, respectively. For optical O₂, response and recovery times are 60 and 65 s, respectively. The optical dual sensor with a new method based on fluorescent dye containing electrospun fibers and coated with CsPbBr₃ PQDs has been successfully developed to detect NO and O₂ gases simultaneously. The optical dual gas sensor provides great potential for practical applications with low cost and ease of fabrication. Full article

(This article belongs to the Collection Recent Advances in Multifunctional Sensing Technology for Gas Analysis)

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13 pages, 3590 KiB

Open AccessArticle

A Metal Organic Framework-Based Light Scattering ELISA for the Detection of Staphylococcal Enterotoxin B

by Kai Mao, Lili Tian, Yujie Luo, Qian Li, Xi Chen, Lei Zhan, Yuanfang Li, Chengzhi Huang and Shujun Zhen

Chemosensors 2023, 11(8), 453; https://doi.org/10.3390/chemosensors11080453 - 13 Aug 2023

Cited by 2 | Viewed by 1641

Abstract

Enzyme-linked immunosorbent assay (ELISA) is one of the most commonly used method for the detection of staphylococcal enterotoxin B (SEB), the main protein toxin causing staphylococcal food poisoning. However, the traditional ELISA reaction needs to be stopped by sulfuric acid to obtain stable [...] Read more.

Enzyme-linked immunosorbent assay (ELISA) is one of the most commonly used method for the detection of staphylococcal enterotoxin B (SEB), the main protein toxin causing staphylococcal food poisoning. However, the traditional ELISA reaction needs to be stopped by sulfuric acid to obtain stable colorimetric signal, and it is easily influenced by a colored sample. In order to address this problem, a new ELISA method using zeolite imidazolate skeleton-8 metal-organic framework (ZIF-8 MOF) as a light scattering (LS) reporter for SEB detection was developed in this work. ZIF-8 MOF has the characteristics of high porosity, large specific surface area, clear pore structure, and adjustable size, which is one of the most representative MOFs constructed from Zn²⁺ and 2-methylimidazole (2-mIM). The 2-mIM ligand of ZIF-8 exhibited antioxidant activity and can strongly react with H₂O₂, which could destroy the structure of ZIF-8, resulting in the obvious decrease in LS intensity. We combined this specific reaction with the sandwich immune reaction to construct the LS ELISA method for the successful detection of SEB. This method is more reliable than commercial tests kits for the detection of colored samples, and it is simple, sensitive, and selective, and has great potential in the detection of other toxins by simply changing the corresponding recognition units. Full article

(This article belongs to the Special Issue Nanoprobes for Biosensing and Bioimaging)

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16 pages, 2981 KiB

Open AccessArticle

Facile Fabrication of a Selective Poly(caffeic acid)@MWCNT-Ni(OH)₂ Hybrid Nanomaterial and Its Application as a Non-Enzymatic Glucose Sensor

by Maria Kuznowicz, Tomasz Rębiś, Artur Jędrzak, Grzegorz Nowaczyk and Teofil Jesionowski

Chemosensors 2023, 11(8), 452; https://doi.org/10.3390/chemosensors11080452 - 13 Aug 2023

Viewed by 1733

Abstract

A novel catechol-based PCA@MWCNT-Ni(OH)₂ hybrid material was prepared and used to construct a non-enzymatic glucose biosensor. In this synthesis, MWCNTs were covered with a poly(caffeic acid) coating and then subjected to a straightforward electrochemical process to decorate the hybrid material with Ni(OH) [...] Read more.

A novel catechol-based PCA@MWCNT-Ni(OH)₂ hybrid material was prepared and used to construct a non-enzymatic glucose biosensor. In this synthesis, MWCNTs were covered with a poly(caffeic acid) coating and then subjected to a straightforward electrochemical process to decorate the hybrid material with Ni(OH)₂ particles. The physicochemical properties and morphology of the nanomaterial were characterized using high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), and atomic force microscopy (AFM). Amperometry and cyclic voltammetric studies demonstrated the enhanced redox properties of a GC/PCA@MWCNT-Ni(OH)₂ electrode and its electrocatalytic activity in glucose detection, with a low detection limit (0.29 μM), a selectivity of 232.7 μA mM⁻¹ cm⁻², and a linear range of 0.05–10 mM, with good stability (5 months) and reproducibility (n = 8). The non-enzymatic sensor was also used for glucose determination in human serum and human blood, with recovery values ranging from 93.3% to 98.2%. In view of the properties demonstrated, the described GC/PCA@MWCNT-Ni(OH)₂ sensor represents a facile synthesis method of obtaining the hybrid nanomaterial and a low-cost approach to electrochemical glucose measurement in real samples (human serum, human blood). Full article

(This article belongs to the Special Issue Advanced Electrochemical Sensors or Biosensors Based on Nanomaterial)

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12 pages, 3151 KiB

Open AccessArticle

Visual Measurement of Fumonisin B₁ with Bipolar Electrodes Array-Based Electrochemiluminescence Biosensor

by Longsheng Jin, Huihui Yu, Weishuai Liu, Ziying Xiao, Haijian Yang, Bing Jin and Meisheng Wu

Chemosensors 2023, 11(8), 451; https://doi.org/10.3390/chemosensors11080451 - 12 Aug 2023

Cited by 3 | Viewed by 1333

Abstract

Fumonisin B₁ (FB₁) is a toxin produced by the metabolism of Fusarium oxysporum, which can cause serious effects on the nervous, respiratory, digestive, and reproductive systems of humans or animals; it is known as one of the highly toxic epidemic [...] Read more.

Fumonisin B₁ (FB₁) is a toxin produced by the metabolism of Fusarium oxysporum, which can cause serious effects on the nervous, respiratory, digestive, and reproductive systems of humans or animals; it is known as one of the highly toxic epidemic contaminants. Herein, we report the visual inspection of FB₁ using bipolar electrodes (BPEs) with an array-based electrochemiluminescence (ECL) platform. The sensor consists of a PDMS cover and a glass substrate containing an array of 10 ITO electrodes. A specific sensing interface was constructed on the cathode of the BPE, which could modulate the ECL reactions that occurred at the anode of BPEs. To amplify the ECL signal, methylene blue (MB)-encapsulated Zr-MOFs (MB@Zr-MOFs) were synthesized and immobilized on the cathode of the BPE, which could amplify the ECL signal at the anode. By coupling the cyclic amplification effect of the DNA walker and nicking endonuclease (Nb.BbvCI), the biosensor can realize the visual measurement of FB₁ in the range of 5 × 10⁻⁵~0.5 ng/mL. In addition, the developed biosensor was used to monitor the concentration of FB₁ in maize and peanut samples. The recoveries were in the range of 99.2%~110.6%, which demonstrated the good accuracy of the designed BPE-ECL biosensor for FB₁ assay in food samples. Full article

(This article belongs to the Special Issue Bionic Recognition and Biosensors: A Theme Issue in Honor of Professor Hong-Yuan Chen)

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20 pages, 2891 KiB

Open AccessArticle

Effect of pH on Electrochemical Impedance Response of Tethered Bilayer Lipid Membranes: Implications for Quantitative Biosensing

by Arun Prabha Shivabalan, Filipas Ambrulevicius, Martynas Talaikis, Vaidas Pudzaitis, Gediminas Niaura and Gintaras Valincius

Chemosensors 2023, 11(8), 450; https://doi.org/10.3390/chemosensors11080450 - 11 Aug 2023

Cited by 3 | Viewed by 1617

Abstract

Tethered bilayer lipid membranes (tBLMs) are increasingly used in biosensor applications where electrochemical impedance spectroscopy (EIS) is the method of choice for amplifying and recording the activity of membrane-damaging agents such as pore-forming toxins or disrupting peptides. While the activity of these biological [...] Read more.

Tethered bilayer lipid membranes (tBLMs) are increasingly used in biosensor applications where electrochemical impedance spectroscopy (EIS) is the method of choice for amplifying and recording the activity of membrane-damaging agents such as pore-forming toxins or disrupting peptides. While the activity of these biological agents may depend on the pH of the analytes, there is increasing evidence that the sensitivity of tethered bilayer sensors depends on the pH of the solutions. In our study, we addressed the question of what are the fundamental reasons for the variability of the EIS signal of the tBLMs with pH. We designed an experiment to compare the EIS response of tBLMs with natural membrane defects and two different membrane disruptors: vaginolysin and melittin. Our experimental design ensured that the same amount of protein and peptide was present in the tBLMs, while the pH was varied by replacing the buffers with different pH values. Using a recently developed EIS data analysis algorithm from our research group, we were able to demonstrate that, in contrast to previous literature which relates the variability of tBLM, EIS response to the variation in defect density, the main reason for the observed variability in EIS response is the change in the sub-membrane properties of tBLMs with pH. Using surface-enhanced infrared absorption spectroscopy (SEIRAS), we have shown that pH changes from neutral to slightly acidic leads to an expulsion of water, presumably bound to ions, from the sub-membrane reservoir, resulting in a marked decrease in the carrier concentration and specific conductance of the sub-membrane reservoir. Such a decrease is recorded by the EIS as a decrease in the conductance of the tBLM complex and affects the sensitivity of a biosensor. Our data provide important evidence of pH-sensitive effects that should be considered in both the development and operation of biosensors. Full article

(This article belongs to the Special Issue Electrochemical Impedance Spectroscopy (EIS): Biosensing Applications)

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16 pages, 6455 KiB

Open AccessArticle

Real-Time Monitoring of Cement Paste Carbonation with In Situ Optical Fiber Sensors

by Pedro M. da Silva, João P. Mendes, Luís C. C. Coelho and José M. M. M. de Almeida

Chemosensors 2023, 11(8), 449; https://doi.org/10.3390/chemosensors11080449 - 11 Aug 2023

Cited by 1 | Viewed by 1392

Abstract

Reinforced concrete structures are prevalent in infrastructure and are of significant economic and social importance to humanity. However, they are prone to decay from cement paste carbonation. pH sensors have been developed to monitor cement paste carbonation, but their adoption by the industry [...] Read more.

Reinforced concrete structures are prevalent in infrastructure and are of significant economic and social importance to humanity. However, they are prone to decay from cement paste carbonation. pH sensors have been developed to monitor cement paste carbonation, but their adoption by the industry remains limited. This work introduces two new methods for monitoring cement paste carbonation in real time that have been validated through the accelerated carbonation of cement paste samples. Both configurations depart from traditional pH monitoring. In the first configuration, the carbonation depth of a cement paste sample is measured using two CO₂ optical fiber sensors. One sensor is positioned on the surface of the sample, while the other is embedded in the middle. As the carbonation depth progresses and reaches the embedded CO₂ sensor, the combined response of the sensors changes. In the second configuration, a multimode fiber is embedded within the paste, and its carbonation is monitored by observing the increase in reflected light intensity (1.6–18%) resulting from the formation of CaCO₃. Its applicability in naturally occurring carbonation is tested at concentrations of 3.2% CO₂, and the influence of water is positively evaluated; thus, this setup is suitable for real-world testing and applications. Full article

(This article belongs to the Section Optical Chemical Sensors)

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12 pages, 1873 KiB

Open AccessArticle

Enhanced Fluorescence in a Lens-Less Fiber-Optic Sensor for C-Reactive Protein Detection

by Victoria Esteso, Pietro Lombardi, Francesco Chiavaioli, Prosenjit Majumder, Maja Colautti, Steffen Howitz, Paolo Cecchi, Francesco Baldini, Ambra Giannetti and Costanza Toninelli

Chemosensors 2023, 11(8), 448; https://doi.org/10.3390/chemosensors11080448 - 11 Aug 2023

Cited by 1 | Viewed by 1518

Abstract

In today’s medicine, the celerity of the bio-assays analysis is crucial for the timely selection of the appropriate therapy and hence its effectiveness, especially in case of diseases characterized by the late onset of symptoms. In this paper, a lens-less fiber optics-based fluorescence [...] Read more.

In today’s medicine, the celerity of the bio-assays analysis is crucial for the timely selection of the appropriate therapy and hence its effectiveness, especially in case of diseases characterized by the late onset of symptoms. In this paper, a lens-less fiber optics-based fluorescence sensor designed for the measurement of labeled bio-assays is presented and its potential for the early diagnosis of sepsis via C-reactive protein (CRP) detection is demonstrated. The sensor performance results from the combination of two key elements: a planar antenna that redirects fluorescence the marker emission and an automated fiber-based optical system for multi-spot analysis. First, the working principle of the device is demonstrated with a well-established antibody–antigen format (immunoglobulin IgG/anti-IgG assay), reporting more than one order of magnitude enhanced limit of detection (LOD) and limit of quantification (LOQ) for the planar antenna with respect to a standard glass substrate. The prototype is then tested against a sample mimicking a realistic case, prepared with commercially available human serum, showing a LOD and LOQ in the clinical range of interest (0.0015 μg/mL and 0.005 μg/mL, respectively) for the investigation of the sepsis biomarker CRP. These results validate the developed prototype as a simple and easy-to-operate device, compatible with standardized micro-well arrays, and potentially suitable for POC applications. Full article

(This article belongs to the Special Issue Tenth Anniversary of Chemosensors—"Optical Chemical Sensors" Section)

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11 pages, 1355 KiB

Open AccessArticle

GC/MS Profile and Antifungal Activity of Zanthoxylum caribaeum Lam Essential Oil against Moniliophthora roreri Cif and Par, a Pathogen That Infects Theobroma cacao L Crops in the Tropics

by Marcial Fuentes-Estrada, Andrea Jiménez-González, Diannefair Duarte, Rogerio Saavedra-Barrera, Carlos Areche, Elena Stashenko, Nayive Pino Benítez, Daniela Bárcenas-Pérez, José Cheel and Olimpo García-Beltrán

Chemosensors 2023, 11(8), 447; https://doi.org/10.3390/chemosensors11080447 - 10 Aug 2023

Viewed by 1542

Abstract

The species Zanthoxylum caribaeum belongs to the Rutaceae family, from which several chemical nuclei are known, including alkaloids and coumarins. In addition, its essential oil has been characterized, showing differences in composition and various antimicrobial activities. In the present study, the essential oil [...] Read more.

The species Zanthoxylum caribaeum belongs to the Rutaceae family, from which several chemical nuclei are known, including alkaloids and coumarins. In addition, its essential oil has been characterized, showing differences in composition and various antimicrobial activities. In the present study, the essential oil of Z. caribaeum collected in the department of Tolima, central Colombia, was characterized by gas chromatography with mass selective detector (GC-MS). The essential oil showed a composition of about 43 compounds (including major and minor), whose main components, according to their abundance, are the following: germacrene D (228.0 ± 1.6 mg/g EO), (E)-β-farnesene (128.0 ± 1.5 mg/g EO), β-elemene (116.0 ± 1.6 mg/g EO) and (E)-nerolidol (74.0 ± 2.2 mg/g EO). This oil was tested against microorganisms that affect cocoa production in Colombia and in tropical countries where the production of this commodity is very important for the economy. The antifungal tests were performed on the fungal species Moniliophthora roreri and showed promising and significant activity, inhibiting growth by more than 95% at concentrations of 50 µL/mL and 100 µL/mL. This remarkable antifungal activity could be due to the presence of major and minor compounds that synergistically enhance the activity. Full article

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

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12 pages, 2352 KiB

Open AccessArticle

Disposable Stochastic Platform for the Simultaneous Determination of Calcipotriol and Betamethasone in Pharmaceutical and Surface Water Samples

by Bianca-Maria Tuchiu, Raluca-Ioana Stefan-van Staden, Jacobus (Koos) Frederick van Staden and Hassan Y. Aboul-Enein

Chemosensors 2023, 11(8), 446; https://doi.org/10.3390/chemosensors11080446 - 10 Aug 2023

Viewed by 1300

Abstract

A disposable stochastic platform based on calix [6]arene modified multi-walled carbon nanotubes-gold nanoparticles screen-printed electrode has been developed for the simultaneous determination of calcipotriol and betamethasone. For both analytes, very wide linear concentration ranges and extremely low limits of quantification (LOQ) were obtained: [...] Read more.

A disposable stochastic platform based on calix [6]arene modified multi-walled carbon nanotubes-gold nanoparticles screen-printed electrode has been developed for the simultaneous determination of calcipotriol and betamethasone. For both analytes, very wide linear concentration ranges and extremely low limits of quantification (LOQ) were obtained: from 1.0 × 10⁻¹⁵ to 1.0 × 10⁻³ mol L⁻¹ and with a 1.0 × 10⁻¹⁵ mol L⁻¹ LOQ for calcipotriol, and from 1.0 × 10⁻¹⁶ to 1.0 × 10⁻² mol L⁻¹ with a 1.0 × 10⁻¹⁶ mol L⁻¹ LOQ for betamethasone. The applicability of the sensing platform was successfully tested in commercially available topical pharmaceutical gel and surface water samples, obtaining recovery values ranging from 99.10 to 99.99% and relative standard deviation values under 0.05%. The obtained results render the proposed platform a viable, robust, selective, and sensitive tool that can be employed for the determination of the analytes in on-site routine quality control of pharmaceuticals and water quality monitoring. Full article

(This article belongs to the Special Issue Recent Developments in Electrochemical Sensing)

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15 pages, 2441 KiB

Open AccessArticle

Real-Time Monitoring of H₂O₂ Sterilization on Individual Bacillus atrophaeus Spores by Optical Sensing with Trapping Raman Spectroscopy

by Morten Bertz, Denise Molinnus, Michael J. Schöning and Takayuki Homma

Chemosensors 2023, 11(8), 445; https://doi.org/10.3390/chemosensors11080445 - 10 Aug 2023

Cited by 4 | Viewed by 1792

Abstract

Hydrogen peroxide (H₂O₂), a strong oxidizer, is a commonly used sterilization agent employed during aseptic food processing and medical applications. To assess the sterilization efficiency with H₂O₂, bacterial spores are common microbial systems due to [...] Read more.

Hydrogen peroxide (H₂O₂), a strong oxidizer, is a commonly used sterilization agent employed during aseptic food processing and medical applications. To assess the sterilization efficiency with H₂O₂, bacterial spores are common microbial systems due to their remarkable robustness against a wide variety of decontamination strategies. Despite their widespread use, there is, however, only little information about the detailed time-resolved mechanism underlying the oxidative spore death by H₂O₂. In this work, we investigate chemical and morphological changes of individual Bacillus atrophaeus spores undergoing oxidative damage using optical sensing with trapping Raman microscopy in real-time. The time-resolved experiments reveal that spore death involves two distinct phases: (i) an initial phase dominated by the fast release of dipicolinic acid (DPA), a major spore biomarker, which indicates the rupture of the spore’s core; and (ii) the oxidation of the remaining spore material resulting in the subsequent fragmentation of the spores’ coat. Simultaneous observation of the spore morphology by optical microscopy corroborates these mechanisms. The dependence of the onset of DPA release and the time constant of spore fragmentation on H₂O₂ shows that the formation of reactive oxygen species from H₂O₂ is the rate-limiting factor of oxidative spore death. Full article

(This article belongs to the Special Issue Biosensors and Chemical Sensors for Food and Healthcare Monitoring—Celebrating the 10th Anniversary)

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14 pages, 2678 KiB

Open AccessPerspective

Linkage Pathways of DNA–Nanoparticle Conjugates and Biological Applications

by Shan Huang and Jun-Jie Zhu

Chemosensors 2023, 11(8), 444; https://doi.org/10.3390/chemosensors11080444 - 10 Aug 2023

Viewed by 1700

Abstract

DNA–nanoparticle conjugates have extraordinary optical and catalytic properties that have attracted great interest in biosensing and biomedical applications. Combining these special qualities has made it possible to create extremely sensitive and selective biomolecule detection methods, as well as effective nanopharmaceutical carriers and therapy [...] Read more.

DNA–nanoparticle conjugates have extraordinary optical and catalytic properties that have attracted great interest in biosensing and biomedical applications. Combining these special qualities has made it possible to create extremely sensitive and selective biomolecule detection methods, as well as effective nanopharmaceutical carriers and therapy medications. In particular, inorganic nanoparticles, such as metal nanoparticles, metal–organic framework nanoparticles, or upconversion nanoparticles with relatively inert surfaces can easily bind to DNA through covalent bonds, ligand bonds, electrostatic adsorption, biotin–streptavidin interactions and click chemistry to form DNA–nanoparticle conjugates for a broad range of applications in biosensing and biomedicine due to their exceptional surface modifiability. In this review, we summarize the recent advances in the assembly mechanism of DNA–nanoparticle conjugates and their biological applications. The challenges of designing DNA–nanoparticle conjugates and their further applications are also discussed. Full article

(This article belongs to the Special Issue Bionic Recognition and Biosensors: A Theme Issue in Honor of Professor Hong-Yuan Chen)

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14 pages, 14107 KiB

Open AccessArticle

Heater Topology Influence on the Functional Characteristics of Thin-Film Gas Sensors Made by MEMS-Silicon Technology

by Gennady Gorokh, Igor Taratyn, Uladzimir Fiadosenka, Olga Reutskaya and Andrei Lozovenko

Chemosensors 2023, 11(8), 443; https://doi.org/10.3390/chemosensors11080443 - 9 Aug 2023

Cited by 4 | Viewed by 1298

Abstract

The design of the heater plays a decisive role in the energy consumption, sensitivity, and speed of chemical sensors. The paper analyzes various options for the topology of meander-type platinum heaters in chemical sensors fabricated on thin dielectric membranes using MEMS-silicon technology. Comprehensive [...] Read more.

The design of the heater plays a decisive role in the energy consumption, sensitivity, and speed of chemical sensors. The paper analyzes various options for the topology of meander-type platinum heaters in chemical sensors fabricated on thin dielectric membranes using MEMS-silicon technology. Comprehensive studies of the heater’s current–voltage characteristics have been carried out, heating rates have been measured at various currents, experimental temperature characteristics for various meander topologies have been obtained, heater options have been determined, and optimal heat transfer processes are ensured at a low power consumption of about 20–25 mW. Sensors with an optimal heater topology based on a double dielectric membrane were fabricated according to the described technological process, and sensory responses to 0.5 vol.% CH₄ and 0.2% C₃H₈ were studied. The obtained results showed good results and confirmed the need to choose the optimal heater topology when designing sensors for recording the given type of gas mixtures in a certain temperature range. Full article

(This article belongs to the Special Issue Gas Sensors and Electronic Noses for the Real Condition Sensing)

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18 pages, 10180 KiB

Open AccessArticle

Fabrication of Electrochemical Sensor for the Detection of Mg(II) Ions Using CeO₂ Microcuboids as an Efficient Electrocatalyst

by Girdega Muruganandam, Noel Nesakumar, Arockia Jayalatha Kulandaisamy, John Bosco Balaguru Rayappan and Balu Mahendran Gunasekaran

Chemosensors 2023, 11(8), 442; https://doi.org/10.3390/chemosensors11080442 - 7 Aug 2023

Cited by 1 | Viewed by 1835

Abstract

In human blood serum, the concentration of magnesium ions typically ranges from 0.7 mM to 1.05 mM. However, exceeding the upper limit of 1.05 mM can lead to the condition known as hypermagnesemia. In this regard, a highly sensitive and selective electrochemical sensor [...] Read more.

In human blood serum, the concentration of magnesium ions typically ranges from 0.7 mM to 1.05 mM. However, exceeding the upper limit of 1.05 mM can lead to the condition known as hypermagnesemia. In this regard, a highly sensitive and selective electrochemical sensor for Mg(II) ion detection was successfully fabricated by immobilizing cerium oxide (CeO₂) microcuboids, synthesized via microwave radiation method, onto the surface of glassy carbon electrode (GCE). Cyclic voltammetry studies revealed the exceptional electrocatalytic effect of CeO₂ microcuboid-modified GC electrode, particularly in relation to the irreversible reduction signal of Mg(II). The microcuboid-like structure of CeO₂ microparticles facilitated enhanced adsorption of Mg(II) ion (

Γ = 2.17 \times 10^{- 7}

mol cm⁻²) and electron transfer (

k_{s} = 8.94

s⁻¹) between the adsorbed Mg(II) ions and GCE. A comprehensive analysis comparing the performance characteristics of amperometry, differential pulse voltammetry, cyclic voltammetry, and square wave voltammetry was conducted. The square wave voltammetry-based Mg(II) sensor exhibited remarkable sensitivity of 2.856 μA mM⁻¹, encompassing a broad linear detection range of 0–3 mM. The detection and quantification limits were impressively low, with values of 19.84 and 66.06 μM, respectively. Remarkably, the developed electrode showed a rapid response time of less than 140 s. Multiple linear regression and partial least squares regression models were employed to establish a mathematical relationship between magnesium ion levels and electrochemical parameters. Notably, the proposed sensor exhibited excellent anti-interferent ability, repeatability, stability, and reproducibility, enabling the fabricated electrode to be used effectively for Mg(II) ion sensing in real-world samples. Full article

(This article belongs to the Collection Sustainable Metal Oxide Materials for Sensing Applications)

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18 pages, 3718 KiB

Open AccessArticle

Fabrication and Characterization of Hybrid and Tunable ZnO@Ag Flexible Thin Films Used as SERS Substrates

by Ioana Andreea Brezeștean, Daniel Marconi, Nicoleta Elena Dina, Maria Suciu and Alia Colniță

Chemosensors 2023, 11(8), 441; https://doi.org/10.3390/chemosensors11080441 - 7 Aug 2023

Cited by 4 | Viewed by 1500

Abstract

Flexible substrates have known increased popularity over rigid ones due to their use in surface-enhanced Raman scattering (SERS). They provide irregular surfaces, ideal for in situ sensing. In this context, we report the SERS performance of hybrid ZnO@Ag thin films deposited by magnetron [...] Read more.

Flexible substrates have known increased popularity over rigid ones due to their use in surface-enhanced Raman scattering (SERS). They provide irregular surfaces, ideal for in situ sensing. In this context, we report the SERS performance of hybrid ZnO@Ag thin films deposited by magnetron sputtering (MS) on flexible, thermoplastic substrates. This physical deposition method is acknowledged for obtaining high-quality and reproducible ZnO films that can be embedded in (bio)sensing devices with various applications. Three types of thermoplastic-based, commercially available substrates with different glass transition temperatures (T_g) were chosen for the variation in flexibility, transparency, and thickness. Zeonor^® (T_g = 136 °C, thickness of 188 μm) and two types of Topas (Topas^®: T_g = 142 °C, thickness of 176 μm; Topas2: T_g = 78 °C, thickness of 140 μm) thermoplastic sheets are nonpolar and amorphous cyclo-olefin polymer (COP) and cyclo-olefin copolymers (COC), respectively. Their thicknesses and different values of T_g can greatly affect the topographical and roughness properties of films with small thicknesses and, thus, can greatly influence the enhancement of the Raman signal. The ZnO films deposited on top of Zeonor^® or Topas^® have identical morphological properties, as shown by the scanning electron microscopy (SEM) characterization. Subsequently, by using the MS technique, we tuned the thickness of the deposited silver (Ag) films in the range of 7–30 nm to assess the growth influence on the morphology and the SERS signal amplification of the substrates with and without the ZnO intermediate layer. The SEM analysis showed that the Ag atoms migrated both into the interstitial areas, filling the voids between the ZnO granular structures, and over the latter, forming, in this case, isolated Ag clusters. SERS analysis performed on the ZnO-Ag hybrid films using crystal violet (CV) molecule revealed a limit of detection (LOD) of 10⁻⁷ M in the case of 15 nm thick Ag/Zeonor^® interlayer films ZnO and relative standard deviation (RSD) below 10%. Full article

(This article belongs to the Special Issue Recent Developments in Platforms for SERS Applications)

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20 pages, 5050 KiB

Open AccessReview

Advances in the Application of Nano-Enzymes in the Electrochemical Detection of Reactive Oxygen Species: A Review

by Rongwei Gao and Shujuan Bao

Chemosensors 2023, 11(8), 440; https://doi.org/10.3390/chemosensors11080440 - 7 Aug 2023

Cited by 1 | Viewed by 2018

Abstract

Reactive oxygen species (ROS) play an important role in maintaining human health and are recognized as indicators of oxidative stress linked to various conditions such as neurodegenerative and cardiovascular diseases, as well as cancer. Consequently, detecting ROS levels in biological systems is crucial [...] Read more.

Reactive oxygen species (ROS) play an important role in maintaining human health and are recognized as indicators of oxidative stress linked to various conditions such as neurodegenerative and cardiovascular diseases, as well as cancer. Consequently, detecting ROS levels in biological systems is crucial for biomedical and analytical research. Electrochemical approaches offer promising opportunities for ROS determination due to their exceptional sensitivity, speed, and simplicity of equipment. This review covers studies using advanced electrochemical nanozyme sensors for detecting ROS in biological samples that were published over the last ten years, from 2013 to 2023. Emphasis is placed on the sensor materials and different types of modifiers employed for selective ROS detection. Furthermore, a comprehensive analysis of the sensors’ selectivity was performed. Full article

(This article belongs to the Special Issue Bionic Recognition and Biosensors: A Theme Issue in Honor of Professor Hong-Yuan Chen)

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13 pages, 3172 KiB

Open AccessArticle

WO₃-LaFeO₃ Nanocomposites for Highly Sensitive Detection of Acetone Vapor at Low Operating Temperatures

by Ensi Cao, Yixuan Zhang, Li Sun, Bing Sun, Wentao Hao, Yongjia Zhang and Zhongquan Nie

Chemosensors 2023, 11(8), 439; https://doi.org/10.3390/chemosensors11080439 - 6 Aug 2023

Cited by 2 | Viewed by 1353

Abstract

The development of a rapid, highly sensitive, and dependable acetone sensor holds significant importance for human health and safety. To enhance the acetone sensing performance of LaFeO₃ nanoparticles for practical applications, commercial n-type WO₃ nanoparticles were incorporated as additives. They were [...] Read more.

The development of a rapid, highly sensitive, and dependable acetone sensor holds significant importance for human health and safety. To enhance the acetone sensing performance of LaFeO₃ nanoparticles for practical applications, commercial n-type WO₃ nanoparticles were incorporated as additives. They were directly mixed with LaFeO₃ nanoparticles produced through a sol-gel method, creating a series of WO₃-LFO nanocomposites with varying mass ratios. These nanocomposites were characterized using XRD, SEM, BET, and XPS techniques. Compared to pure LFO nanoparticles, the prepared nanocomposites exhibited larger specific surface areas with enhanced surface reactivity. The introduction of p-n heterojunctions through the mixing process improved the regulation of acetone molecules on internal carrier conduction within nanocomposites. As a result, the nanocomposites demonstrated superior acetone sensing performance in terms of optimal operating temperature, vapor response value, selectivity, and response/recovery speed. Notably, the nanocomposites with a 5wt% addition of WO₃ showed the lowest optimal operating temperature (132 °C), the fastest response/recovery speed (28/9 s), and the highest selectivity against ethanol, methanol, and EG. On the other hand, the nanocomposites with a 10wt% addition of WO₃ displayed the maximum vapor response value (55.1 to 100 ppm) at an optimal operating temperature of 138 °C, along with relatively good repeatability, stability, and selectivity. Full article

(This article belongs to the Special Issue Chemical Sensors for Bio-Medical and Environmental Applications)

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20 pages, 7558 KiB

Open AccessReview

Current Trends in the Use of Semiconducting Materials for Electrochemical Aptasensing

by Leda Bousiakou, Omar Al-Dosary, Anastasios Economou, Veronika Subjakova and Tibor Hianik

Chemosensors 2023, 11(8), 438; https://doi.org/10.3390/chemosensors11080438 - 6 Aug 2023

Cited by 4 | Viewed by 1948

Abstract

Aptamers are synthetic single-stranded oligonucleotides that exhibit selective binding properties to specific targets, thereby providing a powerful basis for the development of selective and sensitive (bio)chemical assays. Electrochemical biosensors utilizing aptamers as biological recognition elements, namely aptasensors, are at the forefront of current [...] Read more.

Aptamers are synthetic single-stranded oligonucleotides that exhibit selective binding properties to specific targets, thereby providing a powerful basis for the development of selective and sensitive (bio)chemical assays. Electrochemical biosensors utilizing aptamers as biological recognition elements, namely aptasensors, are at the forefront of current research. They exploit the combination of the unique properties of aptamers with the advantages of electrochemical detection with the view to fabricate inexpensive and portable analytical platforms for rapid detection in point-of-care (POC) applications or for on-site monitoring. The immobilization of aptamers on suitable substrates is of paramount importance in order to preserve their functionality and optimize the sensors’ sensitivity. This work describes different immobilization strategies for aptamers on the surface of semiconductor-based working electrodes, including metal oxides, conductive polymers, and carbon allotropes. These are presented as platforms with tunable band gaps and various surface morphologies for the preparation of low cost, highly versatile aptasensor devices in analytical chemistry. A survey of the current literature is provided, discussing each analytical method. Future trends are outlined which envisage aptamer-based biosensing using semiconductors. Full article

(This article belongs to the Special Issue State-of-the-Art (Bio)chemical Sensors—Celebrating 10th Anniversary)

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