Chemosensors, Volume 11, Issue 7 (July 2023) – 65 articles

Adenosine 5′-triphosphate (ATP) is the energy currency in cells. It is involved in numerous cellular life activities and exhibits a close association with the development of certain diseases. Thus, the precise detection of ATP within cells holds immense significance in understanding cell biological events and related disease development. Fluorescent probes have obvious advantages in imaging ATP in cells and in vivo due to their high sensitivity, good selectivity, real-time imaging, and good biocompatibility. Thus far, an extensive array of fluorescent probes targeting ATP has been formulated to enable the visualization of ATP within cells and in vivo. This review summarizes the recent advances in ATP fluorescent probes according to different design strategies, mainly including those based on organic small molecules, metal complexes, and water-soluble conjugated polymers. In addition, the practical applications of ATP fluorescent probes in the imaging of target organelles, cell biological events, and disease markers are highlighted. Finally, the challenges and future trends of ATP detection based on fluorescent probes are discussed. Full article

The early detection at low concentration, by non-invasive methods, of cardiac biomarkers in physiological fluids has attracted the interest of researchers over the last decade. This enables early diagnosis and prediction of the first signs of heart failure (HF). In this respect, the analysis of human saliva remains the most suitable medium for this non-invasive approach, as it contains a highly interesting biological matrix for general health and disease monitoring. In this work, we developed a highly sensitive multiplexed immunosensor for direct simultaneous detection of both N-terminal Natriuretic Peptide (NT-proBNP) and Cortisol in human artificial saliva (AS). The developed biosensor platform based on silicon nitride substrate was composed from four gold working microelectrodes (WEs) and an integrated counter and reference microelectrode. Gold WEs were biofunctionalized through carboxyl diazonium (4-APA) to immobilize both anti-NT-proBNP and anti-Cortisol antibodies for simultaneous detection. The electroaddressing of the 4-APA onto the gold WE surfaces was realized with cyclic voltammetry (CV), while the interaction between antibodies and antigens in PBS was monitored using electrochemical impedance spectroscopy (EIS). The antigen detection in human AS was realized with EIS combined with the standard addition method. The immunosensor was highly sensitive and selective toward the corresponding biomarkers in both PBS and artificial human saliva as well as in the presence of other potential interfering biomarkers such as tumor necrosis factor alpha (TNF-α) and interleukin-10 (IL-10). The limit of detection (LOD) was at 0.2 pg/mL for NT-proBNP within the range of 0.03 to 0.9 pg/mL, while the LOD for Cortisol was 0.06 ng/mL within the range of 0.02 to 0.6 ng/mL for Cortisol in artificial saliva. The developed immunosensor is very promising for significant detection in physiological media, and time reducing as it allows the simultaneous detection of various biomarkers. Full article

Tumor cell-derived exosomes are considered a potential source of cancer biomarkers. Here, we developed an electrochemical sensing platform for the rapid and simple detection of exosomes, using the CCRF-CEM exosome as a model. The platform utilizes cyclic nicking enzyme cleavage and a hybridization chain reaction (HCR) for dual-signal amplification. A hairpin aptamer probe (HAP) containing an aptamer was designed for the assay. The specific binding between the aptamer and PTK7, present on the exosome surface, causes a conformational change in the HAP. This facilitates hybridization between the HAP and the linker DNA, which subsequently triggers cyclic cleavage of the nicking endonuclease towards the linker DNA. Therefore, exosome detection is transformed into DNA detection. By combining this approach with HCR signal amplification, we achieved high-sensitivity electrochemical detection of CCRF-CEM exosomes, down to 1.1 × 10⁴ particles/mL. Importantly, this assay effectively detected tumor exosomes in complex biological fluids, demonstrating the potential for clinical diagnosis. Full article

The present study proposes the application of a recently developed optical–chemical sensor system to glyphosate detection. The device probes the refractive index variation in a chip based on a plastic optical fiber (POF) in which three orthogonal micro-holes were created and filled with an acrylic-based molecularly imprinted polymer (MIP). This sensitive chip, connected in series to a gold-coated SPR-POF platform, can modify the surface plasmon resonance (SPR) phenomena by exploiting the multimode characteristic of the POFs. Therefore, the gold film of the SPR-POF platform is not covered by the MIP layer, improving the sensor’s performance because the interaction between the analyte (glyphosate) and the polymer recognition cavities occurs in the core and not in the cladding of the waveguide. Indeed, the sample solution is dropped on the MIP-based chip while a water drop is constantly maintained above the gold surface of the reference SPR-POF platform to excite the surface plasmons, modulated by the MIP interaction with the target analyte. The device is here for the first time applied for glyphosate sensing in water samples. The high sensitivity and selectivity are proven, and tests on real samples highlight the good performances of the developed sensors. Full article

The selective detection of different gas components will remain of huge importance in the future, either in the ambient air or in flue gases, e.g., for controlling purposes of combustion processes. The focus here is on the development of a highly selective ammonia sensor that will be exemplarily used in the flue gas of biomass combustion plants with catalysts for nitrogen oxide reduction. Such applications require a robust sensor design, in this case, based on a ceramic substrate. The gaseous ammonia is detected with the help of a zeolite film, whose selective adsorption properties towards ammonia are already intensively being used in the field of flue gas catalysis. The adsorption and desorption of ammonia on the gas-sensitive zeolite film lead to changes in the dielectric properties of the functional material. Using an interdigital electrode (IDE) structure below the zeolite film, the capacitance was determined as a measure of the ammonia concentration in the gas. In this context, the fabrication of all layers of the sensor in the thick film with subsequent laser patterning of the IDE structure enables a cost-efficient and effective method. The functionality of this sensor principle was extensively tested during measurements in the laboratory. A high and fast response to ammonia was detected at different sensor temperatures. In addition, very low cross-sensitivities to other gas components such as water (very low) and oxygen (zero) were found. Full article

Toxic pollutants in the environment, such as toxins and abused drugs, have posed a major threat to human health and ecosystem security. It is extremely desirable to develop simple, low-cost, sensitive, and reliable techniques for the detection of these pollutants in the environment. As a booming analytical method, photoelectrochemical (PEC) sensors possess low background noise and high sensitivity. The performances of PEC sensors are fundamentally related to the photoelectric conversion efficiency, which mainly depends on the properties of photoactive materials. This review aims to summarize the engineered photoactive materials, i.e., semiconductors and semiconductor-based heterojunctions, as well as their actual applications, with emphasis on sensing mechanisms in PEC sensors for the analysis of toxins and abused drugs in the environment. Finally, the future research perspectives in this field are also discussed. Full article

Recently, Heptafluoroisobutyronitrile (C₄F₇N) has received widespread attention in replacing one of the most greenhouse-insulating gas, SF₆. However, gas leakage is incredibly harmful to the health of operational personnel and the security of industry production, and developing C₄F₇N detection technology is of great necessity. In this work, the adsorption properties, as well as the sensing performance of C₄F₇N on 3d VIII atom-decorated γ-graphyne (γ-GY), were theoretically discussed. The adsorption structures, adsorption energies, electron transfer, adsorption distance, electron distribution, and electronic properties were compared. The results show that the introduction of Fe and Co atom enhance the chemisorption of C₄F₇N, and the adsorption of C₄F₇N brings the maximum electron redistribution of Fe/γ-GY among three TM/γ-GY. Only the adsorption on Fe/γ-GY leads to the vanishing of the magnetic moment and creates a band gap. For three different modifications of γ-GY, the chemical interactions are highly related to the overlapping of transition metal 3d and N 2p orbitals in the density of states. The adsorption on Co/γ-GY causes the maximum change in work function from 5.06 eV to 5.26 eV. In addition, based on the band structure, work function, and desorption properties, the sensing properties of 3d VIII atom-decorated γ-GY were evaluated in order to promote the experimental exploration and development of high-performance C₄F₇N gas sensors. Full article

Hydrogen (H₂) is a renewable energy source that has the potential to reduce greenhouse gas emissions. However, H₂ is also highly flammable and explosive, requiring sensitive and safe sensors for its detection. This work presents the synthesis and characterization of WO₃/graphene binary and WO₃/graphene/Pd (WG-Pd) ternary nanocomposites with varying graphene and Pd contents using the microwave-assisted hydrothermal method. The excellent catalytic efficacy of Pd nanoparticles facilitated the disintegration of hydrogen molecules into hydrogen atoms with heightened activity, consequently improving the gas-sensing properties of the material. Furthermore, the incorporation of graphene, possessing high conductivity, serves to augment the mobility of charge carriers within the ternary materials, thereby expediting the response/recovery rates of gas sensors. Both graphene and Pd nanoparticles, with work functions distinct from WO₃, engender the formation of a heterojunction at the interface of these diverse materials. This enhances the efficacy of electron–hole pair separation and further amplifies the gas-sensing performance of the ternary materials. Consequently, the WG-Pd based sensors exhibited the best gas-sensing performance when compared to anther materials, such as a wide range of hydrogen concentrations (0.05–4 vol.%), a short response time and a good selectivity below 100 °C, even at room temperature. This result indicates that WG-Pd ternary materials are a promising room-temperature hydrogen-sensing materials for H₂ detection. Full article

As a promising sustainable and clean energy source for the future, hydrogen plays an important role. Due to its high flammability and the explosive nature of hydrogen gas, it is crucial to employ reliable sensors that can detect the presence of hydrogen gas in air at room temperature (RT). By utilizing light, the working temperature of such gas sensors can be reduced whilst simultaneously enhancing sensing performance. In this study, sensors have been fabricated that introduces nano-Schottky junctions (Pd–TiO₂) via a facile chemical method and p–n heterojunctions (PdO–TiO₂), through both chemical and hydrothermal methods, with a mean Pd nanoparticle (NP) diameter of 4.98 ± 0.49 nm and 4.29 ± 0.45 nm, respectively. The hydrothermally treated Pd-decorated TiO₂ nanosphere (HPT NS) shows a response of 100.88% toward 500 ppm hydrogen with a faster response and recovery (77 s and 470 s, respectively). Meanwhile, hydrothermally untreated Pd-decorated TiO₂ (PT) NSs show a response of 100.29% with slow response and recovery times (240 s and 3146 s, respectively) at 30 °C under 565 nm visible light and a bias of 500 mV. The experimental results confirm that introducing both metallic Pd and PdO onto the TiO₂ NSs open a novel approach for detecting hydrogen gas through light-induced sensing at room temperature using low voltage bias. Full article

NO₂ is an important environmental pollutant and is harmful to human health even at very low concentrations. In this paper, we propose a novel chipless RFID sensor able to work at room temperature and to detect sub-ppm concentration of NO₂ in the environment. The sensor is made of a metallic resonator covered with NO₂-sensitive tin oxide and works by monitoring both the frequency and the intensity of the output signal. The experimental measurements show a fast response (a few minutes) but a very slow recovery. The sensor could therefore be used for non-continuous threshold monitoring. However, we also demonstrated that the recovery can be strongly accelerated upon exposure to a UV source. This opens the way to the reuse of the sensor, which can be easily regenerated after prolonged exposure and recycled several times. Full article

A potentiometric electronic tongue (ET) for the analysis of well and ditch irrigation water samples is herein proposed. The sensors’ array is composed of six ion-selective electrodes based on plasticized polymeric membranes with low selectivity profiles, i.e., the membranes do not contain any selective receptor. The sensors differ between them in the type of ion-exchanger (sensors for cations or anions) and the plasticizer used in the membrane composition, while the polymeric matrix and the preparation protocol were maintained. The potentiometric response of each sensor towards the main cations (Na⁺, K⁺, Ca²⁺, Mg²⁺) and anions (HCO₃⁻, Cl⁻, SO₄²⁻, NO₃⁻) expected in irrigation water samples was characterized, revealing a fast response time (<50 s). A total of 19 samples were analyzed with the sensor array at optimized experimental conditions, but, also, a series of complementary analytical techniques were applied to obtain the exact ion composition and conductivity to develop a trustable ET. The principal component analysis of the final potential values of the dynamic response observed with each sensor in the array allows for the differentiation between most of the samples in terms of quality. Furthermore, the ET was treated with a linear multivariate regression method for the quantitative determination of the mentioned ions in the irrigation water samples, revealing rather good prediction of Mg²⁺, Na⁺, and Cl⁻ concentrations and acceptable results for the rest of ions. Overall, the ET is a promising analytical tool for irrigation water quality, exceeding traditional characterization approaches (conductivity, salinity, pH, cations, anions, etc.) in terms of overhead costs, versatility, simplicity, and total time for data provision. Full article

Tin monoselenide (SnSe), which belongs to group IV–VI monochalcogenides, has obtained significant attention in the field of photodetection owing to its ultrahigh carrier mobilities. However, the great challenges of preparing high-quality films and high-performance devices still need to be conquered. Herein, high-density continuous SnSe films were deposited on a Si substrate using magnetron sputtering technology, and a self-driven photovoltaic-type broadband photodetector from the visible light range (VIS) to the near-infrared (NIR) range based on SnSe/Si heterojunction was constructed. Owing to its high carrier mobility, narrow band gap structure, and strong internal electric field, the SnSe/Si heterojunction device exhibits an ultrafast response and high responsivity (R), which achieves a wide spectral response of 405–980 nm. Under zero bias voltage, the greatest R and detectivity (D*) of the heterojunction were 704.6 mA/W and 3.36 × ${10}^{11}$ Jones at 405 nm. Furthermore, the device had a fast response time (rise time) of 20.4 μs at 980 nm of illumination. This work provides a new strategy for the fabrication of high-performance, low-cost, and self-driven photodetectors. Full article

Quantum dots nanomaterials have attracted extensive interest for fluorescence chemical sensors due their attributes, such as excellent optical characteristics, quantum size effects, interface effects, etc. Moreover, the fluorescence properties of quantum dots can be adjusted by changing their structure, size, morphology, composition, doping, and surface modification. In recent years, quantum dots nanomaterials have been considered the preferred sensing materials for the detection of heavy metal ions and pesticide residues by the interactions between quantum dots and various analytes, showing excellent sensitivity, selectivity, and interference, as well as reducing the cost of equipment compared with traditional measurement methods. In this review, the applications and sensing mechanisms of semiconductor quantum dots and carbon-based quantum dots are comprehensively discussed. The application of semiconductor quantum dots, carbon quantum dots, graphene quantum dots, and their nanocomposites that are utilized as fluorescence sensors are discussed in detailed, and the properties of various quantum dots for heavy metal ion and pesticide residue determination are also presented. The recent advances in and application perspectives regarding quantum dots and their composites are also summarized. Full article

A simple and low-cost cathodic photoelectrochemical (PEC) sensor based on Bi₂WO₆@g-C₃N₄ was designed for dopamine (DA) detection. The Bi₂WO₆ nanoflower was first prepared using a simple hydrothermal method followed by the combination with g-C₃N₄ nanosheet to form the Bi₂WO₆@g-C₃N₄ heterostructure. The heterostructure can extend the absorbance to the visible region and accelerate the transfer of charge carriers. Furthermore, DA easily coordinates with exposed Bi³⁺ on the Bi₂WO₆ surface and forms the charge-transfer complex to further enhance the cathodic photocurrent. Under optimal conditions, there are two linear relationships between the concentration of DA and photocurrent intensity. The linear ranges are 0.1–10 µM and 10–250 µM, with a sensitive detection limit (LOD) of 28 nM. Notably, the real sample of human blood serum analysis further revealed the accuracy and feasibility of the Bi₂WO₆@g-C₃N₄-based PEC platform. Convincingly, the heterostructure of Bi₂WO₆ and g-C₃N₄ opened up a new avenue for the construction of DA analysis. Full article

Nowadays, innovation in food technologies is fundamental and consumers are increasingly aware and demanding. To create a final product that is more and more appealing, health and safety guidelines are pushing towards new challenges. It is precisely due to the high quality required by the producers that the aim discussed in this project has been conceived. Until today, the controls on the entire production line have been slowed down by the limitations of the technologies involved, including the high cost of instrumentation for microbiological analysis, the need for qualified personnel to carry them out, the long execution times and the invasiveness of the techniques themselves. This project has, therefore, proposed a user-friendly solution that is minimally invasive, fast and at a lower cost. This system makes use of classical microbiological analysis and, in parallel, use of an innovative electronic-nose small sensor system (S3+), which can be trained to recognize the volatile fingerprint of a specific product and customized for a specific use. The aim of this project was to develop a system that is able to detect the mold contamination on fruit and vegetable jams and marmalades, using a new kind of innovative metal semiconductor gas sensor (MOS) device. The application of this technology has, therefore, made it possible to classify various samples of uncontaminated and contaminated fruit and vegetable preparations. Thanks to the classification implemented by a data-driven algorithm, it has been possible to build an anomaly detector that is able to recognize the occurrence of possible contamination, thus acting as an early alert system in the food chain. All this will occur in less than 1 min once the system is trained, in contrast with classical microbiological or chemical techniques that normally require longer timeframes to obtain a result and involve the use of reagents, increasing the costs. Full article

Identifying the main byproducts of SF₆ decomposition proves to be an effective strategy for determining the nature and severity of internal discharge faults in gas-insulated switchgears (GISs). In this research, it was suggested to utilize the coordination polymer Zr-MOF-808 as a sensor for the main byproducts of SF₆ decomposition. This study examined the adsorption of SF₆ and its main decomposition products (CF₄, CS₂, SO₂, SO₂F₂, and SOF₂) on Zr-MOF-808, utilizing Gaussian16 simulation software through a method anchored on quantum chemistry. Adsorption parameters were calculated and analyzed, including binding energy, charge transfer, adsorption distance, along with variations in bond length, bond angle, density of states, and frontier orbital of gas molecules. Our research indicated that the Zr-MOF-808 cluster demonstrated varying degrees of chemical adsorption for the six gases, leading to differential conductivity changes in each system following adsorption. Consequently, the detection of resistance value alterations in the materials would allow for the identification of the gas products. Full article

Cylindrospermopsin (CYN) is a freshwater algal toxin produced during the proliferation of harmful cyanobacteria, known as cyanobacterial algal blooms (cyano-HABs). Recently, the effects of global warming have facilitated the growth of cyano-HABs, leading to their worldwide occurrence and an increase in toxin-related damage to aquatic ecosystems. CYN is known to exhibit strong cell toxicity upon ingestion, inhibiting protein synthesis and glutathione production and, ultimately, leading to cell death. In addition to cell toxicity, CYN exhibits skin toxicity, genotoxicity, and hepatotoxicity. It can also affect other organs, such as the kidneys (causing tubular necrosis), thymus (causing atrophy), and heart (causing pericardial and myocardial hemorrhage). The standard method used for CYN detection to date, enzyme-linked immunosorbent assay (ELISA), has several drawbacks: it is complex, time-consuming, and requires trained researchers. Recently, biosensors have been shown to offer numerous advantages, such as their simplicity, portability, and rapidity, making them suitable for onsite applications. Consequently, recent studies have actively explored the latest biosensor-based technologies for CYN detection. This review discusses the recent advances in CYN detection platforms that utilize several types of biosensors. Full article

A new method for the determination of the antiplatelet drug dipyridamole (DIP) in pharmaceuticals using a molecularly imprinted polymer (MIP)-modified pencil graphite electrode (PGE) is proposed. The modified electrode was prepared simply and rapidly by electropolymerization of caffeic acid (CA) in the presence of DIP and subsequent DIP extraction with ethanol, resulting in a cost-effective, eco-friendly disposable modified electrode (MIP_PGE). Several working conditions (monomer and template concentration, number of voltametric cycles, scan rate extraction time, and solvent) for the MIP_PGE preparation were optimized. The differential pulse voltammetric (DPV) oxidation signal of DIP obtained at MIP_PGE was 28% higher than that recorded at bare PGE. Cyclic voltammetry emphasized DIP irreversible, pH-dependent, diffusion-controlled oxidation at MIP_PGE. Differential pulse and adsorptive stripping voltammetry at MIP_PGE in phosphate buffer solution pH = 7.00 were applied for the drug quantitative determination in the range of 1.00 × 10⁻⁷–1.00 × 10⁻⁵ and 1.00 × 10⁻⁸–5.00 × 10⁻⁷ mol/L DIP, respectively. The obtained limits of detection were at the tens nanomolar level. Full article

DNA identification is possible by detecting its components through vibrational spectroscopy. Conventional Raman, Surface-enhanced Raman spectroscopy (SERS) and Tip-enhanced Raman spectroscopy (TERS) have shown a high capacity for the exploration of different molecules and materials (semi-conducting material, carbon nanotubes and biologicals molecules as DNA, proteins). Their applications extended to biological systems and brought significant information to this field. This review summarizes a high number of studies and research conducted with conventional Raman, SERS and TERS on every DNA component starting from the four different nucleic acids in their different forms (nucleosides, deoxyribonucleosides, deoxyribonucleotides) to their biological interaction to form one and double DNA strands. As SERS has an advantage on conventional Raman by exploiting the optical properties of metallic nanostructures to detect very small quantities of molecules, it also clarifies the DNA structure’s orientation in addition to its composition. It also clarifies the influence of different parameters, such as the presence of a spacer or a mutation in the strand on the hybridization process. TERS was shown as a relevant tool to scan DNA chemically and to provide information on its sequence. Full article

The threat of glyphosate to food safety has attracted widespread attention. Consequently, it is highly urgent to develop a sensitive and accurate method for glyphosate detection. Herein, a turn-on fluorescent method for glyphosate detection using polydopamine-polyethyleneimine (PDA-PEI) copolymer as a fluorescent probe and p-nitrophenylphosphate (PNPP)/alkaline phosphatase (ALP) as a fluorescence quenching system is developed. The PDA-PEI copolymer was prepared by a one-pot method under mild condition, and its fluorescence kept almost unchanged after storing in a refrigerator for one month. ALP catalyzed the hydrolysis of PNPP to p-nitrophenol (PNP) that caused the fluorescence quenching of PDA-PEI copolymer via the inner filter effect. However, glyphosate inhibited ALP activity, thereby preventing the formation of PNP and restoring the fluorescence signal. Under the optimized conditions, the fluorescence of PDA-PEI copolymer depended on glyphosate concentrations ranging from 0.2 to 10 μg/mL with a detection limit of 0.06 μg/mL. Moreover, this assay was applied to detect glyphosate in real samples using the standard addition method. The recoveries were in the range from 88.8% to 107.0% with RSD less than 7.78%. This study provides a novel insight for glyphosate detection and expands the applications of fluorescent copolymer. Full article

Traditional chemotherapeutic drugs have limitations due to their non-targeted ability toward cancer cells. Stimuli-activatable prodrugs are designed to overcome these obstacles. However, the real-time monitoring of stimuli-activatable theranostic prodrugs still poses challenges. Herein, a prodrug (Fe–SS–HCy), consisting of a ferrocene-modified hemicyanine linked via a disulfide bond, is synthesized for anticancer imaging and therapy. Before activation, the toxicity of Fe–SS–HCy is low. The fluorescence of Fe–SS–HCy is quenched by ferrocene due to photoinduced electron transfer. After being taken up by cancer cells, the intracellular GSH activates Fe–SS–HCy, which releases HCy. The fluorescence of HCy is restored and selectively accumulates in the mitochondria, which further produce reactive oxygen species (ROS) to induce cancer cell death. Thus, this “off-on” fluorogenic HCy presents a new strategy for monitoring prodrug activation in real-time and for enhancing therapeutic efficacy with reduced side effects. Full article

The quality of myrrh decoction pieces can be influenced by factors such as origin, source, and processing methods. The quality of myrrh in the market varies greatly, and adulteration is a serious issue, highlighting the urgent need for improved quality control measures. This study explores the integration of GC–MS analysis and sensor selection in electronic nose technology for the improved classification of myrrh decoction pieces. GC–MS analysis revealed the presence of 130 volatile compounds in the six myrrh samples, primarily composed of alkene compounds, and each sample exhibited variations in composition. An electronic nose system was designed using a sensor array consisting of six sensors selected from twelve sensors capable of detecting volatile compounds consistent with myrrh composition, including WO₃ quantum dots, Fe₂O₃ hollow nanorods, ZnFe₂O₄ nanorods, SnO₂ nanowires, and two commercially available sensors. The sensors exhibited distinct response patterns to the myrrh samples, indicating their suitability for myrrh analysis. Various sensor parameters, including response, response and recovery time, integral area, and slope, were computed to characterize the sensors’ performance. These parameters provided valuable insight into the sensor–gas interactions and the unique chemical profiles of the myrrh samples. The LDA model demonstrated high accuracy in differentiating between the myrrh types, utilizing the discriminative features captured by the sensor array, with a classification accuracy of 90% on the testing set. This research provides a comprehensive evaluation method for the quality control of myrrh pieces and a scientific basis for the development and utilization of myrrh. Full article

The cobalt metal–organic framework (Co-MOF) is a kind of crystalline porous material within a periodic network structure, which is formed via the self-assembly of a Co metal center and a bridged organic ligand. In this paper, a Co-MOF was facilely synthesized via an ultrasonic method and applied to enhance the chemiluminescence (CL) emission of the NaIO₄-H₂O₂ system. The synthesized Co-MOF was nanosheet-like in nature and stacked in 2–3-micrometer flower shapes. Compared to the NaIO₄-H₂O₂ system without a Co-MOF, the CL intensity of the Co-MOF-NaIO₄-H₂O₂ system was enhanced about 70 times. This CL mechanism was determined to be a result of the synergistic effects of chemiluminescence resonance energy transfer (CRET) and electron–hole annihilation (EHA). The Co-MOF not only acted as a catalyst to accelerate the generation of reactive oxygen species in the CL reaction, but also worked as an emitter to further enhance the CL. Based on the Co-MOF-NaIO₄-H₂O₂ system, a highly sensitive CL analysis method was established for pyrogallol (PG) detection. Addition of PG into the CL system generated ¹O₂*, which could transfer energy to the Co-MOF and further enhance the CL response. The enhanced CL was linear with the PG concentration. The CL analysis method exhibited a linear range of 1 × 10⁻⁴ M to 1 × 10⁻⁷ M, as well as having a linear correlation coefficient of 0.9995 and a limit of detection of (S/N = 3) of 34 nM. Full article

Biochar, a biologically originated carbon-rich material derived from the oxygen-limited pyrolysis of biomass, is usually added to the soil for its enrichment, increasing its water-holding capacity and pH. This revolutionary material thus contributes to a reduction in the overall environmental impact and mitigation of climate change. Due to the beneficial properties of this material, especially for electrochemical applications (large active surface area, conductivity, etc.), biochar demonstrates an extremely high capacity for the adsorption and detection of micropollutants simultaneously. However, finding the optimal conditions for the adsorptive and electrochemical properties of prepared biochar-based sensors is crucial. The adsorption efficiency should be sufficient to remove pollutants, even from complex matrices; on the other hand, the electrochemical properties, such as conductivity and charge transfer resistance, are key factors concerning the sensing ability. Therefore, the balanced design of biochar can ensure both the usability and the effectiveness of sensing. To enhance levels of electroactivity that are already high, the pre- or post-modification of biochar can be performed. Such recycled carbon-based materials could be promising candidates among other electrochemical sensing platforms. In this study, different biochar modifications are presented. Utilizing important biochar properties, it should be possible to create a bifunctional platform for removing micropollutants from water systems and simultaneously confirming purification levels via their detection. We reviewed the use of biochar-based materials for the effective removal of micropollutants and the methods for their detection in water matrices. Full article

The use of plasticizers to improve the quality of plastics widely used for household purposes inevitably leads to an increase in their pollution of food and environmental objects. Diisobutyl phthalate (DiBP) is one of the ortho-substituted phthalic acid esters that negatively affect human health and ecosystems. This work is directed to the development of a chemiluminescent enzyme immunoassay (CL-ELISA) for the determination of diisobutyl phthalate in water and food. Luminol, which is oxidized with hydrogen peroxide in the presence of p-iodophenol as an enhancer, was chosen as the substrate for horseradish peroxidase used as a label in the analysis. For this development, rabbit anti-DiBP polyclonal antibodies were generated and tested with the synthesized hapten–protein conjugate. The developed chemiluminescent ELISA has a detection limit of 1.8 ng/mL; the operating range was 5.0–170.8 ng/mL at a content of 10% methanol in the assay medium. The assay was successfully applied to detect diisobutyl phthalate in lettuce leaves, seafood, and water. When using extraction with methanol and hexane, the recovery of DiBP in samples varies in the range of 76.9–134.2%; for assays in natural waters, the recovery rates are from 79.5 to 113.4%. Full article

Artificial nanozymes that are based on ferric oxides have drawn enormous attention due to their high stability, high efficiency, and low cost as compared with natural enzymes. Due to the unique optical plasmonic properties, gold nanoparticles (Au NPs) have been widely utilized in the fields of colorimetric, Raman, and fluorescence sensing. In this work, a photo-responsive Au@Fe₃O₄ nanozyme is prepared with outstanding peroxidase-like activity. The hot electrons of Au NPs that are excited by a surface plasmon resonance (SPR) effect of NPs improve the catalytic activity of Au@Fe₃O₄ in oxidizing 3,3′,5,5′-tetramethylbenzidine (TMB) and the detection of hydroquinone (HQ). The magnetic separation and reusability of the nanozyme further lower its costs. The detection linear range of the sensor is 0–30 μM and the lowest detection limit is 0.29 μM. Especially in the detection of real water samples, a good recovery rate is obtained, which provides promising references for the development of the HQ detection technology in seawater. Full article

Diabetes mellitus has increasingly become a threat to health all over the world. This review focuses on the promoting effect of biosensing technology on the diagnosis and treatment of diabetes mellitus. Types of diabetes and their corresponding pathogeneses are first introduced, followed by the diabetes prevalence and research progress at home and abroad. To emphasize the importance of diabetes diagnosis and treatment, we secondly summarize the breakthrough technology in this field based on biosensing technology at the present stage. In terms of diagnosis, diversified ways of blood glucose detection and multiple combinations of diabetes biomarkers are discussed, while a variety of insulin administration routes and non-drug treatment means are presented in the aspect of treatment. In conclusion, the prospect of the future development of diabetes diagnosis and treatment is put forward at the end of the review. Full article

4-nitrophenol (4-NP) is one of the organic pollutants that can come up from pesticides, explosives, dyes, and pharmaceutical industries. Since it can be extremely harmful to humans and other living organisms, it is crucial to have a system that can effectively detect the presence of 4-NP. Here, we report the microplasma synthesis of nitrogen-doped graphene quantum dots (N-GQDs) for fluorescence-based detection of 4-NP. Through Förster resonance energy transfer (FRET) between donor N-GQDs to the acceptor 4-NP, synthesized N-GQDs can be employed for the detection of 4-NP starting from 0.5 to 100 µM with a limit of detection as low as 95.14 nM. 4-NP detection also demonstrates remarkable stability over all pH values and wide temperatures (10–60 °C), indicating the high possibility for robust organic pollution monitoring. Our work provides insight into a simple, fast, and environmentally friendly method for synthesizing N-GQDs at ambient conditions usable for environmental nanosensors. Full article

There is a growing need for portable, highly sensitive measuring equipment to analyze samples in situ and in real time. For these reasons, it is becoming increasingly important to research new experimental equipment to carry out this work with advanced, robust and low-cost devices. In this framework, a flexible, portable and low-cost fluorimeter (under EUR 500), based on a C12880 MA MEMS micro-spectrometer with an Arduino compatible breakout board, has been developed for the trace analysis of biological substances. The proposed system can employ two selectable excitation sources for flexibility, one in the visible region at 405 nm (incorporated in the board) and an external LED at 365 nm in the UV region. This additional excitation source can be easily interchanged, varying the LED type for investigating any fluorophore compound of interest. The measurement process is micro-controlled, which allows the precise control of the spectrometer sensitivity by adjusting the integration time of each experiment separately. Data acquisition is easy, reliable and interfaced with a spreadsheet for fast spectra visualization and calculations. For testing the performance of the new device in fluorescence measurements, different fluorophore molecules which can be commonly found in biological samples, such as Fluorescein, Riboflavin, Quinine, Rhodamine b and Ru (II)-bipyridyl, have been employed. A high sensitivity and low quantitation limits (in the ppb range) have been found in all cases for the investigated chemicals. The portable device is also suitable for the study of other interesting phenomena, such as fluorescence quenching induced by chemical agents (such as halide anions or even auto-quenching). In this sense, an application for the quantification of chloride anions in aqueous solutions has been performed obtaining a LOD value of 18 ppm. The obtained results for all chemicals investigated with the proposed fluorimeter are always very similar in quantification figures, or even better than the data reported in literature, when using commercial laboratory equipment. Full article

Neurotransmitters (NTs) play a crucial role in regulating the behavioral and physiological functions of the nervous system. Imbalances in the concentrations of NT have been directly linked to various neurological diseases (e.g., Parkinson’s, Huntington’s, and Alzheimer’s disease), in addition to multiple psychotic disorders such as schizophrenia, depression, dementia, and other neurodegenerative disorders. Hence, the rapid and real-time monitoring of the NTs is of utmost importance in comprehending neurological functions and identifying disorders. Among different sensing techniques, electrochemical biosensors have garnered significant interest due to their ability to deliver fast results, compatibility for miniaturization and portability, high sensitivity, and good controllability. Furthermore, the utilization of enzymes as recognition elements in biosensing design has garnered renewed attention due to their unique advantages of catalytic biorecognition coupled with simultaneous signal amplification. This review paper primarily focuses on covering the recent advances in enzymatic electrochemical biosensors for the detection of NTs, encompassing the importance of electrochemical sensors, electrode materials, and electroanalytical techniques. Moreover, we shed light on the applications of enzyme-based biosensors for NTs detection in complex matrices and in vivo monitoring. Despite the numerous advantages of enzymatic biosensors, there are still challenges that need to be addressed, which are thoroughly discussed in this paper. Finally, this review also presents an outlook on future perspectives and opportunities for the development of enzyme-based electrochemical biosensors for NTs detection. Full article