Chemosensors, Volume 11, Issue 10 (October 2023) – 38 articles

This study aims to introduce a fluorescence-based chemosensing method for Zn²⁺ in aqueous suspensions and untreated surface waters, conditions which generally hinder the application of conventional optochemical sensing platforms. A macrocyclic fluoroionophore was covalently bonded to a silica-coated magnetic nanoparticle and applied according to a predetermined protocol for analyzing trace amounts of Zn²⁺ under rarely investigated conditions. Utilizing the reversible complexation of the immobilized fluoroionophore, rapid regeneration was carried out via simple acidification after the magnetic-assisted solid-phase extraction of the particles. Forming inclusion complexes with Zn²⁺ with the receptor units of the particles leads to a significant enhancement in fluorescence intensity at 370 nm, above the detection limit of 5 ppb, with a dynamic linear range of quantification of 15–3000 ppb in a pH range of 5.5–7.5. Practical applicability was confirmed by analyzing untreated river water and an aqueous suspension of pumpkin seed flour as real and relevant heterogeneous multicomponent samples of predetermined sample composition and natural Zn²⁺ content. Our practical approach aims to broaden the applicability range of optochemical sensing platforms for Zn²⁺. Full article

Analytical chemistry applied to medical and diagnostic analysis has recently focused on the development of cost-effective biosensors able to monitor the health status or to assess the level of specific biomarkers that can be indicative of several diseases. The improvement of technologies relating to the possibility of the non-invasive sampling of biological fluids, as well as sensors for the detection of analytical signals and the computational capabilities of the systems routinely employed in everyday life (e.g., smartphones, computers, etc.), makes the complete integration of self-standing analytical devices more accessible. This review aims to discuss the biosensors that have been proposed in the last five years focusing on two principal detecting approaches, optical and electrochemical, which have been employed for quantifying different kinds of target analytes reaching detection limits below the clinical sample levels required. These detection principles applied to point-of-care (POC) devices have been extensively reported in literature, and even the limited examples found on the market are based on these strategies. This work will show the latest innovations considering the integration of optical and electrochemical detection with the most commonly reported analytical platforms for POC applications such as paper-based or wearable and implantable devices. Full article

To investigate the effects of the application of bentonite, tannins, and their combination in alcoholic fermentation, Malvazija istarska (Vitis vinifera L.) white grape must was treated with 95 g/L of bentonite, 25 g/L of a hydrolysable tannin preparation, while the third treatment received the aforementioned doses of both agents. Control grape must was fermented without bentonite and exogenous tannins. All of the produced wines were additionally fined after fermentation with doses of bentonite needed to achieve complete protein stability. Wines were analyzed both after fermentation and after additional bentonite fining. Standard physicochemical parameters were determined by the OIV methods, and phenols were analyzed by high-performance liquid chromatography with diode-array detection (HPLC-DAD), while the concentrations of free and bound volatile aroma compounds were obtained after solid-phase extraction (SPE) followed by gas chromatography–mass spectrometry (GC-MS). Bentonite and tannins in fermentation generally reduced the total dose of bentonite needed for complete stabilization. Treatments with bentonite slightly decreased the concentration of total dry extract, while tannins preserved total acidity. The negative effect of bentonite on flavonoids was more severe. Tannins in fermentation preserved more hydroxycinnamoyltartaric acids with respect to control wine, and this effect was additionally enhanced by bentonite. Volatile and bound aroma composition was affected by all the treatments, while the addition of tannins resulted in higher concentrations of several important odoriferous esters, such as ethyl hexanoate, ethyl decanoate, and hexyl acetate. Additional fining with bentonite to complete protein stabilization annulled some of the positive effects observed after fermentation. Full article

The extensive use of antibiotics has rapidly spread antibiotic resistance, which poses significant health risks to humans. Unfortunately, despite this pressing issue, there is still a lack of a reliable on-site detection method for the residues of antibiotics, such as nilutamide (Nlu). Consequently, there is an urgent need to develop and perfect such a detection method to effectively monitor and control antibiotic residues. In this study, the hydrothermal development of copper-metal-organic framework (Cu-MOF) polyhedrons on the functionalized carbon nanofiber (f-CNF) matrix allowed for the detection of Nlu in biological liquids via a sensitive amperometry technique. Further electrochemical detection of Nlu took place with the cyclic voltammetry (CV) technique Cu-MOF/f-CNF. Analytical and spectroscopic approaches were used to confirm the successful synthesis of Cu-MOF/f-CNF. The prepared material was decorated on the surface of GCE and performed as an electrochemical Nlu sensor, with a broad linear range of 0.01 to 141.4 μM and 2 nM as a lower limit of detection. In addition, the composites had a large surface area and many dedicated sites, which improved electrocatalysis. In practical applications, Cu-MOF/f-CNF/GCE provides a novel strategy for improving electrochemical activity by measuring Nlu concentrations in biological samples. Full article

Volatile organic compounds (VOCs) from wood and wood composites are important contributors to odor profiles of indoor environments and can significantly influence human health and well-being. GC-MS/FID and gas chromatography (GC) with olfactometric detection (GC-O) are employed for the identification and characterization of odorants. Four different sample preparation methods are evaluated on wood strands and isocyanate adhesive–based oriented strand boards (OSBs) made from Pinus sylvestris L.: among these, dynamic headspace extraction thermal desorption ((dynamic) HS-TD), head space solid phase microextraction (HS-SPME), head space solid phase microextraction Arrow (HS-SPME Arrow), and liquid injection of a CH₂Cl₂ solvent extract. The olfactometric investigation revealed over 30 odor-active substances of cyclic and acyclic monoterpene, monoterpenoid ketone, monoterpenoid aldehyde, monoterpenoid alcohol, monoterpenoid ester, aliphatic aldehyde, alcohol, and acid and phenolic chemistry. Compared to liquid injection, (dynamic) HS-TD was found to result in a similar number of odorants (20 vs. 24), whereas HS SPME Arrow shows good performance with minimal instrumental effort, notably for monoterpene and aldehyde compounds. Native wood vs. OSB showed high concentrations of saturated and unsaturated aldehydes for the wood board sample. These findings demonstrate the capability of headspace methods for odorant detection and their suitability for standardization towards a database for wood and wood composites. Full article

Chronic Obstructive Pulmonary Disease (COPD) is a chronic respiratory condition that often goes undiagnosed despite the availability of spirometry for diagnosis, and its exact prevalence remains uncertain. Exhaled breath has been proposed as a source of relevant health information, particularly Volatile Organic Compounds (VOCs), which can be easily obtained and applied in clinical practice. In this study, exhaled breath samples were collected from patients diagnosed with COPD of varying severity during their stable condition using specialized RTubeVOC tubes. Volatile compounds from the air samples were extracted using a 50/30 µm divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber and the analysis was performed using gas chromatography/mass spectrometry (GC/MS) technique. The patients were divided into two groups based on their history of exacerbations, and the aim was to identify VOCs associated with the risk of future COPD exacerbation, thus allowing for more personalized and objective COPD treatment. Blood eosinophil content was also taken into consideration. A panel of distinguishing mass-spectral features was identified between the two patient groups. The discriminating exhaled molecules were heptane 2,2,4,6,6-pentamethyl, gamma-terpinene, 2-ethylhexanol, and undecane demonstrating the potential of analyzing VOCs in exhaled breath for the detection and management of COPD, offering a promising avenue to improve COPD management and treatment approaches. Full article

Gas sensing holds great significance in environment monitoring, real–time security alerts and clinical diagnosis, which require sensing technology to distinguish various target molecules with extreme sensitivity and selectivity. Surface–enhanced Raman spectroscopy (SERS) has great potential in gas sensing for its single molecule sensitivity and fingerprint specificity. However, different from molecule sensing in solutions, SERS detection of gas often suffers from low sensitivity as gas molecules usually display a low Raman cross–section and poor affinity on traditional noble metal nanoparticle (NMNP)–based substrates. Therefore, much effort has been made to solve these problems. Fortunately, the appearance of metal–organic frameworks (MOFs) has shed new light on this direction. Due to the unique functional characteristics of MOFs, such as controllable pore size/shape, structural diversity and large specific surface area, SERS substrates based on MOFs can achieve high sensitivity, excellent selectivity and good stability. Although several reviews on MOF–based SERS substrates have been reported, few focus on gas sensing, which is a great challenge. Here, we mainly review the latest research progress on SERS substrates based on different MOFs. Sensitive and active SERS substrates can be prepared according to the unique advantages of MOFs with different metal centers. Then, we focus on composite SERS substrates based on different MOFs and NMNPs and summarize the application of composite SERS substrates in gas sensing. Finally, the future difficulties and potential possibilities of SERS substrates based on MOFs and NMNPs for gas sensing are discussed. Full article

Many fluorophores display interesting features that make them useful biological labels and chemosensors, in particular in Cell Biology. Changes in the absorption-emission spectra (ortho- and metachromasia) are accounted among them. Acridine orange (AO) is one such fluorochromes that shows a prototypical orthochromatic vs. metachromatic behavior depending on its concentration and binding mode to different cellular substrates. Here, we revisit the differential AO fluorescence that occurs in selected biological examples, which allows for the identification of single-stranded or double-stranded nucleic acids. Although known for long, the ultimate reason for this phenomenon has not been properly advanced. We provide a potential molecular mechanism that adequately accounts for the different aspects of the phenomenon. This theoretical mechanism implies a difference in the degree of overlap of excited state orbitals whenever AO molecules are interacting with a single-stranded or a double-stranded nucleic acid. In the first case, massive π-electron overlapping between bases and intercalated AO leads to a metachromatic red emission. On the contrary, no excited-state orbital overlapping in AO-intercalated DNA duplexes is possible due to excessive separation between AO molecules and compliancy to the nearest neighbor exclusion principle, which manifests as orthochromatic green fluorescence. Full article

To understand the formation process of ordered Au nano-ring arrays (NRA), a series of factors—including etchant gas and flow rate, chamber pressure and RF power—were systematically studied and a set of optimum parameters were deduced to fabricate this interesting structure. With plenty of active sites previously reported, a new role of ordered Au NRA is unlocked in this work. The ordered Au NRA could perform the electrochemical removal of rhodamine 6G (R-6G) at a high concentration in seawater within 12 min and complete discoloration within 9 min, which demonstrates ~7 times efficiency improvement from previous studies. The nanostructured surface also makes the ordered Au NRA a good substrate material in R-6G sensing using surface-enhanced Raman spectroscopy, which performs with better accuracy than the ultraviolet–visible light technique. Full article

Electrochemiluminescence (ECL) is an electrochemically induced light produced by the excitation of luminophores in redox reactions. For the past twenty years, ECL analysis has been continuously developed and applied for the sensitive detection of biomolecules at the single-cell level due to its low background interference and the resultant high sensitivity. In recent times, ECL-based microscopy has combined the elements of imaging and has thus emerged as a fast-developed imaging tool to visualize biomolecules in single cells. The surface-confined features of ECL imaging provide detailed information about cell membranes that is not easily obtained using classical fluorescence microscopy. In this review, we summarize the recent works on the detection and imaging of biomolecules at the single-cell level using ECL and discuss the development prospects and challenges in the biological application of this technology in the field of cell analysis. Full article

The necessity for complex functionality materials is increasing due to the emergence of high-tech technologies and the deepening needs of B-to-B companies in the industry. Study on advanced multifunctional materials is also increasing due to interest in fields such as the the Internet of Things (IOT), Fourth Industrial Revolution, and artificial intelligence (AI). Nanomaterials have the advantage of having a large surface area, making it easier to express more efficient properties, and they have been widely applied recently in various fields. When designing new materials for specific applications, it is often important to control the shape, size distribution, surface properties, dispersion, and agglomeration stability of synthetic nanoparticles, as well as the elemental and nanocrystalline compositions of the materials. Nanomaterials have infinite potential, but there are not many cases of collection and structural classification. Therefore, I attempted to conduct an in-depth systematic review by categorizing nanomaterials into nanoparticles, nanoplates, nanowires, and nanorolls according to their nanostructures. Additionally, the representative materials of nanowires include CuNW (copper nanowire), AgNW (silver nanowire), and GaAsP single nanowire. Moreover, nanoroll-type materials include SWCNTs (single-walled carbon nanotubes), DWCNTs (double-walled carbon nanotubes), and MWCNTs (multi-walled carbon nanotubes). In conclusion, this study, through a systematic review, is intended to provide a cornerstone for application plans when designing cutting-edge chemosensors. Full article

The research into and applications of wood origin traceability technology are of great significance for promoting the standardization and legality of the global timber trade. This paper focuses on analyzing the content of ten mineral elements and the ratios of stable isotopes δ¹³C and δ¹⁵N in ash samples. Furthermore, multivariate statistical analysis was conducted to assess the clusters and differences in mineral elements, as well as δ¹³C and δ¹⁵N, among the samples, for identifying the different factors used to trace the origin of ash imported from different regions. Through unsupervised clustering and supervised discriminant modeling, a highly accurate method for discriminant analysis was developed. The results reveal significant differences (p < 0.05) in the contents of Mg, Cu, and Sr, as well as δ¹⁵N, between European and American samples. Additionally, the normalized results of mineral elements and isotope ratios were then subjected to partial least squares–discriminant analysis (PLS-DA), resulting in the highest level of separation. This analysis achieved an overall accuracy of 96.2% in discriminating between samples of European and American ash. The chemometrics analysis method integrating stable isotope analysis with elemental analysis exhibited potential for discriminating between samples from European and American ash. Full article

Nowadays, indoor air pollution is a major problem that affects human health. For that reason, measuring indoor air quality has an increasing interest. Electronic noses are low-cost instruments (compared with reference methods) capable of measuring air components and pollutants at different concentrations. In this paper, an electro-optical nose (electronic nose that includes optical sensors) with non-dispersive infrared sensors and metal oxide semiconductor sensors is used to measure gases that affect indoor air quality. To validate the developed prototype, different gas mixtures (CH₄ and CO₂) with variable concentrations and humidity values are generated to confirm the discrimination capabilities of the device. Principal Component Analysis (PCA) was used for dimensionality reduction purposes to show the measurements in a plot. Partial Least Squares Regression (PLS) was also performed to calculate the predictive capabilities of the device. PCA results using all the measurements from all the sensors obtained PC1 = 47% and PC2 = 10%; results are improved using only the relevant information of the sensors obtaining PC1 = 79% and PC2 = 9%. PLS results with CH₄ using only MOX sensors received an RMSE = 118.8. When using NDIR and MOX sensors, RMSE is reduced to 19.868; this tendency is also observed in CO₂ (RMSE = 116.35 with MOX and RMSE = 20.548 with MOX and NDIR). The results confirm that the designed electro-optical nose can detect different gas concentrations and discriminate between different mixtures of gases; also, a better correlation and dispersion is achieved. The addition of NDIR sensors gives better results in measuring specific gases, discrimination, and concentration prediction capabilities in comparison to electronic noses with metal oxide gas sensors. Full article

A significant number of research papers regarding biosensor-related assays for key food safety pathogens based on the use of mammalian cells has been reported. In this study, the Salmonella typhimurium infection progression was monitored in the human colon cancer cell line Caco-2 and the mucus-secreting HT29-MTX-E12, after treatment with five different bacterial MOI for 30 min by comparing the alterations of frequencies recordings with impedance spectroscopy measurements. For this purpose, bacterial adhesion and invasion assays were initially performed. Then, the data obtained from impedance spectroscopy recordings were compared to cell viability data derived from the MTT uptake cell proliferation assay as well as from live cell analysis assays of mitochondrial membrane potential alterations. From our findings a concentration-dependent increase in bacterial colonies occurring from invaded cells was observed upon a higher multiplicity of infection (MOI) bacterial infection at both cell lines. On the contrary, the bacteria infection did not have any impact on the viability of the cells after 1 h of treatment. Differential results were obtained from the measurement of mitochondrial potential at both cell lines. Finally, the impedance values recorded from the 2D, and 3D cultures were concentration-dependent for both cell lines whereas a characteristic pattern specific to each cell line was revealed. Our results indicate that human cell-based bio-electric assays can be a valuable tool for obtaining a unique fingerprint for each bacterial infection in the near future. Full article

Biosensors are analytical devices that use biological interactions to detect and quantify single molecules, clinical biomarkers, contaminants, allergens, and microorganisms. By coupling bioreceptors with transducers, such as nucleic acids or proteins, biosensors convert biological interactions into electrical signals. Electrochemical and optical transductions are the most widely used methods due to their high detection capability and compatibility with miniaturization. Biosensors are valuable in analytical chemistry, especially for health diagnostics, as they offer simplicity and sensitivity. Despite their usefulness, challenges persist in immobilizing biorecognition elements on the transducer surface, leading to issues such as loss of sensitivity and selectivity. To address these problems, the introduction of nanomaterials, in particular magnetic nanoparticles (MNPs) and magnetic beads, has been implemented. MNPs combine their magnetic properties with other interesting characteristics, such as their small size, high surface-to-volume ratio, easy handling, and excellent biocompatibility, resulting in improved specificity and sensitivity and reduced matrix effects. They can be tailored to specific applications and have been extensively used in various fields, including biosensing and clinical diagnosis. In addition, MNPs simplify sample preparation by isolating the target analytes via magnetic separation, thus reducing the analysis time and interference phenomena and improving the analytical performance of detection. The synthesis and modification of MNPs play a crucial role in adjusting their properties for different applications. This review presents an overview of the synthesis and surface modifications of magnetic nanoparticles and their contributions to the development of biosensors and bioassays for their applications across different areas. The future challenges of MNP synthesis and integration in assays are focused on their stability, multiplex detection, simplification and portability of test platforms, and in vivo applications, among other areas of development. Full article

Hydrogen peroxide is essential for biological processes and normally occurs in low concentrations in living organisms. However, exposure of plants to biotic and abiotic stressors can disrupt their defense mechanisms, resulting in oxidative stress with elevated H₂O₂ levels. This oxidative stress can damage cell membranes, impair photosynthesis, and hinder crucial plant functions. The primary focus of this article is to investigate the effects of salt and herbicide stress factors on the growth of rye samples. For precise quantification of the released H₂O₂ concentration caused by these stress factors, a non-enzymatic electrochemical sensor was developed, employing nanostructured CuO and Co₃O₄ oxides. Nanostructured electrodes exhibit high sensitivity and selectivity towards H₂O₂, making them suitable for detecting H₂O₂ in real samples with complex compositions. Rye samples exposed to NaCl- and glyphosate-induced stress demonstrated notable concentrations of released H₂O₂, displaying an increase of up to 30% compared to the control sample. Moreover, optical absorption measurements revealed a substantial decrease in chlorophyll concentration (up to 35% compared to the control group) in rye samples where elevated H₂O₂ levels were detected through electrochemical methods. These findings provide further evidence of the harmful effects of elevated H₂O₂ concentrations on plant vital functions. Full article

Micro/nanoplastics are widespread in the environment and may cause severe damage to creatures and human beings. Micro/nanoplastic pollution has become a global focus issue; hence, the rapid and accurate detection of micro/nanoplastics is an essential step to ensure health. Herein, we report a surface-enhanced Raman scattering (SERS) technique to sensitively and quantitatively identify micro/nanoplastics in environmental water samples. A three-dimensional hierarchical Au@Ag nanostar (NSs) was synthesized and employed as an efficient SERS substrate. The “lightning rod effect” generated by tip branches of the nanostars and the coupling effect of the neighboring branches of the nanostar array enabled the ultra-trace detection of crystal violet (CV) down to 10⁻⁹ M, even with a portable Raman device. Moreover, the hydrophobic property of the SERS substrate endowed it with a desirable enrichment effect, which meant an increase in the concentration or quantity of the micro/nanoplastic particles. And thereafter, the SERS sensor achieved a highly sensitive detection of polystyrene (PS) particle standard solution at a low concentration of 25 μg/mL or 2.5 μg/mL. Importantly, the detected concentration and the SERS intensity followed a nearly linear relationship, indicating the capability of quantitative analysis of micro/nanoplastics. In addition, the SERS sensor was successfully extended to detect PS particles in environmental water samples, including tap water, sea water, and soil water, and the detection concentration was determined to be 25 μg/mL, 2.5 μg/mL, and 25 μg/mL, respectively. The present Au@AgNSs array substrate with a two-order magnitude signal amplification further exhibited significant advantages in the label-free analysis of micro/nanoplastics in real water samples. Full article

Unlike transition metal oxides and sulfides, transition metal-based selenides display higher electrical conductivity, more electroactive unsaturated edge sites, and better chemical stability, which have found extensive usage in electrocatalysis. In this work, simple hydrothermal and solvothermal procedures were employed to synthesize quaternary (Ni, Co, Cu)Se₂ nanosheet arrays on carbon cloth (CC) to measure glucose. The conductivity of the material can be effectively elevated by adding Se element to form selenides, and the synergistic effect between the three selenides can improve the electrocatalytic performance. Consequently, in the ranges of 0.01–600 μM and 600–9000 μM, respectively, the current response of the synthesized material to glucose concentration exhibited linear relationships. The sensor demonstrated excellent sensitivity and a low detection limit of 5.82 nM. Furthermore, the practical applicability of the constructed biosensor was proved by using it to quantify the amount of glucose in human serum. Full article

Bending strain sensors based on one-dimensional ZnO nanorod (NR) arrays cross-linked with interdigitated electrodes were fabricated on polyethylene terephthalate (PET) substrates. ZnO NRs were grown using the hydrothermal method through the dopings with different transition metals, such as Co, Ni, or Co-plus-Ni, on PET substrates, and their microstructural morphology and crystalline properties were examined by a variety of surface analysis methods. Ultraviolet photoresponse and normalized resistance change were measured according to the bending strains to concave and convex directions, and the highest gauge factors of 175 and 83 were achieved in the convex and concave directions, respectively, at a bending strain of 1.75%, when Co-plus-Ni was doped to the NRs. Full article

In modern materials research, nanotechnology will play a game-changing role, with nanoarchitectonics as an overarching integrator of the field and artificial intelligence hastening its progress as a super-accelerator. We would like to discuss how this schema can be utilized in the context of specific applications, with exemplification using disease diagnosis. In this paper, we focus on early, noninvasive disease diagnosis as a target application. In particular, recent trends in chemosensing in the detection of cancer and Parkinson’s disease are reviewed. The concept has been gaining traction as dynamic volatile metabolite profiles have been increasingly associated with disease onset, making them promising diagnostic tools in early stages of disease. We also discuss advances in nanoarchitectonic chemosensors, which are theoretically ideal form factors for diagnostic chemosensing devices. Last but not least, we shine the spotlight on the rise to prominence and emergent contributions of artificial intelligence (AI) in recent works, which have elucidated a strong synergy between chemosensing and AI. The powerful combination of nanoarchitectonic chemosensors and AI could challenge our current notions of disease diagnosis. Disease diagnosis and detection of emerging viruses are important challenges facing society. The parallel development of advanced functional materials for sensing is necessary to support and enable AI methodologies in making technological leaps in applications. The material and structural formative technologies of nanoarchitectonics are critical in meeting these challenges. Full article

The investigation of novel sample matrices in the forensic sciences offers several possible advantages, such as allowing for results to be obtained in cases where common sample types are absent. This review focuses on the application of gas chromatography and gas chromatography–mass spectrometry (GC-MS) for the determination of drugs in alternative sample matrices, including hair, sweat, meconium, breast milk, and vitreous humour. Less common sample types are also reported including air, cerumen, insects, and their larvae and pupae. The application of pyrolysis GC-MS (Py GC-MS) is also reviewed, showing the possibility of determining high molecular weight drugs which would commonly be unattainable by GC-MS. The application of Py GC-MS for the simulation and investigation of the underlying chemistry and the products formed in the smoking of drugs is also reported. Full article

Tin oxide (SnO₂) is a traditional gas-sensitive semiconductor with excellent response to various gases. However, its sensor performances are attenuated by the utility factor during gas diffusion in the sensing body. Therefore, the rational design of microstructure of devices is attractive and necessary because it may provide a sensible and controllable microstructure, which facilitates gas diffusion and inhibits the utility factor. Herein, the mesoporous tin oxide (MPTD) quantum dot thin film for H₂S gas sensors is prepared by a facile route, which creates a mesoporous microstructure for thin films by the thermal decomposition of NH₄Cl. The pore size of the thin films is controlled to be 19.36–40.13 nm. The mesoporous microstructure exhibits enhanced gas-sensing properties amounting to a 30-fold increase in response and 1/3 reduction in recovery time in H₂S detection at room temperature (25 °C), with a limit of detection of 0.4 ppm. To determine the importance of sensor parameters such as pore size, film thickness, and grain size, an eXtreme Gradient Boosting (XGBoost) algorithm model was developed to examine the feature importance of each parameter on the gas-sensing performance of the MPTD sensors. The visual illustration of parameter importance is revealed to facilitate the optimization of technical preparation parameters as well as the rational design of semiconductor gas sensors. Full article

In recent decades, many research efforts have been dedicated to finding highly sensitive devices for fast and reliable identification and quantification of an expanding range of analytes. As a result, there has been an increased number of publications dedicated to this area and a consequent increase in the number of review papers on the subject. However, unlike most review articles, we chose to explore the impact of supramolecular arrangement (or deeper, when possible, approaching the molecular organization) and assembly variables on sensing performance. This review briefly discusses the methods used to determine the molecular organization of thin films. We also examine various deposition techniques, including Langmuir-Blodgett, Langmuir-Schaefer, Layer-by-Layer assembly, electrodeposition, and spray pyrolysis, describing mainly (but not limited to) the advances in the last five years in developing thin films for sensors, with a particular emphasis on how the supramolecular arrangement can influence the sensing properties of these films. Full article

L-Dopa is an intermediate amino acid in the biosynthesis of endogenous catecholamines, such as dopamine. It is currently considered to be the optimal dopaminergic treatment for Parkinson’s disease, a neurodegenerative disorder affecting around 1% of the population. In an advanced stage of the disease, complications such as dyskinesia and psychosis are caused by fluctuations in plasma drug levels. Real-time monitoring of L-Dopa levels would be advantageous for properly adjusting drug dosing, thus improving therapeutic efficacy. Electrochemical methods have advantages such as easy-to-use instrumentation, fast response time, and high sensitivity, and are suitable for miniaturization, enabling the fabrication of implantable or wearable devices. This review reports on research papers of the past 20 years (2003–2023) dealing with enzyme-based biosensors for the electrochemical detection of L-Dopa in biological samples. Specifically, amperometric and voltammetric biosensors, whose output signal is a measurable current, are discussed. The approach adopted includes an initial study of the steps required to assemble the devices, i.e., electrode modification and enzyme immobilization. Then, all issues related to their analytical performance in terms of sensitivity, selectivity, and capability to analyze real samples are critically discussed. The paper aims to provide an assessment of recent developments while highlighting limitations such as poor selectivity and long-term stability, and the laborious and time-consuming fabrication protocol that needs to be addressed from the perspective of the integrated clinical management of Parkinson’s disease. Full article

Adenosine is a vital biological small molecule that regulates various physiological processes in the human body. A high expression of adenosine in cells can facilitate tumor growth. Therefore, detecting adenosine is crucial for early disease diagnosis. In this paper, we designed a fluorescent biosensor for the sensitive detection of adenosine based on the cationic comb-type copolymer PLL-g-Dex for assisted rapid hybridization of nucleic acids at room temperature. In this strategy, adenosine preferentially binds to the aptamer immobilized on the surface of magnetic nanobeads, releasing free aDNA in solution as the primer strand, which rapidly forms DNA nanowires with auxiliary probes of bDNA with the assistance of PLL-g-Dex. SYBR Green I is embedded in DNA duplexes to generate strong fluorescence. The experimental results showed that PLL-g-Dex promotes DNA hybridization reactions at room temperature to form ultra-long DNA nanowires, thus achieving signal amplification and shortening the detection time. In addition, magnetic nanobeads can reduce the background signal during the reaction. Compared with several previous studies on the fluorescence detection of adenosine, this strategy has a lower detection limit of 2.32 nM. Furthermore, this novel system exhibited a good detection performance even under complex environments, such as serum, providing some reference for the quantitative detection of adenosine in early disease diagnosis. Full article

Recently, rapid progress has been achieved in the field of nanomaterial preparation and investigation. Many nanomaterials have been employed in optical chemical sensors and biosensors. This review is focused on fiber-optic nanosensors for chemical sensing based on silica and plastic optical fibers. Four types of fiber-optic chemical nanosensors, namely fiber nanotip sensors, fiber nanoarray sensors, fiber-optic surface plasmon resonance sensors, and fiber-optic nanomaterial-based sensors, are discussed in the paper. The preparation, materials, and sensing characteristics of the selected fiber-optic nanosensors are employed to show the performance of such nanosensors for chemical sensing. Examples of fiber-optic nanobiosensors are also included in the paper to document the broad sensing performance of fiber-optic nanosensors. The employment of fiber-nanotips and nanoarrays for surface-enhanced Raman scattering and nanosensors employing both electrical and optical principles and “Lab-on-fiber” sensors are also included in the paper. The paper deals with fiber-optic nanosensors based on quantum dots, nanotubes, nanorods, and nanosheets of graphene materials, MoS₂, and MXenes. Full article

The detection of aflatoxins is essential for the food industry to ensure the safety and quality of food products before their release to the market. The lateral-flow immunochromatography assay (LFIA) is a simple technique that allows the rapid on-site detection of aflatoxins. The purpose of this review is to evaluate and compare the limits of detection reported in the most recent research articles, published between the years of 2015 and 2023. The limits of detection (LODs) were compared against the particle type and particle size, as well as other variables, to identify trends and correlations among the parameters. A growing interest in the use of different metal and non-metal nanoparticles was observed over the years of 2015–2023. The diameters of the nanoparticles used were reportedly between 1 nm and 100 nm. Most of these particles displayed lower LODs in the range of 0.01 to 1.0 ng/mL. Furthermore, there was a significant level of interest in detecting aflatoxin B1, perhaps due to its high level of toxicity and common appearance in food products. This study also compares the use of metallic and non-metallic nanoparticles in detecting aflatoxins and the dependence of nanoparticles’ sizes on the detection range. Overall, the type of particle and particle size used in the development of LFIA strips can affect the sensitivity and LOD; hence, the optimization of these parameters and their modulation with respect to certain requirements can enhance the overall assay performance in terms of the reproducibility of results and commercialization. Full article

The necessity of detecting and recognizing gases is crucial in many research and application fields, boosting, in the last years, their continuously evolving technology. The basic detection principle of gas sensors relies on the conversion of gas concentration changes into a readable signal that can be analyzed to calibrate sensors to detect specific gases or mixtures. The large variety of gas sensor types is here examined in detail, along with an accurate description of their fundamental characteristics and functioning principles, classified based on their working mechanisms (electrochemical, resonant, optical, chemoresistive, capacitive, and catalytic). This review is particularly focused on chemoresistive sensors, whose electrical resistance changes because of chemical reactions between the gas and the sensor surface, and, in particular, we focus on the ones developed by us and their applications in the medical field as an example of the technological transfer of this technology to medicine. Nowadays, chemoresistive sensors are, in fact, strong candidates for the implementation of devices for the screening and monitoring of tumors (the second worldwide cause of death, with ~9 million deaths) and other pathologies, with promising future perspectives that are briefly discussed as well. Full article

In this study, an innovative approach for the integration of silver nanoparticles (AgNPs) into poly(ethylene glycol) diacrylate (PEGDA) hydrogels is described. The composite material is the first in the literature where AgNPs were doped into PEGDA using photo-polymerization technique for a double function: detection and elimination of Hg(II) ions from water. The doping of AgNPs into PEGDA-based matrices was performed using a photo-polymerizable process. The Hg(II) sensing properties were explored in a concentration range from 0 to 20 mg/L. Notably, a linear dependence was observed up to 1 mg/L, accompanied by a limit of detection of 0.3 mg/L. Beyond sensing, the efficiency of the doped hydrogel in removing Hg(II) ions was also investigated and compared with an undoped PEGDA matrix. The outcome highlighted an enhanced removal efficiency of the doped material of approximately 23%. Finally, the experimental data suggested that the interaction between Hg(II) ions and the modified hydrogel adhered to the Langmuir isotherm model, which suggested that chemisorption was the driving mechanism of the adsorption of Hg(II) onto the modified hydrogel matrix. Full article