Search Results (2,273)

This study explores the development of a non-enzymatic electrochemical glucose sensor based on poly(3-aminobenzoic acid) (P3ABA) combined with silver nanoparticles (AgNPs). Incorporating AgNPs into the P3ABA matrix enhances the sensor’s electrocatalytic properties, leading to a system with greater stability. Cyclic voltammetry and chronoamperometry were employed to evaluate the sensor’s performance, demonstrating a sensitivity of 50.71 µA mM⁻¹ cm⁻² and a limit of detection (LOD) of 0.2 µM. The sensor exhibited a linear response over a broad concentration range (1 to 16 mM), with a coefficient of determination (R²) of 0.998, indicating good reproducibility and precision. These results highlight the potential of the P3ABA/AgNP composite for glucose sensing applications, offering an extended linear range, allowing for the quantification of glucose concentrations from very low to significantly high levels, covering both physiological and pathological conditions. Full article

There are many compounds used to treat cancer, but still, only 20% of proposed anticancer agents have been commercialized after clinical trials due to serious side effects and unsatisfactory results. To screen potential drugs precisely and quickly, this study develops a flexible bioimpedance sensor. The sensor positively detects the half maximal inhibitory concentration (IC50) of drugs in real time by analyzing phase angle changes during cell mortality. The best results are achieved using a probe separation of A12B34 at logarithmic frequencies of 163 Hz and 77.87 kHz. At these two frequencies, there is a linear relationship with the phase angle at 0% and 50% of the dead cells. Dividing the phase angle at the two frequencies shows a 17.98% change in the phase angle, which allows self-correction and insensitivity to the number of cells. A custom phase angle measurement device is developed for detection at 163 Hz and 77.87 kHz, respectively. This study develops a novel sensor that is precise and fast and allows high-throughput analysis to detect the inhibition of cancer in real time. This sensor is an alternative to traditional chemical detection methods because it is faster, cheaper, and more accurate. Full article

Gas chromatography–ion mobility spectrometry (GC-IMS) is a powerful technique in the field of food and flavor analysis specifically, as well as for the determination of volatile organic compounds (VOCs) in general. It offers high sensitivity and selectivity, combined with a robust design. Sample preparation is typically not required, and operating principles under ambient conditions facilitate routine analysis and usage at points of care. As of now, a plethora of applications of GC-IMS exist in the fields of food analysis, primarily for determining flavors and evaluating the authenticity of food. However, the general issue of peak tailing has, so far, not been addressed in IMS. Typical drift tube applications (DTIMS) are designed with emphasis to high detection sensitivities and feature large void volumes. This study aimed to develop an optimized IMS instrument design (“focus IMS”) which allows for signal mapping of eluting compounds. Due to an optimized flow architecture of sample and drift gases, in combination with an increased drift tube temperature, peak tailing is decreased significantly. In this study, the influence of drift gas flow and IMS cell temperature on the peak shape of several relevant allergenic terpenes was investigated. The peak quality optimization of DTIMS approaches for especially high-boiling substances facilitates the analysis of complex matrices, such as cosmetics, Citrus peel, and essence oils, as well as terpenes and terpenoids in general. Full article

This article outlines the method of creating electrodes for electrochemical sensors using hybrid nanostructures composed of graphene and conducting polymers with insertion of gold nanoparticles. The technology employed for graphene dispersion and support stabilization was based on the chemical vapor deposition technique followed by electrochemical delamination. The method used to obtain hybrid nanostructures from graphene and conductive polymers was drop-casting, utilizing solutions of P3HT, PANI-EB, and F8T2. Additionally, the insertion of gold nanoparticles utilized an innovative dip-coating technique, with the graphene-conducting polymer frameworks submerged in a HAuCl₄/2-propanol solution and subsequently subjected to controlled heating. The integration of gold nanoparticles differs notably, with P3HT showing the least adhesion of gold nanoparticles, while PANI-EB exhibits the highest. An inkjet printer was employed to create electrodes with metallization accomplished through the use of commercial silver ink. Notable variations in roughness (grain size) result in unique behaviors of these structures, and therefore, any potential differences in the sensitivity of the generated sensing structures can be more thoroughly understood through this spatial arrangement. The electrochemical experiments utilized a diluted sulfuric acid solution at three different scan rates. The oxidation and reduction potentials of the structures seem fairly alike. Nevertheless, a notable difference is seen in the anodic and cathodic current densities, which appear to be largely influenced by the active surface of gold nanoparticles linked to the polymeric grains. The graphene–PANI-EB structure with Au nanoparticles showed the highest responsiveness and will be further evaluated for biomedical applications. Full article

Traditional detection methods such as atomic absorption spectroscopy offer high sensitivity and accuracy for heavy metal ion detection; however, they are often limited to laboratory environments due to bulky equipment and complex procedures. To meet the demand for rapid on-site detection, this study employs electrochemical analysis and utilizes Micro-Electro-Mechanical Systems (MEMS) technology to fabricate a microelectrode sensor chip for the electrochemical detection of heavy metal ions, Hg(II) and As(III). Nano-gold particles were electrodeposited on the sensing area of the working electrode of this chip using a constant-potential deposition method. Uniform distribution of the nanoparticles was obtained, which enhanced the effective specific surface area and electrochemical activity of the working electrode. Therefore, wide detection concentration ranges for Hg(II) of 5 to 1000 µg/L and for As(III) of 5 to 5000 µg/L were displayed, with detection limits of 1.4 µg/L and 2.4 µg/L, respectively. Moreover, the sensor exhibited satisfactory reproducibility, stability and anti-interference capability. These characteristics enable the developed microelectrode sensor chip to be utilized in the monitoring of a diverse range of pollution sources. Full article

A device was developed to study the evolution of fluorescence spectra as a function of time. A previously designed fluorimeter based on the diode array mini-spectrometer CM12880MA was used. The control and measurement were carried out by programming a SAM21D microcontroller. Considerations regarding the optimization of acquisition speed, memory, and computer interface have been analyzed and optimized. As a result, a very versatile device with great adaptability, reduced dimensions, portability, and a low budget (under EUR 500) has been built. The sensitivity, controlled by the integration time of the photodiodes, can be adjusted between 10 µs and 20 s, thus allowing sampling times ranging from 10 ms to more than 10 h. Under these conditions, chemical rate constants from 20 s⁻¹ to 10⁻⁸ s⁻¹ can be experimentally determined. It has a very wide operating range for the kinetic rate constant determination, over six orders of magnitude. As proof of the system performance, the oxidation reaction of Thiamine in a basic medium to form fluorescent Thiochrome has been employed. The evolution of the emission spectrum has been followed, and the decomposition rate constant has been measured at 2.1 × 10⁻³ s⁻¹, a value which matches those values reported in the literature for this system. A Thiochrome calibration curve has also been performed, obtaining a detection limit of 13 nM, consistent with literature data. Additionally, the stability of Thiochrome has been tested, being the photo-decomposition rate constants 1.8 × 10⁻⁴ s⁻¹ and 3.0 × 10⁻⁷ s⁻¹, in the presence and absence of UV light (365 nm), respectively. Finally, experiments have been designed to obtain, in a single measurement, the values of both rate constants: the formation of Thiochrome from Thiamine and its photo-decomposition under UV light to a non-fluorescent product. The rate constant values obtained are in good agreement with those previously obtained through independent experiments under the same experimental conditions. These results show that, under these conditions, Thiochrome can be considered an unstable intermediate in a chemical reaction with successive stages. Full article

Bio-sniffers represent a novel detection technology that demonstrates significant potential in medical diagnostics. Specifically, they assess disease conditions and metabolic status through the detection of volatile organic compounds (VOCs) in exhaled breath. Unlike conventional methods such as gas chromatography-mass spectrometry (GC-MS) and gas chromatography time-of-flight mass spectrometry (GC-TOF-MS), bio-sniffers provide rapid, sensitive, and portable detection capabilities. In this review, we examine the metabolic pathways and detection methods of specific VOCs in the human body, and their roles as disease biomarkers, and focus on the detection principles, performance characteristics, and medical applications of two bio-sniffer types: electrical and optical sensors. Finally, we systematically discuss the current challenges facing bio-sniffers in VOC monitoring, outline future development directions, and provide suggestions for improving sensitivity and reducing environmental interference. Full article

In this study, a quantitative profiling method for detecting free fatty acids in crude lanolin based on the Quality by Design (QbD) concept was developed. High-performance liquid chromatography (HPLC) equipped with a charged aerosol detector (CAD) and a Proshell 120 EC C18 column was employed for the separation of crude lanolin components. Initially, the analytical target profile and critical method attributes were defined. Potential critical method parameters, including column temperature, flow rate, isocratic run time, gradient end organic phase ratio, and gradient time, were identified using fishbone diagrams and single-factor experiments. The definitive screening design (DSD) was then utilized to screen and optimize these parameters. Stepwise regression was applied to establish quantitative models between the critical method attributes and the method parameters. Subsequently, the method operable design region (MODR) was calculated and was successfully verified. The analytical conditions established were configured with 0.1% formic acid in water and 0.1% formic acid in acetonitrile serving as the mobile phases. The flow rate was set at 0.8 mL/min, and the column temperature was maintained at 35 °C with the evaporation tube temperature also set at 35 °C. An injection volume of 10 μL was used for each analysis. The gradient elution conditions were as follows: from 0 to 30 min, 75% of solvent B was used, and from 30 to 60 min, the proportion of solvent B was increased from 75% to 79%. Ten components, including 12-hydroxystearic acid, 2-hexyldecanoic acid, and palmitic acid, were identified by mass spectrometry, and seven common peaks were found in the fingerprints. The contents of palmitic acid, oleic acid, and stearic acid in the crude lanolin were quantitatively determined. Both the fingerprint and quantitative analysis methods were validated. The method was applied to analyze 15 batches of crude lanolin from different sources. The new established quantitative profiling method for free fatty acids can be potentially used for industrial applications to enhance the quality control of crude lanolin. Full article

The sensing of surfactants is a topic of interest for industrial and environmental purposes. Polydopamine-coated magnetite (Fe₃O₄@PDA) can be a relevant support for the detection of cationic surfactants in water samples. The negative charge in the surface of the PDA material favors the interaction with cationic molecules and allows the design of a chemoreagent for the detection of cationic surfactants by displacement or competition with methylene blue (MB). Magnetite nanoparticles with single and double PDA coating have been prepared and characterized. The PDA surface effectively coats magnetite nanoparticles with a thickness of 5 or 19 nm and a Z potential of −30 mV. The adsorption of MB follows second-order kinetics, and up 33 mg of dye can be loaded in 1 g of the support. The cationic surfactants can displace MB from the Fe₃O₄@PDA surface, coloring the solution. Thus, it can be applied for the analysis of water samples. The system is selective towards cationic molecules with long alkyl chains, but the response is influenced by high concentrations of divalent cations. The material can be used following diverse sensing protocols with a detection range from 4 × 10⁻⁶ to 2 × 10⁻⁴ M. The simplicity of its handling together with the naked eye detection allows its application in kits for field analysis with screening purposes. Full article

This paper focuses on the development of an environmentally friendly sequential injection (SI) method for the determination of chloride in water samples from dynamic water systems. Chloride quantification is highly relevant, as it may affect metal ion bioavailability and potential toxicity to the environment. The approach was established based on the catalytic reaction of chloride ions in the colorimetric reaction between 3,3′,5,5′-tetramethylbenzidine (TMB) and hydrogen peroxide. Optimisation studies were performed regarding several parameters such as reaction pH, reagent volume and concentration, reaction time, and flow rates. As such, it was possible to obtain a wide dynamic range of 60 to 1000 mM, with a limit of detection and quantification of 17 and 58 mM, respectively, and a relative standard deviation of 7%. Validation was performed by analysing 13 water samples from dynamic water systems, namely seawater, estuarine water, and estuarine harbour water, with the SI method developed and by comparing the results obtained to potentiometric titration as the reference method. The relative error of these comparisons was not significant (<10%). Interference studies were also performed and showed no significant effect on the performance of the system (interference percentage < 10%), proving that a robust and sensitive system was developed. Full article

MircroRNA (miRNA) exhibits abnormal expression in many cancer diseases, and the detection and analysis of miRNA are significant for the early diagnosis of diseases and research on miRNA functions. In this work, we construct a UV-triggered DNAzyme (UTD) nanosensor for the early detection of miRNA in tumor cells. As the nanodevice was delivered into cells and irradiated by UV light, the controllable imaging of miRNA in living cells was achieved. This method effectively avoids false signal issues, providing a new strategy for high-spatiotemporal-resolution imaging of miRNA in living cells. Full article

Flexible, wearable biomedical sensors based on laser-induced graphene (LIG) have garnered significant attention due to a straightforward fabrication process and exceptional electrical and mechanical properties. However, most relevant studies rely on commercial polyimide precursors, which suffer from inadequate biocompatibility and weak adhesion between the precursor material and the LIG layer. To address these challenges, we synthesized cross-linked polyurethanes (PUs) with good biocompatibility and used them as substrates for LIG-based wearable pulse sensors. During fabrication, we employed two methods of LIG transfer to achieve optimal transfer yield. We adjusted the thickness of PU films and tailored their mechanical and physicochemical properties by varying the soft segment content to achieve optimal sensor performance. Our findings demonstrate that the success of LIG transfer is strongly influenced by the structure and composition of the polymeric substrate. Tensile testing revealed that increasing the soft segment content in PU films significantly improved their tensile strength, elongation at break, and flexibility, with PU based on 50 wt.% soft segment content (PU-50) showing the best mechanical properties. LIG exhibited minimal sensitivity to humidity, while PU films maintained high transparency (>80% at 500 nm), and PU-50 was non-toxic, with less than 5% lactate dehydrogenase (LDH) release in endothelial cell cultures, confirming its biocompatibility. Adhesion tests demonstrated that LIG transferred onto PU-50 exhibited significantly stronger adhesion compared to other tested substrates, with only a 30% increase in electrical resistance after the Scotch tape test, ensuring stability for wearable sensors. The optimal substrate, a semicrystalline PU-50, yielded superior transfer efficiency. Among all tested sensors, the LIG/PU-50, featuring a 77 μm thick substrate with good mechanical properties and improved adhesion, exhibited the highest signal-to-noise ratio (SNR). This study showcases a skin-safe LIG/PU-based pulse sensor that has significant potential for applications as a wearable patch in medical and sports monitoring. Full article

Notwithstanding the success of SnO₂ as a fundamental material for gas sensing, it has often been criticized for its cross-sensitivity and high operational temperatures. Therefore, in this study, RF-sputtered SnO₂ thin films were subjected to a modification process through doping with a rare earth element, dysprosium (Dy), and subsequently deposited onto two different types of substrates: alumina and glass substrates. All thin films underwent a comprehensive series of characterizations aimed at ensuring their suitability as NO₂ sensors. The dysprosium doping levels ranged from 1 to 7 wt.% in increments of 2% (wt.%). X-ray patterns showed that all deposited films exhibited the tetragonal rutile structure of SnO₂. The optical band gap energy (Eg) increased with Dy doping, while the Urbach energy decreased with Dy doping. Field emission scanning electron microscopy (FESEM) revealed highly compacted grainy surfaces with high roughness for alumina substrate thin films, which also exhibited higher resistivity that increased with the levels of Dy doping. Energy-dispersive X-ray spectroscopy (EDX) analyses confirmed the stoichiometry of both types of thin films. Gas sensing tests were conducted at different operating temperatures, where the highest response to nitrogen dioxide, over 42%, was recorded for the higher dopant level at 250 °C. Moreover, the sensor’s selectivity toward nitrogen dioxide traces was evaluated by introducing interfering gases at higher concentrations. However, the sensors showed also significant responses when operated at room temperature. Also, we have demonstrated that higher stability is related to the temperature of the sensors and Dy ratio. Hence, a detailed discussion of the gas-sensing mechanisms was undertaken to gain a deeper insight into the NO₂ sensitivity exhibited by the Dy-doped SnO₂ layer. Full article

Monitoring hazardous gases is increasingly critical for environmental protection and human health. As a novel class of two-dimensional nanomaterials, layered metal chalcogenides have attracted substantial research attention in recent years. This is attributed to their unique physical and chemical characteristics, which endow them with remarkable potential for applications in gas sensing. In particular, bismuth sulfide (Bi₂S₃) has been extensively studied recently due to its cost-effectiveness, abundance, and eco-friendliness, aligning with the requirements of advanced sensing platforms. This article systematically summarizes recent advancements in gas sensors based on Bi₂S₃. Initially, the structural and functional properties of Bi₂S₃ are outlined, emphasizing its potential in detecting toxic gases. Subsequently, innovative methodologies aimed at enhancing room-temperature sensing efficiency are critically analyzed. The discussion concludes by addressing existing limitations and proposing future research directions to optimize Bi₂S₃ for practical applications. This review aims to systematically examine the design and optimization of next-generation gas detection nanomaterials, offering fundamental understanding of their performance enhancement mechanisms and exploring their potential implementation across multiple technological platforms. Full article

This paper presents a low-cost wireless prototype designed for point-of-care DNA sensing based on square wave voltammetry (SWV) measurements. Unlike other designs found in the literature, this prototype employs dedicated ADC and DAC components to reduce noise and allows for lower voltage steps in SWV scans. On-board signal processing makes the device suitable for use by inexperienced end-users. The prototype transmits data via Bluetooth Low-Energy (BLE) to a mobile app, which records the measurements on a cloud platform. The prototype was employed to detect a 23-base single-stranded DNA (ssDNA) sequence, within the range of 1 nM to 10 nM. The results obtained with the prototype showed good agreement when compared to a commercial electrochemical analyzer. This study demonstrates the feasibility of using such a device for DNA sensing, highlighting its potential for broader biosensing applications. Full article