Label-free impedimetric immunosensor for the detection of Fibulin-2 as a novel biomarker for the diagnosis of hypertrophic cardiomyopathy in human saliva.

Method validation and uncertainty evaluation in trace element analysis of high-purity silver by ICP-OES.

Visual and rapid detection of glyphosate in tea using a MOF-driven fluorescent paper sensor.

Hydroquinone (HQ) is a redox-active organic compound widely used in cosmetics, pharmaceuticals, photography, and dye manufacturing. Despite its industrial utility, hydroquinone is considered toxic and potentially carcinogenic, necessitating the development of sensitive, rapid, and selective methods for its detection in environmental and biological samples. Traditional analytical techniques such as high-performance liquid chromatography, spectrophotometry, and fluorimetry, while effective, often suffer from drawbacks, including expensive instrumentation, time-consuming procedures, and complex sample preparation. In contrast, electrochemical biosensing offers a promising alternative due to its simplicity, portability, high sensitivity, and suitability for real-time monitoring.In the present work, we report the design and fabrication of a highly sensitive electrochemical biosensor based on a novel nanocomposite comprising Flavin Adenine Dinucleotide (FAD) functionalized fluorapatite (FA) and single-walled carbon nanotubes (SWCNTs). The FAD/FA/SWCNT composite was synthesized via a mechanochemical method, a green and scalable approach that eliminates the need for complex chemical treatments or high-temperature processes. Dimethyl sulfoxide (DMSO) was used as a dispersing solvent to ensure the homogeneous distribution of FAD molecules and nanotubes within the FA matrix. The synthesized composite was drop-cast onto a glassy carbon electrode (GCE) to construct the biosensor platform.The structural and physicochemical properties of the FAD/FA/SWCNT nanocomposite were characterized using a combination of high-resolution scanning electron microscopy (HR-SEM), X-ray diffraction (XRD), and UV–Visible spectroscopy. SEM analysis revealed a uniform, sheet-like morphology with well-dispersed nanotubes, providing a high surface area conducive to electrochemical reactions. XRD confirmed the crystalline structure of fluorapatite and the successful incorporation of SWCNTs, while UV–vis spectroscopy identified the characteristic absorption peak of FAD at 450 nm, indicating successful functionalization.The electrochemical properties of the modified electrode were evaluated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and amperometry in 0.1 M phosphate buffer solution (PBS) at pH 7.4. The FAD/FA/SWCNT-modified GCE displayed a distinct redox peak at –0.45 V, attributed to the electroactive nature of FAD. The composite exhibited a significantly lower charge transfer resistance (Rct) compared to the bare and partially modified electrodes, highlighting the synergistic enhancement of electron transfer due to the integrated functionalities of FAD, FA, and SWCNTs.The electrocatalytic activity of the biosensor was systematically investigated for hydroquinone detection. The sensor showed a linear detection range from 0.005 µM to 258.2 µM, with a limit of detection (LOD) of 2.70 nM. This remarkable sensitivity is primarily attributed to the combined effects of: FAD serves as a redox-active mediator facilitating electron transfer, FA contributes to high surface area and biocompatibility, SWCNTs, which provide excellent electrical conductivity and enhance charge mobility. Scan rate studies indicated that the electrochemical response involves a mixed control mechanism, with contributions from both diffusion and surface-confined processes. The calculated charge transfer coefficient (α = 0.53) and linear dependence of peak current on both the square root and logarithm of scan rate further confirmed favorable reaction kinetics. The biosensor exhibited excellent reproducibility and operational stability, with consistent responses over 20 continuous cycles and minimal signal degradation.To validate the sensor’s real-world applicability, HQ detection was performed in spiked water samples (tap and mineral water) using the standard addition method. The biosensor demonstrated excellent recovery rates ranging from 100.4% to 103.0%, affirming its accuracy and reliability in complex sample matrices. Additionally, the sensor displayed a fast amperometric response time of approximately 4 seconds under optimized conditions at an applied potential of 0.09 V.When compared to existing HQ sensors based on advanced nanomaterials such as MoS₂/RGO, COF/CPE, and MWCNT-COOH/CTF-1, the FAD/FA/SWCNT-modified GCE outperformed in both detection range and sensitivity, demonstrating the strong potential of this composite for next-generation electrochemical biosensors.Importantly, this work marks the first report on the use of fluorapatite functionalized with a redox cofactor (FAD) for biosensing applications. The mechanochemical synthesis approach not only offers a sustainable and straightforward fabrication method but also enhances the composite’s performance due to the uniform dispersion and intimate interaction of all components. Conclusion: The FAD/FA/SWCNT-based electrochemical biosensor developed in this study offers a novel, efficient, and highly sensitive platform for hydroquinone detection. Its excellent analytical performance, combined with ease of fabrication and low detection limit, makes it a promising candidate for environmental monitoring and point-of-care diagnostics. This research also opens new avenues for incorporating bio-functionalized bioceramics into sensor technology, bridging the gap between nanomaterials, green chemistry, and practical biosensing applications. Figure 1

The monitoring of heavy metal ions in environmental and biological systems is of critical importance due to their widespread toxicity and bioaccumulative potential. Among these, ferric ions (Fe³⁺) are essential for human health but toxic in excess, leading to organ damage and oxidative stress. In this study, we present a green, cost-effective, and scalable method for synthesizing carbon quantum dots (CQDs) using Damask rose petals as a natural carbon precursor. These Damask Rose Carbon Quantum Dots (DRCQDs) exhibit excellent optical properties and were explored as a fluorometric sensor for the selective and sensitive detection of Fe³⁺ ions.CQDs were synthesized via a single-step hydrothermal treatment of finely powdered Damask rose petals in deionized water at 175°C for 24 hours. The resulting brown-colored solution indicated successful synthesis and was characterized using UV–Visible spectroscopy, fluorescence spectrophotometry, and field emission scanning electron microscopy (FE-SEM) coupled with energy dispersive spectroscopy (EDS) and elemental mapping. The average size of the CQDs was estimated to be 16.7 nm, with a spherical morphology and good dispersion. Elemental mapping confirmed the presence of carbon and oxygen, with minor contributions from aluminum due to the substrate.The optical properties of the DRCQDs were investigated under UV illumination and fluorescence spectroscopy. The CQDs exhibited strong blue fluorescence, with the emission peak centered at 420 nm when excited at 330 nm. Interestingly, the emission wavelength varied with the excitation wavelength from 280 to 400 nm, indicating excitation-dependent fluorescence—an important characteristic for tunable sensing applications. A concentration-dependent quenching effect was observed, consistent with known photophysical properties of CQDs, where highly concentrated solutions showed reduced fluorescence due to aggregation-induced quenching.The sensing performance of DRCQDs for Fe³⁺ ions was evaluated through fluorescence titration and selectivity experiments. Among various metal ions tested (Cd²⁺, Mg²⁺, Co²⁺, Cu²⁺, Zn²⁺, and Hg²⁺), only Fe³⁺ induced a significant and consistent fluorescence quenching effect, attributed to the strong affinity between Fe³⁺ and surface functional groups (hydroxyl, carboxyl) on the CQDs. The fluorescence quenching mechanism is presumed to be based on non-radiative electron–hole recombination, facilitated by the half-filled 3d orbital of Fe³⁺, which promotes energy transfer and complex formation with CQDs.The limit of detection (LOD) for Fe³⁺ was determined to be 1.11 µM, with a wide linear detection range from 0 to 80 µM and a correlation coefficient of R² = 0.9971, confirming the high sensitivity of DRCQDs for Fe³⁺ ion quantification. The fluorescence intensity decreased progressively with increasing Fe³⁺ concentration, enabling a quantitative relationship for analytical purposes. Optimization of sensing parameters such as pH, CQD concentration, and excitation wavelength was also carried out. DRCQDs displayed stable fluorescence across a wide pH range (4–12), making them suitable for real-sample applications.The selectivity of the DRCQDs toward Fe³⁺ was validated by minimal interference from other commonly co-existing metal ions. Though Cu²⁺ showed moderate quenching (~41.6%), the effect was not comparable to Fe³⁺ (~81% quenching at 50 µM), demonstrating that Fe³⁺ has a unique and stronger binding affinity to the CQD surface functional groups. This specificity is crucial for practical sensing applications in complex matrices.To demonstrate real-world applicability, the sensor was tested in spiked tap water samples using the standard addition method. The recovery values ranged from 93.96% to 104.05%, and relative standard deviation (RSD) values were consistently below 1.4%, confirming the accuracy and precision of the sensor in real conditions.A comparative analysis (Table 1 of the original article) with other green-synthesized CQDs from various natural sources revealed that Damask rose-derived CQDs offer superior sensitivity and selectivity for Fe³⁺ detection. With a lower detection limit and broader linear range, this system performs on par with or better than CQDs derived from blueberry, sugarcane molasses, and citric acid derivatives. Conclusion: This study presents a novel, eco-friendly, and highly effective fluorometric sensor for Fe³⁺ ions based on carbon quantum dots synthesized from Damask rose petals. The DRCQDs demonstrated strong blue fluorescence, excellent selectivity, and high sensitivity for Fe³⁺ ions, with successful application in real water samples. The ease of synthesis, use of natural materials, and impressive sensing performance make DRCQDs a promising candidate for environmental monitoring, water quality assessment, and biosensing applications. Future work could focus on extending the application of DRCQDs to other metal ions, cellular imaging, and nanotherapeutics. Figure 1

The widespread use of nitrofurantoin (NFT), a nitrofuran-based antibiotic commonly prescribed for urinary tract infections (UTIs), has raised concerns due to its potential side effects, including neurological and gastrointestinal toxicity. Monitoring NFT levels in biological fluids such as urine is critical to ensuring patient safety and therapeutic efficacy. In this study, we developed a novel electrochemical sensor based on a nanocomposite of iron oxide (α-Fe₂O₃) and hexagonal boron nitride (h-BN) for the selective and sensitive detection of NFT in human urine samples.The α-Fe₂O₃/h-BN nanocomposite was synthesized via a hydrothermal method, with humic acid serving as a stabilizing agent. The morphology, structure, and composition of the composite were comprehensively characterized using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), elemental mapping (E-Map), X-ray diffraction (XRD), and UV–Visible spectroscopy. The FE-SEM analysis confirmed the formation of spherical α-Fe₂O₃ nanoparticles uniformly anchored on the hexagonal sheets of h-BN. XRD patterns validated the crystalline nature of both components, while UV–vis spectra and Tauc plots revealed a blue shift and bandgap widening in the composite due to quantum confinement effects and increased microstrain, confirming the successful integration of materials.For sensor fabrication, the α-Fe₂O₃/h-BN nanocomposite was drop-cast onto a pre-treated glassy carbon electrode (GCE). The modified GCE demonstrated enhanced electrochemical properties, as evaluated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and amperometry (AMP). The nanocomposite-coated electrode exhibited a significantly improved cathodic peak current and reduced overpotential (−0.49 V) for NFT reduction, indicating superior electrocatalytic activity compared to bare and h-BN-only modified GCEs. EIS analysis further confirmed the enhancement in charge transfer capabilities due to the presence of the nanocomposite.The electrochemical detection of NFT was carried out using amperometry, where the sensor showed two linear response ranges: from 0.025 to 0.45 µM and from 0.70 to 22.95 µM. The sensor achieved an outstanding detection limit of 15 nM and a rapid response time of 2 seconds, with a calculated sensitivity of 2.36 µA µM⁻¹ cm⁻². Scan rate studies revealed that the electrochemical reduction of NFT on the α-Fe₂O₃/h-BN/GCE was diffusion-controlled, as evidenced by the linear relationship between the square root of the scan rate and the peak current.To evaluate its real-world applicability, the sensor was tested for NFT detection in human urine samples using the standard addition method. The recovery rates ranged from 99.47% to 99.93%, and the relative standard deviation (RSD) values were all below 0.5%, confirming excellent accuracy and repeatability. Furthermore, interference studies involving common urine constituents (e.g., urea, uric acid, NaCl, oxalic acid) revealed minimal impact on NFT detection (<4% signal deviation), showcasing the sensor’s high selectivity.The stability and reproducibility of the sensor were also validated. After 50 consecutive CV cycles, the sensor retained approximately 70% of its initial response, indicating commendable operational stability. Repeatability tests conducted with five independently prepared sensors showed a relative standard deviation of 3.72%, reflecting strong fabrication consistency.The high-performance characteristics of this sensor—low detection limit, fast response, high selectivity, and successful detection in real samples—are attributed to the synergistic effect between α-Fe₂O₃ nanoparticles and h-BN nanosheets. The integration of these materials creates a porous and conductive interface that facilitates efficient electron transfer and increases surface area for NFT adsorption. Moreover, including humic acid during synthesis promotes the uniform anchoring of α-Fe₂O₃ on h-BN, enhancing the composite's overall stability and electrocatalytic activity.This work is among the first to employ α-Fe₂O₃/h-BN nanocomposites for the electrochemical detection of nitrofurantoin. The results demonstrate its potential as a robust, cost-effective, and non-invasive diagnostic tool for monitoring antibiotic levels in biological fluids. Beyond NFT detection, the synthesized nanocomposite is promising for broader biosensing, environmental monitoring, and point-of-care diagnostics applications. Keywords: Nitrofurantoin, Electrochemical Sensor, α-Fe₂O₃, Hexagonal Boron Nitride, Human Urine, Amperometry, Nanocomposite, Urinary Tract Infections Figure 1

The accurate, fast, and low-cost detection of epinephrine (Epi), also called adrenaline, a key neurotransmitter and hormone involved in cardiovascular function and metabolic regulation, is essential for clinical diagnostics and pharmaceutical quality control. Traditional analytical methods such as mass spectrometry and HPLC, though sensitive, are time-consuming and require complex instrumentation. In this work, we report a novel and efficient electrochemical sensor based on a polyluminol-coated graphitic carbon nitride (PLUM/GCN) nanocomposite for the sensitive and selective detection of epinephrine in pharmaceutical injections and human bodily fluids, such as serum and urine.Graphitic carbon nitride (GCN), synthesized via thermal polymerization and exfoliated using hydrothermal treatment, served as the base material owing to its excellent electron transfer capabilities, large surface area, and biocompatibility. To enhance sensitivity, a conducting polymer, polyluminol (PLUM), was electropolymerized onto the GCN-modified glassy carbon electrode (GCE). The successful formation of the PLUM/GCN composite was confirmed by UV–visible spectroscopy, FTIR, XRD, and HR-SEM. The XRD revealed characteristic peaks at 12.8° and 27.5°, indicating a well-organized layered GCN structure. The FTIR spectra confirmed the presence of triazine units, while the Tauc plot showed a band gap of 2.9 eV. The FESEM and EDX analysis demonstrated a uniform 2D-layered morphology with enhanced nitrogen content, indicating successful PLUM coating.The electropolymerization process was validated by cyclic voltammetry (CV) in 0.1 M sulfuric acid, displaying characteristic redox peaks associated with PLUM. Electrochemical impedance spectroscopy (EIS) revealed significantly increased charge transfer resistance upon PLUM modification due to repulsive interactions with negatively charged redox probes. However, this behavior favored selective interaction with positively charged epinephrine molecules, especially in physiological pH environments.Electrochemical sensing performance was evaluated using CV and amperometry. The PLUM/GCN/GCE exhibited a well-defined anodic peak at 0.22 V for epinephrine oxidation, significantly lower than the peak potential observed on bare GCE (0.28 V), with ~2.5-fold enhancement in current response. The sensor showed a wide linear range of 0.05–278.9 µM and an impressively low limit of detection (LOD) of 27 nM. The oxidation reaction followed a mixed kinetic behavior, confirmed by scan rate studies showing both adsorption- and diffusion-controlled processes. The Tafel analysis yielded an electron transfer coefficient (α) of 0.64, indicating efficient redox kinetics.The impact of pH was systematically studied, revealing optimum sensor performance at pH 7.4, aligning with physiological conditions. The linear shift in oxidation potential with pH followed the Nernst equation slope of –0.0590 V/pH, confirming equal participation of protons and electrons in the redox process.Amperometric studies at 0.22 V under continuous stirring showed a fast, stepwise increase in oxidation current upon successive addition of Epi. A highly linear correlation (R² = 0.9992) between current and concentration was obtained in the low-concentration range of 0.05–2 µM. The calculated LOD of 27 nM outperforms many previously reported sensors, as summarized in comparative Table 1. The improved sensing performance is attributed to the synergistic effect of GCN’s electronic conductivity and PLUM’s high surface charge, which facilitates selective adsorption and rapid electron transfer.To evaluate the stability and repeatability, the sensor was subjected to 20 consecutive CV cycles, exhibiting negligible signal degradation. Repeatability tests over five consecutive runs yielded a relative standard deviation (RSD) of 3.4%, confirming excellent electrode stability. The sensor's selectivity was tested in the presence of common interfering biomolecules like ascorbic acid, uric acid, glucose, tyrosine, and urea. Minimal interference was observed, as the interfering species either had significantly different oxidation potentials or were repelled by the negatively charged PLUM layer.Finally, the sensor’s real-world applicability was assessed in spiked pharmaceutical injection, blood serum, and urine samples using the standard addition method. The sensor exhibited excellent recovery rates ranging from 91.81% to 103.60%, with RSD values below 6%, confirming its robustness and potential for clinical diagnostics. Conclusion: A novel electrochemical sensor using a PLUM/GCN nanocomposite modified electrode was developed and demonstrated superior performance for the rapid and sensitive detection of epinephrine. The hybrid structure combines the redox-active functionality of PLUM with the semiconducting and surface-enhancing properties of GCN, enabling a wide detection range, low LOD, and high selectivity. The sensor performs reliably in complex biological matrices and pharmaceutical samples, making it a promising platform for future point-of-care diagnostics and pharmaceutical quality control applications. Figure 1

The widespread and often concurrent usage of acetaminophen (paracetamol, PCM) and amoxicillin (AMX) in clinical and over-the-counter medications has led to increased attention on their potential health risks and environmental impact. Overdose or improper disposal of these drugs contributes to toxicity in humans and contamination of water systems. Therefore, developing a sensitive, reliable, and cost-effective platform for the simultaneous detection of these pharmaceutical compounds is of utmost importance. In this study, we report the fabrication and application of a novel electrochemical sensor based on a Copper Oxide (CuO)/graphitic carbon nitride (GCN) hybrid nanocomposite for the selective detection of PCM and AMX in biological and environmental samples.The CuO/GCN composite was synthesized using a combination of thermal decomposition, hydrothermal, and sonochemical techniques. GCN was prepared through the thermal polymerization of melamine, followed by exfoliation via hydrothermal and ultrasonic treatment. CuO was synthesized by hydrothermal precipitation and subsequently calcined at 600°C. The composite was obtained by dispersing equal quantities of GCN and CuO and subjecting them to probe sonication. This hybrid material, characterized by UV–Vis spectroscopy, Fourier Transform Infra-Red spectroscopy (FTIR), X-ray Diffraction (XRD), High Resolution-Scanning Electron Microscopy (HRSEM), and Energy Dispersive Spectroscopy (EDS), displayed a layered, sheet-like structure with nanosized CuO particles uniformly embedded, leading to an increased electrochemically active surface area.A modified glassy carbon electrode (GCE) coated with the CuO/GCN composite was employed as the working electrode. The electrocatalytic behavior of this sensor toward PCM and AMX oxidation was evaluated using cyclic voltammetry (CV) and amperometry (AMP) in 0.1 M phosphate buffer solution (PBS, pH 7.4). The CuO/GCN-modified GCE exhibited a marked enhancement in peak currents with reduced overpotentials (0.48 V for PCM and 0.88 V for AMX) compared to bare or GCN-only modified electrodes, indicating excellent catalytic activity. The anodic peak currents increased linearly with analyte concentrations, confirming the electrode’s suitability for quantification.The simultaneous detection of PCM and AMX was effectively demonstrated, with linear responses observed in the range of 10–100 µM. Separate calibration experiments showed extended linear detection ranges from 0.025–939.15 µM for PCM and 0.025–8.55 µM for AMX, with limits of detection (LOD) calculated to be 6.8 nM and 12.9 nM, respectively. These values are among the lowest reported for non-enzymatic electrochemical sensors targeting these analytes. The sensor also exhibited fast response times (within 2 seconds), high repeatability (RSD < 2.5%), and excellent reproducibility across multiple fabricated electrodes (RSD ~3.2%).The influence of pH on oxidation behavior was investigated, showing optimal responses at physiological pH and indicating proton-coupled electron transfer mechanisms. Scan rate studies further revealed that the oxidation of PCM and AMX followed a diffusion-controlled process, with calculated electron transfer coefficients (α) of 0.58 for PCM and 0.78 for AMX, validating the electrocatalytic efficiency of the CuO/GCN system.To evaluate selectivity, the sensor was tested in the presence of common interfering ions and structurally similar molecules such as urea, glucose, chloramphenicol, and sulfamethazine. Even at fivefold higher concentrations, these interferents caused negligible signal variation (<5%), confirming the sensor’s high specificity for PCM and AMX. The excellent antifouling characteristics were attributed to the synergistic action between CuO nanoparticles and the nitrogen-rich framework of GCN, which enhances both conductivity and selective analyte adsorption.Real-world applicability was demonstrated through the analysis of spiked tap water and human urine samples using the standard addition method. The recovery rates were exceptionally high, ranging from 100.4% to 100.7% for PCM and 102.0% to 104.7% for AMX, with low relative standard deviations (RSDs < 4%). These results confirm the robustness and practical reliability of the sensor in complex matrices.Compared to other reported materials, such as AuNP-based sensors or those involving advanced polymers and metal–organic frameworks, the CuO/GCN hybrid system stands out for its simplicity, low cost, green synthesis approach, and high performance. The synergy between the p-type semiconductor CuO and the π-conjugated GCN matrix facilitates improved charge transfer and electron mobility, essential for fast and accurate sensing. Conclusion: This study presents a cost-effective, environmentally friendly, and highly efficient electrochemical sensor for the detection of two widely consumed pharmaceutical compounds. The CuO/GCN-modified GCE exhibits excellent sensitivity, selectivity, and stability for the simultaneous detection of PCM and AMX in both synthetic and real-world samples. These findings highlight the sensor’s potential for integration into portable, point-of-care diagnostic platforms and environmental monitoring systems aimed at tracking pharmaceutical residues. Future work may explore the integration of this nanocomposite into flexible substrates and its application toward the multiplexed detection of co-administered drugs in clinical settings. Figure 1

An efficient and eco-friendly indirect spectrophotometric method has been devised to determine the amount of atenolol in both pure form and in tablet formulations. This method relies on the oxidation of atenolol using an excess of standard potassium permanganate in an acidic medium. The remaining oxidant is determined by measuring the decrease in absorbance of toluidine blue dye at a suitable wavelength of 600 nm. The method followed Beer’s law across concentrations in the ranges of 0.5-14 µg/mL for atenolol with molar absorptivity of 1.6×104 L·mol-1·cm-1. The method proved effective in the estimation of atenolol in tablets, and the results were compared favorably with the standard addition method.

There is an urgent need for reference methodologies to assign SI traceable values to quality control (QC) materials for protein biomarkers to validate biochemical tests currently used in disease diagnosis and patient-specific therapeutics. Here we describe a novel methodology specifically developed for the SI traceable quantification of human serum ferritin light chain (FTL), an established biomarker for the diagnosis of iron-related disorders such as hemochromatosis. Natural and 34S isotopically enriched human FTL standards were recombinantly expressed using the HEK-293 mammalian cell system. Both standards were fully characterized for their total sulfur content, isotopic abundance, species distribution and primary sequence before using them for isotope dilution analysis (IDA). Treatment of serum spiked with FTL was optimized to selectively remove high abundant serum proteins without affecting significantly the integrity of the FTL. This was achieved by using methanol protein precipitation in combination with heat treatment and ultrafiltration. Complementary asymmetrical field-flow-fractionation (AF4) and anion-exchange high performance liquid chromatography (AE-HPLC) coupled to inductively coupled plasma mass spectrometry (ICP-MS) were used to monitor the impact of sample treatment on protein removal and FTL recovery. Both standards, natural and enriched, were used with the optimal sample treatment in a double species-specific isotope dilution analysis (SS-IDA) workflow for the determination of FTL in the WHO "4th International Standard for Ferritin" (NIBSC 19/118) resulting in a protein mass fraction of 11.0 with an expanded uncertainty (U, k = 2) of 1.0 μg mL-1 (RSU of 9.4%). The method was validated by standard addition experiments, and a full uncertainty budget was established. For the first time sulfur SS-IDA has been used to assign an SI traceable value to a relatively low abundance serum protein biomarker at supraphysiological concentrations in a WHO standard. This methodology will be invaluable for adding SI traceability to existing QC materials and for the certification of new biomarker reference materials.

This study aims to evaluate the performance of NoSQL databases in distributed cloud computing environments, addressing the lack of comprehensive benchmarking in this domain. Specifically, it investigates MongoDB and Riak KV, two widely used NoSQL systems, across diverse cloud platforms, including Google Cloud, DigitalOcean, and OpenStack. Using the Yahoo Cloud Serving Benchmark, we designed and implemented a benchmarking model to measure key performance indicators, including latency, throughput, and scalability, under varying workloads and data sizes. The analysis revealed that MongoDB integrated with Google Cloud consistently outperformed other configurations, demonstrating superior throughput and lower latency in read and write operations. In contrast, Riak Key Value generally exhibited higher latency, especially in scan-intensive workloads. To support practical decision-making, a decision tree model was developed based on empirical findings to guide optimal selection of cloud computing platforms and databases. The proposed benchmarking framework is modular and extensible, allowing adaptation to other NoSQL technologies, cloud providers, and performance metrics. This research presents a novel, systematic methodology for evaluating NoSQL database performance in cloud environments, providing actionable insights for selecting high-performing, scalable solutions in big data applications. This modular design enables the addition of more database technologies, deployment options, and performance standards in the future, thereby supporting broader research and real-world applications in distributed systems and cloud computing.

The main idea of this work was to investigate the voltammetric behavior of theophylline using cyclic voltammetry (CV), and to compare differential pulse voltammetry (DPV) and square wave voltammetry (SWV) for application in the development of a method for this analyte. The electrochemical results indicate that the homely printed sensor with a boron doped diamond electrode can significantly improve the electrocatalytic activity towards the oxidation of theophylline in 0.5 M sulfuric acid. After parameter optimization and comparison of the DPV and SWV methods, it was shown that both methods can effectively detect theophylline in the same concentration range from 3.8 to 27 µM. Slightly better analytical parameters in terms of detection limit and quantification limit were obtained by the SWV method and were 0.24 µM and 0.73 µM, respectively. In the case of DPV, the detection limit was 0.39 µM, while the quantification limit was at a value of 1.17 µM. The practical applicability was demonstrated through the development of the SWV method for the detection of theophylline in pharmaceutical formulations. The tests were performed in triplicate and using the standard addition method. Excellent agreement with the declared values showed that the proposed sensor can be a satisfactory alternative for fast, precise and accurate monitoring of theophylline concentration in real samples, with great potential for further modification and technology transfer for miniaturization and disposable sensing.

Challenges in quality and safety analysis of fresh chili and powder thereof.

Protein-based APIs represent a big group of modern therapeutics. Their characterization involves complex analytical protocols which require special methods, especially in the case when the protein drug is included into tablet dosage forms. Although the fluorescence polarization assay (FPA) is not currently regulated by many national Pharmacopeias, it represents a promising approach for protein drug standardization, considering their rapid, sensitive, and automatable detection suitable for high-throughput analysis and real-time quality control. To evaluate the applicability of FPA for the analysis of protein drugs in tablets, the quantifying of lysozyme in tablet dosage forms was studied by this method with the use of a fluorescently labeled synthetic chitooligosaccharide tracer. It was shown that this approach overcomes the limitations of the conventional turbidimetric assay of lysozyme determination, which is labor-intensive and relies on unstable reagents. Measurements were performed with both portable and stationary fluorescence polarization readers. Commercial tablets from five manufacturers containing lysozyme (20 mg) and pyridoxine hydrochloride (10 mg) together with other excipients were analyzed. The FPIA method showed a linear range of 5.0–70 µg/mL, with specificity confirmed by the absence of interference from excipients. Accuracy, evaluated by standard addition (10–20 mg), yielded recoveries of 100.2–106.0%. Placebo spiked with lysozyme at 80–120% of nominal content demonstrated recoveries of 98.0–100.1%, with RSD (n = 6) not exceeding 13.7%, indicating good precision. The developed method enables reliable lysozyme quantification in tablets, offering speed, simplicity, and robustness, and shows its suitability for the routine quality control of protein-containing dosage forms including the enzyme ones.

Cu,Fe,B/Cur-CDs with peroxidase- and ascorbic acid oxidase-like catalytic activity for dual-signal fluorescence sensing of metronidazole.

Phosphorus in the form of phytic acid or myo-inositol hexakisphosphate is not absorbable by animals, leading to decreased bioavailability of essential minerals such as iron, zinc, and calcium. This study aimed to develop and validate a simple and efficient method for measuring inositol phosphates in soybeans. The four types of inositol phosphates analyzed were D-myo-inositol-1,5,6-triphosphate, D-myo-inositol-1,4,5,6-tetraphosphate, D-myo-inositol-1,3,4,5,6-pentaphosphate, and D-myo-inositol-1,2,3,4,5,6-hexakisphosphate using high pressure ion chromatography. For method validation, we assessed specificity, linearity, limit of detection, limit of quantification, precision, and accuracy for the four inositol phosphate types. Calibration curves for each inositol phosphate indicated high linearity (r2≥0.9999). The intra and interday precision of the assays ranged from 0.22% to 2.80% and 1.02% to 8.57%, respectively. Recoveries measured using the standard addition method in soybeans varied from 97.04% to 99.05%. Accordingly, the analytical method was validated for detecting inositol phosphates in soybeans. Our results provide data on the phytic acid content of wild type and gene-edited soybeans by measuring individual inositol phosphates, which is expected to aid in breeding soybeans with reduced phytic acid levels.

Extrusion 3D printing has advanced the manufacturing of complex liquid crystal elastomer (LCE) architectures. In parallel, donor-acceptor Stenhouse adducts (DASAs), a class of white-light-responsive photoswitches, have enabled both photochemical and photothermal LCE actuation. However, DASA-LCEs have yet to be extruded and 3D-printed. Two key challenges exist: DASA's inherent sensitivity to heat and radicals can lead to degradation during ink preparation and printing, and small changes in the concentration of the added DASA component impact the properties of the extrudable ink, requiring reoptimization of well-established 3D-printing protocols. To overcome these challenges, we present a post-printing functionalization strategy that circumvents these limitations. Residual secondary amines, inherent to inks synthesized via standard aza-Michael addition, serve as active sites for covalent attachment of DASA photoresponsive groups following printing and cross-linking. Our method means that DASAs can be directly grafted onto 3D-printed aza-Michael LCEs without modifying the ink formulation or processing. The resulting DASA-LCEs exhibit wavelength tunability within the visible range and a variety of photothermal and photochemical responses. The post-functionalization can occur within 2 min and enables spatial control of the DASA concentration, producing films with tunable color gradients and locally varied photothermal and photochemical responses under visible light. This approach enables the rapid fabrication of DASA-based light-responsive LCEs using established ink formulations with the potential for the design of complex 3D architectures.

A novel and meticulously optimised continuous flow injection analysis (CFIA) protocol was developed for the spectrophotometric quantification of ascorbic acid using a locally engineered optical system. The detection unit incorporated eight blue light-emitting diodes (LEDs) arranged in a matrix geometry distributed across two angular regions: 0–90° and 0–180°, while dual solar cells served as photonic detectors. Spectral measurements were specifically conducted at 0–180°, yielding enhanced absorbance stability and signal quality. Based on a redox-induced quenching mechanism, the system utilises a chromogenic FeSCN2+ complex, formed in situ through the controlled mixing of ferric (Fe3+) and thiocyanate (SCN−) ions under strictly maintained physical and chemical conditions. Upon interaction at the Y-point junction, injected ascorbic acid reduces the complex, yielding a quantifiable decrease in absorbance intensity proportional to its concentration. A linear calibration range was established from 0.5 to 40 mmol L−1 (r2 = 0.9986), LOD of 0.05 mmol L−1 (1.3209 μg per sample) (S/N = 3) and LOQ of 0.131 mmol L−1 (S/N = 10). Method precision was evaluated at two concentrations, 12 and 30 mmol L−1, showing intra-day RSD% < 1% and inter-day RSD% < 2%, affirming excellent repeatability and method reliability. Validation was extended to three commercial pharmaceutical preparations containing 500 mg of ascorbic acid using the standard addition method. Comparative assessment against UV spectrophotometry and HPLC, with statistical evaluation via Student's t-test and one-way ANOVA, confirming no significant differences among techniques (t_cal < t_tab; F_cal < F_tab, α = 0.05), with recovery values between 97.13% and 103.6%.

This study introduces a facile and sensitive ratiometric electrochemical sensor based on the modification of a screen-printed carbon electrode (SPCE) with poly(methylene blue) (PMB) and reduced graphene oxide-carbon nanotube (rGO-CNT) nanocomposites for the simultaneous detection of uric acid (UA) and xanthine (XT). PMB, used as an internal reference, was prepared via electropolymerization on the rGO-CNT/SPCE synthesized through electrodeposition/co-reduction. The PMB/rGO-CNT/SPCE was characterized using field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and electrochemical impedance spectroscopy. The electrochemical behavior of UA and XT on PMB/rGO-CNT/SPCE was evaluated using cyclic voltammetry and square wave voltammetry (SWV). The optimal experimental parameters were determined by the Taguchi method. The sensor displayed a detection limit of 2.1 μM for UA and 1.3 μM for XT, and exhibited excellent selectivity and reproducibility, using ratiometric signals from SWV. Tests on real samples were conducted using the standard addition method with a bovine serum albumin solution and human serum. Furthermore, the PMB/rGO-CNT/SPCE sensor proved to be both environmentally friendly and practical. Therefore, the PMB/rGO-CNT/SPCE sensor is a reliable and effective tool for detecting UA and XT, applicable to the diagnosis, treatment, and management of related diseases.

This research involved the design, preparation, and both structural and fluorescent characterization of a novel fluorescent probe (probe 2) for H2S detection in human blood serum as well as in samples from patients with hypertension. The fluorophore 1,8-naphthalimide was selected, while an azide group served as the chemical reactive site for H2S. To increase the bioavailability of the prepared fluorescent probe, the basic 1,8-naphthalimide scaffold was modified by introducing a 2-aminopropane-1,3-diol (serinol) moiety. Fluorescence spectra were recorded to evaluate the effects of pH, time, selectivity, and H₂S concentration on fluorescence intensity. The detection limit of the target fluorescent probe was found to be 0.16 µmol L-1. Probe 2 was successfully employed for the detection of H₂S in human blood serum, with a measured concentration of 17.98 µmol L⁻¹. The accuracy of H₂S quantification was validated using the standard addition method and confirmed by UV-Vis spectrophotometry employing the methylene blue assay, whereby the concentration was found to be 17.32 µmol L⁻¹. Ultimately, probe 2 was utilized to determine H₂S levels in samples from patients with hypertension, revealing decreased concentrations relative to the concentration observed in a human serum sample as a healthy control.