Limit Of Detection Values Research Articles

Comparison of EV characterization by commercial high-sensitivity flow cytometers and a custom single-molecule flow cytometer.

High-sensitivity flow cytometers have been developed for multi-parameter characterization of single extracellular vesicles (EVs), but performance varies among instruments and calibration methods. Here we compare the characterization of identical (split) EV samples derived from human colorectal cancer (DiFi) cells by three high-sensitivity flow cytometers, two commercial instruments, CytoFLEX/CellStream, and a custom single-molecule flow cytometer (SMFC). DiFi EVs were stained with the membrane dye di-8-ANEPPS and with PE-conjugated anti-EGFR or anti-tetraspanin (CD9/CD63/CD81) antibodies for estimation of EV size and surface protein copy numbers. The limits of detection (LODs) for immunofluorescence and vesicle size based on calibration using cross-calibrated, hard-dyed beads were ∼10 PE/∼80nm EV diameter for CytoFLEX and ∼10 PEs/∼67nm for CellStream. For the SMFC, the LOD for immunofluorescence was 1 PE and ≤ 35nm for size. The population of EVs detected by each system (di-8-ANEPPS+/PE+ particles) differed widely depending on the LOD of the system; for example, CellStream/CytoFLEX detected only 5.7% and 1.5% of the tetraspanin-labelled EVs detected by SMFC, respectively, and median EV diameter and antibody copy numbers were much larger for CellStream/CytoFLEX than for SMFC as measured and validated using super-resolution/single-molecule TIRF microscopy. To obtain a dataset representing a common EV population analysed by all three platforms, we filtered out SMFC and CellStream measurements for EVs below the CytoFLEX LODs as determined by bead calibration (10 PE/80nm). The inter-platform agreement using this filtered dataset was significantly better than for the unfiltered dataset, but even better concordance between results was obtained by applying higher cutoffs (21 PE/120nm) determined by threshold analysis using the SMFC data. The results demonstrate the impact of specifying LODs to define the EV population analysed on inter-instrument reproducibility in EV flow cytometry studies, and the utility of threshold analysis of SMFC data for providing semi-quantitative LOD values for other flow cytometers.

Designing Fe8-N2 Catalytic Sites of Nitrogen-Doped Iron-Based Nanoparticles with Oxidase-Like Activity: Characterization, Calculation and Application.

Designing metal nanoparticles with oxidase-mimicking capabilities has garnered significant attention due to their promising attributes. However, understanding the intricate catalytic mechanisms underlying these nanoparticles poses a formidable challenge. In this study, a straightforward pyrolysis procedure was employed to synthesize nitrogen-doped iron-based nanoparticles (Fe NPs-N@C) with Fe8-N2 serving as active sites. The confirmation of these sites was thoroughly confirmed through density functional theory (DFT) calculations complemented by experimental validation. The resulting Fe NPs-N@C nanoparticles, averaging 5.45 nm in size, exhibited excellent oxidase-mimicking activity, with vmax=1.11×10-7 M s-1and km=1.67 mM, employing 3,3',5,5'-tetramethylbenzidine as a substrate. The oxidation pathway and catalytic mechanism of Fe NPs-N@C involved 1O2⋅ radicals, validated through electron paramagnetic resonance analysis and DFT calculations. Furthermore, Fe NPs-N@C/TMB system was devised for ascorbic acid and nitrite quantitative detection. This method demonstrated the capability to detect ascorbic acid within concentrations ranging from 1 to 55 μM, with a limit of detection (LOD) of 0.81 μM, and nitrite within concentrations from 1 to 160 μM, with a LOD value of 0.45 μM. These findings offer a comprehensive understanding of the catalytic mechanisms of Fe NPs-N@C nanoparticles at the atomic level, along with its potential for colorimetric sensor in future.

Dye‐based recombinase‐aided amplification assay with enhanced sensitivity and specificity

AbstractObjectiveFluorescent recombinase‐aided amplification (RAA) assays are increasingly being used in the detection of a variety of pathogens and have the advantages of rapidity and simplicity and similar sensitivity and specificity, compared with real‐time PCR (qPCR) assays, but they require a complex probe design. To eliminate the addition of fluorescent probes for RAA, an EvaGreen dye‐based recombinase‐aided amplification (EvaGreen‐RAA) assay using self‐avoiding molecular recognition system (SAMRS) primers was developed.MethodsThe SAMRS primers effectively avoided the production of primer dimers, thus improving the detection sensitivity, while EvaGreen dye was used to quantitatively measure the amplified products in real time. Using Staphylococcus aureus (SA) and Listeria monocytogenes (LM) as examples, EvaGreen‐RAA with SAMRS primers was developed. As a reference and comparison, a traditional fluorescence probe RAA method and a RAA with SAMRS primers (SAMRS‐RAA) for detecting SA and LM were also investigated. Serial dilutions of recombinant plasmids were used to evaluate the sensitivity of the assays. Unenriched and enriched simulated milk samples were used to evaluate the limits of detection (LOD) of these methods. Using high‐resolution melting (HRM) was used to explore the sensitivity of the dual EvaGreen‐RAA assay.ResultsThe sensitivity of the fluorescent RAA method for detecting SA and LM was 10 copies/μL using plasmids and the sensitivity of the SAMRS‐RAA and EvaGreen‐RAA for detecting SA and LM plasmids was 1 copies/μL. The LOD values of the EvaGreen‐RAA for SA and LM in unenriched simulated milk samples were 100 and 50 CFU/mL, respectively, and the LOD value for both SA and LM using enriched simulated milk samples was 10 CFU/mL. EvaGreen‐RAA had linear amplification in real time in the range of 1–105 copies/μL of the plasmids of SA and LM. The sensitivity of the dual EvaGreen‐RAA assay for SA and LM was estimated to be 102 CFU/mL.ConclusionA real‐time quantitative EvaGreen‐RAA method for detecting SA and LM was developed, which eliminates the need to design complex RAA probes. This dye‐based RAA with SARMS primers provides a new strategy for simplifying fluorescence probe RAA and allowing the detection of multiple pathogens, which has many potential applications.

Selective determination of Fe (III) with carbon dots as photoluminescence Probes: Chemometric analysis using Excitation-Emission matrices

The selective and accurate determination of metal ions, crucial in various physiological processes within the human body, is of paramount importance, particularly when these ions, such as Fe(III), coexist with others in the sample. The manuscript addresses the challenge of determining Fe(III) selectively in the presence of interfering species. To achieve this, carbon dots (CDs) are employed as photoluminescence probes due to their biocompatibility and low cytotoxicity. The chemometric analysis of photoluminescence (PL) data was used to overcome selectivity challenges associated with CDs. This study utilized fluorescence excitation-emission matrices (EEMs), considered as second-order data, and applied unfolded partial least squares followed by residual bilinearization (U-PLS/RBL) to account for uncalibrated species.The developed model methodology was assessed using spiked samples containing uncalibrated and interfering species, namely Al(III), Pb(II) and Ni(II), at different concentration levels. The achieved limits of detection (LOD) and quantification (LOQ) at 0.02 and 0.06 mmol/L, respectively, highlight the high sensitivity of the approach. Notably, the application of one RBL component significantly reduces RMSEP values in samples spiked individually with each uncalibrated and interfering species, demonstrating the methodology’s effectiveness in overcoming strong interactions with CDs. Interestingly, this reduction was not observed in test samples containing only Fe(III), where optimal results were achieved without the application of the RBL component.This study introduces a novel approach by formulating a selective methodology for the determination of Fe(III) in the presence of interfering species, employing carbon dots (CDs) as photoluminescence probes. The application of chemometric analysis, specifically U-PLS/RBL, to mitigate selectivity challenges, coupled with the demonstrated sensitivity characterized by low LOD and LOQ values, emphasizes the scientific significance of this research. The results highlight the practical viability of the methodology, particularly in complex samples, contributing valuable insights to the field.

Preparation of pyridoxine-based polyurethane modified sensors and their use in simultaneous determination of Cu(II) – Co(II) ions

In this study, pyridoxine-based polyurethane-modified electrodes were prepared to simultaneously and sensitively measure copper (Cu(II)) and cobalt (Co(II)) ions in complex matrix samples. For the production of the electrodes, firstly, the synthesis of pyridoxine-based polyurethane structures was carried out. In these syntheses, the polymer structure was diversified by using different isocyanates. Polyethyleneglycol-200 (PEG), pyridoxine (B6), and β-cyclodextrin (β-CD) groups were used as the source of polyol. The synthesized polyurethane structures were characterized by different instrumental techniques and used in gold electrode surface modification. Modified sensor surfaces were examined by scanning electron microscopy and atomic force microscopy techniques. The prepared modified sensors were used for the simultaneous detection of Cu(II) and Co(II) ions using the differential pulse voltammetry technique. The limit of detection (LOD), limit of quantitation (LOQ), and R2 values for Cu(II) ions were calculated as 8.81 μM, 29.4 μM, and 0.993, respectively. LOD, LOQ, and R2 values for Co(II) ions were calculated as 9.84 μM, 32.8 μM, and 0.9935, respectively. For repeatability, the relative standard deviation (RSD %) of the prepared simultaneous sensors was determined as 1.54 and 1.71 for Cu(II) and Co(II), respectively. As a result, Cu(II) and Co(II) ions were measured independently and simultaneously with high sensitivity. According to these results, it is predicted that pyridoxine-based polyurethane-modified sensors may be suitable for the simultaneous detection of Cu(II) and Co(II) in medical, food, and agricultural samples.

Ambipolar Heterojunction Sensors: Another Way to Detect Polluting Gases.

Gas sensors based on ambipolar materials offer significant advantages in reducing the size of the analytical system and enhancing its efficiency. Here, bilayer heterojunction devices are constructed using different octafluorinated phthalocyanine complexes, with Zn and Co as metal centers, combined with a lutetium bisphthalocyanine complex (LuPc2). Stable p-type behavior is observed for the ZnF8Pc/LuPc2 device under both electron-donating (NH3) and -oxidizing (NO2 and O3) gaseous species, while the CoF8Pc/LuPc2 device exhibits n-type behavior under reducing gases and p-type behavior under oxidizing gases. The nature of majority of the charge carriers of Co-based devices varies depending on the nature of target gases, displaying an ambipolar behavior. Both heterojunction devices demonstrate stable and observable response toward all three toxic gases in the sub-ppm range. Remarkably, the Co-based device is highly sensitive toward ammonia with a limit of detection (LOD) of 200 ppb, whereas the Zn-based device demonstrates exceptional sensitivity toward oxidizing gases, with excellent LOD values of 4.9 and 0.75 ppb toward NO2 and O3, respectively, which makes it one of the most effective organic heterojunction sensors reported so far for oxidizing gases.

Ionic-liquid/Carbowax 20 M functionalized capsule phase microextraction platform for the extraction of phosphodiesterase-5 inhibitors from human serum and urine prior to their determination by LC–MS

Capsule phase microextraction (CPME) is an efficient bioanalytical technique that streamlines the sample preparation by integrating the filtration and stirring mechanism directly into the device. A novel composite sorbent designed to be selective towards the target analytes consisting of mixed-mode sorbent chemistry synthesized by sol–gel technology is found promising and superior to the conventional C18 sorbents. Herein we describe the encapsulation of an ionic liquid (IL)/Carbowax 20M-functionalized sol–gel sorbent (sol–gel IL/Carbowax 20 M) in the lumen of porous polypropylene tubes for the capsule phase microextraction of three phosphodiesterase-5 inhibitors namely avanafil, sildenafil, and tadalafil in human serum and urine samples. The CPME device was characterized by Scanning Electron Microscopy (SEM) and Fourier-Transform Infrared Spectroscopy (FT-IR). The experimental parameters of CPME procedure (e.g. sample pH and ionic strength, extraction time, stirring rate, elution solvent and volume) were carefully optimized to achieve the highest possible extraction efficiency for the analytes. Method validation was conducted in terms of precision, linearity, accuracy, matrix effect, lower limits of quantification, and limits of detection (LOD). The method linearity was investigated in the range of 50–1000 ng mL−1 for all analytes while the precision was less than 11.8 % in all cases. For all analytes, the LOD values were 17 ng mL−1. The IL/CW 20M-functionalized microextraction capsules could be reused at least 25 times both for urine and serum samples. The green character and the applicability of the proposed method were evaluated using the ComplexGAPI and BAGI indexes. The optimized CPME protocol exhibited reduced consumption of organic solvent and generation of waste, cost-effectiveness, and simplicity. Finally, the proposed method was successfully applied to the analysis of sildenafil in human urine after administration of drug-containing formulation.

Metal-free Carbon Material Derived from Lantana Camara for the Detection and Removal of Ciprofloxacin.

This work reports the preparation of a metal-free nitrogen and sulphur functionalized graphitic carbon sheets from a unique and less expensive precursor Lantana camara, which is a common hazardous weed in India. The synthesized material NS-CN-180 was successfully tested for the adsorption and removal of fluoroquinolone antibiotics ciprofloxacin. The surface morphology and elemental composition of NS-CN-180 were investigated through FESEM and XPS analyses. The SEM data reveals the graphitic sheets stacked onto each other with cavities in between them. The presence of various functional groups was identified through FT-IR spectroscopy and the degree of graphitization was calculated from XRD pattern. The probable mechanism of interaction for ciprofloxacin molecule with NS-CN-180 was also investigated with the help of FT-IR and zeta potential analyses. The fabricated material was found to be excellent for ciprofloxacin detection with a limit of detection value 16.08nM. Also, the prepared material efficiently removes the 66.2% ciprofloxacin drug in 1h. Adsorption and desorption experiments were performed to demonstrate the reusability of the material.

Estimating LoD-s Based on the Ionization Efficiency Values for the Reporting and Harmonization of Amenable Chemical Space in Nontargeted Screening LC/ESI/HRMS.

Nontargeted LC/ESI/HRMS aims to detect and identify organic compounds present in the environment without prior knowledge; however, in practice no LC/ESI/HRMS method is capable of detecting all chemicals, and the scope depends on the instrumental conditions. Different experimental conditions, instruments, and methods used for sample preparation and nontargeted LC/ESI/HRMS as well as different workflows for data processing may lead to challenges in communicating the results and sharing data between laboratories as well as reduced reproducibility. One of the reasons is that only a fraction of method performance characteristics can be determined for a nontargeted analysis method due to the lack of prior information and analytical standards of the chemicals present in the sample. The limit of detection (LoD) is one of the most important performance characteristics in target analysis and directly describes the detectability of a chemical. Recently, the identification and quantification in nontargeted LC/ESI/HRMS (e.g., via predicting ionization efficiency, risk scores, and retention times) have significantly improved due to employing machine learning. In this work, we hypothesize that the predicted ionization efficiency could be used to estimate LoD and thereby enable evaluating the suitability of the LC/ESI/HRMS nontargeted method for the detection of suspected chemicals even if analytical standards are lacking. For this, 221 representative compounds were selected from the NORMAN SusDat list (S0), and LoD values were determined by using 4 complementary approaches. The LoD values were correlated to ionization efficiency values predicted with previously trained random forest regression. A robust regression was then used to estimate LoD values of unknown features detected in the nontargeted screening of wastewater samples. These estimated LoD values were used for prioritization of the unknown features. Furthermore, we present LoD values for the NORMAN SusDat list with a reversed-phase C18 LC method.

Fast Determination of Fat-soluble Vitamins in Pharmaceutical Preparations by High-Performance Liquid Chromatography

Background: Vitamins are needed for the healthy functioning of the body. When these vitamins are not in sufficient amounts in the body, they are usually taken externally with pharmaceutical preparations. Taking vitamins into the body in the right amounts is possible by analyzing the amounts in pharmaceutical preparations with validated methods. Methods: In this study, a fast, simple, easily applicable, and selective normal-phase HPLC method was developed for the simultaneous determination of fat-soluble A, D3, E, and K1 vitamins in pharmaceutical preparations from syrup and tablets. Separation of the vitamins was carried out on a Zorbax CN column (250 x 4.6 mm, 5 µm) using a mixture of hexane-isopropyl alcohol (98:2, v/v) at 30°C column temperature and 1 ml/min flow rate. The detection wavelength is 280 nm. The developed method has been validated according to ICH Harmonised Tripartite Guideline Validation of Analytical Procedures: Text and Methodology Q2(R1) rules. Results: Calibration graphs are linear over the range of 10-1000 µg ml-1 , 1-50 µg ml-1 , 10-2000 µg ml-1 , 0.5-20 µg ml-1, and the limit of detection values were found to be 1.496, 0.280, 1.388 and 0.040 µg ml-1 for A, D3, E and K1 vitamins, respectively. Relative standard deviation values, which express within-day and between-day repeatability, were found below 2.54%. Average recovery values were also found at about 100.28, 101.46, 100.65, and 100.29% for A, D3, E, and K1 vitamins, respectively Conclusion: The developed and validated method was successfully applied to the simultaneous analysis of fat-soluble vitamins A, D3, E, and K1 in pharmaceutical preparations in syrup and tablet form.

Application of a Green Deep Eutectic Solvent for Preconcentration and Determination of Copper and Cadmium in Food, Cosmetic, and Water Samples

Background:: Determination of environmental pollutants is important due to their harmful effects on the health of living organisms. However, direct measurement of many of these pollutants is not possible due to their low concentrations, which necessitates the need for sample preparation methods. One of the rapid and simple sample preparation methods is the Air-Agitated Liquid-Liquid Microextraction (AALLME) method, which requires toxic organic solvents that can lead to environmental pollution. Therefore, finding green solvents like Deep Eutectic Solvents (DESs) to replace them can be investigated. Methods:: A novel Deep Eutectic Solvent (DES) was synthesized from a combination of choline chloride and 2-phenylethanol with a molar ratio of 1:4, and it was examined using FT-IR analysis. This solvent was used in an AALLME method for measuring copper and cadmium heavy metal ions in complex real samples with Flame Atomic Absorption Spectroscopy (FAAS). Results:: The influential parameters of this method, such as solution pH (5.4), extraction cycles (12), and extraction solvent volume (440 μL), were optimized utilizing central composite design (CCD). Underneath the optimized circumstances, the detection limits for Cu2+ and Cd2+ were 0.14 and 0.09 ng mL-1, and the linear dynamic range was 0.47-50.0 and 0.32-22.5 ng mL-1, respectively. The preconcentration factors for these cations were 139.7 and 133.4, respectively. Conclusion:: Combining this novel green solvent and rapid sample preparation method for the preconcentration and determination of the studied heavy metal ions has shown promising results in terms of enrichment factors and detection limit values.

Techniques for quantification of organochlorine pesticides from a validated method by using gas chromatography-electron capture detector

Organochlorine pesticides (OCPs) are persistent organic compounds found in aquatic environments worldwide. A well-validated and well-established analytical method is crucial for detecting OCPs in the environment. In this study, an analytical method for quantifying OCPs in water was developed and evaluated. Here, the range of linearity, reproducibility, uncertainty, specificity, method detection limits (MDL), and special emphasis on detection and quantitation limits were assessed. Recovery studies were performed to measure the accuracy and precision of the method. This method exhibited excellent linearity in the range of 2.5–20 μg/L for all compounds. As none of the targeted compounds was detected in the chromatograms of the blank sample with no baseline noise, the limits of detection (LOD) and limits of quantification (LOQ) were determined using the linear regression method, external calibration curve slope, and laboratory fortified blank-based detection. All compounds showed different LOD and LOQ values, depending on the approach used. In particular, endosulfan sulfate, methoxychlor, endrin ketone, H. epoxide, heptachlor, and 4,4ʹ-DDT exhibited high detection limits. The recovery percentage of the 15 compounds at 5 μg/L spiked concentration was between 50 and 150 %, which is consistent with the accuracy of the APHA method. Except for endosulfan sulfate, the relative standard deviations of all other compounds were below 20 %, indicating good precision. This method has also been applied to real water samples. This validation technique is reliable, sensitive, simple, rapid, easy to comprehend, and reproducible. The application of this method in the real water samples was also conducted. Only α-BHC and γ-Chlordane were detected in the water sample.

Fabrication and evaluation of a plasmonic biosensor based on silica-coated gold nanorods for highly-sensitive detection of anti-Müllerian hormone

Anti-müllerian hormone is a crucial biomarker for reproductive potential, but current detection methods are not cost-effective or time-efficient. In this study, we set out to develop a biosensor using gold nanorods (Au-NRs) coated with a functionalized silica network. The biosensor structure was completed by covalently binding the anti-Müllerian hormone antibody to SiO2@Au-NRs. We confirmed the proper coating of the gold nanorods using HR-TEM, EDS/EDAX, zeta potential, and FT-IR analysis. To assess the sensitivity of SiO2@Au-NRs, we analyzed the LSPR peak position redshift in different concentrations of ethylene glycol. The biosensor was then used to recognize the AMH antigen and determine the limit of detection (LoD) and quantification (LoQ) for the biosensor. Our research has shown that the SiO2@Au-NRs have a suitable thickness. The SiO2@Au-NRs demonstrated impressive sensitivity as a nano biosensor. The AMH antigen identification results indicated that the nano biosensor was highly sensitive. The LoD and LoQ values were 0.086 and 0.262 ng ml−1, respectively, very close to the values obtained by the ELISA kit. Furthermore, LSPR biosensors have reduced detection costs and measurement time. Their high sensitivity makes them excellent candidates for use in diagnostic kits.

Spectrophotometric determination of the Levofloxacin using green nanochemistry applications

In this study, a simple, rapid and accurate spectrophotometric method was proposed for the determination of the Levofloxacin using Nickel Oxide nanoparticles NiONPs (which were synthesized in a green way using dried mint leaves extract), It gave the highest value of absorption at 294 nm wavelength , and the linear relationship followed the Beer-Lambert law in the range of concentrations (2-24 µg/mL) with a good correlation coefficient, where its value was R = 0.9996 which indicates good linearity, the value of the molar absorptivity =2.9704×104 L/mol.cm , and the value of the Sandell’s significance = 0.0122 µg/cm2 . The validity of the proposed method was validated statistically and quantitatively, as the detection limit value = 0.2799 µg/mL and the quantitative limit value =0.9330 µg/mL. The method proved to be of good accuracy and precision, as the recovery rate was %Rec =98.05, and the relative standard deviation %RSD did not exceed 0.42 . The formation of these particles was tested using FT-IR technology and scanning electron microscopy (SEM), and the binding of the drug to the nanoparticles was confirmed by using UV-VIS spectroscopy

A rapid method to monitor structural perturbations of high-concentrated therapeutic antibody solutions using Intrinsic Tryptophan Fluorescence Emission spectroscopy

Drug product development of therapeutic antibody formulations is still dictated by the risk of protein particle formation during processing or storage, which can lead to loss of potency and potential immunogenic reactions. Since structural perturbations are the main driver for irreversible protein aggregation, the conformational integrity of antibodies should be closely monitored. The present study evaluated the applicability of a plate reader-based high throughput method for Intrinsic Tryptophan Fluorescence Emission (ITFE) spectroscopy to detect protein aggregation due to protein unfolding in high-concentrated therapeutic antibody samples. The impact of fluorophore concentration on the ITFE signal in microplate readers was investigated by analysis of dilution series of two therapeutic antibodies and pure tryptophan. At low antibody concentrations (< 5 mg/mL, equivalent to 0.8 mM tryptophan), the low inner filter effect suggests a quasi-linear relationship between antibody concentration and ITFE intensity. In contrast, the constant ITFE intensity at high protein concentrations (> 40 mg/mL, equivalent to 6.1 mM tryptophan) indicate that ITFE spectroscopy measurements of IgG1 antibodies are feasible in therapeutically relevant concentrations (up to 223 mg/mL). Furthermore, the capability of the method to detect low levels of unfolding (around 1 %) was confirmed by limit of detection (LOD) determination with temperature-stressed antibody samples as degradation standards. Change of fluorescence intensity at the maximum (ΔIaM) was identified as sensitive descriptor for protein degradation, providing the lowest LOD values. The results demonstrate that ITFE spectroscopy performed in a microplate reader is a valuable tool for high-throughput monitoring of protein degradation in therapeutic antibody formulations.

Chronocoulometric Quantum Dot Aptasensor for SARS‐CoV‐2 Nucleocapsid Protein Biomarker

AbstractFor the first time, a novel mercaptosuccinic acid‐capped tungsten telluride quantum dot (MSA‐WTe3‐QD)‐based electrochemical aptasensor was designed for the determination of SARS‐CoV‐2 N‐protein in synthetic human serum, plasma and urine. The MSA‐WTe3‐QD which exhibited spherical morphology and an average diameter of 3.56 nm were synthesized through a bottom‐up approach. The aptasensor was prepared by firstly immobilizing MSA‐WTe3‐QD on a screen‐printed carbon electrode (SPCE) by using the 1‐ethyl‐3‐(3‐dimethylaminopropyl)carbodiimide/N‐hydroxysuccinimide (EDC/NHS) coupling chemistry. Thereafter, amine‐terminated 90‐mer ssDNA aptamer was deposited on the modified SPCE and left to cure to form the aptasensor. Using the chronocoulometry signal transduction technique, the aptasensor's calibration with N‐protein gave a linear range value of 1–9 pg.mL−1 and a limit of detection (LOD) value of 0.08 pg.mL−1. The LOD value of the aptasensor was 8 times lower than the LOD value of 0.71 pg.mL−1 obtained with a commercial N‐protein ELISA kit. When tested in simulated real samples the aptasensor recovery rates of 95–103.33 % were obtained. In the presence of various interferents, the aptasensor displayed good selectivity to N‐protein.

Three robust luminescent Cd(II) coordination polymers as multi-responsive fluorescent sensors for Cu2+, Hg2+, levofloxacin, and acetylacetone in water

Employing coordination polymers (CPs) developing effective organic contaminants and heavy metal ions luminescent detection systems is an ongoing challenge. Three ternary Cd(II) CPs namely [Cd(MIP)(L)0.5(H2O)]n (1), [Cd2(TPA)2(L)(H2O)]n (2), and [Cd2(DCTP)2(L)(H2O)]n (3), (L = 1,6-bis(2-((1H-imidazol-1-yl)methyl)-1H-benzo[d]imidazol-1-yl)hexane, H2MIP = 5-methylisophthalic acid, H2TPA = terephthalic acid, and H2DCTP = 2,5-dichloroterephthalic acid) containing new L ligands, were hydrothermally synthesized and characterized. 1 displays a (4,4)-connected 4,4L28 layer and further extended into the 3D supramolecular framework via π−π stacking interactions. 2 exhibits a (4,4,5)-connected trinodal network with the point symbol of {42.5.62.8}{42.52.72}{42.53.62.73}2. 3 takes on a (3,5,6)-connected framework with the point symbol {3.42.52.7}{3.82}2{33.44.5.62.82.92.10}2. 1 − 3 show highly good thermal stability, and highly acid-base tolerance. The limits of detection (LOD) of 1 − 3 were calculated as follows: for Cu2+, the LODs are 8.92 × 10−8, 5.74 × 10−7, and 9.37 × 10−8 mol L−1, respectively; for Hg²⁺, the LOD values are 3.73 × 10−7, 5.22 × 10−7, and 8.45 × 10−7 mol L−1, respectively. Regarding levofloxacin (LEV), the LODs for 1 − 3 were found to be 5.11 × 10−8 mol L−1, 2.45 × 10−8 mol L−1, and 8.54 × 10−8 mol L−1, respectively. Finally, for acetylacetone (acac), the LODs of 1 − 3 are 5.53 × 10−6, 5.66 × 10−6, and 1.23 × 10−6 mol L−1, respectively. 1 − 3 represent the first examples of exceptional multi-responsive sensing platforms for the detecting of Cu2+, Hg2+, LEV, and acac with high sensitivity, outstanding anti-interference abilities, and low LODs. The possible sensing mechanisms were investigated in detail.

Lutetium Copper@Hexagonal Boron Nitride Nanocomposite Electrode System for Sensing and Signalling Ciprofloxacin

AbstractHerein, a new electrochemical sensing system based on lutetium copper nanoparticles supported on hexagonal boron nitride (Lu‐Cu@h‐BN) was designed for the sensitive detection of ciprofloxacin (CIP) antibiotic. A simple hydrothermal method was used to synthesize the nanocomposite. The structural and morphological characteristics of the as‐prepared nanocomposite were investigated using various analytical techniques such as Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), scanning electron microscopy (SEM), and X‐ray photoelectron spectroscopy (XPS). The newly developed Lu‐Cu@h‐BN nanocomposite was used as an electrode modifier for sensing and signalling of CIP. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to study the electrochemical activities of the bare GCE, Cu‐h‐BN/GCE, Lu‐h‐BN/GCE, Lu‐Cu/GCE, and Lu‐Cu@h‐BN/GCE. The electro‐oxidation of CIP on electrode surface exhibited an irreversible, diffusion‐controlled process. The sensor system obtained a wider linear range of (0.05–100 μM) with a lower detection limit value of 0.03 μM and sensitivity 0.7443 μA μM−1 cm−2. Furthermore, the sensor demonstrated an excellent selectivity, good stability, and reproducibility, with acceptable recoveries of 96 % to 104 % in real water sample analysis.

Rapid sequential determination of the explosives 2,4,6-trinitrotoluene and cyclotrimethylenetrinitramine in forensic samples employing a graphite sheet sensor and cyclic square-wave stripping voltammetry.

The development of a portable analytical procedure is described for rapid sequential detection and quantification of the explosives 2,4,6-trinitrotoluene (TNT) and cyclotrimethylenetrinitramine (RDX) in forensic samples using a graphite sheet (GS). A single GS platform works as a collector of explosive residues and detector after its assembly into a 3D-printed cell. The detection strategy is based on cyclic square-wave stripping voltammetry. The cathodic scan from + 0.1 to -1.0V with accumulation at 0.0V enables the TNT detection (three reduction peaks), and the anodic scan from + 0.2 to + 1.55V with accumulation at -0.9V provides the RDX detection (two oxidation processes). Low detection limit values (0.1 µmol L-1 for TNT and 2.4 µmol L-1 for RDX) and wide linear ranges (from 1 to 150 µmol L-1 for TNT and from 20 to 300 µmol L-1 for RDX) were obtained. The sensor did not respond to pentaerythritol tetranitrate (PETN), which was evaluated as a potential interferent, because plastic explosives contain mixtures of TNT, RDX, and PETN. The GS electrode was also evaluated as a collector of TNT and RDX residues spread on different surfaces to simulate forensic scenarios. After swiping over different surfaces (metal, granite, wood, cloths, hands, money bills, and cellphone), the GS electrode was assembled in the 3D-printed cell ready to measure both explosives by the proposed method. In all cases, the presence of TNT and RDX was confirmed, attesting the reliability of the proposed device to act as collector and sensor.

Synthesis of Phenol-Hydrazide-Appended Tetraphenylethenes as Novel On-Off-On Cascade Sensors of Copper and Glutathione.

This study reports the synthesis of novel fluorescent probes, phenol-hydrazide-appended tetraphenylethenes (TPEs I and II), and explores their photochemical properties. The probes exhibit aggregation-induced emission (AIE) in increasing water content, as observed using fluorescence spectroscopy. Further investigation with UV-vis and fluorescence techniques revealed their potential as ion sensors. Both TPE I and TPE II act as "turn-off" sensors for Cu2+ ions, showing decreased fluorescence intensity in their presence. Their limit of detection (LOD) and association constant (K a) for Cu2+ were found to be comparable at 747 nM/597 nM, and 2.46 × 105 M-1/2/1.78 × 105 M-1/2, respectively. Moreover, the quantum yields of TPE I and TPE II were also calculated and found to be 0.651 and 0.325, respectively. Interestingly, these probes also function as "turn-on" sensors for glutathione (GSH) in the presence of copper. This means their fluorescence can be reversibly switched off and on by alternating CuCl2 and GSH additions. Moreover, the LOD values for GSH with TPE II-Cu2+ were calculated to be 544 nM. In addition, the investigation also employed visual analysis to assess the color alterations of TPEs on filter paper and in real water samples. Overall, this research introduces promising new probes with potential applications in copper ion detection and biomolecule glutathione sensing in real water samples.