Limit Of Detection Values Research Articles

Ergot alkaloid control in biotechnological processes and pharmaceuticals (a mini review).

The control of ergot alkaloids in biotechnological processes is important in the context of obtaining new strain producers and studying the mechanisms of the biosynthesis, accumulation and secretion of alkaloids and the manufacturing of alkaloids. In pharmaceuticals, it is important to analyze the purity of raw materials, especially those capable of racemization, quality control of dosage forms and bulk drugs, stability during storage, etc. This review describes the methods used for qualitative and quantitative chemical analysis of ergot alkaloids in tablets and pharmaceutic forms, liquid cultural media and mycelia from submerged cultures of ergot and other organisms producing ergoalkaloid, sclerotias of industrial Claviceps spp. parasitic strains. We reviewed analytical approaches for the determination of ergopeptines (including their dihydro- and bromine derivatives) and semisynthetic ergot-derived medicines such as cabergoline, necergoline and pergolide, including precursors for their synthesis. Over the last few decades, strategies and approaches for the analysis of ergoalkaloids for medical use have changed, but the general principles and objectives have remained the same as before. These changes are related to the development of new genetically improved strains producing ergoalkaloids and the development of technologies for the online control of biotechnological processes and pharmaceutical manufacturing ("process analytical technologies," PAT). Overall, the industry is moving toward "smart manufacturing." The development of approaches to production cost estimation and product quality management, manufacturing management, increasing profitability and reducing the negative impact on personnel and the environment are integral components of sustainable development. Analytical approaches for the analysis of ergot alkaloids in pharmaceutical raw materials should have high enough specificity for the separation of dihydro derivatives, enantiomers and R-S epimers of alkaloids, but low values of the quantitative detection limit are less frequently needed. In terms of methodology, detection methods based on mass spectrometry have become more developed and widespread, but NMR analysis remains in demand because of its high accuracy and specificity. Both rapid methods and liquid chromatography remain in demand in routine practice, with rapid analysis evolving toward higher accuracy owing to improved analytical performance and new equipment. New composite electrochemical sensors (including disposable sensors) have demonstrated potential for real-time process control.

π-Conjugated Porous Polymer Nanosheets for Explosive Sensing: Investigation on the Role of H-Bonding.

Nitroaromatic explosive sensing plays a critical role in ensuring public security and environmental protection. Herein, we report 2-pyridyl-thiazolothiazole (pyTTz) integrated blue-fluorescent π-conjugated porous polymer nanosheets, NTzCMP and TzCMP for selective sensing of picric acid (PA) among nitrophenol explosives. Acid-base interactions between PA and pyTTz of CMP lead to H-bonding interactions, where the hydroxy group of PA engaged in weak H-bonding interactions with pyridine and TTz of pyTTz moiety. This led to a strong fluorescence quenching of CMPs-such formation of ground state complex was supported by linear Stern-Volmer quenching plots, unaltered excited state lifetimes, and detailed FTIR analysis of PA exposed CMPs. Interestingly, both CMPs exhibited an excellent response to smaller analytes such as o-nitrotoluene compared to electron-deficient 2,4-dinitrotoluene. Both NTzCMP and TzCMP CMPs exhibited high KSV values of 9×103 and 2.1×103 M-1 for PA and the corresponding limit of detection values were found to be 0.46 and 1.6 ppm, respectively.

Voltammetric and electro-kinetic assessment of prucalopride at MnO2-rGO fabricated pencil graphite electrode

Development and design of rGO-based nanocomposite-modified carbon-based electrodes are necessary to enhance the selectivity and desired selectivity of the voltammetric sensors. In this work, a manganese dioxide-reduced graphene oxide (MnO2-rGO) fabricated pencil graphite electrode is described for the detection of prucalopride (PRU), which is used to treat chronic idiopathic constipation. A simple cost effective hydrothermal method was used to synthesize the needle-shaped MnO2. The MnO2-rGO nanocomposite was characterized using XRD, SEM, and FTIR spectroscopy to examine its microstructure and morphology. The results revealed that MnO2 needles are distributed on the flakes of the rGO, thereby enhancing the electro-catalytic activity of MnO2-rGO/PGE. The electrochemical performance of the developed MnO2-rGO/PGE was examined using CV, chronocoulometry, SWSV, and DPSV methods. The diffusion-controlled oxidation of the PRU at the MnO2-rGO/PGE produces an irreversible peak in all the voltammograms which were used to calculate several electro-kinetic parameters like electron transfer coefficient (α = 0.598), diffusion coefficient (Do = 1.62 × 10−5 cm2s−1), surface coverage (Γo = 1.55 × 10−9 molcm−2), and effective surface area. Furthermore, advanced SWSV and DPSV methods are proposed for the accurate, selective, and sensitive detection of the PRU in pharmaceutical samples. The reported values of detection limit (LOD) for the proposed SWSV and DPSV methods are 20.39 μM and 14.53 μM, respectively, which make them eco-friendly and affordable alternative tools for the quantification of the PRU in pharmaceutical samples.

Determination of limit of detection (LOD) for loop-mediated isothermal amplification (LAMP) of human cytomegalovirus (hCMV) DNA

The importance of cytomegalovirus in clinical practice remains and samples are monitored for CMV DNA titers to predict the development of disease. LAMP assays have gained increasing interest in the diagnosis of many pathogens since they do not require thermocycling, reduce the complexity of the required instrumentation as well as providing sensitivity and rapidity. So far, very few studies on CMV detection by LAMP have been reported in the literature and therefore the performance of LAMP CMV assays needs to be further characterized. In a set-up for biometrological evaluation of the suitability of the LAMP assay for CMV diagnosis, a LAMP assay was performed on a total of 192 samples with 24 replicates of 8 different hCMV DNA concentrations. The LOD was calculated as 39.09 copy/reaction (25.33 copy/reaction to 65.84 copy/reaction) with 95% confidence, representing a range that is suitable for qualitative detection. Furthermore, the lower limit of quantification was estimated at approximately 100 copy/reaction. The LOD and LLOQ values obtained in this first study to assess the biometrological relevance of LAMP CMV tests are consistent when compared to studies published before. However further study under different conditions is needed for the use of LAMP tests in clinical applications.

Aminothiophenol and 7-diethylamino-4-hydroxycoumarin derived probe for reversible turn off–on–off detection of Cu2+ ions and cysteine

Here, we present a simple disulfide linked probe HTP for rapid detection of Cu2+ ions, which was prepared by a condensation reaction between 7-diethylamino-4-hydroxycoumarin aldehyde and 2-aminothiophenol. The disulfide linked probe HTP was characterized using 1H NMR, 13C NMR, and HRMS spectroscopic analysis and confirmed by single crystal X-ray diffraction analysis. The photophysical behavior of HTP in various solvents (non-polar to polar) was studied and HTP displayed aggregation induced emission (AIE) characteristics in CH3CN-water mixtures (0–99 %). Upon binding with Cu2+ ions, emission enhancement occurs along with color changes from weak green to intense yellow emission in CH3CN/Tris-HCl buffer (20 μM, 9:1, 10 mM Tris HCl Buffer, pH = 7.4). Detection limit for Cu2+ ions was found to be 0.97 nM which is lower than the recommended tolerance limit by the WHO and the association constant 0.42 × 108 M−1 was obtained using B-H plot. Furthermore, the stoichiometric ratio 1:1 was confirmed by job’s plot, 1H NMR, mass spectral analysis and DFT calculations were supported the formation of HTP-Cu2+ complex. The reversibility of HTP with Cu2+ ions was achieved by cysteine with detection limit and association constant value of 1.64 µM and 0.15 × 107 M−1 respectively. The reversible sensing nature of HTP with Cu2+/cysteine was further applied for constructing a molecular logic gate (INHIBIT) and practical applications such as paper strips, cotton swabs and real water analysis.

Occurrence of organophosphate flame retardants in agricultural products from Korean markets

Organophosphate flame retardants (OPFRs) are widely used in various products encountered in daily life including home appliances, furniture, and plastics. This study developed a method to determine the presence of 11 OPFRs in agricultural products to monitor OPFR contamination in Korean local markets. The method was based on QuEChERS extraction with liquid chromatography-tandem mass spectrometry using gradient elution with a run time of 13 min. The selectivity, linearity, limit of detection (LOD), limit of quantification (LOQ), recovery, and precision of developed method were validated based on the CODEX guidelines. The LOD values for 11 OPFRs ranged from 0.05 to 0.66 ng/g, which were comparable to the values obtained in previous studies. The established method was successfully applied to agricultural products collected in a Korean market. A 32 product types with seven replicates (total 224 samples) were monitored for OPFR contamination. These products included popular fruits and vegetables in Korea such as apples, cucumber, corn, etc. The agricultural products with the highest average of total OPFR concentration was eggplants (12.50 ng/g ww), and the OPFR types with the highest average concentration across all tested agricultural products was tris (1-chloropropan-2-yl) phosphate (TCIPP), with an average value of 1.48 ng/g. The estimated daily intake values were much lower than the reference dose values of OPFRs, which showed that exposure to OPFRs through agricultural products is generally safe. The results of this study could be used as the basis for expanding monitoring of OPFRs to aquatic and meat products, and will also be helpful in informing industries about the current risk of OPFR contamination.

Protein assay and immunoassay based on nematic thermotropic and lyotropic liquid crystals quantitated by haze measurement

Haze measurement is the cornerstone for assessing the transparency or opaqueness of liquid crystals (LCs) in applications such as smart windows and display technologies. In this study, we present a novel application of haze measurement as the quantitative approach for LC-based biosensing. Protein assay with bovine serum albumin (BSA) as the protein standard and immunoassay of the cancer biomarker CA125 were performed with the thermotropic LC 5CB and the nematic phase of the lyotropic chromonic LC sunset yellow. We observed that the brightness of LC optical texture increased with increasing analyte concentration due to enhanced light leakage caused by the attenuation of the vertical anchoring force of the surface alignment reagent coated on the glass surface. On the other hand, the haze value decreased as the amount of BSA or CA125 at the LC–glass interface increased, indicating that the scattering angle of the incident light was reduced. By calculating the percent difference in haze value, W (%), which gave rise to a positive correlation between the result of haze analysis and analyte concentration, a limit of detection (LOD) of 1.2 × 10−3 and 5.6 × 10−5 g/mL for BSA and CA125, respectively, was achieved by detection with 5CB, whereas the LOD values for BSA and CA125 were 1.0 × 10−12 and 1.9 × 10−9 g/mL, respectively, when detected with nematic sunset yellow. To the best of our knowledge, this study provides the first demonstration of the feasibility and simplicity of quantitative analysis by haze measurement in LC-based biosensing.

Laser Desorption of Explosives from the Surface of Different Real-World Materials Studied Using C2Cl6-Dopant-Assisted Ion Mobility Spectrometry.

A highly efficient and sensitive ion mobility spectrometry (IMS) system with laser desorption sampling was applied for rapid explosive detection using different surface materials. This portable IMS detector, powered by a battery, offers mobility and is suitable for use in the field or combat zones. The laser desorption (LD) sampling of common explosives (Trinitrotoluene-TNT; Dinitrotoluenes-DNTs; Hexogene-RDX; pentaerythritol tetranitrate-PETN; plastic explosives-Compound 4 (C-4) and Semtex) on a wide range of common surface materials, such as metal, ceramic, plastic, glass, drywall, paper, wood, and textiles, was studied. Successful detection was achieved on nearly all surfaces except flammable materials (paper, wood, and textiles). The limit of detection (LOD) was determined for each explosive and specific surface, demonstrating an impressive LOD of 7 ng/mm2 for TNT. RDX, C-4, PETN, and Semtex achieved LOD values of 15 ng/mm2, while DNTs showed an LOD of approximately 50 ng/mm2.

Critical evaluation of high-resolution and low-resolution mass spectrometry for biomonitoring of human environmental exposure to pesticides

Despite increasing debates about their potential side effects on human health, data concerning the risks and the impacts associated with pesticides remains scarce. Analytical tools allowing the measurement of most pesticides and/or their metabolites to which the population can be exposed are also of need. In the present study, the limits of detection (LODs) of 3 different screening procedures based on either Low-Resolution and High-Resolution Mass Spectrometry (LR-MS and HR-MS) for the determination of pesticides in serum (among which carbamates, dithiocarbamates, neonicotinoids, organochlorines, organophosphates and pyrethroids) were explored. For HR-MS, a quadrupole time-of-flight was used in positive and negative electrospray ionization modes and data were obtained from either a targeted scheduled MSMS acquisition (HR-MSMS) or a data-independent acquisition (HR-DIA). For LR-MS, a triple quadrupole was used and data were acquired with a classical multiple-reaction monitoring (MRM) mode. Depending on the approach, the LOD values varied from 0.05 to 10 ng/mL. For the lowest concentrations, the proportion of molecules detected was systematically greater for the LR-MS approach, while those of HR-MSMS were better than those of HR-DIA. These differences in the LOD values were confirmed in a sample of 174 serums in which LR-MRM detected 89 compounds while HR-MSMS and HR-DIA detected 79 and 75 compounds, respectively. Nevertheless, for environmental and occupational purposes, HRMS approach could probably be efficient to detect most of pesticides and their metabolites in human serum and could be suitable for human biomonitoring studies or fundamental research exploring the impact of exposure to pesticides on human health.

Natural deep eutectic based dispersive liquid-liquid microextraction and solidified floating organic drop for cadmium determination by electrothermal atomic absorption spectrometry with multivariate optimization (DLLME-SFOD-NADES-ETAAS)

A novel method was developed for cadmium determination based on dispersive liquid-liquid microextraction and solidified floating organic drop by multivariate optimization with electrothermal atomic absorption spectrometric detection using a natural deep eutectic solvent (NADES) of (L)-menthol and formic acid. Important factors, including pH, final concentration of PAN, mole ratio of formic acid, volume of NADES, type of dispersive solvent, and vortex time, were assessed using two-level fractional factorial design (FFD), and circumscribed central composite design (CCC). The analytical performance parameters, encompassing linearity range, limit of detection (LOD), limit of quantification (LOQ), and precision, were evaluated. The linearity range ranged from 0.72 to 2.50 ng/L, with corresponding LOD and LOQ values of 0.22 and 0.72 ng/L, respectively. Precision was evaluated by conducting three replicates of the three concentration levels, resulting in %RSD values of 11.8 %, 5.1 %, and 3.9 %, respectively. An enrichment factor (EF) of 112 was achieved. The optimized method was applied for cadmium determination in various matrices, including drinking water, environmental water, seafoods, yielding %recovery in the ranges of 78.05–102.41 %. Finally, comparison of t-values between the developed method and CRMs demonstrated satisfactory results at a 95 % confidence level.

Intelligent Analysis of Avian Influenza Virus Biomarkers Based on Chemiluminescence Resonance Energy Transfer and DNA Logic Analysis.

A one-step logical analysis of multiple targets remains challenging. Herein, we report a one-pot and intelligent DNA logical analysis platform for the diagnosis of avian influenza virus (AIV) biomarkers based on chemiluminescence resonance energy transfer (CRET) and logic operations. On the surface of Lum/PEI/CaCO3 microparticles, the excited state of luminol underwent CRET with fluorescein isothiocyanate or rhodamine B isothiocyanate, producing three well-separated light emissions at 425, 530, and 590 nm, respectively. Taking advantage of the close distance between fluorophores aligned by the catalytic hairpin assembly reaction, the CRET efficiency was greatly enhanced (53.1%). H1N1, H7N9, and H5N1 were detected with limits of detection values as low as 15, 34, and 58 pM, respectively. Three-input logic circuits were simultaneously conducted on the surface of Lum/PEI/CaCO3 microparticles, enabling the rapid and accurate discrimination of multiple AIV biomarkers in one solution. In terms of peak positions and the normalized value of the total peak intensity, three biomarkers can be simultaneously discriminated without any other complex operations. In summary, the CRET-based multiple analytical assay was developed as an intelligent biosensor for identifying AIV biomarkers, having promising application prospects in the field of multiple analysis and precise disease diagnosis.

‘Turn On’ fluorescent imine linked 1,2,3-triazole based chemosensor for detection of mercuric ions

The exorbitant use or erroneous management of metal ions has been incurred with catastrophic pollution of our ecological system, particularly in soil and water bodies, resulting in significant repercussions. Hence, precise identification and analysis of heavy-metal ions in intricate hydrological environments is imperative. Therefore, an imine conjugated 1,2,3-triazole derivative VPT was synthesized, characterized via FTIR, NMR (1H &13C), LCMS spectroscopic techniques and was employed for the exclusive identification of Hg2+ ions in the presence of various other metal ions via UV–Visible and fluorescence spectroscopy. The sensor VPT exhibited binding constant (Ka) value of 2.93 × 104 M−1 and detection limit value of 0.5 × 10−9 M in the ACN:H2O::4:1 medium. The stoichiometric ratio was determined using Job’s plot, which revealed a (1:1) ratio of VPT with Hg2+ ions. In addition, time-dependent, temperature-dependent, and pH titration studies were conducted via U.V-Visible spectroscopy to expand the sensor’s applicability. The viable configurations of probe VPT and its 1:1 stoichiometric with Hg2+ ion were optimized using the B3LYP/6-311G++(d,p)/LANL2DZ levels of theory in the Gaussian 09 program respectively and this semi-empirical quantum mechanics approach demonstrated a reduction in the energy gap confirming the stable formation of [VPT-Hg2+] complex. These insights facilitate the design offluorescent probe VPT for detecting Hg2+ in both environmental and biological context.

SPRi Biosensor for Simultaneous Determination of HIF-1α, Angiopoietin-2, and Interleukin-1β in Blood Plasma.

A new analytical method, based on SPRi biosensors, has been developed for the simultaneous determination of the pro-angiogenic factors HIF-1α, angiopoietin-2 (ANG-2), and interleukin-1β (IL-1β) in biological fluids. These proteins take part in the process of angiogenesis, i.e., the creation of new blood vessels, which is a key stage of cancer development and metastasis. A separate validation process was carried out for each individual compound, indicating that the method can also be used to study one selected protein. Low values of the limit of detection (LOD) and quantification (LOQ) indicate that the developed method enables the determination of very low concentrations, in the order of pg/mL. The LOD values obtained for HIF-1α, ANG-2, and IL-1β were 0.09, 0.01, and 0.01 pg/mL, respectively. The LOQ values were 0.27, 0.039, and 0.02 pg/mL, and the response ranges of the biosensor were 5.00-100.00, 1.00-20.00, and 1.00-15.00 pg/mL. Moreover, determining the appropriate validation parameters confirmed that the design offers high precision, accuracy, and sensitivity. To prove the usefulness of the biosensor in practice, determinations were made in plasma samples from a control group and from a study group consisting of patients with diagnosed bladder cancer. The preliminary results obtained indicate that this biosensor can be used for broader analyses of bladder cancer. Each of the potential biomarkers, HIF-1α, ANG-2, and IL-1β, produced higher concentrations in the study group than in the control group. These are preliminary studies that serve to develop hypotheses, and their confirmation requires the analysis of a larger number of samples. However, the constructed biosensor is characterized by its ease and speed of measurement, and the method does not require special preparation of samples. SPRi biosensors can be used as a sensitive and highly selective method for determining potential blood biomarkers, which in the future may become part of the routine diagnosis of cancers.

Development of dispersive solid phase extraction method for the preconcentration of parathion ethyl as a simulant of nerve agent sarin from soil, plant and water samples prior to GC-MS determination.

In the presented study, an efficient and fast analytical method was developed for the determination of parathion ethyl as sarin simulant by gas chromatography-mass spectrometry (GC-MS). Dispersive solid phase extraction (DSPE) was performed to concentrate parathion ethyl from soil, plant and water samples. Reduced graphene oxide-iron (II, III) oxide (rGO-Fe3O4) nanocomposite was used as an adsorbent to collect the target analyte from the aqueous sample solutions. After the optimization of extraction/preconcentration parameters, optimum conditions for adsorbent amount, eluent type, mixing type/period, eluent volume and initial sample volume were determined as 15mg, acetonitrile, vortex/30s, 100 µL and 10mL, respectively. Under the optimum conditions, analytical performance of the developed DSPE-GC-MS method was evaluated in terms of limit of detection (LOD), limit of quantitation (LOQ) and dynamic range. Dynamic range, LOD and LOQ values were figured out to be 0.94-235.15µg/kg, 0.41µg/kg and 1.36µg/kg (mass based), respectively. Satisfactory percent recovery results (90.3-125% for soil, 93.5-108.7% for plant, 88.5-112.9% for tap water) were achieved for soil, plant and tap water samples which proved the accuracy and applicability of the developed method. It is predicted that the DSPE-GC-MS method can be accurately used for the detection of sarin in soil, plant and water samples taken from war territories.

Ferricyanide-Mediated, Electrocatalytic Mechanism of Electrochemical Aptamer-Based Sensor Supports Ultrasensitive Analysis of Cardiac Troponin I in Clinical Samples.

Rapid, reagent-free, and ultrasensitive analysis of cardiac troponin I (cTnI) is of significance for early diagnosis of acute myocardial infarction (AMI). The electrochemical aptamer-based (EAB) sensors are promising candidates to fill this role as they are reagentless and can be directly interrogated in complex matrices (e.g., blood). To achieve high sensitivity, EAB sensors typically require nanomaterials or other amplification strategies, which often involves a cumbersome fabrication process. To circumvent this, here we develop a simple yet effective electrocatalytic electrochemical aptamer-based (Ec-EAB) sensor that utilizes target-induced regulation of the catalytic mechanism to achieve ultrasensitive measurement of cTnI. In this assay, we employed a probe-attached redox reporter (i.e., methylene blue, MB) and a solution-diffusive redox reporter (i.e., Fe(CN)63-) to generate two signals, of which the latter is used to catalyze MB to amplify aptamer-mediated charge transfer. The recognition of target altered the diffusion of catalysts (2.2 × 10-9 mol/cm2 in the target-free state versus 1.2 × 10-9 mol/cm2 in the target-bound state) and thus electrocatalytical efficiency, enabling ultrasensitive measurement of cTnI with a 1000-fold improvement in their sensitivity (a limit of detection value: 10 pg/mL).

Effect of NiAl alloy microparticles deposited in flexible SERS substrates on the limit of detection of rhodamine B molecules.

Flexible-SERS (FSERS) substrates were fabricated by depositing Ni64Al36(NiAl)-alloy-microparticles and/or spherical Ag-NPs (sizes of 10-40 nm) on recycled plastics, which had an aluminum layer on their surface. First, FSERS substrates made of Al + Ag-NPs and an area of 1 cm2 were used to detect rhodamine B (RhB) molecules. The limit-of-detection (LOD) for RhB was 8.35 × 10-22 moles (∼503 molecules), and the enhancement factor (EF) was 3.11 × 1015. After adding NiAl-microparticles to the substrate, the LOD decreased to 8.35 × 10-24 moles (∼5 molecules) and the EF was increased to 2.05 × 1017. Such EF values were calculated with respect to substrates made only with Al + NiAl-alloy (without Ag-NPs), which did not show any Raman signal. Other FSERS substrates were made with graphene-layer + Ag-NPs or graphene-layer + NiAl-alloy + Ag-Nps, and the best LOD and EF values were 8.35 × 10-22 moles and 6.89 × 1015, respectively. Overall, combining the Ag-NPs and NiAl-alloy microparticles allowed for the zeptomole detection of RhB. This was possible due to the formation of Ag aggregates around the alloy microparticles, which enhanced the number of hotspots. If no alloy is present in the FSERS substrates, the detection of RhB is lowered. Overall, we presented a low-cost FSERS substrate that does not require expensive Au films or Au-NPs (as previously reported) to detect RhB at the zeptomole level.

Comparison of permeability of topical Cream drug through polymer synthetic membranes of different structures using Franz Cell diffusion test

In this study, in-vitro release experiments were performed using a Franz Diffusion Cell system for Terbinafine Hydrochloride, which is used in the treatment of various fungal infections in the skin caused by many susceptible dermatophytes. In order to evaluate TH transdermally, it was aimed to compare the permeability between polymeric membranes synthesized with polyvinyl alcohol and chitosan mixtures and commercial membranes. In the transdermal drug delivery system calculations, the Fick Diffusion Law was modified and the obtained data were compared. The study was evaluated according to the USP <1724> topical drug products in semisolid form - performance tests. A new high-performance liquid chromatography method was validated for the assay of TH released into the receptor medium in accordance with the ICH guideline. According to the results obtained during the validation process, the limit of detection value was calculated as 0.005 µg/mL and the limit of quantification value was 0.013 µg/mL. Since polymer-based synthetic membranes provide permeability according to molecular size, properties and the ideal environment for measuring and analyzing the diffusion rate of a compound, in experiments conducted using membranes of different structures, the permeability profiles of selected polymer synthetic membranes were statistically evaluated. It has been noted that the hydroxyl groups in PVA and the hydrophilic CS-g-PNDMAAm graft copolymer act at varying rates to enhance or reduce the permeability across the membrane by promoting its diffusion. NaY zeolite has been shown to function as an adsorbent against the medication, lessening the impact of hydrophilic PVA without supplying permeability.

Bismuth oxide nanoparticles enabled sensitive electrochemical determination of Vitamin B12

The intake and monitoring of vitamin B12 levels are highly essential to maintain a healthy body condition. Herein, we report bismuth oxide nanoparticles (Bi2O3 NPs) facilitated electrochemical sensing of vitamin B12 with admirable sensitivity, selectivity, and low detection limit. A facile hydrothermal method was adopted for synthesizing Bi2O3 NPs and their physico-chemical properties were analyzed using various techniques. The electrochemical sensing of vitamin B12 was validated through cyclic voltammetry and differential pulse voltammetry techniques. The sensing results illustrate that the modified electrode exhibits a wide linear range between 10 nM and 275 nM with a low detection limit value of 3.66 nM. In addition to the enhanced electrocatalytic behavior, the Bi2O3 NPs have also enabled the discrimination of vitamin B12 from various potential interfering molecules (even adding a 5-fold concentration). The developed sensor also exhibits better stability, selectivity, and reproducibility towards the target analyte. Finally, the fabricated electrode was applied for the determination of vitamin B12 in serum, and plasma samples, and the results were highly satisfactory with recovery values of 98.4 % to 99.8 %.

Nucleic acid-functionalized nanoscale porous carbon-based electrochemical genosensor for detection of Nocardia spp. in real samples

In this study, a porous carbon derived from a metal-organic framework (PCMOF) as a target-responsive material functionalized with Nocardia particular antisense ssDNA oligonucleotide (ssDNA capture probe) was developed to construct a simple genosensor based on biogatekeeper strategy for sensitive detection of Nocardia in complex biological samples. The PCMOF with suitable pores volume was used to encapsulate electroactive dye methylene blue (MB), and the ssDNA capture probe was used as a gatekeeper to cap PCMOF. Without the presence of Nocardia target, the electrochemical signal of trapped MB was high. Upon adding the target, the hybridization of ssDNA capture probe and target led to the formation of a probe-target double-stranded (dsDNA) structure which dissociated from PCMOF and allowed MB molecules to be released. Therefore, the electrochemical signal of the genosensor decreased. The detection of Nocardia was accomplished by observing variations in the MB peak current intensity in a dose-dependent manner. For this genosensor, a linearity range from 10−18 to 10−7 M for synthetic ssDNA target and 10 to 108 copies/mL for two standard isolates, Nocardia farcinica PTCC 1309 and Nocardia brasiliensis ATCC 19296 as well as for clinical isolates (identified as Nocardia otitidiscaviarum) was observed, respectively. The detection limit (DL) values were 0.54 aM for synthetic ssDNA target and 5, 7, and 4 copies/mL for N. farcinica, N. brasiliensis, and N. otitidiscaviarum, respectively. This genosensor was also characterized by good specificity, reproducibility, and stability.

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.