Chromogenic Reagent Research Articles

Detection of atomoxetine and its metabolites in the urine by thin-layer chromatography and mass spectrometry

The aim of the study was the detection of atomoxetine and its biotransformation products in the urine under TLC screening conditions and identification of the metabolites using mass spectrometry method. Materials and methods. The volunteer’s urine samples after taking a single therapeutic dose of atomoxetine (2 capsules of 60 mg each of Strattera®) were studied. Sample preparation included diluting acid hydrolysis followed by the native compound and metabolites extraction with chloroform from the saturated solution of ammonium sulfate at pH of 11–12. Thin-layer chromatography studies of the extracts were carried out in 18 mobile phases including those proposed by The International Association of Forensic Toxicologists for general drug screening, and those widely used in forensic toxicological studies. The color reactions were carried out using a range of chromogenic reagents. A Varian 1200 L mass spectrometer (Netherlands) equipped with a dual quadrupole mass analyzer was applied for analysis of the eluates from chromatograms. Identification was undertaken at the direct introduction of the sample into the ion chamber, electron-impact ionization (70 eV), and full ion scanning mode. Results. The spot of the native drug on the chromatogram was identified by the Rf, value. Two atomoxetine biotransformation products were identified by the molecular weights that correspond to the molecular ion peaks in the mass spectra. Conclusions. Atomoxetine and its biotransformation products were detected in the urine under TLC screening conditions and identified using mass spectrometry method. Chromatographic mobility of the native compound, hydroxyatomoxetine, and dihydroxyatomoxetine in the TLC screening systems as well as the results of their visualization using chromogenic reagents applied for toxicological drug screening in the systematic toxicological analysis have been determined.

SPECTROPHOTOMETRIC METHODS FOR THE QUANTITATIVE DETERMINATION OF MEMANTINE HYDROCHLORIDE IN PURE FORM AND PHARMACEUTICAL FORMULATIONS

Objective: Three simple, sensitive, accurate, and precise spectrophotometric methods have been developed and validated for the determination of Alzheimer’s disease drug memantine HCl (MEM) in pure form and pharmaceutical formulations. Methods: The method was based on the formation of charge transfer complex between MEM as n-electron donor and various π-acceptors quinalizarin (Quinz) in methanol, p-chloranilic acid (p-CA) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) in acetonitrile as chromogenic reagents which showed an absorption maximum at 558, 532 and 840 nm using Quinz, p-CA and TCNQ, respectively. The optimization of the reaction conditions such as the type of solvent, reagent concentration and reaction time were investigated. Results: Under the optimum conditions, beer’s law is obeyed in the concentration ranges 4.0–24, 10–160 and 5.0–50 μg/mlusing Quinz, p-CA and TCNQ, respectively with good correlation coefficient (r2 ≥ 0.9995) and with a relative standard deviation (RSD% ≤ 1.11). For more accurate analysis, Ringbom optimum concentration ranges were found to be between 8.0–20, 15–140 and 10–45 μg/ml using Quinz, p-CA and TCNQ, respectively. The limits of detection were found to be 1.2, 2.70 and 1.45 µg/ml and the limits of quantification were found to be 4.0, 9.0 and 4.83 µg/ml for Quinz, p-CA and TCNQ, respectively. A Job's plot of the absorbance versus the molar ratio of MEM to each of the acceptors under consideration indicated (1:1) ratio. Conclusion: The methods were successfully applied to the determination of MEM in its pharmaceutical formulations and the validity assessed by applying the standard addition technique. Results obtained by the proposed methods for the pure MEM and commercial tablets agreed well with those obtained by the reported method.

PHYTOCHEMICAL PROFILING, HPTLC FINGERPRINT AND ANTIBACTERIAL, ANTI-FUNGAL, AND ANTIOXIDANT PROPERTIES OF ESSENTIAL OILS EXTRACTED FROM CUMMINUM CYMINUM, ZINGIBER OFFICINALE, TRACHYSPERMUM AMMI, ALIPNIA GALANGA, CEDRUS DEODARA, AND ELETTARIA CARDAMOMUM

Objective: The objective of the study was to carry out the phytochemical profiling of essential oils (EOs) and evaluation of their anti-microbial activity. Methods: The EOs extracted from Cumminum cyminum, Zingiber officinale, Trachyspermum ammi, Alipnia galanga, Cedrus deodara, and Elettaria cardamomum using clavenger apparatus. Phytochemical analysis and high-performance thin layer chromatography (HPTLC) fingerprinting were carried out for the EO. The antibacterial and antifungal activity were evaluated using agar well-diffusion method against two bacterial strains, Escherichia coli, Staphylococcus aureus and two fungal strains, Candida albicans, and Aspergillus brasiliensis. Positive controls ciprofloxacin-30 mg, azithromycin-15 mg, and nystatin NS-50 mg were used. Antioxidant potential of the EOs was investigated by TLC-bioautography method using 1,1-diphenyl-2-picrylhydrazyl derivatization. Results: The phytochemical analysis reveals presence of various phytochemical such as steroids, terpenoids, and phenylpropanoids. The HPTLC fingerprint is found to be unique for each of the oil. The EO of Z. officinale and T. ammi showed strong antibacterial activity against S. aureus. The EOs of C. cyminum, Tachyspermum ommi and A. galanga displayed prominent antioxidant activity on TLC bioautography. The herbs Cuminum cynimun, T. ammi, C. deodara, and Ellateria cardamomum produce reasonable amount of essentials oil, which can be explored for useful their industrial applications. Conclusions: These EOs can be explored further for their antimicrobial activity. The HPTLC analysis along with derivatization with suitable chromogenic reagents can be a rapid and simple tool for quality control of various EOs.

Aggregation-Induced Emission Luminogen-Based Dual-Mode Enzyme-Linked Immunosorbent Assay for Ultrasensitive Detection of Cancer Biomarkers in a Broad Concentration Range.

The enzyme-linked immunosorbent assay (ELISA) is one of the most commonly used methods for measuring antibodies and antigens in biological samples. However, developing new ELISAs with high detection sensitivity and broad detection dynamic ranges without resorting to complicated signal processing and equipment setups remains a challenge. In this work, we report a strategy to simultaneously improve the detection sensitivity and broaden the dynamic range by replacing the chromogenic reagents used in traditional ELISAs with an aggregation-induced emission luminogen (AIEgen). The developed AIE-ELISA could generate complementary absorbance and fluorescence signals with a linear detection range of 1.6-25,000 pg/mL. The application of this dual-mode AIE-ELISA in the detection of the prostate-specific antigen (PSA) realized a limit of detection of 1.3 pg/mL (3.78 × 10-14 M) and dynamic range improvement of approximately 2 orders of magnitude compared to a single-mode ELISA, which enabled it to discriminate a minor PSA difference in a patient's serum. The simpler experimental operation, faster enzyme response speed, and better photostability of AIEgen than the traditional chromogenic reagents used in ELISAs showed that our developed AIE-ELISA holds great potential in the fields of immunoassay, immunohistochemistry, and immunocytochemistry.

Screening LiMn2O4 Surface Modification Schemes under Theoretical Guidance

Mn dissolution is one of the most important factors for the failure of LiMn2O4 batteries. Doping has been widely adopted in the modification of LiMn2O4 cathodes; however, there is still a lack of theoretical guidance on screening the dopants. Here, through first-principles calculations, we systematically investigated the effects of all 3, 4d transition metals as well as Mg, Ca, Sr, Al, Ga, and In on the surface oxygen stability of LiMn2O4 cathodes, which has been proved to be correlated with the stability of the surface Mn atoms. Six competitive dopants, namely Nb, Ru, Mo, V, Tc, and Ti, were screened out. Besides, for three dopants in low valence states (Mg, Cu, and Zn), their Li-site doping can more effectively stabilize the surface oxygen atoms compared with Mn-site doping. Finally, we synthesized LiMn2O4 samples with Mg, Mo, and Nb surface doping to validate the rationality of the computational results. We found that particle morphology should also be considered in addition to surface oxygen stability for controlling Mn dissolution. Moreover, the electrochemical performance of LiMn2O4 batteries is a more complex issue and cannot be solely regulated by Mn dissolution. During the experiments, we have explored novel efficient binary chromogenic reagents for ultraviolet-visible spectroscopy analysis that can be used for rapid and low-cost Mn dissolution detection. This work provides a paradigm for the systematic design of the surface modification of the LiMn2O4 cathode under theoretical guidance.

Spectrophotometric Determination of Molybdenum(VI) as a Ternary Complex with 4-Nitrocatechol and Benzalkonium Chloride.

A new liquid—liquid extraction system for molybdenum(VI) was studied. It contains 4-nitrocatechol (4NC) as a complexing chromogenic reagent and benzalkonium chloride (BZC) as a source of heavy cations (BZ+), which are prone to form chloroform-extractable ion-association complexes. The optimum conditions for the determination of trace molybdenum(VI) were found: concentrations of 4NC and BZC (7.5 × 10−4 mol dm−3 and 1.9 × 10−4 mol dm−3, respectively), acidity (3.75 × 10−2 mol dm−3 H2SO4), extraction time (3 min), and wavelength (439 nm). The molar absorptivity, limit of detection, and linear working range were 5.5 × 104 dm3 mol−1 cm−1, 5.6 ng cm−3, and 18.6–3100 μg cm−3, respectively. The effect of foreign ions was examined, and the developed procedure was applied to the analysis of synthetic mixtures and real samples (potable waters and steels). The composition of the extracted complex was 1:1:2 (Mo:4NC:BZ). Three possible structures of its anionic part [MoVI(4NC)O2(OH)2]2− were discussed based on optimizations at the B3LYP/3-21G level of theory, and simulated UV/Vis absorption spectra were obtained with the TD Hamiltonian.

Development of conditions for Pyrazidol identification in the urine in the presence of its biotransformation products by thin layer chromatography and mass spectrometry

For the analytical diagnosis of drug poisoning, it is important to develop conditions for the detection of both native compounds and products of their biotransformation in biological samples. Aim. To develop a method for isolating the antidepressant drug Pyrazidol from the human urine in the presence of its biotransformation products and determine the conditions that are suitable for analytical diagnostics of thymoleptic intoxication for their detection by thin layer chromatography. Materials and methods. The study was conducted with the human urine samples collected after taking a single therapeutic dose of Pyrazidol. The urine was subjected to the acid hydrolysis, and the antidepressant and its metabolites were extracted from the hydrolysate with chloroform from an alkaline medium at pH 8-9. Concomitant endogenous admixtures were removed by extraction with diethyl ether from an acidic medium at pH 1. For the chromatographic study of the extracts, four mobile phases recommended by the International Association of Forensic Toxicologists for TLC screening of drugs, and Merck chromatographic plates were used. Color reactions were performed on pieces of chromatographic plates with a number of chromogenic reagents most commonly used in chemico-toxicological analysis. Metabolites were identified by electron impact mass spectrometry. Results and discussion. The native substance and dehydropyrazidol were detected in the urine hydrolysates by TLC, their chromatographic mobility parameters in four TLC screening systems, as well as the results of their color reactions with the chromogenic reagents were determined. Conclusions. Conditions for isolating Pyrazidol and its biotransformation product from the urine have been proposed. The method for detecting the native compound and dehydropyrazidol in the urine extracts by TLC and mass spectrometry after taking a single therapeutic dose of the drug has been developed. The method is recommended for use in the practice of forensic and clinical toxicology.

Development of method for determination and preconcentration of uranium in water samples using XAD-4 resin loaded with Br-PADAP

In the present work, a minicolumn of XAD-4 loaded with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (Br-PADAP) is proposed as a preconcentration system for uranium determination in well, tap and mineral water samples by spectrophotometer using arsenazo III as the chromogenic reagent. Initially, a two-level (23) full factorial design was used for the preliminary evaluation of three factors, involving the following variables: sampling flow rate, elution flow rate, and pH. This design has revealed that, for the studied levels, buffer concentration and pH were significant factors. When the experimental conditions established in the optimization step were pH = 8.6, and an elution flow rate of 8.6 mL min−1 using 0.5% m/v ascorbic acid, this system has allowed for the determination of uranium with a detection limit (LOD) (3σ/S) of 0.05 μg L−1 and a quantification limit (LOQ) (10σ/S) of 0.16 μg L−1. The precision expressed as the relative standard deviation (R.S.D.) of 0.8% and 1.9% at 10.0 and 1.0 μg L−1, respectively- and a preconcentration factor of 184.5 for a sample volume of 50.0 mL. Accuracy was confirmed by uranium determination in the standard reference material, NIST SRM 1566b trace element units in Oyster Tissue samples, and spike tests with recuperations ranging from 93.2 to 105%; the procedure were applied for uranium determination in tap water, well water, and drinking water samples collected from Caetité and Cruz das Almas Cities, Bahia, Brazil. Five water samples were analyzed the uranium concentrations varied from 0.50 to 2.07 μg L−1

Spectrophotometric determination of clotrimazole and Phenylephrine-HCl in pharmaceutical formulation using 1, 2-naphthoquinone-4-Sulphonic acid sodium salt (NQS) as a chromogenic reagent

A sensitive, rapid and economical spectrophotometric method based on their interaction with NQS reagent in basic medium, which produces orange-colored complexes, has been devised to identify many drugs with amino groups (clotrimazole and phenylephrine-HCl). The maximum absorption for the complexes of clotrimazole and phenylephrine-HCl is 455 and 484 nm, respectively. Beer's law is applicable in the concentration ranges of (2–40) μg/ml for clotrimazole and (0–20) μg/ml for phenylephrine-HCl. The molar absorptivity values are 3931.1760 L/mol.cm and 4521.4074 L/mol.cm of clotrimazole and phenylephrine-HCl respectively with accuracy of 100.0285%–103.1456% and RSD better than 3.3211%. The method has been successfully used to determine these medications in pharmaceutical formulations, and it has been found to be superior to British Pharmacopeia standard procedures. At a 95% confidence level, F and t-tests are less than the tabulated values.

Ratiometric fluorescence and colorimetric dual-mode sensing platform based on carbon dots for detecting copper(II) ions and D-penicillamine.

A sensing platform with both ratiometric fluorescence and colorimetric responses towards copper(II) ions (Cu2+) andD-penicillamine (D-pen) was constructed based on carbon dots (CDs). o-Phenylenediamine (OPD) was employed as a chromogenic development reagent for reaction with Cu2+to generate the oxidation product 2,3-diaminophenazine (oxOPD), which not only emits green fluorescence at 555nm, but also quenches the blue fluorescence of CDs at 443nm via the inner filter effect (IFE) and Förster resonance energy transfer (FRET). Additionally, oxOPD exhibits obvious absorption at 420nm. Since the intense chelation affinity of D-pen to Cu2+ greatly inhibits the oxidation of OPD, the intensity ratio of fluorescence at 443nm to that at 555nm (F443/F555) and the absorbance at 420nm (A420) were conveniently employed as spectral response signals to represent the amount of D-pen introduced into the testing system. This dual-signal sensing platform exhibits excellent selectivity and sensitivity towards both Cu2+ and D-pen, with low detection limits of 0.019μM and 0.092μM, respectively. In addition, the low cytotoxicity of the testing reagents involved in the proposed sensing platform facilitates its application for live cell imaging.

ISOLATION, IDENTIFICATION, AND DETECTION OF LIGNINOLYTIC CAPABILITY OF SOME FUNGI ISOLATED FROM SOIL SAMPLES IN EGYPT.

In the present study, twenty-seven fungal species were isolated, purified, and identified from five mixed soil samples collected from Tanta City, Gharbia Governorate, Egypt. The isolated fungal species belonging to nine genera i.e., Aspergillus, Cephalosporium, Fusarium, Penicillium, Botritrichom, Trichoderma, Alternaria, Cladosporium and Scopulariopsis, in addition to two white rot fungi Ganoderma lucidum and Lentinula edodes obtained from Mushroom Laboratory Culture Collection (MLCC), El-Giza, Egypt. The ligninolytic activities of the isolated fungi were evaluated on PDA plates containing 0.02% guaiacol as a chromogenic reagent. Out of the twenty-nine fungal species tested, only three fungi G. lucidum, L. edodes and T. harzianum (isolate 2) showed ligninolytic potential and reddish-brown color zone formed due to guaiacol oxidation. The three positive fungal strains were screened quantitively for Laccase (Lac; E.C. 1.10.3.2), Manganese dependent peroxidase (MnP; E.C. 1.11.1.13), and Lignin peroxidase (LiP; E.C. 1.11.1.14) activities. The highest total ligninase activity was recorded by G. lucidum followed by L. edodes and T. harzianum, respectively.

A microplate spectrophotometric method for analysis of indole-3-carbinol in dietary supplements using p-dimethylaminocinnamaldehyde (DMACA) as a chromogenic reagent.

This work presents the development of a microplate spectrophotometric method for determination of indole-3-carbinol in dietary supplements. The colorimetric procedure is based on the reaction of indole-3-carbinol with the p-dimethylaminocinnamaldehyde (DMACA) reagent under acidic conditions. The absorbance of the colored product measured at 675 nm was used to determine the target analyte. To achieve optimal spectrophotometric performance, the DMACA reagent concentration, the hydrochloric acid concentration, and the reaction time were optimized. The developed technique performed well under the optimal conditions, with a linear calibration range of 30 to 300 mg L-1 and a high correlation coefficient (r2 = 0.9954). The limit of detection and limit of quantification were 7.8 mg L-1 and 26.2 mg L-1, respectively. This approach demonstrated good repeatability (intra- and inter-day precision) with a % RSD lower than 9.4%, good accuracy with acceptable relative recoveries in the range of 98 to 106%, and high sample throughput (24 detection per min). This simple, rapid, and multi-sample analysis approach for routine analysis of indole-3-carbinol has the potential to be used for the quality control of dietary supplements.

Sequential injection method for bi-parametric determination of iron and manganese in soil leachates.

The aim of this work was to develop a sequential injection (SI) method for the determination of the micronutrients iron and manganese, in soil leachates, as a tool to assess potential groundwater contamination. The described sequential injection method was based on the reaction of iron with chelator MRB12, a greener alternative chromogenic reagent, and the reaction of manganese with zincon, within a single manifold. The developed SI method enabled the determination of iron in the range 0.10-1.00 mg L-1, and manganese in the range 0.25-2.5 mg L-1 with a limit of detection of 0.08 mg L-1 for iron and 0.24 mg L-1 for manganese. The determination of both parameters was made in 6 minutes, in triplicate. The application to monitor laboratory scale soil core columns (LSSCs), as a simulation of the soil leaching process, proved its efficiency to assess potential contamination of ground waters. Iron and manganese contents were effectively analysed in two different scenarios to mimic the leaching process with rainwater and fertilizer.

Spectrofluorimetric Determination of Some N. Containing Medicines Using Rhodamine 6G as a Chromogenic Reagent

A sensitive spectrofluorimetric method has been developed for the analysis of some medicines containing primary, secondary, and tertiary amino groups, namely Diclofenac (DIC), Domperidone (DOM), Famotidine (FAM), and Propranolol (PRO), in their pure and medicinal forms. The method is based on the quenching of the fluorescence intensity of rhodamine 6G (R6G) through the formation of ion-pair complexes between the above medicines and the R-6G reagent, which is measured at 552 nm after excitation at 402 nm. The calibration graphs were rectilinear in the concentration ranges of 0.10- 9.00, 0.05-15.00, 0.10-14.0 and 0.05-5.00 µg mL-1 for above medicines respectively. The recovery (%) values were ranged between 99.45%- 100.97%. The detection limits ranged in the concentration of 0.243-0.754 µg/mL, and the limits of quantitation were 0.806- 2.420 µgmL-1 for all drugs. The method was successfully applied for the determination of these drugs in their pharmaceutical preparations.

STUDY OF TECHNICAL CELLULOSE AS A MATRIX-SORBENT TO DEVELOP EXPRESS ANALYTIC SYSTEM FOR WATER SAFETY CONTROL

The study presented by the authors is devoted to the study of the properties and the possibility of using technical cellulose from non-wood plant raw materials as a solid-phase matrix to obtain solid-phase reactive indicator systems by the following methods: synthesis method on the base of a hetarylformazane immobilized on a cellulose matrix and development of analytical systems based on preconcentration of the determined metal ion by a matrix with subsequent its «revealing» by the formazan («revealing» method).
 The article focuses on determination of optimal combinations of chromogenic organic reagents (hetarylformazanes) and cellulose-based matrices for developing solid-phase reaction-based indicator systems. Adsorption features of formazan reagents onto cellulose matrices was studied. It has been established the relation between the reagent molecule structure, composition of cellulose matrix and analytical properties of the test-systems synthesized to determine metal ions. Different approaches were developed and applied to reveal the visually observable and easily measured effect due to cellulose properties as well as properties of hetarylformazanes fixed on the surface of the matrix. This fact allows to control sensitivity and selectivity of solid-phase reactive indicator systems for water quality assessment.

A colorimetric sensing strategy for detecting 10-hydroxy-2-decenoic acid in royal jelly based on Ag(I)-tetramethylbenzidine

Royal jelly as a functional food has great potential to promote human health. As a unique ingredient in royal jelly, 10-hydroxy-2-decenoic acid (10-HDA) is a vital criterion to evaluate the quality of royal jelly. Current approaches for 10-HDA detection mainly rely on high-performance liquid chromatographic (HPLC), but it requires large-scale equipment and skilled technicians that are costly and time-consuming. Herein, we report a colorimetric sensing strategy for 10-HDA detection based on Ag(I) and tetramethylbenzidine (TMB), a widely used chromogenic reagent. Ag(I) can oxidize TMB to generate oxidized TMB (oxTMB) showing a light-blue color. Due to the chelation with Ag (I), the introduction of 10-HDA can prevent the generation of oxTMB that results in a color fading and a decrease in absorbance. This colorimetric sensing strategy enables highly sensitive detection of 10-HDA with a linear range from 1 μM to 10 μM and a limit of detection of 0.13 μM. More importantly, this 10-HDA assay allows for a visual readout either by a smartphone or the naked eye with low cost, convenience, and rapid response that has been successfully applied for evaluating the quality of royal jelly in actual samples. The sensing strategy developed in this work provides a new colorimetric approach that holds great promise as a point-of-care platform for the food industry.

Hydrogel Paper-Based Analytical Devices: Separation-Free In Situ Assay of Small-Molecule Targets in Whole Blood.

While colorimetric-based assays are very convenient to determine biomarkers in point-of-care testing (POCT), they often suffer from pretreatment procedures for separation of plasma or serum from whole blood samples. Here, we report a simple colorimetric paper-based analytical device (c-PAD) that is capable of performing sample-to-answer analysis by directly dropping the whole blood sample on paper. This is accomplished by utilizing sodium alginate hydrogel, which exhibits a nanometer-scale porous structure to effectively prevent the passage of large red blood cells and hemoglobin molecules, to encapsulate enzymes and chromogenic reagents. As the small targets in the blood sample enter the sensing region to trigger a chromogenic reaction, the resulting color signal is recorded by a smartphone. The interference from the red blood to the color signal can be completely avoided without the requirement of any separation process. The analytical performance of the method is evaluated by assaying glucose in real blood samples. The results show that rapid and accurate analysis can be achieved with the limit of detection as low as 0.12 mM. In addition, simultaneous detection of different targets (glucose, cholesterol, and triglycerides) in whole blood can be achieved by fabricating c-PAD with multiple sensing regions. Owing to its several essential advantages including an extremely simple procedure for fabrication, sample-to-answer analysis without tedious pretreatment, and capability to perform high-throughput analysis, the proposed c-PAD will be of great value in POCT applications of whole blood samples.

Microfluidic paper-based analytical device by using Pt nanoparticles as highly active peroxidase mimic for simultaneous detection of glucose and uric acid with use of a smartphone

Herein, a simple microfluidic paper-based analytical device (μPAD) by using platinum nanoparticles (Pt NPs) as highly active peroxidase mimic for simultaneous determination of glucose and uric acid was fabricated. The μPAD consisted of one sample transportation layer, four paper-based detection chips, and two layers of hydrophobic polyethylene terephthalate (PET) films. The four detection chips were immobilized with various chromogenic reagents, Pt NPs, and specific oxidase (glucose oxidase or uricase). H2O2 generated by specific enzymatic reactions could oxidize co-immobilized chromogenic reagents to produce colored products by using Pt NPs as efficient catalyst. The multi-layered structure of μPAD could effectively improve the color uniformity and color intensity. Total color intensity from each two detection chips modified with distinct chromogenic reagents were used for quantitative analysis of glucose and uric acid, respectively, resulting in significantly improved sensitivity. The linear range for glucose and uric acid detection was 0.01–5.0 mM and 0.01–2.5 mM, respectively. Satisfied results were obtained for glucose and uric acid detection in real serum samples. An easy-to-use smartphone APP was developed for convenient and intelligent detection. The developed μPAD integrated with smartphone as detector holds great applicability for simple and portable on-site analysis.

Biocatalytic CsPbX3 Perovskite Nanocrystals: A Self-Reporting Nanoprobe for Metabolism Analysis.

CsPbX3 perovskite nanocrystals (NCs), with excellent optical properties, have drawn considerable attention in recent years. However, they also suffer from inherent vulnerability and hydrolysis, causing the new understanding or new applications to be difficultly explored. Herein, for the first time, it is discovered that the phospholipid membrane (PM)-coated CsPbX3 NCs have intrinsic biocatalytic activity. Different from other peroxidase-like nanozymes relying on extra chromogenic reagents, the PM-CsPbX3 NCs can be used as a self-reporting nanoprobe, allowing an "add-to-answer" detection model. Notably, the fluorescence of PM-CsPbX3 NCs can be rapidly quenched by adding H2 O2 and then be restored by removing excess H2 O2 . Initiated from this unexpected observation, the PM-CsPbX3 NCs can be explored to prepare multi-color bioinks and metabolite-responsive paper analytical devices, demonstrating the great potential of CsPbX3 NCs in bioanalysis. This is the first report on the discovery of nanozyme-like property of all-inorganic CsPbX3 perovskite NCs, which adds another piece to the nanozyme puzzle and opens new avenues for in vitro disease diagnostics.

Neutralization antibody titers against SARS-CoV-2 in an infant born to a mother with COVID-19

Neutralization antibody titers against SARS-CoV-2 in an infant born to a mother with COVID-19