Color Reaction Research Articles

Construction of a dual-model aptasensor based on G-quadruplexes generated via rolling circle amplification for visual/sensitive detection of kanamycin

A dual-model colorimetric and electrochemical aptasensor was designed using a large number of G-quadruplexes generated by rolling circle amplification (RCA). Specific binding between target and aptamer during RCA yielded large numbers of G-quadruplexes. A colorimetric sensor was fabricated based on the interaction between the G-quadruplex and hemin, which altered the 3,3′,5,5′-Tetramethylbenzidine (TMB)-catalyzed color reaction and facilitated the visual and semi-quantitative detection of kanamycin. An electrochemical sensor was constructed based on the strong interaction between the G-quadruplex and the methylene blue electrical signal molecule. Combining nanocomposites multi-walled carbon nanotubes-chitosan/gold nanoparticles (MWCNTs-CS/AuNPs) and RCA realized double-amplified electrochemical signals. Under optimized conditions, a linear relationship was obtained as the logarithm of different concentrations of kanamycin (KAN). The colorimetric aptasensor had a linear range of 1 × 102 nM to 1 × 103 nM with a detection limit of 1.949 nM. The electrochemical aptasensor had wider a linear range from 1 × 10−3 nM to 2.5 × 103 nM and a lower detection limit of 0.333 pM. The sensor combined the advantages of simple colorimetric visualization with the ultra-precision of electrochemical methods. Aptasensor showed good specificity and prevented interference. Furthermore, the prepared dual-model aptasensor facilitated the practical monitoring of KAN in milk.

Didymodonmanhanensis (Pottiaceae, Bryophyta), a new species from Inner Mongolia steppe, China and its phylogenetic position, based on molecular data.

Inner Mongolia steppe is one of the suitable habitats for Didymodon species and a new species, Didymodonmanhanensis C. Feng & J. Kou from Manhan Mountain in semi-arid region in Inner Mongolia, China is described and illustrated. It is characterised by leaves incurved and slightly twisted when dry, spreading when moist, narrowly lanceolate from an ovate base; subulate and fragile leaf apices; distally bistratose leaf margins that are recurved in proximal 2/3-3/4; excurrent costa with guide cells in 2-3 layers and without ventral stereids; smooth laminal cells and red KOH laminal colour reaction. Our morphological analyses and molecular results, based on DNA sequences of ITS, rps4 and trnM-trnV, confirm that D.manhanensis belongs to a group that includes D.obtusus J. Kou, X.-M. Shao & C. Feng and D.daqingii J. Kou, R.H. Zander & C. Feng. This new species is compared with similar species and its phylogenetic position and ecology are discussed.

Analysis of Methanol Yellow in Yellow Food Circulating in the Jambi City Market

Introduction: Metanil yellow is a synthetic dye commonly used in the textile, paper, paint industry, but is sometimes misused as a food coloring. The misuse of methanil yellow coloring includes noodles, crackers and snacks and tofu which has a striking yellow color. Research Objectives: To determine the presence of Methanyl Yellow dye in yellow food circulating in Angso Duo. Research Methods: By using the identification of Color Reaction, Thin Layer Chromatography (TLC) and UV-VIS Spectrophotometry. Research Results: Based on the results of research conducted on 9 yellow food samples circulating in the Angso Duo market using the Color Reaction method, Simple Application, Thin Layer Chromatography (TLC) and UV-Vis Spectrophotometry showed negative results (-). Conclusion: In this study, it can be concluded that the 9 food samples did not identify any prohibited dyes, namely methanyl yellow and free from the colorant content of methanyl yellow.

Construction of Pd Single Site Anchored on Nitrogen-Doped Porous Carbon and Its Application for Total Antioxidant Level Detection

Natural enzymes have excellent catalytic activity. However, due to their unstable nature and high cost, current research has turned to the synthesis and development of enzyme-like nanomaterials and single-atomic nanozymes. In this study, a single-atomic palladium-loaded nitrogen-doped porous carbon catalyst (SA-Pd/NPC) was prepared and used as a mimetic peroxidase to catalyze the substrates oxidation. The catalytic capability of the SA-Pd/NPC was tested by the TMB-H2O2 system, and it expressed a superior catalytic capability owing to the plentiful catalytic centers of the single-atom Pd, its high porosity, the large specific surface area, and the strong electron transfer capability of the NPC. For the color reaction of TMB, thiol antioxidants (e.g., glutathione, GSH) and non-thiol antioxidants (e.g., ascorbic acid, AA) are suitable for different inhibition mechanisms. GSH and AA are typical substances of these two main antioxidant types, respectively. Here, we demonstrate that this prepared catalyst could be used to simultaneously determine a variety of major known physiologically relevant thiol-containing and thiol-free antioxidants, accompanied by a blue color gradient change with UV–Vis spectra at 652 nm through the SA-Pd/NPC-catalyzed TMB-H2O2 system. Linear responses to GSH and AA could be obtained in the concentration ranges of 0.01–0.10 mM and 1–13 μM (both R2 values were greater than 0.970), respectively, while the limits of detection were 3 μM and 0.3 μM, respectively. The ability of the nanozyme to detect overall antioxidant levels (TAL) was also confirmed in subsequent tests on artificial saliva and biological samples.

Mechanism of bluish pigment formation in lotus rhizome starch with ferrous sulfate and its application in rapid detection of adulteration

ABSTRACT Lotus rhizome starch (LRS) is an important traditional processed product of lotus rhizome in China due to its good taste and high nutritional value. However, adulterated lotus rhizome starches are prevalent on the market. In this study, a novel method for the rapid detection of adulteration in LRS based on color reaction between ferrous sulfate (FS) and (-)-gallocatechin (GC) in LRS was studied. The polyphenols in LRS were analyzed by liquid chromatography-mass spectrometry (LC-MS/MS) as GC and (+)-catechin, and GC could show a bluish color with FS solution. LRS showed a bluish color when FS solution (0.01 mol/L) was used as the chromogenic agent, which was not observed for other ten kinds of starches tested in this work. There was an obvious color gradient when FS solution was used to react with adulterated LRS at different proportions, and the change in blue color was obvious when maize starch or cassava starch was adulterated in LRS at the ratio of 6:4. Then, a semi-quantitative method was used to make a color card according to the color gradient, which was then successfully used to detect the adulteration of four kinds of commercial LRS. The results indicate that the proposed method may facilitate the simple, effective and efficient detection of adulteration in LRS.

Recent Advances in Analytical Methods for Determination of Polyphenols in Tea: A Comprehensive Review.

Polyphenols, the most abundant components in tea, determine the quality and health function of tea. The analysis of polyphenols in tea is a topic of increasing interest. However, the complexity of the tea matrix, the wide variety of teas, and the difference in determination purposes puts forward higher requirements for the detection of tea polyphenols. Many efforts have been made to provide a highly sensitive and selective analytical method for the determination and characterization of tea polyphenols. In order to provide new insight for the further development of polyphenols in tea, in the present review we summarize the recent literature for the detection of tea polyphenols from the perspectives of determining total polyphenols and individual polyphenols in tea. There are a variety of methods for the analysis of total tea polyphenols, which range from the traditional titration method, to the widely used spectrophotometry based on the color reaction of Folin–Ciocalteu, and then to the current electrochemical sensor for rapid on-site detection. Additionally, the application of improved liquid chromatography (LC) and high-resolution mass spectrometry (HRMS) were emphasized for the simultaneous determination of multiple polyphenols and the identification of novel polyphenols. Finally, a brief outline of future development trends are discussed.

Interfacial Reinitiation of Free Radicals Enables the Regeneration of Broken Polymeric Hydrogel Actuators

Interfacial Reinitiation of Free Radicals Enables the Regeneration of Broken Polymeric Hydrogel Actuators

Salivary TIMP1 and predicted mir-141, possible transcript biomarkers for estrus in the buffalo (Bubalus bubalis)

Successful reproductive management of buffaloes depends primarily upon timely estrus identification. However, 50% of the estrus events are undetected in buffaloes with the available estrus identification methods, leading to huge financial loss to buffalo farmers. Hence, there is an urgent need to develop an alternative and accurate estrus identification method, particularly on the basis of biomarkers in non-invasive fluids. Thus, the present study aimed to identify RNA based estrus biomarkers in cell free saliva in Bubalus bubalis, so that they can be used for future field applicable RT-LAMP colour reactions. RNA-Seq analysis of cell free salivary RNA showed 49 differentially abundant mRNAs between the estrus and diestrus stages. Among five mature miRNAs predicted from the RNA-Seq data, four were found differentially altered at the estrus stage than the diestrus stage. Validation study by direct salivary transcript analysis (DSTA) on 6 selected mRNAs (PPARGC1a, TIMP1, PEBP4, CSPG5, PRHR and ATOH7) and 5 miRNAs (bta-miR-92b, bta-miR-302d, bta-miR-141, bta-miR-27a and bta-let-7a-5p) showed significantly higher levels of TIMP1 (3.46 fold; P<0.5) and bta-mir-141 (1.33 fold; P<0.5) in cell-free saliva at the estrus stage compared to the diestrus stage. Hence, TIMP1 and miR-141 appear to be the possible transcript biomarkers for estrus in the cell free saliva of the buffalo. However, further validation studies are required in a large population of buffaloes to determine their estrus biomarker potential before considering them for RT-LAMP colour reaction.

Neuropeptide FF-related gene in fish (Larimichthys polyactis): identification, characterization, and potential anti-inflammatory function.

Neuropeptide FF (NPFF), an octapeptide of the RFamide-related peptides (FaRPs), is involved in regulatory function in various biological processes. The regulatory role of NPFF in the immune and inflammatory response was currently being revealed. Neuropeptide FF-related gene (termed LpNPFF) and its two receptors, NPFF receptor 1 (LpNPFFR1) and NPFF receptor 2 (LpNPFFR2) were identified by PCR and Semi-quantitative RT-PCR assay. Effect of LpNPFF on the production of nitric oxide (NO) in macrophage RAW264.7 cell was divided into PBS group, lipopolysaccharide (LPS) group, LPS treated with LpNPFF group, and LPS treated with LpNPFF and receptor antagonist RF9 group. Then specimens were measured by color reaction at 570nm absorbance value. Sequence analysis showed that LpNPFF cDNA consists of 835 nucleotides with a 5'- untranslated region (UTR) of 150 base pair (bp), an open reading frame (ORF) of 384bp and a 3'-UTR of 300bp (Accession No. MT012894). The ORF encodes 127 amino acid (aa) residues with a hydrophobic signal peptide at N-terminus and two presumptive peptides with -PQRFa structure, LpNPFF (1) and LpNPFF (2). LpNPFFR1 and LpNPFFR2 encode 427 and 444 aa residues respectively, which both have seven hydrophobic TMDs and identified as G protein coupled receptors (GPCRs). Results of tissue distribution showed that LpNPFF and receptors were highly expressed in the brain and gonad. Furtherly, in vitro assay found LpNPFF could inhibit NO production in RAW 264.7 macrophages under inflammatory stress with LPS, while its receptor antagonist RF9 caused the evoke of NO generation. These results contribute to the further study of neuropeptide evolution in marine organisms, and also provide a new research idea for exploring the related functions of NPFF gene.

Comparative assessment of the co-production of bioethanol and single cell proteins from Sugarcane Bagasse, Rice Husks, and cassava peels using Saccharomyces cerevisiae

This work compares various waste sources of feedstock (cassava peels, sugarcane bagasse, and rice husks) for the co-production of bioethanol and single cell protein using Saccharomyces Cerevisiae as fermentation enzyme. Sulphuric acid solution was used for the pre-treatment, dilute hydrochloric acid was used for hydrolysis, temperature, time, and pH of 131.8 °C, 1 hr, and 5.3 respectively. Sodium hydroxide (NaOH) was used to adjust the pH of the hydrolysate to neutral (6.7). The primary component of the single-cell protein was ammonia (NH3), which was quantified using Kjeldahl's technique of analysis, while the bioethanol produced was assessed using the colorimetric and colored reaction method using a spectrophotometer. Sugarcane bagasse showed the highest amount of bioethanol (36.57 %) while Rice husks and Cassava peels showed 30.97 % and 29.31 % respectively. The greatest bioethanol production (47.85 %) was achieved by combining feedstock, cassava, and sugar cane feedstocks. The percentage of single cell protein generated from individual feedstock was the highest using sugarcane bagasse (29.4 %) while a sugarcane bagasse and cassava peels combination gave the highest concentration for single cell protein (43.6 %). The study has demonstrated efficient bioethanol and single cell protein (SCP) co-production from Saccharomyces Cerevisiae using sugarcane bagasse, cassava peels, and rice husk as feedstock.

Pharmacognostic and Phytochemical Evaluation of Leaf of Jatropha nana var. bengalense C.H. Rahaman and S. Mondal: An Endemic Member of Euphorbiaceae

Pharmacognosy Research,2022,14,2,204-210.DOI:10.5530/pres.14.2.29Published:April 2022Type:Original ArticleAuthors:Swarnendu Mondal, and Nayan Roy Author(s) affiliations:Swarnendu Mondal1,*, Nayan Roy2 1Department of Botany, Tribal Medicine and Pharmacognosy Lab., MUC Women’s College, Burdwan, West Bengal, INDIA. 2Department of Zoology, Ecology Research Unit, MUC Women’s College, Burdwan, West Bengal, INDIA. Abstract:Background: Pharmacognostic and phytochemical studies helps to maintain the quality of herbal products and purity of crude drugs by means of standardized parameters which will lead to developing the safest and efficacious natural products. Objectives: This study was undertaken to carry out pharmacognostic and phytochemical investigation of the leaves of the Jatropha nana var. bengalense (Euphorbiaceae), an ethnomedicinal plant. Materials and Methods: Epidermal Micromorphology, physical and physicochemical constants like ash value determination and UV-fluorescence study have been employed for pharmacognostic evaluation. For qualitative phytochemistry, microchemical color reaction test and TLC studies performed. Variations in different biochemical parameters of leaves of different developmental stages have been examined and the obtained data statistically analyzed following standard methods. Results: Typical paracytic type of stomata is found in hypostomatic condition distributed in irregular-shaped epidermal cells. Index of these stomata was found 20.251%. Phytochemical analysis in qualitative and quantitative approaches has also been done to describe its chemical variability. Ash value was found above 8% which shows more than 50% solubility in acid whereas water and ethanol solubility is found to be just below and above the 30% respectively. In UV- fluorescence study very distinctive colour changes of the powdered leaf have been recorded. Alcoholic extracts have shown positive results for presence of most of the phytochemical groups. Quantitative phytochemical analysis confirms that a range of phytochemicals are present in good amount in the leaves of this medicinal plant which could vary in amount in different developmental states. Thin Layer Chromatography has been carried out on ethanolic extract in two different solvent systems which show 6 different Rf values further indicates the presence of important phytochemical derivatives. Conclusion: This study will finally be needful for standardization of identification of the genuine drug, its adulterants and of the chemical constituents present in the leaves and finally bioprospection. Key words: Adulteration, Bioprospection, Euphorbiaceae, Jatropha nana var. bengalense, Pharmacognosy. View:PDF (450.58 KB)

Determination of Ultra-Trace Cobalt in Water Samples Using Dispersive Liquid-Liquid Microextraction Followed by Graphite Furnace Atomic Absorption Spectrometry.

A novel method for the determination of ultra-trace cobalt by dispersive liquid–liquid microextraction (DLLME) coupled with graphite furnace atomic absorption spectrometry has been developed. It is based on the color reaction of Co2+ with 2-(5-bromo-2-pyridylazo)-5-dimethylaminoaniline (5-Br-PADMA) in a Britton–Robinson buffer solution at pH 6.0 to form stable hydrophobic chelates, which were separated and enriched by DLLME with 1,2-dichloroethane (CH2ClCH2Cl) as extraction and acetonitrile (CH3CN) as a dispersive solvent. The sedimented phase containing the chelates is then determined with GFAAS. Parameters that affect extraction efficiency, such as types and volumes of extraction and disperser solvents, pH of sample solution, extraction time, concentration of the chelating agent 5-Br-PADMA, and salt effect, were investigated. Under optimal conditions, the calibration graph was linear over the range 0.05–1.0 ng/mL, with a correlation coefficient of 0.9922 and a detection limit of 0.03 ng/mL. Preconcentration factor (PF) is calculated as the ratio of the aqueous solution volume (5 mL) to that of the organic phase volume (40 μL), and enrichment factor (EF) is calculated as the ratio of the slopes of the calibration graphs obtained with and without DLLME for 5.0 mL of sample solution, which were 120 and 112.5, respectively. The extraction efficiency, calculated by EF/PF·100, was 93.8%. The relative standard deviation (RSD) at the 0.5 ng/mL Co2+ level was 3.8% (n = 6). The method has been applied to the determination of trace cobalt in water samples with satisfactory results.

Effect of color protection treatment on the browning and enzyme activity of Lentinus edodes during processing.

Fresh Lentinus edodes (L. edodes) are prone to browning (including enzymatic and nonenzymatic browning), which affects their quality and leads to economic losses during later processing. This study explored various effective color protection methods (color protection reagent and/or blanching) for inhibiting the browning of L. edodes. First, a single‐factor experiment and a response surface method were used to optimize the concentration of the color retention reagent. The compound color retention reagent (comprising 0.1% phytic acid, 0.8% sodium citrate, and 0.5% d‐sodium erythorbate) had the smallest total color difference (ΔE) value, suggesting that the compound color reagent had a better inhibiting effect than the single agent. Following this, the blanching conditions were studied; the polyphenol oxidase (PPO) activity was the lowest when the blanching temperature was 90°C and blanching time 180 s, indicating that browning is likely to be minimal. Finally, comparing the oxidase activity and total color difference (ΔE) revealed that combining the two color protection methods inhibits browning better than using a single method (color protection reagent or blanching). In addition, the polysaccharide and vitamin C (VC) contents of L. edodes under optimal color protection conditions were determined, which were 0.96 and 2.54 g/100 g fresh weight (FW), respectively. The results demonstrated that this color protection method effectively inhibits browning, reduces the nutritional loss, and improves the quality of L. edodes.

Development of total coliform detection kit using body temperature

Technological advances have increased access to clean water, but 3.4 million people around the world die from waterborne disease every year. Currently, there is equipment capable of detecting pathogens that cause waterborne disease, but access to detection equipment is limited in areas where power supply to use detection equipment is unavailable or where standard detection equipment is too expensive to purchase. In this paper, we will deal with the total coliform detection kit using body temperature that can be used in areas suffering from above difficulties. ColiQuant, total coliform detection kit using body temperature, is a method of putting sample water in a tube containing a substrate that shows a color reaction by an enzyme, culturing the total coliform using body temperature, and determining the presence of the total coliform through color change. In addition, it is possible to detect the total coliform at a lower price (3,000 won/$3) than existing equipment of millions of won or more, so it can be used easily in developing and underdeveloped countries. This paper introduces the research and development process of the total coliform detection kit using body temperature and present the social value of the ColiQuant.

In Situ Microreaction Platform Based on Acoustic Droplet Manipulation for Ultra-High-Precision Multiplex Bioassay.

Liquid droplets rectors have been used in clinical diagnosis, high throughput screening and bioassay. However, it is challenging for droplet reactors to be used in practical applications due to the difficulty of uniformly mixing ultrasmall volumes of samples and the lack of rapid and high-precision detection protocols. Here, we have developed an acoustic droplet system for rapid and efficient biological detection and chemical screening. By employing acoustic wave devices, rapid and nondestructive uniform mixing of ∼nL-μL droplets can be achieved. By the acoustophoretic force, the perturbation of the droplets can quickly concentrate the sample and increase the detection limit by five times. Through the color reaction and the coordinated detection of photodiodes, we have developed a biomarker detection protocol with short reaction time and high accuracy. As a proof-of-concept application, we demonstrated that this system can detect ultrasmall or low-abundance samples faster and more accurately, highlighting its wide application in analytical chemistry, basic research, and clinical medicine.

A novel design for split-and-recombine micromixer with double-layer Y-shaped mixing units

A novel split-and-recombine (SAR) micromixer with Y-shaped mixing units is proposed. The two sets of Y-shaped units are distributed periodically and in opposite directions. The micromixer has better mixing performance and smaller pressure loss due to the three-dimensional Y-shaped structure, splitting recombination, and chaotic convection mechanism. First, based on the finite element theory, with the mixing index and pressure loss as the objective function, the software COMSOL was used to simulate and analyze the structure parameters and performance of the micromixer. Then, a prototype was manufactured, and experimental platforms were set up in the lab. Finally, the color reaction and silver nanoparticle synthesis experiments were carried out to characterize and verify that the micromixer is feasible. Simulation and experimental results show that, as an important structural parameter of the micromixer, the channel aspect ratio φ has a great impact on its mixing performance and pressure loss. When the aspect ratio φ = 0.5, the micromixer has excellent overall performance; With the increase of the Reynolds number (Re =0.5–100), the mixing index tends to decrease and then increase, while the pressure loss gradually increases. It has a mixing index of 0.966 at Re = 5, and the mixing index reaches 0.9992 at Re = 100. The pressure loss ∆P is less than 350 Pa through seven Y-shaped units at Re = 100; The micromixer enables to obtain uniform and efficient color reactions and to synthesize silver nanoparticles with good size, morphology, and monodispersity. The micromixer has broad application prospects in chemical synthesis, biochemical analysis, and biomedicine.

3-Layer Immunoperoxidase Protocol Reaction, Endomucin, and Alpha-smooth Muscle Actin Detection

Background and objectives. Immunohistochemistry (IHC) is the detection of antigens in tissue sections by specific antibodies. It has the unique advantage over other methods for detection proteins like α-Smooth Muscle Actin and endomucin, enabling the correlation of antigens with their location within a tissue. The aim of the study was to identify α-SMA and endomucin in cardiac muscle tissue and arterial blood vessels which have important diagnostic purposes. Methods. Three Specimens (aSMA, Endomucin and control) of formalin-fixed paraffin embedded mouse embryo tissue sections have been de-waxed, rehydrated. Then they were covered with accurate primary antibody: αSMA slide in dilute mouse monoclonal anti-smooth muscle actin, Endomucin slide in dilute rat monoclonal anti-endomucin and the control slide gets just PBS (no-primary control). Then the sections were covered with the right secondary antibody: αSMA slide with biotinylated rabbit anti-mouse IgGIgG diluted and Endomucin slide with biotinylated rabbit anti-rat IgG, control slide with either antibody. Next color reagent was applied; it contains 3,3′-Diaminobenzidine and 0.3% hydrogen peroxide. Finally examine slides using a microscope. Results. The results showed that there was different brown 3,3′-Diaminobenzidine staining patterns in the two test slides for the individual primary antibodies. The 3,3′-Diaminobenzidine Staining was highly expressed in the external part of the section as a result of the presence of α-Smooth Muscle Actin. Whereas, in case of Endomucin, the stain is expressed in the central part of specimens due to presence of the endothelial tissue. and no staining in the primary control sections. Conclusion. As a result of the presence of α-Smooth Muscle Actin in the muscular tissue,3,3′-Diaminobenzidine Staining was highly expressed in the external part of the section. However, in case of Endomucin the stain is expressed in the central part of specimens due to presence of the endothelial tissue.

Analisis Kualitatif dan Kuantitatif Kandungan Hidrokuinon dalam Krim Pemutih Wajah yang Beredar di Pasar Tradisional Kabupaten Blora Jawa Tengah

Beautifying self with cosmetics is one of the ways that people interested. Consumer demand for face whitening cream is so high that many manufacturers market non-certified products containing harmful ingredients such as hydroquinone. In BPOM Regulation No. 23 of 2019 the use of hydroquinone in skin whitening is no longer allowed. Whitening cream is spread in traditional markets where a place to buy and sell various of products freely. This study aims to find out whether or not hydroquinone and its content in face whitening creams are circulating in the traditional market of Blora Regency. Sampling using pusposive sampling technique in the traditional market of Blora Regency. Samples obtained from 4 traditional markets as many as 8 samples consist of 4 samples with registration number BPOM (codes A, B, C and D) and 4 samples without registration number BPOM (codes E, F, G and H). Hydroquinone content examination includes qualitative analysis with pH measurement, color reagent and TLC and quantitative analysis with UV Spectrophotometry. The results of the hydroquine standard pH measurement showed an acid pH of 3.53-3.64 positive samples i.e. E-H samples ranging from 3.30-3.64. In the color reaction hydroquinone formed a black color with sediment, and in TLC obtained a hydroquinone Rf value of 0.9610 with a positive sample Rf value ranging from 0.9444-0.9610 so that the positive result of hydroquinone in the E-H sample. Quantitative analysis using UV Spectrophotometry showed hydroquinone levels in non BPOM code samples E, F, G and H ranging from 0.00123 % - 0.00178 %.

Exo-III enzyme based colorimetric small extracellular vesicles (sEVs) detection via G-quadruplex-based signal quenching strategy

Small extracellular vesicles (sEVs) are closely associated with physiological and pathological processes of a variety of diseases, such as osteosarcoma. Developing a simple and sensitive sEVs detection strategy is crucial to the in-deep study and clinical diagnosis of many disease. We developed here a colorimetric sEVs detection strategy based on SMBs (streptavidin magnetic beads)-capture probe-assisted sEVs recognition and Exo-III assisted signal amplification. Three processes were included in the established strategy: target sEVs recognition-mediated liberation of trigger sequence, Exo-III based signal amplification and DNAzyme catalyzed color reaction for signal output. Eventually, the proposed method exhibited a wide sEVs detection range from 102 to 106 particles/L, and possesses an excellent capability in discriminating CD63 positive sEVs. In addition, the detection assay can be potentially applied to accurate quantification of sEVs in constructed clinical samples, maintaining a favorable recovery rate of 98.7% to 102.4%. This method is easy-to-operate, highly sensitive, and free of complicated sEVs separation procedures and dye label.

A Robust Flow-Based System for the Spectrophotometric Determination of Cr(VI) in Recreational Waters.

A flow-based method for the spectrophotometric determination of chromium (VI) in recreational waters with different salinities was developed. Chromium can occur in the environment in different oxidation states with different related physiological properties. With regard to chromium, the speciation is particularly important, as the hexavalent chromium is considered to be carcinogenic. To achieve that purpose, the use of the diphenylcarbazide (DPC) selective colored reaction with the hexavalent chromium was the chosen strategy. The main objective was to develop a direct and simple spectrophotometric method that could cope with the analysis of different types of environmental waters, within different salinity ranges (fresh to marine waters). The potential interference of metal ions, that can usually be present in environmental waters, was assessed and no significant interferences were observed (<10%). For a complete Cr(VI) determination (three replicas) cycle, the corresponding reagents consumption was 75 µg of DPC, 9 mg of ethanol and 54 mg of sulfuric acid. Each cycle takes about 5 min, including the system clean-up. The limit of detection was 6.9 and 12.2 µg L−1 for waters with low and high salt content, respectively. The method was applied for the quantification of chromium (VI) in both fresh and marine water, and the results were in agreement with the reference procedure.