Chromogenic Agent Research Articles

A Facile and Highly Efficient Approach to Obtain a Fluorescent Chromogenic Porous Organic Polymer for Lymphatic Targeting Imaging.

Porous organic polymers have an open architecture, excellent stability, and tunable structural components, revealing great application potential in the field of fluorescence imaging, but this part of the research is still in its infancy. In this study, we aimed to tailor the physical and chemical characteristics of indocyanine green using sulfonic acid groups and conjugated fragments, and prepared amino-grafted porous polymers. The resulting material had excellent solvent and thermal stability, and possessed a relatively large pore structure with a size of 3.4 nm. Based on the synergistic effect of electrostatic bonding and π–π interactions, the fluorescent chromogenic agent, indocyanine green, was tightly incorporated into the pore cavity of POP solids through a one-step immersion method. Accordingly, the fluorescent chromogenic POP demonstrated excellent imaging capabilities in biological experiments. This preparation of fluorescent chromogenic porous organic polymer illustrates a promising application of POP-based solids in both fluorescence imaging and biomedicine applications.

Synthesis of carnation flower-like Bi2O2CO3 photocatalyst and its promising application for photoreduction of Cr(VI)

In this study, we have synthesized high-quality carnation flower-like Bi2O2CO3 hierarchical architectures via a hydrothermal route. The as-synthesized Bi2O2CO3 photocatalyst was systematically characterized and analyzed by various techniques. Its photocatalytic activity was investigated by simulated-sunlight driving photoreduction of Cr(VI), revealing that it exhibits excellent photocatalytic removal of Cr(VI). The effects of various factors (H2SO4, NaOH, Cr(VI) concentration, catalyst dosage) on the photoreduction efficiency and involved mechanism were systematically investigated and discussed. In addition, we have also systematically examined the effects of various parameters (H2SO4 concentration, 1,5-diphenylcarbazide (DPC) concentration, Cr(VI) concentration, reaction time t and reaction temperature T) on the absorbance of the Cr(VI) solution, with the aim of correctly determining the Cr(VI) concentration according to UV–vis absorption measurements using DPC as the chromogenic agent.

Novel nanocomposite film developed via screen-printing of viologen polymer for anti-counterfeiting applications: Photochromism, thermochromism and vapochromic

Novel photochromic, thermochromic and gaseous ammonia sensing paper sheets were developed via screen-printing with a viologen-based covalent polymer, resulting in multi-stimuli responsive chromogenic paper substrates. The viologen-based covalent polymer was synthesized from the polymerization of a hydroxyl-substituted aryl-dihydrazide with a viologen-dialdehyde in an acidic aqueous medium. Translucent viologen/resin nanocomposite films prepared on the surface of the paper sheets were developed by the well-dispersion of the covalent organic viologen polymer as a chromogenic agent in a resin-based binder solution without aggregation. As shown by CIE coloration measurements, the translucent film immobilized on cellulose paper surface became green when exposed to UV light. Organic nanocomposite-containing a covalent organic polymer of viologen and a resin binder was used to make a new photochromic film for anti-counterfeiting papers. The photochromic impact was explored at various concentrations of the covalent organic viologen polymer. When exposed to ammonia gas, the viologen-coated paper strips changed color from yellow to green very rapidly. It recovered to yellow immediately after being removed away from the ammonia stimulus. The present paper strip demonstrated a detection limit for aqueous ammonia ranging between 15 and 350 ppm. In addition, heat (95 °C) was able to reversibly trigger the color transformation process. The thermal properties of the synthesized viologen-based covalent polymer were also investigated. Under UV irradiation, the screen-printed documents exhibited a reversible photochromism with high photostability. In addition to examining the rheologies of the generated nanocomposites, the screen-printed papers mechanical and morphological properties were also explored.

Color-deconvolution-based feature image extraction and application in water quality analysis.

We propose a feature color extraction method that improves the accuracy of water quality analysis using a digital image and eliminates the effect of interfering ions and chromogenic agents on the color after a color reaction. The proposed method is based on color deconvolution (CD) combined with machine learning for substance measurement in water. After an ordinary camera acquires the solution image after color reaction, the CD algorithm is applied to extract the feature image, calculate the first-order, second-order, and third-order color moments corresponding to RGB channels, and construct a gradient boosting regression tree prediction model based on color moment features to detect substances in water. In predicting ammonia, nitrite, and orthophosphate concentrations, the mean square error values were 0.01029, 0.00063, and 0.1361, and the mean absolute error values were 0.08103, 0.02231, and 0.32886, respectively. There was no significant difference in the results of the comparative spectrophotometric method on the actual water samples. The spiked recoveries of the samples ranged from 94% to 120%, confirming that the method can effectively measure the content of substances in water.

Long-term stable, high accuracy, and visual detection platform for In-field analysis of nitrite in food based on colorimetric test paper and deep convolutional neural networks

Nitrite is one of the most common carcinogens in daily food. Its simple, rapid, inexpensive, and in-field measurement is important for food safety, based on the requirements of the standard from Codex Alimentarius Commission and China. Using polyacrylonitrile (PAN) and thin layer silica gel (SG), p-aminophenylcyclic acid (SA) and naphthalene ethylenediamine hydrochloride (NEH), as carriers and chromogenic agents, respectively, PAN-NSS as nitrite color sensor is proposed. After fixing and protecting of SA and NEH with layer-upon-layer PAN, the validity period of the test paper can be prolonged from 7 days to more than 30 days. The reproducibility of PAN-NSS preparation is ensured by electrospinning. Combined with PAN-NSS, deep convolutional neural network (DCNN) and APP as a visual monitoring platform, which has the functions of rapid sampling, data processing and transmission, intuitive feedback, etc., and provides a fully integrated detection system for field detection.

Optical Determination of Lithium Levels in Artificial Interstitial Fluid for Treatment Management of Bipolar Disorder.

Bipolar Disorder (BD), characterized by mood fluctuating between episodes of mood elevation and depression, is a leading cause of disability worldwide. Lithium continues to be prescribed as a first-line mood stabilizer for the management of BD. However, lithium has a very narrow therapeutic index and it is crucial to carefully monitor lithium plasma levels as concentrations greater than 1.2 mmol/L are potentially toxic and can be fatal. The current techniques of lithium monitoring are cumbersome and require frequent blood tests with the consequent discomfort which results in patients evading treatment. Dermal interstitial fluid (ISF), an underutilized information-rich biofluid, can be a proxy for direct blood sampling and allow lithium drug monitoring as its lithium concentration is proportional to the concentrations in blood. Therefore, in this study we seek to investigate the measurement of lithium therapeutic concentrations in artificial ISF. Our study employs a colorimetric method, based on the reaction between chromogenic agent Quinizarin and Li+ ion which can be detected using optical spectroscopy in the visible region (400-800 nm), to determine lithium levels in artificial ISF. The resulting spectra of our experiments show spectral variations which are related to lithium concentrations in spiked samples of artificial ISF, with a correlation coefficient (R) of 0.9. Future work will focus on investigating the feasibility of utilizing ISF for real-time and minimally-invasive lithium drug monitoring.

A Novel Colorimetric Chemosensor Based on Ferene-S-Conjugated Silver Nanoparticles for Selective Recognition of Fe2+

Ferene is the most commonly used chromogenic agent for the determination of serum iron in blood. In this work we have successfully synthesized Ferene-S-conjugated silver nanoparticles (Ferene-S-AgNPs) for the first time characterized by UV-visible, Fourier-Transform Infrared Spectroscopy (FTIR), and Matrix-Assisted Laser Desorption/Ionization-Time Of Flight (MALDI-TOF) mass spectrometry techniques. Particle size of the synthesized nanoparticles was determined by atomic-force microscopy and scanning electron microscopy techniques with size ranges from 10–90 nm in diameter. Ferene-S-AgNPs were explored for their chemosensing potential with various metal ions such as Sb3+, Pb2+, Ca2+, Fe2+, K+, Co2+, Ba2+, V5+, Cu+, Cd2+, Hg2+, Ni2+, Cu2+, Fe3+, Mg2+, Mn2+, Al3+, and Cr3+. Ferene-S-AgNPs were found to show selective quenching effects and slight bathochromic shifts to the surface plasmon resonance absorption band after treatment with Fe2+. Furthermore, the developed chemosensor also exhibited substantial selectivity towards Fe2+ in the presence of other competitive ions. We observed that Ferene-S-AgNPs mimic the selectivity of the parent compound of Ferene towards Fe2+. The system obeyed Beer’s law over concentration ranges of 110–190 nM. The detection limit was found to be 110 nM.

Dual-mode immunoassay for diethylstilbestrol based on peroxidase activity and photothermal effect of black phosphorus-gold nanoparticle nanohybrids

Nanozyme-mediated 3,3′,5,5′-tetramethylbenzidine (TMB) - H2O2 systems have spawned the establishment of multiple colorimetric sensing platforms that are effective but sometimes subject to low sensitivity. Taking temperature as the output signal, photothermal effects lead to new strategies for sensitive detection. In this paper, a colorimetric and photothermal dual-mode immunoassay for diethylstilbestrol (DES) was constructed. It is based on the oxidation reaction of TMB catalyzed by black phosphorus-gold nanoparticle (BP/Au) nanohybrids, and the kinetics as well as catalytic mechanism of the nanohybrids were investigated in detail for the first time. Herein, the nanohybrids playcatalytic and photothermal dual roles. Moreover, the one-electron oxidation product of TMB (oxidized TMB) not only acts as chromogenic agent but also an excellent NIR laser-driven photothermal agent. The temperature (ΔT/°C) was gauged by a portable digital thermometer. Through an indirect competition strategy, a simple, sensitive, and economic immunosensor was proposed. Higher DES content in the sample correlated with less BP/Au nanohybrids conjugated to the surface of ELISA microplate, a weaker color change, and a lower temperature variation when exposed to laser irradiation. This method was applied for DES determination in real samples with gratifying recovery rates, showing great promise in food safety inspection applications.

Preparation and process optimization of microbial organic copper as a feed additive

ABSTRACT As an essential trace element for animals, copper significantly contributes to the growth and health of animals. Compared to inorganic trace elements, organic trace elements are better supplements; notably, they are acquired through microbial transformation. Therefore, we screened for copper-enriched microorganisms from high copper content soil to obtain organic copper. Sodium diethyldithio carbamate trihydrate was applied as a chromogenic agent for determining micro amounts of intracellular copper through spectrophotometry. In total, 50 fungi were isolated after the successful application of the screening platform for copper-rich microbes. Following morphological and molecular biology analyses, the N-2 strain, identified as Aspergillus niger sp. demonstrated showed better copper enrichment potential than others. Notably, the strain tolerance to copper was nearly thrice that of Saccharomyces cerevisiae, up to 1600mg/L. The content of the organic bound copper was 22.84mg Cu/g dry cell. Using the Central Composite Design (CCD) response surface method, we optimized the fermentation condition (inoculation amount, 13%; temperature, 28(C; pH, 5.0). Compared to the original strain results under the single factor fermentation condition, we reported an increase by 24.18% under the optimized conditions. Collectively, these findings provide a reference for uncovering new and low-cost organic copper additives.

Detection of tyrosine catalyzed by a Tb-MOF luminescent nanozyme

A luminescent nanozyme was designed and synthesized for the enzymatic luminescence assay of tyrosine. This luminescent nanozyme is composed of luminescent Tb3+, catalytic Fe3O4 nanoparticle and antenna ligand 4,5-imidazoledicarboxylic acid (IDA) through flexible MOF (metal-organic framework) structure, and has dual functions of luminescence-sensing and catalysis like peroxidase. The catalytic reaction-triggered-luminescence of Tb3+ ion is able to sense pM level of tyrosine in human serum. Such a luminescent nanozyme can be used to replace the combination of natural enzymes and chromogenic agents currently widely used in enzyme-based assays, providing a promising prospect for innovating various enzyme-based assays.

Comparison of color stability of different coated esthetic orthodontic archwires using spectrocolorimeter – An invitro study

Aim: The aim of this study was to evaluate and compare the colour stability of three different esthetic archwires (rhodium, teflon and epoxy coated) immersed in three different staining solutions (tea, coffee and artificial aerated orange drink) at different time intervals (0, 7, 14, 21, 45 day) using spectrocolorimeter and also to determine the most chromogenic agent. Materials and Methods: A total of 54 esthetic coated archwires (rhodium, teflon and epoxy) were evaluated. They were divided into 3 groups (archwires) with each group having 3 subgroups (staining solutions) and six samples in each sub group. The baseline value (T0) was measured before the samples were immersed in the staining solutions. The samples were immersed in the staining solution for 3 hours a day for 45 days. The ?E values were recorded on 7, 14, 21 and 45 day using spectrocolorimeter. Using these values NBS units were calculated. The experimental data were analyzed using descriptive statistics, analysis of variance, and post hoc Bonferroni test. Results: It was found that teflon coated esthetic archwires were the least colour stable when compared with rhodium and epoxy coated esthetic archwires. Artificial aerated orange drink caused higher ?E* values than tea and coffee. The ?E* value increases as the time interval increases. Conclusions: All esthetic archwires evaluated in the present study were stained the most by an artificial aerated orange drink in comparison with coffee and tea. The overall study outcome indicates that archwires coated with epoxy resin are more advisable for patients because of their colour stability. Keywords : Colour stability, Esthetic archwires, Staining solutions, Spectrocolorimeter.

Photochemical Vapor Generation of Halides in Organic-Acid-Free Media: Mechanism Study and Analysis of Water Samples.

Herein, we report a discovery that photochemical vapor generation (PCVG) of halides (bromide, chloride, and fluoride) can be realized in organic-acid-free media, with figures of merit comparable to those in classical scenarios employing acetic acid. Metal acetates, copper salts, and mixtures of different acetates and copper salts were evaluated for their performance in facilitating PCVG of halides; the formation of copper acetate complexes turned out to play a crucial role. Methyl halides (CH3X, X = Br, Cl, F) were identified by gas chromatography-mass spectrometry (GC-MS) as principal volatile compounds. Several important intermediate species, including cuprous ions (Cu+), methyl (•CH3), and hydroxyl (•OH) free radicals, were confirmed using cuproine, 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO), and coumarin as a chromogenic agent, radical tracer, and fluorescence probe based on UV-vis, GC-MS, and fluorescence spectroscopy, respectively. The ligand to metal charge transfer (LMCT) between acetate and copper and the charge transfer to solvent (CTTS) excitation of halides were considered to account for the generation of methyl halides in organic-acid-free media. The presence of 100 and 200 μg mL-1 of CuAc2, as well as sample delivery rates of 10.7 and 3.3 mL min-1, yielded limits of detection of 0.03 and 3 μg L-1 for Br- and Cl-, respectively, by inductively coupled plasma mass spectrometry (ICPMS). The method was applied to the analysis of bottled water and seawater, achieving spike recoveries between 92 and 101%.

Molecularly imprinted electrospun fiber membrane for colorimetric detection of hexanoic acid

Abstract An imprinted electrospun fiber membrane was developed for the detection of volatile organic acids, which are key components of human body odor. In this study, hexanoic acid (HA) was selected as the target, polymethyl methacrylate (PMMA) was used as the substrate, and colorimetric detection of HA was achieved by a bromocresol purple (BCP) chromogenic agent. The results showed that the morphology of the fiber membrane was uniform and continuous, and it showed excellent selectivity and specificity to HA. Photographs of the color changes before and after fiber membrane adsorption were recorded by a camera and quantified by ImageJ software by the difference in gray value (ΔGray). This method is simple, intuitive, and low cost and has great potential for application in human odor analysis.

Determination of available phosphorus in alkaline soil by molybdenum blue spectrophotometry

A rapid and accurate method for the determination of available phosphorus in alkaline soil by molybdenum blue spectrophotometry was established. The alkaline soil samples were extracted by Olsen method. The effects of absorption wavelength, amount of chromogenic agent, amount of reducing agent and colour reaction time on the determination results were investigated. The results showed that the optimal conditions were as follows: the maximum absorption wavelength was 700 nm, the amount of chromogenic agent was 1 mL, the amount of reducing agent was 1 mL, and the colour reaction time was 15 min. The linear range of phosphorus concentration was 0.3 μg/mL ~ 1.8 μg/mL, and the recoveries ranged from 88.67 % to 92.17 %. The method is simple, sensitive and accurate.

Teeth discolouration and prescribed slimming magistral formula: a case report

Introduction Tooth discolouration is a common subject of aesthetic dissatisfaction for which patients seek dental care [1,2]. Discolouration can be extrinsic (chromogenic agents deposited on the tooth surface – enamel), intrinsic (chromogens deposited within the bulk of the tooth – dentin), and internalised discolouration, a combination of both [1,2]. Different factors can be accountable for dental staining, such as certain medicines, smoking, some foods/beverages (e.g. coffee, tea, wine), poor oral hygiene (e.g. chromogenic bacteria), advancing age, trauma or disease [3]. Medicines known to discolour teeth, especially during tooth development, include antibiotics, antihistamines, antihypertensives, antipsychotics and fluoride [2,3]. Yet, there are numerous drugs with scarce information in literature about its potential for tooth discolouration. To the best of our knowledge this is the first report of a patient´s tooth discolouration by staining, suspected to result from a prescribed magistral formula (MF) for weight loss. Materials and methods This study details a case of a non-smoking 51-year-old Caucasian woman presenting severely stained teeth and a clinical history of depression and pre-obesity, medicated with escitalopram (20 mg; antidepressant) and loflazepate (2 mg in SOS; anxiolytic). The patient referred taking hard gelatine capsules for weight loss (once daily for 3 weeks), prescribed as a MF; each unit was composed of chlordiazepoxide (8 mg; anxiolytic), phenolphthalein (PhP; 65 mg; laxative), furosemide (20 mg; diuretic), metformine (280 mg; antidiabetic), bupropion (120 mg; antidepressant), artichoke extract (110 mg; allegedly choleretic and diuretic), Citrus aurantium extract (150 mg; claimed stimulant and thermogenic). Written consent for data use was obtained from the patient. Results Several teeth presented discolouration by staining as dark brown spots, which together with the clinical history, allowed the establishment of aetiology and selection of treatment. The dental cleaning procedure (with ultrasound and final polishing with a zirconium silicate particles-based prophylaxis paste, without fluoride) was effective. Slimming MF was discontinued and staining did not reappear (up to 3 months), even though the patient maintained her other habits. Neither drugs, nor botanicals, in the patient’s MF were identified in literature as tooth stain-causing molecules. Discussion and conclusions The colour and type of staining is consistent with deposition of chromogens in tooth crests. Xerostomia, a common side-effect of the antidepressants, may have potentiated the chromogens' deposition, although the medicine did not enter in close contact with teeth. A systemic manifestation of the drug, as a result of a combination of intrinsic and extrinsic factors, is also possible. Stains may have originated from tainted plant extracts (containing tannins or uncontrolled/unlabeled heavy metals − Fe, Cu, Cd, Sn − due to phytogeography; contaminants) or PhP (an acid–base titration reagent, changing colour according to pH), here used as a stimulant laxative, withdrawn from medicines in many European countries due to its carcinogenic potential. The hypotheses raised warrant further investigation and clarification of the role of drugs/botanicals and contaminants in tooth staining.

Magnetic separation and enzymatic catalysis conjugated colorimetric immunosensor for Hepatitis B surface antigen detection

Hepatitis B Surface Antigen (HBsAg) is usually recognized as an earliest diagnostic markers for Hepatitis B Virus (HBV) infections. The precise and sensitive determination of HBsAg is crucial for the diagnostic of HBV infection. In this paper, a colorimetric immunosensor has been successfully designed and fabricated based on conjugating magnetic separation and enzymatic catalysis, for point-of-care detection of HBsAg. The HBsAg was simultaneously captured by the biotinylated HBsAg primary antibody (biotin-Ab1) labeled immunomagnetic nanoparticles and detection antibody (Ab2). In conjugation with Ab2, horseradish peroxidase (HRP) labeled rabbit anti-goat secondary antibody was linked with chromogenic agents to induce the colorimetric signal. As a result, a good linear relation was achieved between the concentration of HBsAg and OD450 nm (absorbance values at 450 nm) in the 0.1–20 ng mL−1 ranges, demonstrating a great specificity to HBsAg with a limit of detection of 0.012 ng mL−1. Furthermore, considering its succeed in real human serum sample test, this immunosensor could make contribute to potential applications in rapid diagnosis, effective prevention of epidemic and infectious diseases.

Selective colorimetric detection of copper (II) by a protein-based nanoprobe

In this work, we report a novel protein-based nanoprobe (PNP) that can be employed for quantitative analysis of Cu2+ in pure water medium and real samples. Structurally, the proposed nanoprobe comprises a biofriendly protein (hen egg-white lysozyme (HEWL)) and a Cu2+-specific chromogenic agent, where HEWL acts as a nanocarrier encapsulating a structurally tailored rhodamine B derivate. The resulting PNP exhibits a hydrodynamic diameter of ~ 106 nm and efficiently disperses in water, enabling the detection of Cu2+ in pure aqueous systems without the aid of any organic co-solvents. The high sensitivity and selectivity of PNP allow the colorimetric detection of Cu2+ in the presence of other metal interferents with a low detection limit of 160 nM. The satisfying recovery of trace level Cu2+ in environmental samples demonstrate the great potential of employing PNP for the determination of Cu2+ in actual applications. Most importantly, the simple co-grinding method employing proteins and chromogenic agents provides a novel strategy to generate sensing systems that are useful detection of pollutants in aqueous samples.

Reversible Thermochromic Ink based on Crystal Violet Lactone/Boric Acid/Hexadecyl Alcohol for Anti-Counterfeiting Printing

The purpose of the study is to prepare reversible thermochromic materials with good discoloration properties, which are used as fillers to prepare a new type of reversible thermochromic ink. Reversible thermochromic materials were prepared by solid phase method with crystal violet lactone as chromogenic agent, boric acid as chromogenic agent and hexadecanol as cosolvent, and reversible thermochromic ink was prepared by using thermochromic material as filler. The scanning electron microscope images of reversible thermochromic materials showed that the prepared materials were spherical and had the advantages of non-adhesion. The printability of reversible thermochromic ink was discussed by changing the parameters including content of thermochromic material, printing pressure, ink sequence and using printability tester. The test of color change performance of thermochromic ink showed that the color change temperature range was 47.5–51.1 ◦ C, the color change time was 46 s, the recolor time was 29 s, and the stability was excellent. The reversible thermochromic ink has a certain application value in anti-counterfeiting printing.

Advances in the study of chromogenic agents in meat products

In order to improve the organoleptic properties, edible quality and flavor of meat products, and extend its shelf life, some additives are commonly used to guarantee the color retention of meat products. Nitrate and sodium nitrite are frequently-used chromogenic reagents, but it has been proven that their usage has potential safety risks. Excessive consumption of them can cause carcinogenesis, teratogenesis, and mutation. Therefore, the search for other effective alternatives is imminent, which has become a research hotspot at home and abroad. This paper expounds the problems in the processing of meat products and the mechanism of chromogenic reagents. The effect of chromogenic reagents on the preservation of meat products is also discussed, which provides a reference for further research on meat chromogenic reagents.

Development of Sars-Cov-2 Isothermal Amplification Detection Kits

The SARS-CoV-2 isothermal amplification detection kits based on loop-mediated isothermal amplification (LAMP) were developed and evaluated on three types samples of SARS-CoV-2 The kits included enzyme reaction mixtures and chromogenic agents After the isothermal amplification reactions were completed, the reaction results were judged by using the chromogenic agents to determine whether SARS-CoV-2 exists in the samples to be tested The detection kits have the advantages of convenient operation, fast detection speed and high sensitivity up to 1 copy of virus particles per reaction, which can speed up the detection speed of suspected cases, and avoid the missing detection problems caused by the low detection sensitivity