Carbon isotope ratio of organic acids in sake and wine by solid-phase extraction combined with LC/IRMS.

We developed an analytical procedure for determining the δ13C values of organic acids in sake and wine using solid-phase extraction combined with liquid chromatography/isotope ratio mass spectrometry (LC/IRMS). First, the solid-phase extraction (SPE) procedure was performed and various tests were conducted to extract organic acids from alcoholic beverages using the simulated sake sample. Under the optimal SPE procedure, high recovery rates (96-118%) and good accuracies (≤ 0.7‰) were thus achieved for the simulated sake and wine samples. Next, we determined the δ13C of organic acid (tartaric acid, malic acid, lactic acid, succinic acid) in 9 sake and 11 wine samples. Finally, the δ13C values of lactic acid in nine sake samples suggested that lactic acid had been added during the brewing process. The high correlation between the δ13C values of tartaric acid and malic acid in 11 wine samples was consistent with their common source, grapes. This analytical method may help to identify when organic acids have been added to sake and wine and to elucidate the process of organic acid production therein. Graphical abstract.

Simultaneous quantification of peroxidase and ascorbic acid in biosamples with an automatic system based on a Fe(iii)/methylthymol blue-carbon dot simulative enzyme.

Peroxidase (POD) and ascorbic acid (AsA) usually coexist in organisms to synergistically protect them from reactive oxygen damage, and their contents undergo dynamic changes under different physiological conditions. What's more, the response of POD-catalytic activity in spectrophotometry has to be corrected using the content of concomitant AsA because we found that there is an extinction reaction between AsA and chromogenic products obtained from POD catalysis. With these implications, by skilfully using the chromogenic and the extinction phenomena in the guaiacol/POD/H2O2 reaction, an automatic analysis system for simultaneous quantification of POD (73-440 U L-1) and AsA (4-60 mg L-1) was successfully established based on flow injection analysis (FIA). Furthermore, under acidic conditions (0.5 mol L-1 of HCl), hydrothermal synthesis (250 °C for 1 h) was used for synthesizing new carbon dots (sPOD-CDs) of methylthymol blue (0.08 g L-1)/FeCl3 (0.8 g L-1), which is a simulative enzyme for POD, and it was first used for catalyzing the guaiacol/H2O2 reaction within the FIA system to replace natural HRP in the extinction reaction. This sPOD-CD solution has no background absorption and its concentration shows excellent correlation with simulative POD-activity. Finally, after optimization, this FIA system was utilized to testify that the reducibility of AsA is due to ascorbate ions and to determine POD and AsA in some plant samples. The standard addition recovery experiment showed that there was no interference from the matrix in real samples (recoveries: 95%-105%), and the obtained POD and AsA results were also consistent with the reference experiments (relative deviation ≤ 2.80%, t-test ≥ 0.07). The proposed FIA system is characterized by high sample-throughput (40 samples per h), better repeatability (relative standard deviation ≤ 1.4%), etc.

Two-layer Electrospun System Enabling Wound Exudate Management and Visual Infection Response.

The spread of antimicrobial resistance calls for chronic wound management devices that can engage with the wound exudate and signal infection by prompt visual effects. Here, the manufacture of a two-layer fibrous device with independently-controlled exudate management capability and visual infection responsivity was investigated by sequential free surface electrospinning of poly(methyl methacrylate-co-methacrylic acid) (PMMA-co-MAA) and poly(acrylic acid) (PAA). By selecting wound pH as infection indicator, PMMA-co-MAA fibres were encapsulated with halochromic bromothymol blue (BTB) to trigger colour changes at infection-induced alkaline pH. Likewise, the exudate management capability was integrated via the synthesis of a thermally-crosslinked network in electrospun PAA layer. PMMA-co-MAA fibres revealed high BTB loading efficiency (>80 wt.%) and demonstrated prompt colour change and selective dye release at infected-like media (pH > 7). The synthesis of the thermally-crosslinked PAA network successfully enabled high water uptake (WU = 1291 ± 48 - 2369 ± 34 wt.%) and swelling index (SI = 272 ± 4 - 285 ± 3 a.%), in contrast to electrospun PAA controls. This dual device functionality was lost when the same building blocks were configured in a single-layer mesh of core-shell fibres, whereby significant BTB release (~70 wt.%) was measured even at acidic pH. This study therefore demonstrates how the fibrous configuration can be conveniently manipulated to trigger structure-induced functionalities critical to chronic wound management and monitoring.

A Convenient, Rapid, Sensitive, and Reliable Spectrophotometric Assay for Adenylate Kinase Activity.

Enzymatic activity assays are essential and critical for the study of enzyme kinetics. Adenylate kinase (Adk) plays a fundamental role in cellular energy and nucleotide homeostasis. To date, assays based on different principles have been used for the determination of Adk activity. Here, we show a spectrophotometric analysis technique to determine Adk activity with bromothymol blue as a pH indicator. We analyzed the effects of substrates and the pH indicator on the assay using orthogonal design and then established the most optimal assay for Adk activity. Subsequently, we evaluated the thermostability of Adk and the inhibitory effect of KCl on Adk activity with this assay. Our results show that this assay is simple, rapid, and precise. It shows great potential as an alternative to the conventional Adk activity assay. Our results also suggest that orthogonal design is an effective approach, which is very suitable for the optimization of complex enzyme reaction conditions.

A rapid and sensitive colorimetric assay for the determination of adenosine kinase activity.

Adenosine kinase (ADK) plays an important role in the growth and development of organisms. A convenient, quick, reliable, sensitive and low-cost assay for ADK activity is of great significance. Here, we found the reaction system with bromothymol blue as the pH indicator had a maximum absorption peak at 614 nm. The absorbance change in 614 nm was positively correlated with the generated hydrogen ions in the reaction catalyzed by ADK. Then, we demonstrated this assay was feasible for ADK activity. Further, we analyzed the effects of buffer, bromothymol blue concentrations on the sensitivity of the assay, and investigated the sensitivity of ADK contents and adenosine concentration on the assay. Finally, we calculated the Km and Vmax of ADK from Bombyx mori with this assay. Our results suggested this assay was quick, convenient, reliable, sensitive and economic for the activity of ADK. It is an excellent alternative for the conventional ADK assays.

SIMPLE, SENSITIVE AND SELECTIVE SPECTROPHOTOMETRIC ASSAY OF NAPROXEN IN PURE, PHARMACEUTICAL PREPARATION AND HUMAN SERUM SAMPLES.

Two simple, rapid and sensitive spectrophotometric methods have been developed for the determination of naproxen in pure, pharmaceutical preparation and human serum samples. These methods are based on the formation of yellow ion-pair complexes between naproxen and two sulfophthalein acid dyes, namely bromocresol green (BCG method) and bromothymol blue (BTB method). The resulting complexes were measured at 424 nm (BCG method) and at 422 nm (BTB method). The effects of variables such as reagent concentration and reaction time were investigated to optimize the procedure. Beer's law was obeyed in the concentration range of 10-105 µg/mL and 5-85 µg/mL and the detection limits were found to be 0.347 and 0.31 µg/mL for BCG and BTB methods, respectively. The developed methods have been successfully applied for the determination of naproxen in bulk drugs, pharmaceutical formulations and human serum samples with good accuracy and precision. The results are comparable to those of reference methods, and hence are recommended for quality control and routine analysis.

Allosteric strand displacement isothermal amplification for the visual detection of Toxoplasma gondii in 30 minutes.

Early detection of Toxoplasma gondii (T. gondii) is critical due to a lack of effective treatment for toxoplasmosis.This study established a simple, cost-effective, and rapid colorimetric detection method for T. gondii. The entire testing process, from sample collection to results, takes only 0.5 h. These characteristics fulfill the demands of researchers seeking rapid target detection with minimal equipment reliance. For genomic extraction, this study evaluated the ability of two filter papers to capture genomes. A rapid genomic extraction device combined with the two filter papers was designed to simplify the genomic extraction process, which was completed within 10 min and increased the detection sensitivity tenfold. The method utilized a simplified primer design for isothermal amplification, namely allosteric strand displacement (ASD), and employed an underutilized commercial color indicator, Bromothymol Blue (BTB), for signal output. Compared with other reported indicators, BTB exhibited a more pronounced color change, shifting from blue to yellow in positive samples, facilitating easier visual differentiation. The reaction was completed in 20 min with a limit of detection (LOD) as low as 0.014 T. gondii per microliter.

Novel pH-responsive indicator films based on bromothymol blue-anchored chitin for shrimp freshness monitoring.

The cellulose nanofibers (CNFs) based pH-sensitive indicator films were developed by mixing guar gum (GG) with bromothymol blue-anchored chitin (BTB-Chitin) as an indicator to monitor shrimp freshness. The BTB-Chitin was prepared by grafting hydroxypropyltriethylamine groups (HPTA) to chitin first, then anchoring bromothymol blue (BTB) to prepare intelligent pH response BTB-Chitin. The 0.08 BTB-Chitin films had a good tensile strength of 11.76 MPa and the water contact angle values were 125°, which displayed obvious color response to pH buffers and acid base volatile gas. Besides, the homogeneous and flexible composite films showed good color stability and reversibility. The released amount of BTB was very low from the BTB-Chitin films in heptane and corn oil. The composite films had been degraded completely in 15 days in soil. The pH and volatile base nitrogen were measured to determine the degree decay of shrimp (Litopenaeus vannamei), and the prepared pH-sensitive films changed from yellow (fresh) to cyan (spoiled) with the freshness of shrimp decreased, indicating the BTB-Chitin films could detect the shrimp freshness in real-time and high visibility.

Development of a calcium hydroxide-dye kimchi ripening indicator and its application in kimchi packaging.

Intelligent packaging that provides real-time information on food quality is useful for consumers. We developed a kimchi ripening indicator that can determine the ripeness of kimchi inside packaging and evaluated its applicability and limitations. The indicator was made using calcium hydroxide, which captures CO2, and four pH-sensitive dyes (cresol red, bromothymol blue, bromocresol purple, and methyl red). Fourier-transform infrared spectra of the prepared powders showed shapes similar to that of calcium hydroxide, and the dyes were evenly distributed on the calcium hydroxide surfaces. When the developed indicators were evaluated for kimchi packaging application, the indicator made from synthesized calcium hydroxide and bromothymol blue was the most reliable and clearly reflected useful kimchi ripening information. The indicator developed in this study is judged to be practically usable at temperatures of 4-15 °C. However, its usefulness is limited in that the seller cannot change the packaging capacity or kimchi capacity.

Silk fibroin-based colorimetric microneedle patch for rapid detection of spoilage in packaged salmon samples.

Spoiled salmon can cause foodborne diseases and severely affects human health. Herein, we report a pH-responsive colorimetric microneedle (MN) patch fabricated from bromothymol blue (BTB) and silk fibroin meth acryloyl (SilMA) (BTB/SilMA@MN patch) for sensing salmon spoilage. The needle tips of MN could penetrate food cling film and insert into fish to extract tissue fluids directly and transport the extracted fluids to the backing layer for color displaying. The color change of BTB/SilMA@MN patches depended on the pH variation resulting from the increase of total volatile basic nitrogen in salmon during storage. The color of MN patches changed from yellow to yellowish green and to final green, indicating salmon changed from fresh to medium fresh and then to putrefied, respectively. Salmon spoilage can be rapidly determined via naked eye recognition and also analyzed on a smartphone in a nondestructive way, allowing consumers to estimate food quality easily and reliably.

A collagen-based theranostic wound dressing with visual, long-lasting infection detection capability.

Continuous wound monitoring is one strategy to minimise infection severity and inform prompt variations in therapeutic care following infection diagnosis. However, integration of this functionality in therapeutic wound dressings is still challenging. We hypothesised that a theranostic dressing could be realised by integrating a collagen-based wound contact layer with previously demonstrated wound healing capability, and a halochromic dye, i.e. bromothymol blue (BTB), undergoing colour change following infection-associated pH changes (pH: 5-6 ➔ >7). Two different BTB integration strategies, i.e. electrospinning and drop-casting, were pursued to introduce long-lasting visual infection detection capability through retention of BTB within the dressing. Both systems had an average BTB loading efficiency of 99 wt% and displayed a colour change within 1 min of contact with simulated wound fluid. Drop-cast samples retained up to 85 wt% of BTB after 96 h in a near-infected wound environment, in contrast to the fibre-bearing prototypes, which released over 80 wt% of BTB over the same time period. An increase in collagen denaturation temperature (DSC) and red shifts (ATR-FTIR) suggest the formation of secondary interactions between the collagen-based hydrogel and the BTB, which are attributed to count for the long-lasting dye confinement and durable dressing colour change. Given the high L929 fibroblast viability in drop-cast sample extracts (92 %, 7 days), the presented multiscale design is simple, cell- and regulatory-friendly, and compliant with industrial scale-up. This design, therefore, offers a new platform for the development of theranostic dressings enabling accelerated wound healing and prompt infection diagnosis.

Development of real time-pH sensitive intelligent indicators for monitoring chicken breast freshness/spoilage using real packaging practices.

Real-real time CO2-sensitive freshness indicators, phenol red (PR) and bromothymol blue (BTB) dyes, in three-layer system using cellulose based binder was developed to determine the freshness/spoilage of chicken breast. The developed indicators were used to monitor chicken meat spoilage packaged in polyamide/polyethylene (PA/PE) pouches under air and 100% nitrogen (N2) at 4 °C for 10 days. Changes in the ΔE and ΔRGB values of the indicators, CO2/O2 gas composition of packs, and chemical (TVBN, pH, trimethylamine), microbial, and sensory quality parameters of chicken breast meat were analyzed. The visual color change in the PR-based indicator was insufficient for the consumer to detect the spoilage with the naked eye in both simulation and food trial. However, three stage color (dark blue-turquoise-green) change was occurred in BTB-based indicators, and the color transition in the spoilage level of CO2 (10-15% (v/v)) is supported by the physicochemical, microbiological and sensorial properties of the chicken breast. The shelf life of chicken breast under air was limited to 4 days, while the shelf life under 100% N2 was 6 days which are supported by the visual color change of BTB indicator. The BTB-based indicators were found promising on a real packaging conditions and could be adapted to industrial scale for monitoring real-time freshness/spoilage of poultry, ensuring food safety.

Recyclable waste Dry-cell batteries derived carbon dots (CDs) for detection of Two-fold metal ions and degradation of BTB dye.

In modern era, electronic wastes are one of the major threats around us, most of them are reused with less efficiency instead of re-usage, and conversion into valuable products is highly recommended. In this work, we report an innovative approach for the synthesis of highly photoluminescent CDs from waste dry-cell batteries through one-step hydrothermal treatment for the detection and degradation of environmental pollutants. The as-prepared CDs were studied by X-ray photoelectron spectroscopy (XPS), HR-TEM studies, X-ray diffractometer (XRD), Raman spectrometer, FTIR spectroscopy, UV-visible spectrophotometer, and spectrofluorometric measurements. The calculated quantum yield for synthesized CDs was around 13 %. The CDs have uniform particle size distribution, strong photoluminescent behavior, and possess high stability against various environmental conditions. Also, CDs display the selective and sensitive detection of Cr6+ and Co2+ and ions with a detection limit of around 0.11 µM and 0.10 µM respectively. The possible mechanism of CDs was also examined. Moreover, the photocatalytic activity of CDs with Bromothymol Blue (BTB) dye was studied. The degradation efficiency of BTB dye can be achieved at around 84 % over 180 min under the irradiation of direct sunlight in presence of H2O2. To date, it's the first time we have recycled waste dry-cell batteries into CDs as an effective probe for the detection and decomposition of environmental pollution. Furthermore, this work provides not only an easier route to make good quality and improved photoluminescent CDs from waste material like used batteries and also paves way for the reconversion of global treating waste. Finally, the outstanding detection capability with multiple properties of as-prepared CDs provides various environmental applications like the detection of pollutants and carcinogenic polluted water treatment.

An antibacterial and intelligent cellulose-based label self-assembled via electrovalent bonds for a multi-range sensing of food freshness.

Intelligent labels provide customers with food freshness information. However, the existing label response is limited and can only detect a single kind of food. Here, an intelligent cellulose-based label with highly antibacterial activity for a multi-range sensing freshness was developed to overcome the limitation. Cellulose fibers were modified using oxalic acid to graft -COO- followed by binding chitosan quaternary ammonium salt (CQAS), the remaining charges of which attached methylene red and bromothymol blue to form response fibers and to further self-assemble into the intelligent label. CQAS electrostatically gathered the dispersed fibers, resulting in an increase in TS and EB of 282 % and 16.2 %, respectively. After that, the rest positive charges fixed the anionic dyes to broaden pH response range of 3-9 effectively. More significantly, the intelligent label exhibited highly antimicrobial activity, killing 100 % of staphylococcus aureus. The rapid acid-base response revealed the potential for practical application in which the label color from green to orange represented the milk or spinach from fresh to close to spoiled, and from green to yellow, and to light green indicated the pork fresh, acceptable, and close to spoiled. This study paves a way for the preparation of intelligent labels in large-scale and promote the commercial application to improve food safety.

Near-IR-Regulated Composite Hydrogel with Real-Time Infection Monitoring and a Combined Antibacterial Effect for Efficient Wound Management.

Chronic wounds induced by bacterial infection have seriously affected the health of people in the world. So, it is meaningful to develop a novel strategy with real-time infection monitoring and excellent antibacterial performance for enhancing wound management. Herein, we constructed a composite hydrogel by loading the pH indicator bromothymol blue (BTB) and gold nanocages containing 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride (Au NCs@AIPH) into a polyacrylamide-co-poly(acrylic anhydride-modified oxidized sodium alginate) (PAM-co-PAOSA) hydrogel. In vitro and in vivo experimental results demonstrated that the composite hydrogel could effectively detect bacteria and diagnose the infection status of a wound in real time by showing visible color changes. In addition, the composite hydrogel containing Au NCs@AIPH possessed an excellent photothermal effect under near-IR (NIR) laser irradiation. The photothermal effect further activated AIPH to generate toxic free radicals to form combined antibacterial therapy for accelerating wound healing. Moreover, the composite hydrogel showed great biocompatibility. Therefore, the multifunctional hydrogel provided a novel wound management strategy for bacterial infection diagnosis and combined therapy in an infected wound.

Extractional spectrophotometric analysis of metronidazole, tinidazole, ornidazole and secnidazole bases through acid-dye complexation using bromothymol blue dye.

An easy, precise and valid extractional-spectrophotometric technique is described for the assessment of metronidazole (MNZ), tinidazole (TNZ), ornidazole (ONZ) and secnidazole (SNZ) in pure state and in their pharmaceutical formulations. The technique includes first the reduction of above cited drugs using HCl and zinc powder, then the formation of intense yellow colored ion-association complex species (1:3 drug/dye) using bromothymol blue (BTB) in a buffered aqueous acidic medium at pH 3-3.50. The colored products are extracted into dichloromethane and quantitatively determined at 416-420 nm. The experimental operating factors influencing the ion-pairs development were studied and optimized to obtain the maximum color intensity. The Beer plots are obeyed in the concentration ranges 2.50-22.50, 2.50-30, 7.50-35 and 5-30 µgml-1 for MNZ, TNZ, ONZ and SNZ, respectively, with correlation coefficients not less than 0.9995. The proposed technique is recommended for the routine quality control analysis of the investigated drugs in commercial tablets with no observed interference from common pharmaceutical adjuvants. Results of such analysis were statistically validated and through recovery studies, showing excellent agreement with those achieved by the reported techniques.

High Spatial Resolution Chemical Imaging of Implant-Associated Infections with X-ray Excited Luminescence Chemical Imaging Through Tissue.

Microbial infections associated with implantable medical devices are a major concern in fracture fixation failure. Early diagnosis of such infection will allow successful eradication with antibiotics without an extra cost for a second surgery. Herein, we describe XELCI as a technique with high X-ray resolution, implant specificity, and chemical sensitivity to noninvasively image chemical concentrations near the surface of implanted medical devices. The devices are coated with chemically reporting surfaces. This chemically responsive surface consists of two layers coated on an implantable medical device; a pH-sensitive layer (bromothymol blue or bromocresol green incorporated hydrogel) which is coated over a red-light emitting scintillator (Gd2O2S: Eu) layer for monitoring. A focused X-ray beam irradiates a spot on the implant, and the red light generated by the scintillator (with 620 nm and 700 nm peaks) is transmitted through the sensing layer which alters the spectral ratio depending on the pH. An image is generated by scanning the X-ray beam across the implant and measuring the spectral ratio of light passing through the tissue point-by-point. We used this imaging technique for monitoring implant-associated infections previously on the bone surface of the femur with a modified implantable plate sensor. Now we are studying pH changes that occur from tibial intramedullary rod infections. Two different types of intramedullary rod designs are used in pre-pilot rabbit studies, and we learned that the XELCI technique could be used to monitor any chemical changes that occur not only on the bone surface but also inside the bone. Thus, this enables noninvasive, high spatial resolution, low background local pH imaging to study implant-associated infection biochemistry.

Fluorescence property of ZnO nanoparticles and the interaction with bromothymol blue.

We synthesized ZnO quantum dots (QDs) simply in alcoholic solution, and investigated the interaction between ZnO QDs and bromothymol blue. The structural, morphological, size and spectral properties of ZnO QDs were studied. It was found that ZnO QDs were spherical nanoparticles in the crystal structure, and the average diameter of ZnO QDs was about 4.8 nm. The excitation and emission peaks were located at 346 nm and 520 nm, respectively, which were obtained on a common fluorophotometer. The quantum yield of ZnO QDs was obtained by using quinine sulfate as a reference reagent. In addition, the fluorescence of ZnO QDs can be quenched by bromothymol blue, and the quenching mechanism was proposed in a dynamic quenching mode.

The microwave-assisted photo-catalytic degradation of organic dyes.

In this study, TiO(2) photo-catalyst balls produced by the chemical vapour deposition method were used for degradation of organic dyes in which simultaneous irradiation of microwave and UV was evaluated. An electrodeless UV lamp that emits UV upon the irradiation of microwave was developed to irradiate microwave and UV simultaneously. The degradation reaction rate was shown to be higher with higher microwave intensity, under stronger acidic or basic conditions, and with a larger amount of O(2) gas or H(2)O(2) addition. The effect of addition of H(2)O(2) was not significant when photo-catalysis was used without additional microwave irradiation or when microwave was irradiated without the use of photo-catalysts. When H(2)O(2) was added under simultaneous use of photo-catalysis and microwave irradiation, however, considerably higher degradation reaction rates were observed.