Colorless Products Research Articles

Development of an automated yeast-based spectrophotometric method for toxicity screening: Application to ionic liquids, GUMBOS, and deep eutectic solvents

Saccharomyces cerevisiae has been used as a eukaryotic model organism for studying the toxic effects of various compounds. In this context, an automated spectrophotometric method based on the enzymatic reduction of methylene blue dye to a colorless product by living yeast cells was implemented in a sequential injection analysis system. Loss of yeast viability/impaired metabolic activity was monitored by an increase in optical density at 664 nm. To prove the usefulness of this approach, the toxicity of ILs (ionic liquids), GUMBOS (group of uniform materials based on organic salts), and DESs (deep eutectic solvents) was examined. Differences obtained between IC50 values confirmed the impact of structural elements on each compounds’ toxicity. While DESs appeared to be less toxic than ILs, GUMBOS were found to be among the most toxic compounds to yeast cells and thus can be viewed as promising antimicrobial candidates. The automated methodology showed satisfactory repeatability and reproducibility (RSD < 9%), which is in good agreement with Green Chemistry principles. In fact, the method required consumption of only 40 μL of reagents and produced less than 2 mL of effluents per cycle. Thus, the developed assay can be used as an alternative tool for toxicity screening.

Concerning Synthesis of New Biobased Polycarbonates with Curcumin in Replacement of Bisphenol A and Recycled Diphenyl Carbonate as Example of Circular Economy.

Curcumin (CM) is a natural polyphenol well-known for its antioxidant and pharmaceutical properties, that can represent a renewable alternative to bisphenol A (BPA) for the synthesis of bio-based polycarbonates (PC). In the presented strategy, preparation of the CM-based PC was coupled with chemical recycling of the fossil-based BPA polycarbonate (BPA-PC) conducting a two-steps trans-polymerization that replaces BPA monomer with CM or its tetrahydrogenated colorless product (THCM). In the first step of synthetic strategy, depolymerization of commercial BPA-PC was carried out with phenol as nucleophile, according to our previous procedure based on zinc derivatives and ionic liquids as catalysts, thus producing quantitatively diphenyl carbonate (DPC) e BPA. In the second step, DPC underwent a melt transesterification with CM or THCM monomers affording the corresponding bio-based polycarbonates, CM-PC and THCM-PC, respectively. THCM was prepared by reducing natural bis-phenol with cyclohexene as a hydrogen donor and characterized by 1H-NMR and MS techniques. Polymerization reactions were monitored by infrared spectroscopy and average molecular weights and dispersity of the two biobased polymers THCM-PC and CM-PC were determined by means of gel permeation chromatography (GPC). Optical properties of the prepared polymers were also measured.

Tetramethylbenzidine: An Acoustogenic Photoacoustic Probe for Reactive Oxygen Species Detection.

Photoacoustic imaging is attracting a great deal of interest owing to its distinct advantages over other imaging techniques such as fluorescence or magnetic resonance image. The availability of photoacoustic probes for reactive oxygen and nitrogen species (ROS/RNS) could shed light on a plethora of biological processes mediated by these key intermediates. Tetramethylbenzidine (TMB) is a non-toxic and non-mutagenic colorless dye that develops a distinctive blue color upon oxidation. In this work, we have investigated the potential of TMB as an acoustogenic photoacoustic probe for ROS/RNS. Our results indicate that TMB reacts with hypochlorite, hydrogen peroxide, singlet oxygen, and nitrogen dioxide to produce the blue oxidation product, while ROS, such as the superoxide radical anion, sodium peroxide, hydroxyl radical, or peroxynitrite, yield a colorless oxidation product. TMB does not penetrate the Escherichia coli cytoplasm but is capable of detecting singlet oxygen generated in its outer membrane.

Peroxidase‐Mimetic and Fenton‐Like Activities of Molybdenum Oxide Quantum Dots

AbstractMolybdenum oxide nanomaterials have become a popular nanomaterial while its catalysis behavior especially the bio‐catalysis property is little understood, even though molybdenum has been employed as a key cofactor in several important enzymes in biological system. On the basis of these, the Fenton and peroxidase‐like property of molybdenum oxide quantum dots (MoOx QDs) with mixed valence state was carefully investigated using tetramethylbenzidine (TMB) and methyl orange (MO) as the substrates. The results showed that MoOx QDs not only serve as a Fenton reagent, degrading MO to colorless products, but also exhibit intrinsic peroxidase‐mimetic activity, oxidizing TMB to the oxidized state oxTMB. The catalysis mechanism of MoOx QDs is that MoOx QDs can facilitate the decomposition of H2O2 and a large amount of radicals was generated, leading to MO decomposing and TMB oxidizing subsequently. Inspired by the findings, a visible method was developed for sensitive and selective detection of H2O2 and glucose, and the limit of detection for H2O2 and glucose is 7.75 μM and 8.95 μM (3σ/K), respectively. Moreover, glucose content in human serum samples was successfully determined by the proposed visible method, and the results are consistent well with those obtained by handheld glucose meter, suggesting a high accuracy of the present method.

Activity of hydrogenated curcuminoid on Pd/C catalyst and its antibacterial activity against Staphylococcus aureus and Streptococcus mutans

Turmeric (Curcuma longa) has been known for its benefit as one of medicinal herbs. Curcuminoids, the active compounds in turmeric, consist of three structurally related compounds, curcumin, demethoxycurcumin, and bisdemethoxycurcumin. Curcuminoid has been reported to be effective for the treatment of chronic gingivitis and hence it can be a potential candidate to be used as an active ingredient for antimicrobial in a mouthwash. However, its yellow color has hampered its application as a mouthwash as it may cause the aesthetical problem to the teeth. In this study, curcuminoids, obtained from Soxhlet extraction of turmeric powder, were reduced by hydrogenation on Pd/C catalyst to remove the color. TLC analysis revealed that the products consist of three compounds as expected. The product was purified from unreacted curcuminoids by column chromatography on silica gel, to obtain a colorless product with percent conversion of 23.45 %. These three compounds were characterized by Uv-Vis spectrophotometer resulted in three peaks in three different wavelengths: 282, 283 and 280 nm. Characterization with FT-IR spectrometer showed an increase intensity of CH-sp3 peak (2932 cm−1) when compared to the IR spectrum of standard curcuminoids, and the shift in C-O absorption (1231 cm−1), indicated the existence of methoxy groups that can distinguish one to the other compounds. These three compounds then were evaluated for their antibacterial activity against Staphylococcus aureus and Streptococcus mutans. The result showed that the tetrahydrocurcumin had moderate antibacterial activity against S. aureus with inhibition zone of 5.5 mm and tetrahydro desmethoxycurcumin also showed moderate antibacterial activity against S. mutans with inhibition zone of 5.5 mm.

Influence of Alkaline Treatment on Structural Modifications of Chlorophyll Pigments in NaOH-Treated Table Olives Preserved without Fermentation.

Alkaline treatment is a key stage in the production of green table olives and its main aim is rapid debittering of the fruit. Its action is complex, with structural changes in both the skin and the pulp, and loss of bioactive components in addition to the bitter glycoside oleuropein. One of the components seriously affected are chlorophylls, which are located mainly in the skin of the fresh fruit. Chlorophyll pigments are responsible for the highly-valued green color typical of table olive specialties not preserved by fermentation. Subsequently, the effect on chlorophylls of nine processes, differentiated by NaOH concentration and/or treatment time, after one year of fruit preservation under refrigeration conditions, was investigated. A direct relationship was found between the intensity of the alkali treatment and the degree of chlorophyll degradation, with losses of more than 60% being recorded when NaOH concentration of 4% or greater were used. Oxidation with opening of the isocyclic ring was the main structural change, followed by pheophytinization and degradation to colorless products. To a lesser extent, decarbomethoxylation and dephytylation reactions were detected. An increase in NaOH from 2% to 5% reduced the treatment time from 7 to 4 h, but fostered greater formation of allomerized derivatives, and caused a significant decrease in the chlorophyll content of the olives. However, NaOH concentrations between 6% and 10% did not lead to further time reductions, which remained at 3 h, nor to a significant increase in oxidized compounds, though the proportion of isochlorin e4-type derivatives was modified. Chlorophyll compounds of series b were more prone to oxidation and degradation reactions to colorless products than those of series a. However, the latter showed a higher degree of pheophytinization, and, exclusively, decarbomethoxylation and dephytylation reactions.

A facile Pt-doped g-C3N4 photocatalytic biosensor for visual detection of superoxide dismutase in serum samples

In this work, we reported a photocatalytic biosensor for visual detection of superoxide dismutase (SOD) based on Pt-doped graphite phase carbon nitride (g-C3N4). Upon illumination by a violet light-emitting diode (LED), Pt-doped g-C3N4 absorbed the light energy and catalytically produced O2− which further oxidized the dyes into a colorless end product. In the presence of SOD, it can specifically catalyze O2− into oxygen and hydrogen peroxide, leading to a reduced photooxidation and a visual color display. After screening a series of dyes, the azo dye amaranth (AM) was proven to be the best indicator for O2− since the azo bond is active and easily oxidized by O2−, resulting in a low background. Such a simple photocatalytic sensor allows visual detection of SOD at a nM level without the need of any sophisticated instrument; using spectrometry, the linear response for SOD detection ranges from 1.5 to 4500 nM with a limit of detection (LOD, 3σ) down to 0.3 nM. The sensor was also successfully applied for label-free and wash-free detection of SOD in human serum samples with a satisfactory recovery.

Increasing BOD5/COD ratio of non-biodegradable compound (reactive black 5) with ozone and catalase enzyme combination

The effect of ozone and ozone plus a biological catalyst (catalase) on the degradation processes of Reactive Black 5 was investigated. The ozonation process was carried out in a laboratory-scale batch reactor with a volume of 500 ml. Chemical oxygen demand (COD), pH, color removal and the BOD5/COD ratio were measured during the process. At the first stage, only ozonation was performed, at the second stage, ozonation plus NaCl and Na2CO3, and at the third stage, ozonation plus catalase enzyme were used. As a result of the oxidation of Reactive Black 5 with only ozone and ozone plus textile auxiliaries, chemical oxygen demand (COD) removal was 34% and 19%, respectively. COD removal efficiency was 43% when 10 ml of catalase was added to the ozone reactor. Carbonate and salt have a negative effect on the oxidation of reactive Black 5 with ozone. Reactive Black 5 was degraded into sub-components, and the biodegradability of the wastewater increased. The pH value decreased from 3.3 down to 1.6, which showed that organic acids were formed as a result of degradation. The use of enzymes in combination with ozonation shows that Reactive Black5 can rapidly convert into the intermediate within the 270-min ozonation time (BOD5/COD = 0.46). COD removal was not as high as color removal efficiency. This may have resulted from the formation of colorless oxidation products. The significant increase in biodegradability after ozonation in the presence of the catalyst may also be seen as a reduction of toxic intermediates.

Colorants in cheese manufacture: Production, chemistry, interactions, and regulation.

Colored Cheddar cheeses are prepared by adding an aqueous annatto extract (norbixin) to cheese milk; however, a considerable proportion (∼20%) of such colorant is transferred to whey, which can limit the end use applications of whey products. Different geographical regions have adopted various strategies for handling whey derived from colored cheeses production. For example, in the United States, whey products are treated with oxidizing agents such as hydrogen peroxide and benzoyl peroxide to obtain white and colorless spray-dried products; however, chemical bleaching of whey is prohibited in Europe and China. Fundamental studies have focused on understanding the interactions between colorants molecules and various components of cheese. In addition, the selective delivery of colorants to the cheese curd through approaches such as encapsulated norbixin and microcapsules of bixin or use of alternative colorants, including fat-soluble/emulsified versions of annatto or beta-carotene, has been studied. This review provides a critical analysis of pertinent scientific and patent literature pertaining to colorant delivery in cheese and various types of colorant products on the market for cheese manufacture, and also considers interactions between colorant molecules and cheese components; various strategies for elimination of color transfer to whey during cheese manufacture are also discussed.

Measurement of tropospheric ozone by digital image analysis of indigotrisulfonate-impregnated passive sampling pads using a smartphone camera

In this work, we propose a low cost and portable method for the monitoring of daily tropospheric ozone levels, through the combination of passive sampling and digital analysis of images taken with the camera of a smartphone. The analytical signal used is the degradation of the blue color of indigotrisulfonate deposited on a passive sampling device, depending on its reaction with ozone to form colorless products. The discoloration was measured by tracking the RGB parameters obtained from images taken with the camera. The RGB signals were processed using different mathematical algorithms of digital image analysis, of which the effective absorbance from R channel (EAR) was selected as optimal. The detection limit was 3.3 μg m−3. The linear range obtained was between 11 and 109 μg m−3 for EAR, sufficient for the measurement of usual environmental levels of ozone in urban or rural environments. The practical application of the method was tested by measuring 24 h average levels of ozone in an suburban environment for three months, finding a good precision (RSD = 6.8%), accuracy (relative errors from −14.0 to 5.7%) and an adequate correlation (r = 0.77) against a spectrophotometric reference method. These results demonstrate the potential of the method as an auxiliary tool for the standard instruments, providing a rapid and decentralized measurement of ozone levels with adequate reliability.

Grown to be Blue-Antioxidant Properties and Health Effects of Colored Vegetables. Part I: Root Vegetables.

During the last few decades, the food and beverage industry faced increasing demand for the design of new functional food products free of synthetic compounds and artificial additives. Anthocyanins are widely used as natural colorants in various food products to replenish blue color losses during processing and to add blue color to colorless products, while other compounds such as carotenoids and betalains are considered as good sources of other shades. Root vegetables are well known for their broad palette of colors, and some species, such as black carrot and beet root, are already widely used as sources of natural colorants in the food and drug industry. Ongoing research aims at identifying alternative vegetable sources with diverse functional and structural features imparting beneficial effects onto human health. The current review provides a systematic description of colored root vegetables based on their belowground edible parts, and it highlights species and/or cultivars that present atypical colors, especially those containing pigment compounds responsible for hues of blue color. Finally, the main health effects and antioxidant properties associated with the presence of coloring compounds are presented, as well as the effects that processing treatments may have on chemical composition and coloring compounds in particular.

583. Improving Catheter Scrub Technique and Compliance in a Level IV Neonatal ICU

BackgroundCentral line-associated bloodstream infections (CLABSIs) are challenging to prevent in the neonatal population due to the long-term necessity of central access for nutrition and medication. Neonates are a population at high risk for CLABSIs, and infections in this group are associated with prolonged hospitalization, greater healthcare costs, and increased mortality. Current bundles for CLABSI prevention include a friction scrub of the catheter hub prior to each use. Real-time audits of correct technique can be challenging. In July of 2018, our team developed a new strategy for auditing scrub technique in an attempt to reduce CLABSI rates.MethodsThis project took place in a NICU with 118 level 4 beds from July 2018 to February 2019. Our NICU is located in a large metropolitan area and serves as a referral center for complex neonates throughout the region. The intervention period encompassed 25,085 patient-days and 6,206 line days. Real-time friction scrub audits were performed for both dedicated line team staff as well as bedside nurses. In order to determine whether a healthcare worker’s (HCW) scrub technique was successful, a colorless luminescent product was applied to a practice catheter hub that adhered to the hub, but was not visible to the HCW. The HCW would then demonstrate a friction scrub on the practice catheter, and the hub was placed under a black light to show where any residual product may be present. This process was repeated until the staff member was able to remove the product from the hub. Once the staff was successful, monthly real-time audits were continued to reinforce the correct technique.ResultsBetween July 2018 and February 2019, compliance with scrub technique and ability to clear product from catheter hubs increased by 50%. The CLABSI rate in the first 9 months after intervention was 0.806 per 1000 line days as compared with 2.170 per 1000 line days in the previous fiscal year.ConclusionThe number of CLABSI’s during the intervention period was 63% less when compared with the previous fiscal year. This process, in conjunction with our other CLABSI prevention practices, has significantly decreased both our CLABSI rate and overall numbers. This project emphasizes the importance of focusing on the basics of infection prevention practices and continual auditing to prevent practice creep.Disclosures All authors: No reported disclosures.

An improved phenol-sulfuric acid method for the determination of carbohydrates in the presence of persulfate

Advanced oxidation processes (AOPs) based on activated persulfate have received extensive attention for sludge pretreatment. Persulfate (PS) is a persistent oxidant and the excess persulfate in the sludge affects the carbohydrate analysis using the traditional phenol-sulfuric acid method. In this study, an improved phenol-sulfuric acid method was developed for the determination of carbohydrates in the presence of persulfate, and a critical procedure was introduced before the conventional determination with the assistance of the chemical pretreatments. The best reagent was screened from four reductants (i.e. Na2S, KI, Na2SO3 and Na2S2O3) and two free-radical scavengers (i.e. phenol and benzoic), and the optimal conditions were determined based on the monosaccharides (i.e. glucose, galactose and mannose) and the polysaccharides in different EPS fractions from two activated sludges. The results showed that Na2SO3 was the best reagent for chemical pretreatment due to redox reaction, high selectivity and colorless oxidation product, and the others were not suitable as pretreatment reagents mainly since the reaction products affect the final spectral analysis. Besides, the optimal Na2SO3 concentration for eliminating the impact of PS was 150 mmol/L, and the relative deviation of measurement is less than 5% if the PS concentration was on more than 100 mmol/L, regardless of the kinds of carbohydrates. Compared with the anthrone-sulfuric acid method and the sulfuric method, the improved phenol-sulfuric acid method has a great advantage for determining the carbohydrate concentration in the presence of PS.

Ionic liquid as a moderator for improved sensing properties of TiO2 nanostructures for the detection of acetone biomarker in diabetes mellitus

In the present work, TiO2 nanoparticles have been synthesized by hydrothermal process and characterized using the techniques like FTIR, XRD, and SEM analysis. FTIR spectral analysis confirms the presence of TiO characteristic bond in TiO2 nanoparticles. The rutile phase of TiO2 nanoparticles having an average crystallite size of 26.8 nm was confirmed by XRD analysis. The SEM images indicate that the prepared nanoparticles are crystalline having a strong tendency to agglomerate. The 1-H-3-methylimidazolium acetate ionic liquid having aromaticity and conductive sites in its structure were synthesized using the simple neutralization method. A new colorimetric method was developed for acetone detection based on low-cost stable eosin dye as a substrate which reacts with acetone in the presence of ionic liquid coated TiO2 nanoparticles. The colored eosin dye (brown color) solution has been changed to the colorless product after reaction with acetone as analyzed by UV–Vis spectrophotometry. The optimization of different parameters (time, pH, temperature, concentrations, loading of nanoparticles, etc.) was conducted in order to get the best results of the proposed sensor. This sensor shows a wide linear range of 1.6 × 10−6–6.1 × 10−5 mol L−1 and low limit of detection i.e. 2.7023 × 10−5 mol L−1 with an R2 value of 0.9995. The selectivity of the sensor was excellent when compared with the potential interfering substances. The response time was measured only 5 min for the proposed sensor. Moreover, the sensor was successfully applied to test acetone in the urine samples of diabetic patients having a blood sugar level in the range of 245–370 mg/dL.

Graft modification of methyl acrylate onto chicken feather via surface initiated Cu(0)‐mediated reversible‐deactivation radical polymerization

ABSTRACTIn this study, chicken feather was functionalized with 2‐Bromoisobutyryl bromide (BIBB) where methyl acrylate (MA) was grafted through Cu(0)‐mediated reversible‐deactivation radical polymerization (RDRP) catalyzed by copper wire. Feather‐g‐PMAs with three different target degrees of polymerization (Dp) were prepared fast. Besides, molecular mass of PMA was closely associated with the theoretical value; PMA also exhibited relatively low polydispersity (~1.17). The catalyst was removed through simple washing, and thus a colorless product was yielded. However, Cu(0)‐mediated RDRP in the presence of the unmodified chicken feather caused the loss of control. Feather‐g‐PMA with a short graft chain exhibited a uniform interface coated on the feather fiber. Because the grafted PMA and the feather substrate had a strong interaction, and the graft ratio was less, there was only one stage of decomposition, and no glass transition temperature was detected. We detected a rough surface on feather‐g‐PMA with a longer graft chain and observed the glass transition of PMA and obviously two stages of decomposition. After densely graft, the hydrophilicity of chicken feather decreased. These feather‐g‐PMAs exhibited better compatibility in organic solvents (e.g., acetone and toluene). © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48246.

Life history and behavior effects of synthetic and natural dyes on Daphnia magna

Azo dyes are the largest class of dyes extensively used by industries despite their mutagenic potential for humans. As such, natural dyes have been reemerging as an important alternative to human safety. However, limited studies have focused on the effect of dyes on the environment, thus their ecotoxicological investigation is imperative. Here, we aimed to evaluate toxic effects induced by the synthetic azo dye Basic Red 51 (BR51) in comparison with natural dye erythrostominone (Ery) in the microcrustacean Daphnia magna, a standard organism used to assess the risk of chemicals to aquatic organisms. The colorless product formed after the photodegradation of Ery (DEry) was also evaluated, addressing an easy and low cost alternative for industrial effluent treatments. The results showed that both dyes are acutely toxic to D. magna. BR51 and Ery reduced the intrinsic rate of D. magna population increase, which generated fewer neonates per brood. BR51 also increased daphnids respiration rates. In contrast, DEry did not alter any of the analyzed parameters. No locomotor changes were observed when daphnids were exposed to sub-lethal concentrations of Ery or BR51. These results indicate that both dyes can induce deleterious consequences for daphnids including population level effects, but the natural dye Ery presents 100-fold lower toxicity in comparison with the azo dye BR51. Also, that photodegradation of Ery is an efficient method to reduce and prevent previously observed toxic effects, suggesting an inexpensive, fast and easy alternative for treatment of effluents containing this natural dye.

Biocatalytic solutions to cyclomethicones problem in cosmetics.

Silicones are polymers that have properties of great interest for cosmetic and personal care industry, especially D4 (octamethylcyclotetrasiloxane) and D5 (decamethylcyclopentasiloxane), generically named cyclomethicones. However, different studies show the hypothesis that the use of these products is harmful and, therefore, several countries have adopted legislative actions to limit their use in personal care and cosmetic products. Faced with this new situation, different cosmetic companies began to look for different alternatives to cyclomethicones, mainly: organomodified silicones or esters. The former are based on the addition of functional groups to the main chain of silicon and oxygen. The latter represent a totally different line, since their functional group is the ester, but they have properties similar to silicones. Esters, especially branched-chain ones are currently the more promising alternative to replace cyclomethicones in cosmetic formulations. Nowadays, most of them are obtained by chemical reactions that require high temperatures and non-selective /contaminant catalysts that lead to low-quality final products. As an alternative, biocatalytic synthesis occurs always at mild operation conditions supplying ultra-pure, odor, and colorless products with less wastes and side reactions. Therefore, biocatalysis is a valid and environmentally sustainable option for the synthesis of silicone-substitute esters used in cosmetic formulations.

Easy Diagnosis of Jaundice: A Smartphone-Based Nanosensor Bioplatform Using Photoluminescent Bacterial Nanopaper for Point-of-Care Diagnosis of Hyperbilirubinemia.

One of the concerns of parents in the first days of their baby's birth is the baby's risk of jaundice/hyperbilirubinemia. This is because more than 60% of babies are born with jaundice that, if not timely diagnosed and subsequently treated, can lead to serious damage to their health. On the other hand, despite recent progress in sensor technology for clinical applications, the development of easy-to-use, cost-effective, sensitive, specific, and portable diagnostic devices, which use nontoxic and biodegradable materials in their design and fabrication, is still in high demand. Herein we present an easy-to-use, cost-effective, selective, nontoxic, and disposable photoluminescent nanopaper-based assay kit with a smartphone readout for easy diagnosis of neonatal jaundice through visual determination of Bilirubin (BR) in infants' blood samples. The developed BR assay kit comprises highly photoluminescent carbon dot (CD) sensing probes embedded in a bacterial cellulose (BC) nanopaper substrate (CDBN). The photoluminescence (PL) of the developed BR sensor is quenched in the presence of BR as a PL quencher and then selectively recovered upon blue light (λ = 470 nm) exposure, due to conversion of the unconjugated BR to the colorless oxidation products (non-PL quencher) through BR photoisomerization and photooxidation, that subsequently leads to selective PL enhancement of CDBN. The recovered PL intensity of the developed BR assay kit, which was monitored by integrated smartphone camera, was linearly proportional to the concentration of BR in the range of 2-20 mg dL-1. The feasibility of real application of the fabricated smartphone-based BR assay kit was also confirmed via comparing the results of our method with a clinical reference method for determination of BR concentration in infant's blood samples. With the advantages of nontoxicity and the extraordinary physicochemical properties of photoluminescent BC nanopaper as the sensing substrate, along with those of smartphone technology, we believe that our developed smartphone-based BR assay kit, as an easy-to-use, cost-effective (∼0.01 Euro per test), portable and novel sensing bioplatform, can be potentially exploited for sensitive, specific, rapid, and easy BR detection and jaundice diagnosis at the point of care (POC) and in routine clinical laboratories as well.

A rapid method to detect and estimate the activity of the enzyme, alcohol oxidase by the use of two chemical complexes - acetylacetone (3,5-diacetyl-1,4-dihydrolutidine) and acetylacetanilide (3,5-di-N-phenylacetyl-1,4-dihydrolutidine)

A rapid and sensitive method has been devised in order to detect and estimate the synthesis of the enzyme alcohol oxidase (AOX) by fungi, by way of the use of two chemical complexes, namely, acetylacetone (3,5-diacetyl-1,4-dihydrolutidine) and acetylacetanilide (3,5-di-N-phenylacetyl-1,4-dihydrolutidine). This method involves the use of the AOX enzyme that could specifically oxidize methanol, giving rise to equimolar equivalents each of formaldehyde (HCHO) and hydrogen peroxide (H2O2) as the end products. Further, the formaldehyde, thus produced was allowed to interact with the neutral solutions of acetylacetone and the ammonium salt, gradually developing a yellow color, owing to the synthesis and release of 3,5-diacetyl-1,4-dihydrolutidine (yellow product; λ = 420 nm; λex/em = 390/470 nm) and the product, so generated was quantified spectrophotometrically by measureing its absorbance at 412 nm. In another set up, the amount of formaldehyde produced as a sequel to the oxidation of methanol by the AOX enzyme was determined by allowing it to react with the acetylacetanilide reagent, after which the volume of the fluorescent product - 3,5-di-N-phenylacetyl-1,4-dihydrolutidine (colorless product; λex/em = 390/470 nm) that was generated was estimated by measuring its emission at 460 nm (excitation wavelength at 360 nm) in a spectrophotometer. Of the various substrates tested, a commercial source of the AOX enzyme appreciably oxidizes methanol, thereby generating formaldehyde, and further reacts with acetylacetone, to give rise to a bright yellow complex, displaying a maximum activity of 1402 U/mL. Determination of the AOX activity by the use of acetylacetone and acetylacetanilide could serve as a viable alternative to the conventional alcohol oxidase-peroxidase-2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid (AOX-POD-ABTS) based method. In view of this, this method appears to be invaluable for application at the various food, pharmaceutical, fuel, biosensor, biorefinery, biopolymer, biomaterial, platform chemical, and biodiesel industries.

Colorimetric copper ion sensing in solution phase and on paper substrate based on catalytic decomposition of S-nitrosothiol

A S-nitrosothiol (RSNO) is used for highly selective and sensitive copper ion sensing for the first time. Cu(II) in the sample is reduced to Cu(I) by a low amount of thiols generated from hydrolysis of RSNO molecules or added thiols such as l-glutathione or l-cysteine. Cu(I) is able to trigger cleavage of the SNO bond, which converts colored RSNOs to colorless products. The dark green S-nitroso-N-acetylpenicillamine is used as an exemplary RSNO in this report. In the spectrophotometric test, the detection limit toward Cu(II) is 0.23 μM without added thiol reductants, and 0.08 and 0.06 μM in the presence of l-glutathione and l-cysteine, respectively. Furthermore, we prepared fully inkjet printed paper-based sensors by deposition of all reaction reagents and buffers on the same piece of cellulose paper. A smartphone equipped with a color analysis app enables quantification of the color change of the paper-based Cu(II) sensors. In this method, a detection limit of 1.2 μM and a linear range of 0–10 μM were obtained. Finally, we successfully applied this instrumentation-free and reagent-free senor for Cu(II) analysis in real drinking water and river water samples.