Metabolism of azo dyes: implication for detoxication and activation

Sonochemical synthesis of SnS and SnS2 quantum dots from aqueous solutions, and their photo- and sonocatalytic activity

Our study reports the ultrasound-assisted synthesis of SnS and SnS2 in the form of nanoparticles using aqueous solutions of respective tin chloride and thioacetamide varying sonication time. The presence of both compounds is confirmed by powder X-ray diffraction, energy-dispersive X-ray spectroscopy, as well as Raman and FT-IR spectroscopic techniques. The existence of nanoparticles is proven by powder X-ray diffraction investigation and by high resolution transmission electron microscopy observations. The size of nanocrystallites are in the range of 3-8 nm and 30 50 nm for SnS, and 1.5-10 nm for SnS2. X-ray photoelectron spectroscopy measurements, used to investigate the chemical state of tin and sulphur atoms on the surface of nanoparticles, reveal that they are typically covered with tin on the same oxidation degree as respective bulk compound. Values of optical bandgaps of synthesized nanoparticles, according to the Tauc method, were 2.31, 1.47 and 1.05 eV for SnS (60, 90 and 120 min long synthesis, respectively), and 2.81, 2.78 and 2.70 eV for SnS2 (60, 90 and 120 min long synthesis, respectively). Obtained nanoparticles were utilized as photo- and sonocatalysts in the process of degradation of model azo-dye molecules by UV-C light or ultrasound. Quantum dots of SnS2 obtained under sonication lasting 120 min were the best photocatalyst (66.9 % color removal), while quantum dots of SnS obtained under similar sonication time were the best sonocatalyst (85.2 % color removal).

Photochemistry in Medicinal Chemistry and Chemical Biology

Photochemistry has emerged as a transformative force in organic chemistry, significantly expanding the chemical space accessible for medicinal chemistry. Light-induced reactions enable the efficient synthesis of intricate organic structures and have found applications throughout the different stages of the drug discovery and development processes. Moreover, photochemical techniques provide innovative solutions in chemical biology, allowing precise spatiotemporal drug activation and targeted delivery. In this Perspective, we highlight the already numerous remarkable applications and the even more promising future of photochemistry in medicinal chemistry and chemical biology.

Degradation of Procion Brilliant Purple H-3R using ultrasound coupled with advanced oxidation processes

The complexity of wastewater matrix poses a challenge for conventional processes especially due to the presence of refractory compounds such as dyes. The present work focuses on utilizing ultrasound-induced cavitation in conjunction with different oxidants such as hydrogen peroxide, Fenton's reagent and potassium persulfate to treat Procion Brilliant Purple H-3R dye containing wastewater. The impact of various operating parameters as pH, frequency, and power on degradation levels has been studied with the aim of optimizing degradation. The optimal conditions for the degradation of Procion Brilliant Purple H-3R were determined as pH of 12, frequency of 22 kHz, and power of 250 W, resulting in a maximum degradation of 70.25%. Combination of a cavitation reactor with hydrogen peroxide, Fenton reagent, and KPS was then applied at optimized conditions, which confirmed a notable enhancement in degradation compared to the only ultrasound based process. Specifically, the degradation extent was 95.99% for combination with H2O2 at 0.5 g/L loading, 99.79% for combination with Fenton at H2O2/Fe2+ ratio of 50:1, and 99.05% for combination with KPS at loading of 0.75 g/L. The kinetic rate constant for the combined approach of US + Fenton was also maximum at 7.47 × 10-1 L mg-1 min-1. Toxicity analysis was conducted on two bacterial strains, Escherichia coli and Staphylococcus aureus, using the wastewater in native form and after treatment. The various processes were evaluated in terms of the cavitational yield and overall treatment cost and it was determined that US + Fenton process is the most efficient treatment method for fully degrading Procion Brilliant Purple H-3R, particularly at larger scales of operation and cost efficiently as demonstrated in the work.

N-Succinylaspartic-Acid-Conjugated Riluzole Is a Safe and Potent Colon-Targeted Prodrug of Riluzole against DNBS-Induced Rat Colitis

In our previous study, riluzole azo-linked to salicylic acid (RAS) was prepared as a colon-targeted prodrug of riluzole (RLZ) to facilitate the repositioning of RLZ as an anticolitic drug. RAS is more effective against rat colitis than RLZ and sulfasalazine, currently used as an anti-inflammatory bowel disease drug. The aim of this study is to further improve colon specificity, anticolitic potency, and safety of RAS. N-succinylaspart-1-ylRLZ (SAR) and N-succinylglutam-1-ylRLZ (SGR) were synthesized and evaluated as a "me-better" colon-targeted prodrug of RLZ against rat colitis. SAR but not SGR was converted to RLZ in the cecal contents, whereas both conjugates remained intact in the small intestine. When comparing the colon specificity of SAR with that of RAS, the distribution coefficient and cell permeability of SAR were lower than those of RAS. In parallel, oral SAR delivered a greater amount of RLZ to the cecum of rats than oral RAS. In a DNBS-induced rat model of colitis, oral SAR mitigated colonic damage and inflammation and was more potent than oral RAS. Moreover, upon oral administration, SAR had a greater ability to limit the systemic absorption of RLZ than RAS, indicating a reduced risk of systemic side effects of SAR. Taken together, SAR may be a "me-better" colon-targeted prodrug of RLZ to improve the safety and anticolitic potency of RAS, an azo-type colon-targeted prodrug of RLZ.

Solvent-free automated thermal desorption-gas chromatography/mass spectrometry for direct screening of hazardous compounds in consumer textiles

The global production of textiles utilizes numerous large-volume chemicals that may remain to some extent in the finished garments. Arylamines, quinolines, and halogenated nitrobenzene compounds are possible mutagens, carcinogens and/or skin sensitizers. For prevention, control of clothing and other textiles must be improved, especially those imported from countries without regulations of textile chemicals. An automated analytical methodology with on-line extraction, separation, and detection would largely simplify screening surveys of hazardous chemicals in textiles. Automated thermal desorption-gas chromatography/mass spectrometry (ATD-GC/MS) was developed and evaluated as a solvent-free, direct chemical analysis for screening of textiles. It requires a minimum of sample handling with a total run time of 38 min including sample desorption, chromatographic separation, and mass spectrometric detection. For most of the studied compounds, method quantification limit (MQL) was below 5 µg/g for 5 mg of textile sample, which is sufficiently low for screening and control of quinoline and arylamines regulated by EU. Several chemicals were detected and quantified when the ATD-GC/MS method was applied in a limited pilot screening of synthetic fiber garments. A number of arylamines were detected, where some of the halogenated dinitroanilines were found in concentrations up to 300 µg/g. This is ten times higher than the concentration limit for similar arylamines listed by the EU REACH regulation. Other chemicals detected in the investigated textiles were several quinolines, benzothiazole, naphthalene, and 3,5-dinitrobromobenzene. Based on the present results, we suggest ATD-GC/MS as a screening method for the control of harmful chemicals in clothing garments and other textiles.

Application of systematic evidence mapping to identify available data on the potential human health hazards of selected market-relevant azo dyes

BACKGROUND

Azo dyes are used in textiles and leather clothing. Human exposure can occur from wearing textiles containing azo dyes. Since the body's enzymes and microbiome can cleave azo dyes, potentially resulting in mutagenic or carcinogenic metabolites, there is also an indirect health concern on the parent compounds. While several hazardous azo dyes are banned, many more are still in use that have not been evaluated systematically for potential health concerns. This systematic evidence map (SEM) aims to compile and categorize the available toxicological evidence on the potential human health risks of a set of 30 market-relevant azo dyes.

METHODS

Peer-reviewed and gray literature was searched and over 20,000 studies were identified. These were filtered using Sciome Workbench for Interactive computer-Facilitated Text-mining (SWIFT) Review software with evidence stream tags (human, animal, in vitro) yielding 12,800 unique records. SWIFT Active (a machine-learning software) further facilitated title/abstract screening. DistillerSR software was used for additional title/abstract, full-text screening, and data extraction.

RESULTS

187 studies were identified that met populations, exposures, comparators, and outcomes (PECO) criteria. From this pool, 54 human, 78 animal, and 61 genotoxicity studies were extracted into a literature inventory. Toxicological evidence was abundant for three azo dyes (also used as food additives) and sparse for five of the remaining 27 compounds. Complementary search in ECHA's REACH database for summaries of unpublished study reports revealed evidence for all 30 dyes. The question arose of how this information can be fed into an SEM process. Proper identification of prioritized dyes from various databases (including U.S. EPA's CompTox Chemicals Dashboard) turned out to be a challenge. Evidence compiled by this SEM project can be evaluated for subsequent use in problem formulation efforts to inform potential regulatory needs and prepare for a more efficient and targeted evaluation in the future for human health assessments.

The interactions between Reactive Black 5 and human serum albumin: combined spectroscopic and molecular dynamics simulation approaches

Azo dyes are made in significant amounts annually and released into the environment after being employed in the industry. There are some reports about the toxic effects of these dyes on several organisms. Thus, the textile dye Reactive Black 5 (RB5) has been examined for its cytotoxic effects on the human serum albumin (HSA) structure. Molecular interaction between RB5 and HSA indicated the combination of docking methods, molecular dynamic simulation, and multi-spectroscopic approaches. HSA's intrinsic fluorescence was well quenched with enhancing RB5 level, confirming complex formation. Molecular dynamics (MD) simulation was done to study the cytotoxic effects of RB5 and HSA conformation. Molecular modeling revealed that the RB5-HSA complex was stabilized by hydrogen bonds and van der Waals interactions. The results of molecular docking revealed that the binding energy of RB5 to HSA was - 27.94 kJ/mol. The change in secondary structure causes the annihilation of hydrogen bonding networks and the reduction of biological activity. This research can indicate a suitable molecular modeling interaction of RB5 and HAS and broaden our knowledge for azo dye toxicity under natural conditions.

Optical Modulation of Antibiotic Resistance by Photoswitchable Cystobactamids

The rise of antibiotic resistance causes a serious health care problem, and its counterfeit demands novel, innovative concepts. The combination of photopharmacology, enabling a light-controlled reversible modulation of drug activity, with antibiotic drug design has led to first photoswitchable antibiotic compounds derived from established scaffolds. In this study, we converted cystobactamids, gyrase-inhibiting natural products with an oligoaryl scaffold and highly potent antibacterial activities, into photoswitchable agents by inserting azobenzene in the N-terminal part and/or an acylhydrazone moiety near the C-terminus, yielding twenty analogs that contain mono- as well as double-switches. Antibiotic and gyrase inhibition properties could be modulated 3.4-fold and 5-fold by light, respectively. Notably, the sensitivity of photoswitchable cystobactamids towards two known resistance factors, the peptidase AlbD and the scavenger protein AlbA, was light-dependent. While irradiation of an analog with an N-terminal azobenzene with 365 nm light led to less degradation by AlbD, the AlbA-mediated inactivation was induced. This provides a proof-of-principle that resistance towards photoswitchable antibiotics can be optically controlled.

Oxidation-Induced and Hydrothermal-Assisted Template-Free Synthesis of Mesoporous CeO2 for Adsorption of Acid Orange 7

Hydrogen peroxide (H2O2), an accessible and eco-friendly oxidant, was employed for the template-free hydrothermal synthesis of mesoporous CeO2 based on a cerium carbonate precursor (Ce2(CO3)3•xH2O). Its microstructure and physicochemical properties were characterized by XRD, TEM and N2 sorption techniques. The formation of the CeO2 phase with a porous structure was strongly dependent on the presence of H2O2, while the values of the BET surface area, pore diameter and pore volume of CeO2 were generally related to the amount of H2O2 in the template-free hydrothermal synthesis. The BET surface area and pore volume of the mesoporous CeO2 synthesized hydrothermally at 180 °C with 10 mL H2O2 were 112.8 m2/g and 0.1436 cm3/g, respectively. The adsorption process had basically finished within 30 min, and the maximum adsorption efficiency within 30 min was 99.8% for the mesoporous CeO2 synthesized hydrothermally at 140 °C with 10 mL, when the initial AO7 concentration was 120 mg/L without pH preadjustment. The experimental data of AO7 adsorption were analyzed using the Langmuir and Freundlich isotherm modes. Moreover, the mesoporous CeO2 synthesized at 140 °C with 10 mL H2O2 was regenerated in successive adsorption-desorption cycles eight times without significant loss in adsorption capacity, suggesting that the as-synthesized mesoporous CeO2 in this work was suitable as an adsorbent for the efficient adsorption of AO7 dye from an aqueous solution.

Structure-related endocrine-disrupting potential of environmental transformation products of benzophenone-type UV filters: A review

Benzophenone-type UV filters (BPs) represent a very diverse group of chemicals that are used across a range of industrial sectors around the world. They are found within different environmental compartments (e.g. surface water, groundwater, wastewater, sediments and biota) at concentrations ranging from ng/L to mg/L. Some are known as endocrine disruptors and are currently within the scope of international regulations. A structural alert for high potential of endocrine disrupting activity was assigned to 11 BP derivatives. Due to the widespread use, distribution and disruptive effects of some BPs, knowledge of their elimination pathways is required. This review demonstrates that biodegradation and photolytic decomposition are the major elimination processes for BP-type UV filters in the environment. Under aerobic conditions, transformation pathways have only been reported for BP, BP-3 and BP-4, which are also the most common derivatives. Primary biodegradation mainly results in the formation of hydroxylated BPs, which exhibit a structure-related increase in endocrine activity when compared to their parent substances. By combining 76 literature-based transformation products (TPs) with in silico results relating to their receptor activity, it is demonstrated that 32 TPs may retain activity and that further knowledge of the degradation of BPs in the environment is needed.

Urinary and fecal excretion of aromatic amines in pet dogs and cats from the United States

Several primary aromatic amines (AAs) are known or suspected carcinogens. Despite this, the exposure of pet animals to this class of chemicals is unknown. In this study, we investigated the occurrence of 30 AAs and two tobacco chemical markers (nicotine and cotinine) in 63 pet urine (42 dog and 21 cat) and 77 pet feces (37 dog and 40 cat) samples collected from the Albany area of New York State. Eight of the 30 AAs (∑₈AAs) were found in > 38% of dog and cat urine samples, at median concentrations of 7.99 (range: 0.42-52.3 ng/mL) and 31.4 (2.63-75.9) ng/mL, respectively. Nine of the 30 AAs (∑₉AAs) were found in > 73% of dog and cat feces samples, at median concentrations of 278 (range: 61.7-613 ng/g) and 240 (55.4-645) ng/g dry wt, respectively. Among the 30 AAs, 2,6-dimethylaniline (2,6-DMA) accounted for the highest median concentrations in both urine and fecal samples. Median concentrations of nicotine and cotinine were below 0.92 ng/mL in urine and below 3.86 ng/g in feces of both dogs and cats. No significant relationship was found between AA concentrations and pet age or gender. The lack of significant Spearman's rank correlation between the concentrations of AA and nicotine in pet urine/feces suggested that sources other than tobacco smoke contributed to AA exposure in pets. Furthermore, the calculated fecal excretion rates of AAs were higher than the intake rates (estimated through reverse dosimetry), which indicates that cats and dogs are exposed to AA precursors such as azo dyes. Concentrations in urine and feces reflected exposure to direct and indirect exposure sources, respectively, of AAs.

Systematic virtual screening in search of SARS CoV-2 inhibitors against spike glycoprotein: pharmacophore screening, molecular docking, ADMET analysis and MD simulations

In the absence of efficient anti-viral medications, the coronavirus disease 2019 (COVID-19), stemming from severe acute respiratory syndrome coronavirus-2 (SARS CoV-2), has spawned a worldwide catastrophe and global emergency. Amidst several anti-viral targets of COVID-19, spike glycoprotein has been recognized as an essential target for the viral entry into the host cell. In the search of effective SARS CoV-2 inhibitors acting against spike glycoprotein, the virtual screening of 175,851 ligands from the 2020.1 Asinex BioDesign library has been performed using in silico tools like SiteMap analysis, pharmacophore-based screening, molecular docking using different levels of precision, such as high throughput virtual screening, standard precision and extra precision, followed by absorption, distribution, metabolism, excretion and toxicity analysis, and molecular dynamics (MD) simulation. Following a molecular docking study, seventeen molecules (with a docking score of less than - 6.0) were identified having the substantial interactions with the catalytic amino acid and nucleic acid residues of spike glycoprotein at the binding site. In investigations using MD simulations for 10 ns, the hit molecules (1 and 2) showed adequate compactness and uniqueness, as well as satisfactory stability. These computational research findings have offered a key starting point in the field of design and development of novel SARS CoV-2 entry inhibitors with appropriate drug likeliness.

Precision Biotransformation of Emerging Pollutants by Human Cytochrome P450 Using Computational-Experimental Synergy: A Case Study of Tris(1,3-dichloro-2-propyl) Phosphate

Precision biotransformation is an envisioned strategy offering detailed insights into biotransformation pathways in real environmental settings using experimentally guided high-accuracy quantum chemistry. Emerging pollutants, whose metabolites are easily overlooked but may cause idiosyncratic toxicity, are important targets of such a strategy. We demonstrate here that complex metabolic reactions of tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) catalyzed by human CYP450 enzymes can be mapped via a three-step synergy strategy: (i) screening the possible metabolites via high-throughout (moderate-accuracy) computations; (ii) analyzing the proposed metabolites in vitro by human liver microsomes and recombinant human CYP450 enzymes; and (iii) rationalizing the experimental data via precise mechanisms using high-level targeted computations. Through the bilateral dialogues from qualitative to semi-quantitative to quantitative levels, we show how TDCIPP metabolism especially by CYP3A4 generates bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) as an O-dealkylation metabolite and bis(1,3-dichloro-2-propyl) 3-chloro-1-hydroxy-2-propyl phosphate (alcohol_β-dehalogen) as a dehalogenation/reduction metabolite via the initial rate-determining H-abstraction from αC- and βC-positions. The relative yield ratio [dehalogenation/reduction]/[O-dealkylation] is derived from the relative barriers of H-abstraction at the βC- and αC-positions by CYP3A4, estimated as 0.002 to 0.23, viz., an in vitro measured ratio of 0.04. Importantly, alcohol_β-dehalogen formation points to a new mechanism involving successive oxidation and reduction functions of CYP450, with its precursor aldehyde_β-dehalogen being a key intermediate detected by trapping assays and rationalized by computations. We conclude that the proposed three-step synergy strategy may meet the increasing challenge of elucidating biotransformation mechanisms of substantial synthesized organic compounds in the future.

Enhanced degradation of 4-aminobenzenesulfonate by a co-culture of Afipia sp. 624S and Diaphorobacter sp. 624L

Two strains, Afipia sp. 624S and Diaphorobacter sp. 624L, were isolated from an enrichment culture with 4-aminobenzenesulfonate (4-ABS) as the only carbon source. Strain 624S utilized 4-ABS as the only source of carbon and energy and degraded 3.8 mM 4-ABS in 2 weeks, releasing a small amount of sulfate ions. On the other hand, strain 624L did not utilize 4-ABS. Additionally, a co-culture of strains 624S and 624L resulted in the enhanced degradation of 4-ABS, and no sulfite was accumulated in the degradation of 4-ABS. When incubated in 50 mM Tris-HCl buffer (pH 8.0) containing 2.2 mM sodium sulfite, strain 624S exhibited no sulfite oxidation; however, strain 624L completely oxidized the sulfite after 2 days. Furthermore, when manganase, which has the ability to oxidize sulfite, was added to the medium, the degradation rate of 4-ABS was increased in comparison with the non-addition control. These results indicate that the sulfite oxidation might stimulate the degradation of 4-ABS by strain 624S, suggesting syntrophic interaction between strains 624S and 624L based on sulfite oxidation.

Small-Molecule Inhibitors of the Coronavirus Spike: ACE2 Protein-Protein Interaction as Blockers of Viral Attachment and Entry for SARS-CoV-2

Inhibitors of the protein-protein interaction (PPI) between the SARS-CoV-2 spike protein and human ACE2 (hACE2), which acts as a ligand-receptor pair that initiates the viral attachment and cellular entry of this coronavirus causing the ongoing COVID-19 pandemic, are of considerable interest as potential antiviral agents. While blockade of such PPIs with small molecules is more challenging than that with antibodies, small-molecule inhibitors (SMIs) might offer alternatives that are less strain- and mutation-sensitive, suitable for oral or inhaled administration, and more controllable/less immunogenic. Here, we report the identification of SMIs of this PPI by screening our compound library focused around the chemical space of organic dyes. Among promising candidates identified, several dyes (Congo red, direct violet 1, Evans blue) and novel druglike compounds (DRI-C23041, DRI-C91005) inhibited the interaction of hACE2 with the spike proteins of SARS-CoV-2 as well as SARS-CoV with low micromolar activity in our cell-free ELISA-type assays (IC50's of 0.2-3.0 μM), whereas control compounds, such as sunset yellow FCF, chloroquine, and suramin, showed no activity. Protein thermal shift assays indicated that the SMIs of interest identified here bind SARS-CoV-2-S and not hACE2. While dyes seemed to be promiscuous inhibitors, DRI-C23041 showed some selectivity and inhibited the entry of two different SARS-CoV-2-S expressing pseudoviruses into hACE2-expressing cells in a concentration-dependent manner with low micromolar IC50's (6-7 μM). This provides proof-of-principle evidence for the feasibility of small-molecule inhibition of PPIs critical for SARS-CoV-2 attachment/entry and serves as a first guide in the search for SMI-based alternative antiviral therapies for the prevention and treatment of diseases caused by coronaviruses in general and COVID-19 in particular.

Methylene Blue Inhibits the SARS-CoV-2 Spike-ACE2 Protein-Protein Interaction-a Mechanism that can Contribute to its Antiviral Activity Against COVID-19

Due to our interest in the chemical space of organic dyes to identify potential small-molecule inhibitors (SMIs) for protein-protein interactions (PPIs), we initiated a screen of such compounds to assess their inhibitory activity against the interaction between SARS-CoV-2 spike protein and its cognate receptor ACE2, which is the first critical step initiating the viral attachment and entry of this coronavirus responsible for the ongoing COVID-19 pandemic. As part of this, we found that methylene blue, a tricyclic phenothiazine compound approved by the FDA for the treatment of methemoglobinemia and used for other medical applications (including the inactivation of viruses in blood products prior to transfusion when activated by light), inhibits this interaction. We confirmed that it does so in a concentration-dependent manner with a low micromolar half-maximal inhibitory concentration (IC50 = 3 μM) in our protein-based ELISA-type setup, while chloroquine, siramesine, and suramin showed no inhibitory activity in this assay. Erythrosine B, which we have shown before to be a promiscuous SMI of PPIs, also inhibited this interaction. Methylene blue inhibited the entry of a SARS-CoV-2 spike bearing pseudovirus into ACE2-expressing cells with similar IC50 (3.5 μM). Hence, this PPI inhibitory activity could contribute to its antiviral activity against SARS-CoV-2 even in the absence of light by blocking its attachment to ACE2-expressing cells and making this inexpensive and widely available drug potentially useful in the prevention and treatment of COVID-19 as an oral or inhaled medication.

Assessing the effects of textile leachates in fish using multiple testing methods: From gene expression to behavior

The textile industry, while of major importance in the world economy, is a toxic industry utilizing and emitting thousands of chemical substances into the aquatic environment. The aim of this project was to study the potentially harmful effects associated with the leaching of chemical residues from three different types of textiles: sportswear, children's bath towels, and denim using different fish models (cell lines, fish larvae and juvenile fish). A combination of in vitro and in vivo test systems was used. Numerous biomarkers, ranging from gene expression, cytotoxicity and biochemical analysis to behavior, were measured to detect effects of leached chemicals. Principle findings indicate that leachates from all three types of textiles induced cytotoxicity on fish cell lines (RTgill-W1). Leachates from sportswear and towels induced mortality in zebrafish embryos, and chemical residues from sportswear reduced locomotion responses in developing larval fish. Sportswear leachate increased Cyp1a mRNA expression and EROD activity in liver of exposed brown trout. Leachates from towels induced EROD activity and VTG in rainbow trout, and these effects were mitigated by the temperature of the extraction process. All indicators of toxicity tested showed that exposure to textile leachate can cause adverse reactions in fish. These findings suggested that chemical leaching from textiles from domestic households could pose an ecotoxicological threat to the health of the aquatic environment.

A scientific review of colorful textiles

Textiles, especially apparel, play an essential role in our daily life. Given that nearly everybody is in contact with clothes and other textiles 24 h a day, they have to be safe. Today’s manufacturing processes depend on the use of many different chemicals, including dyes. An ideal dye would stay within the fabric during use. However, most textile dyes are prone to leaching and wear-off. Ideally, the industry is trying to keep the respective release of dyestuffs as low as possible. Concomitantly, toxicological risk assessment has to evaluate whether the released amounts are safe based on the substance-inherent characteristics and expected levels of exposure. So far, assessments of the latter are mostly based on what little data is available. Although the use of worst-case scenarios makes systematic overestimation likely and thus warrants a sufficiently high level of consumer protection, existing data gaps should be filled in order to end this unsatisfactory situation. Hence, in a first step this paper compiles and analyzes available data on the migration of dyes from textile materials, dermal dye uptake, and possible reductive cleavage of azo dyes by the skin microbiome as well as the dermal uptake of the resulting cleavage products.

On the Promise of Photopharmacology Using Photoswitches: A Medicinal Chemist's Perspective

Photopharmacology is a growing area of endeavor that employs photoswitchable ligands to allow for light-dependent pharmacological activity. By coupling light to therapeutic action, improved spatial and temporal selectivity can be achieved and subsequently harnessed for new concepts in therapy. Tremendous progress has already been made, with photopharmacological agents now reported against a wide array of target classes and light-dependent results demonstrated in a range of live cell and animal models. Several challenges remain, however, especially in order for photopharmacology to truly impact the clinical management of disease. This Perspective aims to summarize these challenges, particularly with attention to the medicinal chemistry that will be unavoidably required for the further translation of these agents/approaches. By clearly defining challenges for drug hunters, it is hoped that further research into the medicinal chemistry of photopharmacological agents will be stimulated, ultimately enabling full realization of the huge potential for this exciting field.

Screening of five marine-derived fungal strains for their potential to produce oxidases with laccase activities suitable for biotechnological applications

BACKGROUND

Environmental pollution is one of the major problems that the world is facing today. Several approaches have been taken, from physical and chemical methods to biotechnological strategies (e.g. the use of oxidoreductases). Oxidative enzymes from microorganisms offer eco-friendly, cost-effective processes amenable to biotechnological applications, such as in industrial dye decolorization. The aim of this study was to screen marine-derived fungal strains isolated from three coastal areas in Tunisia to identify laccase-like activities, and to produce and characterize active cell-free supernatants of interest for dye decolorization.

RESULTS

Following the screening of 20 fungal strains isolated from the harbors of Sfax and Monastir (Tunisia), five strains were identified that displayed laccase-like activities. Molecular-based taxonomic approaches identified these strains as belonging to the species Trichoderma asperellum, Stemphylium lucomagnoense and Aspergillus nidulans. Among these five isolates, one T. asperellum strain (T. asperellum 1) gave the highest level of secreted oxidative activities, and so was chosen for further studies. Optimization of the growth medium for liquid cultures was first undertaken to improve the level of laccase-like activity in culture supernatants. Finally, the culture supernatant of T. asperellum 1 decolorized different synthetic dyes belonging to diverse dye families, in the presence or absence of 1-hydroxybenzotriazole (HBT) as a mediator.

CONCLUSIONS

The optimal growth conditions to produce laccase-like active cell-free supernatants from T. asperellum 1 were 1.8 mM CuSO₄ as an inducer, 1% NaCl to mimic a seawater environment and 3% sucrose as a carbon source. The culture supernatant of T. asperellum 1 effectively decolorized different synthetic dyes belonging to diverse chemical classes, and the presence of HBT as a mediator improved the decolorization process.

Gut microbiota in reductive drug metabolism

Gut bacteria are predominant microorganisms in the gut microbiota and have been recognized to mediate a variety of biotransformations of xenobiotic compounds in the gut. This review is focused on one of the gut bacterial xenobiotic metabolisms, reduction. Xenobiotics undergo different types of reductive metabolisms depending on chemically distinct groups: azo (-NN-), nitro (-NO₂), alkene (-CC-), ketone (-CO), N-oxide (-NO), and sulfoxide (-SO). In this review, we have provided select examples of drugs in six chemically distinct groups that are known or suspected to be subjected to the reduction by gut bacteria. For some drugs, responsible enzymes in specific gut bacteria have been identified and characterized, but for many drugs, only circumstantial evidence is available that indicates gut bacteria-mediated reductive metabolism. The physiological roles of even known gut bacterial enzymes have not been well defined.

Scented Candles as an Unrecognized Factor that Increases the Risk of Bladder Cancer; Is There Enough Evidence to Raise a Red Flag?

The causes of bladder cancer are not yet fully uncovered, however the research has identified a number of factors that may increase the risk of developing this cancer. The chemical carcinogenesis of bladder cancer due to chronic exposure to aromatic hydrocarbons has been well-established. The identification of this correlation led to an improvement of safety measures in chemical industry and a gradual decrease of bladder cancer cases among workers. Nevertheless, in the majority of bladder cancer cases, the specific cause of the disease still can't be specified. It makes the question of unrecognized factors associated with bladder cancer development even more relevant. Taking under consideration known chemical carcinogenesis of bladder cancer, this minireview takes under investigation the possible link between using scented candles and a risk of bladder cancer development. Burning scented candles contain many of the substances that are associated with a bladder cancer. Furthermore the scented candles are not only very popular but also widely available on the market, with limited quality regulations and unspecified raw materials determining a spectrum of potentially dangerous substances emitted during burning.

Exploration of the key functional strains from an azo dye degradation microbial community by DGGE and high-throughput sequencing technology

This study investigated a previously developed thermophilic microbial community with the ability to effectively degrade azo dyes. To identify the key microbes of this microbial community, a dilution-to-extinction approach was combined with polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and Illumina high-throughput sequencing technology (HTST). Strains belonging to Tepidiphilus sp. almost disappeared from the degradation solution at dilution ratios above 10^-7; furthermore, at this ratio, the diluted microbial community almost lost their decolorization ability, indicating this ratio as the critical point for effective azo dye decolorization. Strains belonging to Tepidiphilus sp. were indicated as possible key functional microbes of this microbial community for effective azo dye decolorization. Moreover, the synergistic action of other microbes, such as Anoxybacillus sp., Clostridium sp., and Bacillus sp., was suggested to further promote the decolorization process by secreting azoreductase and laccase. Caloramator spp. were found have the ability to degrade proteins and amino acids, which might promote the degradation process with further degradation microbes. The loss of these bacteria might diminish the synergistic relationships among different strains, which further results in the failure of efficient azo dye decolorization and degradation by this microbial community.

2-Azo-, 2-diazocine-thiazols and 2-azo-imidazoles as photoswitchable kinase inhibitors: limitations and pitfalls of the photoswitchable inhibitor approach

In photopharmacology, photoswitchable compounds including azobenzene or other diarylazo moieties exhibit bioactivity against a target protein typically in the slender E-configuration, whereas the rather bulky Z-configuration usually is pharmacologically less potent. Herein we report the design, synthesis and photochemical/inhibitory characterization of new photoswitchable kinase inhibitors targeting p38α MAPK and CK1δ. A well characterized inhibitor scaffold was used to attach arylazo- and diazocine moieties. When the isolated isomers, or the photostationary state (PSS) of isomers, were tested in commonly used in vitro kinase assays, however, only small differences in activity were observed. X-ray analyses of ligand-bound p38α MAPK and CK1δ complexes revealed dynamic conformational adaptations of the protein with respect to both isomers. More importantly, irreversible reduction of the azo group to the corresponding hydrazine was observed. Independent experiments revealed that reducing agents such as DTT (dithiothreitol) and GSH (glutathione) that are typically used for protein stabilization in biological assays were responsible. Two further sources of error are the concentration dependence of the E-Z-switching efficiency and artefacts due to incomplete exclusion of light during testing. Our findings may also apply to a number of previously investigated azobenzene-based photoswitchable inhibitors.

Iminothioindoxyl as a molecular photoswitch with 100 nm band separation in the visible range

Light is an exceptional external stimulus for establishing precise control over the properties and functions of chemical and biological systems, which is enabled through the use of molecular photoswitches. Ideal photoswitches are operated with visible light only, show large separation of absorption bands and are functional in various solvents including water, posing an unmet challenge. Here we show a class of fully-visible-light-operated molecular photoswitches, Iminothioindoxyls (ITIs) that meet these requirements. ITIs show a band separation of over 100 nm, isomerize on picosecond time scale and thermally relax on millisecond time scale. Using a combination of advanced spectroscopic and computational techniques, we provide the rationale for the switching behavior of ITIs and the influence of structural modifications and environment, including aqueous solution, on their photochemical properties. This research paves the way for the development of improved photo-controlled systems for a wide variety of applications that require fast responsive functions.

The design of photoswitches which operate in the visible light regime, show a large separation of absorption bands and are functional in various solvents is challenging. Here the authors report Iminothioindoxyls as visible-light operated photoswitches with a band separation of 100 nm.

Crystal structure of 3-meth-oxy-4-[2-(thia-zol-2-yl)diazen-1-yl]aniline monohydrate

In the title hydrated azo dye, C10H10N4OS·H2O, the benzene and thia-zole, are nearly coplanar, with a dihedral angle between their mean planes of 4.69 (17)°. The aromatic rings on the -N=N- moiety exhibit a trans configuration. The crystal structure features many types of inter-molecular inter-actions involving all the functional groups - strong hydrogen bonds (N⋯H and O⋯H), weak hydrogen bonds (C-H⋯O and C-H⋯N), C-H⋯π and π-π inter-actions - resulting in the formation of a three-dimensional framework.

Fabrication and Highly Efficient Dye Removal Characterization of Beta-Cyclodextrin-Based Composite Polymer Fibers by Electrospinning

Dye wastewater is one of the most important problems to be faced and solved in wastewater treatment. However, the treatment cannot be single and simple adsorption due to the complexity of dye species. In this work, we prepared novel composite fiber adsorbent materials consisting of ε-polycaprolactone (PCL) and beta-cyclodextrin-based polymer (PCD) by electrospinning. The morphological and spectral characterization demonstrated the successful preparation of a series of composite fibers with different mass ratios. The obtained fiber materials have demonstrated remarkable selective adsorption for MB and 4-aminoazobenzene solutions. The addition of a PCD component in composite fibers enhanced the mechanical strength of membranes and changed the adsorption uptake due to the cavity molecular structure via host⁻guest interaction. The dye removal efficiency could reach 24.1 mg/g towards 4-aminoazobenzene. Due to the admirable stability and selectivity adsorption process, the present prepared beta-cyclodextrin-based composite fibers have demonstrated potential large-scale applications in dye uptake and wastewater treatment.

Organismic-level acute toxicology profiling of reactive azo dyes

In the present study, organismic-level acute toxicology profile of three reactive azo dyes, viz. Reactive Blue 221, Reactive Red 195, and Reactive Yellow 145, was investigated, by using bacterial (Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Listeria monocytogenes, and Bacillus subtilis), fungal (Trichoderma asperellum, Aspergillus flavus, Fusarium fujikuroi, and Rhizoctonia solani), plant (Raphanus sativus, Triticum aestivum, Sorghum bicolor, and Phaseolus mungo), and aquatic (Artemia salina and Daphnia magna) specimens. Microbial test organisms (all the six bacteria and two fungi, i.e., T. asperellum and A. flavus) and D. magna were found to be relatively more sensitive towards the reactive azo dyes and their mixture, as the EC50 values were in the range of 80-330, 135-360, and 108-242 ppm for bacteria, fungi, and D. magna, respectively (but the effect was not acutely toxic). Moreover, the effect of dye mixture was comparable tothe individual dyes in almost all the tested microbial specimens. For plant seeds, the dye mixture was found to be relatively more inhibitory towards T. aestivum and R. sativus than the individual dyes. For S. bicolor and P. mungo seeds, the effect of the dye mixture was almost identical to the individual dyes. However, in all cases, EC50 values were in the range of 950-3500 ppm, which indicates a non-toxic effect on plant seed germination potential. Likewise, the dyes and their mixture were not acutely toxic for Artemia salina larvae (more sensitive to the dye mixture) and Daphnia magna neonates (EC50, 516-950 and 108-242 ppm, respectively).

Arylazopyrazole Photoswitches in Aqueous Solution: Substituent Effects, Photophysical Properties, and Host-Guest Chemistry

Getting the green light! Substituted arylazopyrazoles (AAPs) have been investigated as supramolecular photoswitches in aqueous solution. Selective photostationary states (PSSs) and improved binding affinities to β-cyclodextrin have been determined. The experimental findings are supported by results from DFT calculations.

R software package based statistical optimization of process components to simultaneously enhance the bacterial growth, laccase production and textile dye decolorization with cytotoxicity study

The thermophilic bacterium, Bacillus licheniformis U1 is used for the optimization of bacterial growth (R1), laccase production (R2) and synthetic disperse blue DBR textile dye decolorization (R3) in the present study. Preliminary optimization has been performed by one variable at time (OVAT) approach using four media components viz., dye concentration, copper sulphate concentration, pH, and inoculum size. Based on OVAT result further statistical optimization of R1, R2 and R3 performed by Box–Behnken design (BBD) using response surface methodology (RSM) in R software with R Commander package. The total 29 experimental runs conducted in the experimental design study towards the construction of a quadratic model. The model indicated that dye concentration 110 ppm, copper sulphate 0.2 mM, pH 7.5 and inoculum size 6% v/v were found to be optimum to maximize the laccase production and bacterial growth. Whereas, maximum dye decolorization achieved in media containing dye concentration 110 ppm, copper sulphate 0.6 mM, pH 6 and inoculum size 6% v/v. R package predicted R² of R1, R2 and R3 were 0.9917, 0.9831 and 0.9703 respectively; likened to Design-Expert (Stat-Ease) (DOE) predicted R² of R1, R2, and R3 were 0.9893, 0.9822 and 0.8442 respectively. The values obtained by R software were more precise, reliable and reproducible, compared to the DOE model. The laccase production was 1.80 fold increased, and 2.24 fold enhancement in dye decolorization was achieved using optimized medium than initial experiments. Moreover, the laccase-treated sample demonstrated the less cytotoxic effect on L132 and MCF-7 cell lines compared to untreated sample using MTT assay. Higher cell viability and lower cytotoxicity observed in a laccase-treated sample suggest the impending application of bacterial laccase in the reduction of toxicity of dye to design rapid biodegradation process.

Toward Small-Molecule Inhibition of Protein-Protein Interactions: General Aspects and Recent Progress in Targeting Costimulatory and Coinhibitory (Immune Checkpoint) Interactions

Protein-Protein Interactions (PPIs) that are part of the costimulatory and coinhibitory (immune checkpoint) signaling are critical for adequate T cell response and are important therapeutic targets for immunomodulation. Biologics targeting them have already achieved considerable clinical success in the treatment of autoimmune diseases or transplant recipients (e.g., abatacept, belatacept, and belimumab) as well as cancer (e.g., ipilimumab, nivolumab, pembrolizumab, atezolizumab, durvalumab, and avelumab). In view of such progress, there have been only relatively limited efforts toward developing small-molecule PPI inhibitors (SMPPIIs) targeting these cosignaling interactions, possibly because they, as all other PPIs, are difficult to target by small molecules and were not considered druggable. Nevertheless, substantial progress has been achieved during the last decade. SMPPIIs proving the feasibility of such approaches have been identified through various strategies for a number of cosignaling interactions including CD40-CD40L, OX40-OX40L, BAFFR-BAFF, CD80-CD28, and PD-1-PD-L1s. Here, after an overview of the general aspects and challenges of SMPPII-focused drug discovery, we review them briefly together with relevant structural, immune-signaling, physicochemical, and medicinal chemistry aspects. While so far only a few of these SMPPIIs have shown activity in animal models (DRI-C21045 for CD40-D40L, KR33426 for BAFFR-BAFF) or reached clinical development (RhuDex for CD80-CD28, CA-170 for PD-1-PD-L1), there is proof-of-principle evidence for the feasibility of such approaches in immunomodulation. They can result in products that are easier to develop/ manufacture and are less likely to be immunogenic or encounter postmarket safety events than corresponding biologics, and, contrary to them, can even become orally bioavailable.

Small-Molecule Inhibitors of the CD40-CD40L Costimulatory Protein-Protein Interaction

Costimulatory interactions are required for T cell activation and development of an effective immune response; hence, they are valuable therapeutic targets for immunomodulation. However, they, as all other protein-protein interactions, are difficult to target by small molecules. Here, we report the identification of novel small-molecule inhibitors of the CD40-CD40L interaction designed starting from the chemical space of organic dyes. For the most promising compounds such as DRI-C21045, activity (IC50) in the low micromolar range has been confirmed in cell assays including inhibition of CD40L-induced activation in NF-κB sensor cells, THP-1 myeloid cells, and primary human B cells as well as in murine allogeneic skin transplant and alloantigen-induced T cell expansion in draining lymph node experiments. Specificity versus other TNF-superfamily interactions (TNF-R1-TNF-α) and lack of cytotoxicity have also been confirmed at these concentrations. These novel compounds provide proof-of-principle evidence for the possibility of small-molecule inhibition of costimulatory protein-protein interactions, establish the structural requirements needed for efficient CD40-CD40L inhibition, and serve to guide the search for such immune therapeutics.

Fungal Unspecific Peroxygenases Oxidize the Majority of Organic EPA Priority Pollutants

Unspecific peroxygenases (UPOs) are secreted fungal enzymes with promiscuity for oxygen transfer and oxidation reactions. Functionally, they represent hybrids of P450 monooxygenases and heme peroxidases; phylogenetically they belong to the family of heme-thiolate peroxidases. Two UPOs from the basidiomycetous fungi Agrocybe aegerita (AaeUPO) and Marasmius rotula (MroUPO) converted 35 out of 40 compounds listed as EPA priority pollutants, including chlorinated benzenes and their derivatives, halogenated biphenyl ethers, nitroaromatic compounds, polycyclic aromatic hydrocarbons (PAHs) and phthalic acid derivatives. These oxygenations and oxidations resulted in diverse products and—if at all—were limited for three reasons: (i) steric hindrance caused by multiple substitutions or bulkiness of the compound as such (e.g., hexachlorobenzene or large PAHs), (ii) strong inactivation of aromatic rings (e.g., nitrobenzene), and (iii) low water solubility (e.g., complex arenes). The general outcome of our study is that UPOs can be considered as extracellular counterparts of intracellular monooxygenases, both with respect to catalyzed reactions and catalytic versatility. Therefore, they should be taken into consideration as a relevant biocatalytic detoxification and biodegradation tool used by fungi when confronted with toxins, xenobiotics and pollutants in their natural environments.

Evaluation of metabolism of azo dyes and their effects on Staphylococcus aureus metabolome

Dyes containing one or more azo linkages are widely applied in cosmetics, tattooing, food and drinks, pharmaceuticals, printing inks, plastics, leather, as well as paper industries. Previously we reported that bacteria living on human skin have the ability to reduce some azo dyes to aromatic amines, which raises potential safety concerns regarding human dermal exposure to azo dyes such as those in tattoo ink and cosmetic colorant formulations. To comprehensively investigate azo dye-induced toxicity by skin bacteria activation, it is very critical to understand the mechanism of metabolism of the azo dyes at the systems biology level. In this study, an LC/MS-based metabolomics approach was employed to globally investigate metabolism of azo dyes by Staphylococcus aureus as well as their effects on the metabolome of the bacterium. Growth of S. aureus in the presence of Sudan III or Orange II was not affected during the incubation period. Metabolomics results showed that Sudan III was metabolized to 4-(phenyldiazenyl) aniline (48%), 1-[(4-aminophenyl) diazenyl]-2-naphthol (4%) and eicosenoic acid Sudan III (0.9%). These findings indicated that the azo bond close to naphthalene group of Sudan III was preferentially cleaved compared with the other azo bond. The metabolite from Orange II was identified as 4-aminobenzene sulfonic acid (35%). A much higher amount of Orange II (~90×) was detected in the cell pellets from the active viable cells compared with those from boiled cells incubated with the same concentration of Orange II. This finding suggests that Orange II was primarily transported into the S. aureus cells for metabolism, instead of the theory that the azo dye metabolism occurs extracellularly. In addition, the metabolomics results showed that Sudan III affected energy pathways of the S. aureus cells, while Orange II had less noticeable effects on the cells. In summary, this study provided novel information regarding azo dye metabolism by the skin bacterium, the effects of azo dyes on the bacterial cells and the important role on the toxicity and/or inactivation of these compounds due to microbial metabolism.

Anaerobic biodegradation of (emerging) organic contaminants in the aquatic environment

Although strictly anaerobic conditions prevail in several environmental compartments, up to now, biodegradation studies with emerging organic contaminants (EOCs), such as pharmaceuticals and personal care products, have mainly focused on aerobic conditions. One of the reasons probably is the assumption that the aerobic degradation is more energetically favorable than degradation under strictly anaerobic conditions. Certain aerobically recalcitrant contaminants, however, are biodegraded under strictly anaerobic conditions and little is known about the organisms and enzymatic processes involved in their degradation. This review provides a comprehensive survey of characteristic anaerobic biotransformation reactions for a variety of well-studied, structurally rather simple contaminants (SMOCs) bearing one or a few different functional groups/structural moieties. Furthermore it summarizes anaerobic degradation studies of more complex contaminants with several functional groups (CMCs), in soil, sediment and wastewater treatment. While strictly anaerobic conditions are able to promote the transformation of several aerobically persistent contaminants, the variety of observed reactions is limited, with reductive dehalogenations and the cleavage of ether bonds being the most prevalent. Thus, it becomes clear that the transferability of degradation mechanisms deduced from culture studies of SMOCs to predict the degradation of CMCs, such as EOCs, in environmental matrices is hampered due the more complex chemical structure bearing different functional groups, different environmental conditions (e.g. matrix, redox, pH), the microbial community (e.g. adaptation, competition) and the low concentrations typical for EOCs.

Analysis of Primary Aromatic Amines Derived from Azo Colorants in Textile Products and Determination of Their Source Colorant

Twenty-four primary aromatic amines (PAAs) derived from azo colorants, which are controlled by the Act on Control of Household Products Containing Harmful Substances by the Japan Ministry of Health, Labour and Welfare, aniline and 1,4-phenylendiamine were analyzed in 86 samples of 40 textile products by GC-MS. Even though these PAAs detected in the samples did not exceed the regulation value (30 μg/g), 14 kinds of PAAs were detected that exceeded the limit of quantification. 4,4'-Methylenedianiline, in amounts that exceeded the limit of quantification, was detected in 20 textile samples containing synthesis fiber (16 samples made from polyurethane, two samples made from polyester, and two samples made from acryl); however, it was not detected in natural fiber textile samples. Of these samples, 4,4'-methylenedianiline was detected in 16 out of 19 samples (84%) made from polyurethane fiber. This suggests that 4,4'-methylenedianiline is formed from polyurethane. The origin of 3,3'-dichlorobenzidine was investigated in three samples releasing more than 3 μg/g (3.9-15 μg/g) of 3,3'-dichlorobenzidine using atmospheric pressure solids analysis probe-mass spectrometry and Pigment Orange 13 was identified as the orange colorant in the textile printing parts. This result suggests that 3,3'-dichlorobenzidine detected in these three samples was generated by the reduction of Pigment Orange 13.

Assessment of the cytotoxic, genotoxic and mutagenic effects of the commercial black dye in Allium cepa cells before and after bacterial biodegradation treatment

The present study evaluated the cytotoxic, genotoxic and mutagenic actions of different concentrations (50 and 200 μg/L) of BDCP (Black Dye Commercial Product) used by textile industries, before and after bacterial biodegradation, by the conventional staining cytogenetic technique and NOR-banding in Allium cepa cells. Differences in the chromosomal and nuclear aberrations and alterations in the number of nucleoli were observed in cells exposed to BDCP with and without the microbial treatment. The significant frequencies of chromosome and nuclear aberrations noted in the tests with bacterially biodegraded BDCP indicate that the metabolites generated by degradation are more genotoxic than the chemical itself. Losses of genetic material characterize a type of alteration that was mainly associated with the action of the original BDCP, whereas chromosome stickiness, nuclear buds and binucleated cells were the aberrations that were preferentially induced by BDCP metabolites after biodegradation. The significant frequencies of cell death observed in the tests with biodegraded BDCP also show the cytotoxic effects of the BDCP metabolites. The reduction in the total frequency of altered cells after the recovery treatments showed that the test organism A. cepa has the ability to recover from damage induced by BDCP and its metabolites after the exposure conditions are normalized.

Graphene oxide supported copper oxide nanoneedles: An efficient hybrid material for removal of toxic azo dyes

Herein, we report a simple, one step synthesis of hybrid copper oxide nanoneedles on graphene oxide sheets (GO-CuONNs) through sonochemical method. The present method affords a facile mean for controlling effective concentration of the active CuO nanoneedles on the graphene oxide sheets, and also offers the necessary stability to the resulting GO-CuONNs structure for adsorption transformations.Furthermore, this hybrid GO-CuONNs is successfully employed in the removal of a series of hazardous ionic organic dyes namely coomassie brilliant blue, methylene blue, congo red and amidoblack 10B. Through careful investigation of the material, we found that the synergetic effect between CuONNs and GO play a significant role in the adsorption of all the dyes studied. The prepared hybrid material contains both hydrophobic and hydrophilic environment which is expected to enhance the electrostatic interaction between the adsorbent and the dye molecules, consequently favouring the adsorption process.

Isolation and characterization of Bradyrhizobium sp. 224 capable of degrading sulfanilic acid

A bacterial strain (strain 224), which has the ability to utilize sulfanilic acid as a sole source of carbon, was isolated from soil. 16S rRNA gene sequence obtained from strain 224 exhibited 100% identical to that of species in the genus Bradyrhizobium. Strain 224 degraded 4.7 mM of sulfanilic acid and released almost the same molar concentration of sulfate ion

Detoxification of azo dyes in the context of environmental processes

Azo dyes account for >70% of the global industrial demand (∼9 million tons). Owing to their genotoxic/carcinogenic potential, the annual disposal of ∼4,500,000 tons of dyes and/or degraded products is an environmental and socio-economic concern. In comparison to physico-chemical methods, microbe-mediated dye degradation is considered to be low-input, cost-effective and environmentally-safe. However, under different environmental conditions, interactions of chemically diverse dyes with metabolically diverse microbes produce metabolites of varying toxicity. In addition, majority of studies on microbial dye-degradation focus on decolorization with least attention towards detoxification. Therefore, the environmental significance of microbial dye detoxification research of past >3 decades is critically evaluated with reference to dye structure and the possible influence of microbial interactions in different environments. In the absence of ecosystem-based studies, the results of laboratory-based studies on dye degradation, metabolite production and their genotoxic impact on model organisms are used to predict the possible fate and consequences of azo dyes/metabolites in the environment. In such studies, the predominance of fewer numbers of toxicological assays that too at lower levels of biological organization (molecular/cellular/organismic) suggests its limited ecological significance. Based on critical evaluation of these studies the recommendations on inclusion of multilevel approach (assessment at multiple levels of biological organization), multispecies microcosm approach and native species approach in conjunction with identification of dye metabolites have been made for future studies. Such studies will bridge the gap between the fundamental knowledge on dye-microbe-environment interactions and its application to combat dye-induced environmental toxicity. Thus an environmental perspective on dye toxicity in the background of dye structure and effects of environmental processes has been developed. Based on past 3 decades of research on microbial dye detoxification, the current state of knowledge has been analyzed, environmental relevance of these studies was ascertained, research gaps in microbe-mediated azo dye detoxification have been identified and a research framework emphasizing a better understanding of complex interactions between dye-microbe and environmental processes has been proposed. It provides directions for undertaking environmentally sound microbial dye detoxification research.