Azure B Research Articles

Exploration of the role of Hibiscus esculentus (okra) mucilage for the removal of phenothiazinium dyes from water body: Spectroscopic, thermodynamic and molecular modeling study

Environmental pollution poses a major problem now a day. Several dyes, in the form of industrial waste, pollute water body and may cause adverse effects to human health. In this paper ADME and toxicity of fives Phenothiazinium group of dyes Methylene blue (MB), Azure A (AA), Azure B (AB), Azure C (AC) and Toluidine Blue O (TBO) were predicted using Swiss ADME and Protox II tools. Results showed these dyes may herm for living organism due to their carcinogenic, mutagenic and hepatotoxic properties. Removal efficiency of these dyes using okra plant product were determined using spectroscopic, thermodynamic and molecular modeling study. It was revealed that these dyes adsorb on the surface of okra leaf mostly at pH 7.0 and the adsorption isotherms were found to fit in Langmuir and Freundlich isotherm model, while Temkin model fails to do this. Mucilage present in different parts of okra plant plays a significant role on removal of these dyes and is able to remove near about 71–92 % of dyes from water body by itself. As this process did not fit in any of above said adsorption isotherm model, it may be suggested that some other mechanism may happen. Further studies explore that these dyes bound to the hydrophobic pocket of mucilage with binding affinity in the order of 105 M−1 and the bindings were exothermic in nature with enthalpy change in the range of − 2.94 to − 4.28 kcal/mole. Molecular docking study validate all the experimental results obtained from spectroscopic and thermodynamic study and enlighten the role of structure of dyes on their binding affinity to mucilage. This paper will help to systematically understand the role of okra plant products on removal efficiency of Phenothiazinium group of dyes with their structural variations.

Design and Application of an In Situ Traceable Nitric OxideDonor for Promoting the Healing of Wound Infections.

Therapies for wound infections require medications with antibacterial and wound-healing functions. However, it remains a challenge to produce a single drug that can perform dual functions. Nitric oxide (NO), with its antibacterial and wound-healing activities, is an ideal solution to address this challenge. However, many controlled-release strategies for NO rely on external probes for tracing the release in situ, making it difficult to precisely assess the location and magnitude. To address this issue, this study describes a novel NO donor, DHU-NO1, capable of efficiently releasing NO under mild conditions (450nm illumination). Simultaneously, DHU-NO1 generates the fluorophore Azure B (AZB), which enables direct, non-consumptive tracing of the NO release by monitoring the fluorescence and absorption changes in AZB. Given that NO can be conveniently traced, the amount of released NO can be controlled during biological applications, thereby allowing both functions of NO to be performed. When applied to the affected area, DHU-NO1, illuminated by both a simple light-emitting diode (LED) light source and natural light, achieves significant antibacterial effects against wound infections and promotes wound healing in mice. This study offers a novel and effective approach for treating wound infections.

Efficient Dye Extraction from Wastewater Using Indium-MOF-Immobilized Polyvinylidene Fluoride Membranes with Selective Filtration for Enhanced Remediation.

Industrial activities have led to releasing harmful substances into the environment, necessitating the elimination of these toxic compounds from wastewater. Organic dyes, commonly found in industrial effluents, pose a threat to ecosystems and human health. Conventional treatment methods often suffer from limitations such as high cost and poor efficiency. Metal-organic frameworks (MOFs) have emerged as promising materials for selective separation, including membrane filtration (MF). Mixed-matrix membranes (MMMs) combining MOFs with polymers offer improved filtration properties. In this study, MMMs were fabricated by incorporating synthesized In-MOF with a polyvinylidene fluoride (PVDF) polymer (In-MOF@PVDF MMMs) using the nonsolvent-induced phase separation process. The MMMs were evaluated for the MF of various organic dyes, achieving notable removal efficiencies. The membrane containing 20% In-MOF (M4) demonstrated exceptional performance, removing 99% of the methylene blue (MB) dye. Additionally, membrane M4 effectively filtered Azure A (AZA), Azure B (AZB), and toluidine blue O (TOLO) with a removal efficiency of 99%. However, for Rhodamine B (RHB) and methyl orange (MO), the removal efficiencies were slightly lower at 74 and 39%, respectively. Further, these membranes are utilized in selective dye filtration in the MB+/RHB+ and MB+/MO- systems, where the selectivity was found for MB. The isothermal and DFT studies revealed the membrane's behavior with dye mixtures, while water stability and regeneration studies confirmed its durability. Thus, these findings highlight the potential of In-MOF@PVDF MMMs for effective and selective dye removal in wastewater treatment applications.

Sonochemical surface modification of a novel Sm2O3@g-C3N4@Bi2O3 ternary hybrid photocatalyst exhibiting efficient solar light harvesting: Degradation of Azure b and photoelectrochemical water splitting

Engineered Z-scheme photocatalysts have a strong redox activity while also reducing the annihilation of light-induced charge bearers. In this investigation, a solid state twin Z-scheme Sm2O3@g-C3N4@Bi2O3 nanocomposite has been successfully prepared employing bismuth (III) nitrate, samarium chloride and urea as precursor chemicals in a single co-calcination procedure followed by sonochemical surface modification. The formation of flower like multiphasic material is confirmed from SEM and HRTEM images. BET findings suggested the enhancement in specific surface area of Sm2O3@g-C3N4@Bi2O3 and reduced band gap from UV–visible data. Photoluminescence results confirmed the reduction in rate of charge carrier recombination of Sm2O3@g-C3N4@Bi2O3. Presence of samarium is confirmed from XPS analysis. Under direct solar radiation, the surface modified Sm2O3@g-C3N4@Bi2O3 hybrid demonstrated amplified photo-assisted catalytic activity for the degradation of Azure B (AzB) than pristine g-C3N4 and their binary composite Sm2O3@g-C3N4. It is possible to attribute the better solar light absorption, higher separation efficacy of photo-promoted electron-holes to the amplified photo-assisted degradation performance of the Sm2O3@g-C3N4@Bi2O3 composite. The photodegradaton of AzB follows pseudo-first order kinetics and the observed rate constants are 0.0014, 0.0026, and 0.0316 min−1 for g-C3N4, Sm2O3@g-C3N4, and Sm2O3@g-C3N4@Bi2O3 ternary composite. The nanocomposite also demonstrates good stability and recyclability. A unique solid-state twin Z-scheme photocatalytic pathway was also hypothesized in light of the findings. The fabricated ternary hybrid shown efficient photoelectrochemical water splitting reaction for H2 and O2 generation.

Synthesis of a coordination polymer based on Zn(DMF)(Tp) as a novel adsorbent for the simultaneous removal of quinoline yellow and azure B

In this study, a Zn(DMF)(Tp) coordination polymer was synthesized by solvothermal method using dimethylformamide (DMF) and terephthalic acid (TP). It was then characterized by single crystal X-ray diffraction (SCXRD), thermal gravimetric analysis (TGA), X-ray diffraction (XRD), and Fourier-transform infrared spectrometer (FT-IR). The polymer was used as an adsorbent for the simultaneous removal of quinoline yellow (QY) and azure B (AZB) dyes. Accordingly, the effects of four parameters, including pH, amount of adsorbent, contact time, and initial dye concentration, on removal efficiency were studied and optimized by response surface methodology based on the central composite design (RSM-CCD). The optimal conditions for maximum adsorption theoretically determined by RSM-CCD were as follows: 6 min contact time, 15 mg Zn(DMF)(Tp), pH of 3, 10 mg/L AZB, and 13 mg/L QY, with percentage removal values of 94.70 and 90.79 for QY and AZB, respectively. The monolayer adsorption capacity was 46.57 and 40.983 mg/g for QY and AZB, respectively. A kinetic study was performed under optimal conditions. In addition, all data corresponding to the process were fitted with pseudo-second-order model. The adsorbent provides fast adsorption due to its porous structure and high removal efficiency due to its high specific surface area.

Fabrication of Curcuma longa mediated novel Ni@ZnO/MoO3 composite anchored with g-C3N4 for sunlight driven photocatalytic activity

The extreme toxicity, genotoxicity, and carcinogenicity of Azure B in the aquatic environment have drawn attention to grow solar-driven techniques using effective photocatalysts for environment friendly remediation. We created Ni@ZnO/MoO3 z-scheme type structures supported on g-C3N4 photocatalyst by the sonochemically assisted biochemical method using Curcuma longa leaf extract. Structural, morphological, and surface features were investigated using X-ray diffraction (XRD), FTIR, UV–Visible, SEM/EDX, HR-TEM, XPS, and BET for surface analysis. Results indicated that MoO3 nanoplates and Ni@ZnO nanorods are beautifully oriented and interconnected, and these two crystalline materials are wrapped with a stacked layer of g-C3N4 which developed the proper charge flow resulting in the enhanced photo-assisted catalytic performance of the composite. Ternary composite has a large surface area as well as pore volume which automatically increased active site on the surface which enhanced photoactivity. In comparison to the g-C3N4 and Ni@ZnO/MoO3 composite, the Ni@ZnO/MoO3/g-C3N4 ternary nanocomposite displayed superior photocatalytic efficiency for the degradation of Azure B (AzB). Recyclability study showed its prolonged reusability. At optimized conditions, the photodegradation of AzB by ternary composite exhibited pseudo-first-order kinetics with the rate constant value of 0.074 min−1. It is found that h+ and •-O2are the active species for the photodegradation of AzB.

Construction of Cu-N coordination into natural biopolymer lignin backbone for highly efficient and selective removal of cationic dyes

Here, a Cu2+-doped lignin-based adsorbent (Cu-AL) was fabricated via the amination and Cu2+-doping of industrial alkali lignin for massive and selective adsorption of cationic dyes azure B (AB) and saffron T (ST). The Cu-N coordination structures endowed Cu-AL with stronger electronegativity and higher dispersity. Through the electrostatic attraction, π-π interaction, H-bonding, and Cu2+ coordination, the adsorption capacities of AB and ST reached up to 1168 and 1420 mg g−1, respectively. The pseudo-second-order model and Langmuir isotherm model were more relevant to the AB and ST adsorption on Cu-AL. Based on the thermodynamic study, the adsorption progresses were endothermic, spontaneous, and feasible. The Cu-AL maintained high removal efficiency to dyes after 4 reuses (>80%). Importantly, the Cu-AL could efficiently remove and separate AB and ST from dye mixtures even in real time. All the above characteristics demonstrated that Cu-AL was an excellent adsorbent for fast wastewater treatment.

Platinum nanoparticles confined within TiO2 nanotube matrix for enhanced catalytic reduction of azure b dye

• PtNPs confined TiO 2 nanotubes were successfully obtained. • HR-TEM analysis confirmed that the PtNPs (particle size ∼ 2–3 nm) were inside of the TiO 2 NTs. • The PtNPs-TiO 2 NTs were highly efficient for the catalytic reduction of AZB dye. • The PtNPs-TiO 2 NTs catalyst was active over 8 recycles. In this work, we report the synthesis of TiO 2 nanotubes encapsulated platinum nanoparticles (PtNPs-TiO 2 NTs) as a highly efficient catalyst for the catalytic reduction of azure B (AZB) dye in the sodium borohydride (NaBH 4 ) medium. The encapsulation of PtNPs (particle size ∼ 2–3 nm) inside the TiO 2 NTs was confirmed by HR-TEM analysis. The as-prepared PtNPs-TiO 2 NTs exhibit higher conversion efficiency than 99 % with a pseudo-first order rate constant of 2.6 × 10 -3 s −1 . Owing to the confinement effect of PtNPs inside the TiO 2 NTs, the synthesized catalyst shows the superior operative stability even after 8 consecutive recycles without any loss in its activity. This work opens up new avenue for the designing of confined catalyst for various industrial catalytic reactions.

Gold nanoparticle-decorated earth-abundant clay nanotubes as catalyst for the degradation of phenothiazine dyes and reduction of 4-(4-nitrophenyl)morpholine.

In the present work, halloysite nanotubes modified with gold nanoparticles (AuNPs-HNT) are successfully prepared by wet chemical method for the catalytic degradation of phenothiazine dyes (azure B (AZB) and toluidine blue O (TBO)) and also cleaner reduction of 4-(4-nitrophenyl)morpholine (4NM) in the sodium borohydride (NaBH4) media. The catalyst is formulated by modifying the HNT support with a 0.964% metal loading using the HNT supports modified with 3-aminopropyl-trimethoxysilane (APTMS) coupling agent to facilitate the anchoring sites to trap the AuNPs and to prevent their agglomeration/aggregation. The AuNPs-HNT catalyst is investigated for structural and morphological characterization to get insights about the formation of the catalyst for the effective catalytic reduction of dyes and 4NM. The microscopic studies demonstrate that AuNPs (2.75nm) are decorated on the outer surface of HNT. The as-prepared AuNPs-HNT catalyst demonstrates AZB and TBO dye degradation efficiency up to 96% in 10 and 11min, respectively, and catalytic reduction of 4NM to 4-morpholinoaniline (MAN) is achieved up to 97% in 11min, in the presence of NaBH4 without the formation of any by-products. The pseudo-first-order rate constant (K1) value of the AuNPs-HNT catalyst for AZB, TBO, and 4NM were calculated to be 0.0078, 0.0055, and 0.0066s-1, respectively. Moreover, the synthesized catalyst shows an excellent reusability with stable catalytic reduction for 7 successive cycles for both the dyes and 4NM. A plausible mechanism for the catalytic dye degradation and reduction of 4NM by AuNPs-HNT catalyst is proposed as well. The obtained results clearly indicate the potential of AuNPs-HNT as an efficient catalyst for the removal of dye contaminants from the aquatic environments and cleaner reduction of 4NM to MAN, insinuating future pharmaceutical applications.

Probing multifunctional azure B conjugated gold nanoparticles with serum protein binding properties for trimodal photothermal, photodynamic, and chemo therapy: Biophysical and photophysical investigations

Multimodal or combination therapy has been considered as a powerful approach for treatment of complex diseases like cancer. The fascinating physicochemical and optoelectronic properties of gold nanoparticles make them potential candidate for cancer therapeutic and diagnostic applications. Herein, we design a multifunctional nanosystem by conjugating a photosensitizer, Azure B (AB) with citrate reduced gold nanoparticles (CI-Au NPs) through non-covalent interactions. The conjugation of AB with CI-Au NPs was confirmed through UV–Visible absorption spectroscopy and Fourier Transform Infra-red (FT-IR) spectroscopy. The morphology, size, and charge of the prepared nano-conjugates (AB@CI-Au NPs) were determined by transmission electron microscopy (TEM), Dynamic light scattering (DLS), and zeta potential measurements. The proficiency of AB@CI-Au NPs for cancer photo-therapies was demonstrated by evaluating their potential for photothermal heating and singlet oxygen generation in solution upon Visible laser (635 nm, 500 mW/cm2) irradiation. The AB@CI-Au NPs display superior heating efficiency than CI-Au NPs alone or free AB, and offer better photostability as well as singlet oxygen generation rate compared to free photosensitizer. The interaction of AB@CI-Au NPs with Calf thymus DNA (Ct-DNA) and transport protein Bovine Serum Albumin (BSA) were studied using various biophysical techniques including Circular dichroism, UV–Visible and fluorescence spectroscopic studies. AB@CI-Au NPs show intercalative binding with Ct-DNA by inducing local perturbations in double helical structure and hence can exert chemotherapeutic action by targeting DNA. AB@CI-Au NPs also display moderate binding with BSA without any adverse effect on BSA structure, which is desirable for significant biodistribution and pharmacokinetics of AB@CI-Au NPs. Also, in vitro cytotoxicity of the AB@CI-Au NPs with and without laser irradiation (635 nm, 500 mW/cm2) was demonstrated using the hepatocellular carcinoma (HepG2) cell lines. Our findings through photophysical and biophysical studies strongly recommend the exploitation of AB@CI-Au NPs nanoconjugates as a multifunctional probe for trimodal anticancer therapy.

Green synthesis of fluorescent carbon dots from canon ball fruit for sensitive detection of Fe3+ and catalytic reduction of textile dyes

In this work, a simple, sustainable and economically feasible approach has been reported to synthesis Carbon Dots (CDs) by taking Canon Ball (CB) fruit as a bio-mass precursor. The properties of the synthesized CDs were analysed using various characterization techniques such as TEM, FTIR, PSA, Raman, UV–Visible and Fluorescence spectroscopy. The CDs have particle size of 11.2 nm, showed blue emission when exposing to UV light at wavelength of 365 nm and excitation dependent fluorescence behaviour with appreciable quantum yield of 7.01%. The synthesized CDs have excellent stability on exposure to different environments like pH, ionic concentrations and storage time. Further, it served as a probe for sensing Fe3+ ions selectively among different metal ions investigated. The Limit of Detection (LOD) was found to be 0.071 μM in the dynamic range of 0.6–3.3 μM of ferric ion concentration. Additionally, the CDs showed excellent catalytic activity in the treatment of two harmful textile dyes Azure B (AB) and Toluidine Blue (TB) via catalytic reduction with the assistance of NaBH4.

Determination of Methylene Blue and Its Metabolite Residues in Aquatic Products by High-Performance Liquid Chromatography-Tandem Mass Spectrometry.

A sensitive and reliable method was developed to determine methylene blue (MB) and its metabolite residues, including azure A (AZA), azure B (AZB), and azure C (AZC) in aquatic products by HPLC–MS/MS. The samples were extracted by acetonitrile and cleaned up by alumina-neutral (ALN) cartridges. The analytes were separated on a Sunfire C18 column (150 mm × 2.1 mm, 5 µm). The method was validated according to the European criteria of Commission Decision 2002/657/CE. Good linearity between 1–500 µg/L was obtained with correlation coefficients (R2) greater than 0.99. The limit of quantification (LOQ) was 1.0 µg/kg. The average recoveries at three levels of each compound (1, 5, and 10 µg/kg) were demonstrated to be in the range of 71.8–97.5%, with relative standard deviations (RSDs) from 1.05% to 8.63%. This method was suitable for the detection of methylene blue and its metabolite residues in aquatic products.

The photodynamic and intrinsic effects of Azure B on mitochondrial bioenergetics and the consequences of its intrinsic effects on hepatic energy metabolism

BackgroundThe present study aimed to characterize the intrinsic and photodynamic effects of azure B (AB) on mitochondrial bioenergetics, as well as the consequences of its intrinsic effects on hepatic energy metabolism. MethodsTwo experimental systems were utilized: (a) isolated rat liver mitochondria and (b) isolated perfused rat liver. ResultsAB interacted with mitochondria regardless of photostimulation, but its binding degree was reduced by mitochondrial energization. Under photostimulation, AB caused lipid peroxidation and protein carbonylation and decreased the content of reduced glutathione (GSH) in mitochondria. AB impaired mitochondrial bioenergetics in at least three distinct ways: (1) uncoupling of oxidative phosphorylation; (2) photoinactivation of complexes I and II; and (3) photoinactivation of the FoF1–ATP synthase complex. Without photostimulation, AB also demonstrated mitochondrial toxicity, which was characterized by the induction of lipid peroxidation, loss of inner mitochondrial membrane integrity, and uncoupling of oxidative phosphorylation. The perfused rat liver experiments showed that mitochondria were one of the major targets of AB, even in intact cells. AB inhibited gluconeogenesis and ureagenesis, two biosynthetic pathways strictly dependent on intramitochondrially generated ATP. Contrariwise, AB stimulated glycogenolysis and glycolysis, which are required compensatory pathways for the inhibited oxidative phosphorylation. Similarly, AB reduced the cellular ATP content and the ATP/ADP and ATP/AMP ratios. ConclusionsAlthough the properties and severe photodynamic effects of AB on rat liver mitochondria might suggest its usefulness in PDT treatment of liver tumors, this possibility should be considered with precaution given the toxic intrinsic effects of AB on mitochondrial bioenergetics and energy-linked hepatic metabolism.

The vibronic absorption spectrum and electronic properties of Azure B in aqueous solution: TD-DFT/DFT study

The vibronic absorption spectrum of Azure B (AB) in an aqueous solution is calculated using the time-dependent density functional theory (TD-DFT). The results of calculations are analyzed using all hybrid functionals supported by Gaussian16, the 6-31++G(d,p) basis set, and the IEFPCM and SMD solvent models. The solvent model IEFPCM gave significantly underestimated values of λmax in comparison with the experiment. This is a manifestation of the TD-DFT “cyanine failure”. However, the SMD model made it possible to obtain good agreement between the calculation results and experimental data. The best fit was achieved using the X3LYP functional. According to our calculations, the shoulder in the visible absorption spectrum of AB has a vibronic origin. However, the calculated shoulder is weaker than the experimental one. Explicit assignment of two water molecules, which form strong hydrogen bonds with a dye molecule, leads to a shift of the calculated absorption spectrum to longer wavelengths by approximately 17 nm but does not lead to an improvement in its shape. Comparative analysis of the calculated vibronic absorption spectra of Azure B with those obtained earlier for Azure A and methylene blue showed that the presence and intensity of the short-wavelength shoulder are determined by the location of the bands of higher vibronic transitions relative to the band of the 00 → 00 main transitions. Photoexcitation leads to an increase in the dipole moment of the dye molecule. An insignificant photoinduced electron transfer was found in the central ring of the chromophore of the dye molecule.

Comparative kinetic study on biodecolorization of synthetic dyes by Bjerkandera adusta SM46 in alginate beads-packed bioreactor system and shaking culture under saline-alkaline stress

Industrial dye wastewater contains a high saline concentration and is of an alkaline condition that may inhibit biological treatment. Finding suitable methods for the application of biological decolorisation is important. This research aimed to compare dye biodecolorization by Bjerkandera adusta SM46 using three different methods: (1) alginate-packed bioreactor (APB), (2) submerged-immobilised beads (SIB), and (3) submerged-free cell (SFC) under saline-alkaline and non-saline conditions. Five synthetic dyes with different molecular properties were used: Remazol brilliant blue R (RBBR), Azure B (AB), Brilliant red (BR), Brilliant green (BG), and Reactive green (RG). The results show that B. adusta SM46 was able to decolourise 10.8–97.3% of the dye samples in all methods and conditions, and even up to concentration 500 mg/L under the saline-alkaline condition. Evaluation of kinetic studies revealed the effectivity of the dye removal in SFC over SIB and APB. The highest degradation rate constant (k 1) was achieved for RBBR and the lowest k 1 was for RG. The values of k 1 for SFC, SIB and APB were 0.034, 0.024, and 0.015 respectively for RBBR and 0.013, 0.003, and 0.004 respectively for RG. Treatment using submerged-free cell (SFC) resulted in the greatest and most rapid decolorisation, compared with all other treatments except BR. However, immobilisation on alginate beads increased the reusability of the fungus for sequential batches under saline-alkaline stress. Therefore, selection of a suitable method for dye decolorisation could be proposed, allowing enhancement of the removal process under high saline-alkaline stress, which is usually found in industrial dye wastewater.

Microwave assisted synthesis of karaya gum based montmorillonite nanocomposite: Characterisation, swelling and dye adsorption studies

A polymer–clay hybrid composite material, (KG-g-PMETAC/MMT) has been synthesised by microwave assisted free radical polymerisation using modified karaya gum and clay mineral and was characterised by various techniques. The karaya gum has been modified by grafting with (2-methacryloyloxy ethyl) trimethyl ammonium chloride prior to making the clay composite. Montmorillonite was used as the clay component. The nanocomposite exhibited pH responsive swelling behaviour. The maximum swelling of 42.23 g/g was observed at pH 7.0 and minimum of 17.28 g/g was noticed at pH 9.2. The water transport mechanism was Fickian in nature and followed second order kinetic model. The adsorption capacities of the nanocomposite for the chosen cationic dyes, methylene blue (MB), toluidine blue (TB), crystal violet (CV) and azure B (AB) were found to 155.85, 149.64, 137.77 and 128.78 mg/g respectively. The dye adsorption was found to be a pseudo-first order kinetic process. The adsorption data is found to best fit with Freundlich isotherm model indicating heterogeneous adsorption and possibility of multilayer formation. Negative value of ΔG indicated the spontaneous nature of adsorption process at the temperatures under study. The reusability studies indicated that desorption of about 70% of the adsorbed dyes can be achieved after two consecutive cycles.

Azure B as a novel cyanide antidote: Preclinical in-vivo studies

We have determined the effects of azure B (AzB), the main demethylated metabolite of methylene blue (MB), on a model of lethal cyanide intoxication. Our rationale was the following: AzB 1- possesses redox properties very similar to those of MB, which is a potent cyanide antidote, 2- may present a higher intracellular diffusibility than MB, 3- is already present in commercially available solutions of MB, and 4- appears very quickly in the blood after MB administration. AzB could therefore be a member of the phenothiazium chromophore family of interest to treat cyanide intoxication. We found, in spontaneously breathing urethane sedated rats, that AzB mimicked the effects of MB by increasing metabolism, ventilation and cardiac contractility up to 30−40 mg/kg. AzB had a lethal toxicity when the dose of 60 mg/kg was reached. Doses of AzB were therefore chosen in keeping with these data and the doses of MB previously used against cyanide intoxication (4–20 mg/kg) in the rat – doses corresponding to those used in humans to treat methemoglobinemia. KCN, infused at the rate of 0.375 mg/kg/min iv for 13 min, was fatal within 15 min in 100 % of our un-anesthetized rats. AzB at the dose of 4 mg/kg (n = 5) or 10 mg/kg (n = 5) administered 3 min into cyanide infusion allowed 100 % of the animals to survive with no clinical sequelae. The onset of coma was also significantly delayed and no apnea or gasping occurred. At the dose of 20 mg/kg, AzB was much less effective.At 4 mg/kg, the antidotal effects of AzB were significantly better than those produced by MB at the same dose and were not different from the effects produced by 20 mg/kg MB. We conclude that AzB is a potent cyanide antidote at relatively low doses.

Activated Complex Approach to Describe Bovine Serum Albumin-Azure A and Bovine Serum Albumin-Azure B Intermolecular Interactions

Azure A (AZA) and azure B (AZB) phenothiazine dyes are used for clinical and medical purposes, and their functions can be altered via interactions with proteins. However, no kinetics information on the interactions between phenothiazine dyes and bovine serum albumin (BSA) is available. Surface plasmon resonance was used to determine the energetic and dynamic of the BSA-AZA and BSA-AZB complexes formation at pH 7.4. At temperature ≤ 16 °C, the formation of activated (DH‡a,12°C,AZA= -310.57 kJ mol-1 and DH‡a,12 °C,AZB= -256.37 kJ mol-1) and thermodynamically stable (DH°12°C,AZA= -314.56 kJ mol-1 and DH°12°C,AZB= -265.73 kJ mol-1) complexes was driven by enthalpy, while at temperature ≥ 20 °C, by entropy, (TDS‡a,28°C,AZA= 207.49 and TDS‡a,28°C,AZB= 190.69; TDS°28°C,AZA= 277.50 and TDS°28°C,AZB= 257.26 kJ mol-1). Hydrophobic interactions were fundamental to the complex stability and the increase in number of -CH3 groups in the dyes do not affect kinetic and thermodynamic parameters. Our results could help optimize the medical and pharmaceutical applications of phenothiazine dyes.

Photodynamic antimicrobial chemotherapy action of phenothiazinium dyes in planktonic Candida albicans is increased in sodium dodecyl sulfate.

Photodynamic antimicrobial chemotherapy (PACT) is an important therapeutic platform for antimicrobial activity, especially due to the resistant strains, however, the physical-chemical properties of the photosensitizers may affect the final outcome. Recently, this research group showed that the control of aggregation potentiates the PACT action of Methylene Blue. In this study, the researchers investigated the PACT action of other phenothiazinium dyes (PDs), such as Azure A, Azure B (AB), and 1,9-dimethyl methylene blue (DMMB), and the effects of different mediums which modulate PD aggregation were studied. The C. albicans planktonic culture was treated with PDs at different concentrations (0-100.00 mg/L), both in the dark (5 min) and irradiated (640 ± 12 nm LED during 30 min, 2.60 mW/cm2). After the treatments, the diluted samples were grown on Sabouraud Dextrose Agar and maintained at 37 °C for 24 h. Later, one single concentration was defined and the inoculum was treated with the compounds in different media (water, phosphate buffer saline - PBS, physiological solution - 0.90 % NaCl, urea 1.00 mol/L, and sodium dodecyl sulfate 0.25 % - SDS), at 20.00 mg/L for AA and AB, and at 0.50 mg/L for DMMB. The cell uptake and the dimer to the monomer ratios were determined by spectrophotometry. PACT with the PDs showed a reduction in the CFU/mL, with DMMB being the most effective due to the higher cell uptake within the series. When PACT was applied in the different mediums, the inactivation response was influenced by the medium. In water, the physiological solution, PBS, and urea showed no significant differences in relation to the control group. On the other hand, SDS potentiated the PACT action, and the inactivation of the microorganism was achieved with AB and DMMB. In water, DMMB presented the highest PACT action within the PDs being studied, reaching a microorganism inactivation with a 1.00 mg/L solution, mainly due to its high cell uptake. SDS 0.25 % increased the PACT action of the PDs studied, mainly with DMMB and AB, and this may be used in formulations to develop antimicrobial treatments to be used in clinics.

Halogenated phenotiazine as photoantimicrobial agent against Staphylococcus aureus. Evaluation of the vehiculization in polymeric nanoparticles

A thiazine derivative of AzB, the monoiodinated Azure B (AzBI), was designed, characterized, chemical and photochemically evaluated, and screened for antibacterial activity.The monoiodinated derivative showed better chemical and photochemical properties compared to the leading compound Azure B (AzB). Also, AzBI exhibited good antibacterial activity against methicillin-sensitive Staphylococcus aureus (MSSA) ATCC 29213 and methicillin-resistant S. aureus (MRSA) ATCC 43300. The assayed compound represents a promising structure for the development of a new synthetic photosensitizer with improved properties and biological activity.Based on the results obtained for AzBI, this compound was loaded in the polymeric nanoparticles synthesized by our working group in order to improve some of its physicochemical properties. In this way, it was possible to successfully load the monoiodinated derivative and yield a promising drug transport system. The latter presented better characteristics and antimicrobial activity than AzBI against the different strains tested. All these results make AzBI an excellent candidate for application in photodynamic therapy.