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A voltammetric DNA sensor is developed for the determination of doxorubicin, the signal of which is the change in the current of the redox mediator Methylene green, recorded by cyclic voltammetry on a glassy carbon electrode modified by electrochemically reduced graphene oxide, electropolymerized Azure A, and DNA saturated with Methylene green. The influence of the nature of the polymer layer and the redox mediator used on the sensitivity of the determination of doxorubicin is revealed. With an optimal composition of the surface layer, the DNA sensor allows the determination of up to 0.01 pM of doxorubicin. The sensor was tested on a number of model (artificial urine, Ringer−Locke solution, bovine serum albumin solution) and biological samples (saliva, urine) containing doxorubicin. [ABSTRACT FROM AUTHOR]

A novel non-enzymatic electrochemical sensor was developed with high selectivity and sensitivity for detecting biologically significant hydrogen peroxide (H2O2). The sensor utilized an electrode modified with graphite oxide/Nafion/Azure A (GO/Nf/AzA) fabricated by simple chemical adsorption method. The incorporation of AzA into the GO/Nf matrix was verified through UV–Vis and FTIR spectroscopy. Electrochemical investigations via cyclic voltammetry and differential pulse voltammetry elucidated the modified electrode's properties. Optimization of experimental parameters, including pH and scan rates, enhanced its electrochemical behavior. Cyclic voltammetry analysis revealed an apparent electron transfer rate constant (Ks) of 1.14 cm/s and a charge transfer coefficient (α) of 0.74. Compared to the bare graphite electrode, the modified electrode exhibited significantly higher current densities in response to H2O2 with reduced overvoltage. The reduction peak currents for H2O2 demonstrated a linear correlation with concentrations ranging from 1.3 × 10−6 M to 3.6 × 10−3 M, with a detection limit of 4.3 × 10−7 M (S/N = 3). Notably, the proposed modified electrode displayed excellent sensitivity and selectivity, presenting a promising avenue for H2O2 determination. In amperometric methods, it showcased stable and rapid responses, indicating potential for application in flow system analysis. Real sample analysis involving two distinct milk samples validated the electrodes' good recovery capabilities. [ABSTRACT FROM AUTHOR]

Abstract A novel electrochemical sensor was developed for the detection of Epinephrine (EP) utilizing Azure A (AzA), a phenothiazine dye, and citrate-capped silver nanoparticles. The interaction between Azure A and silver nanoparticles facilitated the formation of AzA/silver nanoclusters through a self-assembled approach. The morphological analysis of AzA/silver nanoclusters was conducted using field-emission scanning electron microscopy (FESEM). The nanoclusters were then immobilized on a graphite electrode via a simple drop-casting method, resulting in a modified electrode. The electrochemical properties of the modified electrode were investigated using cyclic voltammetry and linear sweep voltammetry techniques. The modified electrode exhibited enhanced electrocatalytic oxidation of EP at a lower oxidation potential of 0.27 V. The electrochemical analysis demonstrated that the modified electrode functioned as an amperometric sensor, enabling the detection of EP within a concentration range of 4.6 × 10–7 to 3.6 × 10–3 M, with a correlation coefficient of 0.9950 and a detection limit of 2.2 × 10–7 M (S/N = 3). The modified electrode exhibited excellent selectivity, sensitivity, and a remarkably low detection limit, making it highly suitable for EP determination. Its ease of preparation further adds to the practicality and potential applications of this electrode.

Azure A, a phenothiazine dye was functionalized at graphite oxide through EDC/NHS coupling chemistry. The Azure A–functionalized graphite oxide (AzA-GO) was modified at paraffin impregnated graphite electrode (PIGE) and was used in the precise electrochemical determination of dopamine (DA) in the presence of ascorbic acid (AA). The functionalized AzA-GO was characterized using FTIR, UV–visible spectroscopy, and scanning electron microscopy (SEM). The AzA-GO–modified electrode was characterized by cyclic voltammetry (CV). The electrocatalytic oxidation of DA was found to happen at a low oxidation potential of 0.14 V by the modified electrode. The determination of DA was linear in the concentration range of 8.6 × 10−6 to 9.09 × 10−3 M with the detection limit of 7.2 × 10−7 M. The selective determination of DA in the presence of 100 times higher concentration of AA was achieved by differential pulse voltammetry (DPV). The modified electrode offered a simple, sensitive, and selective determination of low levels of DA at the lower oxidation potential. The proposed sensor has the advantage of easy fabrication, low cost, good sensitivity, selectivity, reproducibility, and stability. [ABSTRACT FROM AUTHOR]

A novel electrochemical sensor was developed for the detection of Epinephrine (EP) utilizing Azure A (AzA), a phenothiazine dye, and citrate-capped silver nanoparticles. The interaction between Azure A and silver nanoparticles facilitated the formation of AzA/silver nanoclusters through a self-assembled approach. The morphological analysis of AzA/silver nanoclusters was conducted using field-emission scanning electron microscopy (FESEM). The nanoclusters were then immobilized on a graphite electrode via a simple drop-casting method, resulting in a modified electrode. The electrochemical properties of the modified electrode were investigated using cyclic voltammetry and linear sweep voltammetry techniques. The modified electrode exhibited enhanced electrocatalytic oxidation of EP at a lower oxidation potential of 0.27 V. The electrochemical analysis demonstrated that the modified electrode functioned as an amperometric sensor, enabling the detection of EP within a concentration range of 4.6 × 10–7 to 3.6 × 10–3 M, with a correlation coefficient of 0.9950 and a detection limit of 2.2 × 10–7 M (S/N = 3). The modified electrode exhibited excellent selectivity, sensitivity, and a remarkably low detection limit, making it highly suitable for EP determination. Its ease of preparation further adds to the practicality and potential applications of this electrode. [ABSTRACT FROM AUTHOR]

The insertion of various nanomaterials and technologies in the search for antimicrobial textiles has grown in recent years, especially after the SARS-CoV-2 pandemic. Despite the efficiency, the design of a safe, scalable, low-cost, and robust antimicrobial textiles that cover all the spectra of microorganisms continues to be challenging. This gap can be filled using antimicrobial Photodynamic Therapy, a new promising approach that inactivates microorganisms in a very efficient way. In this contribution, we develop antibacterial textiles using photodynamic inactivation. To achieve that, we firstly synthesized amino functionalized mesoporous silica nanoparticles that were loaded with either Azure A or Rose Bengal. First the nanoparticles were characterized by X-ray Diffractometry, Transmission Electronic Microscopy, Thermogravimetric Analysis, N 2 adsorption/desorption and dye loading. Further the nanoparticles (0.2 % w/w) were incorporated into cotton fabrics by exhaustion methodology. The antibacterial textiles were characterized by ATR-FTIR, Diffuse Reflectance, Fluorescence Microscopy, Scanning Electronic Microscopy, Fluorescence Lifetime, and singlet oxygen generation. The results showed that silica nanoparticles prevent the premature leakage of dyes from the fibers and retaining their photophysical properties, specifically their singlet oxygen production. The efficiency of antibacterial textiles was proven by the inactivation of Staphylococcus aureus and Escherichia coli. The developed materials showed antibacterial activity even in the dark, but enhanced in the light in some cases. Therefore, both systems have great potential as smart textiles for use in hospital clothing or wound dressings. [Display omitted] • New approach to antimicrobial textile finishes: marriage between silica nanoparticles and photosensitizers dyes. • Fabrics containing Rose Bengal and Azure A incorporated into MSN are efficient in inactivating S. aureus and E. coli. • Incorporation into MSN preserves the photodynamic potential of the dyes and prevents premature release. [ABSTRACT FROM AUTHOR]

The vibronic absorption spectrum of Azure A cation (AA+) in an aqueous solution was calculated using the time‐dependent density functional theory (TD‐DFT). The calculations were performed using all hybrid functionals supported by Gaussian16 software, 6‐31++G(d,p) basis set and polarizable continuum model with external integration formalism (IEFPCM) and solvation model based on solute electron density (SMD) solvent models. The IEFPCM gave significantly underestimated values of λmax in comparison with the experiment, what is a manifestation of the well‐known TD‐DFT "cyanine failure." However, the SMD made it possible to obtain good agreement between the calculation results and experimental data. The best fit was achieved using the X3LYP functional. The dipole moments and atomic charges of the ground and excited states of the AA+ molecule were calculated. 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. [ABSTRACT FROM AUTHOR]

Background: Oral lichen planus (OLP) is characterized histologically by epithelial basal cell destruction and a dense subepithelial lymphocytic infiltrate. Mast cells (MCs) play a role in the pathogenesis and progression of the disease causing changes in the basement membrane (BM). BM is seen as continuous or fragmented, distinct or indistinct, and afibrillar or fibrillar extensions. Aims and Objectives: This study was done to demonstrate the BM using acriflavine stain in addition to hematoxylin and eosin (H-E) stain. An attempt was also made to study MC using Azure A stain and assess the degree of changes in the thickness of BM associated with degranulated MC in patients with OLP. Materials and Methods: A total of 66 paraffin-embedded tissue sections which included 30 inflamed gingival mucosa (IGM) and 36 OLP were stained with H-E stain, Azure A, and fluorescent periodic acid–acriflavine stain. Results: MC density was higher in OLP when compared with MC in IGM. Degranulated MCs were found in abundance in OLP. Thickness of BM was significantly less in OLP when compared with IGM. Significant fragmentation was seen in OLP when compared with BM of IGM. Conclusion: Degranulated MC in OLP may or may not alter the quality of BM but definitely seems to influence the thickness of the BM both directly and indirectly.

Azure‐A is one of the phenothiazines (PTZs) derivatives which for decades have been used as antipsychotic drugs due to good lipophilic characteristics which enable them to pass through the blood brain barrier (BBB), besides the important property of enabeling investigation of the pathological forms of aggregated tau protein found in the neurons of the central nervous system. Radioiodination of Azure‐A was carried out via an electrophilic substitution reaction using chloramine‐T as oxidizing agent. The influence of various reaction parameters and conditions on radioiodination efficiency was investigated, and a high radiochemical yield of 92.07 ± 0.9 % was obtained. An in vitro cytotoxicity study of iodinated Azure‐A on three cell lines (HCT‐116, human colon carcinoma cell line; Hep‐G2, liver carcinoma cell line and HFB‐4, normal human melanocytes) was carried out, and the data revealed that ioiodinated Azure A has no to very low toxic effect. The in vivo biodistribution study of 131I‐Azure A showed a high brain uptake of 6.15 ± 0.09 % injected dose/g tissue organ at 30 minutes post‐injection, and its retention in brain remained high up to 2 hours, whereas the clearance from the body appeared to proceed via the renal system. The experimental data were confirmed by the molecular docking studies to predict the effect of radioiodination on the binding affinity of the parent molecule (Azure A) to tau paired helical filaments (PHFs). Both ligands showed better binding to S2 and S3 pockets of (PHFs). Consequently, radioiodinated Azure A seems to be a good candidate as an imaging agent for taupathies such as Alzheimer's disease, chronic traumatic encephalopathy, and corticobasal degeneration. Furthermore, it could be a very potent theranostics agent for brain tumors. [ABSTRACT FROM AUTHOR]

Electropolymerized redox polymers offer broad opportunities in detection of biospecific interactions of DNA. In this work, Azure A was electrochemically polymerized by multiple cycling of the potential in phosphate buffer saturated with chloroform and applied for discrimination of the DNA damage. The influence of organic solvent on electrochemical properties of the coating was quantified and conditions for implementation of DNA in the growing polymer film were assessed using cyclic voltammetry, quartz crystal microbalance, and electrochemical impedance spectroscopy. As shown, both chloroform and DNA affected the morphology of the polymer surface and electropolymerization efficiency. The electrochemical DNA sensor developed made it possible to distinguish native and thermally and chemically damaged DNA by changes in the charge transfer resistance and capacitance.

Background: Oral lichen planus (OLP) is characterized histologically by epithelial basal cell destruction and a dense subepithelial lymphocytic infiltrate. Mast cells (MCs) play a role in the pathogenesis and progression of the disease causing changes in the basement membrane (BM). BM is seen as continuous or fragmented, distinct or indistinct, and afibrillar or fibrillar extensions. Aims and Objectives: This study was done to demonstrate the BM using acriflavine stain in addition to hematoxylin and eosin (H-E) stain. An attempt was also made to study MC using Azure A stain and assess the degree of changes in the thickness of BM associated with degranulated MC in patients with OLP. Materials and Methods: A total of 66 paraffin-embedded tissue sections which included 30 inflamed gingival mucosa (IGM) and 36 OLP were stained with H-E stain, Azure A, and fluorescent periodic acid–acriflavine stain. Results: MC density was higher in OLP when compared with MC in IGM. Degranulated MCs were found in abundance in OLP. Thickness of BM was significantly less in OLP when compared with IGM. Significant fragmentation was seen in OLP when compared with BM of IGM. Conclusion: Degranulated MC in OLP may or may not alter the quality of BM but definitely seems to influence the thickness of the BM both directly and indirectly. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the interaction of phenothiazine (PHZ) dyes (Azure A (AZA) and thionine (TH)) with gold nanostars (Au NSs) were studied using absorption spectroscopy, steady state emission spectroscopy, high resolution transmission electron microscopy (HR-TEM), dynamic light scattering (DLS), Zetapotential measurements and Fourier transform infrared (FT-IR) spectroscopy. Absorption spectral studies of Au NSs in the presence of dyes resulted in a slight red shift on the surface plasmon resonance band (SPR) of Au NSs, suggesting the changes in the Au NSs surface owing to the adsorption of dyes. The phenomena of hypochromism and the appearance of coupled localized surface plasmon resonance (LSPR) bands in the absorption spectral studies of the AZA-Au NSs and TH–Au NSs systems suggested the vital role of electrostatic interactions between PHZ dyes and Au NSs. The formation of the ground state complex between dyes and Au NSs were evident from the outcome of the steady-state emission titration experiments of the dyes-Au NSs system. Further, the cytotoxic activity of AZA, TH, AZA-Au NSs and TH-Au NSs complexes on breast cancer (MCF-7) and A-549 cell lines were also investigated. These studies revealed that AZA-Au NSs, TH-Au NSs complexes s howed the higher level of cytotoxicity than PHZ dyes treated cells. Graphical abstract Image 1 Highlights • Seed less preparation of Au NSs is a simplistic and innovative method of synthesis. • Optical spectral studies support the binding mechanism of PHZ-dyes with Au NSs. • PHZ dyes-Au NSs system as a chemotherapeutic agent for MCF-7 and A-549 cells. [ABSTRACT FROM AUTHOR]

Abstract Phenothiazine derivatives are extensively explored dye molecules, which present interesting electrochemical and optical properties. In recent years, the possibility of transforming some phenothiazines in their aryl diazonium salt derivatives has been proved, what allows them to be electrochemically reduced and electrografted onto conductive surfaces. This is a smart way to modify these surfaces and enable them with specific functionalities. In order to better comprehend the electrografting process and consequently have a higher control of it, in this work we have carried out an exhaustive study by operando UV–Vis spectroelectrochemistry of the electrografting of a phenothiazine aryl diazonium salt onto amide carbon nanodots. As a model of phenothiazine dye we have chosen Azure A. The electrografting onto carbon nanodots has been stablished by comparison with the results obtained on bare gold electrodes in this novel study. The presence of carbon dots improves the reversibility of the electrochemical process as derived from the results obtained by operando UV–Vis spectroelectrochemistry. In addition, to asses that the electrochemical process studied corresponds to the electrografting, the results have been compared to those obtained for the simple Azure A adsorption. This study shows the advantages of obtaining simultaneously the electrochemical and the spectroscopic evolution of an electron-transfer process in a single experiment, in a particular electrochemical reaction. This work could be the starting point for the study of the electrografting on other nanomaterials. Graphical abstract Image 1 Highlights • Electrografting of Azure A diazonium salt on amide C-nanodots/gold electrodes. • Operando Spectroelectrochemistry study of the electrografting process. • EQCM and XPS characterization of electrografted Azure A/amide C-nanodots surfaces. [ABSTRACT FROM AUTHOR]

Carbon nanodots (CNDs) with enriched periphery carboxylic groups were synthesized using the low-cost starting material glucose. The obtained CNDs were assembled onto Au electrodes following one of two strategies: covalent bonding, using cystamine as a cross-linker, or by drop-casting. The immobilized CNDs were covalently modified with the phenothiazine Azure A via electron transfer chemistry; in particular via reactions with aryl diazonium salts. The reaction mechanism for the diazonium functionalization of CNDs was investigated. Spectroelectrochemistry experiments confirmed that electrografting, rather than adsorption, governs the functionalization of CNDs with Azure A. Finally, the application of these CNDs as electrocatalysts for the oxidation of hydrazine was demonstrated. [ABSTRACT FROM AUTHOR]

In this paper, multi-walled carbon nanotube/Azure A/gold nanoparticle composites (Nafion/AuNPs/AzA/MWCNTs) were prepared by binding gold nanoparticles to the surfaces of Azure A-coated carbon nanotubes. Nafion/AuNPs/AzA/MWCNTs based electrochemical sensor was fabricated for the simultaneous determination of ascorbic acid, dopamine, uric acid, and tryptophan. Cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the electrochemical properties of the modified electrodes. The modified electrode showed excellent electrocatalytic activity toward ascorbic acid, dopamine, uric acid, and tryptophan (pH 7.0). The experiment results showed that the linear response range for simultaneous detection of AA, DA, UA and Trp were 300–10,000 μM, 0.5–50 μM, 0.5–50 μM and 1.0–100 μM, respectively, and the detection limits were 16 μM, 0.014 μM, 0.028 μM and 0.56 μM (S/N = 3). The proposed method offers promise for simple, rapid, selective and cost-effective analysis of small biomolecules. The procedure was also applied to the determination of tryptophan in spiked milk samples.

pH is one of the most important properties associated with an aqueous solution and various pH measurement techniques are available. In this study, Azure A-modified poly(methacrylic acid) (AA-PMA) was synthesized used to prepare a layer-by-layer deposited film with poly(allylamine hydrochloride) (PAH) on a glassy carbon electrode via electrostatic interactions and the multilayer film-immobilized electrode was used to measure pH. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) measurement were performed. Consequently, the oxidation potential of AA on the electrode changed with pH. As per Nernst’s equation, because H+ ions are involved in the redox reaction, the peak potential shifted depending on the pH of the solution. The peak potential shifts are easier to detect by DPV than CV measurement. Accordingly, using electrochemical responses, the pH was successfully measured in the pH range of 3 to 9, and the electrodes were usable for 50 repeated measurements. Moreover, these electrochemical responses were not affected by interfering substances.

In the present study, in depth characterization of binding aspects of Azure A (AZA) and Azure B (AZB) with transfer Ribonucleic acid (t-RNA) from Escherichia coli (E.coli) is investigated using spectroscopic techniques. The absorbance and fluorescence properties of these dyes have been remarkably changed upon binding with t-RNA. Significant changes in the absorption maxima of the dyes evidence the t-RNA induced metachromasy and the binding clearly revealed the high affinity of AZA and AZB to t-RNA. Strong emission polarization of the bound dyes and strong energy transfer from the guanine base pairs of t-RNA suggested intercalative binding interaction. The stoichiometry of AZA and AZB with t-RNA complexes are determined by the Benesi-Hildebrand plot from emission data. The negative values of free energy change indicated the involvement of hydrophobic forces and noncovalent interactions in the complexation of both the dyes with t-RNA. The 3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric assay in A-549 human lung cancer cell lines reveals that binding of t-RNA reduces the toxicity of AZA and AZB. The utility of the present work explores the potential binding applicability of these dyes to t-RNA for their development as effective therapeutic agents and its target at molecular level for the treatment of diseases like cancer. [ABSTRACT FROM AUTHOR]

An aldehyde functionalized ionic liquid, (3-(3-formyl-4-hydroxybenzyl)-3-methylimidazolium hexafluorophosphate) (CHO-IL) has been employed herein as a multiple host platform for the covalent immobilization of mediator as well as enzyme. The CHO-IL was immobilized on electrochemically reduced graphene oxide (ERGO) through the π-π stacking of hydroxybenzyl and imidazolium groups with ERGO and subjected to further covalent attachment of Azure A (Azu-A) mediator or glucose oxidase (GOx) enzyme. Electroactive, water soluble organic dye Azu-A was effectively immobilized to the host IL through simple Schiff base reaction. Azu-A was rendered leak-free in the electrode setup and also responded well for the amperometric determination of H 2 O 2 over a linear range of 0.03–1 mM with a detection limit and sensitivity of 11.5 µM and 133.2 µA mM −1 cm −2 , respectively. Further, attempts were made to explore the CHO-IL platform for the covalent immobilization of GOx enzyme which served well in retaining the enzyme nativity, reactivity and stability. Under optimized conditions, mediatorless GOx biosensor developed based on direct electrochemistry has exhibited an impressive analytical signal towards glucose detection in the linear range of 0.05–2.4 mM with a detection limit and sensitivity of 17 µM and 17.7 µA mM −1 cm −2 , respectively. The reliability of the proposed Azu-A based chemical sensor and GOx based biosensor towards the determination of H 2 O 2 and glucose in the real samples have been demonstrated. The remarkable analytical parameters and long term stability of both the sensors could be envisioned as a result of facile immobilization platform and immobilization strategy. [ABSTRACT FROM AUTHOR]

Introduction: Mast Cells (MCs) are bone marrow derived granular cells, distributed throughout the body near blood vessels, nerves and subepithelial areas. MC granules stain by basic dyes but are most readily demonstrated by metachromatic dyes such as toluidine blue and azure A. Aim: This study focuses on evaluating and comparing the count of MCs by identification and staining of these cells by azure A with toluidine blue as a control, in normal oral mucosa and in various other oral pathologies. Materials and Methods: Five cases each of Normal Oral Mucosa (NOM), Inflammatory Fibrous Hyperplasia (IFH), Oral Pyogenic Granuloma (OPG), Oral Lichen Planus (OLP) and Oral Squamous Cell Carcinoma (OSCC) were stained with 1% toluidine blue and azure A. Results: Mean MC count was higher in all four lesions when compared to normal oral mucosa with both stains. OLP exhibited the maximum amount of mean MC count when compared to other pathologies under study. With all four lesions, toluidine blue exhibited higher number of MC density (count/high power field) compared to azure A. Conclusion: Higher count of MCs was noticed in all four lesions indicating a possible role of MCs in their pathogenesis either directly or indirectly. Also, the number of degranulated MCs was more in OLP followed by OSCC, IFH and OPG.

Oxazinium derivatives have recently played an important role in bioanalysis attributing to the distinguished properties, thus a detailed study of the structure-property relationship is especially significant. Herein, pH-sensitive optical properties of Nile Blue ( 1a), N-monoalkyl-Nile Blue ( 1b) and Azure A ( 1c) have been carried out in extreme acid and base conditions. Dyes 1a and 1c showed colorimetric changes by the protonation of nitrogen atom in strong acidic condition (pH < 2.0), and dyes 1a − c exhibited colorimetric changes by equilibrium between amino and imide groups in very strong basic case (pH > 7.6). Besides, their fluorescent properties were closed to ON − OFF and OFF − ON emissions at 640-820 nm under strong acidic and basic conditions. Moreover, the absorption and emission properties were reversible, and there were no remarkable optical intensity changes of dyes 1a − c under subacidic and neutral solutions (pH = 3.0-7.0). The (TD) DFT calculations were used to optimize the most stable structures of their corresponding protonated and deprotonated forms, and their absorption and emission properties were also explained. Their fluorescent properties nearly ON-OFF and OFF − ON in strong acidic and basic conditions at near-infrared region will give the possible application in pH detection for extreme conditions. [ABSTRACT FROM AUTHOR]

Carbon nanodots modified with azure A (AA-CDs) have been synthesized and applied as redox mediator of bioelectrocatalytic reactions. A deep characterization of AA-CDs nanomaterial has been carried out, proving the covalent attachment of azure A molecules into the carbon dots nanostructure. Disposable screen-printed carbon electrodes (SPCE) have been modified with AA-CDs, through the action of chitosan polymer (Chit-AA-CDs/SPCE). The Chit-AA-CDs/SPCE electrocatalytic activity towards the oxidation of NADH has been proved, obtaining excellent results regarding the low oxidation potential achieved (−0.15 V vs. Ag) and low detection and quantification limits (LOD and LOQ) for NADH, 16 and 53 µM, respectively. The developed electrochemical platform has been applied for the construction of a glutamate biosensor by immobilizing L -glutamic dehydrogenase (GLDH/Chit-AA-CDs/SPCE). The morphology of GLDH/Chit-AA-CDs/SPCE platform was analysed by AFM at each different step of the electrode modification process. The resulting biosensing platform is capable of detect NADH enzymatically generated by GLDH in the presence of glutamate and NAD+. Good analytical parameters were obtained for glutamate analysis using GLDH/Chit-AA-CDs/SPCE, as LOD and LOQ of 3.3 and 11 µM, respectively. The biosensor has been successfully applied to the analysis of food and biological samples. • Azure A modified Carbon nanodots (AA-CDs) as electrocatalyst for NADH oxidation. • A disposable enzymatic electrochemical biosensor for glutamate determination. • Phenothiazine covalent insertion in carbon nanodot structure. [ABSTRACT FROM AUTHOR]

In this paper, multi-walled carbon nanotube/Azure A/gold nanoparticle composites (Nafion/AuNPs/AzA/MWCNTs) were prepared by binding gold nanoparticles to the surfaces of Azure A-coated carbon nanotubes. Nafion/AuNPs/AzA/MWCNTs based electrochemical sensor was fabricated for the simultaneous determination of ascorbic acid, dopamine, uric acid, and tryptophan. Cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the electrochemical properties of the modified electrodes. The modified electrode showed excellent electrocatalytic activity toward ascorbic acid, dopamine, uric acid, and tryptophan (pH 7.0). The experiment results showed that the linear response range for simultaneous detection of AA, DA, UA and Trp were 300–10,000 μM, 0.5–50 μM, 0.5–50 μM and 1.0–100 μM, respectively, and the detection limits were 16 μM, 0.014 μM, 0.028 μM and 0.56 μM (S/N = 3). The proposed method offers promise for simple, rapid, selective and cost-effective analysis of small biomolecules. The procedure was also applied to the determination of tryptophan in spiked milk samples. [ABSTRACT FROM AUTHOR]

We describe an electrochemical immunosensor for the simultaneous determination of alpha-fetoprotein (AFP) and prostate specific antigen (PSA) via a modified glassy carbon electrode. Silica nanoparticles (200-300 nm i.d.) with good monodispersity and uniform shape were synthesized, and the following species were then consecutively immobilized on their surface: gold nanoparticles (AuNPs; 5-15 nm i.d.), secondary antibody (Ab) and the redox-probes Azure A or ferrocenecarboxy acid (Fc). In parallel, two types of primary antibodies (Ab) were co-immobilized on the surface of the dissolved reduced graphene oxide sheets (rGO) that were also decorated with AuNPs. In the presence of antigens (AFP or PSA), the Ab/Si@AuNPs carrying Azure A and Fc are attached to the AuNP/rGO conjugate via a sandwich type immunoreaction. Differential pulse voltammetry (DPV) was employed to measure the resulting changes in the signal of Fc or Azure A. Two well-resolved oxidation peaks, one at −0.48 V (corresponding to Azure A) and other at + 0.12 V (corresponding to Fc; both vs. SCE) can be observed in the DPV curves. Under optimal conditions, AFP and PSA can be simultaneously determined in the range from 0.01 to 25 ng mL‾ for AFP, and from 0.012 to 25 ng mL‾ for PSA. The detection limits are 3.3 pg mL‾ for AFP and 4.0 pg mL‾ for PSA (at a signal-to-noise ratio of 3). The method was applied to (spiked) real sample analysis, and the recoveries are within 96.0 and 107.2 % for PSA, and within 100.9 and 105.8 % for AFP, indicating that this dual immunosensor matches the requirements of clinical analysis. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Introduction: Mast Cells (MCs) are bone marrow derived granular cells, distributed throughout the body near blood vessels, nerves and subepithelial areas. MC granules stain by basic dyes but are most readily demonstrated by metachromatic dyes such as toluidine blue and azure A. Aim: This study focuses on evaluating and comparing the count of MCs by identification and staining of these cells by azure A with toluidine blue as a control, in normal oral mucosa and in various other oral pathologies. Materials and Methods: Five cases each of Normal Oral Mucosa (NOM), Inflammatory Fibrous Hyperplasia (IFH), Oral Pyogenic Granuloma (OPG), Oral Lichen Planus (OLP) and Oral Squamous Cell Carcinoma (OSCC) were stained with 1% toluidine blue and azure A. Results: Mean MC count was higher in all four lesions when compared to normal oral mucosa with both stains. OLP exhibited the maximum amount of mean MC count when compared to other pathologies under study. With all four lesions, toluidine blue exhibited higher number of MC density (count/high power field) compared to azure A. Conclusion: Higher count of MCs was noticed in all four lesions indicating a possible role of MCs in their pathogenesis either directly or indirectly. Also, the number of degranulated MCs was more in OLP followed by OSCC, IFH and OPG. [ABSTRACT FROM AUTHOR]

The mechanism of Azure A (AA) biosorption byZea maysbiomass (ZMB) was studied. Surface chemistry and morphology were characterized by potentiometric titration, pH of zero charge, FTIR, and microscope analysis. The equilibrium data was modeled by Langmuir, Freundlich, Redlich-Peterson, Temkin, and multilayer models. AA biosorption was mainly limited by chemisorption, but the role of intraparticle diffusion could not be neglected. The integrative analysis of surface chemistry/biosorption studies showed that chemisorption, ion exchange, complexation, and/or electrostatic attraction were involved during AA biosorption. The maximum biosorption capacity of ZMB (q 5.84 mg/g) was registered at pH 7.6. [ABSTRACT FROM PUBLISHER]