Ratiometric electrochemical immunoassay based on 2D Co/Fe MOF decorated with toluidine blue and Fc-labeled Schiff base for accurate assay of alpha-fetoprotein in clinical serum

The high level of alpha-fetoprotein (AFP) expression is closely related to hepatocellular carcinoma (HCC). Herein, a dual signal ratiometric electrochemical immunosensor based on chitosan-ferrocenecarboxaldehyde-spindle gold (Chit-Fc-SAu) and Co/Fe metal-organic framework-toluidine blue/polydopamine (Co/Fe MOF-TB/PDA) was proposed for quantitative analysis of AFP. Specifically, Chit-Fc-SAu worked as a substrate to trap more primary antibodies (Ab1) generating the first electrochemical signal from Fc. Thanks to the large specific surface area, the synergistic and electronic effects of Co/Fe MOF nanosheets, and the rich functional groups of PDA, Co/Fe MOF-TB/PDA could load more secondary antibodies (Ab2) and signal molecules (TB) providing another amplified electrochemical signal. In the presence of AFP, Ab1-AFP-Ab2 formed a sandwich structure, and as the AFP concentration increased, the peak current ratio of TB to Fc (ITB/IFc) also increased. The dual signal ratiometric strategy can avoid environmental signal interference and achieve signal self-calibration, thereby improving the accuracy and reproducibility of detection. After a series of exploration, this self-calibrated ratiometric immunosensor exhibited a wide linear range (0.001-200 ng mL-1), a low detection limit (0.34 pg mL-1), and good repeatability. When applied to the assay of clinical serum samples, the detection results of ratiometric sensor were consistent with that of commercial electrochemiluminescence (ECL) immunoassay, significantly superior to that of non-ratiometric sensor. The self-calibrated strategy based on ratiometric sensor helps to improve the accuracy of AFP in clinical diagnosis.

Toluidine blue O photosensitizer combined with caffeic acid improves antibacterial performance by increasing the permeability of cell membrane

Photodynamic therapy has always been an antibacterial tool for solving multi-drug resistant bacteria problem, but the side effects and the low efficiency due to the high aggregation and low solubility of photosensitizers limit its application. Due to the anti-inflammatory effect of caffeic acid, two novel photosensitizers (CA-1-TBO, CA-TBO) were synthesized by conjugating caffeic acid with toluidine blue O (TBO). The structures have been characterized by 1HNMR and high-resolution mass spectrometry. The UV-vis absorption, fluorescence spectra and the octanol-water partition coefficient of two photosensitizers were measured to evaluate their photophysical properties and hydrophilic/hydrophobic properties. Compared with parent TBO, the two modified photosensitizers have shown a higher quantum yield and kinetics constants of singlet oxygen, which has been supported by the simulation results of density functional theory. As drug-resistant representatives of gram-positive and gram-negative bacteria, respectively, S. aureus and P. aeruginosa have been used for in vitro antibacterial experiments. The sterilization efficiencies of the two modified photosensitizers far exceed that of parent TBO. The results of the octanol-water partition coefficient and fluorescence quantification showed that modified photosensitizers CA-1-TBO and CA-TBO could be more accumulated than parent TBO. Based on scanning electron microscopy images, protein gel electrophoresis, and the conductivity of the bacterial solution, the possible mechanism of improved antibacterial photodynamic efficiencies could be induced by membrane permeability due to the caffeic acid effect. The findings demonstrate the significant potential of natural phenolic compounds in the development of photosensitizer molecules with characteristics such as more efficient, biocompatible and less side effects.

Performance comparison of photodynamic antimicrobial chemotherapy with visible-light-activated organic dyes: Rose bengal, crystal violet, methylene blue, and toluidine blue O

This study evaluated the photobiocidal performance of four widely distributed visible-light-activated (VLA) dyes against two bacteria (Staphylococcus epidermidis and Escherichia coli) and two bacteriophages (phages MS2 and phi 6): rose bengal (RB), crystal violet, methylene blue, and toluidine blue O (TBO). The photobiocidal performance of each dye depended on the relationship between the type of dye and microorganism. Gram-negative E. coli and the non-enveloped structure of phage MS2 showed more resistance to the photobiocidal reaction than Gram-positive S. epidermidis and the enveloped structure of phage phi 6. RB had the highest potential to yield reactive oxygen species. However, the photobiocidal performance of RB was dependent on the magnitude of the surface charge of the microorganisms; for example, anionic RB induced a negative surface charge and thus electrical repulsion. On the other hand, the photobiocidal performance of TBO was observed to be less affected by the microorganism type. The comparative results presented in our study have significant implications for selecting photodynamic antimicrobial chemotherapy (PACT) dyes suitable for specific situations and purposes. Furthermore, they contribute to the advancement of PACT-related technologies by enhancing their applicability and scalability.

Ratiometric electrochemical sensor for bisphenol A detection using a glassy carbon electrode modified with a poly(toluidine blue)/gold nanoparticle composite

A ratiometric electrochemical sensor for bisphenol A (BPA) detection is developed using a glassy carbon electrode modified with a poly(toluidine blue)/gold nanoparticle composite (PTB/AuNP/GCE). The ratiometric signal, namely, the oxidation peak current ratio of BPA to PTB, increases linearly with BPA concentration in the 0.2-5.0 μM range, with a detection limit of 0.15 μM. The electrochemical mechanism of BPA is studied at the PTB/AuNP/GCE, and the results show that BPA undergoes an electrooxidation process of two electrons and two protons at the PTB/AuNP/GCE. The proposed sensor has high sensitivity, high stability and good selectivity. The application of BPA in water samples is successfully verified using the proposed ratiometric electrochemical sensor.

Target-triggered configuration change of DNA tetrahedron for SERS assay of microRNA 122

A surface-enhanced Raman scattering (SERS) method is proposed for the assay of microRNA 122 based on configuration change of DNA tetrahedron. Firstly, a DNA tetrahedron was self-assembled with one vertex labeled with toluidine blue (TB). Then, it was immobilized on the porous Ni/SiO₂@PEI@Au as a SERS platform, which was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). At this time, the DNA tetrahedron was contracted; so, the TB is close to AuNPs and the Raman signal is high. When target microRNA 122 existed, with the nicking enzyme amplification strategy, a great deal of DNA signal chains (S5) was obtained, which can extend the contracted DNA tetrahedron and change it into a three-dimensional DNA tetrahedron. In this case, the TB was far from AuNPs, resulting in a lower Raman signal. Due to the configuration change of DNA tetrahedron, the Raman signal at 1624 cm^-1 (with the excitation wavelength of 633 nm) has a linear relationship with the logarithm concentration of microRNA 122. This SERS assay has high sensitivity for microRNA 122 with a determination range from 0.01 aM to 10 fM and a detection limit of 0.009 aM. The recoveries from spiked samples were in the range 95 to 109%. This SERS strategy is designed based on the target-triggered configuration change of DNA tetrahedron, which can give new insight for DNA structures in bioanalysis. Graphical abstract A sensitive surface-enhanced Raman scattering (SERS) biosensor was developed to detect microRNA 122 using the configuration change of DNA tetrahedron to indirectly control the position of TB and hot spot.

Utilisation of Toluidine blue O pH 4.0 and histochemical inferences in plant sections obtained by free-hand

For the observation of plant material under a light microscope, free-hand sectioning is usually the fastest and most practical procedure. The staining of the obtained cuts is a crucial step and the action mechanism of the dye is variable. Toluidine blue O is a cationic dye whose metachromatic potential for free-hand sections has long been known. Thus, this work aimed at analysing the performance of Toluidine blue O for this type of sectioning with a systematic and comparative approach. The action of Toluidine blue O pH 4.0 was tested for both fresh and previously clarified free-hand sections from leaves of different species of plant. These sections were compared with sections embedded in glycol-methacrylate resin stained with the same dye or submitted to different histochemical tests. The fresh sections obtained by free-hand and stained with Toluidine blue O permitted the accomplishment of histochemical inferences, with the advantage of maintaining the natural colours from the tissues. The previously clarified sections presented the advantage of having a clearer image, allowing a better cellular delimitation. We concluded that Toluidine blue O is very informative for sections of plant material obtained by free-hand, being, therefore, a procedure that is fast, inexpensive and with excellent results.

Role of Toluidine Blue-O Binding Mechanism for Photooxidation in Bioinspired Bacterial Membranes

The alarming increase in bacterial resistance to antibiotics has demanded new strategies for microbial inactivation, which include photodynamic therapy whose activity relies on the photoreaction damage to the microorganism membrane. Herein, the binding mechanisms of the photosensitizer toluidine blue-O (TBO) on simplified models of bacterial membrane with Langmuir monolayers of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) and 1,2-dioleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DOPG) were correlated to the effects of the photoinduced lipid oxidation. Langmuir monolayers of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) were also used as a reference of mammalian membranes. The surface pressure isotherms combined with polarization-modulated infrared reflection absorption spectroscopy revealed that TBO expands DOPC, DOPE, and DOPG monolayers owing to electrostatic interactions with the negatively charged groups in the phospholipids, with a stronger adsorption on DOPG, which has a net surface charge. Light irradiation made the TBO-containing DOPC and DOPE monolayers less unstable as a result of the singlet oxygen (¹O₂) reaction with the chain unsaturation and hydroperoxide formation. In contrast, the decreased stability of the irradiated TBO-containing DOPG monolayer suggests the cleavage of carbon chains. The anionic nature of DOPG allowed a deeper penetration of TBO into the chain region, favoring contact-dependent reactions between the excited triplet state of TBO and lipid unsaturations or/and hydroperoxide groups, which is the key for the cleavage reactions and further membrane permeabilization.

Interactions between natural organic matter (NOM) and the cationic dye toluidine blue at varying pHs and ionic strengths: Effects of NOM charges and Donnan gel potentials

This study examined effects of charges of molecules of natural organic matter (NOM) on its interactions with organic cations represented by toluidine blue (TB). NOM was exemplified in this study by Suwannee River (SR) and South Platte (SP) NOM. TB/NOM interactions were probed in the range of pH 3 to 11, DOC concentrations 0-10.6 mg L^-1 and ionic strengths 0.001-0.1 mol L^-1. Changes of TB absorbance at indicative wavelengths of 640 and 550 nm located in the characteristic absorbance band of TB and their ratio R_640/550 were used to quantify TB/NOM binding and the formation of TB dimers and possibly higher order aggregates in the Donnan volume of NOM molecules. These effects were interpreted based on the modeling of NOM charges and their Donnan gel potentials (ψ_D). The spectroscopic and modeling data showed that TB/NOM binding can be quantified via a complexation model that reflects the extent of electrostatic attraction between TB cations and anionic NOM molecules. The dependence of the apparent formation constant vs. ionic strength was shown to be qualitatively correlated with the ψ_D potentials of NOM molecules.

Morphological characterization of the adherence and invasion of Streptococcus agalactiae to the intestinal mucosa of tilapia Oreochromis sp.: An in vitro model

Streptococcosis in tilapia Oreochromis sp. is possibly the most important bacterial disease for fish production worldwide. In Colombia, streptococcosis is caused by Streptococcus agalactiae (GBS), but in other countries, Streptococcus iniae is also involved. Prevention of streptococcosis is required and must be addressed for economic, social, international trade and public health reasons. This research used an in vitro culture of tilapia intestine to detail the intestinal mucosal response once the pathogen contacts the epithelium. We show that S. agalactiae sheds off its capsule to adhere to the epithelium. The bacterium adheres as a single individuum, in groups or in chains and is able to divide on the apical border of enterocytes. GBS adheres at and invades exclusively through the apical portion of the intestinal folds, using the transepithelial route. Once within the cytoplasm of enterocytes, the bacteria continue to divide. On the basolateral side of the epithelium, the microorganisms leave the cells to reach the propria and travel through the microcirculation. No evidence of an immuno-inflammatory reaction or goblet cell response in the epithelium or the lamina propria was seen during the process of adherence and invasion of the pathogen.

Decolorization of dyes by a novel sodium azide-resistant spore laccase from a halotolerant bacterium, Bacillus safensis sp. strain S31

The aim of this work was to find a new stable laccase against inhibitors and study the decolorization ability of free and immobilized laccase on different classes of dyes. Spores from a halotolerant bacterium, Bacillus safensis sp. strain S31, isolated from soil samples from a chromite mine in Iran showed laccase activity with maximum activity at 30 °C and pH 5.0 using 2, 2-azino-bis (3-ethylbenzothiazoline-6-sulfonate) (ABTS) as the substrate. The enzyme retained about 60% of its initial activity in the presence of 10% (v v^-1) methanol, ethanol, and acetone. In contrast to many other laccases, NaN₃, at 0.1 and 1 mM concentrations, showed a slight inhibitory effect on the enzyme activity. Also, the spore laccase (8 U l^-1) decolorized malachite green, toluidine blue, and reactive black 5 at acidic pH values; the highest decolorization percent was 75% against reactive black 5. It was observed that addition of ABTS as a redox mediator enhanced the decolorization activity. Furthermore, immobilized spore laccase encased in calcium alginate beads decolorized 95% of reactive black 5 in the absence of mediators. Overall, this isolated spore laccase might be a potent enzyme to decolorize dyes in polluted wastewaters, especially those containing metals, salts, solvents, and sodium azide.

Biofunctionalization of PEDOT films with laminin-derived peptides

Poly(3,4-ethylenedioxythiophenes) (PEDOT) have been extensively explored as materials for biomedical implants such as biosensors, tissue engineering scaffolds and microelectronic devices. Considerable effort has been made to incorporate biologically active molecules into the conducting polymer films in order to improve their long term performance at the soft tissue interface of devices, and the development of functionalized conducting polymers that can be modified with biomolecules would offer important options for device improvement. Here we report surface modification, via straightforward protocols, of carboxylic-acid-functional PEDOT copolymer films with the nonapeptide, CDPGYIGSR, derived from the basement membrane protein laminin. Evaluation of the modified surfaces via XPS and toluidine blue O assay confirmed the presence of the peptide on the surface and electrochemical analysis demonstrated unaltered properties of the peptide-modified films. The efficacy of the peptide, along with the impact of a spacer molecule, for cell adhesion and differentiation was tested in cell culture assays employing the rat pheochromocytoma (PC12) cell line. Peptide-modified films comprising the longest poly(ethylene glycol) (PEG) spacer used in this study, a PEG with ten ethylene glycol repeats, demonstrated the best attachment and neurite outgrowth compared to films with peptides alone or those with a PEG spacer comprising three ethylene glycol units. The films with PEG10-CDPGYISGR covalently modified to the surface demonstrated 11.5% neurite expression with a mean neurite length of 90μm. This peptide immobilization technique provides an effective approach to biofunctionalize conducting polymer films.

STATEMENT OF SIGNIFICANCE

For enhanced diagnosis and treatment, electronic devices that interface with living tissue with minimum shortcomings are critical. Towards these ends, conducting polymers have proven to be excellent materials for electrode-tissue interface for a variety of biomedical devices ranging from deep brain stimulators, cochlear implants, and microfabricated cortical electrodes. To improve the electrode-tissue interface, one strategy utilized by many researchers is incorporating relevant biological molecules within or on the conducting polymer thin films to provide a surface for cell attachment and/or provide biological cues for cell growth. The present study provides a facile means for generating PEDOT films grafted with a laminin peptide with or without a spacer molecule for enhanced cell attachment and neurite extension.

Observation of a Flowing Duct in the Abdominal Wall by Using Nanoparticles

The primo vascular system (PVS) is being established as a circulatory system that corresponds to acupuncture meridians. There have been two critical questions in making the PVS accepted as a novel liquid flowing system. The first one was directly to show the flow of liquid in PVS and the second one was to explain why it was not observed in the conventional histological study of animal tissues. Flow in the PVS in the abdominal cavity was previously verified by injecting Alcian blue into a primo node. However, the tracing of the dye to other subsystems of the PVS has not been done. In the current work we injected fluorescent nanoparticles (FNPs) into a primo node and traced them along a primo vessel which was inside a fat tissue in the abdominal wall. Linea alba is a white middle line in the abdominal skin of a mammal and a band of fat tissue is located in parallel to the linea alba in the parietal side of the abdominal wall of a rat. In this fat band a primo vessel runs parallel to the prominent blood vessels in the fat band and is located just inside the parietal peritoneum. About the second question on the reason why the PVS was not in conventional histological study the current work provided the answer. Histological analysis with hematoxyline and eosine, Masson’s trichrome, and Toluidine blue could not discriminate the primo vessel even when we knew the location of the PVS by the trace of the FNPs. This clearly explains why the PVS is hard to observe in conventional histology: it is not a matter of resolution but the contrast. The PVS has very similar structure to the connective tissues that surround the PVS. In the current work we propose a method to find the PVS: Observation of mast cell distribution with toluidine blue staining and the PN has a high density of mast cells, while the lymph node has low density.

Metal Organic Frameworks Combining CoFe2O4 Magnetic Nanoparticles as Highly Efficient SERS Sensing Platform for Ultrasensitive Detection of N-Terminal Pro-Brain Natriuretic Peptide

N-terminal pro-brain natriuretic peptide (NT-proBNP) has been demonstrated to be a sensitive and specific biomarker for heart failure (HF). Surface-enhanced Raman spectroscopy (SERS) technology can be used to accurately detect NT-proBNP at an early stage for its advantages of high sensitivity, less wastage and time consumption. In this work, we have demonstrated a new SERS-based immunosensor for ultrasensitive analysis of NT-proBNP by using metal-organic frameworks (MOFs)@Au tetrapods (AuTPs) immobilized toluidine blue as SERS tag. Here, MOFs@AuTPs complexes were utilized to immobilize antibody and Raman probe for their excellent characteristics of high porosity, large surface area, and good biocompatibility which can obviously enhance the fixing amount of biomolecule. To simplify the experimental operation and improve the uniformity of the substrate, Au nanoparticles functionalized CoFe2O4 magnetic nanospheres (CoFe2O4@AuNPs) were further prepared to assemble primary antibody. Through sandwiched antibody-antigen interactions, the immunosensor can produce a strong SERS signal to detect NT-proBNP fast and effectively. With such design, the proposed immunosensor can achieve a large dynamic range of 6 orders of magnitude from 1 fg mL(-1) to 1 ng mL(-1) with a detection limit of 0.75 fg mL(-1). And this newly designed amplification strategy holds high probability for ultrasensitive immunoassay of NT-proBNP.

Effects of cigarette smoke extract on human airway smooth muscle cells in COPD

We hypothesised that the response to cigarette smoke in airway smooth muscle (ASM) cells from smokers with chronic obstructive pulmonary disease (COPD) would be intrinsically different from smokers without COPD, producing greater pro-inflammatory mediators and factors relating to airway remodelling. ASM cells were obtained from smokers with or without COPD, and then stimulated with cigarette smoke extract (CSE) or transforming growth factor-β1. The production of chemokines and matrix metalloproteinases (MMPs) were measured by ELISA, and the deposition of collagens by extracellular matrix ELISA. The effects of CSE on cell attachment and wound healing were measured by toluidine blue attachment and cell tracker green wound healing assays. CSE increased the release of CXCL8 and CXCL1 from human ASM cells, and cells from smokers with COPD produced more CSE-induced CXCL1. The production of MMP-1, -3 and -10, and the deposition of collagen VIII alpha 1 (COL8A1) were increased by CSE, especially in the COPD group which had higher production of MMP-1 and deposition of COL8A1. CSE decreased ASM cell attachment and wound healing in the COPD group only. ASM cells from smokers with COPD were more sensitive to CSE stimulation, which may explain, in part, why some smokers develop COPD.

[A comparison of methods for identifying mast cells of Cyprinus carpio]

OBJECTIVE

To compare different identifying methods of the mast cells of red crucian carp (Cyprinus carpio).

METHODS

The gill filaments were taken from Cyprinus carpio infected with Edwardsiella tarda and fixed in Bouin's solution. The hematoxylin-eosin (HE), toluidine blue (TB), Alcian blue (AB), neutral red, Masson trichrome, May-Grunwald Giemsa (MGG) stainings and streptavidin-biotin complex (SABC) immunohistochemical method were used to observe the mast cells. The smears of head kidney stained by Wright-Giemsa were used as a supplementary method.

RESULTS

AB and TB were desirable staining solutions for clearly displaying mast cells, and MGG staining came second. Immunohistochemical method showed the small number of tryptase-positive mast cells and a weak positive reaction. The cells in smears were dispersed and showed different developmental stages.

CONCLUSION

The immunohistochemistry and the histochemical staining combined with Wright-Giemsa-stained smears are two good ways to identify the mast cells of fish.

Enhanced repair of a critical-sized segmental bone defect in rabbit femur by surface microstructured porous titanium

Repair of load-bearing bone defects remains a challenge in the field of orthopaedic surgery. In the current study, a surface microstructured porous titanium (STPT) successively treated with H2O2/TaCl5 solution and simulated body fluid was used to repair the critical-sized segmental bone defects in rabbit femur, and non-treated porous titanium (NTPT) and porous biphasic calcium phosphate ceramics (PBCP) were used as control, respectively. A 15 mm long implant was positioned in the femoral defect and stabilized by a plate and screws fixation. After implantation into the body for 1, 3 and 6 months, X-ray observation confirmed that porous titanium groups (NTPT and STPT) provided better mechanical support than PBCP group at the early stage. However, there was no obvious difference in the formed bony callus between PBCP and STPT groups in the later stage, and they both showed better shape of bony callus than NTPT group. Micro-CT and histomorphometric analysis for the samples of 6-month implantation demonstrated that more new bone formed in the inner pores of PBCP and STPT groups than that in NTPT group. Moreover, the biomechanical tests revealed that STPT group could bear larger compressive load than NTPT and PBCP groups, almost reaching the level of the normal rabbit femur. STPT exhibited the enhanced repairing effect on the critical-sized segmental bone defect in rabbit femur, meaning that it could be an ideal material for the repair of large bone defect in load-bearing site.

Phenothiazine-modified electrodes: a useful platform for protein adsorption study

Using glucose oxidase (GOx) as a target protein, we studied the adsorption of protein on the phenothiazine-modified electrodes and assessed the potential of using the electrodes in biochemical applications. Experiment results showed that thionine chloride (TC) and its structural analogues, such as toluidine blue and methylene blue, fluoresced under photochemical excitation after being immobilized on indium-doped tin oxide (ITO) electrodes fabricated using either diazotization-reduction or oxidative polymerization. The surface-bound phenothiazines exhibited substantial binding affinities to the protein. At a pH > 5, the adsorbate showed no sign of desorption even the electrodes were electrically biased with voltages between ±0.3 V vs SCE. Thus, emission decay occurred while GOx was injected over the electrodes, which was consistent with the observations made using conductive-mode atomic force microscopy (CM-AFM). Under a quiescent condition, the protein interacted with the immobilized TC via a pseudo-first-order kinetic mechanism. The reaction reached a maximum rate at a pH > 5, at which the rate constant was approximately 7 × 10(-8) L/(U s). Under this condition, the adsorption rate increased as the level of the protein increased, regardless of pH, revealing application potential for GOx quantitation. The adsorption rate, however, decreased with a decrease in pH if the pH < 5. We concluded that static interactions played a crucial role. By monitoring Fe(CN)6(3-/4-) taking place at the TC-modified electrodes in pH 7 solutions, we observed that the adsorption of GOx imposed impedance on Fe(CN)6(3-/4-). The resulting charge-transfer resistance (RCT) increased as the amount of the protein increased, leading to a conclusion that the protein could reach the maximum surface coverage when its concentrations were greater than 100 U/mL. The protein molecules were likely repel each other as approaching the TC sites. Despite this, they maintained the native bioactivity after being adsorbed, enabling the TC-modified electrodes to function as glucose sensors. Glucose concentrations between 1 and 60 mM could be detected. Long-term analysis, in addition, showed that the electrode responses to the analyte were consistent and reproducible. Phenothiazine-modified electrodes are evident as a useful tool for understanding the adsorption of protein on solid surfaces and quantifying proteins.

Targeting ribonucleic acids by toxic small molecules: structural perturbation and energetics of interaction of phenothiazinium dyes thionine and toluidine blue O to tRNA phe

This study was designed to examine the toxic interaction of two phenothiazinium dyes thionine (TO) and toluidine blue O (TBO) with tRNA(phe) by spectroscopic and calorimetric techniques. While phenothiazinium dye complexation with DNA is known, their bindings to RNA are not fully investigated. The non cooperative binding of both the dyes to tRNA was revealed from absorbance and fluorescence studies. From absorption, steady-state emission, the effect of ferrocyanide ion-induced steady-state fluorescence quenching, circular dichroism, the mode of binding of these dyes into the tRNA helix has been substantiated to be principally by intercalative in nature. Both dyes enhanced the thermal stability of tRNA. Circular dichroism studies provided evidence for the structural perturbations associated with the tRNA structure with induction of optical activity in the CD inactive dye molecules. Results from isothermal titration calorimetry experiments suggested that the binding of both dyes was predominantly entropy driven with a smaller but favorable enthalpy term that increased with temperature. The binding was dependent on the Na(+) concentration, but had a larger non-electrostatic contribution to the Gibbs energy. A small heat capacity value and the enthalpy-entropy compensation in the energetics of the interaction characterized the binding of the dyes to tRNA. This study confirms that the tRNA(phe) binding affinity is greater for TO compared to TBO. The utility of the present work lies in understanding the potential binding and consequent damage to tRNA by these toxic dyes in their development as therapeutic agents.

Comparative antifungal efficacy of light-activated disinfection and octenidine hydrochloride with contemporary endodontic irrigants

The aim of this study was to evaluate the antifungal effects of light-activated disinfection (LAD) in comparison with contemporary root canal irrigation solutions: sodium hypochlorite and 2% chlorhexidine gluconate and a new wound antiseptic, octenidine hydrochloride. Seventy extracted teeth having single root canals were contaminated with Candida albicans for 14 days. The samples were divided into five experimental (n = 10) and two control (positive and negative) groups (n = 10): (1) LAD with toluidine blue O, (2) octenidine hydrochloride (OCT), (3) 2.5% sodium hypochlorite (2.5% NaOCl), (4) 5.25% sodium hypochlorite (5.25% NaOCl) and (5) 2% chlorhexidine. Five millilitres of each test solution was applied for 3 min, and irradiation time used for LAD was 30 s. After treatment, the dentin chips were collected from inner canal walls into vials containing phosphate buffered saline, vortexed, serially diluted, seeded on Tryptic Soy Agar plates and incubated (37 °C, 48 h). The number of colony-forming units was then counted. Differences between LAD group and positive control group were statistically significant (P < 0.05). All Candida cells were totally eliminated in root canals irrigated with OCT, 2.5% NaOCl, 5.25% NaOCl and 2% chlorhexidine groups (CFU = 0). Within the limitations of this ex vivo study, LAD had minimal antimicrobial effect on C. albicans when used 30 s, and further modifications in LAD protocol are required to improve its antifungal capability. A new wound antiseptic, octenidine hydrochloride, demonstrated better potential than LAD in elimination of Candida albicans cells and may be a promising alternative to NaOCl and chlorhexidine solutions in future.

Photosensitizer and light diffusion through dentin in photodynamic therapy

Photodynamic therapy has been considered a potential antimicrobial modality against oral infections, including dental caries. A model to estimate the penetration of both photosensitizers and light through human dentin, a factor of interest in photodynamic therapy, is proposed. The photoacoustic spectroscopy technique was used to evaluate in vitro dentin permeability of three different photosensitizers. Using the dentin optical absorption and scattering coefficients, it was possible to propose a semi-quantitative model predicting both photosensitizer and light doses within dentin. The graphic illustrations obtained provided guidelines that may be useful in photodynamic therapy protocols used as antimicrobial tools in caries lesions.

Spectroscopic investigations on the photodegradation of toluidine blue dye using cadmium sulphide nanoparticles prepared by a novel method

A novel method to prepare cadmium sulphide nanoparticles (CdS NPs) possessing nearly uniform size was adopted using eggshell membrane (ESM), under different pH conditions. Significant yield of CdS NPs with smallest possible size was obtained by increasing the pH of the reaction medium from acidic to alkaline. The above prepared CdS NPs have been characterized by UV-vis absorption as well as emission spectra, powder X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The efficiency of the above prepared CdS NPs as a catalyst for the photodegradation of toluidine blue (TB) dye, as a function of pH as well as the ratio between the catalyst and the substrate was studied after irradiation with UV light. The results showed that an efficient interaction took place between the catalyst and the substrate to cause degradation of the selected dye. A maximum degradation of toluidine blue dye (90%) was observed at pH 8 which is higher than that of the efficiencies at pH 4 and pH 6.

Electropolymerized poly(Toluidine blue)-modified carbon felt for highly sensitive amperometric determination of NADH in flow injection analysis

Poly(pheniothiazine) films were prepared on a porous carbon felt (CF) electrode surface by an electrooxidative polymerization of three phenothiazine derivatives (i.e.,Tthionine (TN), Toluidine Blue (TB) and Methylene Blue (MB)) from 0.1 mol/L phosphate buffer solution (pH 7.0). Among the three phenothiazies, the poly(TB) film-modified CF exhibited an excellent electrocatalytic activity for the oxidation of nicotinamide adenine dinucleotide reduced form (NADH) at +0.2 V vs. Ag/AgCl. The poly(TB) film-modified CF was successfully used as working electrode unit of highly sensitive amperometric flow-through detector for NADH. The peak currents (peak heights) were almost unchanged, irrespective of a carrier flow rate ranging from 2.0 to 4.1 mL/min, resulting in the measurement of NADH (ca. 30 samples/hr) at 4.1 mL/min. The peak current responses of NADH showed linear relationship over the concentration range from 1 to 30 micromol/L (sensitivity: 0.318 microA/(micromol/L); correlation coefficient: 0.997). The lower detection limit was found to be 0.3 micromol/L (S/N = 3).

Investigation on the toxic interaction of toluidine blue with calf thymus DNA

The gene toxic interactions of toluidine blue (TB) with calf thymus DNA (ct-DNA) were examined in vitro with UV-visible absorption spectroscopy, fluorescence spectroscopy, fluorescence polarization and circular dichroism techniques. The experimental results showed that TB interacted with ct-DNA by two binding modes. At low TB concentrations, TB intercalated into the DNA base pairs. At higher TB concentrations, TB was attached to the negatively charged phosphate groups. For the intercalation binding mode and electrostatic binding mode, the binding constants were 1.76 x1 0(6)L mol(-1) and 6.18 x 10(5)L mol(-1) and the number of binding sites was 0.48 and 0.79, respectively. Circular dichroism results showed that the two binding modes had different effects on the ct-DNA conformation. At high dye concentrations, Z-form DNA appears, while at low TB concentrations, a B to A form transition is observed.

Frictional properties of light-activated antimicrobial polymers in blood vessels

The adhesion of microbes to catheter surfaces is a serious problem and the resulting infections frequently lead to longer hospitalisation and higher risk for the patient. Several approaches have been developed to produce materials that are less susceptible to microbial colonisation. One such approach is the incorporation of photoactivated compounds, such as Toluidine Blue O (TBO), in the polymeric matrix resulting in 'light-activated antimicrobial materials'. The insertion and removal of catheters can cause tissue damage and patient discomfort through frictional forces; hence the lubricity of a catheter material is also very important. In this work the tribological performance of silicone and polyurethane containing TBO and gold nanoparticles were evaluated using two different surfaces, the inner part of the aorta and the superior vena cava of sheep. Static and kinetic friction coefficients of these materials were measured using a tribometric device developed for in vitro applications using dry materials and those lubricated with blood. It was found that neither the preparation process nor the presence of TBO or gold nanoparticles, had an effect on the friction factors in comparison to those of untreated materials. In all cases, static and kinetic friction coefficients on aorta tissue were higher than those on vena cava due to higher surface roughness of the aorta. The presence of blood as a lubricant resulted in lower friction coefficients.

Electron microscopic demonstration of Romhányi's aldehyde-bisulphite-toluidine blue (ABT)-topo-optical staining reaction

Romhányi's aldehyde-bisulphite-toluidine blue (ABT) topo-optical reaction was checked electron microscopically. The reaction product was found localized on the sarcolemma membrane and intercalated disc. The findings suggest that the topo-optical ABT-reaction is suitable for molecular analysis. In addition to confirming the electron microscopic suitability of the ABT-reaction it has also offered ultrastructural evidence for the reliability of the topo-optical method.

The relevance of the aldehyde bisulfite toluidine blue reaction and its variants in the submicroscopic carbohydrate research

Carbohydrates are chemical compounds that contain only oxygen, hydrogen and carbon. They are classified by their number of sugar units: monosaccharides (such as glucose and fructose), and disaccharides (such as sucrose and lactose) are simple carbohydrates; oligosaccharides and polysaccharides (such as starch, glycogen and cellulose) are complex carbohydrates. Carbohydrates play a crucial role in diverse biological systems [Hricovín M. Structural aspects of carbohydrates and the relation with their biological properties. Curr Med Chem 2004;11:2565-83]. According to Roseman [Sugars of the cell membrane. In: Weissmann G, Clairborn E, editors. Cell membranes. Biochemistry, Cell Biology, Pathology. New York: H. P. Publ. Co; 1975. p. 55-64], two classes of glycoproteins are described. Free glycoproteins are localised in the surface coat of the membranes and form a thick mobile layer, without any association to the membrane itself. Functionally, however, they are located in a close association with the membrane (e.g. in the duodenal mucosa). The other group consists of the membrane glycoproteins, which are integral to the membranes and are located in the outer layer. The oligosaccharide chains are bound to the N-terminal part of proteins, and are situated in the hydrophilic zone. Glycoproteins have diverse functions. They are important in specific receptor functions, in immunological cell destruction and play a significant role in reactions with lectins, antibodies, as well as in cell association and mutual recognition of the cells. This paper focuses on aspects of a summary of polarisation optical investigations and biological functions of the following three groups of carbohydrates: oligosaccharides, glycoproteins and glycosaminoglycans.

Polarization optical analysis of the surface structures of various fungi

Vicinal hydroxyl groups of the sugar compounds sialic acid and 9-O-acyl sialic acid can be visualised for polarization optical analysis on the surface of different fungi using several topo-optical reactions. We investigated the presence of these molecules in cultures of Cryptococcus neoformans (heterogeneous form), Saccharomyces cerevisiae, Candida albicans, Candida glabrata, Candida krusei and Candida tropicalis by topo-optical reactions. Additionally, we examined brain and stomach tissues of patients with infections by C. neoformans and C. albicans, respectively. The results suggest a highly fashioned orientation of the sugar chains on the fungal surface. Terminal sialic- and O-acyl sialic acid residues are permanently present and orientated in a highly specific way in the cell wall of fungi. Based on the polarization optical analysis after the ABT-r (anisotropic PAS-r), the linear oriented hydroxyl groups of the sugar molecules are localized either perpendicular or parallel to the surface coat, depending on the species. According to the orientation of the vicinal hydroxyl groups, the oligosaccharide chains are orientated vertically. The capsule of the heterogeneous form of C. neoformans presented an especially strong metachromatic reaction and anisotropy. It is especially remarkable that the sterical orientation of sugar chains, and the terminal sialic acid and 9-O-acyl sialic acid molecules, was opposite in the inner and outer layer of the capsule.

The leukotriene d4 receptor antagonist, montelukast, inhibits mast cell degranulation in the dermis induced by water avoidance stress

Cysteinyl leukotrienes play a part in inflammatory reactions such as asthma and inflammatory bowel diseases. The leukotrienes exert their actions by binding to and activating various receptors. Montelukast, a leukotriene receptor antagonist, which is used in the treatment of asthma has been shown to be effective in inhibiting the action or formation of leukotrienes. Many skin disorders, such as atopic dermatitis and psoriasis, worsen during stress and seem to be related to infiltration and activation of mast cells that are releasing vasoactive and pro-inflammatory mediators. The aim of the present study was to investigate the effects of montelukast on the degranulation of mast cells in the dermis that is induced by water avoidance stress (WAS). Wistar albino rats were divided into four groups of 8 animals each. Control rats were injected with (1) the vehicle solution or (2) the montelukast solution in the absence of WAS. (3) the WAS group of rats was administered vehicle solution following WAS exposure for 2h daily for 5 days. (4) The WAS+ML group was administered montelukast 10mg/kg; i.p. following WAS exposure for 2h daily for 5 days. Dermal mast cell numbers were determined with toluidine blue and tryptase immunohistochemistry and observed using a light microscope. Numbers of both granulated and degranulated mast cells were significantly increased in the WAS group when compared to control rats. Montelukast treatment decreased the number of both mature granulated and degranulated mast cells in rats subjected to WAS. In conclusion, chronic montelukast treatment reduced WAS-induced infiltration and activation of mast cells in the dermis and may provide a useful therapeutic option in stress-induced skin disorders.

The adsorption kinetics and removal of cationic dye, Toluidine Blue O, from aqueous solution with Turkish zeolite

Clinoptilolite, a natural zeolite, was investigated as an inexpensive and effective adsorbent for the adsorption of Toluidine Blue O (TBO) from its aqueous solution. The effect of parameters such as the initial concentration of TBO, the solution of pH, contact time, temperature and particle size on the TBO adsorption was examined. The adsorption rate data were analysed according to the first and second-order kinetic models. Kinetic studies show that adsorption of TBO on clinoptilolite was fitted to the second-order adsorption model with two-step diffusion process. The activation energies for TBO adsorption on clinoptilolite for the first and second diffusion processes were 8.72 kJ mol(-1) and 19.02 kJ mol(-1), respectively. The adsorption isotherm was well fitted to both the Langmuir and Freundlich models. The maximum adsorption capacity of clinoptilolite for TBO was 2.1x10(-4) mol g(-1) at solution pH of 11.0.

Effect of fibroblast growth factor-2 on equine mesenchymal stem cell monolayer expansion and chondrogenesis

OBJECTIVE

To determine whether fibroblast growth factor-2 (FGF-2) treatment of equine mesenchymal stem cells (MSCs) during monolayer expansion enhances subsequent chondrogenesis in a 3-dimensional culture system.

ANIMALS

6 healthy horses, 6 months to 5 years of age.

PROCEDURES

Bone marrow-derived MSCs were obtained from 6 horses. First-passage MSCs were seeded as monolayers at 10,000 cells/cm(2) and in medium containing 0, 1, 10, or 100 ng of FGF-2/mL. After 6 days, MSCs were transferred to pellet cultures (200,000 cells/pellet) and maintained in chondrogenic medium. Pellets were collected after 15 days. Pellets were analyzed for collagen type II content by use of an ELISA, total glycosaminoglycan content by use of the dimethylmethylene blue dye-binding assay, and DNA content by use of fluorometric quantification. Semiquantitative PCR assay was performed to assess relative concentrations of collagen type II and aggrecan mRNAs.

RESULTS

Use of 100 ng of FGF-2/mL significantly increased pellet DNA and glycosaminoglycan content. Collagen type II content of the pellet was also increased by use of 10 and 100 ng of FGF-2/mL. Collagen type II and aggrecan mRNA transcripts were increased by treatment with FGF-2. Some control samples had minimal evidence of collagen type II and aggrecan transcripts after 35 cycles of amplification.

CONCLUSIONS AND CLINICAL RELEVANCE

FGF-2 treatment of bone marrow-derived MSC monolayers enhanced subsequent chondrogenic differentiation in a 3-dimensional culture. This result is important for tissue engineering strategies dependent on MSC expansion for cartilage repair.

RGD peptides grafting onto poly(ethylene terephthalate) with well controlled densities

The aim of this study was to graft RGD peptides with well controlled densities onto poly(ethylene terephthalate) (PET) film surfaces. Biomimetic modifications were performed by means of a four-step reaction procedure: surface modification in order to create -COOH groups onto polymer surface, coupling agent grafting and finally immobilization of peptides. The originality of this work is to evaluate several grafted densities peptides. Toluidine blue and high-resolution mu-imager (using [(3)H]-Lys) were used to evaluate densities. Moreover, mu-imager has exhibited the stability of peptides grafted onto the surface when treated under harsh conditions. Benefits of the as-proposed method were related to the different concentrations of peptides grafted onto the surface as well as the capacity of RGD peptide to interact with integrin receptors.

A Disposable Multianalyte Electrochemical Immunosensor Array for Automated Simultaneous Determination of Tumor Markers

Background: Automated and convenient multianalyte detection with high throughput is increasingly needed in clinical diagnosis. We developed a disposable 4-by-2 array for programmed simultaneous amperometric immunoassay of 4 tumor markers.

Methods: We used a screen-printed technique, 1-step immobilization method, and flow injection technique. We immobilized carcinoembryonic antigen, α-fetoprotein, β-human choriogonadotropin, and carcinoma antigen 125 as model analytes in a redox mediator–grafted, biopolymer-modified, screen-printed carbon electrode array to capture corresponding horseradish peroxidase-labeled antibodies in competitive immunoreactions. The simultaneous multianalyte immunoassay was automatically carried out to amperometrically monitor the mediator-catalyzed enzymatic response to hydrogen peroxide, which decreased in proportion to the concentrations of analytes in samples.

Results: The multianalyte immunosensor array had a throughput of 60 samples/h and allowed simultaneous detection of carcinoembryonic antigen, α-fetoprotein, β-human choriogonadotropin, and carcinoma antigen 125 in clinical serum samples with concentrations up to 188 μg/L, 250 μg/L, 266 IU/L, and 334 kIU/L, respectively. The detection limits (limits of the blank, mean of blank plus 3 SD) were 1.1 μg/L, 1.7 μg/L, 1.2 IU/L, and 1.7 kIU/L. The inter- and intraassay imprecision (CVs) of the immunosensor arrays were &lt;7.8% and &lt;9.0%, respectively. The immunosensor arrays were stable for 28 days.

Conclusions: This newly constructed immunosensor array provides a simple, automated, simultaneous multianalyte immunoassay with high throughput, short analytical time, and sufficiently low detection limits for clinical application. This method offers the capability of miniaturizing the multianalyte detection device.

Low-potential nicotinamide adenine dinucleotide detection at a glassy carbon electrode modified with toluidine blue O functionalized multiwall carbon nanotubes

The toluidine blue O (TBO) functionalized multiwall carbon nanotubes (MWNTs) nanomaterials (TBO-MWNTs) were prepared by assembling TBO onto the surface of a MWNTs modified glassy carbon (GC) electrode. Also TBO-MWNTs modified GC electrodes exhibiting a strong and stable electrocatalytic response toward beta-nicotinamide adenine dinucleotide (NADH) were described. Compared with a bare GC electrode, the TBO-MWNTs modified GC electrodes could decrease the oxidization overpotential of NADH by 730 mV, with a peak current at 0.0 V, since there was a positively synergistic electrocatalytic effect between the MWNTs and TBO toward NADH. Furthermore, the TBO-MWNTs modified GC electrodes had perfect performances, such as a low detection limit (down to 0.5 microM), being very stable (the current diminutions is lower than 6% in a period over 35 min), a fast response (within 3 s), and a wide linear range (from 2.0 microM to 3.5 mM). Such an ability of TBO-MWNTs to promote the NADH electron-transfer reaction suggests great promise for dehydrogenase-based amperometric biosensors.

Amperometric determination of hydrogen peroxide by functionalized carbon nanotubes through EDC/NHS coupling chemistry

The electrochemistry of the redox mediator Toluidine blue (TB) which was covalently linked to the carboxyl group of the multiwalled carbon nanotubes (MWNTs) by coupling reactions, in which N-hydroxysuccinimide was used to assist 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride catalyzed amidation reaction is described. The results from cyclic voltammetry (CV) and amperometry suggested that the redox mediator is linked to the surface of the MWNTs and the nanotubes showed an obvious promotion for the direct electron-transfer between the redox mediator and the electrode. A couple of well-defined redox peak of TB was observed in a phosphate buffer solution (pH 7.0). The redox mediator immobilized to MWNTs exhibits remarkable electrocatalytic activity for the reduction of hydrogen peroxide (H2O2). The analytical applicability of the modified electrode for the determination of hydrogen peroxide was examined. A linear response in the concentration range of 6.8 x 10(-7)-3.4 x 10(-2) M (r = 0.9958) was obtained with detection limit of 3.4 x 10(-7) M for the determination of hydrogen peroxide. The modified electrode has advantages of being highly stable, sensitive, ease of construction and use.

[Oxygen can be replaced by artificial electron acceptors in reactions catalyzed by alcohol oxidase]

For the first time, spectrometric and electrochemical studies demonstrated the possibility of using artificial electron acceptors in reactions catalyzed by alcohol oxidase. We report kinetic parameters of homogenous catalytic oxidation of formaldehyde by organic redox compounds belonging to different structural classes (toluidine blue, methylene blue, 2,6-dichlorophenolindo-phenol, and p-benzoquinone) and replacing dioxygen in these reactions. p-Benzoquinone, having the highest redox potential, proved to be the most efficient artificial electron acceptor of all compounds studied.

Amperometric hydrogen peroxide sensor based on a sol-gel-derived ceramic carbon composite electrode with toluidine blue covalently immobilized using 3-aminopropyltrimethoxysilane

A carbon composite amperometric hydrogen peroxide sensor has been developed using a sol-gel technique. Toluidine blue (TB), which acts as the redox mediator, was covalently immobilized via glutaraldehyde crosslinking with an organically modified silane, namely 3-aminopropyltrimethoxysilane (APTMOS). Methyltrimethoxysilane (MTMOS) was used as the additional monomer; this controls the hydrophobicity of the electrode surface, thus limiting the wettability. The immobilization of TB within the sol-gel matrix was confirmed with FTIR studies. The sol-gel mixture containing TB immobilized in APTMOS and MTMOS was mixed with graphite powder in order to prepare the carbon composite electrode. The electrode was characterized using voltammetric techniques and its electrocatalytic activity for the reduction of hydrogen peroxide was also studied. The carbon composite electrode has the advantage of sensing H(2)O(2) at a lower potential and with a higher sensitivity, and interferences due to ascorbic acid, uric acid and acetaminophen were greatly minimized. The linear range for the determination of H(2)O(2) extends from 5.37 x 10(-6) to 6.15 x 10(-3) M, with a correlation coefficient of 0.9981. The detection limit was found to be 2.15 x 10(-6) M. The covalent immobilization of TB effectively prevents the leakage of the water-soluble mediator during measurements. The modified electrode, aside from electrocatalyzing the reduction of H(2)O(2), exhibits distinct advantages in terms of surface renewal in the event of surface fouling, as well as simple preparation, good chemical and mechanical stability, and good reproducibility.

Delivery of photosensitisers and light through mucus: investigations into the potential use of photodynamic therapy for treatment of Pseudomonas aeruginosa cystic fibrosis pulmonary infection

Respiratory disease is the main cause of morbidity and mortality in patients with cystic fibrosis (CF). In such patients chronic Pseudomonas aeruginosa infection is virtually impossible to eradicate using antibiotic therapy. Photodynamic antimicrobial chemotherapy (PACT) could be one potential alternative antimicrobial method. As photosensitisers could be delivered to the lungs of CF patients via inhalation, the current in vitro study investigated the potential use of PACT in the treatment of P. aeruginosa CF pulmonary infection. Delivery of red light (635 nm) and two photosensitisers (toluidine blue O (TBO) and meso-tetra (N-methyl-4-pyridyl) porphine tetra tosylate (TMP)) across artificial CF mucus was successfully achieved. Artificial CF mucus reduced the measured fluence of incident light in an almost exponential manner with increasing depth. The presence of dissolved photosensitisers also reduced light fluence. TMP diffused more efficiently across artificial CF mucus than TBO. However, receiver compartment concentrations of both drugs after 6 h were of the same order as those required to achieve high rates of kill (>99%) of P. aeruginosa isolates growing both planktonically and in biofilms. TMP required significantly higher concentrations (2.5 mg ml(-1)) than TBO to achieve high rates of kill (>99%) of P. aeruginosa isolates growing planktonically. Higher concentrations (5.0 mg ml(-1)) of both photosensitisers were required to achieve high rates of kill (>99%) of P. aeruginosa isolates growing in biofilms. When photosensitisers were prepared in artificial mucus, higher concentrations were required to achieve reasonably high kill rates (>80%) of P. aeruginosa (PAO1) growing both planktonically and in biofilm.

Cellulose acetate containing toluidine blue and rose bengal is an effective antimicrobial coating when exposed to white light

Simple methods of reducing the microbial load on surfaces in hospitals are needed to reduce the risk of hospital-associated infections. Here we report on the ability of a cellulose acetate coating containing the photosensitizers toluidine blue and rose bengal to kill microbes (Staphylococcus aureus, Escherichia coli, Clostridium difficile, a bacteriophage, and Candida albicans) on its surface when illuminated with white light.

Amperometric immunosensor based on toluidine blue/nano-Au through electrostatic interaction for determination of carcinoembryonic antigen

A new current amplified immunosensor for the determination of carcinoembryonic antigen (CEA) was demonstrated in this work. The electrode architecture was fabricated by positively charged toluidine blue (TB) coated on negatively charged poly-sulfanilic acid (PSAA) modified glassy carbon electrode (GCE) surface through electrostatic interactions to form a TB/PSAA film, which provided an interface containing amine groups to assemble gold nanoparticles (nano-Au) for immobilization of carcinoembryonic antibody (anti-CEA) and horseradish peroxidase (HRP) instead of bovine serum albumin (BSA) to block sites against non-specific binding. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were employed to characterize the electrochemical properties of the modified processes. The CVs reduction current of the immunosensor charged linearly in two concentration ranges of CEA from 0.5 to 5.0 and 5.0 to 120.0 ng/ml in presence of 0.3mM H2O2 in analyte solution, and the detection limit was 0.2 ng/ml at three times background noise. The proposed method is economical, efficient and potentially attractive for clinical immunoassays.

Cationic fullerenes are effective and selective antimicrobial photosensitizers

Fullerenes are soccer ball-shaped molecules composed of carbon atoms, and, when derivatized with functional groups, they become soluble and can act as photosensitizers. Antimicrobial photodynamic therapy combines a nontoxic photosensitizer with harmless visible light to generate reactive oxygen species that kill microbial cells. We have compared the antimicrobial activity of six functionalized C(60) compounds with one, two, or three hydrophilic or cationic groups in combination with white light against gram-positive bacteria, gram-negative bacteria, and fungi. After a 10 min incubation, the bis- and tris-cationic fullerenes were highly active in killing all tested microbes (4-6 logs) under conditions in which mammalian cells were comparatively unharmed. These compounds performed significantly better than a widely used antimicrobial photosensitizer, toluidine blue O. The high selectivity and efficacy exhibited by these photosensitizers encourage further testing for antimicrobial applications.

Photodynamic inactivation of Bacillus spores, mediated by phenothiazinium dyes

Spore formation is a sophisticated mechanism by which some bacteria survive conditions of stress and starvation by producing a multilayered protective capsule enclosing their condensed DNA. Spores are highly resistant to damage by heat, radiation, and commonly employed antibacterial agents. Previously, spores have also been shown to be resistant to photodynamic inactivation using dyes and light that easily destroy the corresponding vegetative bacteria. We have discovered that Bacillus spores are susceptible to photoinactivation by phenothiazinium dyes and low doses of red light. Dimethylmethylene blue, methylene blue, new methylene blue, and toluidine blue O are all effective, while alternative photosensitizers such as Rose Bengal, polylysine chlorin(e6) conjugate, a tricationic porphyrin, and a benzoporphyrin derivative, which easily kill vegetative cells, are ineffective. Spores of Bacillus cereus and B. thuringiensis are most susceptible, B. subtilis and B. atrophaeus are also killed, and B. megaterium is resistant. Photoinactivation is most effective when excess dye is washed from the spores, showing that the dye binds to the spores and that excess dye in solution can quench light delivery. The relatively mild conditions needed for spore killing could have applications for treating wounds contaminated by anthrax spores, for which conventional sporicides would have unacceptable tissue toxicity.

Effect of cell-photosensitizer binding and cell density on microbial photoinactivation

Photodynamic therapy involves the use of nontoxic dyes called photosensitizers and visible light to produce reactive oxygen species and cell killing. It is being studied as an alternative method of killing pathogens in localized infections due to the increasing problem of multiantibiotic resistance. Although much has been learned about the mechanisms of microbial killing, there is still uncertainty about whether dyes must bind to and penetrate various classes of microbe in order to produce effective killing after illumination. In this report, we compare the interactions of three antimicrobial photosensitizers: rose bengal (RB), toluidine blue O (TBO), and a poly-L-lysine chlorin(e6) conjugate (pL-ce6) with representative members of three classes of pathogens; Escherichia coli (gram-negative bacteria), Staphylococcus aureus (gram-positive bacteria), Candida albicans (yeast). We compared fluence-dependent cell survival after illumination with the appropriate wavelengths of light before and after extracellular dye had been washed out and used three 10-fold dilutions of cell concentration. pL-ce6 was overall the most powerful photosensitizer, was equally effective with and without washing, and showed a strong dependence on cell concentration. TBO was less effective in all cases after washing, and the dependence on cell concentration was less pronounced. RB was ineffective after washing (except for S. aureus) but still showed a dependence on cell concentration. The overall order of susceptibility was S. aureus>E. coli>C. albicans, but C. albicans cells were 10 to 50 times bigger than the bacteria. We conclude that the number and mass of the cells compete both for available dye binding and for extracellularly generated reactive oxygen species.

Electrochemical sensing platform based on the carbon nanotubes/redox mediators-biopolymer system

A new electrochemical sensing platform was developed that relied on synergy between carbon nanotubes (CNT) and redox mediators that were co-immobilized in the biopolymer chitosan (CHIT). To demonstrate the concept, the redox mediator Toluidine Blue O (TBO) and CNT were integrated in CHIT and used for the determination of a reduced form of nicotinamide adenine dinucleotide (NADH). As compared to CHIT-TBO, the CHIT-TBO/CNT films displayed large amplification of a current due to the TBO-mediated oxidation of NADH at -0.10 V. This was discussed in terms of the TBO/CNT synergy that resulted in the improved charge propagation through the CHIT-TBO/CNT matrix.

Quantification of polyphosphate: different sensitivities to short-chain polyphosphate using enzymatic and colorimetric methods as revealed by ion chromatography

Polyphosphate is ubiquitous and has a variety of biochemical functions. Among polyphosphate quantification methods, an enzymatic assay using Escherichia coli polyphosphate kinase (PPK), in which polyphosphate is converted to adenosine 5'-triphosphate and quantified by luciferase assay, is the most specific and most sensitive. However, chain-length specificity of the assay has not been analyzed in detail so far. Ion chromatography equipped with an on-line hydroxide eluent generator enabled us to analyze polyphosphate up to 50 inorganic phosphate (P(i)) residues, and we employed this method to investigate the chain-length specificity of PPK in this study. Several fractions of short-chain polyphosphate were prepared by electrophoresis, and the chain-length distribution was analyzed before and after 1-6 h PPK reaction by ion chromatography. Polyphosphates longer than 23 P(i) residues were processed by PPK completely after 1 h incubation, but complete processing of those between 11 and 22 P(i) residues required 6h incubation. Limited processing of polyphosphates of 10 P(i) residues or shorter were observed even after 6h incubation. Metachromasy of Toluidine blue O, an alternative method for polyphosphate quantification, showed broader chain-length specificity although it was not as sensitive as the enzymatic assay. Combination of these two methods would be practically applicable to analysis of polyphosphate dynamics in living organisms.

Multilayer assembly of Prussian blue nanoclusters and enzyme-immobilized poly(toluidine blue) films and its application in glucose biosensor construction

A multilayered glucose biosensor via sequential deposition of Prussian blue (PB) nanoclusters and enzyme-immobilized poly(toluidine blue) films was constructed on a bare Au electrode using electrochemical methods. The whole configuration of the present biosensor can be considered as an integration of several independent hydrogen peroxide sensing elements. In each sensing element, the poly(toluidine blue) film functioned as both the supporting matrix for the glucose oxidase immobilization and the inhibitor for the diffusion of interferences, such as ascorbic acid and uric acid. Meanwhile, the deposited Prussian blue nanocluster layers acts as a catalyst for the electrochemical reduction of hydrogen peroxide formed from enzymatic reaction. Performance of the whole multilayer configuration can be tailored by artificially arranging the sensing elements assembled on the electrode. Under optimal conditions, the biosensors exhibit a linear relationship in the range of 1 x 10(-4) to 1 x 10(-2) mol/L with the detection limit down to 10(-5) mol/L. A rapid response for glucose could be achieved in less than 3 s. For 1 mM glucose, 0.5 mM acetaminophen, 0.2 mM uric acid, and 0.1 mM ascorbic acid have no obvious interferences (<5%) for glucose detection at an optimized detection potential. The present multilayered glucose biosensor with a high selectivity and sensitivity is promising for practical applications.

The role of the methylene blue and toluidine blue monomers and dimers in the photoinactivation of bacteria

The interactions between the phenothiazine dyes, methylene blue (MB) and toluidine blue (TB), and bacteria (Staphylococcus aureus, Streptococcus pneumoniae, Enterococcus faecalis, Hemophilus influenzae, Escherichia coli and Pseudomonas aeruginosa) were studied spectrophotometrically. This demonstrated that a metachromatic reaction took place between the dyes and bacteria. Furthermore, bacteria induced additional dimerization of MB and TB. The effective dimerization constants of MB and TB were evaluated in the presence of each bacterial strain at a concentration of 10(8) CFU/ml. The analysis of the effective dimerization constants for MB and TB in the presence of bacteria indicated that the ability to form dimers was greater for TB than for MB. Gram-negative bacteria induced the dye dimerization more intensely than gram-positive bacteria. There was a correlation between the ability of each dye to form dimers in the presence of bacteria and the relative photobactericidal efficacy of each dye against these bacteria. These results provide evidence confirming the essential role of the dye dimers in bacterial photodamage.

Localization of Mast Cells in Endometrial Cysts

PROBLEM

Although the presence of mast cells in endometriosis lesions has been reported, there have been no reports of their pathological localization in ovarian endometrial cysts.

METHODS OF STUDY

The localization of mast cells in ovarian endometrial cysts were investigated using hematoxyline and eosin and toluidine blue staining with light microscopy, immunohistochemical c-kits, and electron microscopy.

RESULTS

Mast cells were identified in endometrial cyst tissues. Few mast cells were localized in the endometrial stroma, which is characteristic of endometrial gland-like regions. Many mast cells were noted around blood vessels and the interstitium with fibrosis, that is, the fibrotic interstitium of endometrial cysts.

CONCLUSIONS

Mast cells may be involved in the development and progression of endometriosis. Localization of mast cells suggests a particularly close relationship with fibrosis and adhesion.

[Determination of deoxyribonucleic acids at nanograms levels with toluidine blue by a resonance light-scattering method]

Resonance light scattering (RLS) spectra of toluidine blue (TB) with DNA was studied. The RLS of TB was greatly enhanced by DNA in the range of pH 10-11. A RLS peak at 350 nm was found, and the enhanced intensity of RLS at this wavelength was proportional to the concentration of DNA. The linear range of the calibration curve was 0-900 ng x mL(-1) with the detection limit of 6.75 ng x mL(-1) for the ctDNA, and for fsDNA the linear range was 0-900 ng x mL(-1) with the detection limit of 2.99 ng x mL(-1). Precision at 500 ng x mL(-1) for the two nucleic acids was 3.7% and 5.6%, respectively. Four synthetic samples were determined satisfactorily.