Xanthene dyes induce membrane permeabilization of bacteria and erythrocytes by photoinactivation

We analyzed the photoinactivation of the membrane functions of bacteria and erythrocytes induced by xanthene dyes. The dyes tested were rose bengal, phloxine B, erythrosine B and eosin B. These dyes induced the leakage of K(+) from Staphylococcus aureus cells within minutes of photoirradiation, in the order of rose bengal > phloxine B > erythrosine B > eosin B. The ability of dyes to inhibit respiration was weak, except for rose bengal, and the dyes dissipated the membrane potential in similar time traces with changes in K(+) permeability. The xanthene dyes also induced the leakage of K(+) from bovine erythrocytes upon photoirradiation in the same order as that observed with bacteria. Furthermore, we found that the ability to cause the leakage of K(+) from erythrocytes was associated with dye-induced morphological changes, forming a crenated form from the normal discoid. These results are discussed in connection with the ability of xanthene dyes to generate singlet oxygen and bind to bacterial cells, and further compared with the actions of cationic porphyrins, which induced photoinactivation of bacteria through respiratory inhibition.     

Adsorption of xanthene dyes by lysozyme crystals

Adsorption characteristics of cross-linked lysozyme crystals of different morphologies (tetragonal, orthorhombic, triclinic and monoclinic) were examined using four anionic dyes (fluorescein, eosin, erythrosin, and rose bengal), one zwitterionic dye (rhodamine B), and one cationic dye (rhodamine 6G). The adsorption isotherms were of the Langmuir type for all examined systems with the exception of rhodamine B adsorption by monoclinic crystals. The weakest adsorption was observed for the cationic dye, rhodamine B, whereas dianionic dyes, eosin, rose bengal, and erythrosin were strongly adsorbed on the protein surface. The adsorption capacities of the crystals for the dyes were found to depend on both charge and hydrophobicity of the dye, reflecting the heterogeneous character of the lysozyme pore surface. The adsorption affinity of the crystals for the dyes was a function of the dyes' hydrophobicity. Furthermore, the crystal morphology was identified as an additional factor determining capacity and affinity for dye adsorption. Differences between crystals prepared in the presence of the same precipitant were lower than between morphologies prepared with different precipitants.     

Visible light-sensitized semiconductor photocatalytic degradation of 2,4-dichlorophenol

Sensitized-photocatalytic decomposition of 2,4-dichlorophenol (2,4-DCP) using xan-thene dyes as photosensitizer on TiO2 particles under visible light irradiation was studied. 2,4-DCP can be decomposed efficiently by this method and the decomposition efficiency of 2,4-DCP decreases in the following order: eosin Y ≈ rose bengal > erythrosine B > rhodamine B.     

Photodynamic activities of food additive dyes on the yeast Saccharomyces cerevisiae

Photodynamic cell-inactivating activities of food additive dyes on the yeast Saccharomyces cerevisiae were investigated. Activities of dyes not permitted as food additives were also examined. Red No. 105 (rose bengal), Red No. 3 (erythrosine) and Red No. 104 (phloxine), which are permitted as food additives, markedly inactivated yeast cells by photodynamic action. Eosine, matius yellow and guinia green B, which are not permitted, also exhibited moderate cell-inactivating activity by photodynamic action. None of the dyes used in this experiment exhibited petite induction by photodynamic action.     

Photophysics of xanthene dyes in surfactant solution

The spectral (both absorption and fluorescence) and photoelectrochemical studies of some anionic xanthene dyes namely erythrosine B, rose bengal and eosin have been carried out in micellar solution of cationic cetyl trimethyl ammonium bromide (CTAB), anionic sodium dodecyl sulphate (SDS) and neutral triton X-100 (TX-100). The results show that all these dyes form 1:1 electron-donor-acceptor (EDA) or charge-transfer (CT) complexes with TX-100, which acts as an electron donor. There is no interaction of these dyes with SDS, whereas the interaction with CTAB is mainly electrostatic in nature. In presence of TX-100, these dyes show enhancement of fluorescence intensity with a red shift and develop photovoltage in a photoelectrochemical cell. A good correlation has been found among the photovoltage generation in the systems consisting of these dyes and TX-100, spectral shift due to complex formation and thermodynamic properties of these complexes.     

ISOLATION OF UNIQUE DIMER SPECTRA OF DYES FROM THE COMPOSITE SPECTRA OF AGGREGATED SOLUTIONS

Abstract— Aggregation of fluorescein, eosin and rose bengal in aqueous solutions has been studied. Mathematical expressions are derived to calculate the monomer mole fractions in moderately and highly concentrated solutions. The average values of the dimer dissociation constant, K_d , for fluorescein, eosin and rose bengal in aqueous solutions at pH 12 are 0.20, 9.0×10^-3 and 40 × 10^-3 moles/l respectively. A method is developed here to isolate the dimer spectrum from the composite spectrum. The uniqueness of this method is established by comparison with other known methods. The dimer spectra of all the three dyes are reported.     

Xanthene Dyes and Green LED for the Inactivation of Foodborne Pathogens in Planktonic and Biofilm States

This study evaluated the rose bengal‐ and erythrosine‐mediated photoinactivation against Salmonella Typhimurium and Staphylococcus aureus planktonic and sessile cells using green LED as a light source. The free‐living or 2‐day‐old biofilm cells were treated with different concentrations of the photosensitizing agents and subjected to irradiation. Only 5 min photosensitization with rose bengal at 25 nmol L^?1 and 75 μmol L^?1 completely eliminated S. aureus and S. Typhimurium planktonic cells, respectively. Erythrosine at 500 nmol L^?1 and 5 min of light exposure also reduced S. aureus planktonic cells to undetectable levels. Eradication of S. aureus biofilms was achieved when 500 μmol L^?1 of erythrosine or 250 μmol L^?1 of rose bengal was combined with 30 min of irradiation. Scanning electron microscopy allowed the observation of morphological changes in planktonic cells and disruption of the biofilm architecture after photodynamic treatment. The overall data demonstrate that rose bengal and erythrosine activated by green LED may be a targeted strategy for controlling foodborne pathogens in both planktonic and sessile states.     

Photodegradation of environmental mutagens by visible irradiation in the presence of xanthene dyes as photosensitizers

The photodegradation of environmental mutagens, such as 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1), 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2), 2-amino-3-methyl-9H-pyrido[2,3-b]indole (MeAαC), and 2-amino-3-methyl-imidazo[4,5-f]quinoline (IQ), was investigated by visible irradiation in the presence of xanthene dyes as photosensitizers. Although the environmental mutagens themselves were very stable during visible irradiation under the conditions in this study, they were effectively photodegraded in the presence of the xanthene dyes (erythrosine, rose bengal, and phloxine). Moreover, photodegradation of the mutagens was further enhanced for xanthene dyes loaded onto a water-soluble diethylaminoethyl (DEAE)-dextran anion-exchanger via ionic interactions (xanthene-dyeDEX). Photodegradation was inhibited by O2 removal from the reaction solution. In ESR spin-trapping experiments using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a trapping reagent, signals characteristic of DMPO-?OH (hydroxyl radical) were observed in the presence of xanthene-dyeDEX. These results suggest that reactive oxygen species derived from O2, such as singlet molecular oxygen (?1O2) and/or ?OH, were active participants in photodegradation of the mutagens in the presence of xanthene dyes or xanthene-dyeDEX.     

Adsorption of xanthene food additive dyes to cellulose granules

It was found that three kinds of the synthetic food additive dyes, red nr. 3 (erythrosine), nr. 104 (phloxine), and nr. 105 (rose bengal) were adsorbed to the surface of charred cellulose granules and the maximum amounts of adsorption of these dyes were 3.75, 3.42, and 4.74 mg/g cellulose, respectively. Scanning electron microscopy-electron probe micro analysis (SEM-EPMA) showed a coating of the dyes on the surface of charred cellulose granules. Electron spectroscopy for chemical analysis (ESCA) suggested the presence of NH₃ ⁺ in the surface of charred cellulose granules. Since all three dye compounds have both anionic carboxylate and hydrophobic groups and were released from the surface of charred cellulose granules by 0.1 N NaOH solution, it was surmised that these three food additive dyes were bound to the surface of cellulose granules by both ionic and physical interactions.     

Supramolecular fuzzy recognition leads to effective differentiation of similar molecules

The separation of structurally similar molecules remains a general challenge; here, we report that a roughly defined macromolecular nanocapsule can efficiently separate a variety of structurally similar mixtures. The nanocapsule is a core?shell amphiphilic macromolecule (CAM) hydrophobically derived from hyperbranched polyethylenimine with 2‐hexadecyloxymethyloxirane. It is found that with further chemical core engineering of the CAM, its guest selectivity can be radically enhanced, although specific host?guest interaction is absent or ignorable in the system. As a result, two groups of structurally similar guests such as fluorescein/tetrachlorofluorescein, and rose bengal/erythrosine B/eosin Y, can be well recognized by the CAMs. It is known that a complex (fuzzy) system is generally characterized by complexity and nonlinearity; thus core engineering of a CAM is possible to amplify the difference of the competitive guests and lead to effective guest differentiation, such a mechanism is called supramolecular fuzzy recognition (SFR). Our results demonstrate that with appropriate combination of various elementary interaction styles, SFR can lead to effective recognition of a wide spectrum of mixtures. Moreover, a SFR host can be roughly defined in structure and thus readily available. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Diffusion and birefringence of bioactive dyes in a supramolecular guanosine hydrogel

Transparent self-standing supramolecular hydrogels were readily prepared by the potassium-ion-mediated self-organization of guanosine and 8-bromoguanosine whilst the individual components precipitated within a few hours. VT-NMR spectroscopy showed that bromoguanosine was a superior gelator compared to guanosine. XRD analysis showed that gel formation was caused by stacked G-quartets. AFM analysis revealed dendritic architectures of the nanofibers in the two-component hydrogel network. DSC profiles showed that the hybrid hydrogels underwent sol-gel transition at lower temperature than the pure guanosine and bromoguanosine hydrogels. Interestingly, bioactive dyes, such as rose bengal, rhodamine-6-G, and fluorescein, could be diffused and released in a controlled manner. UV/Vis absorption and fluorescence spectroscopy and CLSM were used to investigate the diffusion behavior of dyes in the hydrogel network. These dyes exhibited strong birefringence in the gel network (0.07-0.1) as a result of the anisotropic organization.     

Analysis of association constant for ground‐state dye‐electron acceptor complex of photoinitiator systems and the association constant effect on the kinetics of visible‐light‐induced polymerizations

We investigated the formation of ground‐state donor/acceptor complexes between xanthene dyes [rose bengal (RB) and fluorescein (FL)] and a diphenyliodonium (DPI) salt, which is dissolved in 2‐hydroxyethyl methacrylate (HEMA) monomer. To characterize the association constant of the complex, we have suggested a new analysis model based upon the Benesi–Hildebrand model. Because the assumption of the original Benesi–Hildebrand model is that the absorption bands are only due to the presence of the complex and that the absorption by the free component is negligible, the model cannot be applied to our systems, which is a dye‐based initiator system. For each dye, the molar absorptivity of the ground‐state complex was evaluated as a function of wavelength, and this analysis confirmed the validity of the modified Benesi–Hildebrand model. In addition, we observed that the RB/DPI photoinitiator system failed to produce a perceptible polymerization rate but the FL/DPI photoinitiator system provided high rates of polymerization. On the basis of the association constant for these complexes, we concluded that the observed kinetic differences arise from the different association constant values of the ground‐state dye‐acceptor complex, resulting in back‐electron transfer reaction. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1429–1439, 2009     

Separation of fluorescein dyes by capillary electrophoresis using β-cyclodextrin

Summary A capillary electrophoresis method for the separation and determination of five synthetic dyes used in pharmaceutical preparations, cosmetics and as food additives is described. The dyes, fluorescein, dichlorofluorescein, Rose Bengal erythrosine and eosine are well separated in less than 12 min using an electrolyte of 50 mM phosphate buffer (pH 7.5), 10 mM β-cyclodextrin and 5% (v/v) methanol. A linear relationship between concentration and peak area for each dye was obtained in the concentration range 0.3–500 μg mL⁻¹, with a correlation coefficient greater than 0.999. Intra- and inter-day precision of about 0.2–2.6% RSD (n=11) and 4.9–9.7% RSD (n=30), respectively, were obtained. The method has been used for determining the purity of fluorescein and erythrosine in practical samples.     

Laser flash photolysis of dyed fabrics and polymers—I. Rose bengal as a photosensitizing dye

We report emission and transient absorption observed using diffuse reflectance following pulsed laser excitation of rose bengal in a variety of opaque heterogeneous environments. These include kinetic transient absorption studies for the first time on dyed fabrics and within cross-linked polymer beads to which rose bengal has been chemically attached. The transient absorption difference spectra which sometime show ground state depletion and isosbestic points upon decay are assigned to the production of triplet rose bengal. The transient decay is a mixture of first and second order kinetic processes. A strong contribution due to triplet-triplet annihilation is interesting in connection with the possibility of energy transfer between dyes attached to or adsorbed on polymers. These measurements illustrate that the primary photochemical processes of heterogeneous sensitizers and dyed fabrics can now be studied directly using diffuse reflectance flash photolysis.     

pKa determinations of xanthene derivates in aqueous solutions by multivariate analysis applied to UV-Vis spectrophotometric data

Xanthenes form to an important class of dyes which are widely used. Most of them present three acid-base groups: two phenolic sites and one carboxylic site. Therefore, the pKa determination and the attribution of each group to the corresponding pKa value is a very important feature. Attempts to obtain reliable pKa through the potentiometry titration and the electronic absorption spectrophotometry using the first and second orders derivative failed. Due to the close pKa values allied to strong UV-Vis spectral overlap, multivariate analysis, a powerful chemometric method, is applied in this work. The determination was performed for eosin Y, erythrosin B, and bengal rose B, and also for other synthesized derivatives such as 2-(3,6-dihydroxy-9-acridinyl) benzoic acid, 2,4,5,7-tetranitrofluorescein, eosin methyl ester, and erythrosin methyl ester in water. These last two compounds (esters) permitted to attribute the pKa of the phenolic group, which is not easily recognizable for some investigated dyes. Besides the pKa determination, the chemometry allowed for estimating the electronic spectrum of some prevalent protolytic species and the substituents effects evaluation.     

两亲性超支化聚砜胺对染料的可逆高装载

采用戊酰氯、壬酰氯和棕榈酰氯对超支化聚砜胺(HPSA)进行封端,合成了3种不同烷基末端的两亲性核壳型超支化聚砜胺,并将其用于小分子装载.发现它们对刚果红(CR)、甲基橙(MO)、虎红(RB)等水溶性染料具有很强的装载能力,且对同种染料的封装载荷随着末端亲油性烷基链的增长而增大.对于末端为棕榈酰基的HPSA-PC,平均每个大分子可以捕捉CR和MO分子的数目分别高达41.8和19.4个,远高于已报道的树枝状聚合物和超支化聚合物对这些染料的封装载荷.这主要是聚砜胺内核的高度亲水性及其与亲油性烷基外壳的极性差所致.与已报道的聚合物不同,两亲性超支化聚砜胺装载的染料用纯水洗涤可以释放出来.这种高装载性能和可逆性赋予超支化聚砜胺在药物释放、分子识别和分离以及纳米催化剂和纳米涂料等领域具有广阔的应用前景.     

Charge-controlled permeability of polyelectrolyte microcapsules

Multilayer microcapsules showing unique charge-controlled permeability have been successfully fabricated by employing poly(styrene sulfonate) (PSS)-doped CaCO3 particles as templates. Encapsulation of the PSS molecules is thus achieved after core removal. Scanning force microscopy (SFM), UV-vis, Raman spectroscopy, and zeta-potential confirm the existence of the PSS molecules in the CaCO3 particles and the resultant microcapsules, which are initially incorporated during the core fabrication process. A part of these additionally introduced PSS molecules interacts with PAH molecules residing on the inner surface of the multilayer wall to form a stable complex, while the other part is intertwined in the capsule wall or in a free state. Capsules with this structure possess many special features, such as highly sensitive permeability tuned by probe charge and environmentally controlled gating. They can completely reject negatively charged probes, but attract positively charged species to form a higher concentration in the capsule interior, as evidenced by confocal microscopy. For example, the capsules completely exclude dextran labeled with fluorescein isothiocyanate (FITC-dextran), but are permeable for dextran labeled with tetramethylrhodamine isothiocyanate (TRITC-dextran) having similar molecular mass (from 4 to 70 kDa), although there are only few charged dyes in a dextran chain. By reversing the charge of the probes through pH change, or by suppressing charge repulsion through salt addition, the permeation can be readily switched for proteins such as albumin or small dyes such as fluorescein sodium salt.     

SENSITIZED PHOTODEGRADATION OF CELLULOSE AND CELLULOSIC WASTES

Abstract— The photodegradation of cellulose and cellulose–containing waste sensitized by a variety of dyes was measured by means of viscosity, tensile strength, and scanning electron microscopy. Anthraquinone-2-sulfonate and proflavin dihydrochloride were both more effective than either rose bengal or methylene blue for degradation. Samples degraded by these dyes were similar in appearance to enzyme-degraded ones, but were less susceptible to further degradative action by enzymes.     

DYE-SENSITIZED PHOTOLYSTS OF DISODIUM PHENYL PHOSPHATE IN AQUEOUS SOLUTION UNDER OXYGEN: INVOLVEMENT OF SINGLET OXYGEN

Abstract— The release of orthophosphate from oxygen-saturated aqueous solutions of disodium phenyl phosphate by near-UV and visible light was enhanced in the presence of the sensitizing dyes methylene blue, rose bengal and thionine. The reaction was accompanied by the bleaching of these dyes. In the absence of oxygen, under nitrogen, the photodecomposition was very much slower. In deuterium oxide as the solvent, the dye-sensitized photodecomposition was 9 times faster than in normal water. This result suggests that singlet oxygen is probably the reactive species in the dye-sensitized reaction.     

CELL MEMBRANE PHOTOMODIFICATION: RELATIVE EFFECTIVENESS OF HALOGENATED FLUORESCEINS FOR PHOTOHEMOLYSIS

Abstract— Relative potency of 10 fluorescein derivatives as sensitizers of delayed photohemolysis of human erythrocytes has been assessed. Dilute suspensions of washed cells were illuminated in the presence of sensitizer at different concentrations for 1 h and analyzed for percent hemolysis following 23 h of dark incubation. Plots of percent hemolysis versus concentration showed a steep dependence on concentration for all sensitizers. Additional measurements of octanol/water partition coefficients, photon absorption in octanol and in saline and photobleach rates were made. After correction for absorption cross section, the effectiveness values ranged over more than three orders of magnitude with fluorescein being the least potent and rose bengal the most. A reasonable prediction of potency is obtained by taking the product of partition coefficient, relative absorption in octanol versus water and molecular weight of the substituents added to the fluorescein skeleton. The results suggest that the influence of halogen substitution on sensitizing potency is exerted by four factors; (1) distribution of sensitizer into a low polarity region of the cell membrane, (2) absorption efficiency in a low polarity region, (3) triplet quantum yield, and (4) photobleach rate.