Opinion of the Scientific Panel on food additives, flavourings, processing aids and materials in contact with food (AFC) to review the toxicology of a number of dyes illegally present in food in the EU

Unveiling the tartrazine binding mode with ds-DNA by UV-visible spectroscopy, electrochemical, and QM/MM methods

Here, we studied the interaction between the food colorant tartrazine (TZ) and double stranded DNA (dsDNA), using spectroscopic, electrochemical, and computational methods such as QM/MM combined with TD-DFT. Despite the UV-vis spectroscopy is widely used to study the interaction between molecules, for the case of TZ there are discrepancies in the analyses presented in the literature available, presenting both hyperchromic and hypochromic effects and consequently different rationalizations for their results. Herein we propose the combination of UV-vis experiments with the design of high-level computational models capable of reproducing the experimental behavior to finally define the proper binding mode at the molecular scale together with the rationalization of the experimental optical response due to the complex formation. To complement the UV-vis experiments, we propose the use of electrochemical measurements, to support the results obtained through UV-vis spectroscopy, as it has been successfully used for the determination of interaction modes between small molecules and biomolecules in any condition. Our UV-vis spectroscopy experiments showed only a hypochromic effect of the absorption spectra of TZ after interaction with DNA, indicative of TZ being deeply buried in the DNA structure. The effect of ionic strength in the experimental procedures led to the dissociation of TZ, thus indicating that the interaction mode was groove binding. On the other hand, the electrochemical studies showed an irreversible reduction peak of TZ, which after the interaction with DNA exhibited a positive shift in potential that can be attributed to groove binding. The binding constant for TZ-DNA was calculated as 4.45x10⁴M^-1 (UV-vis) and 5.75x10⁴M^-1 (electrochemistry), in line with other groove binder azo dyes. Finally, through the QM/MM calculations we found that the minor-groove binding mode interacting in zones rich in adenine and thymine was the model best suited to reproduce the experimental UV-vis response.

Trends in the Implementation of Advanced Plasmonic Materials in Optical Fiber Sensors (2010–2020)

In recent years, the interaction between light and metallic films have been proven to be a highly powerful tool for optical sensing applications. We have witnessed the development of highly sensitive commercial devices based on Surface Plasmon Resonances. There has been continuous effort to integrate this plasmonic sensing technology using micro and nanofabrication techniques with the optical fiber sensor world, trying to get better, smaller and cost-effective high performance sensing solutions. In this work, we present a review of the latest and more relevant scientific contributions to the optical fiber sensors field using plasmonic materials over the last decade. The combination of optical fiber technology with metallic micro and nanostructures that allow plasmonic interactions have opened a complete new and promising field of study. We review the main advances in the integration of such metallic micro/nanostructures onto the optical fibers, discuss the most promising fabrication techniques and show the new trends in physical, chemical and biological sensing applications.

New combination chemotherapy of cisplatin with an electron-donating compound for treatment of multiple cancers

Cisplatin is the first and most widely used platinum-based chemotherapy drug and is the cornerstone agent in treating a broad spectrum of cancers. However, its clinical application is often limited by severe toxic side effects and drug resistance. Based on the discovered dissociative electron transfer mechanism of cisplatin, a novel combination of cisplatin with [9-(2-carboxyphenyl)-6-diethylamino-3-xanthenylidene]-diethylammonium chloride (basic violet 10, BV10) is proposed to potentiate the chemotherapeutic effect of cisplatin. Here, we show that this combination enhances the anti-cancer effect of cisplatin in both in vitro cell lines and in vivo xenograft mouse models of cisplatin-sensitive and -resistant lung, ovarian and cervical cancers while introducing minimal additional toxic side effects. Furthermore, femtosecond time-resolved laser spectroscopic measurements demonstrate that cisplatin reacts with BV10 via an electron transfer mechanism. These results indicate that the combination of cisplatin with BV10 is promising for improving the chemotherapy of cancers with various extents of cisplatin resistance.

Analysis of decolorization potential of Myrothecium roridum in the light of its secretome and toxicological studies

To identify the enzymes potentially useful for the decolorization of azo dyes, the secretome of the ascomycetous fungus Myrothecium roridum IM6482 was studied by using a bottom-up proteomic approach. Among the identified proteins, the most promising for dye removal was laccase, which decolorized respectively, 66, 91, 79, and 80% of Acid Blue 113 (AB 113), Acid Red 27 (AR 27), Direct Blue 14 (DB 14), and Acid Orange 7 (AO 7). The degradation of dyes was enhanced at the wide range of pH from 4 to 8. The addition of redox mediators allowed eliminating AB 113 in concentrations up to 400 mg/L and decolorization of the simulated textile effluent. Microbial toxicity and phytotoxicity tests indicated that dyes are converted into low-toxicity metabolites. This is the first insight into the M. roridum secretome, its identification and its application for removal of select azo dyes. Obtained results extended knowledge concerning biodegradative potential of ascomycetous, ligninolytic fungi and will contribute to the improvement of dye removal by fungi.

Rhodamine B induces oxidative stress and cervical epithelial cell proliferation in the uterus

This study aimed to investigate the effect of Rhodamine B exposure on oxidative stress and cervical epithelial cells proliferation in the uterus. Twenty eight female Wistar albino rats were divided into four groups (n = 7 each): one control (untreated) group; and three Rhodamine B groups at several doses (4.5, 9, 18 mg/200 g body weight/day) for 36 days. Colometric analysis of malondialdehyde (MDA) level as a marker of lipid peroxidation and histological analysis of the cervical epithelial cells proliferation was performed. The MDA levels and proliferation of epithelial cells were significantly higher in all Rhodamine B groups compared to control group (P < 0.05). The MDA levels were increased in a dose-dependent manner in the Rhodamine B groups. Moreover, the proliferation of epithelial cells was also increased by Rhodamine B in a dose-dependent manner. In conclusion, subchronic Rhodamine B administration induces lipid peroxidation and cervical epithelial cells proliferation in a dose dependent manner.

In vitro genotoxicity evaluation of 4-carboxyl-2,6-dinitrophenylazohydroxynaphthalenes using human lymphocytes

The genotoxicity of a new monoazo dye series, 4-carboxyl-2,6-dinitrophenylazohydroxynaphthalenes has been evaluated using human lymphocytes by alkaline comet assay. Freshly isolated human lymphocytes were exposed to the dyes (AZ-01, -02, -03 and -04) at concentrations ranging from 0 to 500 μM for 3h at 37 °C. Appropriate negative (culture medium) and positive (100 μM methyl methane sulfonate) controls were set up alongside with the dye-treated cells. Comet assay was performed to assess the extent of DNA damage. The four dyes gave varying results with respect to the parameters of DNA damage studied. AZ-01 showed concentration-dependent DNA damage (% Tail DNA) while lower concentrations (31.25-62.5 μM) did not produce any significant difference in the tail extent moment. AZ-02, the positional isomer of AZ-01, gave non-genotoxic effects at lower concentrations for the two DNA parameters. AZ-03 and AZ-04 (possessing additional C-7 substituents) did not produce significant genotoxic effect at all concentrations relative to the negative control. Two of these monoazo dyes show the potential of being used as edible colorants. The results revealed that genotoxicity of congeneric dyes bear a direct relationship to their chemical structure.

Removal of the hazardous dye rhodamine B through photocatalytic and adsorption treatments

This paper reports on photocatalytic and adsorptive treatment of a hazardous xanthene dye, Rohdamine B, in wastewater. The photocatalytic degradation was carried out in the presence of the catalyst TiO(2) and the effects of pH, concentration of the dye, amount of TiO(2), temperature and electron acceptor H(2)O(2) on the degradation process were observed. It was found that photocatalytic degradation by TiO(2) is an effective, economical and faster mode of removing Rohdamine B from aqueous solutions. Attempts were also made to utilize activated carbon and rice husk as potential adsorbents to remove Rhodamine B from wastewater. The adsorption studies were carried out at 40, 50 and 60 degrees C, and the effects of pH, temperature, amount of adsorbents, concentration of adsorbate, etc., on the adsorption were measured. On the basis of adsorption data the Langmuir and Freundlich adsorption isotherm models were also confirmed. The adsorption isotherm constants thus obtained were employed to calculate thermodynamic parameters like Gibb's free energy, change in enthalpy and entropy. In order to observe the quality of wastewater COD measurements were also carried out before and after the treatments. A significant decrease in the COD values was observed, which clearly indicates that both photocatalytic and adsorption methods offer good potential to remove Rhodamine B from industrial effluents.