The challenge of testing chemicals for potential carcinogenicity using multiple short-term assays: An analysis of a proposed test battery for hair dyes

Photocatalytic Activity of Revolutionary Galaxaura elongata, Turbinaria ornata, and Enteromorpha flexuosa's Bio-Capped Silver Nanoparticles for Industrial Wastewater Treatment

More suitable wastewater treatment schemes need to be developed to get rid of harmful dyes and pigments before they are discharged, primarily from apparel and textile factories, into water bodies. Silver nanoparticles (Ag-NPs) are very effective, reductive nanocatalysts that can degrade many organic dyes. In this study, Ag-NPs are stabilized and capped with bioactive compounds such as Galaxaura elongata, Turbinaria ornata, and Enteromorpha flexuosa from marine macroalgae extracts to produce Ag[GE], Ag[TE], and Ag[EE] NPs. The reduction of Ag ions and the production of Ag[GE], Ag[TE], and Ag[EE] NPs have been substantiated by UV-Vis spectroscopy, SEM, EDX, and XRD tests. The NPs are sphere and crystalline shaped in nature with dimensions ranging from 20 to 25 nm. The biosynthesized Ag[GE], Ag[TE], Ag[EE] NPs were applied to photodegrade hazardous pigments such as methylene blue, Congo red, safranine O, and crystal violet under sunlight irradiation. In addition to the stability analysis, various experimental parameters, including dye concentration, exposure period, photocatalyst dose, and temperature, were optimized to achieve 100% photodegradation of the dyes. Moreover, the thermodynamic and kinetic parameters were calculated and the impact of scavengers on the photocatalytic mechanism was also investigated.

Comparison of activated carbon and iron/cerium modified activated carbon to remove methylene blue from wastewater

The methylene blue (MB) removal abilities of raw activated carbon and iron/cerium modified raw activated carbon (Fe-Ce-AC) by adsorption were researched and compared. The characteristics of Fe-Ce-AC were examined by N₂ adsorption, zeta potential measurement, FTIR, Raman, XRD, XPS, SEM and EDS. After modification, the following phenomena occurred: The BET surface area, average pore diameter and total pore volume decreased; the degree of graphitization also decreased. Moreover, the presence of Fe₃O₄ led to Fe-Ce-AC having magnetic properties, which makes it easy to separate from dye wastewater in an external magnetic field and subsequently recycle. In addition, the equilibrium isotherms and kinetics of MB adsorption on raw activated carbon and Fe-Ce-AC were systematically examined. The equilibrium adsorption data indicated that the adsorption behavior followed the Langmuir isotherm, and the pseudo-second-order model matched the kinetic data well. Compared with raw activated carbon, the maximum monolayer adsorption capacity of Fe-Ce-AC increased by 27.31%. According to the experimental results, Fe-Ce-AC can be used as an effective adsorbent for the removal of MB from dye wastewater.

Cationic surfactant-modified biosorption of anionic dyes by dried Rhizopus arrhizus

The biosorption of an anionic dye Remazol Black B onto a filamentous, dried fungus, Rhizopus arrhizus, was studied in the presence of the cationic surfactant cetyl trimethyl ammonium bromide (CTAB), which was used as a pH shifter. Without surfactant, the maximum dye uptake capacity was achieved at pH 2.0 and was 434.0 mg dye g^-1 dried fungal biomass. Again, without surfactant, the highest dye uptake capacity, 27.8 mg dye g^-1 dried biomass, occurred at pH 8.0 calculated from the Langmuir adsorption model. Addition of CTAB changed the pH at which the highest dye uptake was obtained. At an initial pH of 8.0 with different CTAB concentrations, the dye uptake capacity increased from 27.8 to 500.0 mg dye g^-1 dried biomass. Furthermore, when 200 mg L^-1 surfactant was added to the biosorption medium at pH 8.0, the amount of dye removed increased significantly. Four equilibrium adsorption models were applied to the results. The applicability of each isotherm was determined using regression correlation and fitting curves. According to the Langmuir model, without surfactant, the highest dye removal capacity at pH 8.0 was found to be 27.8 mg dye g^-1 dried biomass, rising to 500.0 mg g^-1 dried biomass with 200 mg L^-1 CTAB.

Cytotoxic and genotoxic effects of two hair dyes used in the formulation of black color

According to the International Agency for Research on Cancer (IARC), some hair dyes are considered mutagenic and carcinogenic in in vitro assays and exposed human populations. Epidemiological studies indicate that hairdressers occupationally exposed to hair dyes have a higher risk of developing bladder cancer. In Brazil, 26% of the adults use hair dye. In this study, we investigated the toxic effects of two hair dyes, Basic Red 51 (BR51) and Basic Brown 17 (BB17), which are temporary dyes of the azo group (R-N=N-R'), used in the composition of the black hair dye. To this end, MTT and trypan blue assays (cytotoxicity), comet and micronucleus assay (genotoxicity) were applied, with HepG2 cells. For cytotoxic assessment, dyes were tested in serial dilutions, being the highest concentrations those used in the commercial formula for hair dyes. For genotoxic assessment concentrations were selected according to cell viability. Results showed that both dyes induced significant cytotoxic and genotoxic effects in the cells, in concentrations much lower than those used in the commercial formula. Genotoxic effects could be related to the azo structure present in the composition of the dyes, which is known as mutagenic and carcinogenic. These results point to the hazard of the hair dye exposure to human health.

Removal of safranin-O dye from aqueous solution using modified red mud: kinetics and equilibrium studies

Adsorption of safranin-O dye on SDS modified red mud at different pH.

Application of cupuassu shell as biosorbent for the removal of textile dyes from aqueous solution

The cupuassu shell (Theobroma grandiflorum) which is a food residue was used in its natural form as biosorbent for the removal of C.I. Reactive Red 194 and C.I. Direct Blue 53 dyes from aqueous solutions. This biosorbent was characterized by infrared spectroscopy, scanning electron microscopy, and nitrogen adsorption/desorption curves. The effects of pH, biosorbent dosage and shaking time on biosorption capacities were studied. In acidic pH region (pH 2.0) the biosorption of the dyes were favorable. The contact time required to obtain the equilibrium was 8 and 18 h at 298 K, for Reactive Red 194 and Direct Blue 53, respectively. The Avrami fractionary-order kinetic model provided the best fit to experimental data compared with pseudo-first-order, pseudo-second-order and chemisorption kinetic adsorption models. The equilibrium data were fitted to Langmuir, Freundlich, Sips and Radke-Prausnitz isotherm models. For both dyes the equilibrium data were best fitted to the Sips isotherm model.

Mammary carcinogen-protein binding potentials: novel and biologically relevant structure-activity relationship model descriptors

Previously, SAR models for carcinogenesis used descriptors that are essentially chemical descriptors. Herein we report the development of models with the cat-SAR expert system using biological descriptors (i.e., ligand-receptor interactions) rat mammary carcinogens. These new descriptors are derived from the virtual screening for ligand-receptor interactions of carcinogens, non-carcinogens, and mammary carcinogens to a set of 5494 target proteins. Leave-one-out validations of the ligand mammary carcinogen-non-carcinogen model had a concordance between experimental and predicted results of 71%, and the mammary carcinogen-non-mammary carcinogen model was 72% concordant. The development of a hybrid fragment-ligand model improved the concordances to 85 and 83%, respectively. In a separate external validation exercise, hybrid fragment-ligand models had concordances of 81 and 76%. Analyses of example rat mammary carcinogens including the food mutagen and oestrogenic compound PhIP, the herbicide atrazine, and the drug indomethacin; the ligand model identified a number of proteins associated with each compound that had previously been referenced in Medline in conjunction with the test chemical and separately with association to breast cancer. This new modelling approach can enhance model predictivity and help bridge the gap between chemical structure and carcinogenic activity by descriptors that are related to biological targets.