RESUMEN
Silver nanoparticles (AgNPs) pose a high risk of exposure to the natural environment owing to their extensive usage in various consumer products. In the present study we attempted to understand the harmful effect of AgNPs at environmentally relevant low concentration levels (≤1ppm) towards two different freshwater bacterial isolates and their consortium. The standard plate count assay suggested that the AgNPs were toxic towards the fresh water bacterial isolates as well as the consortium, though toxicity was significantly reduced for the cells in the consortium. The oxidative stress assessment and membrane permeability studies corroborated with the toxicity data. The detailed electron microscopic studies suggested the cell degrading potential of the AgNPs, and the FT-IR studies confirmed the involvement of the surface groups in the toxic effects. No significant ion leaching from the AgNPs was observed at the applied concentration levels signifying the dominant role of the particle size, and size distribution in bacterial toxicity. The reduced toxicity for the cells in the consortium than the individual isolates has major significance in further studies on the ecotoxicity of the AgNPs.
Asunto(s)
Nanopartículas del Metal/toxicidad , Consorcios Microbianos/efectos de los fármacos , Plata/toxicidad , Permeabilidad de la Membrana Celular/efectos de los fármacos , Agua Dulce/microbiología , Microscopía Electrónica de Rastreo , Microscopía Electrónica de Transmisión , Estrés Oxidativo/efectos de los fármacos , Tamaño de la Partícula , Espectroscopía Infrarroja por Transformada de Fourier , Pruebas de ToxicidadRESUMEN
Crystalline structure of nanoparticles may influence their physicochemical behaviour as well as their toxicological impact on biota. The differences in orientation of the atoms result in the variations in chemical stability. Thus, toxicological impacts of different crystalline phases of aluminium oxide nanoparticles are expected to vary. The present study brings out a comparative toxicity analysis of γ-phase and α-phase aluminium oxide nanoparticles of comparable hydrodynamic size range towards a freshwater bacterial isolate Bacillus licheniformis at low exposure concentrations (5, 1, 0.5 and 0.05 µg/mL). Upon 2-h exposure, the α-aluminium oxide particles showed lower toxicity than the γ-phase aluminium oxide. The lower level of oxidative stress generation and cell membrane damage in case of the α-phase aluminium oxide nanoparticles substantiated the toxicity results. The involvement of protein, lipopolysaccharides in nanoparticle-cell surface interaction, was noted in both the cases. To conclude, the crystallinity of aluminium oxide nanoparticles played an important role in the interaction and the toxicity response.
Asunto(s)
Óxido de Aluminio/toxicidad , Bacillus/efectos de los fármacos , Nanopartículas del Metal/toxicidad , Contaminantes Químicos del Agua/toxicidad , Membrana Celular/metabolismo , Relación Dosis-Respuesta a Droga , Agua Dulce , Iones , L-Lactato Deshidrogenasa/metabolismo , Luz , Nanotecnología , Estrés Oxidativo , Tamaño de la Partícula , Especies Reactivas de Oxígeno/metabolismo , Dispersión de Radiación , Espectroscopía Infrarroja por Transformada de Fourier , Pruebas de Toxicidad , Difracción de Rayos XRESUMEN
This study on a microcosm, brings out the temporal changes in physico-chemical behavior of aluminum oxide nanoparticles (for a period of 210 days), at environmentally relevant concentrations (1000 µg/L and below). The dynamics of particle behavior in terms of mean hydrodynamic diameter, specific surface area and dissolution of soluble aluminum and, their possible ecological implications have been presented in this study. A thorough statistical analysis brings out nanoparticle behavior, where a rapid aggregation of particles (79±13 nm at 0 h to 1464±80 nm at 48 h), with a decrease in specific surface area (32 m2/g at 0 h to 1.7 m2/g at 48 h) was observed. Ion release profile indicated a significant increase in soluble aluminum concentration only after 36 h (277±15 µg/L at 0 h to 462±3 µg/L at 36 h) which reduced over a period of 60 days (279±20 µg/L). A differential response at 1000 µg/L concentration was observed, short term exposure (5 days) showed an immediate effect on the resident algal population (â¼25% decreased viability) and the long term (7 months/210 days) exposure showed a gradual recovery. Thus, nanomaterials may not have the stipulated toxic response, at low concentration and longer standing period, presumably owing to the complexity of the natural systems.
Asunto(s)
Óxido de Aluminio/química , Monitoreo del Ambiente , Agua Dulce/química , Nanopartículas/química , Aluminio/análisis , Óxido de Aluminio/análisis , Óxido de Aluminio/metabolismo , Óxido de Aluminio/toxicidad , Chlorophyta/efectos de los fármacos , Hidrodinámica , Concentración de Iones de Hidrógeno , Nanopartículas/análisis , Nanopartículas/toxicidad , Nanopartículas/ultraestructura , Factores de Tiempo , Contaminantes Químicos del Agua/análisis , Contaminantes Químicos del Agua/química , Contaminantes Químicos del Agua/toxicidadRESUMEN
The cytotoxicity of Al(2)O(3) nanoparticles (NP) at very low exposure levels (1 µg/mL and less) to a dominant bacterial isolate from freshwater (lake water), Bacillus licheniformis, was examined. Sterile lake water was directly used as a test medium or matrix to simulate the freshwater environment. Exposure to 1 µg/mL Al(2)O(3) NP for 2 h caused a 17% decrease in cell viability (as determined by plate count and MTT assay). During the test period, the particles were found to be stable against aggregation in the matrix and exerted a nano-size effect on the exposed test organisms. The decrease in cell viability was proven not to be due to the release of Al(3+) ions from the nanoparticles in the dispersion. The zeta potential and FT-IR analyses suggested that the surface charge based attachment of nanoparticles on to the bacterial cell wall was responsible for flocculation leading to toxicity. The cell wall damage confirmed through SEM and the lipid peroxidation assay also contributed toward toxicity. This study warns of possible ecotoxicity of nanoparticles even at environmentally relevant concentrations. However, detailed studies need to be carried out to establish probable mechanistic aspects of this low concentration toxicity phenomenon.
Asunto(s)
Óxido de Aluminio/toxicidad , Bacillus/efectos de los fármacos , Contaminación Ambiental/prevención & control , Agua Dulce/química , Nanopartículas del Metal/toxicidad , Adsorción , Óxido de Aluminio/efectos adversos , Óxido de Aluminio/metabolismo , Bacillus/crecimiento & desarrollo , Bacillus/metabolismo , Adhesión Bacteriana , Pared Celular/efectos de los fármacos , Pared Celular/metabolismo , Relación Dosis-Respuesta a Droga , Peroxidación de Lípido/efectos de los fármacos , Nanopartículas del Metal/química , Microscopía Electrónica de Rastreo , Tamaño de la Partícula , Espectroscopía Infrarroja por Transformada de Fourier , Propiedades de SuperficieRESUMEN
In the present study, we tested whether bioaccumulation in specific tissues of Daphnia magna could explain silver nanoparticle (AgNP) toxicity. Daphnids were exposed to different concentrations of well-suspended AgNPs and AgNO3 . The accumulations of Ag in the whole body, gut, and nongut tissues, as well as the mortality of daphnids, were recorded over a period of 7 d. Regression analysis showed a higher degree of positive correlation between the concentration of Ag in the nongut tissues than gut tissues and the mortality of daphnids. The results strongly suggested that the toxicity of AgNPs could be better explained in terms of bioaccumulation of AgNPs in the nongut tissues. We further tested the maternal transfer of AgNPs in daphnids into the next generation using radioactive tracers, which were able to detect as low as 1.0 to 3.2% of total accumulated Ag transferred to the neonates. The AgNPs significantly affected the reproduction process during the first 2 broods after exposure, whereas AgNO3 only had significant effects on the first brood. It is possible that AgNPs have longer adverse effects than AgNO3 on the reproduction of Daphnia. The present study identified the sensitive site of AgNP toxic action in daphnids and documented the extent of maternal transfer and the significant influence of AgNPs on the reproduction of daphnids. Environ Toxicol Chem 2017;36:3359-3366. © 2017 SETAC.
Asunto(s)
Daphnia/efectos de los fármacos , Nanopartículas del Metal/toxicidad , Plata/toxicidad , Animales , Daphnia/metabolismo , Reproducción/efectos de los fármacos , Nitrato de Plata/toxicidadRESUMEN
The transfer of nanoparticles through the food chain can lead to bioaccumulation and biomagnification resulting in a long term negative impact on the ecosystem functions. The primary objective of this study was evaluation of aluminium oxide nanoparticles transfer from primary producers to primary consumers. A simple set up consisting of a primary producer (Chlorella ellipsoides) and a primary consumer (Ceriodaphnia dubia) was used. Here, C. ellipsoides were exposed to the varying concentrations of the nanoparticles ranging from 20 to 120µg/mL (196 to 1176µM) for 48h and the infested algal cells were used as the feed to C. dubia. The bioaccumulation of the nanoparticles into the daphnids was noted and the biomagnification factors were computed. The exposure was noted to cause subtle alterations in the feeding behaviour of the daphnids. This might have long term consequences in the energy flow through the food chain. The reproductive behaviour of the daphnids remained unaffected upon exposure to nanoparticle infested algal feed. Distinct observations at ultra-structural scale using transmission electron microscopy provided visual evidences for the disrupted feeding behaviour upon exposure to nanoparticle treated algae. Internalization of nanoparticle like inclusion bodies in the intracellular space of algae was also detected. The findings were further substantiated by a detailed analysis of hydrodynamic stability, bioavailability and dissolution of ions from the nanoparticles over the exposure period. Altogether, the study brings out the first of its kind of observation of trophic transfer potential/behaviour of aluminium oxide nanoparticles and its probable impacts on the energy flow in the fresh water aquatic ecosystem.
Asunto(s)
Óxido de Aluminio/metabolismo , Chlorella/metabolismo , Cladóceros/metabolismo , Cadena Alimentaria , Nanopartículas/metabolismo , Contaminantes Químicos del Agua/metabolismo , Óxido de Aluminio/análisis , Óxido de Aluminio/toxicidad , Animales , Chlorella/química , Chlorella/efectos de los fármacos , Cladóceros/química , Cladóceros/efectos de los fármacos , Conducta Alimentaria/efectos de los fármacos , Microscopía Electrónica de Transmisión , Nanopartículas/análisis , Nanopartículas/toxicidad , Conducta Sexual Animal/efectos de los fármacos , Contaminantes Químicos del Agua/análisis , Contaminantes Químicos del Agua/toxicidadRESUMEN
The extensive environmental exposure of engineered metal oxide nanoparticles (NPs) may result in their bioaccumulation in aquatic organisms leading to their biotransfer in a food chain through various routes in a freshwater ecosystem. The present study focuses on the possible modes of TiO2 NP trophic transfer to Ceriodaphnia dubia, in presence and/absence of its diet, Scenedesmus obliquus (primary producer). The acute exposure studies (48h) were designed to have daphnids exposed to (i) the free NPs, (ii) both the free and the algae-borne NPs; and (iii) only the algae-borne NPs in separate tests to understand the possible routes of NP transfer. The dietary uptake of TiO2 NPs (algae-borne) was found to be the primary route for NP biotransfer with â¼70% of total NP uptake. Interestingly, in a separate study it was noticed that the NPs coated with algal exudates were easily taken up by daphnids as compared to pristine NPs of same concentrations, leading to their higher bioaccumulation. A chronic toxicity study, where daphnids were exposed to both free and algae-borne NPs for 21 days was undertaken to comprehend the TiO2 NP effect on daphnia growth and reproduction upon chronic exposure and also the bioaccumulation potential. Both acute and chronic exposure studies suggested higher bioaccumulation of TiO2 in daphnids when the particles were less toxic to the diet (algae).
Asunto(s)
Chlorophyta/metabolismo , Daphnia , Cadena Alimentaria , Nanopartículas/metabolismo , Nanopartículas/toxicidad , Titanio/metabolismo , Titanio/toxicidad , Animales , Organismos Acuáticos/química , Organismos Acuáticos/efectos de los fármacos , Organismos Acuáticos/metabolismo , Chlorophyta/química , Daphnia/efectos de los fármacos , Daphnia/metabolismo , Titanio/análisis , Contaminantes Químicos del Agua/análisis , Contaminantes Químicos del Agua/metabolismo , Contaminantes Químicos del Agua/toxicidadRESUMEN
The reactivity and toxicity of the soluble toxicants in the presence of the engineered nanomaterials is not well explored. In this study, the probable effects of TiO2 and Al2O3 nanoparticles (n-TiO2, n-Al2O3) on the toxicity of Cr(VI) were assessed with the dominant freshwater algae, Scenedesmus obliquus, in a low range of exposure concentrations (0.05, 0.5 and 1µg/mL). In the presence of 0.05µg/mL n-TiO2, the toxicity of Cr(VI) decreased considerably, which was presumably due to the Cr(VI) adsorption on the nanoparticle surface leading to its aggregation and precipitation. The elevated n-TiO2 concentrations (0.5 and 1µg/mL) did not significantly influence Cr(VI) bio-availability, and a dose dependent toxicity of Cr(VI) was observed. On the other hand, n-Al2O3 did not have any significant effect on the Cr(VI) toxicity. The microscopic observations presented additional information on the morphological changes of the algal cells in the presence of the binary toxicants. The generation of reactive oxygen species (ROS) suggested contribution of oxidative stress on toxicity and LDH release confirmed membrane permeability of algal cells upon stress.
Asunto(s)
Óxido de Aluminio/toxicidad , Cromo/toxicidad , Nanopartículas del Metal/toxicidad , Scenedesmus/efectos de los fármacos , Titanio/toxicidad , Contaminantes Químicos del Agua/toxicidad , Interacciones Farmacológicas , Agua Dulce , Estrés Oxidativo/efectos de los fármacos , Especies Reactivas de Oxígeno/metabolismoRESUMEN
The industrial production and commercial applications of titanium dioxide nanoparticles have increased considerably in recent times, which has increased the probability of environmental contamination with these agents and their adverse effects on living systems. This study was designed to assess the genotoxicity potential of TiO2 NPs at high exposure concentrations, its bio-uptake, and the oxidative stress it generated, a recognised cause of genotoxicity. Allium cepa root tips were treated with TiO2 NP dispersions at four different concentrations (12.5, 25, 50, 100 µg/mL). A dose dependant decrease in the mitotic index (69 to 21) and an increase in the number of distinctive chromosomal aberrations were observed. Optical, fluorescence and confocal laser scanning microscopy revealed chromosomal aberrations, including chromosomal breaks and sticky, multipolar, and laggard chromosomes, and micronucleus formation. The chromosomal aberrations and DNA damage were also validated by the comet assay. The bio-uptake of TiO2 in particulate form was the key cause of reactive oxygen species generation, which in turn was probably the cause of the DNA aberrations and genotoxicity observed in this study.
Asunto(s)
Nanopartículas del Metal/toxicidad , Cebollas/citología , Raíces de Plantas/citología , Titanio/toxicidad , Toxicología/métodos , Aberraciones Cromosómicas/inducido químicamente , Ensayo Cometa , Daño del ADN , Nanopartículas del Metal/administración & dosificación , Nanopartículas del Metal/química , Micronúcleos con Defecto Cromosómico/inducido químicamente , Microscopía Confocal , Estrés Oxidativo , Titanio/químicaRESUMEN
The ever increasing industrial and consumer applications of titanium dioxide nanoparticles (TiO2 NPs) raise concern over the possible risk associated with their environmental exposure. Still, the knowledge regarding nanoparticle behavior in a freshwater ecosystem is lacking. The current study focuses on the toxicity of TiO2 NPs towards Ceriodaphnia dubia (a dominant daphnid isolated from the freshwater) under two different conditions; (1) light and dark photoperiod (16:8 h) and (2) continuous dark conditions, for a period of 48 h. An increase in toxicity was observed with an increase in the concentration, until a certain threshold level (under both photoperiod and dark conditions), and beyond which, reduction was noted. The decrease in toxicity would have resulted from the aggregation and settling of NPs, making them less bioavailable. The oxidative stress was one of the major contributors towards cytotoxicity under both photoperiod and dark conditions. The slow depuration of TiO2 NPs under the photoperiod conditions confirmed a higher NP bioaccumulation and thus a higher bioconcentration factor (BCF) compared to dark conditions. The transmission electron micrographs confirmed the bioaccumulation of NPs and damage of tissues in the gut lining.
Asunto(s)
Cladóceros/efectos de los fármacos , Tracto Gastrointestinal/efectos de los fármacos , Nanopartículas del Metal/toxicidad , Titanio/toxicidad , Contaminantes Químicos del Agua/toxicidad , Animales , Cladóceros/fisiología , Cladóceros/ultraestructura , Agua Dulce , Tracto Gastrointestinal/fisiología , Tracto Gastrointestinal/ultraestructura , Luz , Estrés Oxidativo , FotoperiodoRESUMEN
Growing nanomaterials based consumer applications have raised concerns about their potential release into the aquatic ecosystems and the consequent toxicological impacts. So environmental monitoring of the nanomaterials in aqueous systems becomes imperative. The current study reveals the potential of Ceriodaphnia dubia (C. dubia) as a bio-indicator for aluminum oxide nanoparticles in a fresh water aquatic ecosystem where it occupies an important ecological niche as a primary consumer. This study aims to investigate the aluminium oxide nanoparticle induced acute toxicity on Ceriodaphnia dubia in a freshwater system. The bioavailability of the aluminum oxide nanoparticles has been studied with respect to their aggregation behavior in the system and correlated with the toxicity endpoints. The oxidative stress generated by the particles contributed greatly toward their toxicity. The crucial role of leached aluminium ion mediated toxicity in the later phases (48 h and 72 h) in conjunction with the effects from the nano-sized particles in the initial phases (24 h) puts forth the dynamics of nanotoxicity in the test system. The internalization of nanoparticles (both gross and systemic uptake) as substantiated through the transmission electron microscopy (TEM) and inductively coupled plasma optical emission spectral (ICP-OES) analysis was another major contributor toward acute toxicity. Concluding the present study, Ceriodaphnia dubia can be a promising candidate for bio-monitoring the aluminium oxide nanoparticles in a fresh water system.
Asunto(s)
Óxido de Aluminio/toxicidad , Cladóceros/efectos de los fármacos , Agua Dulce/química , Nanopartículas del Metal/toxicidad , Contaminantes Químicos del Agua/toxicidad , Calidad del Agua/normas , Óxido de Aluminio/química , Animales , Disponibilidad Biológica , Cladóceros/metabolismo , Monitoreo del Ambiente/métodos , Nanopartículas del Metal/química , Nanopartículas del Metal/ultraestructura , Estrés Oxidativo , Especies Reactivas de Oxígeno/metabolismo , Solubilidad , Difracción de Rayos XRESUMEN
The growing commercial applications had brought aluminium oxide nanoparticles under toxicologists' purview. In the present study, the cytotoxicity of two different sized aluminium oxide nanoparticles (ANP(1), mean hydrodynamic diameter 82.6±22nm and ANP(2), mean hydrodynamic diameter 246.9±39nm) towards freshwater algal isolate Chlorella ellipsoids at low exposure levels (≤1µg/mL) using sterile lake water as the test medium was assessed. The dissolution of alumina nanoparticles and consequent contribution towards toxicity remained largely unexplored owing to its presumed insoluble nature. Herein, the leached Al(3+) ion mediated toxicity has been studied along with direct particulate toxicity to bring out the dynamics of toxicity through colloidal stability, biochemical, spectroscopic and microscopic analyses. The mean hydrodynamic diameter increased with time both for ANP(1) [82.6±22nm (0h) to 246.3±59nm (24h), to 1204±140nm (72h)] and ANP(2) [246.9±39nm (0h) to 368.28±48nm (24h), to 1225.96±186nm (72h)] signifying decreased relative abundance of submicron sized particles (<1000nm). The detailed cytotoxicity assays showed a significant reduction in the viability dependent on dose and exposure. A significant increase in ROS and LDH levels were noted for both ANPs at 1µg/mL concentration. The zeta potential and FT-IR analyses suggested surface chemical interaction between nanoparticles and algal cells. The substantial morphological changes and cell wall damage were confirmed through microscopic analyses (SEM, TEM, and CLSM). At 72h, significant Al(3+) ion release in the test medium [0.092µg/mL for ANP(1), and 0.19µg/mL for ANP(2)] was noted, and the resulting suspension containing leached ions caused significant cytotoxicity, revealing a substantial ionic contribution. This study indicates that both the nano-size and ionic dissolution play a significant role in the cytotoxicity of ANPs towards freshwater algae, and the exposure period largely determines the prevalent mode of nano-toxicity.
Asunto(s)
Óxido de Aluminio/toxicidad , Chlorella/efectos de los fármacos , Nanopartículas del Metal/toxicidad , Contaminantes Químicos del Agua/toxicidad , Relación Dosis-Respuesta a Droga , Tamaño de la Partícula , Espectroscopía Infrarroja por Transformada de FourierRESUMEN
In the current study, two aspects concerning (i) the cytotoxicity potential of TiO2 nanoparticles (NPs) toward freshwater algal isolate Scenedesmus obliquus and (ii) the potential detoxification of NPs by the microalgae were assessed under light (UV-illumination) and dark conditions at low exposure levels (≤1 µg/mL), using sterile freshwater as the test medium. The statistically significant reduction in cell viability, increase in reactive oxygen species production and membrane permeability (light vs. dark) suggested photo-induced toxicity of TiO2 NPs. The electron micrographs demonstrated adsorption of the NPs onto the cell surface and substantiated their internalization/uptake. The fluorescence micrographs and the confocal laser scanning (CLSM) images suggested the absence of a definite/intact nucleus in the light treated cells pointing toward the probable genotoxic effects of NPs. In a separate three cycle experiment, a continuous decrease in the cytotoxicity was observed, whereas, at the end of each cycle only fresh algae were added to the supernatant containing NPs from the previous cycle. The decreasing concentrations of the NPs in the subsequent cycles owing to agglomeration-sedimentation processes exacerbated by the algal interactions played a crucial role in the detoxification. In addition, the exo-polymeric substances produced by the cells could have rendered the available NPs less reactive, thereby, enhancing the detoxification effects.
Asunto(s)
Contaminantes Ambientales/toxicidad , Nanopartículas del Metal/toxicidad , Scenedesmus/efectos de los fármacos , Titanio/toxicidad , Adsorción , Biodegradación Ambiental , Recuento de Células , Permeabilidad de la Membrana Celular/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Agua Dulce , Nanopartículas del Metal/ultraestructura , Microscopía Electrónica de Rastreo , Tamaño de la Partícula , Especies Reactivas de Oxígeno/metabolismo , Scenedesmus/ultraestructura , Sales de Tetrazolio , Tiazoles , Pruebas de Toxicidad , Rayos UltravioletaRESUMEN
Increasing use of zinc oxide nanoparticles (ZnO NP) in consumer products may enhance its release into the environment. Phytotoxicity study is important to understand its possible environmental impact. Allium cepa (Onion bulb) is the best model organism to study genetic toxicology of nanoparticles. Here we have reported cytogenetic and genotoxic effects of ZnO NPs on the root cells of A. cepa. The effects of ZnO NPs on the mitotic index (MI), micronuclei index (MN index), chromosomal aberration index, and lipid peroxidation were determined through the hydroponic culturing of A. cepa. A. cepa roots were treated with the dispersions of ZnO NPs at four different concentrations (25, 50, 75, and 100 µg ml(-1)). With the increasing concentrations of ZnO NPs MI decreased with the increase of pycnotic cells, on the other hand MN and chromosomal aberration index increased. The frequency of micronucleated cells was higher in ZnO NPs treated cells as compared to control (deionized distilled water). The number of cells in each mitotic phase changed upon ZnO NPs treatment. The effect of ZnO NPs on lipid peroxidation as examined by measuring TBARS concentration was evident at all the concentrations compared to bulk ZnO. The TEM image showed internalization of ZnO NPs like particles. SEM image of treated A. cepa demonstrated that the internalized nanoparticles agglomerated depending on the physico-chemical environment inside the cell. Our results demonstrated that ZnO NPs can be a clastogenic/genotoxic and cytotoxic agent. In conclusion, the A. cepa cytogenetic test can be used for the genotoxicity monitoring of novel nanomaterials like ZnO NPs, which is used in many consumer products.