Claudio Martín Jonsson

Toxicity assessment of TiO2 nanoparticles in zebrafish embryos under different exposure conditions

The popularity of TiO2 nanoparticles (nano-TiO2) lies in their wide range of nanotechnological applications, together with low toxicity. Meanwhile, recent studies have shown that the photocatalytic properties of this material can result in alterations in their behavior in the environment, causing effects that have not yet been fully elucidated. The objective of this study was to evaluate the toxicity of two formulations of nano-TiO2 under different illumination conditions, using an experimental model coherent with the principle of the three Rs of alternative animal experimentation (reduction, refinement, and replacement). Embryos of the fish Danio rerio were exposed for 96h to different concentrations of nano-TiO2 in the form of anatase (TA) or an anatase/rutile mixture (TM), under either visible light or a combination of visible and ultraviolet light (UV). The acute toxicity and sublethal parameters evaluated included survival rates, malformation, hatching, equilibrium, and overall length of the larvae, together with biochemical biomarkers (specific activities of catalase (CAT), glutathione S-transferase (GST), and acid phosphatase (AP)). Both TA and TM caused accelerated hatching of the larvae. Under UV irradiation, there was greater mortality of the larvae of the groups exposed to TM, compared to those exposed to TA. Exposure to TM under UV irradiation altered the equilibrium of the larvae. Alterations in the activities of CAT and GST were indicative of oxidative stress, although no clear dose-response relationship was observed. The effects of nano-TiO2 appeared to depend on both the type of formulation and the illumination condition. The findings contribute to elucidation of the factors involved in the toxicity of these nanoparticles, as well as to the establishment of protocols for risk assessments of nanotechnology.

Fish exposure to nano-TiO2 under different experimental conditions: Methodological aspects for nanoecotoxicology investigations

The ecotoxicology of nano-TiO2 has been extensively studied in recent years; however, few toxicological investigations have considered the photocatalytic properties of the substance, which can increase its toxicity to aquatic biota. The aim of this work was to evaluate the effects on fish exposed to different nano-TiO2 concentrations and illumination conditions. The interaction of these variables was investigated by observing the survival of the organisms, together with biomarkers of biochemical and genetic alterations. Fish (Piaractus mesopotamicus) were exposed for 96 h to 0, 1, 10, and 100 mg/L of nano-TiO2, under visible light, and visible light with ultraviolet (UV) light (22.47 J/cm(2)/h). The following biomarkers of oxidative stress were monitored in the liver: concentrations of lipid hydroperoxide and carbonylated protein, and specific activities of superoxide dismutase, catalase, and glutathione S-transferase. Other biomarkers of physiological function were also studied: the specific activities of acid phosphatase and Na,K-ATPase were analyzed in the liver and brain, respectively, and the concentration of metallothionein was measured in the gills. In addition, micronucleus and comet assays were performed with blood as genotoxic biomarkers. Nano-TiO2 caused no mortality under any of the conditions tested, but induced sublethal effects that were influenced by illumination condition. Under both illumination conditions tested, exposure to 100 mg/L showed an inhibition of acid phosphatase activity. Under visible light, there was an increase in metallothionein level in fish exposed to 1 mg/L of nano-TiO2. Under UV light, protein carbonylation was reduced in groups exposed to 1 and 10 mg/L, while nucleus alterations in erythrocytes were higher in fish exposed to 10 mg/L. As well as improving the understanding of nano-TiO2 toxicity, the findings demonstrated the importance of considering the experimental conditions in nanoecotoxicological tests. This work provides information for the development of protocols to study substances whose toxicity is affected by illumination conditions.

Acute toxicity of endosulfan to the fishHyphessobrycon bifasciatus andBrachydanio rerio

Acute toxicity of endosulfan to zebra fish (Brachydanio rerio) and yellow tetra (Hyphessobrycon bifasciatus) was determined by semi-static bioassay. The 24-h LC50 values were 2.6 (2.3–2.9) and 1.6 (1.3–2.1) μg/L forHyphessobrycon bifasciatus andBrachydanio rerio, respectively. Behavioral changes including hyperactivity, erratic swimming and convulsions were observed at the highest exposure levels. Histological studies showed predominant acute effects in the gills, with inflammatory infiltration necrosis and separation of respiratory gill epithelium. Degradation studies with endosulfan showed that both α- and β-isomers were very unstable under the test conditions, presenting half-lives of approximately 24 h.

Bioconcentration of the insecticide pyridaphenthion by the green algae Chlorella saccharophila

A study was undertaken to examine the uptake of the organophosphate insecticide pyridaphenthion in the chlorophyta Chlorella saccharophila. Algae cultures were exposed to the initial nominal concentration 10.0 mg l(-1) pyridaphention during seven days. The insecticide bioconcentrates in the biomass to the highest level of 441.5 +/- 25.9 mg kg(-1) on the fifth day of exposure and was followed by a decrease to 76.6 +/- 5.1 mg kg(-1) on the seventh day. A model was constructed to describe the dynamic process, which estimated a bioconcentration factor (BCF) equal to 28. The study demonstrates the potential of accumulation of pyridaphenthion in aquatic organisms and helps to expand the pyridaphenthion toxicity database. The replacement of fenitrothion by pyridaphenthion concerning their use in rice flooded cultures is discussed.

Acute toxicity and bioconcentration of fungicide tebuconazole in zebrafish (Danio rerio)

This research work investigated the bioconcentration of tebuconazole [(±)‐α‐[2‐(4‐chlorophenyl)ethyl]‐α‐(1,1‐dimethylethyl)‐1H‐1,2,4‐triazole‐1‐ethanol] fungicide in zebrafish (Danio rerio) under laboratory conditions and a first‐order kinetic pesticide dissipation in the water. The concentrations of tebuconazole fitted to an equivalent nonlinear kinetic type model which allowed the calculation of the following parameters: bioconcentration factor (38.80 L kg−1), time to reach maximum fish concentration (6 days), maximum concentration in fish (0.0075 μg mg−1), half‐life in fish (24 days) and time needed for the fish to eliminate 95% of the maximum concentration (105 days). These calculations permitted the establishment of theoretical reference limit values for human consumption of fish and the establishment of safe limits for the water pesticide concentration. The data would also be useful in safe strategies associated with fishery activities that are conducted in aquatic regions close to crops using tebuconazole. The information will contribute to enlarge the tebuconazole toxicokinetics database of aquatic organisms.

Chitosan nanoparticles loaded the herbicide paraquat: the influence of the aquatic humic substances on the colloidal stability and toxicity.

Polymeric nanoparticles have been developed for several applications, among them as carrier system of pesticides. However, few studies have investigated the fate of these materials in the environment in relation to colloidal stability and toxicity. In nature, humic substances are the main agents responsible for complexation with metals and organic compounds, as well as responsible for the dynamics of these nanoparticles in aquatic and terrestrial environments. In this context, the evaluation of the influence of aquatic humic substances (AHS) on the colloidal stability and toxicity of polymeric nanoparticles of chitosan/tripolyphosphate with or without paraquat was performed. In this study, the nanoparticles were prepared by the ionic gelation method and characterized by size distribution measurements (DLS and NTA), zeta potential, infrared and fluorescence spectroscopy. Allium cepa genotoxicity studies and ecotoxicity assays with the alga Pseudokirchneriella subcapitata were used to investigate the effect of aquatic humic substances (AHS) on the toxicity of this delivery system. No changes were observed in the physical-chemical stability of the nanoparticles due to the presence of AHS using DLS and NTA techniques. However some evidence of interaction between the nanoparticles and AHS was observed by infrared and fluorescence spectroscopies. The ecotoxicity and genotoxicity assays showed that humic substances can decrease the toxic effects of nanoparticles containing paraquat. These results are interesting because they are important for understanding the interaction of these nanostructured carrier systems with species present in aquatic ecosystems such as humic substances, and in this way, opening new perspectives for studies on the dynamics of these carrier systems in the ecosystem.

Extraction, partial characterization and susceptibility to Hg2+ of acid phosphatase from the microalgae Pseudokirchneriella subcapitata

Pseudokirchneriella subcapitata e uma alga verde unicelular amplamente distribuida em corpos d´agua e solos. Devido a sua natureza cosmopolita, seu uso e recomendado por protocolos nacionais e internacionais na realizacao de estudos de ecotoxicidade. A alteracao da atividade de fosfatases por agentes poluentes de origem agricola, como metais pesados, tem sido largamente usada como um biomarcador na avaliacao de risco e biomonitoramento. No presente trabalho foi comparada a extracao da fosfatase acida de P. subcapitata por diferentes metodos e estudada a sua estabilidade, especificidade por substratos, cinetica e efeito do Hg2+ no extrato bruto. O congelamento e descongelamento, associado com ultrassom, foi o metodo que proporcionou maior rendimento de extracao. A enzima, praticamente estavel por armazenamento a -20oC, durante aproximadamente seis meses, demonstrou uma atividade otima em pH 5 e um valor de Km para o p-nitrofenilfostato (pNPP) de 0,27 mM. Alguns substratos naturais foram hidrolisados com uma intensidade semelhante a do substrato sintetico pNPP. Diferentemente dos estudos de exposicao a curto prazo (24 horas), observou-se inibicao da atividade especifica nas culturas expostas durante 7 dias, com um valor de CE50 (concentracao de Hg2+ que promove 50% de decrescimo da atividade especifica) equivalente a 12,63 μM Hg2+.

Susceptibility of non-target invertebrates to Brazilian microbial pest control agents

Microbial pest control agents or entomopathogens have been considered an interesting alternative to use instead of chemical insecticides. Knowledge of ecotoxicity data is very important to predict the hazard of any product released in the environment and subsidize the regulation of these products by governmental agencies. In the present study four new Brazilian strains of Bacillus and one fungus were tested to evaluate their acute toxicity to the microcrustacean Daphnia similis, the snail Biomphalaria glabrata and the dung beetle Digitonthophagus gazella. The microcrustaceans and the snails were exposed to entomopathogens in synthetic softwater and the beetles were exposed directly in cattle dung. Obtained data reveal low susceptibility of the non-target species to tested microorganisms, with lethal concentrations being observed only at much higher concentrations than that effective against target insects. These results show that the tested strains are selective in their action mode and seem to be non-hazardous to non-target species.

Alterações bioquímicas e acúmulo em pacus (Metynnis argenteus) expostos ao paclobutrazol

O paclobutrazol, um regulador de crescimento vegetal com propriedades fungicidas, e muito utilizado na regiao Nordeste do Brasil em areas de producao de frutiferas. Este composto pode permanecer estavel por varios meses apos sua aplicacao no solo, sendo sua meia vida na agua superior a tres semanas. Corpos de agua superficiais nas proximidades das culturas sao portanto susceptiveis de serem contaminados pelo paclobutrazol, com o risco de promover efeitos adversos para a fauna aquatica e para a saude humana. No presente trabalho foi estudada a bioconcentracao e algumas alteracoes bioquimicas, medidas pela atividade das enzimas transaminase glutâmico-oxalacetica (TGO), lactato desidrogenase (LDH) e glutationa S-transferase (GST) em tecidos do peixe pacu prata (Metynnis argenteus), exposto ao paclobutrazol durante 28 dias. O paclobutrazol aumentou a atividade de LDH e GST no figado para as concentracoes de 3 mg L-1 (28o dia de exposicao) e 30 mg L-1 (7o dia de exposicao), respectivamente. No 28o dia, a concentracao de paclobutrazol no musculo atingiu niveis residuais de 166 mg kg-1 para a concentracao media determinada na agua de 2,7 mg L-1, estimando-se um fator de bioconcentracao (FBC) para a situacao de equilibrio equivalente a 73. A medida da atividade de LDH e GST pode ser utilizada como biomarcador de exposicao ao paclobutrazol. Esta exposicao deve estar em situacoes extremas para proporcionar risco significativo em humanos que se alimentam de peixes contendo residuos do agroquimico.

Nanoecotoxicity assessment of graphene oxide and its relationship with humic acid

The risk assessment of nanomaterials is essential for regulatory purposes and for sustainable nanotechnological development. Although the application of graphene oxide has been widely exploited, its environmental risk is not well understood because several environmental conditions can affect its behavior and toxicity. In the present study, the graphene oxide effect from aquatic ecosystems was assessed considering the interaction with humic acid on 9 organisms: Raphidocelis subcapitata (green algae), Lemna minor (aquatic plant), Lactuca sativa (lettuce), Daphnia magna (planktonic microcrustacean), Artemia salina (brine shrimp), Chironomus sancticaroli (Chironomidae), Hydra attenuata (freshwater polyp), and Caenorhabditis elegans and Panagrolaimus sp. (nematodes). The no-observed-effect concentration (NOEC) was calculated for each organism. The different criteria used to calculate NOEC values were transformed and plotted as a log-logistic function. The hypothetical 5 to 50% hazardous concentration values were, respectively, 0.023 (0.005-0.056) and 0.10 (0.031-0.31) mg L-1 for graphene oxide with and without humic acid, respectively. The safest scenario associated with the predicted no-effect concentration values for graphene oxide in the aquatic compartment were estimated as 20 to 100 μg L-1 (in the absence of humic acid) and 5 to 23 μg L-1 (in the presence of humic acid). Finally, the present approach contributed to the risk assessment of graphene oxide-based nanomaterials and the establishment of nano-regulations. Environ Toxicol Chem 2018;37:1998-2012.