Toxicity of gold nanorods on Ceriodaphnia dubia and Danio rerio after sub-lethal exposure and recovery.

Gold nanorods (AuNRs) are rod-shaped nanoparticles (NPs) with special optical properties that allow their application in several areas including photothermal therapy, diagnosis, drug and gene delivery, cellular imaging, and biosensors. Their high potential for many applications increases the possibility of release in aquatic environments, which can cause risks to organisms. In this study, we evaluated toxic effects of AuNRs on cladoceran and fish (Ceriodaphnia dubia and Danio rerio) and their recovery after post-exposure periods. The EC50 of 0.03 mg L-1 was found for C. dubia in the acute exposure. There was a significant decrease in the number of neonates produced and in the filtration rate of C. dubia after sub-lethal exposure to AuNRs. The toxic mechanism of these NPs to cladocerans was attributed to increases in the reactive oxygen species (ROS) generation. After 4 h of recovery in clean medium, C. dubia were able to reestablish the filtration rate. Enzymatic biomarkers for D. rerio showed significant increases in the activity of superoxide dismutase, catalase, and lipid peroxidation after sub-lethal exposure to AuNRs. These biomarkers were recovered after 168 h in clean water. These results are pivotal on the comprehension of AuNR toxicity to aquatic organisms and are useful in assessing this novel nanomaterial impacts on aquatic biota.

Antioxidant metabolism of zebrafish after sub-lethal exposure to graphene oxide and recovery.

Graphene oxide (GO) is a carbon nanomaterial with specific properties, which allow its use in several areas. Some studies have characterized the effects of GO on aquatic organisms, but the ability of recovery after exposure remains largely unknown. In this study, we evaluated the effects of GO on the antioxidant metabolism of zebrafish after 48 h of sub-lethal exposure, and the fish recovery after 168 h in nanoparticle-free water. After the sub-lethal exposure, superoxide dismutase (SOD) activity was significantly increased in 20 mg L-1, as well as catalase (CAT) activity in 2, 10, and 20 mg L-1, and the lipid peroxidation (LPO) had an increase in 2 mg L-1. On other hand, the glutathione peroxidase (GPx) activity was inhibited at 20 mg L-1. After 168 h of recovery in clean water, the SOD activity remained significantly increased in 20 mg L-1; the CAT activity was unchanged in all tested concentrations; the GPx activity was inhibited in 2, 10, and 20 mg L-1; and the LPO significantly decreased in 2 mg L-1. Our study suggests that GO exposure disrupts the antioxidant metabolism of adult zebrafish. Even after 168 h of recovery in clean water, homeostasis was not completely restored, although organisms developed mechanisms of recovery, and toxic effects were more subtle. Our results are pivotal to better understanding the physiological mechanisms involved in the detoxification process after GO exposure, and for strategies of protection on fish species.

Toxicity of copper oxide nanoparticles to Neotropical species Ceriodaphnia silvestrii and Hyphessobrycon eques.

The increase of production and consumption of copper oxide nanostructures in several areas contributes to their release into aquatic ecosystems. Toxic effects of copper oxide nanoparticles (CuO NPs), in particular, on tropical aquatic organisms are still unknown, representing a risk for biota. In this study, the effects of rod-shaped CuO NPs on the Neotropical species Ceriodaphnia silvestrii and Hyphessobrycon eques were investigated. We also compared the toxicity of CuO NPs and CuCl2 on these species to investigate the contribution of particles and cupper ions to the CuO NPs toxicity. Considering the low copper ions release from CuO NPs (<1%), our results revealed that the toxicity of CuO NPs to C. silvestrii and H. eques was mainly induced by the NPs. The 48 h EC50 for C. silvestrii was 12.6 ±â€¯0.7 µg Cu L-1 and for H. eques the 96 h LC50 was 211.4 ±â€¯57.5 µg Cu L-1 of CuO NPs. There was significant decrease in reproduction, feeding inhibition and increase in reactive oxidative species (ROS) generation in C. silvestrii exposed to CuO NPs. In fish H. eques, sublethal exposure to CuO NPs caused an increase in ROS generation in gill cells and an increase in cells number that were in early apoptotic and necrotic stages. Our results showed that CuO NPs caused toxic effects to C. silvestrii and H. eques and ROS play an important role in the toxicity pathway observed. Data also indicated that C. silvestrii was among the most sensitive species for CuO NPs. Based on predicted environmental concentration in water bodies, CuO NPs pose potential ecological risks for C. silvestrii and H. eques and other tropical freshwater organisms.

Chronic toxicity in Ceriodaphnia dubia induced by graphene oxide.

The unique physico-chemical properties of nanomaterials have allowed their application in different areas including electronics, energy storage, nanomedicine, environmental remediation and biotechnology. Graphene and its derivatives, in particular, have been commercially available, with prediction for increasing their production in the next years, in a way that their release into aquatic environments is very likely to occur, and the impacts of such situation on organisms are still not completely understood. In this context, we evaluated graphene oxide (GO) effects on the freshwater cladoceran Ceriodaphnia dubia through acute and chronic toxicity, feeding rates, and reactive oxygen species (ROS) generation. The mean effective concentration (EC50) estimated during acute exposure was 1.25 mg L-1 of GO. The chronic exposure resulted in significant decrease in the number of neonates. The feeding rates were also decreased by GO exposure. Sub-lethal concentrations of GO caused an increase in ROS generation in the organisms. Our results indicated that GO cause acute and chronic effects to C. dubia. In the presence of GO there was a shift in the available energy for self-maintenance rather than feeding or reproduction activities. This study provides useful information on GO concentrations that might impair the aquatic biota, and supports regulatory efforts concerning the environmental safety of this product.

Evaluation of Potential Probiotics Isolated from Human Milk and Colostrum.

Several studies have demonstrated a diversity of bacterial species in human milk, even in aseptically collected samples. The present study evaluated potential probiotic bacteria isolated from human milk and associated maternal variables. Milk samples were collected from 47 healthy women and cultured on selective and universal agar media under aerobic and anaerobic conditions. Bacterial isolates were counted and identified by Biotyper Matrix-Assisted Laser Desorption Ionization-Time of Flight mass spectrometry and then tested for probiotic properties. Total bacteria in human milk ranged from 1.5 to 4.0 log10 CFU/mL. The higher bacterial counts were found in colostrum (mean = 3.9 log10 CFU/mL, 95% CI 3.14-4.22, p = 0.00001). The most abundant species was Staphylococcus epidermidis (n = 76). The potential probiotic candidates were Lactobacillus gasseri (n = 4), Bifidobacterium breve (n = 1), and Streptococcus salivarius (n = 4). Despite the small sample size, L. gasseri was isolated only in breast milk from mothers classified into a normal weight range and after a vaginally delivered partum. No potential probiotics showed antagonism against pathogens, but all of them agglutinated different pathogens. Nine bacterial isolates belonging to the species L. gasseri, B. breve, and S. salivarius were selected as potential probiotics. The present study confirms the presence in breast milk of a bacterial microbiota that could be the source of potential probiotic candidates to be used in the formula of simulated maternal milk.

Toxicological effects of graphene oxide on adult zebrafish (Danio rerio).

Graphene exhibits unique physical and chemical properties that facilitate its application in many fields, including electronics and biomedical areas. However, the use of graphene and its derivatives could result in accumulation in aquatic environments, and the risks posed by these compounds for organisms are not completely understood. In this study, we investigated the effects of graphene oxide (GO) on adult zebrafish (Danio rerio). Experimental fish were exposed to 2, 10 or 20mgL-1 GO, and the cytotoxicity, genotoxicity and oxidative stress were assessed. The morphology of the gills and liver tissues was also analyzed. Graphene oxide exposure led to an increase in the number of gill cells that were in early apoptotic and necrotic stages, but genotoxicity was not observed in blood cells. We also observed the generation of Reactive Oxygen Species (ROS) in gill cells. Structural analysis revealed injuries to gill tissues, including a dilated marginal channel, lamellar fusion, clubbed tips, swollen mucocytes, epithelial lifting, aneurysms, and necrosis. Liver tissues also presented lesions such as peripherally located nuclei. Furthermore, hepatocytes exhibited a non-uniform shape, picnotic nuclei, vacuole formation, cell rupture, and necrosis. Our results showed that sub-lethal doses of graphene oxide could be harmful to fish species and thus represent risks for the aquatic food chain.

Acute toxicity and environmental risk of teflubenzuron to Daphnia magna, Poecilia reticulata and Lemna minor in the absence and presence of sediment.

This study aimed to estimate the acute toxicity of teflubenzuron (1-(3,5-dichloro-2,4-difluorophenyl)-3-(2,6-difluorobenzoyl)urea) (TFB) for Daphnia magna, Lemna minor and Poecilia reticulata, in the absence and presence of sediment; evaluate the effect of sediment on the TFB bioavailability; and to classify this insecticide according to its environmental poisoning risk for agricultural and aquaculture uses. The tests of TFB acute toxicity were conducted in static system in a completely randomized design with increasing TFB concentrations, and a control group. The TFB has been classified according to the estimated values of EC50 and LC50 by its acute toxicity and environmental risk. The sediment significantly reduced toxicity and bioavailability of TFB in water column. Therefore, the insecticide can be classified as being highly toxic to Daphnia magna, which means the agricultural and aquacultural uses of TFB pose a high risk of environmental toxicity to non-target organisms. However, it was practically non-toxic to L. minor and P. reticulata.