Environmental Fate of Metal Nanoparticles in Estuarine Environments

Integrating chemical and biological data by chemometrics to evaluate detoxification responses of a neotropical bivalve to metal and metalloid contamination

Mangroves represent a challenge in monitoring studies due to their physical and chemical conditions under constant marine and anthropogenic influences. This study investigated metals/metalloids whole-body bioaccumulation (soft tissues) and the risk associated with their uptake, biochemical and morphological detoxification processes in gills and metals/metalloids immobilisation in shells of the neotropical sentinel oyster Crassostrea rhizophorae from two Brazilian estuarine sites. Biochemical and morphological responses indicated three main mechanisms: (1) catalase, superoxide dismutase and glutathione played important roles as the first defence against reactive oxygen species; (2) antioxidant capacity against peroxyl radicals, glutathione S-transferase, metallothionein prevent protein damage and (3) metals/metalloids sequestration into oyster shells as a mechanism of oyster detoxification. However, the estimated daily intake, target hazard quotient, and hazard index showed that the human consumption of oysters would not represent a human health risk. Among 14 analysed metals/metalloids, chemometrics indicate that Mn, As, Pb, Zn and Fe overload the antioxidant system leading to morphological alterations in gills. Overall, results indicated cellular vacuolization and increases in mucous cell density as defence mechanisms to prevent metals/metalloids accumulation and the reduction in gill cilia; these have long-term implications in respiration and feeding and, consequently, for growth and development. The integration of data from different sites and environmental conditions using chemometrics highlights the main biological patterns of detoxification from a neotropical estuarine bivalve, indicating the way in which species can cope with metals/metalloids contamination and its ecological consequences.

Zinc Oxide Nanoparticles Blunt Potassium-Bromate-Induced Renal Toxicity by Reinforcing the Redox System

Potassium bromate (PB) is a general food additive, a significant by-product during water disinfection, and a carcinogen (Class II B). The compound emits toxicity depending on the extent of its exposure and dose through consumable items. The current study targeted disclosing the ameliorative efficacy of zinc oxide nanoparticles (ZnO NPs) prepared by green technology in PB-exposed Swiss albino rats. The rats were separated into six treatment groups: control without any treatment (Group I), PB alone (Group II), ZnO alone (Group III), ZnO NP alone (Group IV), PB + ZnO (Group V), and PB + ZnO NPs (Group VI). The blood and kidney samples were retrieved from the animals after following the treatment plan and kept at -20 °C until further analysis. Contrary to the control (Group I), PB-treated rats (Group II) exhibited a prominent trend in alteration in the established kidney function markers and disturbed redox status. Further, the analysis of the tissue and nuclear DNA also reinforced the biochemical results of the same treatment group. Hitherto, Groups III and IV also showed moderate toxic insults. However, Group VI showed a significant improvement from the PB-induced toxic insults compared to Group II. Hence, the present study revealed the significant therapeutic potential of the NPs against PB-induced nephrotoxicity in vivo, pleading for their usage in medicines having nephrotoxicity as a side effect or in enhancing the safety of the industrial use of PB.

Characterization and Behaviour of Silica Engineered Nanocontainers in Low and High Ionic Strength Media

Mesoporous silica engineered nanomaterials are of interest to the industry due to their drug-carrier ability. Advances in coating technology include using mesoporous silica nanocontainers (SiNC) loaded with organic molecules as additives in protective coatings. The SiNC loaded with the biocide 4,5-dichloro-2-octyl-4-isothiazolin-3-one (DCOIT), i.e., SiNC-DCOIT, is proposed as an additive for antifouling marine paints. As the instability of nanomaterials in ionic-rich media has been reported and related to shifting key properties and its environmental fate, this study aims at understanding the behaviour of SiNC and SiNC-DCOIT in aqueous media with distinct ionic strengths. Both nanomaterials were dispersed in (i) low- (ultrapure water-UP) and (ii) high- ionic strength media-artificial seawater (ASW) and f/2 medium enriched in ASW (f/2 medium). The morphology, size and zeta potential (ζP) of both engineering nanomaterials were evaluated at different timepoints and concentrations. Results showed that both nanomaterials were unstable in aqueous suspensions, with the initial ζP values in UP below -30 mV and the particle size varying from 148 to 235 nm and 153 to 173 nm for SiNC and SiNC-DCOIT, respectively. In UP, aggregation occurs over time, regardless of the concentration. Additionally, the formation of larger complexes was associated with modifications in the ζP values towards the threshold of stable nanoparticles. In ASW, SiNC and SiNC-DCOIT formed aggregates (<300 nm) independently of the time or concentration, while larger and heterogeneous nanostructures (>300 nm) were detected in the f/2 medium. The pattern of aggregation detected may increase engineering nanomaterial sedimentation rates and enhance the risks towards dwelling organisms.