Nanosilver and Silver Nitrate Toxicity in Ex Vivo-Exposed Gills of Fish and Mitigation by Humic Acids

Development of Films for Wound Healing Based on Gelatin and Oil/Water Emulsions as Carriers of Bioactive Compounds

Background: Natural biopolymeric matrices for developing dressings have been extensively studied, as they may exhibit beneficial properties for wound healing. Gelatin possesses promising structural and physicochemical properties for incorporating active compounds (ACs). O/W emulsions are an alternative delivery system for AC with different properties and solubilities, promoting wound healing. Objective: This study aimed to develop gelatin films by adding silver nanoparticles and healing agents encapsulated in an O/W emulsion to treat skin wounds. Methods: A film-forming dispersion was prepared using gelatin and glycerol as a plasticizer, and films were obtained using the casting technique. Emulsions with ACs (EAs) and without ACs (ECs) were incorporated into the films. The formulations were analyzed by FESEM and characterized for their mechanical, thermal, and swelling properties, as well as their water vapor permeability. Results: The results showed that films with a higher amount of emulsion exhibited greater structural rigidity and lower permeability, while films with lower amounts of emulsion demonstrated more elasticity and higher permeability. General and organ-specific toxicity were evaluated in zebrafish larvae. The films showed no lethal or sub-lethal effects on the morphology or activity of the brain, heart, and liver. Conclusions: The active films developed could provide stable support and a safe delivery system for active compounds to treat skin lesions, minimizing the risk of infection and the need to heal a wound.

Metal-based nanomaterials in aquatic environments: What do we know so far about their ecotoxicity?

The wide range of applications of nanomaterials (NM) in different fields has led to both uncontrolled production and release into environmental compartments, such as aquatic systems, where final disposal occurs. Some efforts have been made to estimate their concentrations in environmental matrices; however, little is known about the actual effects of environmental NM concentrations on biota. The aims of the present review are to (i) expose the state of the art of the most applied NM and their actual concentrations regarding how much is being released to the aquatic environment and which are the predicted ones; (ii) analyze the current literature to elucidate if the aforementioned conditions were proven to cause deleterious effects on the associated organisms; and (iii) identify gaps in the knowledge regarding whether the actual NM concentrations are harmful to aquatic biota. These novel materials are expected to being released into the environment in the range of hundreds to thousands of tons per year, with Si- and Ti-based NM being the two most important. The estimated environmental NM concentrations are in the low range of ng to µg/L, except for Ti-based ones, which concentrations reach values on the order of mg/L. Empirical information regarding the ecotoxicity of environmental NM concentrations mainly focused on metal-based NM, however, it resulted poor and unbalanced in terms of materials and test species. Given its high predicted environmental concentration in comparison with the others, the ecotoxicity of Ti-based NM has been well assessed in algae and fish, while little is known regarding other NM types. While only a few marine species were addressed, the freshwater species Daphnia magna and Danio rerio accounted for the majority of studies on invertebrate and fish groups, respectively. Most of the reported responses are related to oxidative stress. Overall, we consider that invertebrate groups are the most vulnerable, with emphasis on microcrustaceans, as environmentally realistic metal-based NM concentration even caused mortality in some species. In the case of fish, we assumed that environmental concentrations of Ti-based NM represent a growing concern and threat; however, further studies should be carried out by employing other kinds of NM. Furthermore, more ecotoxicological information is needed in the case of carbon-based NM, as they are expected to considerably increase in terms of released amounts and applications in the near future.

Nanosilica and copper ecotoxicity in Gambusia holbrooki fish

When silica nanoparticles (SiNP) reach the water bodies interact with the already existing pollutants in the environments. This study aimed to evaluate the ecotoxicity of SiNP under the presence/absence of Cu in mosquitofish (Gambusia holbrooki). Fish were exposed to 0, 10 and 100 mg SiNP L-1, alone or mixed with Cu (0.25 mg L-1). After 96 h, the amount of colony forming units (CFU) of bacteria living on the skin mucus was analysed, and oxidative stress, tissue damage enzymes, and neurotoxicity were evaluated. We observed a reduction in CFU when Cu was present in the media. The liver was the target organ, evidencing a decrease in tissue damage enzymatic activities, activation of the antioxidant system in all treatments, and lipid oxidative damage when the SiNP and Cu were mixed. Overall, SiNP ecotoxicity was proved, which could also be enhanced by the presence of ubiquitous elements such as metals.

Proteomic profiling reveals mitochondrial toxicity of nanosilver and silver nitrate in the gill of common carp

Mitochondria are recognized as an important target organelle for the toxicity of nanomaterials. Although the toxic effects of silver nanoparticles (AgNPs) on mitochondria have been widely reported, the mechanism behind the toxicity remains unclear. In this study, the effects of two forms of silver (AgNPs and AgNO₃) on carp gill mitochondria were investigated by analyzing the mitochondrial ultrastructure, physicochemical properties of mitochondrial membrane, and mitochondrial proteomics. After exposure of common carp to AgNPs (0.75 mg/L) and AgNO₃ (0.05 mg/L) for 96 h, both forms of silver were shown to cause gill mitochondrial lesions, including irregular shape, loss of mitochondrial cristae, and increased mitochondrial membrane permeability. Proteomics results revealed that AgNPs and AgNO₃ induced 362 and 297 differentially expressed proteins (DEPs) in gill mitochondria, respectively. Among the DEPs, 244 were shared between AgNPs and AgNO₃ treatments. These shared proteins were mainly distributed in the mitochondrial membrane and matrix, and were significantly enriched in the tricarboxylic acid (TCA) cycle and oxidative phosphorylation pathway. The functional annotation of DEPs induced by both silver forms was mainly involved in energy production and conversion. These results indicated that the toxic mechanism of AgNPs and AgNO₃ on gill mitochondria were comparable and the two forms of silver caused mitochondrial dysfunction in fish gills by inhibiting the TCA cycle and disrupting the electron transport chain.

Comparative toxicity of silver nanoparticles and silver nitrate in freshwater fish Oreochromis mossambicus: A multi-biomarker approach

Silver nanoparticles (AgNPs) in the aquatic environment affect ecological repercussions and have fatal impacts on aquatic animals. The current study examined and correlated the toxicity of silver nitrate (AgNO₃) and silver nanoparticles (AgNPs) to the Mozambique tilapia, Oreochromis mossambicus. The comparative toxicity studies were done by exposing O. mossambicus to various doses of AgNO₃ and AgNPs (0, 25, 50, 75, and 100 μg/L) over a 7-day subacute exposure period. AAS analysis was used to detect Ag accumulation, while the histological examination established gill tissue damage. Oxidative stress affects lipid peroxidation (LPO) and protein carbonyl activity (PCA) in the gill tissue. Antioxidant parameters such as glutathione-S-transferase (GST), glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase activity (CAT), and non-enzymatic antioxidants such as metallothionein (MT) and reduced glutathione. The serum in the blood was used to determine non-specific immunological characteristics such as lysozyme (LYZ), myeloperoxidase (MPO), and respiratory burst activity (RBA). The neurotoxic impact of acetylcholine esterase activity (AChE) was investigated in brain tissues. The findings demonstrated that larger concentrations of AgNO₃ than AgNPs improved enzymatic antioxidant activities in the gill tissue. Histological examination of fish gills demonstrated that both AgNPs and AgNO₃ induced telangiectasia and epithelial cell hyperplasia. By increasing the concentration of AgNPs and AgNO₃, the present research demonstrated that silver accumulation leads to inefficient oxidative stress and altered enzymatic and non-enzymatic parameters, leading to cellular damage.

Building the Bridge From Aquatic Nanotoxicology to Safety by Design Silver Nanoparticles

Nanotechnologies have rapidly grown, and they are considered the new industrial revolution. However, the augmented production and wide applications of engineered nanomaterials (ENMs) and nanoparticles (NPs) inevitably lead to environmental exposure with consequences on human and environmental health. Engineered nanomaterial and nanoparticle (ENM/P) effects on humans and the environment are complex and largely depend on the interplay between their peculiar properties such as size, shape, coating, surface charge, and degree of agglomeration or aggregation and those of the receiving media/body. These rebounds on ENM/P safety and newly developed concepts such as the safety by design are gaining importance in the field of sustainable nanotechnologies. This article aims to review the critical characteristics of the ENM/Ps that need to be addressed in the safe by design process to develop ENM/Ps with the ablility to reduce/minimize any potential toxicological risks for living beings associated with their exposure. Specifically, we focused on silver nanoparticles (AgNPs) due to an increasing number of nanoproducts containing AgNPs, as well as an increasing knowledge about these nanomaterials (NMs) and their effects. We review the ecotoxicological effects documented on freshwater and marine species that demonstrate the importance of the relationship between the ENM/P design and their biological outcomes in terms of environmental safety.