Toxicity of engineered micro- and nanomaterials with antifouling properties to the brine shrimp Artemia salina and embryonic stages of the sea urchin Paracentrotus lividus

Ageing influences the toxicity of two innovative nanofertilizers to the soil invertebrates Enchytraeus crypticus and Folsomia candida

The increasing global food demand is threatening the sustainability of agrifood production systems. The intensification of agricultural practices, with inadequate use of pesticides and fertilizers, poses major challenges to the good functioning of agroecosystems and drastically degrades the soil quality. Nanotechnology is expected to optimize the current farming practices and mitigate some associated impacts. Layered double hydroxides (LDHs) are a class of nanomaterials with high potential for use in agricultural productions, mostly due to their sustained release of nutrients. Considering its novelty and lack of studies on the terrestrial ecosystem, it is essential to assess potential long-term harmful consequences to non-target organisms. Our study aimed to evaluate the effect of Zn-Al-NO3 LDH and Mg-Al-NO3 LDH ageing on the survival and reproduction of two soil invertebrate species Enchytraeus crypticus and Folsomia candida. We postulated that the toxicity of nanomaterials to soil invertebrates would change with time, such that the ageing of soil amendments would mediate their impacts on both species. Our results showed that the toxicity of LDHs was species-dependent, with Zn-Al-NO3 LDH being more toxic to E. crypticus, while Mg-Al-NO3 LDH affected more F. candida, especially in the last ageing period, where reproduction was the most sensitive biological parameter. The toxicity of both nanomaterials increased with ageing time, as shown by the decrease of the EC50 values over time. The influence of LDH dissolution and availability of Zn and Mg in the soil pore water was the main factor related to the toxicity, although we cannot rule out the influence of other structural constituents of LDHs (e.g., nitrates and aluminium). This study supports the importance of incorporating ageing in the ecotoxicity testing of nanomaterials, considering their slow release, as effects on soil organisms can change and lead to more severe impacts on the ecosystem functioning.

High-Performance Polyurea Improved by Reactive Nanocluster for Antibiofouling

Polyurea has found applications in protective coatings. Yet, the too fast polymerization and lack of functions limit its application. Herein, we report a high-performance polyurea via the stepwise polymerization of an isocyanate (NCO)-terminated prepolymer consisting of poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) (PPG-b-PEG-b-PPG) with a nanocluster synthesized via the hydrolysis of N-phenylaminomethyltriethoxysilane. Such a nanocluster contains low-reactivity secondary amines, so the polymerization of polyurea can be slowed down (over 1 h), which improves its wetting and adhesion to a substrate. The residual silanol groups on the nanocluster further increase the adhesion. Such polyurea exhibits high adhesion on various substrates, including glass, ceramic, steel, copper, titanium, wood, and natural rubber (∼2.35-14.64 MPa). Besides, the nanoclusters can cross-link the prepolymer into a tough network, endowing the polyurea with a high mechanical strength of ∼25 MPa, much higher than the traditional polyaspartic ester polyurea. On the other hand, the PEG segments enable the polyurea to have good fouling resistance against proteins (fibrinogen absorption was reduced by over 90%), bacteria (RBA of S. aureusE. coli and Pseudomonas sp. was less than 10%), as well as diatom (diatom density was less than 100 cells/mm2). The polyurea is expected to find applications in biomedical engineering and marine antifouling.

Harmonizing nanomaterial exposure methodologies in ecotoxicology: the effects of two innovative nanoclays in the freshwater microalgae Raphidocelis subcapitata

Layered double hydroxides (LDHs) are innovative nanomaterials (NMs) with a typical nanoclay structure (height <40 nm) consisting of layers of metallic cations and hydroxides stabilized by anions and water molecules. Upon specific triggers, anions can exchange by others in the surrounding environment. Due to this stimuli-responsive behavior, LDHs are used as carriers of active ingredients in the industrial or pharmaceutical sectors. Available technical guidelines to evaluate the ecotoxicity of conventional substances do not account for the specificities of NMs, leading to inaccuracies and uncertainty. The present study aimed to assess two different exposure methodologies (serial dilutions of the stock dispersion vs. direct addition of NM powder to each concentration) on the ecotoxicological profile of different powder grain sizes of Zn-Al LDH-NO3 and Cu-Al LDH-NO3 (bulk, <25, 25-63, 63-125, 125-250, and >250 µm) in the growth of the freshwater microalgae Raphidocelis subcapitata. Results revealed that the serial dilutions methodology was preferable for Zn-Al LDH-NO3, whereas for Cu-Al LDH-NO3 both methodologies were suitable. Thus, the serial dilutions methodology was selected to assess the ecotoxicity of different grain sizes for both LDHs. All Zn-Al LDH-NO3 grain sizes yielded similar toxicity, while Cu-Al LDH-NO3 powders with smaller grain sizes caused a higher effect on microalgae growth; thus, grain size separation might be advantageous for future applications of Cu-Al LDH-NO3s. Considering the differences between exposure methodologies for the Zn-Al LDH-NO3, further research involving other NMs and species must be carried out to achieve harmonization and validation for inter-laboratory comparison.

Zn-Al layered double hydroxides induce embryo malformations and impair locomotion behavior in Danio rerio

Layered double hydroxides (LDHs) are stimuli-responsive anionic nanoclays. The vast possibilities of using LDHs can lead to their existence in the ecosystem, raising a question of potential ecological concern. However, little is known about the effect of these nanomaterials on freshwater organisms. The present study aimed to assess the ecotoxicological effects of Zinc-Aluminium LDH-nitrate (ZnAl LDH-NO₃) in zebrafish (Danio rerio) early life stages. The endpoints measured were mortality, malformations and hatching rate after exposure of D. rerio embryos and larvae to ZnAl LDH-NO₃ following the OECD 236 guideline. The behavioral, biochemical (markers of oxidative stress and neurotoxicity), and molecular (at DNA level) alterations were also assessed using sub-lethal concentrations. No observable acute effects were detected up to 415.2 mg LDH/L while the 96 h-LC₅₀ was estimated as 559.9 mg/L. Tested LDH caused malformations in D. rerio embryos, such as pericardial edema, incomplete yolk sac absorption and tail deformities (96 h-EC₅₀ = 172.4 mg/L). During the dark periods, the locomotor behavior in zebrafish larvae was affected upon ZnAl LDH-NO₃ exposure. However, no significant biochemical and molecular changes were recorded. The present findings suggest that ZnAl LDH-NO₃ can be regarded as a non-toxic nanomaterial towards D. rerio (E/LC₅₀ > > 100 mg/L) although impairment of the locomotion behavior on zebrafish embryos can be expected at concentrations below 100 mg/L.

Layered double hydroxides for corrosion-related applications—Main developments from 20 years of research at CICECO

This work describes the main advances carried out in the field of corrosion protection using layered double hydroxides (LDH), both as additive/pigment-based systems in organic coatings and as conversion films/pre-treatments. In the context of the research topic “Celebrating 20 years of CICECO”, the main works reported herein are based on SECOP’s group (CICECO) main advances over the years. More specifically, this review describes structure and properties of LDH, delving into the corrosion field with description of pioneering works, use of LDH as additives to organic coatings, conversion layers, application in reinforced concrete and corrosion detection, and environmental impact of these materials. Moreover, the use of computational tools for the design of LDH materials and understanding of ion-exchange reactions is also presented. The review ends with a critical analysis of the field and future perspectives on the use of LDH for corrosion protection. From the work carried out LDH seem very tenable, versatile, and advantageous for corrosion protection applications, although several obstacles will have to be overcome before their use become commonplace.

Genotoxicity in Artemia spp.: An old model with new sensitive endpoints

Artemia spp. represent models species widely used in ecotoxicological studies due to its simple and fast manipulation in laboratory conditions that makes this crustacean well adaptable to several methodological approaches. Although cysts hatching, swimming behavior, reproductive success and mortality are the main endpoints used for the determination of toxicity, the detection of slight alterations induced by certain substances found at low concentrations in the environment may require more sensitive biomarkers. For this reason, the identification of DNA or chromosomal damages has been proposed as an additional and appreciable endpoint for the ecotoxicological assessment of environmental chemicals. Concerning Artemia models, only few studies indicated that the exposure to organic and inorganic compounds (i.e. pesticides, nanoparticles, bacterial products or heavy metals) can reduce the survival and fitness through the onset of DNA breaks or the dysregulation of key genes. In contrast, literature research revealed a lot of works primarily focusing on the mortality and hatching rates of Artemia nauplii and cysts despite the well-known low sensitivity of these species. The present review reports the current state of knowledge concerning the effects induced by various chemicals, including organic and inorganic compounds, on the common parameters and genotoxicity in both Artemia franciscana and Artemia salina. Advantages and limitations of Artemia spp. models in eco-toxicological investigations together with the most used classes of compounds are briefly discussed. Moreover, a mention is also addressed to scarce availability of literature data focusing on genotoxic effects and the great reliability of molecular approaches observed in this poorly sensitive model organism. Thus, the opportunity to take advantage of genotoxic analyses has also been highlighted, by suggesting this approach as a novel endpoint to be used for the eco-toxicological assessment of several stressors.

Biocides and techniques for their encapsulation: a review

Biocides are compounds that are broadly used to protect products and equipment against microbiological damage. Encapsulation can effectively increase physicochemical stability and allow for controlled release of encapsulated biocides. We categorized microencapsulation into coacervation, sol-gel, and self-assembly methods. The former comprises internal phase separation, interfacial polymerization, and multiple emulsions, and the latter include polymersomes and layer-by-layer techniques. The focus of this review is the description of these categories based on their microencapsulation methods and mechanisms. We discuss the key features and potential applications of each method according to the characteristics of the biocide to be encapsulated, relating the solubility of biocides to the capsule-forming materials, the reactivity between them and the desired release rate. The role of encapsulation in the safety and toxicity of biocide applications is also discussed. Furthermore, future perspectives for biocide applications and encapsulation techniques are presented.

"Smart" nanosensors for early detection of corrosion: Environmental behavior and effects on marine organisms

Corrosion is an environmental and economic global problem. "Smart" or stimuli-responsive colorimetric nanosensors for maritime coatings have been proposed as an asset to overcome the limitations of the current monitoring techniques by changing color in the presence of triggers associated with the early stages of corrosion. Layered double hydroxides (Zn-Al LDH; Mg-Al LDH) and silica mesoporous nanocapsules (SiNC) were used as precursor nanocarriers of active compounds: hexacyanoferrate ions ([Fe(CN)₆]^3-) and phenolphthalein (PhPh), respectively. Additionally, the safer-by-design principles were employed to optimize the nanosensors in an eco-friendly perspective (e.g., regular vs. warm-washed SiNC-PhPh; immobilization using different carriers: Zn-Al LDH-[Fe(CN)₆]^3- vs. Mg-Al LDH-[Fe(CN)₆]^3-). Therefore, the present study aims to assess the environmental behavior in saltwater and the toxic effects of the nanosensors, their nanocarriers, and the active compounds on the marine microalgae Tetraselmis chuii and the crustacean Artemia salina. Briefly, tested compounds exhibited no acute toxic effects towards A. salina (NOEC = 100 mg/L), apart from SiNC-PhPh (LC₅₀ = 2.96 mg/L) while tested active compounds and nanosensors caused significant growth inhibition on T. chuii (lowest IC₅₀ = 0.40 mg/L for SiNC-PhPh). The effects of [Fe(CN)₆]^3- were similar regardless of the nanocarrier choice. Regarding SiNC-PhPh, its toxicity can be decreased at least twice by simply reinforcing the nanocapsules washing, which contributes to the removal (at least partially) of the surfactants residues. Thus, implementing safe-by-design strategies in the early stages of research proved to be critical, although further progress is still needed towards the development of truly eco-friendly nanosensors.

Toxicity of innovative antifouling additives on an early life stage of the oyster Crassostrea gigas: short- and long-term exposure effects

Recent advances in nanotechnology have allowed the encapsulation of hazardous antifouling (AF) biocides in silica mesoporous nanocapsules (SiNC) reducing their short-term toxicity. However, the chronic effects of such novel nanoadditives remain understudied. The present study aimed to assess short- and long-term sub-lethal effects of soluble forms (DCOIT and Ag) and nanostructured forms (SiNC-DCOIT and SiNC-DCOIT-Ag) of two AF biocides and the "empty" nanocapsule (SiNC) on juveniles of Crassostrea gigas after 96 h and 14 days of exposure. Juvenile oysters exposed for a short period to free DCOIT and AgNO₃ presented worse physiological status comparing with those exposed to the nanostructured forms. The long-term exposure to DCOIT and Ag⁺ caused an extensive biochemical impairment comparing with the tested nanomaterials, which included oxidative damage, activation of the antioxidant defense system, and neurotransmission impairment. Despite the negative effects mostly observed on the health condition index and AChE, the encapsulation of the abovementioned AF biocides into SiNC seems to be a technological advantage towards the development of AF nanoadditives with lower long-term toxicity comparing with the soluble forms of such biocides.

Can the toxicity of polyethylene microplastics and engineered nanoclays on flatfish (Solea senegalensis) be influenced by the presence of each other?

Microplastics and nanomaterials are applied in a myriad of commercial and industrial applications. When leaked to natural environments, such small particles might threaten living organisms' health, particularly when considering their potential combination that remains poorly investigated. This study investigated the physiological and biochemical effects of polyethylene (PE; 64-125 μm in size, 0.1, 1.0, and 10.0 mg·L^-1) single and combined with an engineered nanomaterial applied in antifouling coatings, the copper-aluminium layered double hydroxides (Cu-Al LDH; 0.33, 1.0, and 3.33 mg·L^-1) in the flatfish Solea senegalensis larvae (8 dph) after 3 h exposure, in a full factorial design. Particles ingestion, histopathology, and biochemical biomarkers were assessed. Fish larvae presented <1 PE particles in their gut, independently of their concentration in the medium. The histological health index showed minimal pathological alterations at PE combined exposure, with a higher value observed at 1 mg LDH·L^-1 × 0.1 mg PE·L^-1. Gut deformity and increased antioxidant defences (catalase), neurotransmission (acetylcholinesterase), and aerobic energy production (electron transport system) were observed at PE ≥ 1.0 mg·L^-1. No oxidative damage (lipid peroxidation) or alterations in the detoxification capacity (glutathione-S-transferase) was observed on single and combined exposures. PE, combined or not with Cu-Al LDH, does not seem to compromise larvae's homeostasis considering levels reported so far in the marine and aquaculture environments. However, harsh effects are expected with MP contamination rise, as projections suggest.

Use of Nanotechnology to Mitigate Biofouling in Stainless Steel Devices Used in Food Processing, Healthcare, and Marine Environments

In humid environments, the formation of biofilms and microfouling are known to be the detrimental processes that first occur on stainless steel surfaces. This is known as biofouling. Subsequently, the conditions created by metabolites and the activity of organisms trigger corrosion of the metal and accelerate corrosion locally, causing a deterioration in, and alterations to, the performance of devices made of stainless steel. The microorganisms which thus affect stainless steel are mainly algae and bacteria. Within the macroorganisms that then damage the steel, mollusks and crustaceans are the most commonly observed. The aim of this review was to identify the mechanisms involved in biofouling on stainless steel and to evaluate the research done on preventing or mitigating this problem using nanotechnology in humid environments in three areas of human activity: food manufacturing, the implantation of medical devices, and infrastructure in marine settings. Of these protective processes that modify the steel surfaces, three approaches were examined: the use of inorganic nanoparticles; the use of polymeric coatings; and, finally, the generation of nanotextures.

Effects of nanostructure antifouling biocides towards a coral species in the context of global changes

Biofouling prevention is one of the biggest challenges faced by the maritime industry, but antifouling agents commonly impact marine ecosystems. Advances in antifouling technology include the use of nanomaterials. Herein we test an antifouling nano-additive based on the encapsulation of the biocide 4,5-dichloro-2-octyl-4-isothiazolin-3-one (DCOIT) in engineered silica nanocontainers (SiNC). The work aims to assess the biochemical and physiological effects on the symbiotic coral Sarcophyton cf. glaucum caused by (1) thermal stress and (2) DCOIT exposure (free or nanoencapsulated forms), in a climate change scenario. Accordingly, the following hypotheses were addressed: (H1) ocean warming can cause toxicity on S. cf. glaucum; (H2) the nanoencapsulation process decreases DCOIT toxicity towards this species; (H3) the biocide toxicity, free or encapsulated forms, can be affected by ocean warming. Coral fragments were exposed for seven days to DCOIT in both free and encapsulated forms, SiNC and negative controls, under two water temperature regimes (26 °C and 30.5 °C). Coral polyp behavior and photosynthetic efficiency were determined in the holobiont, while biochemical markers were assessed individually in the endosymbiont and coral host. Results showed transient coral polyp retraction and diminished photosynthetic efficiency in the presence of heat stress or free DCOIT, with effects being magnified in the presence of both stressors. The activity of catalase and glutathione-S-transferase were modulated by temperature in each partner of the symbiosis. The shifts in enzymatic activity were more pronounced in the presence of free DCOIT, but to a lower extent for encapsulated DCOIT. Increased levels of oxidative damage were detected under heat conditions. The findings highlight the physiological constrains elicited by the increase of seawater temperature to symbiotic corals and demonstrate that DCOIT toxicity can be minimized through encapsulation in SiNC. The presence of both stressors magnifies toxicity and confirm that ocean warming enhances the vulnerability of tropical photosynthetic corals to local stressors.

Functional nanomaterials, synergisms, and biomimicry for environmentally benign marine antifouling technology

Marine biofouling remains one of the key challenges for maritime industries, both for seafaring and stationary structures. Currently used biocide-based approaches suffer from significant drawbacks, coming at a significant cost to the environment into which the biocides are released, whereas novel environmentally friendly approaches are often difficult to translate from lab bench to commercial scale. In this article, current biocide-based strategies and their adverse environmental effects are briefly outlined, showing significant gaps that could be addressed through advanced materials engineering. Current research towards the use of natural antifouling products and strategies based on physio-chemical properties is then reviewed, focusing on the recent progress and promising novel developments in the field of environmentally benign marine antifouling technologies based on advanced nanocomposites, synergistic effects and biomimetic approaches are discussed and their benefits and potential drawbacks are compared to existing techniques.

A Review on Nanopesticides for Plant Protection Synthesized Using the Supramolecular Chemistry of Layered Hydroxide Hosts

The rapid growth in the human population has triggered increased demand for food supply, and in turn has prompted a higher amount of agrochemical usage to meet the gaps between food production and consumption. The problem with conventional agro-nanochemicals is the reduced effectiveness of the active ingredient in reaching the target, along with leaching, evaporation, etc., which ultimately affect the environment and life, including humans. Fortunately, nanotechnology platforms offer a new life for conventional pesticides, which improves bioavailability through different kinetics, mechanisms and pathways on their target organisms, thus enabling them to suitably bypass biological and other unwanted resistances and therefore increase their efficacy. This review is intended to serve the scientific community for research, development and innovation (RDI) purposes, by providing an overview on the current status of the host-guest supramolecular chemistry of nanopesticides, focusing on only the two-dimensional (2D), brucite-like inorganic layered hydroxides, layered hydroxide salts and layered double hydroxides as the functional nanocarriers or as the hosts in smart nanodelivery systems of pesticides for plant protection. Zinc layered hydroxides and zinc/aluminum-layered double hydroxides were found to be the most popular choices of hosts, presumably due to their relative ease to prepare and cheap cost. Other hosts including Mg/Al-, Co/Cr-, Mg/Fe-, Mg/Al/Fe-, Zn/Cr- and Zn/Cu-LDHs were also used. This review also covers various pesticides which were used as the guest active agents using supramolecular host-guest chemistry to combat various pests for plant protection. This looks towards a new generation of agrochemicals, "agro-nanochemicals", which are more effective, and friendly to life, humans and the environment.

Molecular mechanisms of zooplanktonic toxicity in the okadaic acid-producing dinoflagellate Prorocentrum lima

Prorocentrum lima is a dinoflagellate that forms hazardous blooms and produces okadaic acid (OA), leading to adverse environmental consequences associated with the declines of zooplankton populations. However, little is known about the toxic effects and molecular mechanisms of P. lima or OA on zooplankton. Here, their toxic effects were investigated using the brine shrimp Artemia salina. Acute exposure of A. salina to P. lima resulted in lethality at concentrations 100-fold lower than densities observed during blooms. The first comprehensive results from global transcriptomic and metabolomic analyses in A. salina showed up-regulated mRNA expression of antioxidant enzymes and reduced non-enzyme antioxidants, indicating general detoxification responses to oxidative stress after exposure to P. lima. The significantly up-regulated mRNA expression of proteasome, spliceosome, and ribosome, as well as the increased fatty acid oxidation and oxidative phosphorylation suggested the proteolysis of damaged proteins and induction of energy expenditure. Exposure to OA increased catabolism of chitin, which may further disrupt the molting and reproduction activities of A. salina. Our data shed new insights on the molecular responses and toxicity mechanisms of A. salina to P. lima or OA. The simple zooplankton model integrated with omic methods provides a sensitive assessment approach for studying hazardous algae.

Acute and chronic effects of innovative antifouling nanostructured biocides on a tropical marine microcrustacean

This study aimed to investigate the toxicity of innovative antifouling nanostructured biocides DCOIT and silver associated to silica nanocapsules (SiNC) on the tropical microcrustacean Mysidopsis juniae. The toxicity of the tested compounds can be summarized as follows (acute tests): DCOIT > SiNC-Ag > SiNC-DCOIT > SiNC-DCOIT-Ag > SiNC > Ag; (chronic tests): SiNC-Ag > SiNC-DCOIT-Ag > DCOIT > Ag > SiNC, although it was not possible to determine the chronic toxicity of SiNC-DCOIT. In general, our data demonstrated that mysids were more sensitive than most temperate species, and it was possible to conclude that the combination SiNC-DCOIT-Ag showed less acute toxicity in comparison to the isolated active compounds, reinforcing data obtained for species from temperate environments on the potential use of nanomaterial to reduce toxicity to non-target species. However, despite representing less risk to the environment, the compound SiNC-DCOIT-Ag is still very toxic to the non-target tropical mysid.

Can Encapsulation of the Biocide DCOIT Affect the Anti-Fouling Efficacy and Toxicity on Tropical Bivalves?

The encapsulation of the biocide DCOIT in mesoporous silica nanocapsules (SiNC) has been applied to reduce the leaching rate and the associated environmental impacts of coatings containing this biocide. This research aimed to evaluate the effects of DCOIT in both free and nanostructured forms (DCOIT vs. SiNC-DCOIT, respectively) and the unloaded SiNC on different life stages of the bivalve Perna perna: (a) gametes (fertilization success), (b) embryos (larval development), and (c) juveniles mussels (byssus threads production and air survival after 72 h of aqueous exposure). The effects on fertilization success showed high toxicity of DCOIT (40 min-EC50 = 0.063 μg L−1), followed by SiNC-DCOIT (8.6 μg L−1) and SiNC (161 μg L−1). The estimated 48 h-EC50 of SiNC, DCOIT and SiNC-DCOIT on larval development were 39.8, 12.4 and 6.8 μg L−1, respectively. The estimated 72 h-EC50 for byssus thread production were 96.1 and 305.5 µg L−1, for free DCOIT and SiNC-DCOIT, respectively. Air survival was significantly reduced only for mussels exposed to free DCOIT. Compared to its free form, SiNC-DCOIT presented a balanced alternative between efficacy and toxicity, inhibiting efficiently the development of the target stage (larvae that is prone to settle) and satisfactorily preventing the juvenile attachment.

Gemini Surfactant as a Template Agent for the Synthesis of More Eco-Friendly Silica Nanocapsules

Silica mesoporous nanocapsules are a class of “smart” engineered nanomaterials (ENMs) applied in several fields. Recent studies have highlighted that they can exert deleterious effects into marine organisms, attributed to the use of the toxic cationic surfactant N-hexadecyl-N,N,N-trimethylammonium bromide (CTAB) during the synthesis of ENMs. The present study reports the successful synthesis and characterization of novel gemini surfactant-based silica nanocapsules. The gemini surfactant 1,4-bis-[N-(1-dodecyl)-N,N-dimethylammoniummethyl]benzene dibromide (QSB2-12) was chosen as a more environmentally-friendly replacement of CTAB. Nanocapsules were characterized by scanning electron microscopy (SEM), Fourier-transformed infrared spectroscopy (FTIR), dynamic light scattering (DLS), thermogravimetric analysis (TGA) and N2 adsorption-desorption isotherms. Short-term exposure effects of new ENMs were evaluated in four marine species (Nannochloropsis gaditana, Tetraselmis chuii and Phaeodactylum tricornutum) and the microcrustacean (Artemia salina). The replacement of the commercial cationic surfactant by the gemini surfactant does not change the structure nor the environmental behaviour in seawater of the newly synthesised silica nanocontainers. Additionally, it is demonstrated that using gemini surfactants can reduce the toxicity of novel silica nanocapsules towards the tested marine species. As a result, environmentally-friendly ENMs can be obtained based on a safe-by-design approach, thereby fitting the concept of Green Chemistry.

Combined effects of nano-TiO2 and hexavalent chromium towards marine crustacean Artemia salina

There has been a significant increased concern of the impact of the toxicity of multiple contaminants in the marine environment. Thus, this study was aimed at determining whether the interaction between nano-TiO₂ and Cr(VI) would modulate their toxic effects with the marine crustacean, Artemia salina. Nano-TiO₂ agglomerated in artificial sea water (ASW) and readily formed micron-sized particles that settled down in the medium. The addition of Cr(VI) to nano-TiO₂ aggravated their agglomeration through sorption of Cr(VI) onto nano-TiO₂. This was reflected by a decrease in the residual concentration of Cr in the suspension. Acute toxicity tests performed using pristine nano-TiO₂ (0.25, 0.5, 1, 2, and 4 mg/L) and Cr(VI) (0.125, 0.25, 0.5, and 1 mg/L) displayed a concentration dependent rise in the mortality of Artemia salina. To examine the effects of mixtures of nano-TiO₂ and Cr(VI) on Artemia salina, two groups of experiments were designed. The former group studied the toxic effect of nano-TiO₂ (0.5, 1, 2, and 4 mg/L) with a fixed concentration (0.125 mg/L) of Cr(VI). While the latter group studied the toxicity of Cr(VI) (0.25, 0.5, and 1 mg/L) with a fixed concentration (0.25 mg/L) of nano-TiO₂. The toxic effects of nano-TiO₂ was not significantly reduced at a fixed concentration of Cr(VI) but in contrast, a significant reduction in the Cr(VI) toxicity by fixed concentration of nano-TiO₂ was observed. Toxicity data was well supported by an independent action model that proved the mode of action between nano-TiO₂ and Cr(VI) to be antagonistic. Furthermore, ROS generation and measurement of antioxidant enzyme activities were also in line with toxicity results. From this study, the modification of Cr(VI) toxicity at fixed concentration of nano-TiO₂ could have a huge impact on the reduction in Cr(VI) toxicity across trophic levels.

Zein Nanoparticles Impregnated with Eugenol and Garlic Essential Oils for Treating Fish Pathogens

The supply of food derived from aquaculture has increased significantly in recent years. The aim of this industrial sector is to produce sustainable products to meet the needs of consumers, providing food security and nutritional benefits. The development of aquaculture has faced challenges including disease outbreaks that can cause substantial economic losses. These diseases can be controlled using chemicals such as antibiotics. However, the indiscriminate use of these substances can have major negative impacts on human health and the environment with the additional risk of the emergence of resistant organisms. The present manuscript describes the use of phytotherapy in association with nanotechnology in order to obtain a more effective and less harmful system for the control of bacterial diseases in fish. Zein nanoparticles associated with eugenol and garlic essential oil were prepared through antisolvent precipitation and characterized. Zein nanoparticles are promising carrier systems as zein proteins are biodegradable and biocompatible and, in this way, good candidates for encapsulation of active ingredients. The system presented good physicochemical properties with an average particle diameter of approximately 150 nm, a polydispersity index lower than 0.2, and a zeta potential of approximately 30 mV. High encapsulation efficiency was obtained for the active compounds with values higher than 90%, and the compounds were protected against degradation during storage (90 days). The nanoparticle formulations containing the botanical compounds also showed less toxicity in the tests performed with a biomarker (Artemia salina). In addition, the systems showed bactericidal activity against the important fish pathogenic bacteria Aeromonas hydrophila, Edwardsiella tarda, and Streptococcus iniae in vitro. The present study opens new perspectives for the use of botanical compounds in combination with nanotechnology to treat fish diseases caused by bacteria, contributing to a more sustainable fish chain production.