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Nanosilver applications, including sensing and water treatment, have significantly increased in recent years, although safety for humans and the environment is still under debate. Here, we tested the environmental safety of a novel formulation of silver nanoparticles functionalized with citrate and L-cysteine (AgNPcitLcys) on freshwater cnidarian

Nanosilver, widely employed in consumer products as biocide, has been recently proposed as sensor, adsorbent and photocatalyst for water pollution monitoring and remediation. Since nanosilver ecotoxicity still pose limitations to its environmental application, a more ecological exposure testing strategy should be coupled to the development of safer formulations. Here, we tested the environmental safety of novel bifunctionalized nanosilver capped with citrate and L-cysteine (AgNPcitLcys) as sensor/sorbent of Hg2+ in terms of behaviour and ecotoxicity on microalgae (1-1000µg/L) and microcrustaceans (0.001-100mg/L), from the freshwater and marine environment, in acute and chronic scenarios. Acute toxicity resulted poorly descriptive of nanosilver safety while chronic exposure revealed stronger effects up to lethality. Low dissolution of silver ions from AgNPcitLcys was observed, however a nano-related ecotoxicity is hypothesized. Double coating of AgNPcitLcys succeeded in mitigating ecotoxicity to tested organisms, hence encouraging further research on safer nanosilver formulations. Environmentally safe applications of nanosilver should focus on ecologically relevant exposure scenarios rather than relying only on acute exposure data.

Plastic pollution is a global issue posing a threat to marine biota with ecological implications on ecosystem functioning. Micro and nanoplastic impact on phytoplankton autotrophic species (e.g., cell growth inhibition, decrease in chlorophyll a and photosynthetic efficiency and hetero-aggregates formation) have been largely documented. However, the heterogeneity of data makes rather difficult a comparison based on size (i.e. micro vs nano). In addition, knowledge gaps on the ecological impact on phytoplankton assemblage structure and functioning are evident. A new virtual meta-analysis on cause-effect relationships of micro and nanoplastics on phytoplankton species revealed the significant effect posed by polymer type on reducing cell density for tested PVC, PS and PE plastics. Linked with autotrophic phytoplankton role in atmospheric CO2 fixation, a potential impact of plastics on marine carbon pump is discussed. The understanding of the effects of microplastics and nanoplastics on the phytoplankton functioning is fundamental to raise awareness on the overall impact on the first level of marine food web. Interactions between micro and nanoplastics and phytoplankton assemblages have been quite documented by in vitro examinations; but, further studies considering natural plankton assemblages and/or large mesocosm experiments should be performed to evaluate and try predicting ecological impacts on primary producers.

Along with social and economic development, population growth and the increasing interests in exploitation of marine resources, a progressively increase of marine pollution is expected. Both marine communities populating coastal areas as well as the deep sea have been continuously threatened by various classes of chemical pollutants with associated environmental deterioration and reduction of ecosystem services. Since the sustainable development and ecological protection of the ocean means that of human beings, efficient solutions for pollution monitoring and hazards mitigation are mandatory. Here we propose innovative nano-based solutions developed in the framework of an ecologically based design strategy (eco-design) able to quick and efficient detect and remove chemical pollutants from marine waters with no further associated risk for humans and the environment.

Silver nanoparticles (AgNPs) are widely used as engineered nanomaterials (ENMs) in many advanced nanotechnologies, due to their versatile, easy and cheap preparations combined with peculiar chemical-physical properties. Their increased production and integration in environmental applications including water treatment raise concerns for their impact on humans and the environment. An eco-design strategy that makes it possible to combine the best material performances with no risk for the natural ecosystems and living beings has been recently proposed. This review envisages potential hybrid solutions of AgNPs for water pollution monitoring and remediation to satisfy their successful, environmentally safe (ecosafe) application. Being extremely efficient in pollutants sensing and degradation, their ecosafe application can be achieved in combination with polymeric-based materials, especially with cellulose, by following an eco-design approach. In fact, (AgNPs)–cellulose hybrids have the double advantage of being easily produced using recycled material, with low costs and possible reuse, and of being ecosafe, if properly designed. An updated view of the use and prospects of these advanced hybrids AgNP-based materials is provided, which will surely speed their environmental application with consequent significant economic and environmental impact.

Marine diatoms have been identified among the most abundant taxa of microorganisms associated with plastic waste collected at sea. However, the impact of nano-sized plastic fragments (nanoplastics) at single cell and population level is almost unknown. We exposed the marine diatom Skeletonema marinoi to model polystyrene nanoparticles with carboxylic acid groups (PS–COOH NPs, 90 nm) for 15 days (1, 10, 50 μg/mL). Growth, reactive oxygen species (ROS) production, and nano-bio-interactions were investigated. No effect on diatom growth was observed, however Dynamic light scattering (DLS) demonstrated the formation of large PS aggregates which were localized at the diatoms’ fultoportula process (FPP), as shown by TEM images. Increase production of ROS and reduction in chain length were also observed upon PS NPs exposure (p < 0.005). The observed PS-diatom interaction could have serious consequences on diatoms ecological role on the biogeochemical cycle of carbon, by impairing the formation of fast-sinking aggregates responsible for atmospheric carbon fixation and sequestration in the ocean sea floor. S. marinoi exposure to PS NPs caused an increase of intracellular and extracellular oxidative stress, the reduction of diatom's chain length and the adhesion of PS NPs onto the algal surface.

In this work, hydrophilic silver nanoparticles (AgNPs), bifunctionalized with citrate (Cit) and L-cysteine (L-cys), were synthesized. The typical local surface plasmon resonance (LSPR) at &lambda, max = 400 nm together with Dynamic Light Scattering (DLS) measurements (&lt, 2RH&gt, = 8 &plusmn, 1 nm) and TEM studies (&Oslash, = 5 &plusmn, 2 nm) confirmed the system nanodimension and the stability in water. Molecular and electronic structures of AgNPs were investigated by FTIR, SR-XPS, and NEXAFS techniques. We tested the system as plasmonic sensor in water with 16 different metal ions, finding sensitivity to Hg2+ in the range 1&ndash, 10 ppm. After this first screening, the molecular and electronic structure of the AgNPs-Hg2+ conjugated system was deeply investigated by SR-XPS. Moreover, in view of AgNPs application as sensors in real water systems, environmental safety assessment (ecosafety) was performed by using standardized ecotoxicity bioassay as algal growth inhibition tests (OECD 201, ISO 10253:2006), coupled with determination of Ag+ release from the nanoparticles in fresh and marine aqueous exposure media, by means of ICP-MS. These latest studies confirmed low toxicity and low Ag+ release. Therefore, these ecosafe AgNPs demonstrate a great potential in selective detection of environmental Hg2+, which may attract a great interest for several biological research fields.

Nanoplastics are recognized as able to interact with other pollutants including heavy metals, and with natural organic matter, with implications for the potential risks to biota. We investigated the interaction of carboxylated polystyrene nanoparticles (PS–COOH NPs) with copper (Cu) and algal exudates (EPS) and how such interaction could affect Cu toxicity towards the freshwater microalga Raphidocelis subcapitata. PS–COOH NPs behavior in the presence of Cu and EPS was determined by dynamic light scattering (DLS), while PS–COOH NPs surface interaction with Cu ions and EPS was investigated by fluorimetric analysis. ICP-MS was used to test Cu ion adsorption to PS–COOH NPs in the presence and absence of algae. The interaction between PS–COOH NPs and the algal cell wall was assessed by fluorescence microscopy. Short- and long-term toxicity tests were carried out in parallel to assess the impact of PS–COOH NPs on algal growth. Results showed altered nanoparticle surface charge and hydrodynamic diameter following algal EPS exposure, supporting the hypothesis of a protein corona formation. In contrast, no absorption of Cu ions was observed on PS–COOH NPs, either in the presence or absence of algae. No differences on algal growth inhibition were observed between exposure to Cu only, and to Cu in combination with PS–COOH NPs, in short-term as well as long-term tests. However, after 72 h of exposure, the adsorption of PS-COOH NPs to algal cell walls appeared to correspond to morphological alterations, revealing potential disturbances in the mitotic cycle. Our findings confirm the ability of PS–COOH NPs to interact with EPS as shown for other nanomaterials. Environmentally realistic exposure scenarios are thus needed for evaluating nanoplastic toxicity, as nanoparticles will not maintain their pristine nature once released into natural media. Prolonged exposure and use of different end-points such as cell morphological changes and EPS production seem more reliable for the investigation of nanoplastic/algal cell interactions which can drive food chain transfer of nanoplastics and ultimately toxicity.

Acid mine drainage (AMD) is a global environmental challenge that represents a primary source of contamination of heavy metals in both active and abandoned mining areas. The present study explored the suitability of a carboxymethylcellulose (CMC) hydrogel cross-linked with functionalized magnetite (Fe3O4) nanoparticles, (CMC-Fe3O4), for the removal of heavy metals from AMD-affected stream waters and tested its eco-friendly nature. AMD-affected stream waters, collected in a former mining site located in the Metalliferous Hills ore district (Central Italy), were chosen as a suitable benchmark for validating the CMC-Fe3O4 hydrogel applications. The remediation capability of the CMC-Fe3O4 hydrogel was investigated on solutions of Zn(II) in deionized (DI) water and on samples of AMD-affected stream waters. The CMC-Fe3O4 hydrogel was able to adsorb Zn(II) from DI water solutions as well as to reduce significantly the concentration of Zn and other heavy metals such as Cd, Co, Cu, Ni and Pb, in AMD-affected stream waters. CMC-Fe3O4 hydrogel and treated waters (both Zn-solution and AMD-affected stream waters) were tested for their effects on the freshwater green alga R. subcapitata by using 72-h growth inhibition tests. No effects were observed on the R. subcapitata growth upon exposure to CMC-Fe3O4 hydrogel, suggesting its eco-friendly nature. Moreover, CMC-Fe3O4 hydrogel was able to reduce the toxicity of heavy metals to the green alga, both in DI and AMD-affected stream water. Based on our findings, CMC-Fe3O4 hydrogel could be considered as a valuable tool for an environmentally safe treatment of AMD-affected stream waters.