Environmental safety data on CuO and TiO2 nanoparticles for multiple algal species in natural water: Filling the data gaps for risk assessment

Cellular uptake of multi-walled carbon nanotubes is associated to genotoxic and teratogenic effects towards the freshwater diatom Nitzschia linearis

The increase in industrial production of multi-walled carbon nanotubes (MWCNTs) raises concerns about their potential adverse effects associated to environmental releases, especially in aquatic environments where they are likely to accumulate. This study focuses on the environmental impact of MWCNTs, specifically on a benthic freshwater diatom (Nitzschia linearis), which plays a major role in the primary production of water bodies. The obtained results indicate that exposure to MWCNTs in the presence of natural organic matter (NOM) inhibits diatom's growth in a dose-dependent manner after 72 h of exposure. Interestingly, the photosystem II quantum yield (PSIIQY) in diatoms remains unaffected even after exposure to MWCNTs at 10 mg/L. After 48 h of exposure, MWCNTs are found to bind preferentially to extracellular polymeric substances (EPS) produced by diatoms, which could decrease their toxicity by limiting their interaction with this organism. However, measurement of genotoxicity and teratogenicity in diatoms exposed to MWCNTs revealed that the exposure to MWCNTs increased the occurrence of cells with micronuclei and abnormal frustules. Microscopy analyses including two-photon excitation microscopy (TPEM) revealed the internalization of MWCNTs. Investigations of the diatom's frustule structure using Scanning electron microscopy (SEM) indicated that the presence of pore structures constitutes a pathway allowing MWCNTs uptake. The presence in the diatom's cytoplasm of MWCNTs might possibly induce disturbances of the cellular components, leading to the observed genotoxic and teratogenic effects. In view of previous studies, this work underscores the need for further studies on the interaction between nanomaterials and different diatom species, given the species-specific nature of the interactions.

Toxic effect of mussel Mytilus galloprovincialis exposed to Ag-TiO2 and ZnTi2O4-TiO2 bicomponent nanoparticles

Nanoparticles (NPs) are widely used in various fields, including antifouling paints for ships and industrial structures submerged in water. The potential impact of NPs on aquatic organisms, particularly their potential toxicity, is a significant concern, as their negative impact has been relatively poorly studied. In this study, we evaluated the effect of different concentrations of bimetallic Ag-TiO₂ and ZnTi₂O₄-TiO₂ NPs, which could potentially be used in antifouling coatings, on the hemocytes of the Mediterranean mussel Mytilus galloprovincialis. Hemocytes were exposed to NPs at concentrations of 0.1-1 mg/L for 1 and 2 h, and the production of reactive oxygen species (ROS), levels of DNA damage, and number of dead cells were measured. Exposure to Ag-TiO₂ NPs at 1 mg/L concentration for 1 h suppressed ROS production in hemocytes and reduced the relative number of agranulocytes in cell suspensions, without inducing DNA damage or cell death. Exposure to ZnTi2O4-TiO2 NPs did not cause changes in the ratio of granulocytes to agranulocytes in suspensions, nor did it affect other functional parameters of hemocytes. However, after a 2 h exposure period, ZnTi2O4-TiO2 NPs (1 mg/L) significantly reduced the production of ROS by hemocytes. These findings suggest that Ag-TiO2 and ZnTi2O4-TiO2 NPs have low acute toxicity for marine bivalves.

CuO nanoparticles' effect on the photosynthetic performance in seed tissues of Inga laurina (Fabaceae)

Copper oxide nanoparticles (CuONPs) have been produced on a large scale because they can be applied across various fields, especially in nano-enabled healthcare and agricultural products. However, the increasing use of CuONPs leads to their release and accumulation into the environment. The CuONPs uptaken by seeds and their implications on germination behavior have been reported, but little is known or understood about their impact on photosynthesis in seed tissues. To fill knowledge gaps, this study evaluated the effects of CuONP concentrations (0-300 mg L-1) on the photosynthetic activity of Inga laurina seeds. The microscopy data showed that CuONPs had an average size distribution of 57.5 ± 0.7 nm. Copper ion release and production of reactive oxygen species (ROS) by CuONPs were also evaluated by dialysis and spectroscopy experiments, respectively. CuONPs were not able to intrinsically generate ROS and released a low content of Cu2⁺ ions (4.5%, w/w). Time evolution of chlorophyll fluorescence imaging and laser-induced fluorescence spectroscopy were used to monitor the seeds subjected to nanoparticles during 168 h. The data demonstrate that CuONPs affected the steady-state maximum chlorophyll fluorescence (F m ' ), the photochemical efficiency of photosystem II (F v / F m ), and non-photochemical quenching ( NPQ ) of Inga laurina seeds over time. Besides, the NPQ significantly increased at the seed development stage, near the root protrusion stage, probably due to energy dissipation at this germination step. Additionally, the results indicated that CuONPs can change the oscillatory rhythms of energy dissipation of the seeds, disturbing the circadian clock. In conclusion, the results indicate that CuONPs can affect the photosynthetic behavior of I. laurina seeds. These findings open opportunities for using chlorophyll fluorescence as a non-destructive tool to evaluate nanoparticle impact on photosynthetic activity in seed tissues.

Environmental fate of aquatic pollutants and their mitigation by phycoremediation for the clean and sustainable environment: A review

Emerging pollutants such as natural and manufactured chemicals, insecticides, pesticides, surfactants, and other biological agents such as personal care products, cosmetics, pharmaceuticals, and many industrial discharges hamper the aquatic environment. Nanomaterials and microplastics, among the categories of pollutants, can directly interfere with the marine ecosystem and translate into deleterious effects for humans and animals. They are either uncontrolled or poorly governed. Due to their known or suspected effects on human and environmental health, some chemicals are currently causing concern. The aquatic ecology is at risk from these toxins, which have spread worldwide. This review assesses the prevalence of emerging and hazardous pollutants that have effects on aquatic ecosystems and contaminated water bodies and their toxicity to non-target organisms. Microalgae are found to be a suitable source to remediate the above-mentioned risks. Microalgae based mitigation techniques are currently emerging approaches for all such contaminants, including the other categories that are discussed above. These studies describe the mechanism of phycoremediation, provide outrage factors that may significantly affect the efficiency of contaminants removal, and discuss the future directions and challenges of microalgal mediated remediations.

Advanced technologies for the determination of quantitative structure-activity relationships and degradation efficiency of micropollutants and their removal in water - A review

The growing concentrations of micropollutants in aquatic ecosystems are a global water quality issue. Understanding micropollutants varied chemical composition and potency is essential to solving this complex issue. Micropollutants management requires identifying contaminants to reduce, optimal reduction targets, and the best wastewater recycling locations. Management requires appropriate technological measures. Pharmaceuticals, antibiotics, hormones, and other micropollutants can enter the aquatic environment from point and diffuse sources, with wastewater treatment plants (WWTPs) distributing them in urban areas. Micropollutants like pharmaceuticals and hormones may not be removed by conventional WWTPs. Micropollutants affect the EU, especially in densely populated areas where surface water is consumed. This review examines several technological options that can be integrated into existing treatment methods to address this issue. In this work, oxidation, activated carbon, and their combinations as potential solutions, considering their efficacy and cost were evaluated. This study illuminates micropollutants origin and physico-chemical properties, which affect distribution, persistence, and environmental impacts. Understanding these factors helps us develop targeted micropollutant mitigation strategies to protect water quality. This review can inform policy and decision-making to reduce micropollutant impacts on aquatic ecosystems and human health.

Differential toxicity of various mineral nanoparticles to Synechocystis sp.: With and without ciprofloxacin

Mineral nanoparticles (M-NPs) are ubiquitous in aquatic environments, but their potential harms to primary producers and impacts on the toxicity of coexisting pollutants are largely unknown. Herein, the toxicity mechanisms of various M-NPs (i.e., SiO2, Fe2O3, Al2O3, and TiO2 NPs) to Synechocystis sp. in absence and presence of ciprofloxacin (CIP) were comprehensively investigated. The heteroaggregation of cells and M-NPs can hinder substrate transfer or light acquisition. The attraction between Synechocystis sp. and M-NPs increased in the order of SiO2 < Fe2O3 < Al2O3 ≈ TiO2 NPs. Therefore, SiO2 and Fe2O3 NPs exerted slight effects on physiology and proteome of Synechocystis sp.. Al2O3 NPs with the rod-like shape caused physical damage to cells. Differently, TiO2 NPs with photocatalytic activities provided photogenerated electrons for Synechocystis sp., promoting photosynthesis and the Calvin cycle for CO2 fixation. SiO2, Fe2O3, and Al2O3 NPs alleviated the toxicity of CIP in an adsorption-depended manner. Conversely, the combination of CIP and TiO2 NPs exerted more pronounced toxic effects compared to their individuals, and CIP disturbed the extracellular electron transfer from TiO2 NPs to cells. The findings highlight the different effects of TiO2 NPs from other M-NPs on cyanobacteria, either alone or in combination with CIP, and improve the understanding of toxic mechanisms of M-NPs.

Effect of Exposure Concentration and Growth Conditions on the Association of Cerium Oxide Nanoparticles with Green Algae

The increasing release of engineered nanoparticles (NPs) into aquatic ecosystems makes it crucial to understand the interactions of NPs with aquatic organisms, such as algae. In this study, the association of CeO2 NPs with unicellular algae (Raphidocelis subcapitata) and changes to the cellular elemental profile were investigated using three exposure concentrations (1, 50, and 1000 µg CeO2/L) at two different algal growth conditions-exponential and inhibited growth (1% glutaraldehyde). After a 24 h-exposure, algal suspensions were settled by gravity and CeO2-NP/algae association was analyzed by single-cell inductively coupled plasma quadrupole mass spectrometry (sc-ICP-QMS) and ICP time-of-flight MS (sc-ICP-TOFMS). Concurrent detection of the cellular fingerprint with cerium indicated NP association with algae (adsorption/uptake) and changes in the cellular elemental profiles. Less than 5% of cells were associated with NPs when exposed to 1 µg/L. For 50 µg/L exposures in growing and inhibited cell treatments, 4% and 16% of cells were associated with CeO2 NPs, respectively. ICP-TOFMS analysis made it possible to exclude cellular exudates associated with CeO2 NPs due to the cellular fingerprint. Growing and inhibited cells had different elemental profile changes following exposure to CeO2 NPs-e.g., growing cells had higher Mg and lower P contents independent of CeO2 concentration compared to inhibited cells.

Assessment of the Tolerance of a Chlorophyte Desmodesmus to CuO-NP for Evaluation of the Nanopollution Bioremediation Potential of This Microalga

Broad application of CuO nanoparticles (CuO-NP) for industrial and household purposes leads to a continuous increase in their discharge to, and, hence, ever-increasing environmental hazards for aquatic ecosystems. Microalgae-based technologies hold promise for bioremediation of diverse hazardous micropollutants (HMP), including NP, from wastewater. In this study, we tested the ability of the green microalga Desmodesmus sp. to accumulate CuO-NP or their components. We also assessed the tolerance of this microalga to the environmentally relevant concentrations of CuO-NP. Using scanning electron microscopy, we demonstrated that the average size of CuO-NP was 50-100 nm, and their purity was confirmed with elemental composition analysis. Tests of the colloidal suspensions of CuO-NP showed that the hydrodynamic diameter of CuO-NP and their aggregates was below 100 nm. Flow cytometry analysis showed that CuO-NP at a concentration of 100 µg L-1 slightly inhibited the viability of microalgae cells and led to an increase in their oxidative stress. The assessment of the condition of photosystem II showed that CuO-NP exert a multifaceted effect on the photosynthetic apparatus of Desmodesmus sp., depending on the concentration of and the exposure to the CuO-NP. Desmodesmus sp. turned to be relatively tolerant to CuO-NP. In addition, the ICP-MS method revealed increased bioaccumulation of copper by microalgae cells in the experimental groups. The outcomes of this study indicate that the Desmodesmus sp. has a significant potential for bioremoval of the copper-based nanostructured HMP from an aquatic environment.

Differential responses of Pleurochrysis sp. (Haptophyta) to the effect of copper and light intensity

The effect of light, copper ions, copper oxide nanoparticles on the change in the structural, functional, cytometric, fluorescent parameters of coccolithophore Pleurochrysis sp. was investigated. The culture Pleurochrysis sp. was represented by two cell forms: (1) covered with coccoliths; and (2) not covered, the ratio of which depends from growth conditions. An increase in light from 20 to 650μEm-2 s-1 led to a decrease in the concentration of cells covered with coccoliths from 90 to 35%. With an increase in light, the decrease in the values of variable chlorophyll a fluorescence was observed, a decrease in the chlorophyll concentration was noted, and an increase in cell volumes and their granularity due to coccoliths 'overproduction' was recorded. A tolerance of Pleurochrysis sp. to the effect of copper was registered, both in the ionic form and in the form of a nanopowder. This is probably due to the morphological (presence of coccoliths) and physiological (ligand production) peculiarities of species. Copper did not affect the ratio of cells covered with coccoliths; its value was about 85%. Growth inhibition, a 2-fold decrease in the intracellular chlorophyll content, a decrease in F v /F m , and a pronounced cell coagulation were recorded at the maximum Cu2+ concentration (625μgL-1 ). The mechanical effect was registered of CuO nanoparticles on the surface of Pleurochrysis sp. coccosphere, which results in the emergence of destroyed and deformed coccoliths. A hypothesis is proposed considering the protective function of coccoliths acting as a barrier when the cells are exposed to nanoparticles and copper ions.

Aquatic organisms modulate the bioreactivity of engineered nanoparticles: focus on biomolecular corona

The increased use of nanoparticle (NP)-enabled materials in everyday-life products have raised concerns about their environmental implications and safety. This motivated the extensive research in nanoecotoxicology showing the possibility that NPs could cause harm to the aquatic organisms if present at high concentrations. By contrast, studies dealing with influence that organisms could exert on the fate and thus effects of NPs are still very rare. Drawing on the existing up-to-date knowledge we critically discuss the formation of biomolecular corona as one of the mechanisms by which organisms exerted control on the NPs fate in the aquatic and biotic environments. We focused the formation of corona by exogeneous and endogenous biomolecules and illustrated the discussion with the specific example of phytoplankton and aquatic invertebrate species. We highlighted the necessity to incorporate the concept of biomolecular corona within more general framework considering the feedback of aquatic organisms and the control they exert in shaping the fate and impact of NPs in the aquatic and biological environment. In our view such broader perspective will contribute to get novel insights into the drivers of environmental transformations of NPs and their mechanisms, which are important in environmental risk assessment.

Responses of Prorocentrum cordatum (Ostenfeld) Dodge, 1975 (Dinoflagellata) to copper nanoparticles and copper ions effect

In the present study, changes were determined in morphological, structural-functional, and fluorescent parameters of Prorocentrum cordatum with the addition of CuO nanoparticles (NPs) and copper ions (CuSO₄). A stimulating effect of low Cu²⁺ concentrations (30 μg L^-1) on algal growth characteristics was observed. Higher Cu²⁺ concentration of 60-600 μg L^-1 and CuO NPs concentration of 100-520 μg L^-1 inhibited algal growth. Ionic copper is more toxic to P. cordatum than NPs. After 72 h of algae cultivation in the medium supplemented with CuSO₄ and CuO NPs, EC₅₀ values (calculated based on cell abundance) were of 60 and 300 μg L^-1 (in terms of copper ions), respectively. Reduction in algal growth rate is due to disruption in cell cycle, changes in nuclear morphology, chromatin dispersion, and DNA damage. The studied pollutants slightly affected the efficiency of P. cordatum photosynthetic apparatus. Addition of the pollutants resulted in an increased production of reactive oxygen species (ROS). At a concentration of Cu²⁺ of 120 μg L^-1 and a concentration of CuO NPs 0-300 μg L^-1 of CuO NPs increase in ROS production is short-term with a decrease at later stages of the experiment. This is probably due to the activation of antioxidant mechanisms in cells and an increase in the concentration of carotenoids (peridinin) in cells. The high values of ROS production persisted throughout the experiment at sublethal copper concentrations (400-600 μg L^-1 of CuSO₄ and 520 μg L^-1 of CuO NPs). Sublethal concentrations of pollutants caused restructuring of cell membranes in P. cordatum. Shedding of cell membranes (ecdysis) and formation of immobile stages (temporary or resting cysts) were recorded. The pronounced mechanical impact of NPs on the cell surface was observed such as-deformation and damage of a cell wall, its "wrinkling" and shrinkage, and adsorption of NP aggregates.

Quantifying impacts of titanium dioxide nanoparticles on natural assemblages of riverine phytobenthos and phytoplankton in an outdoor setting

Impacts of widespread release of engineered titanium dioxide nanoparticles (nTiO₂) on freshwater phytoplankton and phytobenthic assemblages in the field, represents a significant knowledge gap. Using outdoor experiments, we quantified impacts of nTiO₂ on phytoplankton and periphyton from UK rivers, applied at levels representative of environmentally realistic concentrations (0.05 mg/L) and hot spots of accumulation (5.0 mg/L). Addition of nTiO₂ to river water led to rapid temporal size changes in homoagglomerates and many heteroaggregates of nTiO₂ with cells in the phytoplankton, including green algae, pennate and centric diatoms, increasing settlement of some cells. Changes in phytoplankton composition were evident after 72-h resulting from a significant decline in the relative abundance of very small phytoplankton cells (1-3 μm), often accompanied by increases in centric diatoms at both concentrations. Significant changes detected in the composition of the phytobenthos after 12 days, following nTiO₂ treatments, were not evident when using benthic diatoms alone after 56 days. A lack of inhibition in the maximum quantum yield (Fv/Fm) in phytobenthos after 72-h exposures contrasted with a significant inhibition in Fv/Fm in 75% of phytoplankton samples, the highest recorded in Rutile nTiO₂ exposures at both concentrations of nTiO₂. After 12 days, strong positive stimulatory responses were recorded in the maximum relative electron transport rate (rETR_max) and the maximum non-photochemical coefficient (NPQ_max), in phytoplankton and phytobenthos samples exposed to the higher Anatase nTiO₂ concentration, were not measured in Rutile exposed biota. Collectively, these results indicate that the Rutile phase of nTiO₂ has more negative impacts on freshwater algae than the Anatase form, at specific time scales, and phytoplankton may be more impacted by nTiO₂ than phytobenthos. We caution that repeated release of nTiO₂, could lead to significant changes in riverine algal biomass and species composition, dependent on the phase and concentration of nTiO₂.

Toxicity of selenium nanoparticles on Poterioochromonas malhamensis algae in Waris-H culture medium and Lake Geneva water: Effect of nanoparticle coating, dissolution, and aggregation

Understanding the algal toxicity of selenium nanoparticles (SeNPs) in aquatic systems by considering SeNPs physicochemical properties and environmental media characteristics is a concern of high importance for the evaluation and prediction of risk assessment. In this study, chitosan (CS) and sodium carboxymethyl cellulose (CMC) coated SeNPs are considered using Lake Geneva water and a Waris-H cell culture medium to investigate the effect of SeNPs on the toxicity of algae Poterioochromonas malhamensis, a widespread mixotrophic flagellate. The influence of surface coating, z-average diameters, ζ-potentials, aggregation behavior, ions release, and medium properties on the toxicity of SeNPs to algae P. malhamensi was investigated. It is found that SeNPs are 5-10 times more toxic in Lake Geneva water compared to the culture medium, suggesting that the traditional algal tests in Waris-H culture medium currently underestimate the toxicity of NPs in a natural water environment. Despite significant dissolution, it is also found that SeNPs themselves are the toxicity driver, and dissolved ions have only a marginal influence on toxicity. SeNPs diameter is found a minor factor in toxicity. Based on a principal component analysis (PCA) it is found that in Lake Geneva water, the nature of the surface coating (CMC versus CS) is the most influential factor controlling the toxicity of SeNPs. In the culture medium, surface coating, ζ-potential, and aggregation are found to contribute at the same level. These results highlight the importance of considering in details both NPs intrinsic and media properties in the evaluation of NPs biological effects.

Double-dose responses of Scenedesmus capricornus microalgae exposed to humic acid

Dissolved organic matter (DOM) has been found to attenuate the ecotoxicity of various environmental pollutants, but research on its own toxic effects in aquatic ecosystems has been very limited. Herein, the toxic effects of humic acid (HA), a represent DOM typically found in natural waters, on the freshwater alga Scenedesmus capricornus were investigated. As result, HA exerted a double-dose effect on the growth of Scenedesmus capricornus. At HA concentrations below 2.0 mgC/L, the growth of Scenedesmus capricornus was slightly promoted, as was the synthesis of chlorophyll and macromolecules in the algae. Moreover, S. capricornus can maintain its growth by secreting fulvic acid as a nutrient carbon source. However, the growth of Scenedesmus capricornus was significantly inhibited when HA was beyond 2.0 mgC/L. The main mechanisms of humic acid's toxicity were membrane damage and oxidative stress. Particularly, when the oxidative stress exceeds the algae's carrying capacity, the synthesis of EPS is greatly inhibited and HA damage results. Taken together, DOM may have both positive and negative effects on aquatic ecosystems.

The effects of copper ions and copper nanomaterials on the output of amino acids from marine microalgae

In this study, the marine microalgae Skeletonema costatum and Nitzschia closterium were exposed to different forms of copper, such as a metal salt (Cu²⁺), a nano-metal (nano-Cu), and nano-metal oxide (nano-CuO). During a 96-h exposure to nanoparticles (NPs) and salt, the cell number, Cu²⁺ concentration in the culture medium, morphology, and intracellular amino acids were measured to assess the toxicity of the copper materials and the toxicity mechanism of the NPs. As results, the toxicity of Cu²⁺, nano-Cu, and nano-CuO to marine phytoplankton decreased in order. The EC₅₀ values of Cu²⁺ and nano-Cu for S. costatum and N. closterium ranged from 0.356 to 0.991 mg/L and 0.663 to 2.455 mg/L, respectively. Nano-Cu inhibits the growth of marine phytoplankton by releasing Cu²⁺; however, nano-CuO is harmful to microalgae because of the effect of NPs. The secretion of extracellular polymeric substances by microalgae could also affect the toxicity of nano-Cu and nano-CuO to microalgae. S. costatum was more sensitive to copper than N. closterium. Cu²⁺, nano-Cu, and nano-CuO all reduced per-cell amino acids and the total output of algae-derived amino acids by affecting the growth of the phytoplankton. This study helps to understand the risk assessment of nano-Cu and nano-CuO to marine microalgae.

Mutual impacts and interactions of antibiotic resistance genes, microcystin synthetase genes, graphene oxide, and Microcystis aeruginosa in synthetic wastewater

The physiological impacts and interactions of antibiotic resistance gene (ARG) abundance, microcystin synthetase gene expression, graphene oxide (GO), and Microcystis aeruginosa in synthetic wastewater were investigated. The results demonstrated that the absolute abundance of sul1, sul2, tetW, and tetM in synthetic wastewater dramatically increased to 365.2%, 427.1%, 375.2%, and 231.7%, respectively, when the GO concentration was 0.01 mg/L. Even more interesting is that the sum gene copy numbers of mcyA-J also increased to 243.2%. The appearance of GO made the significant correlation exist between ARGs abundance and mcyA-J expression. Furthermore, M. aeruginosa displayed better photosynthetic performance and more MCs production at 0.01 mg/L GO. There were 65 pairs of positive correlations between the intracellular differential metabolites of M. aeruginosa and the abundance of sul1, sul2, tetM, and tetW with various GO concentrations. The GO will impact the metabolites and metabolic pathway in M. aeruginosa. The metabolic changes impacted the ARGs, microcystin synthetase genes, and physiological characters in algal cells. Furthermore, there were complex correlations among sul1, sul2, tetM, tetW, mcyA-J, MCs, photosynthetic performance parameters, and ROS. The different concentration of GO will aggravate the hazards of M. aeruginosa by promoting the expression of mcyA-J, producing more MCs; simultaneously, it may cause the spread of ARGs.

Colorants in coatings

The aim of this chapter is to provide a compact overview of colorants and their use in coatings including a brief introduction to paint technology and its raw materials. In addition, it will focus on individual colorants by collecting information from the available literature mainly for their use in coatings. Publications on colorants in coatings applications are in many cases standard works that cover the wider aspects of color chemistry and paint technology and are explicitly recommended for a more detailed study of the subject [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18]. Articles or information on paint formulation using coatings which contain colorants are rare [19]. This formulation expertise is often company property as it is the result of many years of effort built up over very long series of practical “trial-and-error” optimization tests and, more recently, supported by design of experiment and laboratory process automation [20, 21]. Therefore, it is protected by rigorous secrecy agreements. Formulations are in many ways part of a paint manufacturer’s capital, because of their use in automotive coatings, coil coatings, powder coatings, and specialist knowledge is indispensable to ensure their successful industrial use [22]. An important source to learn about the use of pigments in different coating formulations are guidance or starting formulations offered by pigment, additive, and resin manufacturers. These are available upon request from the technical service unit of these companies. Coating formulations can also be found scattered in books on coating and formulation technology [4, 5, 18, 23,24,25,26,27]. This overview can in no way claim to be complete, as the literature and relevant journals in this field are far too extensive. Nevertheless, it remains the author’s hope that the reader will gain a comprehensive insight into the fascinating field of colorants for coatings, including its literature and current research activities and last but not least its scientific attractiveness and industrial relevance.

Cytotoxicological evaluation of copper oxide nanoparticles on green algae, bacteria and crustacean systems

PURPOSE

Copper oxide (CuO) nanoparticles (NPs) have been utilized in several industries including textile, consumer products, medical, automobiles etc. The discharge of industrial effluents in environment increased the probability of CuO NPs contamination in the ecosystem.

METHODS

The present investigation used CuO NPs to determine the toxic effect on Lyngbya species, fresh water algae isolated from natural pond, bacterial species Pseudomonas aeruginosa and Staphylococcus aureus and a crustacean species Daphnia magna.

RESULTS

The NPs average diameter and zeta potential was estimated to be 45 ± 3 nm and 29 ± 1.78 mV respectively. The results showed that 0.1 µg/mL CuO NPs showed the growth inhibition of 47 ± 2% on Lyngbya sp. after 5 days of incubation. The CuO NPs also showed toxic effect to bacterial systems such as P. aeruginosa and S. aureus and crustacean system D. magna. Further, there was an increased lipid peroxidation and generation of reactive oxygen species (ROS) in algal cells observed up on NPs exposure. The exposure of NPs suppressed the antioxidant defense system. The amount of glutathione was reduced after the exposure of NPs.

CONCLUSION

The study suggested the role of ROS in toxicity of algal and bacterial systems. The present study pointed out the potent toxicity of CuO NPs to the organisms present in the aquatic environment.

Can the properties of engineered nanoparticles be indicative of their functions and effects in plants?

The extensive applicability of engineered nanoparticles (ENPs) in various fields such as environment, agriculture, medicine or biotechnology has mostly been attributed to their better physicochemical properties as compared with conventional bulk materials. However, functions and biological effects of ENPs change across different scenarios which impede the progress in their risk assessment and safety management. This review thus intends to figure out whether properties of ENPs can be indicators of their behavior through summarizing and analyzing the available literature and knowledge. The studies have indicated that size, shape, solubility, specific surface area, surface charge and surface reactivity constitute a more accurate measure of ENPs functions and toxic effects in addition to mass concentration. Effects of ENPs are also highly dependent on dose metrics, species and strains of organisms, environmental conditions, exposure route and duration. Searching correlations between properties and functions or biological effects may serve as an effective way in understanding positive and negative impacts of ENPs. This will ensure safe design and sustainable future use of ENPs.

Photosynthetic, morphological and biochemical biomarkers as tools to investigate copper oxide nanoparticle toxicity to a freshwater chlorophyceae

Copper oxide nanoparticles (CuO NP) have been produced on a large scale due to their economically interesting thermophysical properties. This heightens the concern about risks they may pose on their release into the environment, possibly affecting non-target organisms. Microalga are important organisms in ecotoxicological studies as they are at the base of the aquatic food chain, but information about their biochemical and photosynthetic changes in response CuO NP are still scarce. We studied the effects of CuO NP in Raphidocelis subcapitata using morphological, photosynthetic and biochemical biomarkers. Our results showed that the NP affected microalgal population growth with 0.70 mg Cu L^-1 IC_50-96 h (inhibition concentration). Based on predicted environmental concentrations of Cu NPs in aquatic environments, our results indicate potential risks of the NP to microalgae. Algal cell size, granularity and photosynthetic efficiencies were affected by the CuO NP at 0.97 and 11.74 mg Cu L^-1. Furthermore, lipid metabolism was affected mostly at the highest NP concentration, but at environmentally relevant values (0.012 and 0.065 mg Cu L^-1) the production of sterols (structural lipids) and triacylglycerols (reserve lipid) increased. Moreover, we found evidence of cell membrane impairment at the highest CuO NP concentration, and, as a photosynthetic response, the oxygen evolving complex was its main site of action. To the best of our knowledge, this is the first study to date to investigate microalgal lipid composition during CuO NP exposure, showing that it is a sensitive diagnostic tool. This research demonstrated that CuO NP may affect the physiology of R. subcapitata, and because they were observed in a primary producer, we foresee consequences to higher trophic levels in aquatic communities.

Effects of environmental factors on the growth and microcystin production of Microcystis aeruginosa under TiO2 nanoparticles stress

Due to the growing use and release of nanomaterials, their toxic impacts on aquatic ecosystems have drawn widespread attention in recent years. In this study, we exposed Microcystis aeruginosa to 5 mg/L titanium dioxide nanoparticles (nTiO₂) under different culture conditions (pH 6, 7, 8, 9; 20 °C, 25 °C, 30 °C). The results showed that algae had the worst growth status with lowest biomass, lowest photosynthetic activity and highest reactive oxygen species (ROS) generation under 5 mg/L nTiO₂ at pH 6 and 20 °C. Images by scanning electron microscopy (SEM) revealed that nTiO₂ hindered light absorption by algal cells by wrapping the algal surface, which led to obvious cell surface deformation at pH 6 or 20 °C. In addition, microcystin-LR (MC-LR) production increased as temperature or pH decreased when exposed to nTiO₂ at 5 mg/L, demonstrating that falling pH or temperature enhanced the adverse effects toward algal cells under nTiO₂ stress and the potential risk of algae to the environment.

In vitro and in vivo impact assessment of eco-designed CuO nanoparticles on non-target aquatic photoautotrophic organisms

This work has assessed the impact of copper oxide nanoparticles (CuONPs), designed via green route, toward photosynthetic apparatus on aquatic photoautotrophic organisms. In order to filling knowledge gaps, in vitro and in vivo assays were performed, using cyanobacterial phycocyanin (C-PC) from Arthrospira platensis and Lemna valdiviana plants (duckweed), respectively. Impairment in light energy transfer became evident in C-PC exposed to CuONPs, giving rise to an increase of light absorption and a suppression of fluorescence emission. Fourier transform infrared spectroscopy (FTIR) results showed that C-PC structures might be altered by the nanoparticles, also revealed that CuONPs preferably interacts with -NH functional groups. The data also revealed that CuONPs affected the chlorophyll a content in duckweed leaves. In addition, photosystem II (PSII) performance was significantly affected by CuONPs, negatively impacting the PSII photochemical network. In summary, the results point out that, even eco-friendly designed, CuONPs may negatively affect the photosynthetic process when accumulated by aquatic photoautotrophs.

Characterization of the nano-bio interaction between metallic oxide nanomaterials and freshwater microalgae using flow cytometry

Since nanomaterials (NMs) are particulate contaminants, their first contact with organisms is a physical encounter ruled by physic-chemical processes that can determinate the potential NMs accumulation, toxicity, and trophic transfer. Freshwater ecosystems often become a final depository for NMs, so they can get in contact with the biota, especially primary organisms as algae. There are almost none comparative studies of this interaction using various NMs in the same conditions. This work identifies, analyzes, and compares the algae-NMs interaction by flow cytometry after a short-term contact test in which three freshwater algae (Raphidocelis subcapitata, Desmodesmus subspicatus, and Chlorella vulgaris) interact individually with a set of twelve metallic oxide NMs. Dose-response profiles and differences in the algae-NMs interaction were found according to each algae species (C. vulgaris had the most affinity, starting the interaction from 0.5 mg/L and D. subspicatus had the less affinity starting at 5 mg/L). Flow cytometry results were confirmed by optical microscopy. Some NMs characteristics were identified as key-factors that govern the algae-NMs interaction: NMs composition (no interaction for SiO₂ NMs), surface electric charge (higher interaction for the positively charged NMs and lower interaction for the negatively charged ones) and crystalline form (for TiO₂ NMs). The presented method can be useful for a rapid determination of the interaction between free cells organisms as microalgae and (nano)particulate substances.

Synthesis, Characterization, and Anti-Algal Activity of Molybdenum-Doped Metal Oxides

In this study, we attempted to synthesize visible light active nano-sized photocatalysts using metal oxides such as zinc oxide, zirconium oxide, tungsten oxide, and strontium titanium oxide with (MoCl5)2 as a dopant by the simple ball-milling method. Fourier-transform infrared spectroscopy data confirmed the presence of M-O-Mo linkage (M = Zn, Zr, W, and SrTi) in all the molybdenum-doped metal oxides (MoMOs), but only MoZnO inhibited the growth of the bloom-forming Microcystis aeruginosa under visible light in a concentration-dependent manner up to 10 mg/L. Further, structural characterization of MoZnO using FESEM and XRD exhibited the formation of typical hexagonal wurtzite nanocrystals of approximately 4 nm. Hydroxyl radical (·OH), reactive oxygen species (ROS), and lipid peroxidation assays revealed ·OH generated by MoZnO under the visible light seemed to cause peroxidation of the lipid membrane of M. aeruginosa, which led to an upsurge of intracellular ROS and consequently introduced the agglomeration of cyanobacteria. These results demonstrated that nano-sized MoZnO photocatalyst can be easily synthesized in a cost-effective ball-mill method and utilized for biological applications such as the reduction of harmful algal blooms. Further, our study implies that a simple ball-milling method can provide an easy, green, and scalable route for the synthesis of visible light active doped metal oxides.

Toxicity evaluation of iron oxide nanoparticles and accumulation by microalgae Coelastrella terrestris

Uses of iron oxide nanoparticles have increased in the last decade. The increased application marked a concern regarding their fate and behavior in the environment. Especially towards the aquatic ecosystems, as the ultimate descend of these iron oxide nanoparticles are aquatic bodies. The greater surface area per mass compared with larger-sized materials of the same chemistry renders these nanoparticles biologically more active. Therefore, it is imperative to assess their eco-toxicogical impact on aquatic eco-systems. In the present study, comparative assessment of iron oxide nanoparticles and their bulk counterpart have been monitored using Coelastrella terrestris up to 40 days. Interestingly, study reveals the potential of Coelastrella terrestris as tool for the bioremediation of iron nanoparticles to combat nano-pollution. Adsorption/absorption kinetics measured after 25 days of treatments with iron oxide nanoparticle and its bulk counterpart revealed higher absorption levels in comparison to the adsorption with maximum accumulation factor (AF) of 2.984 at 50 mg L^-1 in nano-form. Iron oxide absorption was found linearly related with concentration in both cases (y = 11.313x-12.165, R² = 0.8691 in nano; y = 6.35x-5.74, R² = 0.8128 in bulk). However, 50-mg L^-1 nanoparticle concentration was perceived sub-lethal for the algae with 33.33% algal growth reduction under nano and 27.77% under bulk counterpart. Other biochemical parameters, i.e., SOD, CAT, MDA, and lipid quantification, were also quantified to correlate the state of metabolism of treated algal cells in comparison to the control and these exhibited reduction in algal growth due to oxidative stress. Morphological changes were monitored through SEM and TEM.

What occurs in colloidal gas aphron-induced separation of titanium dioxide nanoparticles? Particle fate analysis by tracking technologies

As an important method of enriching, separating and removing nanoparticles, colloidal gas aphrons (CGAs) need to be investigated for the fate and interfacial behaviors of particles during the process. It is beneficial to sufficiently interpreting the process performance and mechanisms. This study employed complementary tracking technologies to analyze the extensively-used engineered nanoparticles - TiO₂ nanoparticles (TiO₂-NPs) in effluent and floats of CGA process. Results denote that, at the optimum SDS relative dosage of 0.78 mg/mg TiO₂, the particle number concentration was largely reduced by 2-4 orders of magnitude based on nanoparticle tracking analysis (NTA) whilst approximately 84.0% of TiO_2-NPs were separated according to inductively coupled plasma-mass spectrometry (ICP-MS). NTA shows the change of overall particle dispersion status in the water phase while ICP-MS provides the Ti-related separation effect. Particularly, the particle size variation for the scenario of overdosing CGAs was clearly observed by NTA. Micro-Raman, dynamic laser scattering and small angle laser light scattering exhibited advantages in obtaining the configuration and morphology of flocs. The large flocs with open structure were apt to form and be favorably separated at the appropriate CGA dosage. However, overdosing CGAs weakened the capture capacity of bubbles and gave rise to small and dense aggregates. This work, for the first time, shows the change of nanoparticles in water and solid phases using the important and novel nanoparticle collection method - CGA technology. It also provides a reference to other flotation-related technologies for studying the nanoparticle fate and the process performance.

Effects of Mixtures of Engineered Nanoparticles and Metallic Pollutants on Aquatic Organisms

In aquatic environment, engineered nanoparticles (ENPs) are present as complex mixtures with other pollutants, such as trace metals, which could result in synergism, additivity or antagonism of their combined effects. Despite the fact that the toxicity and environmental risk of the ENPs have received extensive attention in the recent years, the interactions of ENPs with other pollutants and the consequent effects on aquatic organisms represent an important challenge in (nano)ecotoxicology. The present review provides an overview of the state-of-the-art and critically discusses the existing knowledge on combined effects of mixtures of ENPs and metallic pollutants on aquatic organisms. The specific emphasis is on the adsorption of metallic pollutants on metal-containing ENPs, transformation and bioavailability of ENPs and metallic pollutants in mixtures. Antagonistic, additive and synergistic effects observed in aquatic organisms co-exposed to ENPs and metallic pollutants are discussed in the case of “particle-proof” and “particle-ingestive” organisms. This knowledge is important in developing efficient strategies for sound environmental impact assessment of mixture exposure in complex environments.

Effects of titanium dioxide nanoparticles on Microcystis aeruginosa and microcystins production and release

Due to growing production and use, release of nanoparticles (NPs) into the aquatic environment may pose a hazard to ecosystem. In this study, Microcystis aeruginosa was exposed to different concentrations (0.1, 1, 10, 50, 100 mg/L) of titanium dioxide (TiO₂) NPs to assess their impact on algae. Meanwhile, the production and release of microcystins (MCs) was determined. Results showed that TiO₂ NPs significantly decreased the maximal photochemical efficiency of photosystem II, and thus inhibited the photosynthetic activity of M. aeruginosa. They also increased the content of reactive oxygen species (ROS) and malondialdehyde (MDA), indicating their oxidative damage on algae. Besides, TiO₂ NPs at high concentrations (50 and 100 mg/L) aggregated on the algal surface and block the light, herein inhibited algae growth (16.03%±2.50% and 54.13%±0.93%) but induced the production (25.02%±1.23% and 114.43%±2.96%) and release (20.96%±13.30% and 12.10%±8.80%) of MCs. These results indicated that high concentrations of TiO2 NPs increased MCs concentration in water system, which may be harmful to aquatic ecosystem.

Novel Route of Synthesis of PCL-CuONPs Composites With Antimicrobial Properties

Nanoparticles of metals can be toxic to bacteria, showing biocidal activities at low concentrations. Metal, oxide, or compounds based on copper are applied like antimicrobial agents. The capacity of integration of metallic nanoparticles in polymer matrices has improved the antimicrobial behavior, resulting in the search for composites with increased bactericidal properties. A polycaprolactone (PCL) film polymer with copper oxide nanoparticles (CuONPs) was prepared. Dynamic light scattering analysis showed the sizes from 88 to 97 nm of CuONPs. Scanning electron microscopy (SEM) revealed CuONPs with semispherical shapes with diameter 35 nm. The prepared PCL-CuONPs exhibited a nanoporous structure by SEM. The antibacterial applicability of the composite was evaluated to determine the minimum inhibitory concentration in 6 different bacteria and the experimental tests were carried by disk diffusion and spectrophotometric methods. The PCL-CuONPs exhibit a considerable antibacterial effect in gram-positive bacteria in contrast to gram-negative bacteria. The preparation of PCL-CuONPs was simple, fast, and low cost for practical application as wound dressings.