Ecotoxicology of Nanoparticles in Aquatic Systems

Julian Blasco, Ilaria Corsi, Julian Blasco, Ilaria Corsi

• Publisher: CRC Press
• Year: 2019
• ISBN:
  9781351657549
• Edition: 1
• Topic: Biological Sciences
• Subtopic: Environmental Science
• Index: Biological Sciences

The use of nanoparticles in medicine, industrial, and other applications has triggered an interest in their potential. This book explores the use of nanoparticles related to their occurrence in the environment, their impact on biota in aquatic systems, application of new methodologies, and changes associated with new global scenarios. The book also covers the bioaccumulation and internalization of nanoparticles as key aspects to assess their uptake and discusses the methodologies for testing ENPs ecotoxicity at different trophic levels.

1

Toxicity of Metal and Metal Oxide Engineered Nanoparticles to Phytoplankton

Marta Sendra, Ignacio Moreno and Julián Blasco*

Institute of Marine Sciences of Andalusia (CSIC). Campus Rio San Pedro, 11510 Puerto Real (Cádiz), Spain.

* Corresponding author: [email protected]

Introduction

Microalgae (unicellular or filamentous microscopic primary producers) is a miscellaneous ecological group which include cyanobacteria and prochlorophyceae, green algae, euglenophyceae, dinoflagellates, some species of red algae, and a wide diversity of chromists (such as diatoms, coccolitophorides, eustigmatophiceae, and diverse brown-golden algae), among other groups. It means that organisms called “microalgae” could belong to at least three natural kingdoms. Those organisms conform the basis of the aquatic trophic nets and support at least a half of the planetary primary production (Falkowski 1980). Recent studies reveal that those data could underestimate the real importance of marine phytoplankton, as techniques such as flow cytometry point out that the abundance of micro and nanoplankton could be higher than expected in the past (González-García et al. 2018).

In any case, perturbations in phytoplankton communities due to toxic processes caused by any xenobiotic could propagate to the rest of ecosystems. Not only is the abundance of microalgal biomass important, as taxonomic diversity of the microalgal assemblage has also been demonstrated to be a key issue in the maintenance of certain grazers (Moreno-Garrido et al. 1999).

Nowadays, the occurrence of the legacy and emergent pollutants in the aquatic ecosystems can represent a real risk for aquatic organisms depending on their concentrations, environmental conditions, and species sensitivity. Among emergent pollutants, nanomaterials and specifically engineered nanoparticles (ENPs) have aroused a great attention due to their wide use and applications.

Nanotechnology is one of the more important emerging technologies identified in the European Union (EU) 2020 Strategy (EU Commission 2013). It has demonstrated to promote innovation, development, and economic growth (Hristozov et al. 2016). The goal of nanotechnology research funding is to improve industrial applications and commercial products through new physicochemical properties of engineered nanomaterials (ENMs) that may influence their kinetics, bioavailability, toxicity, and fate. Among the applications of ENMs found, some are: catalysis, lubricants, paints, cosmetic products, sensor device, bio-remediation, antibacterial and antifungal agents, drugs delivery, medical diagnosis, aquaculture, water treatments, air disinfection, food packing, clothes, toys, goods sports, plastic and archaeological stones (Moreno-Garrido et al. 2015). The fascinating physico-chemical properties (such as size, surface area, photocatalytic and redox capacity among others) (Hendren et al. 2011, Piccinno et al. 2012) need to be investigated during different steps: the release in the environment, transformation in different media, and exposure to organisms and hazard assessment in order to increase the level of certainty in the risk assessment results (Stone et al. 2014). The requirements for an environmental risk assessment of ENMs require the knowledge of their environmental concentrations. Despite significant advances in analytical methods, it is a complicated task, because the methods are not sensitive enough for current environmentally realistic concentration, and they cannot distinguish natural NMs from engineered ones. The improvement of recent studies in evolving from static to dynamic mathematical models has allowed researchers to know the Predicted Environmental Concentration (PEC) through materials flow and environment (Sun et al. 2016).

ENMs are releasing during their life cycle, from (1) synthesis and production, (2) handling, (3) transport, (4) incorporation to application and products, (5) use of products or applications that incorporate them (such as textile, sunscreen, sport goods…), to (6) disposal of products or applications which incorporate them (incineration, landfill, sewage treatments) (Caballero-Guzman and Nowack 2016).

Intrinsic Characteristic of ENPs that Influence Microalgae Toxicity

The novel and intrinsic physicochemical properties of ENPs with respect to conventional materials (bulk) are of great importance and should be considered in toxicological test with microalgae. They are: (1) particle nominal size, (2) specific surface area, (3) shape, (4) zeta potential, (5) water solubility, (6) photocatalytic activity, (7) crystallization, (8) purity of samples, (9) redox potential, and (10) composition coating, among the most studied characteristics.

Nominal Size of ENPs

Nominal size of ENPs is the most remarkable characteristic which make ENPs a perfect candidate in new applications and commercial products. However, differences in toxicity taking into account EC₅₀ of growth inhibition for different NPs size will be closely related with the composition of ENPs.

With respect to titanium dioxide NP (TiO₂ NPs), one of most used chemicals in cosmetic products, with low toxicity to microalgae when they are not exposed to UV-A/B and C, it is possible to observe how smaller size of ENPs did not show important differences in toxicity to both freshwater and marine microalgae (Table 1) (Hund-Rinke and Simon 2006, Hartmann and Baun 2010, Ji et al. 2011, Xia et al. 2015, Sendra et al. 2017f). However, in other studies, small differences are found between NPs form and bulk (Aruoja et al. 2009, Clément et al. 2013, Sendra et al. 2017f).

In the case of silver (Ag) NPs, some authors have demonstrated that particles size is important in their toxicity, finding higher toxicity in small Ag NPs in different freshwater microalgae (Angel et al. 2013, Ivask et al. 2014, Sendra et al. 2017d); however, the same trend was not observed in marine microalgae where small Ag NPs were not related with smaller values of EC₅₀ (Sendra et al. 2017d). Contrary to TiO₂ NPs, Ag NPs are reactive, showing a rate of dissolution inversely proportional to NPs size. From this dissolution of Ag NPs are released ions (Ag⁺) to the culture media, making them mainly responsible for Ag NPs toxicity to microalgae (Navarro et al. 2008b).

In relation to cerium oxide (CeO₂) NPs, most of the authors found a relation between toxicity and particle size for different microalgae species (Hoecke et al. 2009, Rogers et al. 2010, Rodea-Palomares et al. 2011). Sendra et al. (2017) found no relation between toxicity and CeO₂ NPs size. In this study, the NPs with the middle size showed to be to more toxic that the other two tested microalgae in the different environment. This NPs differed in one and important intrinsic property, that is, it showed positive zeta potential in the culture media (Sendra et al. 2017f). In another study, with freshwater microalgae Pseudokirchneriella subcapitata exposed to different CeO₂ NPs with different nominal size, zeta potential, shape, and Ce³⁺/Ce⁴⁺ ratio in NPs surface, the main drivers of toxicity was the percentage of Ce³⁺ in NPs surface (Pulido-Reyes et al. 2015).

Table 1. EC₅₀ (growth inhibition) in freshwater and marine microalgae exposed TiO₂, Ag and CeO₂ NPs of different size.

Sometimes in studies which compare NPs with different nominal size given by suppliers or even measured by TEM, the smallest NPs have not always had correlation with the mean size and peak of hydrodynamic radii measured by DLS in the culture media. Therefore, agglomerate size for NPs in a certain size range could not be related with a nominal size. To assess the importance of NPs size in toxicity test to microalgae is necessary to know size distribution of NPs and the percentage of NPs agglomerates lower than 20 nm. The importance of knowing the volume of NPs < 20 nm is related to the fact that the microalgae cell wall has a pore size between 5–20 nm (Moore 2006, Navarro et al. 2008a).

Specific Surface Area of NPs

Specific surface area (S_BET) is a very important intrinsic characteristic of ENPs and it is inversely proportional to NPs size. ENPs with higher S_BET will be more reactive with their surrounding environment. For instance, ENPs with high values of S_BET will have higher dissolution rate, photocatalytic and redox activity. Furthermore, higher values of S_BET provokes higher contact between ENPs and organisms and molecules. Most of the articles published which assess the toxicity of intrinsic characteristic of ENPs are not focused on S_BET (Baer 2011).

Shape of ENPs

Another contributing intrinsic characteristic of ENPs toxicity is their shape (Nangia and Sureshkumar 2012, Mortazavi et al. 2017).

Information about toxicity of different shape of NPs in microalgae is scarce. Most of the studies are developed in macrophages. A recent study demonstrated that rod shape CeO₂ NPs was more toxic than cubic/octahedral CeO₂ NPs (Forest et al. 2017). Nangia et al. (2012) observed translocation rate constants of functionalized cone, cube, rod, rice, pyramid, and sphere shaped NPs through lipid membranes. The results indicate that depending on the NP’s shape a...

Table of contents

• Cover
• Title Page
• Copyright Page
• Preface
• Acknowledgement
• Table of Contents
• 1. Toxicity of Metal and Metal Oxide Engineered Nanoparticles to Phytoplankton
• 2. Sublethal Effects of Nanoparticles on Aquatic Invertebrates, from Molecular to Organism Level
• 3. In Vitro Testing: In Vitro Toxicity Testing with Bivalve Mollusc and Fish Cells for the Risk Assessment of Nanoparticles in the Aquatic Environment
• 4. Toxicity Tests and Bioassays for Aquatic Ecotoxicology of Engineered Nanomaterials
• 5. Nanomaterial Transport and Ecotoxicity in Fish Embryos
• 6. Effects of Nanomaterials on the Body Systems of Fishes—An Overview from Target Organ Pathology
• 7. Nanoparticles Under the Spotlight: Intracellular Fate and Toxic Effects on Cells of Aquatic Organisms as Revealed by Microscopy
• 8. Insights from ‘Omics on the Exposure and Effects of Engineered Nanomaterials on Aquatic Organisms
• 9. Nanomaterials in Aquatic Sediments
• 10. The Role of Ecotoxicology in the Eco-Design of Nanomaterials for Water Remediation
• 11. Analytical Tools Able to Detect ENP/NM/MNs in both Artificial and Natural Environmental Water Media
• Index