Towards sensible toxicity testing for nanomaterials: proposal for the specification of test design

An insight into impact of nanomaterials toxicity on human health

In recent years, advances in nanotechnology have significantly influenced electronics manufacturing, industrial processes, and medical research. Various industries have seen a surge in the use of nanomaterials. However, several researchers have raised the alarm about the toxicological nature of nanomaterials, which appear to be quite different from their crude forms. This altered nature can be attributed to their unique physicochemical profile. They can adversely affect human health and the environment. Nanomaterials that have been released into the environment tend to accumulate over time and can cause a significant impact on the ecosystem and organisms with adverse health effects. Increased use of nanoparticles has led to increased human exposure in their daily lives, making them more vulnerable to nanoparticle toxicity. Because of their small size, nanomaterials can readily cross biological membranes and enter cells, tissues, and organs. Therefore, the effect of nanomaterials on the human environment is of particular concern. The toxicological effects of nanomaterials and their mechanisms of action are being researched worldwide. Technological advances also support monitoring new nanomaterials marketed for industrial and household purposes. It is a challenging area because of the exceptional physicochemical properties of nanomaterials. This updated review focuses on the diverse toxicological perspective of nanomaterials. We have discussed the use of different types of nanoparticles and their physiochemical properties responsible for toxicity, routes of exposure, bio-distribution, and mechanism of toxicity. The review also includes various in vivo and in vitro methods of assessing the toxicity of nanomaterials. Finally, this review will provide a detailed insight into nano material-induced toxicological response, which can be beneficial in designing safe and effective nanoparticles.

Environmental Risk Assessment of Nanomaterials in the Light of New Obligations Under the REACH Regulation: Which Challenges Remain and How to Approach Them?

Within the European regulation on the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH, EC No 1907/2006) specific provisions for nanomaterials were included, which have become effective on 1 January 2020. Although knowledge on the peculiarities of testing and assessing fate and effects of nanomaterials in the environment strongly increased in the last years, uncertainties about how to perform a reliable and robust environmental risk assessment for nanomaterials still remain. These uncertainties are of special relevance in a regulatory context, challenging both industry and regulators. The present paper presents current challenges in regulatory hazard and exposure assessment under REACH, as well as classification of nanomaterials, and makes proposals to address them. Still, the nanospecific considerations made here are expected to also be valid for environmental risk assessment approaches in other regulations of chemical safety. Inter alia, these proposals include a way forward to account for exposure concentrations in aquatic toxicity test systems, a discussion of how to account for availability of dissolving nanomaterials in aquatic test systems, and a pragmatic proposal to deduce effect data for soil organisms. Furthermore, it specifies how to potentially deal with nanoforms under the European regulation on Classification, Labelling and Packaging of substances and mixtures (CLP) and outlines the needs for proper exposure assessments of nanomaterials from a regulatory perspective. Integr Environ Assess Manag 2020;16:706-717. © 2020 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Translating Scientific Advances in the AOP Framework to Decision Making for Nanomaterials

Much of the current innovation in advanced materials is occurring at the nanoscale, specifically in manufactured nanomaterials (MNs). MNs display unique attributes and behaviors, and may be biologically and physically unique, making them valuable across a wide range of applications. However, as the number, diversity and complexity of MNs coming to market continue to grow, assessing their health and environmental risks with traditional animal testing approaches is too time- and cost-intensive to be practical, and is undesirable for ethical reasons. New approaches are needed that meet current requirements for regulatory risk assessment while reducing reliance on animal testing and enabling safer-by-design product development strategies to be implemented. The adverse outcome pathway (AOP) framework presents a sound model for the advancement of MN decision making. Yet, there are currently gaps in technical and policy aspects of AOPs that hinder the adoption and use for MN risk assessment and regulatory decision making. This review outlines the current status and next steps for the development and use of the AOP framework in decision making regarding the safety of MNs. Opportunities and challenges are identified concerning the advancement and adoption of AOPs as part of an integrated approach to testing and assessing (IATA) MNs, as are specific actions proposed to advance the development, use and acceptance of the AOP framework and associated testing strategies for MN risk assessment and decision making. The intention of this review is to reflect the views of a diversity of stakeholders including experts, researchers, policymakers, regulators, risk assessors and industry representatives on the current status, needs and requirements to facilitate the future use of AOPs in MN risk assessment. It incorporates the views and feedback of experts that participated in two workshops hosted as part of an Organization for Economic Cooperation and Development (OECD) Working Party on Manufactured Nanomaterials (WPMN) project titled, "Advancing AOP Development for Nanomaterial Risk Assessment and Categorization", as well as input from several EU-funded nanosafety research consortia.

Translational challenges in advancing regenerative therapy for treating neurological disorders using nanotechnology

The focus of regenerative therapies is to replace or enrich diseased or injured cells and tissue in an attempt to replenish the local environment and function, while slowing or halting further degeneration. Targeting neurological diseases specifically is difficult, due to the complex nature of the central nervous system, including the difficulty of bypassing the brain's natural defense systems. While cell-based regenerative therapies show promise in select tissues, preclinical and clinical studies have been largely unable to transfer these successes to the brain. Advancements in nanotechnologies have provided new methods of central nervous system access, drug and cell delivery, as well as new systems of cell maintenance and support that may bridge the gap between regenerative therapies and the brain. In this review, we discuss current regenerative therapies for neurological diseases, nanotechnology as nanocarriers, and the technical, manufacturing, and regulatory challenges that arise from inception to formulation of nanoparticle-regenerative therapies.

Biochemical functionality of magnetic particles as nanosensors: how far away are we to implement them into clinical practice?

Magnetic nanosensors have become attractive instruments for the diagnosis and treatment of different diseases. They represent an efficient carrier system in drug delivery or in transporting contrast agents. For such purposes, magnetic nanosensors are used in vivo (intracorporeal application). To remove specific compounds from blood, magnetic nanosensors act as elimination system, which represents an extracorporeal approach. This review discusses principles, advantages and risks on recent advances in the field of magnetic nanosensors. First, synthesis methods for magnetic nanosensors and possibilities for enhancement of biocompatibility with different coating materials are addressed. Then, attention is devoted to clinical applications, in which nanosensors are or may be used as carrier- and elimination systems in the near future. Finally, risk considerations and possible effects of nanomaterials are discussed when working towards clinical applications with magnetic nanosensors.

From the sea to the laboratory: Characterization of microplastic as prerequisite for the assessment of ecotoxicological impact

The presence of microplastic (MP) in the aquatic environment is recognized as a global-scale pollution issue. Secondary MP particles result from an ongoing fragmentation process governed by various biotic and abiotic factors. For a reliable risk assessment of these MP particles, knowledge about interactions with biota is needed. However, extensive testing with standard organisms under reproducible laboratory conditions with well-characterized MP suspensions is not available yet. As MP in the environment represents a mixture of particles differing in properties (e.g., size, color, polymer type, surface characteristics), it is likely that only specific particle fractions pose a threat towards organisms. In order to assign hazardous effects to specific particle properties, these characteristics need to be analyzed. As shown by the testing of particles (e.g. nanoparticles), characteristics other than chemical properties are important for the emergence of toxicity in organisms, and parameters such as surface area or size distribution need consideration. Therefore, the use of "well-defined" particles for ecotoxicological testing (i.e., standard particles) facilitates the establishment of causal links between physical-chemical properties of MP particles and toxic effects in organisms. However, the benefits of well-defined particles under laboratory conditions are offset by the disadvantage of the unknown comparability with MP in the environment. Therefore, weathering effects caused by biological, chemical, physical or mechanical processes have to be considered. To date, the characterization of the progression of MP weathering based on powder and suspension characterization methods is in its infancy. The aim of this commentary is to illustrate the prerequisites for testing MP in the laboratory from 3 perspectives: (i) knowledge of particle properties; (ii) behavior of MP in test setups involving ecotoxicological test organisms; and (iii) accordingly, test conditions that may need adjustment. Only under those prerequisites will reliable hazard assessment of MP be feasible. Integr Environ Assess Manag 2017;13:500-504. © 2017 SETAC.

Environmental benefits and concerns on safety: communicating latest results on nanotechnology safety research-the project DaNa2.0

The use of nanotechnology and advanced materials promises to revolutionise many areas of technology and improve our daily life. In that respect, many positive effects on the environment are expected, either directly, by developing new technologies for remediation, filtering techniques or energy generation, or indirectly, by e.g. saving resources due to lower consumption of raw materials, or lower energy and fuel consumption due to reduced weight of vehicles. However, such beneficial effects of new technologies are often confronted by concerns regarding the safety of novel substances or materials. During the past 10 years, great effort has been put into research on potential hazards of nanomaterials towards environmental organisms. As the methodology for reliable assessment of nanomaterials was immature, many studies reporting contradictory results have been published, hindering both risk assessment for nanomaterials, as well as the knowledge communication to all involved stakeholders. Thus, DaNa^2.0 serves as a platform to implement trusted knowledge on nanomaterials for an objective discussion.

Safety assessment of nanomaterials using an advanced decision-making framework, the DF4nanoGrouping

As presented at the 2016 TechConnect World Innovation Conference on 22-25 May 2016 in Washington DC, USA, the European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC) 'Nano Task Force' proposes a Decision-making framework for the grouping and testing of nanomaterials (DF4nanoGrouping) consisting of three tiers to assign nanomaterials to four main groups with possible further subgrouping to refine specific information needs. The DF4nanoGrouping covers all relevant aspects of a nanomaterial's life cycle and biological pathways: intrinsic material properties and system-dependent properties (that depend upon the nanomaterial's respective surroundings), biopersistence, uptake and biodistribution, and cellular and apical toxic effects. Use, release, and exposure route may be applied as 'qualifiers' to determine if, e.g., nanomaterials cannot be released from products, which may justify waiving of testing. The four main groups encompass (1) soluble, (2) biopersistent high aspect ratio, (3) passive, and (4) active nanomaterials. The DF4nanoGrouping foresees a stepwise evaluation of nanomaterial properties and effects with increasing biological complexity. In case studies covering carbonaceous nanomaterials, metal oxide, and metal sulfate nanomaterials, amorphous silica and organic pigments (all nanomaterials having primary particle sizes below 100 nm), the usefulness of the DF4nanoGrouping for nanomaterial hazard assessment was confirmed. The DF4nanoGrouping facilitates grouping and targeted testing of nanomaterials. It ensures that sufficient data for the risk assessment of a nanomaterial are available, and it fosters the use of non-animal methods. No studies are performed that do not provide crucial data. Thereby, the DF4nanoGrouping serves to save both animals and resources.

Nano-Inclusions Applied in Cement-Matrix Composites: A Review

Research on cement-based materials is trying to exploit the synergies that nanomaterials can provide. This paper describes the findings reported in the last decade on the improvement of these materials regarding, on the one hand, their mechanical performance and, on the other hand, the new properties they provide. These features are mainly based on the electrical and chemical characteristics of nanomaterials, thus allowing cement-based elements to acquire "smart" functions. In this paper, we provide a quantitative approach to the reinforcements achieved to date. The fundamental concepts of nanoscience are introduced and the need of both sophisticated devices to identify nanostructures and techniques to disperse nanomaterials in the cement paste are also highlighted. Promising results have been obtained, but, in order to turn these advances into commercial products, technical, social and standardisation barriers should be overcome. From the results collected, it can be deduced that nanomaterials are able to reduce the consumption of cement because of their reinforcing effect, as well as to convert cement-based products into electric/thermal sensors or crack repairing materials. The main obstacle to foster the implementation of such applications worldwide is the high cost of their synthesis and dispersion techniques, especially for carbon nanotubes and graphene oxide.

A case study to optimise and validate the brine shrimp Artemia franciscana immobilisation assay with silver nanoparticles: The role of harmonisation

Brine shrimp Artemia sp. has been recognised as an important ecotoxicity and nanotoxicity test model organism for salt-rich aquatic environments, but currently there is still no harmonised testing protocol which would ensure the comparable results for hazard identification. In this paper we aimed to design the harmonised protocol for nanomaterial toxicity testing using Artemia franciscana and present a case study to validate the protocol with silver nanoparticles (AgNPs). We (i) revised the existing nanotoxicity test protocols with Artemia sp. (ii) optimised certain methodological steps based on the experiments with AgNPs and potassium dichromate (K2Cr2O7) as a soluble reference chemical and (iii) tested the optimised protocol in an international inter-laboratory exercise conducted within the EU FP7 NanoValid project. The intra- and inter-laboratory reproducibility of the proposed protocol with a soluble reference chemical K2Cr2O7 was good, which confirms the suitability of this assay for conventional chemicals. However, the variability of AgNPs toxicity results was very high showing again that nanomaterials are inherently challenging for toxicity studies, especially those which toxic effect is linked to shed metal ions. Among the identified sources for this variability were: the hatching conditions, the type of test plate incubation and the illumination regime. The latter induced variations assumingly due to the changes in bioavailable silver species concentrations. Up to our knowledge this is the first inter-laboratory comparison of the Artemia sp. toxicity study involving nanomaterials. Although the inter-laboratory exercise revealed poor repeatability of AgNPs toxicity results, this study provides valuable information regarding the importance of harmonisation of all steps in the test procedure. Also, the presented AgNPs toxicity case study may serve as a platform for further validation steps with other types of NMs.