Nanomaterial Characterization Methods: Leaping Towards Validation

Dear Colleagues,

SCOPE: In this special volume, we openly invite papers on characterization methods that support the identification, registration, characterization of nanomaterials and that have been demonstrated via in-house, intra-, and/or inter-laboratory comparison. Exemplary elements of a method standard operational procedure include: methods description, sample preparation, instructions, data reduction and evaluation, benchmarking or validation of results. In this context, contributions that report on different (nano)forms of the same substance or other systematic variations of nanomaterials are welcome.

BACKGROUND: Over the last approximately 15 years, there has been extensive research and development focus on manufactured 1D, 2D and 3D nanomaterials and their use as for example catalysts, conductors, magnetics, colorants, optical sources, flame-retardants, biocides with application in electronics, ceramics, construction materials, coatings, food, feed, medicinal and medical devices, environmental remediation etc. The list of both nanomaterials and applications is very long and reflects the growing success of manufactured nanomaterials as a key-enabling technology.

In parallel with the technological developments, the small sizes, and in some cases high chemical and structural complexity of manufactured nanomaterials, have challenged many established physicochemical characterization and test methods. High-quality characterization and measurement of intrinsic and extrinsic properties is essential to establish good and reliable data and to transfer knowledge from research to industry, as well as transferring data from material producers to regulators and downstream users.

While research laboratories can simply adapt to new characterization requirements, any change of methods for regulatory use is a long process before data is mutually accepted. However, it has been identified that several international standard methods accepted for regulatory characterization and testing are not or only partially adequate for characterization and testing of manufactured nanomaterials. Moreover, a need for new characteristics have emerged to improve material and hazard grouping, read-across and quantitative structural activity relationships(QSAR), and fate modelling in human and environmental compartments. In consequence, there is an urgent need to revise regulatory guidance on how to characterize, test, and even assess the risk of manufactured nanomaterials.

At this stage, the characterization community must find a balance between data reliability (repeatability, accuracy, precision) with cost and practical implementation. Several regulatory bodies have already made their decisions on which methods must be improved and which new characteristics that must be reported, or are in the process of doing so. This generates high pressure on the developers of regulatory characterization methods to identify and validate suitable methods to meet the regulatory needs.

REGULATORY RELEVANCE: There is particular interest in contributions that can support, by robust scientific data, the further selection and guidance and standardization at OECD and ISO level. In this regard, there is high interest in methods documentation on materials where eco- and toxicological assessments have already been published elsewhere to allow future testing and calibration of grouping and predictive risk assessment methods. Lower priority will be given to novel and yet not validated methods.

Yours sincerely,

Prof. Dr. Keld Alstrup Jensen
Dr. Wendel Wohlleben
Guest Editors

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• nanomaterials
• characterization methods
• validation
• material grouping
• regulation