Research project S4P/25/EM4definingNM (Research action S4P)
EM4definingNM is a 4-year project focusing on the development and validation of EM-based methods for the physicochemical characterization of nanomaterials applied in food to support the legislation.
The project is carried out by the electron microscopy (EM) unit of Sciensano. As the Belgian reference laboratory for nanoparticles in food and the European reference laboratory for food improvement agents, Sciensano supports the federal public service Health, Food Chain Safety and Environment implementing the (novel) foods regulation for nanomaterials, and specifically the definition of nanomaterials in foods by developing and applying optimized electron microscopy-based analysis methods. A collaboration with Prof. Sara Bals from UAntwerp allows access to advanced infrastructure and expertise in analysis of (nano)particles.
Hereto, a series of particulate materials with a relevance for food, covering a wide variety in size and shape, is examined focusing on insoluble, manufactured, inorganic particulate materials.
Specific sample preparation procedures are evaluated. To examine sampling bias, EM specimen preparation using drop deposition and on-grid ultracentrifugation of dispersed materials with narrow and broad size distributions are compared. Ultramicrotomy of resin-embedded samples is evaluated as a sample preparation method to measure the minimum external dimension of (plate-like) materials with a preferential orientation on the EM-grid. The possibilities of different imaging modes such as SEM, TEM, and STEM, and more advanced EM-based approaches (e.g. 4D STEM) and conventional and AI-assisted image analysis approaches are evaluated. This approach allows to propose a guidance for selecting the most suitable approach for each type of material, detailing the sample preparation, imaging mode and image analysis routines.
For the optimized conditions, standardized methods, provided as standard operating procedures (SOPs), and validation studies are delivered providing the measurement uncertainties for particle size and shape measurements.
All acquired measurement results with associated metadata are systematically reported in line with EFSA’s instruction for reporting the results of EM analysis. They are stored in a format allowing eventual later re-use and public access, following the FAIR principle. Existing information and developments from other (Sciensano) projects will be integrated.
The results of the project allows commercial operators and control laboratories to select the most suitable EM-based methods, presented as validated SOPs, for characterizing a specific material, depending on its physicochemical properties. This allows competent authorities to evaluate whether legal obligations associated with the regulatory definition are respected. The approach is also useful for nanomaterial characterization in the context of risk assessment according to the EFSA guidance. Moreover, the estimated measurement uncertainties will contribute to evaluate the setting of a quantitative threshold (e.g. 50%) applied in definitions of nanomaterials supporting on experimental data.
The dissemination of the outcomes on a EU-wide level will be assured in European nano-related work groups (CEN, EFSA), through the organization of a scientific symposium and the participation to conferences. They will be published and shared with organizations such as JRC, EFSA and CEN.
