In Vitro Toxicity Testing for Orally Ingested Nanomaterials: New OECD Guidance
The OECD has published the new Guidance Document for In Vitro Testing of the Intestinal Fate of Orally Ingested Nanomaterials, providing a scientific and regulatory framework for investigating what happens to nanomaterials after oral ingestion.
Our team of scientists, led by Federico Benetti, contributed to the drafting of the Guidance Document as part of the Italian expert group, alongside representatives from leading national and international scientific and regulatory institutions.
Why intestinal fate matters in nanoparticle toxicity assessment
Nanomaterials are increasingly used in consumer products and may be present in pharmaceuticals, cosmetics, food, feed and food-contact materials.
Once ingested, however, a nanomaterial does not necessarily retain the same properties it had in its original form. During its passage through the oro-gastrointestinal tract, it may undergo significant physicochemical transformations, including dissolution, changes in particle distribution and the formation of new nano-entities.
Understanding these transformations is therefore essential to determine whether nano-specific properties persist after digestion and whether further hazard assessment is required.
A tiered approach to nanomaterial assessment
The OECD Guidance introduces a tiered screening strategy combining complementary in chemico and in vitro approaches.
Tier 1: Simulated digestion and dissolution
In chemico dissolution assays using simulated oro-gastrointestinal fluids are used to investigate whether nanomaterials retain nano-specific characteristics following digestion. If the material dissolves completely and no nano-specific features remain, further nano-specific testing is generally not considered necessary. If particulate forms persist or new nanoforms may be generated, additional investigation may be warranted.
Tier 2 | Interaction with the intestinal barrier
Advanced in vitro intestinal barrier models can then be used to investigate biological endpoints including cytotoxicity, permeability, cellular uptake and translocation across the intestinal epithelium.
Among the approaches described, the Guidance identifies a tri-culture intestinal barrier model based on Caco-2, HT29-MTX E12 and Raji B cells as a suitable New Approach Methodology (NAM) for investigating nanomaterial uptake and translocation.
From experimental methods to regulatory-relevant evidence
A key aspect of the new OECD Guidance is its focus on generating fit-for-purpose and decision-relevant data.
The document provides recommendations on physiologically relevant experimental conditions, analytical characterisation, barrier integrity, controls, data interpretation and reporting. It is also accompanied by Standard Operating Procedures covering dissolution testing, the tri-culture intestinal barrier model and uptake/translocation studies, together with harmonised data-reporting templates.
This approach supports the broader transition towards New Approach Methodologies (NAMs), Integrated Approaches to Testing and Assessment (IATA) and Next Generation Risk Assessment (NGRA), generating human-relevant evidence while reducing reliance on animal studies.
Scientific expertise contributing to international harmonisation
The participation of our scientists in the drafting of this OECD Guidance reflects our continued commitment to the development of scientifically robust and transferable approaches for nanomaterial safety assessment.
By combining expertise in simulated digestion, advanced intestinal models and nanomaterial characterisation, we contribute not only to the application of emerging methodologies, but also to the scientific discussion shaping their future regulatory use.
