The role of the food matrix and gastrointestinal tract in the assessment of biological properties of ingested engineered nanomaterials (iENMs): State of the science and knowledge gaps

• Many foods contain organic or inorganic engineered nanomaterials (ENMs), added either intentionally or unintentionally.
• There is presently a poor understanding of how ingested ENMs (iENMs) behave or interact in foods or the GI tract.
• Understanding the transformations and behavior of iENMs in food and the GI tract are critical to assessing impacts on health.
• Current understanding of the fate of iENMs in the GI tract and critical knowledge gaps requiring research are reviewed.
• Development of standardized methodologies is required to accurately assess the toxicological properties and risks of iENMs.

Many foods contain appreciable levels of engineered nanomaterials (ENMs) (diameter < 100 nm) that may be either intentionally or unintentionally added. These ENMs vary considerably in their compositions, dimensions, morphologies, physicochemical properties, and biological responses. From a toxicological point of view, it is often convenient to classify ingested ENMs (iENMs) as being either inorganic (such as TiO2, SiO2, Fe2O3, or Ag) or organic (such as lipid, protein, or carbohydrate), since the former tend to be indigestible and the latter are generally digestible. At present there is a relatively poor understanding of how different types of iENMs behave within the human gastrointestinal tract (GIT), and how the food matrix and biopolymers transform their physico-chemical properties and influence their gastrointestinal fate. This lack of knowledge confounds an understanding of their potential harmful effects on human health. The purpose of this article is to review our current understanding of the GIT fate of iENMs, and to highlight gaps where further research is urgently needed in assessing potential risks and toxicological implications of iENMs. In particular, a strong emphasis is given to the development of standardized screening methods that can be used to rapidly and accurately assess the toxicological properties of iENMs.

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