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

Abstract

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.

Keywords: engineered nanomaterials; food matrix effects; food nanotechnology; gastrointestinal tract; in vitro models; nanotoxicology.

Figure 1

A variety of structures can be assembled using lipid nanoparticles as building blocks, including nanoparticle filled droplets and hydrogels, nanoparticle clusters, nanoparticle colloidosomes, solid lipid nanoparticles, and nanolaminated nanoparticles (McClements, 2012; McClements, 2014).

Figure 2

Food grade nanoparticles may vary in particle characteristics, such as size, shape, composition, and charge.

Figure 3

Schematic diagram of the physicochemical and physiological conditions in different regions of the human gastrointestinal tract. The diagram of the human body was taken from http://en.wikipedia.org/wiki/Digestive_tract (Copyright free).

Figure 4

The properties of nanoparticles may occur in a number of different ways as they pass through the GIT. Some potential changes in particle dimensions and interfacial properties are illustrated here.