Methods to Evaluate Uptake of Engineered Nanomaterials by the Alimentary Tract

Toxicity of transition metal nanoparticles: A review of different experimental models in the gastrointestinal tract

The development of nanotechnology is becoming a major trend nowadays. Nanoparticles (NPs) have been widely used in fields including food, biomedicine, and cosmetics, endowing NPs more opportunities to enter the human body. It is well-known that the gut microbiome plays a key role in human health, and the exposure of intestines to NPs is unavoidable. Accordingly, the toxicity of NPs has attracted more attention than before. This review mainly highlights recent advances in the evaluation of NPs' toxicity in the gastrointestinal system from the existing cell-based experimental models, such as the original mono-culture models, co-culture models, three-dimensional (3D) culture models, and the models established on microfluidic chips, to those in vivo experiments, such as mice models, Caenorhabditis elegans models, zebrafish models, human volunteers, as well as computer-simulated toxicity models. Owing to these models, especially those more biomimetic models, the outcome of the toxicity of NPs acting in the gastrointestinal tract can get results closer to what happened inside the real human microenvironment.

Recent progress in using zein nanoparticles-loaded nanocomposites for food packaging applications

Biopolymers are important due to their exceptional functional and barrier properties and also their non-toxicity and eco-friendly nature for various food, biomedical, and pharmaceutical applications. However, biopolymers usually need reinforcement strategies to address their poor mechanical, thermal, and physical properties as well as processability aspects. Several natural nanoparticles have been proposed as reinforcing agents for biopolymeric food packaging materials. Among them, zein nanoparticles (ZNPs) have attracted a lot of interest, being an environmentally friendly material. The purpose of the present review paper is to provide a comprehensive overview of the ZNPs-loaded nanocomposites for food packaging applications, starting from the synthesis, characteristics and properties of ZNPs, to the physicochemical properties of the ZNPs-loaded nanocomposites, in terms of morphology, permeability, solubility, optical features, hydrophobic/hydrophilic behavior, structural characteristics, thermal features, and mechanical attributes. Finally, at the end of this review, some considerations about the safety issues and gastrointestinal fate of ZNPs, as well as the use of ZNPs-based nanocomposites as food packaging, are reported, taking into account that, despite the enormous benefits, nanotechnology also presents some risks associated to the use of nanometric materials.

Nanocarriers for Drug Delivery: An Overview with Emphasis on Vitamin D and K Transportation

Mounting evidence shows that supplementation with vitamin D and K or their analogs induces beneficial effects in various diseases, e.g., osteoarticular, cardiovascular, or carcinogenesis. The use of drugs delivery systems via organic and inorganic nanocarriers increases the bioavailability of vitamins and analogs, enhancing their cellular delivery and effects. The nanotechnology-based dietary supplements and drugs produced by the food and pharmaceutical industries overcome the issues associated with vitamin administration, such as stability, absorption or low bioavailability. Consequently, there is a continuous interest in optimizing the carriers' systems in order to make them more efficient and specific for the targeted tissue. In this pioneer review, we try to circumscribe the most relevant aspects related to nanocarriers for drug delivery, compare different types of nanoparticles for vitamin D and K transportation, and critically address their benefits and disadvantages.

Is "nano safe to eat or not"? A review of the state-of-the art in soft engineered nanoparticle (sENP) formulation and delivery in foods

With superior physicochemical properties, soft engineered nanoparticles (sENP) (protein, carbohydrate, lipids and other biomaterials) are widely used in foods. The preparation, functionalities, applications, transformations in gastrointestinal (GI) tract, and effects on gut microbiota of sENP directly incorporated for ingestion are reviewed herein. At the time of this review, there is no notable report of safety concerns of these nanomaterials found in the literature. Meanwhile, various beneficial effects have been demonstrated for the application of sENP. To address public perception and safety concerns of nanoscale materials in food, methodologies for evaluation of physiological effects of nanomaterials are reviewed. The combination of these complementary methods will be useful for the establishment of a comprehensive risk assessment system.

Guidance on risk assessment of the application of nanoscience and nanotechnologies in the food and feed chain: Part 1, human and animal health

The European Food Safety Authority has produced this Guidance on human and animal health aspects (Part 1) of the risk assessment of nanoscience and nanotechnology applications in the food and feed chain. It covers the application areas within EFSA's remit, e.g. novel foods, food contact materials, food/feed additives and pesticides. The Guidance takes account of the new developments that have taken place since publication of the previous Guidance in 2011. Potential future developments are suggested in the scientific literature for nanoencapsulated delivery systems and nanocomposites in applications such as novel foods, food/feed additives, biocides, pesticides and food contact materials. Therefore, the Guidance has taken account of relevant new scientific studies that provide more insights to physicochemical properties, exposure assessment and hazard characterisation of nanomaterials. It specifically elaborates on physicochemical characterisation of nanomaterials in terms of how to establish whether a material is a nanomaterial, the key parameters that should be measured, the methods and techniques that can be used for characterisation of nanomaterials and their determination in complex matrices. It also details the aspects relating to exposure assessment and hazard identification and characterisation. In particular, nanospecific considerations relating to in vivo/in vitro toxicological studies are discussed and a tiered framework for toxicological testing is outlined. It describes in vitro degradation, toxicokinetics, genotoxicity as well as general issues relating to testing of nanomaterials. Depending on the initial tier results, studies may be needed to investigate reproductive and developmental toxicity, immunotoxicity, allergenicity, neurotoxicity, effects on gut microbiome and endocrine activity. The possible use of read‐across to fill data gaps as well as the potential use of integrated testing strategies and the knowledge of modes/mechanisms of action are also discussed. The Guidance proposes approaches to risk characterisation and uncertainty analysis, and provides recommendations for further research in this area.

This publication is linked to the following EFSA Supporting Publications article: http://onlinelibrary.wiley.com/doi/10.2903/sp.efsa.2018.EN-1430/full

Nanomaterials in Food Products: A New Analytical Challenge

This chapter focuses on the problem of detecting, characterizing, and determining the concentration of nanomaterials in foods and other biological matrices. After providing an overview of the unique challenges associated with nanoparticle metrology in complex media, sample pretreatment methods (including extraction, digestion, and inline chromatographic separation), imaging analysis, and nanomaterial quantification methods are presented in detail. The chapter also addresses numerous methods under development, including atmospheric scanning electron microscopy, single-particle inductively coupled plasma mass spectrometry, immunological detection methods, and optical techniques such surface plasmon resonance. The chapter concludes with an overview of the research needs in this area.

Engineered Nanoparticles as Potential Food Contaminants and Their Toxicity to Caco-2 Cells

Engineered nanoparticles (ENPs), such as metallic or metallic oxide nanoparticles (NPs), have gained much attention in recent years. Increasing use of ENPs in various areas may lead to the release of ENPs into the environment and cause the contamination of agricultural and food products by ENPs. In this study, we selected two important ENPs (zinc oxide [ZnO] and silver [Ag] NPs) as potential food contaminants and investigated their toxicity via an in vitro model using Caco-2 cells. The physical properties of ENPs and their effects on Caco-2 cells were characterized by electron microscopy and energy dispersive X-ray spectroscopic (EDS) techniques. Results demonstrate that a significant inhibition of cell viability was observed after a 24-h of exposure of Caco-2 cells to 3-, 6-, and 12-mM ZnO NPs or 0.5-, 1.5-, and 3-mM Ag NPs. The noticeable changes of cells include the alteration in cell shape, abnormal nuclear structure, membrane blebbing, and cytoplasmic deterioration. The toxicity of ZnO NPs, but not that of Ag NPs after exposure to simulated gastric fluid, significantly decreased. Scanning transmission electron microscopy shows that ZnO and Ag NPs penetrated the membrane of Caco-2 cells. EDS results also confirm the presence of NPs in the cytoplasm of the cells. This study demonstrates that ZnO and Ag NPs have cytotoxic effects and can inhibit the growth of Caco-2 cells.

Organic Nanoparticles in Foods: Fabrication, Characterization, and Utilization

In the context of food systems, organic nanoparticles (ONPs) are fabricated from proteins, carbohydrates, lipids, and other organic compounds to a characteristic dimension, such as a radius smaller than 100 nm. ONPs can be fabricated with bottom-up and top-down approaches, or a combination of both, on the basis of the physicochemical properties of the source materials and the fundamental principles of physical chemistry, colloidal and polymer sciences, and materials science and engineering. ONPs are characterized for dimension, morphology, surface properties, internal structures, and biological properties to understand structure-function correlations and to explore their applications. These potential applications include modifying physical properties, improving sensory attributes and food quality, protecting labile compounds, and delivering encapsulated bioactive compounds for improved bioactivity and bioavailability. Because ONPs can have digestion and absorption properties different from conventional materials, the eventual applications of ONPs require in vitro and in vivo studies to guide the development of safe food products that utilize the unique functionalities of ONPs.

Single-Cell Mechanics Provides an Effective Means To Probe in Vivo Interactions between Alveolar Macrophages and Silver Nanoparticles

Single-cell mechanics, derived from atomic force microscopy-based technology, provides a new and effective means to investigate nanomaterial-cell interactions upon in vivo exposure. Lung macrophages represent initial and important responses upon introducing nanoparticles into the respiratory tract, as well as particle clearance with time. Cellular mechanics has previously proven effective to probe in vitro nanomaterial-cell interactions. This study extends technology further to probe the interactions between primary alveolar macrophages (AM) and silver nanoparticles (AgNPs) upon in vivo exposure. Two types of AgNPs, 20 and 110 nm, were instilled to rat lung at 0.5 mg AgNPs/kg body weight, and allowed 24 h interaction. The consequences of these interactions were investigated by harvesting the primary AMs while maintaining their biological status. Cellular mechanics measurements revealed the diverse responses among AM cells, due to variations in AgNP uptake and oxidative dissolving into Ag(+). Three major responses are evident: zero to low uptake that does not alter cellular mechanics, intracellular accumulation of AgNPs trigger cytoskeleton rearrangement resulting in the stiffening of mechanics, and damage of cytoskeleton that softens the mechanical profile. These effects were confirmed using confocal imaging of F-actin and measurements of reactive oxygen species production. More detailed intracellular interactions will also be discussed on the basis of this study in conjunction with prior knowledge of AgNP toxicity.

Mammalian gastrointestinal tract parameters modulating the integrity, surface properties, and absorption of food-relevant nanomaterials

Many natural chemicals in food are in the nanometer size range, and the selective uptake of nutrients with nanoscale dimensions by the gastrointestinal (GI) tract is a normal physiological process. Novel engineered nanomaterials (NMs) can bring various benefits to food, e.g., enhancing nutrition. Assessing potential risks requires an understanding of the stability of these entities in the GI lumen, and an understanding of whether or not they can be absorbed and thus become systemically available. Data are emerging on the mammalian in vivo absorption of engineered NMs composed of chemicals with a range of properties, including metal, mineral, biochemical macromolecules, and lipid-based entities. In vitro and in silico fluid incubation data has also provided some evidence of changes in particle stability, aggregation, and surface properties following interaction with luminal factors present in the GI tract. The variables include physical forces, osmotic concentration, pH, digestive enzymes, other food, and endogenous biochemicals, and commensal microbes. Further research is required to fill remaining data gaps on the effects of these parameters on NM integrity, physicochemical properties, and GI absorption. Knowledge of the most influential luminal parameters will be essential when developing models of the GI tract to quantify the percent absorption of food-relevant engineered NMs for risk assessment.

Utility of models of the gastrointestinal tract for assessment of the digestion and absorption of engineered nanomaterials released from food matrices

Engineered metal/mineral, lipid and biochemical macromolecule nanomaterials (NMs) have potential applications in food. Methodologies for the assessment of NM digestion and bioavailability in the gastrointestinal tract are nascent and require refinement. A working group was tasked by the International Life Sciences Institute NanoRelease Food Additive project to review existing models of the gastrointestinal tract in health and disease, and the utility of these models for the assessment of the uptake of NMs intended for food. Gastrointestinal digestion and absorption could be addressed in a tiered approach using in silico computational models, in vitro non-cellular fluid systems and in vitro cell culture models, after which the necessity of ex vivo organ culture and in vivo animal studies can be considered. Examples of NM quantification in gastrointestinal tract fluids and tissues are emerging; however, few standardized analytical techniques are available. Coupling of these techniques to gastrointestinal models, along with further standardization, will further strengthen methodologies for risk assessment.

Measurement Methods to Detect, Characterize, and Quantify Engineered Nanomaterials in Foods

This article is one of a series of 4 that reports on a task of the NanoRelease Food Additive project of the International Life Science Institute Center for Risk Science Innovation and Application to identify, evaluate, and develop methods that are needed to confidently detect, characterize, and quantify intentionally produced engineered nanomaterials (ENMs) released from food along the alimentary tract. This particular article focuses on the problem of detecting ENMs in food, paying special attention to matrix interferences and how to deal with them. In this review, an in-depth analysis of the literature related to detection of ENMs in complex matrices is presented. The literature review includes discussions of sampling methods, such as centrifugation and ENM extraction. Available analytical methods, as well as emerging methods, are also presented. The article concludes with a summary of findings and an overview of potential knowledge gaps and targets for method development in this area.

Measurement of nanomaterials in foods: integrative consideration of challenges and future prospects

The risks and benefits of nanomaterials in foods and food contact materials receive conflicting international attention across expert stakeholder groups as well as in news media coverage and published research. Current nanomaterial characterization is complicated by the lack of accepted approaches to measure exposure-relevant occurrences of suspected nanomaterials in food and by broad definitions related to food processing and additive materials. Therefore, to improve understanding of risk and benefit, analytical methods are needed to identify what materials, new or traditional, are "nanorelevant" with respect to biological interaction and/or uptake during alimentary tract transit. Challenges to method development in this arena include heterogeneity in nanomaterial composition and morphology, food matrix complexity, alimentary tract diversity, and analytical method limitations. Clear problem formulation is required to overcome these and other challenges and to improve understanding of biological fate in facilitating the assessment of nanomaterial safety or benefit, including sampling strategies relevant to food production/consumption and alimentary tract transit. In this Perspective, we discuss critical knowledge gaps that must be addressed so that measurement methods can better inform risk management and public policy.