Table 3 Overview of the key findings regarding the state of science in in vivo nanotoxicity testing of food-grade nanomaterials, categorized by nanomaterial type
First author | Year | Test system | Dose range | Nanomaterial grade | PCM characterization | Standardized dispersion and characterization | Dose range rationale | Dissolution biokinetics | Main conclusions from study | Ref |
|---|---|---|---|---|---|---|---|---|---|---|
Titanium dioxide | ||||||||||
Jiangxue Wang | 2007 | CD-1 (ICR) mouse model | 5 g/kg bw | Not reported | XRF analysis only | Not reported | Not reported | Not reported | TiO2 retained in liver, spleen, kidneys and lung tissues, suggesting uptake by gastrointestinal tract | [21] |
Yanmei Duan | 2010 | CD-1 (ICR) female mouse model | 62.5, 125 and 250 mg/kg bw | Not reported (self-synthesized) | XRD, ICP-MS analysis | Not reported | Not reported | Not reported | Intragastric TiO2 administration in mice damages homeostasis blood system and generates immune response resulting in disruption of liver function | [85] |
Carolina M. Nogueira | 2012 | Bl 57/6 male mouse model | 100 mg/kg bw | Commercially available for use in food, pharmaceuticals and cosmetics | DLS, XRD | No standard dispersion protocol specified | Not reported | Not reported | TiO2 micro and nanoparticles induce a Th1-mediated inflammatory response in the small intestine, especially ileum | [48] |
Yun Wang | 2013 | Sprague Dawley male rat model | 10, 50 and 200 mg/kg bw | Not reported | TEM, ICP-AES, XRD, FTIR, SSA by BET method, hydrodynamic size, zeta potential | No standard dispersion protocol specified | Intragastric doses selected based on the intake of dietary TiO2 particles in the UK | ICP-MS and ICP-OES to measure Ti content in tissues | Young rats seem more susceptible to TiO2 nanoparticle exposure, which can provoke reductive stress in the plasma of both young and old rats but through different mechanisms | [96] |
Zhangjian Chen | 2014 | Sprague Dawley male rat model | 10, 50 and 200 mg/kg bw/day for 30 days | Not reported | Previously characterized [96] | No standard dispersion protocol specified | Intragastric doses selected based on the intake of dietary TiO2 particles in the UK | Not reported | TiO2 nanoparticles induce DNA double strand breaks in rat bone marrow cells after repeated oral administration for 30 days. It might be practical to control the application of TiO2 nanoparticles as food additives | [62] |
Roberta Tassinari | 2014 | Sprague Dawley rat model | 1 and 2 mg/kg bw/day for 5 days | Not reported | TEM, SEM, ICP-MS | No standard dispersion protocol specified | Dose levels selected based on the available data on the effects of TiO2 nanomaterials | ICP-MS to measure Ti content in tissues | TiO2 nanoparticles target endocrine-active tissues at dose levels relevant to human dietary intake; with no observable general toxicity and limited tissue deposition and damage in spleen | [126] |
Emilie Brun | 2014 | Peyer’s patches and regular ileum (ex vivo), mice model (in vivo) | 12.5 mg/kg bw | Not reported (self-synthesized) | SSA by BET, XRD, TEM, agglomeration state (DLS), zeta potential, XAS | For ex vivo experiments, nanoparticle suspensions pulse sonicated at 28% amplitude– corresponding power measured using a calorimetric procedure [104]. Not reported for in vivo experiments | Dose level selected based on daily intake of TiO2 by US children | Not reported | TiO2 nanoparticles pass paracellularly through the regular intestinal epithelium by disrupting tight junctions and localize in tissues beneath these epithelial layers | [46] |
Zhangjian Chen | 2015 | Sprague Dawley rat model | 2, 10 and 50 mg/kg bw/day for 30 or 90 days | Not reported | TEM, ICP-AES, XRD, FTIR spectroscopy, SSA by BET, hydrodynamic diameter (DLS), zeta potential | No standard dispersion protocol specified | Intragastric doses for rats selected based on the daily oral intake of TiO2 nanoparticles for children under the age of 10 years in the US | Not reported | TiO2 nanoparticles alone or in combination with glucose induce liver, kidney and heart injuries as well as changes in white blood cells and red blood cells in young rats. Interactions between TiO2 nanoparticles and glucose was different in different body systems, leading to synergistic or antagonistic effects accordingly | [123] |
Fashui Hong | 2015 | ICR male mice model | 2.5, 5 and 10 mg/kg bw/day for 60 days | Not reported (self-synthesized) | TEM, XRD, SSA by BET, hydrodynamic diameter (DLS), zeta potential | No standard dispersion protocol specified | Dose levels were selected based on a report of the World Health Organization from 1969 | Not reported | TiO2 nanoparticles cause testicular toxicity, reduced sperm production, and induced sperm lesions in a dose dependent manner. These effects are in close relation to reductions in daily food and water intake, biochemical dysfunctions and oxidative stress | [65] |
Zhangjian Chen | 2015 | Sprague Dawley rat model | 2, 10 and 50 mg/kg bw/day for 30 or 90 days | Not reported | TEM, ICP-AES, XRD, FTIR spectroscopy, SSA by BET, hydrodynamic diameter (DLS), zeta potential | No standard dispersion protocol specified | Intragastric doses for rats selected based on the daily oral intake of TiO2 nanoparticles for children under the age of 10 years in the US | Not reported | Long-term (90 days) daily ingestion of TiO2 nanoparticles can exert mild and temporary cardiovascular toxicity by reduction in heart rate and systolic blood pressure, and increase in diastolic blood pressure | [149] |
Ismael M. Urrutia-Ortega | 2016 | BALB/c male mice model | 5 mg/kg bw for 10 weeks | Food grade TiO2 (E171) | SEM, TEM, Raman spectroscopy, hydrodynamic diameter (NTA), zeta potential | No standard dispersion protocol specified | Intragastric doses justified based on collective exposure to TiO2 from nominal consumption estimates and other sources | Not reported | TiO2 E171 nanoparticles enhance tumor formation in the distal colon of chemical induced colitis-associated cancer (CAC) model of male BALB/c adult mice, marked by increase in CAC tumor progression markers. | [49] |
Hanqing Chen | 2017 | CD-1 (ICR) male mouse model | 2.5 mg/kg bw/day for 7 days | Not reported to be food-grade | TEM, hydrodynamic diameter (DLS), zeta potential | No standard dispersion protocol specified | Oral gavage doses justified based on estimated daily intake of TiO2 and SiO2, and recommendation of OECD for Ag [150] | Not reported | Ag nanoparticles cause colitis-like symptoms in intestinal tract, and changes in gut microbiome. SiO2 nanoparticles cause significant increase in proinflammatory cytokines and microbial species diversity. TiO2 nanoparticles did not induce obvious changes in GIT histology or gut microbiota composition | [124] |
Maria G. Ammendolia | 2017 | Sprague Dawley rat model | 1 and 2 mg/kg bw/day for 5 days | Not reported | TEM, SEM, hydrodynamic diameter (DLS), PdI. SSA and purity (provided by manufacturer) | No standard dispersion protocol specified | Dose levels selected based on the available data on the effects of TiO2 nanomaterials | ICP-MS to measure Ti in gut tissue | Higher dose of TiO2 nanoparticles in male rats causes increase in height and width of villus, and dose-related increase in density of goblet cells. No such effects are seen on female rats. TiO2 nanoparticles penetrate intestinal mucosa (suggested by ICP-MS data) | [125] |
Fashui Hong | 2017 | ICR male mice model | 1.25, 2.5 and 5 mg/kg bw/day for 9 months | Not reported (self-synthesized) | TEM, XRD, SSA by BET, hydrodynamic diameter (DLS) [151] | No standard dispersion protocol specified | Dose levels were selected based on a report of the National Institute for Occupational Safety & Health (NIOSH) from 2011 [152] | ICP-MS to measure Ti in gastric tissues | Long term exposure to nano TiO2 results in dysfunction of gastric secretion, inflammation, atrophy, and other lesions of gastric mucosa, which is closely associated with alterations of inflammation responding signal pathways in the stomach. | [100] |
Sarah Bettini | 2017 | Adult male Wistar rat model | 10 mg/kg bw/day for 7 days | Food grade TiO2 (E171) | TEM, TEM-EDX, XANES, hydrodynamic diameter, PdI, zeta potential | TiO2 products prepared following the generic Nanogenotox dispersion protocol [153] | Not reported | TEM-EDX analysis in liver and intestine, and NanoSIMS analysis in Peyer’s Patches | Intragastric food-grade TiO2 administration for one week impairs intestinal immune homeostasis through Th17-driven autoimmune complications. Chronic exposures correlating with the development of an inflammatory microenvironment, may initiate and promote expansion of preneoplastic lesions in the colon. | [50] |
Silicon dioxide | ||||||||||
Hanqing Chen | 2017 | CD-1 (ICR) male mouse model | 2.5 mg/kg bw/day for 7 days | Not reported to be food-grade | TEM, hydrodynamic diameter (DLS), zeta potential | No standard dispersion protocol specified | Oral gavage doses justified based on estimated daily intake of TiO2 and SiO2, and recommendation of OECD for Ag [150] | Not reported | Ag nanoparticles cause colitis-like symptoms in intestinal tract, and changes in gut microbiome. SiO2 nanoparticles cause significant increase in proinflammatory cytokines and microbial species diversity. TiO2 nanoparticles did not induce obvious changes in GIT histology or gut microbiota composition | [124] |
Zinc oxide | ||||||||||
Vyom Sharma | 2012 | Swiss albino male mouse model | 50 and 300 mg/kg bw | Not reported | DLS and TEM | No standard dispersion protocol specified | Followed OECD guidelines [154] | Not reported | Sub-acute oral exposure to ZnO nanoparticles leads to their accumulation in liver causing oxidative stress-mediated DNA damage and apoptosis | [81] |
Surekha Pasupuleti | 2012 | Sprague Dawley rat model | 5, 50, 300, 1000 and 2000 mg/kg bw | Not reported | DLS, zeta potential, SEM | Not reported | Followed OECD guidelines [155] | Not reported | Nano-sized ZnO exhibit toxic effects (increased AST and ALT serum levels, microscopic lesions in various organs) at lower doses in comparison to micron-sized ZnO | [79] |
Miri Baek | 2012 | Sprague Dawley rat model | 50, 300 and 2000 mg/kg bw | Not reported | XRD, SEM, TEM, zeta potential | No standard dispersion protocol specified | Not reported | ICP-AES to measure Zn content in tissues | ZnO nanoparticles accumulate in the form of zinc ions in the liver, kidney and lung irrespective of the gender or particle size. Excretion occurs via feces with higher rate of clearance for smaller particles | [117] |
Yanli Wang | 2014 | Kunming male mice model | Not reported | XRD, TEM, XRF, hydrodynamic size (DLS) in water and cell culture medium, zeta potential | Not reported | Dose levels agreed with the European food additives standard and Chinese food additive standard | ICP-MS to measure Zn content in tissues | ZnO nanoparticles, in the presence of Vitamin C, induce significant changes in the TBIL (total bilirubin levels) and BUN (blood urea nitrogen) of liver and kidney, and trigger injury to the main organs | [63] | |