Effects of oral exposure to titanium dioxide nanoparticles on gut microbiota and gut-associated metabolism in vivo

I, Six JL, Ferji K, Jaafar J, Boer JC, Plebanski M, Uskoković V, Mohamud R. Nanoparticles and Gut Microbiota in Colorectal Cancer

Recent years have witnessed an unprecedented growth in the research area of nanomedicine. There is an increasing optimism that nanotechnology applied to medicine will bring significant advances in the diagnosis and treatment of various diseases, including colorectal cancer (CRC), a type of neoplasm affecting cells in the colon or the rectum. Recent findings suggest that the role of microbiota is crucial in the development of CRC and its progression. Dysbiosis is a condition that disturbs the normal microbial environment in the gut and is often observed in CRC patients. In order to detect and treat precancerous lesions, new tools such as nanotechnology-based theranostics, provide a promising option for targeted marker detection or therapy for CRC. Because the presence of gut microbiota influences the route of biomarker detection and the route of the interaction of nanoparticle/drug complexes with target cells, the development of nanoparticles with appropriate sizes, morphologies, chemical compositions and concentrations might overcome this fundamental barrier. Metallic particles are good candidates for nanoparticle-induced intestinal dysbiosis, but this aspect has been poorly explored to date. Herein, we focus on reviewing and discussing nanotechnologies with potential applications in CRC through the involvement of gut microbiota and highlight the clinical areas that would benefit from these new medical technologies.

Fecal microbiota transplantation attenuates nano-plastics induced toxicity in Caenorhabditis elegans

Current studies simply focus on the toxicity of nano-plastics, while the correlation between their toxicity and bio-distribution, as well as intestinal microorganisms is still blank. Therefore, we systematically evaluated the toxicity based on the accumulation characteristics of nano-plastics in C. elegans. Meanwhile, for the first time, human fecal microbiota was transplanted into the gut of C. elegans and found that nano-plastics can through the intestinal barrier to the whole body after oral intake and can't be drastically excreted until die, thus causing toxic effects; while human fecal microbiota transplantation can significantly improve the living state via activating PMK-1/SKN-1 pathway to promote the production of intracellular glutathione, and exogenous glutathione addition can also markedly protect nematodes against nano-plastics induced toxicity. Our results not only provide a fully understand between the accumulation characteristic and health risk of nano-plastics, but also take C. elegans and intestinal flora into the field of toxicity evolution of nanomaterials.

Effects of Oral Exposure to Mn-Doped ZnS Quantum Dots on Intestinal Tract and Gut Microbiota in Mice

Mn-doped ZnS quantum dots (QDs) with excellent optical properties have been explored in a wide range of fields. Their potential adverse effects on biological systems and human health should be evaluated before biological application. In the present study, we investigated the effect of Mn-doped ZnS QDs on the intestinal tract and gut microbiota structures at 2 h and 14 days (d) after 14 d repeated oral exposure in mice. Flame atomic absorption spectrophotometry (FAAS), histopathological examination, and transmission electron microscopy (TEM) were used to assess the absorption and toxicity of Mn-doped ZnS QDs on the intestinal tract. The 16S rRNA gene sequencing was used to evaluate the gut microbial communities. Mn-doped ZnS QDs did not accumulate in the duodenum, jejunum, ileum, or colon. The Zn content of feces was not significantly higher than in the control group. No major histological changes were found in these tissues. The intestinal microvilli remained regular, but swelling of mitochondria and endoplasmic reticulum was detected by TEM at 14 d after the last gavage. A total of 2,712 operational taxonomic units (OTUs) were generated. Mn-doped ZnS QDs treatment did not significantly change the α-diversity of Richness, Chao1, Shannon, and Simpson indexes. According to principal component analysis (PCA), Mn-doped ZnS QDs had no effect on the overall structure of the gut microbiota. No significant change occurred at the phylum level, while three genera were downregulated at 2 h and seven changed at 14 d after the last gavage. Our findings revealed that Mn-doped ZnS QDs had a little stimulation of the intestinal tract and gut microbiota, and oral administration may be a safe route for biological application (such as bioimaging and drug delivery).

Modern Sensing Approaches for Predicting Toxicological Responses of Food- and Drug-Based Bioactives on Microbiomes of Gut Origin

Recent scientific findings have correlated the gut microbes with homeostasis of human health by delineating their role in pathogen resistance, bioactive metabolization, and immune responses. Foreign materials, like xenobiotics, that induce an altering effect to the human body also influence the gut microbiome to some extent and often limit their use as a result of significant side effects. Investigating the xenobiotic effect of new therapeutic material or edible could be quite painstaking and economically non-viable. Thus, the use of predictive toxicology methods can be an innovative strategy in the food, pharma, and agriculture industries. There are reported in silico, ex vivo, in vitro, and in vivo methods to evaluate such effects but with added drawbacks, such as lower predictability, physiological dissimilarities, and high cost of associated invasive procedures. This review highlights the current and future possibilities with newer modern sensing approaches of economic and time-scale advantages for predicting toxicological responses on gut microbiomes.

Review of gut nanotoxicology in mammals: Exposure, transformation, distribution and toxicity

Nanomaterials are increasingly used in food processing, daily necessities and other fields due to their excellent properties, and increase the environmental contamination. Human beings will inevitably come into contact with these nanomaterials through multiple exposure routes especially oral exposure. The intestine is an important organ for nutrient absorption and physiologic barrier, which may be the main target of nanoparticles (NPs) exposure. However, for a long time, research on the toxicity of NPs has mainly focused on organs such as liver, kidney and brain. There are few assessment data over the intestinal safety. Recently, as reported, NPs can be translocated to the intestinal part in mammals and would be distributed in different substructures of intestines, thus causing damage to the structure and function of the intestine, in which the gut microbiota and its metabolites play important roles. In addition, due to the special physiological environment of gut, nanomaterials will undergo complex transformations that may cause different biological effects from their original form. Therefore, this review aims to assess the potential adverse effects of NPs on intestine and its possible mechanisms through the results of in vivo mammalian experiments. In addition, the exposure pathway, biodistribution and biotransformation of NPs in the intestine are also considered. We hope this review will arouse people's attention to the intestinal nanotoxicology and provide basic information for further related studies.

Safety assessment of titanium dioxide (E171) as a food additive

The present opinion deals with an updated safety assessment of the food additive titanium dioxide (E 171) based on new relevant scientific evidence considered by the Panel to be reliable, including data obtained with TiO2 nanoparticles (NPs) and data from an extended one-generation reproductive toxicity (EOGRT) study. Less than 50% of constituent particles by number in E 171 have a minimum external dimension < 100 nm. In addition, the Panel noted that constituent particles < 30 nm amounted to less than 1% of particles by number. The Panel therefore considered that studies with TiO2 NPs < 30 nm were of limited relevance to the safety assessment of E 171. The Panel concluded that although gastrointestinal absorption of TiO2 particles is low, they may accumulate in the body. Studies on general and organ toxicity did not indicate adverse effects with either E 171 up to a dose of 1,000 mg/kg body weight (bw) per day or with TiO2 NPs (> 30 nm) up to the highest dose tested of 100 mg/kg bw per day. No effects on reproductive and developmental toxicity were observed up to a dose of 1,000 mg E 171/kg bw per day, the highest dose tested in the EOGRT study. However, observations of potential immunotoxicity and inflammation with E 171 and potential neurotoxicity with TiO2 NPs, together with the potential induction of aberrant crypt foci with E 171, may indicate adverse effects. With respect to genotoxicity, the Panel concluded that TiO2 particles have the potential to induce DNA strand breaks and chromosomal damage, but not gene mutations. No clear correlation was observed between the physico-chemical properties of TiO2 particles and the outcome of either in vitro or in vivo genotoxicity assays. A concern for genotoxicity of TiO2 particles that may be present in E 171 could therefore not be ruled out. Several modes of action for the genotoxicity may operate in parallel and the relative contributions of different molecular mechanisms elicited by TiO2 particles are not known. There was uncertainty as to whether a threshold mode of action could be assumed. In addition, a cut-off value for TiO2 particle size with respect to genotoxicity could not be identified. No appropriately designed study was available to investigate the potential carcinogenic effects of TiO2 NPs. Based on all the evidence available, a concern for genotoxicity could not be ruled out, and given the many uncertainties, the Panel concluded that E 171 can no longer be considered as safe when used as a food additive.

Changes induced by chronic exposure to high arsenic concentrations in the intestine and its microenvironment

The perturbation of intestinal microbes may serve as a mechanism by which arsenic exposure causes or exacerbates diseases in humans. However, the changes in the intestinal microbiome and metabolome induced by long-term exposure to high concentrations of arsenic have not been extensively studied. In this study, C57BL/6 mice were exposed to sodium arsenite (As) (50 ppm) for 6 months. Our results show that long-term exposure to high As concentrations changed the structure of intestinal tissues and the expression of As resistance related genes in intestinal microbes. In addition, 16S rRNA gene sequencing revealed that As exposure significantly affected the Beta diversity of intestinal flora but had no significant effect on the Alpha diversity (except ACE index). Moreover, As exposure altered the composition of the intestinal microbiota from phylum to species. Non-targeted metabolomics profiling revealed that As exposure significantly changed the composition of metabolites, specifically those related to phenylalanine metabolism. Correlation analysis demonstrated that the changes in microbial communities and metabolites were highly correlated under As exposure. Overall, this study demonstrates that long-term exposure to high As concentrations disrupted the intestinal microbiome and metabolome, which may indicate the role of As exposure at inducing human diseases under similar conditions.

Metal- and metal/oxide-based engineered nanoparticles and nanostructures: a review on the applications, nanotoxicological effects, and risk control strategies

The production and demand of nanoparticles in the manufacturing sector and personal care products, release a large number of engineered nanoparticles (ENPs) into the atmosphere, aquatic ecosystems, and terrestrial environments. The intentional or involuntary incorporation of ENPs into the environment is carried out through different processes. The ENPs are combined with other compounds and release into the atmosphere, settling on the ground due to the water cycle or other atmospheric phenomena. In the case of aquatic ecosystems, the ENPs undergo hetero-aggregation and sedimentation, reaching different living organisms and flora, as well as groundwater. Accordingly, the high mobility of ENPs in diverse ecosystems is strongly related to physical, chemical, and biological processes. Recent studies have been focused on the toxicological effects of a wide variety of ENPs using different validated biological models. This literature review emphasizes the study of toxicological effects related to using the most common ENPs, specifically metal and metal/oxides-based nanoparticles, addressing different synthesis methodologies, applications, and toxicological evaluations. The results suggest negative impacts on biological models, such as oxidative stress, metabolic and locomotive toxicity, DNA replication dysfunction, and bioaccumulation. Finally, it was consulted the protocols for the control of risks, following the assessment and management process, as well as the classification system for technological alternatives and risk management measures of ENPs, which are useful for the transfer of technology and nanoparticles commercialization.

Altered protein S-glutathionylation depicts redox imbalance triggered by transition metal oxide nanoparticles in a breastfeeding system

Nanosafety has become a public concern following nanotechnology development. By now, attention has seldom been paid to breastfeeding system, which is constructed by mammary physiological structure and derived substances (endogenous or exogenous), cells, tissues, organs, and individuals (mother and child), connecting environment and organism, and spans across mother-child dyad. Thus, breastfeeding system is a center of nutrients transport and a unique window of toxic susceptibility in the mother-child dyad. We applied metabolomics combined with redox proteomics to depict how nanoparticles cause metabolic burden via their spontaneous redox cycling in lactating mammary glands. Two widely used nanoparticles [titanium dioxide (nTiO₂) and zinc oxide (nZnO)] were exposed to lactating mice via intranasal administration. Biodistribution and biopersistence of nTiO₂ and nZnO in mammary glands destroyed its structure, reflective of significantly reduced claudin-3 protein level by 32.1% (P < 0.01) and 47.8% (P < 0.01), and significantly increased apoptosis index by 85.7 (P < 0.01) and 100.3 (P < 0.01) fold change, respectively. Airway exposure of nTiO₂ trended to reduced milk production by 22.7% (P = 0.06), while nZnO significantly reduced milk production by 33.0% (P < 0.01). Metabolomics analysis revealed a metabolic shift by nTiO₂ or nZnO, such as increased glycolysis (nTiO₂: fold enrichment = 3.31, P < 0.05; nZnO: fold enrichment = 3.68, P < 0.05), glutathione metabolism (nTiO₂: fold enrichment = 5.57, P < 0.01; nZnO: fold enrichment = 4.43, P < 0.05), and fatty acid biosynthesis (nTiO₂: fold enrichment = 3.52, P < 0.05; nZnO: fold enrichment = 3.51, P < 0.05) for tissue repair at expense of lower milk fat synthesis (35.7% reduction by nTiO₂; 51.8% reduction by nZnO), and finally led to oxidative stress of mammary glands. The increased GSSG/GSH ratio (57.5% increase by nTiO₂; 105% increase by nZnO) with nanoparticle exposure confirmed an alteration in the redox state and a metabolic shift in mammary glands. Redox proteomics showed that nanoparticles induced S-glutathionylation (SSG) modification at Cys sites of proteins in a nanoparticle type-dependent manner. The nTiO₂ induced more protein SSG modification sites (nTiO₂: 21; nZnO:16), whereas nZnO induced fewer protein SSG modification sites but at deeper SSG levels (26.6% higher in average of nZnO than that of nTiO₂). In detail, SSG modification by nTiO₂ was characterized by Ltf at Cys⁴²³ (25.3% increase), and Trf at Cys^386;395;583 (42.3%, 42.3%, 22.8% increase) compared with control group. While, SSG modification by nZnO was characterized by Trfc at Cys³⁶⁵ (71.3% increase) and Fasn at Cys¹⁰¹⁰ (41.0% increase). The discovery of SSG-modified proteins under airway nanoparticle exposure further supplemented the oxidative stress index and mammary injury index, and deciphered precise mechanisms of nanotoxicity into a molecular level. The unique quantitative site-specific redox proteomics and metabolomics can serve as a new technique to identify nanotoxicity and provide deep insights into nanoparticle-triggered oxidative stress, contributing to a healthy breastfeeding environment.

The Influence of Diet on Oxidative Stress and Inflammation Induced by Bacterial Biofilms in the Human Oral Cavity

The article is a concise compendium of knowledge on the etiology of pathogenic microorganisms of all complexes causing oral diseases. The influence of particular components of the diet and the role of oxidative stress in periodontal diseases were described. The study investigated the bacteriostatic effect of the diet of adults in in vivo and in vitro tests on the formation of bacterial biofilms living in the subgingival plaque, causing diseases called periodontitis. If left untreated, periodontitis can damage the gums and alveolar bones. Anaerobic bacteria, called periopathogens or periodontopathogens, play a key role in the etiopathogenesis of periodontitis. The most important periopathogens of the oral microbiota are bacteria of all complexes, including the red complex. The obtained results suggest the possibility of using a specific diet in the prevention and treatment of periodontal diseases-already treated as a disease of civilization. The quoted article is an innovative compilation of knowledge on this subject and it can be a valuable source of knowledge for professional hygienists, dentists, peridontologists, dentistry students and anyone who cares about proper oral hygiene. The obtained results suggest the possibility of using this type of diet in the prophylaxis of the oral cavity in order to avoid periodontitis.

Acute and chronic effects of Titanium dioxide (TiO2) PM1 on honey bee gut microbiota under laboratory conditions

Apis mellifera is an important provider of ecosystem services, and during flight and foraging behaviour is exposed to environmental pollutants including airborne particulate matter (PM). While exposure to insecticides, antibiotics, and herbicides may compromise bee health through alterations of the gut microbial community, no data are available on the impacts of PM on the bee microbiota. Here we tested the effects of ultrapure Titanium dioxide (TiO₂) submicrometric PM (i.e., PM₁, less than 1 µm in diameter) on the gut microbiota of adult bees. TiO₂ PM₁ is widely used as a filler and whitening agent in a range of manufactured objects, and ultrapure TiO₂ PM₁ is also a common food additive, even if it has been classified by the International Agency for Research on Cancer (IARC) as a possible human carcinogen in Group 2B. Due to its ubiquitous use, honey bees may be severely exposed to TiO₂ ingestion through contaminated honey and pollen. Here, we demonstrated that acute and chronic oral administration of ultrapure TiO₂ PM₁ to adult bees alters the bee microbial community; therefore, airborne PM may represent a further risk factor for the honey bee health, promoting sublethal effects against the gut microbiota.

Exploring urine biomarkers of early health effects for occupational exposure to titanium dioxide nanoparticles using metabolomics

Many experimental studies have demonstrated that titanium dioxide nanoparticles (TiO2 NPs) could induce adverse health effects in vivo and in vitro. But epidemiological evidence and biomarkers related to early health effects are still lacking. This study aimed to explore biomarkers in the urine samples of workers occupationally exposed to a relatively low concentration of TiO2 NPs. A cross-sectional study was conducted in Jinan, China, involving 132 employees of a TiO2 NP manufacturing plant, among which the exposed group and control group were 1 : 1 matched by confounding factors such as gender, age, BMI, smoking and drinking. Untargeted metabolomics was performed in urine samples using high performance liquid chromatography-mass spectrometry (HPLC-MS) technology. The differential metabolites between the TiO2 NP exposed group and the control group were analyzed and then screened for potential biomarkers using bioinformatics methods. Metabolomics found a total of 1760 differentially expressed metabolites in the TiO2 NP exposed group, of which 60 differential metabolites were simultaneously confirmed by one-dimensional and multi-dimensional statistical analysis. Among these 60 differential metabolites, the relative expression of 27 metabolites increased, and the remaining 33 decreased. Pathway enrichment analysis further found that the metabolic pathway of long chain acyl-coa dehydrogenase deficiency (Lcad) was significantly enriched. Ten differential metabolites were selected as potential biomarkers of occupational exposure to TiO2 NPs using machine learning methods, including dibenzyl ether, quassimarin, tryptophan, etc. The receiver operating characteristic curves (ROCs) of these potential biomarkers showed good sensitivity and specificity. These potential biomarkers also had biological basis for occupational exposure to TiO2 NPs. Therefore, urine metabolites represented by dibenzyl ether are considered as good biomarkers of early health effects for occupational exposure to TiO2 NPs.

Impact of Food Additive Titanium Dioxide on Gut Microbiota Composition, Microbiota-Associated Functions, and Gut Barrier: A Systematic Review of In Vivo Animal Studies

Background: Titanium dioxide (TiO₂) is used as a food additive in pastries, sweets, and sauces. It is recognized as safe by food safety authorities, but in recent years, governments and scientists have raised concerns about its genotoxicity. This systematic review aims to assess the potential associations between food TiO₂ exposure and microbiota composition and functions. Methods: A systematic literature search was performed up to December 2020 in PubMed, Web of Science, and Scopus databases. The PRISMA guidelines followed. The risk of bias was assessed from ARRIVE and SYRCLE tools. Results: A total of 18 animal studies were included (n = 10 mice, n = 5 rats, n = 2 fruit flies, n = 1 silkworm). Studies varied significantly in protocols and outcomes assessment. TiO₂ exposure might cause variations in abundance in specific bacterial species and lead to gut dysfunctions such as a reduction in SCFAs levels, goblet cells and crypts, mucus production, and increased biomarkers of intestinal inflammation. Conclusions: Although the extrapolation of these results from animals to humans remains difficult, this review highlights the key role of gut microbiota in gut nanotoxicology and stimulates discussions on the safe TiO₂ use in food and dietary supplements. This systematic review was registered at PROSPERO as CRD42020223968.

Molecular and cellular cues governing nanomaterial-mucosae interactions: from nanomedicine to nanotoxicology

Mucosal tissues constitute the largest interface between the body and the surrounding environment and they regulate the access of molecules, supramolecular structures, particulate matter, and pathogens into it. All mucosae are characterized by an outer mucus layer that protects the underlying cells from physicochemical, biological and mechanical insults, a mono-layered or stratified epithelium that forms tight junctions and controls the selective transport of solutes across it and associated lymphoid tissues that play a sentinel role. Mucus is a gel-like material comprised mainly of the glycoprotein mucin and water and it displays both hydrophilic and hydrophobic domains, a net negative charge, and high porosity and pore interconnectivity, providing an efficient barrier for the absorption of therapeutic agents. To prolong the residence time, absorption and bioavailability of a broad spectrum of active compounds upon mucosal administration, mucus-penetrating and mucoadhesive particles have been designed by tuning the chemical composition, the size, the density, and the surface properties. The benefits of utilizing nanomaterials that interact intimately with mucosae by different mechanisms in the nanomedicine field have been extensively reported. To ensure the safety of these nanosystems, their compatibility is evaluated in vitro and in vivo in preclinical and clinical trials. Conversely, there is a growing concern about the toxicity of nanomaterials dispersed in air and water effluents that unintentionally come into contact with the airways and the gastrointestinal tract. Thus, deep understanding of the key nanomaterial properties that govern the interplay with mucus and tissues is crucial for the rational design of more efficient drug delivery nanosystems (nanomedicine) and to anticipate the fate and side-effects of nanoparticulate matter upon acute or chronic exposure (nanotoxicology). This review initially overviews the complex structural features of mucosal tissues, including the structure of mucus, the epithelial barrier, the mucosal-associated lymphatic tissues and microbiota. Then, the most relevant investigations attempting to identify and validate the key particle features that govern nanomaterial-mucosa interactions and that are relevant in both nanomedicine and nanotoxicology are discussed in a holistic manner. Finally, the most popular experimental techniques and the incipient use of mathematical and computational models to characterize these interactions are described.

Impact of titanium dioxide nanoparticles on intestinal community in 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced acute colitis mice and the intervention effect of vitamin E

Titanium dioxide nanoparticles (TiO2-NPs) are widely applied as additives in foods due to their excellent whitening and brightening capability. Although the toxicity and antibacterial activity of TiO2-NPs have been extensively studied, their impact on the gut microbiota in vivo still remains unclear, especially in animals with gastrointestinal disorders. In the present study, healthy mice and TNBS-induced colitis mice were administered with TiO2-NPs (38.3 ± 9.3 nm) orally at a dose of 100 mg per kg bw daily for 10 days to study the impact of TiO2-NPs on the gut microbiota and colitis development. Moreover, the mechanism of TiO2-NPs on the gut microbiota was also discussed when the colitis mice were additionally administered with vitamin E to remove ROS. Changes in the microbiota community structure and gut-associated function prediction were analyzed through bioinformatics. The result showed that the oral administration of TiO2-NPs mitigated colitis symptoms by reducing the DAI and CMDI scores and TNF-α level. Furthermore, 16S rDNA sequencing analysis showed that the structure and function prediction of gut microbiota could be modified in healthy mice and colitis mice after exposure to TiO2-NPs, but the opposite physiological effect occurred since the dominant flora varied in these two groups. Moreover, vitamin E intervention did not change the effects of TiO2-NPs on the microbiota community structure and gut-associated function, which indicates that the mechanism of the biological effects of TiO2-NPs on the gut microbiota may not be associated with their ability to induce the generation of ROS. In summary, our work firstly found that TiO2-NPs could regulate the gut microbiota of colitis mice and participate in the mitigation of TNBS-induced acute colitis, and the capability of TiO2-NPs to induce the generation of ROS inducement did not contribute to this process.

A review of the impact of xenobiotics from dietary sources on infant health: Early life exposures and the role of the microbiota

Xenobiotics are worldwide distributed and humans are unavoidably exposed to multiple chemical compounds during life, from preconception to adulthood. The human microbiota is mainly settled during early life and modulate host health and fitness. One of the main routes for chemical exposure is by intake of contaminated food and water. Thus, the interplay between diet-xenobiotics-microbiota during pregnancy and perinatal period may have relevant consequences for infant and adult health. Maternal exposure to metal(oid)s, persistent organic pollutants, and some food additives can modify the infant's microbiota with unknown consequences for child or adult health. Toxicants' exposure may also modulate the maternal transfer of microorganisms to the progeny during birth and breastfeeding; however, scarce information is available. The rapid increase in releasing novel chemicals to the environment, the exposure to chemical mixtures, the chronic/low dose scenario, and the delay in science-stakeholders action call for novel and groundbreaking approaches to improve a comprehensive risk assessment in sensitive population groups like pregnant women and neonates, with emphasis on microbiota as modulating factor and target-organ of xenobiotic's toxicity.

Gut Microbiota Combined With Metabolomics Reveals the Repeated Dose Oral Toxicity of β-Cyclodextrin in Mice

Βeta-cyclodextrin (β-CD) with a hydrophobic cavity enables the formation of inclusion complexes with organic molecules. The formation of host–guest complexes makes the application of β-CD popular in many fields, but their interaction with organisms is poorly understood. In the present study, the effect of β-CD on gut microbiota (16S rRNA gene sequencing), serum metabolites (gas chromatography–mass spectrometry platform), and their correlation (Pearson correlation analysis) was investigated after 14 days repeated oral exposure in mice. β-CD did not significantly affect the α-diversity indexes, including Richness, Chao1, Shannon and Simpson indexes, but disturbed the structure of the gut bacteria according to the result of principal component analysis (PCA). After taxonomic assignment, 1 in 27 phyla, 2 in 48 classes, 3 in 107 orders, 6 in 192 families, and 8 in 332 genera were significantly different between control and β-CD treated groups. The serum metabolites were significantly changed after β-CD treatment according to the result of unsupervized PCA and supervised partial least squares-discriminant analysis (PLS-DA). A total of 112 differential metabolites (89 downregulated and 23 upregulated) were identified based on the VIP >1 from orthogonal PLS-DA and p <0.05 from Student’s t-test. The metabolic pathways, including ABC transporters, pyrimidine metabolism, purine metabolism, glucagon signaling pathway, insulin signaling pathway, and glycolysis/gluconeogenesis, were enriched by KEGG pathway analysis. Our study provides a general observation of gut microbiota, serum metabolites and their correlation after exposure to β-CD in mice, which will be helpful for future research and application of β-CD.

Oral intake of silica nanoparticles exacerbates intestinal inflammation

Nanoparticles, i.e., particles with a diameter of ≤100 nm regardless of their composing material, are added to various foods as moisturizers, coloring agents, and preservatives. Silicon dioxide (SiO2, silica) nanoparticles in particular are widely used as food additives. However, the influence of SiO2 nanoparticle oral consumption on intestinal homeostasis remains unclear. The daily intake of 10-nm-sized SiO2 nanoparticles exacerbates dextran sulfate sodium (DSS)-induced colitis, whereas the daily intake of 30-nm-sized SiO2 nanoparticles has no influence on intestinal inflammation. The exacerbation of colitis induced by consuming 10-nm-sized SiO2 nanoparticles was abolished in mice deficient in apoptosis-associated speck-like protein containing a CARD (ASC). Our study indicates that the oral intake of small SiO2 nanoparticles poses a risk for worsening intestinal inflammation through activation of the ASC inflammasome.

Rapid and continuous fabrication of TiO2 nanoparticles encapsulated by polyimide fine particles using a multistep flow-system and their application

PI fine particles encapsulating a large number of TiO₂ nanoparticles (PI FPs/TiO₂ NPs) were successfully fabricated rapidly and continuously by the emulsion re-precipitation method using a multistep flow synthetic system. The fabricated material, PI FPs/TiO₂ NPs, was spherical in structure with a diameter of 214 nm, and the mean size of TiO₂ NPs was 5.2 nm. Line scan elemental analysis with SEM-EDX showed that the TiO₂ NPs were disproportionately embedded near the surface of the PI FPs. UV-vis transmission spectra revealed high UV shielding efficiency of the PI FPs/TiO₂ NPs as the NPs are located near the surface.

We rapidly and continuously fabricated TiO₂ nanoparticles encapsulated by polymer fine particles, and the fabricated nanomaterials showed high UV shielding efficiency.

Ecological and toxicological assessments of anthropogenic contaminants based on environmental metabolomics

There has long been a great concern with growing anthropogenic contaminants and their ecological and toxicological effects on living organisms and the surrounding environment for decades. Metabolomics, a functional readout of cellular activity, can capture organismal responses to various contaminant-related stressors, acquiring direct signatures to illustrate the environmental behaviours of anthropogenic contaminants better. This review entails the application of metabolomics to profile metabolic responses of environmental organisms, e.g. animals (rodents, fish, crustacean and earthworms) and microorganisms (bacteria, yeast and microalgae) to different anthropogenic contaminants, including heavy metals, nanomaterials, pesticides, pharmaceutical and personal products, persistent organic pollutants, and assesses their ecotoxicological impacts with regard to literature published in the recent five years. Contaminant-induced metabolism alteration and up/down-regulation of metabolic pathways are revealed in typical organisms. The obtained insights of variations in global metabolism provide a distinct understanding of how anthropogenic contaminants exert influences on specific metabolic pathways on living organisms. Thus with a novel ecotechnique of environmental metabolomics, risk assessments of anthropogenic contaminants are profoundly demonstrated.

Chemical Characterization and Quantification of Titanium Dioxide Nanoparticles (TiO2-NPs) in Seafood by Single-Particle ICP-MS: Assessment of Dietary Exposure

The significant increase in the production and variety of nanoparticles (NPs) has led to their release into the environment, especially into the marine environment. Titanium dioxide nanoparticles (TiO₂-NPs) are used in different industrial sectors, from the food industry to several consumer and household products. Since the aquatic environment is highly sensitive to contamination by TiO₂-NPs, this work aimed to give a preliminary assessment of the contamination of packaged seafood, where the food additive TiO₂ (E171) is not to be intentionally added. This allowed providing a chemical characterization and quantification of TiO₂-NPs in processed canned fish products belonging to different trophic positions of the pelagic compartment and in canned clam. The new emerging technique called single-particle inductively coupled plasma mass spectrometry (spICP-MS) was applied, which allows the determination of nanoparticle number-based concentration, as well as the dissolved titanium. This study highlights how processed food, where the pigment E171 was not intentionally added, contains TiO₂ in its nanoparticle form, as well as dissolved titanium. Processed clam represented the seafood with the highest content of TiO₂-NPs. In pelagic fish species, we found progressively higher levels and smaller sizes of TiO₂-NPs from smaller to larger fish. Our results highlight the importance of planning the characterization and quantification of TiO₂-NPs in food both processed and not, as well as where the pigment E171 is intentionally added and not, as it is not the only source of TiO₂-NPs. This result represents a solid step toward being able to estimate the real level of dietary exposure to TiO₂-NPs for the general population and the related health risks.

Implications of the Human Gut-Brain and Gut-Cancer Axes for Future Nanomedicine

Recent clinical and pathological evidence have implicated the gut microbiota as a nexus for modulating the homeostasis of the human body, impacting conditions from cancer and dementia to obesity and social behavior. The connections between microbiota and human diseases offer numerous opportunities in medicine, most of which have limited or no therapeutic solutions available. In light of this paradigm-setting trend in science, this review aims to provide a comprehensive and timely summary of the mechanistic pathways governing the gut microbiota and their implications for nanomedicines targeting cancer and neurodegenerative diseases. Specifically, we discuss in parallel the beneficial and pathogenic relationship of the gut microbiota along the gut-brain and gut-cancer axes, elaborate on the impact of dysbiosis and the gastrointestinal corona on the efficacy of nanomedicines, and highlight a molecular mimicry that manipulates the universal cross-β backbone of bacterial amyloid to accelerate neurological disorders. This review further offers a forward-looking section on the rational design of cancer and dementia nanomedicines exploiting the gut-brain and gut-cancer axes.

Immunotoxicity and intestinal effects of nano- and microplastics: a review of the literature

BACKGROUND

Together with poor biodegradability and insufficient recycling, the massive production and use of plastics have led to widespread environmental contamination by nano- and microplastics. These particles accumulate across ecosystems - even in the most remote habitats - and are transferred through food chains, leading to inevitable human ingestion, that adds to the highest one due to food processes and packaging.

OBJECTIVE

The present review aimed at providing a comprehensive overview of current knowledge regarding the effects of nano- and microplastics on intestinal homeostasis.

METHODS

We conducted a literature search focused on the in vivo effects of nano- and microplastics on gut epithelium and microbiota, as well as on immune response.

RESULTS

Numerous animal studies have shown that exposure to nano- and microplastics leads to impairments in oxidative and inflammatory intestinal balance, and disruption of the gut's epithelial permeability. Other notable effects of nano- and microplastic exposure include dysbiosis (changes in the gut microbiota) and immune cell toxicity. Moreover, microplastics contain additives, adsorb contaminants, and may promote the growth of bacterial pathogens on their surfaces: they are potential carriers of intestinal toxicants and pathogens that can potentially lead to further adverse effects.

CONCLUSION

Despite the scarcity of reports directly relevant to human, this review brings together a growing body of evidence showing that nano- and microplastic exposure disturbs the gut microbiota and critical intestinal functions. Such effects may promote the development of chronic immune disorders. Further investigation of this threat to human health is warranted.

Toxic effects of the food additives titanium dioxide and silica on the murine intestinal tract: Mechanisms related to intestinal barrier dysfunction involved by gut microbiota

This study aimed to compare the effects of three food-grade particles (micro-TiO₂, nano-TiO₂, and nano-SiO₂) on the murine intestinal tract and to investigate their potential mechanisms of action. A 28-day oral exposure murine model was established. Samples of blood, intestinal tissues and colon contents were collected for detection. The results showed that all three particles could cause inflammatory damage to the intestine, with nano-TiO₂ showing the strongest effects. Exposure also led to changes in gut microbiota, especially mucus-associated bacteria. Our results suggest that the toxic effects on the intestine were due to reduced intestinal mucus barrier function and an increase in metabolite lipopolysaccharides which activated the expression of inflammatory factors downstream. In mice exposed to nano-TiO₂, the intestinal PKC/TLR4/NF-κB signalling pathway was activated. These findings will raise awareness of toxicities associated with the use of food-grade TiO₂ and SiO₂.

Nanomaterial-mediated autophagy: coexisting hazard and health benefits in biomedicine

BACKGROUND

Widespread biomedical applications of nanomaterials (NMs) bring about increased human exposure risk due to their unique physicochemical properties. Autophagy, which is of great importance for regulating the physiological or pathological activities of the body, has been reported to play a key role in NM-driven biological effects both in vivo and in vitro. The coexisting hazard and health benefits of NM-mediated autophagy in biomedicine are nonnegligible and require our particular concerns.

MAIN BODY

We collected research on the toxic effects related to NM-mediated autophagy both in vivo and in vitro. Generally, NMs can be delivered into animal models through different administration routes, or internalized by cells through different uptake pathways, exerting varying degrees of damage in tissues, organs, cells, and organelles, eventually being deposited in or excreted from the body. In addition, other biological effects of NMs, such as oxidative stress, inflammation, necroptosis, pyroptosis, and ferroptosis, have been associated with autophagy and cooperate to regulate body activities. We therefore highlight that NM-mediated autophagy serves as a double-edged sword, which could be utilized in the treatment of certain diseases related to autophagy dysfunction, such as cancer, neurodegenerative disease, and cardiovascular disease. Challenges and suggestions for further investigations of NM-mediated autophagy are proposed with the purpose to improve their biosafety evaluation and facilitate their wide application. Databases such as PubMed and Web of Science were utilized to search for relevant literature, which included all published, Epub ahead of print, in-process, and non-indexed citations.

CONCLUSION

In this review, we focus on the dual effect of NM-mediated autophagy in the biomedical field. It has become a trend to use the benefits of NM-mediated autophagy to treat clinical diseases such as cancer and neurodegenerative diseases. Understanding the regulatory mechanism of NM-mediated autophagy in biomedicine is also helpful for reducing the toxic effects of NMs as much as possible.

Tissue-specific oxidative stress and element distribution after oral exposure to titanium dioxide nanoparticles in rats

Dietary and environmental exposure to titanium dioxide nanoparticles (TiO2 NPs) can cause low-dose and long-term oral exposure in the population, posing a potential adverse health risk. Oxidative stress is considered to be the primary effect of TiO2 NPs through biological interaction. In the present study, we conducted an animal experiment to investigate the element distribution and oxidative stress in Sprague-Dawley rats after oral exposure to TiO2 NPs at daily doses of 0, 2, 10, and 50 mg kg-1 for 90 days. Through the detection of Ti element content in various tissues, limited absorption and distribution of TiO2 NPs in rats was found. However, orally ingested TiO2 NPs still induced tissue-specific oxidative stress and imbalance of elements. Liver tissue was the most sensitive tissue to TiO2 NP-induced oxidative stress, showing decreased reduced glutathione (GSH), increased oxidized glutathione (GSSG) and decreased ratio of GSH/GSSG as well as accumulation of lipid peroxidation (malondialdehyde, MDA) in liver tissues of rats after TiO2 NP exposure (10 and 50 mg kg-1). Meanwhile, oral exposure to TiO2 NPs caused a significant reduction in metal elements such as Mg, Ca and Co in various tissues. Through bioinformatics analysis, the tissue specificity and correlation between the imbalance of elements and oxidative stress were statistically confirmed, but it was difficult to understand the causal relationship. Disorder of element distribution and oxidative stress may lead to a series of subsequent adverse health effects and the tissue specificity would partly explain the target effects of TiO2 NPs.

Titanium Dioxide Nanoparticles in Food and Personal Care Products-What Do We Know about Their Safety?

Titanium dioxide (TiO2) is a material of diverse applications commonly used as a food additive or cosmetic ingredient. Its prevalence in products of everyday use, especially in nanosize, raises concerns about safety. Current findings on the safety of titanium dioxide nanoparticles (TiO2 NPs) used as a food additive or a sunscreen compound are reviewed and systematized in this publication. Although some studies state that TiO2 NPs are not harmful to humans through ingestion or via dermal exposure, there is a considerable number of data that demonstrated their toxic effects in animal models. The final agreement on the safety of this nanomaterial has not yet been reached among researchers. There is also a lack of official, standardized guidelines for thorough characterization of TiO2 NPs in food and cosmetic products, provided by international authorities. Recent advances in the application of 'green-synthesized' TiO2 NPs, as well as comparative studies of the properties of 'biogenic' and 'traditional' nanoparticles, are presented. To conclude, perspectives and directions for further studies on the toxicity of TiO2 NPs are proposed.