Lipid and protein corona of food-grade TiO2 nanoparticles in simulated gastrointestinal digestion

Food grade titanium dioxide induced endoplasmic reticulum stress in colon cells: Comparison between normal and colorectal carcinoma cells

BACKGROUND

Food-grade titanium dioxide (E171) has been under scrutiny in the last decade since its possible adverse effects; however, the cellular mechanisms underlying E171 toxicity have not been thoroughly described.

AIM

We aimed to compare the effects of E171 on endoplasmic reticulum (ER) homeostasis in normal and cancer colon cells.

EXPERIMENTAL DESIGN

We exposed normal, carcinoma, and adenocarcinoma cells to 0.1, 1, 10, 50 and 100 μg/cm2 of E171 for 24, 48 and 72 h, and we evaluated ER stress, cell viability, titanium uptake, intracellular calcium concentration, and gene expression related to unfolded protein response (UPR) and chaperone pathways.

RESULTS

Cell viability decreased only after 72 h of exposure to 100 μg/cm2 of E171. Adenocarcinoma cells internalized higher titanium amounts than normal and carcinoma cells, but the effects in ER distribution, intracellular calcium concentration, and gene expression were similar among the three cell lines. The expression of UPR and chaperone pathways were downregulated at the lowest concentrations but upregulated at the highest concentrations in the three cell lines.

CONCLUSION

E171 induces ER stress through alterations in ER distribution, intracellular calcium, and UPR and chaperone protein pathways.

Understanding the role of biomolecular coronas in human exposure to nanomaterials

Nanomaterials (NMs) are increasingly used in medical treatments, electronics, and food additives. However, nanosafety-the possible adverse effects of NMs on human health-is an area of active research. This review provides an overview of the influence of biomolecular coronas on NM transformation following various exposure routes. We discuss potential exposure pathways, including inhalation and ingestion, describing the physiology of exposure routes and emphasising the relevance of coronas in these environments. Additionally, we review other routes to NM exposure, such as synovial fluid, blood (translocation and injection), dermal and ocular exposure, as well as the dose and medium impact on NM interactions. We emphasize the need for an in-depth characterisation of coronas in different biological media, highlighting the need and opportunity to study lung and gastric fluids to understand NM behaviour and potential toxicity. Future research aims to predict better in vivo outcomes and address the complexities of NM interactions with biological systems.

Sources of biases in the in vitro testing of nanomaterials: the role of the biomolecular corona

The biological fate of nanomaterials (NMs) is driven by specific interactions through which biomolecules, naturally adhering onto their surface, engage with cell membrane receptors and intracellular organelles. The molecular composition of this layer, called the biomolecular corona (BMC), depends on both the physical-chemical features of the NMs and the biological media in which the NMs are dispersed and cells grow. In this work, we demonstrate that the widespread use of 10% fetal bovine serum in an in vitro assay cannot recapitulate the complexity of in vivo systemic administration, with NMs being transported by the blood. For this purpose, we undertook a comparative journey involving proteomics, lipidomics, high throughput multiparametric in vitro screening, and single molecular feature analysis to investigate the molecular details behind this in vivo/in vitro bias. Our work indirectly highlights the need to introduce novel, more physiological-like media closer in composition to human plasma to produce realistic in vitro screening data for NMs. We also aim to set the basis to reduce this in vitro-in vivo mismatch, which currently limits the formulation of NMs for clinical settings.

The in vitro gastrointestinal digestion-associated protein corona of polystyrene nano- and microplastics increases their uptake by human THP-1-derived macrophages

BACKGROUND

Micro- and nanoplastics (MNPs) represent one of the most widespread environmental pollutants of the twenty-first century to which all humans are orally exposed. Upon ingestion, MNPs pass harsh biochemical conditions within the gastrointestinal tract, causing a unique protein corona on the MNP surface. Little is known about the digestion-associated protein corona and its impact on the cellular uptake of MNPs. Here, we systematically studied the influence of gastrointestinal digestion on the cellular uptake of neutral and charged polystyrene MNPs using THP-1-derived macrophages.

RESULTS

The protein corona composition was quantified using LC‒MS-MS-based proteomics, and the cellular uptake of MNPs was determined using flow cytometry and confocal microscopy. Gastrointestinal digestion resulted in a distinct protein corona on MNPs that was retained in serum-containing cell culture medium. Digestion increased the uptake of uncharged MNPs below 500 nm by 4.0-6.1-fold but did not affect the uptake of larger sized or charged MNPs. Forty proteins showed a good correlation between protein abundance and MNP uptake, including coagulation factors, apolipoproteins and vitronectin.

CONCLUSION

This study provides quantitative data on the presence of gastrointestinal proteins on MNPs and relates this to cellular uptake, underpinning the need to include the protein corona in hazard assessment of MNPs.

Impact of food matrices on the characteristics and cellular toxicities of ingested nanoplastics in a simulated digestive tract

Microplastic and nanoplastic (MNP) pollution has become a major global food safety concern. MNPs can interact with food matrices, and their passage through the gastrointestinal tract can modify their properties. To explore whether and how food matrices influence MNP toxicity, we investigated the interactions between polystyrene nanoplastics (PS-NPs) and food matrices, using an in vitro gastrointestinal digestion model. Then, we tested cell viability, particle uptake and cellular toxicities induced by PS-NPs with food matrices in Caco-2 cells. The results showed that PS-NPs were aggregated, both with and without food matrices, after in vitro gastrointestinal digestion. Glyceryl trioleate exerted greater ability to stabilize digestas and to disperse PS-NPs than starch and bovine serum albumin. The protein corona's protein composition on PS-NPs varied when it interacted with different food matrices. Moreover, when combined with food matrices, the PS-NPs' uptake was enhanced, thus aggravating cellular inflammation, stress, and apoptosis levels. Finally, through co-exposure to a mixture of food matrices, we found a combined negative effect of PS-NPs and cadmium on cellular inflammation, stress, and apoptosis levels. This is the first study to compare the impact of various food matrices on the characteristics and cellular toxicities of ingested NPs in a simulated digestive tract.

Determinants and mechanisms of inorganic nanoparticle translocation across mammalian biological barriers

Biological barriers protect delicate internal tissues from exposures to and interactions with hazardous materials. Primary anatomical barriers prevent external agents from reaching systemic circulation and include the pulmonary, gastrointestinal, and dermal barriers. Secondary barriers include the blood-brain, blood-testis, and placental barriers. The tissues protected by secondary barriers are particularly sensitive to agents in systemic circulation. Neurons of the brain cannot regenerate and therefore must have limited interaction with cytotoxic agents. In the testis, the delicate process of spermatogenesis requires a specific milieu distinct from the blood. The placenta protects the developing fetus from compounds in the maternal circulation that would impair limb or organ development. Many biological barriers are semi-permeable, allowing only materials or chemicals, with a specific set of properties, that easily pass through or between cells. Nanoparticles (particles less than 100 nm) have recently drawn specific concern due to the possibility of biological barrier translocation and contact with distal tissues. Current evidence suggests that nanoparticles translocate across both primary and secondary barriers. It is known that the physicochemical properties of nanoparticles can affect biological interactions, and it has been shown that nanoparticles can breach primary and some secondary barriers. However, the mechanism by which nanoparticles cross biological barriers has yet to be determined. Therefore, the purpose of this review is to summarize how different nanoparticle physicochemical properties interact with biological barriers and barrier products to govern translocation.

In Vitro Safety Assessment of In-House Synthesized Titanium Dioxide Nanoparticles: Impact of Washing and Temperature Conditions

Titanium dioxide nanoparticles (TiO2 NPs) have been widely used in food, cosmetics, and biomedical research. However, human safety following exposure to TiO2 NPs remains to be fully understood. The aim of this study was to evaluate the in vitro safety and toxicity of TiO2 NPs synthesized via the Stöber method under different washing and temperature conditions. TiO2 NPs were characterized by their size, shape, surface charge, surface area, crystalline pattern, and band gap. Biological studies were conducted on phagocytic (RAW 264.7) and non-phagocytic (HEK-239) cells. Results showed that washing amorphous as-prepared TiO2 NPs (T1) with ethanol while applying heat at 550 °C (T2) resulted in a reduction in the surface area and charge compared to washing with water (T3) or a higher temperature (800 °C) (T4) and influenced the formation of crystalline structures with the anatase phase in T2 and T3 and rutile/anatase mixture in T4. Biological and toxicological responses varied among TiO2 NPs. T1 was associated with significant cellular internalization and toxicity in both cell types compared to other TiO2 NPs. Furthermore, the formation of the crystalline structure induced toxicity independent of other physicochemical properties. Compared with anatase, the rutile phase (T4) reduced cellular internalization and toxicity. However, comparable levels of reactive oxygen species were generated following exposure to the different types of TiO2, indicating that toxicity is partially driven via non-oxidative pathways. TiO2 NPs were able to trigger an inflammatory response, with varying trends among the two tested cell types. Together, the findings emphasize the importance of standardizing engineered nanomaterial synthesis conditions and evaluating the associated biological and toxicological consequences arising from changes in synthesis conditions.

Behaviour and fate of Ag-NPs, TiO2-NPs and ZnO-NPs in the human gastrointestinal tract: Biopersistence rate evaluation

This study aims to provide information on the behaviour and biopersistence rate (BP) of metallic nanoparticles (Ag-NPs, TiO₂-NPs, ZnO-NPs) naturally occurring in canned seafood and subjected to static in vitro digestion. Single particle ICP-MS analysis was performed to determine NPs distribution and concentrations in oral, gastric, and intestinal digests. Depending on the conditions of the digestive phase and the sample matrix, the phenomena of agglomeration and dispersion were highlighted and confirmed by Dynamic Light Scattering (DLS) technique. In standard suspensions, Ag-NPs had lower biopersistence (BP) than ZnO and TiO₂-NPs (BP 34%, 89% and >100%, respectively). Among Ag-NPs and TiO₂-NPs naturally present in the food matrix, those in canned tuna were more degradable than those in canned clam (BP Ag-NPs 36% vs. > 100%; BP TiO₂-NPs 96% vs. > 100%), while BP ZnO-NPs showed high biopersistence in both seafood matrix (>100%). The biopersistence rates were higher than the recommended limit set by European Food Safety Authority (EFSA) (12%), referred to nanotechnologies to be applied in the food and feed chain, thus the investigated naturally occurring NPs cannot be considered readily degradable.

Reduced bioaccessibility of TiO2 (E 171) during puree soup digestion in a gastrointestinal tract simulated in vitro

E171 (TiO₂- Ttitanium dioxide), a food colourant containing nano fractions, is one of the additives used e.g. in the food industry, whose consumption may have a negative impact on human health. In order to determine the ability of food products and intestinal lactic acid bacteria to interact with TiO₂, we conducted in vitro "digestions" of a food matrix (meat/vegetable puree soup) using an advanced in vitro model of the "gastrointestinal tract". The "bioaccessibility" of TiO₂ was simulated using microfiltration (0.2 µm) of the post-digestive fluid. We observed changes in the content of TiO₂ in the microfiltrates obtained at various stages of the in vitro digestions, dependent on the stage of the process. This result suggests that TiO₂ interacts with food components and bacterial cells. Furthermore, scanning electron microscopy revealed visible morphological changes to bacterial cells in the presence of TiO₂.

Nanoparticle Impact on the Bacterial Adaptation: Focus on Nano-Titania

Titanium dioxide nanoparticles (nano-titania/TiO₂ NPs) are used in different fields and applications. However, the release of TiO₂ NPs into the environment has raised concerns about their biosafety and biosecurity. In light of the evidence that TiO₂ NPs could be used to counteract antibiotic resistance, they have been investigated for their antibacterial activity. Studies reported so far indicate a good performance of TiO₂ NPs against bacteria, alone or in combination with antibiotics. However, bacteria are able to invoke multiple response mechanisms in an attempt to adapt to TiO₂ NPs. Bacterial adaption arises from global changes in metabolic pathways via the modulation of regulatory networks and can be related to single-cell or multicellular communities. This review describes how the impact of TiO₂ NPs on bacteria leads to several changes in microorganisms, mainly during long-term exposure, that can evolve towards adaptation and/or increased virulence. Strategies employed by bacteria to cope with TiO₂ NPs suggest that their use as an antibacterial agent has still to be extensively investigated from the point of view of the risk of adaptation, to prevent the development of resistance. At the same time, possible effects on increased virulence following bacterial target modifications by TiO₂ NPs on cells or tissues have to be considered.

Prospects for the next generation of artificial enzymes for ensuring the quality of chilled meat: Opportunities and challenges

As living standards rise, the demand for high-quality chilled meat among consumers also grows. Researchers and enterprises have been interested in ensuring the quality of chilled meat in all links of the downstream industry. Nanozyme has shown the potential to address the aforementioned requirements. Reasons and approaches for the application of nanozymes in the freshness assessment or shelf life extension of chilled meat were discussed. The challenges for applying these nanozymes to ensure the quality of chilled meat were also summarized. Finally, this review examined the safety, regulatory status, and consumer attitudes toward nanozymes. This review revealed that the freshness assessment of chilled meat is closely related to mimicking the enzyme activities of nanozymes, whereas the shelf life changes of chilled meat are mostly dependent on the photothermal activities and pseudophotodynamic activities of nanozymes. In contrast, studies regarding the shelf life of chilled meat are more challenging to develop, as excessive heat or reactive oxygen species impair its quality. Notably, meat contains a complex matrix composition that may interact with the nanozyme, reducing its effectiveness. Nanopollution and mass manufacturing are additional obstacles that must be overcome. Therefore, it is vital to choose suitable approaches to ensure meat quality. Furthermore, the safety of nanozymes in meat applications still needs careful consideration owing to their widespread usage.

Incineration-Generated Polyethylene Micro-Nanoplastics Increase Triglyceride Lipolysis and Absorption in an In Vitro Small Intestinal Epithelium Model

Despite mounting evidence of micro-nanoplastics (MNPs) in food and drinking water, little is known of the potential health risks of ingested MNPs, and nothing is known of their potential impact on nutrient digestion and absorption. We assessed the effects of environmentally relevant secondary MNPs generated by incineration of polyethylene (PE-I), on digestion and absorption of fat in a high fat food model using a 3-phase in vitro simulated digestion coupled with a tri-culture small intestinal epithelium model. The presence of 400 μg/mL PE-I increased fat digestion by 33% and increased fat absorption by 147 and 145% 1 and 2 h after exposure. Analysis of the PE-I lipid corona during digestion revealed predominantly triacylglycerols with enrichment of fatty acids in the small intestinal phase. Protein corona analysis showed enrichment of triacylglycerol lipase and depletion of β-casein in the small intestinal phase. These findings suggest digestion of triacylglycerol by lipase on the surface of lipid-coated MNPs as a potential mechanism. Further studies are needed to investigate the mechanisms underlying the greater observed increase in fat absorption, to verify these results in an animal model, and to determine the MNP properties governing their effects on lipid digestion and absorption.

Smoothies Reduce the "Bioaccessibility" of TiO2 (E 171) in the Model of the In Vitro Gastrointestinal Tract

The food colorant E171 (TiO2) containing nano fractions can cause potential health problems. In the presented work, we used a "gastrointestinal tract" model (oral→large intestine) to "digest" a fruit smoothie in the presence of TiO2 nanoparticles and the Lactiplantibacillus plantarum B strain. The TiO2 migration was measured using the microfiltration membrane (0.2 µm; model of "TiO2 bioacessability"). We observed that the addition of the smoothie reduced the Ti content in the microfiltrate (reduced "bioacessability") at the "mouth", "stomach" and "large intestine" stages, probably due to the entrapment of Ti by the smoothie components. A significant decrease in Ti "bioaccessibility" at the "gastric" stage may have resulted from the agglomeration of nanoparticles at a low pH. Additionally, the presence of bacterial cells reduced the "bioaccessibility" at the "large intestine" stage. Microscopic imaging (SEM) revealed clear morphological changes to the bacterial cells in the presence of TiO2 (altered topography, shrunk-deformed cells with collapsed walls due to leakage of the content, indentations). Additionally, TiO2 significantly reduced the growth of the tested bacteria. It can be stated that the interactions (most probably entrapment) of TiO2 in the food matrix can occur during the digestion. This can influence the physicochemical properties, bioavailability and in vivo effect of TiO2. Research aimed at understanding the interactions between TiO2 and food components is in progress.

Comprehensive and systematic characterization of multi-functionalized cisplatin nano-conjugate: from the chemistry and proteomic biocompatibility to the animal model

Background

Nowadays, nanoparticles (NPs) have evolved as multifunctional systems combining different custom anchorages which opens a wide range of applications in biomedical research. Thus, their pharmacological involvements require more comprehensive analysis and novel nanodrugs should be characterized by both chemically and biological point of view. Within the wide variety of biocompatible nanosystems, iron oxide nanoparticles (IONPs) present mostly of the required features which make them suitable for multifunctional NPs with many biopharmaceutical applications.

Results

Cisplatin-IONPs and different functionalization stages have been broadly evaluated. The potential application of these nanodrugs in onco-therapies has been assessed by studying in vitro biocompatibility (interactions with environment) by proteomics characterization the determination of protein corona in different proximal fluids (human plasma, rabbit plasma and fetal bovine serum),. Moreover, protein labeling and LC–MS/MS analysis provided more than 4000 proteins de novo synthetized as consequence of the nanodrugs presence defending cell signaling in different tumor cell types (data available via ProteomeXchanges with identified PXD026615). Further in vivo studies have provided a more integrative view of the biopharmaceutical perspectives of IONPs.

Conclusions

Pharmacological proteomic profile different behavior between species and different affinity of protein coating layers (soft and hard corona). Also, intracellular signaling exposed differences between tumor cell lines studied. First approaches in animal model reveal the potential of theses NPs as drug delivery vehicles and confirm cisplatin compounds as strengthened antitumoral agents.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01546-y.

Changes of physico-chemical properties of nano-biomaterials by digestion fluids affect the physiological properties of epithelial intestinal cells and barrier models

Background

The widespread use of nano-biomaterials (NBMs) has increased the chance of human exposure. Although ingestion is one of the major routes of exposure to NBMs, it is not thoroughly studied to date. NBMs are expected to be dramatically modified following the transit into the oral-gastric-intestinal (OGI) tract. How these transformations affect their interaction with intestinal cells is still poorly understood. NBMs of different chemical nature—lipid-surfactant nanoparticles (LSNPs), carbon nanoparticles (CNPs), surface modified Fe₃O₄ nanoparticles (FNPs) and hydroxyapatite nanoparticles (HNPs)—were treated in a simulated human digestive system (SHDS) and then characterised. The biological effects of SHDS-treated and untreated NBMs were evaluated on primary (HCoEpiC) and immortalised (Caco-2, HCT116) epithelial intestinal cells and on an intestinal barrier model.

Results

The application of the in vitro SDHS modified the biocompatibility of NBMs on gastrointestinal cells. The differences between SHDS-treated and untreated NBMs could be attributed to the irreversible modification of the NBMs in the SHDS. Aggregation was detected for all NBMs regardless of their chemical nature, while pH- or enzyme-mediated partial degradation was detected for hydroxyapatite or polymer-coated iron oxide nanoparticles and lipid nanoparticles, respectively. The formation of a bio-corona, which contains proteases, was also demonstrated on all the analysed NBMs. In viability assays, undifferentiated primary cells were more sensitive than immortalised cells to digested NBMs, but neither pristine nor treated NBMs affected the intestinal barrier viability and permeability. SHDS-treated NBMs up-regulated the tight junction genes (claudin 3 and 5, occludin, zonula occludens 1) in intestinal barrier, with different patterns between each NBM, and increase the expression of both pro- and anti-inflammatory cytokines (IL-1β, TNF-α, IL-22, IL-10). Notably, none of these NBMs showed any significant genotoxic effect.

Conclusions

Overall, the results add a piece of evidence on the importance of applying validated in vitro SHDS models for the assessment of NBM intestinal toxicity/biocompatibility. We propose the association of chemical and microscopic characterization, SHDS and in vitro tests on both immortalised and primary cells as a robust screening pipeline useful to monitor the changes in the physico-chemical properties of ingested NBMs and their effects on intestinal cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-022-00491-w.

SiO2 Fibers of Two Lengths and Their Effect on Cellular Responses of Macrophage-like Cells

The immunoreactivity or/and stress response can be induced by nanomaterials' different properties, such as size, shape, etc. These effects are, however, not yet fully understood. This study aimed to clarify the effects of SiO2 nanofibers (SiO2NFs) on the cellular responses of THP-1-derived macrophage-like cells. The effects of SiO2NFs with different lengths on reactive oxygen species (ROS) and pro-inflammatory cytokines TNF-α and IL-1β in THP-1 cells were evaluated. From the two tested lengths, it was only the L-SiO2NFs with a length ≈ 44 ± 22 µm that could induce ROS. Compared to this, only S-SiO2NFs with a length ≈ 14 ± 17 µm could enhance TNF-α and IL-1β expression. Our results suggested that L-SiO2NFs disassembled by THP-1 cells produced ROS and that the inflammatory reaction was induced by the uptake of S-SiO2NFs by THP-1 cells. The F-actin staining results indicated that SiO2NFs induced cell motility and phagocytosis. There was no difference in cytotoxicity between L- and S-SiO2NFs. However, our results suggested that the lengths of SiO2NFs induced different cellular responses.

In vitro to in vivo extrapolation to support the development of the next generation risk assessment (NGRA) strategy for nanomaterials

There is growing interest in developing novel strategies to support assessment of human health risks due to chemicals. Regulatory and decision-making agencies have recommended that non-animal-based alternatives should be applied whenever possible instead of experimentation on living animals. These alternative methods are beneficial because they are ethical, inexpensive, and rapid. Herein, we review recent activities aimed at developing in vitro to in vivo extrapolation (IVIVE) models as a part of the Next Generation Risk Assessment (NGRA) of nanomaterials. In this context, we show the adverse outcome pathway (AOP)-based methodology for the identification of mechanistically relevant events serving as biomarkers for the targeted selection of in vitro assays. Considered events need to be biologically plausible, regulatory relevant, and crucial for the examination of occurrence of adverse outcomes. The promising advantages of using high-throughout-based omics data are highlighted. Furthermore, the application of 3D in vitro models and nano genome atlases to study nanoparticle toxicity is briefly summarized. Additionally, the challenges related to the extrapolation of in vitro doses into in vivo-relevant responses are presented. We also discuss the limitations of models applied thus far to study the fate of chemicals in the human body, which exist due to the lack of available knowledge regarding transformations of nanomaterials occurring in biological systems.

Recent Advances in the Gastrointestinal Fate of Organic and Inorganic Nanoparticles in Foods

Inorganic or organic nanoparticles are often incorporated into foods to enhance their quality, stability, nutrition, or safety. When they pass through the gastrointestinal environment, the properties of these nanoparticles are altered, which impacts their biological effects and potential toxicity. Consequently, there is a need to understand how different kinds of nanoparticles behave within the gastrointestinal tract. In this article, the current understanding of the gastrointestinal fate of nanoparticles in foods is reviewed. Initially, the fundamental physicochemical and structural properties of nanoparticles are discussed, including their compositions, sizes, shapes, and surface chemistries. Then, the impact of food matrix effects and gastrointestinal environments on the fate of ingested nanoparticles is discussed. In particular, the influence of nanoparticle properties on food digestion and nutraceutical bioavailability is highlighted. Finally, future research directions are highlighted that will enable the successful utilization of nanotechnology in foods while also ensuring they are safe.

Protein corona mitigated the cytotoxicity of CdTe QDs to macrophages by targeting mitochondria

Despite the potential of cadmium telluride quantum dots (CdTe QDs) in bioimaging and drug delivery, their toxic effects have been documented. It is known that the immunotoxicity of CdTe QDs targeting macrophages is one of their adverse effects, and the protein corona (PC) will affect the biological effects of QDs. In order to prove whether the PC-CdTe QDs complexes could alleviate the toxicity of CdTe QDs without weakening their luminescence, we investigated the impact of protein corona formed in fetal bovine serum (FBS) on the cytotoxicity of CdTe QDs to mitochondria. RAW264.7 cells were used as the model to compare the effects of CdTe QDs and PC-CdTe QDs complexes on the structure, function, quantity, morphology, and mitochondrial quality control of mitochondria. As result, the protein corona form in FBS alleviated the inhibition of CdTe QDs on mitochondrial activity, the damage to mitochondrial membrane, the increase of ROS, and the reduction of ATP content. Also, CdTe QDs increased the number of mitochondria in macrophages, while the complexes did not. In line with this, the morphology of mitochondrial network in macrophages which were exposed to CdTe QDs and PC-CdTe QDs complexes was different. CdTe QDs transformed the network into fragments, punctuations, and short rods, while PC-CdTe QDs complexes made the mitochondrial network highly branched, which was related to the imbalance of mitochondrial fission and fusion. Mechanically, CdTe QDs facilitated mitochondrial fission and inhibited mitochondrial fusion, while protein corona reversed the phenomenon caused by QDs. Besides mitochondrial dynamics, mitochondrial biogenesis and mitophagy were also affected. CdTe QDs increased the expression of mitochondrial biogenesis signaling molecules including PGC-1α, NRF-1 and TFAM, while PC-CdTe QDs complexes played the opposite role. With regard to mitophagy, they both showed promoting effect. In conclusion, the formation of protein corona alleviated the toxic effects of CdTe QDs on the mitochondria in macrophages and affected mitochondrial quality control. Under the premise of ensuring the fluorescence properties of CdTe QDs, these findings provided useful insight into reducing the toxicity of CdTe QDs from two perspectives: protein corona and mitochondria, and shared valuable information for the safe use of QDs.

Bibliometric landscape of the researches on protein corona of nanoparticles

Unclear biological fate hampers the clinical translation of nanoparticles for biomedical uses. In recent years, it is documented that the formation of protein corona upon nanoparticles is a critical factor leading to the ambiguous biological fate. Efforts have been made to explore the protein corona forming behaviors on nanoparticles, and rearrangement of the relevant studies will help to understand the current trend of such a topic. In this work, the publications about protein corona of nanoparticles in Science Citation Index Expanded database of Web of Science from 2007 to 2020 (1417 in total) were analyzed in detail, and the bibliometrics landscape of them was showcased. The basic bibliometrics characteristics were summarized to provide an overall understanding. Citation analysis was performed to scrutinize the peer interests of these papers. The research hotspots in the field were evaluated, based on which some feasible topics for future studies were proposed. In general, the results demonstrated that protein corona of nanoparticles was a prospective research area, and had attracted global research interests. It was believed that this work could comprehensively highlight the bibliometrics landscape, inspire further exploitation on protein corona of nanoparticles, and ultimately promote the clinical translation of nanoparticles.

Biotransformations and cytotoxicity of eleven graphene and inorganic two-dimensional nanomaterials using simulated digestions coupled with a triculture in vitro model of the human gastrointestinal epithelium

Background

Engineered nanomaterials (ENMs) have already made their way into myriad applications and products across multiple industries. However, the potential health risks of exposure to ENMs remain poorly understood. This is particularly true for the emerging class of ENMs know as 2-dimensional nanomaterials (2DNMs), with a thickness of one or a few layers of atoms arranged in a planar structure.

Methods

The present study assesses the biotransformations and in vitro cytotoxicity in the gastrointestinal tract of 11 2DNMs, namely graphene, graphene oxide (GO), partially reduced graphene oxide (prGO), reduced graphene oxide (rGO), hexagonal boron nitride (h-BN), molybdenum disulphide (MoS2), and tungsten disulphide (WS2). The evaluated pristine materials were either readily dispersed in water or dispersed with the use of a surfactant (Na-cholate or PF108). Materials dispersed in a fasting food model (FFM, water) were subjected to simulated 3-phase (oral, gastric, and small intestinal) digestion to replicate the biotransformations that would occur in the GIT after ingestion. A triculture model of small intestinal epithelium was used to assess the effects of the digested products (digestas) on epithelial layer integrity, cytotoxicity, viability, oxidative stress, and initiation of apoptosis.

Results

Physicochemical characterization of the 2DNMs in FFM dispersions and in small intestinal digestas revealed significant agglomeration by all materials during digestion, most prominently by graphene, which was likely caused by interactions with digestive proteins. Also, MoS2 had dissolved by ~75% by the end of simulated digestion. Other than a low but statistically significant increase in cytotoxicity observed with all inorganic materials and graphene dispersed in PF108, no adverse effects were observed in the exposed tricultures.

Conclusions

Our results suggest that occasional ingestion of small quantities of 2DNMs may not be highly cytotoxic in a physiologically relevant in vitro model of the intestinal epithelium. Still, their inflammatory or genotoxic potential after short- or long-term ingestion remains unclear and needs to be studied in future in vitro and in vivo studies. These would include studies of effects on co-ingested nutrient digestion and absorption, which have been documented for numerous ingested ENMs, as well as effects on the gut microbiome, which can have important health implications.

Interaction between ZnO Nanoparticles and Albumin and Its Effect on Cytotoxicity, Cellular Uptake, Intestinal Transport, Toxicokinetics, and Acute Oral Toxicity

Zinc oxide (ZnO) nanoparticles (NPs) are used as zinc supplements due to the nutritional value of Zn. The toxicity of ZnO NPs in the food industry is required to be elucidated because they have large surface area and high reactivity compared with bulk-sized materials and have potentials to interact with food matrices, which may lead to different biological responses. In this study, interactions between ZnO NPs and food proteins (albumin, casein, and zein) were evaluated by measuring changes in physicochemical property, fluorescence quenching ratios, and structural protein stability compared with ZnO interaction with glucose, the most interacted saccharide in our previous report. The interaction effects on cytotoxicity, cellular uptake, intestinal transport, toxicokinetics, and acute oral toxicity were also investigated. The results demonstrate that interaction between ZnO and albumin reduced hydrodynamic diameters, but increased cytotoxicity, cellular uptake, and intestinal transport in a similar manner to ZnO interaction with glucose, without affecting primary structural protein stability and toxicokinetic behaviors. Hematological, serum biochemical, and histopathological analysis reveal no toxicological findings after orally administered ZnO NPs interacted with albumin or glucose in rats for 14 consecutive days, suggesting their low oral toxicity. In conclusion, the interactions between ZnO NPs and food proteins modulate in vitro biological responses, but do not affect in vivo acute oral toxicity. Further study is required to ascertain the interaction effects on chronic oral toxicity.

Atomistic Molecular Dynamics Simulations of Lipids Near TiO2 Nanosurfaces

Understanding of interactions between inorganic nanomaterials and biomolecules, and particularly lipid bilayers, is crucial in many biotechnological and biomedical applications, as well as for the evaluation of possible toxic effects caused by nanoparticles. Here, we present a molecular dynamics study of adsorption of two important constituents of the cell membranes, 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE), lipids to a number of titanium dioxide planar surfaces, and a spherical nanoparticle under physiological conditions. By constructing the number density profiles of the lipid headgroup atoms, we have identified several possible binding modes and calculated their relative prevalence in the simulated systems. Our estimates of the adsorption strength, based on the total fraction of adsorbed lipids, show that POPE binds to the selected titanium dioxide surfaces stronger than DMPC, due to the ethanolamine group forming hydrogen bonds with the surface. Moreover, while POPE shows a clear preference toward anatase surfaces over rutile, DMPC has a particularly high affinity to rutile(101) and a lower affinity to other surfaces. Finally, we study how lipid concentration, addition of cholesterol, as well as titanium dioxide surface curvature may affect overall adsorption.

Fate, cytotoxicity and cellular metabolomic impact of ingested nanoscale carbon dots using simulated digestion and a triculture small intestinal epithelial model

Carbon dots (CDs) are a promising material currently being explored in many industrial applications in the biomedical and agri-food areas; however, studies supporting the environmental health risk assessment of CDs are needed. This study focuses on various CD forms including iron (FeCD) and copper (CuCD) doped CDs synthesized using hydrothermal method, their fate in gastrointestinal tract, and their cytotoxicity and potential changes to cellular metabolome in a triculture small intestinal epithelial model. Physicochemical characterization revealed that 75% of Fe in FeCD and 95% of Cu in CuCD were dissolved during digestion. No significant toxic effects were observed for pristine CDs and FeCDs. However, CuCD induced significant dose-dependent toxic effects including decreases in TEER and cell viability, increases in cytotoxicity and ROS production, and alterations in important metabolites, including D-glucose, L-cysteine, uridine, citric acid and multiple fatty acids. These results support the current understanding that pristine CDs are relatively non-toxic and the cytotoxicity is dependent on the doping molecules.

In vitro digestion of food grade TiO2 (E171) and TiO2 nanoparticles: physicochemical characterization and impact on the activity of digestive enzymes

Titanium dioxide is a food additive that has raised some concerns for humans due to the presence of nanoparticles. We were interested in knowing the fate of TiO2 particles in the gastro-intestinal tract and their potential effect on digestive enzymes. For this purpose, we analysed the behaviour of two different food grade TiO2 samples (E171) and one nano-sized TiO2 sample (P25) through a standardized static in vitro digestion protocol simulating the oral, gastric and intestinal phases with appropriate juices including enzymes. Both E171 and P25 TiO2 particles remained intact in the digestive fluids but formed large agglomerates, and especially in the intestinal fluid where up to 500 μm sized particles have been identified. The formation of these agglomerates is mediated by the adsorption of mainly α-amylase and divalent cations. Pepsin was also identified to adsorb onto TiO2 particles but only in the case of silica-covered E171. In the salivary conditions, TiO2 exerted an inhibitory action on the enzymatic activity of α-amylase. The activity was reduced by a factor dependent on enzyme concentrations (up to 34% at 1 mg mL-1) but this inhibitory effect was reduced to hardly 10% in the intestinal fluid. In the gastric phase, pepsin was not affected by any form of TiO2. Our results hint that food grade TiO2 has a limited impact on the global digestion of carbohydrates and proteins. However, the reduced activity specifically observed in the oral phase deserves deeper investigation to prevent any adverse health effects related to the slowdown of carbohydrate metabolism.