Emilie Brun

Titanium dioxide nanoparticle impact and translocation through ex vivo, in vivo and in vitro gut epithelia

BackgroundTiO2 particles are commonly used as dietary supplements and may contain up to 36% of nano-sized particles (TiO2-NPs). Still impact and translocation of NPs through the gut epithelium is poorly documented.ResultsWe show that, in vivo and ex vivo, agglomerates of TiO2-NPs cross both the regular ileum epithelium and the follicle-associated epithelium (FAE) and alter the paracellular permeability of the ileum and colon epithelia. In vitro, they accumulate in M-cells and mucus-secreting cells, much less in enterocytes. They do not cause overt cytotoxicity or apoptosis. They translocate through a model of FAE only, but induce tight junctions remodeling in the regular ileum epithelium, which is a sign of integrity alteration and suggests paracellular passage of NPs. Finally we prove that TiO2-NPs do not dissolve when sequestered up to 24 h in gut cells.ConclusionsTaken together these data prove that TiO2-NPs would possibly translocate through both the regular epithelium lining the ileum and through Peyer’s patches, would induce epithelium impairment, and would persist in gut cells where they would possibly induce chronic damage.

Parameters governing gold nanoparticle X-ray radiosensitization of DNA in solution.

Radiosensitization by gold nanoparticles (GNP) is a promising approach for improving radiotherapy. We report herein the results of an investigation of three key-parameters governing such radiosensitization in DNA, namely, DNA:GNP molar ratio, GNP diameter and incident X-ray energy. We performed irradiations with a clinical orthovoltage source and tested concentration ratios up to 1:1, five sizes of GNP from 8 to 92 nm and six effective X-ray energies from 14.8 to 70 keV. The most efficient parameters are found to be large-sized GNP, high molar concentration and 50-keV photons, which could potentially result in a dose enhancement factor of 6. The relevance of such parameters as regards the development of future therapeutic applications is discussed. To the best of our knowledge, this study constitutes the first report of systematic data on radiosensitization by GNP.

In vitro evidence of dysregulation of blood–brain barrier function after acute and repeated/long-term exposure to TiO2 nanoparticles

The effects of titanium dioxide nanoparticles (TiO(2) NPs) on blood-brain barrier (BBB) function are unknown. Here, we report such evidence of adverse effects after in vitro exposure of a rat primary cell-based BBB model to NPs. BBB integrity was studied by measuring the flux of sucrose through the monolayer. P-glycoprotein (P-gp) activity was assessed by measuring the passage of vinblastine. Transcription profiles of P-gp and other ABC transporters as well as of cytokines were investigated by real-time PCR. Electron microscopy and particle-induced X-ray emission measurements were performed. We compared several exposure modalities, from early to chronic, mimicking a brain-to-blood transport or a systemic contamination. In the first case, BBB integrity was preserved, but P-gp activity of endothelial cells (BECs) was reduced. In the second case, BBB integrity and P-gp function were impaired from 5 μg/mL for 24 h and expression of tight junction proteins and efflux transporters was modulated. An inflammatory response had repercussions on ABC transporter expression of glial cells. We demonstrate that NPs accumulated in BECs and crossed the cell monolayer. These findings suggest that there is an immunoregulatory loop between inflammatory components, BECs and glial cells in the dysfunction of the BBB during exposure to TiO(2) NPs.

Damage induced to DNA by low-energy (0-30 eV) electrons under vacuum and atmospheric conditions.

In this study, we show that it is possible to obtain data on DNA damage induced by low-energy (0-30 eV) electrons under atmospheric conditions. Five monolayer films of plasmid DNA (3197 base pairs) deposited on glass and gold substrates are irradiated with 1.5 keV X-rays in ultrahigh vacuum and under atmospheric conditions. The total damage is analyzed by agarose gel electrophoresis. The damage produced on the glass substrate is attributed to energy absorption from X-rays, whereas that produced on the gold substrate arises from energy absorption from both the X-ray beam and secondary electrons emitted from the gold surface. By analysis of the energy of these secondary electrons, 96% are found to have energies below 30 eV with a distribution peaking at 1.4 eV. The differences in damage yields recorded with the gold and glass substrates is therefore essentially attributed to the interaction of low-energy electrons with DNA under vacuum and hydrated conditions. From these results, the G values for low-energy electrons are determined to be four and six strand breaks per 100 eV, respectively.

Could nanoparticle corona characterization help for biological consequence prediction

As soon as they enter a biological medium (cell culture medium for in vitro, blood or plasma for in vivo studies), nanoparticles, in most cases, see their surface covered by biomolecules, especially proteins. What the cells see is thus not the ideal nanoparticle concocted by chemists, meaning the biomolecular corona could have great biological and physiological repercussions, sometimes masking the expected effects of purposely grafted molecules. In this review, we will mainly focus on gold nanoparticles. In the first part, we will discuss the fate of these particles once in a biological medium, especially in terms of size, and the protein composition of the corona. We will highlight the parameters influencing the quantity and the identity of the adsorbed proteins. In a second part, we will resume the main findings about the influence of a biomolecular corona on cellular uptake, toxicity, biodistribution and targeting ability. To be noticed is the need for standardized experiments and very precise reports of the protocols and methods used in the experimental sections to extract informative data. Given the biological consequences of this corona, we suggest that it should be taken into account in theoretical studies dealing with nanomaterials to better represent the biological environment.

Impact of gold nanoparticles combined to X-Ray irradiation on bacteria

Recent increase of multi drug-resistant bacteria represents a crucial issue of public health. As novative approaches are required to face that problem, those emerging from nanotechnology are of great interest. In that context we propose the possibility to use gold nanoparticles combined with ionising radiation to destroy pathogenic bacteria. For that, we investigated the potential X-Rays enhanced reduction of bacterial cell viability, following nanoparticle exposure, on a bacterial model,Escherichia coli. Our first concern was to confirm the absence of toxicity of the colloidal solution used. Then, we developed an X-Ray irradiation system and showed that gold nanoparticles increased the efficiency of ionising radiation to induce bacteria cell death.

Gold nanoparticles functionalization notably decreases radiosensitization through hydroxyl radical production under ionizing radiation

The purpose of this work was to study the influence of gold nanoparticles (GNP) coating on hydroxyl radical (HO) production under ionizing radiation. Though radiosensitizing mechanisms are still unknown, radical oxygen species are likely to be involved, especially HO. We synthesized six different types of GNP, choosing relevant ligands such as polyethylene glycol or human serum albumin. A great attention was paid to characterize these GNP in terms of size, charge and number of atoms in the coating. Our results show that functionalization dramatically decreases HO production, which is correlated to reduced plasmidic DNA damages. These findings are of high importance as GNP translation from fundamental research to applied medicine requires their functionalization to increase blood circulation time and specific cancerous cells addressing. We suggest that to keep GNP efficient for radiotherapy, a wispy coating is required.

Biopersistence and translocation to extrapulmonary organs of titanium dioxide nanoparticles after subacute inhalation exposure to aerosol in adult and elderly rats.

The increasing industrial use of nanoparticles (NPs) has raised concerns about their impact on human health. Since aging and exposure to environmental factors are linked to the risk for developing pathologies, we address the question of TiO2 NPs toxicokinetics in the context of a realistic occupational exposure. We report the biodistribution of titanium in healthy young adults (12-13-week-old) and in elderly rats (19-month-old) exposed to 10mg/m3 of a TiO2 nanostructured aerosol 6h/day, 5days/week for 4 weeks. We measured Ti content in major organs using inductively coupled plasma mass spectrometry immediately and up to 180days after the end of exposure. Large amounts of titanium were initially found in lung which were slowly cleared during the post-exposure period. From day 28, a small increase of Ti was found in the spleen and liver of exposed young adult rats. Such an increase was however never found in their blood, kidneys or brain. In the elderly group, translocation to extra-pulmonary organs was significant at day 90. Ti recovered from the spleen and liver of exposed elderly rats was higher than in exposed young adults. These data suggest that TiO2 NPs may translocate from the lung to extra-pulmonary organs where they could possibly promote systemic health effects.

Structural properties of rutile TiO2 nanoparticles accumulated in a model of gastrointestinal epithelium elucidated by micro-beam x-ray absorption fine structure spectroscopy

Micro-beam x-ray absorption fine structure spectroscopy was used to investigate rutile TiO2 nanoparticles internalized into gastrointestinal cells during their crossing of a gut model barrier. Nanoparticles diluted in culture medium tend to accumulate in cells after 48 h exposure; however, no spectral differences arise between particles in cellular and in acellular environments, as corroborated by quantitative analysis. This finding establishes that no modification of the lattice properties of the nanoparticles occurs upon interaction with the barrier. These measurements demonstrate the possibility of interrogating nanoparticles in situ within cells, suggesting a way to investigate their fate when incorporated in biological hosts.

Investigation of TiO2 nanoparticles translocation through a Caco-2 monolayer

Nanoparticles (NPs) are introduced in a growing number of commercial products, including food and beverage but their effects on gastrointestinal tract are poorly investigated. Here we focused on the translocation of TiO2 NPs through Caco-2 monolayers exposed to anatase and rutile NPs up to 24 h. Internalization was followed by transmission electronic microscopy and μ-XRF elemental mapping, coupled to XAS analysis of Ti atoms environment. This innovative technique is among the best techniques to get insights on NP fate after internalization. The originality of this project relies on the panel of microscopy techniques implemented to investigate digestive barrier translocation, bringing together biologists, chemists and physicists in a pluridisciplinary research program.