Dosimetric Quantification of Coating-Related Uptake of Silver Nanoparticles

Complex intestinal and hepatic in vitro barrier models reveal information on uptake and impact of micro-, submicro- and nanoplastics

Plastic particles are found almost ubiquitously in the environment and can get ingested orally by humans. We have used food-relevant microplastics (2 µm polylactic acid), submicroplastics (250 nm polylactic acid and 366 nm melamine formaldehyde resin) and nanoplastics (25 nm polymethylmethacrylate) to study material- and size-dependent uptake and transport across the human intestinal barrier and liver. Therefore, different Transwell™-based in vitro (co-)culture models were used: Differentiated Caco-2 cells mimicking the intestinal enterocyte monolayer, an M-cell model complementing the Caco-2 monoculture with antigen uptake-specialized cells, a mucus model complementing the barrier with an intestinal mucus layer, and an intestinal-liver co-culture combining differentiated Caco-2 cells with differentiated HepaRG cells. Using these complex barrier models, uptake and transport of particles were analyzed based on the fluorescence of the particles using confocal microscopy and a fluorescence-based quantification method. Additionally, the results were verified by Time-of-Flight - Secondary Ion Mass Spectrometry (ToF-SIMS) analysis. Furthermore, an effect screening at the mRNA level was done to investigate oxidative stress response, inflammation and changes to xenobiotic metabolism in intestinal and hepatic cells after exposure to plastic particles. Oxidative stress and inflammation were additionally analyzed using a flow-cytometric assay for reactive oxygen species and cytokine measurements. The results reveal a noteworthy uptake into and transport of microplastic and submicroplastic particles across the intestinal epithelium. Particularly, we show a pronounced uptake of particles into liver cells after crossing of the intestinal epithelium, using the intestinal-liver co-culture. The particles evoke some alterations in xenobiotic metabolism, but did not cause increased oxidative stress or inflammatory response on protein level. Taken together, these complex barrier models can be applied on micro-, submicro- and nanoplastics and reveal information in particle uptake, transport and cellular impact.

Method for assessing coating uniformity of angioplasty balloons coated with poly(lactic-co-glycolic acid) nanoparticles loaded with quercetin

SIGNIFICANCE

Drug-coated angioplasty balloons (DCBs) are used to treat peripheral artery disease, and proper dosage depends on coating characteristics like uniformity and number of layers.

AIM

Quantify coating uniformity and correlate fluorescence intensity to drug loading for DCBs coated with 5, 10, 15, or 20 layers of poly(lactic-co-glycolic acid) nanoparticles (NPs) entrapped with quercetin.

APPROACH

Images of DCBs were acquired using fluorescence microscopy. Coating uniformity was quantified from histograms and horizontal line profiles, and cracks on the balloons were measured and counted. Fluorescence intensity was correlated with the drug loading of quercetin found from gravimetric analysis coupled with high-performance liquid chromatography (HPLC).

RESULTS

Higher numbers of coating layers on DCBs may be associated with less uniform coatings. Cracks in the coating were present on all balloons, and the length of cracks was not significantly different between balloons coated with different numbers of layers or balloons coated with the same number of layers. A strong positive correlation was identified between fluorescence intensity and drug loading.

CONCLUSION

There may be a relationship between the number of NP layers and the uniformity of the coating, but further investigation is needed to confirm this. Fluorescence intensity appears to be a strong predictor of drug loading on DCBs coated with quercetin-entrapped NPs, demonstrating that fluorescent imaging may be a viable alternative to drug release studies.

Microplastics and nanoplastics: Size, surface and dispersant - What causes the effect?

There is increasing evidence that humans are exposed to microplastic particles through contaminated food. Although suitable analytical methods are still lacking, it is likely that these contaminations also contain a nanoplastics fraction. It is known from nanotoxicology that particles may acquire altered toxicological properties with decreasing particle sizes. Particles can also have different surface modalities and functionalizations. Moreover, nano- and microplastics as materials with probably a relatively low toxicity are often applied at high concentrations in in vitro tests, and therefore the solvating agent, namely the dispersant in which the particles are supplied may have a major impact on the outcome. This might be misinterpreted as particle effect. Therefore, it is crucial to determine what causes the effect - size, surface or dispersant? In this study this question was investigated by applying established in vitro models for the intestinal barrier (differentiated Caco-2 monoculture and mucus- and M-cell co-culture) and hepatocytes (differentiated HepaRG cells), mimicking the oral route of particle uptake. A complex set of nine different polystyrene micro- and nanoparticles was used to elucidate the effect of particle size, surface modification and dispersant. Uptake and transport as well as biochemical endpoints were measured, complemented by particle characterization. The results show that indeed some dispersants can cause a more pronounced cytotoxic effect than the particles themselves. Surface modification and particle size show a clear influence on the uptake and cytotoxicity of nano- and microplastic particles.

Understanding nano-engineered particle-cell interactions: biological insights from mathematical models

Understanding the interactions between nano-engineered particles and cells is necessary for the rational design of particles for therapeutic, diagnostic and imaging purposes. In particular, the informed design of particles relies on the quantification of the relationship between the physicochemical properties of the particles and the rate at which cells interact with, and subsequently internalise, particles. Quantitative models, both mathematical and computational, provide a powerful tool for elucidating this relationship, as well as for understanding the mechanisms governing the intertwined processes of interaction and internalisation. Here we review the different types of mathematical and computational models that have been used to examine particle-cell interactions and particle internalisation. We detail the mathematical methodology for each type of model, the benefits and limitations associated with the different types of models, and highlight the advances in understanding gleaned from the application of these models to experimental observations of particle internalisation. We discuss the recent proposal and ongoing community adoption of standardised experimental reporting, and how this adoption is an important step toward unlocking the full potential of modelling approaches. Finally, we consider future directions in quantitative models of particle-cell interactions and highlight the need for hybrid experimental and theoretical investigations to address hitherto unanswered questions.

Cytotoxic effects in transformed and non-transformed human breast cell lines after exposure to silver nanoparticles in combination with selected aluminium compounds, parabens or phthalates

This study was undertaken to assess cytotoxic effects of selected aluminium compounds, parabens and phthalates in combination with silver nanoparticles (AgNP, 15 and 45 nm by STEM, Ag15 and Ag45, respectively) on cell lines of the human breast epithelium, normal (MCF-10A) and transformed (MDA-MB-231 and MCF-7). Combination indices were the most spectacular at effective concentrations (ED) inducing 25 % decrease in viability for the combinations of Ag15 with AlCl₃ for MDA-MB-231 cells or aluminium zirconium tetrachlorohydrex Gly (AlZr) for MCF-10A and MCF-7 cells, where rather strong antagonism was revealed. As the ED values increased, those effects were enhanced (e.g. Ag15+AlCl₃ for MDA-MB-231) or reversed into synergism (e.g. Ag15+AlZr for MCF-7). Another strong effect was observed for aluminium chloride hydroxide, which increasing ED, induced synergistic effect with both Ag15 and Ag45 on MCF-10A cells. Another interesting synergistic effect was observed for DBPh, but only in combination with Ag45 on MCF-10A and MCF-7. The results on cytotoxicity, cell cycle and oxidative stress induction indicate complex response of the cell lines to combined treatment with silver nanoparticles and the chemicals, which were influenced by diverse factors, such as physico-chemical characteristics of AgNP, method of their synthesis, concentrations used, and finally cell type.

Organ burden of inhaled nanoceria in a 2-year low-dose exposure study: dump or depot?

No detailed information on in vivo biokinetics of CeO₂ nanoparticles (NPs) following chronic low-dose inhalation is available. The CeO₂ burden for lung, lung-associated lymph nodes, and major non-pulmonary organs, blood, and feces, was determined in a chronic whole-body inhalation study in female Wistar rats undertaken according to OECD TG453 (6 h per day for 5 days per week for a 104 weeks with the following concentrations: 0, 0.1, 0.3, 1.0, and 3.0 mg/m³, animals were sacrificed after 3, 12, 24 months). Different spectroscopy methods (ICP-MS, ion-beam-microscopy) were used for the quantification of organ burden and for visualization of NP distribution patterns in tissues. After 24 months of exposure, the highest CeO₂ lung burden (4.41 mg per lung) was associated with the highest aerosol concentration and was proportionally lower for the other groups in a dose-dependent manner. Imaging techniques confirmed the presence of CeO₂ agglomerates of different size categories within lung tissue with a non-homogenous distribution. For the highest exposure group, after 24 months in total 1.2% of the dose retained in the lung was found in the organs and tissues analyzed in this study, excluding lymph nodes and skeleton. The CeO₂ burden per tissue decreased from lungs > lymph nodes > hard bone > liver > bone marrow. For two dosage groups, the liver organ burden showed a low accumulation rate. Here, the liver can be regarded as depot, whereas kidneys, the skeleton, and bone marrow seem to be dumps due to steadily increasing NP burden over time.

Gold Nanoparticles as Boron Carriers for Boron Neutron Capture Therapy: Synthesis, Radiolabelling and In vivo Evaluation

Background: Boron Neutron Capture Therapy (BNCT) is a binary approach to cancer therapy that requires accumulation of boron atoms preferentially in tumour cells. This can be achieved by using nanoparticles as boron carriers and taking advantage of the enhanced permeability and retention (EPR) effect. Here, we present the preparation and characterization of size and shape-tuned gold NPs (AuNPs) stabilised with polyethylene glycol (PEG) and functionalized with the boron-rich anion cobalt bis(dicarbollide), commonly known as COSAN. The resulting NPs were radiolabelled with 124I both at the core and the shell, and were evaluated in vivo in a mouse model of human fibrosarcoma (HT1080 cells) using positron emission tomography (PET). Methods: The thiolated COSAN derivatives for subsequent attachment to the gold surface were synthesized by reaction of COSAN with tetrahydropyran (THP) followed by ring opening using potassium thioacetate (KSAc). Iodination on one of the boron atoms of the cluster was also carried out to enable subsequent radiolabelling of the boron cage. AuNPs grafted with mPEG-SH (5 Kda) and thiolated COSAN were prepared by ligand displacement. Radiolabelling was carried out both at the shell (isotopic exchange) and at the core (anionic absorption) of the NPs using 124I to enable PET imaging. Results: Stable gold nanoparticles simultaneously functionalised with PEG and COSAN (PEG-AuNPs@[4]-) with hydrodynamic diameter of 37.8 ± 0.5 nm, core diameter of 19.2 ± 1.4 nm and ξ-potential of -18.0 ± 0.7 mV were obtained. The presence of the COSAN on the surface of the NPs was confirmed by Raman Spectroscopy and UV-Vis spectrophotometry. PEG-AuNPs@[4]- could be efficiently labelled with 124I both at the core and the shell. Biodistribution studies in a xenograft mouse model of human fibrosarcoma showed major accumulation in liver, lungs and spleen, and poor accumulation in the tumour. The dual labelling approach confirmed the in vivo stability of the PEG-AuNPs@[4]-. Conclusions: PEG stabilized, COSAN-functionalised AuNPs could be synthesized, radiolabelled and evaluated in vivo using PET. The low tumour accumulation in the animal model assayed points to the need of tuning the size and geometry of the gold core for future studies.

Polymer-Coated Gold Nanospheres Do Not Impair the Innate Immune Function of Human B Lymphocytes in Vitro

Gold nanoparticles (GNPs) are intended for use within a variety of biomedical applications due to their physicochemical properties. Although, in general, biocompatibility of GNPs with immune cells such as macrophages and dendritic cells is well established, the impact of GNPs on B lymphocyte immune function remains to be determined. Since B lymphocytes play an important role in health and disease, the suitability of GNPs as a B cell-targeting tool is of high relevance. Thus, we provide information on the interactions of GNPs with B lymphocytes. Herein, we exposed freshly isolated human B lymphocytes to a set of well-characterized and biomedically relevant GNPs with distinct surface (polyethylene glycol (PEG), PEG/poly(vinyl alcohol) (PEG/PVA)) and shape (spheres, rods) characteristics. Polymer-coated GNPs poorly interacted with B lymphocytes, in contrast to uncoated GNPs. Importantly, none of the GNPs significantly affected cell viability, even at the highest concentration of 20 μg/mL over a 24 h suspension exposure period. Furthermore, none of the nanosphere formulations affected the expression of activation markers (CD69, CD86, MHC II) of the naive B lymphocytes, nor did they cause an increase in the secretion of pro-inflammatory cytokines ( i.e. , IL-6, IL-1β). However, the absence of polymer coating on the sphere GNPs and the rod shape caused a decrease in IL-6 cytokine production by activated B lymphocytes, suggesting a functional impairment. With these findings, the present study contributes imperative knowledge toward the safe-by-design approaches being conducted to benefit the development of nanomaterials, specifically those as theranostic tools.

In vitro nanoparticle dosimetry for adherent growing cell monolayers covering bottom and lateral walls

Background

Even though a continuously high number of in vitro studies on nanoparticles are being published, the issue of correct dose matter is often not sufficiently taken into account. Due to their size, the diffusion of nanoparticles is slower, as compared to soluble chemicals, and they sediment slowly. Therefore, the administered dose of particles in in vitro experiments is not necessarily the same (effective) dose that comes into contact with the cellular system. This can lead to misinterpretations of experimental toxic effects and disturbs the meaningfulness of in vitro studies. In silico calculations of the effective nanoparticle dose can help circumventing this problem.

Results

This study addresses more complex in vitro models like the human intestinal cell line Caco-2 or the human liver cell line HepaRG, which need to be differentiated over a few weeks to reach their full complexity. During the differentiation time the cells grow up the wall of the cell culture dishes and therefore a three-dimensional-based in silico model of the nanoparticle dose was developed to calculate the administered dose received by different cell populations at the bottom and the walls of the culture dish. Moreover, the model can perform calculations based on the hydrodynamic diameter which is measured by light scattering methods, or based on the diffusion coefficient measured by nanoparticle tracking analysis (NTA). This 3DSDD (3D-sedimentation-diffusion-dosimetry) model was experimentally verified against existing dosimetry models and was applied to differentiated Caco-2 cells incubated with silver nanoparticles.

Conclusions

The 3DSDD accounts for the 3D distribution of cells in in vitro cell culture dishes and is therefore suitable for differentiated cells. To encourage the use of dosimetry calculating software, our model can be downloaded from the supporting information.

Electronic supplementary material

The online version of this article (10.1186/s12989-018-0278-9) contains supplementary material, which is available to authorized users.

Uptake and molecular impact of aluminum-containing nanomaterials on human intestinal caco-2 cells

Aluminum (Al) is one of the most common elements in the earth crust and increasingly used in food, consumer products and packaging. Its hazard potential for humans is still not completely understood. Besides the metallic form, Al also exists as mineral, including the insoluble oxide, and in soluble ionic forms. Representatives of these three species, namely a metallic and an oxidic species of Al-containing nanoparticles and soluble aluminum chloride, were applied to human intestinal cell lines as models for the intestinal barrier. We characterized physicochemical particle parameters, protein corona composition, ion release and cellular uptake. Different in vitro assays were performed to determine potential effects and molecular modes of action related to the individual chemical species. For a deeper insight into signaling processes, microarray transcriptome analyses followed by bioinformatic data analysis were employed. The particulate Al species showed different solubility in biological media. Metallic Al nanoparticles released more ions than Al₂O₃ nanoparticles, while AlCl₃ showed a mixture of dissolved and agglomerated particulate entities in biological media. The protein corona composition differed between both nanoparticle species. Cellular uptake, investigated in transwell experiments, occurred predominantly in particulate form, whereas ionic Al was not taken up by intestinal cell lines. Transcellular transport was not observed. None of the Al species showed cytotoxic effects up to 200 µg Al/mL. The transcriptome analysis indicated mainly effects on oxidative stress pathways, xenobiotic metabolism and metal homeostasis. We have shown for the first time that intestinal cellular uptake of Al occurs preferably in the particle form, while toxicological effects appear to be ion-related.