Silica coating influences the corona and biokinetics of cerium oxide nanoparticles

Surface Chemistry of Biologically Active Reducible Oxide Nanozymes

Reducible metal oxide nanozymes (rNZs) are a subject of intense recent interest due to their catalytic nature, ease of synthesis, and complex surface character. Such materials contain surface sites which facilitate enzyme-mimetic reactions via substrate coordination and redox cycling. Further, these surface reactive sites are shown to be highly sensitive to stresses within the nanomaterial lattice, the physicochemical environment, and to processing conditions occurring as part of their syntheses. When administered in vivo, a complex protein corona binds to the surface, redefining its biological identity and subsequent interactions within the biological system. Catalytic activities of rNZs each deliver a differing impact on protein corona formation, its composition, and in turn, their recognition, and internalization by host cells. Improving the understanding of the precise principles that dominate rNZ surface-biomolecule adsorption raises the question of whether designer rNZs can be engineered to prevent corona formation, or indeed to produce "custom" protein coronas applied either in vitro, and preadministration, or formed immediately upon their exposure to body fluids. Here, fundamental surface chemistry processes and their implications in rNZ material performance are considered. In particular, material structures which inform component adsorption from the application environment, including substrates for enzyme-mimetic reactions are discussed.

Toxicokinetics of rare earth element oxides administered intravenously to rats

Rare earth elements (REEs) are increasingly used in a wide range of applications. However, their toxicokinetic behaviors in animals and humans are not yet fully documented, hindering health risk assessments. We used a rat experimental model to provide novel data on the toxicokinetics of the insoluble oxide forms of praseodymium (Pr), neodymium (Nd), cerium (Ce) and yttrium (Y) administered intravenously. Detailed blood, urinary and fecal time courses were documented through serial sampling over 21 days in male Sprague-Dawley rats exposed to a mixture of these REE oxides administered at two different doses (0.3 or 1 mg kg-1 bw of each REE oxide commercially sold as bulk μm-sized particles). Tissue REE levels at the time of sacrifice were also measured. Significant effects of the dose on REE time courses in blood and on cumulative urinary and fecal excretion rates were observed for all four REE oxides assessed, as lower cumulative excretion rates were noted at the higher REE dose. In the liver, the main accumulation organ, the fraction of the administered REE dose remaining in the tissue at necropsy was similar at both doses. Toxicokinetic data for the REE oxides were compared to similar data for their chloride salts (also administered intravenously in a mixture, at 0.3 and 1 mg kg-1 bw of each REE chloride) obtained from a previous study. Compared to their chloride counterparts, faster elimination of REE oxides from the blood was observed in the first hours post-dosing. Furthermore, higher mean residence time (MRT) values as well as slower cumulative urinary and fecal excretion were determined for the REE oxides. Also, while liver REE retention was similar for both REE forms, the fractions of the administered REEs recovered in the spleen and lungs were noticeably higher for the REE oxides, at both dose levels. This study highlights the importance of both the dose and form of the administered REEs on their toxicokinetic profiles. Results indicate that chronic exposure and increased doses of REEs may favor bioaccumulation in the body, in particular for insoluble oxide forms of REEs, which are eliminated more slowly from the body.

The role of protein corona on nanodrugs for organ-targeting and its prospects of application

Nowadays, nanodrugs become a hotspot in the high-end medical field. They have the ability to deliver drugs to reach their destination more effectively due to their unique properties and flexible functionalization. However, the fate of nanodrugs in vivo is not the same as those presented in vitro, which indeed influenced their therapeutic efficacy in vivo. When entering the biological organism, nanodrugs will first come into contact with biological fluids and then be covered by some biomacromolecules, especially proteins. The proteins adsorbed on the surface of nanodrugs are known as protein corona (PC), which causes the loss of prospective organ-targeting abilities. Fortunately, the reasonable utilization of PC may determine the organ-targeting efficiency of systemically administered nanodrugs based on the diverse expression of receptors on cells in different organs. In addition, the nanodrugs for local administration targeting diverse lesion sites will also form unique PC, which plays an important role in the therapeutic effect of nanodrugs. This article introduced the formation of PC on the surface of nanodrugs and summarized the recent studies about the roles of diversified proteins adsorbed on nanodrugs and relevant protein for organ-targeting receptor through different administration pathways, which may deepen our understanding of the role that PC played on organ-targeting and improve the therapeutic efficacy of nanodrugs to promote their clinical translation.

Lessons from the history of inorganic nanoparticles for inhalable diagnostics and therapeutics

The respiratory tract is one of the most accessible ones to exogenous nanoparticles, yet drug delivery by their means to it is made extraordinarily challenging because of the plexus of aerodynamic, hemodynamic and biomolecular factors at cellular and extracellular levels that synergistically define the safety and efficacy of this process. Here, the use of inorganic nanoparticles (INPs) for inhalable diagnostics and therapies of the lung is viewed through the prism of the history of studies on the interaction of INPs with the lower respiratory tract. The most conceptually and methodologically innovative and illuminative studies are referred to in the chronological order, as they were reported in the literature, and the trends in the progress of understanding this interaction of immense therapeutic and toxicological significance are being deduced from it. The most outstanding actual trends delineated include the diminishment of toxicity via surface functionalization, cell targeting, tagging and tracking via controlled binding and uptake, hybrid INP treatments, magnetic guidance, combined drug and gene delivery, use as adjuvants in inhalable vaccines, and other. Many of the understudied research directions, which have been accomplished by the nanostructured organic polymers in the pulmonary niche, are discussed. The progress in the use of INPs as inhalable diagnostics or therapeutics has been hampered by their well-recognized inflammatory potential and toxicity in the respiratory tract. However, the annual numbers of methodologically innovative studies have been on the rise throughout the past two decades, suggesting that this is a prolific direction of research, its comparatively poor commercial takings notwithstanding. Still, the lack of consensus on the effects of many INP compositions at low but therapeutically effective doses, the plethora of contradictory reports on ostensibly identical chemical compositions and NP properties, and the many cases of antagonism in combinatorial NP treatments imply that the rational design of inhalable medical devices based on INPs must rely on qualitative principles for the most part and embrace a partially stochastic approach as well. At the same time, the fact that the most studied INPs for pulmonary applications have been those with some of the thickest records of pulmonary toxicity, e.g., carbon, silver, gold, silica and iron oxide, is a silent call for the expansion of the search for new inorganic compositions for use in inhalable therapies to new territories.

Ingested Polystyrene Nanospheres Translocate to Placenta and Fetal Tissues in Pregnant Rats: Potential Health Implications

Recent studies in experimental animals found that oral exposure to micro- and nano-plastics (MNPs) during pregnancy had multiple adverse effects on outcomes and progeny, although no study has yet identified the translocation of ingested MNPs to the placenta or fetal tissues, which might account for those effects. We therefore assessed the placental and fetal translocation of ingested nanoscale polystyrene MNPs in pregnant rats. Sprague Dawley rats (N = 5) were gavaged on gestational day 19 with 10 mL/kg of 250 µg/mL 25 nm carboxylated polystyrene spheres (PS25C) and sacrificed after 24 h. Hyperspectral imaging of harvested placental and fetal tissues identified abundant PS25C within the placenta and in all fetal tissues examined, including liver, kidney, heart, lung and brain, where they appeared in 10-25 µm clusters. These findings demonstrate that ingested nanoscale polystyrene MNPs can breach the intestinal barrier and subsequently the maternal-fetal barrier of the placenta to access the fetal circulation and all fetal tissues. Further studies are needed to assess the mechanisms of MNP translocation across the intestinal and placental barriers, the effects of MNP polymer, size and other physicochemical properties on translocation, as well as the potential adverse effects of MNP translocation on the developing fetus.

An In Vitro Dosimetry Tool for the Numerical Transport Modeling of Engineered Nanomaterials Powered by the Enalos RiskGONE Cloud Platform

A freely available "in vitro dosimetry" web application is presented enabling users to predict the concentration of nanomaterials reaching the cell surface, and therefore available for attachment and internalization, from initial dispersion concentrations. The web application is based on the distorted grid (DG) model for the dispersion of engineered nanoparticles (NPs) in culture medium used for in vitro cellular experiments, in accordance with previously published protocols for cellular dosimetry determination. A series of in vitro experiments for six different NPs, with Ag and Au cores, are performed to demonstrate the convenience of the web application for calculation of exposure concentrations of NPs. Our results show that the exposure concentrations at the cell surface can be more than 30 times higher compared to the nominal or dispersed concentrations, depending on the NPs' properties and their behavior in the cell culture medium. Therefore, the importance of calculating the exposure concentration at the bottom of the cell culture wells used for in vitro arrays, i.e., the particle concentration at the cell surface, is clearly presented, and the tool introduced here allows users easy access to such calculations. Widespread application of this web tool will increase the reliability of subsequent toxicity data, allowing improved correlation of the real exposure concentration with the observed toxicity, enabling the hazard potentials of different NPs to be compared on a more robust basis.

Comparison of biodistribution of cerium oxide nanoparticles after repeated oral administration by gavage or snack in Sprague Dawley rats

The rate of translocation of ingested nanoparticles (NPs) and how the uptake is affected by a food matrix are key aspects of health risk assessment. In this study, female Sprague Dawley rats (N = 4/group) received 0, 1.4, or 13 mg of cerium oxide (CeO₂ NM-212) NPs/rat/day by gavage or in a chocolate spread snack 5 days/week for 1 or 2 weeks followed by 2 weeks of recovery. A dose and time-dependent uptake in the liver and spleen of 0.1-0.3 and 0.004-0.005 parts per million (ng/mg) of the total administered dose was found, respectively. There was no statistically significant difference in cerium concentration in the liver or spleen after gavage compared to snack dosing. Microscopy revealed indications of necrotic changes in the liver and decreased cellularity in white pulp in the spleen. The snack provided precise administration and a more human-relevant exposure of NPs and could improve animal welfare as alternative to gavage.

Impact of surface chemistry of ultrasmall superparamagnetic iron oxide nanoparticles on protein corona formation and endothelial cell uptake, toxicity, and barrier function

Ultrasmall superparamagnetic iron oxide nanoparticles (USPION) have been investigated for biomedical applications, including novel contrast agents, magnetic tracers for tumor imaging, targeted drug delivery vehicles, and magneto-mechanical actuators for hyperthermia and thrombolysis. Despite significant progress, recent clinical reports have raised concerns regarding USPION safety related to endothelial cell dysfunction; however, there is limited information on factors contributing to these clinical responses. The influence of USPION surface chemistry on nanoparticle interactions with proteins may impact endothelial cell function leading to adverse responses. Therefore, the goal of this study was to assess the effects of carboxyl-functionalized USPION (CU) or amine-functionalized USPION (AU) (∼30 nm diameter) on biological responses in human coronary artery endothelial cells. Increased protein adsorption was observed for AU compared to CU after exposure to serum proteins. Exposure to CU, but not AU, resulted in a concentration-dependent decrease in cell viability and perinuclear accumulation inside cytoplasmic vesicles. Internalization of CU was correlated with endothelial cell functional changes under non-cytotoxic conditions, as evidenced by a marked decreased expression of endothelial-specific adhesion proteins (e.g., VE-cadherin and PECAM-1) and increased endothelial permeability. Evaluation of downstream signaling indicated endothelial permeability is associated with actin cytoskeleton remodeling, possibly elicited by intracellular events involving reactive oxygen species, calcium ions, and the nanoparticle cellular uptake pathway. This study demonstrated that USPION surface chemistry significantly impacts protein adsorption and endothelial cell uptake, viability, and barrier function. This information will advance the current toxicological profile of USPION and improve development, safety assessment, and clinical outcomes of USPION-enabled medical products.

Controlled decoration of nanoceria on the surface of MoS2nanoflowers to improve the biodegradability and biocompatibility inDrosophila melanogastermodel

In recent years, nanozymes based on two-dimensional (2D) nanomaterials have been receiving great interest for cancer photothermal therapy. 2D materials decorated with nanoparticles (NPs) on their surface are advantageous over conventional NPs and 2D material based systems because of their ability to synergistically improve the unique properties of both NPs and 2D materials. In this work, we report a nanozyme based on flower-like MoS₂nanoflakes (NFs) by decorating their flower petals with NCeO₂using polyethylenimine (PEI) as a linker molecule. A detailed investigation on toxicity, biocompatibility and degradation behavior of fabricated nanozymes in wild-typeDrosophila melanogastermodel revealed that there were no significant effects on the larval size, morphology, larval length, breadth and no time delay in changing larvae to the third instar stage at 7-10 d for MoS₂NFs before and after NCeO₂decoration. The muscle contraction and locomotion behavior of third instar larvae exhibited high distance coverage for NCeO₂decorated MoS₂NFs when compared to bare MoS₂NFs and control groups. Notably, the MoS₂and NCeO₂-PEI-MoS₂NFs treated groups at 100μg ml^-1covered a distance of 38.2 mm (19.4% increase when compared with control) and 49.88 mm (no change when compared with control), respectively. High-resolution transmission electron microscopy investigations on the new born fly gut showed that the NCeO₂decoration improved the degradation rate of MoS₂NFs. Hence, nanozymes reported here have huge potential in various fields ranging from biosensing, cancer therapy and theranostics to tissue engineering and the treatment of Alzheimer's disease and retinal therapy.

Silica encapsulation of ZnO nanoparticles reduces their toxicity for cumulus cell-oocyte-complex expansion

Background

Metal oxide nanoparticles (NPs) are increasingly used in many industrial and biomedical applications, hence their impact on occupational and public health has become a concern. In recent years, interest on the effect that exposure to NPs may exert on human reproduction has grown, however data are still scant. In the present work, we investigated whether different metal oxide NPs interfere with mouse cumulus cell-oocyte complex (COC) expansion.

Methods

Mouse COCs from pre-ovulatory follicles were cultured in vitro in the presence of various concentrations of two types of TiO₂ NPs (JRC NM-103 and NM-104) and four types of ZnO NPs (JRC NM-110, NM-111, and in-house prepared uncoated and SiO₂-coated NPs) and the organization of a muco-elastic extracellular matrix by cumulus cells during the process named cumulus expansion was investigated.

Results

We show that COC expansion was not affected by the presence of both types of TiO₂ NPs at all tested doses, while ZnO NM-110 and NM-111 induced strong toxicity and inhibited COCs expansion at relatively low concentration. Medium conditioned by these NPs showed lower toxicity, suggesting that, beside ion release, inhibition of COC expansion also depends on NPs per se. To further elucidate this, we compared COC expansion in the presence of uncoated or SiO₂-coated NPs. Differently from the uncoated NPs, SiO₂-coated NPs underwent slower dissolution, were not internalized by the cells, and showed an overall lower toxicity. Gene expression analysis demonstrated that ZnO NPs, but not SiO₂-coated ZnO NPs, affected the expression of genes fundamental for COC expansion. Dosimetry analysis revealed that the delivered-to-cell mass fractions for both NPs was very low.

Conclusions

Altogether, these results suggest that chemical composition, dissolution, and cell internalization are all responsible for the adverse effects of the tested NPs and support the importance of a tailored, safer-by-design production of NPs to reduce toxicity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-021-00424-z.

Pulmonary fate and consequences of transferrin-functionalized gold nanoparticles

Surface functionalization of nanoparticles (NPs) may alter their biological interactions such as uptake by alveolar macrophages (AMs). Pulmonary delivery of gold NPs (Au NPs) has theranostic potential due to their optoelectronic properties, minimal alveoli to blood translocation, and possibility of specific cell targeting. Here, we examined whether coating Au NPs with transferrin alters their protein corona, uptake by macrophages, and pulmonary translocation.

Methods: Rats were intratracheally instilled with transferrin-coated Au NPs (Tf-Au NPs) or polyethylene glycol-coated Au NPs (PEG-Au NPs). AMs were collected and processed for quantitation of Au cell uptake using ICP-MS and electron microscopy. Au retention in the lungs and other organs was also determined. The uptake of fluorescently labeled Tf-Au NPs and PEG-Au NPs by monocyte-derived human macrophages was also evaluated in vitro.

Results: We showed that Tf-Au NPs were endocytosed by AMs and were retained in the lungs to a greater extent than PEG-Au NPs. Both Au NPs acquired similar protein coronas after incubation in rat broncho-alveolar lavage fluid (BALf). The translocation of Au from both NPs to other organs was less than 0.5% of the instilled dose. Transferrin coating enhanced the uptake of Au NPs by primary monocyte-derived human macrophages.

Conclusions: We report that coating of NP surface with transferrin can target them to rat AMs and human monocyte-derived macrophages. NP functionalization with transferrin may enhance NP-based therapeutic strategies for lung diseases.

Molecular Mechanisms, Characterization Methods, and Utilities of Nanoparticle Biotransformation in Nanosafety Assessments

It is a big challenge to reveal the intrinsic cause of a nanotoxic effect due to diverse branches of signaling pathways induced by engineered nanomaterials (ENMs). Biotransformation of toxic ENMs involving biochemical reactions between nanoparticles (NPs) and biological systems has recently attracted substantial attention as it is regarded as the upstream signal in nanotoxicology pathways, the molecular initiating event (MIE). Considering that different exposure routes of ENMs may lead to different interfaces for the arising of biotransformation, this work summarizes the nano-bio interfaces and dose calculation in inhalation, dermal, ingestion, and injection exposures to humans. Then, five types of biotransformation are shown, including aggregation and agglomeration, corona formation, decomposition, recrystallization, and redox reactions. Besides, the characterization methods for investigation of biotransformation as well as the safe design of ENMs to improve the sustainable development of nanotechnology are also discussed. Finally, future perspectives on the implications of biotransformation in clinical translation of nanomedicine and commercialization of nanoproducts are provided.

Isolation methods for particle protein corona complexes from protein-rich matrices

Background: Nanoparticles become rapidly encased by a protein layer when they are in contact with biological fluids. This protein shell is called a corona. The composition of the corona has a strong influence on the surface properties of the nanoparticles. It can affect their cellular interactions, uptake and signaling properties. For this reason, protein coronae are investigated frequently as an important part of particle characterization. Main body of the abstract: The protein corona can be analyzed by different methods, which have their individual advantages and challenges. The separation techniques to isolate corona-bound particles from the surrounding matrices include centrifugation, magnetism and chromatographic methods. Different organic matrices, such as blood, blood serum, plasma or different complex protein mixtures, are used and the approaches vary in parameters such as time, concentration and temperature. Depending on the investigated particle type, the choice of separation method can be crucial for the subsequent results. In addition, it is important to include suitable controls to avoid misinterpretation and false-positive or false-negative results, thus allowing the achievement of a valuable protein corona analysis result. Conclusion: Protein corona studies are an important part of particle characterization in biological matrices. This review gives a comparative overview about separation techniques, experimental parameters and challenges which occur during the investigation of the protein coronae of different particle types.

Physicochemical and Morphological Transformations of Chitosan Nanoparticles across the Gastrointestinal Tract and Cellular Toxicity in an In Vitro Model of the Small Intestinal Epithelium

Nanoscale chitosan materials exhibit size-specific properties that make them useful in agri-food and biomedical applications. Chitosan nanoparticles (Chnps) are being explored as nanocarrier platforms to increase oral bioavailability of drugs and nutraceuticals, but little is known of their fate and transformations in the gastrointestinal tract (GIT) or of their potential toxicity. Here, the GIT fate and cytotoxicity of Chnps, soluble starch-coated Chnps (SS-Chnps), and bulk chitosan powder (Chp), were assessed using a 3-phase simulated digestion and an in vitro cellular small intestinal epithelium model. Physico-chemical characterization revealed dissolution of Chp, but not of Chnps or SS-Chnps, during the gastric phase of digestion, stability of the starch coating of SS-Chnps in the oral and gastric phases, and agglomeration of all materials during the small intestinal phase. A slight but significant (10%, p < 0.01) increase in cytotoxicity (LDH release) was observed with exposure to digested Chnps but not Chp or SS-Chnps.

Iron Oxide Nanoparticle-Induced Neoplastic-Like Cell Transformation in Vitro Is Reduced with a Protective Amorphous Silica Coating

Iron oxide nanoparticles (IONP) have recently surged in production and use in a wide variety of biomedical and environmental applications. However, their potential long-term health effects, including carcinogenesis, are unknown. Limited research suggests IONP can induce genotoxicity and neoplastic transformation associated with particle dissolution and release of free iron ions. "Safe by design" strategies involve the modification of particle physicochemical properties to affect subsequent adverse outcomes, such as an amorphous silica coating to reduce IONP dissolution and direct interaction with cells. We hypothesized that long-term exposure to a specific IONP (nFe₂O₃) would induce neoplastic-like cell transformation, which could be prevented with an amorphous silica coating (SiO₂-nFe₂O₃). To test this hypothesis, human bronchial epithelial cells (Beas-2B) were continuously exposed to a 0.6 μg/cm² administered a dose of nFe₂O₃ (∼0.58 μg/cm² delivered dose), SiO₂-nFe₂O₃ (∼0.55 μg/cm² delivered dose), or gas metal arc mild steel welding fumes (GMA-MS, ∼0.58 μg/cm² delivered dose) for 6.5 months. GMA-MS are composed of roughly 80% iron/iron oxide and were recently classified as a total human carcinogen. Our results showed that low-dose/long-term in vitro exposure to nFe₂O₃ induced a time-dependent neoplastic-like cell transformation, as indicated by increased cell proliferation and attachment-independent colony formation, which closely matched that induced by GMA-MS. This transformation was associated with decreases in intracellular iron, minimal changes in reactive oxygen species (ROS) production, and the induction of double-stranded DNA damage. An amorphous silica-coated but otherwise identical particle (SiO₂-nFe₂O₃) did not induce this neoplastic-like phenotype or changes in the parameters mentioned above. Overall, the presented data suggest the carcinogenic potential of long-term nFe₂O₃ exposure and the utility of an amorphous silica coating in a "safe by design" hazard reduction strategy, within the context of a physiologically relevant exposure scenario (low-dose/long-term), with model validation using GMA-MS.

Dissolution Behavior and Biodurability of Ingested Engineered Nanomaterials in the Gastrointestinal Environment

Engineered nanomaterials (ENM) are extensively used as food additives in numerous food products, and at present, little is known about the fate of ingested ENM (iENM) in the gastrointestinal (GI) environment. Here, we investigated the dissolution behavior, biodurability, and persistence of four major iENM (TiO₂, SiO₂, ZnO, and two Fe₂O₃) in individual simulated GI fluids (saliva, gastric, and intestinal) and a physiologically relevant digestion cascade (saliva → gastric → intestinal) in the fasted state over physiologically relevant time frames. TiO₂ was found to be the most biodurable and persistent iENM in simulated GI fluids with a maximum of only 0.42% (4 μM Ti⁴⁺ ion release) dissolution in cascade digestion, followed by iron oxides, of which the rod-like morphology was more biodurable and persistent (0.7% maximum dissolution, 8.7 μM Fe³⁺) than the acicular one (2.27% maximum dissolution, 16.7 μM Fe³⁺) in the cascade digestion, respectively. SiO₂ and ZnO were less biodurable than Fe₂O₃, with 65.5% (416 μM Si⁴⁺) and 100% (1718.1 μM Zn²⁺) dissolution in the gastric phase, respectively. In the intestinal phase, however, Si⁴⁺ ions reprecipitated, possibly due to sudden pH changes, while ZnO remained completely dissolved. These observations were also confirmed using high-resolution particle size and concentration, and electron microscopy, time-dependent analysis. In terms of decreasing biodurability and persistence in the simulated GI environment, the tested nanomaterials can be ranked as follows: TiO₂ ≫ rod-like Fe₂O₃ > acicular Fe₂O₃ ≫ SiO₂ > ZnO, which is in agreement with limited animal biokinetics data. Chronic uptake of these iENM as particles or ions by the GI tract, especially in the presence of a food matrix and authentic digestive media, and associated implications for human health warrants further investigation.

Influence of Silica Nanoparticle Density and Flow Conditions on Sedimentation, Cell Uptake, and Cytotoxicity

Careful evaluation of the toxicological response of engineered nanomaterials (ENMs) as a function of physicochemical properties can aid in the design of safe platforms for biomedical applications including drug delivery. Typically, in vitro ENM cytotoxicity assessments are performed under conventional static cell culture conditions. However, such conditions do not take into account the sedimentation rate of ENMs. Herein, we synthesized four types of similar size silica nanoparticles (SNPs) with modified surface roughness, charge, and density and characterized their cytotoxicity under static and dynamic conditions. Influence of particle density on sedimentation and diffusion velocities were studied by comparing solid dense silica nanoparticles of approximately 350 nm in diameter with hollow rattle shape particles of similar size. Surface roughness and charge had negligible impact on sedimentation and diffusion velocities. Lower cellular uptake and toxicity was observed by rattle particles and under dynamic conditions. Dosimetry of ENMs are primarily reported by particle concentration, assuming homogeneous distribution of nanoparticles in cell culture media. However, under static conditions, nanoparticles tend to sediment at a higher rate due to gravitational forces and hence increase effective doses of nanoparticles exposed to cells. By introducing shear flow to SNP suspensions, we reduced sedimentation and nonhomogeneous particle distribution. These results have implications for design of in vitro cytotoxicity assessment of ENMs and suggest that among other factors, sedimentation of nanoparticles in toxicity assessment should be carefully considered.

The impact of nanomaterial characteristics on inhalation toxicity

During the last few decades, nanotechnology has evolved into a success story, apparent from a steadily increasing number of scientific publications as well as a large number of applications based on engineered nanomaterials (ENMs). Its widespread uses suggest a high relevance for consumers, workers and the environment, hence justifying intensive investigations into ENM-related adverse effects as a prerequisite for nano-specific regulations. In particular, the inhalation of airborne ENMs, being assumed to represent the most hazardous type of human exposure to these kinds of particles, needs to be scrutinized. Due to an increased awareness of possible health effects, which have already been seen in the case of ultrafine particles (UFPs), research and regulatory measures have set in to identify and address toxic implications following their almost ubiquitous occurrence. Although ENM properties differ from those of the respective bulk materials, the available assessment protocols are often designed for the latter. Despite the large benefit ensuing from the application of nanotechnology, many issues related to ENM behavior and adverse effects are not fully understood or should be examined anew. The traditional hypothesis that ENMs exhibit different or additional hazards due to their "nano" size has been challenged in recent years and ENM categorization according to their properties and toxicity mechanisms has been proposed instead. This review summarizes the toxicological effects of inhaled ENMs identified to date, elucidating the modes of action which provoke different mechanisms in the respiratory tract and their resulting effects. By linking particular mechanisms and adverse effects to ENM properties, grouping of ENMs based on toxicity-related properties is supposed to facilitate toxicological risk assessment. As intensive studies are still required to identify these "ENM classes", the need for alternatives to animal studies is evident and advances in cell-based test systems for pulmonary research are presented here. We hope to encourage the ongoing discussion about ENM risks and to advocate the further development and practice of suitable testing and grouping methods.

Physiologically based pharmacokinetic modeling of nanoceria systemic distribution in rats suggests dose- and route-dependent biokinetics

BACKGROUND

Cerium dioxide nanoparticles (nanoceria) are increasingly being used in a variety of products as catalysts, coatings, and polishing agents. Furthermore, their antioxidant properties make nanoceria potential candidates for biomedical applications. To predict and avoid toxicity, information about their biokinetics is essential. A useful tool to explore such associations between exposure and internal target dose is physiologically based pharmacokinetic (PBPK) modeling. The aim of this study was to test the appropriateness of our previously published PBPK model developed for intravenous (IV) administration when applied to various sizes of nanoceria and to exposure routes relevant for humans.

METHODS

Experimental biokinetic data on nanoceria (obtained from various exposure routes, sizes, coatings, doses, and tissues sampled) in rats were collected from the literature and also obtained from the researchers. The PBPK model was first calibrated and validated against IV data for 30 nm citrate coated ceria and then recalibrated for 5 nm ceria. Finally, the model was modified and tested against inhalation, intratracheal (IT) instillation, and oral nanoceria data.

RESULTS

The PBPK model adequately described nanoceria time courses in various tissues for 5 nm ceria given IV. The time courses of 30 nm ceria were reasonably well predicted for liver and spleen, whereas the biokinetics in other tissues were not well captured. For the inhalation, IT instillation, and oral exposure routes, re-optimization was difficult due to low absorption and, hence, low and variable nanoceria tissue levels. Moreover, the nanoceria properties and exposure conditions varied widely among the inhalation, IT instillation, and oral studies, making it difficult to assess the importance of different factors.

CONCLUSION

Overall, our modeling efforts suggest that nanoceria biokinetics depend largely on the exposure route and dose.

Development of reference metal and metal oxide engineered nanomaterials for nanotoxicology research using high throughput and precision flame spray synthesis approaches

There is a growing need to develop and characterize reference metal and metal oxide engineered nanomaterials (ENMs) of high purity and tunable intrinsic properties suitable for nanotoxicology research. Here a high throughput (volume) and precision flame spray pyrolysis (FSP) approach coupled with state-of-the-art characterization techniques are utilized to generate such reference ENMs. The lab-based and industrially relevant FSP system, termed as Versatile Engineered Nanomaterials Generation System (VENGES), synthesizes the metals and metal oxides, at high throughput manner with controlled properties, such as primary particle size, aggregate diameter, shape, crystallinity, stoichiometry and surface chemistry. A nanopanel of nine reference ENMs (silica, silver, silver supported on silica, alumina, ceria and iron oxide) was synthesized and characterized using combined electron microscopy, advanced spectroscopic techniques and physical analyses (e.g., BET, XRD, TEM, pycnometry, XPS, ICP-MS and FTIR). ENMs show a high degree of chemical purity and stoichiometry, and low content of carbon residuals, and are sterile and free of bacteria and endotoxins. Further, their colloidal properties and their implication in in-vitro dosimetry have been also investigated in both environmental and test biological media. The suitability of reference ENMs and protocols developed in this study brings forth new arenas to generate reliable and reproducible toxicological data in an effort to reduce conflicting and contradicting inter-laboratory data on relative toxic effects of ENMs.

Preparation and Characterization of WS₂@SiO₂ and WS₂@PANI Core-Shell Nanocomposites

Two tungsten disulfide (WS₂)-based core-shell nanocomposites were fabricated using readily available reagents and simple procedures. The surface was pre-treated with a surfactant couple in a layer-by-layer approach, enabling good dispersion of the WS₂ nanostructures in aqueous media and providing a template for the polymerization of a silica (SiO₂) shell. After a Stöber-like reaction, a conformal silica coating was achieved. Inspired by the resulting nanocomposite, a second one was prepared by reacting the surfactant-modified WS₂ nanostructures with aniline and an oxidizing agent in an aqueous medium. Here too, a conformal coating of polyaniline (PANI) was obtained, giving a WS₂@PANI nanocomposite. Both nanocomposites were analyzed by electron microscopy, energy dispersive X-ray spectroscopy (EDS) and FTIR, verifying the core-shell structure and the character of shells. The silica shell was amorphous and mesoporous and the surface area of the composite increases with shell thickness. Polyaniline shells slightly differ in their morphologies dependent on the acid used in the polymerization process and are amorphous like the silica shell. Electron paramagnetic resonance (EPR) spectroscopy of the WS₂@PANI nanocomposite showed variation between bulk PANI and the PANI shell. These two nanocomposites have great potential to expand the use of transition metals dichalcogenides (TMDCs) for new applications in different fields.

Protein corona: implications for nanoparticle interactions with pulmonary cells

Background

We previously showed that cerium oxide (CeO₂), barium sulfate (BaSO₄) and zinc oxide (ZnO) nanoparticles (NPs) exhibited different lung toxicity and pulmonary clearance in rats. We hypothesize that these NPs acquire coronas with different protein compositions that may influence their clearance from the lungs.

Methods

CeO₂, silica-coated CeO₂, BaSO₄, and ZnO NPs were incubated in rat lung lining fluid in vitro. Then, gel electrophoresis followed by quantitative mass spectrometry was used to characterize the adsorbed proteins stripped from these NPs. We also measured uptake of instilled NPs by alveolar macrophages (AMs) in rat lungs using electron microscopy. Finally, we tested whether coating of gold NPs with albumin would alter their lung clearance in rats.

Results

We found that the amounts of nine proteins in the coronas formed on the four NPs varied significantly. The amounts of albumin, transferrin and α-1 antitrypsin were greater in the coronas of BaSO₄ and ZnO than that of the two CeO₂ NPs. The uptake of BaSO₄ in AMs was less than CeO₂ and silica-coated CeO₂ NPs. No identifiable ZnO NPs were observed in AMs. Gold NPs coated with albumin or citrate instilled into the lungs of rats acquired the similar protein coronas and were cleared from the lungs to the same extent.

Conclusions

We show that different NPs variably adsorb proteins from the lung lining fluid. The amount of albumin in the NP corona varies as does NP uptake by AMs. However, albumin coating does not affect the translocation of gold NPs across the air-blood barrier. A more extensive database of corona composition of a diverse NP library will develop a platform to help predict the effects and biokinetics of inhaled NPs.

An integrated methodology for assessing the impact of food matrix and gastrointestinal effects on the biokinetics and cellular toxicity of ingested engineered nanomaterials

BACKGROUND

Engineered nanomaterials (ENMs) are increasingly added to foods to improve their quality, sensory appeal, safety and shelf-life. Human exposure to these ingested ENMs (iENMS) is inevitable, yet little is known of their hazards. To assess potential hazards, efficient in vitro methodologies are needed to evaluate particle biokinetics and toxicity. These methodologies must account for interactions and transformations of iENMs in foods (food matrix effect) and in the gastrointestinal tract (GIT) that are likely to determine nano-biointeractions. Here we report the development and application of an integrated methodology consisting of three interconnected stages: 1) assessment of iENM-food interactions (food matrix effect) using model foods; 2) assessment of gastrointestinal transformations of the nano-enabled model foods using a three-stage GIT simulator; 3) assessment of iENMs biokinetics and cellular toxicity after exposure to simulated GIT conditions using a triculture cell model. As a case study, a model food (corn oil-in-water emulsion) was infused with Fe2O3 (Iron(III) oxide or ferric oxide) ENMs and processed using this three-stage integrated platform to study the impact of food matrix and GIT effects on nanoparticle biokinetics and cytotoxicity .

METHODS

A corn oil in phosphate buffer emulsion was prepared using a high speed blender and high pressure homogenizer. Iron oxide ENM was dispersed in water by sonication and combined with the food model. The resulting nano-enabled food was passed through a three stage (mouth, stomach and small intestine) GIT simulator. Size distributions of nano-enabled food model and digestae at each stage were analyzed by DLS and laser diffraction. TEM and confocal imaging were used to assess morphology of digestae at each phase. Dissolution of Fe2O3 ENM along the GIT was assessed by ICP-MS analysis of supernatants and pellets following centrifugation of digestae. An in vitro transwell triculture epithelial model was used to assess biokinetics and toxicity of ingested Fe2O3 ENM. Translocation of Fe2O3 ENM was determined by ICP-MS analysis of cell lysates and basolateral compartment fluid over time.

RESULTS

It was demonstrated that the interactions of iENMs with food and GIT components influenced nanoparticle fate and transport, biokinetics and toxicological profile. Large differences in particle size, charge, and morphology were observed in the model food with and without Fe2O3 and among digestae from different stages of the simulated GIT (mouth, stomach, and small intestine). Immunoflorescence and TEM imaging of the cell culture model revealed markers and morphology of small intestinal epithelium including enterocytes, goblet cells and M cells. Fe2O3 was not toxic at concentrations tested in the digesta. In biokinetics studies, translocation of Fe2O3 after 4 h was <1% and ~2% for digesta with and without serum, respectively, suggesting that use of serum proteins alters iENMs biokinetics and raises concerns about commonly-used approaches that neglect iENM - food-GIT interactions or dilute digestae in serum-containing media.

CONCLUSIONS

We present a simple integrated methodology for studying the biokinetics and toxicology of iENMs, which takes into consideration nanoparticle-food-GIT interactions. The importance of food matrix and GIT effects on biointeractions was demonstrated, as well as the incorporation of these critical factors into a cellular toxicity screening model. Standardized food models still need to be developed and used to assess the effect of the food matrix effects on the fate and bioactivity of iENMs since commercial foods vary considerably in their compositions and structures.

Anti-inflammatory and antioxidant effect of cerium dioxide nanoparticles immobilized on the surface of silica nanoparticles in rat experimental pneumonia

A massage with the potent counter-inflammatory material, cerium dioxide nanoparticles, is promising and the antioxidant properties of CeO₂ are considered the main, if not the only, mechanism of this action. Nevertheless, the elimination of ceria nano-particles from the organism is very slow and there is a strong concern for toxic effect of ceria due to its accumulation. To overcome this problem, we engineered a combined material in which cerium nanoparticles were immobilized on the surface of silica nanoparticles (CeO₂ NP), which is shown to be easily removed from an organism and could be used as carriers for nano-ceria. In our study particle size was 220±5nm, Zeta-potential -4.5mV (in water), surface charge density -17.22μC/cm² (at pH 7). Thirty-six male Wistar rats, 5 months old and 250-290g were divided into four groups: 1) control; 2) CeO₂ NP treatment; 3) experimental pneumonia (i/p LPS injection, 1mg/kg); and 4) experimental pneumonia treated with CeO₂ NP (4 times during the study in dosage of 0.6mg/kg with an orogastric catheter). Gas exchange and pulmonary ventilation were measured four times: 0, 1, 3 and 24h after LPS injection in both untreated and CeO₂ NP-treated animals. The mRNA of TNF-α, Il-6, and CxCL2 were determined by RT-PCR. ROS-generation in blood plasma and lung tissue homogenates were measured by means of lucigenin- and luminol-enhanced chemiluminescence. Endotoxemia in the acute phase was associated with: (1) pathological changes in lung morphology; (2) increase of ROS generation; (3) enhanced expression of CxCL2; and (4) a gradual decrease of VO₂ and V_E. CeO2 NP treatment of intact animals did not make any changes in all studied parameters except for a significant augmentation of VO₂ and V_E. CeO₂ NP treatment of rats with pneumonia created positive changes in diminishing lung tissue injury, decreasing ROS generation in blood and lung tissue and decreasing pro-inflammatory cytokine expression (TNF-α, Il-6 and CxCL2). Oxygen consumption in this group was increased compared to the LPS pneumonia group. In our study we have shown anti-inflammatory and antioxidant effects of CeO₂ NP. In addition, this paper is the first to report that CeO₂ NP stimulates oxygen consumption in both healthy rats, and rats with pneumonia. We propose the key in understanding the mechanisms behind the phenomena lies in the property of CeO₂ NP to scavenge ROS and the influence of this potent antioxidant on mitochondrial function. The study of biodistribution and elimination of СеО₂NP is the purpose of our ongoing study.

Nanoparticle exposures from nano-enabled toner-based printing equipment and human health: state of science and future research needs

Toner formulations used by laser printers (LP) and photocopiers (PC), collectively called "toner-based printing equipment" (TPE), are nano-enabled products (NEP) because they contain several engineered nanomaterials (ENM) that improve toner performance. It has been shown that during consumer use (printing), these ENM are released in the air, together with other semi-volatile organic nanoparticles, and newly formed gaseous co-pollutants such as volatile organic compounds (VOC). The aim of this review is to detail and analyze physico-chemical and morphological (PCM), as well as the toxicological properties of particulate matter (PM) emissions from TPE. The review covers evolution of science since the early 2000, when this printing technology first became a subject of public interest, as well as the lagging regulatory framework around it. Important studies that have significantly changed our understanding of these exposures are also highlighted. The review continues with a critical appraisal of the most up-to-date cellular, animal and human toxicological evidence on the potential adverse human health effects of PM emitted from TPE. We highlight several limitations of existing studies, including (i) use of high and often unrealistic doses in vitro or in vivo; (ii) unrealistically high-dose rates in intratracheal instillation studies; (iii) improper use of toners as surrogate for emitted nanoparticles; (iv) lack of or inadequate PCM characterization of exposures; and (v) lack of dosimetry considerations in in vitro studies. Presently, there is compelling evidence that the PM_0.1 from TPE are biologically active and capable of inducing oxidative stress in vitro and in vivo, respiratory tract inflammation in vivo (in rats) and in humans, several endpoints of cellular injury in monocultures and co-cultures, including moderate epigenetic modifications in vitro. In humans, limited epidemiological studies report typically 2-3 times higher prevalence of chronic cough, wheezing, nasal blockage, excessive sputum production, breathing difficulties, and shortness of breath, in copier operators relative to controls. Such symptoms can be exacerbated during chronic exposures, and in individuals susceptible to inhaled pollutants. Thus respiratory, immunological, cardiovascular, and other disorders may be developed following such exposures; however, further toxicological and larger scale molecular epidemiological studies must be done to fully understand the mechanism of action of these TPE emitted nanoparticles. Major research gaps have also been identified. Among them, a methodical risk assessment based on "real world" exposures rather than on the toner particles alone needs to be performed to provide the much-needed data to establish regulatory guidelines protective of individuals exposed to TPE emissions at both the occupational and consumer level. Industry-wide molecular epidemiology as well as mechanistic animal and human studies are also urgently needed.

Isotope Tracers To Study the Environmental Fate and Bioaccumulation of Metal-Containing Engineered Nanoparticles: Techniques and Applications

The rapidly growing applicability of metal-containing engineered nanoparticles (MENPs) has made their environmental fate, biouptake, and transformation important research topics. However, considering the relatively low concentration of MENPs and the high concentration of background metals in the environment and in organisms, tracking the fate of MENPs in environment-related scenarios remains a challenge. Intrinsic labeling of MENPs with radioactive or stable isotopes is a useful tool for the highly sensitive and selective detection of MENPs in the environment and organisms, thus enabling tracing of their transformation, uptake, distribution, and clearance. In this review, we focus on radioactive/stable isotope labeling of MENPs for their environmental and biological tracing. We summarize the advantages of intrinsic radioactive/stable isotopes for MENP labeling and discuss the considerations in labeling isotope selection and preparation of labeled MENPs, as well as exposure routes and detection of labeled MENPs. In addition, current practice in the use of radioactive/stable isotope labeling of MENPs to study their environmental fate and bioaccumulation is reviewed. Future perspectives and potential applications are also discussed, including imaging techniques for radioactive- and stable-isotope-labeled MENPs, hyphenated multistable isotope tracers with speciation analysis, and isotope fractionation as a MENP tracer. It is expected that this critical review could provide the necessary background information to further advance the applications of isotope tracers to study the environmental fate and bioaccumulation of MENPs.

Preparation, characterization, and in vitro dosimetry of dispersed, engineered nanomaterials

Evidence continues to grow of the importance of in vitro and in vivo dosimetry in the hazard assessment and ranking of engineered nanomaterials (ENMs). Accurate dose metrics are particularly important for in vitro cellular screening to assess the potential health risks or bioactivity of ENMs. To ensure meaningful and reproducible quantification of in vitro dose, with consistent measurement and reporting between laboratories, it is necessary to adopt standardized and integrated methodologies for (i) generation of stable ENM suspensions in cell culture media; (ii) colloidal characterization of suspended ENMs, particularly of properties that determine particle kinetics in an in vitro system (size distribution and formed agglomerate effective density); and (iii) robust numerical fate and transport modeling for accurate determination of the ENM dose delivered to cells over the course of the in vitro exposure. Here we present an integrated comprehensive protocol based on such a methodology for in vitro dosimetry, including detailed standardized procedures for each of these three critical aims. The entire protocol requires ∼6-12 h to complete.

Transport phenomena of nanoparticles in plants and animals/humans

The interaction of a plethora nanoparticles with major biota such as plants and animals/humans has been the subject of various multidisciplinary studies with special emphasis on toxicity aspects. However, reports are meager on the transport phenomena of nanoparticles in the plant-animal/human system. Since plants and animals/humans are closely linked via food chain, discussion is imperative on the main processes and mechanisms underlying the transport phenomena of nanoparticles in the plant-animal/human system, which is the main objective of this paper. Based on the literature appraised herein, it is recommended to perform an exhaustive exploration of so far least explored aspects such as reproducibility, predictability, and compliance risks of nanoparticles, and insights into underlying mechanisms in context with their transport phenomenon in the plant-animal/human system. The outcomes of the suggested studies can provide important clues for fetching significant benefits of rapidly expanding nanotechnology to the plant-animal/human health-improvements and protection as well.

The Role of the Food Matrix and Gastrointestinal Tract in the assessment of biological properties of ingested engineered nanomaterials (iENMs): State of the science and knowledge gaps

Many foods contain appreciable levels of engineered nanomaterials (ENMs) (diameter < 100 nm) that may be either intentionally or unintentionally added. These ENMs vary considerably in their compositions, dimensions, morphologies, physicochemical properties, and biological responses. From a toxicological point of view, it is often convenient to classify ingested ENMs (iENMs) as being either inorganic (such as TiO₂, SiO₂, Fe₂O₃, or Ag) or organic (such as lipid, protein, or carbohydrate), since the former tend to be indigestible and the latter are generally digestible. At present there is a relatively poor understanding of how different types of iENMs behave within the human gastrointestinal tract (GIT), and how the food matrix and biopolymers transform their physico-chemical properties and influence their gastrointestinal fate. This lack of knowledge confounds an understanding of their potential harmful effects on human health. The purpose of this article is to review our current understanding of the GIT fate of iENMs, and to highlight gaps where further research is urgently needed in assessing potential risks and toxicological implications of iENMs. In particular, a strong emphasis is given to the development of standardized screening methods that can be used to rapidly and accurately assess the toxicological properties of iENMs.

Buoyant Nanoparticles: Implications for Nano-Biointeractions in Cellular Studies

In the safety and efficacy assessment of novel nanomaterials, the role of nanoparticle (NP) kinetics in in vitro studies is often ignored although it has significant implications in dosimetry, hazard ranking, and nanomedicine efficacy. It is demonstrated here that certain nanoparticles are buoyant due to low effective densities of their formed agglomerates in culture media, which alters particle transport and deposition, dose-response relationships, and underestimates toxicity and bioactivity. To investigate this phenomenon, this study determines the size distribution, effective density, and assesses fate and transport for a test buoyant NP (polypropylene). To enable accurate dose-response assessment, an inverted 96-well cell culture platform is developed in which adherent cells are incubated above the buoyant particle suspension. The effect of buoyancy is assessed by comparing dose-toxicity responses in human macrophages after 24 h incubation in conventional and inverted culture systems. In the conventional culture system, no adverse effects are observed at any NP concentration tested (up to 250 μg mL(-1) ), whereas dose-dependent decreases in viability and increases in reactive oxygen species are observed in the inverted system. This work sheds light on an unknown issue that plays a significant role in vitro hazard screening and proposes a standardized methodology for buoyant NP assessments.

Direct stimulation of human fibroblasts by nCeO2 in vitro is attenuated with an amorphous silica coating

Background

Nano-scaled cerium oxide (nCeO₂) is used in a variety of applications, including use as a fuel additive, catalyst, and polishing agent, yet potential adverse health effects associated with nCeO₂ exposure remain incompletely understood. Given the increasing utility and demand for engineered nanomaterials (ENMs) such as nCeO₂, “safety-by-design” approaches are currently being sought, meaning that the physicochemical properties (e.g., size and surface chemistry) of the ENMs are altered in an effort to maximize functionality while minimizing potential toxicity. In vivo studies have shown in a rat model that inhaled nCeO₂ deposited deep in the lung and induced fibrosis. However, little is known about how the physicochemical properties of nCeO_2, or the coating of the particles with a material such as amorphous silica (aSiO₂), may affect the bio-activity of these particles. Thus, we hypothesized that the physicochemical properties of nCeO₂ may explain its potential to induce fibrogenesis, and that a nano-thin aSiO₂ coating on nCeO₂ may counteract that effect.

Results

Primary normal human lung fibroblasts were treated at occupationally relevant doses with nCeO₂ that was either left uncoated or was coated with aSiO₂ (amsCeO₂). Subsequently, fibroblasts were analyzed for known hallmarks of fibrogenesis, including cell proliferation and collagen production, as well as the formation of fibroblastic nodules. The results of this study are consistent with this hypothesis, as we found that nCeO₂ directly induced significant production of collagen I and increased cell proliferation in vitro, while amsCeO₂ did not. Furthermore, treatment of fibroblasts with nCeO₂, but not amsCeO₂, significantly induced the formation of fibroblastic nodules, a clear indicator of fibrogenicity. Such in vitro data is consistent with recent in vivo observations using the same nCeO₂ nanoparticles and relevant doses. This effect appeared to be mediated through TGFβ signaling since chemical inhibition of the TGFβ receptor abolished these responses.

Conclusions

These results indicate that differences in the physicochemical properties of nCeO₂ may alter the fibrogenicity of this material, thus highlighting the potential benefits of “safety-by-design” strategies. In addition, this study provides an efficient in vitro method for testing the fibrogenicity of ENMs that strongly correlates with in vivo findings.

Effects of engineered nanomaterial exposure on macrophage innate immune function

Increasing use of engineered nanomaterials (ENMs) means increased human exposures. Potential adverse effects include those on the immune system, ranging from direct toxicity to impairment of defenses against environmental pathogens and toxins. Effects on lung macrophages may be especially prominent, because they serve to clear foreign materials like ENMs and bacterial pathogens. We investigated the effects of 4 hour exposures over a range of concentrations, of a panel of industry-relevant ENMs, including SiO₂, Fe₂O₃, ZnO, CeO₂, TiO₂, and an Ag/SiO2 composite, on human THP-1 macrophages. Effects on phagocytosis of latex beads, and phagocytosis and killing of Francisella tularensis (FT), as well as viability, oxidative stress and mitochondrial integrity, were measured by automated scanning confocal microscopy and image analysis. Results revealed some notable patterns: 1) Phagocytosis of unopsonized beads was increased, whereas that of opsonized beads was decreased, by all ENMs, with the exception of ZnO, which reduced both opsonized and unopsonized uptake; 2) Uptake of opsonized and unopsonized FT was either impaired or unaffected by all ENMs, with the exception of CeO₂, which increased phagocytosis of unopsonized FT; 3) Macrophage killing of FT tended to improve with all ENMs; and 4) Viability was unaffected immediately following exposures with all ENMs tested, but was significantly decreased 24 hours after exposures to Ag/SiO₂ and ZnO ENMs. The results reveal a complex landscape of ENM effects on macrophage host defenses, including both enhanced and reduced capacities, and underscore the importance of robust hazard assessment, including immunotoxicity assessment, of ENMs.

Reactivity of nanoceria particles exposed to biologically relevant catechol-containing molecules

The interaction of nanoceria with catecholic molecules was investigated to obtain mechanistic information of the surface reactivity of these particles, and develop predictive models of their behavior and potential effects in complex environments.

Surface modification of zinc oxide nanoparticles with amorphous silica alters their fate in the circulation

Nanoparticle (NP) pharmacokinetics and biological effects are influenced by many factors, especially surface physicochemical properties. We assessed the effects of an amorphous silica coating on the fate of zinc after intravenous (IV) injection of neutron activated uncoated (65)ZnO or silica-coated (65)ZnO NPs in male Wistar Han rats. Groups of IV-injected rats were sequentially euthanized, and 18 tissues were collected and analyzed for (65)Zn radioactivity. The protein coronas on each ZnO NP after incubation in rat plasma were analyzed by SDS-PAGE gel electrophoresis and mass spectrometry of selected gel bands. Plasma clearance for both NPs was biphasic with rapid initial and slower terminal clearance rates. Half-lives of plasma clearance of silica-coated (65)ZnO were shorter (initial - <1 min; terminal - 2.5 min) than uncoated (65)ZnO (initial - 1.9 min; terminal - 38 min). Interestingly, the silica-coated (65)ZnO group had higher (65)Zn associated with red blood cells and higher initial uptake in the liver. The (65)Zn concentrations in all the other tissues were significantly lower in the silica-coated than uncoated groups. We also found that the protein corona formed on silica-coated ZnO NPs had higher amounts of plasma proteins, particularly albumin, transferrin, A1 inhibitor 3, α-2-hs-glycoprotein, apoprotein E and α-1 antitrypsin. Surface modification with amorphous silica alters the protein corona, agglomerate size, and zeta potential of ZnO NPs, which in turn influences ZnO biokinetic behavior in the circulation. This emphasizes the critical role of the protein corona in the biokinetics, toxicology and nanomedical applications of NPs.