Analytical Aspects of Nanotoxicology

Comprehensive insights into mechanism of nanotoxicity, assessment methods and regulatory challenges of nanomedicines

Nanomedicine has the potential to transform healthcare by offering targeted therapies, precise diagnostics, and enhanced drug delivery systems. The National Institutes of Health has coined the term "nanomedicine" to describe the use of nanotechnology in biological system monitoring, control, diagnosis, and treatment. Nanomedicine continues to receive increasing interest for the rationalized delivery of therapeutics and pharmaceutical agents to achieve the required response while reducing its side effects. However, as nanotechnology continues to advance, concerns about its potential toxicological effects have also grown. This review explores the current state of nanomedicine, focusing on the types of nanoparticles used and their associated properties that contribute to nanotoxicity. It examines the mechanisms through which nanoparticles exert toxicity, encompassing various cellular and molecular interactions. Furthermore, it discusses the assessment methods employed to evaluate nanotoxicity, encompassing in-vitro and in-vivo models, as well as emerging techniques. The review also addresses the regulatory issues surrounding nanotoxicology, highlighting the challenges in developing standardized guidelines and ensuring the secure translation of nanomedicine into clinical settings. It also explores into the challenges and ethical issues associated with nanotoxicology, as understanding the safety profile of nanoparticles is essential for their effective translation into therapeutic applications.

Toxicity of gold nanoparticles complicated by the co-existence multiscale plastics

Introduction

Gold nanoparticles (AuNPs) have been developed as treatment materials for various diseases and shown magnificent potential. By contrast to the broad toxicological studies on the single exposure (AuNPs), how the other health risks modulate the toxicological profile of AuNPs remains to be investigated. Plastics are among the most common health risks in daily life due to the broad utilization of plastic products. Therefore, in this study, we aimed to reveal the toxicological effects induced by co-exposure of gold nanorod (AuR) and polystyrene micro- and nano-plastics (hereinafter, referred to as AuRmPS and AuRnPS, respectively) in mice.

Methods

Systematic biochemical characterizations were performed to investigate the hepatotoxicity, nephrotoxicity, neurotoxicity, inflammatory responses, alterations in gut microbiota induced by co-exposure, and to analyze the toxicological phenomena from the roles of reactive oxygen species and gut-organ axis.

Results

It has been found that hepatotoxicity, nephrotoxicity, neurotoxicity, and inflammation were exacerbated in AuRnPS and AuRmPS, and gut microbiota composition was more severely altered in AuRnPS exposure. These results suggest the necessity of reducing plastics exposure in AuNPs-based therapies. Moreover, protection against the nano-sized plastic particles holds higher priority.

Conclusion

These findings will facilitate the explorations of methods to reduce therapeutic toxicity and improve biosafety for specific treatments by referring to the orders of importance in protecting different organs.

Persistence of algal toxicity induced by polystyrene nanoplastics at environmentally relevant concentrations

Polystyrene (PS) often found in the ocean is one of the most commonly used plastic polymers in the world and can exist in different particle sizes. In particular, PS degrades relatively faster and widely accumulates at the nanoscale. Therefore, the penetration is strong and it is easy to enter the body and cause adverse effects. However, the persistence or recovery of their toxicity remains largely unclear. Here, we designed two subexperiments (exposure and recovery experiments) and investigated the persistence of the toxicity of polystyrene (PS) NPs at a wide concentration range (0.01-10 mg/L) to diatoms (Phaeodactylum tricornutum). PS-NPs significantly inhibited algal growth and clearly wrinkled the surfaces of cells, membrane permeability was significantly increased, and the steady-state state of cell redox and mitochondrial membrane potential was disturbed. However, in the recovery experiment, the increased membrane permeability was observed to persist, but the induced oxidative damage was reversible, and the absorbed NPs could be excreted. Integrated omics techniques (metabolomics and transcriptomics) revealed that PS-NPs significantly disrupts cell metabolism, including disturbances in fatty acid biosynthesis and enhanced biosynthesis of phenylalanine, tyrosine, and tryptophan. Inhibition of fatty acid, amino acid, energy and carbohydrate metabolism and disturbance of the antioxidant system contribute to the persistence of toxicity. These findings highlight the phenomena and mechanisms of the persistence of phytotoxicity and are critical to the accurate assessment of NPs.

Systematic stress persistence and recovery patterns of rice (Oryza sativa L.) roots in response to molybdenum disulfide nanosheets

The increasing application of engineered nanomaterials (ENMs) unavoidably leads to environmental release and biological exposure. Understanding the potential hazards of ENMs on crops is essential for appropriate utilization and management. Herein, rice seedlings were hydroponically exposed to molybdenum sulfide (MoS₂, a typical ENM) nanosheets at 5-20 mg/L for 7 days and then depurated for another 7 days in a fresh culture medium. Exposure to MoS₂ triggered irreversible reductions in root length (by 26.3%-69.9%) and tip number (by 22.2%-66.0%). Integration of biochemical assays, transcriptomic and metabolomics found that oxidative stress induced by MoS₂ in roots was persistent, whereas the activation of aquaporins, ionic transportation, and energy synthesis was normalized due to the recovery of nutrient uptake. The down-regulated levels of genes and metabolites associated with peroxidases, hemicellulose synthesis, expansins, and auxins caused persistent structural damages (sclerosis and rupture) of root cell walls. Approximately 64.5%-84.8% of internalized MoS₂ nanosheets were degraded, and the successive up-regulation of genes encoding cytochrome P450s and glutathione S-transferases reflected the biotransformation and detoxification of MoS₂ in the depuration period. These findings provide novel insights into the persistence and recovery of MoS₂ phytotoxicity, which will help advance the risk assessment of MoS₂ application on environment.

Role of the Protein Corona in the Colloidal Behavior of Microplastics

Microparticles of polyethylene and polypropylene are largely found in aquatic environments because they are the most produced and persistent plastic materials. Once in biological media, they are covered by a layer of molecules, the so-called corona, mostly composed of proteins. A yeast protein extract from Saccharomyces cerevisiae was used as a protein system to observe interactions in complex biological media. Proteins, acting as surfactants and providing hydrophilic surfaces, allow the dispersion of highly hydrophobic particles in water and stabilize them. After 24 h, the microplastic quantity was up to 1 × 10¹¹ particles per liter, whereas without protein, no particles remained in solution. Label-free imaging of the protein corona by synchrotron radiation deep UV fluorescence microscopy (SR-DUV) was performed. In situ images of the protein corona were obtained, and the adsorbed protein quantity, the coverage rate, and the corona heterogeneity were determined. The stability kinetics of the microplastic suspensions were measured by light transmission using a Turbiscan analyzer. Together, the microscopic and kinetics results demonstrate that the protein corona can very efficiently stabilize microplastics in solution provided that the protein corona quality is sufficient. Microplastic stability depends on different parameters such as the particle's intrinsic properties (size, density, hydrophobicity) and the protein corona formation that changes the particle wettability, electrostatic charge, and steric hindrance. By controlling these parameters with proteins, it becomes possible to keep microplastics in and out of solution, paving the way for applications in the field of microplastic pollution control and remediation.

In-vivo processing of nanoassemblies: a neglected framework for recycling to bypass nanotoxicological therapeutics

The proof-of-concept of nanomaterials (NMs) in the fields of imaging, diagnosis, treatment, and theranostics shows the importance in biopharmaceuticals development due to structural orientation, on-targeting, and long-term stability. However, biotransformation of NMs and their modified form in human body via recyclable techniques are not explored owing to tiny structures and cytotoxic effects. Recycling of NMs offers advantages of dose reduction, re-utilization of the administered therapeutics providing secondary release, and decrease in nanotoxicity in human body. Therefore, approaches like in-vivo re-processing and bio-recycling are essential to overcome nanocargo system-associated toxicities such as hepatotoxicity, nephrotoxicity, neurotoxicity, and lung toxicity. After 3-5 stages of recycling process of some NMs of gold, lipid, iron oxide, polymer, silver, and graphene in spleen, kidney, and Kupffer's cells retain biological efficiency in the body. Thus, substantial attention towards recyclability and reusability of NMs for sustainable development necessitates further advancement in healthcare for effective therapy. This review article outlines biotransformation of engineered NMs as a valuable source of drug carriers and biocatalyst with critical strategies like pH modification, flocculation, or magnetization for recovery of NMs in the body. Furthermore, this article summarizes the challenges of recycled NMs and advances in integrated technologies such as artificial intelligence, machine learning, in-silico assay, etc. Therefore, potential contribution of NM's life-cycle in the recovery of nanosystems for futuristic developments require consideration in site-specific delivery, reduction of dose, remodeling in breast cancer therapy, wound healing action, antibacterial effect, and for bioremediation to develop ideal nanotherapeutics.

Graphene quantum dots disturbed the energy homeostasis by influencing lipid metabolism of macrophages

To investigate the potential factors of graphene quantum dots (GQDs), the assessment impact on the innate immune system is one of the most important. As the innate immune cell, macrophages possess phagocytosis activity and affect immunomodulation. Higher oxygen consumption rates (OCR) are used to gain insight into GQDs' effects on macrophages. Metabolomics profiling also revealed that GQDs exposure provoked an increase in phosphoglycerides, sphingolipids, and oxidized lipids in macrophages. The molecular pathways disrupted by GQDs were associated with lipid and energy metabolisms. Metabolite flux analysis was used to evaluate changes in the lipid metabolism of macrophages exposed to 100 µg mL^-1 GQDs for 24 and 48 h. A combination of ¹³C-flux analysis and metabolomics revealed the regulation of lipid biosynthesis influenced the balance of energy metabolism. Integrated proteomics and metabolomics analyses showed that nicotinic acid adenine dinucleotide and coenzyme Q10 were significantly increased under GQDs treatment, alongside upregulated protein activity (e.g., Cox5b and Cd36). The experimental evidences were expected to be provided in this study to reveal the potential harmful effect from exposure to GQDs.

Short-Wavelength Aggregation-Induced Emission Photosensitizers for Solid Tumor Therapy: Enhanced with White-Light Fiber Optic

Background

White-light photodynamic therapy (wPDT) has been used in the treatment of cancer due to its convenience, effectiveness and less painful. However, the limited penetration of white-light into the tissues leads to a reduced effectiveness of solid tumor treatment.

Methods

Two short-wavelength aggregation-induced emission (AIE) nanoparticles were prepared, PyTPA@PEG and TB@PEG, which have excitation wavelengths of 440 nm and 524 nm, respectively. They were characterized by UV, fluorescence, particle size and TEM. The ability of nanoparticles to produce reactive oxygen species (ROS) and kill cancer cells under different conditions was investigated in vitro, including white-light, after white-light penetrating the skin, laser. A white-light fiber for intra-tumor irradiation was customized. Finally, induced tumor elimination with fiber-mediated wPDT was confirmed in vivo.

Results

In vitro, both PyTPA@PEG and TB@PEG are more efficient in the production ROS when exposed to white-light compared to laser. However, wPDT also has a fatal flaw in that its level of ROS production after penetrating the skin is reduced to 20-40% of the original level. To this end, we have customized a white-light fiber for intra-tumor irradiation. In vivo, the fiber-mediated wPDT significantly induces tumor elimination with maximized therapeutic outcomes by irradiating the interior of the tumor. In addition, wPDT also has the advantage that its light source can be adapted to a wide range of photosensitizers (wavelength range 400-700 nm), whereas a laser of single wavelength can only target a specific photosensitizer.

Conclusion

This method of using optical fiber to increase the tissue penetration of white light can greatly improve the therapeutic effect of AIE photosensitizers, which is needed for the treatment of large/deep tumors and holds great promise in cancer treatment.

Use of Magnetic Modulation of Nitrogen-Vacancy Center Fluorescence in Nanodiamonds for Quantitative Analysis of Nanoparticles in Organisms

The fluorescence intensity emitted by nitrogen-vacancy (NV) centers in diamond nanoparticles can be readily modulated by the application of a magnetic field using a small electromagnet. By acquiring interleaved images acquired in the presence and absence of the magnetic field and performing digital subtraction, the fluorescence intensity of the NV nanodiamond can be isolated from scattering and autofluorescence even when these backgrounds are changing monotonically during the experiments. This approach has the potential to enable the robust identification of nanodiamonds in organisms and other complex environments. Yet, the practical application of magnetic modulation imaging to realistic systems requires the use of quantitative analysis methods based on signal-to-noise considerations. Here, we describe the use of magnetic modulation to analyze the uptake of diamond nanoparticles from an aqueous environment into Caenorhabditis elegans, used here as a model system for identification and quantification of nanodiamonds in complex matrices. Based on the observed signal-to-noise ratio of sets of digitally subtracted images, we show that nanodiamonds can be identified on an individual pixel basis with a >99.95% confidence. To determine whether surface functionalization of the nanodiamond significantly impacted uptake, we used this approach to analyze the presence of nanodiamonds in C. elegans that had been exposed to these functionalized nanodiamonds in the water column, with uptake likely occurring by ingestion. In each case, the images show a significant nanoparticle uptake. However, differences in uptake between the three ligands were not outside of the experimental error, indicating that additional factors beyond the surface charge are important factors controlling uptake. Analysis of the number of pixels above the threshold in individual C. elegans organisms revealed distributions that deviate significantly from a Poisson distribution, suggesting that uptake of nanoparticles may not be a statistically independent event. The results presented here demonstrate that magnetic modulation combined with quantitative analysis of the resulting images can be used to robustly characterize nanoparticle uptake into organisms.

Preconcentration and determination of trace Hg(ii) using ultrasound-assisted dispersive solid phase microextraction

Defect rich molybdenum disulfide (MoS₂) nanosheets were hydrothermally synthesized and their potential for ultrasound assisted dispersive solid phase microextraction of trace Hg(ii) ions was assessed. Ultrasonic dispersion allows the MoS₂ nanosheets to chelate rapidly and evenly with Hg(ii) ions and results in improving the precision and minimizing the extraction time. The multiple defect rich surface was characterized by X-ray diffraction and high-resolution transmission electron microscopy. The surface charge of intrinsically sulfur rich MoS₂ nanosheets and their elemental composition was characterized by zeta potential measurements, energy dispersive spectroscopy, and X-ray photoelectron spectroscopy. The cracks and holes on the basal planes of MoS₂ led to diffusion of the Hg(ii) ions into the interior channels. Inner-sphere chelation along with outer-sphere electrostatic interaction were the proposed mechanism for the Hg(ii) adsorption onto the MoS₂ surface. The experimental data showed good selectivity of MoS₂ nanosheets towards Hg(ii) adsorption. The systematic and constant errors of the proposed method were ruled out by the analysis of the Standard Reference Material (>95% recovery with <5% RSD). The Student's t-test values for the analyzed Standard Reference Material were found to be less than the critical Student's t value at 95% confidence level. The limit of detection (3S) was found to be 0.01 ng mL⁻¹. The MoS₂ nanosheets were successfully employed for the analysis of Hg(ii) in environmental water samples.

Hg(ii) ion adsorption onto an MoS₂ surface.

Identifying the Phytotoxicity and Defense Mechanisms Associated with Graphene-Based Nanomaterials by Integrating Multiomics and Regular Analysis

The application of graphene-based nanomaterials (GBNs) has attracted global attention in various fields, and understanding defense mechanisms against the phytotoxicity of GBNs is crucial for assessing their environmental risks and safe-by-design. However, the related information is lacking, especially for edible vegetable crops. In the present study, GBNs (0.25, 2.5, and 25 mg/kg plant fresh weight) were injected into the stems of pepper plants. The results showed that the plant defense was regulated by reducing the calcium content by 21.7-48.3%, intercellular CO₂ concentration by 12.0-35.2%, transpiration rate by 8.7-40.2%, and stomatal conductance by 16.9-50.5%. The defense pathways of plants in response to stress were further verified by the downregulation of endocytosis and transmembrane transport proteins, leading to a decrease in the nanomaterial uptake. The phytohormone gibberellin and abscisic acid receptor PYL8 were upregulated, indicating the activation of defense systems. However, reduced graphene oxide and graphene oxide quantum dots trigger stronger oxidative stress (e.g., H₂O₂ and malondialdehyde) than graphene oxide in fruits due to the breakdown of antioxidant defense systems (e.g., cytochrome P450 86A22 and P450 77A1). Both nontargeted proteomics and metabolomics consistently demonstrated that the downregulation of carbohydrate and upregulation of amino acid metabolism were the main mechanisms underlying the phytotoxicity and defense mechanisms, respectively.

Influence of Size and Phase on the Biodegradation, Excretion, and Phytotoxicity Persistence of Single-Layer Molybdenum Disulfide

The increasing applications of single-layer molybdenum disulfide (SLMoS₂) pose great potential risks associated with environmental exposure. This study found that metallic-phase SLMoS₂ with nanoscale (N-1T-SLMoS₂, ∼400 nm) and microscale (M-1T-SLMoS₂, ∼3.6 μm) diameters at 10-25 mg/L induced significant algal growth inhibition (maximum 72.7 and 74.6%, respectively), plasmolysis, and oxidative damage, but these alterations were recoverable. Nevertheless, membrane permeability, chloroplast damage, and chlorophyll biosynthesis reduction were persistent. By contrast, the growth inhibition (maximum 55.3%) and adverse effects of nano-sized semiconductive-phase SLMoS₂ (N-2H-SLMoS₂, ∼400 nm) were weak and easily alleviated after 96 h of recovery. N-1T-SLMoS₂ (0.011 μg/h) and N-2H-SLMoS₂ (0.008 μg/h) were quickly biodegraded to soluble Mo compared with M-1T-SLMoS₂ (0.004 μg/h) and excreted by algae. Incomplete biodegradation of SLMoS₂ (26.8-43.9%) did not significantly mitigate its toxicity. Proteomics and metabolomics indicated that the downregulation of proteins (50.7-99.2%) related to antioxidants and photosynthesis and inhibition of carbon fixation and carbohydrate metabolism contributed to the persistent phytotoxicity. These findings highlight the roles and mechanisms of the size and phase in the persistent phytotoxicity of SLMoS₂, which has potential implications for risk assessment and environmental applications of nanomaterials.

The Importance of Evaluating the Lot-to-Lot Batch Consistency of Commercial Multi-Walled Carbon Nanotube Products

The biological response of multi-walled carbon nanotubes (MWNTs) is related to their physicochemical properties and a thorough MWNT characterization should accompany an assessment of their biological activity, including their potential toxicity. Beyond characterizing the physicochemical properties of MWNTs from different sources or manufacturers, it is also important to characterize different production lots of the same MWNT product from the same vendor (i.e., lot-to-lot batch consistency). Herein, we present a comprehensive physicochemical characterization of two lots of commercial pristine MWNTs (pMWNTs) and carboxylated MWNTs (cMWNTs) used to study the response of mammalian macrophages to MWNTs. There were many similarities between the physicochemical properties of the two lots of cMWNTs and neither significantly diminished the 24-h proliferation of RAW 264.7 macrophages up to the highest concentration tested (200 μg cMWNTs/mL). Conversely, several physicochemical properties of the two lots of pMWNTs were different; notably, the newer lot of pMWNTs displayed less oxidative stability, a higher defect density, and a smaller amount of surface oxygen species relative to the original lot. Furthermore, a 72-h half maximal inhibitory concentration (IC-50) of ~90 µg pMWNTs/mL was determined for RAW 264.7 cells with the new lot of pMWNTs. These results demonstrate that subtle physicochemical differences can lead to significantly dissimilar cellular responses, and that production-lot consistency must be considered when assessing the toxicity of MWNTs.

Analytical methods and environmental processes of nanoplastics

The degradation of plastic debris may result in the generation of nanoplastics (NPs). Their high specific surface area for the sorption of organic pollutions and toxic heavy metals and possible transfer between organisms at different nutrient levels make the study of NPs an urgent priority. However, there is very limited understanding on the occurrence, distribution, abundant, and fate of NPs in the environment, partially due to the lack of suitable techniques for the separation and identification of NPs from complex environmental matrices. In this review, we first overviewed the state-of-the-art methods for the extraction, separation, identification and quantification of NPs in the environment. Some of them have been successfully applied for the field determination of NPs, while some are borrowed from the detection of microplastics or engineered nanomaterials. Then the possible fate and transport of NPs in the environment are thoroughly described. Although great efforts have been made during the recent years, large knowledge gaps still exist, such as the relatively high detection limit of existing method failing to detect ultralow masses of NPs in the environment, and spherical polystyrene NP models failing to represent the various compositions of NPs with different irregular shapes, which needs further investigation.

Untargeted Metabolic Pathway Analysis as an Effective Strategy to Connect Various Nanoparticle Properties to Nanoparticle-Induced Ecotoxicity

Elucidation of the relationships between nanoparticle properties and ecotoxicity is a fundamental issue for environmental applications and risk assessment of nanoparticles. However, effective strategies to connect the various properties of nanoparticles with their ecotoxicity remain largely unavailable. Herein, an untargeted metabolic pathway analysis was employed to investigate the environmental risk posed by 10 typical nanoparticles (AgNPs, CuNPs, FeNPs, ZnONPs, SiO₂NPs, TiO₂NPs, GO, GOQDs, SWCNTs, and C₆₀) to rice (a staple food for half of the world's population). Downregulation of carbohydrate metabolism and upregulation of amino acid metabolism were the two dominant metabolic effects induced by all tested nanoparticles. Partial least-squares regression analysis indicated that a zerovalent metal and high specific surface area positively contributed to the downregulation of carbohydrate metabolism, indicating strong abiotic stress. In contrast, the carbon type, the presence of a spherical or sheet shape, and the absence of oxygen functional groups in the nanoparticles positively contributed to the upregulation of amino acid metabolism, indicating adaptation to abiotic stress. Moreover, network relationships among five properties of nanoparticles were established for these metabolic pathways. The results of the present study will aid in the understanding and prediction of environmental risks and in the design of environmentally friendly nanoparticles.

Phytotoxicity induced by engineered nanomaterials as explored by metabolomics: Perspectives and challenges

Given the wide applications of engineered nanomaterials (ENMs) in various fields, the ecotoxicology of ENMs has attracted much attention. The traditional plant physiological activity (e.g., reactive oxygen species and antioxidant enzymes) are limited in that they probe one specific process of nanotoxicity, which may result in the loss of understanding of other important biological reactions. Metabolites, which are downstream of gene and protein expression, are directly related to biological phenomena. Metabolomics is an easily performed and efficient tool for solving the aforementioned problems because it involves the comprehensive exploration of metabolic profiles. To understand the roles of metabolomics in phytotoxicity, the analytical methods for metabolomics should be organized and discussed. Moreover, the dominant metabolites and metabolic pathways are similar in different plants, which determines the universal applicability of metabolomics analysis. The analysis of regulated metabolism will globally and scientifically help determine the ecotoxicology that is induced by ENMs. In the past several years, great developments in nanotoxicology have been achieved using metabolomics. However, many knowledge gaps remain, such as the relationships between biological responses that are induced by ENMs and the regulation of metabolism (e.g., carbohydrate, energy, amino acid, lipid and secondary metabolism). The phytotoxicity that is induced by ENMs has been explored by metabolomics, which is still in its infancy. The detrimental and defence mechanisms of plants in their response to ENMs at the level of metabolomics also deserve much attention. In addition, owing to the regulation of metabolism in plants by ENMs affected by multiple factors, it is meaningful to uniformly identify the key influencing factor.

Read-across predictions of nanoparticle hazard endpoints: a mathematical optimization approach

In the present study, a novel read-across methodology for the prediction of toxicity related end-points of engineered nanomaterials (ENMs) is developed. The proposed method lies in the interface between the two main read-across approaches, namely the analogue and the grouping methods, and can employ a single criterion or multiple criteria for defining similarities among ENMs. The main advantage of the proposed method is that there is no need of defining a prior read-across hypothesis. Based on the formulation and the solution of a mathematical optimization problem, the method searches over a space of alternative hypotheses, and determines the one providing the most accurate read-across predictions. The procedure is automated and only two parameters are user-defined: the balance between the level of predictive accuracy and the number of predicted samples, and the similarity criteria, which define the neighbors of a target ENM.

Study of the Persistence of the Phytotoxicity Induced by Graphene Oxide Quantum Dots and of the Specific Molecular Mechanisms by Integrating Omics and Regular Analyses

Although increasing attention has been paid to the nanotoxicity of graphene oxide quantum dots (GOQDs) due to their broad range of applications, the persistence and recoverability associated with GOQDs had been widely ignored. Interestingly, stress-response hormesis for algal growth was observed for Chlorella vulgaris as a single-celled model organism. Few physiological parameters, such as algal density, plasmolysis, and levels of reactive oxygen species, exhibited facile recovery. In contrast, the effects on chlorophyll a levels, permeability, and starch grain accumulation exhibited persistent toxicity. In the exposure stage, the downregulation of genes related to unsaturated fatty acid biosynthesis, carotenoid biosynthesis, phenylpropanoid biosynthesis, and binding contributed to toxic effects on photosynthesis. In the recovery stage, downregulation of genes related to the cis-Golgi network, photosystem I, photosynthetic membrane, and thylakoid was linked to the persistence of toxic effects on photosynthesis. The upregulated galactose metabolism and downregulated aminoacyl-tRNA biosynthesis also indicated toxicity persistence in the recovery stage. The downregulation and upregulation of phenylalanine metabolism in the exposure and recovery stages, respectively, reflected the tolerance of the algae to GOQDs. The present study highlights the importance of studying nanotoxicity by elucidation of stress and recovery patterns with metabolomics and transcriptomics.

Critical Considerations on the Clinical Translation of Upconversion Nanoparticles (UCNPs): Recommendations from the European Upconversion Network (COST Action CM1403)

The unique photoluminescent properties of upconversion nanoparticles (UCNPs) have attracted worldwide research interest and inspired many bioanalytical applications. The anti-Stokes emission with long luminescence lifetimes, narrow and multiple absorption and emission bands, and excellent photostability enable background-free and multiplexed detection in deep tissues. So far, however, in vitro and in vivo applications of UCNPs are restricted to the laboratory use due to safety concerns. Possible harmful effects may originate from the chemical composition but also from the small size of UCNPs. Potential end users must rely on well-founded safety data. Thus, a risk to benefit assessment of the envisioned combined therapeutic and diagnostic ("theranostic") applications is fundamentally important to bridge the translational gap between laboratory and clinics. The COST Action CM1403 "The European Upconversion Network-From the Design of Photon-Upconverting Nanomaterials to Biomedical Applications" integrates research on UCNPs ranging from fundamental materials synthesis and research, detection instrumentation, biofunctionalization, and bioassay development to toxicity testing. Such an interdisciplinary approach is necessary for a better and safer theranostic use of UCNPs. Here, the status of nanotoxicity research on UCNPs is compared to other nanomaterials, and routes for the translation of UCNPs into clinical applications are delineated.

The Phases of WS2 Nanosheets Influence Uptake, Oxidative Stress, Lipid Peroxidation, Membrane Damage, and Metabolism in Algae

Application of transition metal dichalcogenide (TMDC) nanosheets with different phases have attracted much attention in various fields. However, the effects of TMDC phases on environmental biology remain largely unknown. In this study, chemically exfoliated WS₂ nanosheets (Ce-WS₂, mainly the 1T phase) and annealed exfoliated WS₂ nanosheets (Ae-WS₂, 2H phase) were fabricated to serve as representative TMDC nanomaterials. Ce-WS₂ showed higher levels of cellular uptake, oxidative stress, lipid peroxidation, membrane damage, and inhibition of photosynthesis than Ae-WS₂ in Chlorella vulgaris. These differences were attributed to the higher electron conductivity and higher separation efficiency of electrons and holes in the 1T phase, a typical feature of Ce-WS₂. Correspondingly, 2H-phase Ae-WS₂ exhibited lower photooxidation/reduction activity and a lower ability to generate reactive oxygen species (mainly •OH) under visible-light irradiation. 1T-phase Ce-WS₂ dissolved more readily than Ae-WS₂ and released more W ions into aqueous environments, but the W ions exhibited negligible toxicity. Metabolomic analysis revealed that Ce-WS₂ induced more obvious alterations in metabolites (e.g., amino acids and fatty acids) and metabolic pathways (e.g., starch and sucrose metabolism) than Ae-WS₂. These alterations correlated with cell membrane damage, oxidative stress and photosynthesis inhibition. The present work provides insights into the environmentally friendly design of two-dimensional TMDCs.

Dissolution of Complex Metal Oxides from First-Principles and Thermodynamics: Cation Removal from the (001) Surface of Li(Ni1/3Mn1/3Co1/3)O2

The rapid increase in use of Li-ion batteries in portable electronics has created a pressing need to understand the environmental impact and long-term fate of electonic waste (e-waste) products such as heavy and/or reactive metals. The type of e-waste that we focus on here are the complex metal oxide nanomaterials that compose Li-ion battery cathodes. While in operation the complex metal oxides are in a hermetically sealed container. However, at the end of life, improper disposal can cause structural transformations such as dissolution and metal leaching, resulting in a significant exposure risk to the surrounding environment. The transformations that occur between operational to environmental settings gives rise to a stark knowledge gap between macroscopic design and molecular-level behavior. In this study we use theory and modeling to describe and explain previously published experimental data for cation release from Li(Ni_1/3Mn_1/3Co_1/3)O₂ (NMC) nanoparticles in an aqueous environment ( Chem. Mater. 2016 (28) 1092-1100). To better understand the transformations that may occur when this material is exposed to the environment, we compute the free energy of surface dissolution, Δ G, from the complex metal oxide NMC for a range of surface terminations and pH.

Linking nanomaterial properties to biological outcomes: analytical chemistry challenges in nanotoxicology for the next decade

This article provides our perspective on the analytical challenges in nanotoxicology as the field is entering its third decade.

Size, Stability, and Porosity of Mesoporous Nanoparticles Characterized with Light Scattering

Silicon-based mesoporous nanoparticles have been extensively studied to meet the challenges in the drug delivery. Functionality of these nanoparticles depends on their properties which are often changing as a function of particle size and surrounding medium. Widely used characterization methods, dynamic light scattering (DLS), and transmission electron microscope (TEM) have both their weaknesses. We hypothesize that conventional light scattering (LS) methods can be used for a rigorous characterization of medium sensitive nanoparticles' properties, like size, stability, and porosity. Two fundamentally different silicon-based nanoparticles were made: porous silicon (PSi) from crystalline silicon and silica nanoparticles (SN) through sol-gel process. We studied the properties of these mesoporous nanoparticles with two different multiangle LS techniques, DLS and static light scattering (SLS), and compared the results to dry-state techniques, TEM, and nitrogen sorption. Comparison of particle radius from TEM and DLS revealed significant overestimation of the DLS result. Regarding to silica nanoparticles, the overestimation was attributed to agglomeration by analyzing radius of gyration and hydrodynamic radius. In case of PSi nanoparticles, strong correlation between LS result and specific surface area was found. Our results suggest that the multiangle LS methods could be used for the size, stability, and structure characterization of mesoporous nanoparticles.

Aqueously Released Graphene Oxide Embedded in Epoxy Resin Exhibits Different Characteristics and Phytotoxicity of Chlorella vulgaris from the Pristine Form

The environmental release of nanoparticles is attracting increasing attention. Graphene oxide (GO) embedded in epoxy resin (ER) is a popular composite that has been used in various fields, but the environmental release of GO-ER composites and the effects on organisms in the environment remain unknown. The present work found that GO-ER composites in water for 2-7 days resulted in the release of 0.3-2.1% GO-ER at nanoscale (2-3 nm thickness and approximately 70-130 nm lateral length). Interestingly, pristine GO quenched 30-45% hydroxyl and 12% nitroxide free radicals, whereas this capacity was not observed for the released particles from GO-ER. At environmentally relevant concentrations (μg/L), released GO-ER particles, but not GO or ER matrix, promoted algal reproduction by 34% and chlorophyll biosynthesis by 65-127% at 96 h. Released GO-ER entered algal cells and induced a slight increase in reactive oxygen species but did not elicit notable cell structure damage. The upregulated amino acids and phenylalanine metabolism, and the downregulated fatty acid biosynthesis contributed to algal growth promoted by released GO-ER. Previous studies of pristine nanoparticles were unable to reflect the environmental effects of released nanoparticles into the environment, and our research on the exposure-toxicological continuum adds important contributions to this field.

Graphene Oxide Quantum Dots as Novel Nanozymes for Alcohol Intoxication

Alcohol overconsumption as a worldwide issue results in alcoholic liver disease (ALD), such as steatosis, alcoholic hepatitis, and cirrhosis. The treatment of ALD has been widely investigated but remains challenging. In this work, the protective effects of graphene oxide quantum dots (GOQDs) as novel nanozymes against alcohol overconsumption are discovered, and the specific mechanisms underlying these effects are elucidated via omics analysis. GOQDs dramatically alleviate the reduction of cell viability induced by ethanol and can act as nanozymes to accelerate ethanol metabolism and avoid the accumulation of toxic intermediates in cells. Mitochondrial damage and the excessive generation of free radicals were mitigated by GOQDs. The mechanisms underlying the cellular protective effects were also related to alterations in metabolic and protein signals, especially those involved in lipid metabolism. The moderately increased autophagy induced by GOQDs explained the removal of accumulated lipids and the subsequent elimination of excessive GOQDs. These findings suggest that GOQDs have an antagonistic capacity against the adverse effects caused by ethanol and provide new insights into the direct applications of GOQDs. In addition to traditional antioxidation, this work also establishes metabolomics and proteomics techniques as effective tools to discover the multiple functions of nanozymes.

Structure and Function of Adsorbed Hemoglobin on Silica Nanoparticles: Relationship between the Adsorption Process and the Oxygen Binding Properties

The connection between the mechanisms of protein adsorption on nanoparticles and the structural and functional properties of the adsorbed protein often remains unclear. We investigate porcine hemoglobin adsorption on silica nanoparticles, and we analyze the structural and functional modifications of adsorbed hemoglobin by UV-vis spectrophotometry, circular dichroism, and oxygen binding measurement. The structural analysis of adsorbed hemoglobin on silica nanoparticles reveals a significant loss of secondary structure and a preservation of the heme electronic structure. However, adsorbed hemoglobin retains its quaternary structure and exhibits an enhanced oxygen affinity with cooperative binding. Moreover, the structural and functional modifications are fully reversible after complete desorption from silica nanoparticles at pH 8.7. The tunable adsorption and desorption of hemoglobin on SNPs with pH change, and the full control of hemoglobin activity by pH, temperature, and the addition of inorganic phosphate effectors opens the way to an interesting system whereby protein adsorption on nanoparticles can allow for full control over hemoglobin oxygen binding activity. Our results suggest that adsorption of hemoglobin on silica nanoparticles leads to a new structural, functional, and dynamic state with full reversibility in a way that significantly differs from protein denaturation.

Systemic Stress and Recovery Patterns of Rice Roots in Response to Graphene Oxide Nanosheets

The interactions between nanomaterials and plants have attracted increasing attention. However, the systemic stress and recovery patterns of plants in response to nanomaterials and the connections between the molecular responses and the phenotypes remain unclear. Herein, rice was exposed to graphene oxide (GO) nanosheets at 0.01-1.0 mg/L for 7 days under hydroponic exposure, followed by a 7-day post exposure (GO-free). The significant upregulation (p < 0.05) of phenylalanine metabolism, secondary metabolism, and heme peroxidase reflected the stress and recovery patterns of rice roots exposed to GO. GO triggered 27% and more than 50% decreases in hydraulic conductivity and aquaporin gene expression (PIP1-3 and PIP2-2), respectively. The uptake of GO was mediated by aquaporin inhibition. Nanomaterial biotransformation reflected the potential for rice roots to adapt to GO stress. Oxidative stress, especially the downregulation of class III peroxidase mRNAs, were suppressed by GO. Lateral root inhibition, primary root growth, and cell wall synthesis, as forms of resistance to GO stress, were related to the significant (p < 0.05) downregulation of salicylic acid and lignin biosynthesis, as well as the upregulation of jasmonic acid and laccases. The present study helps elucidate the molecular and phenotypic responses of plants to nanomaterials, which are closely linked to their environmental risk assessment.

Silver Nanoparticles: Technological Advances, Societal Impacts, and Metrological Challenges

Silver nanoparticles (AgNPs) show different physical and chemical properties compared to their macroscale analogs. This is primarily due to their small size and, consequently, the exceptional surface area of these materials. Presently, advances in the synthesis, stabilization, and production of AgNPs have fostered a new generation of commercial products and intensified scientific investigation within the nanotechnology field. The use of AgNPs in commercial products is increasing and impacts on the environment and human health are largely unknown. This article discusses advances in AgNP production and presents an overview of the commercial, societal, and environmental impacts of this emerging nanoparticle (NP), and nanomaterials in general. Finally, we examine the challenges associated with AgNP characterization, discuss the importance of the development of NP reference materials (RMs) and explore their role as a metrological mechanism to improve the quality and comparability of NP measurements.

Amorphous Silica Particles Relevant in Food Industry Influence Cellular Growth and Associated Signaling Pathways in Human Gastric Carcinoma Cells

Nanostructured silica particles are commonly used in biomedical and biotechnical fields, as well as, in cosmetics and food industry. Thus, their environmental and health impacts are of great interest and effects after oral uptake are only rarely investigated. In the present study, the toxicological effects of commercially available nano-scaled silica with a nominal primary diameter of 12 nm were investigated on the human gastric carcinoma cell line GXF251L. Besides the analysis of cytotoxic and proliferative effects and the comparison with effects of particles with a nominal primary diameter of 200 nm, emphasis was also given to their influence on the cellular epidermal growth factor receptor (EGFR) and mitogen-activated protein kinases (MAPK) signaling pathways—both of them deeply involved in the regulation of cellular processes like cell cycle progression, differentiation or proliferation. The investigated silica nanoparticles (NPs) were found to stimulate cell proliferation as measured by microscopy and the sulforhodamine B assay. In accordance, the nuclear level of the proliferation marker Ki-67 was enhanced in a concentration-dependent manner. At high particle concentrations also necrosis was induced. Finally, silica NPs affected the EGFR and MAPK pathways at various levels dependent on concentration and time. However, classical activation of the EGFR, to be reflected by enhanced levels of phosphorylation, could be excluded as major trigger of the proliferative stimulus. After 45 min of incubation the level of phosphorylated EGFR did not increase, whereas enhanced levels of total EGFR protein were observed. These results indicate interference with the complex homeostasis of the EGFR protein, whereby up to 24 h no impact on the transcription level was detected. In addition, downstream on the level of the MAP kinases ERK1/2 short term incubation appeared to affect total protein levels without clear increase in phosphorylation. Depending on the concentration range, enhanced levels of ERK1/2 phosphorylation were only observed after 24 h of incubation. Taken together, the present study demonstrates the potential of the tested silica particles to enhance the growth of gastric carcinoma cells. Although interference with the EGFR/MAPK cascade is observed, additional mechanisms are likely to be involved in the onset of the proliferative stimulus.

Surface PEGylation of Silver Nanoparticles: Kinetics of Simultaneous Surface Dissolution and Molecular Desorption

A quantitative study of the stability of silver nanoparticles (AgNPs) conjugated with thiolated polyethylene glycol (SH-PEG) was conducted using gas-phase ion-mobility and mass analyses. The extents of aggregation and surface dissolution of AgNPs, as well as the amount of SH-PEG adsorption and desorption, were able to be characterized simultaneously for the kinetic study. The results show that the SH-PEG with a molecular mass of 6 kg/mol (SH-PEG6K) was able to adsorb to the surface of AgNP to form PEG6K-HS-AgNP conjugates, with the maximum surface adsorbate density of ∼0.10 nm(-2). The equilibrium binding constant for SH-PEG6K on AgNPs was calculated as ∼(4.4 ± 0.9) × 10(5) L/mol, suggesting a strong affinity due to thiol bonding to the AgNP surface. The formation of SH-PEG6K corona prevented PEG6K-HS-AgNP conjugates from aggregation under the acidic environment (pH 1.5), but dissolution of core AgNPs occurred following a first-order reaction. The rate constant of Ag dissolution from PEG6K-HS-AgNP was independent of the starting surface packing density of SH-PEG6K on AgNP (σ0), indicating that the interactions of H(+) with core AgNP were not interfered by the presence of SH-PEG6K corona. The surface packing density of SH-PEG6K decreased simultaneously following a first-order reaction, and the desorption rate constant of SH-PEG6K from the conjugates was proportional to σ0. Our work presents the first quantitative study to illustrate the complex mechanism that involves simultaneous aggregation and dissolution of core AgNPs in combination with adsorption and desorption of SH-PEG. This work also provides a prototype method of coupled experimental scheme to quantify the change of particle mass versus the corresponding surface density of functional molecular species on nanoparticles.

Functionalized Mesoporous Silica Nanoparticle with Antioxidants as a New Carrier That Generates Lower Oxidative Stress Impact on Cells

Mesoporous silica nanoparticles (MSNs) were covalently coated with antioxidant molecules, namely, caffeic acid (MSN-CAF) or rutin (MSN-RUT), in order to diminish the impact of oxidative stress induced after transfection into cells, thus generating safer carriers used for either drug delivery or other applications. Two cellular models involved in the entry of NPs in the body were used for this purpose: the intestinal Caco-2 and the epidermal HaCaT cell lines. Rutin gave the best results in terms of antioxidant capacities preservation during coupling procedures, cellular toxicity alleviation, and decrease of ROS level after 24 h incubation of cells with grafted nanoparticles. These protective effects of rutin were found more pronounced in HaCaT than in Caco-2 cells, indicating some cellular specificity toward defense against oxidative stress. In order to gain more insight about the Nrf2 response, a stable transfected HaCaT cell line bearing repeats of the antioxidant response element (ARE) in front of a luciferase reporter gene was generated. In this cell line, both tBHQ and quercetin (Nrf2 agonists), but not rutin, were able to induce, in a dose-dependent fashion, the luciferase response. Interestingly, at high concentration, MSN-RUT was able to induce a strong Nrf2 protective response in HaCaT cells, accompanied by a comparable induction of HO-1 mRNA. The level of these responses was again less important in Caco-2 cells. To conclude, in keratinocyte cell line, the coupling of rutin to silica nanoparticles was beneficial in term of ROS reduction, cellular viability, and protective effects mediated through the activation of the Nrf2 antioxidant pathway.

How should the completeness and quality of curated nanomaterial data be evaluated?

Nanotechnology is of increasing significance. Curation of nanomaterial data into electronic databases offers opportunities to better understand and predict nanomaterials' behaviour. This supports innovation in, and regulation of, nanotechnology. It is commonly understood that curated data need to be sufficiently complete and of sufficient quality to serve their intended purpose. However, assessing data completeness and quality is non-trivial in general and is arguably especially difficult in the nanoscience area, given its highly multidisciplinary nature. The current article, part of the Nanomaterial Data Curation Initiative series, addresses how to assess the completeness and quality of (curated) nanomaterial data. In order to address this key challenge, a variety of related issues are discussed: the meaning and importance of data completeness and quality, existing approaches to their assessment and the key challenges associated with evaluating the completeness and quality of curated nanomaterial data. Considerations which are specific to the nanoscience area and lessons which can be learned from other relevant scientific disciplines are considered. Hence, the scope of this discussion ranges from physicochemical characterisation requirements for nanomaterials and interference of nanomaterials with nanotoxicology assays to broader issues such as minimum information checklists, toxicology data quality schemes and computational approaches that facilitate evaluation of the completeness and quality of (curated) data. This discussion is informed by a literature review and a survey of key nanomaterial data curation stakeholders. Finally, drawing upon this discussion, recommendations are presented concerning the central question: how should the completeness and quality of curated nanomaterial data be evaluated?