Redox Activity and Nano-Bio Interactions Determine the Skin Injury Potential of Co3O4-Based Metal Oxide Nanoparticles toward Zebrafish

Machine Learning Allowed Interpreting Toxicity of a Fe-Doped CuO NM Library Large Data Set─An Environmental In Vivo Case Study

The wide variation of nanomaterial (NM) characters (size, shape, and properties) and the related impacts on living organisms make it virtually impossible to assess their safety; the need for modeling has been urged for long. We here investigate the custom-designed 1-10% Fe-doped CuO NM library. Effects were assessed using the soil ecotoxicology model Enchytraeus crypticus (Oligochaeta) in the standard 21 days plus its extension (49 days). Results showed that 10%Fe-CuO was the most toxic (21 days reproduction EC50 = 650 mg NM/kg soil) and Fe3O4 NM was the least toxic (no effects up to 3200 mg NM/kg soil). All other NMs caused similar effects to E. crypticus (21 days reproduction EC50 ranging from 875 to 1923 mg NM/kg soil, with overlapping confidence intervals). Aiming to identify the key NM characteristics responsible for the toxicity, machine learning (ML) modeling was used to analyze the large data set [9 NMs, 68 descriptors, 6 concentrations, 2 exposure times (21 and 49 days), 2 endpoints (survival and reproduction)]. ML allowed us to separate experimental related parameters (e.g., zeta potential) from particle-specific descriptors (e.g., force vectors) for the best identification of important descriptors. We observed that concentration-dependent descriptors (environmental parameters, e.g., zeta potential) were the most important under standard test duration (21 day) but not for longer exposure (closer representation of real-world conditions). In the longer exposure (49 days), the particle-specific descriptors were more important than the concentration-dependent parameters. The longer-term exposure showed that the steepness of the concentration-response decreased with an increased Fe content in the NMs. Longer-term exposure should be a requirement in the hazard assessment of NMs in addition to the standard in OECD guidelines for chemicals. The progress toward ML analysis is desirable given its need for such large data sets and significant power to link NM descriptors to effects in animals. This is beyond the current univariate and concentration-response modeling analysis.

Co-exposure of polystyrene nanoplastics and copper induces development toxicity and intestinal mitochondrial dysfunction in vivo and in vitro

Nanoplastics (NPs) have raised concerns about the combined toxicity to living organisms due to their ability to adsorb heavy metals. There is still uncertainty, however, whether NPs combined with heavy metals exert adverse effects on intestinal microenvironment, especially the intestinal cells and microbiota. Herein, the combined effects of 500 nm spherical-shaped polystyrene nanoplastics (PSNPs) and copper ions (Cu2+) on intestinal cells and gut microbiota were assessed using HCT-116 cells and zebrafish models. The combined exposure of PSNPs (10 mg/L) and Cu2+ (0.5 mg/L) induced more severer hatching interference of zebrafish embryos, deformation, and mortality. In larval stage, PSNPs (10 mg/L) accumulated and carried more Cu2+ in the gastrointestinal tract (GIT) of zebrafish after co-exposure for 5 days. Excessive neutrophil recruitment and oxidative stress in GIT of zebrafish larvae were observed. The mechanism of the combined toxicity was revealed by transmission electron microscopy (TEM) showing the injuries of GIT, transcriptome and 16S rDNA gene sequencing showing the toxicity pathways, including oxidative phosphorylation and respiratory electron transport chain, as well as microbial community analysis showing the induced microbiota dysbiosis. In vitro tests using HCT-116 cells showed that PSNPs (10 mg/L) and Cu2+ (0.5 mg/L) increased cell death while decreasing ATP concentration and mitochondrial membrane potential after 48 h exposure. These findings may provide new insights into the combined toxicity of nanoplastics and heavy metals in the intestinal microenvironment.

Remediation of Metal Oxide Nanotoxicity with a Functional Amyloid

Understanding the environmental health and safety of nanomaterials (NanoEHS) is essential for the sustained development of nanotechnology. Although extensive research over the past two decades has elucidated the phenomena, mechanisms, and implications of nanomaterials in cellular and organismal models, the active remediation of the adverse biological and environmental effects of nanomaterials remains largely unexplored. Inspired by recent developments in functional amyloids for biomedical and environmental engineering, this work shows their new utility as metallothionein mimics in the strategically important area of NanoEHS. Specifically, metal ions released from CuO and ZnO nanoparticles are sequestered through cysteine coordination and electrostatic interactions with beta-lactoglobulin (bLg) amyloid, as revealed by inductively coupled plasma mass spectrometry and molecular dynamics simulations. The toxicity of the metal oxide nanoparticles is subsequently mitigated by functional amyloids, as validated by cell viability and apoptosis assays in vitro and murine survival and biomarker assays in vivo. As bLg amyloid fibrils can be readily produced from whey in large quantities at a low cost, the study offers a crucial strategy for remediating the biological and environmental footprints of transition metal oxide nanomaterials.

Multienzyme Active Manganese Oxide Alleviates Acute Liver Injury by Mimicking Redox Regulatory System and Inhibiting Ferroptosis

Drug-induced liver injury (DILI) is a severe condition characterized by impaired liver function and the excessive activation of ferroptosis. Unfortunately, there are limited options currently available for preventing or treating DILI. In this study, MnO2 nanoflowers (MnO2Nfs) with remarkable capabilities of mimicking essential antioxidant enzymes, including catalase, superoxide dismutase (SOD), and glutathione peroxidase are successfully synthesized, and SOD is the dominant enzyme among them by density functional theory. Notably, MnO2Nfs demonstrate high efficiency in effectively eliminating diverse reactive oxygen species (ROS) such as hydrogen peroxide (H2O2), superoxide anion (O2 •-), and hydroxyl radical (•OH). Through in vitro experiments, it is demonstrated that MnO2Nfs significantly enhance the recovery of intracellular glutathione content, acting as a potent inhibitor of ferroptosis even in the presence of ferroptosis activators. Moreover, MnO2Nfs exhibit excellent liver accumulation properties, providing robust protection against oxidative damage. Specifically, they attenuate acetaminophen-induced ferroptosis by inhibiting ferritinophagy and activating the P62-NRF2-GPX4 antioxidation signaling pathways. These findings highlight the remarkable ROS scavenging ability of MnO2Nfs and hold great promise as an innovative and potential clinical therapy for DILI and other ROS-related liver diseases.

Zebrafish Insights into Nanomaterial Toxicity: A Focused Exploration on Metallic, Metal Oxide, Semiconductor, and Mixed-Metal Nanoparticles

Nanomaterials are widely used in various fields, and ongoing research is focused on developing safe and sustainable nanomaterials. Using zebrafish as a model organism for studying the potentially toxic effects of nanomaterials highlights the importance of developing safe and sustainable nanomaterials. Studies conducted on nanomaterials and their toxicity and potential risks to human and environmental health are vital in biomedical sciences. In the present review, we discuss the potential toxicity of nanomaterials (inorganic and organic) and exposure risks based on size, shape, and concentration. The review further explores various types of nanomaterials and their impacts on zebrafish at different levels, indicating that exposure to nanomaterials can lead to developmental defects, changes in gene expressions, and various toxicities. The review also covers the importance of considering natural organic matter and chorion membranes in standardized nanotoxicity testing. While some nanomaterials are biologically compatible, metal and semiconductor nanomaterials that enter the water environment can increase toxicity to aquatic creatures and can potentially accumulate in the human body. Further investigations are necessary to assess the safety of nanomaterials and their impacts on the environment and human health.

Deep Learning-Enabled Morphometric Analysis for Toxicity Screening Using Zebrafish Larvae

Toxicology studies heavily rely on morphometric analysis to detect abnormalities and diagnose disease processes. The emergence of ever-increasing varieties of environmental pollutants makes it difficult to perform timely assessments, especially using in vivo models. Herein, we propose a deep learning-based morphometric analysis (DLMA) to quantitatively identify eight abnormal phenotypes (head hemorrhage, jaw malformation, uninflated swim bladder, pericardial edema, yolk edema, bent spine, dead, unhatched) and eight vital organ features (eye, head, jaw, heart, yolk, swim bladder, body length, and curvature) of zebrafish larvae. A data set composed of 2532 bright-field micrographs of zebrafish larvae at 120 h post fertilization was generated from toxicity screening of three categories of chemicals, i.e., endocrine disruptors (perfluorooctanesulfonate and bisphenol A), heavy metals (CdCl2 and PbI2), and emerging organic pollutants (acetaminophen, 2,7-dibromocarbazole, 3-monobromocarbazo, 3,6-dibromocarbazole, and 1,3,6,8-tetrabromocarbazo). Two typical deep learning models, one-stage and two-stage models (TensorMask, Mask R-CNN), were trained to implement phenotypic feature classification and segmentation. The accuracy was statistically validated with a mean average precision >0.93 in unlabeled data sets and a mean accuracy >0.86 in previously published data sets. Such a method effectively enables subjective morphometric analysis of zebrafish larvae to achieve efficient hazard identification of both chemicals and environmental pollutants.

Surface Modification Determines the Distribution and Toxicity of Quantum Dots during the Development of Early Staged Zebrafish

Surface modifications are generally used to functionalize QDots to improve their properties for practical applications, but the relationship between QDot modification and biological activity is not well understood. Using an early staged zebrafish model, we investigated the biodistribution and toxicity of CdSe/ZnS QDots with four types of modifications, including anionic poly(ethylene glycol)-carboxyl ((PEG)n-COOH), anionic mercaptopropionic acid (MPA), zwitterionic glutathione (GSH), and cationic cysteamine (CA). None of the QDots showed obvious toxicity to zebrafish embryos prior to hatching because the zebrafish chorion is an effective barrier that protects against QDot exposure. The QDots were mainly absorbed on the epidermis of the target organs after hatching and were primarily deposited in the mouth and gastrointestinal tract when the zebrafish started feeding. CA-QDots possessed the highest adsorption capacity; however, (PEG)n-COOH-QDots showed the most severe toxicity to zebrafish, as determined by mortality, hatching rate, heartbeat, and malformation assessments. It shows that the toxicity of the QDots is mainly attributed to ROS generation rather than Cd2+ release. This study provides a comprehensive understanding of the environmental and ecological risks of nanoparticles in relation to their surface modification.

TiO2 nanoparticles' library toxicity (UV and non-UV exposure) - High-throughput in vivo transcriptomics reveals mechanisms

The hazards of nanomaterials/nanoparticles (NMs/NPs) are mostly assessed using individual NMs, and a more systematic approach, using many NMs, is needed to evaluate its risks in the environment. Libraries of NMs, with a range of identified different but related characters/descriptors allow the comparison of effects across many NMs. The effects of a custom designed Fe-doped TiO₂ NMs library containing 11 NMs was assessed on the soil model Enchytraeus crypticus (Oligochaeta), both with and without UV (standard fluorescent) radiation. Effects were analyzed at organism (phenotypic, survival and reproduction) and gene expression level (transcriptomics, high-throughput 4x44K microarray) to understand the underlying mechanisms. A total of 48 microarrays (20 test conditions) were done plus controls (UV and non-UV). Unique mechanisms induced by TiO₂ NPs exposure included the impairment in RNA processing for TiO₂_10nm, or deregulated apoptosis for 2%FeTiO₂_10nm. Strikingly apparent was the size dependent effects such as induction of reproductive effects via smaller TiO₂ NPs (≤12 nm) - embryo interaction, while larger particles (27 nm) caused reproductive effects through different mechanisms. Also, phagocytosis was affected by 12 and 27 nm NPs, but not by ≤11 nm. The organism level study shows the integrated response, i.e. the result after a cascade of events. While uni-cell models offer key mechanistic information, we here deliver a combined biological system level (phenotype and genotype), seldom available, especially for environmental models.

Disproportional surface segregation in ligand-free gold-silver alloy solid solution nanoparticles, and its implication for catalysis and biomedicine

Catalytic activity and toxicity of mixed-metal nanoparticles have been shown to correlate and are known to be dependent on surface composition. The surface chemistry of the fully inorganic, ligand-free silver-gold alloy nanoparticle molar fraction series, is highly interesting for applications in heterogeneous catalysis, which is determined by active surface sites which are also relevant for understanding their dissolution behavior in biomedically-relevant ion-release scenarios. However, such information has never been systematically obtained for colloidal nanoparticles without organic surface ligands and has to date, not been analyzed in a surface-normalized manner to exclude density effects. For this, we used detailed electrochemical measurements based on cyclic voltammetry to systematically analyze the redox chemistry of particle-surface-normalized gold-silver alloy nanoparticles with varying gold molar fractions. The study addressed a broad range of gold molar fractions (Ag₉₀Au₁₀, Ag₈₀Au₂₀, Ag₇₀Au₃₀, Ag₅₀Au₅₀, Ag₄₀Au₆₀, and Ag₂₀Au₈₀) as well as monometallic Ag and Au nanoparticle controls. Oxygen reduction reaction (ORR) measurements in O₂ saturated 0.1 M KOH revealed a linear reduction of the overpotential with increasing gold content on the surface, probably attributed to the higher ORR activity of gold over silver, verified by monometallic Ag and Au controls. These findings were complemented by detailed XPS studies revealing an accumulation of the minor constituent of the alloy on the surface, e.g., silver surface enrichment in gold-rich particles. Furthermore, highly oxidized Ag surface site enrichment was detected after the ORR reaction, most pronounced in gold-rich alloys. Further, detailed CV studies at acidic pH, analyzing the position, onset potential, and peak integrals of silver oxidation and silver reduction peaks revealed particularly low reactivity and high chemical stability of the equimolar Au₅₀Ag₅₀ composition, a phenomenon attributed to the outstanding thermodynamic, entropically driven, stabilization arising at this composition.

Titanium dioxide nanoparticles decreases bioconcentration of azoxystrobin in zebrafish larvae leading to the alleviation of cardiotoxicity

Interactions between titanium dioxide nanoparticles (n-TiO₂) and pollutants in the aquatic environment may alter the bioavailability of pollutants, and thus altering their toxicity and fate. In order to investigate the bioconcentration of azoxystrobin (AZ) and its mechanism of cardiotoxicity in the presence of n-TiO₂, the experiment was divided into control, n-TiO₂ (100 μg/L), AZ (40, 200 and 1000 μg/L) and AZ (40, 200, 1000 μg/L) + n-TiO₂ groups, and the zebrafish embryos were exposed to the exposure solution until 72 h post-fertilization. Results suggested the presence of n-TiO₂ notably reduced the accumulation of AZ in larvae compared with exposure to AZ alone, thereby significantly decreasing AZ-induced cardiotoxicity, including heart rate changes, pericardium edema, venous thrombosis, increased sinus venosus and bulbus arteriosus distance and changes in cardiac-related gene expression. Further studies showed that AZ + n-TiO₂ together restrained total-ATPase and Ca²⁺-ATPase activities, while the activity of Na⁺K⁺-ATPase increased at first and then decreased. Furthermore, there were significant changes in the expressions of oxidative phosphorylation and calcium channel-related genes, suggesting mitochondrial dysfunction may be the potential mechanism of cardiotoxicity induced by AZ and n-TiO₂. This study supplies a new perspective for the joint action of AZ and environmental coexisting pollutants and provides a basis for ecological risk management of pesticides.

Where Is Nano Today and Where Is It Headed? A Review of Nanomedicine and the Dilemma of Nanotoxicology

Worldwide nanotechnology development and application have fueled many scientific advances, but technophilic expectations and technophobic demands must be counterbalanced in parallel. Some of the burning issues today are the following: (1) Where is nano today? (2) How good are the communication and investment networks between academia/research and governments? (3) Is there any spotlight application for nanotechnology? Nanomedicine is a particular arm of nanotechnology within the healthcare landscape, focused on diagnosis, treatment, and monitoring of emerging (such as coronavirus disease 2019, COVID-19) and contemporary (including diabetes, cardiovascular diseases, neurodegenerative disorders, and cancer) diseases. However, it may only represent the bright side of the coin. In fact, in the recent past, the concept of nanotoxicology has emerged to address the dark shadows of nanomedicine. The nanomedicine field requires more nanotoxicological studies to identify undesirable effects and guarantee safety. Here, we provide an overall perspective on nanomedicine and nanotoxicology as central pieces of the giant puzzle of nanotechnology. First, the impact of nanotechnology on education and research is highlighted, followed by market trends and scientific output tendencies. In the next section, the nanomedicine and nanotoxicology dilemma is addressed through the interplay of in silico, in vitro, and in vivo models with the support of omics and microfluidic approaches. Lastly, a reflection on the regulatory issues and clinical trials is provided. Finally, some conclusions and future perspectives are proposed for a clearer and safer translation of nanomedicines from the bench to the bedside.

"Fishing" nano-bio interactions at the key biological barriers

Understanding nano-bio interactions is pivotal to the safe implementation of nanotechnology for both biological and environmental applications. Zebrafish as a model organism provides unique opportunities to dissect nano-bio interactions occurring at different biological barriers. In this review, we focus on four key biological barriers, namely cell membrane, blood-brain barrier (BBB), skin and gill epithelia, and gastrointestinal tract (GIT), and highlight recent advancement achieved by using zebrafish to conduct both visualized observations and mechanistic investigations on a diversity of nano-bio interactions.