Gold nanorods induce early embryonic developmental delay and lethality in zebrafish (Danio rerio)

Nano-alumina induced developmental and neurobehavioral toxicity in the early life stage of zebrafish, associated with mTOR

The study aims to investigate the effects of nano-alumina (AlNPs) on the early development and neurobehavior of zebrafish and the role of mTOR in this process. After embryos and grown-up larvae exposed to AlNPs from 0 to 200 μg/mL, we examined the development, neurobehavior, AlNPs content, and mTOR pathway genes. Moreover, embryos were randomly administered with control, negative control, mTOR knockdown, AlNPs, and mTOR knockdown + AlNPs, then examined for development, neurobehavior, oxidative stress, neurotransmitters, and development genes. As AlNPs increased, swimming speed and distance initially increased and then decreased; thigmotaxis and panic-avoidance reflex substantially decreased in the high-dose AlNPs group; aluminum and nanoparticles considerably accumulated in the 100 μg/mL AlNPs group; AlNPs at high dose decreased mTOR gene and protein levels, stimulating autophagy via increasing ULK1 and ULK2. mTOR knockdown exacerbated the harm to normal development rate, eye and body length, and neurobehavior induced by AlNPs through raising ROS, SOD, and ACH levels but decreasing AchE activity and development genes. Therefore, AlNPs suppress neurobehavior through downregulating mTOR, and mTOR knockdown further aggravates their early development and neurobehavior loss, suggesting mTOR could be a potential target for the toxicity of AlNPs.

Automated staging of zebrafish embryos with deep learning

The zebrafish (Danio rerio) is an important biomedical model organism used in many disciplines. The phenomenon of developmental delay in zebrafish embryos has been widely reported as part of a mutant or treatment-induced phenotype. However, the detection and quantification of these delays is often achieved through manual observation, which is both time-consuming and subjective. We present KimmelNet, a deep learning model trained to predict embryo age (hours post fertilisation) from 2D brightfield images. KimmelNet's predictions agree closely with established staging methods and can detect developmental delays between populations with high confidence using as few as 100 images. Moreover, KimmelNet generalises to previously unseen data, with transfer learning enhancing its performance. With the ability to analyse tens of thousands of standard brightfield microscopy images on a timescale of minutes, we envisage that KimmelNet will be a valuable resource for the developmental biology community. Furthermore, the approach we have used could easily be adapted to generate models for other organisms.

Uncovering developmental time and tempo using deep learning

During animal development, embryos undergo complex morphological changes over time. Differences in developmental tempo between species are emerging as principal drivers of evolutionary novelty, but accurate description of these processes is very challenging. To address this challenge, we present here an automated and unbiased deep learning approach to analyze the similarity between embryos of different timepoints. Calculation of similarities across stages resulted in complex phenotypic fingerprints, which carry characteristic information about developmental time and tempo. Using this approach, we were able to accurately stage embryos, quantitatively determine temperature-dependent developmental tempo, detect naturally occurring and induced changes in the developmental progression of individual embryos, and derive staging atlases for several species de novo in an unsupervised manner. Our approach allows us to quantify developmental time and tempo objectively and provides a standardized way to analyze early embryogenesis.

Automated staging of zebrafish embryos using machine learning

The zebrafish ( Danio rerio), is an important biomedical model organism used in many disciplines, including development, disease modeling and toxicology, to better understand vertebrate biology. The phenomenon of developmental delay in zebrafish embryos has been widely reported as part of a mutant or treatment-induced phenotype, and accurate characterization of such delays is imperative. Despite this, the only way at present to identify and quantify these delays is through manual observation, which is both time-consuming and subjective. Machine learning approaches in biology are rapidly becoming part of the toolkit used by researchers to address complex questions. In this work, we introduce a machine learning-based classifier that has been trained to detect temporal developmental differences across groups of zebrafish embryos. Our classifier is capable of rapidly analyzing thousands of images, allowing comparisons of developmental temporal rates to be assessed across and between experimental groups of embryos. Finally, as our classifier uses images obtained from a standard live-imaging widefield microscope and camera set-up, we envisage it will be readily accessible to the zebrafish community, and prove to be a valuable resource.

Automated staging of zebrafish embryos using machine learning

The zebrafish ( Danio rerio), is an important biomedical model organism used in many disciplines, including development, disease modeling and toxicology, to better understand vertebrate biology. The phenomenon of developmental delay in zebrafish embryos has been widely reported as part of a mutant or treatment-induced phenotype, and accurate characterization of such delays is imperative. Despite this, the only way at present to identify and quantify these delays is through manual observation, which is both time-consuming and subjective. Machine learning approaches in biology are rapidly becoming part of the toolkit used by researchers to address complex questions. In this work, we introduce a machine learning-based classifier that has been trained to detect temporal developmental differences across groups of zebrafish embryos. Our classifier is capable of rapidly analyzing thousands of images, allowing comparisons of developmental temporal rates to be assessed across and between experimental groups of embryos. Finally, as our classifier uses images obtained from a standard live-imaging widefield microscope and camera set-up, we envisage it will be readily accessible to the zebrafish community, and prove to be a valuable resource.

Automated staging of zebrafish embryos using machine learning

The zebrafish (Danio rerio), is an important biomedical model organism used in many disciplines, including development, disease modeling and toxicology, to better understand vertebrate biology. The phenomenon of developmental delay in zebrafish embryos has been widely reported as part of a mutant or treatment-induced phenotype, and accurate characterization of such delays is imperative. Despite this, the only way at present to identify and quantify these delays is through manual observation, which is both time-consuming and subjective. Machine learning approaches in biology are rapidly becoming part of the toolkit used by researchers to address complex questions. In this work, we introduce a machine learning-based classifier that has been trained to detect temporal developmental differences across groups of zebrafish embryos. Our classifier is capable of rapidly analyzing thousands of images, allowing comparisons of developmental temporal rates to be assessed across and between experimental groups of embryos. Finally, as our classifier uses images obtained from a standard live-imaging widefield microscope and camera set-up, we envisage it will be readily accessible to the zebrafish community, and prove to be a valuable resource.

Developmental Toxicity of Surface-Modified Gold Nanorods in the Zebrafish Model

BACKGROUND

nanotechnology is one of the fastest-growing areas, and it is expected to have a substantial economic and social impact in the upcoming years. Gold particles (AuNPs) offer an opportunity for wide-ranging applications in diverse fields such as biomedicine, catalysis, and electronics, making them the focus of great attention and in parallel necessitating a thorough evaluation of their risk for humans and ecosystems. Accordingly, this study aims to evaluate the acute and developmental toxicity of surface-modified gold nanorods (AuNRs), on zebrafish (Danio rerio) early life stages.

METHODS

in this study, zebrafish embryos were exposed to surface-modified AuNRs at concentrations ranging from 1 to 20 μg/mL. Lethality and developmental endpoints such as hatching, tail flicking, and developmental delays were assessed until 96 h post-fertilization (hpf).

RESULTS

we found that AuNR treatment decreases the survival rate in embryos in a dose-dependent manner. Our data showed that AuNRs caused mortality with a calculated LC50 of EC_50,24hpf of AuNRs being 9.1 μg/mL, while a higher concentration of AuNRs was revealed to elicit developmental abnormalities. Moreover, exposure to high concentrations of the nanorods significantly decreased locomotion compared to untreated embryos and caused a decrease in all tested parameters for cardiac output and blood flow analyses, leading to significantly elevated expression levels of cardiac failure markers ANP/NPPA and BNP/NPPB.

CONCLUSIONS

our results revealed that AuNR treatment at the EC₅₀ induces apoptosis significantly through the P53, BAX/BCL-2, and CASPASE pathways as a suggested mechanism of action and toxicity modality.

Toxicological Profile of Plasmonic Nanoparticles in Zebrafish Model

Plasmonic nanoparticles are increasingly employed in several fields, thanks to their unique, promising properties. In particular, these particles exhibit a surface plasmon resonance combined with outstanding absorption and scattering properties. They are also easy to synthesize and functionalize, making them ideal for nanotechnology applications. However, the physicochemical properties of these nanoparticles can make them potentially toxic, even if their bulk metallic forms are almost inert. In this review, we aim to provide a more comprehensive understanding of the potential adverse effects of plasmonic nanoparticles in zebrafish (Danio rerio) during both development and adulthood, focusing our attention on the most common materials used, i.e., gold and silver.

Zebrafish (Danio rerio) using as model for genotoxicity and DNA repair assessments: Historical review, current status and trends

Genotoxic pollutants lead to both DNA damage and changes in cell repair mechanisms. Selecting suitable biomonitors is a fundamental step in genotoxicity studies. Thus, zebrafish have become a popular model used to assess the genotoxicity of different pollutants in recent years. They have orthologous genes with humans and hold almost all genes involved in different repair pathways. Therefore, the aim of the current study is to summarize the existing literature on zebrafish using as model system to assess the genotoxicity of different pollutants. Revised data have shown that comet assay is the main technique adopted in these studies. However, it is necessary standardizing the technique applied to zebrafish in order to enable better result interpretation and comparisons. Overall, pollutants lead to single-strand breaks (SSB), double-strand breaks (DSB), adduct formation, as well as to changes in the expression of genes involved in repair mechanisms. Although analyzing repair mechanisms is essential to better understand the genotoxic effects caused by pollutants, few studies have analyzed repair capacity. The current review reinforces the need of conducting further studies on the role played by repair pathways in zebrafish subjected to DNA damage. Revised data have shown that zebrafish are a suitable model to assess pollutant-induced genotoxicity.

The aspect ratio of gold nanorods as a cytotoxicity factor on Raphidocelis subcaptata

Gold nanorods (AuNRs) are promising nanoscale materials for several technological and biomedical applications. The physicochemical properties of AuNRs, including size, shape and surface features, are crucial factors affecting their cytotoxicity. In this study, we investigated the effects of different aspect ratios of AuNRs (1.90, 2.35, 3.25 and 3.50) at concentrations of 2 and 10 μg mL^-1 on their cytotoxicity and cellular uptake in green algae Raphidocelis subcaptata. The experiment was performed in oligotrophic freshwater medium in a growth chamber with constant agitation of 80 rpm under controlled conditions (120 μEm^-2s^-1 illumination; 12:12h light dark cycle and constant temperature of 22 ± 2 °C). The algal growth was monitored daily for 96 h via electronic absorbance scanning at 600-750 nm. Oxidative stress, cell viability and autofluorescence were evaluated using a flow cytometer. Oxidative stress quantified by loading cultures with the fluorescent dye 2', 7'-dichlorofluorescein diacetate. To assess algal cell viability, propidium iodide was selected as the fluorescent probe. Our results indicated that the aspect ratio of AuNRs mediates their biological effects in green algae R. subcaptata. A positive correlation between oxidative stress and increase of aspect ratio was found at concentration of 10 μg mL^-1. Higher cytotoxicity and mortality were observed for algae incubated with higher aspect ratios AuNRs (3.50). These findings may be useful to understand the impact of the AuNRs in aquatic environments, contributing to ecosystem management and nanomaterials regulation.

Effect of Gold Nanoparticles and Ions Exposure on the Aquatic Organisms

An increase in the production and usage of gold nanoparticles (AuNPs) triggers the necessity to focus on their impact on ecosystems. Therefore, the purpose of this study was to investigate the acute toxicity of AuNPs and ionic gold (Au (III)) to organisms representing all trophic levels of the aquatic ecosystem, namely producers (duckweed Lemna minor), consumers (crustacean Daphnia magna, embryos of Danio rerio) and decomposers (bacteria Vibrio fischeri). The organisms were exposed according to a standardized protocol for each species and endpoints. The AuNPs (1.16 and 11.6 d.nm) were synthesized using citrate (CIT) and polyvinylpyrrolidone (PVP) as capping agents, respectively. It was found, that Au (III) was significantly more toxic than AuNPs PVP and AuNPs CIT. AuNPs showed significant toxicity only at high concentrations (mg/L), which are not environmentally relevant in the present time, but a cautious approach is advised, due to the possibility of interactions with other contaminants.

Nd2O3 Nanoparticles Induce Toxicity and Cardiac/Cerebrovascular Abnormality in Zebrafish Embryos via the Apoptosis Pathway

Introduction

Rare-earth nanoparticles in the environment and human body pose a potential threat to human health. Although toxic effects of rare-earth nanoparticles have been extensively studied, the effects on the early development are not well understood. In this study, we attempted to explain the toxic effects of neodymium oxide (Nd₂O₃) nanoparticles on early development.

Methods

We added the Nd₂O₃ nanoparticles at different concentrations and recorded the mortality and malformation rate per 24 hrs under a microscope. The live embryos treated with Nd₂O₃ nanoparticles were imaged as movies and Z step lapses with a confocal microscope, and heart rates were counted for 30 s to measure the cardiac function. The live Tg (Flk1:EGFP) transgenic embryos exposed to Nd₂O₃ nanoparticles were observed under confocal microscope to measure the cerebrovascular development. Subsequently, we extracted the total protein for Western blot at 5 days post-fertilisation (dpf). Embryos were collected to undergo TUNEL staining for apoptosis detection.

Results

Nd₂O₃ nanoparticles disturbed embryo development at high concentrations (>200 μg/mL). The mortality and malformation rate gradually increased in a dose-dependent manner by morphological observation, while the Nd₂O₃ median lethal concentration (LD50) was 203.4 μg/mL at 120 hrs post-fertilisation (hpf). Furthermore, the Nd₂O₃-treated embryos showed severe arrhythmia and reduced heart rate. We also observed the markedly cerebrovascular disappearance at middle concentration (100 and 200 μg/mL). The downregulated autophagy flux in brain blood vessels and increased apoptosis level in neurons might affect vessels sprouting and contribute to the vanished cerebrovascular.

Conclusion

The results suggested that the embryos exposed to Nd₂O₃ activated the apoptosis pathway and induced toxicity and abnormal cardiac/cerebrovascular development.

Effects of long-term exposure to colloidal gold nanorods on freshwater microalgae

Gold nanorods have shown to pose adverse effects to biota. Whether these effects may be potentiated through prolonged exposure has been rarely studied. Therefore, this work aimed at evaluating the effects of long-term exposure to sublethal levels of cetyltrimethylammonium bromide (CTAB) coated gold nanorods (Au-NR) on two freshwater microalgae: Chlorella vulgaris and Raphidocelis subcapitata. These algae were exposed to several concentrations of Au-NR for 72 h and, afterwards, to the corresponding EC_5,72h, for growth, during 16 days. The sensitivity of the two algae to Au-NR was assessed at days 0, 4, 8, 12 and 16 (D0, D4, D8, D12 and D16, respectively) after a 72-h exposure to several concentrations of Au-NR. At the end of the assays, effects on yield and population growth rate were evaluated. Raphidocelis subcapitata was slightly more sensitive to Au-NR than C. vulgaris: EC_50,72h,D0 for yield were 48.1 (35.3-60.9) and 70.5 (52.4-88.6) μg/L Au-NR, respectively while for population growth rate were above the highest tested concentrations (53 and 90 μg/L, respectively). For R. subcapitata the long-term exposure to Au-NR increased its sensitivity to this type of nanostructures. For C. vulgaris, a decrease on the effects caused by Au-NR occurred over time, with no significant effects being observed for yield or population growth rate at D12 and D16. The capping agent CTAB caused reductions in yield above 30% (D0) for both algae at the concentration matching the one at the highest Au-NR tested concentration. When exposed to CTAB, the highest inhibition values were 69% (D4) and 21.3% (D8) for R. subcapitata, and 64% (D12) and 21% (D16) to C. vulgaris, for yield and population growth rate, respectively. These results suggested long-term exposures should be included in ecological risk assessments since short-term standard toxicity may either under- or overestimate the risk posed by Au-NR.

The biodistribution and immuno-responses of differently shaped non-modified gold particles in zebrafish embryos

Important questions raised in (nano)ecotoxicology are whether biodistribution of nanoparticles (NPs) is affected by particle shape and to what extent local adverse responses are subsequently initiated. For nanomedicine, these same questions become important when the labeled NPs lose the labeling. In this study, we investigated the biodistribution patterns of gold nanoparticles (AuNPs) as well as immune-related local and systemic sublethal markers of exposure and behavioral assessment. Hatched zebrafish embryos were exposed to four differently shaped non-coated AuNPs with comparable sizes: nanospheres, nanorods, nano-urchins, and nano-bipyramids. Shape-dependent trafficking of the particles resulted in a different distribution of the particles over the target organs. The differences across the distribution patterns indicate that the particles behave slightly different, although they eventually reach the same target organs - yet in different ratios. Mainly local induction of the immune system was observed, whereas systemic immune responses were not clearly visible. Macrophages were found to take AuNPs from the body fluid, be transferred into the veins and transported to digestive organs for clearance. No significant behavioral toxicological responses in zebrafish embryos were observed after exposure. The trafficking of the particles in the macrophages indicates that the particles are removed via the mononuclear phagocytic system. The different ratios in which the particles are distributed over the target organs indicate that the shape influences their behavior and eventually possibly the toxicity of the particles. The observed shape-dependent biodistribution patterns might be beneficial for shape-specific targeting in nanomedicine and stress the importance of incorporating shape-features in nanosafety assessment.

In vitro genotoxicity assessment of an oxidized dextrin-based hydrogel for biomedical applications

Hydrogels are three-dimensional, crosslinked networks of hydrophilic polymers swollen with a large amount of water or biological fluids, without dissolving. Dextrin, a low-molecular-weight carbohydrate composed by glucose residues, has been used to develop an injectable hydrogel for biomedical applications. Dextrin was first oxidized to introduce aldehyde groups, which then reticulate with adipic acid dihydrazide, forming the dextrin-based hydrogel (HG). The HG and its components were tested for cyto- and genotoxicity according to the International Standard ISO 10993-3 on the biological evaluation of medical devices. To assess genotoxicity, a battery of in vitro genotoxicity tests employing both eukaryotic and prokaryotic models was performed: comet assay, cytokinesis-block micronucleus assay and Ames test. Our data revealed that the HG (IC₅₀  = 2.8 mg/mL) and oxidized dextrin by itself (IC₅₀  = 1.2 mg/mL) caused a concentration-dependent decrease in cellular viability of human lymphoblastoid TK6 cells after 24 hours of exposure to the test agents. However, these concentrations are unlikely to be reached in vivo. In addition, no significant increase in the DNA and chromosomal damage of TK6 cells exposed to non-cytotoxic concentrations of the HG and its isolated components was detected. Furthermore, neither the HG nor its metabolites exerted a mutagenic effect in different of Salmonella typhimurium strains and in an Escherichia coli mix. Our data demonstrated the genocompatibility of the HG (up to 3.5 mg/mL) for biomedical applications. To our best acknowledge, this is the first report with a detailed genotoxicity assessment of an aldehyde-modified polysaccharide/adipic acid dihydrazide hydrogel.

In vitro and in vivo toxicity evaluation of halloysite nanotubes

Because of their outstanding properties, increasing numbers of research studies and emerging applications for manufacturing products are currently in progress for halloysite nanotubes (HNTs). Therefore, the impact of HNTs on the environment and human health should be taken into consideration. In order to clearly show the cell uptake of HNTs and the biodistribution of HNTs in zebrafish, HNTs are labeled with fluorescein isothiocyanate (FITC-HNTs). The cytotoxicity assays showed that the cell viabilities of human umbilical vein endothelial cells (HUVECs) and human breast adenocarcinoma (MCF-7) cells were above 60% after being treated with different concentrations of HNTs (2.5-200 μg mL^-1) for 72 h. Confocal laser scanning microscopy (CLSM) results showed the uptake of HNTs by HUVECs and MCF-7 cells. The in vivo toxicity of HNTs was then investigated in the early development of zebrafish embryos. The percent survival of zebrafish embryos and larvae showed no significant changes at different developmental stages (24, 48, 72, 96, and 120 hpf) when treated with various concentrations of HNTs (0.25-10 mg mL^-1). Besides, HNTs could promote the hatchability of zebrafish embryos and did not affect the morphological development of zebrafish at a concentration of ≤25 mg mL^-1. HNTs could also be ingested by zebrafish larvae and accumulated predominantly in the gastrointestinal tract. The fluorescence intensity of FITC-HNTs decreased gradually with time, which suggested that HNTs could be excreted by zebrafish larvae through the gastrointestinal metabolism. Therefore, it can be concluded that HNTs are relatively biocompatible nanomaterials, which can be utilized in many fields.

Ractopamine hydrochloride induces behavioral alterations and oxidative status imbalance in zebrafish

The occurrence of ractopamine (RAC) hydrochloride in water bodies is of significant concern due to its ecological impacts and toxicity to humans. RAC hydrochloride is a β-adrenergic agonist drug used as a feed additive to (1) improve feed efficiency, (2) rate of weight gain, and (3) increase carcass leanness in animals raised for their meat. This drug is excreted by animals in urine and introduced into the environment affecting nontarget organisms including fish. In wastewater released from farms, RAC concentrations were detected from 0.124 µg/L to 30.1 µg/L, and in levels ranging from 1.3 × 10^-5 to 5.4 × 10^-4 μg/L in watersheds. The aim of this study was to examine the effects of exposure to RAC at 0.1, 0.2, 0.85, 8.5, or 85 µg/L dissolved in water on behavior and oxidative status in adult zebrafish. At 0.85 µg/L, RAC treatment increased exploratory behavior of zebrafish; while at 8.5 µg/L, decreased locomotor and exploratory activities were noted. With respect to oxidative stress biomarkers, results showed that RAC at 0.2 µg/L induced lipid peroxidation and elevated total thiol content in zebrafish brain. All drug tested concentrations produced a fall in nonprotein thiol content. Finally, RAC at 0.85, 8.5, or 85 µg/L increased catalase enzyme activity. Our results demonstrated that the exposure to RAC induced behavioral alterations and oxidative stress in zebrafish.