Neutral red retention time assay in determination of toxicity of nanoparticles

An Overview of the Current State of Cell Viability Assessment Methods Using OECD Classification

Over the past century, numerous methods for assessing cell viability have been developed, and there are many different ways to categorize these methods accordingly. We have chosen to use the Organisation for Economic Co-operation and Development (OECD) classification due to its regulatory importance. The OECD categorizes these methods into four groups: non-invasive cell structure damage, invasive cell structure damage, cell growth, and cellular metabolism. Despite the variety of cell viability methods available, they can all be categorized within these four groups, except for two novel methods based on the cell membrane potential, which we added to the list. Each method operates on different principles and has its own advantages and disadvantages, making it essential for researchers to choose the method that best fits their experimental design. This review aims to assist researchers in making this decision by describing these methods regarding their potential use and providing direct references to the cell viability assessment methods. Additionally, we use the OECD classification to facilitate potential regulatory use and to highlight the need for adding a new category to their list.

Investigation of a broad diversity of nanoparticles, including their processes, as well as toxicity testing in diverse organs and systems

Nanotechnology arising in wide-ranging areas, covers extensively different ranges of approaches attained from fields such as biology, chemistry, physics, and medicine engineering. Nanoparticles are a necessary part of nanotechnology effectually applied in the cure of a number of diseases. Nanoparticles have gained significant importance due to their unique properties, which differ from their bulk counterparts. These distinct properties of nanoparticles are primarily influenced by their morphology, size, and size distribution. At the nanoscale, nanoparticles exhibit behaviours that can enhance therapeutic efficacy and reduce drug toxicity. Their small size and large surface area make them promising candidates for applications such as targeted drug delivery, where they can improve treatment outcomes while minimizing adverse effects. The harmful effects of nanoparticles on the environment were critically investigated to obtain appropriate results and reduce the risk by incorporating the materials. Nanoparticles tend to penetrate the human body, clear the biological barriers to reach sensitive organs and are easily incorporated into human tissue, as well as dispersing to the hepatic tissues, heart tissues, encephalum, and GI tract. This study aims to examine a wide variety of nanoparticles, focusing on their manufacturing methods, functional characteristics, and interactions within biological systems. Particular attention will be directed towards assessing the toxicity of nanoparticles in different organs and physiological systems, yielding a thorough comprehension of their potential health hazards and the processes that drive nanoparticle-induced toxicity. This analysis will also emphasize recent developments in nanoparticle applications and safety assessment methodologies.

Quantitative Phase Imaging as Sensitive Screening Method for Nanoparticle-Induced Cytotoxicity Assessment

The assessment of nanoparticle cytotoxicity is challenging due to the lack of customized and standardized guidelines for nanoparticle testing. Nanoparticles, with their unique properties, can interfere with biochemical test methods, so multiple tests are required to fully assess their cellular effects. For a more reliable and comprehensive assessment, it is therefore imperative to include methods in nanoparticle testing routines that are not affected by particles and allow for the efficient integration of additional molecular techniques into the workflow. Digital holographic microscopy (DHM), an interferometric variant of quantitative phase imaging (QPI), has been demonstrated as a promising method for the label-free assessment of the cytotoxic potential of nanoparticles. Due to minimal interactions with the sample, DHM allows for further downstream analyses. In this study, we investigated the capabilities of DHM in a multimodal approach to assess cytotoxicity by directly comparing DHM-detected effects on the same cell population with two downstream biochemical assays. Therefore, the dry mass increase in RAW 264.7 macrophages and NIH-3T3 fibroblast populations measured by quantitative DHM phase contrast after incubation with poly(alkyl cyanoacrylate) nanoparticles for 24 h was compared to the cytotoxic control digitonin, and cell culture medium control. Viability was then determined using a metabolic activity assay (WST-8). Moreover, to determine cell death, supernatants were analyzed for the release of the enzyme lactate dehydrogenase (LDH assay). In a comparative analysis, in which the average half-maximal effective concentration (EC50) of the nanocarriers on the cells was determined, DHM was more sensitive to the effect of the nanoparticles on the used cell lines compared to the biochemical assays.

Size-dominated biotoxicity of microplastics laden with benzophenone-3 and ciprofloxacin: Enhanced integrated biomarker evaluation on mussels

Microplastics (MPs) are emerging pollutants with diverse sizes in aquatic environments. This paper investigates the toxicity of micron- and nano-scale polystyrene (50 μm, 5 μm, 0.5 μm) loaded with 2-hydroxy-4-methoxy-benzophenone (BP-3) and ciprofloxacin (CIP) by eight biomarker responses in mussels, perna viridis. The mussels were exposed to MPs and chemicals for 7 days before 7 days of depuration. Eight biomarkers were measured to determine biotoxicity over time by using the weighted integrated biomarkers index evaluation (EIBR). Mussels exposed to MPs on a daily basis demonstrated a cumulative toxic effect. The toxicity of MPs for mussels was inversely related to the size at which they can be ingested. Then toxicity was reversed when exposure was halted. EIBR mold has shown a significant difference in the biotoxicity of each biological level under different exposure scenarios. In general, the mussel toxicity influenced by BP-3 and CIP exposure without an adsorbent was insignificant. MPs laden with them increased the toxicity of mussels. Under condition of lower concentration of ECs (Emerging contaminants), the presence of MPs as a component of a combined pollutant in water dominated the biotoxicity for mussels. The EIBR assessment further validated that the biotoxicity of mussels was size-dependent. Its application simplified the biomarkers' response index and enhanced the accuracy of evaluation by weighing on molecular, cellular and physiological level. Specifically, mussels were physiologically sensitive to nano-scale plastics, with nano-scale plastics causing a higher level of cellular immunity destruction and genotoxicity than micron-scale plastics. Enzymatic antioxidant systemswere upregulated based on size-differential plastics; however, the total antioxidant effect of non-enzymatic defenses appeared to be least affected by the size effect.

Low dose γ-radiation induced effects on wax moth (Galleria mellonella) larvae

Larvae of the greater wax moth Galleria mellonella are common pests of beehives and commercial apiaries, and in more applied settings, these insects act as alternative in vivo bioassays to rodents for studying microbial virulence, antibiotic development, and toxicology. In the current study, our aim was to assess the putative adverse effects of background gamma radiation levels on G. mellonella. To achieve this, we exposed larvae to low (0.014 mGy/h), medium (0.056 mGy/h), and high (1.33 mGy/h) doses of caesium-137 and measured larval pupation events, weight, faecal discharge, susceptibility to bacterial and fungal challenges, immune cell counts, activity, and viability (i.e., haemocyte encapsulation) and melanisation levels. The effects of low and medium levels of radiation were distinguishable from the highest dose rates used - the latter insects weighed the least and pupated earlier. In general, radiation exposure modulated cellular and humoral immunity over time, with larvae showing heightened encapsulation/melanisation levels at the higher dose rates but were more susceptible to bacterial (Photorhabdus luminescens) infection. There were few signs of radiation impacts after 7 days exposure, whereas marked changes were recorded between 14 and 28 days. Our data suggest that G. mellonella demonstrates plasticity at the whole organism and cellular levels when irradiated and offers insight into how such animals may cope in radiologically contaminated environments (e.g. Chornobyl Exclusion Zone).

Impacts of size-fractionation on toxicity of marine microplastics: Enhanced integrated biomarker assessment in the tropical mussels, Perna viridis

Accumulation of microplastics (MP) in oceanic waters is eroding the health of marine biota. We investigated how size-fractionated MP influence the toxicity risks towards a tropical keystone species, Perna viridis. Tissue-specific bioaccumulation and in vivo toxicity of polystyrene (PS) particles (0.5, 5, and 50 μm) were measured upon continuous exposure for 7 days, followed by 7 days depuration. P. viridis were exposed to equivalent mass (0.6 mg/L), corresponding to 4.0-4.6 particles/mL, 4.6-7.1 × 10³ particles/mL, and 1.1-4.8 × 10⁶ particles/mL for 50 μm, 5 μm and 0.5 μm PS particles, respectively. Onset toxicity were quantified through the enhanced integrated multi-biomarker response (EIBR) model, measured by weighting of biological organisation levels of eight biomarkers: (i) molecular (i.e., DNA damage (comet), 7-ethoxy resorufin O-deethylase (EROD), Catalase (CAT), Superoxide dismutase (SOD), Ferric Reducing Antioxidant Power (FRAP)); (ii) cellular (i.e., Neutral red retention (NRR), phagocytosis); and (iii) physiological (i.e., filtration rate). Data showed slightly elevated lysosomal instability (NRR) and antioxidant defences (FRAP, SOD, CAT, EROD) in specimens exposed to nano-PS (0.5 μm) compared to micro-PS (5 and 50 μm). Immunotoxicity (phagocytosis) and genotoxicity (comet) for haemocyte cells were significantly higher in specimens exposed to nano-PS (p < 0.05). EIBR index corroborated increasing toxicity modulated by MP sizes in descending order: 0.5 μm > 5 μm > 50 μm, with nano-PS exerted significantly higher biological effects (EIBR = 19.77 ± 5.89) than the unexposed group (EIBR = 10.97 ± 2.02; p < 0.05). Symptomatic organismal depression was manifested by the depleting filtering proficiency and weakened defence against invasive Zymosan bioparticles in the phagocytosis assay. Although impaired mussels duly recovered during depuration, individuals affected by nano-PS showed immunocompetence deficiency and gill responses that were not readily reversible, which could potentially increase their vulnerability towards further environmental stressors.

Review: Mytilus galloprovincialis: An essential, low-cost model organism for the impact of xenobiotics on oxidative stress and public health

The level of pollution becomes more and more of a pressuring matter for humankind at a worldwide level. Often the focus is on the effects that we can directly and see such as decreased air quality and higher than normal temperatures and weather, but the effects we cannot see are frequently overlooked. For at least the past decade increasing importance has been given towards the effects of pollution of living animals or non-target organisms and plants. For this purpose, one model animal that surfaced is the purpose, one model animal surfaced is Mytilus galloprovincialis. As all mussels, this species is capable of bio-accumulating important quantities of different xenobiotics such as pesticides, paints, medicines, heavy metals, industrial compounds, and even compounds marketed as antioxidants and antivirals. Their toxic effects can be assessed through their impact on oxidative stress, lysosomal membrane stability, and cell viability through trypan blue exclusion test and neutral red retention assay techniques. The purpose of this paper is to highlight the benefits of using M. galloprovincialis as an animal model for toxicological assays of various classes of xenobiotics by bringing to light the studies that have approached the matter.

Environmental Fate of Metal Nanoparticles in Estuarine Environments

In the last decade, metal engineered nanomaterials (ENMs) have seen an exponential use in many critical technologies and products, as well an increasing release into the environment. Coastal ecosystems worldwide may receive ENM-polluted waters and wastes, with a consequent alteration of habitats and contamination of aquatic biota. There is a scarcity of data regarding the fate of these emerging contaminants in such environments. Open issues include the determination of the sources, the quantification of the interactions with marine sediments, the bioaccumulation pathways, the ecotoxicology on marine fauna and the identification of the principal biotic and abiotic factors that may alter metal ENMs toxicity. Little is known about their potential transference into the food web, as well toxicity features and co-stressors of single or multiple ENMs under laboratory and real environmental conditions for various taxonomic phyla. This review reports current knowledge on the ecological impact of ENMs under the complex environmental conditions of estuary systems, identifies gaps in current knowledge and provides directions for future research.

Effect of micro- and nanoparticle shape on biological processes

In the drug delivery field, there is beyond doubt that the shape of micro- and nanoparticles (M&NPs) critically affects their biological fate. Herein, following an introduction describing recent technological advances for designing nonspherical M&NPs, we highlight the role of particle shape in cell capture, subcellular distribution, intracellular drug delivery, and cytotoxicity. Then, we discuss theoretical approaches for understanding the effect of particle shape on internalization by the cell membrane. Subsequently, recent advances on shape-dependent behaviors of M&NPs in the systemic circulation are detailed. In particular, the interaction of M&NPs with blood proteins, biodistribution, and circulation under flow conditions are analyzed. Finally, the hurdles and future directions for developing nonspherical M&NPs are underscored.

A Review on Conventional and Advanced Methods for Nanotoxicology Evaluation of Engineered Nanomaterials

Nanotechnology can be defined as the field of science and technology that studies material at nanoscale (1-100 nm). These nanomaterials, especially carbon nanostructure-based composites and biopolymer-based nanocomposites, exhibit excellent chemical, physical, mechanical, electrical, and many other properties beneficial for their application in many consumer products (e.g., industrial, food, pharmaceutical, and medical). The current literature reports that the increased exposure of humans to nanomaterials could toxicologically affect their environment. Hence, this paper aims to present a review on the possible nanotoxicology assays that can be used to evaluate the toxicity of engineered nanomaterials. The different ways humans are exposed to nanomaterials are discussed, and the recent toxicity evaluation approaches of these nanomaterials are critically assessed.

Recent Advances in the Use of Iron-Gold Hybrid Nanoparticles for Biomedical Applications

Recently, there has been an increased interest in iron-gold-based hybrid nanostructures, due to their combined outstanding optical and magnetic properties resulting from the usage of two separate metals. The synthesis of these nanoparticles involves thermal decomposition and modification of their surfaces using a variety of different methods, which are discussed in this review. In addition, different forms such as core-shell, dumbbell, flower, octahedral, star, rod, and Janus-shaped hybrids are discussed, and their unique properties are highlighted. Studies on combining optical response in the near-infrared window and magnetic properties of iron-gold-based hybrid nanoparticles as multifunctional nanoprobes for drug delivery, magnetic-photothermal heating as well as contrast agents during magnetic and optical imaging and magnetically-assisted optical biosensing to detect traces of targeted analytes inside the body has been reviewed.

Biochemical toxicity, lysosomal membrane stability and DNA damage induced by graphene oxide in earthworms

With the growing production and use of carbon nanomaterials (CNMs), the risk of their releases to the environment has drawn much attention. However, their potential effect on soil invertebrates has not yet been systematically assessed. Herein, the toxic effects of graphene oxide (GO) on earthworms (Eisenia fetida) were thoroughly investigated. Exposure to different doses of GO (0, 5, 10, 20, and 30 g kg^-1) was conducted for 7, 14, 21, and 28 days. The results showed that enzymatic activity was stimulated at the early stages of exposure (7 days and 14 days) and inhibited after 14 days for catalase (CAT) and after 21 days for peroxidase (POD) and superoxide dismutase (SOD), especially at high GO doses. The content of MDA showed an increasing trend over the whole exposure period and was significantly elevated by GO from 21 days except at the dose of 5 g kg^-1on day 21. Lysosomal membrane stability and DNA damage presented dose- and time-dependent relationships. Graphene oxide remarkably decreased lysosomal membrane stability except at the dose of 5 g kg^-1 on day 7. The tail DNA%, tail length and olive tail moment increased with increasing GO dose throughout the exposure duration, reaching maximum values at the end of exposure (28 days). These findings suggest that GO induces oxidative stress and genotoxicity in Eisenia fetida, resulting in lipid peroxidation, decreased lysosomal membrane stability and DNA damage. Therefore, attention should be paid to the potential pollution and risk associated with graphene oxide application. The results can provide valuable information for environmental safety assessment of graphene nanomaterials in soil.

Microplastics, microfibres and nanoplastics cause variable sub-lethal responses in mussels (Mytilus spp.)

We compare the toxicity of microplastics, microfibres and nanoplastics on mussels. Mussels (Mytilus spp.) were exposed to 500 ng mL-1 of 20 μm polystyrene microplastics, 10 × 30 μm polyamide microfibres or 50 nm polystyrene nanoplastics for 24 h or 7 days. Biomarkers of immune response, oxidative stress response, lysosomal destabilisation and genotoxic damage were measured in haemolymph, digestive gland and gills. Microplastics and microfibres were observed in the digestive glands, with significantly higher plastic concentrations after 7-days exposure (ANOVA, P < 0.05). Nanoplastics had a significant effect on hyalinocyte-granulocyte ratios (ANOVA, P < 0.05), indicative of a heightened immune response. SOD activity was significantly increased followed 24 h exposure to plastics (two-way ANOVA, P < 0.05), but returned to normal levels after 7-days exposure. No evidence of lysosomal destabilisation or genotoxic damage was observed from any form of plastic. The study highlights how particle size is a key factor in plastic particulate toxicity.

Insights into the toxicity of iron oxides nanoparticles in land snails

The use of manufactured nanoparticles (NPs) is spreading rapidly across technology and medicine fields, posing concerns about their consequence on ecosystems and human health. The present study aims to assess the biological responses triggered by iron oxide NPs (IONPs) and iron oxide NPs incorporated into zeolite (IONPZ) in relation to oxidative stress on the land snail Helix aspersa in order to investigate its use as a biomarker for terrestrial environments. Morphology and structure of both NPs were characterized. Snail food was supplemented with a range of concentrations of IONPs and IONPZ and values of the hemocyte lysosomal membranes' destabilization by 50% were estimated by the neutral red retention (NRRT50) assay. Subsequently, snails were fed with NPs concentrations equal to half of the NRRT50 values, 0.05 mg L^-1 for IONPs and 1 mg L^-1 for IONPZ, for 1, 5, 10 and 20 days. Both effectors induced oxidative stress in snails' hemocytes compared to untreated animals. The latter was detected by NRRT changes, reactive oxygen species (ROS) production, lipid peroxidation estimation, DNA integrity loss, measurement of protein carbonyl content by an enzyme-linked immunoabsorbent assay (ELISA), determination of ubiquitin conjugates and cleaved caspases conjugates levels. The results showed that the simultaneous use of the parameters tested could constitute possible reliable biomarkers for the evaluation of NPs toxicity. However, more research is required in order to enlighten the disposal and toxic impact of iron oxide NPs on the environment to ensure their safe use in the future.