Toxicological assessment of mesoporous silica particles in the nematode Caenorhabditis elegans

Evaluating the adverse effects and mechanisms of nanomaterial exposure on longevity of C. elegans: A literature meta-analysis and bioinformatics analysis of multi-transcriptome data

Exposure to large-size particulate air pollution (PM2.5 or PM10) has been reported to increase risks of aging-related diseases and human death, indicating the potential pro-aging effects of airborne nanomaterials with ultra-fine particle size (which have been widely applied in various fields). However, this hypothesis remains inconclusive. Here, a meta-analysis of 99 published literatures collected from electronic databases (PubMed, EMBASE and Cochrane Library; from inception to June 2023) was performed to confirm the effects of nanomaterial exposure on aging-related indicators and molecular mechanisms in model animal C. elegans. The pooled analysis by Stata software showed that compared with the control, nanomaterial exposure significantly shortened the mean lifespan [standardized mean difference (SMD) = -2.30], reduced the survival rate (SMD = -4.57) and increased the death risk (hazard ratio = 1.36) accompanied by upregulation of ced-3, ced-4 and cep-1, while downregulation of ctl-2, ape-1, aak-2 and pmk-1. Furthermore, multi-transcriptome data associated with nanomaterial exposure were retrieved from Gene Expression Omnibus (GSE32521, GSE41486, GSE24847, GSE59470, GSE70509, GSE14932, GSE93187, GSE114881, and GSE122728) and bioinformatics analyses showed that pseudogene prg-2, mRNAs of abu, car-1, gipc-1, gsp-3, kat-1, pod-2, acdh-8, hsp-60 and egrh-2 were downregulated, while R04A9.7 was upregulated after exposure to at least two types of nanomaterials. Resveratrol (abu, hsp-60, pod-2, egrh-2, acdh-8, gsp-3, car-1, kat-1, gipc-1), naringenin (kat-1, egrh-2), coumestrol (egrh-2) or swainsonine/niacin/ferulic acid (R04A9.7) exerted therapeutic effects by reversing the expression levels of target genes. In conclusion, our study demonstrates the necessity to use phytomedicines that target hub genes to delay aging for populations with nanomaterial exposure.

Prospects and hazards of silica nanoparticles: Biological impacts and implicated mechanisms

With the thrive of nanotechnology, silica nanoparticles (SiNPs) have been extensively adopted in the agriculture, food, cosmetic, and even biomedical industries. Due to the mass production and use, SiNPs inevitably entered the environment, resulting in ecological toxicity and even posing a threat to human health. Although considerable investigations have been conducted to assess the toxicity of SiNPs, the correlation between SiNPs exposure and consequent health risks remains ambiguous. Since the biological impacts of SiNPs can differ from their design and application, the toxicity assessment for SiNPs may be extremely difficult. This review discussed the application of SiNPs in different fields, especially their biomedical use, and documented their potential release pathways into the environment. Meanwhile, the current process of assessing SiNPs-related toxicity on various model organisms and cell lines was also detailed, thus estimating the health threats posed by SiNPs exposure. Finally, the potential toxic mechanisms of SiNPs were also elaborated based on results obtained from both in vivo and in vitro trials. This review generally summarizes the biological effects of SiNPs, which will build up a comprehensive perspective of the application and toxicity of SiNPs.

In vivo toxicity assessment of eugenol and vanillin-functionalised silica particles using Caenorhabditis elegans

The toxicological properties of different silica particles functionalised with essential oil components (EOCs) were herein assessed using the in vivo model C. elegans. In particular, the effects of the acute and long-term exposure to three silica particle types (SAS, MCM-41 micro, MCM-41 nano), either bare or functionalised with eugenol or vanillin, were evaluated on different biological parameters of nematodes. Acute exposure to the different particles did not reduce nematodes survival, brood growth or locomotion, but reproduction was impaired by all the materials, except for vanillin-functionalised MCM-41 nano. Moreover, long-term exposure to particles led to strongly inhibited nematodes growth and reproduction. The eugenol-functionalised particles exhibited higher functionalisation yields and had the strongest effects during acute and long-term exposures. Overall, the vanillin-functionalised particles displayed milder acute toxic effects on reproduction than pristine materials, but severer toxicological responses for the 96-hour exposure assays. Our findings suggest that the EOC type anchored to silica surfaces and functionalisation yield are crucial for determining the toxicological effects of particles on C. elegans. The results obtained with this alternative in vivo model can help to anticipate potential toxic responses to these new materials for human health and the environment.

Effects of essential oil components exposure on biological parameters of Caenorhabditis elegans

The extensive use of essential oil components in an increasing number of applications can substantially enhance exposure to these compounds, which leads to potential health and environmental hazards. This work aimed to evaluate the toxicity of four widely used essential oil components (carvacrol, eugenol, thymol, vanillin) using the in vivo model Caenorhabditis elegans. For this purpose, the LC₅₀ value of acute exposure to these components was first established; then the effect of sublethal concentrations on nematodes' locomotion behaviour, reproduction, heat and oxidative stress resistance and chemotaxis was evaluated. The results showed that all the components had a concentration-dependent effect on nematode survival at moderate to high concentrations. Carvacrol and thymol were the two most toxic compounds, while vanillin had the mildest toxicological effect. Reproduction resulted in a more sensitive endpoint than lethality to evaluate toxicity. Only pre-exposure to carvacrol and eugenol at the highest tested sublethal concentrations conferred worms oxidative stress resistance. However, at these and lower concentrations, both components induced reproductive toxicity. Our results evidence that these compounds can be toxic at lower doses than those required for their biological action. These findings highlight the need for a specific toxicological assessment of every EOC application.

Research Advances on the Adverse Effects of Nanomaterials in a Model Organism, Caenorhabditis elegans

Along with the rapid development of nanotechnology, the biosafety assessment of nanotechnology products, including nanomaterials (NMs), has become more and more important. The nematode Caenorhabditis elegans is a valuable model organism that has been widely used in the field of biology because of its excellent advantages, including low cost, small size, short life span, and highly conservative genomes with vertebral animals. In recent years, the number of nanotoxicological researchers using C. elegans has been growing. According to these available studies, the present review classified the adverse effects of NMs in C. elegans into systematic, cellular, and molecular toxicity, and focused on summarizing and analyzing the underlying mechanisms of metal, metal oxide, and nonmetallic NMs causing toxic effects in C. elegans. Our findings provide insights into what further studies are needed to assess the biosafety of NMs in the ecosystem using C. elegans. Environ Toxicol Chem 2021;40:2406-2424. © 2021 SETAC.

Fecal microbiota transplantation attenuates nano-plastics induced toxicity in Caenorhabditis elegans

Current studies simply focus on the toxicity of nano-plastics, while the correlation between their toxicity and bio-distribution, as well as intestinal microorganisms is still blank. Therefore, we systematically evaluated the toxicity based on the accumulation characteristics of nano-plastics in C. elegans. Meanwhile, for the first time, human fecal microbiota was transplanted into the gut of C. elegans and found that nano-plastics can through the intestinal barrier to the whole body after oral intake and can't be drastically excreted until die, thus causing toxic effects; while human fecal microbiota transplantation can significantly improve the living state via activating PMK-1/SKN-1 pathway to promote the production of intracellular glutathione, and exogenous glutathione addition can also markedly protect nematodes against nano-plastics induced toxicity. Our results not only provide a fully understand between the accumulation characteristic and health risk of nano-plastics, but also take C. elegans and intestinal flora into the field of toxicity evolution of nanomaterials.

In Vitro and In Vivo Models for Evaluating the Oral Toxicity of Nanomedicines

Toxicity studies for conventional oral drug formulations are standardized and well documented, as required by the guidelines of administrative agencies such as the US Food & Drug Administration (FDA), the European Medicines Agency (EMA) or European Medicines Evaluation Agency (EMEA), and the Japanese Pharmaceuticals and Medical Devices Agency (PMDA). Researchers tend to extrapolate these standardized protocols to evaluate nanoformulations (NFs) because standard nanotoxicity protocols are still lacking in nonclinical studies for testing orally delivered NFs. However, such strategies have generated many inconsistent results because they do not account for the specific physicochemical properties of nanomedicines. Due to their tiny size, accumulated surface charge and tension, sizeable surface-area-to-volume ratio, and high chemical/structural complexity, orally delivered NFs may generate severe topical toxicities to the gastrointestinal tract and metabolic organs, including the liver and kidney. Such toxicities involve immune responses that reflect different mechanisms than those triggered by conventional formulations. Herein, we briefly analyze the potential oral toxicity mechanisms of NFs and describe recently reported in vitro and in vivo models that attempt to address the specific oral toxicity of nanomedicines. We also discuss approaches that may be used to develop nontoxic NFs for oral drug delivery.

Toxicity evaluation of barium ferrite nanoparticles in bacteria, yeast and nematode

Barium ferrite nanoparticles (BaFeNPs) are a permanent magnetic nanomaterial widely used in electrical energy storage, recording media or in the improvement of the magnetic properties of other nanoparticles (NPs). However, the information about the toxicity of BaFeNPs is almost non-existent. Thus, in the present work, the antimicrobial effect of BaFeNPs was evaluated for the first time in gram-negative and gram-positive bacteria and yeast showing neither antibacterial nor antifungal activity at moderate concentrations. On the other hand, in order to assess the in vivo toxicity of BaFeNPs the model organism Caenorhabditis elegans was used and ingestion, survival, reproduction and ROS production were evaluated in worms treated with different concentrations of BaFeNPs. Our results show that worms ingest these NPs through the digestive system affecting survival, reproduction and ROS production.

Mesoporous Silica Nanoparticles at Predicted Environmentally Relevant Concentrations Cause Impairments in GABAergic Motor Neurons of Nematode Caenorhabditis elegans

Available safety evaluations regarding mesoporous silica nanoparticles (mSiNPs) are based on the assumption of a relatively high exposure concentration, which makes the findings less valuable in a realistic environment. In this study, we employed Caenorhabditis elegans (C. elegans) as a model to assess the neuronal damage caused by mSiNPs at the predicted environmentally relevant concentrations. After nematodes were acute and prolonged exposed to mSiNPs at concentrations over 300 μg/L, locomotion degeneration, shrinking behavior, and abnormal foraging behavior were observed, which were associated with the deficits in the development of GABAergic neurons, including D-type and RME motor neurons. Furthermore, the oxidative stress evidenced by excessive ROS generation might contribute to the mechanism of mSiNPs damaging neurons. Although the neurotoxicity of mSiNPs was weaker than (nonmesoporous) SiNPs, it is still necessary for researchers to pay attention to the adverse effects caused by mSiNPs in the environmental animals, especially with the rapid increase in mSiNPs application. Considering the conserved property of GABAergic neurons during evolution, these findings will shed light on our understanding of the potential eco-risks of NPs to the nervous system of other animal models.

Ecotoxicity assessment of sodium dimethyldithiocarbamate and its micro-sized metal chelates in Caenorhabditis elegans

Sodium dimethyldithiocarbamate (SDDC) is a widely used heavy metal chelating agent in harmless treatment of wastewater and hazardous waste, but SDDC and its heavy metal chelates may leak into the environment and bring potential ecological risks. In this study, the model organism Caenorhabditis elegans was used to evaluate the toxic effect of SDDC and its heavy metal Cu, Pb chelates. Multiple endpoints were investigated by subacute exposure to SDDC (0.01-100 mg/L) and micro-sized Cu, Pb chelates of SDDC (1-100 mg/L). Our data indicated that the LC₅₀ value of SDDC was 139.39 mg/L (95% Cl: 111.03, 174.75 mg/L). In addition, SDDC was found that concentration of 1 mg/L is a safe limit value for nematode C. elegans, and concentration above 1 mg/L caused adverse effects on the survival, growth, locomotion behaviors and reactive oxygen species (ROS) production of exposed nematodes. Furthermore, all tested SDDC-Cu and SDDC-Pb chelates had obviously lower toxic effect than untreated Cu, Pb metals. These two chelates also had a lower toxic effect than SDDC agent due to its more stable structure. Moreover, SDDC-Cu had a higher toxic effect than SDDC-Pb at the same concentration. Thus, our results suggest that SDDC as a kind of chelating agent applied in harmless treatment of heavy metals, the safe addition limit should not be exceeded.

Quantum dots functionalized with gH625 attenuate QDs oxidative stress and lethality in Caenorhabditis elegans: a model system

Nanomaterials have revolutionized many scientific fields and are widely applied to address environmental problems and to develop novel health care strategies. However, their mechanism of action is still poorly understood. Several nanomaterials for medical applications are based on quantum dots (QDs). Despite their amazing physico-chemical properties, quantum dots display significant adverse effects. In the present study, the effects of QDs on the motor nervous system of nematodes Caenorhabditis elegans have been investigated as a non-mammalian alternative model. We also explored the possibility of modifying the toxicity of QDs by coating with a cell-penetrating peptide gH625 and thus we analysed the effects determined by QDs-gH625 complexes on the nematodes. With this work, we have demonstrated, by in vivo experiments, that the peptide gH625 is able to reduce the side effects of metallic nanoparticle making them more suitable for medical applications.

A Novel Micronutrient Blend Mimics Calorie Restriction Transcriptomics in Multiple Tissues of Mice and Increases Lifespan and Mobility in C. elegans

Background: We previously described a novel micronutrient blend that behaves like a putative calorie restriction mimetic. The aim of this paper was to analyze the beneficial effects of our micronutrient blend in mice and C. elegans, and compare them with calorie restriction. Methods: Whole transcriptomic analysis was performed in the brain cortex, skeletal muscle and heart in three groups of mice: old controls (30 months), old + calorie restriction and old + novel micronutrient blend. Longevity and vitality were tested in C. elegans. Results: The micronutrient blend elicited transcriptomic changes in a manner similar to those in the calorie-restricted group and different from those in the control group. Subgroup analysis revealed that nuclear hormone receptor, proteasome complex and angiotensinogen genes, all of which are known to be directly related to aging, were the most affected. Furthermore, a functional analysis in C. elegans was used. We found that feeding C. elegans the micronutrient blend increased longevity as well as vitality. Conclusions: We describe a micronutrient supplement that causes similar changes (transcriptomic and promoting longevity and vitality) as a calorie restriction in mice and C. elegans, respectively, but further studies are required to confirm these effects in humans.

Protective role of citric acid against oxidative stress induced by heavy metals in Caenorhabditis elegans

The adverse effects of heavy metals, such as cadmium, zinc, and copper, occur due to the generation of reactive oxygen species (ROS). The use of Caenorhabditis elegans for the purposes of conservation and biomonitoring is of great interest. In the present study, ROS, malondialdehyde (MDA), and citric acid levels and superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities in a model organism were tested to study toxicity. C. elegans was exposed to three different concentrations of cadmium (CdCl₂, 5, 10, 50 μM), zinc (ZnSO₄, 10, 100, 500 μM), and copper (CuSO₄, 10, 100, 500 μM) for 3 days. ROS levels increased by 1.3- to 2.1-fold with increasing metal concentrations. The MDA content increased by approximately 7-, 5-, 2-fold after exposure to high concentrations of cadmium, zinc, and copper, respectively. Furthermore, the citric acid content increased by approximately 3-fold in the cadmium (Cd, 5 μM), zinc (Zn, 10 μM), and copper (Cu, 100 μM) treatment groups compared to that in untreated C. elegans. Therefore, citric acid may play an important role in heavy metal detoxification. Excess citric acid also slightly increased the LC₅₀ by 1.3- to 2.0-fold, basic movements by 1.0- to 1.5-fold, decreased the ROS content by 2.4- to 2.1-fold, the MDA content by 4- to 2-fold, the SOD activity by 9- to 3-fold, the GPx activity by 4.0- to 3.0-fold, and the mRNA expression levels of GPxs by 3.2- to 1.8-fold after metals treatment. And it is most significantly in the alleviation of citric acid to cadmium. This study not only provides information to further understand the effects of heavy metal exposure on ROS, MDA, GPx, SOD, and citric acid in worms but also indicates that supplemental citric acid can protect animals from heavy metal stress and has broad application prospects in decreasing oxidative damage caused by heavy metals.

Mesoporous Silica-Based Materials with Bactericidal Properties

Bacterial infections are the main cause of chronic infections and even mortality. In fact, due to extensive use of antibiotics and, then, emergence of antibiotic resistance, treatment of such infections by conventional antibiotics has become a major concern worldwide. One of the promising strategies to treat infection diseases is the use of nanomaterials. Among them, mesoporous silica materials (MSMs) have attracted burgeoning attention due to high surface area, tunable pore/particle size, and easy surface functionalization. This review discusses how one can exploit capacities of MSMs to design and fabricate multifunctional/controllable drug delivery systems (DDSs) to combat bacterial infections. At first, the emergency of bacterial and biofilm resistance toward conventional antimicrobials is described and then how nanoparticles exert their toxic effects upon pathogenic cells is discussed. Next, the main aspects of MSMs (e.g., physicochemical properties, multifunctionality, and biosafety) which one should consider in the design of MSM-based DDSs against bacterial infections are introduced. Finally, a comprehensive analysis of all the papers published dealing with the use of MSMs for delivery of antibacterial chemicals (antimicrobial agents functionalized/adsorbed on mesoporous silica (MS), MS-loaded with antimicrobial agents, gated MS-loaded with antimicrobial agents, MS with metal-based nanoparticles, and MS-loaded with metal ions) is provided.