In vivo testing of gold nanoparticles using the Caenorhabditis elegans model organism

Size, polyglycerol grafting, and net surface charge of iron oxide nanoparticles determine their interaction and toxicity in Caenorhabditis elegans

The widespread application of engineered nanoparticles (NPs) in environmental remediation has raised public concerns about their toxicity to aquatic organisms. Although appropriate surface modification can mitigate the ecotoxicity of NPs, the lack of polymer coating to inhibit toxicity completely and the insufficient knowledge about charge effect hinder the development of safe nanomaterials. Herein, we explored the potential of polyglycerol (PG) functionalization in alleviating the environmental risks of NPs. Iron oxide NPs (ION) of 20, 100, and 200 nm sizes (IONS, IONM and IONL, respectively) were grafted with PG to afford ION-PG. We examined the interaction of ION and ION-PG with Caenorhabditis elegans (C. elegans) and found that PG suppressed non-specific interaction of ION with C. elegans to reduce their accumulation and to inhibit their translocation. Particularly, IONS-PG was completely excluded from worms of all developmental stages. By covalently introducing sulfate, carboxyl and amino groups onto IONS-PG, we further demonstrated that positively charged IONS-PG-NH3+ induced high intestinal accumulation, cuticle adhesion and distal translocation, whereas the negatively charged IONS-PG-OSO3- and IONS-PG-COO- were excreted out. Consequently, no apparent deleterious effects on brood size and life span were observed in worms treated by IONS-PG and IONS-PG bearing negatively charged groups. This study presents new surface functionalization approaches for developing ecofriendly nanomaterials.

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.

Biosafety evaluation of etoposide lipid nanomedicines in C. elegans

Neuroblastoma is a pediatric tumor that originates during embryonic development and progresses into aggressive tumors, primarily affecting children under two years old. Many patients are diagnosed as high-risk and undergo chemotherapy, often leading to short- and long-term toxicities. Nanomedicine offers a promising solution to enhance drug efficacy and improve physical properties. In this study, lipid-based nanomedicines were developed with an average size of 140 nm, achieving a high encapsulation efficiency of over 90% for the anticancer drug etoposide. Then, cytotoxicity and apoptosis-inducing effects of these etoposide nanomedicines were assessed in vitro using human cell lines, both cancerous and non-cancerous. The results demonstrated that etoposide nanomedicines exhibited high toxicity and selectively induced apoptosis only in cancerous cells.Next, the biosafety of these nanomedicines in C. elegans, a model organism, was evaluated by measuring survival, body size, and the effect on dividing cells. The findings showed that the nanomedicines had a safer profile than the free etoposide in this model. Notably, nanomedicines exerted etoposide's antiproliferative effect only in highly proliferative germline cells. Therefore, the developed nanomedicines hold promise as safe drug delivery systems for etoposide, potentially leading to an improved therapeutic index for neuroblastoma treatment.

Gliadin nanoparticles for oral administration of bioactives: Ex vivo and in vivo investigations

This study aims to provide a thorough characterization of Brij O2-stabilized gliadin nanoparticles to be used for the potential oral administration of various compounds. Different techniques were used in order to evaluate their physico-chemical features and then in vivo studies in rats were performed for the investigation of their biodistribution and gastrointestinal transit profiles. The results showed that the gliadin nanoparticles accumulated in the mucus layer of the bowel mucosa and evidenced their ability to move along the digestive systems of the animals. The incubation of the nanosystems with Caenorhabditis elegans, used as an additional in vivo model, confirmed the intake of the particles and evidenced their presence along the entire gastrointestinal tract of these nematodes. The gliadin nanoparticles influenced neither the egg-laying activity of the worms nor their metabolism of lipids up to 10 μg/mL of nanoformulation. The systems decreased the content of the age-related lipofuscin pigment in the nematodes in a dose-dependent manner, demonstrating a certain antioxidant activity. Lastly, dihydroethidium staining showed the absence of oxidative stress upon incubation of the worms together with the formulations, confirming their safe profile. This data paves the way for the future application of the proposed nanosystems regarding the oral delivery of various bioactives.

Boron clusters (ferrabisdicarbollides) shaping the future as radiosensitizers for multimodal (chemo/radio/PBFR) therapy of glioblastoma

Glioblastoma multiforme (GBM) is the most common and fatal primary brain tumor, and is highly resistant to conventional radiotherapy and chemotherapy. Therefore, the development of multidrug resistance and tumor recurrence are frequent. Given the poor survival with the current treatments, new therapeutic strategies are urgently needed. Radiotherapy (RT) is a common cancer treatment modality for GBM. However, there is still a need to improve RT efficiency, while reducing the severe side effects. Radiosensitizers can enhance the killing effect on tumor cells with less side effects on healthy tissues. Herein, we present our pioneering study on the highly stable and amphiphilic metallacarboranes, ferrabis(dicarbollides) ([o-FESAN]^- and [8,8'-I2-o-FESAN]^-), as potential radiosensitizers for GBM radiotherapy. We propose radiation methodologies that utilize secondary radiation emissions from iodine and iron, using ferrabis(dicarbollides) as iodine/iron donors, aiming to achieve a greater therapeutic effect than that of a conventional radiotherapy. As a proof-of-concept, we show that using 2D and 3D models of U87 cells, the cellular viability and survival were reduced using this treatment approach. We also tested for the first time the proton boron fusion reaction (PBFR) with ferrabis(dicarbollides), taking advantage of their high boron (¹¹B) content. The results from the cellular damage response obtained suggest that proton boron fusion radiation therapy, when combined with boron-rich compounds, is a promising modality to fight against resistant tumors. Although these results are encouraging, more developments are needed to further explore ferrabis(dicarbollides) as radiosensitizers towards a positive impact on the therapeutic strategies for GBM.

A critical review of advances in reproductive toxicity of common nanomaterials to Caenorhabditis elegans and influencing factors

In recent decades, nanotechnology has rapidly developed. Therefore, there is growing concern about the potential environmental risks of nanoparticles (NPs). Caenorhabditis elegans (C. elegans) has been used as a powerful tool for studying the potential ecotoxicological impacts of nanomaterials from the whole animal level to single cell level, especially in the area of reproduction. In this review, we discuss the reproductive toxicity of common nanomaterials in C. elegans, such as metal-based nanomaterial (silver nanoparticles (NPs), gold NPs, zinc oxide NPs, copper oxide NPs), carbon-based nanomaterial (graphene oxide, multi-walled carbon nanotubes, fullerene nanoparticles), polymeric NPs, silica NPs, quantum dots, and the potential mechanisms involved. This insights into the toxic effects of existing nanomaterials on the human reproductive system. In addition, we summarize how the physicochemical properties (e.g., size, charge, surface modification, shape) of nanomaterials influence their reproductive toxicity. Overall, using C. elegans as a platform to develop rapid detection techniques and prediction methods for nanomaterial reproductive toxicity is expected to reduce the gap between biosafety evaluation of nanomaterials and their application.

Neurotoxicity Evaluation of Nanomaterials Using C. elegans: Survival, Locomotion Behaviors, and Oxidative Stress

Nanomaterials are broadly used in a variety of industries and consumer products. However, studies have demonstrated that many nanomaterials, including metal-containing nanoparticles and nanoplastics, have neurotoxic effects. Caenorhabditis elegans (C. elegans) is a widely used model organism with numerous advantages for research, including transparency, short life span, well-characterized nervous system, complete connectome, available genome, and numerous genetic tools. C. elegans has been extensively used to assess the neurotoxicity of multiple chemicals via survival assays, behavioral tests, neuronal morphology studies, and various molecular and mechanistic analyses. However, detailed protocols describing general assays in C. elegans to examine the neurotoxic effects of nanomaterials are limited. Here, we describe protocols for assessing nanomaterial neurotoxicity in C. elegans. We describe the steps for exposure and subsequent evaluation of survival, locomotion behavior, and oxidative stress. Survival and locomotion behavior are measured in wild-type N2 strains to assess acute neurotoxicity. Oxidative stress is used as an endpoint here since it is one of the most predominant and common changes induced by nanomaterials. VP596 nematodes, which express GFP upon activation of skn-1 (the worm homolog of Nrf2), are evaluated for assays of oxidative stress in response to test nanomaterials. These assays can be readily used to quickly examine the neurotoxicity of nanomaterials in vivo, laying the foundation for mechanistic studies of nanomaterials and their impacts on health and physiology. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Exposure of C. elegans to nanomaterials Basic Protocol 2: Survival assessment Basic Protocol 3: Assessment of locomotion behavior Basic Protocol 4: Analysis of oxidative stress.

Pushing the Limits on the Intestinal Crossing of Metal-Organic Frameworks: An Ex Vivo and In Vivo Detailed Study

Biocompatible nanoscaled metal-organic frameworks (nanoMOFs) have been widely studied as drug delivery systems (DDSs), through different administration routes, with rare examples in the convenient and commonly used oral administration. So far, the main objective of nanoMOFs as oral DDSs was to increase the bioavailability of the cargo, without considering the MOF intestinal crossing with potential advantages (e.g., increasing drug availability, direct transport to systemic circulation). Thus, we propose to address the direct quantification and visualization of MOFs' intestinal bypass. For that purpose, we select the microporous Fe-based nanoMOF, MIL-127, exhibiting interesting properties as a nanocarrier (great biocompatibility, large porosity accessible to different drugs, green and multigram scale synthesis, outstanding stability along the gastrointestinal tract). Additionally, the outer surface of MIL-127 was engineered with the biopolymer chitosan (CS@MIL-127) to improve the nanoMOF intestinal permeation. The biocompatibility and intestinal crossing of nanoMOFs is confirmed using a simple and relevant in vivo model, Caenorhabditis elegans; these worms are able to ingest enormous amounts of nanoMOFs (up to 35 g per kg of body weight). Finally, an ex vivo intestinal model (rat) is used to further support the nanoMOFs' bypass across the intestinal barrier, demonstrating a fast crossing (only 2 h). To the best of our knowledge, this report on the intestinal crossing of intact nanoMOFs sheds light on the safe and efficient application of MOFs as oral DDSs.

Impacts of Longer-Term Exposure to AuNPs on Two Soil Ecotoxicological Model Species

The production, use and disposal of nanoparticles (NPs) has been increasing continuously. Due to its unique properties, such as a high resistance to oxidation, gold NPs (AuNPs) are persistent in the environment, including the terrestrial, one of the major sinks of NPs. The present study aimed to assess the effects of AuNPs (from 10 to 1000 mg/kg) on two OECD standard ecotoxicological soil model species, Enchytraeus crypticus and Folsomia candida, based on the reproduction test (28 days) and on a longer-term exposure (56 days), and survival, reproduction, and size were assessed. AuNPs caused no significant hazard to F. candida, but for E. crypticus the lowest tested concentrations (10 and 100 mg AuNPs/kg) reduced reproduction. Further, AuNPs’ toxicity increased from the 28th to the 56th day mainly to F. candida, as observed in animals’ size reduction. Therefore, longer-term exposure tests are recommended as these often reveal increased hazards, not predicted when based on shorter exposures. Additionally, special attention should be given to the higher hazard of low concentrations of NPs, compared to higher concentrations.

Current hurdles to the translation of nanomedicines from bench to the clinic

The field of nanomedicine has significantly influenced research areas such as drug delivery, diagnostics, theranostics, and regenerative medicine; however, the further development of this field will face significant challenges at the regulatory level if related guidance remains unclear and unconsolidated. This review describes those features and pathways crucial to the clinical translation of nanomedicine and highlights considerations for early-stage product development. These include identifying those critical quality attributes of the drug product essential for activity and safety, appropriate analytical methods (physical, chemical, biological) for characterization, important process parameters, and adequate pre-clinical models. Additional concerns include the evaluation of batch-to-batch consistency and considerations regarding scaling up that will ensure a successful reproducible manufacturing process. Furthermore, we advise close collaboration with regulatory agencies from the early stages of development to assure an aligned position to accelerate the development of future nanomedicines.

Novel dual labelled nanoprobes for nanosafety studies: Quantification and imaging experiment of CuO nanoparticles in C. elegans

Metal oxide nanoparticles have been extensively studied for their toxicological impacts. However, accurate tracing/quantification of the nanomaterials and their biological responses are difficult to measure at low concentrations. To overcome the challenge, we developed a dual-labelling technique of CuO nanoparticles with a stable isotope of ⁶⁵Cu, and with rhodamine dye. In vivo experiments on C. elegans were performed using natural feeding of Rhodamine B isothiocyanate-(3 aminopropyl) triethoxysilane functionalized ⁶⁵CuO nanoprobes (RBITC-APTES@⁶⁵CuO) (size = 7.41 ± 1 nm) within the range of Predicted Environmental Concentration (PEC) of CuO nanoparticles in soil and sediments. Fluorescence emission (570 nm) was detected in the lumen of the intestine and the pharynx of C. elegans with no impact of nanoparticle exposure on the brood size and life span of worms. The ingested fluorescent labelled RBITC-APTES@⁶⁵CuO nanoprobes did not enter the reproductive system and were distributed in the alimentary canal of C. elegans. Strong fluorescent signals from the ingested RBITC-APTES@⁶⁵CuO nanoprobes were achieved even after 24 h of exposure demonstrating the high stability of these nanoprobes in vivo. The net accumulation measured of ⁶⁵Cu in C. elegans after background subtraction was 0.001 μg mg^-1 (3.52 %), 0.005 μg mg^-1 (1.76 %) and 0.024 μg mg^-1 (1.69 %) for an exposure concentration of 0.0284 μg mg^-1, 0.284 μg mg^-1, and 1.42 μg mg^-1 of ⁶⁵Cu, respectively. Using C. elegans as a model organism, we demonstrated that RBITC-APTES tagged ⁶⁵CuO nanoparticles acted as novel nanoprobes for measuring the uptake, accumulation, and biodistribution through quantification and imaging the nanoprobes at a very low exposure concentration (⁶⁵CuO concentration: 0.033 μg mg^-1).

Cobaltabis(dicarbollide) ([o-COSAN]-) as Multifunctional Chemotherapeutics: A Prospective Application in Boron Neutron Capture Therapy (BNCT) for Glioblastoma

PURPOSE

The aim of our study was to assess if the sodium salt of cobaltabis(dicarbollide) and its di-iodinated derivative (Na[o-COSAN] and Na[8,8'-I2-o-COSAN]) could be promising agents for dual anti-cancer treatment (chemotherapy + BNCT) for GBM.

METHODS

The biological activities of the small molecules were evaluated in vitro with glioblastoma cells lines U87 and T98G in 2D and 3D cell models and in vivo in the small model animal Caenorhabditis elegans (C. elegans) at the L4-stage and using the eggs.

RESULTS

Our studies indicated that only spheroids from the U87 cell line have impaired growth after treatment with both compounds, suggesting an increased resistance from T98G spheroids, contrary to what was observed in the monolayer culture, which highlights the need to employ 3D models for future GBM studies. In vitro tests in U87 and T98G cells conclude that the amount of 10B inside the cells is enough for BNCT irradiation. BNCT becomes more effective on T98G after their incubation with Na[8,8'-I2-o-COSAN], whereas no apparent cell-killing effect was observed for untreated cells.

CONCLUSIONS

These small molecules, particularly [8,8'-I2-o-COSAN]-, are serious candidates for BNCT now that the facilities of accelerator-based neutron sources are more accessible, providing an alternative treatment for resistant glioblastoma.

Dendrimer-modified gold nanorods as a platform for combinational gene therapy and photothermal therapy of tumors

Background

The exploitation of novel nanomaterials combining diagnostic and therapeutic functionalities within one single nanoplatform is challenging for tumor theranostics.

Methods

We synthesized dendrimer-modified gold nanorods for combinational gene therapy and photothermal therapy (PTT) of colon cancer. Poly(amidoamine) dendrimers (PAMAM, G3) grafted gold nanorods were modified with GX1 peptide (a cyclic 7-mer peptide, CGNSNPKSC). The obtained Au NR@PAMAM-GX1 are proposed as a gene delivery vector to gene (FAM172A, regulates the proliferation and apoptosis of colon cancer cells) for the combination of photothermal therapy (PTT) and gene therapy of Colon cancer cells (HCT-8 cells). In addition, the CT imaging function of Au NR can provide imaging evidence for the diagnosis of colon cancer.

Results

The results display that Au NR@PAMAM-GX1 can specifically deliver FAM172A to cancer cells with excellent transfection efficiency. The HCT-8 cells treated with the Au NR@PAMAM-GX1/FAM172A under laser irradiation have a viability of 20.45%, which is much lower than the survival rate of other single-mode PTT treatment or single-mode gene therapy. Furthermore, animal experiment results confirm that Au NR@PAMAM-GX1/FAM172A complexes can achieve tumor thermal imaging, targeted CT imaging, PTT and gene therapy after tail vein injection.

Conclusion

Our findings demonstrate that the synthesized Au NR@PAMAM-GX1 offer a facile platform to exert antitumor and improve the diagnostic level of tumor.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-02105-3.

Investigation into the trophic transfer and acute toxicity of phosphorus-based nano-agromaterials in Caenorhabditis elegans

Biogenic phosphorus (P) based - nanomaterials (NMs) are currently being explored as nanofertilizers. In this study, the acute toxic effects and trophic transfer of multiple types of P-based NMs were examined on soil-dwelling nematode, Caenorhabditis elegans. The study involved four variants of nanohydroxyapatites (nHAPs) synthesized either via a biogenic or a chemical route and another NM, nanophosphorus (nP), biosynthesized from bulk rock phosphate (RP). The pristine NMs differed in their physicochemical properties with each possessing different shapes (biogenic nHAP: platelet-shaped, ˜35 nm; biogenic nP, ˜5-10 nm: dots; chemically synthesized nHAPs: spherical, ˜33 nm, rod, ˜80 nm and needle-shaped, ˜64 nm). The toxic effects of NMs' in C. elegans were assessed using survival, hatching and reproductive cycle as the key endpoints in comparison to bulk controls, calcium phosphate and RP. The interactions and potential uptake of fluorescent-tagged nHAP to E. coli OP50 and C. elegans were investigated using confocal microscopy. The transformation of NMs within the nematode gut was also explored using dynamic light scattering and electron microscopy. C. elegans exposed to all of the variants of nHAP and the nP had 88-100% survival and 82-100% hatch rates and insignificant effects on brood size as observed at the tested environmentally relevant concentrations ranging from 5 to 100 μg.mL^-1. Confocal microscopy confirmed the interaction and binding of fluorescent-tagged nHAP with the surface of E. coli OP50 and their trophic transfer and internalization into C. elegans. Interestingly, there was only a small reduction in the hydrodynamic diameter of the nHAP after their uptake into C. elegans and the transformed NMs did not induce any additional toxicity as evident by healthy brood sizes after 72 h. This study provides key information about the environmental safety of agriculturally relevant P-based NMs on non-target species.

In vivo assessments for predicting the bioavailability of nanoencapsulated food bioactives and the safety of nanomaterials

Use of nano-sized materials to design novel delivery systems is actually a double-edged sword regarding the enhancement of absorption and bioavailability of encapsulated bioactives as well as the unpredictable phenomena inside the living cells causing health concerns. So, comprehensive investigations on the use of nanomaterials in foods and their biological fate are needed. To reach this goal, both in vitro and in vivo techniques have been extensively applied. Besides the in vitro models such as cell culture and yeast/bacteria, different live animal models like mice, rat, Drosophila melanogaster, Caenorhabditis elegans, Zebrafish and dog can be applied to study bioavailability and safety of nanodelivery systems. However, considering the low correlation between the achieved results of in vitro and in vivo assays, in vivo tests are the first priority due to providing a real physiological condition. On the other hand, uncorrelated results by in vivo assays represent a serious problem to compare them. To defeat the issues in setting an in vivo research for the nanodelivery systems, all restrictions and FDA regulations is likely to be considered to improve the assays authenticity. This review takes a comprehensive look at the different types of in vivo assays and model organisms that has been utilized for the investigation of bioavailability, release profile and possible toxicity of food-based nanomaterials so far.

Xenobiotic metabolism and transport in Caenorhabditis elegans

Caenorhabditis elegans has emerged as a major model in biomedical and environmental toxicology. Numerous papers on toxicology and pharmacology in C. elegans have been published, and this species has now been adopted by investigators in academic toxicology, pharmacology, and drug discovery labs. C. elegans has also attracted the interest of governmental regulatory agencies charged with evaluating the safety of chemicals. However, a major, fundamental aspect of toxicological science remains underdeveloped in C. elegans: xenobiotic metabolism and transport processes that are critical to understanding toxicokinetics and toxicodynamics, and extrapolation to other species. The aim of this review was to initially briefly describe the history and trajectory of the use of C. elegans in toxicological and pharmacological studies. Subsequently, physical barriers to chemical uptake and the role of the worm microbiome in xenobiotic transformation were described. Then a review of what is and is not known regarding the classic Phase I, Phase II, and Phase III processes was performed. In addition, the following were discussed (1) regulation of xenobiotic metabolism; (2) review of published toxicokinetics for specific chemicals; and (3) genetic diversity of these processes in C. elegans. Finally, worm xenobiotic transport and metabolism was placed in an evolutionary context; key areas for future research highlighted; and implications for extrapolating C. elegans toxicity results to other species discussed.

Evaluation of the influence of food intake on the incorporation and excretion kinetics of mesoporous silica particles in C.elegans

The effect of the presence of food on the incorporation and excretion of silica particles was studied in this work using the biological model Caenorhabditis elegans and image analysis techniques. The experiment was based on two 24-hour phases: exposure and depuration. During exposure, nematodes were maintained for 24 h in liquid medium with silica particles, but some with and others without food. During depuration, nematodes were transferred to medium without particles. Nematodes were analysed by an image analysis in both phases to quantify the properties of particle distributions in nematodes' bodies with time. No differences were found in the proportion of nematodes carrying particles in the exposure phase when food was present. However in the depuration phase, lack of food generated a high proportion of particle carriers. Particle distribution properties were also similar in the exposure phase. Nevertheless, lack of food produced particle accumulation due to decelerated excretion because digestive tube relaxed under these conditions. Thus after the depuration phase, lack of food led particles to persist in digestive tubes. According to these results, intake of silica particles had no retention effects when a food flux was provided, but particles were not easily excreted when the food flux was interrupted.

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.

Incorporation of Nonyl 3,4-Dihydroxybenzoate Into Nanostructured Lipid Systems: Effective Alternative for Maintaining Anti-Dermatophytic and Antibiofilm Activities and Reducing Toxicity at High Concentrations

Dermatophytosis is the most common mycosis worldwide, affecting approximately 20 to 25% of the population, regardless of gender, race, color, and age. Most antifungal agents used for the treatment of dermatophytosis belong to the azole and allylamine classes. Dermatophytes are reported to be resistant to most commercial drugs, especially microbial biofilms, in addition to their considerable toxicity. It should be emphasized the importance of looking for new molecules with reduced toxicity, as well as new targets and mechanisms of action. This work aims to incorporate nonyl 3,4-dihydroxybenzoate, a potent fungicide compound against planktonic cells and dermatophyte biofilms in nanostructured lipid systems (NLS), in order to reduce toxicity in high concentrations, improve its solubility and maintain its effectiveness. The compound was incorporated into NLS constituted by cholesterol, mixture of polyoxyethylene (23) lauryl ether (Brij^®98) and soybean phosphatidylcholine (Epikuron^® 200)], 2: 1 ratio and PBS (phosphate-buffered saline). The characterization of the incorporation was performed. Susceptibility tests were conducted according to document M38-A2 by CLSI (2008). The toxicity of the NLS compound was evaluated in HaCaT cell lines by the sulforhodamine B method and in alternative models Caenorhabditis elegans and zebrafish. Finally, its efficacy was evaluated against the mature Trichophyton rubrum and Trichophyton mentagrophytes biofilms. NLS and nonyl 3,4-dihydroxybenzoate loaded into NLS displayed sizes ranging from 137.8 ± 1.815 to 167.9 ± 4.070 nm; the polydispersity index (PDI) varying from 0.331 ± 0.020 to 0.377 ± 0.004 and zeta potential ranging from −1.46 ± 0.157 to −4.63 ± 0.398 mV, respectively. Polarized light microscopy results confirmed the formation of NLS of the microemulsion type. Nonyl incorporated into NLS showed minimum inhibitory concentration (MIC) values, ranging from 2 to 15.6 mg/L. The toxicity tests presented cell viability higher than 80% in all tested concentrations, as well as, a significantly increased of the survival of Caenorhabditis elegans and zebrafish models. Anti-biofilm tests proved the efficacy of the incorporation. These findings contribute significantly to the search for new antifungals and allow the systemic administration of the compound, since the incorporation can increase the solubility of non-polar compounds, improve bioavailability, effectiveness and reduce toxicity.

β-cyclodextrin coating: improving biocompatibility of magnetic nanocomposites for biomedical applications

The role Beta-cyclodextrin (βCD) on improving biocompatibility on healthy cellular and animal models was studied upon a formulation obtained from the development of a simple coating procedure. The obtained nanosystems were thoroughly characterized by FTIR, TGA, atomic absorption spectroscopy, dynamic light scattering and zeta potential, TEM/HR-TEM and magnetic properties. βCD might interact with the magnetic core through hosting OA. It is feasible that the nanocomposite is formed by nanoparticles of MG@OA dispersed in a βCD matrix. The evaluation of βCD role on biocompatibility was performed on two healthy models. To this end, in vivo studies were carried out on Caenorhabditis elegans. Locomotion and progeny were evaluated after exposure animals to MG, MG@OA, and MG@OA-βCD (10 to 500 µg/mL). The influence of βCD on cytotoxicity was explored in vitro on healthy rat aortic endothelial cells, avoiding alteration in the results derived from the use of transformed cell lines. Biological studies demonstrated that βCD attaching improves MG biocompatibility.

Zebrafish as a preclinical in vivo screening model for nanomedicines

The interactions of nanomedicines with biological environments is heavily influenced by their physicochemical properties. Formulation design and optimization are therefore key steps towards successful nanomedicine development. Unfortunately, detailed assessment of nanomedicine formulations, at a macromolecular level, in rodents is severely limited by the restricted imaging possibilities within these animals. Moreover, rodent in vivo studies are time consuming and expensive, limiting the number of formulations that can be practically assessed in any one study. Consequently, screening and optimisation of nanomedicine formulations is most commonly performed in surrogate biological model systems, such as human-derived cell cultures. However, despite the time and cost advantages of classical in vitro models, these artificial systems fail to reflect and mimic the complex biological situation a nanomedicine will encounter in vivo. This has acutely hampered the selection of potentially successful nanomedicines for subsequent rodent in vivo studies. Recently, zebrafish have emerged as a promising in vivo model, within nanomedicine development pipelines, by offering opportunities to quickly screen nanomedicines under in vivo conditions and in a cost-effective manner so as to bridge the current gap between in vitro and rodent studies. In this review, we outline several advantageous features of the zebrafish model, such as biological conservation, imaging modalities, availability of genetic tools and disease models, as well as their various applications in nanomedicine development. Critical experimental parameters are discussed and the most beneficial applications of the zebrafish model, in the context of nanomedicine development, are highlighted.

Reproductive Toxicity of Pomegranate Peel Extract Synthesized Gold Nanoparticles: A Multigeneration Study in C. elegans

C. elegans is a preferential model for testing environmental toxicity of compounds including nanomaterials. The impact of multigeneration exposure of gold nanoparticles (AuNPs) on the lifespan and fertility of C. elegans is not known and therefore is investigated in this study. We used pomegranate (Punica granatum) peel extracts as a reducing agent to synthesize gold nanoparticles (PPE-AuNPs) from chloroauric acid. Nematodes were grown till adult stage and then exposed to 25, 50, and 100 μg/ml of PPE-AuNPs at 20°C for 72 hours and then assessed for lifespan and fertility. The same protocols were followed for subsequent F1, F2, and F3 generations. The results showed that PPE-AuNPs dose-dependently but insignificantly reduced the lifespan of C. elegans. Exposure of PPE-AuNPs significantly and dose-dependently reduced the fertility of C. elegans in terms of the number of eggs produced. The reproductive toxicity of PPE-AuNPs was found to be minimal in parental generation (F0) and maximal in F3 generation. In conclusion, biologically synthesized PPE-AuNPs adversely affect the fertility of C. elegans while the factors responsible for reproductive toxicity are inherited by subsequent generations.

Caenorhabditis elegans as a complete model organism for biosafety assessments of nanoparticles

The number of biosafety evaluation studies of nanoparticles (NPs) using different biological models is increasing with the rapid development of nanotechnology. Thus far, nematode Caenorhabditis elegans (C. elegans), as a complete model organism, has become an important in vivo alternative assay system to assess the risk of NPs, especially at the environmental level. According to results of qualitative and quantitative analyses, it can be concluded that studies of nanoscientific research using C. elegans is persistently growing. However, the comprehensive conclusion and analysis of toxic effects of NPs in C. elegans are limited and chaotic. This review focused on the effects, especially sublethal ones, induced by NPs in C. elegans, including the development, intestinal function, immune response, neuronal function, and reproduction, as well as the underlying mechanisms of NPs causing these effects, including oxidative stress and alterations of several signaling pathways. Furthermore, we presented some factors that influence the toxic effects of NPs in C. elegans. The advantages and limitations of using nematodes in the nanotoxicology study were also discussed. Finally, we predicted that the application of C. elegans to assess long-term impacts of metal oxide NPs in the ecosystem would become a vital part of the nanoscientific research field, which provided an insight for further study.

Cationic gold nanoparticles elicit mitochondrial dysfunction: a multi-omics study

Systems biology is increasingly being applied in nanosafety research for observing and predicting the biological perturbations inflicted by exposure to nanoparticles (NPs). In the present study, we used a combined transcriptomics and proteomics approach to assess the responses of human monocytic cells to Au-NPs of two different sizes with three different surface functional groups, i.e., alkyl ammonium bromide, alkyl sodium carboxylate, or poly(ethylene glycol) (PEG)-terminated Au-NPs. Cytotoxicity screening using THP-1 cells revealed a pronounced cytotoxicity for the ammonium-terminated Au-NPs, while no cell death was seen after exposure to the carboxylated or PEG-modified Au-NPs. Moreover, Au-NR3+ NPs, but not the Au-COOH NPs, were found to trigger dose-dependent lethality in vivo in the model organism, Caenorhabditis elegans. RNA sequencing combined with mass spectrometry-based proteomics predicted that the ammonium-modified Au-NPs elicited mitochondrial dysfunction. The latter results were validated by using an array of assays to monitor mitochondrial function. Au-NR3+ NPs were localized in mitochondria of THP-1 cells. Moreover, the cationic Au-NPs triggered autophagy in macrophage-like RFP-GFP-LC3 reporter cells, and cell death was aggravated upon inhibition of autophagy. Taken together, these studies have disclosed mitochondria-dependent effects of cationic Au-NPs resulting in the rapid demise of the cells.

Sublethal Effects of Ionic and Nanogold on the Nematode Caenorhabditis elegans

The nematode Caenorhabditis elegans is used as an ecotoxicological model species in both aqueous medium and solid substrates. It is easy and of low cost to maintain in the laboratory and it produces hundreds of offspring within a short period of time. It also has a small body size (1 mm), making it possible for in vivo assays to be conducted in 12-well plates. Engineered nanomaterials (ENMs) are a class of emerging pollutants. Nanogold (nAu) is used in many consumer products and in vivo drug delivery. These materials can be released into the aquatic environment during production or discarding of consumer products. As nAu is insoluble in water, the sediment would become the final depository for the materials. It has become increasingly important to use sediment dwelling organisms to screen for possible toxicity of these ENMs. In this study C. elegans was exposed to a range of concentrations of nAu and ionic gold in M9-media, acting as a substitute for pore water. After 96-hour growth, fertility and reproduction were determined. Internal structure damage and internalisation of particles in C. elegans were determined by using SEM and CytoViva® Darkfield Imaging. From these images the nanomaterials are distributed around the oocytes in the reproductive organs, as well as the pharynx. Results obtained indicate that nAu affects reproduction more than growth due to internal gonad damage, albeit at very high exposure concentrations, indicating no toxicity at environmentally relevant concentrations. Ionic Au is more toxic than nAu and effects fertility and reproduction due to ion release. These results give more information regarding the toxicity and in vivo uptake of nAu and form part of an environmental risk assessment of ENMs.

Laser-induced vapour nanobubbles improve drug diffusion and efficiency in bacterial biofilms

Hindered penetration of antibiotics through biofilms is one of the reasons for the alarming increase in bacterial tolerance to antibiotics. Here, we investigate the potential of laser-induced vapour nanobubbles (VNBs) formed around plasmonic nanoparticles to locally disturb biofilm integrity and improve antibiotics diffusion. Our results show that biofilms of both Gram-negative (Burkholderia multivorans, Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus) bacteria can be loaded with cationic 70-nm gold nanoparticles and that subsequent laser illumination results in VNB formation inside the biofilms. In all types of biofilms tested, VNB formation leads to substantial local biofilm disruption, increasing tobramycin efficacy up to 1-3 orders of magnitude depending on the organism and treatment conditions. Altogether, our results support the potential of laser-induced VNBs as a new approach to disrupt biofilms of a broad range of organisms, resulting in improved antibiotic diffusion and more effective biofilm eradication.

Toxic Effects of Size-tunable Gold Nanoparticles on Caenorhabditis elegans Development and Gene Regulation

We utilized size-tunable gold nanoparticles (Au NPs) to investigate the toxicogenomic responses of the model organism Caenorhabditis elegans. We demonstrated that the nematode C. elegans can uptake Au NPs coated with or without 11-mercaptoundecanoic acid (MUA), and Au NPs are detectable in worm intestines using X-ray microscopy and confocal optical microscopy. After Au NP exposure, C. elegans neurons grew shorter axons, which may have been related to the impeded worm locomotion behavior detected. Furthermore, we determined that MUA to Au ratios of 0.5, 1 and 3 reduced the worm population by more than 50% within 72 hours. In addition, these MUA to Au ratios reduced the worm body size, thrashing frequency (worm mobility) and brood size. MTT assays were employed to analyze the viability of cultured C. elegans primary neurons exposed to MUA-Au NPs. Increasing the MUA to Au ratios increasingly reduced neuronal survival. To understand how developmental changes (after MUA-Au NP treatment) are related to changes in gene expression, we employed DNA microarray assays and identified changes in gene expression (e.g., clec-174 (involved in cellular defense), cut-3 and fil-1 (both involved in body morphogenesis), dpy-14 (expressed in embryonic neurons), and mtl-1 (functions in metal detoxification and homeostasis)).

Materials and toxicological approaches to study metal and metal-oxide nanoparticles in the model organism Caenorhabditis elegans

Understanding the in vivo fate and transport of nanoparticles (NPs) is challenging, but critical. We review recent studies of metal and metal oxide NPs using the model organism Caenorhabditis elegans, summarizing major findings to date. In a joint transdisciplinary effort, we highlight underutilized opportunities offered by powerful techniques lying at the intersection of mechanistic toxicology and materials science,. To this end, we firstly summarize the influence of exposure conditions (media, duration, C. elegans lifestage) and NP physicochemical properties (size, coating, composition) on the response of C. elegans to NP treatment. Next, we focus on the techniques employed to study NP entrance route, uptake, biodistribution and fate, emphasizing the potential of extending the toolkit available with novel and powerful techniques. Next, we review findings on several NP-induced biological responses, namely transport routes and altered molecular pathways, and illustrate the molecular biology and genetic strategies applied, critically reviewing their strengths and weaknesses. Finally, we advocate the incorporation of a set of minimal materials and toxicological science experiments that will permit meta-analysis and synthesis of multiple studies in the future. We believe this review will facilitate coordinated integration of both well-established and underutilized approaches in mechanistic toxicology and materials science by the nanomaterials research community.

Bio-identity and fate of albumin-coated SPIONs evaluated in cells and by the C. elegans model

Nanoparticles which surface adsorb proteins in an uncontrolled and non-reproducible manner will have limited uses as nanomedicinal products. A promising approach to avoid nanoparticle non-specific interactions with proteins is to design bio-hybrids by purposely pre-forming a protein corona around the inorganic cores. Here, we investigate, in vitro and in vivo, the newly acquired bio-identity of superparamagnetic iron oxide nanoparticles (SPIONs) upon their functionalization with a pre-formed and well-defined bovine serum albumin (BSA) corona. Cellular uptake, intracellular particle distribution and cytotoxicity were studied in two cell lines: adherent and non-adherent cells. BSA decreases nanoparticle internalization in both cell lines and protects the iron core once they have been internalized. The physiological response to the nanoparticles is then in vivo evaluated by oral administration to Caenorhabditis elegans, which was selected as a model of a functional intestinal barrier. Nanoparticle biodistribution, at single particle resolution, is studied by transmission electron microscopy. The analysis reveals that the acidic intestinal environment partially digests uncoated SPIONs but does not affect BSA-coated ones. It also discloses that some particles could enter the nematode's enterocytes, likely by endocytosis which is a different pathway than the one described for the worm nutrients.

STATEMENT OF SIGNIFICANCE

Unravelling meaningful relationships between the physiological impact of engineered nanoparticles and their synthetic and biological identity is of vital importance when considering nanoparticles biomedical uses and when establishing their nanotoxicological profile. This study contributes to better comprehend the inorganic nanoparticles' behavior in real biological milieus. We synthesized a controlled pre-formed BSA protein corona on SPIONs to lower unspecific cell uptake and decrease nanoparticle fouling with other proteins. Such findings may be of relevance considering clinical translation and regulatory issues of inorganic nanoparticles. Moreover, we have advanced in the validation of C. elegans as a simple animal model for assessing biological responses of engineering nanomaterials. The physiological response of BSA coated SPIONs was evaluated in vivo after their oral administration to C. elegans. Analyzing ultra-thin cross-sections of the worms by TEM with single-particle precision, we could track NP biodistribution along the digestive tract and determine unambiguously their translocation through biological barriers and cell membranes.