The first inorganic mitogens: Cerium oxide and cerium fluoride nanoparticles stimulate planarian regeneration via neoblastic activation

Redox-Active Cerium Fluoride Nanoparticles Selectively Modulate Cellular Response against X-ray Irradiation In Vitro

Ionizing radiation-induced damage in cancer and normal cells leads to apoptosis and cell death, through the intracellular oxidative stress, DNA damage and disorders of their metabolism. Irradiation doses that do not lead to the death of tumor cells can result in the emergence of radioresistant clones of these cells due to the rearrangement of metabolism and the emergence of new mutations, including those in the genes responsible for DNA repair. The search for the substances capable of modulating the functioning of the tumor cell repair system is an urgent task. Here we analyzed the effect of cerium(III) fluoride nanoparticles (CeF3 NPs) on normal (human mesenchymal stem cells-hMSC) and cancer (MCF-7 line) human cells after X-ray radiation. CeF3 NPs effectively prevent the formation of hydrogen peroxide and hydroxyl radicals in an irradiated aqueous solution, showing pronounced antioxidant properties. CeF3 NPs are able to protect hMSC from radiation-induced proliferation arrest, increasing their viability and mitochondrial membrane potential, and, conversely, inducing the cell death of MCF-7 cancer cells, causing radiation-induced mitochondrial hyperpolarization. CeF3 NPs provided a significant decrease in the number of double-strand breaks (DSBs) in hMSC, while in MCF-7 cells the number of γ-H2AX foci dramatically increased in the presence of CeF3 4 h after irradiation. In the presence of CeF3 NPs, there was a tendency to modulate the expression of most analyzed genes associated with the development of intracellular oxidative stress, cell redox status and the DNA-repair system after X-ray irradiation. Cerium-containing nanoparticles are capable of providing selective protection of hMSC from radiation-induced injuries and are considered as a platform for the development of promising clinical radioprotectors.

Toxicokinetics and bioaccumulation of silver sulfide nanoparticles in benthic invertebrates in an indoor stream mesocosm

Mesocosms allow the simulation of environmentally relevant conditions and can be used to establish more realistic scenarios of organism exposure to nanoparticles. An indoor mesocosm experiment simulating an aquatic stream ecosystem was conducted to assess the toxicokinetics and bioaccumulation of silver sulfide nanoparticles (Ag₂S NPs) and AgNO₃ in the freshwater invertebrates Girardia tigrina, Physa acuta and Chironomus riparius, and determine if previous single-species tests can predict bioaccumulation in the mesocosm. Water was daily spiked at 10 μg Ag L^-1. Ag concentrations in water and sediment reached values of 13.4 μg Ag L^-1 and 0.30 μg Ag g^-1 in the Ag₂S NP exposure, and 12.8 μg Ag L^-1 and 0.20 μg Ag g^-1 in the AgNO₃. Silver was bioaccumulated by the species from both treatments, but with approximately 1.5, 3 and 11 times higher body Ag concentrations in AgNO₃ compared to Ag₂S NP exposures in snails, chironomids and planarians, respectively. In the Ag₂S NP exposures, the observed uptake was probably of the particulate form. This demonstrates that this more environmentally relevant Ag nanoform may be bioavailable for uptake by benthic organisms. Interspecies interactions likely occurred, namely predation (planarians fed on chironomids and snails), which somehow influenced Ag uptake/bioaccumulation, possibly by altering organisms´ foraging behaviour. Higher Ag uptake rate constants were determined for AgNO₃ (0.64, 80.4 and 1.12 L_water g^-1_organism day^-1) than for Ag₂S NPs (0.05, 2.65 and 0.32 L_water g^-1_organism day^-1) for planarians, snails and chironomids, respectively. Biomagnification under environmentally realistic exposure seemed to be low, although it was likely to occur in the food chain P. acuta to G. tigrina exposed to AgNO₃. Single-species tests generally could not reliably predict Ag bioaccumulation in the more complex mesocosm scenario. This study provides methodologies/data to better understand exposure, toxicokinetics and bioaccumulation of Ag in complex systems, reinforcing the need to use mesocosm studies to improve the risk assessment of environmental contaminants, specifically NPs, in aquatic environments.

A Study on the Planarian Model Confirms the Antioxidant Properties of Tameron against X-ray- and Menadione-Induced Oxidative Stress

Ionizing radiation and radiation-related oxidative stress are two important factors responsible for the death of actively proliferating cells, thus drastically reducing the regeneration capacity of living organisms. Planarian flatworms are freshwater invertebrates that are rich in stem cells called neoblasts and, therefore, present a well-established model for studies on regeneration and the testing of novel antioxidant and radioprotective substances. In this work, we tested an antiviral and antioxidant drug Tameron (Monosodium α-Luminol or 5-amino-2,3-dihydro-1,4-phthalazinedione sodium salt) for its ability to reduce the harm of X-ray- and chemically induced oxidative stress on a planarian model. Our study has revealed the ability of Tameron to effectively protect planarians from oxidative stress while enhancing their regenerative capacity by modulating the expression of neoblast marker genes and NRF-2-controlled oxidative stress response genes.

Toxicity of ceria nanoparticles to the regeneration of freshwater planarian Dugesia japonica: The role of biotransformation

Cerium oxide nanoparticles (n-CeO₂) have wide applications ranging from industrial to consumer products, which would inevitably lead to their release into the environment. Despite the toxicity of n-CeO₂ on aquatic organisms has been largely reported, research on developing organisms is still lacking. In this study, we investigate the toxic effects of n-CeO₂ on the stem cells, tissue- and neuro-regeneration, using freshwater planarian Dugesia japonica as a model. Effects of bulk sized (μ-) CeO₂ and ionic Ce (Ce³⁺) were compared with that of n-CeO₂ to explore the origin of the toxic effects of n-CeO₂. No overt toxicity was observed in μ-CeO₂ treatment. n-CeO₂ not only impaired the homeostasis of normal planarians, but also inhibited the regeneration processes of regenerated planarians, demonstrated by the inhibited blastema growth, disturbed antioxidant defense system at molecular levels, elevated DNA-damage and decreased stem cell proliferation. Regenerating organisms are more susceptible to n-CeO₂ than the normal ones. Ce³⁺ exhibited significantly higher toxicity than n-CeO₂, even though the total Ce uptake is 0.2 % less in Ce³⁺ than in n-CeO₂ treated in planarian. X-ray absorption near edge spectroscopy (XANES) analysis revealed that 12.8 % of n-CeO₂ (5.95 mg/kg Ce per planarian) was transformed to Ce³⁺ after interaction with planarian, suggesting that biotransformation at the nano-bio interface might play an important role in the observed toxicity. Since the biotransformation of n-CeO₂ is a slow process, it may cause long-term chronic toxicity to planarians due to the slow while sustained release of toxic Ce³⁺ ions.

Mitogen-like Cerium-Based Nanoparticles Protect Schmidtea mediterranea against Severe Doses of X-rays

Novel radioprotectors are strongly demanded due to their numerous applications in radiobiology and biomedicine, e.g., for facilitating the remedy after cancer radiotherapy. Currently, cerium-containing nanomaterials are regarded as promising inorganic radioprotectors due to their unrivaled antioxidant activity based on their ability to mimic the action of natural redox enzymes like catalase and superoxide dismutase and to neutralize reactive oxygen species (ROS), which are by far the main damaging factors of ionizing radiation. The freshwater planarian flatworms are considered a promising system for testing new radioprotectors, due to the high regenerative potential of these species and an excessive amount of proliferating stem cells (neoblasts) in their bodies. Using planarian Schmidtea mediterranea, we tested CeO₂ nanoparticles, well known for their antioxidant activity, along with much less studied CeF₃ nanoparticles, for their radioprotective potential. In addition, both CeO₂ and CeF₃ nanoparticles improve planarian head blastema regeneration after ionizing irradiation by enhancing blastema growth, increasing the number of mitoses and neoblasts' survival, and modulating the expression of genes responsible for the proliferation and differentiation of neoblasts. The CeO₂ nanoparticles' action stems directly from their redox activity as ROS scavengers, while the CeF₃ nanoparticles' action is mediated by overexpression of "wound-induced genes" and neoblast- and stem cell-regulating genes.

Graphene oxide disruption of homeostasis and regeneration processes in freshwater planarian Dugesia japonica via intracellular redox deviation and apoptosis

The aquatic system is a major sink for engineered nanomaterials released into the environment. Here, we assessed the toxicity of graphene oxide (GO) using the freshwater planarian Dugesia japonica, an invertebrate model that has been widely used for studying the effects of toxins on tissue regeneration and neuronal development. GO not only impaired the growth of normal (homeostatic) worms, but also inhibited the regeneration processes of regenerating (amputated) worms, with LC₁₀ values of 9.86 mg/L and 9.32 mg/L for the 48-h acute toxicity test, respectively. High concentration (200 mg/L) of GO killed all the worms after 3 (regenerating) or 4 (homeostasis) days of exposure. Whole-mount in situ hybridization (WISH) and immunofluorescence analyses suggest GO impaired stem cell proliferation and differentiation, and subsequently caused cell apoptosis and oxidative DNA damage during planarian regeneration. Mechanistic analysis suggests that GO disturbed the antioxidative system (enzymatic and non-enzymatic) and energy metabolism in the planarian at both molecular and genetic levels, thus causing reactive oxygen species (ROS) over accumulation and oxidative damage, including oxidative DNA damage, loss of mitochondrial membrane integrity, lack of energy supply for cell differentiation and proliferation leading to retardance of neuron regeneration. The intrinsic oxidative potential of GO contributes to the GO-induced toxicity in planarians. These data suggest that GO in aquatic systems can cause oxidative stress and neurotoxicity in planarians. Overall, regenerated tissues are more sensitive to GO toxicity than homeostatic ones, suggesting that careful handling and appropriate decisions are needed in the application of GO to achieve healing and tissue regeneration.

The Strong Protective Action of Ce3+/F- Combined Treatment on Tooth Enamel and Epithelial Cells

We studied the toxic effects of cerium and fluoride species on human dental pulp stem cells and epithelial cells of Cercopithecus aethiops as a surrogate for the human oral mucosa. The sequential use of CeCl₃ and NH₄F solutions in equimolar sub-toxic concentrations enabled the possible toxic effects of individual components to be avoided, ensuring the preservation of the metabolic activity of the cells due to the formation of CeF₃ nanoparticles. Cerium fluoride nanoparticles and terbium-doped cerium fluoride nanoparticles exhibited neither cytotoxicity nor genotoxicity to dental pulp stem cells, even at high concentrations (10^-4 M). In millimolar concentrations (from 10^-5-10^-6 M), these nanoparticles significantly increased the expression of genes responsible for the cell cycle, differentiation and proliferation. The formation of cerium fluoride on the surface of the mucous membrane and teeth provided protection against the development of carious lesions, periodontitis, ROS attacks and other inflammatory diseases of the oral cavity. Luminescent CeF₃: Tb nanoparticles enabled the visualization of tooth enamel microcracks.

Bioaccumulation but no biomagnification of silver sulfide nanoparticles in freshwater snails and planarians

Bioaccumulation studies are critical in regulatory decision making on the potential environmental risks of engineered nanoparticles (NPs). The present study evaluated the toxicokinetics of silver, taken up from sulfide nanoparticles (Ag₂S NPs; simulating an aged Ag NP form) and AgNO₃ (ionic counterpart), in the pulmonate snail Physa acuta and the planarian Girardia tigrina. The snails were first exposed for 7 days to Ag-spiked water, along with the microalgae Raphidocelis subcapitata upon which they fed setting up a double route exposure, and subsequently provided as pre-exposed food to the planarians. Ag toxicokinetics and bioaccumulation were assessed in planarians and snails, and potential biomagnification from snail to planarian was evaluated. Gut depuration was also explored to understand whether it constitutes a factor likely to influence Ag toxicokinetics and internal concentrations in the test species. Both species revealed Ag uptake in Ag₂S NP and AgNO₃ treatments, with higher uptake from the latter. Uptake by the snails was probably via a combination of water exposure and ingested algae provided as food, but ingestion of algae possibly had higher relevance for Ag uptake from the Ag₂S NPs compared to AgNO₃. For planarians, diet probably was the most important exposure route since no Ag uptake was observed in previous waterborne exposures to Ag₂S NPs. Kinetics and internal Ag concentrations did not significantly differ between depurated and non-depurated snails or planarians. The planarians fed on snails revealed no biomagnification. To the best of our knowledge this is the first study investigating the toxicokinetics and biomagnification of NPs in planarians, and with that providing important data on the kinetics and bioaccumulation of NPs in a relevant benthic species.

Planarians as an In Vivo Experimental Model for the Study of New Radioprotective Substances

Ionising radiation causes the death of the most actively dividing cells, thus leading to depletion of the stem cell pool. Planarians are invertebrate flatworms that are unique in that their stem cells, called neoblasts, constantly replace old, damaged, or dying cells. Amenability to efficient RNAi treatments, the rapid development of clear phenotypes, and sensitivity to ionising radiation, combined with new genomic technologies, make planarians an outstanding tool for the discovery of potential radioprotective agents. In this work, using the well-known antioxidant N-acetylcysteine, planarians are, for the first time, shown to be an excellent model system for the fast and effective screening of novel radioprotective and radio-sensitising substances. In addition, a panel of measurable parameters that can be used for the study of radioprotective effects on this model is suggested.

Biocompatible dextran-coated gadolinium-doped cerium oxide nanoparticles as MRI contrast agents with high T1 relaxivity and selective cytotoxicity to cancer cells

Gd-based complexes are widely used as magnetic resonance imaging (MRI) contrast agents. The safety of previously approved contrast agents is questionable and is being re-assessed. The main causes of concern are possible gadolinium deposition in the brain and the development of systemic nephrogenic fibrosis after repeated use of MRI contrasts. Thus, there is an urgent need to develop a new generation of MRI contrasts that are safe and that have high selectivity in tissue accumulation with improved local contrast. Here, we report on a new type of theranostic MRI contrast, namely dextran stabilised, gadolinium doped cerium dioxide nanoparticles. These ultra-small (4-6 nm) Ce_0.9Gd_0.1O_1.95 nanoparticles have been shown to possess excellent colloidal stability and high r₁-relaxivity (3.6 mM^-1 s^-1). They are effectively internalised by human normal and cancer cells and demonstrate dose-dependent selective cytotoxicity to cancer cells.

Application of Polymer Drugs with Cerium Dioxide Nanomolecules and Mesenchymal Stem Cells for the Treatment of Skin Wounds in Aged Rats

The urgency of the problem of wound healing is not in doubt, given the global trend of an increase in the number of operations and injuries with skin damage, as well as the lack of universal means of treating wounds.

STUDY OBJECTIVE

To compare the effectiveness of the developed drugs, smart polymeric nano-drug with cerium oxide nanoparticles (SPN), and smart polymeric nano-drug in combination with mesenchymal stem cells (SPN + SC) on the healing process of skin wounds.

MATERIAL AND METHODS

An experimental study was carried out using Wistar rats of post-reproductive age, which had dermis and epidermis removed on their backs. There were four groups of wounds in total: control, treatment with mesenchymal stem cells (SC), SPN, and SPN + SC.

RESULTS

A positive therapeutic effect of polymeric drugs on the dynamics of wound area reduction was established, which was most typical for wounds of the SPN group and, particularly, the SPN + SC group. On the third day, an anti-inflammatory effect was revealed in the SC and the SPN + SC groups in particular, which was expressed in a reduced leukocyte infiltration and an increase in the level of microcirculation during this period. The fastest transition from the phase of exudation to proliferation was recorded in the SPN and SPN + SC groups. Histologically, these groups showed faster regeneration, including the epithelialization of wounds.

CONCLUSION

The results obtained in the course of the study open up possibilities for the development of fundamentally new, highly effective wound healing agents.

CeO2 Nanoparticle-Containing Polymers for Biomedical Applications: A Review

The development of advanced composite biomaterials combining the versatility and biodegradability of polymers and the unique characteristics of metal oxide nanoparticles unveils new horizons in emerging biomedical applications, including tissue regeneration, drug delivery and gene therapy, theranostics and medical imaging. Nanocrystalline cerium(IV) oxide, or nanoceria, stands out from a crowd of other metal oxides as being a truly unique material, showing great potential in biomedicine due to its low systemic toxicity and numerous beneficial effects on living systems. The combination of nanoceria with new generations of biomedical polymers, such as PolyHEMA (poly(2-hydroxyethyl methacrylate)-based hydrogels, electrospun nanofibrous polycaprolactone or natural-based chitosan or cellulose, helps to expand the prospective area of applications by facilitating their bioavailability and averting potential negative effects. This review describes recent advances in biomedical polymeric material practices, highlights up-to-the-minute cerium oxide nanoparticle applications, as well as polymer-nanoceria composites, and aims to address the question: how can nanoceria enhance the biomedical potential of modern polymeric materials?

Nanomaterials for Biomedical Applications: Production, Characterisations, Recent Trends and Difficulties

Designing of nanomaterials has now become a top-priority research goal with a view to developing specific applications in the biomedical fields. In fact, the recent trends in the literature show that there is a lack of in-depth reviews that specifically highlight the current knowledge based on the design and production of nanomaterials. Considerations of size, shape, surface charge and microstructures are important factors in this regard as they affect the performance of nanoparticles (NPs). These parameters are also found to be dependent on their synthesis methods. The characterisation techniques that have been used for the investigation of these nanomaterials are relatively different in their concepts, sample preparation methods and obtained results. Consequently, this review article aims to carry out an in-depth discussion on the recent trends on nanomaterials for biomedical engineering, with a particular emphasis on the choices of the nanomaterials, preparation methods/instruments and characterisations techniques used for designing of nanomaterials. Key applications of these nanomaterials, such as tissue regeneration, medication delivery and wound healing, are also discussed briefly. Covering this knowledge gap will result in a better understanding of the role of nanomaterial design and subsequent larger-scale applications in terms of both its potential and difficulties.

Tuning Properties of Cerium Dioxide Nanoparticles by Surface Modification with Catecholate-type of Ligands

Cerium dioxide (CeO₂) finds applications in areas such as corrosion protection, solar cells, or catalysis, finding increasing applications in biomedicine. This work reports on surface-modified CeO₂ particles in order to tune their applicability in the biomedical field. Stable aqueous CeO₂ sol, consisting of 3-4 nm in size crystallites, was synthesized using forced hydrolysis. The coordination of catecholate-type of ligands (catechol, caffeic acid, tiron, and dopamine) to the surface-Ce atoms is followed with the appearance of absorption in the visible spectral range as a consequence of interfacial charge-transfer complex formation. The spectroscopic observations are complemented with the density functional theory calculations using a cluster model. The synthesized samples were characterized by X-ray diffraction analysis, transmission electron microscopy, and nitrogen adsorption-desorption isotherms. The ζ-potential measurements indicated that the stability of CeO₂ sol is preserved upon surface modification. The pristine CeO₂ nanoparticles (NPs) are nontoxic against pre-osteoblast cells in the entire studied concentration range (up to 1.5 mM). Hybrid CeO₂ NPs, capped with dopamine or caffeic acid, display toxic behavior for concentrations ≥0.17 and 1.5 mM, respectively. On the other hand, surface-modified CeO₂ NPs with catechol and tiron promote the proliferation of pre-osteoblast cells.

5-Fluorouracil-treated planarians, a versatile model system for studying stem cell heterogeneity and tissue aging

BACKGROUND INFORMATION

Planarians are a sound, well-established model system for molecular studies in the field of stem cells, cell differentiation, developmental biology and translational research. Treated stem cell-less planarians produced by X-ray treatment are commonly used to study stem cell transcriptional profile and their role in planarian biological processes. X-ray induces oxidative and DNA damage to differentiated cells, requires expensive radiation machines that are not available in most of the research centres and demand rigorous risk management and dedicated staff.

RESULTS

We tested the use of the well-known antimetabolite genotoxic drug 5-fluorouracil which mainly affects proliferating cells in way to demonstrate its use in replacing X-ray treatment. We succeeded in demonstrating ability of high doses of 5-fluorouracil to deplete Dugesia japonica stem cells and in identifying a 5-fluorouracil transiently resistant population of lineage committed stem cells.

CONCLUSIONS AND SIGNIFICANCE

Our results encourage the use of 5-fluorouracil-treated planarians as a model system for studying mechanisms of resistance to genotoxicants, planarian stem cell heterogeneity and molecular cascades of tissue aging.

Efficacy of A Novel Smart Polymeric Nanodrug in the Treatment of Experimental Wounds in Rats

High-quality and aesthetic wound healing, as well as effective medical support of this process, continue to be relevant. This study aims to evaluate the medical efficacy of a novel smart polymeric nanodrug (SPN) on the rate and mechanism of wound healing in experimental animals. The study was carried out in male Wistar rats (aged 8-9 months). In these animals, identical square wounds down to the fascia were made in non-sterile conditions on the back on both sides of the vertebra. SPN was used for the treatment of one wound, and the other wound was left without treatment (control group). Biocompatible citrate-stabilized cerium oxide nanoparticles integrated into a polysaccharide hydrogel matrix containing natural and synthetic polysaccharide polymers (pectin, alginate, chitosan, agar-agar, water-soluble cellulose derivatives) were used as the therapeutic agent. Changes in the wound sizes (area, volume) over time and wound temperature were assessed on Days 0, 1, 3, 5, 7, and 14. Histological examination of the wounds was performed on Days 3, 7, and 14. The study showed that the use of SPN accelerated wound healing in comparison with control wounds by inhibiting the inflammatory response, which was measured by a decreased number of white blood cells in SPN-treated wounds. It also accelerated the development of fibroblasts, with an early onset of new collagen synthesis, which eventually led to the formation of more tender postoperative scars. Thus, the study demonstrated that the use of SPN for the treatment of wounds was effective and promising.