Cerium oxide nanoparticles at the nano-bio interface: size-dependent cellular uptake

Multifunctional Cerium Oxide Nanozyme for Synergistic Dry Eye Disease Therapy

Dry eye disease (DED) is a chronic multifactorial ocular surface disease mainly caused by the instability of tear film, characterized by a series of ocular discomforts and even visual disorders. Oxidative stress has been recognized as an upstream factor in DED development. Diquafosol sodium (DQS) is an agonist of the P2Y2 receptor to restore the integrity/stability of the tear film. With the ability to alternate between Ce3+ and Ce4+, cerium oxide nanozymes could scavenge overexpressed reactive oxygen species (ROS). Hence, a DQS-loaded cerium oxide nanozyme was designed to boost the synergistic treatment of DED. Cerium oxide with branched polyethylenimine-graft-poly(ethylene glycol) as nucleating agent and dispersant was fabricated followed with DQS immobilization via a dynamic phenylborate ester bond, obtaining the DQS-loaded cerium oxide nanozyme (defined as Ce@PBD). Because of the ability to mimic the cascade processes of superoxide dismutase and catalase, Ce@PBD could scavenge excessive accumulated ROS, showing strong antioxidant and anti-inflammatory properties. Meanwhile, the P2Y2 receptors in the conjunctival cells could be stimulated by DQS in Ce@PBD, which can relieve the incompleteness and instability of the tear film. The animal experiments demonstrated that Ce@PBD significantly restored the defect of the corneal epithelium and increased the number of goblet cells, with the promotion of tear secretion, which was the best among commercial DQS ophthalmic solutions.

Cerium oxide nanoparticles in wound care: a review of mechanisms and therapeutic applications

Skin wound healing is a complex and tightly regulated process. The frequent occurrence and reoccurrence of acute and chronic wounds cause significant skin damage to patients and impose socioeconomic burdens. Therefore, there is an urgent requirement to promote interdisciplinary development in the fields of material science and medicine to investigate novel mechanisms for wound healing. Cerium oxide nanoparticles (CeO2 NPs) are a type of nanomaterials that possess distinct properties and have broad application prospects. They are recognized for their capabilities in enhancing wound closure, minimizing scarring, mitigating inflammation, and exerting antibacterial effects, which has led to their prominence in wound care research. In this paper, the distinctive physicochemical properties of CeO2 NPs and their most recent synthesis approaches are discussed. It further investigates the therapeutic mechanisms of CeO2 NPs in the process of wound healing. Following that, this review critically examines previous studies focusing on the effects of CeO2 NPs on wound healing. Finally, it suggests the potential application of cerium oxide as an innovative nanomaterial in diverse fields and discusses its prospects for future advancements.

Biosafe cerium oxide nanozymes protect human pluripotent stem cells and cardiomyocytes from oxidative stress

BACKGROUND

Cardiovascular diseases (CVDs) have the highest mortality worldwide. Human pluripotent stem cells (hPSCs) and their cardiomyocyte derivatives (hPSC-CMs) offer a valuable resource for disease modeling, pharmacological screening, and regenerative therapy. While most CVDs are linked to significant over-production of reactive oxygen species (ROS), the effects of current antioxidants targeting excessive ROS are limited. Nanotechnology is a powerful tool to develop antioxidants with improved selectivity, solubility, and bioavailability to prevent or treat various diseases related to oxidative stress. Cerium oxide nanozymes (CeONZs) can effectively scavenge excessive ROS by mimicking the activity of endogenous antioxidant enzymes. This study aimed to assess the nanotoxicity of CeONZs and their potential antioxidant benefits in stressed human embryonic stem cells (hESCs) and their derived cardiomyocytes (hESC-CMs).

RESULTS

CeONZs demonstrated reliable nanosafety and biocompatibility in hESCs and hESC-CMs within a broad range of concentrations. CeONZs exhibited protective effects on the cell viability of hESCs and hESC-CMs by alleviating excessive ROS-induced oxidative stress. Moreover, CeONZs protected hESC-CMs from doxorubicin (DOX)-induced cardiotoxicity and partially ameliorated the insults from DOX in neonatal rat cardiomyocytes (NRCMs). Furthermore, during hESCs culture, CeONZs were found to reduce ROS, decrease apoptosis, and enhance cell survival without affecting their self-renewal and differentiation potential.

CONCLUSIONS

CeONZs displayed good safety and biocompatibility, as well as enhanced the cell viability of hESCs and hESC-CMs by shielding them from oxidative damage. These promising results suggest that CeONZs may be crucial, as a safe nanoantioxidant, to potentially improve the therapeutic efficacy of CVDs and be incorporated into regenerative medicine.

Investigating temperature variability on antioxidative behavior of synthesized cerium oxide nanoparticle for potential biomedical application

Cerium oxide nanoparticles (CNP) have garnered significant attention due to their versatile redox properties and wound-healing applications. The antioxidative nature of CNP is due to its ability to be oxidized and reduced, followed by the capture or release of oxygen which is used for scavenging reactive oxygen species (ROS). Herein, CNP is produced through a wet chemistry approach and its tunable redox property is tested across a range of temperatures. The synthesized CNP was observed to reveal the signature peak at 245 nm indicating a high Ce+3/Ce+4 ratio. Towards evaluating the redox antioxidative behavior, CNPs were subjected to a comprehensive analysis for superoxide dismutase mimetic analysis with riboflavin-mediated nitroblue tetrazolium scavenging assay. The results demonstrated that the redox activity of cerium oxide nanoparticles was strongly influenced by the different temperature ranges. Superoxide dismutase mimetic activity was observed to be reduced with a decrease in temperature as we moved from 4°C (80% activity) to -80°C (47% activity) at 1 mM conc of CNP. Similarly, the SOD mimetic activity increased with an increase in temperature from 40°C (72% activity) to 70°C (94% activity). Further, CNP was found to inhibit E. coli (gram+ve) and Enterobacter (gram-ve) beyond 70% simultaneously at 1 mM conc, indicating its potential application as a remarkable antimicrobial agent. CNP also inhibited the alpha-amylase activity up to the 60% at 1 mM conc suggesting its potential application in antidiabetic wound healing therapy. Overall, the CNP finds its application in mitigating the oxidative stress-related disorder exhibited by its high antioxidative, antimicrobial, and antidiabetic behavior.

Transferrin-targeted iridium nanoagglomerates with multi-enzyme activities for cerebral ischemia-reperfusion injury therapy

Cerebral ischemia-reperfusion injury (CIRI) is a complex pathological condition with high mortality. In particular, reperfusion can stimulate overproduction of reactive oxygen species (ROS) and activation of inflammation, causing severe secondary injuries to the brain. Despite tremendous efforts, it remains urgent to rationally design antioxidative agents with straightforward and efficient ROS scavenging capability. Herein, a potent antioxidative agent was explored based on iridium oxide nano-agglomerates (Tf-IrO2 NAs) via the facile transferrin (Tf)-templated biomineralization approach, and innovatively applied to treat CIRI. Containing some small-size IrO2 aggregates, these NAs possess intrinsic hydroxyl radicals (•OH)-scavenging ability and multifarious enzyme activities, such as catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx). Moreover, they also showed improved blood-brain barrier (BBB) penetration and enhanced accumulation in the ischemic brain via Tf receptor-mediated transcytosis. Therefore, Tf-IrO2 NAs achieved robust in vitro anti-inflammatory and cytoprotection effects against oxidative stress. Importantly, mice were effectively protected against CIRI by enhanced ROS scavenging activity in vivo, and the therapeutic mechanism was systematically verified. These findings broaden the idea of expanding Ir-based NAs as potent antioxidative agents to treat CIRI and other ROS-mediated diseases. STATEMENT OF SIGNIFICANCE: (1) The ROS-scavenging activities of IrO2 are demonstrated comprehensively, which enriched the family of nano-antioxidants. (2) The engineering Tf-IrO2 nano-agglomerates present unique multifarious enzyme activities and simultaneous transferrin targeting and BBB crossing ability for cerebral ischemia-reperfusion injury therapy. (3) This work may open an avenue to enable the use of IrO2 to alleviate ROS-mediated inflammatory and brain injury diseases.

Engineered Faceted Cerium Oxide Nanoparticles for Therapeutic miRNA Delivery

In general, wound healing is a highly ordered process, with distinct phases of inflammation, proliferation, and remodeling. However, among diabetic patients, the progression through these phases is often impeded by increased level of oxidative stress and persistent inflammation. Our previous studies demonstrated that cerium oxide nanoparticles (CNPs) conjugated with therapeutic microRNA146a (miR146a) could effectively enhance wound healing by targeting the NFκB pathway, reducing oxidative stress and inflammation. In the present study, we consider the potential effects of nanomaterial surface-faceting and morphology on the efficacy of miRNA delivery. Compared with octahedral-CNPs and cubic-CNPs, rod-CNPs exhibited higher loading capacity. In addition, in comparing the influence of particle morphology on wound healing efficacy, several markers for bioactivity were evaluated and ascribed to the combined effects of the gene delivery and reactive oxygen species (ROS) scavenging properties. In the cellular treatment study, rod-CNP-miR146a displayed the greatest miR146a delivery into cells. However, the reduction of IL-6 was only observed in the octahedral-CNP-miR146a, suggesting that the efficacy of the miRNA delivery is a result of the combination of various factors. Overall, our results give enlightenments into the relative delivery efficiency of the CNPs with different morphology enhancing miRNA delivery efficacy.

A drug-free nanozyme for mitigating oxidative stress and inflammatory bowel disease

Inflammatory bowel disease (IBD) is an incurable disease of the gastrointestinal tract with a lack of effective therapeutic strategies. The proinflammatory microenvironment plays a significant role in both amplifying and sustaining inflammation during IBD progression. Herein, biocompatible drug-free ceria nanoparticles (CeNP-PEG) with regenerable scavenging activities against multiple reactive oxygen species (ROS) were developed. CeNP-PEG exerted therapeutic effect in dextran sulfate sodium (DSS)-induced colitis murine model, evidenced by corrected the disease activity index, restrained colon length shortening, improved intestinal permeability and restored the colonic epithelium disruption. CeNP-PEG ameliorated the proinflammatory microenvironment by persistently scavenging ROS, down-regulating the levels of multiple proinflammatory cytokines, restraining the proinflammatory profile of macrophages and Th1/Th17 response. The underlying mechanism may involve restraining the co-activation of NF-κB and JAK2/STAT3 pathways. In summary, this work demonstrates an effective strategy for IBD treatment by ameliorating the self-perpetuating proinflammatory microenvironment, which offers a new avenue in the treatment of inflammation-related diseases.

Photopolymerized Zwitterionic Hydrogels with a Sustained Delivery of Cerium Oxide Nanoparticle-miR146a Conjugate Accelerate Diabetic Wound Healing

In the United States, $87 billion per year is spent on the care of diabetic ulcers alone. Although the pathophysiology of diabetic wound healing is multifaceted, high systemic levels of inflammation and increased reactive oxygen species are often implicated in the wound healing impairment. Zwitterionic materials have been demonstrated to reduce inflammation and increase extracellular matrix deposition in wound beds, and here, we demonstrate a fabrication method for photopolymerized zwitterionic hydrogels that also enables sustained drug delivery over time. A therapeutic molecule of interest that is examined in this work is cerium oxide nanoparticle tagged with microRNA-146a (CNP-miR146a) to combat both oxidative stress and inflammation. The hydrogels are composed of zwitterionic and nonzwitterionic monomers, and the hydrogel formation occurs in the absence of a crosslinker. The hydrogels exhibit a wide range of stiffness and mechanical properties depending on their monomer content. Additionally, these hydrogels exhibit sustained release of nanoparticles and proteins. Finally, when employed in an in vivo diabetic mouse wound healing model, the zwitterionic hydrogels alone and laden with the CNP-miR146a conjugate significantly improved the rate of diabetic wound healing. Overall, these materials have excellent potential to be used as a topical treatment for chronic diabetic wounds.

ROS-Mediated Anti-Angiogenic Activity of Cerium Oxide Nanoparticles in Melanoma Cells

Angiogenesis plays a key role in cancer progression, including transition to the metastatic phase via reactive oxygen species (ROS)-dependent pathways, among others. Antivascular endothelial growth factor (VEGF) antibodies have been trialed as an anti-angiogenic therapy for cancer but are associated with high cost, limited efficacy, and side effects. Cerium oxide nanoparticles (nanoceria) are promising nanomaterials for biomedical applications due to their ability to modulate intracellular ROS. Nanoceria can be produced by a range of synthesis methods, with chemical precipitation as the most widely explored. It has been reported that chemical precipitation can fine-tune primary particle size where a limited number of synthesis parameters were varied. Here, we explore the effect of temperature, precipitating agent concentration and rate of addition, stirring rate, and surfactant concentration on nanoceria primary particle size using a fractional factorial experimental design approach. We establish a robust synthesis method for faceted nanoceria with primary particle diameters of 5-6 nm. The nanoceria are not cytotoxic to a human melanoma cell line (Mel1007) at doses up to 400 μg/mL and are dose-dependently internalized by the cells. The intracellular ROS level for some cells that internalized the nanoceria is reduced, which correlates with a dose-dependent reduction in angiogenic gene expression including VEGF. These findings contribute to our knowledge of the anti-angiogenic effects of nanoceria and help to develop our understanding of potentially new anti-angiogenic agents for combination cancer therapies.

Cerium oxide nanoparticle conjugation to microRNA-146a mechanism of correction for impaired diabetic wound healing

Diabetic wounds represent a significant healthcare burden and are characterized by impaired wound healing due to increased oxidative stress and persistent inflammation. We have shown that CNP-miR146a synthesized by the conjugation of cerium oxide nanoparticles (CNP) to microRNA (miR)-146a improves diabetic wound healing. CNP are divalent metal oxides that act as free radical scavenger, while miR146a inhibits the pro-inflammatory NFκB pathway, so CNP-miR146a has a synergistic role in modulating both oxidative stress and inflammation. In this study, we define the mechanism(s) by which CNP-miR146a improves diabetic wound healing by examining immunohistochemical and gene expression analysis of markers of inflammation, oxidative stress, fibrosis, and angiogenesis. We have found that intradermal injection of CNP-miR146a increases wound collagen, enhances angiogenesis, and lowers inflammation and oxidative stress, ultimately promoting faster closure of diabetic wounds.

Lung function improves after delayed treatment with CNP-miR146a following acute lung injury

Acute respiratory distress syndrome (ARDS) is a highly morbid pulmonary disease characterized by hypoxic respiratory failure. Its pathogenesis is characterized by unrestrained oxidative stress and inflammation, with long-term sequelae of pulmonary fibrosis and diminished lung function. Unfortunately, prior therapeutic ARDS trials have failed and therapy is limited to supportive measures. Free radical scavenging cerium oxide nanoparticles (CNP) conjugated to the anti-inflammatory microRNA-146a (miR146a), termed CNP-miR146a, have been shown to prevent acute lung injury in a pre-clinical model. In this study, we evaluated the potential of delayed treatment with CNP-miR146a at three or seven days after injury to rescue the lung from acute injury. We found that intratracheal CNP-miR146a administered three days after injury lowers pulmonary leukocyte infiltration, reduce inflammation and oxidative stress, lower pro-fibrotic gene expression and collagen deposition in the lung, and ultimately improve pulmonary function.

On Placental Toxicology Studies and Cerium Dioxide Nanoparticles

The human placenta is a transient organ essential for pregnancy maintenance, fetal development and growth. It has several functions, including that of a selective barrier against pathogens and xenobiotics from maternal blood. However, some pollutants can accumulate in the placenta or pass through with possible repercussions on pregnancy outcomes. Cerium dioxide nanoparticles (CeO₂ NPs), also termed nanoceria, are an emerging pollutant whose impact on pregnancy is starting to be defined. CeO₂ NPs are already used in different fields for industrial and commercial applications and have even been proposed for some biomedical applications. Since 2010, nanoceria have been subject to priority monitoring by the Organization for Economic Co-operation and Development in order to assess their toxicity. This review aims to summarize the current methods and models used for toxicology studies on the placental barrier, from the basic ones to the very latest, as well as to overview the most recent knowledge of the impact of CeO₂ NPs on human health, and more specifically during the sensitive window of pregnancy. Further research is needed to highlight the relationship between environmental exposure to CeO₂ and placental dysfunction with its implications for pregnancy outcome.

Cerium Oxide Nanoparticle Administration to Skeletal Muscle Cells under Different Gravity and Radiation Conditions

For their remarkable biomimetic properties implying strong modulation of the intracellular and extracellular redox state, cerium oxide nanoparticles (also termed "nanoceria") were hypothesized to exert a protective role against oxidative stress associated with the harsh environmental conditions of spaceflight, characterized by microgravity and highly energetic radiations. Nanoparticles were supplied to proliferating C2C12 mouse skeletal muscle cells under different gravity and radiation levels. Biological responses were thus investigated at a transcriptional level by RNA next-generation sequencing. Lists of differentially expressed genes (DEGs) were generated and intersected by taking into consideration relevant comparisons, which led to the observation of prevailing effects of the space environment over those induced by nanoceria. In space, upregulation of transcription was slightly preponderant over downregulation, implying involvement of intracellular compartments, with the majority of DEGs consistently over- or under-expressed whenever present. Cosmic radiations regulated a higher number of DEGs than microgravity and seemed to promote increased cellular catabolism. By taking into consideration space physical stressors alone, microgravity and cosmic radiations appeared to have opposite effects at transcriptional levels despite partial sharing of molecular pathways. Interestingly, gene ontology denoted some enrichment in terms related to vision, when only effects of radiations were assessed. The transcriptional regulation of mitochondrial uncoupling protein 2 in space-relevant samples suggests perturbation of the intracellular redox homeostasis, and leaves open opportunities for antioxidant treatment for oxidative stress reduction in harsh environments.

Nanostructured Ceria: Biomolecular Templates and (Bio)applications

Ceria (CeO2) nanostructures are well-known in catalysis for energy and environmental preservation and remediation. Recently, they have also been gaining momentum for biological applications in virtue of their unique redox properties that make them antioxidant or pro-oxidant, depending on the experimental conditions and ceria nanomorphology. In particular, interest has grown in the use of biotemplates to exert control over ceria morphology and reactivity. However, only a handful of reports exist on the use of specific biomolecules to template ceria nucleation and growth into defined nanostructures. This review focusses on the latest advancements in the area of biomolecular templates for ceria nanostructures and existing opportunities for their (bio)applications.

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.

Understanding the interactions between inorganic-based nanomaterials and biological membranes

The interactions between inorganic-based nanomaterials (NMs) and biological membranes are among the most important phenomena for developing NM-based therapeutics and resolving nanotoxicology. Herein, we introduce the structural and functional effects of inorganic-based NMs on biological membranes, mainly the plasma membrane and the endomembrane system, with an emphasis on the interface, which involves highly complex networks between NMs and biomolecules (such as membrane proteins and lipids). Significant efforts have been devoted to categorizing and analyzing the interaction mechanisms in terms of the physicochemical characteristics and biological effects of NMs, which can directly or indirectly influence the effects of NMs on membranes. Importantly, we summarize that the biological membranes act as platforms and thereby mediate NMs-immune system contacts. In this overview, the existing challenges and potential applications in the areas are addressed. A strong understanding of the discussed concepts will promote therapeutic NM designs for drug delivery systems by leveraging the NMs-membrane interactions and their functions.

Fabrication of cerium doped carbon dots with highly radical scavenging activity alleviates ferroptosis-induced oxidative damage

Ferroptosis as an iron-dependent lipid peroxidation process causes sevely oxidative damage of cell, but lack of highly efficient and recycable antioxidant agents. To this end, cerium doped carbon dots (Ce-doped CDs) with radical scavenging activity were synthesized using a simple microwave-assisted hydrothermal carbonization. The resultant Ce-doped CDs exhibited an ultra-small size of only approximately 2.6 nm, excellent dispersion in water as well as optical performance. Taking advantage of inherent ultra-small size, Ce-doped CDs were endowed with high Ce³⁺/Ce⁴⁺ratio, which significantly enhanced their radical scavenging activity. Meanwhile, the Ce-doped CDs with superior biocompatibility could enter cells quickly and then localized in the cytoplasm. As we expected, the Ce-doped CDs strongly protected cells from oxidative damage of erastin-mediated ferroptosis. These findings suggest that the as-prepared Ce-doped CDs have the potential to be antioxidant drugs against for ferroptosis-induced oxidative damage.

Ameliorating hydroxychloroquine induced retinal toxicity through cerium oxide nanoparticle treatments

The present study investigated the potential protective effects of cerium oxide nanoparticles (CNP) on human retinal pigment epithelium (ARPE-19) cells damaged by hydroxychloroquine (HCQ). Toxicity of HCQ on the ARPE-19 cells was explored with a dose response trial. CNP rescue both a pre-treatment protocol, where CNP were applied 24 hours prior to HCQ application and a simultaneous treatment protocol where both CNP and HCQ were applied together, were used. In the dose response trial, 250 µM HCQ showed 51.84% cell viability after 24 hours and 32.75% after 48 hours time period. This was selected as model HCQ dose for rescue trials. The simultaneous treatment trials did not show a significant increase in viability compared to model toxic dose. The CNP pre-treatment trials showed a significant increase in cellular viability compared to model toxic dose with 68.03% ± 3.27 viability (p = 4.56E-05) at 24 hours and 51.85% ± 4.96 (p = 1.18E-05) at 48 hours time period. CNP pre-treatment showed significant protection of cells from HCQ induced toxicity. The difference in efficacy of simultaneous and pre-treatment is hypothesized to lie in the cellular localization of CNP. Furthermore, including the reactive oxygen species (ROS) scavenging properties of CNP seems to be responsible for protection, the effect of CNP on autophagosome and lysosome colocalization are also hypothesized to play a significant role.

Evaluation of size, shape, and charge effect on the biological interaction and cellular uptake of cerium oxide nanostructures

Cerium oxide (CeO₂) at the nanoscale has prolifically attracted the immense interest of researchers due to its switchable oxidation states (Ce³⁺/Ce⁴⁺) that play a crucial role in many biological activities. The present work reports the evaluation of size, shape, and charge effect on the biological interaction with RAW 264.7 cells for three nanostructures of CeO₂(CeO₂NS) namely nanocubes (NCs), nanorods (NRs), and nanoparticles (NPs). These NS exhibits similar composition and have average diameter values in the order of NCs < NRs ≅ NPs. The values of zeta potential revealed the anionic nature of NS with surface charge in order of NCs < NPs < NRs. The cellular interaction of CeO₂NS was analyzed for cytotoxicity, cellular uptake, and morphological studies. Quantitative determination of the uptake of CeO₂NS exhibited concentration-dependent uptake in the order as NCs > NPs > NRs. The proposed possible mechanisms of cellular uptake revealed that different structures tended to use the various endocytosis pathways in different proportions.

Nanoceria Prevents Glucose-Induced Protein Glycation in Eye Lens Cells

Cerium oxide nanoparticles (nanoceria) are generally known for their recyclable antioxidative properties making them an appealing biomaterial for protecting against physiological and pathological age-related changes that are caused by reactive oxygen species (ROS). Cataract is one such pathology that has been associated with oxidation and glycation of the lens proteins (crystallins) leading to aggregation and opacification. A novel coated nanoceria formulation has been previously shown to enter the human lens epithelial cells (HLECs) and protect them from oxidative stress induced by hydrogen peroxide (H2O2). In this work, the mechanism of nanoceria uptake in HLECs is studied and multiple anti-cataractogenic properties are assessed in vitro. Our results show that the nanoceria provide multiple beneficial actions to delay cataract progression by (1) acting as a catalase mimetic in cells with inhibited catalase, (2) improving reduced to oxidised glutathione ratio (GSH/GSSG) in HLECs, and (3) inhibiting the non-enzymatic glucose-induced glycation of the chaperone lens protein α-crystallin. Given the multifactorial nature of cataract progression, the varied actions of nanoceria render them promising candidates for potential non-surgical therapeutic treatment.

Cerium oxide nanoparticles protect against irradiation-induced cellular damage while augmenting osteogenesis

Increased bone loss and risk of fracture are two of the main challenges for cancer patients who undergo ionizing radiation (IR) therapy. This decline in bone quality is in part, caused by the excessive and sustained release of reactive oxygen species (ROS). Cerium oxide nanoparticles (CeONPs) have proven antioxidant and regenerative properties and the purpose of this study was to investigate the effect of CeONPs in reducing IR-induced functional damage in human bone marrow-derived mesenchymal stromal cells (hBMSCs). hBMSCs were supplemented with CeONPs at a concentration of either 1 or 10 μg/mL 24 h prior to exposure to a single 7 Gy irradiation dose. ROS levels, cellular proliferation, morphology, senescence, DNA damage, p53 expression and autophagy were evaluated as well as alkaline phosphatase, osteogenic protein gene expression and bone matrix deposition following osteogenic differentiation. Results showed that supplementation of CeONPs at a concentration of 1 μg/mL reduced cell senescence and significantly augmented cell autophagy (p = 0.01), osteogenesis and bone matrix deposition >2-fold (p = 0.0001) while under normal, non-irradiated culture conditions. Following irradiation, functional damage was attenuated and CeONPs at both 1 or 10 μg/mL significantly reduced ROS levels (p = 0.05 and 0.001 respectively), DNA damage by >4-fold (p < 0.05) while increasing autophagy >3.5-fold and bone matrix deposition 5-fold (p = 0.0001 in both groups). When supplemented with 10 μg/mL, p53 expression increased 3.5-fold (p < 0.05). We conclude that cellular uptake of CeONPs offered a significant, multifunctional and protective effect against IR-induced cellular damage while also augmenting osteogenic differentiation and subsequent new bone deposition. The use of CeONPs holds promise as a novel multifunctional therapeutic strategy for irradiation-induced bone loss.

Cerium oxide nanoparticle delivery of microRNA-146a for local treatment of acute lung injury

Acute respiratory distress syndrome (ARDS) is a devastating pulmonary disease with significant in-hospital mortality and is the leading cause of death in COVID-19 patients. Excessive leukocyte recruitment, unregulated inflammation, and resultant fibrosis contribute to poor ARDS outcomes. Nanoparticle technology with cerium oxide nanoparticles (CNP) offers a mechanism by which unstable therapeutics such as the anti-inflammatory microRNA-146a can be locally delivered to the injured lung without systemic uptake. In this study, we evaluated the potential of the radical scavenging CNP conjugated to microRNA-146a (termed CNP-miR146a) in preventing acute lung injury (ALI) following exposure to bleomycin. We have found that intratracheal delivery of CNP-miR146a increases pulmonary levels of miR146a without systemic increases, and prevents ALI by altering leukocyte recruitment, reducing inflammation and oxidative stress, and decreasing collagen deposition, ultimately improving pulmonary biomechanics.

Catalytic activity tunable ceria nanoparticles prevent chemotherapy-induced acute kidney injury without interference with chemotherapeutics

Acute kidney injury (AKI) is a prevalent and lethal adverse event that severely affects cancer patients receiving chemotherapy. It is correlated with the collateral damage to renal cells caused by reactive oxygen species (ROS). Currently, ROS management is a practical strategy that can reduce the risk of chemotherapy-related AKI, but at the cost of chemotherapeutic efficacy. Herein, we report catalytic activity tunable ceria nanoparticles (CNPs) that can prevent chemotherapy-induced AKI without interference with chemotherapeutic agents. Specifically, in the renal cortex, CNPs exhibit catalytic activity that decomposes hydrogen peroxide, and subsequently regulate the ROS-involved genes by activating the Nrf2/Keap1 signaling pathway. These restore the redox homeostasis for the protection of kidney tubules. Under an acidic tumor microenvironment, CNPs become inert due to the excessive H+ that disrupts the re-exposure of active catalytic sites, allowing a buildup of chemotherapy-mediated ROS generation to kill cancer cells. As ROS-modulating agents, CNPs incorporated with context-dependent catalytic activity, hold a great potential for clinical prevention and treatment of AKI in cancer patients.

Impact of morphology and collagen-functionalization on the redox equilibria of nanoceria for cancer therapies

The application of nanoparticulate therapies for cancer depends largely on the uptake and redox activity of the particles. The present work reports the fabrication of different morphologies of nanoceria (CeO_2-x) as nanooctahedra (NO), nanorods (NR), and nanocubes (NC) by hydrothermal synthesis at different temperatures (100 °C, 180 °C) of solutions of 0.05 M Ce(NO₃)₃·6H₂O and different concentrations of NaOH (0.01 M, 6.00 M). The characteristics of these nanomorphologies are compared in terms of the crystallinity (XRD), grain size (TEM), surface area (BET), tendency to agglomerate, and the oxygen vacancy concentration ([V_O^••]) as reflected by the [Ce³⁺]/[Ce⁴⁺] ratio (XPS). The effects of these parameters on the potential cellular uptake are canvassed, suggesting that the nonpolarity of the {111} planes of NO and NR facilitate the preferential uptake of these nanomorphologies. These experimental variables then were normalized through the use of NC as a model substrate for the functionalization using gum arabic (GA) and collagen in order to assess their roles in enhancing redox activity. Both the unfunctionalized and functionalized NC were noncytotoxic in in vitro tests with Kuramochi ovarian cancer cells. However, the antioxidant behavior of the collagen-functionalized NC was superior to that of the unfunctionalized NC, which was superior to that of the controls. These results demonstrate that, while the intrinsic V_O^•• of CeO_2-x enhance the destruction of reactive oxygen species (ROS), functionalization by gum arabic and collagen crosslinking as extrinsic additions to the system enhances ROS destruction to an even greater extent. The antioxidant behavior and potential to neutralize superoxide and hydroxyl radicals of these materials offers new potential for the improvement of nanoparticulate cancer therapies.

Nanosilk Increases the Strength of Diabetic Skin and Delivers CNP-miR146a to Improve Wound Healing

Diabetes mellitus is a metabolic disorder associated with properties and an increased risk of chronic wounds due to sustained pro-inflammatory response. We have previously of radical scavenging cerium oxide nanoparticles (CNP) conjugated to the anti-inflammatory microRNA (miR)-146a, termed CNP-miR146a, improves diabetic wound healing by synergistically lowering oxidative stress and inflammation, and we sought to evaluate this treatment in a topical application. Silk fibroin is a biocompatible polymer that can be fabricated into nanostructures, termed nanosilk. Nanosilk is characterized by a high strength-to-density ratio and an ability to exhibit strain hardening. We therefore hypothesized that nanosilk would strengthen the biomechanical properties of diabetic skin and that nanosilk solution could effectively deliver CNP-miR146a to improve diabetic wound healing. The ability of nanosilk to deliver CNP-miR146a to murine diabetic wounds and improve healing was assessed by the rate of wound closure and inflammatory gene expression, as well as histologic analysis. The effect of nanosilk on the properties of human diabetic skin was evaluated by testing the biomechanical properties following topical application of a 7% nanosilk solution. Diabetic murine wounds treated with topical nanosilk and CNP-miR146a healed by day 14.5 compared to day 16.8 in controls (p = 0.0321). Wounds treated with CNP-miR146a had higher collagen levels than controls (p = 0.0126) with higher pro-fibrotic gene expression of TGFβ-1 (p = 0.0092), Col3α1 (p = 0.0369), and Col1α2 (p = 0.0454). Treatment with CNP-miR146a lowered pro-inflammatory gene expression of IL-6 (p = 0.0488) and IL-8 (p = 0.0009). Treatment of human diabetic skin with 7% nanosilk solution resulted in significant improvement in maximum load and modulus (p < 0.05). Nanosilk solution is able to strengthen the biomechanical properties of diabetic skin and can successfully deliver CNP-miR146a to improve diabetic wound healing through inhibition of pro-inflammatory gene signaling and promotion of pro-fibrotic processes.

The Advances of Ceria Nanoparticles for Biomedical Applications in Orthopaedics

The ongoing biomedical nanotechnology has intrigued increasingly intense interests in cerium oxide nanoparticles, ceria nanoparticles or nano-ceria (CeO2-NPs). Their remarkable vacancy-oxygen defect (VO) facilitates the redox process and catalytic activity. The verification has illustrated that CeO2-NPs, a nanozyme based on inorganic nanoparticles, can achieve the anti-inflammatory effect, cancer resistance, and angiogenesis. Also, they can well complement other materials in tissue engineering (TE). Pertinent to the properties of CeO2-NPs and the pragmatic biosynthesis methods, this review will emphasize the recent application of CeO2-NPs to orthopedic biomedicine, in particular, the bone tissue engineering (BTE). The presentation, assessment, and outlook of the orthopedic potential and shortcomings of CeO2-NPs in this review expect to provide reference values for the future research and development of therapeutic agents based on CeO2-NPs.

Ceria Nanoparticles Decrease UVA-Induced Fibroblast Death Through Cell Redox Regulation Leading to Cell Survival, Migration and Proliferation

Exposure to ultraviolet radiation is a major contributor to premature skin aging and carcinogenesis, which is mainly driven by overproduction of reactive oxygen species (ROS). There is growing interest for research on new strategies that address photoaging prevention, such as the use of nanomaterials. Cerium oxide nanoparticles (nanoceria) show enzyme-like activity in scavenging ROS. Herein, our goal was to study whether under ultraviolet A rays (UVA)-induced oxidative redox imbalance, a low dose of nanoceria induces protective effects on cell survival, migration, and proliferation. Fibroblasts cells (L929) were pretreated with nanoceria (100 nM) and exposed to UVA radiation. Pretreatment of cells with nanoceria showed negligible cytotoxicity and protected cells from UVA-induced death. Nanoceria also inhibited ROS production immediately after irradiation and for up to 48 h and restored the superoxide dismutase (SOD) activity and GSH level. Additionally, the nanoceria pretreatment prevented apoptosis by decreasing Caspase 3/7 levels and the loss of mitochondrial membrane potential. Nanoceria significantly improved the cell survival migration and increased proliferation, over a 5 days period, as compared with UVA-irradiated cells, in wound healing assay. Furthermore, it was observed that nanoceria decreased cellular aging and ERK 1/2 phosphorylation. Our study suggests that nanoceria might be a potential ally to endogenous, antioxidant enzymes, and enhancing the redox potentials to fight against UVA-induced photodamage and consequently modulating the cells survival, migration, and proliferation.

Ceria Nanoparticles Mitigate the Iron Oxidative Toxicity of Human Retinal Pigment Epithelium

Oxidative injury is implicated in retinal damage observed in age-related macular degeneration (AMD), as well as other degenerative conditions. Abnormally elevated levels of iron accumulation within the retinal pigment epithelium have been detected in eyes with AMD, and it is suspected to play a role in the pathogenesis through the production of reactive oxygen species (ROS). Ceria nanoparticles (CNP) have the ability to scavenge ROS. This study sought to evaluate the ability of CNP to mitigate iron-induced oxidative stress and assess cell viability in the human ARPE-19 cell line in vitro. Cell viability was measured by an MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and compared between experimental groups undergoing 48-hr exposure to a ferrous iron solution with and without 24-hr CNP pre-treatment. The CNP effect on ROS formation was evaluated additionally by H2DCFDA (2,7-dichlorodihydrofluorescein diacetate) fluorescent probe assay and superoxide dismutase assay. CNP demonstrated a three-fold increase in cell viability and a reduction in ROS generation. The results show a promising treatment modality for diseases causing oxidative damage in the eye.

Cerium Oxide Nanoparticles: Recent Advances in Tissue Engineering

Submicron biomaterials have recently been found with a wide range of applications for biomedical purposes, mostly due to a considerable decrement in size and an increment in surface area. There have been several attempts to use innovative nanoscale biomaterials for tissue repair and tissue regeneration. One of the most significant metal oxide nanoparticles (NPs), with numerous potential uses in future medicine, is engineered cerium oxide (CeO2) nanoparticles (CeONPs), also known as nanoceria. Although many advancements have been reported so far, nanotoxicological studies suggest that the nanomaterial's characteristics lie behind its potential toxicity. Particularly, physicochemical properties can explain the positive and negative interactions between CeONPs and biosystems at molecular levels. This review represents recent advances of CeONPs in biomedical engineering, with a special focus on tissue engineering and regenerative medicine. In addition, a summary report of the toxicity evidence on CeONPs with a view toward their biomedical applications and physicochemical properties is presented. Considering the critical role of nanoengineering in the manipulation and optimization of CeONPs, it is expected that this class of nanoengineered biomaterials plays a promising role in the future of tissue engineering and regenerative medicine.

Uptake of Cerium Dioxide Nanoparticles and Impact on Viability, Differentiation and Functions of Primary Trophoblast Cells from Human Placenta

The human placenta is at the interface between maternal and fetal circulations, and is crucial for fetal development. The nanoparticles of cerium dioxide (CeO₂ NPs) from air pollution are an unevaluated risk during pregnancy. Assessing the consequences of placenta exposure to CeO₂ NPs could contribute to a better understanding of NPs’ effect on the development and functions of the placenta and pregnancy outcome. We used primary villous cytotrophoblasts purified from term human placenta, with a wide range of CeO₂ NPs concentrations (0.1–101 μg/cm²) and exposure time (24–72 h), to assess trophoblast uptake, toxicity and impact on trophoblast differentiation and endocrine function. We have shown the capacity of both cytotrophoblasts and syncytiotrophoblasts to internalize CeO₂ NPs. CeO₂ NPs affected trophoblast metabolic activity in a dose and time dependency, induced caspase activation and a LDH release in the absence of oxidative stress. CeO₂ NPs decreased the fusion capacity of cytotrophoblasts to form a syncytiotrophoblast and disturbed secretion of the pregnancy hormones hCG, hPL, PlGF, P4 and E2, in accordance with NPs concentration. This is the first study on the impact of CeO₂ NPs using human primary trophoblasts that decrypts their toxicity and impact on placental formation and functions.

Engineered defects in cerium oxides: tuning chemical reactivity for biomedical, environmental, & energy applications

Nanocrystalline cerium oxide (nanoceria) is a rare earth oxide with a complex surface chemistry. This material has seen substantial investigation in recent years in both fundamental and applied studies due largely to more precise characterization of the unique surface structures, which mediate its pronounced redox activity. In particular, oxygen storage/buffering capacities have been thoroughly correlated with synthesis and processing condition effects on other material features such as surface (micro-) faceting, reconstruction, and (extent of) hydration. Key material features such as these modulate nanoceria redox performance by changing the crystal microenvironment. In this review, we present nanoengineering methods, which have produced increased nanoceria performance in biomedical, energy, and catalysis applications. The impact of combined/cooperative theoretical and experimental studies are highlighted throughout.

Synthesis of Cerium Oxide Nanoparticles Using Various Methods: Implications for Biomedical Applications

Cerium oxide nanoparticles have been used in a number of non-medical products over the years. The therapeutic application of these nanoparticles has mainly been due to their oxidative stress ameliorating abilities. Their enzyme-mimetic catalytic ability to change between the Ce3+ and Ce4+ species makes them ideal for a role as free-radical scavengers for systemic diseases as well as neurodegenerative diseases. In this review, we look at various methods of synthesis (including the use of stabilizing/capping agents and precursors), and how the synthesis method affects the physicochemical properties, their behavior in biological environments, their catalytic abilities as well as their reported toxicity.

Treatment of Human Lens Epithelium with High Levels of Nanoceria Leads to Reactive Oxygen Species Mediated Apoptosis

Nanoceria (cerium oxide nanoparticles) have been shown to protect human lens epithelial cells (HLECs) from oxidative stress when used at low concentrations. However, there is a lack of understanding about the mechanism of the cytotoxic and genotoxic effects of nanoceria when used at higher concentrations. Here, we investigated the impact of 24-hour exposure to nanoceria in HLECs. Nanoceria's effects on basal reactive oxygen species (ROS), mitochondrial morphology, membrane potential, ATP, genotoxicity, caspase activation and apoptotic hallmarks were investigated. Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) studies on isolated mitochondria revealed significant uptake and localization of nanoceria in the mitochondria. At high nanoceria concentrations (400 µg mL-1), intracellular levels of ROS were increased and the HLECs exhibited classical hallmarks of apoptosis. These findings concur with the cells maintaining normal ATP levels necessary to execute the apoptotic process. These results highlight the need for nanoceria dose-effect studies on a range of cells and tissues to identify therapeutic concentrations in vitro or in vivo.

Injectable, self-healable zwitterionic cryogels with sustained microRNA - cerium oxide nanoparticle release promote accelerated wound healing

Diabetics are prone to chronic wounds that have slower healing, and methods of accelerating the wound closure and to ensure protection from infections are critically needed. MicroRNA-146a gets dysregulated in diabetic wounds and injection of this microRNA combined with reactive oxygen species-scavenging cerium oxide nanoparticles (CNPs) can reduce inflammation and improve wound healing; however, a better delivery method than intradermal injections is needed. Here we demonstrate a biomaterial system of zwitterionic cryogels (gels formed below freezing temperatures) laden with CNP-miR146a that are topically applicable, injectable, self-healable, and provide sustained release of the therapeutic molecules. These cryogels are comprised of CBMA or SBMA and HEMA, and do not contain chemical crosslinkers. Properties of the gels can be manipulated by changing monomer type and ratio. These materials have demonstrated efficacy and viability in vivo with a diabetic mouse wound healing model. Overall, these materials have a high potential for application in wound treatments due to their ease of production, antifouling characteristics, durability, topical application, and sustained release mechanics. STATEMENT OF SIGNIFICANCE: This work presents the development of zwitterionic cryogels with unique physical properties including injectability and self-healing, that also offer highly sustained release of nanoparticles over time to improve wound healing in a diabetic mouse model. The nanoparticles are made of cerium oxide, which is known to scavenge reactive oxygen species and reduce oxidative stress, and these particles have been further tagged with a microRNA146a that has been shown to reduce inflammation. Zwitterionic materials are known for their superior antifouling properties and good biocompatibility and ability to incorporate bioactive factors. Given these properties, the use of these materials as wound healing dressings would be exciting, yet to date it has been difficult to prolong the release of bioactive factors from them due to their hydrophilicity. Previously we developed zwitterionic cyrogels with very sustained protein release over time, but those materials were quite brittle and difficult to handle. Here, we demonstrate for the first time that by removing the crosslinker molecule from our reaction and polymerizing gels under cryo-conditions, we are able to form zwitterionic cryogels that are injectable, self-healing, and with sustained release profiles. The sustained release of miRNA146a-tagged cerium oxide nanoparticles from these gels is demonstrated to speed up diabetic wound healing time and significantly reduce inflammation.

Ethylene glycol coated nanoceria protects against oxidative stress in human lens epithelium

Chronic diseases are rising in incidence and prevalence because of increases in life expectancy in many parts of the world coupled with advances in medicine which manage disease progression, rather than curing and alleviating the causes. Cataract is one such chronic condition. Identifying a therapeutic intervention that is successful in reversing or preventing cataracts may have applications for other chronic diseases of protein misfolding, such as diabetes and Alzheimer's disease as these have similar causation factors, notably oxidative stress and/or glycation. Cerium oxide nanoparticles (nanoceria) which have antioxidant, radioprotective and enzyme-mimetic properties have the potential to lead to an effective non-surgical treatment. However, nanoceria stability in physiological media is poor thus hindering their effective use in biomedical applications. Here we report a highly efficient one-pot synthesis of nanoceria (2-5 nm) coated with ethylene glycol, that is colloidally stable in physiological media and exhibits multiwavelength photoluminescence. The formulation, up to concentrations of 200 μg ml-1, was not toxic to human lens epithelial cells and had no adverse effect on the cellular morphology or proliferation rate. More significantly, these nanoceria showed protective effects against oxidative stress induced by hydrogen peroxide in lens epithelial cells. Electron microscopy studies show the internalization and cytoplasmic localization of the nanoceria was found to be largely in the perinuclear region.