Nanoceria extend photoreceptor cell lifespan in tubby mice by modulation of apoptosis/survival signaling pathways. Neurobiol Dis. 2011;42:514-523. [PMID: 21396448 DOI: 10.1016/j.nbd.2011.03.004]

Cerium oxide nanoparticles: Chemical properties, biological effects and potential therapeutic opportunities (Review)

The chemistry of pure cerium oxide (CeO2-x) nanoparticles has been widely studied since the 1970s, especially for chemical catalysis. CeO2-x nanoparticles have been included in an important class of industrial metal oxide nanoparticles and have been attributed a range of wide applications, such as ultraviolet absorbers, gas sensors, polishing agents, cosmetics, consumer products, high-tech devices and fuel cell conductors. Despite these early applications in the field of chemistry, the biological effects of CeO2-x nanoparticles were only explored in the 2000s. Since then, CeO2-x nanoparticles have gained a spot in research related to various diseases, especially the ones in which oxidative stress plays a part. Due to an innate oxidation state variation on their surface, CeO2-x nanoparticles have exhibited redox activities in diseases, such as cancer, acting either as an oxidizing agent, or as an antioxidant. In biological models, CeO2-x nanoparticles have been shown to modulate cancer cell viability and, more recently, cell death pathways. However, a deeper understanding on how the chemical structure of CeO2-x nanoparticles (including nanoparticle size, shape, suspension, agglomeration in the medium used, pH of the medium, type of synthesis and crystallite size) influences the cellular effects observed remains to be elucidated. In the present review, the chemistry of CeO2-x nanoparticles and their impact on biological models and modulation of cell signalling, particularly focusing on oxidative and cell death pathways, were investigated. The deeper understanding of the chemical activity of CeO2-x nanoparticles may provide the rationale for further biomedical applications towards disease treatment and drug delivery purposes.

Platinum Nanozymes Counteract Photoreceptor Degeneration and Retina Inflammation in a Light-Damage Model of Age-Related Macular Degeneration

Degeneration of photoreceptors in age-related macular degeneration (AMD) is associated with oxidative stress due to the intense aerobic metabolism of rods and cones that if not properly counterbalanced by endogenous antioxidant mechanisms can precipitate photoreceptor degeneration. In spite of being a priority eye disease for its high incidence in the elderly, no effective treatments for AMD exist. While systemic administration of antioxidants has been unsuccessful in slowing down degeneration, locally administered rare-earth nanoparticles were shown to be effective in preventing retinal photo-oxidative damage. However, because of inherent problems of dispersion in biological media, limited antioxidant power, and short lifetimes, these NPs are still confined to the preclinical stage. Here we propose platinum nanoparticles (PtNPs), potent antioxidant nanozymes, as a therapeutic tool for AMD. PtNPs exhibit high catalytic activity at minimal concentrations and protect primary neurons against oxidative insults and the ensuing apoptosis. We tested the efficacy of intravitreally injected PtNPs in preventing or mitigating light damage produced in dark-reared albino Sprague-Dawley rats by in vivo electroretinography (ERG) and ex vivo retina morphology and electrophysiology. We found that both preventive and postlesional treatments with PtNPs increased the amplitude of ERG responses to light stimuli. Ex vivo recordings demonstrated the selective preservation of ON retinal ganglion cell responses to light stimulation in lesioned retinas treated with PtNPs. PtNPs administered after light damage significantly preserved the number of photoreceptors and inhibited the inflammatory response to degeneration, while the preventive treatment had a milder effect. The data indicate that PtNPs can effectively break the vicious cycle linking oxidative stress, degeneration, and inflammation by exerting antioxidant and anti-inflammatory actions. The increased photoreceptor survival and visual performances in degenerated retinas, together with their high biocompatibility, make PtNPs a potential strategy to cure AMD.

Pegylated nanoceria: A versatile nanomaterial for noninvasive treatment of retinal diseases

Oxidative stress induced reactive oxygen species has been implicated as the primary molecular mechanism in the pathogenesis of debilitating retinal diseases such as diabetic retinopathy, neovascularization and age-related macular degeneration. Nanoceria (cerium oxide nanoparticles) has recently received much attention, because of its superior and regenerative radical scavenging properties. This review focuses on retinal applications of nanoceria and functionalized nanoceria. Studies in animal models showed that nanoceria possess antioxidant, anti-inflammatory, anti-angiogenic, anti-apoptotic properties and preserves retinal morphology and prevents loss of retinal functions. Nanoceria have been tested in animal models of age-related macular degeneration and neovascularization and their efficacy have been shown to persist for a long time, without any collateral effects. To date, several pharmaceutical formulations of nanoceria have been developed for their prospective clinical ophthalmic applications such as chitosan coated nanoceria, nanoceria loaded into hydrogels, nanoceria embedded in wafers and contact lens and organosilane or polyethylene glycol functionalized nanoceria. Based on their nano size range, ocular permeation could be achieved to allow topical administration of nanoceria. PEGylation of nanoceria represents the key strategy to support eye drop formulation with enhanced corneal permeation, without altering chemical physical properties. Based on their excellent antioxidant properties, nano-size, safety and tolerability, PEGylated nanoceria represent a new potential therapeutic for the treatment.

Recent advances and prospects for lipid-based nanoparticles as drug carriers in the treatment of human retinal diseases

The delivery of cures for retinal diseases remains problematic. There are four main challenges: passing through multiple barriers of the eye, the delivery to particular retinal cell types, the capability to carry different forms of therapeutic cargo and long-term therapeutic efficacy. Lipid-based nanoparticles (LBNPs) are potent to overcome these challenges due to their unique merits: amphiphilic nanoarchitectures to pass biological barriers, vary modifications with specific affinity to target cell types, flexible capacity for large and mixed types of cargos and slow-release formulations for long-term treatment. We have reviewed the latest research on the applications of LBNPs for treating retinal diseases and categorized them by different payloads. Furthermore, we identified technical barriers and discussed possible future development for LBNPs to expand the therapeutic potential in treating retinal diseases.

Innovative Strategies for Drug Delivery to the Ocular Posterior Segment

Innovative and new drug delivery systems (DDSs) have recently been developed to vehicle treatments and drugs to the ocular posterior segment and the retina. New formulations and technological developments, such as nanotechnology, novel matrices, and non-traditional treatment strategies, open new perspectives in this field. The aim of this mini-review is to highlight promising strategies reported in the current literature based on innovative routes to overcome the anatomical and physiological barriers of the vitreoretinal structures. The paper also describes the challenges in finding appropriate and pertinent treatments that provide safety and efficacy and the problems related to patient compliance, acceptability, effectiveness, and sustained drug delivery. The clinical application of these experimental approaches can help pave the way for standardizing the use of DDSs in developing enhanced treatment strategies and personalized therapeutic options for ocular pathologies.

Intranasal cerium oxide nanoparticles improves locomotor activity and reduces oxidative stress and neuroinflammation in haloperidol-induced parkinsonism in rats

Introduction: Cerium oxide nanoparticles (CONPs) have been investigated for their therapeutic potential in Parkinson's disease (PD) due to their potent and regenerative antioxidant activity. In the present study, CONPs were used to ameliorate the oxidative stress caused by free radicals in haloperidol-induced PD in rats following intranasal administration. Method: The antioxidant potential of the CONPs was evaluated in vitro using ferric reducing antioxidant power (FRAP) assay. The penetration and local toxicity of the CONPs was evaluated ex-vivo using goat nasal mucosa. The acute local toxicity of intranasal CONPs was also studied in rat. Gamma scintigraphy was used to assess the targeted brain delivery of CONPs. Acute toxicity studies were performed in rats to demonstrate safety of intranasal CONPs. Further, open field test, pole test, biochemical estimations and brain histopathology was performed to evaluate efficacy of intranasal CONPs in haloperidol-induced PD rat model. Results: The FRAP assay revealed highest antioxidant activity of prepared CONPs at a concentration of 25 μg/mL. Confocal microscopy showed deep and homogenous distribution of CONPs in the goat nasal mucus layers. No signs of irritation or injury were seen in goat nasal membrane when treated with optimized CONPs. Scintigraphy studies in rats showed targeted brain delivery of intranasal CONPs and acute toxicity study demonstrated safety. The results of open field and pole test showed highly significant (p < 0.001) improvement in locomotor activity of rats treated with intranasal CONPs compared to untreated rats. Further, brain histopathology of treatment group rats showed reduced neurodegeneration with presence of more live cells. The amount of thiobarbituric acid reactive substances (TBARS) was reduced significantly, whereas the levels of catalase (CAT), superoxide dismutase (SOD), and GSH were increased significantly, while amounts of interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-α) showed significant reduction after intranasal administration of CONPs. Also, the intranasal CONPs, significantly high (p < 0.001) dopamine concentration (13.93 ± 0.85 ng/mg protein) as compared to haloperidol-induced control rats (5.76 ± 0.70 ng/mg protein). Conclusion: The overall results concluded that the intranasal CONPs could be safe and effective therapeutics for the management of PD.

Nanomedicine and drug delivery to the retina: current status and implications for gene therapy

Blindness affects more than 60 million people worldwide. Retinal disorders, including age-related macular degeneration (AMD), diabetic retinopathy (DR), and glaucoma, are the leading causes of blindness. Finding means to optimize local and sustained delivery of drugs or genes to the eye and retina is one goal to advance the development of new therapeutics. Despite the ease of accessibility of delivering drugs via the ocular surface, the delivery of drugs to the retina is still challenging due to anatomic and physiologic barriers. Designing a suitable delivery platform to overcome these barriers should enhance drug bioavailability and provide a safe, controlled, and sustained release. Current inventions for posterior segment treatments include intravitreal implants and subretinal viral gene delivery that satisfy these criteria. Several other novel drug delivery technologies, including nanoparticles, micelles, dendrimers, microneedles, liposomes, and nanowires, are now being widely studied for posterior segment drug delivery, and extensive research on gene delivery using siRNA, mRNA, or aptamers is also on the rise. This review discusses the current state of retinal drug/gene delivery and highlights future therapeutic opportunities.

Enhanced Antioxidant Ability of PEG-Coated Ce0.5Zr0.5O2-Based Nanofluids for Scavenging Hydroxyl Radicals

The antioxidant therapy to preserve residual hearing is relatively recent, and the search for effective antioxidants is still ongoing. Though nanoceria has shown promising radical-scavenging capability, improving its antioxidant ability and the dispersion stability of its nanofluid, which is critical to the desired site, i.e., cochlea, still remains a major challenge. The objective of the present work is to study the radical-scavenging capability of poly(ethylene glycol) (PEG)-coated CeO₂ and Ce_0.5Zr_0.5O₂ nanoparticles in water and the biologically relevant fluid (PBS buffer). Nanoparticles in the size range of 4.0-9.0 nm are synthesized using the coprecipitation method and characterized using suitable techniques. The scavenging and dispersion stability of the synthesized nanofluid are analyzed using a UV-vis spectrophotometer. It is found that the addition of PEG during the synthesis process promoted the generation of finer nanoparticles with a narrow size distribution and the doping of zirconium produced a large number of defects in the crystallite structure. The PEG coating over the nanoparticles improved the dispersion stability of nanofluids without affecting their surface reactivity, and it is found to be 94 and 80% in water and PBS, respectively, at 500 μM and 60 min, which is maintained till 90 min. The highest scavenging of hydroxyl radicals by PEG-coated Ce_0.5Zr_0.5O₂ is found to be 60%, which is significantly superior to that of CeO₂. The scavenging capability is found to be increased with the concentration of nanoparticles, showing the best scavenging activity at 190 and 150 μM for PEG-coated CeO₂ and Ce_0.5Zr_0.5O₂, respectively, and the scavenging in water is at par with that of PBS, indicating that these nanoparticles are suitable to be used in sites where a biologically relevant fluid is present, e.g., the cochlea. It is proposed that PEG-coated Ce_0.5Zr_0.5O₂ having an average size of ∼ 4 nm can be a potential antioxidant in relevant biomedical applications.

Rare earth smart nanomaterials for bone tissue engineering and implantology: Advances, challenges, and prospects

Bone grafts or prosthetic implant designing for clinical application is challenging due to the complexity of integrated physiological processes. The revolutionary advances of nanotechnology in the biomaterial field expedite and endorse the current unresolved complexity in functional bone graft and implant design. Rare earth (RE) materials are emerging biomaterials in tissue engineering due to their unique biocompatibility, fluorescence upconversion, antimicrobial, antioxidants, and anti-inflammatory properties. Researchers have developed various RE smart nano-biomaterials for bone tissue engineering and implantology applications in the past two decades. Furthermore, researchers have explored the molecular mechanisms of RE material-mediated tissue regeneration. Recent advances in biomedical applications of micro or nano-scale RE materials have provided a foundation for developing novel, cost-effective bone tissue engineering strategies. This review attempted to provide an overview of RE nanomaterials' technological innovations in bone tissue engineering and implantology and summarized the osteogenic, angiogenic, immunomodulatory, antioxidant, in vivo bone tissue imaging, and antimicrobial properties of various RE nanomaterials, as well as the molecular mechanisms involved in these biological events. Further, we extend to discuss the challenges and prospects of RE smart nano-biomaterials in the field of bone tissue engineering and implantology.

Emerging Theranostic Nanomaterials in Diabetes and Its Complications

Diabetes mellitus (DM) refers to a group of metabolic disorders that are characterized by hyperglycemia. Oral subcutaneously administered antidiabetic drugs such as insulin, glipalamide, and metformin can temporarily balance blood sugar levels, however, long-term administration of these therapies is associated with undesirable side effects on the kidney and liver. In addition, due to overproduction of reactive oxygen species and hyperglycemia-induced macrovascular system damage, diabetics have an increased risk of complications. Fortunately, recent advances in nanomaterials have provided new opportunities for diabetes therapy and diagnosis. This review provides a panoramic overview of the current nanomaterials for the detection of diabetic biomarkers and diabetes treatment. Apart from diabetic sensing mechanisms and antidiabetic activities, the applications of these bioengineered nanoparticles for preventing several diabetic complications are elucidated. This review provides an overall perspective in this field, including current challenges and future trends, which may be helpful in informing the development of novel nanomaterials with new functions and properties for diabetes diagnosis and therapy.

Redox Active Cerium Oxide Nanoparticles: Current Status and Burning Issues

Research on cerium oxide nanoparticles (nanoceria) has captivated the scientific community due to their unique physical and chemical properties, such as redox activity and oxygen buffering capacity, which made them available for many technical applications, including biomedical applications. The redox mimetic antioxidant properties of nanoceria have been effective in the treatment of many diseases caused by reactive oxygen species (ROS) and reactive nitrogen species. The mechanism of ROS scavenging activity of nanoceria is still elusive, and its redox activity is controversial due to mixed reports in the literature showing pro-oxidant and antioxidant activity. In light of its current research interest, it is critical to understand the behavior of nanoceria in the biological environment and provide answers to some of the critical and open issues. This review critically analyzes the status of research on the application of nanoceria to treat diseases caused by ROS. It reviews the proposed mechanism of action and shows the effect of surface coatings on its redox activity. It also discusses some of the crucial issues in deciphering the mechanism and redox activity of nanoceria and suggests areas of future research.

Ameliorative Role of Cerium Oxide Nanoparticles Against Fipronil Impact on Brain Function, Oxidative Stress, and Apoptotic Cascades in Albino Rats

Fipronil (FIP) is an N-phenylpyrazole insecticide that is used extensively in public health and agriculture against a wide range of pests. Exposure to FIP is linked to negative health outcomes in humans and animals including promoting neuronal cell injury, which results in apoptosis through the production of reactive oxygen species (ROS). Therefore, the purpose of the current study was to investigate the neuroprotective effects of cerium oxide nanoparticles (CeNPs) on neuronal dysfunction induced by FIP in albino rats. Male rats were randomly classified into four groups: control, FIP (5 mg/kg bwt), CeNPs (35 mg/kg bwt), and FIP + CeNPs (5 (FIP) + 35 (CeNPs) mg/kg bwt), which were treated orally once daily for 28 consecutive days. Brain antioxidant parameters, histopathology, and mRNA expression of genes related to brain function were evaluated. The results revealed oxidative damage to brain tissues in FIP-treated rats indicated by the elevated levels of malondialdehyde (MDA) and nitric oxide (NO) levels and reduced activities of antioxidant enzymes such as superoxide dismutase (SOD) and glutathione peroxidase (GPx). On the other hand, the FIP’s group that was treated with CeNPs showed decrease in MDA and NO levels and increase in SOD and GPx enzymes activity. Besides, FIP-treated rats showed decreased butyrylcholinesterase (BuChE) activity in comparison to the FIP + CeNPs group. Moreover, FIP caused up-regulation of the expression of neuron-specific enolase (NSE), caspase-3, and glial fibrillary acidic protein (GFAP) but down-regulation of B-cell lymphoma-2 (BCL-2) expression. But the FIP + CeNPs group significantly down-regulated the GFAP, NSE, and caspase-3 and up-regulated the gene expression of BCL-2. Additionally, the FIP-treated group of rats had clear degenerative lesions in brain tissue that was reversed to nearly normal cerebral architecture by the FIP + CeNPs treatment. Immunohistochemical examination of brain tissues of rats-treated with FIP showed abundant ionized calcium-binding adaptor molecule 1 (Iba-1) microglia and caspase-3 and apoptotic cells with nearly negative calbindin and synaptophysin reaction, which were countered by FIP + CeNPs treatment that revealed a critical decrease in caspase-3, Iba-1 reaction with a strong calbindin positive reaction in most of the Purkinje cells and strong synaptophysin reaction in the cerebrum and cerebellum tissues. Based on reported results herein, CeNPs treatment might counteract the neurotoxic effect of FIP pesticide via an antioxidant-mediated mechanism.

Harnessing the tunable cavity of nanoceria for enhancing Y-27632-mediated alleviation of ocular hypertension

Background: Y-27632 is a potent ophthalmic drug for the treatment of ocular hypertension, a globally prevalent eye disease. However, the sustained delivery of Y-27632 by a therapeutic carrier to lesion sites located in the inner segments of the eye for effectively treating the ocular disorder still remains challenging.

Methods: To realize the goal, a strategy based on solvothermal-assisted deposition/infiltration in combination with surface modification is utilized to synthesize hollow mesoporous ceria nanoparticles (HMCNs) with tailorable shell thicknesses and drug release profiles. The shell thickness of HMCNs is rationally exploited for achieving sustained drug release and advanced therapeutic benefits.

Results: The shell thickness can regulate release profiles of Y-27632, displaying that thick and thin (~40 nm and ~10 nm) shelled HMCNs reveal burst release characteristics (within 2 days) or limited drug loading content (~10% for the 40 nm thick). As a compromise, the HMCNs with moderate shell thickness (~20 nm) possess the most sustained drug release over a period of 10 days. In a rabbit model of glaucoma, a single instillation of the optimized Y-27632-loaded HMCNs can effectively treat glaucoma for 10 days via simultaneously repairing the defected cornea (recovery of ~93% ATP1A1 mRNA levels), restoring the reduced thickness of outer nuclear layer to normal (~64 µm), and restoring ~86% of the impaired photoreceptor cells.

Conclusion: A comprehensive study on the importance of HMCN shell thickness in developing long-acting nano eye drops for the efficient management of glaucoma is proposed. The findings suggest a central role of nanobiomaterial structural engineering in developing the long-life eye drops for pharmacological treatment of intraocular diseases.

Emerging Nano-Formulations and Nanomedicines Applications for Ocular Drug Delivery

Ocular diseases can deteriorate vision to the point of blindness and thus can have a major impact on the daily life of an individual. Conventional therapies are unable to provide absolute therapy for all ocular diseases due to the several limitations during drug delivery across the blood-retinal barrier, making it a major clinical challenge. With recent developments, the vast number of publications undergird the need for nanotechnology-based drug delivery systems in treating ocular diseases. The tool of nanotechnology provides several essential advantages, including sustained drug release and specific tissue targeting. Additionally, comprehensive in vitro and in vivo studies have suggested a better uptake of nanoparticles across ocular barriers. Nanoparticles can overcome the blood-retinal barrier and consequently increase ocular penetration and improve the bioavailability of the drug. In this review, we aim to summarize the development of organic and inorganic nanoparticles for ophthalmic applications. We highlight the potential nanoformulations in clinical trials as well as the products that have become a commercial reality.

Oxidative stress as a therapeutic target for the prevention and treatment of early age-related macular degeneration

Age-related macular degeneration, the leading cause of irreversible visual loss among older adults in developed countries, is a chronic, multifactorial, and progressive disease with the development of painless, central vision loss. Retinal pigment epithelial cell dysfunction is a core change in age-related macular degeneration that results from aging and the accumulated effects of genetic and environmental factors that, in part, is both caused by and leads to oxidative stress. In this review, we describe the role of oxidative stress, the cytoprotective oxidative stress pathways, and the impact of oxidative stress on critical cellular processes involved in age-related macular degeneration pathobiology. We also offer targeted therapy that may define how antioxidant therapy can either prevent or improve specific stages of age-related macular degeneration.

An overview on recent in vivo biological application of cerium oxide nanoparticles

Cerium oxide nanoparticles (CNPs) possess a great potential as therapeutic agents due to their ability to self-regenerate by reversibly switching between two valences +3 and +4. This article reviews recent articles dealing with in vivo studies of CNPs towards Alzheimer's disease, obesity, liver inflammation, cancer, sepsis, amyotrophic lateral sclerosis, acute kidney injury, radiation-induced tissue damage, hepatic ischemia reperfusion injury, retinal diseases and constipation. In vivo anti-cancer studies revealed the effectiveness of CNPs to reduce tumor growth and angiogenesis in melanoma, ovarian, breast and retinoblastoma cancer cell-induced mice, with their conjugation with folic acid, doxorubicin, CPM, or CXC receptor-4 antagonist ligand eliciting higher efficiency. After conjugation with triphenylphosphonium or magnetite nanoparticles, CNPs were shown to combat Alzheimer's disease by reducing amyloid-β, glial fibrillary acidic protein, inflammatory and oxidative stress markers in mice. By improving muscle function and longevity, the citrate/EDTA-stabilized CNPs could ameliorate amyotrophic lateral sclerosis. Also, they could effectively reduce obesity in mice by scavenging ROS and reducing adipogenesis, triglyceride synthesis, GAPDH enzyme activity, leptin and insulin levels. In CCl4-induced rats, stress signaling pathways due to inflammatory cytokines, liver enzymes, oxidative and endoplasmic reticulum messengers could be attenuated by CNPs. Commercial CNPs showed protective effects on rats with hepatic ischemia reperfusion and peritonitis-induced hepatic/cardiac injuries by decreasing oxidative stress and hepatic/cardiac inflammation. The same CNPs could improve kidney function by diminishing renal superoxide, hyperglycemia and tubular damage in peritonitis-induced acute kidney injury in rats. Radiation-induced lung and testicular tissue damage could be alleviated in mice, with the former showing improvement in pulmonary distress and bronchoconstriction and the latter exhibiting restoration in spermatogenesis rate and spermatid/spermatocyte number. Through enhancement of gastrointestinal motility, the CNPs could alleviate constipation in both young and old rats. They could also protect rat from light-induced retinal damage by slowing down neurodegenerative process and microglial activation.

Cerium oxide nanoparticles and their importance in cell signaling pathways for predicting cellular behavior

Cerium oxide nanoparticles (CeO₂-NPs) have prolifically attracted immense interest of researchers due to their prominent anti-oxidant nature. However, these characteristics are accompanied by some ambiguities in other studies reporting their oxidant and toxic properties. In this regard previous literature has pointed to the importance of the NPs morphology and environmental conditions as well as biomolecules that induce a different response by initiating a cascade of activities. Therefore, due to the fact that signaling proteins are key mediators in cellular responses, the cognizance of the CeO₂-NP-targeted signaling pathways could facilitate predicting the cellular behavior and thus more efficient applications of these NPs for clinical purposes. Consequently, a comprehensive review is necessary in this field, to clarify the impacts of CeO₂-NPs on various signaling pathways.

Recent developments in regenerative ophthalmology

Regenerative medicine (RM) is one of the most promising disciplines for advancements in modern medicine, and regenerative ophthalmology (RO) is one of the most active fields of regenerative medicine. This review aims to provide an overview of regenerative ophthalmology, including the range of tools and materials being used, and to describe its application in ophthalmologic subspecialties, with the exception of surgical implantation of artificial tissues or organs (e.g., contact lens, artificial cornea, intraocular lens, artificial retina, and bionic eyes) due to space limitations. In addition, current challenges and limitations of regenerative ophthalmology are discussed and future directions are highlighted.

Antioxidant Nanotherapies for the Treatment of Inflammatory Diseases

Reactive oxygen species (ROS) are essential in regulating various physiological functions. However, overproduction of ROS is implicated in the pathogenesis of various inflammatory diseases. Antioxidant therapy has thus represented an effective strategy for the treatment of oxidative stress relevant inflammatory diseases. Conventional anti-oxidative agents showed limited in vivo effects owing to their non-specific distribution and low retention in disease sites. Over the past decades, significant achievements have been made in the development of antioxidant nanotherapies that exhibit multiple advantages such as excellent pharmacokinetics, stable anti-oxidative activity, and intrinsic ROS-scavenging properties. This review provides a comprehensive overview on recent advances in antioxidant nanotherapies, including ROS-scavenging inorganic nanoparticles, organic nanoparticles with intrinsic antioxidant activity, and drug-loaded anti-oxidant nanoparticles. We highlight the biomedical applications of antioxidant nanotherapies in the treatment of different inflammatory diseases, with an emphasis on inflammatory bowel disease, cardiovascular disease, and brain diseases. Current challenges and future perspectives to promote clinical translation of antioxidant nanotherapies are also briefly discussed.

Cerium oxide nanoparticles: properties, biosynthesis and biomedical application

Cerium oxide nanoparticles have revolutionized the biomedical field and is still in very fast pace of development. Hence, this work elaborates the physicochemical properties, biosynthesis, and biomedical applications of cerium oxide nanoparticles.

Cerium oxide nanoparticles: A promising tool for the treatment of fibrosarcoma in-vivo

In this study, we used cerium oxide nanoparticles and evaluated their anti-cancer effects in a mouse model of fibrosarcoma. For evaluation of anti-cancer effects of nanoceria, tumor volume measurement, TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) assay, quantitative real-time PCR (qPCR) for Bax and Bcl2 genes, a panel of liver and kidney function tests and hematoxylin-eosin staining were done. Nanoceria dominantly accumulated in the tumor and it could significantly decrease tumor growth and volume in tumor-bearing mice that received nanoceria for four weeks. Cerium oxide nanoparticle showed potential anti-cancer properties against fibrosarcoma.

Ophthalmic Applications of Cerium Oxide Nanoparticles

Cerium oxide nanoparticles (CeO₂-NPs; or nanoceria) have been largely studied for biomedical applications due to their peculiar auto-regenerative antioxidant activity. This review focuses on ophthalmic applications of nanoceria. Many in vivo data indicate that nanoceria protect the retina from neurodegeneration. In particular, they have been tested in animal models of age-related macular degeneration and retinitis pigmentosa and their neuroprotective properties have been shown to persist for a long time, without any collateral effects. In vitro cytotoxicity studies have shown that CeO₂-NPs could be safe for lens cells and could represent a new therapy for cataract treatment, but further studies are needed. To date, different pharmaceutical formulations based on nanoceria have been created looking at future clinical ophthalmic applications, such as water-soluble nanoceria, glycol chitosan-coated ceria nanoparticles (GCCNPs), and alginate-gelatin hydrogel loaded GCCNPs. GCCNPs were also effective in preventing choroidal neovascularization in vivo. Based on the nanosize of nanoceria, corneal permeation could be achieved to allow topical treatment of nanoceria. PEGylation and encapsulation in liposomes represent the main strategies to support corneal permeation, without altering nanoceria chemical-physical properties. Based on their great antioxidant properties, safety, and nanosize, nanoceria represent a new potential therapeutic for the treatment of several eye disorders.

Nanoceria neuroprotective effects in the light-damaged retina: A focus on retinal function and microglia activation

The use of nanomaterials is an emerging therapeutic approach for the treatment of several pathologies. Cerium oxide nanoparticles have been studied for biomedical application, including neurodegenerative disorders, such as age-related macular degeneration in several animal models. The light damage model is characterised by oxidative stress upregulation followed by photoreceptor death and microglia activation in the outer retina. For this reason, the light damage model mimics some aspects involved in human age-related macular degeneration pathogenesis. In this review, we focus on the neuroprotective effects on retinal function and microglia activation in the light damage model, considering the administration of the nanoparticles both before and after the injury. The electrical responses of the retina and the microglia number and morphology are clearly modulated by the treatment, supporting the beneficial effects of cerium oxide nanoparticles to counteract the degeneration processes in the retina.

Safety Assessment of Nanomaterials to Eyes: An Important but Neglected Issue

The production and application of nanomaterials have grown tremendously during last few decades. The widespread exposure of nanoparticles to the public is provoking great concerns regarding their toxicity to the human body. However, in comparison with the extensive studies carried out to examine nanoparticle toxicity to the human body/organs, one especially vulnerable organ, the eye, is always neglected. Although it is a small part of the body, 90% of outside information is obtained via the ocular system. In addition, eyes usually directly interact with the surrounding environment, which may get severer damage from toxic nanoparticles compared to inner organs. Therefore, the study of assessing the potential nanoparticle toxicity to the eyes is of great importance. Here, the recent advance of some representative manufactured nanomaterials on ocular toxicity is summarized. First, a brief introduction of ocular anatomy and disorders related to particulate matter exposure is presented. Following, the factors that may influence toxicity of nanoparticles to the eye are emphasized. Next, the studies of representative manufactured nanoparticles on eye toxicity are summarized and classified. Finally, the limitations that are associated with current nanoparticle-eye toxicity research are proposed.

Autoregenerative redox nanoparticles as an antioxidant and glycation inhibitor for palliation of diabetic cataracts

Diabetic cataracts (DCs) are one of the most common ocular complications of diabetes, and easily causes blindness among diabetics. However, there are limited drugs to delay and prevent DCs. Research studies indicate that oxidative damage of the crystalline lens and nonenzymatic glycosylation of the lens protein play a key role in the pathogenesis of DCs. Hence, we developed a kind of autoregenerative redox nanoparticle, which was CeO2 NPs coated with PEG-PLGA (PCNPs). We first found that PCNPs could work not only as an antioxidant to protect lens epithelial cells from oxidative stress based on the repetitive elimination of reactive oxygen species (ROS), but also as a glycation inhibitor effectively restraining α-crystallin glycation and crosslinking, thereby keeping the lens transparent and alleviating DCs. Experimental results successfully validated the fact that the PCNPs were able to operate in eyes for a long time to attenuate lens opacity. We expect that this strategy will provide promising potential for the treatment of DCs.

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

We report the first experimental evidence for the mitogenic action of cerium(IV) oxide and cerium(III) fluoride nanoparticles (CONs and CFNs) on the regeneration of a whole organism - freshwater flatworms Schmidtea mediterranea (planarian). Both types of cerium-containing nanoparticles are shown to be a highly potent mitogen for planaria. Both CONs and CFNs, in micro- and nanomolar concentrations, markedly accelerate planarian blastema growth, due to the enhancement of cellular proliferation, causing an increase in the mitotic index and in the quantity of blastema cells in regenerating planaria. CONs provided maximum activity at concentrations which were two orders of magnitude lower than those for CeF₃. The valence state of cerium in cerium-containing nanoparticles plays a significant role in the planarian regeneration mechanism: CeO₂ nanoparticles containing predominantly Ce⁴⁺ species presumably scavenge wound induced reactive oxygen species and moderately activate gene expression processes, while the regenerative action of CeF₃ nanoparticles containing only Ce³⁺ species is manifested in the pronounced expression of the genes involved in cell division, differentiation and migration. This is the first report on the effect of cerium-containing nanoparticles on tissue regeneration in vivo, further revealing the mechanisms of their biological action, which enhances the possibility of their use in cellular technologies.

Retinal long term neuroprotection by Cerium Oxide nanoparticles after an acute damage induced by high intensity light exposure

Cerium Oxide nanoparticles are antioxidant agents with autoregenerative radical scavenging activities, effective in preventing degeneration of photoreceptors of an albino rat when intravitreally injected prior to exposure to high intensity light. In this study, we performed a post injury administration of nanoceria and a long term analysis of their neuroprotective properties in order to better simulate the therapeutic treatment as it is carried out on patients with age related macular degeneration, and while photoreceptor degeneration is ongoing. We also injected nanoceria labelled with fluorescein isothiocianate in order to analyze their persistence after a single administration in a damaged retina and to investigate how long they both maintain their neuroprotective properties and where they localize in the retina. We demonstrated that after a single intravitreal injection, nanoceria remained in the retina for a long time and retained their neuroprotective properties. All these data form excellent bases for future clinical applications.

Therapeutic Benefits from Nanoparticles: The Potential Significance of Nanoscience in Retinal Degenerative Diseases

Several nanotechnology podiums have gained remarkable attention in the area of medical sciences, including diagnostics and treatment. In the past decade, engineered multifunctional nanoparticles have served as drug and gene carriers. The most important aspect of translating nanoparticles from the bench to bedside is safety. These nanoparticles should not elicit any immune response and should not be toxic to humans or the environment. Lipid-based nanoparticles have been shown to be the least toxic for in vivo applications, and significant progress has been made in gene and drug delivery employing lipid-based nanoassemblies. Several excellent reviews and reports discuss the general use and application of lipid-based nanoparticles; our review focuses on the application of lipid-based nanoparticles for the treatment of ocular diseases, and recent advances in and updates on their use.

Biomedical applications of nanoceria: new roles for an old player

The use of different biomaterials with the ability to accelerate the repair and regeneration processes is of great importance in tissue engineering strategies. On this point, cerium oxide nanoparticles (CNPs or nanoceria) have recently attracted much attention due to their excellent biological properties including anti-oxidant, anti-inflammation and antibacterial activities as well as high angiogenic potential. The results of incorporation of these nano-sized particles into various constructs and scaffolds designed for tissue engineering applications have proven the success of this strategy in terms of improving healing process of different tissues. In this review, we first summarize the physicochemical and biological properties of nanoceria in brief and then present its usability in tissue engineering strategies based on the currently available published reports.

Nanoceria-loaded injectable hydrogels for potential age-related macular degeneration treatment

The major purpose of this article is to evaluate oligochitosan coated cerium oxide nanoparticles (OCCNPs) alginate laden injectable hydrogels and their potential treatment for age-related macular degeneration (AMD). The water soluble OCCNPs were loaded within injectable hydrogels as antioxidative agents. The release of OCCNPs from hydrogel, radical scavenging properties, and biocompatibility were evaluated and calculated in vitro. The effects of OCCNP laden hydrogel downregulating expression of angiogenic proteins and proinflammatory cytokines were quantified in human retinal pigment epithlium-19 (ARPE-19) and umbilical endothelium cell lines. The hydrogels behaved with moderate swelling and controllable degradation. The laden OCCNPs were released in a controlled manner in vitro during two months of testing. The OCCNP loaded hydrogels exhibited robust antioxidative properties in oxygen radical absorbance capacity tests and reduced apoptosis in H2 O2 -induced ARPE-19 cells. Furthermore, OCCNP loaded injectable hydrogels are biocompatible and suppressed the ipopolysaccharides-induced inflammation response in ARPE-19 cells, and inhibited expression of vascular endothelium growth factor in human ARPE-19 and umbilical endothelium cell lines. The alginate-gelatin injectable hydrogel loaded OCCNPs are biocompatible and have high potential in protecting cells from apoptosis, angiogenesis, and production of proinflammatory cytokines in AMD cellular models. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2795-2804, 2018.

Amelioration of diabetes-induced testicular and sperm damage in rats by cerium oxide nanoparticle treatment

Cerium oxide nanoparticles (CNPs) as an antioxidant have been used frequently to attenuate hyperglycaemia oxidative damage in different organs. We investigated the impact CNPs on the qualitative and quantitative sperm parameters, spermatogenesis and NFE2-related factor 2 (Nrf2) expression as a major contributor of antioxidant defence in the male diabetic rats. Twenty-four male rats were divided into four groups. Controls received only mouse food and water. Second group were treated with CNPs (30 mg kg^-1  day^-1 ) for 2 weeks. Rats in third group received streptozotocin (STZ) (60 mg/kg). In fourth group, animals became diabetic and received CNPs (30 mg kg^-1  day^-1 ) for 2 weeks. The results showed a significant abnormality in the sperm parameters and histopathological patterns of testes in the diabetic group compared to the control group and CNPs treatment significantly improved all testicular parameters. Following CNPs administration, sperm DNA fragmentation significantly reduced in the STZ-treated rats. Moreover, after CNPs intake in the STZ-treated rats, Nfr2 expression levels increased significantly. Overall, CNPs administration on the diabetic rates can attenuate detrimental effects of diabetes on the sperm potential fertility, sperm parameters, DNA integrity and Nrf2 expression levels. This study gives a future prospect to determine the role of CNPs in the context of diabetes.

Effects of CeO2 nanoparticles on the HO-1, NQO1, and GCLC expression in the testes of diabetic rats

CeO₂ nanoparticles (CNPs) as effective ROS scavengers exhibit potent antioxidant activity. In this study the effect of CNPs investigated was on HO-1, NQO1, and GCLC expression in the streptozotocin (STZ)-induced diabetic rats. Twenty-four male Wistar rats were divided into 4 groups: controls did not receive any treatment; diabetic rats received STZ (60 mg/kg daily); CNPs group received CNPs 30 mg/kg daily for 2 weeks; and rats in STZ + CNPs group received CNPs 30 mg/kg daily for 2 weeks following STZ injection. Oxidative stress was evaluated by measurement of total antioxidant capacity (TAC) and total oxidative status (TOS levels). HO-1, NQO1, and GCLC expression was measured using quantitative real-time PCR. Following STZ injection, significant lower levels of TAC and higher levels of TOS were observed. CNPs could alleviate deleterious effects of diabetes through the enhancement of TAC levels and a significant decline in TOS levels. HO-1, NQO1, and GCLC expression in the diabetic rats were lower than controls. HO-1, NQO1, and GCLC was upregulated in the diabetic rats treated with CNPs. There were significant correlations between NQO1 and GCLC, NQO1 and HO-1, and between HO-1 and GCLC expression. Moreover, Nrf2 was associated with NQO1, GCLC, and HO-1 expression. CNPs as Nrf2 upregulator confer protection against oxidative stress in the testes of STZ-induced diabetic rats by upregulating HO-1, GCLC, and NQO1 cytoprotective genes.

Nanoparticles as Delivery Vehicles for the Treatment of Retinal Degenerative Diseases

Over the last few years, huge progress has been made in the understanding of molecular mechanisms underlying the pathogenesis of retinal degenerative diseases. Such knowledge has led to the development of gene therapy approaches to treat these devastating disorders. Non-viral gene delivery has been recognized as a prospective treatment for retinal degenerative diseases. In this review, we will summarize the constituent characteristics and recent applications of three representative nanoparticles (NPs) in ocular therapy.

Toxicogenomics: A New Paradigm for Nanotoxicity Evaluation

The wider applications of nanoparticles (NPs) has evoked a world-wide concern due to their possible risk of toxicity in humans and other organisms. Aggregation and accumulation of NPs into cell leads to their interaction with biological macromolecules including proteins, nucleic acids and cellular organelles, which eventually induce toxicological effects. Application of toxicogenomics to investigate molecular pathway-based toxicological consequences has opened new vistas in nanotoxicology research. Indeed, genomic approaches appeared as a new paradigm in terms of providing information at molecular levels and have been proven to be as a powerful tool for identification and quantification of global shifts in gene expression. Toxicological responses of NPs have been discussed in this chapter with the aim to provide a clear understanding of the molecular mechanism of NPs induced toxicity both in in vivo and in vitro test models.

Preparation, Characterization, and Preliminary In Vitro Testing of Nanoceria-Loaded Liposomes

Cerium oxide nanoparticles (nanoceria), well known for their pro- and antioxidant features, have been recently proposed for the treatment of several pathologies, including cancer and neurodegenerative diseases. However, interaction between nanoceria and biological molecules such as proteins and lipids, short blood circulation time, and the need of a targeted delivery to desired sites are some aspects that require strong attention for further progresses in the clinical application of these nanoparticles. The aim of this work is the encapsulation of nanoceria into a liposomal formulation in order to improve their therapeutic potentialities. After the preparation through a reverse-phase evaporation method, size, Z-potential, morphology, and loading efficiency of nanoceria-loaded liposomes were investigated. Finally, preliminary in vitro studies were performed to test cell uptake efficiency and preserved antioxidant activity. Nanoceria-loaded liposomes showed a good colloidal stability, an excellent biocompatibility, and strong antioxidant properties due to the unaltered activity of the entrapped nanoceria. With these results, the possibility of exploiting liposomes as carriers for cerium oxide nanoparticles is demonstrated here for the first time, thus opening exciting new opportunities for in vivo applications.

Thioredoxin plays a key role in retinal neuropathy prior to endothelial damage in diabetic mice

Diabetes is a chronic metabolic syndrome that results in changes in carbohydrate, lipid and protein metabolism. With diabetes for a long time, it increases the risk of diabetic retinopathy (DR) and long-term morbidity and mortality. Moreover, emerging evidence suggests that neuron damage occurs earlier than microvascular complications in DR patients, but the underlying mechanism is unclear. We investigated diabetes-induced retinal neuropathy and elucidated key molecular events to identify new therapeutic targets for the clinical treatment and prevention of DR. For in vivo studies, a high-fat diet and streptozotocin (STZ) injection were used to generate the diabetes model. Hematoxylin-eosin staining was used for morphological observations and measurements of the outer nuclear layer thickness. Electroretinography (ERG) was used to assess retinal function. For in vitro studies, Neuro2a cells were incubated in normal (5.5 mM) and high-glucose (30 mM) conditions. Flow cytometry assays were performed to analyze apoptosis. Additionally, real-time PCR and Western blotting analyses were carried out to determine gene and protein expression in vitro and in vivo. Taken together, the results indicated that retinal neuropathy occurred prior to endothelial damage induced by diabetes, and thioredoxin (Trx) plays a key role in this process. This underlying mechanism may be related to activation of the Trx/ASK1/p-p38/Trx-interacting protein pathway.

Glycol Chitosan Engineered Autoregenerative Antioxidant Significantly Attenuates Pathological Damages in Models of Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is the foremost cause of irreversible blindness in people over the age of 65 especially in developing countries. Therefore, an exploration of effective and alternative therapeutic interventions is an unmet medical need. It has been established that oxidative stress plays a key role in the pathogenesis of AMD, and hence, neutralizing oxidative stress is an effective therapeutic strategy for treatment of this serious disorder. Owing to autoregenerative properties, nanoceria has been widely used as a nonenzymatic antioxidant in the treatment of oxidative stress related disorders. Yet, its potential clinical implementation has been greatly hampered by its poor water solubility and lack of reliable tracking methodologies/processes and hence poor absorption, distribution, and targeted delivery. The water solubility and surface engineering of a drug with biocompatible motifs are fundamental to pharmaceutical products and precision medicine. Here, we report an engineered water-soluble, biocompatible, trackable nanoceria with enriched antioxidant activity to scavenge intracellular reactive oxygen species (ROS). Experimental studies with in vitro and in vivo models demonstrated that this antioxidant is autoregenerative and more active in inhibiting laser-induced choroidal neovascularization by decreasing ROS-induced pro-angiogenic vascular endothelial growth factor (VEGF) expression, cumulative oxidative damage, and recruitment of endothelial precursor cells without exhibiting any toxicity. This advanced formulation may offer a superior therapeutic effect to deal with oxidative stress induced pathogeneses, such as AMD.

Cerium oxide nanoparticles could ameliorate behavioral and neurochemical impairments in 6-hydroxydopamine induced Parkinson's disease in rats

BACKGROUND

Cerium oxide nanoparticles (CeO₂NPs) showed promising effects in neurodegenerative diseases including some animal models of Parkinsonism. However, the implication of CeO₂NPs in 6-hydroxydopamine (6-OHDA) induced Parkinsonism remains to be investigated.

AIM

This study was designed to assess whether CeO₂NPs treatment could alleviate neurobehavioral and neurobiochemical deficits in 6-OHDA induced neurotoxicity in rats.

MATERIAL AND METHODS

50 rats received left intrastriatal (IS) injection of either saline (control, n = 10) or 6-OHDA (n = 40). At the third week post-lesion, motor dysfunction was verified using neurobehavioral tests. Then diseased rats received intraperitoneal injection of 0.1, 0.5 or 1 mg/kg of CeO₂NPs or vehicle (10 rats each) for 3 weeks. Rats were subjected to behavioral assessments and then sacrificed for biochemical analyses of the striatum. Striatal dopamine levels, oxidative stress markers including total antioxidant capacity (TAC) and malondialdehyde (MDA), and caspase 3 activity as an apoptotic marker were assessed.

RESULTS

Different doses of CeO₂NPs variably improved motor dysfunctions induced by 6-OHDA injection in open field, Rota Rod and stepping tests. In addition, the neurobiochemical derangements were almost reversed by the 0.5 mg/kg dose of CeO₂NPs, while 0.1 mg/kg dose was not sufficient to alter biochemical measurements in the striatum. Administration of 1 mg/kg of CeO₂NPs partially ameliorated striatal dopamine and decreased apoptosis without significant effect on oxidative stress.

CONCLUSION

The present study showed a putative therapeutic role of CeO2NPs in the treatment of 6-OHDA-induced Parkinsonian rats, and suggested their antioxidant and antiapoptotic effects as possible mechanisms for elevated striatal dopamine level and improved motor performance.

Remote Control of Cellular Functions: The Role of Smart Nanomaterials in the Medicine of the Future

The remote control of cellular functions through smart nanomaterials represents a biomanipulation approach with unprecedented potential applications in many fields of medicine, ranging from cancer therapy to tissue engineering. By actively responding to external stimuli, smart nanomaterials act as real nanotransducers able to mediate and/or convert different forms of energy into both physical and chemical cues, fostering specific cell behaviors. This report describes those classes of nanomaterials that have mostly paved the way to a "wireless" control of biological phenomena, focusing the discussion on some examples close to the clinical practice. In particular, magnetic fields, light irradiation, ultrasound, and pH will be presented as means to manipulate the cellular fate, due to the peculiar physical/chemical properties of some smart nanoparticles, thus providing realistic examples of "nanorobots" approaching the visionary ideas of Richard Feynman.

Mechanism of ROS scavenging and antioxidant signalling by redox metallic and fullerene nanomaterials: Potential implications in ROS associated degenerative disorders

BACKGROUND

The balance between oxidation and anti-oxidation is believed to be critical in maintaining healthy biological systems. However, our endogenous antioxidant defense systems are incomplete without exogenous antioxidants and, therefore, there is a continuous demand for exogenous antioxidants to prevent stress and ageing associated disorders. Nanotechnology has yielded enormous variety of nanomaterials (NMs) of which metallic and carbonic (mainly fullerenes) NMs, with redox property, have been found to be strong scavengers of ROS and antioxidants in preclinical in vitro and in vivo models.

SCOPE OF REVIEW

Redox activity of metal based NMs and membrane translocation time of fullerene NMs seem to be the major determinants in ROS scavenging potential exhibited by these NMs. A comprehensive knowledge about the effects of ROS scavenging NMs in cellular antioxidant signalling is largely lacking. This review compiles the mechanisms of ROS scavenging as well as antioxidant signalling of the aforementioned metallic and fullerene NMs.

MAJOR CONCLUSIONS

Direct interaction between NMs and proteins does greatly affect the corona/adsorption formation dynamics but such interaction does not provide the explanation behind diverse biological outcomes induced by NMs. Indirect interaction, however, that could occur via NMs uptake and dissolution, NMs ROS induction and ROS scavenging property, and NMs membrane translocation time seem to work as a central mode of interaction.

GENERAL SIGNIFICANCE

The usage of potential antioxidant NMs in biological systems would greatly impact the field of nanomedicine. ROS scavenging NMs hold great promise in the future treatment of ROS related degenerative disorders.

Non-toxic retention of nanoceria in murine eyes

PURPOSE

We have shown that cerium oxide nanoparticles (nanoceria), with unique characteristics and catalytic activities, are retained in the retina for more than 1 year after a single intravitreal injection and can be potentially used for the treatment of a variety of eye diseases. The objective of this study is to determine whether the retention of nanoceria in the eye causes inflammation or adverse side effects.

METHODS

Wild-type (C57BL/6J) mice at P30 were intravitreally injected with several concentrations of nanoceria. The health of the photoreceptors was assessed by analyzing the expression of photoreceptor-specific genes, and the retinal structure and function. The effect of nanoceria was investigated by analyzing of the vascular system, the expression of inflammatory cytokines, and cellular infiltration into the eye.

RESULTS

Our data showed that there were no changes in the retinal structure or function, or cytokine gene expression following a single intravitreal injection of nanoceria.

CONCLUSIONS

Nanoceria, at doses ranging from 17.2 ng to 1720 ng per eye, do not cause any damage to the retinal structure and function by 30 days post injection. No cellular infiltration and no increases in inflammatory responses were found in the eyes. Our data indicate that nanoceria are safe to use for treatment of a variety of eye diseases.