Silica-based cerium (III) chloride nanoparticles prevent the fructose-induced glycation of α-crystallin and H₂O₂-induced oxidative stress in human lens epithelial cells

Applications of nanomaterials in anti-VEGF treatment for ophthalmic diseases

Angiogenesis has been determined to be essential in the occurrence and metastasis of diabetic retinopathy (DR), age-related macular degeneration (AMD), retinal vein occlusion (RVO), choroidal neovascularization (CNV), retinopathy of prematurity (ROP), tumor, etc. However, the clinical use of anti-vascular endothelial growth factors (VEGF) drugs is currently limited due to its high cost, potential side effects, and need for repeated injections. In recent years, nanotechnology has shown promising results in inhibiting neovascularization and reducing reactive oxygen species (ROS) or inflammatory factors. Some nanomaterials can also act as vehicles for drug delivery, such as lipid nanoparticles and PLGA. The process of angiogenesis and its molecular mechanism are discussed in this article. At the same time, this study aims to systematically review the research progress of nanotechnology and offer more treatment options for neovascularization-related diseases in clinical ophthalmology.

Recent advances of smart materials for ocular drug delivery

Owing to the variety and complexity of ocular diseases and the natural ocular barriers, drug therapy for ocular diseases has significant limitations, such as poor drug targeting to the site of the disease, poor drug penetration, and short drug retention time in the vitreous body. With the development of biotechnology, biomedical materials have reached the "smart" stage. To date, despite their inability to overcome all the aforementioned drawbacks, a variety of smart materials have been widely tested to treat various ocular diseases. This review analyses the most recent developments in multiple smart materials (inorganic particles, polymeric particles, lipid-based particles, hydrogels, and devices) to treat common ocular diseases and discusses the future directions and perspectives regarding clinical translation issues. This review can help researchers rationally design more smart materials for specific ocular applications.

Metallic Engineered Nanomaterials and Ocular Toxicity: A Current Perspective

The ocular surface, comprised of the transparent cornea, conjunctiva, and protective tear film, forms a protective barrier defending deeper structures of the eye from particulate matter and mechanical trauma. This barrier is routinely exposed to a multitude of naturally occurring and engineered nanomaterials (ENM). Metallic ENMs are particularly ubiquitous in commercial products with a high risk of ocular exposure, such as cosmetics and sunscreens. Additionally, there are several therapeutic uses for metallic ENMs owing to their attractive magnetic, antimicrobial, and functionalization properties. The increasing commercial and therapeutic applications of metallic ENMs come with a high risk of ocular exposure with poorly understood consequences to the health of the eye. While the toxicity of metallic ENMs exposure has been rigorously studied in other tissues and organs, further studies are necessary to understand the potential for adverse effects and inform product usage for individuals whose ocular health may be compromised by injury, disease, or surgical intervention. This review provides an update of current literature on the ocular toxicity of metallic ENMs in vitro and in vivo, as well as the risks and benefits of therapeutic applications of metallic ENMs in ophthalmology.

Protection of Human Lens Epithelial Cells from Oxidative Stress Damage and Cell Apoptosis by KGF-2 through the Akt/Nrf2/HO-1 Pathway

Oxidative stress exerts a significant influence on the pathogenesis of various cataracts by inducing degradation and aggregation of lens proteins and apoptosis of lens epithelial cells. Keratinocyte growth factor-2 (KGF-2) exerts a favorable cytoprotective effect against oxidative stress in vivo and in vitro. In this work, we investigated the molecular mechanisms of KGF-2 against hydrogen peroxide- (H2O2-) induced oxidative stress and apoptosis in human lens epithelial cells (HLECs) and rat lenses. KGF-2 pretreatment could reduce H2O2-induced cytotoxicity as well as reactive oxygen species (ROS) accumulation. KGF-2 also increases B-cell lymphoma-2 (Bcl-2), quinine oxidoreductase-1 (NQO-1), superoxide dismutase (SOD2), and catalase (CAT) levels while decreasing the expression level of Bcl2-associated X (Bax) and cleaved caspase-3 in H2O2-stimulated HLECs. LY294002, the phosphatidylinositol-3-kinase (PI3K)/Akt inhibitor, abolished KGF-2's effect to some extent, demonstrating that KGF-2 protected HLECs via the PI3K/Akt pathway. On the other hand, KGF-2 activated the Nrf2/HO-1 pathway by regulating the PI3K/Akt pathway. Silencing nuclear factor erythroid 2-related factor 2 (Nrf2) by targeted-siRNA and inhibiting heme oxygenase-1 (HO-1) through zinc protoporphyrin IX (ZnPP) significantly decreased cytoprotection of KGF-2. Furthermore, as revealed by lens organ culture assays, KGF-2 treatment decreased H2O2-induced lens opacity in a concentration-dependent manner. As demonstrated by these data, KGF-2 resisted H2O2-mediated apoptosis and oxidative stress in HLECs through Nrf2/HO-1 and PI3K/Akt pathways, suggesting a potential protective effect against the formation of cataracts.

Hallmarks of lens aging and cataractogenesis

Lens homeostasis and transparency are dependent on the function and intercellular communication of its epithelia. While the lens epithelium is uniquely equipped with functional repair systems to withstand reactive oxygen species (ROS)-mediated oxidative insult, ROS are not necessarily detrimental to lens cells. Lens aging, and the onset of pathogenesis leading to cataract share an underlying theme; a progressive breakdown of oxidative stress repair systems driving a pro-oxidant shift in the intracellular environment, with cumulative ROS-induced damage to lens cell biomolecules leading to cellular dysfunction and pathology. Here we provide an overview of our current understanding of the sources and essential functions of lens ROS, antioxidative defenses, and changes in the major regulatory systems that serve to maintain the finely tuned balance of oxidative signaling vs. oxidative stress in lens cells. Age-related breakdown of these redox homeostasis systems in the lens leads to the onset of cataractogenesis. We propose eight candidate hallmarks that represent common denominators of aging and cataractogenesis in the mammalian lens: oxidative stress, altered cell signaling, loss of proteostasis, mitochondrial dysfunction, dysregulated ion homeostasis, cell senescence, genomic instability and intrinsic apoptotic cell death.

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.

Progress of Nanotechnology in Diabetic Retinopathy Treatment

Diabetic retinopathy (DR) is a chronic diabetes complication that progressively manifests itself as blurred vision, eye floaters, distorted vision, and even partial or total loss of vision as a result of retinal detachment in severe cases. Clinically, patients who have undergone variations in the microcirculation of the ocular fundus are treated with laser photocoagulation to improve the circulation of retina; but for patients with macular edema, anti-vascular endothelial growth factor (anti-VEGF) drugs are generally injected to eliminate macular edema and improve vision. The worst cases are patients with fundus hemorrhage or proliferative vitreoretinopathy, for whom vitrectomy has been performed. At present, these clinical treatment methods have widely been used, providing satisfactory results. However, considering the low bioavailability and potential side effects of drugs and the inevitable risks in major surgery, DR prevention, and treatment as well as nerve tissue regeneration in the later stage have always been the focus of research. In recent years, nanotechnology has been increasingly applied in the medical field, leading to new ideas for DR treatment. This study aims to systematically review the research progress of nanotechnology in DR treatment.

Mechanism of Selenium Nanoparticles Inhibiting Advanced Glycation End Products

Selenium nanoparticles (SeNPs) have been applied in fields of nanobiosensors, environment, nanomedicine, etc. as a result of their excellent characteristics. Early studies had shown that SeNPs have certain inhibition ability against glycation, but the inhibition mechanism, especially for the influence of SeNPs on the reaction activity of glycation sites, remains unclear. The aim of the presented research was to reveal the effects of SeNPs on the β-lactoglobulin (β-Lg)/d-ribose glycation system at the molecular level and explore the possible inhibitory mechanism of SeNPs on the formation of advanced glycation end products (AGEs) by analyzing the glycation sites via high-performance liquid chromatography (HPLC)-Orbitrap-tandem mass spectrometry (MS/MS). Changes in contents of AGE formation and free amino acid contents had indicated that SeNPs could significantly slow the glycation process, thus attenuating the formation of AGEs. HPLC-Orbitrap-MS/MS analysis revealed that, at 6, 12, and 24 h, the number of glycation sites of glycated β-Lg decreased from 7, 7, and 9 to 5, 5, and 6 after the intervention of SeNPs, respectively. The glycation extent of each glycation site was controlled, and the dual-glycation ability of K8, K14, K47, K91, and K101 was changed. All of these results confirmed that SeNPs could indeed slow the process of protein glycation at the molecular level. This may be the reason for SeNPs reducing the formation of AGEs during glycation. Therefore, this study shed light on the insight of how SeNPs reduce the formation of AGEs.

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.

Evaluation of epithelial transport and oxidative stress protection of nanoengineered curcumin derivative-cyclodextrin formulation for ocular delivery

Ocular drug delivery has been a well-known route for the drug administration for the treatment of ocular diseases. However, numerous anatomical and physiological barriers prevailing in the eye itself create considerable challenges for achieving the necessitated therapeutic efficacy along with ocular bioavailability. However, recent advances in nanoengineered strategies hold definite promises in terms of devising improved ophthalmic medicines for the effective drug delivery to target the sites with enhanced ocular bioavailability. Curcumin, a hydrophobic polyphenol yellow colored compound, and its metabolic reduced product, tetrahydrocurcumin (THC), have been known for their beneficial pharmacological functions, such as anti-inflammatory or anti-oxidant activities at various tissue sites. However, the low aqueous solubility of these compounds results in their poor bioavailability, thereby limiting their widespread application. Therefore, in the present study, we investigated the changes in drug solubility by forming inclusion complexes with different derivatives of hydroxypropyl (HP)-cyclodextrins (CD). To this end, the spray drying technique was used for nanoengineering curcumin or THC-loaded formulations to improve the stability of formulations during the storage. The formulations were characterized in terms of physicochemical properties and cellular permeability. The results demonstrated that the encapsulation of curcumin (or THC) into the HP-CDs significantly increased the drug solubility and enhanced the corneal and retinal epithelial permeability. Curcumin or THC complexes in HP-CDs with improved bioavailability also induced anti-oxidant activity (SOD1, CAT1, and HMOX1) in higher levels in the ocular epithelial cells and showed oxidative protection effects in rabbit cornea tissues that will boost up their application in ocular medicine.

Drug delivery to the lens for the management of cataracts

Cataracts are one of the most prevalent diseases of the lens, affecting its transparency and are the leading cause of reversible blindness in the world. The clarity of the lens is essential for its normal physiological function of refracting light onto the retina. Currently there is no pharmaceutical treatment for prevention or cure of cataracts and surgery to replace the affected lens remains the gold standard in the management of cataracts. Pharmacological treatment for prevention of cataracts is hindered by many physiological barriers that must be overcome by a therapeutic agent to reach the avascular lens. Various therapeutic agents and formulation strategies are currently being investigated to prevent cataract formation as access to surgery is limited. This review provides a summary of recent research in the field of drug delivery to the lens for the management of cataracts including models used to study cataract treatments and discusses the future perspectives in the field.

Chlorogenic acid attenuates hydrogen peroxide‑induced oxidative stress in lens epithelial cells

Oxidative stress has an important role in the degradation, oxidation, cross‑linking and aggregation of lens proteins, and can trigger lens epithelial cell apoptosis. To investigate the protective effect of chlorogenic acid (CGA) against hydrogen peroxide (H2O2)‑induced oxidative stress, human lens epithelial cells (hLECs) were exposed to various concentrations of H2O2 in the presence and absence of CGA. Using MTT assay, reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) and ELISA techniques, cell viability, and protein/mRNA levels of BCL2 apoptosis regulator (Bcl‑2) and BCL2 associated X apoptosis regulator (Bax) were investigated. Additionally, the levels of intracellular reactive oxygen species (ROS) and apoptosis within cells were measured using flow cytometry to determine the protective effect of CGA on H2O2‑induced oxidative stress. Furthermore, the protective effect of CGA on H2O2‑induced apoptosis was also examined using rabbit lenses ex vivo. The results indicated that CGA reduced H2O2‑induced cytotoxicity in a dose‑dependent manner. Flow cytometry analysis demonstrated that simultaneous exposure of hLECs to H2O2 and CGA significantly decreased apoptosis and the levels of ROS. RT‑qPCR analysis revealed a decrease in Bcl‑2 and an increase in Bax in hLECs following exposure to H2O2 for 24 h, regardless of CGA presence. Furthermore, ELISA results indicate that CGA increased Bcl‑2 expression and decreased Bax expression following treatment with H2O2 for 24 h and the Bax/Bcl-2 ratio was significantly decreased by CGA treatment. Lens organ culture experiments indicated a dose‑dependent decrease in H2O2‑induced lens opacity following CGA treatment. These results suggest that CGA suppresses hLECs apoptosis and prevents lens opacity induced by H2O2 via Bax/Bcl‑2 signaling pathway. CGA may provide effective defenses against oxidative stress and, thus, haσ potential as treatment for a variety of diseases in clinical practice.

Potential of CeCl3@mSiO2 nanoparticles in alleviating diabetic cataract development and progression

Cataract is a major cause of visual impairment for diabetic patients. It is imperative to develop efficient therapeutic agents against diabetic cataract (DC) because diabetes confers higher risk for complications after cataract surgery. We have previously reported the role of CeCl₃ loaded mesoporous silica (CeCl₃@mSiO₂) nanoparticles in reducing the oxidative stress of lens epithelial cells. However, the potential of CeCl₃@mSiO₂ in preventing diabetic cataract development remains unclear. In this study, we applied CeCl₃@mSiO₂ nanoparticles with a size of 87.6±8.9nm to streptozotocin-induced diabetic cataract rat model by intraperitoneal injection. Our results showed that CeCl₃@mSiO₂ efficiently ameliorated the progression of DC. Consistent with antioxidant effect of CeCl₃@mSiO₂in vitro, administration of CeCl₃@mSiO₂ significantly abrogated hyperglycemia-mediated upregulation of advanced glycation end products, lipid peroxidation and protein carbonylation in animal lens. Taken together, our study provides a potential nanodrug to manage the development of DC.

Ameliorating Effects of Green Synthesized Silver Nanoparticles on Glycated End Product Induced Reactive Oxygen Species Production and Cellular Toxicity in Osteogenic Saos-2 Cells

Advanced glycation end-products (AGEs) that result from nonenzymatic glycation are one of the major factors involved in diabetes and its secondary complications and diseases. This necessitates our urge to discover new compounds that may be used as potential AGEs inhibitors without affecting the normal structure and function of biomolecules. In the present study, we investigated the inhibitory effects of AgNP (silver nanoparticles) on AGEs formation as well as their inhibitory effects on glycation mediated cell toxicity via reactive oxygen species (ROS) production and DNA damage. The excitation-emission fluorescence spectroscopy was employed to investigate the interaction of AgNP during glycation. The values of conditional stability constant (log K_a = 4.44) derived from the Stern-Volmer equation indicate that AgNP have strong binding capacity for glycated protein. UV-vis, fluorescence, and Fourier transform infrared spectral data reveal complexation of AgNP with glycated bovine serum albumin, which significantly inhibits AGEs formation in a concentration-dependent manner. Cytotoxic evaluations suggest that simultaneous administration of AgNP and glycated product reduces cell death (42.82% ± 3.54) as compared to the glycated product alone. Similarly, ROS production in AgNP treated cells is significantly less compared to only glycated product treated cells. Although DNA damage studies show DNA damage in both GP and GP-AgNP treated cells, fluorescence activated cell sorting analysis demonstrates that glycated products induce cell death by necrosis, while AgNP cause cell death via apoptotic pathways. AgNP have a positive effect on restoring native protein structure deduced from spectral studies, and hence, inferences can be drawn that AgNP have ameliorating effects on glycated induced cytotoxicity observed in osteogenic Saos-2 cells.

Nanotechnology for the Prevention and Treatment of Cataract

PURPOSE

The purpose of this article was to review recent advances in the applications of nanotechnology in cataract treatment and prevention strategies.

DESIGN

A literature review on the use of nanotechnology for the prevention and treatment of cataract was done.

METHODS

Research articles about nanotechnology-based treatments and prevention technologies for cataract were searched on Web of Science, and the most recent advances were reported.

RESULTS

Nonsteroid anti-inflammatory drugs, natural antioxidants, biologic and chemical chaperones, and chaperones such as molecules have found great application in preventing and treating cataracts. Current scientific research on new treatment strategies, which focuses on the biochemical basis of the disease, will likely result in new anticataract agents. However, none of the drug formulations will be approved for use unless efficient delivery is promised. Nanoparticle engineering together with biomimetic strategies enable the development of next-generation, more efficient, less complex, and personalized treatments.

CONCLUSIONS

The only currently available treatment for cataracts, surgical replacement of the opacified lens, is not an easily accessible option in developing countries. New treatment strategies based on topical drugs would enable treatment to reach massive populations facing the threat of blindness and more effectively deal with the postsurgical complications. Nanotechnology plays a key role in improving drug delivery systems with enhanced controlled release, targeted delivery, and bioavailability to overcome diffusion limitations in the eye.

The inhibitory effect of selenium nanoparticles on protein glycation in vitro

Selenium nanoparticles (Se NPs) possess well-known excellent biological activities and low toxicity, and have been employed for numerous applications except as inhibitors to protein glycation. Herein, the present study is carried out to investigate the inhibitory effect of Se NPs on protein glycation in a bovine serum albumin (BSA)/glucose system. By measuring the amount of glucose covalently bound onto BSA, the formation of fructosamine and fluorescent products, it is found that Se NPs can hinder the development of protein glycation in a dose-dependent but time-independent manner under the selected reaction conditions (55 °C, 40 h). And after comparing the increase of inhibitory rate in different stages, it is observed that Se NPs show the greatest inhibitory effect in the early stage, then in the advanced stage, but no effect in the intermediate stage. Fourier transform infrared spectroscopy characterization of Se NPs collected after glycation and determination of ·OH influence and glyoxal formation show that the mechanism for the inhibitory efficacy of Se NPs is related to their strong competitive activity against available amino groups in proteins, their great scavenging activity on reactive oxygen species and their inhibitory effect on α-dicarbonyl compounds' formation. In addition, it is proved that Se NPs protect proteins from structural modifications in the system and they do not exhibit significant cytotoxicity towards BV-2 and BRL-3A cells at low concentrations (10 and 50 μg mL(-1)). Consequently, Se NPs may be suitable for further in vivo studies as novel anti-glycation agents.

Current nanotechnology approaches for the treatment and management of diabetic retinopathy

Diabetic retinopathy (DR) is a consequence of diabetes mellitus at the ocular level, leading to vision loss, and contributing to the decrease of patient's life quality. The biochemical and anatomic abnormalities that occur in DR are discussed in this review to better understand and manage the development of new therapeutic strategies. The use of new drug delivery systems based on nanoparticles (e.g. liposomes, dendrimers, cationic nanoemulsions, lipid and polymeric nanoparticles) is discussed along with the current traditional treatments, pointing out the advantages of the proposed nanomedicines to target this ocular disease. Despite the multifactorial nature of DR, which is not entirely understood, some strategies based on nanoparticles are being exploited for a more efficient drug delivery to the posterior segment of the eye. On the other hand, the use of some nanoparticles also seems to contribute to the development of DR symptoms (e.g. retinal neovascularization), which are also discussed in light of an efficient management of this ocular chronic disease.