Ocular Drug Delivery: a Comprehensive Review

A water-soluble drug nanoparticle-loaded in situ gel for enhanced precorneal retention and its transduction mechanism of pharmacodynamic effects

Timolol maleate (TM), a hydrophilic small molecule, is widely used in the clinical management of glaucoma. However, the complex physiological barriers of the eyes result in suboptimal bioavailability for traditional ophthalmic formulations. To address these challenges, we have developed an innovative pharmaceutical formulation. The nanoparticles (NPs) were formulated by a multi-step optimization process involving a Plackett-Burman design (PBD), steepest ascent design (SAD), and Box-Behnken design (BBD) to obtain TM-HA/CS@ED NPs. It was then encapsulated in an in situ gel (ISG) system consisting of deacetylated gellan gum (DGG) and xanthan gum (XG) to yield the TM-HA/CS@ED NPs ISG. The formulation demonstrated favorable safety in a series of ocular irritation assays and was characterized as a pseudoplastic fluid by rheological analyses, enhancing spreadability on the ocular surface and prolonging the retention time. Moreover, the NPs exposed after ISG dissolution exhibited strong mucosal adhesion and hydrophobicity, facilitating the hydrophilic TM to penetrate the corneal barrier. In vitro and in vivo retention evaluations and tear elimination pharmacokinetic study confirmed that TM-HA/CS@ED NPs ISG showed superior precorneal retention ability, and favorable sustained drug concentrations, resulting in sustained and stable transcorneal permeation into the eyes and significant intraocular pressure (IOP) lowering efficacy with a duration of 12 h. These results provide valuable insights into the design of ophthalmic drug delivery systems for water-soluble drugs and therapeutic interventions for glaucoma.

The effect of mucoadhesive polymers on ocular permeation of thermoresponsive in situ gel containing dexamethasone-cyclodextrin complex

Dexamethasone (DXM) is a commonly used corticosteroid in the treatment of ocular inflammatory conditions that affect more and more people. The aim of this study was to evaluate the effect of the combination of hydroxypropyl-β-cyclodextrin (HPBCD), in situ gelling formulations, and other mucoadhesive polymers, i.e., hydroxypropyl methylcellulose (HPMC) and zinc-hyaluronate (ZnHA), on permeation by applying in vitro and ex vivo ophthalmic permeation models. Additionally, gelling properties, in vitro drug release, and mucoadhesion were measured to determine the impact of these factors on permeation and ultimately on bioavailability. The results showed that GEL1 and GEL2 had an optimal gelling temperature, 36.3 ℃ and 34.6 ℃, respectively. Moreover, the combination of Poloxamer 407 (P407) with other polymers improved the mucoadhesion (GEL1: 1333.7 mN) compared with formulations containing only P407 (P12: 721.8 mN). Both HPBCD and the gel matrix had a considerable influence on the drug release and permeability of DXM, and the combination could facilitate the permeation into the aqueous humor. After 30 min of treatment, the DXM concentration in the aqueous humor was 1.16-1.37 µg∕mL in case of the gels, whereas DXM could not be detected when treated with the DXM suspension. The results of the experiments using an in vitro cell line indicated that the formulations could be considered safe for topical treatment of the eye. In conclusion, with application of a small amount of HPMC (0.2 % w∕w), the concentration of P407 could be reduced to 12 % w/w while maintaining the ideal gelling properties and gel structure without negatively affecting permeability compared with the formulation containing a higher amount of P407. Furthermore, the gel matrix may also provide programmed and elongated drug release.

Nanocarrier-Based, ocular drug delivery: Challenges, prospects, and the therapeutic landscape in the United Arab Emirates

Human eyes have the most complex and advanced physiological defense barriers. Due to these barriers, efficient delivery of ocular drugs is a major challenge in the treatment of eye diseases and disorders. Posterior eye diseases such as retinopathy are the leading causes of impaired vision and blindness globally. The topical and systemic administration of drugs such as eye drops, ointments, intravitreal injections, intraocular implants, contact lenses, and emulsions are the perennial approaches employed to treat ocular diseases. However, these modalities are inefficient due to the low bioavailability of the active drug and the potential for drug-related cytotoxicity to the ocular tissue. In this review, the conventional approaches in ocular drug delivery systems (DDSs) are explored and the limitations associated with each technique are elucidated. A comparison between the different DDSs is presented, showing the most effective treatment techniques available to date. In addition, this review presents recent advances in the field of nanocarriers and microcarriers used in ocular drug delivery systems such as nanoparticles, nano-suspensions, nanofibers, nanogels, nano-liposomes, nano micelles, dendrimers, contact lens, microneedle, and implants. Further, this review identifies the utility of nano-carriers in enabling the development of new-generation ocular DDSs with low toxicity, high efficiency, and high stability of targeted drug delivery systems to overcome the limitations observed with conventional ocular DDSs. In addition, this manuscript sheds light on the incidence and unique landscape of ocular diseases in the United Arab Emirates (UAE), and the potential for employing novel ocular DDSs for targeted treatment of conditions such as diabetic retinopathy in the UAE. It also discusses the putative role genetic variants of the VEGF gene may play in predisposing the local population in the UAE to developing posterior eye segment diseases such as retinopathy.

Advancements in Ocular Modelling and Simulations: Key Considerations and Case Studies

This review paper discusses the key aspects of ocular biopharmaceutics, with emphasis on the crucial role played by ocular compartmental modelling and simulation in deciphering physiological conditions related to various eye diseases. It describes eye's intricate structure and function and the need for precise and targeted drug delivery systems to address prevalent eye conditions. The review categorizes and discusses various formulations employed in ocular drug delivery, delineating their respective advantages and limitations. Additionally, it probes the challenges inherent in diverse routes of drug administration for ocular therapies and provides insights into the complexities of achieving optimal drug concentrations at the target site within the eye. The central theme of this work is the ocular compartmental modelling and simulations. Hence, this works discusses on the nuanced understanding of physiological conditions within the eye, drug distribution, drug release kinetics, and key considerations for ocular compartmental modelling and simulations. By combining information from various sources, this review aims to serve as a comprehensive reference for researchers, clinicians, and pharmaceutical developers. It covers the multifaceted landscape of ocular biopharmaceutics and the transformative impact of modelling and simulation in optimizing ocular drug delivery strategies.

Development and Characterization of Dual-Loaded Niosomal Ion-Sensitive In Situ Gel for Ocular Delivery

The study investigates the development and characterization of dual-loaded niosomes incorporated into ion-sensitive in situ gel as a potential drug delivery platform for ophthalmic application. Cannabidiol (CBD) and epigallocatechin-3-gallate (EGCG) simultaneously loaded niosomes were prepared via the thin film hydration (TFH) method followed by pulsatile sonication and were subjected to comprehensive physicochemical evaluation. The optimal composition was included in a gellan gum-based in situ gel, and the antimicrobial activity, in vitro toxicity in a suitable corneal epithelial model (HaCaT cell line), and antioxidant potential of the hybrid system were further assessed. Dual-loaded niosomes based on Span 60, Tween 60, and cholesterol (3.5:3.5:3 mol/mol) were characterized by appropriate size (250 nm), high entrapment efficiency values for both compounds (85% for CBD and 50% for EGCG) and sustained release profiles. The developed hybrid in situ gel exhibited suitable rheological characteristics to enhance the residence time on the ocular surface. The conducted microbiological studies reveal superior inhibition of methicillin-resistant Staphylococcus aureus (MRSA) adhesion by means of the niosomal in situ gel compared to the blank gel and untreated control. Regarding the antioxidant potential, the dual loading of CBD and EGCG in niosomes enhances their protective properties, and the inclusion of niosomes in gel form preserves these effects. The obtained outcomes indicate the developed niosomal in situ gel as a promising drug delivery platform in ophthalmology.

Advances in dorzolamide hydrochloride delivery: harnessing nanotechnology for enhanced ocular drug delivery in glaucoma management

Dorzolamide hydrochloride (DRZ) is a carbonic anhydrase inhibitor utilized in managing elevated intraocular pressure (IOP) associated with glaucoma. However, its clinical effectiveness is hindered by a short half-life, low residence time, and the need for frequent dosing, highlighting the necessity for innovative delivery systems. This work reviews recent advancements in DRZ delivery, particularly focusing on cyclodextrin complexation and nanotechnology applications. It explores the potential of cyclodextrin derivatives to enhance DRZ's bioavailability. DRZ cyclodextrin complexes or nanoparticulate systems maintain high drug concentrations in the eye while minimizing irritation and viscosity-related issues. Nanotechnology introduces nanoparticle-based carriers such as polymeric nanoparticles, solid lipid nanoparticles, liposomes, niosomes, and nanoemulsions. These formulations enable sustained drug release, improved corneal permeation, and enhanced patient compliance. Clinical trials have shown that DRZ nanoparticle eye drops and nanoliposome formulations offer efficacy comparable to conventional therapies, with the potential for better tolerability. Overall, this review highlights significant progress in DRZ delivery systems, suggesting their potential to transform glaucoma treatment by addressing current limitations and improving therapeutic outcomes.

A one-platform comparison study of brinzolamide-loaded liposomes, niosomes, transfersomes, and transniosomes for better management of glaucoma

Ocular drug delivery presents significant challenges due to various anatomical and physiological barriers. Ultradeformable vesicles have emerged as better vesicular systems for achieving deeper corneal penetration and enhanced ocular bioavailability. This research aims to develop a hybrid vesicular system with improved deformability and compare it to conventional vesicular carriers. The ultradeformable vesicle, termed "transniosomes," is a combination of niosomes, liposomes, and transfersomes, loaded with brinzolamide as model drug. The brinzolamide-loaded transniosomes (BRZ-TN) was formulated and compared with different vesicular systems through in vitro, ex vivo, and in vivo characterizations. The optimized BRZ-TN demonstrated a vesicle size of 112.06 ± 4.13 nm and an entrapment efficiency of 93.63 ± 0.30 %. With a deformability index of 6.405, the BRZ-TN exhibited a permeability of 86.68 ± 2.51 % over 10 h, which is approximately 1.3 times higher than other conventional vesicular systems. Additionally, the BRZ-TN showed a drug flux of 0.247 ± 0.01 mg/cm2/h and an apparent permeability of 0.09 ± 1.21 cm/s. Pre-clinical experiments confirmed the superiority of the optimized BRZ-TN, achieving a 37 % reduction in intraocular pressure (IOP), post 6hr of administration, indicating its prolonged therapeutic effect and improved ocular bioavailability. The findings of this study suggest that transniosomes are superior to other carriers and hold great promise as a nanocarrier for ocular drug delivery.

From Preformulative Design to In Vivo Tests: A Complex Path of Requisites and Studies for Nanoparticle Ocular Application. Part 1: Design, Characterization, and Preliminary In Vitro Studies

Ocular pathologies are widely diffused worldwide, and their effective treatment, combined with a high patient compliance, is sometimes challenging to achieve due to the barriers of the eye; in this context, the use of nanoparticles for topical ophthalmic application could represent a successful strategy. Aiming to develop nanoplatforms with potential clinical applications, great attention has to be paid to their features, in relation to the route of administration and to the pharmacopoeial requirements. This review (part 1) thus embraces the preliminary steps of nanoparticle development and characterization. At the beginning, the main barriers of the eye and the different administration routes are resumed, followed by a general description of the advantages of the employment of nanoparticles for ocular topical administration. Subsequently, the preformulative steps are discussed, deepening the choice of raw materials and determining the quantitative composition. Then, a detailed report of the physicochemical and technological characterization of nanoparticles is presented, analyzing the most relevant tests that should be performed on nanoparticles to verify their properties and the requisites (both mandatory and suggested) demanded by regulatory agencies. In conclusion, some preliminary noncellular in vitro evaluation methods are described. Studies from in vitro cellular assays to in vivo tests will be discussed in a separate (part 2) review paper. Hence, this overview aims to offer a comprehensive tool to guide researchers in the choice of the most relevant studies to develop a nanoplatform for ophthalmic drug administration.

Bioadhesive hybrid system of niosomes and pH sensitive in situ gel for itraconazole ocular delivery: Dual approach for efficient treatment of fungal infections

Itraconazole (ITZ) is a highly effective antifungal agent. However, its oral application is associated with systemic toxicity and poor topical use. The present study aims to improve the antifungal activity of ITZ by loading it into bioadhesive niosomes. This approach is considered to enhance the ocular permeation of ITZ, thereby boosting its efficacy against fungal infections. Therefore, it was encapsulated into niosomes (F1) and subsequently coated with hyaluronic acid (HA; F2), chitosan (CS; F3), or a bilayer of CS/HA (F4). In addition, they were further incorporated into pH-sensitive in situ gels. This dual approach is expected to increase the amount of corneal-permeated ITZ, facilitating more effective management of ocular fungal infection. Firstly, the niosomes were prepared by hydrating proniosomes using span 60, cholesterol, and phospholipid. ITZ-niosomes showed an increase in vesicle size from 165.5 ± 3.4 (F1) to 378.2 ± 7.2 nm (F3). The zeta potential varied within -20.9 ± 2.1 (F1), -29.5 ± 3.1 (F2), 32.3 ± 1.9 (F3), and 22.6 ± 1.3 mV (F4). The high EE% values ranged from 78.1 ± 2.2 % to 86.6 ± 2.9 %. Regarding ITZ release, F1 demonstrated a high release profile, whereas bioadhesive niosomes showed sustained release patterns. Furthermore, in situ gels containing niosomes displayed excellent gelling capacity and viscosity. Remarkably, F3 laden-in situ gels (F3-ISG) demonstrated the highest ex vivo corneal permeability of ITZ and antifungal activity with a safety effect. These results indicate that F3-ISG presents a promising strategy for boosting the ocular delivery of ITZ, that could help in treating ocular fungal infections.

Promising Pharmacological Interventions for Posterior Capsule Opacification: A Review

Phacoemulsification combined with intraocular lens implantation is the primary treatment for cataract. Although this treatment strategy benefits patients with cataracts, posterior capsule opacification (PCO) remains a common complication that impairs vision and affects treatment outcomes. The pathogenesis of PCO is associated with the proliferation, migration, and fibrogenesis activity of residual lens epithelial cells, with epithelial-mesenchymal transition (EMT) serving as a key mechanism underlying the condition. Transforming growth factor-beta 2 (TGF-β2) is a major promotor of EMT, thereby driving PCO development. Most studies have shown that drugs and miRNAs mitigate EMT by inhibiting, clearing, or eliminating LECs. In addition, targeting EMT-related signaling pathways in TGF-β2-stimulated LECs has garnered attention as a research focus. This review highlights potential treatments for PCO and details the mechanisms by which drugs and miRNAs counter EMT.

Advanced drug delivery strategies for diabetic retinopathy: current therapeutic advancement, and delivery methods overcoming barriers, and experimental modalities

INTRODUCTION

Diabetic retinopathy, a significant trigger for blindness among working age individuals with diabetes, poses a substantial global health challenge. Understanding its underlying mechanisms is pivotal for developing effective treatments. Current treatment options, such as anti-VEGF agents, corticosteroids, laser photocoagulation, and vitreous surgery, have their limitations, prompting the exploration of innovative approaches like nanocapsules based drug-delivery systems. Nanoparticles provide promising solutions to improve drug delivery in ocular medicine, overcoming the complexities of ocular anatomy and existing treatment constraints.

AREAS COVERED

This review explored advanced therapeutic strategies for diabetic retinopathy, focusing on current medications with their limitations, drug delivery methods, device innovations, and overcoming associated barriers. Through comprehensive review, it aimed to contribute to the discovery of more efficient management strategies for diabetic retinopathy in the future.

EXPERT OPINION

In the next five to ten years, we expect a revolutionary shift in how diabetic retinopathy is treated. As we deepen our understanding of oxidative stress and metabolic dysfunction, antioxidants with specialised delivery matrices are poised to take center stage in prevention and treatment strategies. Our vision is to create a more integrated approach to diabetic retinopathy management that not only improves patient outcomes but also reduces the risks associated to traditional therapies.

Absorption enhancement strategies in chitosan-based nanosystems and hydrogels intended for ocular delivery: Latest advances for optimization of drug permeation

Ophthalmic diseases can be presented as acute diseases like allergies, ocular infections, etc., or chronic ones that can be manifested as a result of systemic disorders, like diabetes mellitus, thyroid, rheumatic disorders, and others. Chitosan (CS) and its derivatives have been widely investigated as nanocarriers in the delivery of drugs, genes, and many biological products. The biocompatibility and biodegradability of CS made it a good candidate for ocular delivery of many ingredients, including immunomodulating agents, antibiotics, ocular hypertension medications, etc. CS-based nanosystems have been successfully reported to modulate ocular diseases by penetrating biological ocular barriers and targeting and controlling drug release. This review provides guidance to drug delivery formulators on the most recently published strategies that can enhance drug permeation to the ocular tissues in CS-based nanosystems, thus improving therapeutic effects through enhancing drug bioavailability. This review will highlight the main ocular barriers to drug delivery observed in the nano-delivery system. In addition, the CS physicochemical properties that contribute to formulation aspects are discussed. It also categorized the permeation enhancement strategies that can be optimized in CS-based nanosystems into four aspects: CS-related physicochemical properties, formulation components, fabrication conditions, and adopting a novel delivery system like implants, inserts, etc. as described in the published literature within the last ten years. Finally, challenges encountered in CS-based nanosystems and future perspectives are mentioned.

Enhanced Ocular Drug Delivery of Dexamethasone Using a Chitosan-Coated Soluplus®-Based Mixed Micellar System

BACKGROUND

This study introduces a novel dexamethasone (DEX) mixed micellar system (DEX-MM) using Soluplus® and Pluronic F-127 (PF127) to enhance ocular drug delivery. The enhancement of ocular application properties was achieved by creating a chitosan-coated DEX-MM (DEX-CMM), which promotes better adherence to the ocular surface, thereby improving drug absorption.

METHODS

Using the solvent evaporation method, a formulation was developed with a Soluplus®-to-drug ratio of 1:10, enhanced with 0.25% PF127. After dispersing in water, 1% chitosan (CS) was added. The stability and integrity of DEX within the micelles were verified using attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and differential scanning calorimetry (DSC). Additionally, in vitro and ex vivo drug release studies were conducted.

RESULTS

DEX-CMM (F6) demonstrated a particle size of 151.9 ± 1 nm and a polydispersity index (PDI) of 0.168 ± 0.003, suggesting uniformity and high electrostatic stability with a zeta potential of +35.96 ± 2.13 mV. The non-Fickian drug release mechanism indicated prolonged drug retention. Comparative analyses showed DEX-CMM outperforming a standard DEX suspension in drug release and ocular tissue permeation, with flux measurements significantly higher than the DEX suspension.

CONCLUSION

The study confirmed the efficacy of DEX-CMM in enhancing drug delivery to ocular tissues, evidenced by improved permeability. Safety evaluations using the HET-CAM test demonstrated that DEX-CMM was non-irritant, supporting its potential for effective ocular drug delivery.

Advancements in Ocular Therapy: A Review of Emerging Drug Delivery Approaches and Pharmaceutical Technologies

Eye disorders affect a substantial portion of the global population, yet the availability of efficacious ophthalmic drug products remains limited. This can be partly ascribed to a number of factors: (1) inadequate understanding of physiological barriers, treatment strategies, drug and polymer properties, and delivery systems; (2) challenges in effectively delivering drugs to the anterior and posterior segments of the eye due to anatomical and physiological constraints; and (3) manufacturing and regulatory hurdles in ocular drug product development. The present review discusses innovative ocular delivery and treatments, encompassing implants, liposomes, nanoparticles, nanomicelles, microparticles, iontophoresis, in situ gels, contact lenses, microneedles, hydrogels, bispecific antibodies, and gene delivery strategies. Furthermore, this review also introduces advanced manufacturing technologies such as 3D printing and hot-melt extrusion (HME), aimed at improving bioavailability, reducing therapeutic dosages and side effects, facilitating the design of personalized ophthalmic dosage forms, as well as enhancing patient compliance. This comprehensive review lastly offers insights into digital healthcare, market trends, and industry and regulatory perspectives pertaining to ocular product development.

Beyond the Local Effect: An Examination of Cardiovascular and Other Systemic Complications of Ophthalmologic Drugs

Ophthalmologic drugs may be delivered to the eye via a number of ways, including topical drops and gels, intraocular injections, and parenteral or oral administration. The inadvertent systemic absorption of these drugs may lead to a myriad of side effects, ranging from benign cosmetic changes to potentially fatal cardiovascular complications. Historically, glaucoma treatment, including β-blockers and α-agonists, have been particularly examined for such events. However, recent studies suggest that the systemic absorption of many drugs commonly used in ophthalmology may lead to acute and serious secondary reactions. The following review examines ocular drugs delivered through various pathways, the mechanisms by which they may be systemically absorbed, and the potential adverse events that may ensue.

Age-Related Macular Degeneration (AMD): Pathophysiology, Drug Targeting Approaches, and Recent Developments in Nanotherapeutics

The most prevalent reason for vision impairment in aging inhabitants is age-related macular degeneration (AMD), a posterior ocular disease with a poor understanding of the anatomic, genetic, and pathophysiological progression of the disease. Recently, new insights exploring the role of atrophic changes in the retinal pigment epithelium, extracellular drusen deposits, lysosomal lipofuscin, and various genes have been investigated in the progression of AMD. Hence, this review explores the incidence and risk factors for AMD, such as oxidative stress, inflammation, the complement system, and the involvement of bioactive lipids and their role in angiogenesis. In addition to intravitreal anti-vascular endothelial growth factor (VEGF) therapy and other therapeutic interventions such as oral kinase inhibitors, photodynamic, gene, and antioxidant therapy, as well as their benefits and drawbacks as AMD treatment options, strategic drug delivery methods, including drug delivery routes with a focus on intravitreal pharmacokinetics, are investigated. Further, the recent advancements in nanoformulations such as polymeric and lipid nanocarriers, liposomes, etc., intended for ocular drug delivery with pros and cons are too summarized. Therefore, the purpose of this review is to give new researchers an understanding of AMD pathophysiology, with an emphasis on angiogenesis, inflammation, the function of bioactive lipids, and therapy options. Additionally, drug delivery options that focus on the development of drug delivery system(s) via several routes of delivery can aid in the advancement of therapeutic choices.

IOP Reduction in Nonhuman Primates by Microneedle Injection of Drug-Free Hydrogel to Expand the Suprachoroidal Space

Purpose

Expansion of the suprachoroidal space (SCS) by a hydrogel injection has been shown to reduce intraocular pressure (IOP) in rabbits as a potential treatment for ocular hypertension in glaucoma. Here, we evaluate the safety and efficacy of this approach in hypertensive and normotensive eyes in nonhuman primates.

Methods

A microneedle was used to inject a hyaluronic acid-based hydrogel or saline solution (control) into the SCS of cynomolgus monkey eyes that were either normotensive (n = 7 experimental; n = 2 control eyes) or had induced ocular hypertension (n = 6 experimental; n = 3 control eyes). IOP and the degree of SCS expansion were monitored over time by tonometry and ultrasound biomicroscopy, respectively. Safety was evaluated through slit lamp, fundus, and histology examinations.

Results

In hypertensive eyes, SCS injection with hydrogel initially reduced IOP by 47.5 ± 16.7%, and IOP returned to baseline in 38 days. In normotensive eyes, hydrogel injection initially reduced IOP by 38.8 ± 8.1% and IOP gradually returned to baseline also in 39 days. Sham injections resulted in mild IOP reduction in hypertensive eyes and normotensive eyes. The hydrogel injections were well tolerated by clinical assessments.

Conclusions

IOP was reduced in nonhuman primates for over one month by sustained SCS expansion. This procedure was safe and simple to perform. These data confirm the translational potential of this treatment method. Further optimization of the hydrogel may provide longer durations of IOP reduction.

Translational Relevance

A microneedle injection of hydrogel into the suprachoroidal space may provide a non-surgical, non-pharmacologic treatment for ocular hypertension in glaucoma patients.

Minimizing Oxidative Stress in the Lens: Alternative Measures for Elevating Glutathione in the Lens to Protect against Cataract

Oxidative stress plays a major role in the formation of the cataract that is the result of advancing age, diabetes or which follows vitrectomy surgery. Glutathione (GSH) is the principal antioxidant in the lens, and so supplementation with GSH would seem like an intuitive strategy to counteract oxidative stress there. However, the delivery of glutathione to the lens is fraught with difficulties, including the limited bioavailability of GSH caused by its rapid degradation, anatomical barriers of the anterior eye that result in insufficient delivery of GSH to the lens, and intracellular barriers within the lens that limit delivery of GSH to its different regions. Hence, more attention should be focused on alternative methods by which to enhance GSH levels in the lens. In this review, we focus on the following three strategies, which utilize the natural molecular machinery of the lens to enhance GSH and/or antioxidant potential in its different regions: the NRF2 pathway, which regulates the transcription of genes involved in GSH homeostasis; the use of lipid permeable cysteine-based analogues to increase the availability of cysteine for GSH synthesis; and the upregulation of the lens's internal microcirculation system, which is a circulating current of Na+ ions that drives water transport in the lens and with it the potential delivery of cysteine or GSH. The first two strategies have the potential to restore GSH levels in the epithelium and cortex, while the ability to harness the lens's internal microcirculation system offers the exciting potential to deliver and elevate antioxidant levels in its nucleus. This is an important distinction, as the damage phenotypes for age-related (nuclear) and diabetic (cortical) cataract indicate that antioxidant delivery must be targeted to different regions of the lens in order to alleviate oxidative stress. Given our increasing aging and diabetic populations it has become increasingly important to consider how the natural machinery of the lens can be utilized to restore GSH levels in its different regions and to afford protection from cataract.

Ophthalmic Nanoemulsion Fingolimod Formulation for Topical Application

Purpose: Fingolimod (FTY720; FT), a structural analog of sphingosine, has potential ocular applications. The goal of this study was to develop an FT-loaded nanoemulsion (NE; FT-NE) formulation for the efficient and prolonged delivery of FT to the posterior segment of the eye through the topical route. Methods: FT-NE formulations were prepared using homogenization followed by the probe sonication method. The lead FT-NE formulations (0.15% and 0.3% w/v loading), comprising soybean oil as oil and Tween® 80 and Poloxamer 188 as surfactants, were further evaluated for in vitro release, surface morphology, filtration sterilization, and stability at refrigerated temperature. Ocular bioavailability following topical application of FT-NE (0.3%) was examined in Sprague-Dawley rats. Results: The formulation, at both dose levels, showed desirable physicochemical characteristics, a nearly spherical shape with homogenous nanometric size distribution, and was stable for 180 days (last time point checked) at refrigerated temperature postfiltration through a polyethersulfone (0.22 µm) membrane. In vitro release studies showed prolonged release over 24 h, compared with the control FT solution (FT-S). In vivo studies revealed that effective concentrations of FT were achieved in the vitreous humor and retina following topical application of FT-NE. Conclusions: The results from these studies demonstrate that the FT-NE formulation can serve as a viable platform for the ocular delivery of FT through the topical route.

An innovative rheology analysis method applies to the formulation optimization of Panax notoginseng total saponins ocular gel

Emphasizing the viscoelasticity of ophthalmic gels is crucial for understanding the residence time, structure, and stability of hydrogels. This study primarily aimed to propose an innovative rheology analysis method for ophthalmic gels, considering complex eye movements. This method was applied to select ophthalmic gels with favorable rheological characteristics. Additionally, the physical characteristics and in vitro release of the selected Panax notoginseng total saponins (PNS) gel were demonstrated. The selected PNS gel significantly increased the activities of SOD and decreased intracellular levels of MDA, TNF-α, and IL-1β in H2O2-treated ARPE-19 cells. Finally, the optimal formulation was selected as a suitable platform for ophthalmic delivery and was shown to significantly rescue ARPE-19 cells from oxidative cellular damage.

Lipid-based nanoparticles: innovations in ocular drug delivery

Ocular drug delivery presents significant challenges due to intricate anatomy and the various barriers (corneal, tear, conjunctival, blood-aqueous, blood-retinal, and degradative enzymes) within the eye. Lipid-based nanoparticles (LNPs) have emerged as promising carriers for ocular drug delivery due to their ability to enhance drug solubility, improve bioavailability, and provide sustained release. LNPs, particularly solid lipid nanoparticles (SLNs), nanostructured lipid carriers (NLCs), and cationic nanostructured lipid carriers (CNLCs), have emerged as promising solutions for enhancing ocular drug delivery. This review provides a comprehensive summary of lipid nanoparticle-based drug delivery systems, emphasizing their biocompatibility and efficiency in ocular applications. We evaluated research and review articles sourced from databases such as Google Scholar, TandFonline, SpringerLink, and ScienceDirect, focusing on studies published between 2013 and 2023. The review discusses the materials and methodologies employed in the preparation of SLNs, NLCs, and CNLCs, focusing on their application as proficient carriers for ocular drug delivery. CNLCs, in particular, demonstrate superior effectiveness attributed due to their electrostatic bioadhesion to ocular tissues, enhancing drug delivery. However, continued research efforts are essential to further optimize CNLC formulations and validate their clinical utility, ensuring advancements in ocular drug delivery technology for improved patient outcomes.

Capped flexosomes for prominent anti-inflammatory activity: development, optimization, and ex vivo and in vivo assessments

This study aimed to formulate diacerein (DCN)-loaded flexosomes for enhanced efficacy against osteoarthritis. A 23 D-optimal design was employed, investigating the impact of surfactant type (A), surfactant concentration (%w/v) (B), and oleylamine amount (mg) (C). Flexosomes were formulated using a rotary evaporator, and Design-Expert® software was utilized to statistically analyze entrapment efficiency (EE%), zeta potential (ZP), poly-dispersity index (PDI), and particle size (PS) to determine the optimum formula. The selection criteria prioritized increased ZP (as absolute value) and EE%, coupled with decreased PDI and PS. Rigorous physicochemical, in vivo, and ex vivo tests were conducted to validate the safety, stability, and activity of the optimal formula. Physicochemical assessments encompassed pH measurement, transmission electron microscopy, differential scanning calorimetry, release profiles, storage effects, and Fourier transform infrared spectroscopy. In vivo tests included permeation studies, histopathology, anti-inflammatory activity, and skin irritancy, while ex vivo tests focused on permeation parameters and skin deposition. The optimum formula demonstrated high desirability (0.931), along with favorable EE% (90.93%), ZP (- 40.4 mV), particle size (188.55 nm), and sustained behavior. Notably, improved in vivo permeation (132 µm), skin deposition (193.43 µg/cm2), and antinociceptive activity (66%) compared to DCN suspension (48 µm, 66.31 µg/cm2, and 26%, respectively) were observed. The optimal formula also exhibited excellent safety and storage characteristics. In conclusion, DCN-loaded flexosomes exhibit significant potential for effectively managing osteoarthritis.

Multifunctional cerium oxide nanozymes with high ocular surface retention for dry eye disease treatment achieved by restoring redox balance

Dry eye disease (DED) is a kind of multifactorial ocular surface disease that displays ocular discomfort, visual disturbance, and tear film instability. Oxidative stress is a fundamental pathogenesis in DED. An imbalance between the reactive oxygen species (ROS) level and protective enzyme action will lead to oxidative stress, cell dysfunction, tear hyperosmolarity, and inflammation. Herein, a multifunctional cerium oxide nanozyme with high ocular surface retention property was designed to neutralize over-accumulated ROS and restore redox balance. Cerium oxide nanozymes were fabricated via branched polyethylenimine-graft-poly (ethylene glycol) nucleation and dispersion, followed by phenylboronic acid (PBA) functionalization (defined as Ce@PB). Due to the dynamic chemical bonding formation between the PBA segment and the cis-diol groups in the mucin layer of the tear film, Ce@PB nanozymes possess good adhesive capability to the ocular surface, thus extending the drug's retention time. On the other hand, Ce@PB nanozymes could mimic the cascade processes of superoxide dismutase and catalase to maintain intracellular redox balance. In vitro and in vivo studies suggest that such multifunctional nanozymes possess good biocompatibility and hemocompatibility. More importantly, Ce@PB nanozymes treatment in the animal model could repair corneal epithelial defect, increase the number of goblet cells and promote tear secretion, thus achieving an effective treatment for DED. STATEMENT OF SIGNIFICANCE.

Nanomedicines for Dry Eye Syndrome: Targeting Oxidative Stress with Modern Nanomaterial Strategies

Dry eye syndrome (DES) is a dynamic, chronic disease of the ocular surface and ocular appendages caused by inflammation. The most common symptoms include redness, itching, and blurred vision, resulting from dysfunction of the meibomian glands and impaired tear-film production. Factors contributing to the development of DES include environmental elements, such as UV radiation, and internal elements, such as hormonal imbalances. These factors increase oxidative stress, which exacerbates inflammation on the surface of the eye and accelerates the development of DES. In recent years, the incidence of DES has risen, leading to a greater need to develop effective treatments. Current treatments for dry eye are limited and primarily focus on alleviating individual symptoms, such as reducing inflammation of the ocular surface. However, it is crucial to understand the pathomechanism of the disease and tailor treatment to address the underlying causes to achieve the best possible therapeutic outcomes. Therefore, in this review, we analyzed the impact of oxidative stress on the development of DES to gain a better understanding of its pathomechanism and examined recently developed nanosystems that allow drugs to be delivered directly to the disease site.

Dexamethasone-loaded ROS stimuli-responsive nanogels for topical ocular therapy of corneal neovascularization

Dexamethasone (DEX) has been demonstrated to inhibit the inflammatory corneal neovascularization (CNV). However, the therapeutic efficacy of DEX is limited by the poor bioavailability of conventional eye drops and the increased risk of hormonal glaucoma and cataract associated with prolonged and frequent usage. To address these limitations, we have developed a novel DEX-loaded, reactive oxygen species (ROS)-responsive, controlled-release nanogel, termed DEX@INHANGs. This advanced nanogel system is constructed by the formation of supramolecular host-guest complexes by cyclodextrin (CD) and adamantane (ADA) as a cross-linking force. The introduction of the ROS-responsive material, thioketal (TK), ensures the controlled release of DEX in response to oxidative stress, a characteristic of CNV. Furthermore, the nanogel's prolonged retention on the corneal surface for over 8 h is achieved through covalent binding of the integrin β1 fusion protein, which enhances its bioavailability. Cytotoxicity assays demonstrated that DEX@INHANGs was not notably toxic to human corneal epithelial cells (HCECs). Furthermore, DEX@INHANGs has been demonstrated to effectively inhibit angiogenesis in vitro. In a rabbit model with chemically burned eyes, the once-daily topical application of DEX@INHANGs was observed to effectively suppress CNV. These results collectively indicate that the nanomedicine formulation of DEX@INHANGs may offer a promising treatment option for CNV, offering significant advantages such as reduced dosing frequency and enhanced patient compliance.

Ferulic Acid: A Comprehensive Review

Ferulic acid (FA), a phenolic compound abundant in the cell walls of seeds, leaves, and roots of various fruits, vegetables, cereals, and grains, is renowned for its wide range of biological activities, including antioxidant, anti-inflammatory, antimicrobial, and anticancer properties. Despite its therapeutic potential, the clinical application of FA is hindered by challenges such as poor water solubility, limited bioavailability, rapid metabolism, and instability under physiological conditions. To address these issues, nanotechnology has emerged as a transformative approach, enhancing FA's pharmacokinetic profile. Various nanoparticle-based systems, including polymer-based and lipid-based nanoparticles, have been developed to encapsulate FA. These systems have demonstrated significant improvements in FA's solubility, stability, and bioavailability, with studies showing enhanced antioxidant activity and controlled release profiles. Further, the surface engineering of these nanoparticles provides targeted drug/phytochemical delivery potential. The targeted delivery of drugs/phytochemicals significantly enhances the therapeutic efficacy and minimizes systemic side effects. This review explores the therapeutic potential of FA, the limitations in its clinical application, and the advancements in nanoparticle-based delivery systems that are paving the way for its effective therapeutic use.

What's New in Ocular Drug Delivery: Advances in Suprachoroidal Injection since 2023

Despite significant advancements in ocular drug delivery, challenges persist in treating posterior segment diseases like macular edema (ME) and age-related macular degeneration (AMD). Suprachoroidal (SC) injections are a promising new method for targeted drug delivery to the posterior segment of the eye, providing direct access to the choroid and retina while minimizing systemic exposure and side effects. This review examines the anatomical and physiological foundations of the SC space; evaluates delivery devices such as microcatheters, hypodermic needles, and microneedles; and discusses pharmacokinetic principles. Additionally, advancements in gene delivery through SC injections are explored, emphasizing their potential to transform ocular disease management. This review also highlights clinical applications in treating macular edema, diabetic macular edema, age-related macular degeneration, choroidal melanoma, and glaucoma. Overall, SC injections are emerging as a promising novel route for administering ophthalmic treatments, with high bioavailability, reduced systemic exposure, and favorable safety profiles. Key therapeutic agents such as triamcinolone acetonide, dexamethasone, AAV-based gene therapy, and axitinib have shown promise. The field of suprachoroidal injection is progressing rapidly, and this review article, while attempting to encapsulate most of the published preclinical and clinical studies, mainly focuses on those that are published within 2023 and 2024.

Transdermal application of diacerin loaded-terpene enriched invasomes: an approach to augment anti-edema and nociception inhibition activity

This study aimed to formulate diacerein loaded terpene-enriched invasomes (DCN-TINV) to fulfill a fruitful management of osteoarthritis. A 23 factorial design was adopted, including A: cholesterol concentration (%w/v), B: ethanol volume (mL) and C: phosphatidylcholine: drug ratio as the studied factors. Invasomes were constructed using the thin film hydration technique. Herein, percent entrapment efficiency (EE%), particle size (PS), poly-dispersity index (PDI) and zeta potential (ZP) were statistically analyzed using Design-Expert® software to select the optimum formula. The selected criteria for detecting the optimum formula were restricting PS (<350 nm), dismissing PDI, magnifying ZP (as absolute value) and EE%. The selected formula was further scrutinized through multiple in-vitro studies, including Fourier-transform infrared spectroscopy, differential scanning calorimetry, pH measurement, stability study, release profile and transmission electron microscopy. Furthermore, the ex-vivo performance was evaluated through ex-vivo skin permeation and deposition. Finally, it was subjected to an array of in-vivo tests, namely Draize test, histopathology, In-vivo skin penetration, edema size, and nociception inhibition measurements. The optimum formula with desirability (0.913) demonstrated EE% (89.21% ± 2.12%), PS (319.75 ± 10.11 nm), ZP (-55 ± 3.96 mV) and a prolonged release profile. Intriguingly, revamped skin permeation (1143 ± 32.11 µg/cm2), nociception inhibition (77%) and In-vivo skin penetration (144 µm) compared to DCN suspension (285 ± 21.25 µg/cm2, 26% and 48 µm, respectively) were displayed. The optimum DCN-TINV exhibited plausible safety and stability profiles consolidated with auspicious efficacy for better management of osteoarthritis.

Ocular Surface Fluid: More than a Matrix

Although the eye can be subjected to therapeutic manipulation, some of its structures are highly inaccessible. Thus, conventional therapeutic administration pathways, such as topical or systemic routes, usually show significant limitations in the form of low ocular penetration or the appearance of side effects linked to physiology, among others. The critical feature of many xenobiotics is the drug gradient from the concentrated tear reservoir to the relatively barren corneal and conjunctival epithelia, which forces a passive route of absorption. The same is true in the opposite direction, towards the ocular surface (OS). With the premise that tears can be regarded as equivalent to or a substitute for plasma, researchers may determine drug concentrations in the OS fluid. Within this framework, a survey of scholarly sources on the topic was conducted. It provided an overview of current knowledge, allowing the identification of relevant theories, methods, and gaps in the existing research that can be employed in subsequent research. OS fluid (tears particularly) has enormous potential as a source of biological material for external drug screening and as a biomarker of various systemic diseases. Given the numerous alternate matrices, knowledge of their properties is very important in selecting the most appropriate specimens in toxicological analyses.

Evaluation of the Ocular Safety of Hollow Mesoporous Organosilica Nanoparticles with Different Tetrasulfur Bond Content

Background

Drug therapy for eye diseases has been limited by multiple protective mechanisms of the eye, which can be improved using well-designed drug delivery systems. Mesoporous silica nanoparticles (MSNs) had been used in many studies as carriers of therapeutic agents for ocular diseases treatment. However, no studies have focused on ocular biosafety. Considering that MSNs containing tetrasulfur bonds have unique advantages and have drawn increasing attention in drug delivery systems, it is necessary to explore the ocular biosafety of tetrasulfur bonds before their widespread application as ophthalmic drug carriers.

Methods

In this study, hollow mesoporous silica nanoparticles (HMSNs) with different tetrasulfur bond contents were prepared and characterized. The ocular biosafety of HMSN-E was evaluated in vitro on the three selected ocular cell lines, including corneal epithelial cells, lens epithelial cells and retinal endothelial cells (HREC), and in vivo by using topical eye drops and intravitreal injections.

Results

In cellular experiments, HMSNs caused obvious S content-dependent cytotoxic effect. HMSNs with the highest tetrasulfur bond content (HMSN-E), showed the highest cytotoxicity among all the HMSNs, and HREC was the most vulnerable cell to HMSN-E. It was shown that HMSN-E could react with intracellular GSH to generate H2S and decrease intracellular GSH concentration. Treatment of HREC with HMSN-E increased intracellular ROS, decreased mitochondrial membrane potential, and induced cell cycle arrest at the G1/S checkpoint, finally caused apoptosis and necrosis of HREC. Topical eye drops of HMSN-E could cause corneal damage. The intravitreal injection of HMSN-E could induce inflammation in the vitreum and ganglion cell layers, resulting in vitreous opacities and retinal abnormalities.

Conclusion

The incorporation of tetrasulfur bonds into HMSN can have toxic effects on ocular tissues. Therefore, when mesoporous silica nanocarriers are designed for ophthalmic pharmaceuticals, the ocular toxicity of the tetrasulfur bonds should be considered.

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.

Recent Advances in the Use of Cubosomes as Drug Carriers with Special Emphasis on Topical Applications

Topical drug delivery employing drug nanocarriers has shown prominent results in treating topical ailments, especially those confined to the skin and eyes. Conventional topical formulations persist with drug and disease-related challenges during treatment. Various nanotechnology-driven approaches have been adopted to mitigate the issues associated with conventional formulations. Among these, cubosomes have shown potential applications owing to their liquid crystalline structure, which aids in bioadhesion, retention, sustained release, and loading hydrophilic and hydrophobic moieties. The phase transition behavior of glyceryl monooleate, the concentration of stabilizers, and critical packing parameters are crucial parameters that affect the formation of cubosomes. Microfluidics-based approaches constitute a recent advance in technologies for generating stable cubosomes. This review covers the recent topical applications of cubosomes for treating skin (psoriasis, skin cancer, cutaneous candidiasis, acne, and alopecia) and eye (fungal keratitis, glaucoma, conjunctivitis, and uveitis) diseases. The article summarizes the manufacturing and biological challenges (skin and ocular barriers) that must be considered and encountered for successful clinical outcomes. The patented products are successful examples of technological advancements within cosmeceuticals that support various topical applications with cubosomes in the pharmaceutical field.

Drug-eluting contact lenses: Progress, challenges, and prospects

Topical ophthalmic solutions (eye drops) are becoming increasingly popular in treating and preventing ocular diseases for their safety, noninvasiveness, and ease of handling. However, the static and dynamic barriers of eyes cause the extremely low bioavailability (<5%) of eye drops, making ocular therapy challenging. Thus, drug-eluting corneal contact lenses (DECLs) have been intensively investigated as a drug delivery device for their attractive properties, such as sustained drug release and improved bioavailability. In order to promote the clinical application of DECLs, multiple aspects, i.e., drug release and penetration, safety, and biocompatibility, of these drug delivery systems were thoroughly examined. In this review, we systematically discussed advances in DECLs, including types of preparation materials, drug-loading strategies, drug release mechanisms, strategies for penetrating ocular barriers, in vitro and in vivo drug delivery and penetration detection, safety, and biocompatibility validation methods, as well as challenges and future perspectives.

Smart Contact Lenses in Ophthalmology: Innovations, Applications, and Future Prospects

Smart contact lenses represent a breakthrough in the intersection of medical science and innovative technology, offering transformative potential in ophthalmology. This review article delves into the technological underpinnings of smart contact lenses, emphasizing the current landscape and advancements in biosensors, power supply, biomaterials, and the transmission of ocular information. This review further applies new innovations to their emerging role in the diagnosis, monitoring, and management of various ocular conditions. Moreover, we explore the impact of technical innovations on the application of smart contact lenses in monitoring glaucoma, managing postoperative care, and dry eye syndrome, further elucidating the non-invasive nature of these devices in continuous ocular health monitoring. The therapeutic potential of smart contact lenses such as treatment through targeted drug delivery and the monitoring of inflammatory biomarkers is also highlighted. Despite promising advancements, the implementation of smart contact lenses faces technical, regulatory, and patient compliance challenges. This review synthesizes the recent advances to provide an outlook on the state of smart contact lens technology. Furthermore, we discuss future directions, focusing on potential technological enhancements and new applications within ophthalmology.

Recent updates on ocular disease management with ophthalmic ointments

Ophthalmic diseases can result in permanent vision loss and blindness. Convenient topical and systemic treatments are preferred to address these sight-threatening conditions. However, the unique anatomy of the eye presents challenges for drug delivery. Various ophthalmic ointment formulations have been developed to enhance bioavailability in the eye to prolong residence time and improve corneal permeability. This article explores a wide range of ocular diseases affecting individuals globally and how ointments are used to manage them. From eye to ocular barriers, this review focuses on published scientific research and formulation strategies for severe ocular complications using conventional topical ointments. Additionally, it delves through patented technologies and marketed formulations supporting the use of ointments in ocular drug delivery.

Fostering the unleashing potential of nanocarriers-mediated delivery of ocular therapeutics

Ocular delivery is the most challenging aspect in the field of pharmaceutical research. The major hurdle for the controlled delivery of drugs to the eye includes the physiological static barriers such as the complex layers of the cornea, sclera and retina which restrict the drug from permeating into the anterior and posterior segments of the eye. Recent years have witnessed inventions in the field of conventional and nanocarrier drug delivery which have shown considerable enhancement in delivering small to large molecules across the eye. The dynamic challenges associated with conventional systems include limited drug contact time and inadequate ocular bioavailability resulting from solution drainage, tear turnover, and dilution or lacrimation. To this end, various bioactive-based nanosized carriers including liposomes, ethosomes, niosomes, dendrimer, nanogel, nanofibers, contact lenses, nanoprobes, selenium nanobells, nanosponge, polymeric micelles, silver nanoparticles, and gold nanoparticles among others have been developed to circumvent the limitations associated with the conventional dosage forms. These nanocarriers have been shown to achieve enhanced drug permeation or retention and prolong drug release in the ocular tissue due to their better tissue adherence. The surface charge and the size of nanocarriers (10-1000 nm) are the important key factors to overcome ocular barriers. Various nanocarriers have been shown to deliver active therapeutic molecules including timolol maleate, ampicillin, natamycin, voriconazole, cyclosporine A, dexamethasone, moxifloxacin, and fluconazole among others for the treatment of anterior and posterior eye diseases. Taken together, in a nutshell, this extensive review provides a comprehensive perspective on the numerous facets of ocular drug delivery with a special focus on bioactive nanocarrier-based approaches, including the difficulties and constraints involved in the fabrication of nanocarriers. This also provides the detailed invention, applications, biodistribution and safety-toxicity of nanocarriers-based therapeutcis for the ophthalmic delivery.

Ingestion of Fluids of the Ocular Surface Containing Eye Drops of Imidazole Derivatives-Alpha Adrenergic Receptor Agonists as Paragons

Accidental poisonings by ingesting conjunctival fluid mixed with eye drops commonly involve alpha-2 adrenergic receptor agonists and tetrahydrozoline. These substances are recognized in commonly reported ingestions. Victims of all ages, otherwise in good health, often present as pale and lethargic to the emergency department (ED) after unintentionally ingesting topical eye medication. While eye drop poisoning cases in childhood include accidents during the play and poisonings in adults mean either suicide attempts or side effects caused by the systemic absorption of the substance, fluid of the ocular surface is a risk to all age groups. With this in mind, this study aimed to summarize data in the literature on tetrahydrozoline and alpha-2 adrenergic receptor agonists as dangerous medications, even when administered in low-bioavailability forms, such as eye drops. With this aim, a Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)-compliant systematic review of relevant studies was conducted. A search of PubMed, Scopus, Web of Science, and EBSCOhost yielded nine studies that met the rigorous inclusion criteria. The primary studies were subject to a meta-analysis once a quality appraisal of the studies and a narrative synthesis of the extracted data had been conducted. The author hopes that this information will provide observations that will lead to better designs for over-the-counter eye drops, off-label drug usage policies, and parental attention.

Development and Characterization of a Photocrosslinkable, Chitosan-Based, Nerve Growth Factor-Eluting Hydrogel for the Ocular Surface

Purpose

Recombinant human nerve growth factor (rhNGF; cenegermin-bkbj, OXERVATE) is the first and only U.S. Food and Drug Administration-approved treatment for moderate to severe neurotrophic keratopathy. The aim of this study was to determine the feasibility of incorporating a version of rhNGF in a mucoadhesive hydrogel capable of sustained drug release to the ocular surface.

Methods

Hydrogels loaded with rhNGF were synthesized by conjugating chitosan with azidobenzoic acid (Az-Ch), adding rhNGF, and exposing the solution to ultraviolet (UV) radiation to induce photocrosslinking. Az-Ch hydrogels were evaluated for physical properties and rhNGF release profiles. Cytocompatbility of Az-Ch was assessed using immortalized human corneal limbal epithelial (HCLE) cells. TF1 erythroleukemic cell proliferation and HCLE cell proliferation and migration were used to assess the bioactivity of rhNGF released from Az-Ch hydrogels.

Results

Az-Ch formed hydrogels in <10 seconds of UV exposure and demonstrated high optical transparency (75-85 T%). Az-Ch hydrogels exhibited good cytocompatibility with no demonstratable effect on HCLE cell morphology or viability. rhNGF was released gradually over 24 hours from Az-Ch hydrogels and retained its ability to induce TF1 cell proliferation. No significant difference was observed between rhNGF released from Az-Ch and freshly prepared rhNGF solutions on HCLE cell proliferation or percent wound closure after 12 hours; however, both were significantly better than control (P < 0.01).

Conclusions

rhNGF-loaded Az-Ch hydrogels exhibited favorable physical, optical, and drug-release properties, as well as retained drug bioactivity. This drug delivery system has the potential to be further developed for in vivo and translational clinical applications.

Translational Relevance

Az-Ch hydrogels may be used to enhance rhNGF therapy in patients with NK.

Advancing ophthalmic delivery of flurbiprofen via synergistic chiral resolution and ion-pairing strategies

Flurbiprofen (FB), a nonsteroidal anti-inflammatory drug, is widely employed in treating ocular inflammation owing to its remarkable anti-inflammatory effects. However, the racemic nature of its commercially available formulation (Ocufen®) limits the full potential of its therapeutic activity, as the (S)-enantiomer is responsible for the desired anti-inflammatory effects. Additionally, the limited corneal permeability of FB significantly restricts its bioavailability. In this study, we successfully separated the chiral isomers of FB to obtain the highly active (S)-FB. Subsequently, utilizing ion-pairing technology, we coupled (S)-FB with various counter-ions, such as sodium, diethylamine, trimethamine (TMA), and l-arginine, to enhance its ocular bioavailability. A comprehensive evaluation encompassed balanced solubility, octanol-water partition coefficient, corneal permeability, ocular pharmacokinetics, tissue distribution, and in vivo ocular anti-inflammatory activity of each chiral isomer salt. Among the various formulations, S-FBTMA exhibited superior water solubility (about 1-12 mg/ml), lipid solubility (1< lg Pow < 3) and corneal permeability. In comparison to Ocufen®, S-FBTMA demonstrated significantly higher in vivo anti-inflammatory activity and lower ocular irritability (such as conjunctival congestion and tingling). The findings from this research highlight the potential of chiral separation and ion-pair enhanced permeation techniques in providing pharmaceutical enterprises focused on drug development with a valuable avenue for improving therapeutic outcomes.

Injectable hydrogels based on biopolymers for the treatment of ocular diseases

Injectable hydrogels based on biopolymers, fabricated utilizing diverse chemical and physical methodologies, exhibit exceptional physical, chemical, and biological properties. They have multifaceted applications encompassing wound healing, tissue regeneration, and across diverse scientific realms. This review critically evaluates their largely uncharted potential in ophthalmology, elucidating their diverse applications across an array of ocular diseases. These conditions include glaucoma, cataracts, corneal disorders (spanning from age-related degeneration to trauma, infections, and underlying chronic illnesses), retina-associated ailments (such as diabetic retinopathy, retinitis pigmentosa, and age-related macular degeneration (AMD)), eyelid abnormalities, and uveal melanoma (UM). This study provides a thorough analysis of applications of injectable hydrogels based on biopolymers across these ocular disorders. Injectable hydrogels based on biopolymers can be customized to have specific physical, chemical, and biological properties that make them suitable as drug delivery vehicles, tissue scaffolds, and sealants in the eye. For example, they can be engineered to have optimum viscosity to be injected intravitreally and sustain drug release to treat retinal diseases. Their porous structure and biocompatibility promote cellular infiltration to regenerate diseased corneal tissue. By accentuating their indispensable role in ocular disease treatment, this review strives to present innovative and targeted approaches in this domain, thereby advancing ocular therapeutics.

Nanozymes for Treating Ocular Diseases

Nanozymes, characterized by their nanoscale size and enzyme-like catalytic activities, exhibit diverse therapeutic potentials, including anti-oxidative, anti-inflammatory, anti-microbial, and anti-angiogenic effects. These properties make them highly valuable in nanomedicine, particularly ocular therapy, bypassing the need for systemic delivery. Nanozymes show significant promise in tackling multi-factored ocular diseases, particularly those influenced by oxidation and inflammation, like dry eye disease, and age-related macular degeneration. Their small size, coupled with their ease of modification and integration into soft materials, facilitates the effective penetration of ocular barriers, thereby enabling targeted or prolonged therapy within the eye. This review is dedicated to exploring ocular diseases that are intricately linked to oxidation and inflammation, shedding light on the role of nanozymes in managing these conditions. Additionally, recent studies elucidating advanced applications of nanozymes in ocular therapeutics, along with their integration with soft materials for disease management, are discussed. Finally, this review outlines directions for future investigations aimed at bridging the gap between nanozyme research and clinical applications.

Synergism of polysaccharide polymers in antihistamine eye drops: Influence on physicochemical properties and in vivo efficacy

The incorporation of polymers into drug delivery vehicles has been shown to be a useful approach to prolong the residence time of drugs in the precorneal tear film and to improve penetration into biological membranes. The main objective of this research was to formulate novel viscous eye drops with ketotifen as the active ingredient, containing the polysaccharides: chitosan (MCH), hydroxypropyl guar gum (HPG) and hyaluronic acid (SH) alone and in combination as functional polymers. DSC and FT-IR techniques showed the compatibility between ketotifen and polymers. Physicochemical and rheological analysis at ambient and simulated physiological conditions, as well as the evaluation of mucoadhesive properties showed that vehicles containing combinations of polymers have suitable physicochemical and functional properties with demonstrated synergism between combined polymers (MCH and HPG i.e. SH and HPG). The drug permeability was successfully estimated in vitro using HCE-T cell-based models. MTT cytotoxicity assay demonstrates that the tested formulations were non-toxic and well tolerated. In vivo preclinical study on mice revealed that both vehicles containing mixed polymers enhanced and prolonged the antipruritic/analgesic-like effect of ophthalmic ketotifen. Based on these results, both combinations of polysaccharide polymers, especially SH-HPG, could be considered as potential new carriers for ketotifen for ophthalmic use.

Baicalein glycymicelle ophthalmic solution: Preparation, in vitro antimicrobial activities, and antimicrobial mechanism evaluations

The purpose of this study was to develop a novel baicalein (BAI) loaded glycymicelle ophthalmic solution with small molecule phytochemical glycyrrhizin as nanocarriers and to explore this solution's potential as an antimicrobial agent against ocular infections. The optimized BAI glycymicelles had a high encapsulation efficiency (98.76 ± 1.25 %), a small particle size (54.38 ± 2.41 nm), a uniform size distribution (polydispersity index = 0.293 ± 0.083), and a zeta potential of -28.3 ± 1.17 mV. The BAI glycymicelle ophthalmic solution exhibited an excellent short-term storage stability. BAI glycymicelles significantly increased the apparent solubility and in vitro release capability of BAI. The BAI glycymicelle ophthalmic solution exhibited no hen's egg-chorioallantoic membrane' irritation and strong in vivo ocular tolerance in rabbits. The BAI glycymicelles noticeably enhanced the in vivo corneal permeation. The BAI glycymicelles also precipitated increased in vitro antioxidant activity and significantly improved in vitro antipathogen activities. Various antimicrobial mechanisms, including the destruction of the bacterial cell wall, damage to the bacterial cell membranes, interruptions to the biofilm structure, and the apoptosis of bacteria, were inflicted on BAI glycymicelles. These findings provided useful knowledge regarding the development of a novel ophthalmic solution and formulation of BAI.

Preclinical Development of Antisense Oligonucleotides to Rescue Aberrant Splicing Caused by an Ultrarare ABCA4 Variant in a Child with Early-Onset Stargardt Disease

Precision medicine is rapidly gaining recognition in the field of (ultra)rare conditions, where only a few individuals in the world are affected. Clinical trial design for a small number of patients is extremely challenging, and for this reason, the development of N-of-1 strategies is explored to accelerate customized therapy design for rare cases. A strong candidate for this approach is Stargardt disease (STGD1), an autosomal recessive macular degeneration characterized by high genetic and phenotypic heterogeneity. STGD1 is caused by pathogenic variants in ABCA4, and amongst them, several deep-intronic variants alter the pre-mRNA splicing process, generally resulting in the insertion of pseudoexons (PEs) into the final transcript. In this study, we describe a 10-year-old girl harboring the unique deep-intronic ABCA4 variant c.6817-713A>G. Clinically, she presents with typical early-onset STGD1 with a high disease symmetry between her two eyes. Molecularly, we designed antisense oligonucleotides (AONs) to block the produced PE insertion. Splicing rescue was assessed in three different in vitro models: HEK293T cells, fibroblasts, and photoreceptor precursor cells, the last two being derived from the patient. Overall, our research is intended to serve as the basis for a personalized N-of-1 AON-based treatment to stop early vision loss in this patient.

Eye Drop with Fas-Blocking Peptide Attenuates Age-Related Macular Degeneration

Age-related macular degeneration (AMD), characterized by macular retinal degeneration, poses a significant health concern due to the lack of effective treatments for prevalent dry AMD. The progression of AMD is closely linked to reactive oxygen species and Fas signaling, emphasizing the need for targeted interventions. In this study, we utilized a NaIO3-induced retinal degeneration mouse model to assess the efficacy of Fas-blocking peptide (FBP). Intravitreal administration of FBP successfully suppressed Fas-mediated inflammation and apoptosis, effectively arresting AMD progression in mice. We developed a 6R-conjugated FBP (6R-FBP) for eye drop administration. 6R-FBP, administered as an eye drop, reached the retinal region, attenuating degeneration by modulating the expression of inflammatory cytokines and blocking Fas-mediated apoptosis in rodent and rabbit NaIO3-induced retinal degeneration models to address practical concerns. Intravitreal FBP and 6R-FBP eye drops effectively reduced retinal degeneration and improved retinal thickness in rodent and rabbit models. This study highlights the therapeutic potential of FBP, particularly 6R-FBP as an eye drop, in inhibiting Fas-mediated cell signaling and protecting against retinal cell death and inflammation in dry AMD. Future investigations should explore the translational prospects of this approach in primates with eye structures comparable to those of humans.

Matrix hyaluronic acid and bilayer poly-hydroxyethyl methacrylate-hyaluronic acid films as potential ocular drug delivery platforms

This study aimed to design hydrogel based films comprising hyaluronic acid (HA) to overcome limitations of currently used eye drops. Timolol-loaded crosslinked (X2) HA-based and bilayer (B2) (pHEMA/PVP-HA-based layers) films were designed and characterized. The films were transparent (UV, visual observation) with crosslinked (<80 %) films showing lower light transmittance than bilayer (>80 %) films. X2 showed significantly higher swelling capacity, tensile strength and elastic modulus (5491.6 %, 1539.8 Nmm-2, 1777.2 mPa) than B2 (1905.0 %, 170.0N mm-2, 67.3 mPa) respectively. However, X2 showed lower cumulative drug released and adhesive force (27.3 %, 6.2 N) than B2 (57.5 %, 8.6 N). UV sterilization did not significantly alter physical properties, while SEM and IR microscopy showed smooth surface morphology and homogeneous drug distribution. Timolol permeation (EpiCorneal™/porcine cornea) depended on the film matrix with erodible films showing similar permeation to commercial eyedrops. Drug permeation for porcine cornea (X2 = 549.0.2, B2 = 312.1 μgcm-2 h-1) was significantly faster than EpiCorneal™ (X2 = 55.2, B2 = 37.6 μgcm-2 h-1), but with a linear correlation between them. All the selected optimized films showed acceptable compatibility (MTT assay) with both HeLa cells and EpiCorneal™. In conclusion, crosslinked and bilayer HA based films showed ideal characteristics suitable for potential ocular drug delivery, though further work is required to further optimize these properties and confirm their efficacy including in vivo tests.

Sustained Delivery of Olopatadine from Vitamin-E Loaded Contact Lenses

Purpose: Topical antihistamines, such as olopatadine hydrochloride, an H1 receptor antagonist, are commonly prescribed for treating allergic conjunctivitis. Drug delivery via eye drops has many deficiencies including a short residence time due to tear drainage via the nasolacrimal duct, which results in a low bioavailability and potential for side effects. These deficiencies could be mitigated by a drug-eluting contact lens such as the recently approved ACUVUE® THERAVISION™ WITH KETOTIFEN which is a daily disposable etafilcon, a drug-eluting contact lens with ketotifen (19 μg per lens). Here, we investigate the feasibility of designing a drug-eluting lens with sustained release of olopatadine for treating allergies using an extended wear lens. Methods: Nanobarrier depots composed of vitamin-E (VE) are formed through direct entrapment by ethanol-driven swelling. The drug-loaded lenses are characterized for transparency and water content. In vitro release is measured under sink conditions and fitted to a diffusion control release model to determine diffusivity and partition coefficient. Results: In vitro studies indicate that ACUVUE OASYS® and ACUVUE TruEye™ lenses loaded with ∼0.3 g of VE/g of hydrogel effectively prolong olopatadine dynamics by 7-fold and 375-fold, respectively. Incorporation of VE into the lenses retains visible light transmission and other properties. Conclusion: The VE incorporation in commercial lenses significantly increases the release duration offering the possibility of antiallergy extended wear lenses.

Steroidal nanoformulations for the treatment of uveitis: potential, promises and future perspectives

BACKGROUND

Intraocular inflammation, commonly referred to as uveitis, is a prevalent ocular disease. The categorization of uveitis may be based on the prevailing anatomical site, which includes anterior, intermediate, and posterior uveitis. There exists a significant body of evidence indicating that T cells play a pivotal role in the pathogenesis of autoimmune uveitis. In addition to the presence of T cells, an elevation in levels of inflammatory cytokines and a reduction in regulatory cytokines were also noted. The primary pharmacological interventions for uveitis comprise of corticosteroids, methotrexate, anti-vascular endothelial growth factor (VEGF) agents, anti-tumor necrosis factor-alpha (TNF-α) antibodies, and sirolimus. These medications offer prompt alleviation for inflammation. Nevertheless, prolonged administration of corticosteroids invariably leads to unfavorable adverse reactions. The traditional topical corticosteroids exhibit certain limitations, including inadequate transcorneal permeation and low corneal retention, leading to reduced ocular bioavailability. Consequently, there is a growing inclination towards the creation of innovative steroid drug delivery systems with the aim of reducing the potential for adverse effects, while simultaneously enhancing the drug's corneal permeation and retention.

CONCLUSION

This review is an attempt to compile all the research work done so far in this field and provides a brief overview of the global efforts to develop innovative nanocarrier-based systems for corticosteroids.