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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. 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. 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 H S 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. 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.

Ophthalmic ointments are unique in that they combine features of topical drug delivery, the ophthalmic route and ointment (semisolid) formulations. Accordingly, these complex formulations are challenging to develop and evaluate and therefore it is critically important to understand their physicochemical properties as well as their in vitro drug release characteristics. Previous reports on the characterization of ophthalmic ointments are very limited. Although there are FDA guidance documents and USP monographs covering some aspects of semisolid formulations, there are no FDA guidance documents nor any USP monographs for ophthalmic ointments. This review summarizes the physicochemical and in vitro profiling methods that have been previously reported for ophthalmic ointments. Specifically, insight is provided into physicochemical characterization (rheological parameters, drug content and content uniformity, and particle size of the API in the finished ointments) as well as important considerations (membranes, release media, method comparison, release kinetics and discriminatory ability) in in vitro release testing (IVRT) method development for ophthalmic ointments.

Preclinical models of human diseases are critical to our understanding of disease etiology, pathology, and progression and enable the development of effective treatments. An ideal model of human disease should capture anatomical features and pathophysiological mechanisms, mimic the progression pattern, and should be amenable to evaluating translational endpoints and treatment approaches. Preclinical animal models have been developed for a variety of human ophthalmological diseases to mirror disease mechanisms, location of the affected region in the eye and severity. These models offer clues to aid in our fundamental understanding of disease pathogenesis and enable progression of new therapies to clinical development by providing an opportunity to gain proof of concept (POC). Here, we review preclinical animal models associated with development of new therapies for diseases of the ocular surface, glaucoma, presbyopia, and retinal diseases, including diabetic retinopathy and age-related macular degeneration (AMD). We have focused on summarizing the models critical to new drug development and described the translational features of the models that contributed to our understanding of disease pathogenesis and establishment of preclinical POC.

Silk is a remarkable biopolymer with a long history of medical use. Silk fabrications have a robust track record for load-bearing applications, including surgical threads and meshes, which are clinically approved for use in humans. The progression of top-down and bottom-up engineering approaches using silk as the basis of a drug delivery or cell-loaded matrix helped to re-ignite interest in this ancient material. This review comprehensively summarises the current applications of silk for tissue engineering and drug delivery, with specific reference to the eye. Additionally, the review also covers emerging trends for the use of silk as a biologically active biopolymer for the treatment of eye disorders. The review concludes with future capabilities of silk to contribute to advanced, electronically-enhanced ocular drug delivery concepts.

Background/Objectives: Ocular drug delivery faces significant challenges due to anatomical and physiological barriers that limit drug bioavailability, particularly with conventional eye drops. Levofloxacin (LEVO), a broad-spectrum antibiotic, is widely used in the treatment of bacterial conjunctivitis, but its therapeutic efficacy is hindered by rapid precorneal clearance and short residence time. Methods: This study introduces a biorelevant 2 mL dissolution model to simulate ocular conditions better and evaluate the release kinetics of LEVO-loaded nanofibrous ophthalmic inserts. Compared to the conventional 40 mL setup, the 2 mL system demonstrated a slower and more sustained drug release profile, with kinetic modeling confirming a more controlled release behavior. Difference and similarity factor analysis further validated the distinct release profiles, highlighting the impact of dissolution volume on release dynamics. Results: Preliminary pharmacokinetic modeling suggested that the nanofiber inserts, particularly when applied twice daily, maintained levofloxacin concentrations above minimum inhibitory and bactericidal levels for extended durations across three bacterial strains (Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus), potentially outperforming traditional eye drops. Conclusions: These findings suggest that small-volume dissolution testing may provide a more realistic method for evaluating ophthalmic insert formulations, though in vivo validation is needed. Moreover, the nanofibrous inserts show potential as a sustained-release alternative that warrants further investigation to improve patient compliance and therapeutic outcomes in ocular disease management.

Purpose This study aimed to evaluate a novel microemulsion ion-activated gel system for the ophthalmic delivery of coenzyme Q10 (CoQ10). Methods Various CoQ10 microemulsion ion-activated formulations were prepared and fully assessed for physical and chemical parameters, assay and related substances, in vitro release, rheological properties, in vitro cytotoxicity and ophthalmic retention. A preliminary pharmacokinetic study was also performed in rabbits. Results The formulations met the specified criteria, showing a droplet size of 24.5 ± 2.0 nm for microemulsions, increasing slightly to 39.6 ± 3.5 nm for the microemulsion gels. They exhibited a 24-hour sustained in vitro release (80.0% ± 3.2%) and increased viscosity upon contact with artificial tears containing Ca 2+ and K + ions. The no-film dissolution method and in vitro models indicated first-order release kinetics ( r  = 0.987). The preparations demonstrated good tolerance and non-irritating properties, with a Draize score of 0–0.55 in rabbits, and provided a 2-hour extension in drug retention on the ocular surface compared with microemulsions alone. In ultraviolet B (UVB)-exposed rats, corneal epithelial damage was reduced and antioxidant marker levels (superoxide dismutase, malondialdehyde) were significantly improved. Conclusion This novel system is a promising preparation for ophthalmic CoQ10 delivery, offering sustained release and protection against UVB-induced corneal damage.

This study endeavored to overcome the physiological barriers hindering optimal bioavailability in ophthalmic therapeutics by devising drug delivery platforms that allow therapeutically effective drug concentrations in ocular tissues for prolonged times. Thermosensitive drug delivery platforms were formulated by blending poloxamers (F68 and F127) with low-molecular-weight hyaluronic acid (HA) in various concentrations and loaded with hydrocortisone (HC). Among the formulations examined, only three were deemed suitable based on their desirable gelling properties at a temperature close to the eye’s surface conditions while also ensuring minimal gelation time for swift ocular application. Rheological analyses unveiled the ability of the formulations to develop gels at suitable temperatures, elucidating the gel-like characteristics around the physiological temperature essential for sustained drug release. The differential scanning calorimetry findings elucidated intricate hydrogel–water interactions, indicating that HA affects the water–polymer interactions within the gel by increasing the platform hydrophilicity. Also, in vitro drug release studies demonstrated significant hydrocortisone release within 8 h, governed by an anomalous transport mechanism, prompting further investigation for optimized release kinetics. The produced platforms offer promising prospects for efficacious ocular drug delivery, addressing pivotal challenges in ocular therapeutics and heralding future advancements in the domain.

The purpose of this study was to evaluate the safety and tolerability profile of drugs used for treating common eye disorders when applied to normal healthy volunteers (NHVs) as explored in phase 1 trials. A total of 166 NHVs were identified in six phase 1 trials, examined in a retrospective analysis. The primary endpoints were visual comfort (by ocular comfort index, OCI) and safety (laboratory evaluations, vital signs (VS), visual acuity (VA), intraocular pressure (IOP), lissamine green and fluorescein staining, conjunctival hyperemia, chemosis, and adverse events' incidence (AE)). Compared to baseline, 75.9%, 40.4% and 73.7% of NHV (for lubricant, hypotensive and antibiotic treatments, respectively) improved their OCI score by their final visit. Laboratory evaluations and VS were within normal ranges in 88% of NHV. Similar results were found for VA, corneal and conjunctival staining, and chemosis. IOP decreased significantly in the hypotensive agents' group, trace to mild hyperemia was reported in 32.1%, 27.1%, and 6.8%, respectively. Additionally, lubricant and hypotensive investigational drugs (ID) had a lower risk of incidence of AE than approved drugs (OR 0.856, 95% CI [0.365, 1.999] and 0.636, 95% CI [0.096, 4.197], respectively). Meanwhile, on antibiotic drugs, the risk for ID-related AE was higher (OR 1.313, 95% CI [0.309, 5.583]). Phase 1 trials are important in order to ensure the safety and tolerability of ophthalmic medications. This study demonstrates that NHVs do not face a significant risk of harm in these studies, since 98% of the reported AE were mild, and all AE were resolved by the end of the study in which they appeared. This is a retrospective study of six previously conducted clinical trials, registered on clinicaltrials.gov with the following registration IDs: NCT04081610, NCT03524157, NCT03520348, NCT03966365, NCT03965052 and, NCT03519516.