Trans-corneal drug delivery strategies in the treatment of ocular diseases

Polyoxyethylene and polypropylene emulsification enhances retinol palmitate efficacy in corneal wound healing

Retinol palmitate (VApal), an active ingredient in ophthalmic solution, has been reported to repair corneal injuries. Additionally, it has been suggested that the efficacy of VApal is enhanced by a specific surfactant, polyoxyethylene-polypropylene [EO100PO70EO100 (EOPO)]. We aimed to determine the efficacy of VApal in corneal wound healing in comparison to that of hyaluronic acid (HA), carboxymethyl cellulose (CMC) and hydroxypropyl methylcellulose (HPMC) used in over-the-counter ophthalmic solutions and whether the efficacy of VApal could be enhanced by EOPO compared to the widely used surfactant, polyoxyethylene hydrogenated castor oil 60 (HCO60). To evaluate the efficacy of VApal or VApal emulsified with a surfactant, we performed a wound healing assay using corneal epithelial cells in monolayer (n = 4) or 3D culture (n = 6). Wound closure rates were calculated each time, and the efficacy was compared using the time to reach a 50% wound closure rate (ET50). The ET50 values of VApal, HA, CMC and HPMC were approximately 17.31 h, 26.99 h, 28.98 h and 26.01 h respectively. The ET50 values of VApal emulsified with EOPO or HCO60 were 34.49 h and 43.31 h, respectively. In conclusion, VApal is more beneficial than other ingredients for corneal wound healing. Additionally, the efficacy of VApal can be enhanced using EOPO instead of HCO60.

PROTAC based targeted degradation of LRG1 for mitigating corneal neovascularization

Leucine-rich alpha-2-glycoprotein 1 (LRG1), a secretory glycoprotein associated with angiogenesis, inflammation, fibrosis, and other pivotal pathophysiological processes, is significantly upregulated in corneal neovascularization (CNV), where it drives neovascularization via the TGF-β-Smad signaling pathway, making it a potential therapeutic target for CNV. This study employs proteolysis-targeting chimera (PROTAC) technology, utilizing our newly developed PROTAC agent, ETTAC-2, to selectively degrade LRG1 in a mouse model of alkali burn-induced CNV. The cellular study revealed that ETTAC-2 effectively degraded LRG1 in a time- and dose-dependent manner, with a half-maximal degradation concentration (DC50) of 13.52 μM. In vivo findings confirmed that ETTAC-2 significantly reduced LRG1 levels in corneal neovascular tissues and inhibited the release of angiogenic factors by suppressing the TGF-β-Smad1/5/9 pathway, thus attenuating CNV progression. To enhance corneal drug delivery, ETTAC-2 was encapsulated in liposomes to form Lipo@ETTAC-2, which enhanced drug retention on the corneal surface, resulting in superior therapeutic outcomes in CNV models. This study underscores the pivotal role of LRG1 in CNV and positions Lipo@ETTAC-2 as a promising candidate for CNV therapy.

Silk biomaterials for corneal tissue engineering: From research approaches to therapeutic potentials; A review

The corneal complications can result in opacity and eventual blindness. Furthermore, a shortage of available donors constrains the existing therapeutic options. Therefore, one of the most promising strategies involves the application of biomaterials, particularly silk. Silk has garnered significant attention among these biomaterials due to its natural origin and diverse features derived from different sources. One of the most critical factors of silk is its transparency, which is crucial for the cornea, and there are no concerns about infection. This material also possesses several advantages, including cost-effectiveness in production, biocompatibility in vivo and in vitro, biodegradation, and desirable mechanical characteristics. Modifications in the topographical structure, porosity, and crystallinity of silk enhance its properties and optimize its suitability for wound dressing, efficient drug delivery systems, and various cornea-related treatments. In each layer, silk was examined as a single biomaterial or blended with the others, so, this review aims to explore silk as a potential material for corneal regenerative medicine from a novel viewpoint. By considering a range of studies, a classification system has been developed that categorizes the utilization of silk in the various layers of the cornea and sub-categorizes the different modifications and applications of silk.

Disclosing long-term tolerance, efficacy and penetration properties of hyaluronic acid-coated latanoprost-loaded liposomes as chronic glaucoma therapy

Frequent topical administration of hypotensive eye drops in glaucoma patients may lead to the development of dry eye disease (DED) symptoms, because of tear film destabilization and the adverse effects associated with antiglaucoma formulations. To address all this, in the current study preservative-free latanoprost-loaded (0.005 % w/v) synthetic phosphatidylcholine (1,2-dioleoyl-sn-glycero-3-phosphocholine 0.75 % w/v, 1,2-dimyristoyl-sn-glycero-3-phosphocholine 0.25 % w/v) liposomes dispersed in the mucoadhesive polymer hyaluronic acid (0.2 % w/v), containing the osmoprotective ingredients betaine (0.40 % w/v) and leucine (0.90 % w/v) (LAT-HA-LIP), have been prepared and further characterised. Permeation and retention evaluations on a validated ex vivo porcine eye model revealed that the active metabolite latanoprost acid was quantified only starting from LAT-HA-LIP once passing conjunctiva, sclera and choroid compared to the marketed latanoprost (0.005 % w/v) benchmark (MF). The liposomal formulation outperformed MF when applied to the corneal tissue. Additionally, distribution and interactions within corneal and scleral tissues were investigated by means of two-photon microscopy with liposomal formulations containing coumarin-6. Furthermore, acute and chronic tolerance studies on rabbits revealed no signs of discomfort or ocular damage. Schirmer's test, tear osmolarity, tear breakup time (TBUT) and fluorescence staining evaluated through the Oxford grading scale, were assessed as DED diagnostic parameters over a 25-day monitoring period; LAT-HA-LIP consistently maintained levels comparable to physiological solution (0.9 % w/v NaCl) used as control, with a slight increase of TBUT values from day 15 (6.00 ± 0.63 s for control, 7.00 ± 0.78 s for LAT-HA-LIP at day 15, p = 0.0066). A daily topical application of LAT-HA-LIP for 15 consecutive days, effectively lowered IOP in a sustained way (2.51-3.88 mmHg mean IOP reduction over the 5-15-day period). These results highlight the clinical relevance of the proposed technological platform, able to provide IOP reduction during the simulated long-term administration and simultaneous ocular surface protection with potential for the treatment of glaucoma.

Exosomes derived from adipose mesenchymal stem cells promote corneal injury repair and inhibit the formation of scars by anti-apoptosis

In the corneal wound healing process, epithelial cell re-epithelialization and migration are the critical first steps following an injury. As the disease progresses, orderly regeneration of corneal stromal collagen and mild corneal stromal fibrosis are vital for corneal function reconstruction. Exosomes derived from adipose-derived mesenchymal stem cells (ADSCs-Exos) have emerged as a promising therapy due to their anti-oxidant, anti-apoptosis, and tissue repair properties. In this study, we successfully isolated exosomes via differential centrifugation and verified their effective extraction through transmission electron microscopy and nanoparticle tracking analysis. In vitro, ADSCs-Exos increased corneal epithelial cell migration by 20 % and reduced oxidative damage by 50 %. In addition, ADSCs-Exos demonstrated remarkable wound healing properties in corneal tissue. This effect was attributed to their ability to inhibit apoptosis of corneal stroma cells by upregulating Bax and downregulating Bcl2, reducing the Bax/Bcl2 protein expression ratio from 1 to 0.45. This decrease may subsequently inhibit α-SMA expression, thereby preventing corneal scarring. Overall, this research has elucidated the effects and potential targets of ADSCs-Exos in promoting corneal wound repair, offering a novel and promising approach for treating corneal injuries.

Chemical and biological investigations on modified gemcitabine by nanoliposome structured on cholesterol, pectin, and phosphatidylcholine as an anticancer drug via a drug delivery system

Gemcitabine hydrochloride (GEM) mimics one of the building blocks of DNA and RNA, so it indicates possible chemotherapeutic effects. It prevents cancer cells from producing DNA and proteins, which ultimately leads to their death. The goal of this work is to modify the GEM medication by nanoforming nanoliposomes based on the composition of Cholesterol, pectin nanoparticles, and phosphatidylcholine (PhC). The drug in nanoliposome form is made using the precipitation method, and several approaches are employed to characterize it. UV-Vis spectroscopy is used to measure the release process of GEM from the lipids and its integration with them. Results of the combination efficiency for PhC.Pectin@GEM, PhC.GEM@Pectin, and PhC@Cholestrol.GEM were recorded at 78.8 %, 83 %, and 80 %, respectively. A UV-Vis spectrophotometer was used to determine the release efficiency of the nanoliposomes, which was measured at pH values of 3, 6.8, and 7.4. The in-vitro investigation employed SRB (Routine analysis IC50) to determine the modified drug's toxicity on breast adenocarcinoma (MCF-7) cells, while the in-vitro study assessed the produced nanoliposomes' capacity to do so. The conclusion is that to ascertain whether GEM medicine's nanoliposomes can effectively treat breast cancer in place of GEM medication, clinical trials are necessary to prove the ability for treatment.

ZnFe Layered Double Hydroxide Nanosheets Loaded with Cu Single-Atom Nanozymes with Multi-Enzyme-Like Catalytic Activities as an Effective Treatment for Bacterial Keratitis

Bacterial keratitis (BK) is a type of corneal inflammation resulting from bacterial infection in the eye. Although nanozymes have been explored as promising materials in corneal wound healing, currently available nanozymes lack sufficient catalytic activity and the ability to penetrate bacterial biofilms, limiting their efficacy against the treatment of BK. To remedy this, ZnFe layered double hydroxide (ZnFe-LDH) nanosheets are loaded with Cu single-atom nanozymes (Cu-SAzymes) and aminated dextran (Dex-NH2), resulting in the formation of the nanozyme DT-ZnFe-LDH@Cu, which possesses peroxidase (POD)-, oxidase (OXD)-, and catalase (CAT)-like catalytic activities. This enables the nanozyme to generate reactive oxygen species (ROS), such as hydroxyl radicals (•OH), superoxide anion radical (O2 •-), and singlet oxygen (1O2) from hydrogen peroxide (H2O2), thereby killing the bacteria causing the infections. The surface Dex-NH2 enabled the DT-ZnFe-LDH@Cu to penetrate the biofilm and adsorb onto extracellular polymeric substances (EPS) produced by bacteria in the biofilm. Additionally, the DT-ZnFe-LDH@Cu successfully repaired P. aeruginosa-infected corneal injury in a BK rabbit model more effectively than commercially available tobramycin eye drops. This was enabled, in part, by the ability of DT-ZnFe-LDH@Cu to reduce inflammation by promoting the polarization of pro-inflammatory macrophages (M1) to anti-inflammatory macrophages (M2) and decrease the expression of α-smooth muscle actin (α-SMA) to promote wound healing without scar formation. This study provides an innovative concept for the treatment of BK and holds great scientific value and clinical application potential.

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.

Advancements and Prospects in Nanorobotic Applications for Ophthalmic Therapy

This study provides a bibliometric and bibliographic review of emerging applications of micro- and nanotechnology in treating ocular diseases, with a primary focus on glaucoma. We aim to identify key research trends and analyze advancements in devices and drug delivery systems for ocular treatments. The methodology involved analyzing 385 documents indexed on the Web of Science using tools such as VOSviewer and Bibliometrix. The results show a marked increase in scientific output, highlighting prominent authors and institutions, with England leading in the field. Key findings suggest that nanotechnology holds the potential to address the limitations of conventional treatments, including low ocular bioavailability and adverse side effects. Nanoparticles, nanovesicles, and polymer-based systems appear promising for prolonged and controlled drug release, potentially offering enhanced therapeutic efficacy. In conclusion, micro- and nanotechnology could transform ocular disease treatment, although challenges remain concerning the biocompatibility and scalability of these devices. Further clinical studies are necessary to establish these innovations within the therapeutic context of ophthalmology.

FRET-based analysis on the fate of liposome and cyclodextrin@liposome nanocomposites from ocular surface to the posterior segment of the eye

Investigating the structural integrity of nanocarriers in vivo is vital for exploring the fate of nanocarriers from ocular surface to the posterior segment of the eye. Most of the published studies adopted the structural integrity ratio of nanocarriers to determine the fate of them, which lacked scientific support. In this study, two methods were used to explore the factors which affected the structural integrity of liposomes. A new method with the standard curve of FRET fluorescence intensity and carbocyanine 7 (Cy7) content was drawn for the first time. Secondly, we used the traditional method of drawing the standard curve of FRET fluorescence efficiency and structural integrity ratios. The results showed that liposomes with particle size about 120 nm, positively charged, polyethyleneglycol5000 (PEG5000) and glycine sarcosine (GS) modified had the highest Cy7 content in rabbit tissues. When the dosage of Cy7 was 25 μg, at 60 min, the content of Cy7 in intact liposomes and the structural integrity ratio of liposomes in sclera was 210.5 ± 14.9 ng and 19.8 ± 5.3 %, respectively. Compared with the structural integrity ratio, the Cy7 content in the intact carrier could better estimate the fate of nanocarriers in vivo scientifically. On this basis, the fate of dual-carrier nanocomposites and the inner cyclodextrin complexes in vivo was investigated. The intact cyclodextrin complexes could reach choroid-retina with the protection of outer liposomes. The structural integrity ratios of liposomes were also studied after crossing human conjunctival epithelial cells (HConEpiC) monolayer, but in vitro cellular experiments could not simulate the real situation in vivo. Finally, the tissue distribution of nanocomposites was studied in rabbit eyes. The concentration of dexamethasone (Dex) in choroid-retina was 158 ± 23 ng/g after 3 h, which exhibited better drug delivery ability compared with our previous study. Overall, the present study provides a new scientific method to estimate the structural integrity in vivo, which is beneficial for the rational design of drug delivery systems with more structural integrity in vivo and higher drug delivery efficiency.

Anti-oxidative mesoporous polydopamine-based hypotensive nano-eyedrop for improved glaucoma management

Conventional hypotensive eye drops remain suboptimal for glaucoma management, primarily due to their limited intraocular bioavailability and the growing concern regarding ocular surface side effects. Therefore, there is an urgent need to develop innovative intraocular pressure (IOP)-lowering formulations that not only possess enhanced corneal penetration ability but also provide ocular surface protection. Herein, anti-oxidative mesoporous polydopamine nanoparticles (MPDA NPs) were explored as a nano-carrier for Brimonidine to address the above issues. Nearly monodisperse MPDA NPs with obvious nanopores were successfully prepared by template-removal method and used for encapsulation of Brimonidine benefiting from their high specific surface area. Interestingly, the PEGylated and drug loaded MPDA-PEG@Brim NPs showed a near neutral surface charge, which is expected to enhance intraocular drug delivery. Consequently, much higher concentration of Brimonidine in the aqueous humor was found after topical administration of MPDA-PEG@Brim nano-dispersion as compared to free Brimonidine solution. Accordingly, superior IOP reduction effect was achieved for the nano-formulation in both hypertensive and normotensive rat eyes. Moreover, MPDA-PEG NPs showed good capability in scavenging diverse free radicals, alleviating intracellular oxidative stress, and mitigating ocular surface oxidative level in a mouse model of preservative-induced dry eye. In addition, the excellent biosafety of this novel Brimonidine nanodrug was confirmed both in vitro and in vivo. Therefore, the present work may shed light on the development of next generation hypotensive formulations for extended ocular surface protection and glaucoma management.

Liposome‐Based Permeable Eyedrops for Effective Posterior Segment Drug Delivery

Topical eyedrop administration is identified as an ideal non‐invasive strategy for ocular drug delivery. However, multiple complex ocular barriers greatly restrict their effectiveness in the treatment of posterior ocular disease. Herein, a liposome‐based permeable eyedrops (pDrops) capable of overcoming multiple ocular barriers and achieving efficient posterior drug delivery is presented. pDrops have a core‐shell structure in which drugs are encapsulated inside the liposome core with a chitosan shell. This chitosan coating significantly enhances the pDrops’ binding to mucin in tears and facilitates the temporary opening of tight junctions in cornea/conjunctive epithelial cells, thereby achieving prolonged preocular retention and enhanced posterior segment drug delivery. In this study, hydrophilic ganciclovir (GCV) and hydrophobic curcumin (CUR) are employed as model drugs. Upon topical instillation, pDrops effectively overcome ocular barriers and delivered GCV to the posterior segment in both rat and rabbit eyes. Notably, CUR delivery by pDrops demonstrates significantly enhanced therapeutic efficacy in light‐damaged retina of mice. Considering that pDrops can deliver both hydrophobic and hydrophilic drugs to the posterior segment of the eye, it can potentially become a feasible platform for the non‐invasive delivery of various drug molecules and improve the treatment efficiency of posterior ocular diseases.

Nanostructure-Mediated Transport of Therapeutics through Epithelial Barriers

The ability to precisely treat human disease is facilitated by the sophisticated design of pharmacologic agents. Nanotechnology has emerged as a valuable approach to creating vehicles that can specifically target organ systems, effectively traverse epithelial barriers, and protect agents from premature degradation. In this review, we discuss the molecular basis for epithelial barrier function, focusing on tight junctions, and describe different pathways that drugs can use to cross barrier-forming tissue, including the paracellular route and transcytosis. Unique features of drug delivery applied to different organ systems are addressed: transdermal, ocular, pulmonary, and oral delivery. We also discuss how design elements of different nanoscale systems, such as composition and nanostructured architecture, can be used to specifically enhance transepithelial delivery. The ability to tailor nanoscale drug delivery vehicles to leverage epithelial barrier biology is an emerging theme in the pursuit of facilitating the efficacious delivery of pharmacologic agents.

Controlled release of vitamin A palmitate from crosslinked cyclodextrin organic framework for dry eye disease therapy

Controlled release drug delivery systems of eye drops are a promising ophthalmic therapy with advantages of good patient compliance and low irritation. However, the lack of a suitable drug carrier for ophthalmic use limits the development of the aforementioned system. Herein, the crosslinked cyclodextrin organic framework (COF) with a cubic porous structure and a uniform particle size was synthesized and applied to solidify vitamin A palmitate (VAP) by using the solvent-free method. The VAP@COF suspension eye drops were formulated by screening co-solvents, suspending agents, and stabilizing agents to achieve a homogeneous state and improve stability. According to the in vitro release study, the VAP@COF suspension exhibited a controlled release of VAP within 12 h. Both the ex vivo corneal contact angle and in vivo fluorescence tracking indicated that the VAP@COF suspension prolonged the VAP residence time on the ocular surface. This suspension accelerated the recovery of the dry eye disease (DED) model in New Zealand rabbits. Furthermore, the suspension was non-cytotoxic to human corneal epithelial cells and non-irritation to rabbit eyes. In summary, the particulate COF is an eye-acceptable novel carrier that sustains release and prolongs the VAP residence time on the ocular surface for DED treatment.

Tissue-targeted and localized AAV5-DCN and AAV5-PEDF combination gene therapy abrogates corneal fibrosis and concurrent neovascularization in rabbit eyes in vivo

PURPOSE

Corneal fibrosis and neovascularization (CNV) after ocular trauma impairs vision. This study tested therapeutic potential of tissue-targeted adeno-associated virus5 (AAV5) mediated decorin (DCN) and pigment epithelium-derived factor (PEDF) combination genes in vivo.

METHODS

Corneal fibrosis and CNV were induced in New Zealand White rabbits via chemical trauma. Gene therapy in stroma was delivered 30-min after chemical-trauma via topical AAV5-DCN and AAV5-PEDF application using a cloning cylinder. Clinical eye examinations and multimodal imaging in live rabbits were performed periodically and corneal tissues were collected 9-day and 15-day post euthanasia. Histological, cellular, and molecular and apoptosis assays were used for efficacy, tolerability, and mechanistic studies.

RESULTS

The AAV5-DCN and AAV5-PEDF combination gene therapy significantly reduced corneal fibrosis (p < 0.01 or p < 0.001) and CNV (p < 0.001) in therapy-given (chemical-trauma and AAV5-DCN + AAV5-PEDF) rabbit eyes compared to the no-therapy given eyes (chemical-trauma and AAV5-naked vector). Histopathological analyses demonstrated significantly reduced fibrotic α-smooth muscle actin and endothelial lectin expression in therapy-given corneas compared to no-therapy corneas on day-9 (p < 0.001) and day-15 (p < 0.001). Further, therapy-given corneas showed significantly increased Fas-ligand mRNA levels (p < 0.001) and apoptotic cell death in neovessels (p < 0.001) compared to no-therapy corneas. AAV5 delivered 2.69 × 107 copies of DCN and 2.31 × 107 copies of PEDF genes per μg of DNA. AAV5 vector and delivered DCN and PEDF genes found tolerable to the rabbit eyes and caused no significant toxicity to the cornea.

CONCLUSION

The combination AAV5-DCN and AAV5-PEDF topical gene therapy effectively reduces corneal fibrosis and CNV with high tolerability in vivo in rabbits. Additional studies are warranted.

Preparation and investigation of a novel antibacterial collagen-based material loaded with gentamicin following surface modification with citric acid for corneal tissue engineering

Corneal disease is an important clinical problem that affects millions of blind people and keratoplasty is currently the most successful treatment for corneal blindness. Unfortunately, there is a very high risk of bacterial infection during corneal transplantation. In this study, we proposed a novel synthetic collagen-based film for corneal therapy, and we effectively incorporated aminoglycoside gentamicin molecules onto the surface of the collagen film. We anticipate that this collagen-based substance will be antimicrobial and repair corneal tissue damage. Three steps were used to create this gentamicin-modified carboxylated collagen film, including: (i) Cross-link the collagen molecules with 1-ethyl-3- (3-dimethylaminopropyl) carbodiimide and n-hydroxysuccinimide to create a collagen (Col) film. (ii) Citric acid was used to modify the Col film's surface in order to increase the number of carboxyl groups there (ColCA). (iii) Gentamicin molecules were grafted onto the surface of ColCA film by forming amide bonds (ColCA-GM). We discovered that this ColCA-GM film has good physicochemical properties and excellent biocompatibility. Furthermore, it was demonstrated that treating collagen films with citric acid significantly improved the antibacterial properties of ColCA-GM film. The outcomes point to a variety of potential applications for this novel film in corneal tissue engineering.

The potential benefits of polyphenols for corneal diseases

The cornea functions as the primary barrier of the ocular surface, regulating temperature and humidity while providing protection against oxidative stress, harmful stimuli and pathogenic microorganisms. Corneal diseases can affect the biomechanical and optical properties of the eye, resulting in visual impairment or even blindness. Due to their diverse origins and potent biological activities, plant secondary metabolites known as polyphenols offer potential advantages for treating corneal diseases owing to their anti-inflammatory, antioxidant, and antibacterial properties. Various polyphenols and their derivatives have demonstrated diverse mechanisms of action in vitro and in vivo, exhibiting efficacy against a range of corneal diseases including repair of tissue damage, treatment of keratitis, inhibition of neovascularization, alleviation of dry eye syndrome, among others. Therefore, this article presents a concise overview of corneal and related diseases, along with an update on the research progress of natural polyphenols in safeguarding corneal health. A more comprehensive understanding of natural polyphenols provides a novel perspective for secure treatment of corneal diseases.

Corneal epithelium models for safety assessment in drug development: Present and future directions

The human corneal epithelial barrier plays a crucial role in drug testing studies, including drug absorption, distribution, metabolism, and excretion (ADME), as well as toxicity testing during the preclinical stages of drug development. However, despite the valuable insights gained from animal and current in vitro models, there remains a significant discrepancy between preclinical drug predictions and actual clinical outcomes. Additionally, there is a growing emphasis on adhering to the 3R principles (refine, reduce, replace) to minimize the use of animals in testing. To tackle these challenges, there is a rising demand for alternative in vitro models that closely mimic the human corneal epithelium. Recently, remarkable advancements have been made in two key areas: microphysiological systems (MPS) or organs-on-chips (OoCs), and stem cell-derived organoids. These cutting-edge platforms integrate four major disciplines: stem cells, microfluidics, bioprinting, and biosensing technologies. This integration holds great promise in developing powerful and biomimetic models of the human cornea.