Enhanced Corneal Penetration of a Poorly Permeable Drug Using Bioadhesive Multiple Microemulsion Technology

Biophysics of ophthalmic medications during spaceflight: Principles of ocular fluid dynamics and pharmacokinetics in microgravity

As spaceflight becomes increasingly accessible and expansive to humanity, it is becoming ever more essential to consider the treatment of various eye diseases in these challenging environments. This paper delves into the increasing fascination with interplanetary travel and its implications for health management in varying environments. It specifically discusses the pharmacological management of ocular diseases, focusing on two key delivery methods: topical eye drops and intravitreal injections. The paper explores how microgravity impacts the administration of these treatments, a vital aspect in understanding drug delivery in space. An extensive analysis is presented on the pharmacokinetics of eye medications, examining the interaction between pharmaceuticals and ocular tissues in zero gravity. The goal of the paper is to bridge the understanding of fluid dynamics, microgravity and the human physiological systems to pave the way for innovative solutions faced by individuals in microgravity.

RiTe conjugate mediated corneal collagen crosslinking, a novel therapeutic intervention for keratoconus - in vitro and in vivo study

Corneal collagen crosslinking (CXL) is an effective method to halt the disease progression of keratoconus, a progressive corneal dystrophy leading to cone shaped cornea. Despite the efficacy of standard protocol, the concerning step of this procedure is epithelial debridement performed to facilitate the entry of riboflavin drug. Riboflavin, a key molecule in CXL protocol, is a sparsely permeable hydrophilic drug in corneal tissues. The present study has employed cell penetrating peptide (CPP), Tat2, to enhance the penetration of riboflavin molecule, and thereby improve currently followed CXL protocol. This study demonstrates approximately two-fold enhanced uptake of CPP riboflavin conjugate, Tat2riboflavin-5'Phosphate (RiTe conjugate), both in vitro and in vivo. Two different CXL protocols (Epi ON and Epi OFF) have been introduced and implemented in rabbit corneas using RiTe conjugate in the present study. The standard and RiTe conjugate mediated CXL procedures exhibited an equivalent extent of crosslinking in both the methods. Reduced keratocyte loss and no endothelial damage in RiTe conjugate mediated CXL further ascertains the safety of the proposed CXL protocols. Therefore, RiTe conjugate mediated CXL protocols present as potential alternatives to the standard keratoconus treatment in providing equally effective, less invasive and patient compliant treatment modality.

α-Tocopherol-loaded multi-layer nanoemulsion using chitosan, and dextran sulfate: Cellular uptake, antioxidant activity, and in vitro bioaccessibility

The potential of multi-layer nanoemulsions (NEs) for improving the cellular uptake, antioxidant activity, and in vitro bioaccessibility of α-tocopherol (ToC) was examined. ToC-loaded multi-layer NEs were prepared using lecithin (primary-NEs, P-NEs), chitosan (secondary-NEs, S-NEs), and dextran sulfate (tertiary-NEs, T-NEs) as wall materials. The bioadhesion, cellular permeability, and uptake of the multi-layer NEs were significantly higher than that of the free coumarin 6 (C6). As a result of cellular uptake, the mean fluorescence intensity of T-NEs was the highest among the three types of multi-layer NEs and was 9.8-fold higher than that of free C6. The cellular antioxidant abilities of P-NEs, S-NEs, and T-NEs were 40, 45, and 50 %, respectively. Multi-layer nanoencapsulation sustains free fatty acid release after digestion. Moreover, the bioavailability of T-NEs exhibited a two-fold increase compared with that of the free ToC. These findings indicate that by multi-layer NEs using a layer-by-layer method, the cellular uptake, in vitro bioaccessibility, and antioxidant activity of ToC can be improved. Furthermore, T-NEs using chitosan and dextran sulfate can potentially enhance the cellular uptake, in vitro bioaccessibility, and antioxidant activity of ToC. These findings would facilitate the application of multi-layer NEs for lipophilic bioactive compounds using biopolymers.

Exploring the Versatility of Microemulsions in Cutaneous Drug Delivery: Opportunities and Challenges

Microemulsions are novel drug delivery systems that have garnered significant attention in the pharmaceutical research field. These systems possess several desirable characteristics, such as transparency and thermodynamic stability, which make them suitable for delivering both hydrophilic and hydrophobic drugs. In this comprehensive review, we aim to explore different aspects related to the formulation, characterization, and applications of microemulsions, with a particular emphasis on their potential for cutaneous drug delivery. Microemulsions have shown great promise in overcoming bioavailability concerns and enabling sustained drug delivery. Thus, it is crucial to have a thorough understanding of their formulation and characterization in order to optimize their effectiveness and safety. This review will delve into the different types of microemulsions, their composition, and the factors that affect their stability. Furthermore, the potential of microemulsions as drug delivery systems for skin applications will be discussed. Overall, this review will provide valuable insights into the advantages of microemulsions as drug delivery systems and their potential for improving cutaneous drug delivery.

Fabrication and characterization of electrospun nanofibers using biocompatible polymers for the sustained release of venlafaxine

Recently, drug-controlled release nanotechnology has gained special attention in biomedicine. This work focuses on developing novel electrospun polymeric nanofibers (NFs) for buccal delivery of VEN to avoid the hepatic metabolism and enzymatic degradation in the GIT and develop an effective control of drug release. The optimized NFs were obtained by blending polylactic acid (PLA), and poly (ɛ-caprolactone) (PCL) fixed at a ratio of 1:1. It was characterized for morphology, drug-loading, FTIR, XRD, DSC, and in vitro drug release. Ex vivo permeability of the blend NFs was assessed using chicken pouch mucosa compared to VEN suspension, followed by histopathological examination. Further, the cytotoxic effect in three different cell lines using WST-1 assay. SEM morphologies refer to defect-free uniform NFs of PLA, PCL, and PLA/PCL mats. These fibers had a diameter ranging from 200 to 500 nm. The physico-thermal characterization of NFs depicted that the drug was successfully loaded and in an amorphous state in the PLA/PCL NFs. In vitro release of NFs substantiated a bi-phasic profile with an initial burst release of about 30% in the initial 0.5 h and a prolonged cumulative release pattern that reached 80% over 96 h following a non-Fickian diffusion mechanism. Ex vivo permeation emphasizes the major enhancement of the sustained drug release and the noticeable decrease in the permeability of the drug from NFs. Cytotoxicity data found that IC₅₀ of VEN alone was 217.55 μg/mL, then VEN-NFs recorded an IC₅₀ value of 250.62 μg/mL, and plain NFs showed the lowest toxicity and IC₅₀ 440.48 μg/mL in oral epithelial cells (OEC). Histopathology and cell toxicity studies demonstrated the preserved mucosal architecture and the preclinical safety. The developed PLA/PCL NFs can be promising drug carriers to introduce a step-change in improved psychiatric treatment healthcare.

The Effect of Anti-Inflammatory Topical Ophthalmic Treatments on In Vitro Corneal Epithelial Cells

Purpose

To compare the effect of three commonly prescribed anti-inflammatory eye drops on corneal epithelial cells in vitro.

Methods

Three different lines of human corneal epithelial cells were tested: primary cells cultured from donor tissue, commercially available primary cells, and immortalized cells. Cells were seeded on 96-well plates and treated with the following eye drops: cyclosporine 0.05%, lifitegrast 5%, and tacrolimus 0.03% or 0.1%. Exposure times tested were 30 seconds, 1 minute, 2 minutes, 1 hour, 2 hours, 4 hours, and 24 hours. Brightfield images and viability assays were analyzed 48 to 72 hours after the initiation of treatments. At least five replicates were tested per drug and time exposure.

Results

Commercially obtained primary cells showed reduced viability following 1 hour with tacrolimus 0.1% (8%; P = 0.043%) and 4 hours with tacrolimus 0.03% (17%; P = 0.042%). Lifitegrast exposure reduced primary cell viability after 4 hours (10%; P = 0.042). Cell viability in primary cells was not deleteriously affected following exposure to cyclosporine for up to 4 hours. A similar trend was observed in both primary cells cultured from donor tissue and immortalized human corneal epithelial cells, demonstrating greater decreases in cell viability in tacrolimus compared to lifitegrast and cyclosporine. Light microscopy imaging for analysis of cell morphology and confluence supported the results.

Conclusions

Tacrolimus showed the highest impact on corneal epithelium survival in vitro, and cyclosporine proved the most protective.

Translational Relevance

Comparing anti-inflammatory eye drops on corneal epithelial cells in vitro may inform eye drop selection and development for clinical purposes.

Linoleic Acid-Based Transferosomes for Topical Ocular Delivery of Cyclosporine A

Delivering high-molecular-weight hydrophobic peptides, such as cyclosporine A, across the corneal epithelium remains a challenge that is complicated by other physio-anatomical ocular structures that limit the ocular bioavailability of such peptides. Transferosomes have previously been used to improve transdermal permeability, and have the potential for improving the ocular corneal permeability of applicable drugs. In this study, transferosomes for the potential ocular delivery of cyclosporine A were investigated. Linoleic acid was evaluated for its effect on the stability of the transferosomes and was substituted for a portion of the cholesterol in the vesicles. Additionally, Span® 80 and Tween® 80 were evaluated for their effect on transferosome flexibility and toxicity to ocular cells as edge activators. Attenuated Total Reflectance–Fourier Transform Infrared spectroscopy (ATF-FTIR), differential scanning calorimetry (DSC), and dynamic light scattering (DLS) were used to evaluate the physicochemical parameters of the blank and the cyclosporine A-loaded transferosomes. Cyclosporine A release and corneal permeability were studied in vitro and in a New Zealand albino rabbit corneal model, respectively. The linoleic acid contributed to improved stability and the nano-size of the transferosomes. The Tween®-based formulation was preferred on the basis of a more favorable toxicity profile, as the difference in their corneal permeability was not significant. There was an initial burst release of cyclosporine A in the first 24 h that plateaued over one week. The Tween®-based formulation had a flux of 0.78 µg/cm2/h. The prepared transferosomes demonstrated biocompatibility in the ocular cell line, adequately encapsulated cyclosporine A, ensured the corneal permeability of the enclosed drug, and were stable over the period of investigation of 4 months at −20 °C.

The Caco-2 Model: Modifications and enhancements to improve efficiency and predictive performance

The Caco-2 cell model has been widely used to assess the permeability of drug candidates. It has provided a high throughput in vitro platform, functionally resembling the enterocytes. Since the oral route is the most preferred for drug administration, the Caco-2 cell model acts as a very important tool to elucidate the oral "druggability" of a molecule by providing a fairly reliable estimate of its permeability through the intestinal membrane. Despite its shortcomings (the lack of a mucus layer, long cultivation period, inter-lab variability, and differences in expression of enzymes, transporters, and tight junction complexes) it remains heavily used due to its reliability, predictive performance, and wide acceptance. Various modifications have been made: co-culturing with other intestinal cells, applying biosimilar mucus, reducing culturing time, combining Caco-2 monolayer with the dissolution apparatus, enhancing protein expression, and redesigning the sampling apparatus. These modifications are intended to overcome some of the shortcomings of the Caco-2 model in order to make its use easier, quicker, economical, and more representative of the intestine. The aim of this review is to discuss such modifications to enhance this model's utility, predictive performance, and reproducibility.

ROS-Scavenging Glyco-Nanoplatform for Synergistic Antibacteria and Wound-Healing Therapy of Bacterial Keratitis

Infectious keratitis is a serious disease originating from a corneal trauma infected with bacteria, which is intractable to heal due to stubborn infection and persistent inflammation featured with high reactive...

Ocular Penetrance and Safety of the Dopaminergic Prodrug Etilevodopa

Purpose

Animal models have demonstrated the role of dopamine in regulating axial elongation, the critical feature of myopia. Because frequent delivery of dopaminergic agents via peribulbar, intravitreal, or intraperitoneal injections is not clinically viable, we sought to evaluate ocular penetration and safety of the topically applied dopaminergic prodrug etilevodopa.

Methods

The ocular penetration of dopamine and dopaminergic prodrugs (levodopa and etilevodopa) were quantified using an enzyme-linked immunosorbent assay in enucleated porcine eyes after a single topical administration. The pharmacokinetic profile of the etilevodopa was then assessed in rats. A four-week once-daily application of etilevodopa as a topical eye drop was conducted to establish its safety profile.

Results

At 24 hours, the studied prodrugs showed increased dopaminergic derivatives in the vitreous of porcine eyes. Dopamine 0.5% (P = 0.0123) and etilevodopa 10% (p = 0.370) achieved significant vitreous concentrations. Etilevodopa 10% was able to enter the posterior segment of the eye after topical administration in rats with an intravitreal half-life of eight hours after single topical administration. Monthly application of topical etilevodopa showed no alterations in retinal ocular coherence tomography, electroretinography, caspase staining, or TUNEL staining.

Conclusions

At similar concentrations, no difference in ocular penetration of levodopa and etilevodopa was observed. However, etilevodopa was highly soluble and able to be applied at higher topical concentrations. Dopamine exhibited both high solubility and enhanced penetration into the vitreous as compared to other dopaminergic prodrugs.

Translational Relevance

These findings indicate the potential of topical etilevodopa and dopamine for further study as a therapeutic treatment for myopia.

In Silico Screening and In Vivo Evaluation of Potential CACNA2D1 Antagonists as Intraocular Pressure-Reducing Agents in Glaucoma Therapy

Glaucoma is a leading cause of permanent vision loss and current drugs do not halt disease progression. Thus, new therapies targeting different drug targets with novel mechanisms of action are urgently needed. Previously, we identified CACNA2D1 as a novel modulator of intraocular pressure (IOP) and demonstrated that a topically applied CACNA2D1 antagonist—pregabalin (PRG)—lowered IOP in a dose-dependent manner. To further validate this novel IOP modulator as a drug target for IOP-lowering pharmaceutics, a homology model of CACNA2D1 was built and docked against the NCI library, which is one of the world’s largest and most diverse compound libraries of natural products. Acivicin and zoledronic acid were identified using this method and together with PRG were tested for their plausible IOP-lowering effect on Dutch belted rabbits. Although they have inferior potency to PRG, both of the other compounds lower IOP, which in turn validates CACNA2D1 as a valuable drug target in treating glaucoma.

Proinflammatory Pathways Are Activated in the Human Q344X Rhodopsin Knock-In Mouse Model of Retinitis Pigmentosa

Retinitis pigmentosa (RP) is a hereditary disease of the retina that results in complete blindness. Currently, there are very few treatments for the disease and those that exist work only for the recessively inherited forms. To better understand the pathogenesis of RP, multiple mouse models have been generated bearing mutations found in human patients including the human Q344X rhodopsin knock-in mouse. In recent years, the immune system was shown to play an increasingly important role in RP degeneration. By way of electroretinography, optical coherence tomography, funduscopy, fluorescein angiography, and fluorescent immunohistochemistry, we show degenerative and vascular phenotypes, microglial activation, photoreceptor phagocytosis, and upregulation of proinflammatory pathway proteins in the retinas of the human Q344X rhodopsin knock-in mouse. We also show that an FDA-approved pharmacological agent indicated for the treatment of rheumatoid arthritis is able to halt activation of pro-inflammatory signaling in cultured retinal cells, setting the stage for pre-clinical trials using these mice to inhibit proinflammatory signaling in an attempt to preserve vision. We conclude from this work that pro- and autoinflammatory upregulation likely act to enhance the progression of the degenerative phenotype of rhodopsin Q344X-mediated RP and that inhibition of these pathways may lead to longer-lasting vision in not only the Q344X rhodopsin knock-in mice, but humans as well.

Ocular microemulsion of brinzolamide: Formulation, physicochemical characterization, and in vitro irritation studies based on EpiOcular™ eye irritation assay

In recent years, the hydrophobic active substances have led researchers to develop new formulations to enhance bioavailability and dissolution rate; brinzolamide, a lipophilic drug belongs to carbonic anhydrase inhibitors, which cause reduction of intraocular pressure in patients suffering from glaucoma. Currently, the marketed product of brinzolamide is in the form of ocular drops; nonetheless, the conventional drops provide decreased therapeutic efficacy owing to their low bioavailability and pulsed drug release. Thus, the development of novel ocular formulations such as topical microemulsions is of high importance. In this work, the preparation of new microemulsions containing brinzolamide (0.2, 0.5 and 1% w/w) and comprised from isopropyl myristate, tween 80 and span 20 and Cremophor EL was performed. The obtained microemulsions were further characterized for their physicochemical properties. In addition, Fourier Transformed-Infrared spectroscopy was used touate the compatibility of active ingredients and components. In vitro release studies along with kinetic modeling were performed using the dialysis membrane method in simulated tear fluid. Bioadhesion studies were performed using Texture analysis. Finally, in vitro ocular irritation based on EpiOcular™ Eye Irritation Test and cytocompatibility studies was performed to examine any possible harm on ocular cells and predict in vivo safety profile.

Studies on Surfactants, Cosurfactants, and Oils for Prospective Use in Formulation of Ketorolac Tromethamine Ophthalmic Nanoemulsions

Nanoemulsions (NE) are isotropic, dispersions of oil, water, surfactant(s) and cosurfactant(s). A range of components (11 surfactants, nine cosurfactants, and five oils) were investigated as potential excipients for preparation of ketorolac tromethamine (KT) ocular nanoemulsion. Diol cosurfactants were investigated for the effect of their carbon chain length and dielectric constant (DEC), Log P, and HLB on saturation solubility of KT. Hen's Egg Test-ChorioAllantoic Membrane (HET-CAM) assay was used to evaluate conjunctival irritation of selected excipients. Of the investigated surfactants, Tween 60 achieved the highest KT solubility (9.89 ± 0.17 mg/mL), followed by Cremophor RH 40 (9.00 ± 0.21 mg/mL); amongst cosurfactants of interest ethylene glycol yielded the highest KT solubility (36.84 ± 0.40 mg/mL), followed by propylene glycol (26.23 ± 0.82 mg/mL). The solubility of KT in cosurfactants was affected by four molecular descriptors: carbon chain length, DEC, log P and HLB. KT solubility was directly proportional to DEC and the HLB yet, inversely proportional to carbon chain length and log P. All surfactants, except Labrasol ALF, were non-irritant. The majority of cosurfactants were slightly irritant, butylene glycol was a moderate irritant, pentylene and hexylene glycols were strong irritants. These findings will inform experiments aimed at developing NE formulations for ocular administration of KT.

Strategies to prolong the residence time of drug delivery systems on ocular surface

Ocular diseases may be treated via different routes of administration, such as topical, intracameral, intravitreal, oral and parenteral. Among them the topical route is most accepted by patients, although it provides in many cases the lowest bioavailability. Indeed, when a topical formulation reaches the precorneal area, i.e., the drug absorption and/or action site, it is rapidly eliminated due to eye protection mechanisms such as blinking, basal and reflex tearing, and naso-lacrimal draining. To avoid this and to reduce the frequency of dosing, various strategies have been developed to prolong drug residence time after topical administration. These strategies include the use of viscosity increasing and mucoadhesive excipients as well as combinations thereof. From the drug delivery system point of view, liquid and semisolid formulations are preferred over solid formulations such as ocular inserts and contact lenses. Furthermore, liquid and semisolid formulations can contain nano- and microcarrier systems that contribute to a prolonged residence time. Within this review an overview about the different types of excipients and formulations as well as their performance in valid animal models and clinical trials is provided.