Recent Advances of Ocular Drug Delivery Systems: Prominence of Ocular Implants for Chronic Eye Diseases

Local controlled release of stabilized monoclonal antibodies

Monoclonal antibody (mAb) therapeutics have become widely successful for treatment of any number of diseases. However, for certain hard-to-reach tissues, e.g., eye, brain, tumors, and joints, local delivery is desired and long-term controlled release is necessary to avoid frequent injections and poor patient compliance. If local and sustained exposure of mAbs (or their Fab or nanobody fragments) could be accomplished by injectable polymer long-acting release (LAR) systems, the incredible potential of mAb therapeutics could be extended to additional diseases, e.g., neovascular age-related macular degeneration (wet AMD) and glioblastoma multiforme (GBM). In prior studies, long-acting delivery of mAbs has been limited by the inability to design a delivery system prepared from a biodegradable polymer used in FDA-approved LARs that achieves long-term continuous release of structurally stable and immunoreactive mAb with a low initial burst release that is easily injectable and avoids material build-up upon repeated injection. Here, we present for the first time a long-acting delivery system capable of delivering several different mAbs for multiple indications by developing a novel process to stabilize mAbs through the combination of formulation, micronization and encapsulation conditions, and to control stabilized mAb exposure in vivo for months by formulation with an appropriate biodegradable polymer (poly(lactic-co-glycolic acid) (PLGA)), utilization of a pH- and pore-modifying agent, and development of a novel PLGA coating layer to control osmotic pressure induced by elevated levels of critical co-encapsulated stabilizers, particularly mAb-stabilizing-trehalose. The resulting implants showed long-term efficacy in animal models for both wet AMD and GBM after single local injections. Although much more work needs to be done before their clinical application to these two diseases, the injectable PLGA platform meets several important benchmarks for controlled mAb delivery and can be developed further for delivery of a wide array of mAbs and other cofactors, offering an improved therapeutic option for treating diseases amenable to local antibody therapy. One Sentence Summary: A generalizable injectable biodegradable PLGA implant platform for site-specific and long-term slow and continuous release of stabilized monoclonal antibody drugs demonstrates improved in vivo efficacy for wet AMD and glioblastoma.

Assessment of magnesium-based components for intraocular drug delivery byin vitrobiocompatibility and drug-device interaction

The development of magnesium-based intraocular drug delivery devices holds significant promise for biomedical applications, particularly in treating wet age-related macular degeneration (AMD) using vascular endothelial growth factor inhibitors such as bevacizumab. Magnesium's rapid degradation, which can be finely tuned to achieve the controlled release required for AMD treatment, along with its well-established biocompatibility and biodegradable properties, positioning it as an ideal material for these applications. The study aimed to evaluate magnesium's potential as a carrier for ocular drug delivery systems by demontrating the stability of monoclonal antibodies, specifically bevacizumab, in the presence of magnesium corrosion products and the biocompatibility of these products with various cell lines, including murine fibroblasts (3T3), rat retinal Müller cells, and human retinal pigment epithelial cells (ARPE19). The stability of bevacizumab with pure magnesium (Mg) was investigated through an indirect enzyme-linked immunosorbent assay protocol, developed and customized for this specific aim. The biocompatibility of Mg corrosion products was assessed by toxicological evaluations through MTT and Trypan Blue Viability assays, along with cell cycle analysis. Results demonstrated no significant impact of Mg corrosion products on bevacizumab stability, with changes in mean values consistently below or equal to 10%. Furthermore, Mg extracts showed minimal cytotoxicity, as metabolic activity exceeded 80% across all cell lines, classified as Grade 0/1 cytotoxicity under ISO 10993-5 standards. Cell viability, proliferation, and morphology remained unaffected for up to 72 h of exposure. This study provides the firstin vitroevaluation of bevacizumab's stability in the presence of magnesium corrosion products and its biocompatibility with retinal cell lines, laying the foundation for future ophthalmic research and underscoring magnesium's potential as a material for intraocular drug delivery systems.

Formulation Advances in Posterior Segment Ocular Drug Delivery

Posterior segment ocular diseases, such as diabetic retinopathy, age-related macular degeneration, and retinal vein occlusion, are leading causes of vision impairment and blindness worldwide. Effective management of these conditions remains a formidable challenge due to the unique anatomical and physiological barriers of the eye, including the blood-retinal barrier and rapid drug clearance mechanisms. To address these hurdles, nanostructured drug delivery systems are proposed to overcome ocular barriers, target the retina, and enhance permeation while ensuring controlled release. Traditional therapeutic approaches, such as intravitreal injections, pose significant drawbacks, including patient discomfort, poor compliance, and potential complications. Therefore, understanding the physiology and clearance mechanism of eye could aid in the design of novel formulations that could be noninvasive and deliver drugs to reach the target site is pivotal for effective treatment strategies. This review focuses on recent advances in formulation strategies for posterior segment ocular drug delivery, highlighting their potential to overcome these limitations. Furthermore, the potential of nanocarrier systems such as in-situ gel, niosomes, hydrogels, dendrimers, liposomes, nanoparticles, and nanoemulsions for drug delivery more effectively and selectively is explored, and supplemented with illustrative examples, figures, and tables. This review aims to provide insights into the current state of posterior segment drug delivery, emphasizing the need for interdisciplinary approaches to develop patient-centric, minimally invasive, and effective therapeutic solutions.

A Transformative Wearable Corneal Microneedle Patch for Efficient Therapy of Ocular Injury and Infection

Ocular injury and infection are significant causes of vision impairment and blindness globally. Effective treatment is, however, challenging due to the physical barrier of the cornea, which restricts drug penetration in the eye, as well as the presence of eye injury that necessitates continuous delivery of growth factors on the ocular surface for cornea healing. Here, we introduce a transformative wearable corneal microneedle (MN) patch designed for efficient therapy of ocular injury and infection. The MN patch comprises water-soluble tips that encapsulate antibacterial nanoparticles (NPs), along with a transformative backing layer that contains epidermal growth factor (EGF). Upon insertion into the eye, the MN tips dissolve swiftly within the cornea stroma, resulting in the release of the antimicrobial NPs to efficiently eradicate bacteria. Meanwhile, the residual backing layer undergoes rapid in situ transformation upon contact with mildly acidic fluid from infected corneal edema, converting into a contact lens that conforms to the eye's surface, which facilitates sustained release of EGF on the ocular surface over 8 h to promote corneal healing. Benefiting from these features, the designed transformative corneal MN patch demonstrates superior efficacy in treating ocular injuries and infections in vivo, offering a promising therapeutic strategy to manage eye diseases.

Latest trends & strategies in ocular drug delivery

Ocular drug delivery is one of the most challenging routes of administration, and this may be attributed to the complex interplay of ocular barriers and clearance mechanisms that restrict therapeutic payload residence. Most of the currently approved products that ameliorate ocular disease conditions are topical, i.e., delivering therapeutics to the outside anterior segment of the eye. This site of administration works well for certain conditions such as local infections but due to the presence of numerous ocular barriers, the permeation of therapeutics to the posterior segment of the eye is limited. Conditions such as age-related macular degeneration and diabetic retinopathy that contribute to an extreme deterioration of vision acuity require therapeutic interventions at the posterior segment of the eye. This necessitates development of intraocular delivery systems such as intravitreal injections, implants, and specialized devices that deliver therapeutics to the posterior segment of the eye. Frequent dosing regimens and high concentration formulations have been strategized and developed to achieve desired therapeutic outcomes by overcoming some of the challenges of drug clearance and efficacy. Correspondingly, development of suitable delivery platforms such as biodegradable and non-biodegradable implants, nano delivery systems, and implantable devices have been explored. This article provides an overview of the current trends in the development of suitable formulations & delivery systems for ocular drug delivery with an emphasis on late-stage clinical and approved product. Moreover, this work aims to summarize current challenges and highlights exciting pre-clinical developments, and future opportunities in cell and gene therapies that may be explored for effective ocular therapeutic outcomes.

Sustained release of RNA nanoparticles from reservoir implant for ocular delivery

Previous studies of RNA nanoparticles have demonstrated the potential of these nanoparticles in ocular delivery via the subconjunctival route. Sustained ocular delivery is beneficial for chronic eye disease treatment, and utilizing a reservoir implant in the periocular space (e.g., episcleral implant) can prolong ocular delivery of these nanoparticles. The objectives of the present study were to (a) demonstrate the fabrication of the reservoir implants, (b) evaluate the performance of the implants with model permeants and RNA nanoparticles in vitro, and (c) investigate the applicability of hindered transport theory for the release kinetics from the implants. In vitro release testing was performed with the implants to determine the release kinetics and implant membrane permeability. In addition to RNA nanoparticles, model permeants fluorescein-isothiocyanate (FITC) labeled dextrans (10, 40, and 150 kDa) were examined. The results indicated that the rates of permeant release from the implants were a function of the (a) size and structure of the permeant/nanoparticle and (b) type and pore size of the implant membrane. The model analyses provided insights into implant membrane transport and ocular pharmacokinetics of the nanoparticles for transscleral delivery. The results suggested the potential of prolonged delivery of the RNA nanoparticles with the episcleral implant approach.

The pursuit of linear dosage in pharmacy: reservoir-based drug delivery systems from macro to micro scale

INTRODUCTION

The pursuit of linear dosage in pharmacy is essential for achieving consistent therapeutic release and enhancing patient compliance. This review provides a comprehensive summary of zero-order drug delivery systems, with a particular focus on reservoir-based systems emanated from different microfabrication technologies.

AREAS COVERED

The consideration of recent advances in drug delivery systems is given to encompass the key areas including the importance of achieving a constant drug release rate for therapeutic applications. Detailed examination of reservoir-based systems, their design, mechanisms of action and materials used are highlighted. By addressing these areas, the discussion aims to provide a thorough understanding of most recent zero-order drug delivery systems, their performance advantages and methods of their manufacturing. To ensure the complete coverage of the explored research area, modern AI-assistant tools were used to find not only the most relevant, but also connected and similar articles.

EXPERT OPINION

Future developments in reservoir-based drug delivery systems are expected to significantly enhance therapeutic effectiveness and patient outcomes through the integration of innovative materials and technologies. The fabrication of intelligent drug delivery systems that utilize sensors and feedback mechanisms can enable real-time monitoring of drug release and patient reactions.

Physical and mechanical properties of ocular thin films: a systematic review and meta-analysis

The ocular thin film presents a potential solution for addressing challenges to ocular drug delivery. In this review, we summarise the findings of a comprehensive review analysing 336 formulations from 68 studies. We investigated the physical and mechanical properties of ocular thin films, categorised into natural polymer-based, synthetic polymer-based, and combined polymer films. The results showed that the type of polymers used impacted mucoadhesion force, moisture absorption:moisture loss ratio, pH, swelling index, and elongation percentage. Significant relationships were found between these properties within each subgroup. The results also highlighted the influence of plasticisers on elongation percentage, mucoadhesion force, swelling index, and moisture absorption:moisture loss ratio. These findings have implications for designing and optimising ocular drug formulations and selecting appropriate plasticisers to achieve formulations with the desired properties.

Revamping the corneal permeability and antiglaucoma therapeutic potential of brinzolamide using transniosomes: optimization, in vitro and preclinical evaluation

Aim: This study aims to explore potential of transniosomes, a hybrid vesicular system, as ocular drug-delivery vehicle. Materials & methods: Thin-film hydration technique was used to fabricate brinzolamide-loaded transniosomes (BRZ-TN) and optimized using Box-Behnken design, further exhaustively characterized for physicochemical evaluations, deformability, drug release, permeation and preclinical evaluations for antiglaucoma activity. Results: The BRZ-TN showed ultradeformability (deformability index: 5.71), exhibiting sustained drug release without irritation (irritancy score: 0) and high permeability compared with the marketed formulation or free drug suspension. The extensive in vivo investigations affirmed effective targeted delivery of transniosomes, with brinzolamide reducing intraocular pressure potentially. Conclusion: Our findings anticipated that BRZ-TN is a promising therapeutic nanocarrier for effectively delivering cargo to targeted sites by crossing corneal barriers.

Development of Liposomal and Liquid Crystalline Lipidic Nanoparticles with Non-Ionic Surfactants for Quercetin Incorporation

The aim of the present study is the development, physicochemical characterization, and in vitro cytotoxicity evaluation of both empty and quercetin-loaded HSPC (hydrogenated soy phosphatidylcholine) liposomes, GMO (glyceryl monooleate) liquid crystalline nanoparticles, and PHYT (phytantriol) liquid crystalline nanoparticles. Specifically, HSPC phospholipids were mixed with different non-ionic surfactant molecules (Tween 80 and/or Span 80) for liposomal formulations, whereas both GMO and PHYT lipids were mixed with Span 80 and Tween 80 as alternative stabilizers, as well as with Poloxamer P407 in different ratios for liquid crystalline formulations. Subsequently, their physicochemical properties, such as size, size distribution, and ζ-potential were assessed by the dynamic and electrophoretic light scattering (DLS/ELS) techniques in both aqueous and biological medium with serum proteins. The in vitro biological evaluation of the empty nanosystems was performed by using the MTT cell viability and proliferation assay. Finally, the entrapment efficiency of quercetin was calculated and the differences between the two different categories of lipidic nanoparticles were highlighted. According to the results, the incorporation of the non-ionic surfactants yields a successful stabilization and physicochemical stability of both liposomal and liquid crystalline nanoparticles. Moreover, in combination with an appropriate biosafety in vitro profile, increased encapsulation efficiency of quercetin was achieved. Overall, the addition of surfactants improved the nanosystem's stealth properties. In conclusion, the results indicate that the physicochemical properties were strictly affected by the formulation parameters, such as the type of surfactant.