Injectable biodegradable bi-layered capsule for sustained delivery of bevacizumab in treating wet age-related macular degeneration

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.

Vesicular Drug Delivery Systems: Promising Approaches in Ocular Drug Delivery

Ocular drug delivery poses unique challenges due to the complex anatomical and physiological barriers of the eye. Conventional dosage forms often fail to achieve optimal therapeutic outcomes due to poor bioavailability, short retention time, and off-target effects. In recent years, vesicular drug delivery systems have emerged as promising solutions to address these challenges. Vesicular systems, such as liposome, niosome, ethosome, transfersome, and others (bilosome, transethosome, cubosome, proniosome, chitosome, terpesome, phytosome, discome, and spanlastics), offer several advantages for ocular drug delivery. These include improved drug bioavailability, prolonged retention time on the ocular surface, reduced systemic side effects, and protection of drugs from enzymatic degradation and dilution by tears. Moreover, vesicular formulations can be engineered for targeted delivery to specific ocular tissues or cells, enhancing therapeutic efficacy while minimizing off-target effects. They also enable the encapsulation of a wide range of drug molecules, including hydrophilic, hydrophobic, and macromolecular drugs, and the possibility of combination therapy by facilitating the co-delivery of multiple drugs. This review examines vesicular drug delivery systems, their advantages over conventional drug delivery systems, production techniques, and their applications in management of ocular diseases.

Experimental and mathematical approaches for drug delivery for the treatment of wet age-related macular degeneration

Several chronic eye diseases affect the posterior segment of the eye. Among them age-related macular degeneration can cause vision loss if left untreated and is one of the leading causes of visual impairment in the world. Most treatments are based on intravitreally injected therapeutics that inhibit the action of vascular endothelial growth factor. However, due to the need for monthly injections, this method is associated with poor patient compliance. To address this problem, numerous drug delivery systems (DDSs) have been developed. This review covers a selection of particulate systems, non-stimuli responsive hydrogels, implants, and composite systems that have been developed in the last few decades. Depending on the type of DDS, polymer material, and preparation method, different mechanical properties and drug release profiles can be achieved. Furthermore, DDS development can be optimized by implementing mathematical modeling of both drug release and pharmacokinetic aspects. Several existing mathematical models for diffusion-controlled, swelling-controlled, and erosion-controlled drug delivery from polymeric systems are summarized. Compartmental and physiologically based models for ocular drug transport and pharmacokinetics that have studied drug concentration profiles after intravitreal delivery or release from a DDS are also reviewed. The coupling of drug release models with ocular pharmacokinetic models can lead to obtaining much more efficient DDSs for the treatment of age-related macular degeneration and other diseases of the posterior segment of the eye.

Intravitreal injectable hydrogel rods with long-acting bevacizumab delivery to the retina

Retinal vascular diseases such as neovascular age-related macular degeneration (nAMD) are the leading cause of blindness worldwide. They can be treated with intravitreal injections of anti-vascular endothelial growth factor (anti-VEGF) agents by inhibiting VEGF which is a major agent of abnormal blood vessel growth. However, because of drug's short half-life, clinical treatment often requires monthly repeated intravitreal injections, causing treatment burden and undertreatment. Among various kinds of drug carriers, in situ forming hydrogels have been studied as potential intravitreal drug carriers for the high drug loading, easy injection, controlled drug release, and protection of encapsulated drugs from the environment. However, gelation time, crosslinking degree, and drug release patterns following injection of a liquid that will be subsequently gelled in situ are susceptible to be hindered by dilution of the hydrogel precursor solution with body fluids (e.g., blood or vitreous). Here, we report an injectable pre-crosslinked hydrogel rod to overcome the limitations of in situ forming hydrogels and to extend intravitreal half-life of anti-VEGF for reducing intraocular injection frequency. Hydrogel rods can be simply prepared using in situ forming hydrogels, and injectable using a designed rod injector. The adjustable crosslinking degree of hydrogel rods easily controlled bevacizumab release profiles in a sustained manner. Compared with in situ forming hydrogels, hydrogel rods effectively reduced initial burst release, and showed sustained release with long-term drug efficacy in vitro. From the 4-month in vivo pharmacokinetic analysis, following the intravitreal injection of hydrogel rods, the half-life of bevacizumab in the vitreous and retina was significantly extended, and drug elimination to aqueous humor was effectively reduced. Finally, intraocular stability, degradation, and inflammatory response of hydrogel rods were evaluated. We expect that the hydrogel rod can be a potential drug delivery system for the treatment of nAMD and other conditions that need long-term and local sustained drug administration. STATEMENT OF SIGNIFICANCE: Herein, we report an injectable pre-crosslinked hydrogel rod based on an in situ forming hydrogel to achieve intravitreal long-acting anti-VEGF delivery to reduce injection frequency and improve the long-term visual outcomes of patients with retinal vascular diseases. Hydrogel rods were readily prepared using removable molds and injected using customized injectors. Compared to the in situ forming hydrogel, hydrogel rods showed significantly reduced initial burst release, controllable release profiles for several months, physical stability, and a long-acting anti-angiogenic effect. Animal studies demonstrated that the hydrogel rods dramatically prolonged the intraocular drug half-life while significantly reducing drug elimination for up to four months. Moreover, the biodegradability and safety of the hydrogel rods suggest their suitability as an advanced intravitreal DDS for treating retinal vascular diseases.

Ocular application of electrospun materials for drug delivery and cellular therapies

The constraints of delivering conventional drugs, biologics and cell-based therapeutics to target ocular sites necessitate the fabrication of novel drug delivery systems to treat diverse ocular diseases. Conventional ocular drug delivery approaches are prone to low bioavailability, poor penetration and degradation of therapeutics, including cell-based therapies, leading to the need for frequent topical applications or intraocular injections. However, owing to their exceptional structural properties, nanofibrous and microfibrous electrospun materials have gained significant interest in ocular drug delivery and biomaterial applications. This review covers the recent developments of electrospun fibers for the delivery of drugs, biologics, cells, growth factors and tissue regeneration in treating ocular diseases. The insights from this review can provide a thorough understanding of the selection of materials for the fabrication of nano- and/or micro-fibrous systems for ocular applications, with a particular interest in achieving controlled drug release and cell therapy. A detailed modality for fabricating different types of nano- and micro-fibers produced from electrospinning and factors influencing generation are also discussed.

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

Chronic ocular diseases can seriously impact the eyes and could potentially result in blindness or serious vision loss. According to the most recent data from the WHO, there are more than 2 billion visually impaired people in the world. Therefore, it is pivotal to develop more sophisticated, long-acting drug delivery systems/devices to treat chronic eye conditions. This review covers several drug delivery nanocarriers that can control chronic eye disorders non-invasively. However, most of the developed nanocarriers are still in preclinical or clinical stages. Long-acting drug delivery systems, such as inserts and implants, constitute the majority of the clinically used methods for the treatment of chronic eye diseases due to their steady state release, persistent therapeutic activity, and ability to bypass most ocular barriers. However, implants are considered invasive drug delivery technologies, especially those that are nonbiodegradable. Furthermore, in vitro characterization approaches, although useful, are limited in mimicking or truly representing the in vivo environment. This review focuses on long-acting drug delivery systems (LADDS), particularly implantable drug delivery systems (IDDS), their formulation, methods of characterization, and clinical application for the treatment of eye diseases.

Overcoming Treatment Challenges in Posterior Segment Diseases with Biodegradable Nano-Based Drug Delivery Systems

Posterior segment eye diseases present a challenge in treatment due to the complex structures in the eye that serve as robust static and dynamic barriers, limiting the penetration, residence time, and bioavailability of topical and intraocular medications. This hinders effective treatment and requires frequent dosing, such as the regular use of eye drops or visits to the ophthalmologist for intravitreal injections, to manage the disease. Moreover, the drugs must be biodegradable to minimize toxicity and adverse reactions, as well as small enough to not affect the visual axis. The development of biodegradable nano-based drug delivery systems (DDSs) can be the solution to these challenges. First, they can stay in ocular tissues for longer periods of time, reducing the frequency of drug administration. Second, they can pass through ocular barriers, offering higher bioavailability to targeted tissues that are otherwise inaccessible. Third, they can be made up of polymers that are biodegradable and nanosized. Hence, therapeutic innovations in biodegradable nanosized DDS have been widely explored for ophthalmic drug delivery applications. In this review, we will present a concise overview of DDSs utilized in the treatment of ocular diseases. We will then examine the current therapeutic challenges faced in the management of posterior segment diseases and explore how various types of biodegradable nanocarriers can enhance our therapeutic arsenal. A literature review of the pre-clinical and clinical studies published between 2017 and 2023 was conducted. Through the advances in biodegradable materials, combined with a better understanding of ocular pharmacology, the nano-based DDSs have rapidly evolved, showing great promise to overcome challenges currently encountered by clinicians.

NIR photothermal-activable drug-conjugated microcapsules for in vitro targeted delivery and release: An alternative treatment of diabetic retinopathy

Diabetic retinopathy (DR) is one of the most serious complications of diabetes, which leads to blindness. By addressing the traditional treatment limitations, we developed a novel light-responsive targeted polymeric microcapsule able to encapsulate a near infrared (NIR) photoactive fluorophore - Indocyanine Green, owing to its photothermal properties. Moreover, for an efficient in vitro targeted drug delivery, the fluorescent microsystem was conjugated with a therapeutic agent, i.e., Avastin drug - a Food and Drug Administration approved therapeutic antibody. The microcapsules were fabricated and evaluated in terms of morphology, encapsulation and drug conjugation efficiency and its release capacity. Avastin-conjugated microcapsules with an average dimension of 4.5 ± 0.35 μm were obtained, according to Scanning Electron Microscopy and Re-Scanning Confocal Microscopy (RCM) investigations. The capacity of the microcapsules to operate as effective phototherapeutic agents by generating heat under NIR laser irradiation was evaluated, followed by the investigation of the microcapsule's shell rupture and NIR laser-induced release of Avastin. The biocompatibility of the Avastin-conjugated microcapsules was proven by WST-1 assay. In vitro cellular internalization and localization of the Avastin microcarriers were determined through Conventional fluorescence microscopy, RCM and Transmission Electron Microscopy imaging techniques. Finally, the Avastin-conjugated microcapsules were validated for in vitro targeted drug delivery and release directly under simulated DR conditions, which could certainly become a successful strategy in DR fighting.

Polymer- and lipid-based nanocarriers for ocular drug delivery: Current status and future perspectives

Ocular diseases seriously affect patients' vision and life quality, with a global morbidity of over 43 million blindness. However, efficient drug delivery to treat ocular diseases, particularly intraocular disorders, remains a huge challenge due to multiple ocular barriers that significantly affect the ultimate therapeutic efficacy of drugs. Recent advances in nanocarrier technology offer a promising opportunity to overcome these barriers by providing enhanced penetration, increased retention, improved solubility, reduced toxicity, prolonged release, and targeted delivery of the loaded drug to the eyes. This review primarily provides an overview of the progress and contemporary applications of nanocarriers, mainly polymer- and lipid-based nanocarriers, in treating various eye diseases, highlighting their value in achieving efficient ocular drug delivery. Additionally, the review covers the ocular barriers and administration routes, as well as the prospective future developments and challenges in the field of nanocarriers for treating ocular diseases.

Six-month sustained delivery of anti-VEGF from in-situ forming hydrogel in the suprachoroidal space

Patients with wet age-related macular degeneration (AMD) require intravitreal injections of bevacizumab (Bev) or other drugs, often on a monthly basis, which is a burden on the healthcare system. Here, we developed an in-situ forming hydrogel comprised of Bev and hyaluronic acid (HA) crosslinked with poly(ethylene glycol) diacrylate for slow release of Bev after injection into the suprachoroidal space (SCS) of the eye using a microneedle. Liquid Bev formulations were cleared from SCS within 5 days, even when formulated with high viscosity, unless Bev was conjugated to a high molecular-weight HA (2.6 MDa), which delayed clearance until 1 month. To extend release to 6 months, we synthesized in-situ forming Bev-HA hydrogel initially as a low-viscosity mixture suitable for injection and flow in the SCS to cover a large area extending to the posterior pole of the eye where the macula is located in humans. Within 1 h after injection, Bev and HA were crosslinked, which retained Bev for slow release as the hydrogel biodegraded. In vivo studies in the rabbit eye reported Bev release for >6 months, depending on gel formulation and Bev assay. The in-situ forming Bev-HA hydrogel was well tolerated, as assessed by clinical exam, fundus imaging, histological analysis, and intraocular pressure measurement. We conclude that Bev released from an in-situ forming hydrogel may enable long-acting treatments of AMD and other posterior ocular indications.

Long-acting formulation strategies for protein and peptide delivery in the treatment of PSED

The invigoration of protein and peptides in serious eye disease includes age-related macular degeneration, choroidal neovascularization, retinal neovascularization, and diabetic retinopathy. The transportation of macromolecules like aptamers, recombinant proteins, and monoclonal antibodies to the posterior segment of the eye is challenging due to their high molecular weight, rapid degradation, and low solubility. Moreover, it requires frequent administration for prolonged therapy. The long-acting novel formulation strategies are helpful to overcome these issues and provide superior therapy. It avoids frequent administration, improves stability, high retention time, and avoids burst release. This review briefly enlightens posterior segments of eye diseases with their diagnosis techniques and treatments. This article mainly focuses on recent advanced approaches like intravitreal implants and injectables, electrospun injectables, 3D printed drug-loaded implants, nanostructure thin-film polymer devices encapsulated cell technology-based intravitreal implants, injectable and depots, microneedles, PDS with ranibizumab, polymer nanoparticles, inorganic nanoparticles, hydrogels and microparticles for delivering macromolecules in the eye for intended therapy. Furthermore, novel techniques like aptamer, small Interference RNA, and stem cell therapy were also discussed. It is predicted that these systems will make revolutionary changes in treating posterior segment eye diseases in future.

Cytochrome P450 oxidase 2J inhibition suppresses choroidal neovascularization in mice

INTRODUCTION

Choroidal neovascularization (CNV) in age-related macular degeneration (AMD) leads to blindness. It has been widely reported that increased intake of ω-3 long-chain polyunsaturated fatty acids (LCPUFA) diets reduce CNV. Of the three major pathways metabolizing ω-3 (and ω-6 LCPUFA), the cyclooxygenase and lipoxygenase pathways generally produce pro-angiogenic metabolites from ω-6 LCPUFA and anti-angiogenic ones from ω-3 LCPUFA. Howevehr, cytochrome P450 oxidase (CPY) 2C produces pro-angiogenic metabolites from both ω-6 and ω-3 LCPUFA. The effects of CYP2J2 products on ocular neovascularization are still unknown. Understanding how each metabolic pathway affects the protective effect of ω-3 LCPUFA on retinal neovascularization may lead to therapeutic interventions.

OBJECTIVES

To investigate the effects of LCPUFA metabolites through CYP2J2 pathway and CYP2J2 regulation on CNV both in vivo and ex vivo.

METHODS

The impact of CYP2J2 overexpression and inhibition on neovascularization in the laser-induced CNV mouse model was assessed. The plasma levels of CYP2J2 metabolites were measured by liquid chromatography and tandem mass spectroscopy. The choroidal explant sprouting assay was used to investigate the effects of CYP2J2 inhibition and specific LCPUFA CYP2J2 metabolites on angiogenesis ex vivo.

RESULTS

CNV was exacerbated in Tie2-Cre CYP2J2-overexpressing mice and was associated with increased levels of plasma docosahexaenoic acids. Inhibiting CYP2J2 activity with flunarizine decreased CNV in both ω-6 and ω-3 LCPUFA-fed wild-type mice. In Tie2-Cre CYP2J2-overexpressing mice, flunarizine suppressed CNV by 33 % and 36 % in ω-6, ω-3 LCPUFA diets, respectively, and reduced plasma levels of CYP2J2 metabolites. The pro-angiogenic role of CYP2J2 was corroborated in the choroidal explant sprouting assay. Flunarizine attenuated ex vivo choroidal sprouting, and 19,20-EDP, a ω-3 LCPUFA CYP2J2 metabolite, increased sprouting. The combined inhibition of CYP2J2 with flunarizine and CYP2C8 with montelukast further enhanced CNV suppression via tumor necrosis factor-α suppression.

CONCLUSIONS

CYP2J2 inhibition augmented the inhibitory effect of ω-3 LCPUFA on CNV. Flunarizine suppressed pathological choroidal angiogenesis, and co-treatment with montelukast inhibiting CYP2C8 further enhanced the effect. CYP2 inhibition might be a viable approach to suppress CNV in AMD.

Hyaluronic Acid: Its Versatile Use in Ocular Drug Delivery with a Specific Focus on Hyaluronic Acid-Based Polyelectrolyte Complexes

Extensive research is currently being conducted into novel ocular drug delivery systems (ODDS) that are capable of surpassing the limitations associated with conventional intraocular anterior and posterior segment treatments. Nanoformulations, including those synthesised from the natural, hydrophilic glycosaminoglycan, hyaluronic acid (HA), have gained significant traction due to their enhanced intraocular permeation, longer retention times, high physiological stability, inherent biocompatibility, and biodegradability. However, conventional nanoformulation preparation methods often require large volumes of organic solvent, chemical cross-linkers, and surfactants, which can pose significant toxicity risks. We present a comprehensive, critical review of the use of HA in the field of ophthalmology and ocular drug delivery, with a discussion of the physicochemical and biological properties of HA that render it a suitable excipient for drug delivery to both the anterior and posterior segments of the eye. The pivotal focus of this review is a discussion of the formation of HA-based nanoparticles via polyelectrolyte complexation, a mild method of preparation driven primarily by electrostatic interaction between opposing polyelectrolytes. To the best of our knowledge, despite the growing number of publications centred around the development of HA-based polyelectrolyte complexes (HA-PECs) for ocular drug delivery, no review articles have been published in this area. This review aims to bridge the identified gap in the literature by (1) reviewing recent advances in the area of HA-PECs for anterior and posterior ODD, (2) describing the mechanism and thermodynamics of polyelectrolyte complexation, and (3) critically evaluating the intrinsic and extrinsic formulation parameters that must be considered when designing HA-PECs for ocular application.

Penetrating-peptide-mediated non-invasive Axitinib delivery for anti-neovascularisation

The unique physiological makeup of the eye limits the use of small-molecule drugs for treating the posterior segment of the eye. Nevertheless, transmembrane-peptide-mediated non-invasive drug delivery can serve as an ideal treatment strategy, as it is capable of delivering small-molecule drugs across the membrane in the form of eye drops, thereby achieving the effective treatment of neovascularisation in the posterior cavity. In this study, we screened and compared the posterior segment distribution of two poly(ethylene glycol)-distearoylphosphatidylethanolamine carriers modified using targeting-peptides. Thereafter, a transmembrane peptide (i.e., PENE) with a greater ability of transmembrane delivery was selected for delivering the anti-vascular drug (i.e., Axitinib) to the posterior segment of the eye. Using two different mouse models with fundus neovascular diseases, the complete non-invasive delivery of Axitinib to the posterior segment of the eye was confirmed using the targeted system; the designed eye drops (i.e., PENE-nanoparticles) could achieve drug distribution to the retina and veins of the eye as well as good drug permeability for renewal. Moreover, using the eye-drop treatment, neovascularisation was substantially reduced, demonstrating the high efficacy of this drug delivery system. This study, which combines nanodrug-loading technology and the transmembrane delivery of penetrating-peptides to achieve the goal of the non-invasive delivery of small-molecule drugs through the dense blood vessels of the sclera, shows wide applicability and considerably expands the use of ocular drugs. Thus, this study is expected to help develop a more acceptable drug administration strategy for the drug treatment of the posterior segment of the eye.

Polymer based sustained drug delivery to the ocular posterior segment: barriers and future opportunities for the treatment of neovascular pathologies

There is an increasing momentum in research and pharmaceutical industry communities to design sustained, non-invasive delivery systems to treat chronic neovascular ocular diseases that affect the posterior segment of the eye including age-related macular degeneration and diabetic retinopathy. Current treatments include VEGF blockers, which have revolutionized the standard of care for patients, but their maximum therapeutic benefit is hampered by the need for recurrent and invasive administration procedures. Currently approved delivery systems intended to address these limitations exploit polymer technology to regulate drug release in a sustained manner. Here, we critically review sustained drug delivery approaches for the treatment of chronic neovascular diseases affecting the ocular posterior segment, with a special emphasis on novel and polymeric technologies spanning the spectrum of preclinical and clinical investigation, and those approved for treatment. The mechanism by which each formulation imparts sustained release, the impact of formulation characteristics on release and foreign body reaction, and special considerations related to the translation of these systems are discussed.

Long-Chain Polyunsaturated Fatty Acids and Their Metabolites Regulate Inflammation in Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a blinding eye disease, whose incidence strongly increases with ages. The etiology of AMD is complex, including aging, abnormal lipid metabolism, chronic inflammation and oxidative stress. Long-chain polyunsaturated fatty acids (LCPUFA) are essential for ocular structures and functions. This review summarizes the regulatory effects of LCPUFA on inflammation in AMD. LCPUFA are related to aging, autophagy and chronic inflammation. They are metabolized to pro- and anti-inflammatory metabolites by various enzymes. These metabolites stimulate inflammation in response to oxidative stress, causing innate and acquired immune responses. This review also discusses the possible clinical applications, which provided novel targets for the prevention and treatment of AMD and other age-related diseases.

Considerations for Polymers Used in Ocular Drug Delivery

PURPOSE

Age-related eye diseases are becoming more prevalent. A notable increase has been seen in the most common causes including glaucoma, age-related macular degeneration (AMD), and cataract. Current clinical treatments vary from tissue replacement with polymers to topical eye drops and intravitreal injections. Research and development efforts have increased using polymers for sustained release to the eye to overcome treatment challenges, showing promise in improving drug release and delivery, patient experience, and treatment compliance. Polymers provide unique properties that allow for specific engineered devices to provide improved treatment options. Recent work has shown the utilization of synthetic and biopolymer derived biomaterials in various forms, with this review containing a focus on polymers Food and Drug Administration (FDA) approved for ocular use.

METHODS

This provides an overview of some prevalent synthetic polymers and biopolymers used in ocular delivery and their benefits, brief discussion of the various types and synthesis methods used, and administration techniques. Polymers approved by the FDA for different applications in the eye are listed and compared to new polymers being explored in the literature. This article summarizes research findings using polymers for ocular drug delivery from various stages: laboratory, preclinical studies, clinical trials, and currently approved. This review also focuses on some of the challenges to bringing these new innovations to the clinic, including limited selection of approved polymers.

RESULTS

Polymers help improve drug delivery by increasing solubility, controlling pharmacokinetics, and extending release. Several polymer classes including synthetic, biopolymer, and combinations were discussed along with the benefits and challenges of each class. The ways both polymer synthesis and processing techniques can influence drug release in the eye were discussed.

CONCLUSION

The use of biomaterials, specifically polymers, is a well-studied field for drug delivery, and polymers have been used as implants in the eye for over 75 years. Promising new ocular drug delivery systems are emerging using polymers an innovative option for treating ocular diseases because of their tunable properties. This review touches on important considerations and challenges of using polymers for sustained ocular drug delivery with the goal translating research to the clinic.

Inhibiting corneal neovascularization by sustainably releasing anti-VEGF and anti-inflammation drugs from silica-thermogel nanohybrids

Corneal neovascularization (CNV) is one of the main factors that induce blindness worldwide. To effectively inhibit CNV, a novel nanohybrid has been developed by incorporating anti-VEGF bevacizumab (BEV)-loaded mesoporous silica nanoparticles (BEV@MSN) into the thermogel matrix with anti-inflammation cyclosporine A (CsA) (BEV@MSN-CsA@Thermogel). This nanohybrid regulates the in vitro release of both bevacizumab and cyclosporine A in a sustainable way for up to four weeks to enhance CNV inhibition through the synergistic anti-VEGF and anti-inflammation. The carrier materials (i.e. silica and thermogel) in this nanohybrid do not show any cytotoxicity to human Tenon's fibroblasts, corneal epithelial cells and corneal endothelial cells. BEV@MSN-CsA@Thermogel effectively prevents proliferation, migration, and tube-like structure formation of human umbilical vein endothelial cells. Moreover, subconjunctival injection of BEV@MSN-CsA@Thermogel significantly inhibits corneal neovascularization in terms of the CNV area, the new vessel length, the corneal opaque area, the corneal inflammation and abnormal fibrosis in a rabbit model. This nanohybrid is thus a promising alternative for effective CNV treatment.

In vitro dissolution testing models of ocular implants for posterior segment drug delivery

The delivery of drugs to the posterior segment of the eye remains a tremendously difficult task. Prolonged treatment in conventional intravitreal therapy requires injections that are administered frequently due to the rapid clearance of the drug molecules. As an alternative, intraocular implants can offer drug release for long-term therapy. However, one of the several challenges in developing intraocular implants is selecting an appropriate in vitro dissolution testing model. In order to determine the efficacy of ocular implants in drug release, multiple in vitro test models were emerging. While these in vitro models may be used to analyse drug release profiles, the findings may not predict in vivo retinal drug exposure as this is influenced by metabolic and physiological factors. This review considers various types of in vitro test methods used to test drug release of ocular implants. Importantly, it discusses the challenges and factors that must be considered in the development and testing of the implants in an in vitro setup.

Intra-articular Injection of Bevacizumab Enhances Bone Marrow Stimulation-Mediated Cartilage Repair in a Rabbit Osteochondral Defect Model

BACKGROUND

Bone marrow stimulation (BMS) via microfracture historically has been a first-line treatment for articular cartilage lesions. However, BMS has become less favorable because of resulting fibrocartilage formation. Previous studies have shown that angiogenesis blockade promotes cartilage repair. Bevacizumab is a Food and Drug Administration-approved medication used clinically to prevent angiogenesis.

HYPOTHESIS

The intra-articular injection of bevacizumab would prevent angiogenesis after BMS and lead to improved cartilage repair with more hyaline-like cartilage.

STUDY DESIGN

Controlled laboratory study.

METHODS

The dose of bevacizumab was first optimized in a rabbit osteochondral defect model with BMS. Then, 48 rabbits (n = 8/group/time point) were divided into 3 groups: osteochondral defect (defect), osteochondral defect + BMS (BMS group), and osteochondral defect + BMS + bevacizumab intra-articular injection (bevacizumab group). Rabbits were sacrificed at either 6 or 12 weeks after surgery. Three-dimensional (3D) micro-computed tomography (microCT), macroscope score, modified O'Driscoll histology scores, collagen type 2, Herovici staining, and hematoxylin and eosin staining were performed. Angiogenesis markers were also evaluated.

RESULTS

The intra-articular dose of 12.5 mg/0.5 mL bevacizumab was found to be effective without deleteriously affecting the subchondral bone. Intra-articular injection of bevacizumab resulted in significantly improved cartilage repair for the bevacizumab group compared with the BMS or the defect group based on 3D microCT, the macroscope score (both P < .05), the modified O'Driscoll histology score (P = .0034 and P = .019 vs defect and BMS groups, respectively), collagen type 2, Herovici staining, and hematoxylin and eosin staining at 6 weeks. Cartilage in the bevacizumab group had significantly more hyaline cartilage than did that in other groups. At 12 weeks, the cartilage layer regenerated in all groups; however, the bevacizumab group showed more hyaline-like morphology, as demonstrated by microCT, histology scores (P < .001 and .0225 vs defect and BMS groups, respectively), histology, and immunohistochemistry. The bevacizumab injection did not significantly change mRNA expressions of smooth muscle actin, vascular endothelial growth factor, or hypoxia-inducible factor-1 alpha.

CONCLUSION

Intra-articular injection of bevacizumab significantly enhanced the quality and quantity of hyaline-like cartilage after BMS in a rabbit model. Future large-animal and human studies are necessary to evaluate the clinical effect of this therapy, which may lead to improved BMS outcomes and thus the durability of the regenerated cartilage.

CLINICAL RELEVANCE

The use of bevacizumab may be an important clinical adjunct to improve BMS-mediated cartilage repair.

Long-Acting Formulations: A Promising Approach for the Treatment of Chronic Diseases

Medication and patient adherence are the two main aspects of any successful treatment of chronic disease. Even though diseases and its treatment existed for several hundred years, the treatment optimization for a given patient is still a researcher question for scientists. There are differences in treatment duration, prognostic signs and symptoms between patient to patient. Hence, designing ideal formulation to suit individual patient is a challenging task. The conventional formulations like oral solids and liquids gives a partial or incomplete treatment because the patient needs to follow the daily pills for a longer time. In such cases, the long-acting formulations will have better patient compliances as drug will be released for a longer duration. Many such approaches are under the clinical investigation. The favorable pharmacokinetic and pharmacodynamic relationships, will be promising option for the treatment of chronic diseases. In this review, we have highlighted the importance of long-acting formulations in the treatment of chronic diseases and the advent of newer formulation technologies.

Harnessing molecular recognition for localized drug delivery

A grand challenge in drug delivery is providing the right dose, at the right anatomic location, for the right duration of time to maximize therapeutic efficacy while minimizing off-target toxicity and other deleterious side-effects. Two general modalities are receiving broad attention for localized drug delivery. In the first, referred to as "targeted accumulation", drugs or drug carriers are engineered to have targeting moieties that promote their accumulation at a specific tissue site from circulation. In the second, referred to as "local anchoring", drugs or drug carriers are inserted directly into the tissue site of interest where they persist for a specified duration of time. This review surveys recent advances in harnessing molecular recognition between proteins, peptides, nucleic acids, lipids, and carbohydrates to mediate targeted accumulation and local anchoring of drugs and drug carriers.

Nanoparticle-Hydrogel Composite Drug Delivery System for Potential Ocular Applications

Intravitreal injections are clinically established procedures in the treatment of posterior eye diseases, such as wet age-related macular degeneration (wet AMD) which requires monthly intravitreal injections of anti-vascular endothelial growth factor (anti-VEGF) protein drugs that can lead to complications due to frequent dosing. In this study, we designed a composite drug delivery system (DDS) consisting of drug-loaded poly (lactide–co–glycolide) (PLGA) nanoparticles and a chemically crosslinked hyaluronan hydrogel to reduce the dosing frequency. The morphology, size, composition, and drug loading efficiency of the prepared nanoparticles were characterized. The properties of the modified hyaluronan polymers used were also examined. The degree of swelling/degradation and controlled release ability of the hyaluronan hydrogel and the composite DDS were identified using bovine serum albumin (BSA) as a model drug. The results show that this system can retain 75% of its wet weight without losing its integrity and release the model drug at the rate of 0.4 μg/day for more than two months under physiological conditions. In addition, the nanoparticulate formulation of the system can further improve bioavailability of the drugs by penetrating deep into the retinal layers. In conclusion, the proposed composite DDS is easily prepared with biocompatible materials and is promising for providing the sustained release of the protein drugs as a better treatment for ocular neovascular diseases like wet AMD.

A review of nanocarrier-mediated drug delivery systems for posterior segment eye disease: challenges analysis and recent advances

Posterior segment eye disease is a leading cause of irreversible vision impairment and blindness. As the unique organ for vision, eyes are protected by various protective barriers. The existence of physiological barriers and elimination mechanisms makes it challenging to treat the posterior segment eye diseases. To achieve efficient drug delivery to the posterior segment of eyes, different drug delivery systems have been proposed. Due to their abilities to enhance ocular tissue permeability, make controlled drug release and target retina, nanocarriers, such as lipid nanoparticles, liposomes and polymeric nanomicelles, have been widely studied for posterior segment drug delivery. However, clinical applications of nanocarrier mediated drug delivery systems as non-invasive ocular drops is still not ready. The delivery of nanocarrier-mediated drug for posterior segment disease still faces the choice of being more effective or more invasive for long-term treatment. Therefore, it is necessary to have a clear understanding of the barriers and the routes of ocular drug delivery while developing the delivery systems. In this review, types of ocular barriers and drug administration routes are categorised in a more intuitive way. Recent advances in nanocarrier mediated drug delivery systems with focus on posterior segment are reviewed with illustrative examples.

Electrospinning nanofiber technology: a multifaceted paradigm in biomedical applications

This review focuses on the process of preparation of nanofibers via Es, the design and setup of the instrument, critical parameter optimization, preferable polymers, solvents, characterization techniques, and recent development and biomedical applications of nanofibers.

Alginate-based hydrogels for cancer therapy and research

Cancer is a major health issue concerning to all of us. Current treatment options are still limited due to not-selective action. Encapsulation is contemplated as an innovative approach to address systemic toxicity and tumor resistance caused by traditional therapies, while increasing encapsulated compounds bioavailability. The coating material of capsules strongly determines the success of the system. Since alginate has been proved non-toxic, biocompatible and biodegradable, it is considered a potential vehicle for therapeutic factors encapsulation. Besides, it has the particular ability to form hydrogels, which hold a high-water content and greatly resemble to natural soft tissues. The present review exposes the state-of-the-art and the most sophisticated alginate-based systems for cancer therapy and research. It begins with an overview of alginate hydrogels and the qualities that make them especially suitable for biomedical applications. In the following section, the application of alginate hydrogels as pioneering strategies for cancer treatment is described. Several examples of alginate-based delivery systems of therapeutic drugs, proteins and nucleic acids are provided. Significant emphasis is placed in both oral delivery systems and colorectal cancer therapy. Moreover, the role of alginate 3-D scaffolds for both cell culture and delivery is explained. Lastly, other applications of alginate-based hydrogels such as tumor biomarkers immunosensing and fluorescent surgical marker are included.

The anti-adhesive effect of anti-VEGF agents in experimental models: A systematic review

Adhesions constitute a major problem in abdominal-pelvic and thoracic surgery with significant impact in the postoperative quality of life and healthcare services utilization. Adhesiogenesis is the result of increased fibrin formation, impaired fibrinolysis, angiogenesis, and fibrosis. Despite the recent advancements, the ideal anti-adhesive agent remains to be determined. To this end, we performed a comprehensive literature search in PubMed, EMBASE, and Scopus databases to identify studies investigating the antiadhesive role of anti-VEGF agents in peritoneal, pleural, and pericardial experimental adhesion models. Fifteen studies were eligible for inclusion with a total population of 602 animals (334 rats, 180 rabbits, and 88 mice). The majority of included studies (11/15) used bevacizumab, while three studies used other anti-VEGF antibodies and one study used an anti-VEGFR-antibody. A rat model was used in nine studies, while rabbit (n = 3) or mouse (n = 3) models were used less frequently. Eleven studies used peritoneal models, three studies used pleural models, and one study used a pericardial model. The scales (n = 12) and interval (Range: 1-42 days) used for the evaluation of adhesions varied between the studies. All studies demonstrated a significant decrease in adhesion scores between the anti-VEGF and control groups up to 42 days postprocedure. VEGF blockade resulted in decreased fibrosis in four out of five studies that used peritoneal models, while the effect on pleural models depended on the pleurodesis agent and was significant between 7 and 28 days. The effect of anti-VEGF agents on anastomosis integrity depends on the dose and the model that is used (inconclusive results).Current data support the anti-adhesive role of Anti-VEGF agents in all three serosal surfaces up to 6 weeks postprocedure. Further studies are needed to confirm the anti-adhesive role of anti-VEGF agents in pleural and pericardial adhesion experimental models and investigate any effect on anastomosis integrity in peritoneal models.

Formulation of nanoliposome-encapsulated bevacizumab (Avastin): Statistical optimization for enhanced drug encapsulation and properties evaluation

Bevacizumab (Avastin®), an anti-vascular endothelial growth factor, is one of the most effective drugs widely used to inhibit ocular angiogenesis. Nanoliposomes were recruited to improve the accessibility of bevacizumab (BVZ) during treatment. To optimize drug entrapment efficiency (DEE %), the effect of some independent variables was evaluated utilizing response surface methodology. The optimized formulation containing BVZ (NLP-BVZ) was characterized, and its safety was assessed. Employingarising retinalpigment epithelial (ARPE) cells, the permeability of the nanoliposome was analyzed. Structural stability and integrity of NLP-BVZ were also estimated with different methods. Optimal condition for the maximum DEE (39.9%) was obtained with cholesterol/DPPC (1,2-Dipalimitoyl-Sn-glycero-3-phosphocholine) (%w/w) 13.64, BVZ/DPPC (%w/w) 83.78 and 9 freeze-thaw cycles. Neutral fabricated NLP-BVZ with an average size of 141.5 ± 45.8 nm showed a smooth spherical structure and released the drug in a slow and sustained fashion. The formulation exhibited no obvious effect against human umbilical vein endothelial cells (HUVECs) and ARPEs. Additionally, the pattern of the circular dichroism (CD) and intrinsic fluorescence spectra confirmed the structural integrity of protein remained conserved after encapsulation. Taken together, the analysis indicated that the process of entrapment into nanoliposome meaningfully made the drug safer, more stable, and, therefore, appropriate for treating ocular disorders.

Controlled release of anti-VEGF by redox-responsive polydopamine nanoparticles

Reactive oxidative species (ROS) are the primary mediator of angiogenesis by upregulating the expression of vascular endothelial growth factor (VEGF) in the development of wet age-related macular degeneration (AMD). However, the current treatment of AMD currently relies on monthly intravitreal injection of anti-angiogenic therapeutics to inhibit new choroidal angiogenesis. However, repeated injections have been associated with side-effects, are costly, and may lower patient compliance. Moreover, the intraocular oxidative stress-dependent angiogenesis is not alleviated by current treatments, which limits the overall efficacy of the treatment strategy. Recently, nanoparticle-based devices present potential in sustained delivery of angiogenesis inhibitors and excellent capability of scavenging reactive oxygen species (ROS). Nevertheless, limited efforts have been dedicated to the treatment of oxidative stress-related diseases via a combined anti-angiogenesis and anti-oxidization pathway. For this purpose, we developed anti-angiogenetic protein-loaded polydopamine (PDA) nanoparticles for the enhanced treatment of AMD. Remarkably, the PDA nanoparticles could efficiently scavenge ROS to reduce the expression of angiogenic agents. In parallel, the particles were able to controllably release loaded anti-angiogenic drugs in response to oxidative stress.

Chitosan-Polycaprolactone Core-Shell Microparticles for Sustained Delivery of Bevacizumab

The current therapy for treating neovascular age-related macular degeneration requires monthly intravitreal injection of angiogenesis inhibitors such as bevacizumab or ranibizumab via a 31-gauge needle to inhibit choroidal neovascularization. However, repeated intravitreal injections are associated with poor patient compliance and potential side effects. Microparticle-based injectable devices have shown great promise to address this issue by sustained delivery of protein therapeutics, but critical barriers remain, including limited loading capacity and steady long-term release without compromising the anti-angiogenic activity of drugs. Addressing these challenges, we developed a unique method for synthesizing biodegradable polymer-based core-shell microparticles with sizes around 10 μm, high physical integrity, and uniform size. Subsequent electrostatic and physical interactions to control protein diffusion were designed for the core-shell microparticles to effectively increase the capacity of drug loading to 25%, reduce burst release by almost 30%, and extend the period of drug release from 3 to 6 months. Remarkably, the microparticles enabled a longer-term drug administration and maintained high drug potency up to 6 months in vitro, representing significant advancement compared to conventional microparticle-based delivery platforms or currently commercialized devices. Additionally, the microparticles presented minimal toxicity to human retinal cells in vitro with over 90% cell viability, and they also exhibited good injection feasibility through 31-gauge needles in an ex vivo porcine eye model. These results warrant further studies to evaluate the clinical potential for treating posterior ophthalmic diseases as well as other conditions or injuries requiring long-term local drug administration.