Emerging potential of niosomes in ocular delivery

Block copolymer micelles as ocular drug delivery systems

Block copolymer micelles, formed by the self-assembly of amphiphilic polymers, address formulation challenges, such as poor drug solubility and permeability. These micelles offer advantages including a smaller size, easier preparation, sterilization, and superior solubilization, compared with other nanocarriers. Preclinical studies have shown promising results, advancing them toward clinical trials. Their mucoadhesive properties enhance and prolong contact with the ocular surface, and their small size allows deeper penetration through tissues, such as the cornea. Additionally, copolymeric micelles improve the solubility and stability of hydrophobic drugs, sustain drug release, and allow for surface modifications to enhance biocompatibility. Despite these benefits, long-term stability remains a challenge. In this review, we highlight the preclinical performance, structural frameworks, preparation techniques, physicochemical properties, current developments, and prospects of block copolymer micelles as ocular drug delivery systems.

Intravitreal therapeutic nanoparticles for age-related macular degeneration: Design principles, progress and opportunities

Age-related macular degeneration (AMD) is a leading cause of vision loss in the elderly. The current standard treatment for AMD involves frequent intravitreal administrations of therapeutic agents. While effective, this approach presents challenges, including patient discomfort, inconvenience, and the risk of adverse complications. Nanoparticle-based intravitreal drug delivery platforms offer a promising solution to overcome these limitations. These platforms are engineered to target the retina specifically and control drug release, which enhances drug retention, improves drug concentration and bioavailability at the retinal site, and reduces the frequency of injections. This review aims to uncover the design principles guiding the development of highly effective nanoparticle-based intravitreal drug delivery platforms for AMD treatment. By gaining a deeper understanding of the physiology of ocular barriers and the physicochemical properties of nanoparticles, we establish a basis for designing intravitreal nanoparticles to optimize drug delivery and drug retention in the retina. Furthermore, we review recent nanoparticle-based intravitreal therapeutic strategies to highlight their potential in improving AMD treatment efficiency. Lastly, we address the challenges and opportunities in this field, providing insights into the future of nanoparticle-based drug delivery to improve therapeutic outcomes for AMD patients.

Development of brimonidine niosomes laden contact lenses for extended release and promising delivery system in glaucoma treatment

BACKGROUND

Increased intraocular pressure is a common symptom of glaucoma. In severe circumstances, it may result in loss of eyesight. Glaucoma treatment is difficult due to ocular physiological barriers that prevent medications from reaching the afflicted area. Traditional formulations (eye drops) have a short residence period and are rapidly drained away via the nasolacrimal duct, resulting in increased adverse drug responses and lower efficacy. The usage of nanoparticles such as niosomes could be one potential answer to these problems. While niosomes improve drug penetration, they have little effect on ocular retention of the medication. Contact lenses containing niosomes can assist to overcome this disadvantage.

OBJECTIVE

This study aims to prepare and evaluate Brimonidine niosomes laden contact lenses for the treatment of Glaucoma.

METHODS

Brimonidine niosomes were prepared using thin film hydration method and evaluated. The contact lenses were soaked in the niosomal formulation at varying intervals (3-10 days). Thereafter, the contact lenses were evaluated for %transmittance, %swelling index, drug quantification and in vitro drug release. The pharmacodynamic studies were conducted to assess the reduction in intraocular pressure (IOP) in albino rabbits. The research compared the results of the reduction in intraocular pressure caused by Brimonidine niosomes laden contact lenses with a marketed preparation of niosomes.

RESULTS

Higher concentration of the drug was loaded in contact lenses loaded with Brimonidine niosomes compared to the marketed formulation, by soaking method. The contact lenses exhibited an optimal %transmittance of 98.02 ± 0.36 and %swelling index of 50.35 ± 0.57. Increase in the soaking time up to 7 days led to an increase in the drug concentration in the contact lenses. However, no further increase was observed after the 7th day due to saturation of the contact lenses. Brimonidine niosomes laden contact lenses provided a reduction in intraocular pressure that was similar to the marketed preparation. Further, the contact lenses provided extended release up to 20 h.

CONCLUSION

Brimonidine niosomes laden contact lenses exhibited superior drug loading through the soaking method, displaying optimal %transmittance and %swelling index. Soaking for 7 days increased drug concentration in contact lenses with no further increase due to saturation. These lenses reduced intraocular pressure like the marketed formulation, offering extended release for 20 h.

Steroidal nanoformulations for the treatment of uveitis: potential, promises and future perspectives

BACKGROUND

Intraocular inflammation, commonly referred to as uveitis, is a prevalent ocular disease. The categorization of uveitis may be based on the prevailing anatomical site, which includes anterior, intermediate, and posterior uveitis. There exists a significant body of evidence indicating that T cells play a pivotal role in the pathogenesis of autoimmune uveitis. In addition to the presence of T cells, an elevation in levels of inflammatory cytokines and a reduction in regulatory cytokines were also noted. The primary pharmacological interventions for uveitis comprise of corticosteroids, methotrexate, anti-vascular endothelial growth factor (VEGF) agents, anti-tumor necrosis factor-alpha (TNF-α) antibodies, and sirolimus. These medications offer prompt alleviation for inflammation. Nevertheless, prolonged administration of corticosteroids invariably leads to unfavorable adverse reactions. The traditional topical corticosteroids exhibit certain limitations, including inadequate transcorneal permeation and low corneal retention, leading to reduced ocular bioavailability. Consequently, there is a growing inclination towards the creation of innovative steroid drug delivery systems with the aim of reducing the potential for adverse effects, while simultaneously enhancing the drug's corneal permeation and retention.

CONCLUSION

This review is an attempt to compile all the research work done so far in this field and provides a brief overview of the global efforts to develop innovative nanocarrier-based systems for corticosteroids.

Applications of Nanotechnology-mediated Herbal Nanosystems for Ophthalmic Drug

In recent years, herbal nanomedicines have gained tremendous popularity for novel drug discovery. Nanotechnology has provided several advances in the healthcare sector, emerging several novel nanocarriers that potentiate the bioavailability and therapeutic efficacy of the herbal drug. The recent advances in nanotechnology with accelerated strategies of ophthalmic nanosystems have paved a new path for overcoming the limitations associated with ocular drug delivery systems, such as low bioavailability, poor absorption, stability, and precorneal drug loss. Ophthalmic drug delivery is challenging due to anatomical and physiological barriers. Due to the presence of these barriers, the herbal drug entry into the eyes can be affected when administered by following multiple routes, i.e., topical, injectables, or systemic. However, the advancement of nanotechnology with intelligent systems enables the herbal active constituent to successfully entrap within the system, which is usually difficult to reach employing conventional herbal formulations. Herbal-loaded nanocarrier drug delivery systems demonstrated enhanced herbal drug permeation and prolonged herbal drug delivery. In this current manuscript, an extensive search is conducted for original research papers using databases Viz., PubMed, Google Scholar, Science Direct, Web of Science, etc. Further painstaking efforts are made to compile and update the novel herbal nanocarriers such as liposomes, polymeric nanoparticles, solid lipid nanoparticles, nanostructure lipid carriers, micelles, niosomes, nanoemulsions, dendrimers, etc., which are mostly used for ophthalmic drug delivery system. This article presents a comprehensive survey of diverse applications used for the preventative measures and treatment therapy of varied eye disorders. Further, this article highlights the recent findings that the innovators are exclusively working on ophthalmic nanosystems for herbal drug delivery systems. The nanocarriers are promising drug delivery systems that enable an effective and supreme therapeutic potential circumventing the limitations associated with conventional ocular drug delivery systems. The nanotechnology-based approach is useful to encapsulate the herbal bioactive and prevent them from degradation and therefore providing them for controlled and sustained release with enhanced herbal drug permeation. Extensive research is still being carried out in the field of herbal nanotechnology to design an ophthalmic nanosystem with improved biopharmaceutical properties.

Ophthalmic Bimatoprost-Loaded Niosomal In Situ Gel: Preparation, Optimization, and In Vivo Pharmacodynamics Study

This study aimed at formulating the antiglaucoma agent, Bimatoprost (BMT), into niosomal in situ gel (BMT-ISG) for ocular delivery. Niosomes containing cholesterol/span 60 entrapping BMT were fabricated using a thin-film hydration method. The fabricated niosomes were optimized and characterized for entrapment efficiency (%EE) and size. The optimized BMT-loaded niosomal formulation prepared at a cholesterol/span 60 ratio of 1:2 exhibited the highest entrapment (81.2 ± 1.2%) and a small particle size (167.3 ± 9.1 nm), and they were selected for incorporation into in situ gelling systems (BMT-ISGs) based on Pluronic F127/Pluronic F68. Finally, the in vivo efficiency of the BMT-ISG formulation, in terms of lowering the intraocular pressure (IOP) in normotensive male albino rabbits following ocular administration, was assessed and compared to that of BMT ophthalmic solution. All the formulated BMT-ISGs showed sol-gel transition temperatures ranging from 28.1 °C to 40.5 ± 1.6 °C. In addition, the BMT-ISG formulation sustained in vitro BMT release for up to 24 h. Interestingly, in vivo experiments depicted that topical ocular administration of optimized BMT-ISG formulation elicited a significant decline in IOP, with maximum mean decreases in IOP of 9.7 ± 0.6 mm Hg, compared to BMT aqueous solution (5.8 ± 0.6 mm Hg). Most importantly, no signs of irritation to the rabbit's eye were observed following topical ocular administration of the optimized BMT-ISG formulation. Collectively, our results suggested that niosomal in situ gels might be a feasible delivery vehicle for topical ocular administration of anti-glaucoma agents, particularly those with poor ocular bioavailability.

Gout therapeutics and drug delivery

Gout is a common inflammatory arthritis caused by persistently elevated uric acid levels. With the improvement of people's living standards, the consumption of processed food and the widespread use of drugs that induce elevated uric acid, gout rates are increasing, seriously affecting the human quality of life, and becoming a burden to health systems worldwide. Since the pathological mechanism of gout has been elucidated, there are relatively effective drug treatments in clinical practice. However, due to (bio)pharmaceutical shortcomings of these drugs, such as poor chemical stability and limited ability to target the pathophysiological pathways, traditional drug treatment strategies show low efficacy and safety. In this scenario, drug delivery systems (DDS) design that overcome these drawbacks is urgently called for. In this review, we initially describe the pathological features, the therapeutic targets, and the drugs currently in clinical use and under investigation to treat gout. We also comprehensively summarize recent research efforts utilizing lipid, polymeric and inorganic carriers to develop advanced DDS for improved gout management and therapy.

Nanotechnology-based ocular drug delivery systems: recent advances and future prospects

Ocular drug delivery has constantly challenged ophthalmologists and drug delivery scientists due to various anatomical and physiological barriers. Static and dynamic ocular barriers prevent the entry of exogenous substances and impede therapeutic agents' active absorption. This review elaborates on the anatomy of the eye and the associated constraints. Followed by an illustration of some common ocular diseases, including glaucoma and their current clinical therapies, emphasizing the significance of drug therapy in treating ocular diseases. Subsequently, advances in ocular drug delivery modalities, especially nanotechnology-based ocular drug delivery systems, are recommended, and some typical research is highlighted. Based on the related research, systematic and comprehensive characterizations of the nanocarriers are summarized, hoping to assist with future research. Besides, we summarize the nanotechnology-based ophthalmic drugs currently on the market or still in clinical trials and the recent patents of nanocarriers. Finally, inspired by current trends and therapeutic concepts, we provide an insight into the challenges faced by novel ocular drug delivery systems and further put forward directions for future research. We hope this review can provide inspiration and motivation for better design and development of novel ophthalmic formulations.

Recent trends and updates on ultradeformable and elastic vesicles in ocular drug delivery

Ocular drug delivery is enigmatic on account of various physiological precorneal barriers that ultimately hinder efficient drug penetration and corneal absorption. Ultradeformable vesicles embody non-ionic surfactants, edge activators and vesicular builders that provide enormous elasticity and deformability. The elastic vesicles can cross the ocular barriers owing to their peculiar squeezability and distorting ability and, thus, establish an infallible shot for ocular delivery. This review provides an overview of the recent advancements and updates of elastic vesicles as effective ocular drug delivery vehicles.

Formulation and Characterization of Epalrestat-Loaded Polysorbate 60 Cationic Niosomes for Ocular Delivery

The aim of this work was to develop niosomes for the ocular delivery of epalrestat, a drug that inhibits the polyol pathway and protects diabetic eyes from damage linked to sorbitol production and accumulation. Cationic niosomes were made using polysorbate 60, cholesterol, and 1,2-di-O-octadecenyl-3-trimethylammonium propane. The niosomes were characterized using dynamic light scattering, zeta-potential, and transmission electron microscopy to determine their size (80 nm; polydispersity index 0.3 to 0.5), charge (-23 to +40 mV), and shape (spherical). The encapsulation efficiency (99.76%) and the release (75% drug release over 20 days) were measured with dialysis. The ocular irritability potential (non-irritating) was measured using the Hen's Egg Test on the Chorioallantoic Membrane model, and the blood glucose levels (on par with positive control) were measured using the gluc-HET model. The toxicity of the niosomes (non-toxic) was monitored using a zebrafish embryo model. Finally, corneal and scleral permeation was assessed with the help of Franz diffusion cells and confirmed with Raman spectroscopy. Niosomal permeation was higher than an unencapsulated drug in the sclera, and accumulation in tissues was confirmed with Raman. The prepared niosomes show promise to encapsulate and carry epalrestat through the eye to meet the need for controlled drug systems to treat the diabetic eye.

Nano-based eye drop: Topical and noninvasive therapy for ocular diseases

Eye drops are the most accessible therapy for ocular diseases, while inevitably suffering from their lower bioavailability which highly restricts the treatment efficacy. The introduction of nanotechnology has attracted considerable interest as it has advantages over conventional ones such as prolonged ocular surface retention time and enhanced ocular barrier penetrating properties, and achieving higher bioavailability and improved treatment efficacy. This review describes various ocular diseases treated with eye drops as well as the physiological and anatomical ocular barriers faced with through drug administration. It also summarizes the recent advances regarding the utilization of nanotechnology in developing eye drops, and how to optimize the nanocarrier-based ocular drug delivery systems. The prospective future research directions for nano-based eye drops are also discussed here.

Drug Delivery for Ocular Allergy: Current Formulation Design Strategies and Future Perspectives

The incidences of ocular allergy have been growing with the increase in pollution. Because of challenges in new drug development, there have been efforts to maximize the efficacy of existing drugs through drug delivery approaches. The effectiveness of drugs in ophthalmic conditions is primarily determined by permeability across the barrier, corneal retention, and sustained release. Thus, there have been widespread efforts to optimize these parameters to enhance efficacy through novel formulations. This review aims to analyze the approaches to drug delivery systems to encourage further research to optimize effectiveness. With this objective, research on drug delivery aspects of anti-allergy therapeutics was included and analyzed based on formulation/drug delivery technique, Food and Drug Administration approval limits, residence time, compatibility, pre-clinical efficacy, and potential for translational application. Conventional eye drops have concerns such as poor residence time and ocular bioavailability. The novel formulations have the potential to improve residence and bioavailability. However, the use of preservatives and the lack of regulatory approval for polymers limit the translational application. The review may assist readers in identifying novel drug delivery strategies and their limitations for the development of effective ophthalmic formulations for the treatment of ocular allergy.

Aqueous Prostaglandin Eye Drop Formulations

Glaucoma is one of the leading causes of irreversible blindness worldwide. It is characterized by progressive optic neuropathy in association with damage to the optic nerve head and, subsequently, visual loss if it is left untreated. Among the drug classes used for the long-term treatment of open-angle glaucoma, prostaglandin analogues (PGAs) are the first-line treatment and are available as marketed eye drop formulations for intraocular pressure (IOP) reduction by increasing the trabecular and uveoscleral outflow. PGAs have low aqueous solubility and are very unstable (i.e., hydrolysis) in aqueous solutions, which may hamper their ocular bioavailability and decrease their chemical stability. Additionally, treatment with PGA in conventional eye drops is associated with adverse effects, such as conjunctival hyperemia and trichiasis. It has been a very challenging for formulation scientists to develop stable aqueous eye drop formulations that increase the PGAs' solubility and enhance their therapeutic efficacy while simultaneously lowering their ocular side effects. Here the physiochemical properties and chemical stabilities of the commercially available PGAs are reviewed, and the compositions of their eye drop formulations are discussed. Furthermore, the novel PGA formulations for glaucoma treatment are reviewed.

Ocular Drug Delivery: Advancements and Innovations

Ocular drug delivery has been significantly advanced for not only pharmaceutical compounds, such as steroids, nonsteroidal anti-inflammatory drugs, immune modulators, antibiotics, and so forth, but also for the rapidly progressed gene therapy products. For conventional non-gene therapy drugs, appropriate surgical approaches and releasing systems are the main deliberation to achieve adequate treatment outcomes, whereas the scope of “drug delivery” for gene therapy drugs further expands to transgene construct optimization, vector selection, and vector engineering. The eye is the particularly well-suited organ as the gene therapy target, owing to multiple advantages. In this review, we will delve into three main aspects of ocular drug delivery for both conventional drugs and adeno-associated virus (AAV)-based gene therapy products: (1) the development of AAV vector systems for ocular gene therapy, (2) the innovative carriers of medication, and (3) administration routes progression.

Simvastatin-loaded nano-niosomes efficiently downregulates the MAPK-NF-κB pathway during the acute phase of myocardial ischemia-reperfusion injury

BACKGROUND

Simvastatin can potentially mitigate acute inflammatory phase of myocardial ischemia-reperfusion injury. However, these effects negatively influenced by its poor bioavailability, low water solubility and high metabolism. Here, we investigated the effects of SIM-loaded nano-niosomes on a rat model of MI/R injury to find a drug delivery method to tackle the barriers.

METHODS

Nano-niosomes' characteristics were identified using dynamic light scattering and transmission electron microscopy. Fifty male Wistar rats were divided into five groups: Sham; MI/R; MI/R + nano-niosome; MI/R + SIM; MI/R + SIM-loaded nano-niosomes. Left anterior descending artery was ligated for 45 min, and 3 mg/kg SIM, nano-niosomes, or SIM-loaded nano-niosomes was intramyocardially injected ten min before the onset of reperfusion. ELISA assay was used to assess cardiac injury markers (cTnI, CK-MB) and inflammatory cytokines (TNF-α, IL-6, TGF-β, MPC-1). Expression level of MAPK-NF-κB and histopathological changes were evaluated by western blot and hematoxylin & eosin staining, respectively.

RESULTS

the size of nano-niosome was 137 nm, reached to 163 nm when simvastatin was loaded. To achieve optimized niosomes span 80, a drug/cholesterol ratio of 0.4 and seven min of sonication time was applied. Optimized entrapment efficiency of SIM-loaded nano-niosomes was 98.21%. Inflammatory cytokines and the expression level of MAPK and NF-κB were reduced in rats receiving SIM-loaded nano-niosomes compared to MI/R + SIM and MI/R + SIM-loaded nano-niosomes.

CONCLUSION

Our results showed that SIM-loaded nano-niosomes could act more efficiently than SIM in alleviating the acute inflammatory response of reperfusion injury via downregulating the activation of MAPK-NF-κB.

MiRNA 24-3p-rich exosomes functionalized DEGMA-modified hyaluronic acid hydrogels for corneal epithelial healing

The damage of corneal epithelium may lead to the formation of irreversible corneal opacities and even blindness. The migration rate of corneal epithelial cells directly affects corneal repair. Here, we explored ocu-microRNA 24-3p (miRNA 24-3p) that can promote rabbit corneal epithelial cells migration and cornea repair. Exosomes, an excellent transport carrier, were exacted from adipose derived mesenchymal stem cells for loading with miRNA 24-3p to prepare miRNA 24-3p-rich exosomes (Exos-miRNA 24-3p). It can accelerate corneal epithelial migration in vitro and in vivo. For application in cornea alkali burns, we further modified hyaluronic acid with di(ethylene glycol) monomethyl ether methacrylate (DEGMA) to obtain a thermosensitive hydrogel, also reported a thermosensitive DEGMA-modified hyaluronic acid hydrogel (THH) for the controlled release of Exos-miRNA 24-3p. It formed a highly uniform and clear thin layer on the ocular surface to resist clearance from blinking and extended the drug-ocular-epithelium contact time. The use of THH-3/Exos-miRNA 24-3p for 28 days after alkali burn injury accelerated corneal epithelial defect healing and epithelial maturation. It also reduced corneal stromal fibrosis and macrophage activation. MiRNA 24-3p-rich exosomes functionalized DEGMA-modified hyaluronic acid hydrogel as a multilevel delivery strategy has a potential use for cell-free therapy of corneal epithelial regeneration.

Targeting Colorectal Cancer Cells with Niosomes Systems Loaded with Two Anticancer Drugs Models; Comparative In Vitro and Anticancer Studies

Colorectal cancer (CRC) is considered one of the most commonly diagnosed malignant diseases. Recently, there has been an increased focus on using nanotechnology to resolve most of the limitations in conventional chemotherapy. Niosomes have great advantages that overcome the drawbacks associated with other lipid drug delivery systems. They are simple, cheap, and highly stable nanocarriers. This study investigated the effectiveness of using niosomes with their amphiphilic characteristics in the incorporation of both hydrophilic and hydrophobic anticancer drugs for CRC treatment. Methods: Drug-free niosomes were formulated using a response surface D-optimal factorial design to study the cholesterol molar ratio, surfactant molar ratio and surfactant type effect on the particle size and Z-potential of the prepared niosomes. After numerical and statistical optimization, an optimized formulation having a particle size of 194.4 ± 15.5 nm and a Z-potential of 31.8 ± 1.9 mV was selected to be loaded with Oxaliplatin and Paclitaxel separately in different concentrations. The formulations with the highest entrapment efficiency (EE%) were evaluated for their drug release using the dialysis bag method, in vitro antitumor activity on HT-29 colon cancer cell line and apoptosis activity. Results: Niosomes prepared using d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) at a molar ratio 4, cholesterol (2 molar ratio) and loaded with 1 molar ratio of either Oxaliplatin or Paclitaxel provided nanosized vesicles (278.5 ± 19.7 and 251.6 ± 18.1 nm) with a Z-potential value (32.7 ± 1.01 and 31.69 ± 0.98 mV) with the highest EE% (90.57 ± 2.05 and 93.51 ± 2.97) for Oxaliplatin and Paclitaxel, respectively. These formulations demonstrated up to 48 h drug release and increased the in vitro cytotoxicity and apoptosis efficiency of both drugs up to twice as much as free drugs. Conclusion: These findings suggest that different formulation composition parameters can be adjusted to obtain nanosized niosomal vesicles with an accepted Z-potential. These niosomes could be loaded with either hydrophilic drugs such as Oxaliplatin or hydrophobic drugs such as Paclitaxel. Drug-loaded niosomes, as a unique nanomicellar system, could enhance the cellular uptake of both drugs, resulting in enhanced cytotoxic and apoptosis effects against HT-29 colon cancer cells. Oxaliplatin–niosomes and Paclitaxel–niosomes can be considered promising alternative drug delivery systems with enhanced bioavailability of these two anticancer drugs for colorectal cancer treatment.

Bibliometric and visualized analysis of ocular drug delivery from 2001 to 2020

OBJECTIVE

To perform a bibliometric analysis in the field of ocular drug delivery research to characterize the current international trends and to present visual representations of the past and emerging trends on ocular drug delivery research over the past decade.

METHOD

In this cross-sectional study, a bibliometric analysis of data retrieved and extracted from the Web of Science Core Collection (WoSCC) database was performed to analyze evolution and theme trends on ocular drug delivery research from January 1, 2001, to December 31, 2020. A total of 4334 articles on ocular drug delivery were evaluated for specific characteristics, such as publication year, journals, authors, institutions, countries/regions, references, and keywords. Co-authorship analysis, co-occurrence analysis, co-citation analysis, and network visualization were constructed by VOSviewer. Some important subtopics identified by bibliometric characterization were further discussed and reviewed.

RESULTS

From 2001 to 2020, the annual global publications increased by 746.15%, from 52 to 440. International Journal of Pharmaceutics published the most manuscripts (250 publications) and produced the highest citations (9509 citations), followed by Investigative Ophthalmology & Visual Science (202 publications) and Journal of Ocular Pharmacology and Therapeutics (136 publications). The United States (1289 publications, 31,512 citations), the University of Florida (82 publications, 2986 citations), and Chauhan, Anuj (52 publications, 2354 citations) were the most productive and impactful institution, country, and author respectively. The co-occurrence cluster analysis of the top 100 keywords form five clusters: (1) micro/nano ocular drug delivery systems; (2) the treatment of inflammation and posterior diseases; (3) macroscopic ocular drug delivery systems/devices; (4) the characteristics of drug delivery systems; (5) and the ocular drug delivery for glaucoma treatment. Diabetic macular edema, anti-VEGF, ranibizumab, bevacizumab, micelles and latanoprost, were the latest high-frequency keywords, indicating the emerging frontiers of ocular drug delivery. Further discussions into the subtopics were provided to assist researchers to determine the range of research topics and plan research direction.

CONCLUSIONS

Over the last two decades there has been a progressive increase in the number of publications and citations on research related to ocular drug delivery across many countries, institutions, and authors. The present study sheds light on current trends, global collaboration patterns, basic knowledge, research hotspots, and emerging frontiers of ocular drug delivery. Novel solutions for ocular drug delivery and the treatment of inflammation and posterior diseases were the major themes over the last 20 years.

Polymeric Drug Delivery Devices: Role in Cornea and External Disease

ABSTRACT

The field of ophthalmic drug delivery is undergoing rapid changes not only in the evolution of pharmacologic agents but also in the novel drug delivery vehicles. The ocular surface has limitations to drug penetration because of the presence of tight junctions between basal epithelial cells, which limits the amount of drug that can be absorbed after topical instillation. In addition, nasolacrimal drainage reduces the precorneal residence time significantly. Contact lenses (CLs) have been considered as possible carriers for topical medications because they reside on the ocular surface for a sufficient length of time, and pharmacologic agents may be copolymerized with hydrogels allowing controlled drug diffusion. This strategy reduces the frequency of dosage while improving compliance. Modification of drug delivery vehicles is essential to allow sustained release of the drug from a polymeric complex, facilitate stability and residence time of the drug on the precorneal tear film, and improve penetration into biologic membranes. This review focuses on updates in CL-based and non-CL-based strategies in ophthalmic drug delivery.

Targeted drug delivery vehicles mediated by nanocarriers and aptamers for posterior eye disease therapeutics: barriers, recent advances and potential opportunities

Nanomedicine and aptamer have excellent potential in giving play to passive and active targeting respectively, which are considered to be effective strategies in the retro-ocular drug delivery system. The presence of closely adjoined tissue structures in the eye makes it difficult to administer the drug in the posterior segment of the eye. The application of nanomedicine could represent a new avenue for the treatment, since it could improve penetration, achieve targeted release, and improve bioavailability. Additionally, a novel type of targeted molecule aptamer with identical objective was proposed. As an emerging molecule, aptamer shows the advantages of penetration, non-toxicity, and high biocompatibility, which make it suitable for ocular drug administration. The purpose of this paper is to summarize the recent studies on the effectiveness of nanoparticles as a drug delivery to the posterior segment of the eye. This paper also creatively looks forward to the possibility of the combined application of nanocarriers and aptamers as a new method of targeted drug delivery system in the field of post-ophthalmic therapy.