Recent Developments of Nanostructures for the Ocular Delivery of Natural Compounds

In vitro and in vivo studies of ocular topically administered NLC for the treatment of uveal melanoma

Uveal melanoma is one of the most common and aggressive intraocular malignancies, and, due to its great capability of metastasize, it constitutes the most incident intraocular tumor in adults. However, to date there is no effective treatment since achieving the inner ocular tissues still constitutes one of the greatest challenges in actual medicine, because of the complex structure and barriers. Uncoated and PEGylated nanostructured lipid carriers were developed to achieve physico-chemical properties (mean particle size, homogeneity, zeta potential, pH and osmolality) compatible for the ophthalmic administration of (S)-(-)-MRJF22, a new custom-synthetized prodrug for the potential treatment of uveal melanoma. The colloidal physical stability was investigated at different temperatures by Turbiscan® Ageing Station. Morphology analysis and mucoadhesive studies highlighted the presence of small particles suitable to be topically administered on the ocular surface. In vitro release studies performed using Franz diffusion cells demonstrated that the systems were able to provide a slow and prolonged prodrug release. In vitro cytotoxicity test on Human Corneal Epithelium and Human Uveal Melanoma cell lines and Hen's egg-chorioallantoic membrane test showed a dose-dependent cytotoxic effect of the free prodrug on corneal cells, whose cytocompatibility improved when encapsulated into nanoparticles, as also confirmed by in vivo studies on New Zealand albino rabbits. Antiangiogenic capability and preventive anti-inflammatory properties were also investigated on embryonated eggs and rabbits, respectively. Furthermore, preliminary in vivo biodistribution images of fluorescent nanoparticles after topical instillation in rabbits' eyes, suggested their ability to reach the posterior segment of the eye, as a promising strategy for the treatment of choroidal uveal melanoma.

Potential therapeutic effects of green tea (Camellia sinensis) in eye diseases, a review

This review aims to evaluate the therapeutic potential of green tea (GT), scientifically named Camellia sinensis, in treating eye diseases. We provide an overview of the ingredients and traditional use of Camellia sinensis, followed by a detailed discussion of its therapeutic uses in various eye diseases, including ocular surface diseases (allergic diseases, dry eye, pterygium, and infections), cataract, glaucoma, uveitis, retinal diseases, and optic nerve diseases. The pharmacologic activities related to ocular diseases, such as anti-vascular endothelial growth factor, aldose reductase inhibitor activity, anti-bacterial, anti-inflammatory, and antioxidant effects are also explored in this review. The dose and route of administration of GT in various studies are discussed. Safety issues related to the use of GT, such as the side effects associated with high doses and long-term use, are also addressed. The review highlights the potential of GT as a natural therapeutic agent for a variety of ocular diseases. Its various pharmacologic activities make it a promising treatment option. However, more well-designed studies are needed to determine the optimal dose and route of administration and to assess its long-term safety and efficacy. Overall, GT appears to be a promising adjunct therapy for various ocular diseases.

A Clinical, Pharmacological, and Formulation Evaluation of Melatonin in the Treatment of Ocular Disorders-A Systematic Review

Melatonin's cytoprotective properties may have therapeutic implications in treating ocular diseases like glaucoma and age-related macular degeneration. Literature data suggest that melatonin could potentially protect ocular tissues by decreasing the production of free radicals and pro-inflammatory mediators. This study aims to summarize the screened articles on melatonin's clinical, pharmacological, and formulation evaluation in treating ocular disorders. The identification of relevant studies on the topic in focus was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA 2020) guidelines. The studies were searched in the following databases and web search engines: Pubmed, Scopus, Science Direct, Web of Science, Reaxys, Google Scholar, Google Patents, Espacenet, and Patentscope. The search time interval was 2013-2023, with the following keywords: melatonin AND ocular OR ophthalmic AND formulation OR insert AND disease. Our key conclusion was that using melatonin-loaded nano-delivery systems enabled the improved permeation of the molecule into intraocular tissues and assured controlled release profiles. Although preclinical studies have demonstrated the efficacy of developed formulations, a considerable gap has been observed in the clinical translation of the results. To overcome this failure, revising the preclinical experimental phase might be useful by selecting endpoints close to clinical ones.

A Mini-review on New Developments in Nanocarriers and Polymers for Ophthalmic Drug Delivery Strategies

The eye is an important and vital organ of the human body consisting of two segments - anterior and posterior segments and these segments are associated with many diseases. This review elaborates upon the various eye-related diseases with their medications and carriers used to deliver them. Delivery strategies include drugs encapsulated into liposomes, polymeric micelles of drugs, solid lipid nanoparticles, nanostructured lipid carriers, nano emulsions, and Nanosuspension used to improve penetrating properties, bioavailability, and residence time of the drugs as examples available in the literature. With regard to this, different forms of ocular drug delivery are classified and elaborated. Additionally, the possibility of addressing the physical and chemical complexities of ocular diseases and how they could be overcome with environmentally stable nanoformulations are briefly discussed. Enhanced drug delivery efficiency with various novel pharmaceuticals along with enhanced uptake by different routes/modes of drug administration. Current advancements in drug carrier systems, i.e., nanocarriers, have shown promise for improving the retention time, drug permeation and prolonging the duration of release of the drug in the ocular site. Bio-degradable polymers investigated for the preparation of nanocarriers for the entrapment of drugs and to enhance the efficacy through improved adherence of tissue in the eye, sustained release measures, enhanced bioavailability, lower toxicity, and targeted delivery is applicable. This review covers the introduction of various nanocarriers and polymers for ocular drug delivery with the purpose of enhancing the absorption, retention and bioavailability of medications in the eye.

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.

Preparation of Tetrandrine Nanocrystals by Microfluidic Method and Its In Vitro and In Vivo Evaluation

The anti-hepatocellular carcinoma effects of TET are acknowledged, but its application is hindered by its poor water solubility and low bioavailability. Conventional methods for nanocrystal preparation are laborious and lack control. To address these limitations, we propose employing the microfluidic method in the preparation of TET nanocrystals, aiming to enhance the aforementioned constraints. The objectives of this study were to prepare TET nanocrystals (TET-NC@GL) using a Y-microfluidic method with glycyrrhetinic acid (GL) as a stabilizer. The optimal preparation prescription was determined through a single-factor test and Box-Behnken response surface method. Additionally, the nanocrystals prepared with the commonly used stabilizer polyvinylpyrrolidone K30 (PVPK30), known as TET-NC@PVPK30, were characterized and evaluated for their toxicity to HepG2 cells. Hybridized nanocrystals (TET-HNC@GL and TET-HNC@PVPK30) were synthesized using a water-soluble aggregation-induced emission (AIE) fluorescent probe (TVP). Qualitative and quantitative cellular uptake experiments were conducted using these hybridized nanocrystals. Conducting in vivo pharmacokinetic assays evaluates the relative bioavailability of nanocrystals. The results indicated that TET-NC@GL, optimized using the response surface method, had a particle size of 136.47 ± 3.31 nm and a PDI of 0.219 ± 0.002. The administration of TET-NC@GL significantly enhanced the cell inhibition rate compared to the TET group and the TET-NC@PVPK30 group (P < 0.01). Moreover, the qualitative and quantitative cellular uptake results revealed a significant enhancement in cellular uptake in the TET-HNC@GL administration group compared to the TET-HNC@PVPK30 group (P < 0.01). In vivo pharmacokinetic results showed that the bioavailability of TET-NC@GL group was 3.5 times higher than that of the TET group. The results demonstrate the successful preparation of TET-NC@GL nanocrystals.

Trimethylated chitosan-coated flexible liposomes with resveratrol for topical drug delivery to reduce blue-light-induced retinal damage

LED-related blue-light-induced damage can cause eye diseases. However, drug delivery in patients with ocular diseases is faced with various challenges. In this study, we developed flexible liposomes based on trimethylated chitosan (TMC-Lipo) to deliver resveratrol for the treatment of retinal diseases. Flexible liposomes can easily cross various biological barriers. Chitosan and its derivatives have adhesive properties and are widely used in mucoadhesive drug delivery systems. Therefore, we wrapped flexible liposomes with trimethylated chitosan via electrostatic adsorption. The charge of the flexible liposomes became positive after encapsulation in TMC, and they remained stable in artificial tears. We assessed the safety of TMC-Lipo in cellular and zebrafish experiments and found that it can be safely used. In addition, treatment with TMC-Lipo significantly reduced H2O2-induced damage to ARPE-19 cells, restored mitochondrial membrane potential, and protected the cells. TMC-Lipo more easily reached the posterior ocular segment of the mice than liposome nanoparticles and attenuated blue-light-induced retinal cytopathy. Our study demonstrates that effective eye drop formulations can be developed based on trimethylated chitosan, which provides a promising approach for the treatment of ocular diseases.

Drug delivery methods based on nanotechnology for the treatment of eye diseases

One of the most difficult tasks among the numerous medication delivery methods is ocular drug delivery. Despite having effective medications for treating ocular illness, we have not yet managed to develop an appropriate drug delivery strategy with the fewest side effects. Nanotechnology has the potential to significantly address the drawbacks of current ocular delivery systems, such as their insufficient therapeutic effectiveness and unfavourable side effects from invasive surgery or systemic exposure. The objective of the current research is to highlight and update the most recent developments in nano-based technologies for the detection and treatment of ocular diseases. Even if more work has to be done, the advancements shown here might lead to brand-new, very practical ocular nanomedicines.

Challenges and strategies for ocular posterior diseases therapy via non-invasive advanced drug delivery

Posterior segment diseases, such as age-related macular degeneration (AMD) and diabetic retinopathy (DR) are vital factor that seriously threatens human vision health and quality of life, the treatment of which poses a great challenge to ophthalmologists and ophthalmic scientists. In particular, ocular posterior drug delivery in a non-invasive manner is highly desired but still faces many difficulties such as rapid drug clearance, limited permeability and low drug accumulation at the target site. At present, many novel non-invasive topical ocular drug delivery systems are under development aiming to improve drug delivery efficiency and biocompatibility for better therapy of posterior segment oculopathy. The purpose of this review is to present the challenges in the noninvasive treatment of posterior segment diseases, and to propose strategies to tackle these bottlenecks. First of all, barriers to ocular administration were introduced based on ocular physiological structure and behavior, including analysis and discussion on the influence of ocular structures on noninvasive posterior segment delivery. Thereafter, various routes of posterior drug delivery, both invasive and noninvasive, were illustrated, along with the respective anatomical obstacles that need to be overcome. The widespread and risky application of invasive drug delivery, and the need to develop non-invasive local drug delivery with alternative to injectable therapy were described. Absorption routes through topical administration and strategies to enhance ocular posterior drug delivery were then discussed. As a follow-up, an up-to-date research advances in non-invasive delivery systems for the therapy of ocular fundus lesions were presented, including different nanocarriers, contact lenses, and several other carriers. In conclusion, it seems feasible and promising to treat posterior oculopathy via non-invasive local preparations or in combination with appropriate devices.

Rutin: Family Farming Products' Extraction Sources, Industrial Applications and Current Trends in Biological Activity Protection

In vitro and in vivo studies have demonstrated the bioactivity of rutin, a dietary flavonol naturally found in several plant species. Despite widespread knowledge of its numerous health benefits, such as anti-inflammatory, antidiabetic, hepatoprotective and cardiovascular effects, industrial use of rutin is still limited due to its low solubility in aqueous media, the characteristic bitter and astringent taste of phenolic compounds and its susceptibility to degradation during processing. To expand its applications and preserve its biological activity, novel encapsulation systems have been developed. This review presents updated research on the extraction sources and methodologies of rutin from fruit and vegetable products commonly found in a regular diet and grown using family farming approaches. Additionally, this review covers quantitative analysis techniques, encapsulation methods utilizing nanoparticles, colloidal and heterodisperse systems, as well as industrial applications of rutin.

Candida Biofilm Eye Infection: Main Aspects and Advance in Novel Agents as Potential Source of Treatment

Fungi represent a very important cause of microbial eye infections, especially in tropical and developing countries, as they could cause sight-threating disease, such as keratitis and ocular candidiasis, resulting in irreversible vision loss. Candida species are among the most frequent microorganisms associated with fungal infection. Although Candida albicans is still the most frequently detected organism among Candida subspecies, an important increase in non-albicans species has been reported. Mycotic infections often represent an important diagnostic-clinical problem due to the difficulties in performing the diagnosis and a therapeutic problem due to the limited availability of commercial drugs and the difficult penetration of antifungals into ocular tissues. The ability to form biofilms is another feature that makes Candida a dangerous pathogen. In this review, a summary of the state-of-the-art panorama about candida ocular pathology, diagnosis, and treatment has been conducted. Moreover, we also focused on new prospective natural compounds, including nanoparticles, micelles, and nanocarriers, as promising drug delivery systems to better cure ocular fungal and biofilm-related infections. The effect of the drug combination has also been examined from the perspective of increasing efficacy and improving the course of infections caused by Candida which are difficult to fight.

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.

Dendrimers as Nanocarriers for the Delivery of Drugs Obtained from Natural Products

Natural products have proven their value as drugs that can be therapeutically beneficial in the treatment of various diseases. However, most natural products have low solubility and poor bioavailability, which pose significant challenges. To solve these issues, several drug nanocarriers have been developed. Among these methods, dendrimers have emerged as vectors for natural products due to their superior advantages, such as a controlled molecular structure, narrow polydispersity index, and the availability of multiple functional groups. This review summarizes current knowledge on the structures of dendrimer-based nanocarriers for natural compounds, with a particular focus on applications in alkaloids and polyphenols. Additionally, it highlights the challenges and perspectives for future development in clinical therapy.

Advances in Nanogels for Topical Drug Delivery in Ocular Diseases

Nanotechnology has accelerated the development of the pharmaceutical and medical technology fields, and nanogels for ocular applications have proven to be a promising therapeutic strategy. Traditional ocular preparations are restricted by the anatomical and physiological barriers of the eye, resulting in a short retention time and low drug bioavailability, which is a significant challenge for physicians, patients, and pharmacists. Nanogels, however, have the ability to encapsulate drugs within three-dimensional crosslinked polymeric networks and, through specific structural designs and distinct methods of preparation, achieve the controlled and sustained delivery of loaded drugs, increasing patient compliance and therapeutic efficiency. In addition, nanogels have higher drug-loading capacity and biocompatibility than other nanocarriers. In this review, the main focus is on the applications of nanogels for ocular diseases, whose preparations and stimuli-responsive behaviors are briefly described. The current comprehension of topical drug delivery will be improved by focusing on the advances of nanogels in typical ocular diseases, including glaucoma, cataracts, dry eye syndrome, and bacterial keratitis, as well as related drug-loaded contact lenses and natural active substances.

Enhancing the stability of lutein emulsions with a water-soluble antioxidant and a oil-soluble antioxidant

Lutein is critical for protecting the eye against light damage. The low solubility and high sensitivity of lutein to environmental stresses prevent its further application. The hypothesis is that the combination of one water-soluble antioxidant and one oil-soluble antioxidant will be beneficial to improve the stability of lutein emulsions. A low-energy method was performed to prepare lutein emulsions. The combination of a lipid-soluble antioxidant (propyl gallate or ethylenediaminetetraacetic acid) and a water-soluble antioxidant (tea polyphenol or ascobic acid) were investigated for improving the lutein retention rates. It was shown that the highest lutein retention rate was achieved by using propyl gallate and tea polyphenol, 92.57%, at Day 7. It was proven that the lutein retention rates of emulsions with propyl gallate and tea polyphenol were 89.8%, 73.5% and 55.2% at 4 °C, 25 °C and 37 °C, respectively, at Day 28. The current study is helpful to prepare for the further application of lutein emulsions for ocular delivery.

Nanofibers in Ocular Drug Targeting and Tissue Engineering: Their Importance, Advantages, Advances, and Future Perspectives

Nanofibers are frequently encountered in daily life as a modern material with a wide range of applications. The important advantages of production techniques, such as being easy, cost effective, and industrially applicable are important factors in the preference for nanofibers. Nanofibers, which have a broad scope of use in the field of health, are preferred both in drug delivery systems and tissue engineering. Due to the biocompatible materials used in their construction, they are also frequently preferred in ocular applications. The fact that they have a long drug release time as a drug delivery system and have been used in corneal tissue studies, which have been successfully developed in tissue engineering, stand out as important advantages of nanofibers. This review examines nanofibers, their production techniques and general information, nanofiber-based ocular drug delivery systems, and tissue engineering concepts in detail.

Nanotechnology based drug delivery systems for the treatment of anterior segment eye diseases

Diseases affecting the anterior segment of the eye are the primary causes of vision impairment and blindness globally. Drug administration through the topical ocular route is widely accepted because of its user/patient friendliness - ease of administration and convenience. However, it remains a significant challenge to efficiently deliver drugs to the eye through this route because of various structural and physiological constraints that restrict the distribution of therapeutic molecules into the ocular tissues. The bioavailability of topically applied ocular medications such as eye drops is typically less than 5%. Developing novel delivery systems to increase the retention time on the ocular surfaces and permeation through the cornea is one of the approaches adopted to boost the bioavailability of topically administered medications. Drug delivery systems based on nanotechnology such as micelles, nanosuspensions, nanoparticles, nanoemulsions, liposomes, dendrimers, niosomes, cubosomes and nanowafers have been investigated as effective alternatives to conventional ocular delivery systems in treating diseases of the anterior segment of the eye. This review discussed different nanotechnology-based delivery systems that are currently investigated for treating and managing diseases affecting the anterior ocular tissues. We also looked at the challenges in translating these systems into clinical use and the prospects of nanocarriers as a vehicle for the delivery of phytoactive compounds to the anterior segment of the eye.