Topical ophthalmic lipid nanoparticle formulations (SLN, NLC) of indomethacin for delivery to the posterior segment ocular tissues

Augmented ocular uptake and anti-inflammatory efficacy of decorated Genistein-loaded NLCs incorporated in in situ gel

Genistein (Gen); a naturally occurring isoflavone, acts as a tyrosine kinase inhibitor and efficiently downregulates inflammatory cytokines, which are pivotal in eye inflammation. Also, Gen suffers from sparse ocular bioavailability due to poor solubility. In this work, nanostructured lipid carriers (NLCs) were successfully fabricated by using solid (stearic acid and compritol) and liquid (oleic acid) lipids. The optimized Gen-loaded NLCs showed a nanosize range of 140-246 nm, ≥ 98 % entrapment efficiency, and controlled release over 48 h. The ζ-potential of NLCs was increased from -27.3 mV to 25-27.4 mV due to surface modification with chitosan (CS) or eudragit RS100 (ERS 100). All NLCs showed prominent biocompatibility with enhanced cellular uptake on corneal stromal fibroblasts. Moreover, the different NLCs were incorporated into a mucoadhesive in situ gel. The optimized in situ gel (G9), containing 20 % poloxamers and 0.5 % hydroxyethyl cellulose, exhibited excellent gelling ability within 10.5 s, gelling temperature at 33.1 ± 0.6 ℃, spreadability diameter of 4.73 ± 0.12 cm, shear-thinning behavior, and 20 min ex vivo mucoadhesion time with drug release for 120 h. The in vivo results showed distinguished permeation and distribution potential for ocular delivery. In vivo anti-inflammatory effects after 3 days of treatment with CS-Gen-NLCs/G9 and ERS-Gen-NLCs/G9 revealed a downregulation of interleukin-6 levels in the cornea and retina compared to the untreated group. Our research highlights the promising anti-inflammatory potential of ERS-Gen-NLCs/G9 as an efficient, non-irritant Gen nanodelivery system for managing anterior and posterior ocular inflammation.

Improving corneal permeability of dexamethasone using penetration enhancing agents: First step towards achieving topical drug delivery to the retina

With an ever-increasing burden of vision loss caused by diseases of the posterior ocular segment, there is an unmet clinical need for non-invasive treatment strategies. Topical drug application using eye drops suffers from low to negligible bioavailability to the posterior segment as a result of static and dynamic defensive ocular barriers to penetration, while invasive delivery systems are expensive to administer and suffer potentially severe complications. As the cornea is the main anatomical barrier to uptake of topically applied drugs from the ocular surface, we present an approach to increase corneal permeability of a corticosteroid, dexamethasone sodium-phosphate (DSP), using a novel penetration enhancing agent (PEA). We synthesised a novel polyacetylene (pAc) polymer and compared its activity to two previously described cell penetrating peptide (CPP) based PEAs, TAT and penetratin, with respect to increasing transcorneal permeability of DSP in a rapid ex-vivo porcine corneal assay over 60 min. The transcorneal apparent permeability coefficients (Papp) for diffusion of pAc, and fluorescein isothiocyanate (FITC) conjugated TAT and penetratin were up to 5 times higher (p < 0.001), when compared to controls. When pAc was used in formulation with DSP, an almost 5-fold significant increase was observed in Papp of DSP across the cornea (p = 0.0130), a significant 6-fold increase with TAT (p = 0.0377), and almost 7-fold mean increase with penetratin (p = 0.9540). Furthermore, we investigated whether the PEAs caused any irreversible damage to the barrier integrity of the corneal epithelium by measuring transepithelial electrical resistance (TEER) and immunostaining of tight junction proteins using zonula occludens-1 (ZO-1) and occludin antibodies. There was no damage or structural toxicity, and the barrier integrity was preserved after PEA application. Finally, an in-vitro cytotoxicity assessment of all PEAs in human retinal pigment epithelium cells (ARPE-19) demonstrated that all PEAs were very well-tolerated, with IC50 values of 64.79 mM for pAc and 1335.45 µM and 87.26 µM for TAT and penetratin, respectively. Our results suggest that this drug delivery technology could potentially be used to achieve a significantly higher intraocular therapeutic bioavailability after topical eye drop administration, than currently afforded.

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.

Combination of Indomethacin with Nanostructured Lipid Carriers for Effective Anticancer Therapy

Purpose

The anticancer potential of indomethacin and other nonsteroidal anti-inflammatory drugs (NSAIDs) in vitro, in vivo, and in clinical trials is well known and widely reported in the literature, along with their side effects, which are mainly observed in the gastrointestinal tract. Here, we present a strategy for the application of the old drug indomethacin as an anticancer agent by encapsulating it in nanostructured lipid carriers (NLC). We describe the production method of IND-NLC, their physicochemical parameters, and the results of their antiproliferative activity against selected cancer cell lines, which were found to be higher compared to the activity of free indomethacin.

Methods

IND-NLC were fabricated using the hot high-pressure homogenization method. The nanocarriers were physicochemically characterized, and their biopharmaceutical behaviour and therapeutic efficacy were evaluated in vitro.

Results

Lipid nanoparticles IND-NLC exhibited a particle size of 168.1 nm, a negative surface charge (-30.1 mV), low polydispersity index (PDI of 0.139), and high encapsulation efficiency (over 99%). IND-NLC were stable for over 60 days and retained integrity during storage at 4 °C and 25 °C. The potential therapeutic benefits of IND-NLC were screened using in vitro cancer models, where nanocarriers with encapsulated drug effectively inhibited the growth of breast cancer cell line MDA-MB-468 at dosage 15.7 μM.

Conclusion

We successfully developed IND-NLC for delivery of indomethacin to cancer cells and confirmed their antitumoral efficacy in in vitro studies. The results suggest that indomethacin encapsulated in lipid nanoparticles possesses high anticancer potential. Moreover, the presented strategy is highly promising and may offer a new alternative for future therapeutic drug innovations.

Recent advances and strategies for nanocarrier-mediated topical therapy and theranostic for posterior eye disease

Posterior eye disorders, such as age-related macular degeneration, diabetic retinopathy, and glaucoma, have a significant impact on human quality of life and are the primary cause of age-related retinal diseases among adults. There is a pressing need for innovative topical approaches to treat posterior eye disorders, as current methods often rely on invasive procedures with inherent risks. Limited success was attained in the realm of topical ophthalmic delivery through non-invasive means. Additionally, there exists a dearth of literature that delves into the potential of this approach for drug delivery and theranostic purposes, or that offers comprehensive design strategies for nanocarrier developers to surmount the significant physiological ocular barriers. This review offers a thorough and up-to-date state-of-the-art overview of 40 studies on therapeutic loaded nanocarriers and theranostic devices that, to the best of our knowledge, represent all successful works that reached posterior eye segments through a topical non-invasive administration. Most importantly, based on the successful literature studies, this review provides a comprehensive summary of the potential design strategies that can be implemented during nanocarrier development to overcome each ocular barrier.

Engineering mannose-functionalized nanostructured lipid carriers by sequential design using hybrid artificial intelligence tools

Nanostructured lipid carriers (NLCs) hold significant promise as drug delivery systems (DDS) owing to their small size and efficient drug-loading capabilities. Surface functionalization of NLCs can facilitate interaction with specific cell receptors, enabling targeted cell delivery. Mannosylation has emerged as a valuable tool for increasing the ability of nanoparticles to be recognized and internalized by macrophages. Nevertheless, the design and development of functionalized NLC is a complex task that entails the optimization of numerous variables and steps, making the process challenging and time-consuming. Moreover, no previous studies have been focused on evaluating the functionalization efficiency. In this work, hybrid Artificial Intelligence technologies are used to help in the design of mannosylated drug loaded NLCs. Artificial neural networks combined with fuzzy logic or genetic algorithms were employed to understand the particle formation processes and optimize the combinations of variables for the different steps in the functionalization process. Mannose was chemically modified to allow, for the first time, functionalization efficiency quantification and optimization. The proposed sequential methodology has enabled the design of a robust procedure for obtaining stable mannosylated NLCs with a uniform particle size distribution, small particle size (< 100 nm), and a substantial positive zeta potential (> 20mV). The incorporation of mannose on the surfaces of these DDS following the established protocols achieved > 85% of functionalization efficiency. This high effectiveness should enhance NLC recognition and internalization by macrophages, thereby facilitating the treatment of chronic inflammatory diseases.

Self-assembled sodium alginate polymannuronate nanoparticles for synergistic treatment of ophthalmic infection and inflammation: Preparation optimization and in vitro/vivo evaluation

Frequent administrations are often needed during the treatment of ocular diseases due to the low bioavailability of the existing eye drops owing to inadequate corneal penetration and rapid drug washout. Herein, sodium alginate polymannuronate (SA) nanocarriers were developed using ionic gelation method that can provide better bioavailability through mucoadhesivity and sustained drug release by binding to the ocular mucus layer. This study disproves the common belief that only the G block of SA participates in the crosslinking reaction during ionic gelation. Self-assembly capability due to the linear flexible structure of the M block, better biocompatibility than G block along with the feasibility of controlling physicochemical characteristics postulate a high potential for designing efficient ocular drug delivery systems. Initially, four crosslinkers of varied concentrations were investigated. Taguchi design of experiment revealed the statistically significant effect of the crosslinker type and concentration on the particle size and stability. The best combination was detected by analyzing the particle size and zeta potential values that showed the desired microstructural properties for ocular barrier penetration. The desired combination was SA-Ca-1 that had particle size within the optimal corneal penetration range, that is 10-200 nm (135 nm). The drug carriers demonstrated excellent entrapment efficiency (∼89 % for Ciprofloxacin and ∼96 % for Dexamethasone) along with a sustained and simultaneous release of dual drug for at least 2 days. The nanoparticles also showed biocompatibility (4 ± 0.6 % hemolysis) and high mucoadhesivity (73 ± 2 % for 0.25 g) which was validated by molecular docking analysis. The prepared formulation was able to reduce the scleral inflammation of the rabbit uveitis models significantly within 3 days. Thus, the eye drop showed remarkable potential for efficient drug delivery leading to faster recovery.

Age-Related Macular Degeneration - Therapies and Their Delivery

Age-related macular degeneration (ARMD) is a degenerative ocular disease that is the most important cause of irreversible vision loss in old-aged people in developed countries. Around fifty percent of vision impairments in developed countries are due to ARMD. It is a multifaceted disease that is associated with both genetic and environmental risk factors. The most important treatments option for ARMD includes laser photocoagulation, photodynamic therapy (PDT), Anti-VEGF Injections, and combination therapies. In this review, we also propose that topical ocular drug delivery with nanocarriers has more attention for the treatment of ARMD. The nanocarriers were specially designed for enhanced corneal residential time, prolonged drug release and action, and minimizing the frequency of administrations. Different types of nanocarriers were developed for the topical ocular delivery system, such as nanomicelles, nanoemulsions, nanosuspensions, liposomes, and polymeric nanoparticles. These topical ocular nanocarriers were administered topically, and they can fix the hydrophobic substances, increase solubility and improve the bioavailability of an administered drug. Hence the topical ocular delivery systems with nanocarriers provide a safe and effective therapeutic strategy and promising tool for the treatment of posterior segment ocular diseases ARMD.

Nanostructured Lipid Carriers Mediated Drug Delivery to Posterior Segment of Eye and their In-vivo Successes

BACKGROUND

The disease of the posterior segment of the eye is a major concern worldwide, and it affects more than 300 million people and leads to serious visual deterioration. The current treatment available is invasive and leads to serious eye complications. These shortcomings and patient discomfort lead to poor patient compliance. In the last decade, Nanostructured lipid carriers (NLC) have established a remarkable milestone in the delivery of drug substances to the posterior segment of the eye. Additionally, NLC can reduce the clearance due to adhesive properties which are imparted due to nano-metric size. This attribute might reduce the adverse effects associated with intravitreal therapy and thus enhance therapeutic efficacy, eventually raising patient adherence to therapy. The current review provides an inclusive account of NLC as a carrier to target diseases of the posterior segment of the eye.

OBJECTIVE

The review focuses on the various barrier encountered in the delivery of drugs to the posterior segment of the eye and the detail about the physicochemical property of drug substances that are considered to be suitable candidates for encapsulation to lipid carriers. Therefore, a plethora of literature has been included in this review. The review is an attempt to describe methods adopted for assessing the in-vivo behavior that strengthens the potential of NLC to treat the disease of the posterior segment of the eye.

CONCLUSION

These NLC-based systems have proven to be a promising alternative in place of invasive intravitreal injections with improved patient compliance.

Poloxamer sols endowed with in-situ gelability and mucoadhesion by adding hypromellose and hyaluronan for prolonging corneal retention and drug delivery

The purpose of this study was to develop poloxamer (P407)-based in-situ thermogellable hydrogels with reducing concentration of P407 by adding hypromellose (HPMC) and with enhancing mucoadhesion of resulting hydrogels by adding hyaluronic acid (HA) for prolonging ocular delivery of hydroxypropyl-β-cyclodextrin (HPβCD)-solubilized testosterone (TES). Results demonstrated that 0.5% TES solution was successfully solubilized with adding 10% HPβCD. Non-gellable 13% P407 sol became in-situ gellable with adding 2.0-2.5% HPMC and mucoadhesibility was further imporved with adding 0.3% HA-L (low MW) or HA-H (high MW). Optimized 0.5% HPβCD-solubilized TES P407-based thermogellable hydrogels with enhancement of mucoadhesion for prolonging ocular delivery comprised 13% P407, 2.5% HPMC, and 0.3% HA-L or HA-H. Furthermore, rheological measurements under simulated eye blinking confirmed that non-thixotropic properties of optimized hydrogels could be spreaded evenly and retain a greater amount of drug-loaded hydrogels on the ocular surface for a longer period to prolong drug delivery. Compared with conventional eye drops, the prolonged residence time of optimized hydrogels from ex vivo and in vivo studies were observed, indicating relationships between rheological properties and in vivo performances. It was concluded that P407-based thermosensitive hydrogels with reducing concentration of P407 and enhancing mucoadhesion was successfully formulated by adding 2.5% HPMC and 0.3% HA in 13% P407 for potentially accomplishing effective clinical treatment of DED.

Next-generation nanomaterials: advancing ocular anti-inflammatory drug therapy

Ophthalmic inflammatory diseases, including conjunctivitis, keratitis, uveitis, scleritis, and related conditions, pose considerable challenges to effective management and treatment. This review article investigates the potential of advanced nanomaterials in revolutionizing ocular anti-inflammatory drug interventions. By conducting an exhaustive analysis of recent advancements and assessing the potential benefits and limitations, this review aims to identify promising avenues for future research and clinical applications. The review commences with a detailed exploration of various nanomaterial categories, such as liposomes, dendrimers, nanoparticles (NPs), and hydrogels, emphasizing their unique properties and capabilities for accurate drug delivery. Subsequently, we explore the etiology and pathophysiology of ophthalmic inflammatory disorders, highlighting the urgent necessity for innovative therapeutic strategies and examining recent preclinical and clinical investigations employing nanomaterial-based drug delivery systems. We discuss the advantages of these cutting-edge systems, such as biocompatibility, bioavailability, controlled release, and targeted delivery, alongside potential challenges, which encompass immunogenicity, toxicity, and regulatory hurdles. Furthermore, we emphasize the significance of interdisciplinary collaborations among material scientists, pharmacologists, and clinicians in expediting the translation of these breakthroughs from laboratory environments to clinical practice. In summary, this review accentuates the remarkable potential of advanced nanomaterials in redefining ocular anti-inflammatory drug therapy. We fervently support continued research and development in this rapidly evolving field to overcome existing barriers and improve patient outcomes for ophthalmic inflammatory disorders.

Gatifloxacin Loaded Nano Lipid Carriers for the Management of Bacterial Conjunctivitis

Bacterial conjunctivitis (BC) entails inflammation of the ocular mucous membrane. Early effective treatment of BC can prevent the spread of the infection to the intraocular tissues, which could lead to bacterial endophthalmitis or serious visual disability. In 2003, gatifloxacin (GTX) eyedrops were introduced as a new broad-spectrum fluoroquinolone to treat BC. Subsequently, GTX use was extended to other ocular bacterial infections. However, due to precorneal loss and poor ocular bioavailability, frequent administration of the commercial eyedrops is necessary, leading to poor patient compliance. Thus, the goal of the current investigation was to formulate GTX in a lipid-based drug delivery system to overcome the challenges with the existing marketed eyedrops and, thus, improve the management of bacterial conjunctivitis. GTX-NLCs and SLNs were formulated with a hot homogenization-probe sonication method. The lead GTX-NLC formulation was characterized and assessed for in vitro drug release, antimicrobial efficacy (against methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa), and ex vivo permeation. The lead formulation exhibited desired physicochemical characteristics, an extended release of GTX over a 12 h period, and was stable over three months at the three storage conditions (refrigerated, room temperature, and accelerated). The transcorneal flux and permeability of GTX from the GTX-NLC formulation were 5.5- and 6.0-fold higher in comparison to the commercial eyedrops and exhibited a similar in vitro antibacterial activity. Therefore, GTX-NLCs could serve as an alternative drug delivery platform to improve treatment outcomes in BC.

Natamycin Ocular Delivery: Challenges and Advancements in Ocular Therapeutics

Fungal keratitis, an ocular fungal infection, is one of the leading causes of monocular blindness. Natamycin has long been considered the mainstay drug used for treating fungal keratitis and is the only US Food and Drug Administration (USFDA)-approved drug, commercially available as a topical 5% w/v suspension. Furthermore, ocular fungal infection treatment takes a few weeks to months to recover, and the available marketed antifungal suspensions are associated with poor residence time, limited bioavailability (< 5%) and high dosing frequency as well as minor irritation and discomfort. Despite these challenges, natamycin is still the preferred drug choice for treating fungal keratitis, as it has fewer side effects and less ocular toxicity and is more effective against Fusarium species than other antifungal agents. Several novel therapeutic approaches for the topical delivery of natamycin have been reported to overcome the challenges posed by the conventional dosage forms and to improve ocular bioavailability for the efficient management of fungal keratitis. Current progress in the delivery systems uses approaches aimed at improving the corneal residence time, bioavailability and antifungal potency, thereby reducing the dose and dosing frequency of natamycin. In this review, we discuss the various strategies explored to overcome the challenges present in ocular drug delivery of natamycin and improve its bioavailability for ocular therapeutics.

The effect of charges on the corneal penetration of solid lipid nanoparticles loaded econazole after topical administration in rabbits

Fungal keratitis is an infectious disease caused by pathogenic fungi with a high blindness rate. Econazole (ECZ) is an imidazole antifungal drug with insoluble ability. Econazole-loaded solid lipid nanoparticles (E-SLNs) were prepared by microemulsion method, then modified with positive and negative charge. The mean diameter of cationic E-SLNs, nearly neutral E-SLNs and anionic E-SLNs were 18.73±0.14, 19.05±0.28, 18.54±0.10 nm respectively. The Zeta potential of these different charged SLNs formulations were 19.13±0.89, -2.20±0.10, -27.40±0.67 mV respectively. The Polydispersity Index (PDI) of these three kinds of nanoparticles were about 0.2. The Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC) analysis showed that the nanoparticles were a homogeneous system. Compared with Econazole suspension (E-Susp), SLNs exhibited sustained release capability, stronger corneal penetration and enhanced inhibition of pathogenic fungi without irritation. The antifungal ability was further improved after cationic charge modification compared with E-SLNs. Studies on pharmacokinetics showed that the order of the AUC and t_1/2 of different preparations was cationic E-SLNs > nearly neutral E-SLNs > anionic E-SLNs > E-Susp in cornea and aqueous humor. It was shown that SLNs could increase corneal penetrability and ocular bioavailability while these capabilities were further enhanced with positive charge modification compared with negative charge ones.

Nanomedicine strategies to improve therapeutic agents for the prevention and treatment of preterm birth and future directions

The World Health Organisation (WHO) estimates 15 million babies worldwide are born preterm each year, with 1 million infant mortalities and long-term morbidity in survivors. Whilst the past 40 years have provided some understanding in the causes of preterm birth, along with development of a range of therapeutic options, notably prophylactic use of progesterone or uterine contraction suppressants (tocolytics), the number of preterm births continues to rise. Existing therapeutics used to control uterine contractions are restricted in their clinical use due to pharmacological drawbacks such as poor potency, transfer of drugs to the fetus across the placenta and maternal side effects from activity in other maternal systems. This review focuses on addressing the urgent need for the development of alternative therapeutic systems with improved efficacy and safety for the treatment of preterm birth. We discuss the application of nanomedicine as a viable opportunity to engineer pre-existing tocolytic agents and progestogens into nanoformulations, to improve their efficacy and address current drawbacks to their use. We review different nanomedicines including liposomes, lipid-based carriers, polymers and nanosuspensions highlighting where possible, where these technologies have already been exploited e.g. liposomes, and their significance in improving the properties of pre-existing therapeutic agents within the field of obstetrics. We also highlight where active pharmaceutical agents (APIs) with tocolytic properties have been used for other clinical indications and how these could inform the design of future therapeutics or be repurposed to diversify their application such as for use in preterm birth. Finally we outline and discuss the future challenges.

Loteprednol-Loaded Nanoformulations for Corneal Delivery by Quality-by-Design Concepts: Optimization, Characterization, and Anti-inflammatory Activity

Loteprednol etabonate (LE) is a topical corticosteroid that uses inflammatory conditions of the eye. It has a low ocular bioavailability and side effects such as corneal disorder, eye discharge, and ocular discomfort. Therefore, it was decided to select the delivery systems, which are solid lipid nanoparticles (SLN), nanostructured lipid carriers (NLC), and nanoemulsion (NE). Design of experiments (DoE) of SLN, NLC, and NE formulations were formulated by using the quality by design (QbD) approach. Precirol® ATO 5 and oleic acid were used as solid and liquid lipids, respectively, in SLN, NLC, and NE formulations. Physiochemical characterization was performed on the formulations. The optimized formulations' inflammatory effects have been appraised on human corneal epithelial cells employing the ELISA test. Physicochemical characterization studies and inflammatory effects were appraised. The sizes of optimized formulations of SLN, NLC, and NE were 86.19 nm, 82.38 nm, and 126.35 nm, respectively, with minimum polydispersity. The release behavior of the formulations is composed of both diffusion and erosion. ELISA test results proved that the formulations significantly reduced IL-1 and IL-6 levels (p < 0.05). D-optimal mixture experimental design allowed us to develop the most precise formulations of SLN, NLC, and NE. Furthermore, the optimized formulations could be promising candidates for treating an inflammation-based corneal disease of the eye.

Cannabinoid-Based Ocular Therapies and Formulations

The interest in the pharmacological applications of cannabinoids is largely increasing in a wide range of medical areas. Recently, research on its potential role in eye conditions, many of which are chronic and/or disabling and in need of new alternative treatments, has intensified. However, due to cannabinoids’ unfavorable physicochemical properties and adverse systemic effects, along with ocular biological barriers to local drug administration, drug delivery systems are needed. Hence, this review focused on the following: (i) identifying eye disease conditions potentially subject to treatment with cannabinoids and their pharmacological role, with emphasis on glaucoma, uveitis, diabetic retinopathy, keratitis and the prevention of Pseudomonas aeruginosa infections; (ii) reviewing the physicochemical properties of formulations that must be controlled and/or optimized for successful ocular administration; (iii) analyzing works evaluating cannabinoid-based formulations for ocular administration, with emphasis on results and limitations; and (iv) identifying alternative cannabinoid-based formulations that could potentially be useful for ocular administration strategies. Finally, an overview of the current advances and limitations in the field, the technological challenges to overcome and the prospective further developments, is provided.

Recent Progress of Lipid Nanoparticles-Based Lipophilic Drug Delivery: Focus on Surface Modifications

Numerous drugs have emerged to treat various diseases, such as COVID-19, cancer, and protect human health. Approximately 40% of them are lipophilic and are used for treating diseases through various delivery routes, including skin absorption, oral administration, and injection. However, as lipophilic drugs have a low solubility in the human body, drug delivery systems (DDSs) are being actively developed to increase drug bioavailability. Liposomes, micro-sponges, and polymer-based nanoparticles have been proposed as DDS carriers for lipophilic drugs. However, their instability, cytotoxicity, and lack of targeting ability limit their commercialization. Lipid nanoparticles (LNPs) have fewer side effects, excellent biocompatibility, and high physical stability. LNPs are considered efficient vehicles of lipophilic drugs owing to their lipid-based internal structure. In addition, recent LNP studies suggest that the bioavailability of LNP can be increased through surface modifications, such as PEGylation, chitosan, and surfactant protein coating. Thus, their combinations have an abundant utilization potential in the fields of DDSs for carrying lipophilic drugs. In this review, the functions and efficiencies of various types of LNPs and surface modifications developed to optimize lipophilic drug delivery are discussed.

Ocular Drug Delivery: a Comprehensive Review

The human eye is a sophisticated organ with distinctive anatomy and physiology that hinders the passage of drugs into targeted ophthalmic sites. Effective topical administration is an interest of scientists for many decades. Their difficult mission is to prolong drug residence time and guarantee an appropriate ocular permeation. Several ocular obstacles oppose effective drug delivery such as precorneal, corneal, and blood-corneal barriers. Routes for ocular delivery include topical, intravitreal, intraocular, juxtascleral, subconjunctival, intracameral, and retrobulbar. More than 95% of marketed products exists in liquid state. However, other products could be in semi-solid (ointments and gels), solid state (powder, insert and lens), or mixed (in situ gel). Nowadays, attractiveness to nanotechnology-based carries is resulted from their capabilities to entrap both hydrophilic and lipophilic drugs, enhance ocular permeability, sustain residence time, improve drug stability, and augment bioavailability. Different in vitro, ex vivo, and in vivo characterization approaches help to predict the outcomes of the constructed nanocarriers. This review aims to clarify anatomy of the eye, various ocular diseases, and obstacles to ocular delivery. Moreover, it studies the advantages and drawbacks of different ocular routes of administration and dosage forms. This review also discusses different nanostructured platforms and their characterization approaches. Strategies to enhance ocular bioavailability are also explained. Finally, recent advances in ocular delivery are described.

Lipid-engineered nanotherapeutics for cancer management

Cancer causes significant mortality and morbidity worldwide, but existing pharmacological treatments are greatly limited by the inherent heterogeneity of cancer as a disease, as well as the unsatisfactory efficacy and specificity of therapeutic drugs. Biopharmaceutical barriers such as low permeability and poor water solubility, along with the absence of active targeting capabilities, often result in suboptimal clinical results. The difficulty of successfully reaching and destroying tumor cells is also often compounded with undesirable impacts on healthy tissue, including off-target effects and high toxicity, which further impair the ability to effectively manage the disease and optimize patient outcomes. However, in the last few decades, the development of nanotherapeutics has allowed for the use of rational design in order to maximize therapeutic success. Advances in the fabrication of nano-sized delivery systems, coupled with a variety of surface engineering strategies to promote customization, have resulted in promising approaches for targeted, site-specific drug delivery with fewer unwanted effects and better therapeutic efficacy. These nano systems have been able to overcome some of the challenges of conventional drug delivery related to pharmacokinetics, biodistribution, and target specificity. In particular, lipid-based nanosystems have been extensively explored due to their high biocompatibility, versatility, and adaptability. Lipid-based approaches to cancer treatment are varied and diverse, including liposomal therapeutics, lipidic nanoemulsions, solid lipid nanoparticles, nanostructured lipidic carriers, lipid-polymer nanohybrids, and supramolecular nanolipidic structures. This review aims to provide an overview of the use of diverse formulations of lipid-engineered nanotherapeutics for cancer and current challenges in the field, as researchers attempt to successfully translate these approaches from bench to clinic.

Construction of PEI-EGFR-PD-L1-siRNA dual functional nano-vaccine and therapeutic efficacy evaluation for lung cancer

BACKGROUND

PD-1/PD-L1 tumor immunotherapy shows effective anticancer in treatment of solid tumors, so PEI lipid nanoparticles (PEI-LNP)/siRNA complex (EPV-PEI-LNP-SiRNA) with the therapeutic function of PD-L1-siRNA and EGFR short peptide/PD-L1 double immune-enhancing function were constructed for the prevention and treatment of EGFR-positive lung cancer in this study.

METHOD

In this study, PEI lipid nanoparticles (PEI-LNP)/siRNA complex (EPV-PEI-LNP-siRNA) with the therapeutic function of PD-L1-siRNA and EGFR short peptide/PD-L1 double immune-enhancing function were constructed for the prevention and treatment of EGFR-positive lung cancer and functional evaluation was conducted.

RESULTS

On the basis of the construction of the composite nano-drug delivery system, the binding capacity, cytotoxicity, apoptosis and uptake capacity of siRNA and EPV-PEI-LNP were tested in vitro, and the downregulation effect of PD-L1 on A549 cancer cells and the cytokine levels of cocultured T cells were tested. Lipid nanoparticles delivered siRNA and EGFR short peptide vaccine to non-small cell lung cancer (NSCLC), increasing tumor invasion and activation of CD8 + T cells. Combination therapy is superior to single target therapy.

CONCLUSION

Our constructed lipid nanoparticles of tumor targeted therapy gene siRNA combination had the ability to target cells in vitro and downregulate the expression of PD-L1, realizing the tumor-specific expression of immune-stimulating cytokines, which is a highly efficient and safe targeted therapy nano-vaccine.

Recent achievements in nano-based technologies for ocular disease diagnosis and treatment, review and update

Ocular drug delivery is one of the most challenging endeavors among the various available drug delivery systems. Despite having suitable drugs for the treatment of ophthalmic disease, we have not yet succeeded in achieving a proper drug delivery approach with the least adverse effects. Nanotechnology offers great opportunities to overwhelm the restrictions of common ocular delivery systems, including low therapeutic effects and adverse effects because of invasive surgery or systemic exposure. The present review is dedicated to highlighting and updating the recent achievements of nano-based technologies for ocular disease diagnosis and treatment. While further effort remains, the progress illustrated here might pave the way to new and very useful ocular nanomedicines.

Chitosan/sulfobutylether-β-cyclodextrin based nanoparticles coated with thiolated hyaluronic acid for indomethacin ophthalmic delivery

Indomethacin (IND) is topically administered for the treatment of the anterior segment diseases such as conjunctivitis, uveitis, and inflammation prevention for post-cataract surgery, as well as posterior segment diseases as macular edema. Currently IND is available as 0.1% w/v hydroxypropyl-β-cyclodextrin-based eye drop formulation and its bioavailability is limited by several drawbacks such as the nasolacrimal duct draining, the reflex blinking and the low volume of the conjunctival sac. In this study, chitosan (CS)/sulfobutylether-β-cyclodextrin (SBE-β-CD) based nanoparticles (NPs) with a mean diameter of 340 (±7) nm, a ζ-potential value of +18.3 (±0.5) mV and coated with thiolated low molecular weight hyaluronic acid were formulated to improve both the solubility and the residential time in the conjunctival sac of the loaded drug IND. The NPs were prepared through the ionotropic gelation technique, exploiting the interaction between the positively charged amino group of CS and the negatively charged sulfonic group of SBE-β-CD. The mucoadhesive properties of the NPs were evaluated on chicken trachea and esophagus tissues using a texture analyser. The irritability effects of NPs were disclaimed with Hecam test. The developed coated NPs showed increased residential time in the conjunctival sac, displayed no irritancy or toxicity for local administration, making them an optimal and innovative drug delivery system for the treatment of anterior segment inflammation diseases. On the other hand, the uncoated NPs displayed better permeating properties since they are smaller and could be further exploited for the treatment of posterior segment diseases.

Lipid-Based Nanocarrier Systems for Drug Delivery: Advances and Applications

Lipid-based nanocarriers have been extensively investigated for drug delivery due to their advantages including biodegradability, biocompatibility, nontoxicity, and nonimmunogenicity. However, the shortcomings of traditional lipid-based nanocarriers such as insufficient targeting, capture by the reticuloendothelial system, and fast elimination limit the efficiency of drug delivery and therapeutic efficacy. Therefore, a series of multifunctional lipid-based nanocarriers have been developed to enhance the accumulation of drugs in the lesion site, aiming for improved diagnosis and treatment of various diseases. In this review, we summarized the advances and applications of lipid-based nanocarriers from traditional to novel functional lipid preparations, including liposomes, stimuli-responsive lipid-based nanocarriers, ionizable lipid nanoparticles, lipid hybrid nanocarriers, as well as biomembrane-camouflaged nanoparticles, and further discussed the challenges and prospects of this system. This exploration may give a complete idea viewing the lipid-based nanocarriers as a promising choice for drug delivery system, and fuel the advancement of pharmaceutical products by materials innovation and nanotechnology.

Surface Modification of Lipid-Based Nanoparticles

There is a growing interest in the development of lipid-based nanocarriers for multiple purposes, including the recent increase of these nanocarriers as vaccine components during the COVID-19 pandemic. The number of studies that involve the surface modification of nanocarriers to improve their performance (increase the delivery of a therapeutic to its target site with less off-site accumulation) is enormous. The present review aims to provide an overview of various methods associated with lipid nanoparticle grafting, including techniques used to separate grafted nanoparticles from unbound ligands or to characterize grafted nanoparticles. We also provide a critical perspective on the usefulness and true impact of these modifications on overcoming different biological barriers, with our prediction on what to expect in the near future in this field.

Hybrid Nanobeads for Oral Indomethacin Delivery

The oral administration of the anti-inflammatory indomethacin (INDO) causes severe gastrointestinal side effects, which are intensified in chronic inflammatory conditions when a continuous treatment is mandatory. The development of hybrid delivery systems associates the benefits of different (nano) carriers in a single system, designed to improve the efficacy and/or minimize the toxicity of drugs. This work describes the preparation of hybrid nanobeads composed of nanostructured lipid carriers (NLC) loading INDO (2%; w/v) and chitosan, coated by xanthan. NLC formulations were monitored in a long-term stability study (25 °C). After one year, they showed suitable physicochemical properties (size < 250 nm, polydispersity < 0.2, zeta potential of −30 mV and spherical morphology) and an INDO encapsulation efficiency of 99%. The hybrid (lipid-biopolymers) nanobeads exhibited excellent compatibility between the biomaterials, as revealed by structural and thermodynamic properties, monodisperse size distribution, desirable in vitro water uptake and prolonged in vitro INDO release (26 h). The in vivo safety of hybrid nanobeads was confirmed by the chicken embryo (CE) toxicity test, considering the embryos viability, weights of CE and annexes and changes in the biochemical markers. The results point out a safe gastro-resistant pharmaceutical form for further efficacy assays.

Design of Nanotechnological Carriers for Ocular Delivery of Mangiferin: Preformulation Study

(1) Background: Mangiferin (MGN) is a natural compound, showing anti-inflammatory and antioxidant activities for the potential treatment of eye diseases. The poor physicochemical features of MGN (low solubility and high instability) justify its nanoencapsulation into nanostructured lipid carriers (NLC) to improve its ocular bioavailability. (2) Methods: Firstly, MGN-NLC were prepared by the high shear homogenization coupled with the ultrasound (HSH−US) method. Finally, unloaded and MGN-loaded NLC were analyzed in terms of ocular tolerance. (3) Results: MGN-NLC showed good technological parameters suitable for ocular administration (particle size below 200 nm). The ORAC assay was performed to quantify the antioxidant activity of MGN, showing that the antioxidant activity of MGN-NLC (6494 ± 186 μM TE/g) was higher than that of the free compound (3521 ± 271 μM TE/g). This confirmed that the encapsulation of the drug was able to preserve and increase its activity. In ovo studies (HET-CAM) revealed that the formulation can be considered nonirritant. (4) Conclusions: Therefore, NLC systems are a promising approach for the ocular delivery of MGN.

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.

Topical Drug Delivery to the Posterior Segment of the Eye

Topical drug delivery to the posterior segment of the eye is a very complex challenge. However, topical delivery is highly desired, to achieve an easy-to-use treatment option for retinal diseases. In this review, we focus on the drug characteristics that are relevant to succeed in this challenge. An overview on the ocular barriers that need to be overcome and some relevant animal models to study ocular pharmacokinetics are given. Furthermore, a summary of substances that were able to reach the posterior segment after eye drop application is provided, as well as an outline of investigated delivery systems to improve ocular drug delivery. Some promising results of substances delivered to the retina suggest that topical treatment of retinal diseases might be possible in the future, which warrants further research.

A Rapid Corneal Healing Microneedle for Efficient Ocular Drug Delivery

Fungal keratitis (FK) remains a serious clinical problem worldwide, so the ultimate goal of the treatment is to develop a minimally invasive, safe, and effective method for ocular drug delivery. Here, a minimally invasive delivery system is reported for treating FK by using a dissolving microneedle (MN)-array patch based on Poly(D,L-lactide) (PLA) and hyaluronic acid (HA). By altering the concentration of PLA, MN patches with excellent properties are modified and optimized. The 30% PLA-HA MN patches penetrate the corneal epithelial layer reversibly with no apparent ocular irritation as well as a short recovery time of less than 12 h, and increase the residence time by 2.5 h in the conjunctival sac, thereby offering higher drug bioavailability. Remarkably, the rabbit model of FK shows that the topical MN(+) patch medication exerts superior therapeutic effects compared with the conventional eye drop formulation, and also presents comparable therapeutic efficacy with that of the clinical mainstay strategy (i.e., intrastromal injection). Therefore, the MN patch, acting as an ocular drug delivery system with high efficacy and ability of rapid corneal healing, promises a cost-effective household solution for the treatment of FK, which may also lead to a new approach for treating FK in clinics.

Itraconazole loaded nano-structured lipid carrier for topical ocular delivery: Optimization and evaluation

BACKGROUND & OBJECTIVES

Low penetration efficiency and retention time are the main therapeutic concerns that make it difficult for most of the drugs to be delivered to the intraocular tissues. These challenging issues are often related to those drugs, which have low or poor solubility and low permeability. The goal of this study was designed to develop nanostructured lipid carriers (NLCs) loaded with itraconazole (ITZ) with the objective of enhancing topical ocular permeation and thereby improving clinical efficacy.

MATERIALS AND METHODS

ITZ-loaded NLCs were fabricated by a high-speed homogenization technique using surfactant (Poloxamer 407), and lipids (stearic acid and oleic acid). Optimization of formulations was performed by 3 level factorial design and the selected formulation (F6) was evaluated by differential scanning calorimetry and transmission electron microscopy. Antifungal activity was assessed by measuring the zone of inhibition and irritation potential using the HET-CAM test.

RESULTS

The independent variables (lipid ratio-X1 and percentage of emulsifier-X2) have a positive impact on percentage entrapment efficiency (Y2) and percentage release (Y3) but have a negative impact on particle size (Y1). Based on the better entrapment efficiency (94.65%), optimum particle size (150.67 nm), and percentage cumulative drug release (68.67%), batch F6 was selected for further evaluation. Electron microscopic images revealed that the prepared particles are spherical and have nano size. Antifungal studies demonstrated enhancement in the zone of inhibition by formulation F6 as compared to a commercial eye drop. The non-irritancy of optimized formulation (F6) was confirmed with a zero score.

INTERPRETATION & CONCLUSION

In summary, the optimized NLCs seem to be a potent carrier for the effective delivery of itraconazole in ocular therapy.

Design of Hepatic Targeted Drug Delivery Systems for Natural Products: Insights into Nomenclature Revision of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD), recently renamed metabolic-dysfunction-associated fatty liver disease (MAFLD), affects a quarter of the worldwide population. Natural products have been extensively utilized in treating NAFLD because of their distinctive advantages over chemotherapeutic drugs, despite the fact that there are no approved drugs for therapy. Notably, the limitations of many natural products, such as poor water solubility, low bioavailability in vivo, low hepatic distribution, and lack of targeted effects, have severely restricted their clinical application. These issues could be resolved via hepatic targeted drug delivery systems (HTDDS) that boost clinical efficacy in treating NAFLD and decrease the adverse effects on other organs. Herein an overview of natural products comprising formulas, single medicinal plants, and their crude extracts has been presented to treat NAFLD. Also, the clinical efficacy and molecular mechanism of active monomer compounds against NAFLD are systematically discussed. The targeted delivery of natural products via HTDDS has been explored to provide a different nanotechnology-based NAFLD treatment strategy and to make suggestions for natural-product-based targeted nanocarrier design. Finally, the challenges and opportunities put forth by the nomenclature update of NAFLD are outlined along with insights into how to improve the NAFLD therapy and how to design more rigorous nanocarriers for the HTDDS. In brief, we summarize the up-to-date developments of the NAFLD-HTDDS based on natural products and provide viewpoints for the establishment of more stringent anti-NAFLD natural-product-targeted nanoformulations.

Posterior Segment Ophthalmic Drug Delivery: Role of Muco-Adhesion with a Special Focus on Chitosan

Posterior segment eye diseases (PSEDs) including age macular degeneration (AMD) and diabetic retinopathy (DR) are amongst the major causes of irreversible blindness worldwide. Due to the numerous barriers encountered, highly invasive intravitreal (IVT) injections represent the primary route to deliver drugs to the posterior eye tissues. Thus, the potential of a more patient friendly topical route has been widely investigated. Mucoadhesive formulations can decrease precorneal clearance while prolonging precorneal residence. Thus, they are expected to enhance the chances of adherence to corneal and conjunctival surfaces and as such, enable increased delivery to the posterior eye segment. Among the mucoadhesive polymers available, chitosan is the most widely explored due to its outstanding mucoadhesive characteristics. In this review, the major PSEDs, their treatments, barriers to topical delivery, and routes of topical drug absorption to the posterior eye are presented. To enable the successful design of mucoadhesive ophthalmic drug delivery systems (DDSs), an overview of mucoadhesion, its theory, characterization, and considerations for ocular mucoadhesion is given. Furthermore, chitosan-based DDs that have been explored to promote topical drug delivery to the posterior eye segment are reviewed. Finally, challenges of successful preclinical to clinical translation of these DDSs for posterior eye drug delivery are discussed.

Photodegradation of Anti-Inflammatory Drugs: Stability Tests and Lipid Nanocarriers for Their Photoprotection

The present paper provides an updated overview of the methodologies applied in photodegradation studies of non-steroidal anti-inflammatory drugs. Photostability tests, performed according to international standards, have clearly demonstrated the photolability of many drugs belonging to this class, observed during the preparation of commercial forms, administration or when dispersed in the environment. The photodegradation profile of these drugs is usually monitored by spectrophotometric or chromatographic techniques and in many studies the analytical data are processed by chemometric procedures. The application of multivariate analysis in the resolution of often-complex data sets makes it possible to estimate the pure spectra of the species involved in the degradation process and their concentration profiles. Given the wide use of these drugs, several pharmaceutical formulations have been investigated to improve their photostability in solution or gel, as well as the pharmacokinetic profile. The use of lipid nanocarriers as liposomes, niosomes or solid lipid nanoparticles has demonstrated to both minimize photodegradation and improve the controlled release of the entrapped drugs.

Improved Bioavailability of Ebastine through Development of Transfersomal Oral Films

The main objective of this research work was the development and evaluation of transfersomes integrated oral films for the bioavailability enhancement of Ebastine (EBT) to treat allergic rhinitis. The flexible transfersomes, consisting of drug (EBT), lipid (Phosphatidylcholine) and edge activator (EA) Polyoxyethylene sorbitan monooleate or Sorbitan monolaurate, were prepared with the conventional thin film hydration method. The developed transfersomes were further integrated into oral films using the solvent casting method. Transfersomes were evaluated for their size distribution, surface charge, entrapment efficiency (EE%) and relative deformability, whereas the formulated oral films were characterized for weight, thickness, pH, folding endurance, tensile strength, % of elongation, degree of crystallinity, water content, content uniformity, in vitro drug release and ex vivo permeation, as well as in vivo pharmacokinetic and pharmacodynamics profile. The mean hydrodynamic diameter of transfersomes was detected to be 75.87 ± 0.55 nm with an average PDI and zeta potential of 0.089 ± 0.01 and 33.5 ± 0.39 mV, respectively. The highest deformability of transfersomes of 18.52 mg/s was observed in the VS-3 formulation. The average entrapment efficiency of the transfersomes was about 95.15 ± 1.4%. Transfersomal oral films were found smooth with an average weight, thickness and tensile strength of 174.72 ± 2.3 mg, 0.313 ± 0.03 mm and 36.4 ± 1.1 MPa, respectively. The folding endurance, pH and elongation were found 132 ± 1, 6.8 ± 0.2 and 10.03 ± 0.4%, respectively. The ex vivo permeability of EBT from formulation ETF-5 was found to be approximately 2.86 folds higher than the pure drug and 1.81 folds higher than plain film (i.e., without loaded transfersomes). The relative oral bioavailability of ETF-5 was 2.95- and 1.7-fold higher than that of EBT-suspension and plain film, respectively. In addition, ETF-5 suppressed the wheal and flare completely within 24 h. Based on the physicochemical considerations, as well as in vitro and in vivo characterizations, it is concluded that the highly flexible transfersomal oral films (TOFs) effectively improved the bioavailability and antihistamine activity of EBT.

Choriocapillaris: Fundamentals and advancements

The choriocapillaris is the innermost structure of the choroid that directly nourishes the retinal pigment epithelium and photoreceptors. This article provides an overview of its hemovasculogenesis development to achieve its final architecture as a lobular vasculature, and also summarizes the current histological and molecular knowledge about choriocapillaris and its dysfunction. After describing the existing state-of-the-art tools to image the choriocapillaris, we report the findings in the choriocapillaris encountered in the most frequent retinochoroidal diseases including vascular diseases, inflammatory diseases, myopia, pachychoroid disease spectrum disorders, and glaucoma. The final section focuses on the development of imaging technology to optimize visualization of the choriocapillaris as well as current treatments of retinochoroidal disorders that specifically target the choriocapillaris. We conclude the article with pertinent unanswered questions and future directions in research for the choriocapillaris.

Colloidal nanosystems with mucoadhesive properties designed for ocular topical delivery

Over the last years, the scientific interest about topical ocular delivery targeting the posterior segment of the eye has been increasing. This is probably due to the fact that this is a non-invasive administration route, well tolerated by patients and with fewer local and systemic side effects. However, it is a challenging task due to the external ocular barriers, tear film clearance, blood flow in the conjunctiva and choriocapillaris and due to the blood-retinal barriers, amongst other features. An enhanced intraocular bioavailability of drugs can be achieved by either improving corneal permeability or by improving precorneal retention time. Regarding this last option, increasing residence time in the precorneal area can be achieved using mucoadhesive polymers such as xyloglucan, poly(acrylate), hyaluronic acid, chitosan, and carbomers. On the other hand, colloidal particles can interact with the ocular mucosa and enhance corneal and conjunctival permeability. These nanosystems are able to deliver a wide range of drugs, including macromolecules, providing stability and improving ocular bioavailability. New pharmaceutical approaches based on nanotechnology associated to bioadhesive compounds have emerged as strategies for a more efficient treatment of ocular diseases. Bearing this in mind, this review provides an overview of the current mucoadhesive colloidal nanosystems developed for ocular topical administration, focusing on their advantages and limitations.

Ocular drug delivery to the anterior segment using nanocarriers: A mucoadhesive/mucopenetrative perspective

There is a growing demand for effective treatments for ocular conditions that improve patient compliance and reduce side-effects. While methods such as implants and injections have proven effective, topical administration remains the method of choice for the delivery of therapeutics to the anterior segment of the eye. However, topical administration suffers from multiple drawbacks including low bioavailability of the target therapeutic, systemic toxicity, and the requirement for high therapeutic doses due to the effective clearance mechanisms that exist in the eye. Nanoparticles that have tunable mucoadhesion and/or mucopenetration offer outstanding potential to overcome the anatomical and physiological barriers present to improve ocular bioavailability, reduce toxicity, and increase ocular retention, among other benefits. The current review highlights recent advances in the field of developing nanocarriers with tunable mucoadhesion and mucopenetration for drug delivery to the eye.

Multifunctional nanocomposite eye drops of cyclodextrin complex@layered double hydroxides for relay drug delivery to the posterior segment of the eye

Topical drug delivery system to the posterior segment of the eye is facing many challenges, such as rapid drug elimination, low permeability, and low concentration at the targeted sites. To overcome these challenges, Multifunctional nanocomposite eye drops of dexamethasone-carboxymethyl-β-cyclodextrin@layered double hydroxides-glycylsarcosine (DEX-CM-β-CD@LDH-GS) were developed for relay drug delivery. Herein, our studies demonstrated that DEX-CM-β-CD@LDH-GS could penetrate through human conjunctival epithelial cells with an intact structure and exhibited integrity in the sclera of rabbits' eyes with in vivo fluorescence resonance energy transfer imaging. Consequently, tissue distribution indicated that DEX-CM-β-CD@LDH-GS nanocomposite eye drops could maintain the effective therapeutic concentration of DEX in choroid-retina within 3 h. As a relay drug delivery system, drug-CD@LDH nanocomposites offer an efficient strategy for drug delivery from ocular surface to the posterior segment.

Camelina lipid droplets as skin delivery system promotes wound repair by enhancing the absorption of hFGF2

Human basic fibroblast growth factor (hFGF2) is widely recognized for accelerating skin wound healing in both animal models and randomized clinical trials. However, the low skin permeation and bioavailability of hFGF2 remain the most limiting factors in the pharmacological application. For the first time, Camelina Lipid Droplets (CLD) delivery system was displayed important virtue, by promoting the skin absorption of hFGF2, which is a key factor that accelerates the skin wound repair, and provide a new alternative for skin therapy. In this study, we used the CLD as a safer material to prepare the nanoparticles, which were characterized by size and morphology. Our data revealed that particle sizes of Camelina Lipid Droplets linked to hFGF2 (CLD-hFGF2) were around 133.5 nm; it also displayed that the complex of CLD-hFGF2 penetrates the skin barrier in deeper than an individual hFGF2. This suggests that once the hFGF2 is fixed onto the surface of CLD, it can cross the stratum corneum and play a therapeutic role into the dermis. Furthermore, we demonstrated that CLD-hFGF2 enhances fibroblast migration, and significantly improves skin regeneration for accelerating wound healing without any significant toxicity. This paper highlights the importance of CLD as an emerging delivery system; it is also providing a new and applicable therapeutic research direction through enhancing the skin permeation of hFGF2 to accelerate wound healing.

Emerging innovations in nano-enabled therapy against age-related macular degeneration: A paradigm shift

Age-related macular degeneration (AMD), a degenerative eye disease, is the major cause of irreversible loss of vision among individuals aged 50 and older. Both genetic and environmental factors are responsible for the progressive damage to central vision. It is a multifactorial retinal disease with features such as drusen, hypopigmentation and/or hyperpigmentation of the retinal pigment epithelium, and even choroidal neovascularization in certain patients. AMD is of two major forms: exudative (wet) and atrophic (dry) with changes affecting the macula leading to impaired vision. Although the retina remains an accessible portion for delivering drugs, there are no current options to cure or treat AMD. The existing expensive therapeutics are unable to treat the underlying pathology but display several side effects. However, recent innovations in nanotherapeutics provide an optimal alternative of drug delivery to treat the neovascular condition. These new-age technologies in the nanometer scale would enhance bioactivity and improve the bioavailability of drugs at the site of action to treat AMD. The nanomedicine also provides sustained release of the drug with prolonged retention after penetrating across the ocular tissues. In this review, the insights into the cellular and molecular mechanisms associated with the pathophysiology of AMD are provided. It also serves to review the current progress in nanoparticle-based drug delivery systems that offer feasible treatments in AMD.

Preparation and Characterization of Tacrolimus-Loaded SLNs in situ Gel for Ocular Drug Delivery for the Treatment of Immune Conjunctivitis

Background

The aim of this study is to develop a novel in situ gel of tacrolimus-loaded SLNs (solid lipid nanoparticles) for ocular drug delivery.

Methods

The optimal formulation was characterized by surface morphology, particle size, zeta potential, entrapment efficiency, drug loading and in vitro release behavior. In vivo studies were also conducted to evaluate the pharmacokinetic and pharmacodynamic results.

Results

In this study, TAC-SLNs ISG were prepared using homogenization followed by probe sonication method. The average particle size of TAC-SLNs ISG was observed to be 122.3±4.3 nm. Compared with TAC-SLNs, in situ gel did not increase particle size, and there was no significant difference between them. The results of viscosity measurement showed that TAC SLNs-ISG were typical of pseudo plastic systems and showed a marked increase in viscosity as temperature increased and ultimately formed a rigid gel (32°C). In vitro and in vivo studies illustrated the sustained release model of the drug from TAC-SLNs ISG. Animal model showed that TAC-SLNs ISG had good pharmacodynamics when compared with eye drops and SLNs.

Conclusion

Our results demonstrated that TAC SLNs-ISG had the potential for being an ideal ocular drug delivery system.

Nanotechnology for the Treatment of Allergic Conjunctival Diseases

Allergic conjunctivitis is one of the most common external eye diseases and the prevalence has been increasing. The mainstay of treatment is topical eye drops. However, low bioavailability, low ocular drug penetration, transient resident time on the ocular surface due to tear turnover, frequent topical applications and dependence on patient compliance, are the main drawbacks associated with topical administration. Nanotechnology-based medicine has emerged to circumvent these limitations, by encapsulating the drugs and preventing them from degradation and therefore providing sustained and controlled release. Using a nanotechnology-based approach to load the drug is particularly useful for the delivery of hydrophobic drugs such as immunomodulatory agents, which are commonly used in allergic conjunctival diseases. In this review, different nanotechnology-based drug delivery systems, including nanoemulsions, liposomes, nanomicelles, nanosuspension, polymeric and lipid nanoparticles, and their potential ophthalmic applications, as well as advantages and disadvantages, are discussed. We also summarize the results of present studies on the loading of immunomodulators or nonsteroidal anti-inflammatory drugs to nano-scaled drug delivery systems. For future potential clinical use, research should focus on the optimization of drug delivery designs that provide adequate and effective doses with safe and satisfactory pharmacokinetic and pharmaco-toxic profiles.

HDL nanoparticles have wound healing and anti-inflammatory properties and can topically deliver miRNAs

microRNAs regulate numerous biological processes, making them potential therapeutic agents. Problems with delivery and stability of these molecules have limited their usefulness as treatments. We demonstrate that synthetic high-density lipoprotein nanoparticles (HDL NPs) topically applied to the intact ocular surface are taken up by epithelial and stromal cells. microRNAs complexed to HDL NPs (miR-HDL NPs) are similarly taken up by cells and tissues and retain biological activity. Topical treatment of diabetic mice with either HDL NPs or miR-HDL NPs significantly improved corneal re-epithelialization following wounding compared with controls. Mouse corneas with alkali burn-induced inflammation, topically treated with HDL NPs, displayed clinical, morphological and immunological improvement. These results should yield a novel HDL NP-based eye drop for patients with compromised wound healing ability (diabetics) and/or corneal inflammatory diseases (e.g. dry eye).

Comparison of Different Chitosan Lipid Nanoparticles for Improved Ophthalmic Tetrandrine Delivery: Formulation, Characterization, Pharmacokinetic and Molecular Dynamics Simulation

In this study, three different chitosan, namely carboxymethyl chitosan (CMC), hydroxypropyl chitosan (HPC) and trimethyl chitosan (TMC) were used as cationic materials to prepare tetrandrine lipid nanoparticles (TET-LNPs) for the treatment of glaucoma. In vitro drug release and pre-corneal retention were used to select the optimal chitosan. In vitro drug release curves of three kinds of LNPs showed a sustained release and TMC-TET-LNPs were the slowest. Moreover, compared with CMC-TET-LNPs and HPC-TET-LNPs, TMC-TET-LNPs had longer corneal retention time. Afterwards, the characteristics of TMC-TET-LNPs were investigated. The ocular irritation study revealed no sign of irritation in rabbit eyes. The pharmacokinetic studies showed that the area under the curve of TMC-TET-LNPs was increased by 2.03 times than TET solution (p < 0.01). Furthermore, the drug biofilm interactions were evaluated by molecular dynamics (MD) simulation. In MD simulation, the strong hydrophobic group of TET interacted with the tail of POPC, making it hard to enter the hydrophobic region of the membrane, thereby restricting TET ocular bioavailability. The experiments and MD simulation indicated that TMC-TET-LNPs had great potential for ocular administration and MD simulation could predict transmembrane transport of drugs.