Novel nanosystems for the treatment of ocular inflammation: Current paradigms and future research directions

Optimization of Naringenin-loaded nanoparticles for targeting of Vanin-1, iNOS, and MCP-1 signaling pathway in HFD-induced obesity

Naringenin, a natural dihydrochalcone flavonoid, exhibits diverse pharmacological properties. This study investigates the hypolipidemic effects of Nar-NPs on obese mice. The characteristics of Nar-NPs, including morphology, particle size, zeta potential, UV-vis, and FT-IR spectra, were examined. The anti-obesity properties of Nar-NPs were evaluated in obese rats, considering LD50, 1/20 LD50, and 1/50 LD50 for treatment preparation. Results indicated that synthesized Nar-NPs were uniform, spherical, and well-dispersed, with a size of 130.06 ± 1.98 nm and with a zeta potential of -25.6 ± 0.8 mV. Nar-NPs exhibited enhancement in the cumulative release of naringenin (56.87 ± 2.45 %) as compared to pure naringenin suspension 87.83 ± 1.84 % in 24 h of the study. The LD50 of Nar-NPs was determined as 412.5 mg/kg.b.w. HFD induced elevated glycemic, oxidative stress, and inflammatory biomarkers while reducing HDL-C, GSH, and superoxide dismutase (SOD) levels. Administration of Nar-NPs significantly mitigated body weight, glucose, insulin, leptin, TC, TG, SREBP1c, pAMPK, PPAR-α, as well as vanin-1, MCP-1, and iNOS mRNA gene expression. Histological investigations supported the biochemical and PCR findings. In a nutshell, the study suggests that the Nar-NPs could serve as a promising and viable pharmacological strategy for the treatment of obesity-related disorders.

In-situ forming biodegradable implants for sustained Fluocinolone acetonide release to the posterior eye: In-vitro and in-vivo investigations in rabbits

Delivering medication to the posterior segment of the eye presents a significant challenge. Intravitreal injection has emerged as the preferred method for drug delivery to this area. However, current injectable non-biodegradable implants for fluocinolone acetonide (FA) require surgical removal after prolonged drug release, potentially affecting patient compliance. This study aimed to develop an in-situ forming biodegradable implant (ISFBI) optimal formulation containing PLGA504H and PLGA756S (50:50 w/w%) with the additive NMP solvent. The goal was to achieve slow and controlled release of FA over a two-month period with lower burst release, following a single intravitreal injection. Through morphology, rheology, stability and in-vitro release evaluations, the optimal formulation demonstrated low viscosity (0.12-1.25 Pa. s) and sustained release of FA at a rate of 0.36 µg/day from the third day up to two months. Furthermore, histopathology and in-vivo studies were conducted after intravitreal injection of the optimal formulation in rabbits' eye. Pharmacokinetic analysis demonstrated mean residence time (MRT) of 20.02 ± 0.6 days, half-life (t1/2) of 18.80 ± 0.4 days, and clearance (Cl) of 0.29 ± 0.03 ml/h for FA in the vitreous humor, indicating sustained and slow absorption of FA by the targeted retinal tissue from vitrea over the two-month period and eliminating through the anterior section of the eye, as revealed by its presence in the aqueous humor. Additionally, FA exhibited no detection in the blood and no evidence of systemic side effects or damage on the retinal layer and other organs. Based on these findings, it can be concluded that in-situ forming injectable biodegradable PLGA implants can show promise as a long-acting and controlled-release system for intraocular drug delivery.

Niosome as a promising tool for increasing the effectiveness of anti-inflammatory compounds

Niosomes are drug delivery systems with widespread applications in pharmaceutical research and the cosmetic industry. Niosomes are vesicles of one or more bilayers made of non-ionic surfactants, cholesterol, and charge inducers. Because of their bilayer characteristics, similar to liposomes, niosomes can be loaded with lipophilic and hydrophilic cargos. Therefore, they are more stable and cheaper in preparation than liposomes. They can be classified into four categories according to their sizes and structures, namely small unilamellar vesicles (SUVs), large unilamellar vesicles (LUVs,), multilamellar vesicles (MLVs), and multivesicular vesicles (MVVs). There are many methods for niosome preparation, such as thin-film hydration, solvent injection, and heating method. The current study focuses on the preparation methods and pharmacological effects of niosomes loaded with natural and chemical anti-inflammatory compounds in kinds of literature during the past decade. We found that most research was carried out to load anti-inflammatory agents like non-steroidal anti-inflammatory drugs (NSAIDs) into niosome vesicles. The studies revealed that niosomes could improve anti-inflammatory agents' physicochemical properties, including solubility, cellular uptake, stability, encapsulation, drug release and liberation, efficiency, and oral bioavailability or topical absorption. See also the graphical abstract(Fig. 1).

PLGA Nanoparticles Containing Natural Flavanones for Ocular Inflammation

Flavanones are natural compounds that display anti-inflammatory activity. The aim of this work was to prepare PLGA nanoparticles (NPs) containing natural flavanones I ((2S)-5,7-dihydroxy-6-methyl-8-(3-methyl-2-buten-1-il)-2-phenyl-2,3-dihydro-4H-1-Benzopyran-4-one) and II (2S)-5,7-dihydroxy-2-(4'-methoxyphenyl)-6-methyl-8-(3-methyl-2-buten-1-yl)-2,3-dihydro-4H-1-Benzopyran-4-one) (NP I and NP II, respectively) so as to evaluate their potential for topical anti-inflammatory ocular therapy. An in silico study was carried out using the Molinspiration® and PASS Online web platforms before evaluating the in vitro release study and the ex vivo porcine cornea and sclera permeation. The HPLC analytical method was also established and validated. Finally, the in vitro anti-inflammatory efficacy of NPs was studied in the HCE-2 model. The flavanones I and II could be released following a kinetic hyperbolic model. Neither of the two NPs was able to permeate through the tissues. NP I and NP II were found to be respectful of any changes in the tissues' morphology, as evidenced by histological studies. In HCE-2 cells, NP I and NP II were not cytotoxic at concentrations up to 25 µM. NP I showed higher anti-inflammatory activity than NP II, being able to significantly reduce IL-8 production in LPS-treated HCE-2 cells. In summary, ocular treatment with NP I and NP II could be used as a promising therapy for the inhibition of ocular inflammation.

Trends in Formulation Approaches for Sustained Drug Delivery to the Posterior Segment of the Eye

The eye, an intricate organ comprising physical and physiological barriers, poses a significant challenge for ophthalmic physicians seeking to treat serious ocular diseases affecting the posterior segment, such as age-related macular degeneration (AMD) and diabetic retinopathy (DR). Despite extensive efforts, the delivery of therapeutic drugs to the rear part of the eye remains an unresolved issue. This comprehensive review delves into conventional and innovative formulation strategies for drug delivery to the posterior segment of the eye. By utilizing alternative nanoformulation approaches such as liposomes, nanoparticles, and microneedle patches, researchers and clinicians can overcome the limitations of conventional eye drops and achieve more effective drug delivery to the posterior segment of the eye. These innovative strategies offer improved drug penetration, prolonged residence time, and controlled release, enhancing therapeutic outcomes for ocular diseases. Moreover, this article explores recently approved delivery systems that leverage diverse polymer technologies, such as chitosan and hyaluronic acid, to regulate drug-controlled release over an extended period. By offering a comprehensive understanding of the available formulation strategies, this review aims to empower researchers and clinicians in their pursuit of developing highly effective treatments for posterior-segment ocular diseases.

Lipid nanoparticles for gene therapy in ocular diseases

OBJECTIVES

Lipid nanoparticles, as a nucleic acid delivery system, have been used as an alternative to treat ocular diseases, since they can cross the ocular barrier and efficiently transfecting nucleic acids to various cells of the eye. The size influences the transfection of genes, biological distribution, diffusion, and cellular uptake. It is therefore important to establish a relationship between size, formulation, and encapsulation percentage.

EVIDENCE ACQUISITION

In this review, we used a search strategy to compare studies of nanomedicine systems aimed at eye diseases where the size of the nanoparticles and the efficiency of encapsulation of genetic material are reported based on the criteria of Preferred Reporting Items for Systematic Reviews (PRISMA ScR 2020 guidelines).

RESULTS

Out of the initial 5932, 169 studies met the inclusion criteria and were included to form the basis of the analysis. Nanoparticles reported are composed mainly of PEG-modified lipids, cholesterol, and cationic lipids, that in combination with messenger or interference RNA, allow the formulation of a nanoparticle with an encapsulation efficiency greater than 95%. The diseases treated mainly focus on conditions related to the retina and cornea. Certain characteristics of nanoparticles increase encapsulation efficiency, such as the size of the nanoparticle and the charge of the outer layer of the nanoparticle.

CONCLUSION

It is still unknown what characteristics lipid nanoparticles should have to successfully treat human eye illnesses. The in vitro and in vivo investigations covered in this review, however, present encouraging results. To improve encapsulation effectiveness and disease gene silencing, nanoparticle formulation is essential. The most stable nanoparticles are those made mostly of cationic lipids, PEG lipids, and cholesterol, which also effectively encapsulate RNA. The encapsulation efficiency is not only influenced by size, but also by other factors such as methods of preparation.

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

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

Nanomedicine is more than a supporting role in rheumatoid arthritis therapy

Rheumatoid arthritis(RA) is an autoimmune disorder that affects the joints. Various medications successfully alleviate the symptoms of RA in clinical. Still, few therapy strategies can cure RA, especially when joint destruction begins, and there is currently no effective bone-protective treatment to reverse the articular damage. Furthermore, the RA medications now used in clinical practice accompany various adverse side effects. Nanotechnology can improve the pharmacokinetics of traditional anti-RA drugs and therapeutic precision through targeting modification. Although the clinical application of nanomedicines for RA is in its infancy, preclinical research is rising. Current anti-RA nano-drug studies mainly focus on the following: drug delivery systems, nanomedicines with anti-inflammatory and anti-arthritic properties, biomimetic design with better biocompatibility and therapeutic features, and nanoparticle-dominated energy conversion therapies. These therapies have shown promising therapeutic benefits in animal models, indicating that nanomedicines are a potential solution to the current bottleneck in RA treatment. This review will summarize the present state of anti-RA nano-drug research.

Nanosystems for Brain Targeting of Antipsychotic Drugs: An Update on the Most Promising Nanocarriers for Increased Bioavailability and Therapeutic Efficacy

Orally administered antipsychotic drugs are the first-line treatment for psychotic disorders, such as schizophrenia and bipolar disorder. Nevertheless, adverse drug reactions jeopardize clinical outcomes, resulting in patient non-compliance. The design formulation strategies for enhancing brain drug delivery has been a major challenge, mainly due to the restrictive properties of the blood-brain barrier. However, recent pharmacokinetic and pharmacodynamic in vivo assays confirmed the advantage of the intranasal route when compared to oral and intravenous administration, as it allows direct nose-to-brain drug transport via neuronal pathways, reducing systemic side effects and maximizing therapeutic outcomes. In addition, the incorporation of antipsychotic drugs into nanosystems such as polymeric nanoparticles, polymeric mixed micelles, solid lipid nanoparticles, nanostructured lipid carriers, nanoemulsions, nanoemulgels, nanosuspensions, niosomes and spanlastics, has proven to be quite promising. The developed nanosystems, having a small and homogeneous particle size (ideal for nose-to-brain delivery), high encapsulation efficiency and good stability, resulted in improved brain bioavailability and therapeutic-like effects in animal models. Hence, although it is essential to continue research in this field, the intranasal delivery of nanosystems for the treatment of schizophrenia, bipolar disorder and other related disorders has proven to be quite promising, opening a path for future therapies with higher efficacy.

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.

An Update on Novel Ocular Nanosystems with Possible Benefits in the Treatment of Corneal Neovascularization

Corneal neovascularization (CNV) is an ocular pathological change that results from an imbalance between angiogenic factors and antiangiogenic factors as a result of various ocular insults, including infection, inflammation, hypoxia, trauma, corneal degeneration, and corneal transplantation. Current clinical strategies for the treatment of CNV include pharmacological treatment and surgical intervention. Despite some degree of success, the current treatment strategies are restricted by limited efficacy, adverse effects, and a short duration of action. Recently, gene-based antiangiogenic therapy has become an emerging strategy that has attracted considerable interest. However, potential complications with the use of viral vectors, such as potential genotoxicity resulting from long-term expression and nonspecific targeting, cannot be ignored. The use of ocular nanosystems (ONS) based on nanotechnology has emerged as a great advantage in ocular disease treatment during the last two decades. The potential functions of ONS range from nanocarriers, which deliver drugs and genes to target sites in the eye, to therapeutic agents themselves. Various preclinical studies conducted to date have demonstrated promising results of the use of ONS in the treatment of CNV. In this review, we provide an overview of CNV and its current therapeutic strategies and summarize the properties and applications of various ONS related to the treatment of CNV reported to date. Our goal is to provide a comprehensive review of these considerable advances in ONS in the field of CNV therapy over the past two decades to fill the gaps in previous related reports. Finally, we discuss existing challenges and future perspectives of the use of ONS in CNV therapy, with the goal of providing a theoretical contribution to facilitate future practical growth in the area.

The Use of Polymer Blends in the Treatment of Ocular Diseases

The eye is an organ with limited drug access due to its anatomical and physiological barriers, and the usual forms of ocular administration are limited in terms of drug penetration, residence time, and bioavailability, as well as low patient compliance. Hence, therapeutic innovations in new drug delivery systems (DDS) have been widely explored since they show numerous advantages over conventional methods, besides delivering the content to the eye without interfering with its normal functioning. Polymers are usually used in DDS and many of them are applicable to ophthalmic use, especially biodegradable ones. Even so, it can be a hard task to find a singular polymer with all the desirable properties to deliver the best performance, and combining two or more polymers in a blend has proven to be more convenient, efficient, and cost-effective. This review was carried out to assess the use of polymer blends as DDS. The search conducted in the databases of Pubmed and Scopus for specific terms revealed that although the physical combination of polymers is largely applied, the term polymer blend still has low compliance.

Spanlastics a Novel Nanovesicular Carrier: Its Potential Application and Emerging Trends in Therapeutic Delivery

Nanotechnology-based drug delivery system has played a very crucial role in overpowering the tasks allied with the conventional dosage form. Spanlastics, an elastic nanovesicle with an ability to carry wide range of drug molecules, make it a potential drug delivery carrier. Spanlastics have extended rising curiosity for diverse sort of route of administration. They can squeeze themselves through the skin pore due to elastic and deformable nature which makes them favorable for transdermal delivery. Spanlastics consist of non-ionic surfactant or blend of surfactants. Many researchers proved that spanlastics have been significantly augment therapeutic efficacy, enhanced drug bioavailability, and reduced drug toxicity. This review summarizes various vesicular systems, composition and structure of spanlastics, advantages of spanlastics over other drug delivery systems, and mechanism of drug penetration through skin. It also gives a brief on different types of drug encapsulated in spanlastics vesicles for the treatment of various diseases.

Development, Therapeutic Evaluation and Theranostic Applications of Cubosomes on Cancers: An Updated Review

Cancer is a group of disorders characterized by aberrant gene function and alterations in gene expression patterns. In 2020, it was anticipated that 19 million new cancer cases would be diagnosed globally, with around 10 million cancer deaths. Late diagnosis and interventions are the leading causes of cancer-related mortality. In addition, the absence of comprehensive cancer therapy adds to the burden. Many lyotropic non-lamellar liquid-crystalline-nanoparticle-mediated formulations have been developed in the last few decades, with promising results in drug delivery, therapeutics, and diagnostics. Cubosomes are nano-structured liquid-crystalline particles made of specific amphiphilic lipids in particular proportions. Their ability to encapsulate lipophilic, hydrophilic, and amphiphilic molecules within their structure makes them one of a kind. They are biocompatible, versatile drug carriers that can deliver medications through various routes of administration. Many preclinical studies on the use of cubosomes in cancer treatment and theranostic applications have been conducted. However, before cubosomes may be employed in clinical practice, significant technical advances must be accomplished. This review summarizes the development of cubosomes and their multifunctional role in cancer treatment based on the most recent reports.

Thermosensitive Tri-Block Polymer Nanoparticle-Hydrogel Composites as Payloads of Natamycin for Antifungal Therapy Against Fusarium Solani

Purpose

Fusarium Solani is the principal pathogen associated with fungal keratitis. As a sensitive drug to F. Solani, natamycin (NAT) was limited by the poor penetration and low bioavailability in clinical application. The aim of this study was to develop a new type of tri-block polymer nanoparticle-gel complex (Gel@PLGA-PEI-PEG@NAT) for delivering NAT and evaluate its physicochemical properties, antifungal activity, safety, penetrability, adhesion, and efficacy in treating fungal keratitis.

Methods

PLGA-PEI-PEG@NAT was prepared and characterized with a nano-particle size analyzer, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The minimum inhibitory concentration (MIC), cytotoxicity, penetrability of NAT (Natacyn^® 5% ophthalmic suspension; Alcon) and PLGA-PEI-PEG@NAT with different concentrations were assessed. The eye surface retention time, ocular irritation, and curative effect of the NAT ophthalmic suspension and Gel@PLGA-PEI-PEG@NAT on a rabbit fungal keratitis model were evaluated.

Results

PLGA-PEI-PEG@NAT had a particle size of 150 nm, a positive surface charge, and a sustained-release effect. The MIC for F. Solani was 2 μg/mL. A cytotoxicity test and ocular irritation test showed that PLGA-PEI-PEG@NAT and Gel@PLGA-PEI-PEG@NAT had good biocompatibility and no obvious irritation for rabbit corneas. Penetration experiments confirmed that PLGA-PEI-PEG@NAT can successfully enter corneal epithelial cells and through the cornea to enter the anterior chamber. Compared with NAT ophthalmic suspension, Gel@PLGA-PEI-PEG@NAT had stronger cornea permeation at the same concentration. The therapeutic effect and precorneal retention ability of the NAT ophthalmic suspension and Gel@PLGA-PEI-PEG@NAT on the fungal keratitis rabbit model were compared. Gel@PLGA-PEI-PEG@NAT achieved a better therapeutic effect at a lower drug concentration, and its eye surface retention time was significantly longer than that of the NAT ophthalmic suspension.

Conclusion

Gel@PLGA-PEI-PEG@NAT was shown to be a safe and effective nanodrug delivery system for NAT. It has great potential to improve the cure rate of fungal keratitis, reduce the administration frequency during the treatment process, and improve patient compliance.

Preparation of Liposomal Formulations for Ocular Delivery of Thymoquinone: In Vitro Evaluation in HCEC-2 e HConEC Cells

Thymoquinone (TQ) is the main constituent of Nigella sativa L. essential oil. In vitro studies have shown its protective effect against H₂O₂-induced oxidative stress in human retinal pigment epithelium cells, and in vivo experiments have demonstrated its effect in decreasing corneal neovascularization and reducing the inflammation in an experimental dry eye model in mice. Its therapeutic use is limited by poor bioavailability, low solubility, and scarce permeability. In this study, two liposomal formulations have been developed, both of which consist of phosphatidylcholine and Plurol Oleique, a liquid lipid, and one of which is coated with 0.1% w/v hyaluronic acid (HA) to increase both TQ solubility and its ocular therapeutic potential. Each formulation has a size <200 nm and an EE% around 70%, determined by scattering techniques and the HPLC-DAD analytical method, respectively, and they result in a 2-fold increase in TQ solubility. HA-coated liposomes are stable over 2 months at +4 °C, and coated and uncoated liposomes present a gradual and prolonged release of TQ. Two cell lines, human corneal epithelial cells (HCEC-2) and human conjunctival epithelial cells (HConEC) were used to investigate the safety of the liposomal formulations. Uptake studies were also performed using fluorescent liposomes. Both liposomes and, in particular, HA-coated liposomes reduce the TQ toxicity observed at high doses in both HCEC-2 and HConEC cells, and both formulations increase the absorption at the cellular level and especially at the nucleus level, with a more pronounced effect for HA-coated liposomes.

Recent Advances in Photodynamic Therapy against Fungal Keratitis

Fungal keratitis is a serious clinical infection on the cornea caused by fungi and is one of the leading causes of blindness in Asian countries. The treatment options are currently limited to a few antifungal agents. With the increasing incidence of drug-resistant infections, many patients fail to respond to antibiotics. Riboflavin-mediated corneal crosslinking (similar to photodynamic therapy (PDT)) for corneal ectasia was approved in the US in the early 2000s. Current evidence suggests that PDT could have the potential to inhibit fungal biofilm formation and overcome drug resistance by using riboflavin and rose bengal as photosensitizers. However, only a few clinical trials have been initiated in anti-fungal keratitis PDT treatment. Moreover, the removal of the corneal epithelium and repeated application of riboflavin and rose bengal are required to improve drug penetration before and during PDT. Thus, an improvement in trans-corneal drug delivery is mandatory for a successful and efficient treatment. In this article, we review the studies published to date using PDT against fungal keratitis and aim to enhance the understanding and awareness of this research area. The potential of modifying photosensitizers using nanotechnology to improve the efficacy of PDT on fungal keratitis is also briefly reviewed.

Enhanced topical corticosteroids delivery to the eye: A trade-off in strategy choice

Topical corticosteroids are the primary treatment of ocular inflammation caused by surgery, injury, or other conditions. Drug pre-corneal residence time, drug water solubility, and drug corneal permeability coefficient are the major factors that determine the ocular drug bioavailability after topical administration. Although growing research successfully enhanced local delivery of corticosteroids utilizing various strategies, rational and dynamic approaches to strategy selection are still lacking. Within this review, an overview of the various strategies as well as their performance in retention, solubility, and permeability coefficient of corticosteroids are provided. On this basis, the tradeoff of strategy selection is discussed, which may shed light on the rational choice and application of ophthalmic delivery enhancement strategies.

A Novel Carbon Dots/Thermo-Sensitive In Situ Gel for a Composite Ocular Drug Delivery System: Characterization, Ex-Vivo Imaging, and In Vivo Evaluation

We developed a potential composite ocular drug delivery system for the topical administration of diclofenac sodium (DS). The novel carbon dot CD_C-HP was synthesized by the pyrolysis of hyaluronic acid and carboxymethyl chitosan through a one-step hydrothermal method and then embedded in a thermosensitive in situ gel of poloxamer 407 and poloxamer 188 through swelling loading. The physicochemical characteristics of these carbon dots were investigated. The results of the in vitro release test showed that this composite ocular drug delivery system (DS-CD_C-HP-Gel) exhibited sustained release for 12 h. The study of the ex vivo fluorescence distribution in ocular tissues showed that it could be used for bioimaging and tracing in ocular tissues and prolong precorneal retention. Elimination profiles in tears corresponded to the study of ex vivo fluorescence imaging. The area under the curve of DS in the aqueous humor in the DS-CD_C-HP-Gel group was 3.45-fold that in the DS eye drops group, indicating a longer precorneal retention time. DS-CD_C-HP with a positive charge and combined with a thermosensitive in situ gel might strengthen adherence to the corneal surface and prolong the ocular surface retention time to improve the bioavailability. This composite ocular delivery system possesses potential applications in ocular imaging and drug delivery.

Sustained Release of a Streptococcus pneumoniae Endolysin from Liposomes for Potential Otitis Media Treatment

Local delivery of antimicrobials for otitis media treatment would maximize therapeutic efficacy while minimizing side effects. However, drug transport across the tympanic membrane in the absence of a delivery system is challenging. In this study, the MSlys endolysin was encapsulated in deformable liposomes for a targeted treatment of S. pneumoniae, one of the most important causative agents of otitis media. MSlys was successfully encapsulated in liposomes composed of l-alpha-lecithin and sodium cholate (5:1) or l-alpha-lecithin and PEG2000 PE (10:1), with encapsulation efficiencies of about 35%. The PEGylated and sodium cholate liposomes showed, respectively, mean hydrodynamic diameters of 85 and 115 nm and polydispersity indices of 0.32 and 0.42, both being stable after storage at 4 °C for at least one year. Both liposomal formulations showed a sustained release of MSlys over 7 days. Cytotoxicity studies against fibroblast and keratinocyte cell lines revealed the biocompatible nature of both MSlys and MSlys-loaded liposomes. Additionally, the encapsulated MSlys showed prompt antipneumococcal activity against planktonic and biofilm S. pneumoniae, thus holding great potential for transtympanic treatment against S. pneumoniae otitis media.

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

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

Recent Advances in the Excipients Used for Modified Ocular Drug Delivery

In ocular drug delivery, maintaining an efficient concentration of the drug in the target area for a sufficient period of time is a challenging task. There is a pressing need for the development of effective strategies for drug delivery to the eye using recent advances in material sciences and novel approaches to drug delivery. This review summarizes the important aspects of ocular drug delivery and the factors affecting drug absorption in the eye including encapsulating excipients (chitosan, hyaluronic acid, poloxamer, PLGA, PVCL-PVA-PEG, cetalkonium chloride, and gelatin) for modified drug delivery.

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.

Lipid-Based Nanocarriers as Topical Drug Delivery Systems for Intraocular Diseases

Effective drug delivery to intraocular tissues remains a great challenge due to complex anatomical and physiological barriers that selectively limit the entry of drugs into the eye. To overcome these challenges, frequent topical application and regular intravitreal injections are currently used to achieve the desired drug concentrations into the eye. However, the repetitive installation or recurrent injections may result in several side effects. Recent advancements in the field of nanoparticle-based drug delivery have demonstrated promising results for topical ophthalmic nanotherapies in the treatment of intraocular diseases. Studies have revealed that nanocarriers enhance the intraocular half-life and bioavailability of several therapies including proteins, peptides and genetic material. Amongst the array of nanoparticles available nowadays, lipid-based nanosystems have shown an increased efficiency and feasibility in topical formulations, making them an important target for constant and thorough research in both preclinical and clinical practice. In this review, we will cover the promising lipid-based nanocarriers used in topical ophthalmic formulations for intraocular drug delivery.

Reinforced electrospun nanofiber composites for drug delivery applications

Electrospun technology becomes a valuable means of fabricating functional polymeric nanofibers with distinctive morphological properties for drug delivery applications. Nanofibers are prepared from the polymer solution, which allows the direct incorporation of therapeutics such as small drug molecules, genes, and proteins by merely mixing them into the polymeric solution. Due to their biocompatibility, adhesiveness, sterility, and efficiency in delivering diverse cargoes, electrospun nanofibers have gained much attention. This review discusses the capabilities of the electrospun nanofibers in delivering different therapeutics like small molecules, genes, and proteins to their desired target site for treating various ailments. The potential of nanofibers in administering through multiple administration routes and the associated challenges has also been expounded along with a cross-talk about the commercial products of nanofibers for biomedical applications.

Superoxide Dismutase 1 Nanoparticles (Nano-SOD1) as a Potential Drug for the Treatment of Inflammatory Eye Diseases

Inflammatory eye diseases remain the most common clinical problem in ophthalmology. The secondary processes associated with inflammation, such as overproduction of reactive oxygen species (ROS) and exhaustion of the endogenous antioxidant system, frequently lead to tissue degeneration, vision blurring, and even blindness. Antioxidant enzymes, such as copper-zinc superoxide dismutase (SOD1), could serve as potent scavengers of ROS. However, their delivery into the eye compartments represents a major challenge due to the limited ocular penetration. This work presents a new therapeutic modality specifically formulated for the eye on the basis of multilayer polyion complex nanoparticles of SOD1 (Nano-SOD1), which is characterized by appropriate storage stability and pronounced therapeutic effect without side reactions such as eye irritation; acute, chronic, and reproductive toxicity; allergenicity; immunogenicity; mutagenicity even at high doses. The ability of Nano-SOD1 to reduce inflammatory processes in the eye was examined in vivo in rabbits with a model immunogenic uveitis-the inflammation of the inner vascular tract of the eye. It was shown during preclinical studies that topical instillations of Nano-SOD1 were much more effective compared to the free enzyme in decreasing uveitis manifestations. In particular, we noted statistically significant differences in such inflammatory signs in the eye as corneal and conjunctival edema, iris hyperemia, and fibrin clots. Moreover, Nano-SOD1 penetrates into interior eye structures more effectively than SOD itself and retains enzyme activity in the eye for a much longer period of time, decreasing inflammation and restoring antioxidant activity in the eye. Thus, the presented Nano-SOD1 can be considered as a potentially useful therapeutic agent for the treatment of ocular inflammatory disorders.

Lipid-Based Nanocarriers for Ophthalmic Administration: Towards Experimental Design Implementation

Nanotherapeutics based on biocompatible lipid matrices allow for enhanced solubility of poorly soluble compounds in the treatment of ophthalmic diseases, overcoming the anatomical and physiological barriers present in the eye, which, despite the ease of access, remains strongly protected. Micro-/nanoemulsions, solid lipid nanoparticles (SLN) or nanostructured lipid carriers (NLC) combine liquid and/or solid lipids with surfactants, improving drug stability and ocular bioavailability. Current research and development approaches based on try-and-error methodologies are unable to easily fine-tune nanoparticle populations in order to overcome the numerous constraints of ocular administration routes, which is believed to hamper easy approval from regulatory agencies for these systems. The predictable quality and specifications of the product can be achieved through quality-by-design (QbD) implementation in both research and industrial environments, in contrast to the current quality-by-testing (QbT) framework. Mathematical modelling of the expected final nanoparticle characteristics by variation of operator-controllable variables of the process can be achieved through adequate statistical design-of-experiments (DoE) application. This multivariate approach allows for optimisation of drug delivery platforms, reducing research costs and time, while maximising the understanding of the production process. This review aims to highlight the latest efforts in implementing the design of experiments to produce optimised lipid-based nanocarriers intended for ophthalmic administration. A useful background and an overview of the different possible approaches are presented, serving as a starting point to introduce the design of experiments in current nanoparticle research.

Development of Triamcinolone Acetonide-Loaded Microemulsion as a Prospective Ophthalmic Delivery System for Treatment of Uveitis: In Vitro and In Vivo Evaluation

Treatment of uveitis (i.e., inflammation of the uvea) is challenging due to lack of convenient ophthalmic dosage forms. This work is aimed to determine the efficiency of triamcinolone acetonide (TA)-loaded microemulsion as an ophthalmic delivery system for the treatment of uveitis. Water titration method was used to construct different pseudo-ternary phase diagrams. Twelve microemulsion formulations were prepared using oleic acid, Cremophor EL, and propylene glycol. Among all tested formulations, Formulation F3, composed of oil: surfactant-co-surfactant (1:1): water (15:35:50% w/w, respectively), was found to be stable and showed acceptable pH, viscosity, conductivity, droplet size (211 ± 1.4 nm), and zeta potential (−25 ± 1.7 mV) and almost complete in vitro drug release within 24 h. The in vivo performance of the optimized formulation was evaluated in experimentally uveitis-induced rabbit model and compared with a commercial TA suspension (i.e., Kenacort^®-A) either topically or by subconjunctival injection. Ocular inflammation was evaluated by clinical examination, white blood cell count, protein content measurement, and histopathological examination. The developed TA-loaded microemulsion showed superior therapeutic efficiency in the treatment of uveitis with high patient compliance compared to commercial suspension. Hence, it could be considered as a potential ocular treatment option in controlling of uveitis.

Screening of chemical linkers for development of pullulan bioconjugates for intravitreal ocular applications

The treatment of posterior segment disorders of the eye requires therapeutic strategies to achieve drug effects over prolonged times. Innovative colloidal delivery systems can be designed to deliver drugs to the retina and prolong their intravitreal permanence. In order to exploit pullulan (Pull) as polymeric drug carrier for intravitreal drug delivery, derivatives of hydrophobic model molecule rhodamine B (RhB) were conjugated to the pullulan backbone through linkers with different stability, namely ether (Et), hydrazone (Hy) or ester (Es) bond to obtain Pull-Et-RhB, Pull-Hy-RhB and Pull-Es-RhB, respectively. Dynamic light scattering and transmission electron microscopy analyses showed that the polymer conjugates self-assembled into 20-25 nm particles. Pull-Et-RhB was fairly stable at all tested pH values. At the vitreal pH of 7.4, 50% of RhB was released from Pull-Hy-RhB and Pull-Es-RhB in 11 and 6 days, respectively. At endosomal pH (5.5), 50% of RhB was released from Pull-Hy-RhB and Pull-Es-RhB in 4 and 1 days, respectively. Multiple particle tracking analyses in ex vivo porcine eye model showed that the diffusivity of the bioconjugates in the vitreous was about 10³ times lower than in water. Flow cytometry and confocal microscopy analyses showed that bioconjugates are remarkably taken up by the retinal RPE cells. In vivo studies showed that after intravitreal injection to mice, the bioconjugates localize in the ganglion cell layer and in the inner and outer plexiform layers. Pull-Hy-RhB particles were detected also inside the retinal blood vessels. These results demonstrate that pullulan with tailored linkers for drug conjugation is a promising vehicle for long-acting intravitreal injectables that are capable to permeate to the retina.

Latanoprost-loaded phytantriol cubosomes for the treatment of glaucoma

Glaucoma is a degenerative optic neuropathy characterized by increased intraocular pressure that if untreated can result in blindness. Ophthalmological drug therapy is a challenge of great clinical importance due to the diversity of ocular biological barriers which commonly causes limited or no effectiveness for drugs delivered through the eye. In this work, we proposed the development of nanosized cubic liquid crystals (cubosomes) as a new drug carrier system for latanoprost, an anti-glaucoma drug. Latanoprost-loaded phytantriol cubosomes (CubLnp) were prepared using a top-down method. Latanoprost concentration in the formulations ranged from 0.00125% to 0.02% w/v. All cubosomes displayed an average size around 200 nm, a low polydispersity index of 0.1 and zeta potential values around -25 mV, with an encapsulation efficiency of about 90%. Structural studies revealed that cubosomes displayed a double-diamond surface, Pn3m cubic-phase structure, and was not affected by drug loading. Calorimetric studies revealed a fast and exothermic interaction between latanoprost and cubosomes. According to in vitro essays, latanoprost release from cubosomes was slow in time, evidencing a sustained release profile. Based on this behavior, the in vivo hypotensive intraocular effect was evaluated by means of the subconjunctival administration of CubLnp in normotensive rabbits. We obtained promising results in comparison with a marketed latanoprost formulation (0.005% w/v).

Curcumin-loaded proniosomal gel as a biofreindly alternative for treatment of ocular inflammation: In-vitro and in-vivo assessment

Ocular inflammation is a natural defensive phenomenon, but, it results in discomfort in the eye; as well as makes the eye vulnerable to other diseases. The aim of this work is to investigate that Curcumin (CUR) could be an effective safer biofreindly alternative for treatment of ocular inflammation. Complete in-vitro characterization of proniosomal gel loading-CUR using different surfactants was studied. A comparative in-vivo evaluation of selected formulation to a marketed corticosteroid drops in induced-eye inflammation model in rabbits was assessed. The selected formulation (F_{Cr 300}) composed of Cremophore RH surfactant, lecithin and cholesterol (9:9:1) loading CUR (1.2% w/w). The formulation showed mean PS(212.0 ± 0.1)nm, PDI (0.3 ± 0.1) , ZP(-5.1 ± 0.2)mV and % EE (96.0 ± 0.1). TEM showed multilamellar circular shaped niosomes with smooth surface. SEM showed ruptured vesicles for the lyophilized formula. Selected proniosomal gel showed enhanced permeability 3.22-fold and 1.76-fold higher than CUR dispersion and its lyophilized form respectively. Both proniosomal gel (F_Cr300) and corticosteroid drops reduced the induced inflammatory signs effectively by 40% on day-one and complete recovery on day-four. This anti-inflammatory result was confirmed by histopathological analysis after treatment. Assessment of cumulative IOP as a predicted side effect verified the goal of this work. In conclusion, the use of CUR as a natural biofreindly alternative to the current chemical conventional ocular anti-inflammatory treatment protocols is comparable as an anti-inflammatory drug with much less side effects.

Topical instillation of triamcinolone acetonide-loaded emulsomes for posterior ocular delivery: statistical optimization and in vitro-in vivo studies

The objective of the present investigation was to formulate and characterize a novel lipid-based carrier-emulsomes loaded with triamcinolone acetonide (TA)/Nile red (NR) for non-invasive delivery to the posterior segment of the eye upon topical application. To optimize and delineate the effect of independent variables on dependent variables, Box-Behnken design (BBD) was adopted. The optimized batch was characterized for size, zeta potential, surface morphology by transmission electron microscopy, drug-excipient interaction by differential scanning calorimetry, osmolarity, pH, ex vivo transcorneal permeation, and stability studies. A short-term exposure (STE) test was performed on Statens Seruminstitut Rabbit Corneal (SIRC) cell lines to evaluate the in vitro ocular irritation. Precorneal retention study was performed in rabbit eyes. Confocal microscopy was used for ocular distribution studies in mice eye by preparing dye (Nile red)-loaded formulations. The surface response and contour plots along with ANOVA results demonstrated an interaction between the factors. The optimized batch had particle size of 131.17 ± 3.17 nm and entrapment efficiency of 71.56 ± 4.19%. TEM image showed unimodal, nano-sized emulsomes. TA-loaded emulsomes exhibited higher transcorneal permeation as compared to drug solution. In vitro irritation studies confirmed the safety of excipients for ophthalmic use. Fluorescence microscopic images obtained after ocular distribution studies showed strong fluorescence in inner and outer plexiform layers of the retina in comparison to dye solution confirming the delivery of dye to the posterior segment of mice eye after topical ocular instillation. Graphical abstract.

Recent Advances in the Design of Topical Ophthalmic Delivery Systems in the Treatment of Ocular Surface Inflammation and Their Biopharmaceutical Evaluation

Ocular inflammation is one of the most common symptom of eye disorders and diseases. The therapeutic management of this inflammation must be rapid and effective in order to avoid deleterious effects for the eye and the vision. Steroidal (SAID) and non-steroidal (NSAID) anti-inflammatory drugs and immunosuppressive agents have been shown to be effective in treating inflammation of the ocular surface of the eye by topical administration. However, it is well established that the anatomical and physiological ocular barriers are limiting factors for drug penetration. In addition, such drugs are generally characterized by a very low aqueous solubility, resulting in low bioavailability as only 1% to 5% of the applied drug permeates the cornea. The present review gives an updated insight on the conventional formulations used in the treatment of ocular inflammation, i.e., ointments, eye drops, solutions, suspensions, gels, and emulsions, based on the commercial products available on the US, European, and French markets. Additionally, sophisticated formulations and innovative ocular drug delivery systems will be discussed. Promising results are presented with micro- and nanoparticulated systems, or combined strategies with polymers and colloidal systems, which offer a synergy in bioavailability and sustained release. Finally, different tools allowing the physical characterization of all these delivery systems, as well as in vitro, ex vivo, and in vivo evaluations, will be considered with regards to the safety, the tolerance, and the efficiency of the drug products.

Formulation of Chitosan Polymeric Vesicles of Ciprofloxacin for Ocular Delivery: Box-Behnken Optimization, In Vitro Characterization, HET-CAM Irritation, and Antimicrobial Assessment

Ciprofloxacin is a commonly used antibiotic for treatment of bacterial conjunctivitis. The conventional eye drop dosage form is the widely used mode of treatment, but it has low corneal residence time. This drawback can be overcome by developing a bioadhesive noisome system (chitosan-coated) for enhanced corneal residence time. The niosomes were prepared by thin-film hydration technique and optimized by using Box-Behnken statistical design software. Cholesterol (A), Span 60 (B), and sonication time (C) were selected as independent variables, whereas vesicle size (Y₁ in nm), entrapment efficiency (Y₂ in %), and drug release (Y₃ in %) were chosen as dependent variables. The vesicle size, entrapment efficiency, and drug release of optimized CIP niosomes (CIP-NSMopt) were found to be 180.34 ± 5.13 nm, 78.32 ± 4.49%, and 82.87 ± 4.01% (in 12 h), respectively. Further CIP-NSMopt was coated with different chitosan concentrations (0.1 to 0.3%) to enhance mucoadhesion. Finally, optimized chitosan-coated niosomes (chitosomes; CIP-CHTopt) showed a vesicle size of 210.65 ± 2.76 nm, zeta potential of - 35.17 ± 2.25Mv, and PDI of 0.221. CIP-CHTopt exhibited sustained release profile (75.31% in 12 h) with the Korsmeyer-Peppas kinetic model (R² = 0.980). The permeation study showed 1.79-fold enhancements in corneal permeation compared with marketed CIP eye drop. The hen's egg chorioallantoic membrane (HET-CAM) study showed 0 scores (no irritation), and it was further confirmed by corneal hydration and histopathology study. The antimicrobial study exhibited a significant high zone (P < 0.05) of inhibition against tested organism. Our findings demonstrated that chitosan-coated niosomes are a promising drug carrier to enhance corneal contact time and treatment of bacterial conjunctivitis.

Neuroprotection: A versatile approach to combat glaucoma

In most retinal diseases, neuronal loss is the main cause of vision loss. Neuroprotection is the alteration of neurons and/or their environment to encourage the survival and function of the neurons, especially in environments that are deleterious to the neuronal health. The area of neuroprotection progresses with a therapeutically-based hope of improving vision and clinical outcomes for patients through the developments in neurotrophic therapy, antioxidative therapy, anti-excitotoxic, anti-ischemic, anti-inflammatory, and anti-apoptotic care. In this review, we summarize the various neuroprotection strategies for the treatment of glaucoma, genetics of glaucoma and the role of various nanoplatforms in the treatment of glaucoma.

Functional ibuprofen-loaded cationic nanoemulsion: Development and optimization for dry eye disease treatment

Inflammation plays a key role in dry eye disease (DED) affecting millions of people worldwide. Non-steroidal anti-inflammatory drugs (NSAIDs) can be used topically to act on the inflammatory component of DED, but their limited aqueous solubility raises formulation issues. The aim of this study was development and optimization of functional cationic nanoemulsions (NEs) for DED treatment, as a formulation approach to circumvent solubility problems, prolong drug residence at the ocular surface and stabilize the tear film. Ibuprofen was employed as the model NSAID, chitosan as the cationic agent, and lecithin as the anionic surfactant enabling chitosan incorporation. Moreover, lecithin is a mixture of phospholipids including phosphatidylcholine and phosphatidylethanolamine, two constituents of the natural tear film important for its stability. NEs were characterized in terms of droplet size, polydispersity index, zeta-potential, pH, viscosity, osmolarity, surface tension, entrapment efficiency, stability, sterilizability and in vitro release. NEs mucoadhesive properties were tested rheologically after mixing with mucin dispersion. Biocompatibility was assessed employing 3D HCE-T cell-based model and ex vivo model using porcine corneas. The results of our study pointed out the NE formulation with 0.05% (w/w) chitosan as the lead formulation with physicochemical properties adequate for ophthalmic application, mucoadhesive character and excellent biocompatibility.

Proniosomal gel-derived niosomes: an approach to sustain and improve the ocular delivery of brimonidine tartrate; formulation, in-vitro characterization, and in-vivo pharmacodynamic study

Brimonidine tartrate (BRT) is a hydrophilic α2 adrenergic agonist used for the treatment of glaucoma. Glaucoma is an ocular disease affecting the anterior segment of the eye requiring lifetime treatment. Owing to the obstacles facing ocular delivery systems and hydrophilicity of BRT, frequent administration of the eye drops is required. Niosomes have been widely used to improve the ocular bioavailability of the topically applied drugs and to enhance the ocular residence time. However, they have drawbacks as physical instability, aggregation, and loss of the entrapped drug. For this reason, BRT proniosomes were prepared to overcome niosomal instability issues. A D-optimal design was utilized to determine the optimum conditions for preparation of the proniosomal gels. Independent variables were amount of surfactant, surfactant:cholesterol ratio, and type of surfactant used. The dependent variables were entrapment efficiency (EE%), particle size, percentage of drug released after 2 h (Q2h), and percentage of drug released after 24 h (Q24h). The optimum formula was suggested with desirability 0.732 and the composition of 540 mg Span 60 and 10:1 surfactant:cholesterol ratio. The results obtained after reconstitution were; EE% of 79.23 ± 1.12% particle size of 810.95 ± 16.758 nm, polydispersity index (PDI) 0.6785 ± 0.213, zeta potential 59.1 ± 0.99 mV, Q2h40.98 ± 1.29%, Q8h 63.35 ± 6.07%, and Q24h = 91.11 ± 1.76%. Transmission electron microscope imaging of the formula showed the typical spherical shape of niosomes. In-vivo pharmacodynamic study assured the improved ocular bioavailability of BRT selected formula when compared with Alphagan®P with relative AUC0-24 of 5.024 and 7.90 folds increase in the mean residence time (MRT). Lack of ocular irritation of the formula was assured by Draize test.

Preparation and characterization of β-casein stabilized lipopeptide lyotropic liquid crystal nanoparticles for delivery of doxorubicin

A kind of lyotropic liquid crystal nanoparticle (LLC NPs) has been designed and prepared. LLC NPs are dSMO/OA/β-casein/water quaternary systems, and their cubic or hexagonal microstructures have been characterized by cryogenic transmission electron microscopy (cryo-TEM) and small angle X-ray scattering (SAXS). The phase transition of LLC NPs takes place with ratio and pH adjustments. The properties, such as cytotoxicity, stability, drug encapsulation and release ability, have been investigated with MTT assay, cryo-TEM and UV-Vis spectroscopy. The results showed that LLC NPs were nontoxic to cells and stable to enzymatic degradation. Hydrophilic drug doxorubicin hydrochloride (DOX·HCl) could be effectively encapsulated in LLC NPs and its release rate could be regulated by pH. It was concluded that LLC NPs are potential nanocarriers in nanomedicine technologies. We hope that this work provides new guidelines for the rational design of LLC NP systems with lipopeptides for biomedical applications.

Ultra-small micelles based on polyoxyl 15 hydroxystearate for ocular delivery of myricetin: optimization, in vitro, and in vivo evaluation

The aim was to develop a nanocarrier based on polyoxyl 15 hydroxystearate (Kolliphor® HS15, HS15) micelles for the solubility, stability, and ocular delivery of myricetin (Myr). An optimized ratio of HS15 and Myr was prepared to fabricate HS15-Myr micelle ophthalmic solution. Myr-encapsulating HS15 micelles (HS15-Myr micelles) were subjected to physicochemical characterizations. The chemical stability of Myr in HS15 micelles and storage stability of HS15-Myr micelle ophthalmic solutions were evaluated. In vitro parallel artificial membrane permeability assay and antioxidant activity of Myr in HS15 micelles were also measured. In vivo ocular tolerance, corneal permeation, and anti-inflammatory efficacy studies were conducted following ocular topical administration. HS15-Myr micelles were successfully prepared and presented transparent appearance with high encapsulation (96.12 ± 0.31%), ultra-small micelle size (a mean diameter of 12.17 ± 0.73 nm), uniform size distribution (polydispersity index [PDI] = 0.137 ± 0.013), and negative surface charge (- [4.28 ± 0.42] mV). Myr in HS15 micelle solution demonstrated higher aqueous stability than the free Myr solution among the accepted pH range for eyedrops. HS15-Myr micelle ophthalmic solution demonstrated high storage stability at 4 °C and 25 °C. HS15 micelles could significantly improve in vitro antioxidant activity and faster membrane permeation of Myr. No irritations or corneal damage were revealed in rabbit eyes after ocular administration of HS15-Myr micelle solution. In vivo corneal permeation study demonstrated that HS15-Myr micelles could penetrate the cornea efficiently in mouse eyes. Further, HS15-Myr micelles also demonstrated significant in vivo anti-inflammatory activity. It can be concluded that HS15 micelles are a potential ophthalmic delivery nanocarrier for poorly soluble drugs such as Myr.