A novel cationic nanostructured lipid carrier for improvement of ocular bioavailability: Design, optimization, in vitro and in vivo evaluation

From Preformulative Design to in Vivo Tests: A Complex Path of Requisites and Studies for Nanoparticle Ocular Application. Part 2: In Vitro, Ex Vivo, and In Vivo Studies

The incidence of ocular pathologies is constantly increasing, as is the interest of the researchers in developing new strategies to ameliorate the treatment of these conditions. Nowadays, drug delivery systems are considered among the most relevant approaches due to their applicability in the treatment of a great variety of inner and outer eye pathologies through painless topical administrations. The design of such nanocarriers requires a deep study of many aspects related to the administration route but also a consideration of the authorities and pharmacopeial requirements, in order to achieve a clinical outcome. On such bases, the scope of this review is to describe the path of the analyses that could be performed on nanoparticles, along with the assessment of their applicability for ophthalmic treatments. Preformulation studies, physicochemical and technological characterization, and preliminary noncellular in vitro studies have been described in part 1 of this review. Herein, first the in vitro cellular assays are described; subsequently, nonocular organotypic tests and ex vivo studies are reported, as to present the various analyses to which the formulations can be subjected before in vivo studies, described in the last part. In each step, the models that could be used are presented and compared, highlighting the pros and cons. Moreover, their reliability and eventual acceptance by regulatory agencies are discussed. Hence, this review provides an overview of the most relevant assays applicable for nanocarriers intended for ophthalmic administration to guide researchers in the experimental decision process.

Absorption enhancement strategies in chitosan-based nanosystems and hydrogels intended for ocular delivery: Latest advances for optimization of drug permeation

Ophthalmic diseases can be presented as acute diseases like allergies, ocular infections, etc., or chronic ones that can be manifested as a result of systemic disorders, like diabetes mellitus, thyroid, rheumatic disorders, and others. Chitosan (CS) and its derivatives have been widely investigated as nanocarriers in the delivery of drugs, genes, and many biological products. The biocompatibility and biodegradability of CS made it a good candidate for ocular delivery of many ingredients, including immunomodulating agents, antibiotics, ocular hypertension medications, etc. CS-based nanosystems have been successfully reported to modulate ocular diseases by penetrating biological ocular barriers and targeting and controlling drug release. This review provides guidance to drug delivery formulators on the most recently published strategies that can enhance drug permeation to the ocular tissues in CS-based nanosystems, thus improving therapeutic effects through enhancing drug bioavailability. This review will highlight the main ocular barriers to drug delivery observed in the nano-delivery system. In addition, the CS physicochemical properties that contribute to formulation aspects are discussed. It also categorized the permeation enhancement strategies that can be optimized in CS-based nanosystems into four aspects: CS-related physicochemical properties, formulation components, fabrication conditions, and adopting a novel delivery system like implants, inserts, etc. as described in the published literature within the last ten years. Finally, challenges encountered in CS-based nanosystems and future perspectives are mentioned.

Lipid-based nanoparticles: innovations in ocular drug delivery

Ocular drug delivery presents significant challenges due to intricate anatomy and the various barriers (corneal, tear, conjunctival, blood-aqueous, blood-retinal, and degradative enzymes) within the eye. Lipid-based nanoparticles (LNPs) have emerged as promising carriers for ocular drug delivery due to their ability to enhance drug solubility, improve bioavailability, and provide sustained release. LNPs, particularly solid lipid nanoparticles (SLNs), nanostructured lipid carriers (NLCs), and cationic nanostructured lipid carriers (CNLCs), have emerged as promising solutions for enhancing ocular drug delivery. This review provides a comprehensive summary of lipid nanoparticle-based drug delivery systems, emphasizing their biocompatibility and efficiency in ocular applications. We evaluated research and review articles sourced from databases such as Google Scholar, TandFonline, SpringerLink, and ScienceDirect, focusing on studies published between 2013 and 2023. The review discusses the materials and methodologies employed in the preparation of SLNs, NLCs, and CNLCs, focusing on their application as proficient carriers for ocular drug delivery. CNLCs, in particular, demonstrate superior effectiveness attributed due to their electrostatic bioadhesion to ocular tissues, enhancing drug delivery. However, continued research efforts are essential to further optimize CNLC formulations and validate their clinical utility, ensuring advancements in ocular drug delivery technology for improved patient outcomes.

Enhanced Pharmacokinetics and Anti-inflammatory Activity of Curcumin Using Dry Emulsion as Drug Delivery Vehicle

BACKGROUND AND OBJECTIVE

Many naturally available dietary molecules such as curcumin have not seen the market due to poor solubility, bioavailability, and photodegradability. Successful development of a lipid-based dry emulsion may overcome these issues and help in reaching the markets for natural dietary molecules such as curcumin. The current study aims to develop a dry emulsion formulation of curcumin using natural oil and evaluate its dissolution, photostability, pharmacokinetics, and anti-inflammatory activity.

METHODS

Dry emulsions were prepared using emu oil and corn oil as the lipid phase, Caproyl 90 and Cremophor RH 40 as surfactants, and dextrin as a hydrophilic carrier.

RESULTS

Microscopic studies showed the formation of spherical porous particles, and solid-state characterization using differential scanning calorimetry and powder X-ray diffraction showed the conversion of curcumin to an amorphous form. About 80% drug release was observed from formulation, whereas pure drug showed only 50% drug release in 30 min. In vivo pharmacokinetic studies showed fivefold improvement in the maximum concentration of curcumin in plasma (C_max) and sevenfold improvement in the area under the concentration-time curve of curcumin from emu oil formulation compared with pure curcumin. Significant differences were observed in the anti-inflammatory activity of curcumin dry emulsion and plain curcumin. Emu-oil-based formulations showed synergistic anti-inflammatory activity over corn-oil-based formulations with improved photostability.

CONCLUSION

The present study suggests that the dry emulsion may enhance the bioavailability with synergistic anti-inflammatory activity and photostability of curcumin when given orally.

Effective Ocular Delivery of Eplerenone Using Nanoengineered Lipid Carriers in Rabbit Model

Background

Eplerenone (Epl) is a selective mineralocorticoid-receptor antagonist used for chronic central serous chorioretinopathy treatment. Our goal was to enhance the corneal performance of Epl-loaded nanostructured lipid carriers (NLCs) through surface modification using different coating polymers.

Methods

Epl-loaded modified NLCs (Epl-loaded MNLCs) were prepared by coating the surface of Epl-loaded NLCs using different polymers, namely hyaluronic acid, chitosan oligosaccharide lactate, and hydrogenated collagen. A 3¹×4¹ full factorial design was used to evaluate the effect of the surface modification on the properties of the prepared systems. Selected optimal Epl-loaded MNLCs were further evaluated for in vitro drug release, morphology, pH, rheological properties, corneal mucoadhesion, irritation, and penetration.

Results

Epl-loaded MNLCs were successfully prepared with high drug-entrapment efficiency and nanosized particles with low size distribution. Transmission electron microscopy revealed nanosized spherical particles surrounded by a coating layer of the surface modifier. The pH, refractive index, and viscosity results of the Epl-loaded MNLCs confirmed the ocular compatibility of the systems with no blurring of vision. The safety and ocular tolerance of the optimal MNLCs were confirmed using the hen’s egg test on chorioallantoic membrane and by histopathological evaluation of rabbit eyes treated with the optimal systems. Confocal laser-scanning microscopy of corneal surfaces confirmed successful transcorneal permeation of the Epl-loaded MNLCs compared to the unmodified Epl-loaded NLCs, revealed by higher corneal fluorescence intensity at all time intervals.

Conclusion

Overall, the results confirmed the potential of Epl-loaded MNLCs as a direct approach for Epl ocular delivery.

Therapeutic advancement of simvastatin-loaded solid lipid nanoparticles (SV-SLNs) in treatment of hyperlipidemia and attenuating hepatotoxicity, myopathy and apoptosis: Comprehensive study

This study set out to optimize simvastatin (SV) in lipid nanoparticles (SLNs) to improve bioavailability, efficacy and alleviate adverse effects. Simvastatin-loaded solid lipid nanoparticles (SV-SLNs) were prepared by hot-melt ultrasonication method and optimized by box-Behnken experimental design. Sixty Wister albino rats were randomly assigned into six groups and treated daily for 16 weeks: control group, the group fed with 20 g of high-fat diet (HFD), group treated with vehicle (20 mg/kg, P.O.) for last four weeks, group treated with HFD and SV (20 mg/kg, P.O.) / or SV-SLNs (20 mg/kg/day, P.O.) / or SV-SLNs (5 mg/kg, P.O.) at last four weeks. Blood, liver tissues, and quadriceps muscles were collected for biochemical analysis, histological and immunohistochemical assays. The optimized SV-SLNS showed a particle-size 255.2 ± 7.7 nm, PDI 0.31 ± 0.09, Zeta-potential - 19.30 ± 3.25, and EE% 89.81 ± 2.1%. HFD showed severe changes in body weight liver functions, lipid profiles, atherogenic index (AIX), albumin, glucose, insulin level, alkaline phosphatase as well as muscle injury, oxidative stress biomarkers, and protein expression of caspase-3. Simvastatin treatment in animals feed with HFD showed a significant improvement of all tested parameters, but it was associated with hepatotoxicity, myopathy, and histological changes in quadriceps muscles. SV-SLNs exhibited a significant improvement of all biochemical, histological examinations, and immunohistochemical assays. SV-SLNs (5 mg/kg) treatment returns all measured parameters to control itself. These results represent that SV-SLNs is a promising candidate as a drug carrier for delivering SV with maximum efficacy and limited adverse reaction.

Chitosan and its Derivatives for Ocular Delivery Formulations: Recent Advances and Developments

Chitosan (CS) is a hemi-synthetic cationic linear polysaccharide produced by the deacetylation of chitin. CS is non-toxic, highly biocompatible, and biodegradable, and it has a low immunogenicity. Additionally, CS has inherent antibacterial properties and a mucoadhesive character and can disrupt epithelial tight junctions, thus acting as a permeability enhancer. As such, CS and its derivatives are well-suited for the challenging field of ocular drug delivery. In the present review article, we will discuss the properties of CS that contribute to its successful application in ocular delivery before reviewing the latest advances in the use of CS for the development of novel ophthalmic delivery systems. Colloidal nanocarriers (nanoparticles, micelles, liposomes) will be presented, followed by CS gels and lenses and ocular inserts. Finally, instances of CS coatings, aiming at conferring mucoadhesiveness to other matrixes, will be presented.

Natural Ergot Alkaloids in Ocular Pharmacotherapy: Known Molecules for Novel Nanoparticle-Based Delivery Systems

Several pharmacological properties are attributed to ergot alkaloids as a result of their antibacterial, antiproliferative, and antioxidant effects. Although known for their biomedical applications (e.g., for the treatment of glaucoma), most ergot alkaloids exhibit high toxicological risk and may even be lethal to humans and animals. Their pharmacological profile results from the structural similarity between lysergic acid-derived compounds and noradrenalin, dopamine, and serotonin neurotransmitters. To reduce their toxicological risk, while increasing their bioavailability, improved delivery systems were proposed. This review discusses the safety aspects of using ergot alkaloids in ocular pharmacology and proposes the development of lipid and polymeric nanoparticles for the topical administration of these drugs to enhance their therapeutic efficacy for the treatment of glaucoma.

Recent advances in topical nano drug-delivery systems for the anterior ocular segment

Over the past decade, there has been a rise in the number of clinical cases of moderate to severe anterior segment ocular diseases. Conventional topical ophthalmic formulations have several limitations - to address which, novel drug-delivery systems are needed. Additionally, formidable physiological barriers limit ocular bioavailability through the topical route of application. During the last decade, various nano-scaled ocular drug-delivery strategies have been reported. Some of these exploratory, topical, noninvasive approaches have shown promise in improving penetration into the anterior segment tissues of the eye. In this article, we review the available literature with respect to the safety, efficiency and effectiveness of these nano systems.

Nanoparticles for drug delivery to the anterior segment of the eye

Commercially available ocular drug delivery systems are effective but less efficacious to manage diseases/disorders of the anterior segment of the eye. Recent advances in nanotechnology and molecular biology offer a great opportunity for efficacious ocular drug delivery for the treatments of anterior segment diseases/disorders. Nanoparticles have been designed for preparing eye drops or injectable solutions to surmount ocular obstacles faced after administration. Better drug pharmacokinetics, pharmacodynamics, non-specific toxicity, immunogenicity, and biorecognition can be achieved to improve drug efficacy when drugs are loaded in the nanoparticles. Despite the fact that a number of review articles have been published at various points in the past regarding nanoparticles for drug delivery, there is not a review yet focusing on the development of nanoparticles for ocular drug delivery to the anterior segment of the eye. This review fills in the gap and summarizes the development of nanoparticles as drug carriers for improving the penetration and bioavailability of drugs to the anterior segment of the eye.