Effect of Cyclodextrins on Morphology and Barrier Characteristics of Isolated Rabbit Corneas

Improved Topical Ophthalmic Natamycin Suspension for the Treatment of Fungal Keratitis

Purpose: Natamycin (NT) is used as a first-line antifungal prescription in the treatment of fungal keratitis (FK) and is commercially available as a 5% w/v ophthalmic suspension. NT shows poor water solubility and light sensitivity. Thus, the present investigation is aimed to enhance the fraction of NT in solution in the commercial formulation by adding cyclodextrins (CDs), thereby improving the delivery of the drug into deeper ocular tissues. Methods: The solubility of NT in different CDs, the impact of ultraviolet (UV) light exposure, stability at 4°C and 25°C, in vitro release, and ex vivo transcorneal permeation studies were performed. Results: NT exhibited the highest solubility (66-fold) in randomly methylated-β-cyclodextrin (RM-βCD) with hydroxypropyl-βCD (HP-βCD) showing the next highest solubility (54-fold) increase in comparison to market formulation Natacyn® as control. The stability of NT-CD solutions was monitored for 2 months (last-time point) at both storage conditions. The degradation profile of NT in NT-RM-βCD and NT-HP-βCD solutions under UV-light exposure followed first-order kinetics exhibiting half-lives of 1.2 h and 1.4 h, respectively, an almost 3-fold increase over the control solutions. In vitro release/diffusion studies revealed that suspensions containing RM-βCD and HP-βCD increased transmembrane flux significantly (3.1-fold) compared to the control group. The transcorneal permeability of NT from NT-RM-βCD suspension exhibited an 8.5-fold (P < 0.05) improvement compared to Natacyn eyedrops. Furthermore, the addition of RM-βCD to NT suspension increases the solubilized fraction of NT and enhances transcorneal permeability. Conclusion: Therefore, NT-RM-βCD formulations could potentially lead to a decreased frequency of administration and significantly improved therapeutic outcomes in FK treatment.

Difluprednate-Hydroxypropyl-β-Cyclodextrin-Based Ophthalmic Solution for Improved Delivery in a Porcine Eye Model

Purpose: Difluprednate (DFP) is an approved corticosteroid, available as an ophthalmic emulsion (Durezol^®), used to treat pain and inflammation of the eye following ocular surgeries. This study utilized hydroxypropyl-β-cyclodextrin (HPBCD)-based DFP ophthalmic solution for improved ocular delivery. Methods: The DFP-HPBCD complex formation was studied in the liquid and solid states. Phase solubility, molecular docking studies, differential scanning calorimetry, and Fourier transform infrared spectroscopy suggested inclusion complexation of DFP and HPBCD. Results: DFP-HPBCD-based eye drops (solution) provided 16 and 26 times higher transcorneal permeation when compared to the suspension (no HPBCD, control) and Durezol, respectively (P < 0.001). In addition, ocular drug distribution studies conducted in continuously perfused whole porcine eyes showed DFP permeated into all of the ocular tissues in significantly higher amounts than Durezol. Conclusions: The solution-based eye drops in this study is iso-osmotic, safe, and more permeable in porcine eyes compared to Durezol.

New Approach in Ocular Drug Delivery: In vitro and ex vivo Investigation of Cyclodextrin-Containing, Mucoadhesive Eye Drop Formulations

Background

Optimal transcorneal penetration is necessary for ocular therapy; meanwhile, it is limited by the complex structure and defensive mechanisms of the eye. Antimicrobial stability of topical ophthalmic formulations is especially important. According to previous studies, the mostly used preservative, benzalkonium-chloride is irritative and toxic on corneal epithelial cells; therefore, novel non-toxic, antimicrobial agents are required. In this study, prednisolone-containing ophthalmic formulations were developed with expected optimal permeation without toxic or irritative effects.

Methods

The toxicity and permeability of prednisolone-containing eye drops were studied on a human corneal epithelial cell line (HCE-T) and ex vivo cornea model. The lipophilic drug is dissolved by the formation of cyclodextrin inclusion complex. Zinc-containing mucoadhesive biopolymer was applied as an alternative preservative agent, whose toxicity was compared with benzalkonium-chloride.

Results

As the results show, benzalkonium-chloride-containing samples were toxic on HCE-T cells. The biopolymer caused no cell damage after the treatment. This was confirmed by immunohistochemistry assay. The in vitro permeability was significantly higher in formulations with prednisolone-cyclodextrin complex compared with suspension formulation. According to the ex vivo permeability study, the biopolymer-containing samples had significantly lower permeability.

Conclusion

Considering the mucoadhesive attribute of target formulations, prolonged absorption is expected after application with less frequent administration. It can be stated that the compositions are innovative approaches as novel non-toxic ophthalmic formulations with optimal drug permeability.

Current Approaches to Use Cyclodextrins and Mucoadhesive Polymers in Ocular Drug Delivery—A Mini-Review

Ocular drug delivery provides a challenging opportunity to develop optimal formulations with proper therapeutic effects and acceptable patient compliance because there are many restricting factors involved, such as complex anatomical structures, defensive mechanisms, rapid drainage, and applicability issues. Fortunately, recent advances in the field mean that these problems can be overcome through the formulation of innovative ophthalmic products. Through the addition of solubility enhancer cyclodextrin derivatives and mucoadhesive polymers, the permeability of active ingredients is improved, and retention time is increased in the ocular surface. Therefore, preferable efficacy and bioavailability can be achieved. In this short review, the authors describe the theoretical background, technological possibilities, and the current approaches in the field of ophthalmology.

Directing the nanoparticle formation by the combination with small molecular assembly and polymeric assembly for topical suppression of ocular inflammation

In this paper, we presented a simple yet versatile strategy to generate a high drug payload nanoparticles by the combination with small molecular assembly and polymeric assembly for topical suppression of ocular inflammation. Upon physical mixing of the succinated triamcinolone acetonide (TA-SA) supramolecular hydrogel with the poly (ethylene glycol)-poly (ɛ-caprolactone)-poly (ethylene glycol) (PECE) aqueous solution at 37 °C, TA-SA/PECE nanoparticles formed spontaneously and characterized thoroughly by transmission electron microscopy (TEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The formed TA-SA/PECE nanoparticles displayed a comparable in vitro anti-inflammatory efficacy to that of native triamcinolone acetonide (TA), through a significant downregulation of various proinflammatory cytokines levels (e.g., NO, TNF-α) in a lipopolysaccharide (LPS) actived RAW264.7 macrophage. Meanwhile, the enhanced transcorneal drug permeability of TA-SA/PECE nanoparticles over that of TA suspension was clearly observed in an isolated rabbit cornea. Intraocular biocompatibility test demonstrated that TA-SA/PECE nanoparticles presented good biocompatibility after topical instillation during entire study period. More importantly, the TA-SA/PECE nanoparticles displayed superior therapeutic efficacy over that of the TA suspension in the endotoxin-induced uveitis (EIU) rabbit model via decreasing neutrophil infiltration in anterior chamber. Overall, the proposed TA-SA/PECE nanoparticles might be a promising candidate for uveitis therapy.

Gel in core carbosomes as novel ophthalmic vehicles with enhanced corneal permeation and residence

Carbopol is a good bio-adhesive polymer that increases the residence time in the eye. However, the effect of blinking and lacrimation still reduce the amount of polymer and the incorporated drug available for bioadhesion. Gel-core liposomes are advanced systems offering benefits making it a good tool for improved ocular drug delivery and residence time. Incorporation of carbopol in gel-core liposomes and their potential in ocular delivery have not so far been investigated. Fluconazole (FLZ) was selected as a challenging important ocular antifungal suffering from poor corneal permeation and short residence time. In this study, gel-core carbosomes have been elaborated as novel carbopol-based ophthalmic vehicles to solve ocular delivery obstacles of FLZ and to sustain its effect. Full in vitro appraisal was performed considering gel-core structure, entrapment efficiency, particle size and stability of the vesicles as quality attributes. Structure elucidation of the nanocarrier was performed using optical, polarizing and transmission electron microscopy before and after Triton-X100 addition. Ex-vivo ocular permeation and in vivo performance were investigated on male albino rabbits. Optimized formulation (CBS5) showed gel-core structure, nanosize (339.00 ± 5.50 nm) and not defined before (62.00% ± 1.73) entrapment efficiency. Cumulative amount of CBS5 permeated ex-vivo after 6 h, was 2.43 and 3.43 folds higher than that of conventional liposomes and FLZ suspension, respectively. In-vivo corneal permeation of CBS5 showed significantly higher AUC0-24 h (487.12 ± 74.80) compared to that of FLZ suspension (204.34 ± 7.46) with longer residence time in the eye lasts for more than 18 h. In conclusion, novel gel-core carbosomes could successfully be used as a promising delivery system for chronic ocular diseases.

Ocular disposition of ciprofloxacin from topical, PEGylated nanostructured lipid carriers: Effect of molecular weight and density of poly (ethylene) glycol

Ciprofloxacin (CIP) is an antibacterial agent prescribed for the treatment of ocular infections. The objective of the present project is to investigate the effect of surface PEG functionalization of the Nano structured lipid carriers (NLCs) on formulation stability, ocular penetration and distribution. CIP NLCs were tested with different molecular weight (poly ethylene glycol) PEGs ranging from (2K to 20K) grafted onto the phospholipid and with different chain lengths (14-18 carbons) of phospholipids derivatized with PEG-2K. Drug load in the formulations was maintained at 0.3%w/v. Formulations prepared were evaluated with respect to in vitro release, transcorneal permeation, autoclavability, morphological characteristics and in vivo ocular tissue distribution. Scanning Transmission electron microscopy (STEM) studies revealed that the PEG-CIP-NLCs were spherical in shape. Transcorneal penetration of CIP was optimum with PEG molecular weight in between 2K-10K. Carbon chain length of the phospholipid, however, did not affect transcorneal penetration of CIP. In vivo ocular tissue CIP concentrations attained from the various formulations was consistent with the in vitro data obtained. The results suggest that surface functionalization of PEGs, within a specified range of molecular weight and surface packing density, significantly enhance trans-ocular penetration and impart sterilization-stabilization characteristics into the formulations.