Development of Chitosan–Tripolyphosphate Nanoparticles as Glycopeptide Antibiotic Reservoirs and Ex vivo Evaluation for Their Potential to Enhance the Corneal Permeation in Ocular Drug Delivery

Purpose: The present investigation aimed to prepare Vancomycin-loaded nanoparticles (VAN-NPs) using chitosan (CS) and tripolyphosphate (TPP) besides exploring the effects of changing CS/TPP ratio on the physicochemical properties, corneal permeation, and ocular delivery of the prepared NPs. Methods: Different pre-formulations were prepared using the modified ionic gelation process, then were characterized in terms of size distribution. Optimized formulations were furtherly evaluated by some characteristic tools such as Fourier-transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The in vitro antimicrobial efficacy and drug release amounts along with the Ex-vivo corneal permeation of NPs through the sheep cornea were investigated. Quantification was performed using High-Performance Liquid Chromatography. Results: Spherical and uniformly distributed NPs were developed with a mean particle size varied between 215–290 nm. FTIR spectroscopy confirmed that the CS/TPP cross-linking has taken place without affecting the pharmacologically active moiety of the drug. The obtained zeta potential values were in the range of +34 to +37 mV, which could ensure the stability of formulations. TGA analysis indicated enhanced thermal stability for the encapsulated drug compared to the plain drug. Formulations indicated suitable antimicrobial efficacy while releasing more than 90% of the drug during 24 h. NPs offered a 10-fold enhancement in corneal permeation compared to the drug solution. Conclusions: Although further in vivo evaluation is still required to completely confirm the efficacy of the formulations, the enhanced release and corneal permeation of the drug suggest that the prepared NPs are suitable for ocular delivery of VAN.

Study the Antifungal and Ocular Permeation of Ketoconazole from Ophthalmic Formulations Containing Trans-Ethosomes Nanoparticles

Ketoconazole (KET), a synthetic imidazole broad-spectrum antifungal agent, is characterized by its poor aqueous solubility and high molecular weight, which might hamper its corneal permeation. The aim was to develop an ophthalmic formulation loaded with optimized trans-ethosomal vesicles to enhance KET ocular permeation, antifungal activity, rapid drug drainage, and short elimination half-life. Four formulation factors affecting the vesicles’ size, zeta potential, entrapment efficiency, and flexibility of the trans-ethosomes formulations were optimized. The optimum formulation was characterized, and their morphological and antifungal activity were studied. Different ophthalmic formulations loaded with the optimized vesicles were prepared and characterized. The ocular irritation and in vivo corneal permeation were investigated. Results revealed that the drug-to-phospholipid-molar ratio, the percentage of edge activator, the percentage of ethanol, and the percentage of stearyl amine significantly affect the characteristics of the vesicles. The optimized vesicles were spherical and showed an average size of 151.34 ± 8.73 nm, a zeta potential value of +34.82 ± 2.64 mV, an entrapment efficiency of 94.97 ± 5.41%, and flexibility of 95.44 ± 4.33%. The antifungal activity of KET was significantly improved following treatment with the optimized vesicles. The developed in situ gel formulations were found to be nonirritating to the cornea. The trans-ethosomes vesicles were able to penetrate deeper into the posterior eye segment without any toxic effects. Accordingly, the in situ developed gel formulation loaded with KET trans-ethosomes vesicles represents a promising ocular delivery system for the treatment of deep fungal eye infections.

Graphene Oxide Increases Corneal Permeation of Ciprofloxacin Hydrochloride from Oleogels: A Study with Cocoa Butter-Based Oleogels

In this work, oleogels of cocoa butter (CB), rice bran oil (RBO), and graphene oxide (GO) were prepared. The prepared oleogels were subjected to various characterization techniques such as bright-field microscopy, X-ray diffraction (XRD), crystallization kinetics, differential scanning calorimetry (DSC), and mechanical studies. The influence of increasing GO content on the in vitro drug release and ex vivo corneal permeation of the model drug (ciprofloxacin HCl—CPH) from the oleogels was also investigated. Bright-field micrographs showed that increment in GO content reduced the size of the globular particles of CB. XRD analysis revealed that CB was crystallized in its β’ and β polymorphic forms in the oleogels, which was in agreement with thermal studies. The mechanical characterization demonstrated that the presence of GO improved the elastic nature and stress-bearing properties of the oleogels. Moreover, GO altered the crystallization kinetics of CB in the oleogels in a composition-dependent manner. The in vitro release of CPH from the oleogels occurred through either Fickian diffusion or fat network relaxation or a combination thereof. Furthermore, the inclusion of GO enhanced the ex vivo permeation of CPH molecules across the caprine cornea. Hence, we concluded that the prepared oleogels could be explored as potential delivery systems for ophthalmic applications.

In Situ Gelling Systems Using Pluronic F127 Enhance Corneal Permeability of Indomethacin Nanocrystals

We previously designed an ophthalmic dispersion containing indomethacin nanocrystals (IMC-NCs), showing that multiple energy-dependent endocytoses led to the enhanced absorption of drugs from ocular dosage forms. In this study, we attempted to prepare Pluronic F-127 (PLF-127)-based in situ gel (ISG) incorporating IMC-NCs, and we investigated whether the instillation of the newly developed ISG incorporating IMC-NCs prolonged the precorneal resident time of the drug and improved ocular bioavailability. The IMC-NC-incorporating ISG was prepared using the bead-mill method and PLF-127, which yielded a mean particle size of 50–150 nm. The viscosity of the IMC-NC-incorporating ISG was higher at 37 °C than at 10 °C, and the diffusion and release of IMC-NCs in the IMC-NC-incorporating ISG were decreased by PLF-127 at 37 °C. In experiments using rabbits, the retention time of IMC levels in the lacrimal fluid was enhanced with PLF-127 in the IMC-NC-incorporating ISG, whereby the IMC-NC-incorporating ISG with 5% and 10% PLF-127 increased the transcorneal penetration of the IMCs. In contrast to the results with optimal PLF-127 (5% and 10%), excessive PLF-127 (15%) decreased the uptake of IMC-NCs after instillation. In conclusion, we found that IMC-NC-incorporating ISG with an optimal amount of PLF-127 (5–10%) resulted in higher IMC corneal permeation after instillation than that with excessive PLF-127, probably because of the balance between higher residence time and faster diffusion of IMC-NCs on the ocular surface. These findings provide significant information for developing ophthalmic nanomedicines.

Synthesis and Ex Vivo Trans-Corneal Permeation of Penetratin Analogues as Ophthalmic Carriers: Preliminary Results

Among enhancing strategies proposed in ocular drug delivery, a rising interest is directed to cell penetrating peptides (CPPs), amino acid short sequences primarily known for their intrinsic ability to cell internalization and, by extension, to cross biological barriers. In fact, CPPs may be considered as carrier for delivering therapeutic agents across biological membranes, including ocular tissues. Several CPPs have been proposed in ophthalmic delivery, and, among them, penetratin (PNT), a 16-amino acids natural peptide, stands out. Therefore, we describe the synthesis via the mimotopic approach of short fluorescently labeled analogues of both PNT and its reversed sequence PNT-R. Their ability to cross ocular membranes was checked ex vivo using freshly explanted porcine cornea. Furthermore, some sequences were studied by circular dichroism. Despite the hydrophilic nature and the relatively high molecular weight (approx. 1.6 kDa), all analogues showed a not negligible trans-corneal diffusion, indicating a partial preservation of penetration activity, even if no sequences reached the noteworthy ability of PNT. It was not possible to find a correlation between structure and corneal penetration ability, and further studies, exploring peptides distribution within corneal layers, for example using imaging techniques, deserve to be performed to figure out a possible difference in intracellular delivery.

Optimization of the Interaction between Diclofenac and Ibuprofen with Benzalkonium Chloride to Prepare Ocular Nanosuspension

Background: Non-steroidal anti-inflammatory drugs are most commonly used in the management of ocular inflammations. These drugs have poorly aqueous solubility and weakly acidic nature. They interact with cationic quaternary ammonium compound benzalkonium chloride, used as a preservative in ophthalmic formulations, to form insoluble complexes. To overcome this incompatibility solubilizers like polysorbate 80, lysine salts, tocopheryl polyethylene glycol succinate etc. are used which are quite irritating and affect the corneal integrity. Objective: The objective of the present study is to formulate nonirritating, compatible, microbiologically stable ophthalmic formulation with good corneal permeation characteristics. The interaction between diclofenac sodium or ibuprofen with benzalkonium chloride was optimized using a central composite experimental design to prepare nanosuspensions by nanoprecipitation. Methods: The optimized batches of nanosuspensions were evaluated for ex vivo corneal permeation study, preservative challenge test and physical stability. The optimal concentrations of benzalkonium chloride for diclofenac sodium (0.1%, w/v) and ibuprofen (0.1% w/v) nanosuspensions were determined to be 0.002%(w/v), which had a respective average particle size of 440 nm and 331 nm, respectively. The nanosuspensions of diclofenac sodium and ibuprofen provided 1.6 and 2.1- fold higher ex vivo corneal permeation than their respective conventional aqueous solution dosage forms. Further, the concentration of benzalkonium chloride used in the formulations showed adequate preservative efficacy. Results: The optimized nanosuspension formulations of diclofenac and ibuprofen were found to be physically stable and microbiologically safe with greater corneal penetration than the conventional solution dosage forms.

Development and Characterization of Liposomal formulation for ophthalmic delivery of Prednisolone Acetate

Liposomal vesicular drug carriers for ocular delivery have earned a wide potential nowadays. Prednisolone Acetate liposome as ocular drug carriers have been demonstrated to be a useful mode to ameliorate bioavailability and patient abidance. Liposome was prepared by lipid extruder method. Liposome were characterized for entrapment efficiency (EE %), vesicle size, surface morphology and in vitro drug release. An ex vivo corneal permeation study was performed to determine the level of drug in the external eye tissue of goat and an ocular irritation assessment was done by Hen’s Egg Test - Chorioallantoic Membrane (HET-CAM) method. The optimized formulation of liposome had shown acceptable viscosity (1.21 ± 0.03 cps), refractive index (1.47±0.001), osmolarity (303 ± 3 mOsm) and pH measurement (7.12 ± 0.09). Liposome as drug delivery carriers were evidenced to be a anticipating impendent to enhance corneal contact and penetration as well as retention time in the eye ensuing in a prolonged action and enhanced bioavailability. The results of stability study exhibited stable profile of developed liposomes.