Nanoemulsion-based electrolyte triggered in situ gel for ocular delivery of acetazolamide

Ocular anti-inflammatory activity of prednisolone acetate loaded chitosan-deoxycholate self-assembled nanoparticles

Background and purpose: Conventional topical ophthalmic aqueous solutions and suspensions are often associated with low bioavailability and high administration frequency, pulsatile dose and poor exposure to certain ocular parts. The aim of this study was to develop an ophthalmic nanoparticles loaded gel, for delivering prednisolone acetate (PA), to increase dosing accuracy, bioavailability, and accordingly, efficiency of PA in treating inflammatory ocular diseases. Methods: A novel formulation of self-assembled nanoparticles was prepared by the complexation of chitosan (CS) and, the counter-ion, sodium deoxycholate (SD), loaded with the poorly-water-soluble PA. Particle size, zeta potential, encapsulation efficiency (EE) and drug loading content (LC) of prepared nanoparticles were assessed. Moreover, the nanoparticles were characterized using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). Drug release and eye anti-inflammatory potential of the prepared novel formulation was investigated. Results: Mean particle size of the nanoparticles have dropped from 976 nm ±43 (PDI 1.285) to 480 nm ±28 (PDI 1.396) when the ratio of CS-SD was decreased. The incorporation of 0.1-0.3% of polyvinyl alcohol (PVA), in the preparation stages, resulted in smaller nanoparticles: 462 nm ±19 (PDI 0.942) and 321 nm ±22 (PDI 0.454) respectively. DSC and FTIR results demonstrated the interaction between CS and SD, however, no interactions were detected between PA and CS or SD. Drug release of PA as received, in simulated tears fluid (pH 7.4), showed a twofold increase (reaching an average of 98.6% in 24 hours) when incorporated into an optimized nanoparticle gel formulation (1:5 CS-SD). Conclusion: The anti-inflammatory effect of PA nanoparticles loaded gel on female guinea pig eyes was significantly superior to that of the micronized drug loaded gel (P < 0.05).

Osmoprotectants in Hybrid Liposome/HPMC Systems as Potential Glaucoma Treatment

The combination of acetazolamide-loaded nano-liposomes and Hydroxypropyl methylcellulose (HPMC) with similar components to the preocular tear film in an osmoprotectant media (trehalose and erythritol) is proposed as a novel strategy to increase the ocular bioavailability of poorly soluble drugs. Ophthalmic formulations based on acetazolamide-loaded liposomes, dispersed in the osmoprotectant solution (ACZ-LP) or in combination with HPMC (ACZ-LP-P) were characterized and in vivo evaluated. The pH and tonicity of both formulations resulted in physiological ranges. The inclusion of HPMC produced an increment in viscosity (from 0.9 to 4.7 mPa·s. 64.9 ± 2.6% of acetazolamide initially included in the formulation was retained in vesicles. In both formulations, a similar onset time (1 h) and effective time periods were observed (7 h) after a single instillation (25 μL) in normotensive rabbits' eyes. The AUC_0-8h of the ACZ-LP-P was 1.5-fold higher than of ACZ-LP (p < 0.001) and the maximum hypotensive effect resulted in 1.4-fold higher (p < 0.001). In addition, the formulation of ACZ in the hybrid liposome/HPMC system produced a 30.25-folds total increment in ocular bioavailability, compared with the drug solution. Excellent tolerance in rabbits' eyes was confirmed during the study.

Gellan Gum Based Sol-to-Gel Transforming System of Natamycin Transfersomes Improves Topical Ocular Delivery

Short precorneal residence time and poor transocular membrane permeability are the major challenges associated with topical ocular drug delivery. In the present research, the efficiency of the electrolyte-triggered sol-to-gel-forming system of natamycin (NT) transfersomes was investigated for enhanced and prolonged ophthalmic delivery. Transfersomes were optimized by varying the molar ratios of phospholipid, sorbitan monostearate (Span) and tocopheryl polyethylene glycol succinate (TPGS). NT transfersome formulations (FNs) prepared with a 1:1 molar ratio of phospholipid-to-Span and low levels of TPGS showed optimal morphometric properties, and were thus selected to fabricate the in situ gelling system. Gellan gum-based (0.3% w/v) FN-loaded formulations (FNGs) immediately formed an in situ gel in the simulated tear fluid, with considerable viscoelastic characteristics. In vitro cytotoxicity in corneal epithelial cells and corneal histology studies demonstrated the ocular safety and cytocompatibility of these optimized formulations. Transcorneal permeability of NT from these formulations was significantly higher than in the control suspension. Moreover, the ocular disposition studies of NT, from the FNs and FNGs, in New Zealand male albino rabbits demonstrated the superiority of the electrolyte-sensitive FNGs in terms of NT delivery to the ocular tissues.

In situ gelation of rhEGF-containing liquid crystalline precursor with good cargo stability and system mechanical properties: a novel delivery system for chronic wounds treatment

The objective of this study was to develop a novel delivery system for recombinant human epidermal growth factor (rhEGF) for chronic wound treatment. Such a delivery system should be of good cargo stability and system mechanical properties in order to guarantee a satisfactory wound-healing effect. rhEGF-containing lyotropic liquid crystalline precursors (rhEGF-LLCPs) with in situ gelation capability were considered as a promising candidate to achieve this aim. Various properties of the optimal formulations (rhEGF-LLCP1 and rhEGF-LLCP2) were characterized, including apparent viscosity, gelation time, in vitro release and phase behavior. The stability of rhEGF and system mechanical properties (i.e. mechanical rigidity and bioadhesive force) were verified. Interestingly, rhEGF-LLCP2 with a larger internal water channel diameter exhibited faster release rate in vitro and then better bioactivity in Balb/c 3T3 and HaCaT cell models. Moreover, rhEGF-LLCP2 showed distinct promotion effects on wound closure, inflammatory recovery and re-epithelization process in Sprague-Dawley rat models. In conclusion, rhEGF-LLCP emerged as a prospective candidate to preserve the stability and enhance the wound-healing effect of rhEGF, which might serve as a new delivery system for chronic wound therapies.

Nanostructured lipid carriers-based thermosensitive eye drops for enhanced, sustained delivery of dexamethasone

AIM

Nanostructured lipid carriers in-gel (NLCs-gel) were prepared to enhance and improve the ocular delivery of dexamethasone. Materials & methods: NLCs containing dexamethasone prepared by high-pressure homogenization were characterized and dispersed into thermosensitive gels (Pluronic F127 and F68 as gels material). In vitro drug release studies, ocular irritation tests, ex vivo corneal penetration and drug dynamics of NLCs and NLCs-gel were evaluated in aqueous humor.

RESULTS

NLCs-gel exhibited a rapid sol-gel transition at 34.4°C and presented nano-sized, narrowly distributed particles. Corneal penetration studies revealed steady sustained drug release (Ritger-Peppas); NLCs-gel increased ocular bioavailability by prolonging precorneal retention time and improving corneal permeation.

CONCLUSION

These findings suggest developing NLCs-gel for potential treatment of posterior segment eye diseases.

Ocular administration of acetazolamide microsponges in situ gel formulations

In the present work, the antiglaucoma drug, acetazolamide, was formulated as microsponges in situ gel for ocular drug delivery aiming an improved therapeutic efficacy and reduction in the systemic side effects of oral acetazolamide. The microsponges were prepared by the quasi emulsion solvent diffusion method and were incorporated into 25% pluronic F-127 in situ gel. Ethyl cellulose polymer in different proportions with drug was used to prepare the microsponges. Different parameters were evaluated to select the best formulation. The formula S2 with drug to polymer ratio (2:1) showed high entrapment efficiency of about 82% and mean particle size of about 10 µm with polydispersity index (PDI) of 0.22, which are suitable characters for ocular delivery. The in situ gels were evaluated for physicochemical properties (pH, gelling capacity, gelation time and rheological properties) and in vivo studies. S2 formulation showed higher therapeutic efficacy compared to free drug in gel. It was non irritant to the rabbit's eye. These results indicated that acetazolamide microsponges in situ gel have potential ability for ophthalmic delivery.

Research progress of in-situ gelling ophthalmic drug delivery system

Blindness and vision impairment are the most devastating global health problems resulting in a substantial economic and social burden. Delivery of drug to particular parts of the anterior or posterior segment has been a major challenge due to various protective barriers and elimination mechanisms associated with the unique anatomical and physiological nature of the ocular system. Drug administration to the eye by conventional delivery systems results in poor ocular bioavailability (<5%). The designing of a novel approach for a safe, simple, and effective ocular drug delivery is a major concern and requires innovative strategies to combat the problem. Over the past decades, several novel approaches involving different strategies have been developed to improve the ocular delivery system. Among these, the ophthalmic in-situ gel has attained a great attention over the past few years. This review discussed and summarized the recent and the promising research progress of in-situ gelling in ocular drug delivery system.

In vitro and ex vivo correlation of drug release from ophthalmic ointments

In vitro drug release testing and ex vivo transcorneal drug permeation can provide valuable information on the performance of the Q1/Q2 equivalent ointments prior to any animal studies. Good correlation between in vitro and ex vivo drug release may be indicative of good in vitro and in vivo correlation. Accordingly, it is important to investigate in vitro as well as ex vivo drug release from Q1/Q2 equivalent ophthalmic ointments and evaluate whether a correlation between these release profiles can be established. Four Q1/Q2 equivalent loteprednol etabonate ointments were prepared using different processing methods and excipient sources. The rheological parameters (crossover modulus and K value) of the four formulations were determined. The in vitro drug release testing of the four ointment formulations were performed using three different apparati (Franz diffusion cells, USP apparatus 2 with enhancer cells and USP apparatus 4 with semisolid adapters). Three models (zero order, logarithmic and the Higuchi model) were used to study the release kinetics of the ointment formulations. The transcorneal (rabbit corneas) permeation studies were performed using spherical joint Franz diffusion cells. The USP apparatus 4 method demonstrated better discriminatory ability compared to the USP apparatus 2 and the Franz diffusion cell methods. The in vitro release profiles of the four Q1/Q2 equivalent ointments with manufacturing differences showed a better fit using the Higuchi model (R² > 0.98) for all three release testing methods, compared to the other two models. Ex vivo drug release through the rabbit corneas displayed zero order release kinetics. A logarithmic correlation between rheological parameters (crossover and K value) and transcorneal flux were established. In addition, a plot of the in vitro release rate against the ex vivo release flux of the four ointment formulations, yielded a straight line (R² > 0.98) for all three release methods. Accordingly, the rheological parameters may be useful in predicting in vitro as well as ex vivo release properties.

Ion-sensitive in situ hydrogels of natamycin bilosomes for enhanced and prolonged ocular pharmacotherapy: in vitro permeability, cytotoxicity and in vivo evaluation

Delivery of therapeutic molecules into the deeper ocular compartments is mainly hampered by short precorneal residence and limited transmembrane permeability of topically administered drugs. Hence, the current study was undertaken to fabricate the ion-sensitive in situ gels of natamycin (NT) bilosomes (NB) for efficient ocular delivery. The effect of cholesterol and sodium taurocholate proportion on the properties of the bilosomes were studied and the formulation with better physicochemical properties was optimized and utilized to derive the in situ gelling system (IG). The impact of type/composition of gelling agent on the formation and characteristics of the hydrogel was investigated. The hydrogel formed from IG with 0.3% w/v gellan gum showed optimal viscoelastic and adhesive characteristics. The ocular safety and cytocompatibility of NB and its IG was confirmed by corneal histology and in vitro cytotoxicity evaluation. A 6- to 9-fold enhancement in the transcorneal flux of NB demonstrated efficient ocular penetration of bilosomes. Moreover, the superior mean dose normalized NT levels in the ocular tissues of rabbits treated with optimized NB and IG illustrated the effectiveness of bilosomes loaded ion-sensitive in situ hydrogels as a potential platform for the improved and prolonged ocular pharmacotherapy.

A novel ocular delivery of brinzolamide based on gellan gum: in vitro and in vivo evaluation

Background

The aim of the study was to develop a sustained ocular delivery of brinzolamide (BLZ) based on gellan gum.

Methods

The formulations were characterized for clarity, gelling capacity, rheological studies, pH, drug content, and in vitro drug-release behavior. In vivo rabbit eye irritation test was conducted to evaluate irritation of the BLZ gel drug-delivery system. The prepared BLZ formulations were then investigated in vivo and compared with commercially available BLZ eyedrops with regard to pharmacodynamics.

Results

The results showed that the optimum concentration of gellan gum was 0.25% w/v; the prepared liquid was converted into a flowing gel after the addition of simulated tear fluid. In vitro release profiles showed that the release of BLZ from the in situ gel exhibited sustained characteristics. Draize test results showed that BLZ in situ gels did not stimulate signs of eye tissue activity and were less irritating than BLZ solutions and commercial Azopt.

Conclusion

The results of pharmacodynamics implied that the novel preparation of BLZ in situ gel effectively prolonged the intraocular pressure-lowering effect after administration.

Tailored nanostructured platforms for boosting transcorneal permeation: Box-Behnken statistical optimization, comprehensive in vitro, ex vivo and in vivo characterization

Ocular drug delivery systems suffer from rapid drainage, intractable corneal permeation and short dosing intervals. Transcorneal drug permeation could increase the drug availability and efficiency in the aqueous humor. The aim of this study was to develop and optimize nanostructured formulations to provide accurate doses, long contact time and enhanced drug permeation. Nanovesicles were designed based on Box-Behnken model and prepared using the thin film hydration technique. The formed nanodispersions were evaluated by measuring the particle size, polydispersity index, zeta potential, entrapment efficiency and gelation temperature. The obtained desirability values were utilized to develop an optimized nanostructured in situ gel and insert. The optimized formulations were imaged by transmission and scanning electron microscopes. In addition, rheological characters, in vitro drug diffusion, ex vivo and in vivo permeation and safety of the optimized formulation were investigated. The optimized insert formulation was found to have a relatively lower viscosity, higher diffusion, ex vivo and in vivo permeation, when compared to the optimized in situ gel. So, the lyophilized nanostructured insert could be considered as a promising carrier and transporter for drugs across the cornea with high biocompatibility and effectiveness.

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

Ocular discomforts involve anterior/posterior-segment diseases, symptomatic distress and associated inflammations and severe retinal disorders. Conventionally, the formulations such as eye drops, eye solutions, eye ointments and lotions, etc. were used as modalities to attain relief from such ocular discomforts. However, eye allows limited access to these traditional formulations due to its unique anatomical structure and dynamic ocular environment and therefore calls for improvement in disease intervention. To address these challenges, development of nanotechnology based nanomedicines and novel nanosystems (liposomes, cubosomes, polymeric and lipidic nanoparticles, nanoemulsions, spanlastics and nano micelles) are currently in progress (some of them are already marketed such as Eye-logic liposomal eye spray@Naturalife, Ireland). Today, it is one of the central concept in designing more accessible formulations for deeper segments of the eyes. These nanosystems has largely enabled the availability of medicaments at required site in a required concentration without inversely affecting the eye tissues; and therefore, attaining the excessive considerations from the formulation scientists and pharmacologists worldwide. The entrapment of drugs, genes, and proteins inside these novel systems is the basis that works at the bio-molecular level bestows greater potential to eradicate disease causatives. In this review, we highlighted the recent attempts of nanotechnology-based systems for treating and managing various ocular ailments. The progress described herein may pave the way to new, highly effective and vital ocular nanosystems.