Comparative evaluation of cyclosporine A/HPβCD-incorporated PLGA nanoparticles for development of effective ocular preparations

Research progress of ophthalmic preparations of immunosuppressants

Immune ophthalmopathy is a collection of autoimmune eye diseases. Immunosuppressants are drugs that can inhibit the body's immune response. Considering drug side effects such as hepatorenal toxicity and the unique structure of the eye, incorporating immunosuppressants into ophthalmic nanodrug delivery systems, such as microparticles, nanoparticles, liposomes, micelles, implants, and in situ gels, has the advantages of improving solubility, increasing bioavailability, high eye-target specificity, and reducing side effects. This study reviews recent research and applications of this aspect to provide a reference for the development of an ophthalmic drug delivery system.

Preparation and functional evaluation of electrospun polymeric nanofibers as a new system for sustained topical ocular delivery of itraconazole

Due to the rapid clearance of external agents from the surface of the cornea, conventional ocular formulations usually require frequent and long duration of administration to achieve a therapeutic level of the drug on the cornea which can be conquered using prolonged-release nanofibrous inserts. In the present study, for the first time, polymeric nanofibers of itraconazole (ITZ), a potent triazole antifungal agent, were prepared as ocular inserts to enhance the topical ocular delivery of the drug. Three different nanofibers were prepared by electrospinning using polyvinyl alcohol-cellulose acetate and polycaprolactone-polyethylene glycol 12 000 polymeric blends. Nanofibers indicated uniform structures with the mean diameter ranging between 137 and 180 nm. Differential scanning calorimetry and Fourier-transform infrared spectroscopy confirmed the amorphous state of the drug in the formulations and the no drug-polymer interaction. Appropriate stability, suitable flexibility, and 2.2-3.9 MPa tensile strength were observed. Formulations indicated antifungal efficacy against Candida albicans and Aspergillus fumigatus and cell viability >70% at different concentrations. Results of bioassay against Candida albicans exhibited prolonged in vitro release of 50-70% of ITZ for almost 55 days. The results suggested that the nanofibers could be considered suitable for prolonged delivery of the ITZ as an antifungal requiring frequent and long duration of administration.

Polymeric Inserts Containing Eudragit® L100 Nanoparticle for Improved Ocular Delivery of Azithromycin

Polymeric inserts containing azithromycin-loaded Eudragit® L100 nanoparticles were developed to sustain the drug release and enhance its ocular performance. The solvent diffusion technique was employed to prepare nanoparticles. The developed nanoparticles (NPs) were fully characterized and investigated. The solvent casting method was used to prepare azithromycin ocular inserts (azithromycin, AZM film) by adding hydroxypropyl methylcellulose (HPMC) or hydroxyethyl cellulose (HEC) solutions after the incorporation of AZM-loaded Eudragit® L100 nanoparticles into plasticized PVA (polyvinyl alcohol) solutions. The optimized nanoparticles had a particle size of 78.06 ± 2.3 nm, zeta potential around -2.45 ± 0.69 mV, polydispersity index around 0.179 ± 0.007, and entrapment efficiency 62.167 ± 0.07%. The prepared inserts exhibited an antibacterial effect on Staphylococcus aureus and Escherichia coli cultures. The inserts containing AZM-loaded nanoparticles showed a burst release during the initial hours, followed by a sustained drug release pattern. Higher cumulative corneal permeations from AZM films were observed for the optimized formulation compared to the drug solution in the ex-vivo trans-corneal study. In comparison to the AZM solution, the inserts significantly prolonged the release of AZM in rabbit eyes (121 h). The mucoadhesive inserts containing azithromycin-loaded Eudragit® L100 nanoparticles offer a promising approach for the ocular delivery of azithromycin (antibacterial and anti-inflammatory) to treat ocular infections that require a prolonged drug delivery.

Intestinal uptake of barley protein-based nanoparticles for β-carotene delivery

Our previous study introduced a barley protein microparticle for encapsulation of hydrophobic drug/nutraceutical, which could release nanoparticles upon gastric digestion and deliver encapsulated compound to a simulated intestinal environment intact. This work focused on evaluating the potential of liberated nanoparticles to improve the absorption of encapsulated compounds (e.g., β-carotene) using in vitro Caco-2 cell and ex vivo small intestine models. Nanoparticles obtained from gastric digestion of barley protein microparticles had a spherical shape and an average size of 351 nm. Nanoparticles showed low cytotoxicity in Caco-2 cells and their cellular uptake was dependent on time, concentration and temperature. In a Caco-2 cell monolayer model, significantly greater uptake and transport of β-carotene were observed when it was delivered by nanoparticles (15%), compared to free β-carotene suspension (2.6%). In an ex vivo rat jejunum model, nanoparticles showed the capacity to retain in small intestinal tissue. Approximately 2.24 and 6.04 μg nanoparticle were able to permeate through each cm² intestinal tissue and translocate to the serosal side after 60 and 90 min, respectively. Results from this study demonstrated the absorption improving effect of the barley protein nanoparticles and suggested their potential as vehicles for hydrophobic compounds.

Cyclodextrins and topical drug delivery to the anterior and posterior segments of the eye

It is generally believed that it is virtually impossible to obtain therapeutic drug concentrations in the posterior segment of the eye after topical application of aqueous, low viscosity eye drops. Thus, intravitreal drug injections and drug implants are currently used to treat diseases in the posterior segment such as macular edema. Here it is described how, through proper analysis of the drug permeation barriers and application of well-known pharmaceutical excipients, aqueous eye drops are designed that can deliver lipophilic drugs to the posterior segment as well as how such eye drops can maintain high drug concentrations in the anterior segment. Through stepwise optimization, eye drops containing solid drug/cyclodextrin complex microparticles with a mean diameter of 2-4μm, dissolved drug/cyclodextrin complex nanoparticles and dissolved drug molecules in an aqueous eye drop media of low viscosity were designed. After administration of the eye drops the microparticles slowly dissolved and maintained close to saturated drug concentrations in the aqueous tear fluid for several hours. Studies in rabbits and clinical evaluations in humans, using dorzolamide and dexamethasone as sample drugs, show that the eye drops deliver significant amounts of drugs to both the posterior segment and anterior segment of the eye. Clinical studies indicate that the eye drops can replace intravitreal injections and implants that are currently used to treat ophthalmic diseases and decrease frequency of drug administration, both of which can improve patient compliance.

Molecularly imprinted cryogel membranes for mitomycin C delivery

In this study, cryogel-based implantable molecularly imprinted drug delivery systems were designed for the delivery of antineoplastic agent. Mitomycin C imprinted poly(2-hydroxyethyl methacrylate-N-methacryloyl-l-glutamic acid) cryogel membranes were produced by free-radical bulk polymerization under partially frozen conditions. The membranes were characterized by swelling tests, Fourier transform infrared spectroscopy, scanning electron microscopy, surface area measurements and in vitro hemocompatibility tests. In vitro delivery studies were carried out to examine the effects of cross-linker ratio and template content. Mitomycin C imprinted cryogel membranes have megaporous structure (10-100 μm in diameter). The cumulative release of mitomycin C was decreased with increasing cross-linking agent ratio and increased with the amount of template in the cryogel structure. The nature of transport mechanism of the mitomycin C from the membranes was non-Fickian.

Nanomicelle formulation for topical delivery of cyclosporine A into the cornea: in vitro mechanism and in vivo permeation evaluation

A stable topical ophthalmic cyclosporine A (CsA) formulation with good tolerance and high efficacy is still a desire in pharmaceutics and clinics. This article describes the preparation of CsA containing nanomicelles using a polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol (PVCL-PVA-PEG) graft copolymer. Both the polymer itself and the CsA nanomicelles were evaluated for cytotoxicity and ocular irritation. The in vitro uptake and intracellular fate of nanomicelles were characterized. In vivo cornea permeation test performed with 0.5 mg/mL CsA containing nanomicelles, and compared with a commercially available CsA (10 mg/mL) oil-based ophthalmic solution. The CsA nanomicelle ophthalmic solution was simple to prepare and remained storage stable. PVCL-PVA-PEG had no cytotoxicity as its monomer solution, and as its micelle solution (IC₅₀(48 h) = 14.02 mg/mL). CsA nanomicelles also had excellent ocular tolerance in rabbits. The use of nanomicelles significantly improved in vitro cellular uptake, apparently by an energy dependent intracellular endocytosis pathway that involved early endosomes, late endosomes, lysosomes, and ER. In vivo permeation showed that 0.5 mg/mL CsA nanomicelles delivered high levels of CsA into the cornea, when compared to the oil-based 10 mg/mL CsA ophthalmic solution. These findings indicated PVCL-PVA-PEG nanomicelles could be a promising topical delivery system for ocular administration of CsA.