Microspheres and nanoparticles used in ocular delivery systems

Mechanism of Ocular Penetration of Lipophilic Drugs from Lipophilic Vehicles

Since eyedrops have conventionally been formulated in aqueous vehicles, ocular pharmacokinetic studies are generally performed using aqueous buffers to identify physicochemical properties of the drug and the vehicles that influence drug absorption. In recent years, biocompatible lipophilic vehicles are increasingly finding application in ocular drug delivery; however, the mechanism of drug penetration from these non-aqueous vehicles is poorly understood. This study aims to compare ocular penetration of the model lipophilic drug curcumin when incorporated into lipophilic vehicles. To elucidate whether intrinsic solubility in the lipophilic vehicle influences ocular penetration, a curcumin solution and suspension were prepared in medium chain triglycerides (MCT) and squalane, respectively. Ocular penetration and distribution of curcumin from both vehicles was compared and evaluated qualitatively and quantitatively ex vivo. Significantly greater and faster penetration was observed from the squalane suspension than from the MCT solution in all ocular tissues. Our results suggest that the ability of lipophilic drugs to partition out of lipophilic vehicles and into cell membranes, rather than their intrinsic solubility in the lipophilic vehicle, determines the rate and extent of their ocular penetration.

Formulation and evaluation of Fluconazole Nanosuspensions: In vitro characterization and transcorneal permeability studies

The aim in this study was to develop and evaluate a nanofluconazole (FLZ) formulation with increased solubility and permeation rate using nanosuspensions. The FLZ nanosuspensions were stabilized using a variety of stabilizing agents and surfactants in various concentrations. The FLZ nanosuspension was characterized in vitro using particle size, zeta potential, X-ray powder diffraction (XRPD), and solubility. In addition, the ex vivo ocular permeation of FLZ through a goat cornea was analyzed. The results showed that the particle size of all nanosuspension formulations was in the nanometer range from 174.5 ± 1.9 to 720.2 ± 4.77 nm; that of the untreated drug was 18.34 μm. The zeta potential values were acceptable, which indicated suitable stability for formulations. The solubility of the nanosuspensions was up to 5.7-fold higher compared with that of the untreated drug. The results of the ex vivo ocular diffusion of the FLZ nanosuspensions showed the percentage of FLZ penetrating via the goat cornea increased after using Kollicoat to stabilize the nanosuspension formulation. Consequently, when using a nanosuspension formulation of Kollicoat, the antifungal activity of the drug strengthens.

Subconjunctival injection of rapamycin-loaded polymeric microparticles for effective suppression of noninfectious uveitis in rats

Noninfective uveitis is a major cause of vision impairment, and corticosteroid medication is a mainstay clinical strategy that causes severe side effects. Rapamycin (RAPA), a potent immunomodulator, is a promising treatment for noninfective uveitis. However, because high and frequent dosages are required, it is a great challenge to implement its clinical translation for noninfective uveitis therapy owing to its serious toxicity. In the present study, we engineered an injectable microparticulate drug delivery system based on biodegradable block polymers (i.e., polycaprolactone-poly (ethylene glycol)-polycaprolactone, PCEC) for efficient ocular delivery of RAPA via a subconjunctival injection route and investigated its therapeutic efficacy in an experimental autoimmune uveitis (EAU) rat model. RAPA-PCEC microparticles were fabricated using the emulsion-evaporation method and thoroughly characterized using scanning electron microscopy, fourier transform infrared spectroscopy, X-ray diffraction, and differential scanning calorimetry. The formed microparticles exhibited slow in vitro degradation over 28 days, and provided both in vitro and in vivo sustained release of RAPA over 4 weeks. Additionally, a single subconjunctival injection of PCEC microparticles resulted in high ocular tolerance. More importantly, subconjunctival injection of RAPA-PCEC microparticles significantly attenuated the clinical signs of EAU in a dose-dependent manner by reducing inflammatory cell infiltration (i.e., CD45+ cells and Th17 cells) and inhibiting microglial activation. Overall, this injectable microparticulate system may be promising vehicle for intraocular delivery of RAPA for the treatment of noninfective uveitis.

Microparticles and multi-unit systems for advanced drug delivery

Microparticles have unique benefits in the formulation of multiparticulate and multi-unit type pharmaceutical dosage forms allowing improved drug safety and efficacy with favorable pharmacokinetics and patient centricity. On the other hand, the above advantages are served by high and well reproducible quality attributes of the medicinal product where even flexible design and controlled processability offer success as well as possible longer product life-cycle for the manufacturers. Moreover, the specific demands of patients can be taken into account, including simplified dosing regimens, flexible dosage, drug combinations, palatability, and ease of swallowing. In the more than 70 years since the first modified-release formulation appeared on the market, many new formulations have been marketed and many publications have appeared in the literature. More unique and newer pharmaceutical technologies and excipients have become available for producing tailor-made particles with micrometer dimensions and beyond. All these have contributed to the fact that the sub-units (e.g. minitablets, pellets, microspheres) that make up a multiparticulate system can vary widely in composition and properties. Some units have mucoadhesive properties and others can float to contribute to a suitable release profile that can be designed for the multiparticulate formula as a whole. Nowadays, there are some available formulations on the market, which are able to release the active substance even for several months (3 or 6 months depending on the type of treatment). In this review, the latest developments in technologies that have been used for a long time are presented, as well as innovative solutions such as the applicability of 3D printing to produce subunits of multiparticulate systems. Furthermore, the diversity of multiparticulate systems, different routes of administration are also presented, touching the ones which are capable of carrying the active substance as well as the relevant, commercially available multiparticle-based medical devices. The versatility in size from 1 µm and multiplicity of formulation technologies promise a solid foundation for the future applications of dosage form design and development.

Topical Sustained-Release Dexamethasone-Loaded Chitosan Nanoparticles: Assessment of Drug Delivery Efficiency in a Rabbit Model of Endotoxin-Induced Uveitis

Uveitis is an ocular illness that if not treated properly can lead to a total loss of vision. In this study, we evaluated the utility of HA-coated Dexamethasone-sodium-phosphate (DEX)-chitosan nanoparticles (CSNPs) coated with hyaluronic acid (HA) as a sustained ocular delivery vehicle for the treatment of endotoxin-induced-uveitis (EIU) in rabbits. The CSNPs were characterized for particle size, zeta potential, polydispersity, surface morphology, and physicochemical properties. Drug encapsulation, in vitro drug release, and transcorneal permeation were also evaluated. Finally, eye irritation, ocular pharmacokinetics, and pharmacodynamics were in vivo. The CSNPs ranged from 310.4 nm and 379.3 nm pre-(uncoated) and post-lyophilization (with HA-coated), respectively. The zeta potentials were +32 mV (uncoated) and -5 mV (HA-uncoated), while polydispersity was 0.178-0.427. Drug encapsulation and loading in the CSNPs were 73.56% and 6.94% (uncoated) and 71.07% and 5.54% (HA-coated), respectively. The in vitro DEX release over 12 h was 77.1% from the HA-coated and 74.2% from the uncoated NPs. The physicochemical properties of the CSNPs were stable over a 3-month period when stored at 25 °C. Around a 10-fold increased transcorneal-flux and permeability of DEX was found with HA-CSNPs compared to the DEX-aqueous solution (DEX-AqS), and the eye-irritation experiment indicated its ocular safety. After the ocular application of the CSNPs, DEX was detected in the aqueous humor (AH) till 24 h. The area under the concentrations curve (AUC0-24h) for DEX from the CSNPs was 1.87-fold (uncoated) and 2.36-fold (HA-coated) higher than DEX-AqS. The half-life (t1/2) of DEX from the uncoated and HA-coated NPs was 2.49-and 3.36-fold higher, and the ocular MRT0-inf was 2.47- and 3.15-fold greater, than that of DEX-AqS, respectively. The EIU rabbit model showed increased levels of MPO, TNF-α, and IL-6 in AH. Topical DEX-loaded CSNPs reduced MPO, TNF-α, and IL-6 levels as well as inhibited NF-κB expression. Our findings demonstrate that the DEX-CSNPs platform has improved the delivery properties and, hence, the promising anti-inflammatory effects on EIU in rabbits.

Optimization and in vivo evaluation of triamcinolone acetonide loaded in situ gel prepared using reacted tamarind seed xyloglucan and kappa-carrageenan for ocular delivery

In the current work, triamcinolone acetonide (TAA) loaded dual responsive in situ gelling system was designed and optimized using reacted tamarind seed xyloglucan (RXG) (thermoresponsive) and kappa-Carrageenan (κ-CRG) (ion-sensitive) polymers. Tamarind seed xyloglucan (TSX) was subjected to purification followed by enzymatic treatment to produce RXG with ~40 % reduction in galactose content compared to TSX. RXG was characterized using size exclusion chromatography, Fourier transform infrared and proton nuclear magnetic resonance spectroscopy to confirm the ~40 % reduction in galactoside content compared to TSX. The proportions of RXG and κ-CRG in the in situ gels (TAA loaded RXG-κ-CRG) were optimized based on their rheological properties. The optimized in situ gel exhibited good flow properties at 25 °C, but transformed rapidly into a stronger gel in the presence of STF at 35 °C. The optimized formulation had strong mucoadhesion with good spreadability on the surface of excised goat cornea. The drug release followed zero-order kinetics from the optimized in situ gel. Ex vivo ocular toxicity studies indicate that the optimized formulation was well tolerated. The ocular pharmacokinetic studies in rabbits showed significantly higher and sustained vitreous humor exposure of TAA for optimized in situ gel compared to hydroxypropyl-β-cyclodextrin based aqueous suspension of TAA.

Topical Application of Linezolid-Loaded Chitosan Nanoparticles for the Treatment of Eye Infections

Linezolid (LZ) loaded chitosan-nanoparticles (CSNPs) was developed by the ionic-gelation method using Tripolyphosphate-sodium as a crosslinker for topical application for the treatment of bacterial eye infections. Particles were characterized by Zeta-Sizer (Malvern Nano-series). TEM was used for structural morphology. Encapsulation and drug loading were estimated by measuring the unencapsulated drug. In-vitro drug release in STF (pH 7) was performed through a dialysis membrane. Storage stability of LZ-CSNPs was checked at 25 °C and 40 °C for six months. The antimicrobial potency of NPs was evaluated on different Gram-positive strains. Ocular irritation and pharmacokinetic studies were completed in rabbits. Ex-vivo transcorneal permeation of the drug was determined through the rabbit cornea. Ionic interaction among the oppositely charged functional groups of CS and TPP generated the CSNPs. The weight ratio at 3:1, wt/wt (CS/TPP) with 21.7 mg of LZ produced optimal NPs (213.7 nm with 0.387 of PDI and +23.1 mV of ZP) with 71% and 11.2% encapsulation and drug loading, respectively. Around 76.7% of LZ was released from LZ-AqS within 1 h, while 79.8% of LZ was released from CSNPs at 12 h and 90% at 24 h. The sustained drug release property of CSNPS was evaluated by applying kinetic models. The linearity in the release profile suggested that the release of LZ from CSNPs followed the Higuchi-Matrix model. LZ-CSNPs have shown 1.4 to 1.6-times improved antibacterial activity against the used bacterial strains. The LZ-CSNPs were "minimally-irritating" to rabbit eyes and exhibited 4.4-times increased transcorneal permeation of LZ than from LZ-AqS. Around 3-, 1.2- and 3.1-times improved T_max, C_max, and AUC_{0-24 h}, respectively were found for LZ-CSNPs during the ocular pharmacokinetic study. AqS has shown 3.1-times faster clearance of LZ. Conclusively, LZ-CSNPs could offer a better alternative for the prolonged delivery of LZ for the treatment of bacterial infections in the eyes.

Mesoporous Silica Nanoparticles Coated with Carboxymethyl Chitosan for 5-Fluorouracil Ocular Delivery: Characterization, In Vitro and In Vivo Studies

This study investigates the development of topically applied non-invasive amino-functionalized silica nanoparticles (AMSN) and O-Carboxymethyl chitosan-coated AMSN (AMSN-CMC) for ocular delivery of 5-Fluorouracil (5-FU). Particle characterization was performed by the DLS technique (Zeta-Sizer), and structural morphology was examined by SEM and TEM. The drug encapsulation and loading were determined by the indirect method using HPLC. Physicochemical characterizations were performed by NMR, TGA, FTIR, and PXRD. In vitro release was conducted through a dialysis membrane in PBS (pH 7.4) using modified Vertical Franz diffusion cells. The mucoadhesion ability of the prepared nanoparticles was tested using the particle method by evaluating the change in zeta potential. The transcorneal permeabilities of 5-FU from AMNS-FU and AMSN-CMC-FU gel formulations were estimated through excised goat cornea and compared to that of 5-FU gel formulation. Eye irritation and ocular pharmacokinetic studies from gel formulations were evaluated in rabbit eyes. The optimum formulation of AMSN-CMC-FU was found to be nanoparticles with a particle size of 249.4 nm with a polydispersity of 0.429, encapsulation efficiency of 25.8 ± 5.8%, and drug loading capacity of 5.2 ± 1.2%. NMR spectra confirmed the coating of AMSN with the CMC layer. In addition, TGA, FTIR, and PXRD confirmed the drug loading inside the AMSN-CMC. Release profiles showed 100% of the drug was released from the 5-FU gel within 4 h, while AMSN-FU gel released 20.8% of the drug and AMSN-CMC-FU gel released around 55.6% after 4 h. AMSN-CMC-FU initially exhibited a 2.45-fold increase in transcorneal flux and apparent permeation of 5-FU compared to 5-FU gel, indicating a better corneal permeation. Higher bioavailability of AMSN-FU and AMSN-CMC-FU gel formulations was found compared to 5-FU gel in the ocular pharmacokinetic study with superior pharmacokinetics parameters of AMSN-CMC-FU gel. AMSN-CMC-FU showed 1.52- and 6.14-fold higher AUC0-inf in comparison to AMSN-FU and 5-FU gel, respectively. AMSN-CMC-FU gel and AMSN-FU gel were "minimally irritating" to rabbit eyes but showed minimal eye irritation potency in comparison to the 5 FU gel. Thus, the 5-FU loaded in AMSN-CMC gel could be used as a topical formulation for the treatment of ocular cancer.

Functional Peptide-Loaded Gelatin Nanoparticles as Eyedrops for Cornea Neovascularization Treatment

Background

Corneal neovascularization (NV) is a process of abnormal vessel growth into the transparent cornea from the limbus and can disturb the light passing through the cornea, resulting in vision loss or even blindness. The use of nanomedicine as an effective therapeutic formulation in ophthalmology has led to higher drug bioavailability and a slow drug release rate. In this research, we designed and explored the feasibility of a new nanomedicine, gp91 ds-tat (gp91) peptide-encapsulated gelatin nanoparticles (GNP-gp91), for inhibiting corneal angiogenesis.

Methods

GNP-gp91 were prepared by a two-step desolvation method. The characterization and cytocompatibility of GNP-gp91 were analyzed. The inhibition effect of GNP-gp91 on HUVEC cell migration and tube formation was observed by an inverted microscope. The drug retention test in mouse cornea was observed by in vivo imaging system, fluorescence microscope, and DAPI/TAMRA staining. Finally, the therapeutic efficacy and evaluation of neovascularization-related factors were conducted through the in vivo corneal NV mice model via topical delivery.

Results

The prepared GNP-gp91 had a nano-scale diameter (550.6 nm) with positive charge (21.7 mV) slow-release behavior (25%, 240hr). In vitro test revealed that GNP-gp91 enhanced the inhibition of cell migration and tube formation capacity via higher internalization of HUVEC. Topical administration (eyedrops) of the GNP-gp91 significantly prolongs the retention time (46%, 20 min) in the mouse cornea. In chemically burned corneal neovascularization models, corneal vessel area with a significant reduction in GNP-gp91 group (7.89%) was revealed when compared with PBS (33.99%) and gp91 (19.67%) treated groups via every two days dosing. Moreover, GNP-gp91 significantly reduced the concentration of Nox2, VEGF and MMP9 in NV's cornea.

Conclusion

The nanomedicine, GNP-gp91, was successfully synthesized for ophthalmological application. These data suggest that GNP-gp91 contained eyedrops that not only have a longer retention time on the cornea but also can treat mice corneal NV effectively delivered in a low dosing frequency, GNP-gp91 eyedrops provides an alternative strategy for clinical ocular disease treatment in the culture.

Iontophoretic ocular delivery of latanoprost-loaded nanoparticles via skin-attached electrodes

Prolonged drug efficacy to reduce the number of administrations is a key factor in the successful treatment of glaucoma through topical drug delivery to the eye. Therefore, we propose a new strategy for iontophoretic ocular delivery of drug-loaded nanoparticles. Considering safety and convenience, our strategy is involved with topical administration of the drug-loaded nanoparticles followed by their permeation into the eye tissues via noninvasive iontophoresis, using the skin-attached electrodes. Thus, those nanoparticles stayed longer in the eye, and during this period, the drug was released in a sustained manner, thereby prolonging drug exposure even with one-time treatment. The nanoparticles were made of poly(lactic-co-glycolic acid) (PLGA), which were loaded with a glaucoma drug, latanoprost. We varied the size of the nanoparticles at 100, 200, 300, and 500 nm and sought to find the optimum size under the fixed conditions for iontophoresis proposed in this work (4 mA; 30 min). Even with iontophoresis through the skin-attached electrodes, the nanoparticles were indeed deposited in the eye tissues, where with an increase in particle size, drug release was more sustained, but fewer particles could permeate into the eye tissues. Because of these two competing factors, iontophoretic delivery of the 300-nm particles exhibited the most prolonged drug efficacy in vivo for more than 7 days, and showed an approximately 23-fold increase in drug efficacy compared with that of Xalatan®, a commercially available eye drop of latanoprost developed for once-a-day administration every day. STATEMENT OF SIGNIFICANCE: To treat glaucoma, conventional eye drops are often prescribed; however, they often require multiple daily administrations due to rapid preocular clearance. To resolve this, we suggest a noninvasive iontophoretic ocular delivery of latanoprost-loaded PLGA nanoparticles using the skin-attached electrodes. Even with iontophoresis via the skin-attached electrodes, the nanoparticles can indeed be deposited into the eye tissues. However, with an increase in particle size, fewer particles can permeate into the eye tissues, although drug release is more sustained. Therefore, the particles with a size of 300 nm show the optimal in vivo delivery profile in this work, where the drug efficacy can be extended for more than 7 days with a single administration.

Development and Evaluation of Chitosan Nanoparticles for Ocular Delivery of Tedizolid Phosphate

This study investigates the development of topically applied non-invasive chitosan-nanoparticles (CSNPs) for ocular delivery of tedizolid phosphate (TZP) for the treatment of MRSA-related ocular and orbital infections. An ionic-gelation method was used to prepare TZP-encapsulated CSNPs using tripolyphosphate-sodium (TPP) as cross-linker. Particle characterization was performed by the DLS technique (Zeta-Sizer), structural morphology was observed by SEM. The drug encapsulation and loading were determined by the indirect method. In-vitro release was conducted through dialysis bags in simulated tear fluid (pH 7) with 0.25% Tween-80. Physicochemical characterizations were performed for ocular suitability of CSNPS. An antimicrobial assay was conducted on different strains of Gram-positive bacteria. Eye-irritation from CSNPs was checked in rabbits. Transcorneal flux and apparent permeability of TZP from CSNPs was estimated through excised rabbit cornea. Ionic interaction between the anionic and cationic functional groups of TPP and CS, respectively, resulted in the formation of CSNPs at varying weight ratios of CS/TPP with magnetic stirring (700 rpm) for 4 h. The CS/TPP weight ratio of 3.11:1 with 10 mg of TZP resulted in optimal-sized CSNPs (129.13 nm) with high encapsulation (82%) and better drug loading (7%). Release profiles indicated 82% of the drug was released from the TZP aqueous suspension (TZP-AqS) within 1 h, while it took 12 h from F2 to release 78% of the drug. Sustained release of TZP from F2 was confirmed by applying different release kinetics models. Linearity in the profile (suggested by Higuchi’s model) indicated the sustained release property CSNPs. F2 has shown significantly increased (p < 0.05) antibacterial activity against some Gram-positive strains including one MRSA strain (SA-6538). F2 exhibited a 2.4-fold increased transcorneal flux and apparent permeation of TZP as compared to TZP-AqS, indicating the better corneal retention. No sign or symptoms of discomfort in the rabbits’ eyes were noted during the irritation test with F2 and blank CSNPs, indicating the non-irritant property of the TZP-CSNPs. Thus, the TZP-loaded CSNPs have strong potential for topical use in the treatment of ocular MRSA infections and related inflammatory conditions.

Balance of Drug Residence and Diffusion in Lacrimal Fluid Determine Ocular Bioavailability in In Situ Gels Incorporating Tranilast Nanoparticles

We previously designed ophthalmic formulations (nTRA) containing tranilast nanoparticles (Tra-NPs) with high uptake into ocular tissues. In this study, we used in situ gel (ISG) bases comprising combinations of pluronic F127 (F127) and methylcellulose (MC/F127), pluronic F68 (F68/F127), and Carbopol (Car/F127), and we developed in situ gels incorporating Tra-NPs (Tra-NP-incorporated ISNGs) such as nTRA-F127, nTRA-MC/F127, nTRA-F68/F127, and nTRA-Car/F127. Moreover, we demonstrated the therapeutic effect on conjunctival inflammation using lipopolysaccharide-induced rats. Each Tra-NP-incorporated ISNG was prepared by the bead mill method, the particle size was 40–190 nm, and the tranilast release and diffusion from formulation were nTRA > nTRA-F127 > nTRA-F68/F127 > nTRA-Car/F127 > nTRA-MC/F127. In the Tra-NP-incorporated ISNGs, the tranilast residence time in the lacrimal fluid, cornea, and conjunctiva was prolonged, although the C_max was attenuated in comparison with nTRA. On the other hand, no significant difference in conjunctival inflammation between non- and nTRA-F127-instilled rats was found; however, the nTRA-F68/F127, nTRA-Car/F127, and nTRA-MC/F127 (combination-ISG) attenuated the vessel leakage, nitric oxide, and tumor necrosis factor-α expression. In particular, nTRA-F68/F127 was significant in preventing the conjunctival inflammation. In conclusion, we found that the combination-ISG base prolonged the residence time of Tra-NPs; however, Tra-NP release from the formulation was attenuated, and the T_max was delayed longer than that in nTRA. The balance of drug residence and diffusion in lacrimal fluid may be important in providing high ocular bioavailability in formulations containing solid nanoparticles.

Live In-Vivo Neuroimaging Reveals the Transport of Lipophilic Cargo Through the Blood-Retina Barrier with Modified Amphiphilic Poly-N-Vinylpyrrolidone Nanoparticles

The blood-retina barrier (BRB), analogous to the blood-brain barrier, is a major hurdle for the passage of drugs from the blood to the central nervous system. Here, we designed polymeric nanoparticles from amphiphilic poly-/V-vinylpyrrolidone (Amph-PVP NPs) as a new carrier-system and investigated their ability to pass the BRB using a live In-Vivo neuroimaging system for the retina in rats and ex-vivo wholemounted retinae preparation. Amph-PVP NPs were loaded with hydrophobic fluorescent markers as a surrogate for hydrophobic drugs. Linking these NPs with the hydrophobic fluorescence marker Carboxyfluorescein-succinimidyl-ester (CFSE) to the surface, induced the passage of the cargo into the retina tissue. In particular, we observed a substantial internalization of the CFSE-linked NPs into blood cells. We propose surface- modified Amph-PVP NPs as a potential new nano-carrier platform to target posterior eye and potentially brain diseases while camouflaged by blood cells.

Fluconazole nanoparticles prepared by antisolvent precipitation technique: Physicochemical, in vitro, ex vivo and in vivo ocular evaluation

The goal of this research was to prepare and characterize nanonized particles of the antifungal drug, fluconazole (FLZ) using antisolvent precipitation nanonization technique to improve its ocular permeation. The impact of various concentrations of different stabilizers, namely Pluronic F-127 (PL F 127), Kollicoat IR (KL), hydroxypropyl methylcellulose E3 (HPMC), xanthan gum (XG), polyvinyl pyrrolidone K30 (PVP), and sodium lauryl sulfate (SLS) upon the resulting nanoparticles was investigated. Additionally, the ex vivo release of the FLZ nanonized particles from ophthalmic gel bases was studied by using goat cornea, and the ocular pharmacokinetics of appropriate ophthalmic gel base containing optimized drug nanoparticle formula compared to the untreated drug were studied in rabbits. FLZ nanoparticles were successfully prepared with different concentrations of stabilizers. However, the effects of these stabilizers on nanoparticle size and zeta potential values varied according to the concentration and type of stabilizer used. Based on differential scanning calorimetry, the drug was in its amorphous state in the tested nanoparticle formulations. The results of ex vivo ocular diffusion of the FLZ nanoparticle gel formulations revealed an improvement compared to that with the FLZ untreated gel. Nanoparticle formula (F3) prepared by using 5% PL F127 showed small particle size (352 ± 6.1 nm) with zeta potential value of −18.3 mV with highest ex vivo release rate from goat cornea (100% after 6 h). Moreover, the AUC_0-8h from ocular application of FLZ from sodium alginate gel containing nanoparticle formula F3 was 1.4-fold higher than that after its administration in the untreated formula. Based on our findings, the ophthalmic gel formulations containing FLZ nanoparticles enhanced drug corneal permeation and improved the ocular pharmacokinetic parameters.

Recent advances in the design of microfluidic technologies for the manufacture of drug releasing particles

Drug releasing particles are valued for their ability to deliver therapeutics to targeted locations and for their controllable release patterns. The development of microfluidic technologies, which are designed specifically to manipulate small amounts of fluids, to manufacture particles for drug delivery applications reflects a recent trend due to the advantages they confer in terms of control over particle size and material composition. This review takes a comprehensive look at the different types of microfluidic devices used to fabricate such particles from different types of biomaterials, and at how the on-chip features enable the production of particles with different types of properties. The review concludes by suggesting avenues for future work that will enable these technologies to fulfill their potential and be used in industrial settings for the manufacture of drug releasing particles with unique capabilities.

Review of Approaches for Increasing Ophthalmic Bioavailability for Eye Drop Formulations

Ophthalmic diseases represent a significant problem as over 2 billion people worldwide suffer from vison impairment and blindness. Eye drops account for around 90% of ophthalmic medications but are limited in success due to poor patient compliance and low bioavailability. Low bioavailability can be attributed to short retention times in the eye caused by rapid tear turnover and the difficulty of drug diffusion through the multi-layered structure of the eye that includes lipid-rich endothelial and epithelial layers as well as the stroma which is high in water content. In addition, there are barriers such as tight junctional complexes in the corneal epithelium, lacrimal turnover, nasolacrimal drainage, blinking reflexes, efflux transporters, drug metabolism by ocular enzymes, and drug binding to or repulsion from conjunctival mucins, tear proteins, and melanin. In order to maximize transport through the cornea while minimizing drug loss through other pathways, researchers have developed numerous methods to improve eye drop formulations including the addition of viscosity enhancers, permeability enhancers, mucoadhesives, and vasoconstrictors, or using formulations that include puncta occlusion, nanocarriers, or prodrugs. This review explains the mechanism behind each of these methods, examines their history, analyzes previous and current research, evaluates future applications, and discusses the pros and cons of each technique.

Drug Carriers: Classification, Administration, Release Profiles, and Industrial Approach

This work is aimed at providing a description of the complex world of drug carriers, starting from the description of this particular market in terms of revenue. Then, a brief overview of several types of conventional and innovative drug carrier systems has been included. The types of administration routes were also analyzed, with a critical and qualitative comment on drug release kinetics and drug profile shapes. Carriers were classified according to their ability to provide a prolonged and targeted release. The concept of the therapeutic window has been presented, providing advantages of having pulsed drug release to avoid side effects to target tissues. A critical comment on the use of conventional and innovative techniques for the production of drug carriers by large industrial companies has been proposed. As a final attempt for this work, an overall unique schematization of a drug carrier production process has been added, highlighting the necessity to create a strong double link among world-requested versatility of drug carriers for human applications and the newly developed industrial processes.

A Review: Uses of Chitosan in Pharmaceutical Forms

Chitosan is a natural polysaccharide widespread in nature. It has many unique and attractive properties for the pharmaceutical field: it is biodegradable, safe, hypoallergenic, biocompatible with the body, free of toxicity, with proven anticholesterolemic, antibacterial, and antimycotic action. In this review we highlighted the physical, chemical, mechanical, mucoadhesive, etc. properties of chitosan to be taken into account when obtaining various pharmaceutical forms. The methods by which the pharmaceutical forms based on chitosan are obtained are very extensive, and in this study only the most common ones were presented.

Alginate-Based Platforms for Cancer-Targeted Drug Delivery

As an acidic, ocean colloid polysaccharide, alginate is both a biopolymer and a polyelectrolyte that is considered to be biocompatible, nontoxic, nonimmunogenic, and biodegradable. A significant number of studies have confirmed the potential use of alginate-based platforms as effective vehicles for drug delivery for cancer-targeted treatment. In this review, the focus is on the formation of alginate-based cancer-targeted delivery systems. Specifically, some general chemical and physical properties of alginate and different types of alginate-based delivery systems are discussed, and various kinds of alginate-based carriers are introduced. Finally, recent innovative strategies to functionalize alginate-based vehicles for cancer targeting are described to highlight research towards the optimization of alginate.

Comparison of Different Chitosan Lipid Nanoparticles for Improved Ophthalmic Tetrandrine Delivery: Formulation, Characterization, Pharmacokinetic and Molecular Dynamics Simulation

In this study, three different chitosan, namely carboxymethyl chitosan (CMC), hydroxypropyl chitosan (HPC) and trimethyl chitosan (TMC) were used as cationic materials to prepare tetrandrine lipid nanoparticles (TET-LNPs) for the treatment of glaucoma. In vitro drug release and pre-corneal retention were used to select the optimal chitosan. In vitro drug release curves of three kinds of LNPs showed a sustained release and TMC-TET-LNPs were the slowest. Moreover, compared with CMC-TET-LNPs and HPC-TET-LNPs, TMC-TET-LNPs had longer corneal retention time. Afterwards, the characteristics of TMC-TET-LNPs were investigated. The ocular irritation study revealed no sign of irritation in rabbit eyes. The pharmacokinetic studies showed that the area under the curve of TMC-TET-LNPs was increased by 2.03 times than TET solution (p < 0.01). Furthermore, the drug biofilm interactions were evaluated by molecular dynamics (MD) simulation. In MD simulation, the strong hydrophobic group of TET interacted with the tail of POPC, making it hard to enter the hydrophobic region of the membrane, thereby restricting TET ocular bioavailability. The experiments and MD simulation indicated that TMC-TET-LNPs had great potential for ocular administration and MD simulation could predict transmembrane transport of drugs.

Brimonidine-montmorillonite hybrid formulation for topical drug delivery to the eye

Brimonidine (BMD) is often prescribed as an eye drop to reduce the intraocular pressure (IOP) for glaucoma treatment. However, eye drops are limited by rapid clearance from the preocular surface, and hence a low ocular drug bioavailability. Therefore, in this study, we propose montmorillonite (MMT), as a delivery carrier, hybridized with BMD (BMD-MMT) for topical drug delivery to the eye. The BMD-MMT hybrid was prepared by intercalating the BMD molecules in the interlayer space of the MMT lattice via ion-exchange reaction; it was then formulated with polyvinyl alcohol (PVA) to produce a dry tablet (i.e., BMD-MMT@PVA). The BMD-MMT@PVA hybrid drug released BMD in a sustained manner for more than 5 h under in vitro conditions. When the hybrid drug was administered to rabbit eyes in vivo, 43% and 18.5% BMD-MMT still remained on the preocular surface for 10 and 60 min after administration, respectively. Thus, the BMD-MMT@PVA hybrid drug exhibited a prolonged decrease in IOP, that is, for 12 h, which was approximately two times longer than that observed with the commercially available BMD eye drop, Alphagan® P.

Biodegradable Nanoparticles Based on Pseudo-Proteins Show Promise as Carriers for Ophthalmic Drug Delivery

Purpose: Drug delivery to treat ocular diseases still is a challenge in ophthalmology. One way to achieve drug delivery that is investigated currently is topical administration of drug-loaded polymeric nanoparticles (NPs) that are able to penetrate ocular barriers. The purpose of this study was optimal preparation of NPs made from pseudo-proteins and evaluation of their ability to penetrate ocular tissues. Methods: Biodegradable NPs of various types were prepared by nanoprecipitation of pseudo-protein composed of l-leucine (L), 1,6-hexanediol (6), and sebacic acid (8) (8L6). Arginine-based cationic polyester amides 8R6 and comb-like polyester amide containing lateral PEG-2000 chains along with 8L6 anchoring fragments in the backbones were used to construct positively charged and PEGylated NPs. They were loaded with fluorescein diacetate (FDA) or rhodamine 6G (Rh6G) as fluorescent probes. Suspensions of the NPs were given to cultivated microglial cells and retinal pigment epithelial (RPE) cells as well as topically on eyes of C57BL/6 mice. Penetration of NPs into the eyes was checked by fluorescence analysis. Results: NPs were prepared, and their properties were characterized. Cultured microglial cells and RPE cells took up the NPs. After topical administration, penetration of NPs into the cornea of the eyes was clearly seen. Small amounts of fluorescent dyes were also found in the lens, the retina, and the sclera depending on the type of NPs. Conclusions: The results showed that the new NPs penetrate ocular tissues after topical administration and are internalized by the cells. This raises confidence that the NPs may be useful carriers of therapeutic agents for ocular delivery.

Self-nanoemulsifying drug delivery system to improve transcorneal permeability of voriconazole: in-vivo studies

OBJECTIVE

This study investigates the effectiveness of self-nanoemulsifying drug delivery system (SNEDDS) in improving voriconazole transcorneal permeability.

METHODS

Voriconazole-SNEDDS was prepared with isopropyl myristate, PEG 400, Tween 80^® and Span 80^® and was subjected for physicochemical characterization after reconstitution with NaCl 0.9% (1/9; v/v). In-vitro antifungal activity was assessed and compared with the marketed formulation. In-vivo studies, namely ocular irritation test via modified Draize test and pharmacokinetic study, were investigated using rabbit as animal model.

KEY FINDINGS

Voriconazole-SNEDDS presented a droplet size of 21.353 ± 0.065 nm, a polydispersity index of 0.123 ± 0.003, a pH of 7.205 ± 0.006 and an osmolarity of 342.667 ± 2.517 mOsmol/l after reconstitution with NaCl 0.9%. Voriconazole-SNEDDS minimum inhibitory concentration (MIC₉₀ ) was similar to the one of marketed formulation for Candida species while it was significantly lower (P < 0.001) for Aspergillus fumigatus. Draize test revealed that Voriconazole-SNEDDS was safe for ocular administration. Voriconazole maximum concentration (5.577 ± 0.852 µg/ml) from SNEDDS was higher than marketed formulation (C_max  = 4.307 ± 0.623 µg/ml), and the T_max was delayed to 2 h. The area under the concentration-time curve value of Voriconazole-SNEDDS was improved by 2.419-fold.

CONCLUSION

Our results suggest that SNEDDS is a promising carrier for voriconazole ocular delivery and this encourages further clinical studies.

Effect of Formulation Variables and Gamma Sterilization on Transcorneal Permeation and Stability of Proniosomal Gels as Ocular Platforms for Antiglaucomal Drug

This study aims to evaluate the effect of different formulation variables (surfactant type and HLB value) adopting full factorial design (5¹. 2¹) using coacervation phase technique on in vitro characterization of dorzolamide hydrochloride (DZ)-loaded proniosomal gels, namely, entrapment efficiency percentage (EE%), vesicle size distribution, polydispersion index (PDI), and in vitro DZ release. The optimum formula F2 with a desirability value of 0.937 composed of 40 mg DZ, 500 mg span 60, 500 mg of L-α-Lethicin, and 55.5 mg cholesterol showing EE% of 84.5 ± 1.5%, PS of 189.5 ± 35.76 nm with PDI 0.8 ± 0.28 and 58.51% ± 1.00 of DZ released after 8 h was further evaluated using differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The effect of gamma sterilization on transcorneal permeation and stability of DZ from the selected formulation (F2) revealed that F2 was significantly tolerable, stable, and competent to corneal permeation confirmed by histological examination, confocal laser microscopy, and intraocular pressure (IOP) measurement. Significant corneal bioavailability was attained from formula F2 (370.6 mg. h/m) compared to the market product Trusopt® eye drops (92.59 mg. h/ml) following IOP measurement, thereby proniosomal gels could be considered as tolerable and competent ocular platforms for improving the transcorneal permeation of DZ.

Polysaccharides in Ocular Drug Delivery

Polysaccharides, such as cellulose, hyaluronic acid, alginic acid, and chitosan, as well as polysaccharide derivatives, have been successfully used to augment drug delivery in the treatment of ocular pathologies. The properties of polysaccharides can be extensively modified to optimize ocular drug formulations and to obtain biocompatible and biodegradable drugs with improved bioavailability and tailored pharmacological effects. This review discusses the available polysaccharide choices for overcoming the difficulties associated with ocular drug delivery, and it explores the reasons for the dependence between the physicochemical properties of polysaccharide-based drug carriers and their efficiency in different formulations and applications. Polysaccharides will continue to be of great interest to researchers endeavoring to develop ophthalmic drugs with improved effectiveness and safety.

Development of Kaempferol-Loaded Gelatin Nanoparticles for the Treatment of Corneal Neovascularization in Mice

Cornea is the transparent layer in front of the eye that does not contain blood vessels. Among eye diseases, corneal neovascularization (NV) is one of the major causes of vision loss, since it can also lead to blindness. An herbal extraction containing flavonoid, kaempferol (KA), with antiangiogenic effect was chosen as a candidate drug for inhibited vessel formation. The use of nanomedicine has led to higher drug bioavailability and slow release of the drug as an effective therapeutic formulation in ocular drug delivery. In this study, we prepared gelatin nanoparticles (GNP) with kaempferol encapsulation (GNP-KA) for corneal NV treatment by topical delivery, i.e., eye drops. We found that GNP with/without KA loading was in the size of 85-150 nm, and its zeta potential was around 22-26 mV. The KA entrapment rate of GNP-KA was around 90-98%, and the loading rate was about 4.6%. The TEM results clearly indicated the GNP-KA NPs to be round spheres. The in vitro test involved the adoption of human umbilical vein endothelial cells (HUVECs) for coculture with these nanoparticles. From WST-8 assay, and cell migration examinations, it was evident that GNP-KA had the capacity to inhibit the cell viability and function of HUVECs. The results from in vivo tests such as ocular vessels observation, hematoxylin & eosin (H&E) stain, and metalloproteinases (MMP)/vascular endothelial growth factor (VEGF) quantification revealed the mice's eyes with corneal NV treated by eye drops containing GNP-KA once daily for 7 days had better therapeutic effects with less vessels in-growths in the cornea, compared to the KA solution group by reducing the production of MMP and VEGF in the cornea. Therefore, we expected to achieve a comfortable treatment with a simple method using nanomedicine (GNP-KA) as ophthalmological agent delivered as eye drops.

Nanoparticles for ocular drug delivery: modified and non-modified chitosan as a promising biocompatible carrier

The eye is a very important, yet sensitive organ, presenting complex anatomy. To overcome its protective mechanisms, with the aim of improving drug delivery, drug encapsulation in nanocarriers is considered in this review. Chitosan is found to be an excellent drug carrier and its application in ophthalmology is being extensively researched. This mucoadhesive biopolymer can protect the encapsulated molecule, optimize its mode of action and minimize any existent risk. Moreover, chitosan and its derivatives may provide advantageous properties to the system such as thermoresponsivity and pH dependency. Finally, dual systems of chitosan with other carriers, such as poly (lactic-co-glycolic acid) and alginate, are also mentioned in this review, as they may offer additional benefits such as higher permeation due to different interaction of each carrier with the corneal layers.

Design of Experiments (DoE) Approach to Optimize the Sustained Release Microparticles of Gefitinib

Background:

Gefitinib (GEF), the kinase inhibitor, is presently available as tablets to be taken orally in high doses of 250-500 mg per day due to its poor solubility. The solubility issues affect not only its onset of action but also the bioavailability. These drawbacks foresight the need to have an alternate dosage form, preferably a sustained release formulation.

Methods:

In the present study, microparticles were prepared by emulsion solvent evaporation using PLGA 50:50 (GEF-PLGA MP). A 32 factorial design was used to optimize the critical quality parameters to the set mean particle size in the range of 7.4±2.5 µm and entrapment efficiency of 80%. SEM microscopy of the prepared microparticles confirmed to have a spherical smooth shape. The GEFPLGA- MPs sustained the release of GEF for 72 hours. The first-order kinetics ruled the mechanism of drug release and was predicted to follow Fickian diffusion.

Result:

Anticancer efficacy was judged by the cytotoxicity studies using the L132 lung cancer cells. MTT assay showed 3-fold enhanced cytotoxicity of GEF loaded microparticles against L132 cells as compared to plain GEF.

Conclusion:

It was concluded that gefitinib can be efficiently loaded into the biodegradable polymer PLGA to provide sustained release of the drug.

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.

Employing a PLGA-TPGS based nanoparticle to improve the ocular delivery of Acyclovir

Delivering drugs via the ocular route has always been a challenge for poorly soluble drugs. The various anatomical and physiological barriers in the eye cavity hinder the residence of drugs within the corneal and precorneal regions. In this study, the nanosystem that could sufficiently deliver the poorly soluble Acyclovir topically via ocular route. Our nanosystem is composed of the biocompatible PLGA polymer stabilized with TPGS which possess a high emulsifying capacity and is also known as P-gp inhibitor. The optimized nanoparticles were prepared with 0.3% TPGS and had particle-size of 262.3 nm, zeta-potential of +15.14 mV. The physicochemical-characterization, ex vivo transcorneal permeation, ocular-irritation and Acyclovir ocular-availability, following topical ocular application of PLGA-NPs in rabbit eyes, were performed. The tested parameters and irritation by Draize's test suggested the suitability and safety of PLGA-NPs for ocular use. An ultrahigh performance liquid chromatographic method was developed, validated, and applied to quantify Acyclovir in aqueous humor which was shown to be significantly higher (p < 0.05) using the developed nanoparticles as compared to Acyclovir-aqueous suspension following their single topical ocular administration. Noticeable 2.78-, 1.71- and 2.2-times increased values of AUC_0-24h, t_1/2 (h) and MRT_0-24h were found, respectively, with the PLGA-TPGS-NPs as compared to ACY-AqS. These results demonstrate the superiority of delivering Acyclovir using a nanosystem compared to conventional methods.

A stimulus-responsive, in situ-forming, nanoparticle-laden hydrogel for ocular drug delivery

Most medications targeting optic neuropathies are administered as eye drops. However, their corneal penetration efficiencies are typically < 5%. There is a clear, unmet need for novel transcorneal drug delivery vehicles. To this end, we have developed a stimulus-responsive, in situ-forming, nanoparticle-laden hydrogel for controlled release of poorly bioavailable drugs into the aqueous humor of the eye. The hydrogel is formulated as a composite of hyaluronic acid (HA) and methylcellulose (MC). The amphiphilic nanoparticles are composed of poly(ethylene oxide) (PEO) and poly(lactic acid) (PLA). Experimental design aided the identification of hydrogel composition and nanoparticle content in the formulation, and the formulation reliably switched between thixotropy and temperature-dependent rheopexy when it was tested in a rheometer under conditions that simulate the ocular surface, including blinking. These properties should ensure that the formulation coats the cornea through blinking of the eyelid and facilitate application of the medication as an eye drop immediately prior to the patient’s bedtime. We subsequently tested the efficacy of our formulation in whole-eye experiments by loading the nanoparticles with cannabigerolic acid (CBGA). Our formulation exhibits over a 300% increase in transcorneal penetration over control formulations. This work paves the way for the introduction of novel products targeting ocular diseases to the market.

Metal-organic frameworks, NH2-MIL-88(Fe), as carriers for ophthalmic delivery of brimonidine

We have proposed a metal-organic framework (MOF), NH₂-MIL-88(Fe), as a novel carrier for topical drug delivery to the eye. The NH₂-MIL-88(Fe) particles were prepared via a solvothermal synthesis method and their structure was confirmed by powder X-ray diffraction, Fourier transform infrared analysis, thermogravimetric analysis, electron microscopy, and N₂ adsorption-desorption measurements. When brimonidine, an anti-glaucoma medicine, was encapsulated into NH₂-MIL(Fe)-88 (i.e., NH₂-MIL-88(Fe)/Br), the drug was loaded at 121.3 µg/mg and released in a sustained manner for up to 12 h. The NH₂-MIL-88(Fe)/Br exhibited mucoadhesive properties and remained on rabbit eyes for a period of up to 4 h. Consequently, a high concentration of brimonidine was found in tears for a prolonged period after the administration of NH₂-MIL-88(Fe)/Br, which resulted in a greater than two-fold increase in drug bioavailability and activity period compared with those of Alphagan P, which are brimonidine eye drops already approved for clinical use. Hence, NH₂-MIL-88(Fe) is suggested to be a promising carrier for topical delivery to the eye that provides enhanced bioavailability of ocular drugs.

STATEMENT OF SIGNIFICANCE

We suggest NH₂-MIL(Fe)-88, a type of metal-organic frameworks (MOFs), as delivery carriers of an ophthalmic drug, brimonidine. The NH₂-MIL(Fe)-88 particles possess a mucoadhesive property, hence prolonged retention in the preocular space when topically administered to the eye. The particles can also encapsulate the drug in their micro-pores, through which the drug can be released in a sustained manner. Therefore, when tested to rabbit eyes in vivo, the drug-loaded NH₂-MIL(Fe)-88 particles were shown to enhance the ocular drug bioavailability, as compared with Alphagan P, the marketed eye drops of brimonidine.