Development of an Anti-Inflammatory Drug-Incorporated Biomimetic Scaffold for Corneal Tissue Engineering.

Purpose: The aim of this study was to design naproxen sodium (NS)-containing, biomimetic, porous poly(lactide-co-glycolide) (PLGA) scaffolds for regeneration of damaged corneal epithelium. Methods: NS-incorporated PLGA scaffolds were prepared using the emulsion freeze-drying method and then coated with collagen or poly-l-lysine. Porosity measurements of the scaffolds were performed by the gas adsorption/desorption method and the scaffolds demonstrated highly porous, open-cellular pore structures with pore sizes from 150 to 200 µm. Results: The drug loading efficiency of scaffolds was found to be higher than 84%, and about 90%-98% of NS was released at the end of 7 days with a fast drug release rate at the initial period of time and then in a slow and sustained manner. The corneal epithelial cells were isolated from New Zealand white rabbits. The obtained cells were seeded onto scaffolds and continued to increase during the time period of the study, indicating that the scaffolds might promote corneal epithelial cell proliferation without causing toxic effects for at least 10 days. Conclusions: The NS-loaded PLGA scaffolds exhibited a combination of controlled drug release and biomimetic properties that might be attractive for use in treatment of corneal damage both for controlled release and biomedical applications.

Development and evaluation of orally disintegrating tablets comprising taste-masked mirtazapine granules.

INTRODUCTION: Orally disintegrating tablets (ODTs) provide an important treatment option for pediatric, geriatric and psychiatric patients. In our previous study, we have performed the initial studies for the formulation development and characterization of new ODT formulations containing a bitter taste drug, mirtazapine, coated with 6% (w/w) Eudragit® E-100 (first group of formulations, FGF) without taste evaluation. In present study, coating ratio of the drug was increased to 8% (w/w) (second group of formulations, SGF) to examine the effect of increased coating ratio of drug on in vitro characterization of the formulations including in vitro taste masking study. MATERIALS AND METHODS: Coacervation technique using Eudragit® E-100 was employed to obtain taste-masked mirtazapine granules. FGF and SGF were compared to original product (Remeron SolTab, an antidepressant drug which produced by pellet technology) in terms of in vitro permeability, in vitro taste masking efficiency which was performed by dissolution studies in salivary medium and dissolution stability. Also, the other tablet characteristics (such as diameter, thickness) of SGF were examined. RESULTS AND DISCUSSION: The disintegration time of the SGF were found as A1 < A2 < A3 < A5 < A4 (8% Eudragit® E-100), but all of the formulations dissolved under 30 seconds and friability values were less than 1%. In vitro taste masking efficiency studies demonstrated that C2 formulation (in FGF) had the most similar dissolution profile to Remeron SolTab. CONCLUSIONS: According to these findings, B2 or C2 (with citric acid or sodium bicarbonate, respectively, with 6% Eudragit® E-100) formulations could be promising alternatives to Remeron SolTab.

Dexamethasone - PAMAM dendrimer conjugates for retinal delivery: preparation, characterization and in vivo evaluation.

OBJECTIVE: Ocular diseases affecting retina, such as diabetic retinopathy (DR), age-related macular degeneration (AMD) and glaucoma are the major causes of blindness, and their treatment is still a challenge due to the special structure of the eye. The purpose of this study was to prepare a sustained release DEX conjugate formulation with enhanced ocular permeation using poly(amidoamine) (PAMAM) dendrimers and to evaluate the effects of conjugation on DEX release and ocular residence time. METHODS: PAMAM G3.5 and PAMAM G4.5 dendrimers were used to prepare DEX conjugates, and conjugation was confirmed using (1) H-NMR. Formulations were evaluated in terms of drug release in the presence of ocular enzymes and cytotoxicity on ARPE19 cell lines. Fluorotron analysis was performed and ocular pharmacokinetic properties of DEX-PAMAM conjugates were studied in Sprague Dawley rats following intravitreal and subconjunctival applications. KEY FINDINGS: The results indicated that DEX-PAMAM conjugates were able to enhance ocular permeability and ocular tissue levels of DEX following subconjunctival injection, and results were encouraging when compared to the literature that has reported DEX getting cleared from vitreous in 3 h. CONCLUSION: Current studies are focused on formulation improvement to enhance hydrolysis and clearance time.

In vivo tissue distribution and efficacy studies for cyclosporin A loaded nano-decorated subconjunctival implants.

Biodegradable implants are promising drug delivery systems for sustained release ocular drug delivery with the benefits such as minimum systemic side effects, constant drug concentration at the target site and getting cleared without surgical removal. Dry eye syndrome (DES) is a common disease characterized with the changes in ocular epithelia surface and results in inflammatory reaction that might lead to blindness. Cyclosporin A (CsA) is a cyclic peptide that is frequently employed for the treatment of DES and it needs to be applied several times a day in tear drops form. The aim of this study was to evaluate in vivo behavior and efficacy of the developed nano-decorated subconjunctival implant systems for sustained release CsA delivery. Biodegradable Poly-ɛ-caprolactone (PCL) implant or micro-fiber implants containing CsA loaded poly-lactide-co-glycolide (85:15) (PLGA) or PCL nanoparticles were prepared in order to achieve sustained release. Two of the formulations PCL-PLGA-NP-F and PCL-PCL-NP-I were selected for in vivo evaluation based on their in vitro characteristics determined in our previous study. In this study, formulations were implanted to Swiss Albino mice with induced dry eye syndrome to investigate the ocular distribution of CsA following subconjunctival implantation and to evaluate the efficacy. Tissue distribution study indicated that CsA was present in ocular tissues such as cornea, sclera and lens even 90 days after the application and blood CsA levels were found lower than ocular tissues. Efficacy studies also showed that application of CsA-loaded fiber implant formulation resulted in faster recovery based on their staining scores.

Formulation studies for mirtazapine orally disintegrating tablets.

OBJECTIVE: Orally disintegrating tablets (ODTs) recently have gained much attention to fulfill the needs for pediatric, geriatric, and psychiatric patients with dysphagia. Aim of this study was to develop new ODT formulations containing mirtazapine, an antidepressant drug molecule having bitter taste, by using simple and inexpensive preparation methods such as coacervation, direct compression and to compare their characteristics with those of reference product (Remereon SolTab). MATERIALS AND METHODS: Coacervation method was chosen for taste masking of mirtazapine. In vitro characterization studies such as diameter and thickness, weight variation, tablet hardness, tablet friability and disintegration time were performed on tablet formulations. Wetting time and in vitro dissolution tests of developed ODTs also studied using 900 mL 0.1 N HCl medium, 900 mL pH 6.8 phosphate buffer or 900 mL pH 4.5 acetate buffer at 37 ± 0.2 °C as dissolution medium. RESULTS: Ratio of Eudragit® E-100 was chosen as 6% (w/w) since the dissolution profile of A1 (6% Eudragit® E-100) was found closer to the reference product than A2 (4% Eudragit® E-100) and A3 (8% Eudragit® E-100). Group D, E and F formulations were presented better results in terms of disintegration time. Dissolution results indicated that Group E and F formulations showed optimum properties in all three dissolution media. DISCUSSION: Formulations D1, D4, D5, E3, E4, F1 and F5 found suitable as ODT formulations due to their favorable disintegration times and dissolution profiles. CONCLUSION: Developed mirtazapine ODTs were found promising in terms of showing the similar characteristics to the original formulation.

In Vitro/In Vivo Evaluation of Dexamethasone--PAMAM Dendrimer Complexes for Retinal Drug Delivery.

Current treatment options for diabetic retinopathy (DR) have side effects because of invasive application and topical application does not generally result in therapeutic levels in the target tissue. Therefore, improving the drug delivery to retina, following topical administration, might be a solution to DR treatment problems. The purpose of this study was to investigate the complexation effects of poly(amidoamine) (PAMAM) dendrimers on ocular absorption of dexamethasone (DEX). Using different PAMAM generations, complex formulations were prepared and characterized. Formulations were evaluated in terms of cytotoxicity and cell permeability, as well as ex vivo transport across ocular tissues. The ocular pharmacokinetic properties of DEX formulations were studied in Sprague-Dawley rats following topical and subconjunctival applications, to evaluate the effect of PAMAM on retinal delivery of DEX. Methyl-thiazol-tetrazolium (MTT) assay indicated that all groups resulted in cell viability comparable to DEX solution (87.5%), with the cell viability being the lowest for G3 complex at 73.5%. Transport study results showed that dendrimer complexation increases DEX transport across both cornea and sclera tissues. The results of in vivo studies were also indicated that especially anionic DEX-PAMAM complex formulations have reached higher DEX concentrations in ocular tissues compared with plain DEX suspension.

Preparation and in vitro/in vivo evaluation of cyclosporin A-loaded nanodecorated ocular implants for subconjunctival application.

In terms of ocular drug delivery, biodegradable implant systems have several advantages including the ability to provide constant drug concentration at the target site, no necessity for surgical removal, and minimum systemic side effects. Cyclosporin A (CsA) is a neutral, hydrophobic, cyclic peptide of amino acids that frequently used for dry eye disease treatment. The aim of this study was to develop a nanoparticle-loaded implant system for sustained-release CsA delivery following subconjunctival implantation. Poly(lactide-co-glycolide) (85:15) or poly-ε-caprolactone (PCL) were used to prepare two different nanoparticle formulations. These nanoparticles loaded into PCL or poly(lactide-co-caprolactone) implant formulations were prepared by two different methods, which were molding and electrospinning. Size and zeta potential of nanoparticles were determined and the morphology of the formulations were investigated by scanning electron microscopy. CsA-loading efficiencies were calculated and the in vitro degradation and in vitro release studies were performed. MTT test was also performed using L929 fibroblast cells to evaluate the cytotoxicity of the formulations. PCL-PCL-NP-I formulation was implanted to Swiss Albino mice with induced dry eye syndrome to evaluate the efficacy. In vitro release studies showed that the release from the formulations continues between 30 and 60 days, and the cell viability was found to be 77.4%-99.0%. In vivo studies showed that healing is significantly faster in the presence of the selected implant formulation. Results indicated that nanodecorated implants are promising ocular carriers for controlled-release CsA application.

Dendrimeric systems and their applications in ocular drug delivery.

Ophthalmic drug delivery is one of the most attractive and challenging research area for pharmaceutical scientists and ophthalmologists. Absorption of an ophthalmic drug in conventional dosage forms is seriously limited by physiological conditions. The use of nonionic or ionic biodegradable polymers in aqueous solutions and colloidal dosage forms such as liposomes, nanoparticles, nanocapsules, microspheres, microcapsules, microemulsions, and dendrimers has been studied to overcome the problems mentioned above. Dendrimers are a new class of polymeric materials. The unique nanostructured architecture of dendrimers has been studied to examine their role in delivery of therapeutics and imaging agents. Dendrimers can enhance drug's water solubility, bioavailability, and biocompatibility and can be applied for different routes of drug administration successfully. Permeability enhancer properties of dendrimers were also reported. The use of dendrimers can also reduce toxicity versus activity and following an appropriate application route they allow the delivery of the drug to the targeted site and provide desired pharmacokinetic parameters. Therefore, dendrimeric drug delivery systems are of interest in ocular drug delivery. In this review, the limitations related to eye's unique structure, the advantages of dendrimers, and the potential applications of dendrimeric systems to ophthalmology including imaging, drug, peptide, and gene delivery will be discussed.

An overview on dry eye treatment: approaches for cyclosporin a delivery.

Dry eye syndrome (DES, Keratoconjunctivitis sicca) is a common disorder of the tear film caused by decreased tear production or increased evaporation. Changes in tear composition also promote inflammation on the ocular surface by various mechanisms. Artificial tear drops, tear retention treatment, stimulation of tear secretion, or anti-inflammatory drugs may be used for dry eye treatment according to the severity of the disease. For untreated patients, the risk of ocular infection increases at considerable level and clinical course of the disease may proceed up to infection, corneal ulcer, and blindness. Artificial tears and/or punctual occlusions are used for tear replacement or preservation. New treatment approaches are designed to modify the underlying disease process. For the treatment of severe dry eye disease, cyclosporin A (CsA), the first one of the new generation immunomodulatory drugs, which has an anti-inflammatory effect, is frequently used. CsA has immunosuppressive effects following systemic application. Following local administration of CsA, it is expected to obtain effective drug concentration at the target area and to avoid the various side effects associated with systemic delivery. Microspheres, implants, and liposomes have been developed for administration of CsA subconjunctivally in order to enhance its efficiency.

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

To improve poor water solubility of cyclosporine A (CsA), hydroxypropyl-beta-cyclodextrin (HPßCD) was incorporated into the nanoparticle formulation. Solid complexes of CsA with HPßCD in different ratios were prepared by the kneading method. CsA containing alone or in combination with HPßCD in poly-lactide-co-glycolide (P-CsA or P-CsA-HPßCD) nanoparticles were prepared by the emulsification solvent evaporation method. The mean size of CsA-loaded NPs was found to be approximately 220 nm. The solubility of CsA was significantly improved and the phase solubility diagram of CsA-HPßCD systems showed an A(L) type phase. Nanoparticles showed high CsA encapsulation efficiency (88%) and production yield (89%). Release rate was increased by the presence of HPßCD and total cumulative release ranged from 75% to 96% in 24 h. In vitro cytotoxicity study assay resulted in a low toxicity for all types of nanoparticles. After 6 h incubation period, the cellular uptake was found at 33% and 32% for P-CsA and P-HPßCD-CsA nanoparticles, respectively.

Evaluation of drug-excipient interaction in the formulation of celecoxib tablets.

In the present study, the possible interactions between celecoxib and some excipients (colloidal silicon dioxide (Aerosil), microcrystalline cellulose (Avicel PH 102), lactose anhydrous, magnesium stearate, cross-povidone and talc) were evaluated by examining the pure drug or drug-excipient powder mixtures which were stored under different conditions (25 +/- 2 degrees C, 60% RH +/- 5% RH or 40 + 2 degrees C, 75% RH +/- 5% RH) and different period (30 or 60 days) using DSC, FT-IR and HPLC. In order to investigate the possibility of celecoxib-excipient interaction in aqueous medium, dispersions of the pure drug or drug in physical powder mixture (1:1 w/w) in water (1%, w/v) were also prepared and evaluated by FT-IR and HPLC at day 0 and day 7 (40 +/- 2 degrees C). The interaction between celecoxib and magnesium stearate or colloidal silicon dioxide were determined in the aqueous dispersions by FT-IR. Different tablet formulations with or without excipients tested were prepared, and assessed for drug dissolution and permeability.

Development and characterization of Cyclosporine A loaded nanoparticles for ocular drug delivery: Cellular toxicity, uptake, and kinetic studies.

Dry eye syndrome is a common disorder of the tear film caused by decreased tear production or increased evaporation. The objective of this study was to evaluate the potential effectiveness of Cyclosporine A (CsA) nanoparticles (NPs) for the treatment of inflammation of the eye surface. Topical CsA is currently the only and safe pharmacologic treatment of severe dry eye symptoms. The NPs were prepared using either poly-lactide-co-glycolide (PLGA) or a mixture of PLGA with Eudragit®RL or were coated with Carbopol®. The mean size of CsA loaded NPs was within the range from 148 to 219nm, except for the Carbopol® coated NPs (393nm). The drug entrapment efficiency was very high (from 83 to 95%) and production yield was found between 75 and 92% in all preparations. The zeta potential of the Eudragit® RL containing NPs was positive (19-25mV). The NPs formulations exhibited a biphasic drug release with initial burst followed by a very slow drug release and total cumulative release within 24h ranged from 75 to 90%. Kinetically, the release profiles of CsA from NPs appeared to fit best with the Weibull model. The viability of L929 cells was decreased by increasing the concentration of the various NPs examined as well as the incubation time. The amount of NPs uptake was related to the polymer type used. The highest degree of cellular uptake (52.2%), tear film concentration of the drug (366.3ng/g) and AUC(0→24) (972.6ngh/g) value were obtained from PLGA: Eudragit® RL (75:25)-CsA NPs formulations. The change of surface characteristics of NPs represents a useful approach for improvement of ocular retention and drug availability.

Effect of doxycycline on postoperative scarring after trabeculectomy in an experimental rabbit model.

PURPOSE: To investigate effectiveness of doxycycline after trabeculectomy in rabbits by evaluating bleb appearance, intraocular pressure, and levels of matrix metalloproteinase-1, -2, -3, and -9 and tissue inhibitors of metalloproteinase (TIMP)-1 and -2 in the subconjunctival (sc) area. METHODS: Twenty-nine New Zealand White rabbits were assigned into 1 of 6 groups as follows: topical doxycycline (0.1%), postoperative sc injection of doxycycline (100 mg/2 mL), and intraoperative mitomycin-C (MMC) (0.2 mg/mL) and their respective control groups. RESULTS: There was significant difference between intraocular pressure in the case groups, but there was no significant difference in topical doxycycline and MMC groups during the follow up. In the topical doxycycline group, levels of TIMP-1 and perifericTIMP-1 were higher and levels of perifericMMP-2 and inflammation were lower than their controls. In the sc doxycycline group, peripheral inflammation was higher than in the corresponding control. Only peripheral inflammation was significantly different between case groups, with the highest level in sc and the lowest level in MMC groups. Further, topical doxycycline group showed no significant difference in bleb appearance or peripheral inflammation compared with MMC group. Conjunctival burn and corneal vascularization were detected only in the sc doxycycline group. CONCLUSIONS: Topical doxycycline is more effective than sc doxycycline but is similar to MMC, and it can be an alternative to MMC in trabeculectomy in rabbits.

Formulation and in vitro evaluation of cysteamine hydrochloride viscous solutions for the treatment of corneal cystinosis.

In the present study, viscous solutions of cysteamine hydrochloride (CH) were prepared by using 0.5%, 1.0%, 1.5% or 3.0% of hydroxypropylmethylcellulose (HPMC) and were evaluated for their in-vitro characteristics and stability. Osmolalities, pH and viscosity of the formulations were determined. The influence of benzalkonium chloride and autoclave sterilization on solution characteristics was also investigated. For stability assessment, the viscous solutions were stored at +4 and +25 degrees C over 12 months. In-vitro characteristics and CH contents of the stored solutions were monitored. Irritation tests for the formulations were evaluated on rabbit eyes. Dialysis sac technique was used to perform in vitro release study of the solutions containing 1.0% and 1.5% HPMC. All of the viscous solutions tested showed non-newtonian (dilatant) flow behavior. Osmolality values were ranked between 351.2+/-6.2 and 355.1+/-7.9 mOsm kg(-1), and pH values were between 3.97+/-0.1 and 3.98+/-0.2 for all the solutions. Furthermore, no significant changes in dilatant behavior, osmolality or pH values of the pure HPMC solutions were observed. After addition of the excipients or CH-excipients, increased viscosity values were noted in these formulations. Neither benzalkonium chloride nor autoclave sterilization had any influence on viscosity, pH or osmolality values of the solution containing 1.5% HPMC. Stability studies showed that a faster decrease in the concentration of CH was observed in the formulations stored at 25 degrees C compared to those kept at 4 degrees C; no changes were determined in osmolality values of the solutions at all storage conditions. Increased pH and decreased viscosity values were noted in HPMC solutions containing CH and excipients, while no changes in these values were observed for pure HPMC solutions kept at 4 and 25 degrees C. In vitro release tests revealed that 81.2% and 85.3% of CH were released from the viscous solutions containing 1.5% and 1% HPMC, respectively, in 8h. No irritation was observed when the viscous solutions were tested on rabbit and human eyes.

The effect of paclitaxel on conjunctival wound healing: a pilot study.

PURPOSE: To compare the effects of mitomycin C (MMC) and paclitaxel entrapped within Carbopol 980 hydrogel (CH) on conjunctival wound healing. METHODS: Twenty rabbits were randomized into 2 groups. In group 1, limbal-based conjunctival flaps were created in both eyes. In this stage, eyes were randomized for 4 different processes. In process 1, a dry cellulose sponge soaked with 0.2 mg/mL of MMC was applied to the scleral surface. A cellulose sponge soaked with balanced saline solution was applied in the same manner in process 2. In process 3, paclitaxel 1 mg/mL entrapped within CH was placed between the conjunctiva and sclera. In process 4, CH without paclitaxel was applied in the same manner. The conjunctiva was then sutured. All procedures were applied in the same manner in both eyes of animals in group 2. Eyes from group 1 were sampled at the seventh day, and the sampling was also carried out in group 2 on day 14. The inflammatory response and fibrosis were evaluated with light microscopy. RESULTS: Among 4 different processes, lower cell counts and fibrosis scores were found in eyes treated with MMC and paclitaxel compared with balanced saline solution and CH groups (P<0.05). There was no difference between eyes treated with MMC and paclitaxel in terms of these histopathologic parameters (P>0.05). CONCLUSIONS: Paclitaxel was shown to provide MMC-like antifibrotic effects during conjunctival wound healing, particularly when delivered with CH and might be a promising alternative as an adjunctive antimetabolite in glaucoma filtration surgery.

Formulation and in-vitro characterization of retinoic acid loaded poly (lactic-co-glycolic acid) microspheres.

Poly (lactic-co-glycolic acid) (PLGA) microspheres containing all-trans retinoic acid (atRA) were prepared by emulsion/solvent evaporation technique. PLGA (50:50) with inherent viscosities of 0.17 and 0.39 dL g(-1) was used. Polyvinyl alcohol (PVA) or PVA and sodium oleate (SO) combinations (4:1) were used to stabilize the emulsions. The effect of polymer viscosity, emulsifier type and concentration on the in vitro release of atRA from the microspheres was investigated. The stability of the microparticles was also tested at the temperatures of 4, 25 and 40 degrees C. The particle size ranged between 1-2 microm. Microspheres were smooth and spherical in shape, as determined by scanning electron microscope (SEM) photographs. The yield of microspheres ranged from 50-75% and the encapsulation efficiency was determined between 45-75%. In vitro release studies showed that atRA release from microspheres lasted for 11 days.

Influence of hydroxypropyl beta-cyclodextrin on the corneal permeation of pilocarpine.

The influence of hydroxypropyl beta-cyclodextrin (HPbetaCD) on the corneal permeation of pilocarpine nitrate was investigated by an in vitro permeability study using isolated rabbit cornea. Pupillary-response pattern to pilocarpine nitrate with and without HPbetaCD was examined in rabbit eye. Corneal permeation of pilocarpine nitrate was found to be four times higher after adding HPbetaCD into the formulation. The reduction of pupil diameter (miosis) by pilocarpine nitrate was significantly increased as a result of HPbetaCD addition into the simple aqueous solution of the active substance. The highest miotic response was obtained with the formulation prepared in a vehicle of Carbopol 940. It is suggested that ocular bioavailability of pilocarpine nitrate could be improved by the addition of HPbetaCD.

In vitro evaluation of the effect of a surfactant-containing experimental acid gel on sealant microleakage.

OBJECTIVE: The purpose of this study was to compare the effects of experimentally derived surfactant-containing acid gel with those of different surface-conditioning agents on microleakage of unfilled and filled sealants applied to permanent teeth following noninvasive and invasive procedures. METHOD AND MATERIALS: Four main groups of surface-conditioning agents (NRC; NRC + Prime&Bond NT; Email Preparator Blue; and experimental acid gel) were subdivided into 16 subgroups (n = 8). Subgroups were designed according to the surface preparation procedures applied (noninvasive and invasive) and fissure sealants used (Helioseal and Helioseal F). After application of the test materials, the specimens were subjected to thermocycling and then immersed in 0.5% basic fuchsin dye. Following sectioning, specimens were examined under a stereomicroscope and microleakage scores were assigned. RESULTS: Subgroups 9 (Email Preparator Blue + Helioseal), 11 (invasive + Email Preparator Blue + Helioseal), 13 (experimental acid gel + Helioseal), and 15 (invasive + experimental acid gel + Helioseal) showed no microleakage. The differences between those subgroups and subgroups 1 (NRC + Helioseal), 2 (NRC + Helioseal F), 3 (invasive + NRC + Helioseal), 4 (invasive + NRC + Helioseal F), 5 (NRC + Prime&Bond NT + Helioseal), and 6 (NRC + Prime&Bond NT + Helioseal F) were statistically significant. CONCLUSION: Email Preparator Blue and surfactant-containing experimental acid gel, combined with an invasive/noninvasive surface preparation procedure and Helioseal, significantly prevented microleakage.