Tamer Güneri

Cyclosporine A loaded SLNs: evaluation of cellular uptake and corneal cytotoxicity.

Cyclosporine A (CsA) loaded solid lipid nanoparticles (SLNs) for topical ophthalmic applications were prepared by high shear homogenization and ultrasound method using Compritol 888 ATO, Poloxamer 188 and Tween 80, to investigate the cellular uptake of rabbit corneal epithelial cells (RCE) and to evaluate the cytotoxicity. The size of the optimized formulation was 225.9+/-5.5 nm with a polydispersity index of 0.253+/-0.05. The zeta potential and entrapment efficiency was detected as -16.9+/-0.7 mV and 95.6%, respectively. The CsA release was found to be enzyme (lipase/co-lipase complex) dependent. SLNs were sterilized at 110 and 121 degrees C. The cytotoxicity was evaluated in vitro by means of RCE cells and was higher at 121 degrees C sterilization temperature, probably due to a supposed leakage of Tween 80 following lipid re-crystallization. The permeation and penetration of CsA across/into the corneal cells were evaluated using in vitro and ex vivo experiments. The cellular uptake was investigated by replacing CsA with the fluorescent dye Rhodamine B. The penetration enhancement properties were supported by confocal laser scanning microscopy analysis. The internalization of SLNs in cornea and in RCE cell lines was confirmed, pointing out the possibility of CsA targeting to the cornea.

Transdermal Delivery of Diclofenac Sodium Through Rat Skin From Various Formulations

The aim of this study was to evaluate and compare the in vitro and in vivo transdermal potential of w/o microemulsion (M) and gel (G) bases for diclofenac sodium (DS). The effect of dimethyl sulfoxide (DMSO) as a penetration enhancer was also examined when it was added to the M formulation. To study the in vitro potential of these formulations, permeation studies were performed with Franz diffusion cells using excised dorsal rat skin. To investigate their in vivo performance, a carrageenan-induced rat paw edema model was used. The commercial formulation of DS (C) was used as a reference formulation. The results of the in vitro permeation studies and the paw edema tests were analyzed by repeated-measures analysis of variance. The in vitro permeation studies found that M was superior to G and C and that adding DMSO to M increased the permeation rate. The permeability coefficients (Kp) of DS from M and M+DMSO were higher (Kp=4.9×10−3±3.6×10−4 cm/h and 5.3×10−3±1.2×10−3 cm/h, respectively) than the Kp of DS from C (Kp=2.7×10−3±7.3×10−4 cm/h) and G (Kp=4.5×10−3±4.5×10−5 cm/h). In the paw edema test, M showed the best permeation and effectiveness, and M+DMSO had nearly the same effect as M. The in vitro and in vivo studies showed that M could be a new, alternative dosage form for effective therapy.

Extended release lipophilic indomethacin microspheres: formulation factors and mathematical equations fitted drug release rates

Extended release liphophilic microspheres of indomethacin were prepared using cetostearyl alcohol (CsA), stearyl alcohol (SA) and cetyl alcohol (CA) in the various drug-lipid ratios. The release of indometacin was studied on the basis of USP criteria and the effects of drug-lipid ratio, the size of microspheres and carboxymethylcellulose sodium (CMC-Na) added as a hydrophilic polymer on the drug release were investigated. In vitro dissolution studies were performed using USP XXIII apparatus I at pH 6.2. Release profiles were evaluated according to first order, Higuchi square root of time and Hixson-Crowell cube root models. The best fit was found with the square root of time model (r2=0.991) for the microspheres (125-250 microm) prepared in 1:4:1 drug-lipid-copolymer ratio using stearyl alcohol. With a further regression analysis, an excellent equation (Release%=-10.721+42.549*square root of (t)-4.027*t) was developed for empirical drug estimation (r2=0.998).

Cyclosporine A-Loaded Solid Lipid Nanoparticles: Ocular Tolerance and In Vivo Drug Release in Rabbit Eyes

Purpose: To determine the in vivo efficacy of cyclosporine A-loaded solid lipid nanoparticles (SLNs) in rabbit eyes. Methods: SLNs were prepared and administered to the cul-de-sac of rabbits, and the drug amount in aqueous humor was detected by high performance liquid chromatography (HPLC). The irritation was evaluated by modified Draize testing. Results: The particle size of SLNs was detected as 225.9 ± 5.5 nm with a negative surface charge. Aqueous humor drug levels reached 50.53 ng/mL, and there was no serious irritation in rabbit eyes. Conclusions: Topical ophthalmic efficacy of cyclosporine A was enhanced via administration of SLNs.

Comparison of Different Water/Oil Microemulsions Containing Diclofenac Sodium: Preparation, Characterization, Release Rate, and Skin Irritation Studies

The aim of the present study was to make a comparison of the in vitro release rate of diclofenac sodium (DS) from microemulsion (M) vehicles containing soybean oil, nonionic surfactants (Brij 58 and Span 80), and different alcohols (ethanol [E], isopropyl alcohol [I], and propanol [P]) as cosurfactant. The optimum surfactant:cosurfactant (S:CoS) weight ratios and microemulsion areas were detected by the aid of phase diagrams. Three microemulsion formulations were selected, and their physicochemical properties were examined for the pH, viscosity, and conductivity. According to the release rate of DS, M prepared with P showed the significantly highest flux value (0.059±0.018 mg/cm2/h) among all formulations (P<.05). The conductivity results showed that DS-loaded microemulsions have higher conductivity values (18.8–20.2 microsiemens/cm) than unloaded formulations (16.9–17.9 microsiemens/cm), and loading DS into the formulation had no negative effect on system stability. Moreover, viscosity measurements were examined as a function of shear rate, and Newtonian fluid characterization was observed for each microemulsion system. All formulations had appropriate observed pH values varying from 6.70 to 6.85 for topical application. A skin irritation study was performed with microemulsions on human volunteers, and no visible reaction was observed with any of the formulations. In conclusion, M prepared with P may be a more appropriate formulation than the other 2 formulations studied as drug carrier for topical application.

Rheological and mechanical properties of poloxamer mixtures as a mucoadhesive gel base

This study described the thermosensitive formulations composed of poloxamer mixtures for use as drug delivery platform via mucosal route. It also characterized the poloxamer mixtures’ rheological, mechanical and mucoadhesive properties. Poloxamer (Plx) 407 and Plx 188 were used alone and together for preparing the mucosal drug delivery platform. The mixtures of Plx 407 and Plx 188 in ratio of 15:15 (F5); 15:20 (F6); 20:10 (F7) existed liquid at room temperature, but gelled at physiological temperature. Flow rheometry studies and oscillatory analysis of each formulation were performed at 20 ± 0.1°C and 37 ± 0.1°C. F5 and F7 formulations exhibited typical gel-type mechanical spectra (G′ > G″) after the determined frequency value at 37°C whereas F6 behaved as weakly cross-linked gel. Texture profile analysis presented that F5 and F7 showed similar mechanical properties and can be used as base for mucosal dosage form. Mucoadhesion studies indicated the difference among the formulations and the effect of the mucosal surface on mucoadhesive properties. Mucin disc, bovine vaginal and buccal mucosa were used as mucosal platform for mucoadhesion studies. It is suggested that these investigations may be usefully combined to provide a more rational basis for selecting the ratio of Plx to prepare a topical thermosensitive drug delivery system for mucosal administration.

In-situ gel formulations of econazole nitrate: preparation and in-vitro and in-vivo evaluation

Objectives  This study describes the in‐situ gelling of econazole nitrate containing thermosensitive polymers composed of poloxamer 407 and 188 as a novel treatment platform for vaginal candidiasis.

Pegylation of poly(γ-benzyl-L-glutamate) nanoparticles is efficient for avoiding mononuclear phagocyte system capture in rats.

Poly(γ-benzyl-L-glutamate) (PBLG) derivatives are synthetic polypeptides for preparing nanoparticles with well controlled surface properties. The aim of this paper was to investigate the biodistribution of pegylated PBLG in rats. For this purpose, nanoparticles were prepared by a nanoprecipitation method using mixtures of different PBLG derivates, including a pegylated derivate to avoid mononuclear phagocyte system uptake. The morphology, size distribution, and surface charge of the nanoparticles were investigated as a function of the amount of polymer employed for the preparation. Moderately polydispersed nanoparticles (polydispersity index less than 0.2) were obtained. Their size increased with polymer concentration. The zeta potential values were negative whatever the formulations. The availability of polyethylene glycol chains on the nanoparticles’ surface was confirmed by measuring the decrease in bovine serum albumin adsorption. For in vivo distribution studies, pegylated and nonpegylated nanoparticles were prepared with polymer mixtures containing PBLG-fluorescein isothiocyanate and imaged by fluorescence microscopy to measure their accumulation in liver and spleen tissues of rats after intravenous administration. Injection of stealth formulations resulted in negligible fluorescence in liver and spleen compared with nonpegylated formulations, which suggests that these nanoparticles are promising candidates as a stealth-type long-circulating drug carrier system and could be useful for active targeting of drugs while reducing systemic side effects.

Controlled Release of Methotrexate from W/O Microemulsion and Its In Vitro Antitumor Activity

The objective of this study was to prepare the microemulsion of methotrexate (M-MTX) for oral use and to investigate the suppressive effect of MTX-loaded microemulsion on MCF-7 human breast cancer cells. At the same time this effect of M-MTX was compared with those of a solution of the drug (Sol-MTX). Microemulsion was composed of soybean oil as oil phase, a mixture of Cremophore EL and Span 80 as surfactants, and isopropyl alcohol as co-surfactant, and 0.2 N NaOH as the aqueous phase. MTX was added into microemulsion at the last stage. We clearly demonstrated that M-MTX had a significant cytotoxic effect on breast cancer cell lines and the cytotoxic effect of M-MTX was significantly more than that of solutions (p < 0.05) and IC50 value for M-MTX was 40 ng/mL. We also examined M-MTX and Sol-MTX on a model biological environmental model. For this purpose a gastrointestinal cell culture model, the Caco-2 cell line, was used to investigate the cytotoxic effects of the polymeric carrier and its effect on the cell monolayer integrity. The differences between the viability of cells for M-MTX and Sol-MTX were significantly different when applied to ANOVA according to 2 × 8 factorial randomized design (p:0.016; for α: 0.05, power : 0.695). According to the in vitro cytotoxicity studies, we concluded that when MTX was incorporated into the microemulsion (M-MTX), which is a new drug carrier system, it suppresses tumour cell growth on multiple tumor lines. These results indicate that M-MTX may exert a low cytotoxic effect on normal cells and may be effective as an antitumor agent that induces apoptosis.

Synthesis and characterization of surface‐modified PBLG nanoparticles for bone targeting: In vitro and in vivo evaluations

In this study, poly(γ-benzyl-l-glutamate) (PBLG) polypeptide derivatives were synthesized by ring-opening polymerization of amino acid N-carboxyanhydride using selected amine-terminated initiators. Alendronate, a targeting moiety that has a strong affinity for bone, was conjugated to PBLG. Monomethoxy polyethylene glycol (PEG) was used for a hydrophilic layer on the surface of the nanoparticles (NPs) to avoid reticuloendothelial system uptake. NPs were prepared by nanoprecipitation technique not only for PBLG or PBLG-PEG but also for composite polymers with different ratios. Fluorescein isothiocyanate would be attached to the NPs as a labeling agent. The size and morphology of NPs were evaluated by dynamic laser light scattering and transmission electron microscopy, and were found to be in a useful range (less than 80 nm) for bone-targeted drug delivery. In addition, the PEGylation of NPs was supported by isothermal titration calorimetry analysis. The bone-targeting potential of NPs was evaluated in vitro by calcium binding and hydroxyapatite affinity assays, and in vivo by fluorescent imaging experiments on rats. The targeted NPs showed bright fluorescent labeling in femur tissue. These results demonstrated the possibility of optimized NPs prepared with new PBLG derivatives to accumulate in bone successfully.