Double loading of cyclosporine A in liposomes using cyclodextrin complexes

When liposomes are used as drug delivery systems, it is important that the therapeutic agent is efficiently and adequately encapsulated. In this study, cyclosporine A (CyA) was chosen as a model drug for two reasons. First, liposomes are a potential delivery system for CyA, as it has been shown that CyA has decreased side effects when encapsulated in liposomes. Secondly, if the aqueous solubility of a lipophilic drug can be increased, then it is possible to increase liposomal encapsulation by additionally loading the drug into the liposomes' aqueous compartments. Therefore, we investigated the use cyclodextrins (CDs) for complexing CyA to increase aqueous solubility as a strategy to increase liposomal loading. The effect of CyA loading on the liposomes' characteristics, stability and rigidity of the bilayer, and also the drug release profile were evaluated. Liposomes encapsulating CyA, liposomes containing CyA-CD complexes, and liposomes loaded with both plain drug and complex (double-loaded liposomes) were prepared. For evaluation of the effect of CD on bilayer rigidity and integrity, the permeability of the liposomal membrane in terms of carboxyfluorescein (CF) leakage was studied. Among liposomal formulations containing only CyA, 1, 2-distearoyl-sn-glycero-3- phosphocholine (DSPC):cholesterol (CHOL) (1:1) and hydrogenated soybean phosphatidylcholine (HSPC):CHOL (1:1) formulations demonstrated maximum drug entrapments of 65.94 ± 4.68% and 75.03 ± 4.87%, respectively. There was no significant difference in encapsulation efficiencies between different liposomal formulations for those containing CyA-CD complexes (P > 0.05). Measurement of encapsulation efficiency showed that the amount of drug entrapped in the lipid bilayers was identical when prepared in the form of CyA inclusion complexes. Drug entrapment in double-loaded liposomes was increased by approximately 2-fold. The release profile of all liposomal formulations was biphasic, with an initial rapid phase during the first 5 h followed by a continuous and slower release thereafter. During the first 5 h, CyA used as the complex was released to a greater extent than free CyA. Leakage of CF from liposomes was affected by the inclusion of CD. The leakage rate was minimum for CyA liposomes and maximum for double-loaded (CyA and CyA-CD) liposomes. In conclusion, it is possible to encapsulate CyA both in the aqueous and lipidbilayers of liposomes if the aqueous solubility of CyA is increased by complexation with CD. Although entrapment of a higher amount of drug was achieved, the stability of the liposomes was compromised and should therefore be considered

Enhancement of cyclosporine aqueous solubility using alpha- and hydroxypropyl beta-cyclodextrin mixtures

Cyclodextrins (CDs) are cyclic oligosaccharides that form inclusion complexes with lipophilic molecules through their hydrophobic central cavity. In this study, the effect of alpha-CD, hydroxylpropyl-beta-CD (HP-beta-CD) and mixtures of these two CDs on the aqueous solubility of cyclosporine A (CyA) was investigated. Infrared spectroscopy and thermal analysis were used to confirm CyA-CD complex formation. CyA aqueous solubility was increased by 10 and 80 fold in the presence of alpha-CD and HP beta-CD, respectively. The phase-solubility profile for HP-beta-CD was linear while that for alpha-CD had positive deviation from linearity. In the presence of constant concentration of alpha-CD (15% w/v), aqueous solubility of CyA was further increased upon addition of HP-beta-CD up to a concentration of 20% w/v. At higher HP-beta-CD concentrations, aqueous solubility of CyA was observed to decrease. Addition of sodium acetate (up to 5% w/v) to aqueous solutions containing 20% w/v HP-beta-CD and increasing concentrations of alpha-CD resulted in a significant reduction in CyA solubility. Complex formation between CyA and both alpha-CD and HP-beta-CD was confirmed by differential scanning calorimetry (DSC). No significant changes were observed in the IR spectra of either CyA or CD following complex formation suggesting chemical interaction between CyA and the CD was unlikely. Phase-solubility studies showed that alpha-CD had a much greater effect on the solubility of CyA than HP-beta-CD. Addition of HP-beta-CD to aqueous solutions of alpha-CD affected the solubility of CyA in these systems. A mixture of 15% w/v alpha-CD and 20% w/v HP-beta-CD was optimal for increasing aqueous solubility of CyA

Preparation and in vivo evaluation of nanoliposomes containing melphalan after intravitreal injection in albino rabbits

The aim of present study was to evaluate the stability and toxicity of different doses of liposomal melphalan in rabbit eyes and to investigate the pathological and electrophysiological changes after administration of different doses of free form of melphalan. Liposomes containing melphalan were prepared by solvent evaporation method and mean size of these liposomes and encapsulation efficacy of nanoliposomes were determined. In albino rabbits, intravitreal injections of 10, 20, and 40 µg doses of liposomal melphalan and Alkeran® as the commercial product was performed. The rabbits were euthanized at days 2, 7, 14, and 28, and the eyes were enucleated. Vitreous and aqueous samples and electrophysiological recordings were obtained before euthanization. Histological examination was performed after enucleation. Particle size of prepared liposomes was 143.6 ± 3.2 nm. Liposomes have protected melphalan completely from any undesirable release or hydrolysis for 48 h. In a histopathological study, signs of retinal toxicity were found in all doses in the liposomal group at least at one time point during the study. In melphalan injected eyes, histopathological toxicity was found in the 40 µg dose. Extensive variability was found in electrophysiological recordings, and significant waveform changes were found in all injected eyes at least on one occasion during the study. Intraocular administration of liposomal melphalan cannot prolong the drug clearance time of this drug in the vitreous humor. In the 40 µg injected eyes, significant retinal atrophic changes were detected in all eyes throughout the study, and electrophysiological results were consistent with histopathological findings. © 2016, The Korean Society of Pharmaceutical Sciences and Technology