Papers by Keyword: Liposomes

Abstract: Liposomes are being used as unique drug delivery systems due to their ability to encapsulate both hydrophilic and hydrophobic drugs, as well as for the fact that they improve the disadvantages of free drug administration. However, liposomes have a significant disadvantage - low encapsulation efficiency. In the research carried out, 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and cholesterol (Chol), in the ratio (n/n) of 2:1, 3:1 and 4:1 respectively, were used to prepare the liposomes. Blank liposomes (LIP) and vancomycin hydrochloride (VANKA) containing liposomes (VANKA-LIP) were prepared for each of the DSPC and Chol compositions. The aim of our study was to evaluate the effect of liposome composition on the VANKA encapsulation efficiency and release kinetics.

Abstract: Development of transport systems possessing definite physicochemical and biological properties aimed at the targeted delivery of biologically active compounds remains nowadays among urgent problems of the medicine. In this work we made physical chemical and biological tests liposomal drug delivery systems modified with glycolipids for target properties.

Abstract: The paper describes biophysical processes occurring in membranes under the influence of alpha-radiation of radon isotopes. The basic idea is to experimentally detect the effects of radiation damage to cells of the α-particle with energy of 5.5 MeV, and in particular, to determine the dependence threshold in a function of the "dose-effect" in the presence of DNA molecules into cells. Actuality of work related to the fact that up to now remains open the problem – is whether damageability of radioactive radiation threshold or without threshold phenomenon. It was found that the irradiation of biological models of cells - liposomes and spherosomes uniquely showed the lack threshold of damageability. Irradiation red blood cells not having a cell nucleus, occurs as a threshold phenomenon. Finally, the irradiation of the lactic acid bacteria occurs with a high threshold

Abstract: Topical ocular drug delivery has always been a challenging area due to poor ocular bioavailability. Improved drug delivery systems such as liposomes are capable of entrapping both the lipophilic and hydrophilic substances. Therefore, they are effective formulations for drug delivery to targeted structure. PEGylated-liposomes are known to have stealth properties due to their ability of resisting removal by phagocytic cells. This study compares ability of PEGylated-and nonPEGylated-liposomes in delivering lipophilic fluorescent dye, Dil, to several ocular tissues. Sprague-Dawley rats (190-250g) were divided into 2 groups that received unilateral topical application of single drop of PEGylated-liposome (PEG-Lip) or nonPEGylated-liposome (Lip). Contralateral eyes served as control and received no treatment. Animals were sacrificed at several time points, post-instillation, and eyeballs were enucleated. Cryostat sectioning was done and sections were viewed with fluorescence microscope. Fluorescence intensity (FI) was calculated and quantified. In treated eyes, nonPEGylated-liposomes showed faster corneal permeation compared to PEGylated-liposomes. NonPEGylated-liposomes also showed faster availability in ciliary body and retina of treated eyes, possibly a consequence of faster corneal permeation. Their higher engulfment by macrophages and subsequent localization in vascular tissue may also be a contributing factor. In contralateral eyes, both groups showed dye distribution indicating their significant systemic distribution. Higher availability of non-PEGylated-liposomes in contralateral eyes also indicated that they are more likely to undergo phagocytosis and consequently faster removal. In conclusion, PEG-lip showed slower corneal permeation in the treated eyes. Both types of liposomes undergo significant systemic absorption. Since, PEG-lip are more resistant to phagocytosis, they may provide more sustained drug delivery.

Abstract: In this work we describe the studies of preparation and stability of liposomes formed by 1,1'-[(3,5-didodeciloxycarbonyl-4-phenyl-1,4-dihydropyridine-2,6-diil) dimethylebispyridinium dibromide, novel lipid-like compound. The influence of the amount of amphiphilic compound, solvent and sonication time was studied. Liposomes were prepared by dispersing of compound in the corresponding media at a selected concentration by sonication using a probe type sonicator and characterised by atomic force microscopy (AFM) and dynamic light scattering (DLS) methods.

Abstract: Immobilization of egg lecithin liposomes on Octadecanethiol (ODT) modified gold electrodes has been studied. The changes of the resistance of the layer with deposited liposomes, occurred under stimulation by different concentration of phloretin were measured with electrochemical impedance spectroscopy (EIS) and were used for the calculation of association constants. The binding constants Kb was obtained to be (7.571±0.821)×105 L•mol-1, indicated that high affinity existed between phloretin and liposomes.

Abstract: Hydrophilic CdTe and NIR CdHgTe QDs were successfully transferred from aqueous solution to nonpolar chloroform solvent via efficient phase transfer reagent to synthesize lipid-QDs. The liposomes showed bright fluorescence under the fluorescence microscope. It was confirmed that fluorescence resonance energy transfer (FRET) occurred between two types of QDs encapsulated in lipid bilayer with an excitation wavelength of 370nm, and the FRET efficiencies were satisfied (quenching efficiency was 51% and enhance efficiency was 40%), which laid a foundation for the research of drug release from liposomes.

Abstract: Photophysical studies on oxidative stress induced by illumination with ultraviolet (UV) light from artificial light sources, were performed on small unilamellar liposomes (SUVs) as models of biomembranes. Different liposoluble antioxidants were incorporated in the liposome bilayer during the lipid film preparation. The quercetin containing bilayers exhibited a high tolerance to photooxidative stress. The light-driven reactive oxygen species (ROS) effects on liposomal membranes were monitored by optical methods: UV-VIS absorption, fluorescence and chemiluminescence (CL), exploiting the spectral properties of chlorophyll a (Chla) embedded into some liposome bilayers (Chla/lipid molar ratio = 1/100). The interaction between Chla and the other liposome components resulted in changes in their absorption and emission fluorescence properties.

Abstract: The atomic force microscope (AFM) obtains its topographical information from the short-ranged repulsion resulting from the overlap of electronic shells between tip and hard samples. However, scanning soft samples such as surfactants or biological material within liquid media leads to a very different scenario due to the long-ranged double layer interactions and the specific tip penetration through the scanned layers. We show that AFM images and force vs. distance curves can be used to obtain relevant information on formation, characteristics and behavior of soft self-assembled nanostructures of surfactants, phospholipids and of cells under physiological conditions.