Effect of temperature on the photobehavior of Rose Bengal associated with dipalmitoylphosphatidyl choline liposomes (original) (raw)
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Absorption and emission spectral shifts of rose bengal associated with DMPC liposomes
Dyes and Pigments, 2008
Rose bengal is a water-soluble xanthene dye that is currently used in ophthalmology for the diagnosis of dry eyes. Although the dye is also a potential photosensitizer for photodynamic therapy of tumors, owing to insufficient lipophilicity and tumor accumulation, the clinical application of rose bengal in photodynamic therapy has been hampered. Liposomal encapsulation was seen as a promising approach to overcome these disadvantages, to which end, the spectral properties of the dye in the presence of materials for liposome preparation were studied. The presence of phospholipid influenced the spectral properties of the dye, probably due to the establishment of an equilibrium between monomeric and dimeric forms of the dye, since the photophysical properties of rose bengal depend strongly on its environment. The liposomal encapsulation of the dye generates stronger emission than the free form of the colorant; increased lipid:dye ratio further enhances this emission.
Dye-sensitized destabilization of liposomes bearing photooxidizable lipid head groups
Photochemistry and photobiology, 1993
Liposomes were prepared from mixtures of dipalmitoyl-L-alpha-phosphatidylcholine and up to 40% mol:mol of N-stearoyl-L-histidine (NSH) in the presence of the hydrophobic sensitizer DHE. In the dark such liposomes are stable and retain entrapped salts. On photolysis with visible light, liposomes leak trapped ions at NSH concentrations greater than 10% mol:mol. Up to 15% mol:mol NSH concentration leakage is seen only during the illumination period, whereas at higher concentration the liposomes continue to leak contents after illumination and fuse to form larger structures. Photolysis of the liposomes is accompanied by oxygen uptake in proportion to the NSH concentration within the bilayer. Photocontrol of liposome permeability through oxidation of membrane additives such as NSH offers a potential means for controlled drug delivery and might be useful as an adjunct to photodynamic therapy.
Journal of Liposome Research, 2003
The objective of our work has been the microencapsulation of dyes with lecithin from soybean, with the formation of liposomes, as a substitute for synthetic auxiliaries so as to improve the quality of the effluent. Current scenarios promote the disintegration and leakage of the liposomes, such as, changes in temperature, pH and the use of surfactants. Since dyeing process is a mix of all these parameters, we pretended to study each one separately. Rhodamine 6G fluorescence is known to be concentration quenched through the formation of non-fluorescent dimmers and, additionally, through the energy transfer from rhodamine monomer to these dimmers (Baptista ALF,
Photo and Thermal Control of Liposome Solubilization
Bulletin of the Chemical Society of Japan, 2013
The solubilization of liposomes induced by the addition of surfactants was photocontrolled under temperature control. The instability of the membrane was increased both by photoisomerization of photoresponsive molecules included in the membrane and by changing temperature. By addition of a spiropyran to the liposome membrane, chargeseparated structure was formed by UV irradiation, causing local polarization and subsequent motion in the membrane. We found a difference in the solubilization processes in a specific temperature range under UV irradiated and nonirradiated conditions, and figured out that the solubilization of liposomes smaller than 2¯m can be distinctly photocontrolled in a certain temperature range.
Photophysical Behavior of a Dimeric Cyanine Dye (BOBO-1) Within Cationic Liposomes
Photochemistry and Photobiology, 2005
This study is aimed at establishing optimal conditions for the use of 2,2'-[1,3-propanediyIbis[(dimethyliminio)-3,1propanediyl-1(4H)-pyridinyl-4-ylidenemethy-lidyne]] bis[3methyl]-tetraiodide (BOBO-1) as a fluorescent probe in the characterization of lipidDNA complexes (lipoplexes). The fluorescence spectra, anisotropy, fluorescence lifetimes and fluorescence quantum yields of this dimeric cyanine dye in plasmid DNA (2694 base pairs) with and without cationic liposomes (1,2-dioleoyl-3-trimethylammonium-propane [DO-TAP]), are reported. The photophysical behavior of the dye in the absence of lipid was studied for several dye/DNA ratios using both supercoiled and relaxed plasmid. At dye/DNA ratios (dh) below 0.01 the fluorescence intensity increases linearly, whereas lifetime and anisotropy values of the dye are constant (T -2.5 ns and = 0.20). By agarose gel electrophoresis it was verified that up to d h = 0.01 DNA conformation is not considerably modified, whereas for dh = 0.05-0.06 a single heavy band appears on the gel. For these and higher dyeDNA ratios the fluorescence intensity, anisotropy and average lifetime values decrease with an increase in BOBO-1 concentration. When cationic liposomes are added to the BOBO-1DNA complex, an additional effect is noticed: The difference in the environment probed by BOBO-1 bound to DNA leads to a decrease in quantum yield and average lifetime values, and a redshift is apparent in the emission spectrum. For fluorescence measurements including energy transfer (FRET), a dh ratio of 0.01 seems to be adequate because no considerable change on DNA conformation is Abbreviations: BOBO-1, benzothiazolium, 2,2'-[1,3-propanediylbis[(dimethyliminio)-3, I -propanediyl-1 (4H)-pyridinyl-4-ylidenemethylidyne]]bis [3-methyl]-tetraiodide; DOTAP, 1,2-dioleoyl-3-trimethylammonium-propane; d/b, dyeDNA base ratio; dsDNA, double-stranded DNA; EtBr, 3,8diamino-5-ethyl-6-phenylphenanthridium bromide (commonly, ethidium bromide); FRET, fluorescence resonance energy transfer YOYO-1, 1,l'-[I ,3-propanediylbis[(dimethyliminio)-3,l-propanediyl]]bis[4-[(3-methyl-2( 3H)-benzoxazolylidene)methyl]]-tetraiodide. 0 2005 American Society for Photobiology 003 1-8655/05
Interaction of a cationic phenazinium dye, phenosafranin (PSF), with the anionic liposomal vesicle/bilayer of dimyristoyl-l-␣-phosphatidylglycerol (DMPG) has been demonstrated using steady state and time resolved fluorescence and fluorescence anisotropy techniques. The charge transfer emission spectrum of PSF shows a dramatic modification in terms of fluorescence yield together with an appreciable hypsochromic shift in the lipid environment. The blue shift indicates a lowering in polarity inside the vesicle as compared to that in bulk water. The fluorescence and fluorescence quenching studies and micropolarity determination reveal that the cationic fluorophore has a profound binding interaction with the anionic DMPG membrane. Anisotropy study indicates the imposition of a motional restriction on the probe inside the bilayer. The electrostatic interaction between the cationic dye and the anionic lipid membrane has been argued to be the reason behind all these observations. The results could be useful in analyzing membrane organization and heterogeneity in natural membranes exploiting PSF or alike compounds as fluorescent probes.
Acta Periodica Technologica, 2014
The aim of this work was to examine a possible impact of liposomes lipids microenvironment, dictated by a chemical composition of the fatty acid branches, on incorporation and spectral behaviour of chlorophyll a, and its derivative, chlorophyllide a inside small liposomes. The liposomes with the incorporated chlorophylls were made of dimirystoyl phosphatidylcholine (DMPC), and unsaturated phosphatidylcholine (PC), containing significant fractions of unsaturated fatty acid moieties. In order to achieve the goal, both absorption and fluorescence polarization spectroscopy were applied, and the obtained data for the two incorporated pigments, which play a role of molecular sensors, were compared. In addition, quercetin, a well-known antioxidant, was used as the (chlorophylls) emission quencher, in order to estimate the type of environment sensed by the two pigments for the two liposomes that differ in chemical composition. The results, based primarily on fluorescence polarization data h...
Effect of pH on the Control Release of Microencapsulated Dye in Lecithin Liposomes. II
Journal of Liposome Research, 2003
The objective of our work has been the microencapsulation of dyes with lecithin from soybean, with the formation of liposomes, as a substitute for synthetic auxiliaries so as to improve the quality of the effluent. Current scenarios promote the disintegration and leakage of the liposomes, such as, changes in temperature, pH, and the use of surfactants. Since dyeing process is a mix of all these parameters, we pretended to study each one separately. Changes in pH at constant temperature induce a release of dye similar with changes in temperature. In acid conditions, we found a very fast initial dye release which doesn't occur in basic conditions. Using carboxyfluorescein, as a pH fluorescence probe, we concluded that the liposome membrane doesn't protect the liposome interior from changes on the external pH.