Liposome dynamic light scattering

FIGURE 1 Effect of (sequential) extrusion of MLV dispersions through polycarbonate membrane filters (Unipore) with pore sizes of 1.0, 0.6, 0.4, 0.2, and 0.1 ym on the mean liposome diameter. DXR-containing MLV (phosphatidylcholine/phosphatidylserine/ cholesterol 10 1 4) mean diameter of nonextruded dispersion about 2 ym pH 4. Mean particle size determined by dynamic Light scattering (Nanosizer, Coulter Electronics). (From Crommelin and Storm, 1987.)... 

An alternative approach is the use of pH-sensitive fluorophores (Lichtenberg and Barenholz, lOSS). These probes are located at the lipid-water interface and their fluorescence behavior reflects the local surface pH, which is a function of the surface potential at the interface. This indirect approach allows the use of vesicles independent of their particle size. Recently, techniques to measure the C potential of Liposome dispersions on the basis of dynamic light scattering became commercially available (Muller et al., 1986). 

G-50 column and eluted in 2-(N-Morpholino) ethansulfonic acid hydrate (MES)/N-(2-Hydroxyethyl)piperazine-N-(2-ethane-sulfonic acid) (HEPES) buffer pH 7.2 (50 mM MES, 50 mM HEPES, 75mM NaCl) to remove unencapsulated BPs. Several formulations with different sizes were obtained (0.6, 0.4, 0.2, and 0.1 pm). Liposome size and morphology was determined by dynamic light scattering and cryo-TEM microscopy (Fig. 1). 

D. Gel-to-liquid-crystalline phase transition of liposomes by dynamic light scattering and anisotropy measurements... 

D. Gel-to-Liquid-Crystalline Phase Transition of Liposomes by Dynamic Light Scattering and Anisotropy Measurements... 

The size of the liposomes was determined by dynamic light scattering using a Sub-micron Particle Analyzer (Coulter, Hialeah, FI). 

Size the liposomes by extrusion to an average size of 150 nm and a polydispersity index below 0.2 (see Note 1). Size distribution should be checked with dynamic light scattering. 

Characterize the liposomes with respect to size (e.g. dynamic light scattering) and lipid concentration (e.g. determination of phospholipid content using a method described by Rouser et al.) (14). 

After by diluting of dispersion to an appropriate volume with water, the cumulant particle size of liposomes was determined using a dynamic light scattering instrument as shown in Figs. 1 and 2. 

Size of the liposomes should be between 100 and 200 nm for best circulation times in vivo, this can be checked by a dynamic light scattering method. The size dependency has to do with accumulation in the liver, ability to extravasate into tissues, and any possible immune reactions. 

Finally, size of the sterilized liposomes was measured with dynamic light scattering (ELS-800). The average diameter of... 

The diameter and polidispersity index of the different liposome samples were analyzed by Dynamic Light Scattering for 22 days. The results obtained are indicated in Table 2. It can be predated that liposomes prepared fiom lipids extracted by methanol are stable during all foe study, and foe vesicular size increases a little (270nm of diameter in the first day and 393nm at 22° day). 

Maltose-containing washed or unwashed DRVs (33 /tmole PC) were microfluidized in the presence of water or PBS for up to 10.6 cycles, and samples were measured for vesicle size (diameter in nanometers) by dynamic light scattering (photon correlation spectroscopy). Polydispersity indexes ranging from 0.503 to 0.653 (water) and from 0.517 to 0.653 (PBS) were similar to those obtained with some of the lipid compositions of liposomes employed by others. 

The size distribution of the liposomes is determined by dynamic light scattering (DLS) with a Dynapro apparatus (http //www.wyatt.com). DLS is a hydrodynamic method by which one determines the rate of diffusion of particles through the solvent. The hydrodynamic radius is defined as the radius of a theoretical hard sphere that diffuses with the same speed as the particle under examination. The measurement is performed at 25° and requires about 2 /ul of the extruded liposome suspension diluted in 18 /ul of liposome buffer (final lipid concentration in the range of 0.1 roM). Ten autocorrelation functions are sequentially measured, from which the size distribution of the liposome is determined using the Dynamics v5 software from Dynapro. A complete measurement takes a few minutes. Figure lA shows typical size distributions of extruded liposomes as determined by DLS. Figure IB shows how the actual hydrodynamic radius of the liposomes varies with the pore size of the polycarbonate filter. 

O. Stauch, R. Schubert, G. Savin and W. Burchard, Structure of artificial cytoskeleton containing liposomes in aqueous solution studied by static and dynamic light scattering. Biomacromolecules, 3,565-578 (2002). 

The hydrodynamic size of the liposomes in PBS was measured by dynamic light scattering using Nicomp Particle Sizer Model 370 (Nicomp Particle Sizing Systems, USA). 

Gangliosides were reconstituted in the liposomal membrane according to a method previously established [16,17]. Both the diameter and the size distribution of the liposomes were determined by the dynamic light scatter-... 

Finally, the liposomes are sterilized by filtration (0.45- or 0.2-p,m sterile filters). Mean hydrodynamic diameters of vesicles (liposomes, nanospheres, nanobeads) can be determined with dynamic laser light scattering instruments, e.g. the NICOMP... 

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