Zeta potential liposomes

Size distribution and zeta potential are measured using Brookhaven Instruments Zeta Plus. Particle size measurements confirm the formation ofSUV s (54 22 nm). Measure the zeta potential to establish the STPP incorporation into the liposomes. Zeta potential values of +30 12 mV were... 

The content of vaccine within the small liposomes is estimated as in the section Estimation of Vaccine Entrapment in Dehydration-Rehydration Vesicles Liposomes for both microfluidized and sucrose liposomes and expressed as percentage of DNA and/or protein in the mixture subjected to freeze drying as in the section Preparation of Vaccine-Containing Small Liposomes by the Sucrose Method in the case of sucrose small liposomes or in the original DRV preparation (obtained in the section Estimation of Vaccine Entrapment in DRV Liposomes ) for microfluidized liposomes. Vesicle size measurements are carried out by PCS as described elsewhere (6,8,17). Liposomes can also be subjected to microelectrophoresis in a Zetasizer to determine their zeta potential. This is often required to determine the net surface charge of DNA-containing cationic liposomes. 

The obtained STPP liposomes were characterized by size distribution analysis, P NMR spectroscopy (Fig. 3), and by zeta potential measurements (Fig. 4). The size of liposomes with 20 mol% incorporated STPP was determined to be 132 zb 59 nm, which did not change significantly upon storage at 4°C over several days. The P NMR spectrum of STPP liposomes shows two chemical shifts correlating to the phosphorus in the lipid s phosphate groups and to the positively charged phosphorus of STPP. No differences in both chemical shifts between the free compounds (i.e., free STPP and free... 

Figure 4 Zeta potential of liposomes with varying amounts of incorporated STPP. The zeta potential was determined at 2.5 V, 657 nm, 2.00 Hz and 25°C using the Zeta Potential Analyzer Version 3.26 from Brookhaven Instruments Corporation. For each measurement, 10 pL liposome solution (total lipid 25mg/mL STPP content varying between 0 and 25 mol%) were added into 2mL HBS, pH 7.4 and incubated until temperature equilibration was attained. Abbreviations STPP, stearyl triphenyl-phosphonium. HBS, HEPES-buffered saline. Source From Ref. 30.

The charge on the liposomal surface is a property that has major effects on the stability, biodistribution, and cellular uptake of liposomes, and is governed by lipid headgroup composition and by pH. It can be monitored by micro electrophoresis (i.e., capillary zone electrophoresis), or by measurement of the zeta potential (Egorova, 1994). 

Takeuchi K, Ishihara M, Kawaura C et al (1996) Effect of zeta potential of cationic liposomes containing cationic cholesterol derivatives on gene transfection. FEBS Lett... 

The formation of a coating layer on the surface of liposomes was confirmed and detected by measuring the zeta potential. As shown in Fig. 10.2, the zeta potential of liposomes was changed by increasing the concentration of polymers, because the surface charge of liposomes was neutralized by the opposite charge of the coating polymer. 

Fig. 10.2 Zeta potential of mucoadhesive liposomes in a phosphate buffer solution (pH 7.4) (taken from Takeuchi et al. 1996). Lipid composition DPPC DCP = 8 2...

Microelectrophoresis is used to measure the electrophoretic mobility or, in other words, the movement of liposomes under the influence of an electric field. From the electrophoretic mobility the electrical potential at the plane of shear or (zeta) potential can be determined (by the Helmoholtz-Smoluchowski equation). From the zeta potential values the surface charge density (o) can be calculated. 

Fatouros, D. G, and Antimisiaris, S. G. (2002), Effect of amphiphilic drugs on the stability and zeta-potential of their liposome formulations A study with prednisolone, diazepam and griseofulvin, J. Coll. Interf. Sci., 251, 271-277. 

Liposome Size, Size Distribution and Zeta Potential Determination... 

Determine the zeta potential of liposomes by Laser Doppler Anemometry, using the Zetasizer 3000HS. 

In Fig. 2, the initial diameter and zeta potential values of liposome formulations are presented. 

The initial diameters and zeta potentials are measured with a NanoZS (Malvern Instruments, Germany, HeNe Laser 633 nm, 173°C scattering angle, 25°C) right after mixing the liposomes with buffer solutions. 

Fig. 3. Visualization of the liposome morphology and size distribution determined with AFM and NanoZS. (a, b) Pure phospholipon liposomes adhered on silicon wafer as substrate. The liposomes have diameters between 80 and 250 nm with an average diameter of 178 12 nm. The liposomes tend to spread to the surface, because of the low membrane stability, (c) Pure GDNT liposomes with an average diameter of 137 8 nm (PDI 0.295 0.017) and a zeta potential of -15.3 0.60 mV. The liposomes are stable and show a spherically, round shape, (d) Size distribution of the pure GDNT liposomes measured with NanoZS...

By applying the modified one-step liposome-preparation technique (that is described in detail in Subheading 3), several types of plain or mixed ARSL, composed of different lipids and at different ratios (Table 1), some also PEGylated, were prepared and characterized physicochemically (9-12). Vesicle mean diameters and size distributions, vesicle zeta-potential and efficiency to encapsulate hydrophilic substances (e.g. calcein) have been measured, and the physical stability of ARSL was evaluated by measuring their size distribution during extend periods of storage. 

Particle size, polydispersity index, and zeta potential measurements of mannosylated liposomes are determined by Zetasizer nano ZS-90. 

The zeta potential of AF-liposomes and lipoplexes showed clearly positive values by using amounts of AF lower than I pg. AF-complexes aggregated at 4.5 and 9 pg AF/pg DNA, which corresponds to a value of the zeta potential close to the electroneutrality (Fig. I). 

Anionic liposome was prepared by the film method on a rotary evaporator Heidolph, VWR, equipped with a vacuubrand CVC2 to control the pressure. Sonication was performed on sonicator branson 1210. Size and zeta potentials measurements were performed on a Zeta Sizer NanoSeries from Malvern Instruments equipped with a MPT2 autotitrator. Fluorescence was measured on a multilabel plate reader Wallac Victor2 1420 Multilabel Counter, Perkin Elmer, France, equipped with excitation and emission filters (350 10 nm, 450 10 nm). 

Recently, EHEC and other hydrocolloids were used for the stabilization of lipid microspheres. The coating reduced the zeta potential of the liposomes to a neutral value and decreased their surface fluidity, as measured by fluorescence... 

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