Poly(ethylene glycol)-Modification of the Phospholipid Vesicles by Using the Spontaneous Incorporation of Poly(ethylene glycol)-Lipid into the Vesicles

Abstract

The critical micelle concentrations of 1, 2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-[monomethoxy poly(ethylene glycol) (5000)] (PEG-DPPE) and its distearoyl analogue (PEG-DSPE) were 70 and 9 microM, respectively, in buffer solutions ([Tris] = 20 mM, [NaCl] = 140 mM, pH 7.4) at 37 degrees C. When these PEG-lipid micelle dispersions were mixed with the dispersions of phospholipid vesicles comprised of a C16 membrane, of which the carbon number is 16, or a C18 membrane, the PEG-lipid micelles were dissociated into monomers and then spontaneously incorporated into the surface of the preformed vesicles. The incorporation rates and the enthalpy changes during incorporation were measured with an isothermal titration microcalorimeter. The incorporation rate of PEG-DPPE was faster than that of PEG-DSPE, because the dissociation rate of the PEG-DPPE micelles was faster than that of PEG-DSPE micelles. The incorporation equilibrium constant of PEG-DSPE was larger than that of PEG-DPPE due to its slow dissociation rate from the membrane, caused by the stronger hydrophobic interaction. The combination of PEG-DSPE and the C18 membrane was the most thermodynamically stabilized pair. Furthermore, the dispersion stability of the surface-modified vesicles prepared by this spontaneous incorporation was analyzed by using the critical molecular weight of the polymer for the aggregation of vesicles. The aggregation of the vesicles was successfully supressed with an increase in the molecular weight of the PEG in the PEG-lipid and its incorporation ratio.

RNAi-mediated gene knockdown and anti-angiogenic therapy of RCCs using a cyclic RGD-modified liposomal-siRNA system

“…This saturation might be due to fixed quantity of α V β 3 integrin present on HUVEC cells. In addition, it was previously reported that the PEGylation ratio in liposomes was, at most, 5.0 mol% [35]. Collectively, 5.0 mol% of RGD-PEG might be the optimized modification condition in both aspects of cells and siRNA carriers.…”

Physicochemical characteristics of pH-sensitive poly(l-Histidine)-b-poly(ethylene glycol)/poly(l-Lactide)-b-poly(ethylene glycol) mixed micelles

“…At time t, the fluorescent intensity was I t . The fraction of polymers that remained as micelles at time t after dilution can be expressed as [36]:…”

Gene delivery into ischemic myocardium by double-targeted lipoplexes with anti-myosin antibody and TAT peptide

“…The stabilized TATplipoplexes could be targeted to the myocardium by the disease-specific mAb (to ischemic myocardium with the anti-myosin mAb 2G4). The incorporation of PEG-PE and the attachment of 2G4 antibody to TATp-lipoplexes were accomplished simultaneously by the so-called 'micelle transfer' procedure, 26,27 which provides simultaneous transfer of antibody-coupled micelles to liposome with negligible leakage. Thus, it is unlikely that the antibody coating affect DNA loading.…”

“…The anti-myosin antibody 2G4 was first conjugated to the micelle of pNP-PEG3400-PE and then inserted into the preformed TATp-lipoplexes by the 'micelle transfer' procedure. 26,27 Briefly, an amount of pNP-PEG3400-PE corresponding to 3 mol% of total lipids was hydrated in sodium citrate-buffered saline (5 mM, pH 5.0) and mixed with mAb 2G4 in sodium borate buffer (50 mM, pH 9.0) at a molar ratio of 40:1, corresponding to 169 mg antibody/mmol phospholipids. The mixture was incubated overnight and then dialyzed against 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid-buffered saline (10 mM, pH 7.4) with a cellulose ester membrane of MWCO 250 000 Da (Spectrum Medical Industries, Los Angeles, CA, USA) at 4 1C.…”