Bilayer Stability and Impermeability of Nonionic Surfactant Vesicles Sterically Stabilized by PEG–Cholesterol Conjugates
✍ Scribed by Sophie Beugin-Deroo; Michel Ollivon; Sylviane Lesieur
- Publisher
- Elsevier Science
- Year
- 1998
- Tongue
- English
- Weight
- 850 KB
- Volume
- 202
- Category
- Article
- ISSN
- 0021-9797
No coin nor oath required. For personal study only.
✦ Synopsis
have been detailed and discussed as a function of polymer New vesicles based on diglycerol hexadecyl ether (C 16 G 2 ), chochain incorporation ratio and conformational state. This inlesterol and monomethoxypoly(ethylene glycol) cholesteryl carvestigation has emphasized that, when submitted to ultrabonate (M-PEG-Chol) were prepared by ultrasonic irradiation and sonic irradiation, fully hydrated mixtures of C 16 G 2 , cholescharacterized regarding their size stability and membrane imperterol and low proportions of the M-PEG-grafted cholesterol meability. The influence of polymer level and hydrophilic chain derivatives (M-PEG-Chol) yield relatively homogeneous length (1000 or 2000 molecular weight) was studied and the perunilamellar vesicles, apparently stable. formances compared to those of conventional nonionic surfactant In the present work, the physico-chemical characterization vesicles (NSV) composed of C 16 G 2 , cholesterol and dicetylphosof these new PEG-coated vesicles has been deepen to evaluphate. Intrinsic physical stability at 20ЊC was evaluated by following versus time both the evolution of vesicle mean diameter (MD) ate their size stability and bilayer impermeability, which are by quasi-elastic light scattering and the release of encapsulated among the major concerns for liposome applications (10). calcein by high performance gel exclusion chromatography cou-In this respect, the stability of a vesicle preparation lies first, pled with fluorescence and 90Њ light scattering on-line detections. from a simple physico-chemical point of view, in the particle Good size stability and calcein retention ability (less than 15% resistance to self-aggregation and fusion, and then, if used leakage), comparable to NSV, were observed over a fortnight. as a drug carrier exposed to a biological milieu, in the imper-Longer incubation times yielded slight increase in size; 25-40% meability of the vesicle membrane to the leakage of an enleakages were found, against 17% for NSV. Membrane impermecapsulated component, as well as in its resistance to other ability was also assessed through the resistance to octyl glucoside. amphiphilic compounds, e.g., solubilizing agents, and to pro-M-PEG-Chol-containing vesicles presented slow solubilization kitein adsorption. The size stability with time of the M-PEGnetics mainly governed by surface density of hydrophilic chains.
Chol based vesicles has thus been examined by quasi-elastic
The most efficient steric barrier was achieved at 10 mol% M-PEG1000-Chol (5 mol% M-PEG2000-Chol), which corresponds light scattering measurements. The barrier properties of the to the brush conformational state of the chains. ᭧ 1998 Academic Press mixed membrane have been investigated first by testing the Key Words: solubilization; octyl glucoside; permeability; calcein. ability of the vesicles to encapsulate and retain the fluorescent dye calcein in their internal aqueous volume. Secondly, the resistance towards the lytic effect of the nonionic surfac-1 To whom correspondence should be addressed.
ú 95%) were purchased from Sigma. Dicetyl phosphate 324