Monomethoxypoly(ethylene glysol) cholesteryl carbonates (M-PEG- Chol) with polymer chain molecular weights of 1000 (M-PEG1000-Chol) and 22000 (M-PEG2000-Chol) have been newly synthesized and characterized. Their aggregation behavior in mixture with diglycerol hexadecyl ether (C16G2) and cholesterol has been examined by cryotransmission electron microscopy, high-performance gel exclusion chromatography, and quasielastic light scattering. Nonaggregated stable, unilamellar vesicles were obtained at low polymer levels with optimal shape and size homogeneity at cholesteryl conjugate/lipids ratios of 10 mol% M-PEG1000-Chol or 5 mol% M-PEG2000-Chol, corresponding to the theoretically predicted brush conformational state of the PEG chains. At 20 mol% M-PEG1000-Chol or 10 mol% M- PEG2000-Chol, the saturation threshold of the C16G2/cholesterol membrane in polymer is exceeded, and open disk-shaped aggregates are seen in coexistence with closed vesicles. Higher levels up to 30 mol% lead to the complete solubilization of the vesicles into disk-like structures of decreasing size with increasing PEG content. This study underlines the bivalent role of M-PEG-Chol derivatives: while behaving as solubilizing surfactants, they provide an efficient steric barrier, preventing the vesicles from aggregation and fusion over a period of at least 2 weeks.
Beugin, S., Edwards, K., Karlsson, G., Ollivon, M., & Lesieur, S. (1998). New sterically stabilized vesicles based on nonionic surfactant, choleserol, and poly(ethylene glycol)-cholesterol conjugates. Biophysical Journal, 74(6), 3198–3210. https://doi.org/10.1016/S0006-3495(98)78026-9