Seras M, Ollivon M, Edwards K, Lesieur S
CNRS URA 1218, Université Paris-Sud, Châtenay-Malabry, France.
Chem Phys Lipids. 1993 Nov;66(1-2):93-109. doi: 10.1016/0009-3084(93)90035-2.
Kinetic aspects of the formation of non-ionic surfactant vesicles (NSV) using the mixed micelle dilution procedure are examined. Mixed micelles composed of a mixture of lipids, i.e. diglycerol hexadecylether (C16G2), cholesterol (CHOL), dicetylphosphate (DCP) and detergent, octylglucoside (OG), were diluted with detergent-free buffer added either instantaneously or progressively at different rates ranging from 3.47 x 10(-2) to 6.94 x 10(-4) ml/min. The resulting particles were analysed by quasielastic light scattering (QELS), high performance liquid chromatography (HPLC) on gel exclusion column and cryogenic transmission electron microscopy (cryo-TEM). NSV exhibit mean diameters (MD) varying from 100 to 600 nm depending on the kinetics of OG removal. When the dilution of mixed micelles is instantaneous the vesicles are characterized by a spherical shape and MD values close to 100 nm. They show narrow size distribution and stability for 2 months. NSV recovered with progressive micelle dilution, at fast buffer addition rates (3.47 x 10(-2) and 1.39 x 10(-2) ml/min) exhibit MD values of 170-240 nm, elongated shapes, low polydispersities and 2-month stabilities. When the rate of buffer addition is lowered to 6.94 x 10(-4) ml/min, unstable particles with larger MD values and broad size distributions are obtained. Turbidity monitoring at 350 nm and 25 degrees C was used to characterize the lipids-OG mixed aggregate rearrangements either as a function of time when detergent-free buffer was continously added to the mixed micelles or after equilibrium setting when the micelles were instantaneously diluted. In the latter case the intermediate aggregates were also analysed by QELS. For continuous dilutions, the molecular composition of aggregates, [OG/lip]agg, as well as the OG concentration in the aqueous medium, [OG]bulk, were determined at the break points observed on the plots of optical density (OD) versus total OG concentration ([OG]tot). [OG/lip]agg and [OG]bulk values are independent of the rate of buffer addition, suggesting that the micelle to NSV transition is not mainly limited by the kinetics of the molecular processes involved during detergent removal from the mixed aggregates. The examination of the apparent partition coefficient of OG between the aqueous phase and the lipidic aggregates shows, however, that OG depletion from the bilayered structures is more difficult than its elimination from the mixed micelles. QELS analysis of the intermediate lipids-detergent aggregates, performed with time, demonstrates very slow supramolecular rearrangements during the vesicle closure. These rearrangements explain the significant increase in both size and polydisperity of the final vesicles observed with slow rates of buffer addition.
研究了使用混合胶束稀释法形成非离子表面活性剂囊泡（NSV）的动力学过程。由脂质混合物（即二甘油十六烷基醚（C16G2）、胆固醇（CHOL）、十六烷基磷酸酯（DCP））和去污剂辛基葡糖苷（OG）组成的混合胶束，用不含去污剂的缓冲液以不同速率（范围从3.47×10⁻²到6.94×10⁻⁴ ml/min）瞬间或逐步稀释。通过准弹性光散射（QELS）、凝胶排阻柱上的高效液相色谱（HPLC）和低温透射电子显微镜（cryo-TEM）对所得颗粒进行分析。NSV的平均直径（MD）根据OG去除的动力学而在100至600 nm之间变化。当混合胶束瞬间稀释时，囊泡的特征是呈球形且MD值接近100 nm。它们显示出窄的尺寸分布并在2个月内保持稳定。以快速缓冲液添加速率（3.47×10⁻²和1.39×10⁻² ml/min）通过逐步胶束稀释回收的NSV，其MD值为170 - 240 nm，形状细长，多分散性低且稳定性为2个月。当缓冲液添加速率降至6.94×10⁻⁴ ml/min时，会获得具有较大MD值和宽尺寸分布的不稳定颗粒。在350 nm和25℃下进行浊度监测，以表征脂质 - OG混合聚集体的重排，这既可以是在向混合胶束连续添加不含去污剂的缓冲液时作为时间的函数，也可以是在胶束瞬间稀释达到平衡后进行。在后一种情况下，中间聚集体也通过QELS进行分析。对于连续稀释，在光密度（OD）与总OG浓度（[OG]tot）的图上观察到的断点处，测定聚集体的分子组成[OG/脂质]agg以及水相中OG的浓度[OG]bulk。[OG/脂质]agg和[OG]bulk值与缓冲液添加速率无关，这表明胶束向NSV的转变并不主要受从混合聚集体中去除去污剂过程中所涉及分子过程的动力学限制。然而，对OG在水相和脂质聚集体之间的表观分配系数的研究表明，从双层结构中耗尽OG比从混合胶束中去除它更困难。随着时间对中间脂质 - 去污剂聚集体进行的QELS分析表明，在囊泡闭合过程中超分子重排非常缓慢。这些重排解释了在缓冲液添加速率较慢时观察到的最终囊泡在尺寸和多分散性方面的显著增加。
