Macri Katherine M, Noonan Patrick S, Schwartz Daniel K
Department of Chemical and Biological Engineering, University of Colorado Boulder , Boulder, Colorado 80309-0596, United States.
ACS Appl Mater Interfaces. 2015 Sep 16;7(36):20400-9. doi: 10.1021/acsami.5b06351. Epub 2015 Sep 3.
Membrane fusion events are essential to cell biology, and a number of reductionist systems have been developed to mimic the behavior of these biological motifs. One such system monitors the DNA hybridization-mediated fusion of liposomes with the liquid crystal (LC) interface by observing changes in LC orientation using a simple optical detection scheme. We have systematically explored key parameters of this system to determine their effects on individual elementary steps of the complex fusion mechanism. The liposome composition, specifically the degree of lipid unsaturation and PE content, decreased the bilayer rigidity, thereby increasing the rate of vesicle rupture under the stress applied by DNA hybridization. In contrast, the presence of cholesterol had the opposite effect on the mechanical properties of the bilayer, and hence of the membrane fusion rates. The accessibility of receptor moieties (i.e., complementary DNA oligonucleotides) affected the fusion kinetics by modulating the rate of hybridization events. DNA accessibility was controlled by systematic variation of the length of the DNA receptor molecules and the thickness of the steric barrier comprised of adsorbed PEGylated lipids. These results provide design rules for understanding the trade-offs between response kinetics and other important system properties, such as nonspecific adsorption. Moreover, these findings improve our understanding of the biophysical properties of membrane fusion, an important process in both natural and model systems used for bioassay and bioimaging applications.
膜融合事件对细胞生物学至关重要，人们已开发出许多简化系统来模拟这些生物学基序的行为。其中一个系统通过使用简单的光学检测方案观察液晶（LC）取向的变化，来监测DNA杂交介导的脂质体与液晶界面的融合。我们系统地探索了该系统的关键参数，以确定它们对复杂融合机制中各个基本步骤的影响。脂质体组成，特别是脂质不饱和度和PE含量的程度，降低了双层刚性，从而提高了在DNA杂交施加的应力下囊泡破裂的速率。相反，胆固醇的存在对双层的机械性能以及膜融合速率具有相反的影响。受体部分（即互补DNA寡核苷酸）的可及性通过调节杂交事件的速率来影响融合动力学。DNA可及性通过系统改变DNA受体分子的长度和由吸附的聚乙二醇化脂质组成的空间位垒的厚度来控制。这些结果为理解响应动力学与其他重要系统特性（如非特异性吸附）之间的权衡提供了设计规则。此外，这些发现增进了我们对膜融合生物物理特性的理解，膜融合是用于生物测定和生物成像应用的天然和模型系统中的一个重要过程。
