Collaborative Research: Quantitative Analysis of Liposome Deformation at Nanoscale Using Resistive Pulse Sensing in Solid State Nanopores

微小的脂囊，被称为脂质体，在活细胞中起着至关重要的作用，作为储存和运输物质进出细胞的手段。脂质体的关键任务（储存和运送到靶标）要求它们具有足够的灵活性，以便与靶膜融合以运送其货物，并且具有足够的结构稳定性以保持完整性，而不会在自然动态的生物环境中破裂和丢失储存的材料。因此，了解脂质体的机制对基础科学家和应用科学家都非常有兴趣，他们正在开发人工仿生脂质体作为靶向药物/基因递送系统，以获得更好的治疗方法。然而，一个主要的挑战是缺乏有效的工程工具来探测亚细胞纳米级脂质体的机械灵活性。该研究通过开发一种基于纳米孔技术的新方法来解决这一需求，该方法利用电场使脂质体变形，并利用电测量来表征其形状。总体目标是表征纳米脂质体的机械灵活性，最终目标是建立一种在细胞/分子水平上研究纳米级物体（如病毒和其他生物样品）机械特性的方法。该项目将推进软质生物材料在微/纳米尺度上的力学表征的工程工具。该技术使用纳米孔电阻脉冲传感来检测膜变形。当脂质体通过纳米孔转运时，它们会受到强大的电应力和物理限制，从而导致变形。在这个项目中，脂质体的形状将从离子电流阻断中推断出来，即当脂质体存在于孔中时，欧姆电阻的急剧变化（脉冲）。将建立纳米孔中脂质体变形的理论模型，以获得膜的力学性能。该方法将实现高通量和单颗粒分辨率，因为(1)数千个脂质体通过纳米孔，每个脂质体将记录一个电阻脉冲，(2)通过交替施加电场方向来驱动来回移位，可以对单个脂质体进行数千次测量。从更广泛的角度来看，这种方法将使机械生物学研究在新的前所未有的尺度上，即单病毒和单颗粒水平上。

Tiny lipid sacs, called liposomes, play a crucial role in living cells as means to store and transport material in and out of the cell. The key task of liposomes (storage and delivery to targets) requires them to be flexible enough to merge with target membranes in order to deliver their cargos, and yet to have sufficient structural stability to maintain integrity without rupturing and losing the stored material in the naturally dynamic biological environments. Therefore, understanding the mechanics of liposomes is of great interest to both fundamental and applied scientists who are developing artificial, biomimetic liposomes as targeted drug/gene delivery systems for better therapeutics. A major challenge however, is the lack of efficient engineering tools to probe the mechanical flexibility of the sub-cellular, nanoscale liposomes. The research addresses this need by developing a novel method based on nanopore technology that uses electric fields to deform liposomes and electrical measurements to characterize their shape. The overall goal is to characterize the mechanical flexibility of nano-liposomes with the ultimate goal to establish a method to study mechanical properties of nanoscale objects such as viruses and other biological samples at cellular/molecular level.This project will advance the engineering tools for mechanical characterization of soft biological materials at the micro/nanoscale. The technology uses nanopore resistive pulse sensing to detect membrane deformation. As liposomes translocate through a nanopore, they experience strong electric stresses and physical confinement, which cause deformation. In this project, liposome shapes will be inferred from ionic current blockade, i.e., the sharp change (pulse) in ohmic resistance when a liposome is present in the pore. A theoretical model for liposome deformation in the nanopore will be developed to yield membrane mechanical properties. The method will enable both high-throughput and single-particle resolution because (1) thousands of liposomes pass through the nanopore and a resistive pulse will be recorded for each individual one, and (2) thousands of measurements on a single liposome can be made by alternating the applied electric field direction to drive back-and-forth translocation. In broader terms, this method will enable studying mechanobiology at novel unprecedented scales, which is single-virus and single-particle level.