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

微小的脂囊，称为脂质体，在活细胞中作为储存和运输物质进出细胞的手段发挥着至关重要的作用。脂质体的关键任务(储存和递送到靶)要求它们具有足够的灵活性，可以与靶膜结合以运送其货物，但又必须具有足够的结构稳定性，以在自然动态的生物环境中保持完整性而不破坏和丢失存储的材料。因此，对于基础科学家和应用科学家来说，了解脂质体的作用机制是非常有意义的，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，以更好地治疗疾病。然而，一个主要的挑战是缺乏有效的工程工具来探索亚细胞纳米脂质体的机械弹性。这项研究通过开发一种基于纳米孔技术的新方法来满足这一需求，该方法使用电场来变形脂质体，并通过电测量来表征其形状。本项目的总体目标是表征纳米脂质体的机械柔性，最终目的是建立一种在细胞/分子水平上研究病毒和其他生物样品等纳米尺度物体的力学性质的方法。该项目将推动在微/纳米尺度上对生物软材料进行力学表征的工程工具的发展。该技术使用纳米孔电阻脉冲传感来检测薄膜变形。当脂质体穿过纳米孔时，它们会受到强烈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塞，即当脂质体存在于毛孔中时欧姆电阻的急剧变化(脉冲)中推断出来。将建立脂质体在纳米孔中变形的理论模型，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)数千个脂质体穿过纳米孔，每个单独的脂质体将被记录一个电阻脉冲，(2)通过改变施加的电场方向来驱动来回移位，可以在单个脂质体上进行数千次测量。更广泛地说，这种方法将使机械生物学能够在前所未有的新规模上进行研究，即单病毒和单粒子水平。

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.