Collaborative Research: Mechano-Lipidomics and Mechano-Cytosis of Drug Delivery Liposomes

本课题的研究目标是通过精心设计实验，构建与膜融合力学经典理解一致的基于固体力学的模型，构建机械脂质组学和机械细胞作用的综合模型。利用卵巢癌细胞细胞膜中常见的给药脂质和脂质提取物制备纳米/微尺度脂质体和独立膜。实证研究将包括：(i)膜弹性表征，其中纳米压头或AFM尖端压痕并轻拍样品囊泡和独立膜，光学显微镜在现场监测并记录变形的轮廓；（ii）机械胞吸试验，机械探针迫使脂质体内吞作用进入独立膜或另一个脂质体。将基于(i)线性弹性近似，（ii）脂膜的粘弹性-超弹性行为，（iii）脂质体-膜和脂质体-脂质体界面的非特异性界面力，（iv）黏附-融合的热力学能量平衡，构建变形-黏附-内吞力学的综合模型。解析解将首先通过假设轴对称几何、线性弹性材料响应和方阱粘附势（即内聚区近似）来推导，以确定系统参数。更现实但更复杂的材料定律和表面势将使用数值例程实现。尽管药物递送脂质体的经验设计取得了进展，但在对脂膜融合和内吞能量学的基本理解中缺少机械变形。本研究将通过设计可行的实验来研究脂质膜和脂质体的力学方面，并以机械细胞作用为重点，构建生物力学模型，旨在建立机械脂质组学。这项研究将解决机械脂质组学的一个小而关键的部分，而不是建立一个全面的脂质组学和药物输送模型。这些测量、模型和分析的结果将被药剂师用来设计和制造下一代的药物输送脂质体，以便在未来进行体内测试。

The research goal of this proposal is to build a comprehensive model of mechano-lipidomics and mechanocytosis by designing careful experiments and constructing solid-mechanics based models that are consistent with the classical understanding of membrane fusion mechanics. Nano-/micro-scale liposomes and freestanding membranes will be fabricated using common drug delivery lipids and lipid extracts from cell membrane of ovarian cancer cells. Empirical investigations will include: (i) membrane-elasticity characterization, where a nano-indenter or AFM tip indents and taps the sample vesicles and freestanding membranes, and an optical microscope monitors and records the deformed profiles in-situ; and (ii) mechano-cytosis test, where a mechanical probe forces endocytosis of a liposome into a freestanding membrane or to another liposome. A comprehensive model of deformation-adhesion-endocytosis mechanics will be constructed based on (i) linear elastic approximation, (ii) visco-hyperelastic behavior of lipid membranes, (iii) nonspecific intersurface forces at liposome-membrane and liposome-liposome interfaces, (iv) thermodynamic energy balance for adhesion-fusion. Analytical solutions will first be derived by assuming axisymmetric geometries, linear elastic material responses, and square-well adhesion potential (i.e. cohesive zone approximation), in order to identify the system parameters. The more realistic but sophisticated materials laws and surface potential will then be implemented using numerical routines. Despite progress in empirical design of drug delivery liposomes, mechanical deformation is missing from the fundamental understanding of lipid membrane fusion and endocytotic energetics. This research will address this shortcoming by designing feasible experiments to investigate the mechanical aspects of lipid membranes and liposomes with a focus in mechano-cytosis and constructing biomechanics models, aiming to build mechano-lipidomics. The research will addres a small but critical part of mechano-lipidomics, rather than building a comprehensive model for lipidomics and drug delivery. Outcomes from these measurements, models and analysis will be used by pharmacist to design and fabricate the next generation of drug delivery liposomes to be tested in-vivo in the future.