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

该方案的研究目标是通过精心设计实验并构建与膜融合力学经典理解相一致的基于固体力学的模型，从而建立一个完整的机械-脂质组学和机械细胞吞噬的模型。利用卵巢癌细胞细胞膜中常见的给药脂类和脂类提取物，制备纳米/微米级脂质体和独立膜。实验研究将包括：(I)膜弹性表征，即纳米压头或AFM尖端压入并轻拍样品囊泡和独立膜，光学显微镜原位监测和记录变形的轮廓；(Ii)机械细胞吞噬试验，即机械探针迫使脂质体内吞进入独立膜或另一脂质体。基于(I)线性弹性近似，(Ii)脂膜的粘超弹性行为，(Iii)脂质体-膜和脂质体-脂质体界面的非特定界面作用力，(Iv)黏附-融合的热力学能量平衡，将建立一个变形-黏附-内吞力学的综合模型。为了识别系统参数，首先将通过假设轴对称几何结构、线弹性材料响应和方势垒粘附势(即内聚区近似)来推导解析解。然后将使用数值例程来实现更现实但更复杂的材料定律和表面势能。尽管在药物递送脂质体的经验设计方面取得了进展，但对脂膜融合和内吞能量学的基本理解还缺乏机械变形。这项研究将通过设计可行的实验来研究脂膜和脂质体的力学方面，重点是机械细胞作用，并建立生物力学模型，目的是建立机械脂质组学，以解决这一缺点。这项研究将补充机械脂质组学的一个小但关键的部分，而不是建立一个全面的脂质组学和药物输送模型。药剂师将利用这些测量、模型和分析的结果来设计和制造下一代药物输送脂质体，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.