Panorchan Porntula, Lee Jerry S H, Daniels Brian R, Kole Thomas P, Tseng Yiider, Wirtz Denis
Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, Maryland 21218, USA.
Methods Cell Biol. 2007;83:115-40. doi: 10.1016/S0091-679X(07)83006-8.
We describe a new method to measure the local and global micromechanical properties of the cytoplasm of single living cells in their physiological milieu and subjected to external stimuli. By tracking spontaneous, Brownian movements of individual nanoparticles of diameter>or=100 nm distributed within the cell with high spatial and temporal resolutions, the local viscoelastic properties of the intracellular milieu can be measured in different locations within the cell. The amplitude and the time-dependence of the mean-squared displacement of each nanoparticle directly reflect the elasticity and the viscosity of the cytoplasm in the vicinity of the nanoparticle. In our previous versions of particle tracking, we delivered nanoparticles via microinjection, which limited the number of cells amenable to measurement, rendering our technique incompatible with high-throughput experiments. Here we introduce ballistic injection to effectively deliver a large number of nanoparticles to a large number of cells simultaneously. When coupled with multiple particle tracking, this new method-ballistic intracellular nanorheology (BIN)-makes it now possible to probe the viscoelastic properties of cells in high-throughput experiments, which require large quantities of injected cells for seeding in various conditions. For instance, BIN allows us to probe an ensemble of cells embedded deeply inside a three-dimensional extracellular matrix or as a monolayer of cells subjected to shear flows.
我们描述了一种新方法，用于测量单个活细胞在其生理环境中并受到外部刺激时细胞质的局部和全局微观力学性质。通过以高空间和时间分辨率跟踪分布在细胞内直径大于或等于100 nm的单个纳米颗粒的自发布朗运动，可以测量细胞内不同位置的局部粘弹性性质。每个纳米颗粒的均方位移的幅度和时间依赖性直接反映了纳米颗粒附近细胞质的弹性和粘度。在我们之前的粒子跟踪版本中，我们通过显微注射递送纳米颗粒，这限制了适合测量的细胞数量，使我们的技术与高通量实验不兼容。在这里，我们引入弹道注射，以有效地同时将大量纳米颗粒递送至大量细胞。当与多粒子跟踪相结合时，这种新方法——弹道细胞内纳米流变学（BIN）——现在使得在高通量实验中探测细胞的粘弹性性质成为可能，高通量实验需要大量注射细胞以在各种条件下接种。例如，BIN使我们能够探测深埋在三维细胞外基质中的一组细胞，或作为单层细胞受到剪切流作用的情况。
