Three-Dimensional Characterization of Mechanical Interactions between Endothelial Cells and Extracellular Matrix during Angiogenic Sprouting

We studied the three-dimensional cell-extracellular matrix interactions of endothelial cells that form multicellular structures called sprouts. We analyzed the data collected in-situ from angiogenic sprouting experiments and identified the differentiated interaction behavior exhibited by the tip and stalk cells. Moreover, our analysis of the tip cell lamellipodia revealed the diversity in their interaction behavior under certain conditions (e.g., when the heading of a sprout is switched approximately between the long-axis direction of two different lamellipodia). This study marks the first time that new characteristics of such interactions have been identified with shape changes in the sprouts and the associated rearrangements of collagen fibers. Clear illustrations of such changes are depicted in three-dimensional views.Singapore-MIT Alliance in Research and Technology (SMART

Localized Manipulation of Magnetic Particles in an Ensemble

The ability to manipulate magnetic particles selectively and simultaneously (within a group of such particles) has significant implications in studying cellular behaviors and in manipulating micro-structures at an ensemble-level. The current magnetic manipulation techniques have been demonstrated to be effective for studying cell mechanics. However, they suffer from low throughput, as only one particle is addressed in an individual experiment. This renders them unsuitable for ensemble-level operations. In this paper, we present a magnetic manipulation system that enables (effectively) simultaneous yet localized manipulation of magnetic particles. The proposed system is equipped with a novel device, which realizes magnetic force localization. The properly localized force allows selective manipulation of a single magnetic particle in a group. The localization effects of this device are demonstrated and quantified through analytical modeling and simulations that yielded statistically meaningful results. With the characterized device, experiments were carried out to evaluate the effectiveness of the proposed system. Indes terms: Localized magnetic force, localized manipulation, magnetic actuation

Active Manipulation of ECM Stiffness

The mechanical properties of the microstructures surrounding cells influence the behavior of cells in differentiation, proliferation, and apoptosis, etc. The stiffness of the extra-cellular microenvironment has been shown to be one such mechanical property. Studies reported in the literature concerning the stiffness of the extracellular microenvironment mainly sought to understand the scientific principles and mechanisms underlying its effect on cell-environment interaction. This paper describes an approach that achieves such manipulation, and reports experimental results that demonstrate the effectiveness of this proposed approach