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Lab%20Report%20Example - LAB 3: CELL MECHANICS The effects...

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LAB 3: CELL MECHANICS The effects of tensile forces on endothelial cells EXAMPLE 2008 MEM 380 Introduction to Biomechanical Engineering
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ABSTRACT Beam equations and application of tensile forces were used to determine the mechanical properties of endothelial cells in an effort to understand the role of cytoskeletal elements in cell growth. An AFM cantilever was used to calibrate a PDMS microbeam array and determine its mechanical properties. The PDMS microbeam array was then applied to endothelial cells to stretch the cells and use the deformation to calculate their mechanical properties. Using Hookean approximations for the behavior of the cantilever, the array, and the cells, the stiffnesses were found to be 0.255 N/m, 0.1713 N/m, and 0.0190 N/m. The moduli of elasticity for the array and the cells were found to be 785.2 kPa and 6.31 Pa, respectively. While the mechanical properties of the PDMS array are dependent on the dimensions of the beams and the material properties, the mechanical properties of cells vary depending on the magnitude of the applied tensile force. The interaction of the cytoskeletal elements results in a variance of their arrangement in response to changes in the environment, such as tensile loading. The application of tensile forces to stimulate cell growth may play a future role in brain tissue engineering. The PDMS array is a useful tool to determine the mechanical properties of cells. INTRODUCTION Healthy tissue function is often affected by the mechanics of the cells. Processes such as stem cell differentiation and cell migration, remodeling of airways, vasculature, and bone, and the resting and death of cells are all dependent upon the mechanical environment. Cells interact with this environment primarily through the cytoskeleton, which is made up of three elements: actin filaments, which determine the shape and movement of the cell; intermediate filaments, which provide resistance to shear stresses; and microtubules, which resist compressive loads.
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Each of these filaments interacts with the others while their arrangement varies in response to the environment. The cytoskeletal filaments, cytoplasm, and cell membrane form the foundation of cell mechanics. Several techniques exist to study cell mechanics. Previous research and experimentation has employed the use of magnetic tweezers, optic tweezers, and atomic force microscopy (AFM). In this experiment, a polydimethylsiloxane (PDMS) microbeam array was used. Similar arrays composed of glass have been used in previous research. PDMS was selected for the desirable characteristics of being transparent, non-toxic, and its relatively small modulus of elasticity. A 100 x 100 microbeam array was constructed using microfabrication techniques and used in this experiment. This enables the experimenter to study the cell mechanics using multiple, parallel beams in a one-probe-to-one-cell technique. Knowing the dimensions of the individual beams (length and radius), other the
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This note was uploaded on 11/17/2009 for the course MEM 380 taught by Professor Lau during the Spring '07 term at Drexel.

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Lab%20Report%20Example - LAB 3: CELL MECHANICS The effects...

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