11 research outputs found
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Living microlens arrays
Both individual cells and sheets of cells exert traction forces on the substrate and these forces have been investigated using a wide range of methods. Here we compare the mechanical properties of fibroblasts and epithelial cells using a novel surface geometry. Living cells are added to a thin film of polystyrene [PS] attached to a substrate of crosslinked poly(dimethyl siloxane) [PDMS] microwells. The contractile nature of the cells attached to the surface and the compliance of the PDMS surface geometry allows the PS thin film to buckle, forming arrays of convex microlenses. The resulting curvature of the microlenses allows us to determine the applied strain of growing cell sheets. We report that a monolayer of epithelial cells exerts more stress on the substrate than fibroblasts and attribute this to the collective behavior of the epithelium. By subsequently adding different chemical triggers to the system, the contractile nature of the cells changes, thus modifying the focal length of the microlenses. Together, these findings demonstrate the importance of studying the mechanics of cell sheets and also introduce a new design paradigm for advanced materials, offering great promise for a range of applications
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Cavitation rheology of the vitreous: mechanical properties of biological tissue
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Polymer microlenses for quantifying cell sheet mechanics
Mechanical interactions between individual cells and their substrate have been studied extensively over the past decade; however, understanding how these interactions change as cells interact with neighboring cells in the development of a cell sheet, or early stage tissue, is less developed. We use a recently developed experimental technique for quantifying the mechanics of confluent cell sheets. Living cells are cultured on a thin film of polystyrene [PS], which is attached to a patterned substrate of crosslinked poly(dimethyl siloxane) [PDMS] microwells. As cells attach to the substrate and begin to form a sheet, they apply sufficient contractile force to buckle the PS film over individual microwells to form a microlens array. The curvature for each microlens is measured by confocal microscopy and can be related to the strain and stress applied by the cell sheet using simple mechanical analysis for the buckling of thin films. We demonstrate that this technique can provide insight into the important materials properties and length scales that govern cell sheet responses, especially the role of stiffness of the substrate. We show that intercellular forces can lead to significantly different behaviors than the ones observed for individual cells, where focal adhesion is the relevant parameter