Steven J. Eppell

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The mechanical response of a biological material to applied forces reflects deformation mechanisms occurring within a hierarchical architecture extending over several distinct length scales. Characterizing and in turn predicting the behaviour of such a material requires an understanding of the mechanical properties of the substructures within the hierarchy,(More)
The inorganic phase of bone is comprised primarily of very small mineralites. The size and shape of these mineralites play fundamental roles in maintaining ionic homeostasis and in the biomechanical function of bone. Using atomic force microscopy, we have obtained direct three-dimensional visual evidence of the size and shape of native protein-free(More)
Atomic force microscopy (AFM) was used to obtain three-dimensional images of isolated mineralites extracted from young postnatal bovine bone. The mean mineralite size is 9 nm × 6 nm × 2.0 nm, significantly shorter and thicker than the mineralites of mature bovine bone measured by the same technique. Mineralites of the young postnatal bone can be(More)
Collagen, a molecule consisting of three braided protein helices, is the primary building block of many biological tissues including bone, tendon, cartilage, and skin. Staggered arrays of collagen molecules form fibrils, which arrange into higher-ordered structures such as fibers and fascicles. Because collagen plays a crucial role in determining the(More)
High resolution scanning force microscope (SFM) images of fibrinogen-exposed platelet membranes are presented. Using ultrasharp carbon tips, we are able to obtain submolecular scale resolution of membrane surface features. Corroboration of SFM results is achieved using low voltage, high resolution scanning electron microscopy (LVHRSEM) to image the same(More)
Endothelial cell (EC) movement is an initiating and rate-limiting event in the neogenesis and repair of blood vessels. Here, we explore the hypothesis that microviscosity of the plasma membrane (PM) is a key physiological regulator of cell movement. Aortic ECs treated with membrane-active agents, such as alpha-tocopherol, cholesterol and lysophospholipids,(More)
Collagen, an essential building block of connective tissues, possesses useful mechanical properties due to its hierarchical structure. However, little is known about the mechanical properties of collagen fibril, an intermediate structure between the collagen molecule and connective tissue. Here, we report the results of systematic molecular dynamics(More)
Understanding the viscoelastic behavior of collagenous tissues with complex hierarchical structures requires knowledge of the properties at each structural level. Whole tissues have been studied extensively, but less is known about the mechanical behavior at the submicron, fibrillar level. Using a microelectromechanical systems platform, in vitro coupled(More)
Mechanical properties of living cells can be determined using atomic force microscopy (AFM). In this study, a novel analysis was developed to determine the mechanical properties of adherent monolayers of pulmonary microvascular endothelial cells (ECs) using AFM and finite element modeling, which considers both the finite thickness of ECs and their nonlinear(More)
Mechanical testing of collagenous tissues at different length scales will provide improved understanding of the mechanical behavior of structures such as skin, tendon, and bone, and also guide the development of multiscale mechanical models. Using a microelectromechanical-systems (MEMS) platform, stress-strain response curves up to failure of type I(More)