The goals of this CAREER proposal are (1) to develop the atomic force microscope as a nano-tool for advancing the field of cell biomechanics and (2) to create an integrated hands-on educational program in cellular biomechanics in conjunction with these research efforts.
Biological tissues are comprised of cells, and the mechanical properties of these cells directly impact on their fundamental functions including cell migration, proliferation, viability, and remodeling of the extracellular matrix in response to altered loading conditions. From a basic science standpoint, knowledge of cell mechanical properties is required to elucidate the mechanisms of cell function. Moreover, certain forms of heart disease, cancer and arthritis have been associated with altered mechanical properties of the cells of those tissues. Thus, characterizing cellular mechanical properties may enhance the ability to screen for disease and evaluate potential gene therapies and other treatments.
Atomic force microscopy (AFM) is a recently developed technology that has rapidly gained popularity for measuring cell mechanics. AFM has advantages over alternative techniques including relative ease of use, ability to combine imaging and indentation capabilities, and it is commercially available. However, in contrast to the extensive engineering analysis of e.g. micropipette experiments, relatively little has been done to analyze the AFM experiment. The standard accepted AFM analysis assumes the cell behaves like a simple piece of rubber. Most biological tissues, on the other hand, exhibit complex nonlinear elastic and viscous properties that often vary regionally and have preferred axes of symmetry. These characteristics may extend to the cellular level as well. Therefore, this CAREER application proposes the most sophisticated analysis and validation of the AFM indentation problem to date. Finite elements will be used to simulate the full-scale 3-D AFM indentation experiment, incorporating detailed cell topography and probe geometry. Alternative constitutive models relating stress and strain within the cell, including effects of viscoelasticity, anisotropy, nonlinearity, and heterogeneity of material properties, will also be evaluated. In addition, a number of technological enhancements are proposed to optimize the AFM as a nano-tool for cell mechanics applications. The insights gained will be used to guide cell indentation experiments, to improve data analysis, and to help realize the tremendous potential of this powerful technique.
Connected with the research activity, a new course module in Biomechanics of Cells is proposed in the Department of Biomedical Engineering at Columbia University. The goal is to expose students to biomedical applications of nanotechnology as applied to the field of cell mechanics. Specifically, students in this graduate / advanced undergraduate course will use the AFM to gain hands-on experience interacting with materials at the cellular and sub-cellular scale. New advances in the research program will be integrated into the course and will also be incorporated into an outreach Summer High School Program. In addition, a multimedia web-based training tool will be developed and published on the National Science Digital Library so that it is always available educators and researchers interested in mechanical testing of cells and other biological materials using AFM. The website will include theoretical foundations, detailed methods, and practical "tips for success" enhanced by multi-media content. Through these combined research and educational activities, the PI aims to further the science of nano-scale biomechanics and stimulate interest in this new and exciting field.
