CAREER: Nano-Biomechanics of Living Cells using Atomic Force Microscopy

这份职业计划的目标是(1)开发原子力显微镜作为一种纳米工具，以推动细胞生物力学领域的发展；(2)与这些研究工作相结合，创建一个细胞生物力学的综合实践教育计划。生物组织是由细胞组成的，这些细胞的力学性质直接影响其基本功能，包括细胞的迁移、增殖、活性和细胞外基质在变化的负荷条件下的重塑。从基础科学的观点来看，需要细胞力学性质的知识来阐明细胞功能的机制。此外，某些形式的心脏病、癌症和关节炎与这些组织细胞的机械特性改变有关。因此，表征细胞的机械特性可能会增强筛查疾病和评估潜在的基因疗法和其他治疗方法的能力。原子力显微镜(AFM)是最近发展起来的一项技术，在测量细胞力学方面迅速流行起来。与其他技术相比，原子力显微镜具有优势，包括相对易用性、将成像和压痕能力结合在一起的能力，而且它是商业上可用的。然而，与微吸管实验等广泛的工程分析相比，对AFM实验的分析相对较少。公认的标准AFM分析假设细胞的行为就像一块简单的橡胶。另一方面，大多数生物组织表现出复杂的非线性、弹性和粘性性质，这些性质往往因地区而异，并且具有优先的对称轴。这些特征也可能延伸到细胞水平。因此，这份职业应用程序提出了迄今为止对AFM压痕问题最复杂的分析和验证。有限元将被用来模拟全尺寸的3-D AFM压痕实验，结合了详细的细胞形貌和探针几何形状。还将评估与单元内的应力和应变相关的可选本构模型，包括粘弹性、各向异性、非线性和材料特性的非均质性的影响。此外，还提出了一些技术改进，以优化原子力显微镜作为细胞力学应用的纳米工具。所获得的见解将用于指导细胞压痕实验，改进数据分析，并帮助实现这一强大技术的巨大潜力。结合研究活动，哥伦比亚大学生物医学工程系提出了新的细胞生物力学课程模块。目标是让学生接触纳米技术在细胞力学领域的生物医学应用。具体地说，这门研究生/高级本科课程的学生将使用原子力显微镜在细胞和亚细胞尺度上获得与材料互动的实践经验。研究计划中的新进展将被整合到课程中，也将被纳入一个外展暑期高中计划中。此外，还将开发一个基于网络的多媒体培训工具，并在国家科学数字图书馆上发布，以便对使用原子力显微镜对细胞和其他生物材料进行机械测试的教育工作者和研究人员随时可用。该网站将包括理论基础，详细的方法，以及通过多媒体内容增强的实用的成功秘诀。通过这些结合的研究和教育活动，PI的目标是进一步发展纳米生物力学的科学，并激发人们对这一新的令人兴奋的领域的兴趣。

0239138CostaThe 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.