Quantitative Investigations of Nanoscale Elasticity of Nanofibrillar Matrices
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Quantitative Investigations of Nanoscale Elasticity of Nanofibrillar Matrices Volkan M. Tiryaki1, Adeel A. Khan2, Alicia Pastor3, Raed A. Alduhaileb1, Roberto DelgadoRivera4,5, Ijaz Ahmed5 Sally A. Meiners5, and Virginia M. Ayres1 1 College of Engineering, Michigan State University, East Lansing, MI, 48824, USA 2 College of Engineering and Applied Sciences, Western Michigan University, Kalamazoo, MI 49008, USA 3 Center for Advanced Microscopy, Michigan State University, East Lansing, MI, 48824, USA 4 Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA 5 Department of Pharmacology, University of Medicine and Dentistry of New Jersey, Piscataway, NJ, 08854, USA
ABSTRACT Recent research indicates that nanophysical properties as well as biochemical cues can influence cellular re-colonization of a tissue scaffold. It has also been shown nanoscale elasticity can strongly influence cellular responses. In the present work, quantitative investigations of the elasticity of a nanofibrillar matrix scaffold that has demonstrated promise for spinal cord injury repair are compared with complementary transmission electron microscopy investigations, performed to assess nanofiber internal structures. Interpretive model improvements are identified and discussed.
INTRODUCTION Tissue scaffold engineering is an active research field that merges the disciplines of life sciences and physical sciences to develop functional synthetic tissues that can maintain, restore, or improve damaged organs [1]. One of the major challenges is to develop synthetic scaffolds that mimic all significant aspects of a native extracellular matrix. It has been recently recognized that significant aspects include nanophysical properties such as local elasticity [2,3] and 3D nanofibrillar architecture [4] in addition to the biochemical cues provided by directive growth factors [5]. Nanoscale elasticity may be especially important for actin-based cells such as astrocytes or fibroblasts that can exert strong traction force to actively probe their local environments [2]. Nanoscale elasticity can be investigated using atomic force microscope-based force curves, typically acquired as a raster scan of regularly spaced nano-indentations (force volume imaging). The nano-indentation measurements must then be interpreted using an elasticity model, such as a Hertz or more sophisticated model [6]. All models assume that the indenting tip is normal to the sample surface. For a nanofibrillar matrix, this means taking force curves exclusively at the median points along individual nanofiber and not on the sides or in between. It is not possible to achieve this condition for every data point in a conventional force volume imaging raster scan.
Scanning Probe Recognition Microscopy (SPRM) is a dynamic new mode of atomic force microscopy (AFM) developed within our group that enables auto-tracking along individual nanofibers within a nanofibrillar matrix through incorporation of recognition-based tip con
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