Differences in Nanoscale Elasticity of Planar and Nanofibrillar Tissue Cultures
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Differences in Nanoscale Elasticity of Planar and Nanofibrillar Tissue Cultures Volkan Mujdat Tiryaki1, Virginia M. Ayres1, Ijaz Ahmed2, David I. Shreiber2 1 Electrical and Computer Engineering, Michigan State University, East Lansing, MI, United States. 2 Biomedical Engineering, Rutgers, The State University of New Jersey, Piscataway, NJ, United States.
ABSTRACT Astrocytes are cellular bridges between the neurons and capillaries in the blood brain barrier. It was recently suggested that the nanophysical properties of the basement membrane of the blood brain barrier can influence astrocyte and neuron responses. In this work, cerebral cortical astrocytes were cultured on standard poly-L-Lysine coated glass substrates, Aclar substrates, and electrospun polyamide nanofibers whose properties may recapitulate those of the basement membrane. The nanoscale elasticity of each culture environment was investigated by force curve analysis and compared. The elasticity of the individual nanofibers on nanofibrillar surfaces was also investigated. Finally, variations in elasticity of scaffolds were correlated with astrocyte responses.
INTRODUCTION It has been shown that the elasticity of tissue scaffolds can influence cellular responses [1,2].Therefore, mechanical characterization investigations of promising tissue scaffolds are needed to optimize tissue scaffold design. The mechanical properties of tissue scaffolds can be investigated by atomic force microscopy (AFM) force curve analysis. The strategies of AFM force curve analysis have been presented by Lin et al. [3]. Force curve analysis of biological surfaces was also performed by Heinz and Hoh [4]. In this work, nanoscale elasticity investigations of poly-L-Lysine (PLL) coated glass, polyamide nanofibrillar scaffolds, and Aclar substrates are presented. PLL coated glass surfaces are conventional neural cell cultures, which were used as a control substrate in this work. The polyamide nanofibrillar matrix has demonstrated promise for the repair of the injured spinal cord in vivo investigations [5]. The polyamide nanofibrillar matrices were electrospun onto Aclar substrates, and therefore the elastic properties of this underlying substrate were investigated as well. The AFM surface height images of scaffolds provided the substrate topographies at a nanoscale. The elasticity results were then correlated with the response of cerebral cortical astrocytes to the three culture surfaces, which was investigated by epi-fluorescence microscopy with phalloidin staining for F-actin visualization. These results give insights for more accurate understanding of how the elastic properties of culture surfaces influence cellular responses.
EXPERIMENTAL PROCEDURES Preparation of samples Glass coverslips (12 mm, No. 1 coverglass, Fisher Scientific, Pittsburgh, PA) and Aclar coverslips (Ted Pella, Redding, CA) were used as underlying planar surfaces. Aclar is a transparent fluorinated-chlorinated thermoplastic , and manufactured by Ted Pella, Redding, CA. Glass or Aclar coverslips were placed i
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