Role of Scaffold Architecture and Mechanical Properties of Electrospun Scaffolds in Cell Seeding
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Role of Scaffold Architecture and Mechanical Properties of Electrospun Scaffolds in Cell Seeding Nandula Wanasekara1, Ming Chen2, Vijaya Chalivendra3 and Sankha Bhowmick2,3 1 Materials & Textiles Department 2 Bioengineering & Biotechnology Program 3 Department of Mechanical Engineering University of Massachusetts Dartmouth, MA 02747 ABSTRACT Seeding a layer of cells at specific depths within scaffolds is an important optimization parameter for bi-layer skin models. The work presented investigated the effect of fiber diameter and its mechanical property on the depth of cell seeding for electro-spun fiber scaffold. Polycaprolactone (PCL) is used to generate scaffolds that are submicron (400nm) to micron (1100nm) using electro-spinning. 3T3 fibroblasts were seeded on the electro-spun fiber scaffold mat of 50-70 microns thickness in this study. In order to investigate the effect of fiber diameter on cell migration, first, the electrospun fiber scaffold was studied for variation of mechanical properties as a function of fiber diameters. Atomic force microscopy (AFM) was used to investigate the Young’s modulus (E) values as a function of fiber diameter. It was identified that as the fiber diameter increases, the Young’s modulus values decreases considerably from 1.1GPa to 200MPa. The variation in E is correlated with cell seeding depth as a function of vacuum pressure. A higher E value led to a lower depth of cell seeding (closer to the surface) indicating that nanofibrous scaffolds offer larger resistance to cell movement compared to microfibrous scaffolds. INTRODUCTION Electro-spinning is one of the approaches that allow the fabrication of natural synthetic materials into fibrous structures in the submicron nanometer scale [1-2]. These scaffolds provide excellent framework for cell growth as widely reported in the literature for a variety of materialcell combinations including skin, bone, cartilage, tendons, blood vessels and heart valves [3-6]. Nano-fibrous scaffolds are suitable for replicating the physical structure of extra cellular matrix (ECM). However, the exact role played by the fiber diameter in modulating cellular attachment, proliferation, differentiation and eventual tissue architecture is not clearly understood. Great advances have been made over the past few years in the development of techniques for probing the mechanical properties of materials on the submicron scale. Elastic modulus, E, and the hardness, H are the most common measurements of indentation techniques [7]. Lopez reported the nanoindentation studies on metal fibers of YAG, YAG:Nd and YAG:Eu fibers with different compositions [8]. There are a few literatures on indentation on sub-micron fibers. Wang et. al. [9] have electrospun B. mori silk/poly (ethylene oxide) (PEO) fibers with diameters less than 1 µm. The mechanical properties of single fibers were characterized by AFM nanoindentation. The results have been consistent with uniaxial tensile tests and with the morphological analysis. Tan and Lim [10] have done nanoindentation
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