Structure-property relationships in electrospun scaffolds

Electrospinning is a broadly useful manufacturing technique to create polymer fibers ranging in diameter from 20 nm to 20 microm. This size range is ideal for tissue engineering applications as these fibers can mimic the extracellular matrix found in vivo and provide suitable scaffolds for implantation in vivo or for more realistic in vitro models and diagnostics. Electrospinning is a process that involves dissolving a synthetic or natural polymer in a solvent and applying a large voltage bias, which leads to the formation of a Taylor cone and a small jet that ejects a thin stream of the polymer solution. This thin stream rapidly elongates while the solvent evaporates and solid fibers are collected on a grounded substrate. The electrospinning technique can be used to create a large number of nanofibers relatively cheaply and easily compared to other manufacturing methods used to create nanoscale features.;While electrospun scaffolds are gaining popularity for cell culture and tissue engineering applications, relatively little is understood about the relationship between macroscopic properties and microscopic properties. Researchers need to understand that the bulk properties of a specific polymer are not the same properties that a cell cultured on the surface of a nanofiber are going to experience. To further complicate this issue, electrospun scaffolds are comprised of nanofibers that can act en masse and thus the macroscopic properties are more of a function determined by fiber-fiber interaction rather than individual fiber mechanical properties.;This work strives to establish a baseline of mechanical properties for electrospun fiber scaffolds made of polycaprolactone and various blends of gelatin and relate the macroscopic tensile properties to the underlying microscopic behavior. To investigate how biological environments may affect these properties, scaffolds were subjected to various in vitro exposures and in vivo implantation and then further analyzed for mechanical behavior and microstructure changes. The conclusions from this work show that the cellular response can be influence by the properties of individual fibers, but also how these fibers interact with each other suggesting that no single method can adequately characterize electrospun scaffolds. These complex structures need to be characterized using a variety of tools and techniques at the microscopic level and the macroscopic level and then use the underlying microstructure to determine the relationships between the two levels of characterization.