Defense Date

2009

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Biomedical Engineering

First Advisor

David Simpson

Second Advisor

Gary Bowlin

Abstract

Electrospinning can be used to selectively process a variety of natural and synthetic polymers into highly porous scaffolds composed of nano-to-micron diameter fibers. This process shows great potential as a gateway to the development of physiologically relevant tissue engineering scaffolds. In this study we examine the structural and functional considerations regarding electrospun scaffolds for dermal template applications using novel quantification techniques. In order to characterize scaffold structure, a technique utilizing the fast Fourier transform was developed to systematically quantify fiber alignment and evaluate how different electrospinning parameters impact the structure and material properties of an electrospun scaffold. Gelatin was suspended at varying concentrations (80, 100, 130 and 150 mg/ml) and electrospun from 2,2,2 trifluoroethanol onto a rotating mandrel (200-7000 RPM). Scaffold anisotropy developed as a function of fiber diameter and mandrel speed and the induction of varying degrees of anisotropy imparted distinctive material properties to the electrospun scaffolds. Fiber alignment was the variable most closely associated with the regulation of peak stress, peak strain and modulus of elasticity. Next, we examined how the chemical and physical composition of the local microenvironment and the unmasking of possible RGD sensitive binding sites through collagen denaturation, independent of scaffold architecture and porosity, impacts cellular processes. We cultured human dermal fibroblasts on electrospun nylon coated with a variety of non-denatured and thermally denatured collagen-based proteins, as well as recovered electrospun collagen and gelatin (in an effort to examine if the electrospinning process degrades the collagen α chain). Differences in adhesion, proliferation and migration were exhibited between collagen-based proteins. Adhesion inhibition assays using a cyclic RGD peptide demonstrated no change in cell adhesion on non-denatured proteins and a significant drop in cell adhesion on thermally denatured proteins. Based on gel analysis and the results of our functional assays we conclude that collagen  chain structure is not directly altered by the electrospinning process. Overall, these results are critical to the understanding of how structure and architecture contribute to the overall properties of a scaffold, as well as how molecular variations can modulate scaffold functionality in a cellular environment.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

May 2009

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