Access Type

Open Access Dissertation

Date of Award

January 2011

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Biomedical Engineering

First Advisor

Howard W. Matthew

Abstract

Recent research has demonstrated a strong correlation between the differentiation profile of mesenchymal stem cells (MSCs) and scaffold stiffness. Chitosan is being widely studied for tissue engineering applications due to its biocompatibility and biodegradability. However, its use in load-bearing applications is limited due to moderate to low mechanical properties. In this study, we investigated the effectiveness of a fiber reinforcement method for enhancing the mechanical properties of chitosan scaffolds. Chitosan fibers were fabricated using a solution extrusion and neutralization method and incorporated into porous chitosan scaffolds. The effects of different fiber/scaffold mass ratios, fiber mechanical properties and fiber lengths on scaffold mechanical properties were studied. The results showed that incorporating fibers improved scaffold strength and stiffness in proportion to the fiber/scaffold mass ratio. A fiber-reinforced heart valve leaflet scaffold achieved strength values comparable to the radial values of human pulmonary and aortic valves (220±17 kPa). Additionally, the effects of shorter fibers (2 mm) were found to be up to 3-fold greater than longer fibers (10 mm). Heparin crosslinking of fibers failed to produce additional strength or stiffness improvements to fibers. Despite this reduction in fiber mechanical properties, the heparin-modified fibers still improved the mechanical properties of the reinforced scaffolds, but to a lesser extent than the unmodified fibers. The results demonstrate that chitosan fiber-reinforcement can be used to generate tissue-matching mechanical properties in porous chitosan scaffolds and that fiber length and mechanical properties are important parameters in defining the degree of mechanical improvement.

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