Doctoral Dissertations

Date of Award

12-2013

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Polymer Engineering

Major Professor

Roberto S. Benson

Committee Members

Deidra Mountain, Kevin Kit, Wei He

Abstract

Bacterial cellulose (BC) is a natural hydrogel made of nanofibers. This material has been used in commercial products, including wound dressings. BC can be modified and optimized for improved performance in multiple applications. This work will focus on producing and characterizing resorbable cellulose, a composite for bone applications, and a composite for a synthetic venous valve leaflet.

BC can be produced and modified to perform as a degradable tissue scaffold. This is achieved by an oxidation procedure after the initial production and purification of native BC. A material characterization of oxidized BC was performed to identify the changes in properties associated with varying the degree of oxidation. BC incubated in 20 millimolar periodate solution performed the best during an evaluation with preosteoblast cells.

Another application is as a bone scaffold using hydroxyapatite precipitated on the surface of cellulose fibers. This composite has fibers similar to collagen and a biomimetic ceramic similar to that found in native bone. Evaluation of native BC, oxidized BC, and BC with hydroxyapatite were shown to be effective materials to support cell growth in an animal model.

A separate evaluation utilized BC/hydroxyapatite composites as a source of biomimetic hydroxyapatite for use as a filler or powder in other systems. The extraction of hydroxyapatite from BC can be achieved by either enzymatically or thermally degrading bacterial cellulose. Each method leaves some residual product from the processing procedure, which varies depending on the method of analysis used to quantify the residual product.

Lastly, an alternative application is its use as a fiber-reinforcing component in polyurethane. This cellulose/polyurethane composite is of interest for applications that require high-strength and blood compatibility, such as arterial and venous substitutes. A composite was produced with micron scale thickness, similar to a venous valve leaflet. The polyurethane/cellulose composite exhibited improved strength, modulus, and ductility over native BC. In vitro evaluation showed the scaffolds were non-toxic to endothelial cells and support cell growth.

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