All ETDs from UAB

Advisory Committee Chair

Alan W Eberhardt

Advisory Committee Members

Joel Berry

Jack E Lemons

Document Type

Thesis

Date of Award

2012

Degree Name by School

Master of Science in Biomedical Engineering (MSBME) School of Engineering

Abstract

Bacterial nanocellulose (BNC) is a biopolymer that has been used in a variety of applications ranging from speaker diaphragms to biomedical products. Created by micro-organisms like Gluconacetobacter xylinus, BNC is composed of long cellulose fibers in a highly crystalline hydrogel. Recent interest in BNC based materials has led to the discov-ery of several cultivation and post-processing treatments that have enabled researchers to control the mechanical and structural properties of the hydrogel. Three BNC treatments were mechanically evaluated through tensile testing. Ten-sile tests were conducted using dogbone shape test strips and a video extensometer. Phys-ical compression of a BNC hydrogels not only removes water from the gel but also in-duces hydrogen bonding between cellulose fibers. Results showed that both the ultimate strength of material and the effective modulus were significantly higher in samples with increased cellulose content (p < 0.01), reaching modulus values up to 260 MPa. Unlike the physical compression method, freeze-drying BNC samples can effectively remove water content without damaging or collapsing the cellulose network. Freeze-dried and rehydrated samples showed no difference with effective modulus when compared to samples of identical cellulose percentage (p < 0.001). The implications of freeze-drying are beneficial during shipment of BNC materials, as they can be dehydrated and pack-aged then later rehydrated without loss of mechanical characteristics. Culture media components were also evaluated. A vitamin solution was used in different concentrations to determine its effects on cellulose production and the resulting mechanical strength of the hydrogel. Results showed that a concentrated vitamin solution not only produced thinner pellicles (p < 0.001), but also produced hydrogels with half the ultimate strength of gels made from a diluted vitamin solution (p < 0.01). While these tests have only eval-uated three of the increasing number of BNC treatments, they emphasize the important of mechanical testing during the development of BNC based biomaterials.

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