Date of Award

Summer 8-15-2022

Level of Access Assigned by Author

Open-Access Thesis

Language

English

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Engineering

Advisor

Michael Mason

Second Committee Member

Douglas Bousfield

Third Committee Member

Mehdi Tajvidi

Additional Committee Members

Ian Dickey

Benjamin Lakin

Abstract

Current orthopedics are separated into three different classes of materials, metals, polymers, and ceramics. While these devices have had success throughout the years they are not without their faults. Metallic devices for example are usually extraordinarily stiff when compared with the surrounding bone. This difference in stiffness induces localized stress-shielding promoting cortical atrophy, which can lead to osteoporosis. Polymers while having the capacity of being biodegradable and bioabsorbable also have the potential to incite localized demineralization and weakness in surrounding bone. A result of breakdown byproducts not efficiently being evacuated from the area, which additionally acts as catalysts expediating the degradation rate. Ceramic devices while providing superior osteointegration, with a potential of being comprised from minerals analogous to naturally sourced bone, tend to be extremely brittle causing premature failure of devices. While materials currently used have their benefits, providing medical professionals with sufficient alternatives is imperative, for them to have more variety during operations.

Our proposed solution is the use of a recent biopolymer of interest, cellulose nanofibrils (CNF). CNF is a biopolymer that is incredibly naturally abundant, being the base structure sourced from cellulosic materials and byproducts of many agricultural industries. CNF additionally has physical properties that make it a promising material within the orthopedic field. It is morphologically similar to collagen, can be easily chemically modified, and has tunable mechanical properties. CNF, while heavily studied by many research groups has rarely been studied in large bulk. Throughout this thesis processing and additive properties of CNF were determined, including bulk orientation, effects of composites, and crosslinking. Bulk orientation was determined through a multitude of mechanical testing and found an orientation within the large length direction of molds. Composite films were produced under different conditions and tested to view their effects. Crosslinking of CNF was conducted and viewed with an acute submersion and water absorption testing, viewing effects of crosslinker and amount (~2.5 % crosslinker). Finally, a simple computer simulation was made using CNFs now determined properties and placed under known loads experienced by specific orthopedic devices.

Download

Share