Date of Graduation

5-2023

Document Type

Thesis

Degree Name

Bachelor of Science in Biological Engineering

Degree Level

Undergraduate

Department

Biological and Agricultural Engineering

Advisor/Mentor

Kim, Jin-Woo

Committee Member/Reader

Sakon, Josh

Committee Member/Second Reader

Zhu, Jun

Abstract

Advancements in medicine and our understanding of stem cells have led to a greater emphasis on further developing research focused on tissue engineering. This research has led to the rise of both two-dimensional and three-dimensional scaffolds that can be utilized to repair bone, skin, vascular, and potentially even nervous tissue. One of the prominent compounds used in modern scaffolds is collagen-based hydrogels due to their low antigenicity and ability to provide structure to cells. There is potential to further improve upon this three-dimensional scaffold by incorporating cellulose nanocrystals (CNCs) into a composite hydrogel with collagen. The addition would increase the mechanical strength of the composites compared to collagen alone. However, collagen and cellulose nanocrystals are both highly viscous and concentrated fluids for which improper mixing at inappropriate concentrations can lead to composites that contain aggregates of poorly dispersed collagen and cellulose nanocrystals. To prevent aggregation in the composites, several methods and protocols of mixing have been proposed and tested to create a protocol for homogenizing collagen and CNCs. In addition to this, compressive tests have been performed to determine the amount of mechanical strength that is added to these composites at varying concentrations of CNCs within the composite. The method that has resulted in the best homogenization is a 10-stepwise mixing approach. Using this method yielded a homogenous mixture that only has a 0.39% variance in rheological properties throughout the 10-step sample. It was shown that the Young’s Modulus for collagen composites does not change significantly as CNC concentration increases, but the behavior of the hydrogels under stress changed from solely elastic to stress-softening followed by rapid strain-hardening with increasing CNC concentrations­­. Additionally, it was observed that increasing CNC concentration decreased porosity steadily, but the amount of porosity decrease may not be statistically significant. The porosity data cannot be used to make any conclusions though due to issues that arose during experimentation.

Keywords

Tissue Engineering; Cellulose Nanocrystals; Collagen; Homogeneity; Mechanical Strength; Porosity

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