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Date of Award

5-2025

Document Type

Restricted Thesis: Campus only access

Degree Name

Master of Science in Biology

Department

Biology

First Reader/Committee Chair

Nickerson, Daniel

Abstract

The focus of this study is the optimization of a novel counter rotary wall bioreactor (CRWV), which was developed under Dr. Hideaki Tsutsui at the University of California Riverside in collaboration with Synthecon Incorporated (Houston, Texas). The CRWV was designed to cultivate human embryonic stem cells (hESCs) under laminar fluidic shear. Traditional methods rely on 2D culture methods which are limited by demand for trained culture specialists and by issues in scalability. The CRWV employs counter rotating walls which are capable of antagonistic rotation of 60 rotations per minute. Additionally, bioreactors promote dynamic suspension which allows for more uniform nutrient distribution and gas exchange; laminar flow ensures that each hESC aggregate receives the same amount of fluidic shear. Originally a comparison between laminar and turbulent shear was planned after the temperature calibration, however multiple long-term repairs on the CRWV prevented this. The objective then shifted towards determining the optimal set temperature of the incubator to maintain physiological temperature.

A primary issue addressed by this study is the thermal regulation of the CRWV under load within the incubator altered by byproduct heat and friction. The rotating parts of the CRWV generate heat from friction and the motors which may influence the culture vessel’s temperature beyond the physiological temperature of 37°C required for optimal cell growth. To address this, thermocouples were used to measure the media temperature of the CRWV under load. A Temperature curve was generated which determined the optimal temperature setting to be 34°C was sufficient to maintain the media temperature within physiological range required to grow hESCs. As the CRWV is a novel system it is important to determine design iterations to resolve mechanical issues such as motor torque, unintended inner core rotation, and ease of use. Once optimized the CRWV shows promise as an alternative to turbulent bioreactors, such as spinner flasks. The laminar fluidic shear environment is optimal for studying fluidic shear effect on hESC aggregates as each aggregate should experience an equal amount of fluidic shear. This study lays the groundwork for future studies to explore how controlled laminar fluidic shear influences stem cell growth, differentiation, and overall viability, with potential applications in regenerative medicine, drug discovery, and disease modeling.

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