Degree

Doctor of Philosophy (PhD)

Department

Electrical and Computer Engineering

Document Type

Dissertation

Abstract

With recent advances in biotechnology, there is a strong and urgent need for robust platforms to culture mammalian cells on a large scale to produce biopharmaceuticals. To this end, various bioreactors have been developed over the past decades, but their capacity and efficiency are often limited by insufficient mass transfer rate and excessive shear stress. In this work, multiple novel bioreactors for the large-scale adherent culture of anchorage-dependent cells were developed.

Hollow MicroCarriers (HMC) was developed as an alternative solution for the microcarrier-based culture system in a stirred-tank bioreactor. In the conventional microcarrier technique, cells are exposed to the harmful shear stress in the bioreactor. HMCs are hollow microspheres with openings on their surface to ensure a sufficient mass transfer rate of nutrients and gases. Cells are cultured on the inner surface of HMCs, protected from the shear stress in the bioreactor. I demonstrated the expansion of NIH/3T3 fibroblasts and the expansion and cardiac differentiation of human induced pluripotent stem cells inside the HMC. HMCs are a practical solution for large-scale expansion of shear-sensitive adherent cells on an industrial scale with stirred-tank bioreactors.

I also developed Rolled Scaffold (RS) bioreactor for the high-density adherent culture of mammalian cells. The RS is a polymer film with spacers rolled into a cylinder with a pre-determined gap between layers, and cells adhere to the film. The media flows through the gap via convection in a unidirectional flow, resulting in significantly lower shear stress on cells. CHO cells were expanded in RS and showed a growth rate higher than conventional suspension culture. Also, murine embryonic stem cells were successfully expanded in RS without losing their pluripotency. RS bioreactor achieved a high cell density of 72.8×106 cells/mL. A dialysis module was integrated into the RS bioreactor to remove cellular biowaste and replenish the nutrients while retaining the secreted protein in the reservoir. Various aspects of RS bioreactor were automated to minimize human intervention and improve the culture environment. The RS bioreactor is an affordable, scalable, and reliable platform for the large-scale culture of recombinant cells in biopharmaceutical industries and shear-sensitive stem cells in tissue engineering.

Committee Chair

Park, Kidong

DOI

10.31390/gradschool_dissertations.5786

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