UBC Theses and Dissertations
A microfluidic platform to study real-time tumour cell and tumour spheroid response to chronic and transient hypoxia Grist, Samantha Marie
Cell-based screening of cancer treatments is used early in the drug development process to test the efficacy and toxicity of treatment candidates prior to animal and human testing. Current cell-based screening methods offer limited predictive capacity, contributing to the high percentage of drugs that fail during the clinical trial stage (80-95% for cancer treatments). One shortcoming of traditional cell-based screening platforms is their inability to recreate many aspects of the natural environment of tumour cells, which can affect treatment response. One important aspect of the microenvironment that can affect cell behaviour and treatment response is oxygenation. Irregular blood vessel formation can cause tumour oxygenation to be much lower than that of surrounding tissue, and spatial and temporal variations in oxygen can be present. Temporal variations can occur at timescales up to several cycles/hour: changes that are too fast to recreate using standard technologies like well plates due to their long diffusion distances. This thesis presents a novel microfluidic platform to expose cells to both chronic and time-varying oxygen profiles and study their response. Microfluidics technology is combined with 3-D cell culture in tumour spheroids, which can better recreate other aspects of the tumour microenvironment (such as cell-cell and cell-matrix interactions) than traditional 2-D culture. The functionality of the oxygen control device is verified using both finite-element modelling and integrated optical oxygen sensors. Two novel methods for oxygen sensor microfabrication are presented, and the functionality of sensors during long-term experiments is studied. Precise oxygen control is demonstrated using the microfluidic system, with oxygen switching times of <10 minutes. Because 3-D cultures present imaging challenges confounding their data analysis, new, on-chip strategies for improved imaging of 3-D cultures are studied. Finally, this thesis demonstrates the utility of the platform with preliminary biological experiments. Long-term culture of breast tumour cells is demonstrated, and the response of the cells to oxygen changes is analyzed. The microfluidic platform allowed us to observe for the first time that tumour spheroids can reversibly swell and shrink under changing oxygen conditions. Finally, a preliminary evaluation of the suitability of the platform for drug screening experiments is presented.
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