Abstract
The manipulation and analysis of heterogeneous biological cells play an important role in research and clinical applications. Microfluidics is a powerful approach for the manipulation and analysis of biological cells at multi- and single-cell resolutions given that implementing microstructures/channels with dimensions similar to those of biological cells enables the accurate handling of liquid flow and cell samples. Additional forces, such as electric and magnetic fields, can also be integrated into microfluidic chips for the completion of complex tasks. Although various microfluidic approaches have been developed, approaches for various applications remain challenging. In this study, several novel microfluidic approaches for cell focusing, separation, patterning coculture, and single-cell analysis are proposed and investigated. This thesis mainly includes the following parts:First, a simplified sheathless and tunable cell-focusing approach based on gravitational sedimentation is introduced. By exploiting gravitational sedimentation in a tubing inserted into the inlet of a microfluidic channel with adjustable steer angles, cells can be focused into a stream in a microchannel. The position of the focused cell stream in the microchannel can be easily adjusted by changing the tubing steer angle. The proposed gravitational sedimentation-based cell-focusing approach is then numerically and experimentally investigated.
Second, on the basis of combined gravitational sedimentation-based prefocusing and dielectrophoretic (DEP) separation, a simplified sheathless cell separation approach is developed for cell separation in accordance with size or dielectric property. The combined cell separation system can be easily integrated into other microfluidic functionalities given that it does not require a cumbersome peripheral system for sheath flow. The DEP method enables highly flexible cell separation because it can continuously separate unlabeled cells on the basis of either size or dielectric property. The efficiency of the proposed approach has been experimentally assessed in the separation of human acute monocytic leukemia THP-1 cells from yeast cells on the basis of size and in the separation of THP-1 cells from human acute myelomonocytic leukemia OCI-AML3 cells on the basis of dielectric properties.
Third, on the basis of gravitational sedimentation-based tunable cell focusing in a microchannel, a one-step hydrodynamic approach for patterning multiple cell types in the same microfluidic channel is developed for cellular and drug screening. In contrast to traditional cell patterning approaches, the developed approach allows the rapid patterning of multiple cell types in the same microfluidic channel without the use of sheath flow and prepatterned functional surfaces. It greatly simplifies experimental setup, operation, and chip fabrication. Moreover, the cell pattern in the microchannel can be adjusted by simply changing the steer angle of the cell-loading tubes. This strategy broadens the application range of the proposed approach to tissue engineering and cell migration studies. Finally, a microfluidic gradient generator is integrated with the microfluidic cell patterning chip for drug-screening applications.
Lastly, a microfluidic platform for single-cell and long-term culture is presented. Single cells are deterministically captured in a microchamber array for clonal expansion. The developed platform is used to preliminarily examine the influence of chemical and electrical stimuli on the growth phenotype of the cells. This new platform can facilitate the tracking of heterogeneous cellular growth under chemical/electrical stimuli.
In summary, microfluidic approaches based on gravitational sedimentation are simpler and more flexible than other reported approaches. In addition, the proposed single-cell platform can support on-chip week-scale studies on single-cell clonal expansion under chemical and electrical stimuli. The novel approaches introduced in this thesis provide new concepts for the use of simple and hybrid microfluidic techniques in complex cell manipulation and analysis.
| Date of Award | 1 Aug 2018 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Dong SUN (Supervisor) |