Study of Microfluidic Devices for Biological Cell Patterning and Pairing


Student thesis: Doctoral Thesis

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Award date3 Nov 2020


Intercellular interaction is a natural and common phenomenon in the body. It plays a vital role in participating in the metabolism of organisms. Cellular heterogeneity also has a considerable effect in biological research. However, traditional approaches for studying intercellular interactions in vitro have failed to mimic the complexity of in-vivo niches and ignored the cellular heterogeneity. As an emerging and powerful technique, microfluidic cell patterning and pairing devices have facilitated the cell-cell interaction studies in a more realistic environment, given that microchannels/structures with similar dimensions to cells could even precisely control fluids and cells at the single-cell resolution. Although various microfluidic devices for cell patterning and pairing have been developed, simple, flexible, and reliable approaches for various cellular communication studies in vitro remain challenging. This thesis presented a series of designs in microfluidics for cell patterning and pairing. The study was conducted in three main aspects.

First, the use of gravitational sedimentation of cells in tubing to achieve patterning coculture of multiple cell types in microfluidic channel was investigated. Compared with the current techniques, the proposed gravitational sedimentation-based approach exhibited ultra-simplicity and flexibility. Multiple cell types with considerable differences in cell size could be patterned without using sheath flows or prepatterned functional surfaces. One-step operation could be achieved by simultaneously introducing multiple cell types to the chip. The spatial arrangement of each cell type could be easily adjusted by simply altering the tubing steering angles, flow rate, or cell concentration. The proposed approach made it easy to integrate with other functional modules for various drug screening and cellular interaction studies under patterning coculture condition. A series of experiments was conducted to successfully validate the proposed approach for constructing cell coculture models for drug screening and studying cell-cell interactions.

Second, a positive dielectrophoretic (pDEP)-based single-cell trapping and patterning microfluidic chip was developed. Compared with the current techniques, the proposed pDEP-based approach for single-cell patterning exhibited high-efficiency, high-throughput, and easy-controllability. The developed chip could reduce the damping of electric field intensity in the direction of the channel height and avoid the complex craft fabrication of 3D electrodes. The chip could enhance the capacity to detect cell fluorescence. The maximum diameter of the trapped cells was not restricted. Single-cell could be trapped and selectively released. The electrode could be scalable for high-throughput applications. The chip could be fabricated optimally by simulating the electric field distribution and direction of the DEP force. With the fabricated microfluidic device, the trapping, releasing, and patterning of single cells were successfully demonstrated through experiments.

Third, a versatile microfluidic single-cell pairing and coculture chip was designed on the basis of the combination of hydrodynamics and recirculation flow. Compared with the current techniques, the combination of hydrodynamics and recirculation flow for single-cell pairing exhibited high-efficiency, high-throughput, controllability, and traceability. Single cells could be caged in the coculture chamber by recirculation flow, thereby avoiding the effect of later cellular trapping. This phenomenon could help facilitate two or more single cells while providing the same initialization for the paired cells. The area of coculture chamber could be adjusted flexibly to serve various applications. More pairing units could be integrated on a smaller chip. Moreover, the paired cells could be isolated because of the little interference among different coculture chambers. A series of experiments was conducted to confirm the feasibility and efficiency of the designed chip in single-cell interaction research. As a case study, two breast cell lines were paired and cell entosis was observed.

In summary, the experimental results of this thesis demonstrated an important significance in the field of cell-cell interaction study using microfluidics. The multi/single-cell patterning device based on gravity sedimentation/pDEP developed in this thesis exhibited the advantages of flexibility, simplicity, and reliability. The single-cell pairing chip developed based on the combination of fluid dynamics and recirculation flow allowed high-throughput single-cell analysis on a smaller platform. All of the proposed devices paved an improved way to study cell-cell interactions at multi or single-cell resolution in vitro.