Experimental and computational study of GelMA microgel generation and deformation using a microfluidic device

Abstract

Gene editing is a technique through which DNA segments can be modified within the genome of a living organism. Despite the many potential applications, current gene editing techniques are still low-throughput and have several limitations. On one side, the conventional 2D cell culturing techniques suffer from low cell viability and proliferation. On the other side, transfection techniques commonly using exogenous materials lead to off-target effects in cells. Droplet-based microfluidic devices (DBMD) show great potential for gene editing. They allow precise single-cell manipulation, encapsulation and might eventually achieve high throughput. As an example, using a DBMD, cells encapsulated in GelMA microgels have kept viability and shown proliferation. Moreover, DBMD might play a key role in cell transfection. Particularly, mechanical squeeze of cells encapsulated in droplets and moving through a narrow channel favors the entrance of foreign materials into the cells. This thesis presents the design and implementation of droplet-based microfluidic systems for fabrication of monodisperse GelMA microgels. First, a DBMD was developed using three techniques of soft lithography, stereolithography, and cutter plotting and the comparison between the devices was conducted. Second, fabrication of both, solid-like as well as core-shell microgels with average size of 133.43±5 µm was demonstrated. It was shown the generated microgels have spherical morphology with pore size area of 23.28±6 um2. Finally, computer simulation was used to emulate microgel indentation (solid-like and core-shell) with or without cells; as well as the throughput of the designed confinement channel. From the indentation of particles, it was concluded that lower stiffnesses was obtained for core-shells in comparison to solid-like microgels. It is also shown that a 21% and 24 % deformation in microgels containing cells causes 30% and 40% deformation of encapsulated cells, respectively, vital in cells transfection-based confinement channel application. From computational fluid dynamics (CFD) model, we observed the enhancement of the throughput of the device by selecting a longer confinement length. It is expected these preliminary results presented in this thesis will motivate other works that eventually lead to the development of efficient droplet-based microfluidic devices for cell transfection.