Three-Dimensional Microdroplet Chain Array For Cell Migration Assays And Multi-tissue Co-culture Experiments

Establishing in vitro model for cell migration assays and cell co-culture experiments is important in the study of drug screening, early diagnosis and fundamental biological research. Benefiting from the various chip structures, cell culture materials and microfluid control methods, microfluidic systems have great potentials in controlling and simulating cell microenvironment. Various microfluidic systems have been developed to perform three-dimensional cell cultivation and cell co-culture for the study of cell behavior, pathological and physiological phenomenon, as well as new drug development and screening. However, most of the current microfluidic systems used for cell migration and co-culture, are limited by the complexity in chip fabrication and fluid control. Here, our purpose is to develop a miniaturized and high-throughput microfluidic platform for multiple cell biology experiments, including multi-mode cell migration assays and multi-mode cell co-culture experiments, by combining the traditional membrane-based cell culture technique and the state-of-art droplet-based microfluidic technique.In chapter 1, the current progress of microfluidic systems for cell migration assays, cell co-culture, and three dimensional cell culture is reviewed. In cell migration assays, generating concentration gradients of inducers are usually essential to induce cell migration. We introduce various microfluidic devices for cell migration assay, using concentration gradient generators based on laminar flow, microchannels, hydrogel and porous membranes. The miniaturized systems of 3D cell culture based on hanging droplet and hydrogel techniques, and cell co-culture systems based on patterned structure, microchannels and membranes are also reviewed.In chapter 2, a novel concept of 3D droplet chain based on a porous membrane has been proposed, based on which we built a semi-open oil covered droplet chain array chip for multi-mode cell migration assay. Benefitting from the ability of the present system in flexibly combining different droplets in droplet chains, variable and long-term (from 2 to 48 hours) gradients could be obtained by adjusting the lengths (i.e. droplet number) between inducer droplet and cell droplet or the overlapping area of adjacent droplets in a chain. Cell migration induced by chemotaxin concentration gradient in droplet chains could be flexibly performed with reagent consumption in nanoliter range (500-800 nL) for each assay and a throughput up to 81 assays in parallel in one microchip. We have applied the present platform in multiple modes of cell migration assays including accurate cell migration assay, competitive cell migration assay, biomimetic chemotaxis assay, demonstrating its substantial versatility, broad applicability, and great potentials in cell migration-related researches.In chapter 3, we design a flower-like droplet chain and string bead droplet chains for multi cell co-culture based on the device of chapter 2. In the flower-like droplet chain, liver, lung, kidney, intestine, and heart organ cells were co-cultured under hanging drop mode, and the chip was applied in the research of metastatic breast cancer cell MDA-MB-231 migration tendency to various organs. The string bead droplet chains were preliminarily used to build multi-organ models for mimicking tissue-tissue interactions and in vitro drug metabolism.