Comprehensive Single Cell Assay Chips for the Study of Cancer Metastasis and Heterogeneity
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Due to the genomic and epigenetic instability of cancer cells, tumors are highly heterogeneous and difficult to treat. Additionally, cancer metastasis, which account for 90% of cancer mortality, is a complicated multi-step process. As such ideal assays should be high-throughput and provide single-cell resolution and microenvironment control, enlightening individual cell properties rather than the average behavior of the bulk tumor. Here, we have developed microfluidic platforms meeting these requirements to investigate three critical stages of metastasis. First, a single-cell migration chip was developed to model cancer cell migration from the primary tumor. The motility of cells under the influence of chemo-attractants can be measured on-chip. After the assays, highly motile cells and non-motile cells can be retrieved for further culture and mRNA expression analysis. Second, to understand cell survival in the circulatory system, a single-cell suspension culture chip was developed, improving the throughput of single-cell anoikis assays and single-cell derived sphere formation by orders of magnitude utilizing hydrodynamic single cell positioning. Third, to investigate interactions between cancer cells and stromal cells, three cell-cell interaction platforms were developed. Innovations including control of interacting cell ratios, valveless isolation of co-culture using two-phase flow, continuous nutrient renewal enabled by 3D integration, and dual adherent-suspension co-culture were attained. In addition, a selective single-cell retrieval technique that selectively detaches and retrieves targeted single cells has been developed for incorporation in our microfluidic platforms. The technique neither affects cell viability nor alters mRNA expression for qRT-PCR. These single cell platforms provide numerous advantages over traditional methods including: (1) ability to monitor and track individual cells, (2) control of various micro-environments on-chip for emulation of bio-processes, (3) accommodation of high-throughput screening, (4) capability to handle rare cell samples, and (5) potential to retrieve interesting single cells for further culture and analysis.