A microfluidic platform for single-cell co-culture and characterization

Abstract

We present two microfluidic platforms for single cell trapping and cell migration analysis. The first platform aims at trapping single mammalian cells (average diameter smaller or equal to 20μm) for a throughput of a population of cells. The second platform demonstrates variations in microfluidic dimensions for cell deformation and migration. The objective of our project aims at designing a spatial confinement for researches on interactions of cancers cells (i.e. Human liver cancer cells (Hep G2)) and any other types of cells (i.e. Human dermal fibroblasts, neonatal (HDFn)). Such concept originates from the phenomena which cancer cells mutations and development are affected by the biochemical signaling of other cells types (e.g. endocrine signaling). Since cancer cells are malicious cells that are not localized, what are the attractants for cancer cells to migrate and proliferate are of key interests in cancer research. For example, the correlation of epithelium cells and tumor cells circulation was justified in ovarian cancer. As microfluidics technology has been appraised for its ingenuity in simplifying numerous tedious laboratory operations ever since its development, little is known about a distinguished design and its application on measuring the migration time of cells. From our experiment, we observe that at certain occasions, cells do not proceed in uni-direction. At those channels where cell squeezing regions are designed (the "squeezing regions" of the second platform), cells sometimes proceed backwards along a channel. It is hypothesized that sensing the presence of own kind decides the migration pattern of cells. It is because one of the earliest step a cell takes to commit apoptosis is to halt communicating with its neighbors. In other words, not separating from the initial group of cells is crucial to the survival of cells. Unlike single cell organisms, at the moment there is little evidence on intelligence of single mammalian cell like those of 'microbial intelligence'. Such investigation approach can be substantiated by future microfluidics devices as they are the product of cumulated observation experiences and intelligence of human designers. Our two microfluidic platforms may ultimately integrate into one platform if future research on co-culture of two types of cells conducts. However, at the moment we demonstrate flexibility in operating on two individual platforms because they can also be standing on their own. We have used human dermal fibroblast, neonatal cells and liver cancer cells because they exhibit distinguish size differences and property to deform. Firstly, we present a microfluidic chip for cells trapping with trapping regions on both ends of parallel arrays. The design is based on differential fluidic resistance for heterotypic and homotypic cells co-culture and characterization. Two input channels allow concurrent injection of cells whereas the trapping regions are separated by channels to serve the observation of cells movement in counter direction. Secondly, we present an array platform with channels and cell squeezing regions. We would like to compare how fast do Hep G2 and HDFn migrate from the starting point to the end point. We provided squeezing regions for cells to deform and concluded that at a specific time period, the one with higher population at the endpoint possess more vigorous ability to move. At the end, the experimental results are favorable as our trapping device has successfully singled out small cells out of a population; the migration time also met our expectation as more Hep G2 migrate to the endpoint, compared to HDFn.