(338d) Versatile Microfluidic Platform for Single-Cell Culture and Analysis

Authors: 
Kelly, R. T., Pacific Northwest National Laboratory
Baker, S. E., Pacific Northwest National Laboratory
Evans, J. E., Pacific Northwest National Lab
Long-term tracking of single cells is essential to interrogate cell-to-cell heterogeneity in clonal cell populations, cell fate regulation, and cellular responses to environmental signals. Compared to classical experimental approaches using microscope coverslips, slides, multi-well plates, or agarose plates, microfluidic technology has revolutionized the monitoring and analysis of individual cells due to its benefits of comparable dimension to a cell, precisely controlled microenvironment, and capability of simultaneously visualizing multiple single cells over prolonged periods. Despite the power of previously developed microfluidic cell culture platforms, they are specially designed for either microchemostat or compartmentalized cell growth and for limited cell types.

Here we present a highly versatile microfluidic platform providing various functionalities for single-cell growth and comparative analysis of diverse types of unicellular organisms ranging from yeasts (Yarrowia lipolytica) and bacteria (Shewanella oneidensis MR-1) to microalgae (Chlamydomonas reinhardtii). This is the first demonstration of an all-in-one microfluidic platform for the trapping and growth of cells with two cultivation formats using the same chip architecture. The device features an array of 30 picoliter-scale circular cell growth chambers, each of which is interconnected with two main channels through two narrow connecting channels arranged in parallel. The serpentine main channels transect the parallel connecting channels for the delivery of medium, oil, dye solutions, or other reagents with the guidance of multiple pneumatic valves. A pair of offset castellated microvalves under the main channels is actuated to enable cells to flow through all of the growth chambers, thereby enhancing trapping efficiency. Microchemostat is created by introducing medium into the main channels and rapidly transporting nutrients into the growth chambers via molecular diffusion, while compartmentalized growth is achieved by infusing oil into the main channels and closing the isolation valve under the connecting channels to form stationary droplet arrays in situ. Coupled with live cell imaging, we have probed single-cell division and growth, long-term cellular dynamics under nutrient switching, and intracellular organelle tracking by dye staining. We envision that our broadly applicable device is extensible to other biological systems (i.e., adherent mammalian cells) and functions (i.e., chemotaxis and analysis of extracellular events such as secretion), and could stimulate additional cell biological explorations.